Shifting control apparatus for vehicular automatic transmission

A shifting control apparatus includes an overall-speed-position shifting control portion including: a synchronous shifting control portion to implement a synchronous control of shifting actions of the vehicular automatic transmission and the step-variable transmission portion to respective target ones of the overall speed positions and the gear positions, such that a moment of generation of a command to establish the target overall speed position is delayed with respect to a moment of generation of a command to establish the target gear position, so that the shifting actions take place in synchronization with each other, irrespective of different control response times of the shifting actions; and a multiple-step shifting control portion to command the synchronous shifting control portion such that the vehicular automatic transmission performs a shift-up action from a present one of the overall speed position to the target overall speed position through at least one intermediate overall speed position intermediate.

This application claims priority from Japanese Patent Application No. 2017-159807 filed on Aug. 22, 2017, the disclosure of which is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates in general to a shifting control apparatus for a vehicular automatic transmission, and more particularly to a shifting control apparatus for a vehicular automatic transmission provided with an electrically controlled continuously variable transmission portion and a mechanically operated step-variable transmission portion which are disposed in series with each other.

BACKGROUND OF THE INVENTION

There is well known a vehicular automatic transmission having (a) an electrically controlled continuously variable transmission portion operable to transmit a rotary motion of a drive power source to an intermediate power transmitting member such that a speed ratio of an operating speed of the drive power source to a rotating speed of the intermediate power transmitting member is continuously varied with a torque control by a differential motor/generator, and (b) a mechanically operated step-variable transmission portion which is disposed between the intermediate power transmitting member and drive wheels of a vehicle, and which has a plurality of mechanically established gear positions having respective different ratios of the rotating speed of the intermediate power transmitting member to an output speed of the step-variable transmission portion. JP-2006-321392A discloses an example of this type of vehicular automatic transmission, and a shifting control apparatus for the automatic transmission, which is configured to reduce a shifting shock of the mechanically operated step-variable transmission portion due to speed changes in an inertia phase of its shifting action, by implementing a shifting action of the electrically controlled continuously variable transmission portion while the operating speed of the drive power source is substantially kept unchanged, so that the inertia phase of the shifting action of the mechanically operated step-variable transmission portion is initiated.

However, this shifting control apparatus has difficulty to completely prevent generation of the shifting shock of the mechanically operated step-variable transmission portion, and suffers from a risk that an operator of a vehicle provided with the automatic transmission is given a discomfort due to the shifting shock even when the shifting shock is not so serious, since the operating speed of the drive power source is kept substantially constant.

SUMMARY OF THE INVENTION

The present invention was made in view of the background art described above. It is therefore an object of the present invention to provide a shifting control apparatus for a vehicular automatic transmission having an electrically controlled continuously variable transmission portion and a mechanically operated step-variable transmission portion, which shifting control apparatus permits further reduction of discomfort given to the operator of the vehicle due to the shifting shock of the mechanically operated step-variable transmission portion in the process of its shifting action.

The object indicated above is achieved according to the following modes of the present invention:

According to a first mode of the invention, there is provided a shifting control apparatus for a vehicular automatic transmission having (a) an electrically controlled continuously variable transmission portion configured to transmit a rotary motion of a drive power source to an intermediate power transmitting member such that a speed ratio of an operating speed of the drive power source to a rotating speed of the intermediate power transmitting member is continuously varied with a torque control by a differential motor/generator, and (b) a mechanically operated step-variable transmission portion which is disposed between the intermediate power transmitting member and drive wheels of a vehicle, and which has a plurality of mechanically established gear positions having respective different ratios of the rotating speed of the intermediate power transmitting member to an output speed of the step-variable transmission portion, the shifting control apparatus comprising (c) an overall-speed-position shifting control portion configured to control the electrically controlled continuously variable transmission portion, so as to establish a plurality of overall speed positions of the vehicular automatic transmission having respective different values of a speed ratio which is a ratio of the operating speed of the drive power source to an output speed of the mechanically operated step-variable transmission portion, (d) wherein the overall-speed-position shifting control portion includes: (d-1) a synchronous shifting control portion configured to implement a synchronous control of shifting actions of the vehicular automatic transmission and the mechanically operated step-variable transmission portion to respective target ones of the plurality of overall speed positions and the plurality of gear positions, such that a moment of generation of a command to establish the target overall speed position is delayed with respect to a moment of generation of a command to establish the target gear position, so that the shifting actions take place in synchronization with each other, irrespective of different control response times of the shifting actions; and (d-2) a multiple-step shifting control portion configured to command the synchronous shifting control portion such that the vehicular automatic transmission performs a shift-up action (i.e., shifting to a speed position having lower gear ratio) from a present one of the overall speed position to the target overall speed position through at least one intermediate overall speed position intermediate between the present and target overall speed positions.

It is noted that the synchronous shifting actions to establish the target AT gear position and overall speed position are interpreted to mean that the inertia phases of the two shifting actions (in which a rotating speed of an input-side rotary member varies with a change of the speed ratio) at least partially overlap each other. It is also noted that the control response time of the two shifting actions is a delay time from a moment of generation of a command to establish the target AT or overall speed position to a moment of initiation of the inertia phase.

According to a second mode of the invention, the shifting control apparatus according to the first mode of the invention is configured such that the multiple-step shifting control portion includes a multiple-step shifting determining portion configured to determine, according to a predetermined condition for implementing a multiple-step shifting control, whether the vehicular automatic transmission should be initially shifted to the at least one intermediate overall speed position.

According to a third mode of the invention, the shifting control apparatus according to the second mode of the invention is configured such that the predetermined condition for implementing the multiple-step shifting control is formulated to implement the multiple-step shifting control to initially shift the vehicular automatic transmission to the at least one intermediate overall speed position, where a speed of releasing of an accelerator pedal provided on the vehicle is equal to or higher than a predetermined upper limit, where an amount of reduction of an operation amount of the accelerator pedal is equal to or larger than a predetermined upper limit, or where the operation amount of the accelerator pedal after its releasing operation is equal to or smaller than a predetermined lower limit. In this respect, it is noted that the multiple-step shifting determining portion is required to make a determination with respect to at least one of the speed of releasing of the accelerator pedal, the amount of reduction of the operation amount of the accelerator pedal, and the operation amount of the accelerator pedal after its releasing operation.

According to a fourth mode of the invention, the shifting control apparatus according to the second or third mode of the invention is configured such that the mechanically operated step-variable transmission portion is hydraulically shifted to a selected one of the gear positions with a working fluid, and the predetermined condition for implementing the multiple-step shifting control is formulated to implement the multiple-step shifting control to initially shift the vehicular automatic transmission to the at; least one intermediate overall speed position, where a temperature of the working fluid is equal to or lower than a predetermined lower limit.

According to a fifth mode of the invention, the shifting control apparatus according to any one of the first through fourth modes of the invention is configured such that the multiple-step shifting control portion includes an intermediate overall speed position selecting portion configured to select the at least one intermediate overall speed position according to a running state of the vehicle, where the overall speed positions are present between the present and target overall speed positions.

According to a sixth mode of the invention, the shifting control apparatus according to the fifth mode of the invention is configured such that the intermediate overall speed position selecting portion selects the at least one intermediate overall speed position, according to the speed of releasing of the accelerator pedal, the amount of reduction of the operation amount of the accelerator pedal, and the operation amount of the accelerator pedal after its releasing operation as the running state of the vehicle, such that the selected at least one intermediate overall speed position is closer to the target overall speed position (i.e., to a speed position having lower gear position) when the speed of releasing of the accelerator pedal is relatively high than when the speed of releasing is relatively low, when the amount of reduction of the operation amount of the accelerator pedal is relatively large than when the amount of reduction is relatively small, or when the operation amount of the accelerator pedal after its releasing operation is relatively small than when the operation amount is relatively large.

According to a seventh mode of the invention, the shifting control apparatus according to the fifth or sixth mode of the invention is configured such that the number of the overall speed positions of the vehicular automatic transmission is larger than the number of the gear positions of the mechanically operated step-variable transmission portion, and a plurality of the overall speed positions are assigned to one of the gear positions, and the intermediate overall speed position selecting portion selects the at least one intermediate overall speed position from the overall speed positions assigned to the present gear position, in a running state of the vehicle in which a shifting shock of the mechanically operated step-variable transmission portion is likely to be generated.

According to an eighth node of the invention, the shifting control apparatus according to any one of the fifth through seventh modes of the invention is configured such that the number of the overall speed positions of the vehicular automatic transmission is larger than the number of the gear positions of the mechanically operated step-variable transmission portion, and a plurality of the overall speed positions are assigned to one of the gear positions, and the intermediate overall speed position selecting portion selects the at least one intermediate overall speed position outside a range of the overall speed positions assigned to the present gear position, in a running state of the vehicle in which an operator of the vehicle is likely to feel that the operating speed of the drive power source is kept at a relatively high value for an excessively long length of time.

According to a ninth mode of the invention, the shifting control apparatus according to any one of the first through eighth modes of the invention is configured such that the multiple-step shifting control portion includes a multiple-step shifting commanding portion configured to command the vehicular automatic transmission to be shifted up to the at least one intermediate overall speed position, at a predetermined timing after a moment of determination to shift up the vehicular automatic transmission to the target overall speed position.

According to a tenth mode of the invention, the shifting control apparatus according to the ninth mode of the invention is configured such that the multiple-step shifting commanding portion commands the vehicular automatic transmission to be shifted up to the at least one intermediate overall speed position, immediately after the moment of determination to shift up the vehicular automatic transmission to the target overall speed position. It is noted that the expression “immediately after the moment of determination” is interpreted to mean that the at least one intermediate overall speed position is selected as soon as possible, and that the vehicular automatic transmission is shifted to the selected at least one intermediate overall speed position as soon as possible.

In the shifting control apparatus for the vehicular automatic transmission, which is configured according to the first mode of the invention, the plurality of overall speed positions of the vehicular automatic transmission having the respective different speed ratios of the operating speed of the drive power source to an output speed of the mechanically operated step-variable transmission portion are established by controlling the electrically controlled continuously variable transmission portion, so that the operating speed of the drive power source is variable in steps by shifting the vehicular automatic transmission from one of the overall speed positions to another. Accordingly, the vehicular automatic transmission as a whole can be shifted in a manner like a manner of shifting of a mechanically operated step-variable transmission, as felt by an operator of the vehicle. Further, the synchronous control of the shifting actions of the vehicular automatic transmission and the mechanically operated step-variable transmission portion to the respective target overall speed position and gear position is implemented such that the moment of generation of the command to establish the target overall speed position is delayed with respect to the moment of generation of the command to establish the target gear position, so that the shifting actions take place in synchronization with each other, irrespective of the different control response times of the shifting actions. Accordingly, the degree of discomfort given to the vehicle operator due to different timings of the two shifting actions and the shifting shock of the mechanically operated step-variable transmission portion is reduced, and the drivability of the vehicle is improved. Namely, the control response time of the shifting action of the vehicular automatic transmission performed by the electrically controlled continuously variable transmission portion is shorter than the control response time of the shifting action of the mechanically operated step-variable transmission portion, so that simultaneous generation of the commands to establish the target overall speed position and gear position causes a difference between a state of change of the operating speed of the drive power source in the process of the shifting action of the vehicular automatic transmission and a state of change of the rotating speed of the intermediate power transmitting member in the process of the shifting action of the mechanically operated step-variable transmission portion, whereby the vehicle operator may be given discomfort due to this difference. In addition, since the shifting actions of the vehicular automatic transmission and the mechanically operated step-variable transmission portion to the target overall speed position and gear position take place in synchronization with each other, the shifting action of the mechanically operated step-variable transmission portion is performed together with: a change of the operating speed of the drive power source, so that the vehicle operator is unlikely to feel uncomfortable with a shifting shock of the step-variable transmission portion, even if the shifting shock is generated.

On the other hand, where the shift-up action of the vehicular automatic transmission to the target overall speed position is controlled to take place in synchronization with the shift-up action of the mechanically operated step-variable transmission portion, as described above, the operating speed of the drive power source is kept at a relatively high value until the shift-up action of the step-variable transmission portion is initiated, for example, when the step-variable transmission portion is automatically shifted up as a result of a releasing operation of an accelerator pedal, or manually shifted up as a result of an operation of a shift lever or any other manually operated member by the vehicle operator. In this case, there are a risk that the vehicle operator feels that the operating speed of the drive power source is kept at a relatively high value for an excessively long length of time (that the operating speed of the drive power source is not quickly lowered in spite of the releasing operation of the accelerator pedal or the manual operation to shift up the step-variable transmission portion), and a risk of deterioration of the fuel economy (energy efficiency) of the drive power source. There is also a risk that the vehicle operator feels uncomfortable with a difference of the control response of the synchronous shifting actions of the vehicular automatic transmission and the step-variable transmission portion, with respect to that of a shifting action of the vehicular automatic transmission which takes place alone without a concurrent shifting action of the step-variable transmission portion. In view of these risks, the overall-speed-position shifting control portion includes the multiple-step shifting control portion configured to command the synchronous shifting control portion such that the vehicular automatic transmission performs the shift-up action from the present overall speed position to the target overall speed position through at least one intermediate overall speed position. Thus, the vehicular automatic transmission is initially shifted up to the intermediate overall speed position or positions, before it is eventually shifted up to the target overall speed position, so that the operating speed of the drive power source is lowered at an earlier point of time, whereby the risk of the vehicle operator feeling that the operating speed is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source are reduced, together with an improvement of the drivability of the vehicle.

According to the second mode of the invention wherein the multiple-step shifting determining portion determines, according to the predetermined condition for implementing the multiple-step shifting control, whether the vehicular automatic transmission should be initially shifted to the at least one intermediate overall speed position, the multiple-step shifting control is implemented only where there is the risk of the vehicle operator feeling that the operating speed of the drive power source is kept at the relatively high value for the excessively long length of time, or the risk of deterioration of the fuel economy of the drive power source, for example, where the speed of releasing of the accelerator pedal is higher than a predetermined upper limit, where the amount of reduction of the operation amount of the accelerator pedal is larger than a predetermined upper limit, or where the operation amount of the accelerator pedal after its releasing operation is smaller than a predetermined lower limit, as described above with respect to the third mode of the invention, or where the temperature of the working fluid used for the mechanically operated step-variable transmission portion is lower than a predetermined lower limit, as described above with respect to the fourth mode of the invention. Accordingly, it is possible to reduce the risk of the vehicle operator feeling that the operating speed of the drive power source is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source, while adequately maintaining a high degree of drivability of the vehicle owing to the synchronous shifting actions of the vehicular automatic transmission and the mechanically operated step-variable transmission portion. Namely, it is considered that the vehicle operator expects that the operating speed of the drive power source quickly drops down as a result of the releasing operation of the accelerator pedal, where the speed of releasing of the accelerator pedal is higher than the predetermined upper limit, where the amount of reduction of the operation amount of the accelerator pedal is larger than the predetermined upper limit, or where the operation amount after the releasing operation of the accelerator pedal is smaller than the predetermined lower limit, as described above with respect to the third mode of the invention. Further, where the temperature of the working fluid is lower than the predetermined lower limit, as described above with respect to the fourth mode of the invention, the working fluid has a high degree of viscosity, so that there is a high possibility that the shifting action of the mechanically operated step-variable transmission portion has a relatively long control response time. In any one of the above-described cases, there are the risk of the vehicle operator feeling that the operating speed of the drive power source is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source.

According to the fifth mode of the invention wherein the at least one intermediate overall speed position is selected according to the running state of the vehicle, it is possible to reduce the risk of the vehicle operator feeling the operating speed of the drive power source kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source, so as to assure a good balance between the improvement of the vehicle drivability and the reduction of those risks, according to the running state of the vehicle. For example, the risk of the vehicle operator feeling the operating speed of the drive power source kept at the relatively high value for the excessively long length of time is high where the speed of releasing of the accelerator pedal is relatively high, where the amount of reduction of the operation amount of the accelerator pedal is relatively large, or where the operation amount of the accelerator pedal after its releasing operation is relatively small. Accordingly, the amount, of reduction of the operating speed of the drive power source in the process of the shifting action to the at least one intermediate overall speed position can be adjusted, and the drivability of the vehicle can be improved by the synchronous shifting actions of the vehicular automatic transmission and the mechanically operated step-variable transmission portion, while at the same time the risk of the vehicle operator feeling the operating speed of the drive power source kept at the relatively high value for the excessively long length of time can be adequately reduced according to the state of releasing of the accelerator pedal, where the intermediate overall speed position selecting portion is configured to select the at least one intermediate overall speed position, as described above with respect to the sixth mode of the invention, such that the selected at least one intermediate overall speed position is closer to the target overall speed position when the speed of releasing of the accelerator pedal is relatively high than when the speed of releasing is relatively low, when the amount of reduction of the operation amount of the accelerator pedal is relatively large than when the amount of reduction is relatively small, or when the operation amount of the accelerator pedal after its releasing operation is relatively small than when the operation amount is relatively large. According to the seventh mode of the invention wherein the intermediate overall speed position selecting portion selects the at least one intermediate overall speed position from the overall speed positions assigned to the present gear position. In the running state of the vehicle in which the shifting shock of the mechanically operated step-variable transmission portion is likely to be generated, the vehicular automatic transmission can be suitably shifted in synchronization with the shifting action of the mechanically operated step-variable transmission portion, so that the operating speed of the drive power source is changed so as to adequately reduce the risk of deterioration of the drivability of the vehicle due to a shifting shock of the step-variable transmission portion. That is, the shifting control apparatus according to the seventh mode of the invention is configured to reduce the risk of deterioration of the vehicle drivability due to the shifting shock, with higher priority, rather than to reduce the risk of the vehicle operator feeling uncomfortable with the operating speed of the drive power source kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source. According to the eighth mode of the invention wherein the intermediate overall speed position selecting portion selects the at least one intermediate overall speed position outside the range of the overall speed positions assigned to the present gear position, in the running state of the vehicle in which the vehicle operator is likely to feel that the operating speed of the drive power source is kept at the relatively high value for the excessively long length of time, the operating speed of the drive power source is adequately lowered in the process of the shifting action to the intermediate overall speed position, so that it is possible to adequately reduce the risk of the vehicle operator feeling the operating speed of the drive power source kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source. Namely, the shifting control apparatus according to the eighth mode of the invention is configured to reduce the risk of the vehicle operator feeling the operating speed of the drive power source at the relatively high value for the excessively long length of time, with higher priority, rather than to reduce the risk of deterioration of the drivability of the vehicle due to the shifting shock.

According to the tenth mode of the invention, the multiple-step shifting commanding portion is configured to command the vehicular automatic transmission to be shifted up to the at least one intermediate overall speed position, immediately after the moment of determination to shift up the vehicular automatic transmission to the target overall speed position. Accordingly, when the vehicular automatic transmission is commanded to be shifted up as a result of a releasing operation of the accelerator pedal or an operation of a manually operated member, the vehicular automatic transmission is immediately shifted up to the at least one intermediate overall speed position, and the operating speed of the drive power source is rapidly lowered, so that it is possible to adequately reduce the risk of the vehicle operator feeling the operating speed of the drive power source kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the drive power source.

DETAILED DESCRIPTION OF INVENTION

As the drive power source of the vehicle, an engine such as an internal combustion engine operable to generate a drive force by combustion of a fuel, and an electric motor are preferably used. The electrically controlled continuously variable transmission portion includes a differential mechanism such as a planetary gear device. However, the electrically controlled continuously variable transmission portion may use a twin-rotor electric motor having an inner rotor and an outer rotor. In this case, the drive power source is connected to one of the inner and outer rotors, while the intermediate power transmitting member is connected to the other of the inner and outer rotors. The twin-rotor electric motor can selectively generate a vehicle driving torque or a regenerative torque, like a motor/generator, and can function as a differential motor/generator. The drive power source and the intermediate power transmitting member are connected to the differential mechanism through clutches and speed changing gears, as needed. To the intermediate power transmitting member is connected a vehicle driving motor/generator either directly, or through the speed changing gears, as needed.

As the differential mechanism of the electrically controlled continuously variable transmission portion, a single planetary gear set of a single-pinion type or a double-pinion type is preferably used. This planetary gear set has three rotary elements consisting of a sun gear, a carrier and a ring gear. In this case, the drive power source is connected to an intermediate one of the rotary elements which is intermediate between the other two rotary elements in a collinear chart wherein rotating speeds of the three rotary elements are represented by a single straight line, and the rotary speed of which is intermediate between those of the other two rotary elements. In the planetary gear set of the single-pinion type, the intermediate rotary element is the carrier. In the planetary gear set of the double-pinion type, the intermediate rotary element is the ring gear. The differential motor/generator and the intermediate power transmitting member are connected to the respective other two rotary elements. However, the intermediate power transmitting member may be connected to the intermediate rotary element. The three rotary elements may be always rotatable at different speeds. Alternatively, selected two of the three rotary elements may be connected to each other through a clutch, so that these two rotary elements are rotated as a unit depending upon a running state of the vehicle. Further, one of the three rotary elements which is connected to the differential motor/generator may be held stationary by a brake, so that a differential rotary motion of that rotary element is limited. The differential mechanism may be provided with a plurality of planetary gear sets.

The motor/generator is a rotary type electrically operated device, more specifically, a motor/generator device capable of selectively functioning as an electric motor, an electric generator, or both of an electric motor and an electric generator. It is possible to use an electric generator as the differential motor/generator, and an electric motor as the vehicle driving motor/generator. However, it is preferable to use the motor/generator as the differential motor/generator and the vehicle driving motor/generator, in view of various different running states of the vehicle.

As the mechanically operated step-variable transmission portion, a planetary gear type transmission and a parallel two-axes type transmission are widely used. For example, the mechanically operated step-variable transmission portion is shifted to a selected one of a plurality of gear positions (AT gear positions) with engaging and releasing actions of selected ones of a plurality of hydraulic operated frictional coupling devices. Generally, the plurality of AT gear positions are forward drive gear positions, but may include at least one reverse drive gear position.

The plurality of overall speed positions described above are established by controlling the operating speed of the drive power source according to the output speed of the vehicular automatic transmission, so as to maintain the speed ratios of the respective overall speed positions. However, it is not required to hold the speed ratios of the overall speed positions constant like those of the AT gear positions of the mechanically operated step-variable transmission portion. Namely, the speed ratios of the overall speed positions may be variable within a predetermined range, or may be limited according to upper and lower limits of rotating speeds of various rotary members of the vehicular automatic transmission. The vehicular automatic transmission is preferably configured to be shifted from one of the plurality of overall speed positions to another, according to predetermined overall speed position shifting conditions. The overall speed position shifting conditions are preferably in the form of an overall speed position shifting map having predetermined shift-up boundary lines and shift-down boundary lines representative of parameters of a running state of the vehicle, for example, representative of a relationship between an output speed of the vehicular automatic transmission and an operation amount of an accelerator pedal. However, the vehicular automatic transmission may be shifted according to any other predetermined automatic shifting conditions, or according to a manual operation of a shift lever or a shift-up/shift-down switch by an operator of the vehicle. While the two-step shifting control portion described above controls only a shift-up action of the vehicular automatic transmission, the overall-speed-position shifting control portion and the synchronous shifting control portion control both of the shift-up and shift-down actions, or only the shift-up action. Namely, the vehicular automatic transmission may be shifted up in steps to a selected one of the overall speed positions, and shifted down continuously to the selected overall speed position. The vehicular automatic transmission need not be always shifted in steps to the selected overall speed position, but may be shifted in steps under a predetermined condition, for example, in a sporty drive mode of the vehicle. The two-step shifting control portion is configured to initially implement at least the shift-up action to the intermediate overall speed position, but may be configured to initially implement the shift-down action to the intermediate overall speed position, as well as to initially implement the shift-up action to the intermediate overall speed position.

The number of the plurality of overall speed positions of the vehicular automatic transmission is preferably equal to or larger than that of the AT gear positions of the mechanically operated step-variable transmission portion. For example, at least one overall speed position is assigned to each of the AT gear positions. The mechanically operated step-variable transmission portion is preferably shifted in synchronization with a shifting action of the vehicular automatic transmission to a target overall speed position. In this case, the mechanically operated step-variable transmission portion is shifted with a change of the operating speed of the drive power source, so that the vehicle operator is unlikely to feel uncomfortable, even if a shifting shock is generated in the process of the shifting action of the mechanically operated step-variable transmission portion. The number of the overall speed positions is preferably two or more times (e.g., about two or three times) that of the AT gear positions. The mechanically operated step-variable transmission portion is shifted such that the rotating speed of the intermediate power transmitting member, an operating speed of the vehicle driving motor/generator connected to the intermediate power transmitting member, or a rotating speed of the differential mechanism of the electrically controlled continuously variable transmission portion is held within a predetermined range, and the vehicular automatic transmission is shifted such that the operating speed of the drive power source is held within a predetermined range. The numbers of the AT gear positions and the overall speed positions are suitably determined. In an ordinary type of vehicle, it is preferably that the mechanically operated step-variable transmission portion has one of second through sixth speed AT gear positions, while the vehicular automatic transmission has one of fifth through twelfth overall speed positions.

The determinations to implement the synchronous shifting actions such that the shifting controls to establish the target overall speed position and the target AT gear position overlap each other may be made simultaneously according to a common shifting condition (shifting map). Alternatively; the determination to establish the target overall speed position may be made in the process of the shifting control to establish the target AT gear position. Further, the determinations to establish the target overall speed position and AT gear position may be made with a predetermined time interval between the moments of the determinations. The synchronous shifting control to assure that the two shifting actions to establish the target overall speed position and AT gear position take place in synchronization with each other is implemented by delaying the moment of generation of the command to establish the target overall speed position so that the inertia phases of the two shifting actions (during which the rotating speeds of input rotary members of the vehicular automatic transmission and the mechanically operated step-variable transmission portion change according to changes of their speed ratio) at least partially overlap each other. A length of delay of the moment of generation of the command to establish the target overall speed position, that is, a point of time at which the command is generated can be determined by experimentation or simulation on the basis of a difference between control response times of the two shifting actions after the moment of generation of the command to establish the target AT gear position, for instance. However, the moment of generation of the command to establish the target overall speed position may be determined by detecting the moment of initiation of the inertia phase of the shifting action to the target AT gear position, on the basis of a change of the rotating speed of the intermediate power transmitting member during the shifting action, or by detecting a degree of progress of the shifting action to the target AT gear position, on the basis of a hydraulic pressure applied to the frictional coupling device to establish the target AT gear position, namely, an engaging torque of the frictional coupling device.

As described above, the multiple-step shifting control portion includes (a) the multiple-step shifting determining portion configured to determine, according to the predetermined condition for implementing the multiple-step shifting control, whether the vehicular automatic transmission should be shifted to the intermediate overall speed position, (b) the intermediate overall speed position selecting portion configured to select the intermediate overall speed position, according to the running state of the vehicle, such as an operation amount of an accelerator pedal, and (c) the multiple-step shifting commanding portion configured to command the vehicular automatic transmission to be shifted to the intermediate overall speed position, at the predetermined timing after the moment of determination to shift the vehicular automatic transmission to the target overall speed position. The determination as to whether the condition for implementing the multiple-step shifting control to shift the vehicular automatic transmission eventually to the target overall speed. position through the intermediate overall speed position is made depending upon whether the vehicle operator is likely to feel that an operating speed of the drive power source is kept at a relatively high value for an excessively long length of time, for example. Described more specifically, the vehicle operator is likely to feel the operating speed of the drive power source being kept at the relatively high value for the excessively long length of time, where the speed of releasing of the accelerator pedal is higher than a predetermined upper limit, where the amount of reduction of the operation amount of the accelerator pedal is larger than a predetermined upper limit, where the operation amount after the releasing operation of the accelerator pedal is smaller than a predetermined lower limit, or where the shifting action of the mechanically operated step-variable transmission portion has a relatively long control response time (where a temperature of a working fluid used for the step-variable transmission portion is lower than a predetermined lower limit, for instance). A shift-up action of the mechanically operated step-variable transmission portion to the target AT gear position just after the accelerator pedal has been switched from its ON state to its OFF state is not generally required to have a high degree of control response, so that this shift-up action is controlled to take place for a relatively long length of time, for reducing a shifting shock of the mechanically operated step-variable transmission portion. Where this shift-up action is performed, the vehicle operator is likely to feel that the operating speed of the drive power source is kept at the relatively high value for the excessively long length of time. The intermediate overall speed position selecting portion is configured to select an optimum one of the overall speed positions as the intermediate overall speed position, according to the speed of releasing of the accelerator pedal, the amount of reduction of its operation amount and the operation amount after its releasing operation. However, a range of the intermediate overall speed positions from which the intermediate overall speed position can be selected may be limited to reduce a risk of generation of a shifting shock of the mechanically operated step-variable transmission portion, where the risk of generation of the shifting shock is considered to be high due to a low degree of controllability of the shifting action of the mechanically operated step-variable transmission portion, for example, where the working fluid temperature is not higher than the predetermined lower limit, where a maximum charging or discharging amount of a battery is limited, or where an output of the differential motor/generator is limited. This restriction of selection of the intermediate overall speed position is made according to the present AT gear position. However, the overall speed position which is relatively close to the target overall speed position i.e., higher speed side overall speed position, is desirably selected as the intermediate overall speed position, where the vehicle operator is likely to feel that the operating speed of the drive power source is kept at the relatively high value for the excessively long length of time, for example, where an operating sound of the drive power source is easily audible at a low running speed of the vehicle, where the operating speed of the drive power source is relatively high, or where the operating speed of the drive power source is kept at the relatively high value for a relatively long length of time (where the shifting action of the mechanically operated step-variable transmission portion has a relatively long control response time). The multiple-step shifting commanding portion is preferably configured to command the vehicular automatic transmission to be shifted to the selected intermediate overall speed position, at a timing immediately after the moment of determination to implement the shifting action to the target overall speed position. However, the timing at which the vehicular automatic transmission is commanded to be shifted to the intermediate overall speed position may be suitably determined, as long as the timing is prior to the moment at which the vehicular automatic transmission is commanded to be shifted to the target overall speed position, which moment is a certain length of time after the above-indicated moment of determination to implement the shifting action.

The multiple-step shifting control portion may be configured to implement the shifting action to the target overall speed position through the selected intermediate overall speed position, only where the predetermined condition is satisfied, as described above. However, the multiple-step shifting control portion may be configured to always implement the shift-up action to the target overall speed position through the intermediate overall speed position, where the shift-up action to the target overall speed position is performed together with the shift-up action to the target AT gear position, and where the target overall speed position is other than the speed position next to the present speed position. The intermediate overall speed position is selected according to the running state of the vehicle, such as the operation amount of the accelerator pedal. However, a predetermined one of the overall speed positions may be selected as the intermediate overall speed position. For example, the overall speed position next lower than the target overall speed position, the overall speed position next higher than the present overall speed position, or the overall speed position intermediate in a range of the overall speed positions each available as a candidate of the intermediate overall speed position may be selected as the intermediate overall speed position. The multiple-step shifting control portion may be a two-step shifting control portion configured to command the vehicular automatic transmission to be shifted to the target overall speed position in two steps through only one intermediate overall speed position. However, the multiple-step shifting control portion may be configured to command the vehicular automatic transmission to be shifted up to the target overall speed position in three or more steps through two or more intermediate overall speed positions.

Embodiment

Referring to the drawings, a preferred embodiment of the present invention will be described in detail. Reference is first made toFIG. 1, which is the schematic view showing an arrangement of a drive system12of a vehicle10to be controlled by a control apparatus according to the present invention, and major portions of the control apparatus to perform various controls of the vehicle10. As shown inFIG. 1, the vehicular drive system12is provided with an engine14, an electrically controlled continuously variable transmission portion18connected directly or indirectly via a damper (not shown) or any other device to the engine14, and a mechanically operated step-variable transmission portion20connected to an output rotary member of the continuously variable transmission portion18. The continuously variable transmission portion18and the step-variable transmission portion20are disposed in series with each other within a transmission casing16(hereinafter referred to as “casing16”) functioning as a non-rotatable member fixed to a vehicle body, such that the transmission portions18and20are disposed coaxially with each other on a common axis. The vehicular drive system12is further provided with an output shaft22which is an output rotary member of the mechanically operated step-variable transmission portion20, a differential gear device24connected to the output shaft22, a pair of axles26connected to the differential gear device24, and drive wheels28. In the vehicular drive system12, a drive force (“drive torque” or “drive power” unless otherwise distinguished from the drive force) of the engine14and a second motor/generator MG2(described below) is transmitted to the mechanically operated step-variable transmission portion20, and is transmitted from the step-variable transmission portion20to the drive wheels28through the differential gear device24and other devices. The vehicular drive system12is suitably used in the vehicle10of an FR type (front-engine rear-drive type) in which the axis of the engine14is parallel to the longitudinal direction of the vehicle10. It is noted that the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20are constructed substantially symmetrically with each other about the axis of the engine14(about the above-indicated common axis), and thatFIG. 1does not show the lower halves of the transmission portions18and20.

The engine14is a drive power source to drive the vehicle10, which is a known internal combustion engine such as a gasoline engine or a diesel engine. An engine torque Te, which is an output torque of this engine14, is controlled by an electronic control device80(described below) which controls the operating condition of the engine14as represented by an opening angle of a throttle valve or an intake air quantity, an amount of injection of a fuel and an ignition timing. In the present embodiment, the engine14is connected to the electrically controlled continuously variable transmission portion18, without a fluid-operated type power transmitting device such as a torque converter or a fluid coupling being disposed between the engine14and the continuously variable transmission portion18.

The electrically controlled continuously variable transmission portion18is provided with: a first motor/generator MG1; a differential mechanism32functioning as a power distributing device to mechanically distribute the drive force of the engine14to the first motor/generator MG1, and to an intermediate power transmitting member30which is an output rotary member of the continuously variable transmission portion18; and the above-indicated second motor/generator MG2operatively connected to the intermediate power transmitting member30in a power transmittable manner. The continuously variable transmission portion18is an electrically controlled differential portion wherein a differential state of the differential mechanism32is controllable by controlling an operating state of the first motor/generator MG1as well as an electrically controlled continuously variable transmission. The first motor/generator MG1functions as a differential motor/generator while the second motor/generator MG2is an electric motor which functions as a vehicle driving power source. The vehicle10is a hybrid vehicle provided with the drive power source in the form of the engine14and the second motor/generator MG2.

Each of the first motor/generator MG1and the second motor/generator MG2is an electrically operated rotary device having a function of an electric motor and a function of an electric generator. The first motor/generator MG1and the second motor/generator MG2are connected to a battery52through an inverter50provided on the vehicle10. The inverter50is controlled by the control apparatus in the form of the above-indicated electronic control device80, to control an output torque (regenerative torque) of the first motor/generator MG1, namely, an MG1torque Tg, and an output torque (forward driving torque) of the second motor/generator MG2, namely, an MG2torque Tm. The battery52also provided on the vehicle10is an electric power storage device to and from which an electric power is supplied from and to the first motor/generator MG1and the second motor/generator MG2.

The differential mechanism32is a planetary gear set of a single-pinion type having three rotary elements in the form of a sun gear S0, a carrier CA0and a ring gear R0and performing differential action. The carrier CA0is operatively connected to the engine14through a connecting shaft34in a power transmittable manner, and the sun gear S0is operatively connected to the first motor/generator MG1in a power transmittable manner, while the ring gear R0is operatively connected to the second motor/generator MG2in a power transmittable manner. In the differential mechanism32, the carrier CA0functions as an input rotary element, and the sun gear S0functions as a reaction rotary element, while the ring gear R0functions as an output rotary element.

The mechanically operated step-variable transmission portion20is a step-variable transmission which constitutes a part of a power transmitting path between the intermediate power transmitting member30and the drive wheels28. The intermediate power transmitting member30also functions as an input rotary member (AT input rotary member) of the mechanically operated step-variable transmission portion20. The mechanically operated step-variable transmission portion20is considered to be a step-variable transmission constituting a part of a power transmitting path between the second motor/generator MG2and the drive wheels28, since the second motor/generator MG2is connected to the intermediate power transmitting member30such that the intermediate power transmitting member30is rotated together with the second motor/generator MG2. The mechanically operated step-variable transmission portion20is a known automatic transmission of a planetary gear type which is provided with a plurality of planetary gear sets in the form of a first planetary gear set36and a second planetary gear set38, and a plurality of coupling devices in the form of a clutch C1, a clutch C2, a brake B1and a brake B2(hereinafter referred to as “coupling devices CB” unless otherwise specified).

Each of the coupling devices CB is a hydraulically operated frictional coupling device in the form of a multiple-disc type or a single-disc type clutch or brake that is operatively pressed by a hydraulic actuator, or a band brake that is operatively tightened by a hydraulic actuator. The coupling devices CB are selectively placed in engaged, slipping or released states with their torque capacities (engaging torque values) Tcb being changed according to engaging hydraulic pressures Pcb applied thereto, which are regulated by respective linear solenoid-operated valves SL1-SL4(shown inFIG. 4) incorporated within a hydraulic control unit54.

In the mechanically operated step-variable transmission portion20, selected ones of rotary elements (sun gears S1and S2, carriers CA1and CA2, and ring gears R1and R2) of the first and second planetary gear sets36and38are connected to each other or to the intermediate power transmitting member30, casing16or output shaft22, either directly or indirectly (selectively) through the coupling devices CB or a one-way clutch F1.

The mechanically operated step-variable transmission portion20is shifted to a selected one of four AT gear positions by engaging actions of selected ones of the coupling devices CB. These four AT gear positions have respective different speed ratios γat (=AT input speed ωi/AT output speed ωo). The AT input speed ωi is a rotating speed (angular velocity) of the input rotary member of the mechanically operated step-variable transmission portion20, that is, a rotating speed of the intermediate power transmitting member30, which is equal to MG2speed ωm which is an operating speed of the second motor/generator MG2. Thus, the AT input speed ωi can be represented by the MG2speed ωm. The AT output speed ωo is a rotating speed of the output shaft22of the mechanically operated step-variable transmission portion20, which is considered to be an output speed of a vehicular automatic transmission40which consists of the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20.

As shown in the table ofFIG. 2, the mechanically operated step-variable transmission portion20has the four forward drive AT gear positions consisting of the first (1st) through fourth (4th) speed AT gear positions. The first speed AT gear position has a highest speed ratio γat, while the fourth speed AT gear position a lowest speed ratio γat. The speed ratios γat of the first through fourth speed AT gear positions decrease in the direction from the first speed AT gear position (lowest-speed gear position) toward the fourth speed AT gear position (highest-speed gear position). The table ofFIG. 2indicates the relationship between the first through fourth speed AT gear positions and combinations of the coupling devices CB placed in the engaged states to establish the respective AT gear positions. In the table, “O” indicates the engaged state of the coupling devices CB, “Δ” indicates the engaged state of the coupling device B2during application of an engine brake to the vehicle10or during a shifting action of the mechanically operated step-variable transmission portion20while the vehicle10is in a coasting run, while the blank indicates the released state of the coupling devices CB. The one-way clutch F1indicated above is disposed in parallel to the brake B2which is placed in the engaged state to establish the first speed AT gear position “1st”, so that the brake B2is not required to be placed in the engaged state upon starting or acceleration of the vehicle10. It is noted that the mechanically operated step-variable transmission portion20is placed in a neutral position (a power transmission cutoff state).

The step-variable transmission portion20is shifted up or down to establish a newly selected one of the four AT gear positions, according to an operation amount θacc of an accelerator pedal by a driver (operator) of the vehicle10and a vehicle running speed V, with a releasing action of one of the coupling devices CB and a concurrent engaging action of another coupling device CB, which concurrent releasing and engaging actions are controlled by the above-indicated electronic control device80. Thus, the mechanically operated step-variable transmission portion20is shifted up or down from one of the AT gear positions to another by a. so-called “clutch-to-clutch” shifting operation, namely, concurrent releasing and engaging actions of the selected two coupling devices CB (releasing-side and engaging-side coupling devices CB). For instance, the step-variable transmission portion20is shifted down from the third speed AT gear position “3rd” to the second speed AT gear position “2nd”, with the releasing action of the clutch C2(releasing-side coupling device CB) and the concurrent engaging action of the brake B1(engaging-side coupling device CB), while the clutch C1remains in the engaged state, as indicated in the table ofFIG. 2. In this instance, releasing hydraulic pressure applied to the clutch C2(releasing-side coupling device CB) and engaging hydraulic pressure applied to the brake B1(engaging-side coupling device CB) are transiently controlled according to predetermined patterns of change, to bring these clutch C2and brake B1into the released and engaged states, respectively.

FIG. 4is the circuit diagram of the hydraulic control unit54incorporating the linear solenoid-operated valves SL1-SL4for controlling the engaging and releasing actions of the coupling devices CR The hydraulic control unit54includes a mechanically operated oil pump100operated by the engine14, and an electrically operated oil pump104operated by a pump driving electric motor102, which are provided as a hydraulic pressure source for the coupling devices CR The electrically operated oil pump104is operated while the engine14is at rest. A pressurized working fluid delivered from those oil pumps100and104is fed to a line pressure passage110through respective check valves106and108, and a pressure of the working fluid in the line pressure passage110is regulated to a predetermined line pressure PL by a line pressure control valve112, which is a primary regulator valve, for example. A linear solenoid-operated valve SLT, which is connected to the line pressure control valve112, is electrically controlled by the electronic control device80, to convert a substantially constant modulator pressure Pmo into a pilot pressure Pslt. This pilot pressure Pslt is applied to the line pressure control valve112, so that a spool114of the line pressure control valve112is biased by the pilot pressure Pslt, and is axially moved, whereby a cross-sectional surface area of opening of a port communicating with a drain passage116is changed, so that the line pressure PL is regulated according to the pilot pressure Pslt. This line pressure PL is regulated according to a required vehicle drive force or torque as represented by the accelerator pedal operation amount θacc. The linear solenoid-operated valve SLT indicated above is an electromagnetic pressure regulating valve to be used for regulating the line pressure, and the line pressure control valve112is a hydraulic pressure control valve to regulate the line pressure PL according to the pilot pressure Pslt received from the linear solenoid-operated valve SLT. A line pressure regulating device118is constituted primarily by the line pressure control valve112and the linear solenoid-operated valve SLT.

The pressurized working fluid having the line pressure PL regulated by the line pressure regulating device118is supplied to the linear solenoid-operated valves SL1-SL4, etc. through the line pressure passage110. The linear solenoid-operated valves SL1-SL4are held in communication with respective hydraulic actuators (hydraulic cylinders)120,122,124and126of the respective clutches and brakes C1, C2, B1and B2, and output pressures (engaging hydraulic pressures Pcb) of the linear solenoid-operated valves SL1-SL4are controlled according to hydraulic control command signals Sat generated from the electronic control device80, so that the clutches and brakes C1, C2, B1and B2are individually placed in their engaged or released state, to selectively establish one of the first through fourth speed AT gear positions of the mechanically operated step-variable transmission portion20. The linear solenoid-operated valves SL1-SL4are solenoid-operated valves provided to selectively place the clutches and brakes C1, C2, B1and B2in their engaged states according to the hydraulic control command signals Sat received from the electronic control device80.

The collinear chart ofFIG. 3indicates a relationship among rotating speeds of the rotary elements of the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20. In this collinear chart, three vertical lines Y1, Y2and Y3corresponding to the respective three rotary elements of the differential mechanism32of the continuously variable transmission portion18respectively represent a “g” axis representing the rotating speed (MG1speed ωg) of the second rotary element RE2in the form of the sun gear S0, an “e” axis representing the rotating speed. (engine speed ωe) of the first rotary element RE1in the form of the carrier CA0, and an “m” axis representing the rotating speed (MG2speed ωm, and AT input speed ωi) of the third rotary element RE3in the form of the ring gear R0. Further, four vertical lines Y4, Y5, Y6and Y7corresponding to the respective four rotary elements of the step-variable transmission portion20respectively represent an axis representing the rotating speed of the fourth rotary element RE4in the form of the sun gear S2, an axis representing the rotating speed (output speed ωo) of the fifth rotary element RE5in the form of the ring gear R1and the carrier CA2fixed to each other, namely, the rotating speed of the output shaft22, an axis representing the rotating speed of the sixth rotary element. RE6in the form of the carrier CA1and the ring gear R2fixed to each other, and an axis representing the rotating speed of the seventh rotary element RE7in the form of the sun gear S1. The distances between the adjacent ones of the vertical lines Y1, Y2and Y3are determined by a gear ratio ρ0of the differential mechanism32, while the distances between the adjacent ones of the vertical lines Y4-Y7are determined by gear ratios ρ1and ρ2of the respective first and second planetary gear sets36and38.

Referring to the collinear chart ofFIG. 3, the differential mechanism32of the electrically controlled continuously variable transmission portion18is arranged such that the engine14(represented as “ENG” in the collinear chart) is connected to the first rotary element RE1, and the first motor/generator MG1(represented as “MG1” in the collinear chart) is connected to the second rotary element RE2, while the second motor/generator MG2(represented as “MG2” in the collinear chart) is connected to the third rotary element RE3which is rotated together with the intermediate power transmitting member30. Thus, a rotary motion of the engine14is transmitted to the step-variable transmission portion20through the intermediate power transmitting member30. In a part of the collinear chart corresponding to the electrically controlled continuously variable transmission portion18, straight lines L0and L0R intersecting the vertical line Y2represent relationships among the rotating speeds of the sun gear S0, carrier CA0and ring gear R0.

The mechanically operated step-variable transmission portion20is arranged such that the fourth rotary element RE4is selectively connected to the intermediate power transmitting member30through the clutch C1, the fifth rotary element RE5is connected to the output shaft22, the sixth rotary element RE6is selectively connected to the intermediate power transmitting member30through the clutch C2and is selectively connected to the casing16through the brake B2, and the seventh rotary element RE7is selectively connected to the casing16through the brake B1. In a part of the collinear chart corresponding to the mechanically operated step-variable transmission portion20, straight lines L1, L2, L3, L4and LR intersecting the vertical line Y5represent relationships among the rotating speeds of the rotary elements RE4-RE7in the respective first, second, third, and fourth speed AT gear positions “1st”, “2nd”, “3rd” and “4th” and a reverse drive AT gear position “Rev”, that are selectively established by controlling the engaging and releasing actions of the coupling devices CB. The reverse drive AT gear position “Rev” is established in the engaged states of the clutch C1and the brake B2, like the first speed AT gear position “1st”, while the input rotary element in the form of the fourth rotary element RE4is rotated in the reverse direction.

Solid straight lines L0, L1, L2, L3and L4in the collinear chart ofFIG. 3indicate the relative rotating speeds of the rotary elements in a hybrid drive mode in which the vehicle10is driven in the forward direction with at least the engine14being operated as a drive power source. In the differential mechanism32during this hybrid drive mode, when a torque Te of the engine14(engine torque Te) is applied to the carrier CA0while a reaction torque Tg which is a negative torque (regenerative torque) generated by the first motor/generator MG1operated in the positive direction is applied to the sun gear S0, a directly transmitted engine torque Td (=Te/(1+ρ0)=−(1/ρ0)*Tg) which is a positive torque is applied to the ring gear R0and rotating the ring gear R0in the positive direction. The vehicle10is driven in the forward direction with a vehicle drive torque which is a sum of the directly transmitted engine torque Td and the MG2torque Tm and which is transmitted to the drive wheels28through the mechanically operated step-variable transmission portion20selectively placed in one of the first through fourth speed AT gear positions according to required vehicle drive force as represented by the accelerator pedal operation amount θacc. At this time, the first motor/generator MG1functions as an electric generator operated. In the positive direction and generating a negative torque. An electric power Wg generated by the first motor/generator MG1is stored in the battery52or consumed by the second motor/generator MG2. The second motor/generator MG2is operated to generate the MG2torque Tm, with all or a part of the electric power Wg generated by the first motor/generator MG1, or a sum of the generated electric power Wg and the electric power supplied from the battery52.

In the differential mechanism32during a motor drive mode in which the vehicle10is driven with a drive force generated by the second motor/generator MG2operated as a drive power source while the engine14is held at rest, the carrier CA0is held stationary while the MG2torque Tm which is a positive torque is applied to the ring gear R0and rotating the ring gear R0in the positive direction. The state of the differential mechanism in this motor drive mode is not shown in the collinear chart ofFIG. 3. At this time, the first motor/generator MG1connected to the sun gear S0is placed in a non-load state and freely operated in the negative direction. Namely, in the motor drive mode, the engine14is held in a non-operated state, so that an operating speed ωe of the engine14(engine speed ωe) is kept zero, and the vehicle10is driven in the forward direction with the MG2torque Tm (positive forward driving torque), which is transmitted as a forward drive torque to the drive wheels28through the mechanically operated step-variable transmission portion20placed in one of the first speed AT gear position “1st” through the fourth speed AT gear position “4th”.

Broken straight lines L0R and LR in the collinear chart ofFIG. 3indicate the relative rotating speeds of the rotary elements in a motor drive mode in which the vehicle10is driven in the rearward direction. During driving of the vehicle10in the rearward direction in this motor drive mode, the MG2torque Tm which is a negative torque generated by the second motor/generator MG2operated in the negative direction is applied to the ring gear R0, and is transmitted to the drive wheels28as a drive torque to drive the vehicle10in the rearward direction, through the mechanically operated step-variable transmission portion20placed in the first speed AT gear position. The electronic control device80controls the second motor/generator MG2to permit the vehicle10to be driven in the rearward direction with the reverse driving MG2torque Tm (MG2torque TmR; negative vehicle driving torque) acting in the direction opposite to the direction of acting of the forward driving MG2torque Tm (MG2torque TmF; positive vehicle driving torque), while the mechanically operated step-variable transmission portion20is placed in the forward-drive low-speed gear position (e.g., first speed AT gear position) of the plurality of the AT gear positions (first through fourth speed AT gear positions). Thus, the vehicle10is driven in the rearward direction with the reverse (negative) MG2torque Tm while the mechanically operated step-variable transmission portion20is placed in one of the forward drive AT gear positions. The mechanically operated step-variable transmission portion20does not have an exclusive reverse drive AT gear position in which the direction of the output rotary motion is reversed with respect to that of the input rotary motion. In the hybrid drive mode, too, the second motor/generator MG2can be operated in the negative direction as indicated by the straight line L0R, while the engine14is held operated in the positive direction, so that the vehicle10can be driven in the rearward direction in the hybrid drive mode, as well as in the motor drive mode.

In the vehicular drive system12, the continuously variable transmission portion18functions as an electrically controlled shifting mechanism (electrically controlled differential mechanism) provided with the differential mechanism32the differential state of which is controlled by controlling the operating state of the first motor/generator MG1, and which has the three rotary elements, that is, the first rotary element RE1in the form of the carrier CA0to which the engine14is operatively connected in a power transmittable manner, the second rotary element RE2in the form of the sun gear S0to which the first motor/generator MG1is operatively connected in a power transmittable manner, and the third rotary element RE3in the form of the ring gear R0to which the second motor/generator MG2is operatively connected in a power transmittable manner. Namely, the electrically controlled continuously variable transmission portion18has the differential mechanism32to which the engine14is operatively connected in a power transmittable manner, and the first motor/generator MG1to which the differential mechanism32is operatively connected in a power transmittable manner, and the operating state of which is controlled to control the differential state of the differential mechanism32. The electrically controlled continuously variable transmission portion18is operated as an electrically controlled continuously variable transmission a speed ratio γ0(=ωe/ωm) of which is continuously variable. The speed ratio γ0is a ratio of a rotating speed of the connecting shaft34(namely, engine speed ωe) to the rotating speed of the intermediate power transmitting member30(namely, MG2speed ωm).

In the hybrid drive mode, for instance, the rotating speed of the sun gear S0is raised or lowered by controlling an operating speed of the first motor/generator MG1while the rotating speed of the ring gear R0is determined by the rotating speed of the drive wheels28with the mechanically operated step-variable transmission portion20placed in a selected one of the AT gear positions, so that the rotating speed of the carrier CA0(namely, engine speed ωe) is accordingly raised or lowered. During running of the vehicle10with an operation of the engine14as the drive power source, therefore, the engine14can be operated at an efficient operating point. That is, the mechanically operated step-variable transmission portion20to be placed in a selected one of the AT gear positions and the electrically controlled continuously variable transmission portion18functioning as a continuously variable transmission cooperate to provide the vehicular automatic transmission40which functions as a continuously variable transmission as a whole.

Alternatively, the electrically controlled continuously variable transmission portion18can be shifted like a step-variable transmission. Accordingly, the vehicular automatic transmission40constituted by the mechanically operated step-variable transmission portion20to be placed in one of the AT gear positions and the electrically controlled continuously variable transmission portion18which can be shifted like the step-variable transmission can be shifted like a step-variable transmission as a whole. That is, in the vehicular automatic transmission40, the mechanically operated step-variable transmission portion20and the electrically controlled continuously variable transmission portion18can be controlled to selectively establish a plurality of speed positions (hereinafter referred to as “overall speed positions” although it may be also referred to as “conceptual speed positions”) having respective different values of a speed ratio γt (=ωe/ωo) which is a ratio of the engine speed ωe to the output speed ωo. The speed ratio γt is an overall speed ratio of the vehicular automatic transmission40consisting of the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20which are disposed in series with each other. The overall speed ratio γt is equal to a product of the speed ratio γ0of the continuously variable transmission portion18and the speed ratio γat of the step-variable transmission portion20, namely, γt=γ0*γat.

The plurality of overall speed positions can be established by controlling the first motor/generator MG1so as to change the engine speed ωe according to the output speed ωo so as to maintain the respective values of the speed ratio γt of the respective overall speed positions, as indicated inFIG. 5by way of example. The speed ratio γt of each of the overall speed positions need not be constant over the entire range of the running state of the vehicle10represented by the engine speed ωe and the output speed ωo. That is, the relationship between the engine speed ωe and the output speed ωo for each of the overall speed positions need not be represented by a straight line passing a zero point0in the coordinate system ofFIG. 5, and the speed ratio values γt of the overall speed positions may be set to vary in predetermined areas of the entire range of the running state, or limited by upper and lower limits of the rotating speeds of the rotary elements of the vehicular automatic transmission40,FIG. 5illustrates an example of the relationship between the engine speed ωe and the output speed ωo for the first through tenth overall speed positions. As is apparent fromFIG. 5, the overall speed positions can be established by controlling the engine speed we according to the output speed ωo, irrespective of the presently established AT gear position of the mechanically operated step-variable transmission portion20.

At least one overall speed position is provided for each of the four AT gear positions of the mechanically operated step-variable transmission portion20, with a combination of each AT gear position with at least one of the different speed ratio values γ0of the electrically controlled continuously variable transmission portion18.FIG. 6is the table indicating an example of the overall speed positions of the vehicular automatic transmission40, wherein the first through third overall speed positions are established for the first speed AT gear position, the fourth through sixth overall speed positions are established for the second speed AT gear position, the seventh through ninth overall speed positions are established for the third speed AT gear position, and the tenth overall speed position is established for the fourth speed AT gear position.FIG. 7is the view indicating an example in which the fourth through sixth overall speed positions of the vehicular automatic transmission40are established in the second speed AT gear position of the mechanically operated step-variable transmission portion20, on a collinear chart similar to that ofFIG. 3. In the vehicular automatic transmission40, the electrically controlled continuously variable transmission portion18is controlled to control the engine speed ωe with respect to the output speed ωo for establishing the predetermined overall speed ratio values γt, to thereby establish the fourth through sixth overall speed positions for the second speed AT gear position.

Referring back toFIG. 1, the vehicle10is provided with the control apparatus in the form of the electronic control device80configured to control various devices of the vehicle10such as the engine14, the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20.FIG. 1is the view showing input and output signals of the electronic control device80, and is a functional block diagram showing major control functions and control portions of the electronic control device80. For example, the electronic control device80includes a so-called microcomputer incorporating a CPU, a ROM, a RAM and an input-output interface. The CPU performs control operations of the vehicle10, by processing various input signals, according to control programs stored in the ROM, while utilizing a temporary data storage function of the RAM. The electronic control device80is a shifting control apparatus according to the present invention, and may be constituted by separate control units such as an engine control unit and a hybrid control unit.

The electronic control device80receives various input signals from various sensors provided on the vehicle10, such as: an output signal of an engine speed sensor60indicative of the engine speed ωe; an output signal of an MG1speed sensor62indicative of the MG1speed ωg which is the operating speed of the first motor/generator MG1; an output signal of an MG2speed sensor64indicative of the MG2speed ωm which is the AT input speed ωi; an output signal of an output speed sensor66indicative of the output speed ωo corresponding to the vehicle running speed V; an output signal of an accelerator pedal operation amount sensor68indicative of the operation amount θacc of a vehicle accelerating member in the form of the accelerator pedal, which operation amount θacc represents a degree of acceleration of the vehicle10required by the vehicle operator; an output signal of a throttle valve opening angle sensor70indicative of an angle θth of opening of an electronic throttle valve; an output signal of an oil temperature sensor72indicative of a temperature toil of a working fluid used for the hydraulic control unit54; an output signal of a shift position sensor74indicative of a presently selected one of operating positions POSsh of a manually operated shifting member in the form of a shift lever56provided on the vehicle10; and an output signal of a battery sensor76indicative of a temperature THbat, a charging/discharging electric current Ibat and a voltage Vbat of the battery52. Further, the electronic control device80generates various output signals to the various devices provided on the vehicle10, such as: an engine control command signal Se to be applied to an engine control device58provided to control a throttle actuator, a fuel injecting device and an ignition device, for controlling the engine14; motor/generator control command signals Smg to be applied to the inverter50, for controlling the first motor/generator MG1and the second motor/generator MG2; and hydraulic control command signals Sat to be applied to the hydraulic control unit54, for controlling the pump driving electric motor102and the operating states of the coupling devices CB (namely, for controlling the shifting actions of the mechanically operated step-variable transmission portion20). The hydraulic control command signals Sat are command signals (drive currents) to be applied to the hydraulic control unit54for controlling amounts of electric currents to be applied to the linear solenoid-operated valves SL1-SL4which regulate the engaging hydraulic pressure Pcb to be applied to each of the hydraulic actuators120,122,124and126of the coupling devices CB.

The presently selected operating position POSsh of the shift lever56is one of: a parking position P; a reverse drive position R; a neutral position N; a forward drive position D; and a sequential mode position S, for example. The parking position P is a position in which the mechanically operated step-variable transmission portion20is placed in a neutral state, namely, in a non-power transmittable state with all of the coupling devices CB placed in their released state, and in which the output shaft22is mechanically locked to prevent its rotary motion, for thereby holding the vehicular automatic transmission40in a parking brake position. The reverse drive position R is a position in which the vehicular automatic transmission40is placed in a rear drive state in which the vehicle10can be driven in the rearward direction with the MG2torque TmR while the step-variable transmission portion20is placed in the first speed AT gear position. The neutral position N is a position in which the vehicular automatic transmission40is placed in a neutral state. The forward drive position D is a position in which the vehicular automatic transmission40is placed in a forward drive state in which the vehicle10can be driven in the forward direction according to an automatic shifting control of the vehicular automatic transmission40to selectively establish one of all of the first through tenth overall speed positions, together with a shifting action from one of the first through fourth speed AT gear positions to another, as needed, or according to a continuously variable shifting control of the electrically controlled continuously variable transmission portion18. The sequential mode position S is a position located adjacent to the forward drive position. D. When the shift lever50is operated from the forward drive position D to the sequential mode position S, a selected one of all of the first through tenth overall speed positions can be established together with a shifting action from one of the first through fourth speed AT gear positions of the step-variable transmission portion20to another, as needed, according to a manual operation of a shift-up/shift-down switch or a manual lever. The shift lever56is a manually operable shift position switching member to selectively establish one of a plurality of shift positions. In the present embodiment, the shift lever56also functions as a sequential mode selector switch for establishing the sequential mode position S.

The electronic control device80is configured to calculate a charging state (stored electric power amount) SOC of the battery52on the basis of the charging/discharging electric current Ibat and the voltage Vbat of the battery52. The electronic control device80is further configured to calculate, on the basis of, for example, the temperature THbat and the charging state i.e., stored electric power amount SOC of the battery52, a maximum charging amount Win of electric power that can be stored in the battery52, and a maximum discharging amount Wout of electric power that can be discharged from the battery52. The calculated maximum charging and discharging amounts Win and Wout decrease with a decrease of the battery temperature THbat when the battery temperature THbat is lower than a normal level, and decrease with an increase of the battery temperature THbat when the battery temperature THbat is higher than the normal level. Further, the maximum charging amount Win decreases with an increase of the stored electric power amount SOC when the stored. electric power amount SOC is relatively large. The maximum discharging amount Wout decreases with a decrease of the stored electric power amount SOC when the stored electric energy amount SOC is relatively small.

The electronic control device80includes a hybrid control portion82, a continuously variable shifting control portion84, a step-variable shifting control portion86, and an overall-speed-position shifting control portion88, for implementing various controls of the vehicular drive system12.

The hybrid control portion82has a function of an engine control portion to control the engine14, and a function of a motor/generator control portion to control the first motor/generator MG1and the second motor/generator MG2through the inverter50. Thus, the hybrid control portion82performs hybrid drive controls for controlling the engine14, first motor/generator MG1and second motor/generator MG2. For example, the hybrid control portion82is configured to calculate a required vehicle drive power Pdem on the basis of the accelerator pedal operation amount θacc and the vehicle running speed V, in other words, to calculate a required drive torque Tdem at the present vehicle running speed V. The hybrid control portion82generates the engine control command signal Se to control the engine14, and the motor/generator control command signals Smg to control the first motor/generator MG1and the second motor/generator MG2, for establishing the required vehicle drive power Pdem, while taking account of the maximum charging and discharging amounts Win and Wout of electric power of the battery52. For example, the engine control command signal Se represents a command value of an engine power Pe of the engine14outputting the torque Te at its present operating speed ωe. For example, the motor/generator control command signals Smg represent a command value of an electric power amount Wg to be generated by the first motor/generator MG1to generate the reaction torque acting against the engine torque Te, namely, the MG1torque Tg at the present MG1speed ωg, and an electric power amount Wm to be consumed by the second motor/generator MG2to generate the MG2torque Tm at the present MG2speed ωm.

The hybrid control portion82is configured to selectively establish the motor drive mode or the hybrid drive mode according to the running state of the vehicle10. For instance, the hybrid control portion82establishes the motor drive mode where the required vehicle drive power Pdem is smaller than a predetermined threshold value, that is, falls in a motor drive area in which the vehicle running speed V is relatively low while the vehicle drive torque is relatively small. In the motor drive mode, the vehicle10is driven with only the drive force of the second motor/generator MG2, while the engine14is held at rest. Alternatively, the hybrid control portion82establishes the hybrid drive mode where the required vehicle drive power Pdem is equal to or higher than the predetermined threshold value, that is, falls in a hybrid drive area. In the hybrid drive mode, the vehicle10is driven with an operation of the engine14, while the second motor/generator MG2is operated with an electric energy generated by a regenerative control of the first motor/generator MG1, and/or an electric energy supplied from the battery52, to generate a vehicle driving torque for driving the drive wheels28, whereby an engine assisting drive torque is generated, as needed, to assist the engine14. Further, the hybrid control portion82establishes the hybrid drive mode even where the required vehicle drive power Pdem falls within the motor drive area, if the stored electric power amount SOC or the maximum discharging amount Wout is smaller than a predetermined threshold value. When the vehicle drive mode is switched from the motor drive mode to the hybrid drive mode, the engine14can be started by cranking with the first motor/generator MG1to raise its operating speed ωe, irrespective of whether the vehicle10is running or held stationary.

The continuously variable shifting control portion84is configured to operate the vehicular automatic transmission40as a whole as a continuously variable transmission by controlling the electrically controlled continuously variable transmission portion18to perform as a continuously variable transmission. Described in detail, the speed ratio γ0of the electrically controlled continuously variable transmission portion18is varied by continuously shifting control of the continuously variable transmission portion18which is executed by controlling, for example, the output of the engine14and the electric power Wg generated by the first motor/generator MG1while taking account of a highest fuel economy line of the engine14such that the engine speed ωe and the engine torque Te are controlled to obtain the engine power Pe for establishing the required vehicle drive power Pdem. As a result of this control, the overall speed ratio γt of the vehicular automatic transmission40operated as the continuously variable transmission is controlled.

The step-variable shifting control portion86is configured to determine a shifting action of the mechanically operated step-variable transmission portion20according to a memory-stored AT gear position shifting map obtained by experimentation or theoretical analysis, and to apply the hydraulic control command signals Sat to the hydraulic control unit54, for commanding the solenoid-operated valves SL1-SL4to bring the appropriate ones of the coupling devices CB into the released and engaged states, for automatically shifting up or down the mechanically operated step-variable transmission portion20. The AT gear position shifting map represents conditions of shifting of the step-variable transmission portion20, and is defined by shifting lines indicated with a symbol “AT” inFIG. 8, by way of example. InFIG. 8, solid lines are shift-up boundary lines while broken lines are shift-down boundary lines. Suitable amounts of hysteresis are provided between the corresponding shift-up and shift-down boundary lines. For example, the AT gear position shifting map represents a predetermined relationship between the output speed ωo (equivalent to the vehicle running speed V) and the accelerator pedal operation amount θacc (equivalent to the required drive torque Tdem or the throttle valve opening angle θth), which relationship is defined in a two-dimensional coordinate system. The AT gear position shifting map is formulated such that the mechanically operated step-variable transmission portion20is shifted up to reduce its speed ratio γat as the output speed ωo is raised, and is shifted down to increase its speed ratio γat as the accelerator pedal operation amount θacc is increased. The step-variable shifting control portion86is further configured to shift the mechanically operated step-variable transmission portion20according to the table ofFIG. 6, when the shifting command between different overall speed positions is made based on the driver's operation. For example, the step-variable shifting control portion86commands the step-variable transmission portion20to be shifted up or down between the first and second speed AT gear positions to shift up or down the vehicular automatic transmission40between the third and fourth overall speed positions, or between the second and third speed AT gear positions to shift up or down the vehicular automatic transmission40between the sixth and seventh overall speed positions, or between the third and fourth speed AT gear positions to shift up or down the vehicular automatic transmission40between the ninth and tenth overall speed positions.

The overall-speed-position shifting control, portion88is configured to command the electrically controlled continuously variable transmission portion18to be shifted like a step-variable transmission, for shifting the vehicular automatic transmission40as a whole like a step-variable transmission. The overall-speed-position shifting control portion88determines a shifting action of the vehicular automatic transmission40according to a predetermined overall speed position shifting map, and cooperates with the step-variable shifting control portion86(configured to control the shifting actions of the mechanically operated step-variable transmission portion20), to implement a shifting control of the electrically controlled continuously variable transmission portion18so as to selectively establish one of the plurality of overall speed positions. Like the AT gear position shifting map, the overall speed position shifting map represents a predetermined relationship between the output speed ωo and the accelerator pedal operation amount θacc.FIG. 8shows an example of the overall speed position shifting map. Solid lines are shift-up boundary lines while broken lines are shift-down boundary lines. The vehicular automatic transmission40in which the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20are disposed in series with each other is shifted as a whole like a step-variable transmission, when the vehicular automatic transmission40is shifted from one of the overall speed positions to another according to the overall speed position shifting map. An overall-speed-position shifting control to shift the vehicular automatic transmission40as a whole like the step-variable transmission may be implemented with higher priority to a continuously variable shifting control for shifting the vehicular automatic transmission40as a whole like a continuously variable transmission, only where a sporty drive mode or any other drive mode for driving the vehicle10with a high degree of drivability is selected by the vehicle operator or where the required drive torque Tdem is comparatively high, for instance. However, the overall-speed-position shifting control may be basically implemented except under a predetermined condition in which this overall-speed-position shifting control should be inhibited. The overall-speed-position shifting control portion88is further configured to also implement the overall-speed-position shifting control according to a manual operation of the shift-up/shift-down switch by the vehicle operator, for example.

The overall-speed-position shifting control by the overall-speed-position shifting control portion88and the shifting control of the mechanically operated step-variable transmission portion20by the step-variable shifting control portion86are implemented in cooperation with each other. In the present embodiment, a total of ten overall speed positions, namely, the overall firth through tenth speed positions are assigned to a total of four AT gear positions, namely, the first through fourth speed AT gear positions. According to this assignment, the shifting action (AT1↔2) between the first and second speed AT gear positions is performed when the shifting action (OVERALL3↔4) between the overall third and fourth speed positions is performed, and the shifting action (AT2↔3) between the second and third speed AT gear positions is performed when the shifting action (OVERALL6↔7) between the overall sixth and seventh speed positions is performed. Further, the shifting action (AT3↔4) between the third and fourth speed AT gear positions is performed when the shifting action (OVERALL9↔10) between the overall ninth and tenth speed positions is performed. In this respect, reference is made toFIGS. 6 and 8. The AT gear position shifting map is formulated such that the shifting action between the AT gear positions takes place in synchronization with the corresponding shifting action between the overall speed positions. Described more specifically by reference toFIG. 8, the shift-up boundary lines for the shifting action (OVERALL3→4) from the overall third speed position to the overall fourth speed position, the shifting action (OVERALL6→7) from the overall sixth speed position to the overall seventh speed position and the shifting action (OVERALL9→10) from the overall ninth speed position to the overall tenth speed position are coincident with the respective shift-up boundary lines for the shifting action (AT1→2) from the first speed AT gear position to the second speed AT gear position, the shifting action (AT2→3) from the second speed AT gear position to the third speed AT gear position and the shifting action (AT3→4) from the third speed AT gear position to the fourth speed AT gear position. Similarly, the shift-down boundary lines for the shifting action (OVERALL3←4) from the overall fourth speed position to the overall third speed position, the shifting action (OVERALL6←7) from the overall seventh speed position to the overall sixth speed position and the shifting action (OVERALL9←10) from the overall tenth speed position to the overall ninth speed position are coincident with the respective shift-down boundary lines for the shifting action (AT1←2) from the second speed AT gear position to the first speed AT gear position, the shifting action (AT2←3) from the third speed AT gear position to the second speed AT gear position and the shifting action (AT3←4) from the fourth speed AT gear position to the third speed AT gear position. The step-variable shifting control portion86may be commanded to control the mechanically operated step-variable transmission portion20on the basis of a determination made according to the overall speed position shifting map to shift the vehicular automatic transmission40to the selected overall speed position. Thus, the step-variable shifting control portion86controls the shifting action of the step-variable transmission portion20between the AT gear positions when the corresponding shifting action of the vehicular automatic transmission40between the overall speed positions is performed. Since the shifting action between the AT gear positions is performed in synchronization with the corresponding shifting action between the overall speed positions, the step-variable transmission portion20is shifted with a change of the engine speed ωe, so that the vehicle operator is less likely to be given a discomfort due to a shifting shock of the step-variable transmission portion20, which may be generated in the process of its shifting action.

The overall-speed-position shifting control portion88includes a multiple-step shifting control portion in the form of a two-step shifting control portion90, and a synchronous shifting control portion98, for implementing synchronous shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20to respective newly selected (target) ones of the overall speed positions and the AT gear positions. The synchronous shifting control portion98is provided to implement a synchronous control of shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20to the respective target overall speed position and AT gear position in synchronization with each other, irrespective of different control response times of the two shifting actions. In the present embodiment, the synchronous shifting control portion98generates a shifting command to establish the newly selected overall speed position, that is, a command to change the torque of the first motor/generator MG1for changing the engine speed ωe, after a moment of initiation of an inertia phase of the shifting action to establish the newly selected AT gear position, namely, after a moment of detection of a change of the AT input speed ωi (MG2speed ωm) which is the rotating speed of the intermediate power transmitting member30. This control of the shifting action to establish the newly selected overall speed position by the synchronous shifting control portion98is implemented for both of the shift-up and shift-down actions.

FIGS. 12 and 13are the time charts showing examples of changes of various parameters when the vehicular automatic transmission40is shifted up from the overall first speed position to the overall sixth speed position in synchronization with the shift-up action of the step-variable transmission portion20from the first speed AT gear position to the second speed AT gear position. In these time charts, “t2” represents a moment of generation of a command to implement the shift-up action to the second speed AT gear position, and “t4” represents the moment of initiation of the inertia phase of the shift-up action to the second speed AT gear position, at which reduction of the MG2speed ωm is initiated as a result of the shift-up action. Namely, a length of time from the point of time t2to the point of time t4is a control response time “trm” of the shift-up action from the first speed AT gear position to the second speed AT gear position. A command to implement the shift-up action to the overall sixth speed position which is the newly selected (target) overall speed position is generated at the moment of initiation of the inertia phase of the shift-up action to the second speed AT gear position, that is, at the point of time t4. In other words, the moment of generation of the command to implement the shift-up action to the overall sixth speed position is delayed with respect to the moment of generation of the command to implement the shift-up action to the second speed AT gear position, by a delay time DELi which is equal to the control response time “trm”. A control response time of the shift-up action to the overall sixth speed position is equal to a delay time “tri” which is a length of time from the point of time t4(at which the command to implement the shift-up action to the overall sixth speed position is generated) to a moment of initiation of an inertia phase of the shift-up action to the overall sixth speed position, at which reduction of the engine speed ωe is initiated as a result of the shift-up action. Since this control response time “tri” is short, the reduction of the MG2speed ωm as a result of the shift-up action to the second speed AT gear position and the reduction of the engine speed ωe as a result of the shift-up action to the overall sixth speed position are considered to take place substantially concurrently with each other. Thus, the shift-up action of the mechanically operated step-variable transmission portion20to the second speed AT gear position and the shift-up action of the vehicular automatic transmission40to the overall sixth speed position are performed in synchronization with each other such that the inertia phases of the two shift-up actions at least partially overlap each other, irrespective of a difference between the control response times “trm” and “tri” of the two shift-up actions, so that the degree of discomfort given to the vehicle operator due to different timings of the two shift-up actions and the shifting shock of the mechanically operated step-variable transmission portion20is reduced, and the drivability of the vehicle10is improved. In the examples ofFIGS. 12 and 13, the shift-up actions to the second speed. AT gear position and the overall sixth speed position are terminated substantially simultaneously at a point of time t5.

On the other hand, where the moment of generation of the command to establish the target overall speed position is delayed such that the shifting action to the target overall speed position is performed in synchronization with the shifting action to establish the corresponding newly selected AT gear position, the engine speed ωe is kept at a relatively high value until the shifting action to establish the newly selected AT gear position is initiated, if the vehicular automatic transmission40is automatically shifted up as a result of a releasing operation of the accelerator pedal or shifted up as a result of an operation of the shift-up/shift-down switch or any other member manually operated by the vehicle operator. This shift-up action of the vehicular automatic transmission40gives rise to a risk of the vehicle operator feeling that the engine speed ωe is kept at a relatively high value for an excessively long length of time, namely until the shift-up action of the step-variable transmission portion20is actually initiated, and a risk of deterioration of the fuel economy of the engine14. Further, the control response of the shift-up actions to establish the newly selected AT gear position and overall speed position is different from the control response of the shift-up action performed to establish only the newly selected overall speed position. This difference of the control responses gives rise to a risk that the vehicle operator is given discomfort during the shift-up actions of the step-variable transmission portion20and the vehicular automatic transmission40. In the examples of the time charts ofFIGS. 12-14, the determinations to perform the shift-up actions for establishing the newly selected AT gear position and overall speed position are made at a point of time t1as a result of a releasing operation of the accelerator pedal from its ON state to its OFF state, and the command to implement the shift-up action to establish the newly selected AT gear position is generated at the point of time t2which is a predetermined waiting time after the point of time t1, in order to prevent “busy shifting” operations of the vehicular automatic transmission40. The command to implement the shift-up action to establish the newly selected overall speed position (overall sixth speed position) is generated at the point of time t4which is the delay time DELi after the point of time t2, so that the vehicular automatic transmission40is shifted up from the overall first speed position eventually to the newly selected overall sixth speed position. Accordingly, the engine speed ωe is kept at the relatively high value for the excessively long length of time as felt by the vehicle operator, namely, before initiation of reduction of the engine speed ωe, and the fuel economy of the engine14may be deteriorated.

In the present embodiment, the two-step shifting control portion90is provided to reduce the above-indicated risk of the vehicle operator feeling that the engine speed ωe is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of fuel economy of the engine14. When the vehicular automatic transmission40is shifted up from the present overall speed position to the target overall speed position in synchronization with the shift-up action of the mechanically operated step-variable transmission portion20from the present AT gear position to the target AT gear position, under the control of the synchronous shifting control portion98, the two-step shifting control portion90commands the vehicular automatic transmission40to be once shifted up from the present overall speed position to an intermediate overall speed position between the present overall speed position and the target overall speed position, rather than commanding the vehicular automatic transmission40to be shifted up directly to the target overall speed position. The two-step shifting control portion90includes (a) a multiple-step shifting determining portion in the form of a two-step shifting determining portion92configured to determine, according to a predetermined condition for implementing a two-step shifting control, whether the vehicular automatic transmission40should be initially shifted to the intermediate overall speed position, (b) an intermediate overall speed position selecting portion94configured to select the intermediate overall speed position, according to the running state of the vehicle10, and (c) a multiple-step shifting commanding portion in the form of a two-step shifting commanding portion96configured to command the vehicular automatic transmission40to be shifted up to the intermediate overall speed position, at a predetermined timing after the moment of determination to shift the vehicular automatic transmission40to the target overall speed position. Steps S1-S10illustrated in the flow chart ofFIG. 9indicate details of operations of the two-step shifting control portion90and the synchronous shifting control portion98. The steps S1, S2, S9and S10correspond to a function of the synchronous shifting control portion98, the steps S3and S4correspond to a function of the two-step shifting determining portion92, the steps S5-S7correspond to a function of the intermediate overall speed position selecting portion94, and the step S8corresponds to a function of the two-step shifting commanding portion96.

A control routine illustrated in the flow chart ofFIG. 9is initiated with a step S1to determine whether the determination to implement a shift-up action to establish a target (newly selected) overall speed position has been made. This determination is made according to the overall speed position shifting map, or on the basis of a shift-up command generated by the shift-up/shift-down switch or any other manually operated member. If a negative determination is obtained in the step S1, one cycle execution of the control routine is terminated. If an affirmative determination is obtained in the step S1, the control flow goes to a step S2to determine whether the shift-up action to establish the target overall speed position is performed together with a shift-up action to establish a target (newly selected) AT gear position, namely, to determine whether the determination to implement the shift-up action to establish the target AT gear position has also been made by the step-variable shifting control portion86. If a negative determination is obtained in the step S2, that is, if only the determination to implement the shift-up action to establish the target overall speed position has been made, without the determination to implement the shift-up action to establish the target gear position, the control flow goes directly to a step S10to generate the command to establish the target overall speed position. Namely, a target value ωe* of the engine speed ωe of the target overall speed position is obtained on the basis of the present output speed too, and according to the map ofFIG. 8representing the relationship between the output speed ωo and the engine speed ωe, and the torque of the first motor/generator MG1is controlled so as to establish the obtained target engine speed value ωe*, whereby the target overall speed position is straightly established.

If an affirmative determination is obtained in the step S2, that is, if the determination to implement the shift-up action to establish the target overall speed position together with the shift-up action to establish the target AT gear position has been made, the control flow goes to a step S3. In the examples of the time charts ofFIGS. 12-147, the determination to implement the shift-up action from the overall first speed position to the overall sixth speed position is made substantially concurrently with the determination to implement the shift-up action from the first speed AT gear position to the second speed AT gear position, at the point of time t1, as a result of the releasing operation of the accelerator pedal from its ON state to its OFF state. Referring to the shifting map ofFIG. 8, if the accelerator pedal is abruptly released such that its operation amount θacc is abruptly reduced from a point A, at which the operation amount θacc is relatively large, during starting or acceleration of the vehicle10, to a zero point B, for example, the determinations to implement the shift-up action to establish the target AT gear position and the target overall speed position are made substantially concurrently with each other. The collinear chart ofFIG. 10indicates an example of changes of the rotating speeds of the various portions of the electrically controlled continuously variable transmission portion18and the mechanically operated step-variable transmission portion20, where the electrically controlled continuously variable transmission portion18is controlled to shift the vehicular automatic transmission40from the overall first speed position to the overall sixth speed position while the mechanically operated step-variable transmission portion20is shifted from the first speed AT gear position to the second speed AT gear position. Solid lines indicate the AT gear positions and the overall speed positions prior to the shift-up actions, while one-dot chain lines indicate the target positions established after the shift-up actions. As a result of these shift-up actions, the input speed ωi of the mechanically operated step-variable transmission portion20and the engine speed ωe are reduced according to the speed ratios γat and γt of the respective step-variable and continuously variable transmission portions20and18. It is noted that as a result of the determination to implement the shift-up action to establish the target AT gear position, the step-variable shifting control portion86generates the command to implement the shift-up action from the first speed AT gear position to the second speed AT gear position at time t2. Described more specifically, the hydraulic control command signal Sat is generated so that the brake B1placed in the released state to establish the first speed AT gear position is brought into the engaged state to establish the second speed AT gear position in which the clutch C1is also placed in the engaged state. In the presence of the one-way clutch F1, the brake B2is placed in its released state in the second speed AT gear position, so that the brake B2need not be brought into the released state.

In the step S3, a determination is made as to whether the present running state of the vehicle10satisfies a condition for implementing the two-step shifting control to shift the vehicular automatic transmission40eventually to the target overall speed position through the intermediate overall speed position, namely, as to whether the shift-up action to establish the target AT gear position is estimated to have a low control response in the present running state of the vehicle10, in other words, as to whether the vehicle operator is likely to feel that the engine speed ωe is kept at a relatively high value for an excessively long length of time, in the present running state of the vehicle10. For instance, an affirmative determination is obtained in the step S3where the accelerator pedal is released from its ON state to its OFF state, or where the working fluid temperature toil is lower than a predetermined lower limit. Described more specifically, the shift-up action of the mechanically operated step-variable transmission portion20to the target AT gear position just after the accelerator pedal has been switched from its ON state to its OFF state is not generally required to have a high degree of control response, so that this shift-up action is controlled to take place for a relatively long length of time, for reducing a shifting shock of the mechanically operated step-variable transmission portion20. Where the temperature toil of the working fluid in the hydraulic control unit54is relatively low, and the viscosity of the working fluid is relatively high, the control response of the engaging or releasing action of each coupling device CB is relatively low, so that a relatively long length of time is required until the inertia phase of the shift-up action to establish the target AT gear position is initiated. If the affirmative determination is obtained in the step S3, the control flow goes to steps S5-S8for implementing the two-step shifting control to eventually establish the target overall speed position. If a negative determination is obtained in the step S3, the control flow goes to a step S4to determine whether it is required to prevent the engine speed ωe being kept at a relatively high value for an excessively long length of time, that is, whether the running state of the vehicle10has a risk of the engine speed ωe being kept at the relatively high value for the excessively long length of time, and a risk of consequent deterioration of the fuel economy of the engine14. For instance, it is considered that the vehicle operator expects that the engine speed ωe quickly drops down as a result of the releasing operation of the accelerator pedal, where the speed of releasing of the accelerator pedal is higher than a predetermined upper limit, where the amount of reduction of the operation amount θacc of the accelerator pedal is larger than a predetermined upper limit, or where the operation amount θacc after the releasing operation of the accelerator pedal is smaller than a predetermined lower limit. In these cases, it is determined that it is necessary to prevent the engine speed ωe being kept at the relatively high value for the excessively long length of time. In the step S4, the determination may be made with respect to all of the speed of releasing of the accelerator pedal, the amount of reduction of the operation amount θacc and the operation amount θacc after the releasing operation of the accelerator pedal. In this case, the affirmative determination is obtained in the step S4, if any one of the above-indicated three parameters satisfies the condition described above. However, the determination in the step S4may be made with respect to only one or two of the three parameters. The speed and amount of releasing the accelerator pedal is a rate and variation amount of reduction of the operation amount θacc, respectively. If an affirmative determination is obtained in the step S4, the control flow goes to the steps S5-S8for implementing the two-step shifting control to eventually establish the target overall speed position. If a negative determination is obtained in the step S4, that is, the negative determinations are obtained in both of the steps S3and S4, it is determined that it is not necessary to implement the two-step shifting control, so that the control flow goes to a step S9. The conditions for implementing the two-step shifting control, which are used in the determinations in the steps S3and S4, are suitably determined, and the determination may be made with respect to only one of these two conditions, and any other condition may be set for implementing the two-step shifting control.

In the step S5, the intermediate overall speed position is selected according to a degree of requirement to prevent the engine speed ωe from being kept at the relatively high value for the excessively long length of time as felt by the vehicle operator. Described more specifically, the intermediate overall speed position is selected according to the speed of releasing of the accelerator pedal, the amount of reduction of its operation amount θacc and the operation amount θacc after its releasing operation, such that the selected intermediate overall speed position comes closer to the target overall speed position with an increase of the speed of releasing of the accelerator pedal, with an increase of the amount of reduction of its operation amount θacc, and with a decrease of the operation amount θacc after its releasing operation. The intermediate overall speed position may be selected according to any one of the speed of releasing of the accelerator pedal, the amount of reduction of its operation amount θacc and the operation amount θacc after its releasing operation. Described in detail with respect to the speed of releasing of the accelerator pedal, one of the overall speed positions between the present speed position and the target speed position is selected as the intermediate overall speed position according to the speed of releasing of the accelerator pedal. If there is only one overall speed position between the present and target speed positions, that one overall speed position is selected as the intermediate overall speed position. Where there are two or more speed positions between the present speed position (e.g., the first speed position) and the target speed position (e.g., the sixth speed position), the fourth or fifth speed position is selected as the intermediate overall speed position when the speed of releasing of the accelerator pedal is comparatively high, and the second or third speed position is selected as the intermediate overall speed position when the speed of releasing of the accelerator pedal is comparatively low. Similarly, the intermediate overall speed position is selected depending upon whether the amount of reduction of the operation amount θacc is comparatively large or small, or whether the operation amount θacc after the releasing operation is comparatively large or small. However, a predetermined one of the overall speed positions between the present and target speed positions may be selected as the intermediate overall speed position. For example, the speed position (e.g., fifth speed position) next lower than the target speed position (e.g., sixth speed position), the speed position (e.g., second speed position) next higher than the present speed position (e.g., first speed position), or the speed position (e.g., third or fourth speed position) intermediate between the present and target speed positions (e.g., first and sixth speed positions) may be selected as the intermediate overall speed position.

In the step S5, the intermediate overall speed position is basically selected within a range of the overall speed positions assigned to the AT gear position established prior to the synchronous shifting actions, to reduce the risk of generation of the shifting shock in the process of the synchronous shifting actions. However, where the engine speed ωe is likely to be kept at the relatively high value for the excessively long length of time as felt by the vehicle operator in the present running state of the vehicle10, in other words, where the degree of requirement to prevent the engine speed ωe from being kept at the relatively high value for the excessively long length of time is high, the intermediate overall speed position may be selected outside the range assigned to the AT gear position established prior to the synchronous shifting actions. For example, where the first speed AT gear position is established prior to the synchronous shifting actions, the first through third overall speed positions are assigned to the first speed AT gear position, as indicated in.FIG. 6, so that one of the first through third overall speed positions is basically selected as the intermediate overall speed position. In this case, the vehicular automatic transmission40is shifted from the intermediate overall speed position selected within the range ofFIG. 6, to the target overall speed position, together with the concurrent shifting action of the mechanically operated step-variable transmission portion20from the first speed AT gear position, so that the drivability of the vehicle10is improved without generation of a shifting shock of the vehicular automatic transmission40. However, the intermediate overall speed position may be selected not only from the range assigned to the first speed AT gear position, but also from the range assigned to the target second speed AT gear position, namely, from among the overall fourth through sixth speed positions, in order to reduce a possibility of the engine speed ωe being kept at the relatively high value for the excessively long length of time, rather than to effectively improve the drivability of the vehicle10without generation of the shifting shock, where the degree of requirement to prevent the engine speed ωe from being kept at the relatively high value for the excessively long length of time is high, for instance, where an operating sound of the engine14is easily audible at a low running speed V of the vehicle10, where the engine speed ωe is relatively high, where the operation amount θacc of the accelerator pedal after its releasing operation is not larger than the predetermined value, where the speed of releasing of the accelerator pedal is not lower than the predetermined value, where the amount of reduction of the operation amount θacc is not smaller than the predetermined value, or where the shift-up action to the target AT gear position has a long control response time causing the engine speed ωe to be kept at the relatively high value for the excessively long length of time (in case of e.g. power-off shift-up action). In the example ofFIG. 13, the intermediate overall speed position is selected outside the range assigned to the AT gear position established prior to the synchronous shifting actions, that is, the overall fifth speed position is selected, according to the operation amount θacc of the accelerator pedal after its releasing operation, the speed of releasing of the accelerator pedal, and the amount of reduction of the operation amount θacc. In this example, the shift-up action to the intermediate overall speed position of the vehicular automatic transmission40permits a large amount of reduction of the engine speed ωe, and effective reduction of the risk of the vehicle operator feeling that the engine speed ωe is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the engine14. It is noted that where the degree of requirement to prevent the engine speed ωe from being kept at the relatively high value for the excessively long length of time is extremely high, for example, where the operation amount ωacc of the accelerator pedal after its releasing operation is zero, the target overall speed position according to the overall speed position shifting map may be selected as the intermediate overall speed position. In the example of the time chart ofFIG. 14, the target overall speed position (overall sixth speed position) is selected as the intermediate overall speed position, in the step S5.

The step S5is followed by a step S6to determine whether there is a high risk of generation of a shifting shock of the mechanically operated step-variable transmission portion20. The risk of generation of the shifting shock is considered to be high where the working fluid temperature toil is not higher than the predetermined lower limit, and the viscosity of the working fluid is relatively high, so that the accuracy of control of the engaging and releasing actions of each coupling device CB is low. The risk of generation of the shifting shock is also considered to be high where the temperature of the first or second motor/generator MG1or MG2or the inverter50is relatively high, and the maximum charging or discharging amount Win or Wout of the battery52is limited on the basis of the battery temperature THbat or the electric power amount SOC stored in the battery52. In this case, the torque of the first or second motor/generator MG1, MG2is limited, and the accuracy of control of the engine speed ωe and the input speed on by controlling the MG1and MG2torques is lowered. Namely, the risk of generation of the shifting shock can be considered to be high, where the maximum charging or discharging amount Win or Wout of the battery52is not larger than a predetermined lower limit, or where the temperature of the motor/generator MG1or MG2or the inverter50is not higher than a predetermined lower limit.

If it is determined in the step S6that there is a high risk of generation of the shifting shock, that is, if an affirmative determination is obtained in the step S6, the control flow goes to a step S7to restrict the selection of the intermediate overall speed position. If a negative determination is obtained in the step S6, the control flow goes to a step S8while skipping the step S7. In the step S7, the selection of the intermediate overall speed position is restricted according to the table ofFIG. 6indicating the relationship between the overall speed positions and the AT gear positions, more specifically; limited to within the range assigned to the AT gear position established prior to the synchronous shifting actions, in order to reduce, with higher priority, the risk of deterioration of the drivability of the vehicle10due to the shifting shock, rather than the risk of deterioration in the vehicle operator feeling and the risk of deterioration of the fuel economy of the engine14due to the engine speed ωe kept at the relatively high value for the excessively long length of time. Where the first speed AT gear position is established prior to the synchronous shifting actions, the selection of the intermediate overall speed position is limited to one of the overall first through third speed positions. Where the overall fourth or higher speed position is selected as the intermediate overall speed position in the step S5, the once selected intermediate overall speed position is replaced by the overall third speed position. In the example of the time chart ofFIG. 12, the overall third speed position is selected as the intermediate overall speed position, according to the restriction in the step S7. The restriction of the selection of the intermediate overall speed position as described above permits adequate implementation of the shift-up action to establish the target overall speed position through the restricted intermediate overall speed position, synchronized with the shift-up action to establish the target AT gear position as shown in the table ofFIG. 6, while reducing the risk of the vehicle operator feeling that the engine speed cog is kept at the relatively high value for the excessively long length of time, so that the risk of deterioration of the drivability of the vehicle10due to the shifting shock can be adequately reduced.

The restriction of the selection of the intermediate overall speed position in the step S7may be implemented, not according to the table ofFIG. 6. For instance, the selection of the intermediate overall speed position is limited to within a predetermined range of the overall speed positions available for each of the AT gear position established prior to the synchronous shifting actions, depending upon whether the mechanically operated step-variable transmission portion20is automatically shifted or manually shifted, whether the working fluid temperature toil is held within a normal range or higher than a predetermined upper limit, and/or whether the mechanically operated step-variable transmission portion20is shifted up or shifted down, as indicated inFIG. 11. Where the AT gear position established prior to the synchronous shift-up actions is the first speed AT gear position, for instance, the selection of the overall speed position is limited to one of the overall first through third speed positions, when the mechanically operated step-variable transmission portion20is automatically shifted up. Further, the selection of the intermediate overall speed position is limited to one of the overall first through third speed positions, where the mechanically operated step-variable transmission portion20is manually shifted up while the working fluid temperature toil is held within the normal range, or to one of the overall first through fourth speed positions, where the mechanically operated step-variable transmission portion20is manually shifted up while the working fluid temperature toil is higher than the upper limit. The flow chart ofFIG. 9illustrates the control routine where the vehicular automatic transmission40is shifted up to the target overall speed position. However, the present embodiment is configured to implement the two-step shifting control of the shift-down action to establish the target overall speed position through the intermediate overall speed position, prior to the synchronous shift-down actions, when the predetermined condition is satisfied, as in the case where the synchronous two-step shifting control is implemented with respect to the shift-up action.FIG. 11also indicates the overall speed positions available for each of the shift-down actions of the mechanically operated step-variable transmission portion20, to which the selection of the intermediate overall speed position is limited.

In the step S8, a command to shift up the vehicular automatic transmission40to the intermediate overall speed position selected in the step S5or restricted in the step S7, is generated at a predetermining timing. In the present embodiment, the command to establish the intermediate overall speed position is generated through the processing operations in the steps S2-S7, at the earliest possible point of time after the moment at which the determination to implement the shift-up action to establish the target overall speed position is made. Namely, in the examples of the time charts ofFIGS. 12-14wherein the determinations to implement the shift-up actions establish the target overall speed position and the target AT gear position are made at the point of time t1as a result of the releasing operation of the accelerator pedal from its ON state to its OFF state, the command to establish the intermediate overall speed position is generated immediately after the moment at which the above-indicated determinations are made. Described more specifically, the command to establish the overall third speed position is immediately generated in the example ofFIG. 12, and the command to establish the overall fifth speed position is immediately generated in the example ofFIG. 13, while the command to establish the overall sixth speed position is immediately generated in the example ofFIG. 14. “t3” in the time charts ofFIGS. 12-14represents a point of time at which the shift-up action to establish the intermediate overall speed position is terminated. During a time period from the point of time t2to the point of time t3, the engine speed ωe is lowered at a high rate according to the speed ratio γt of the intermediate overall speed position. In the example ofFIG. 14in which the overall sixth speed position is selected as the intermediate overall speed position, the engine speed ωo is rapidly lowered as a result of the shift-up action from the overall first speed position to the overall sixth speed position, so that the requirement by the vehicle operator with respect to a rate of change of the engine speed ωe after the operation of the accelerator pedal to its fully released position can be satisfied. In this case, the reduction of the MG2speed ωm is initiated at the point of time t4as a result of the shift-up action of the mechanically operated step-variable transmission portion20from the first speed AT gear position to the second speed AT gear position. Although the moment at which the reduction of the MG2speed ωm is initiated is delayed with respect to the moment at which the reduction of the engine speed ωe is initiated, the vehicle operator is not likely to feel uncomfortable with the shift-up action to the second AT gear position, since the rate of drop of the engine speed ωe as a result of the shift-up action to the overall sixth speed position is considerably high.

In the step S9, a determination is made as to whether the shift-up action of the mechanically operated step-variable transmission portion20from the first speed AT gear position to the second speed AT gear position has progressed into the inertia phase under the control of the step-variable shifting control portion86. The step-variable shifting control portion86generates, at the point of time t2, the command to shift, up the mechanically operated step-variable transmission portion20from the first speed AT gear position to the second speed AT gear position, that is, generates the hydraulic control command signal Sat for bringing the brake B1into its engaged state, so that this shift-up action is actually initiated at the point of time t4, namely, the inertia phase of the shift-up action is initiated with initiation of reduction of the input speed ωi (MG2speed ωm) at the point of time t4which is the control response time trm after the point of time t2. Accordingly, an affirmative determination is obtained in the step S9at the point of time t4. The determination as to whether the inertia phase has been initiated or not is made to implement a synchronous control of the shift-up actions to the target overall sixth speed position and the target second speed AT gear position such that the inertia phases of these two shift-up actions at least partially overlap each other. However, the moment of initiation of the inertia phase of the shift-up action to the second speed AT gear position need not be accurately detected. For example, the determination in the step S9may be made depending upon whether the predetermined delay time DELi has passed from the moment of generation of the command to establish the second speed AT gear position, that is, from the point of time t2. The delay time DELi may be a constant value irrespective of the kind of the shift-up action of the mechanically operated step-variable transmission portion20. Alternatively; the delay time DELi may be determined by experimentation or simulation according to the kind of the shift-up action, more specifically; the present and target AT gear positions. Further, parameters other than the kind of the shift-up action may be additionally taken into consideration to determine the delay time DELL For instance, the delay time DELi may be determined depending upon whether a positive forward drive torque or a negative reverse drive torque is transmitted to the mechanically operated step-variable transmission portion20, and/or whether the step-variable transmission portion20is automatically shifted or manually shifted, or on the basis of the temperature toil of the working fluid used for the hydraulic control unit54.

If an affirmative determination is obtained in the step S9upon detection of the moment of initiation of the inertia phase of the shift-up action to the target AT gear position, in other words, when the delay time DELi has passed from the point of time t2, the control flow goes to a step S10to generate the command to establish the target overall speed position, that is, the overall sixth speed position. Accordingly, the reduction of the engine speed ωe as a result of the shift-up action to the overall sixth speed position and the reduction of the input speed ωi (MG2speed ωm) as a result of the shift-up action from the first speed AT gear position to the second speed AT gear position take place concurrently with each other (overlap each other), irrespective of the difference between the control response time tri of the shift-up action to the overall sixth speed position and the control response time trm of the shift-up action to the second AT gear position. In the example of the time chart ofFIG. 12in which the overall third speed position has been established as the intermediate overall speed position according to the command generated in the step S8, the shift-up action from the overall third speed position to the overall sixth speed position takes place concurrently with the shift-up action from the first speed AT gear position to the second speed AT gear position. In the example of the time chart ofFIG. 13in which the overall fifth speed position has been established as the intermediate overall speed position according to the command generated in the step S8, the shift-up action from the overall fifth speed position to the overall sixth speed position takes place concurrently with the shift-up action from the first speed AT gear position to the second speed AT gear position. In the example of the time chart ofFIG. 14in which the vehicular automatic transmission40is shifted up from the overall first speed position directly to the overall sixth speed position according to the command generated. In the step S8, the shift-up action of the vehicular automatic transmission40is no longer implemented and thus, steps S9and S10are skipped.

In the shifting control apparatus (in the form of the electronic control device80) for the vehicular automatic transmission40, which is configured according to the present embodiment, the plurality of overall speed positions of the vehicular automatic transmission40having the respective different speed ratios γt of the engine speed ωe to the output speed ωo of the mechanically operated step-variable transmission portion20are established by controlling the electrically controlled continuously variable transmission portion18, so that the engine speed ωe is variable in steps by shifting the vehicular automatic transmission40from one of the overall speed positions to another. Accordingly, the vehicular automatic transmission40as a whole can be shifted in a manner like a manner of shifting of a mechanically operated step-variable transmission, as felt by the vehicle operator.

Further, the synchronous control of the shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20to the respective target overall speed position and gear position is implemented such that the moment of generation of the command to establish the target overall speed position is delayed with respect to the moment of generation of the command to establish the target gear position, so that the shifting actions take place in synchronization with each other, irrespective of the different control response times tri and trm of the shifting actions. Accordingly; the degree of discomfort given to the vehicle operator due to different timings of the two shifting actions and the shifting shock of the mechanically operated step-variable transmission portion20is reduced, and the drivability of the vehicle10is improved. Namely, the control response time tri of the shifting action of the electrically controlled continuously variable transmission portion18is shorter than the control response time trm of the shifting action of the mechanically operated step-variable transmission portion20, so that simultaneous generation of the commands to establish the target overall speed position and gear position causes an earlier change of the engine speed ωe in the process of the shifting action of the vehicular automatic transmission40by the electrically controlled continuously variable transmission portion18, than a change of the AT input speed ωi in the process of the shifting action of the mechanically operated step-variable transmission portion20, that is, an earlier moment of initiation of the inertia phase of the shifting action of the vehicular automatic transmission40than a moment of initiation of the inertia phase of the shifting action of the step-variable transmission portion20, whereby the vehicle operator may be given discomfort due to this difference.

In addition, since the shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20to the target overall speed position and gear position take place in synchronization with each other, the shifting action of the mechanically operated step-variable transmission portion20is performed together with a change of the engine speed we, so that the vehicle operator is unlikely to feel uncomfortable with a shifting shock of the step-variable transmission portion20, even if the shifting shock is generated.

On the other hand, where the shifting action of the vehicular automatic transmission40to the target overall speed position is controlled to take place in synchronization with the shifting action of the mechanically operated step-variable transmission portion20to the target AT gear position, as described above, the engine speed ωe is kept at a relatively high value until the shift-up action of the step-variable transmission portion20is initiated. In this case, there are a risk that the vehicle operator feels that the engine speed ωe is kept at a relatively high value for an excessively long length of time, and a risk of deterioration of the fuel economy of the engine14. There is also a risk that the vehicle operator feels uncomfortable with a difference of the control response of the synchronous shifting actions of the vehicular automatic transmission40and the step-variable transmission portion20, with respect to the control response of a shifting action of the vehicular automatic transmission40which takes place alone without a concurrent shifting action of the step-variable transmission portion20. In view of these risks, the overall-speed-position shifting control portion88of the present shifting control apparatus includes the two-step shifting control portion90configured to command the synchronous shifting control portion98in the step S8such that the vehicular automatic transmission40performs the shift-up action from the present overall speed position to the target overall speed position through the selected intermediate overall speed position. Thus, the automatic transmission40is initially shifted up to the intermediate overall speed position before it is eventually shifted up to the target overall speed position, so that the engine speed me is lowered at an earlier point of time, whereby the risk of the vehicle operator feeling that the engine speed ωe is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the engine14are reduced, together with an improvement of the drivability of the vehicle10.

The shifting control apparatus according to the present embodiment is further configured such that the two-step shifting determining portion92determines in the steps S3and S4whether the vehicular automatic transmission40should be initially shifted to the intermediate overall speed position. This determination is made according to the predetermined condition for implementing the two-step shifting control. The two-step shifting control is implemented only where there is the risk of the vehicle operator feeling that the engine speed ωe is kept at the relatively high value for the excessively long length of time, or the risk of deterioration of the fuel economy of the engine14, in the following cases, for example: where the mechanically operated step-variable transmission portion20is shifted up as a result of the releasing operation of the accelerator pedal to its OFF state; where the shifting action of the step-variable transmission portion20has a relatively long control response time due to the working fluid temperature toil lower than the predetermined lower limit; where the speed of releasing of the accelerator pedal is higher than the predetermined upper limit; where the amount of reduction of the operation amount θacc of the accelerator pedal is larger than the predetermined upper limit; and where the operation amount θacc of the accelerator pedal after its releasing operation is smaller than the predetermined lower limit. Accordingly it is possible to reduce the risk of the vehicle operator feeling that the engine speed ωe is kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the engine14, while adequately maintaining a high degree of drivability of the vehicle10owing to the synchronous shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20.

The shifting control apparatus according to the present embodiment is also configured such that the intermediate overall speed position is selected in the steps S5-S7according to the running state of the vehicle10, so that it is possible to improve the drivability of the vehicle10owing to the synchronous shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20, and to reduce the risk of the vehicle operator feeling the engine speed ωe kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the engine14, so as to assure a good balance between the improvement of the vehicle drivability and the reduction of those risks, according to the running state of the vehicle10. The risk of the vehicle operator feeling the engine speed we kept at the relatively high value for the excessively long length of time is high, so that the degree of requirement to prevent the engine speed ωe from being kept at the relatively high value for the excessively long length of time as felt by the vehicle operator is high, in the following cases, for example: where the speed of releasing of the accelerator pedal is relatively high; where the amount of reduction of the operation amount θacc of the accelerator pedal is relatively large; and where the operation amount θacc of the accelerator pedal after its releasing operation is relatively small. Accordingly, the amount of reduction of the engine speed ωe in the process of the shifting action to the intermediate overall speed position can be adjusted, and the drivability of the vehicle10can be improved by the synchronous shifting actions of the vehicular automatic transmission40and the mechanically operated step-variable transmission portion20, while at the same time the risk of the vehicle operator feeling the engine speed ωe kept at the relatively high value for the excessively long length of time can be adequately reduced according to the state of releasing of the accelerator pedal, since the intermediate overall speed position selecting portion94is configured to select the intermediate overall speed position such that the selected intermediate overall speed position is closer to the target overall speed position when the degree of requirement to prevent the engine speed ωe from being kept at the relatively high value for the excessively long length of time as felt by the vehicle operator is relatively high than when the degree of requirement is relatively low.

The intermediate overall speed position selecting portion94is basically configured to select the intermediate overall speed position from the overall speed positions assigned to the present AT gear position, so that the vehicular automatic transmission40can be shifted from the intermediate overall speed position to the target overall speed position according to the table ofFIG. 6, in synchronization with the shifting action of the mechanically operated step-variable transmission portion20. Accordingly, it is possible to reduce the risk of the vehicle operator feeling the engine speed ωe kept at the relatively high value for the excessively long length of time, in the process of the shifting action to the intermediate overall speed position, and the risk of deterioration of the fuel economy of the engine14, while assuring a high degree of drivability of the vehicle10with a reduced risk of generation of the shifting shock. On the other hand, the intermediate overall speed position selecting portion94selects the intermediate overall speed position outside the range assigned to the AT gear position established prior to the synchronous shifting actions, to reduce the risk of the vehicle operator feeling the engine speed ωe kept at the relatively high value for the excessively long length of time, with higher priority, rather than to improve the vehicle drivability with a reduced risk of generation of the shifting shock in the process of the synchronous shifting actions, where the degree of requirement to prevent the engine speed we from being kept at the relatively high value for the excessively long length of time as felt by the vehicle operator is relatively high, namely, in the following cases, for example: when the operating sound of the engine14is easily audible at a low running speed of the vehicle10; where the engine speed ωe is relatively high; where the operation amount θacc of the accelerator pedal after its releasing operation is smaller than the predetermined lower limit; where the speed of releasing of the accelerator pedal is higher than the predetermined upper limit; where the amount of reduction of the operation amount θacc of the accelerator pedal is larger than the predetermined upper limit; and where the shifting action of the mechanically operated step-variable transmission portion20to the target AT gear position has a relatively long control response time which causes the engine speed ωe to be kept at the relatively high value for the excessively long time as felt by the vehicle operator (where the step-variable transmission portion20is shifted up as a result of a releasing operation of the accelerator pedal to its OFF state). Accordingly, the engine speed ωe is rapidly lowered in the process of the shifting action to the intermediate overall speed position, so that it is possible to adequately reduce the risk of the vehicle operator feeling the engine speed toe kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the engine14.

The intermediate overall speed position selecting portion94is further configured to determine in the step S6whether there is a high risk of generation of a shifting shock of the mechanically operated step variable transmission portion20. If the affirmative determination is obtained in the step S6, the selection of the intermediate overall speed position is limited in the step S7within the range of the overall speed positions assigned to the AT gear position established prior to the shifting action of the step-variable transmission portion20, in order to reduce the risk of deterioration of the vehicle drivability due to the shifting shock, with higher priority, rather than to reduce the risk of deterioration in the vehicle operator feeling and the risk of deterioration of the fuel economy of the engine14with the engine speed ωe kept at the relatively high value for the relatively long length of time. Accordingly, the shifting action of the vehicular automatic transmission40is suitably performed in synchronization with the shifting action of the step-variable transmission portion20, such that the engine speed ωe is lowered so as to adequately reduce the risk of deterioration of the vehicle drivability due to the shifting shock, while reducing the risk of the vehicle operator feeling the engine speed ωe kept at the relatively high value for the excessively long length of time in the process of the shifting action to the intermediate overall speed position.

Further, the two-step shifting commanding portion96is configured to command the vehicular automatic transmission40to be shifted up to the intermediate overall speed position, immediately after the moment of determination to shift up the vehicular automatic transmission40to the target overall speed position in step S8. Accordingly, when the vehicular automatic transmission40is commanded to be shifted up as a result of a releasing operation of the accelerator pedal or an operation of a manually operated member, the vehicular automatic transmission40is immediately shifted up to the intermediate overall speed position, and the engine speed ωe is rapidly lowered, so that it is possible to adequately reduce the risk of the vehicle operator feeling the engine speed ωe kept at the relatively high value for the excessively long length of time, and the risk of deterioration of the fuel economy of the engine14.

It is to be understood that the embodiment described above is given for illustrative purpose only, and that the present invention may be embodied with various changes and improvements which may occur to these skilled in the art.

NOMENCLATURE OF ELEMENTS