Hybrid vehicle

In the process of cranking and starting an engine by a motor, until a predetermined condition is satisfied, i.e., until a rotation speed Ne of the engine is equal to or higher than a predetermined rotation speed Nstmg and a crank angle θcr of the engine is in a predetermined range of θst1 to θst2, the motor is controlled to increase the torque of the motor from value 0 to a positive specified torque Tst1 and keep the torque of the motor at the specified torque Tst1 by a rate process using a rate value ΔTst1. When the predetermined condition is satisfied, a rate value ΔTst2 is set to increase with an increase in satisfaction time rotation speed Neset that denotes the rotation speed Ne of the engine on satisfaction of the predetermined condition. The motor is then controlled to decrease the torque of the motor from the specified torque Tst1 by a rate process using a rate value ΔTst2.

This application claims priority to Japanese Patent Application No. 2015-32973 filed 23 Feb. 2015, the contents of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a hybrid vehicle or more specifically relates to a hybrid vehicle equipped with an engine, a motor and a battery.

BACKGROUND ART

A proposed configuration of a hybrid vehicle includes an engine, a planetary gear, first and second motors and a battery (for example, Patent Literature 1). The planetary gear includes a sun gear that is connected with a rotor of the first motor. The planetary gear includes a carrier that is connected with a crankshaft of the engine via a damper. The planetary gear includes a ring gear that is connected with a driveshaft linked with drive wheels and a rotor of the second motor. In this hybrid vehicle, in the process of cranking and starting the engine by the first motor, until both a rotation speed condition that the rotation speed of the engine is equal to or higher than a predetermined rotation speed and a crank angle condition that the crank angle of the engine is in a predetermined range are satisfied, the first motor is controlled to increase the torque of the first motor from value 0 to a positive specified torque by a rate process using a first rate value. After both the rotation speed condition and the crank angle condition are satisfied, the first motor is controlled to decrease the torque of the first motor from the positive specified torque by a rate process using a second rate value. This suppresses the occurrence of significantly large vibration in the process of starting the engine.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The hybrid vehicle described above uses a predetermined value (fixed value) as the second rate value. This causes the time period between start of cranking the engine by the first motor and completion of starting the engine (entire starting time period) and the rotation amount of the engine (number of strokes of intake, compression, expansion and exhaust, i.e., total emission) in the entire starting time period to be varied according to the timing when both the rotation speed condition and the crank angle condition are satisfied. This is likely to cause deterioration of drivability (acceleration performance) and emission.

With regard to the hybrid vehicle, an object of the invention is to suppress deterioration of drivability and emission.

Solution to Problem

In order to solve at least part of the problems described above, the hybrid vehicle of the invention may be implemented by the following aspects or configurations.

According to one aspect of the invention, there is provided a first hybrid vehicle including: an engine that is configured to have an output shaft that is connected via a torsion element with a downstream shaft linked with an axle; a motor that is configured to input and output power from and to the downstream shaft; a battery that is configured to transmit electric power to and from the motor; and a controller that is configured to, in a process of cranking and starting the engine by the motor, control the motor such as to increase a torque of the motor from value 0 to a specified torque and keep the torque at the specified torque until a predetermined condition is satisfied that a rotation speed of the engine is equal to or higher than a predetermined rotation speed and a crank angle of the engine is in a predetermined crank angle range, and to control the motor such as to decrease the torque of the motor from the specified torque after the predetermined condition is satisfied, wherein after the predetermined condition is satisfied, the controller controls the motor such as to decrease the torque of the motor at a higher rate with an increase in rotation speed or rotational acceleration of the engine at a time when the predetermined condition is satisfied.

The first hybrid vehicle of the above aspect controls the motor in the following manner in the process of cranking and starting the engine by the motor. Until the predetermined condition is satisfied, i.e., until the rotation speed of the engine is equal to or higher than the predetermined rotation speed and the crank angle of the engine is in the predetermined crank angle range, the motor is controlled to increase the torque of the motor from the value 0 to the specified torque and keep the torque of the motor at the specified torque. After the predetermined condition is satisfied, the motor is controlled to decrease the torque of the motor from the specified torque. In this process of controlling the motor, after the predetermined condition is satisfied, the motor is controlled to decrease the torque of the motor at a higher rate with an increase in rotation speed or rotational acceleration of the engine at the time when the predetermined condition is satisfied. This configuration suppresses the vibration of the vehicle caused by the torsion element in the course of decreasing the torque of the motor. The configuration of decreasing the torque of the motor at the higher rate with an increase in rotation speed or rotational acceleration of the engine at the time when the predetermined condition is satisfied suppresses variations of the time period between start of cranking the engine by the motor and completion of starting the engine (entire starting time period) and the rotation amount of the engine (number of strokes of intake, compression, expansion and exhaust, i.e., total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

According to another aspect of the invention, there is provided a second hybrid vehicle including: an engine that is configured to have an output shaft that is connected via a torsion element with a downstream shaft linked with an axle; a motor that is configured to input and output power from and to the downstream shaft; a battery that is configured to transmit electric power to and from the motor; and a controller that is configured to, in a process of cranking and starting the engine by the motor, control the motor such as to increase a torque of the motor from value 0 to a specified torque and keep the torque at the specified torque until a predetermined condition is satisfied that a rotation speed of the engine is equal to or higher than a predetermined rotation speed and a crank angle of the engine is in a predetermined crank angle range, and to control the motor such as to decrease the torque of the motor from the specified torque after the predetermined condition is satisfied, wherein after the predetermined condition is satisfied, the controller controls the motor such as to decrease the torque of the motor at a higher rate with an increase in time period between start of cranking the engine and satisfaction of the predetermined condition.

The second hybrid vehicle of the above aspect controls the motor in the following manner in the process of cranking and starting the engine by the motor. Until the predetermined condition is satisfied, i.e., until the rotation speed of the engine is equal to or higher than the predetermined rotation speed and the crank angle of the engine is in the predetermined crank angle range, the motor is controlled to increase the torque of the motor from the value 0 to the specified torque and keep the torque of the motor at the specified torque. After the predetermined condition is satisfied, the motor is controlled to decrease the torque of the motor from the specified torque. In this process of controlling the motor, after the predetermined condition is satisfied, the motor is controlled to decrease the torque of the motor at a higher rate with an increase in time period between start of cranking the engine and satisfaction of the predetermined condition. This configuration suppresses the vibration of the vehicle caused by the torsion element in the course of decreasing the torque of the motor. The configuration of decreasing the torque of the motor at the higher rate with an increase in time period between start of cranking the engine and satisfaction of the predetermined condition suppresses variations of the time period between start of cranking the engine by the motor and completion of starting the engine (entire starting time period) and the rotation amount of the engine (number of strokes of intake, compression, expansion and exhaust, i.e., total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

According to another aspect of the invention, there is provided a third hybrid vehicle including: an engine that is configured to have an output shaft that is connected via a torsion element with a downstream shaft linked with an axle; a motor that is configured to input and output power from and to the downstream shaft; a battery that is configured to transmit electric power to and from the motor; and a controller that is configured to, in a process of cranking and starting the engine by the motor, control the motor such as to increase a torque of the motor from value 0 to a specified torque and keep the torque at the specified torque until a predetermined condition is satisfied that a rotation speed of the engine is equal to or higher than a predetermined rotation speed and a crank angle of the engine is in a predetermined crank angle range, and to control the motor such as to decrease the torque of the motor from the specified torque after the predetermined condition is satisfied, wherein after the predetermined condition is satisfied, the controller controls the motor such as to decrease the torque of the motor at a higher rate with an increase in time period between increase of the torque of the motor to the specified torque and satisfaction of the predetermined condition.

The third hybrid vehicle of the above aspect controls the motor in the following manner in the process of cranking and starting the engine by the motor. Until the predetermined condition is satisfied, i.e., until the rotation speed of the engine is equal to or higher than the predetermined rotation speed and the crank angle of the engine is in the predetermined crank angle range, the motor is controlled to increase the torque of the motor from the value 0 to the specified torque and keep the torque of the motor at the specified torque. After the predetermined condition is satisfied, the motor is controlled to decrease the torque of the motor from the specified torque. In this process of controlling the motor, after the predetermined condition is satisfied, the motor is controlled to decrease the torque of the motor at a higher rate with an increase in time period between increase of the torque of the motor to the specified torque and satisfaction of the predetermined condition. This configuration suppresses the vibration of the vehicle caused by the torsion element in the course of decreasing the torque of the motor. The configuration of decreasing the torque of the motor at the higher rate with an increase in time period between increase of the torque of the motor to the specified torque and satisfaction of the predetermined condition suppresses variations of the time period between start of cranking the engine by the motor and completion of starting the engine (entire starting time period) and the rotation amount of the engine (number of strokes of intake, compression, expansion and exhaust, i.e., total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

DESCRIPTION OF EMBODIMENTS

The following describes some aspects of the invention with reference to embodiments.

FIG. 1is a configuration diagram illustrating the schematic configuration of a hybrid vehicle20according to one embodiment of the invention. As illustrated, the hybrid vehicle20of the embodiment includes an engine22, a planetary gear30, motors MG1and MG2, inverters41and42, a battery50, and a hybrid electronic control unit (hereinafter referred to as HVECU)70.

The engine22is configured as a four-cylinder internal combustion engine that uses, for example, gasoline or light oil as fuel to output power. This engine22is operated and controlled by an engine electronic control unit (hereinafter referred to as “engine ECU”)24.

The engine ECU24is implemented by a CPU-based microprocessor and includes a ROM that stores processing programs, a RAM that temporarily stores data, input and output ports and a communication port other than the CPU, although not being illustrated. The engine ECU24inputs, via its input port, signals from various sensors required for operation control of the engine22. The signals from various sensors include, for example, a crank angle θcr from a crank position sensor23configured to detect the rotational position of a crankshaft26of the engine22and a throttle position TH from a throttle valve position sensor configured to detect the position of a throttle valve. The engine ECU24outputs, via its output port, various control signals for operation control of the engine22. The various control signals include, for example, a control signal to a fuel injection valve, a control signal to a throttle motor configured to adjust the position of the throttle valve and a control signal to an ignition coil integrated with an igniter. The engine ECU24is connected with the HVECU70via the respective communication ports. The engine ECU24performs operation control of the engine22, in response to control signals from the HVECU70. The engine ECU24also outputs data regarding the operating conditions of the engine22to the HVECU70as appropriate. The engine ECU24computes a rotation speed Ne of the engine22, based on the crank angle θcr from the crank position sensor23.

The planetary gear30is configured as a single pinion-type planetary gear mechanism. The planetary gear30includes a sun gear that is connected with a rotor of the motor MG1. The planetary gear30also includes a ring gear that is connected with a driveshaft36linked with drive wheels38aand38bvia a differential gear37and is connected with a rotor of the motor MG2. The planetary gear30also includes a carrier that is connected with the crankshaft26of the engine22via a damper28as torsion element.

The motor MG1is configured, for example, as a synchronous motor generator. The motor MG1includes the rotor that is connected with the sun gear of the planetary gear30as described above. The motor MG2is also configured, for example, as a synchronous motor generator. The motor MG2includes the rotor that is connected with the driveshaft36as described above. The inverters41and42as well as the battery50are connected with power lines54. The motors MG1and MG2are rotated and driven by switching control of a plurality of switching elements (not shown) of the inverters41and42by a motor electronic control unit (hereinafter referred to as “motor ECU”)40.

The motor ECU40is implemented by a CPU-based microprocessor and includes a ROM that stores processing programs, a RAM that temporarily stores data, input and output ports and a communication port other than the CPU, although not being illustrated. The motor ECU40inputs, via its input port, signals from various sensors required for drive control of the motors MG1and MG2. The signals from various sensors include, for example, rotational positions θm1and θm2from rotational position detection sensors43and44configured to detect the rotational positions of the rotors of the motors MG1and MG2and phase currents from current sensors configured to detect electric currents flowing through the respective phases of the motors MG1and MG2. The motor ECU40outputs, via its output port, for example, switching control signals to the switching elements (not shown) of the inverters41and42. The motor ECU40is connected with the HVECU70via the respective communication ports. The motor ECU40performs drive control of the motors MG1and MG2in response to control signals from the HVECU70. The motor ECU40also outputs data regarding the driving conditions of the motors MG1and MG2to the HVECU70as appropriate. The motor ECU40computes rotation speeds Nm1and Nm2of the motors MG1and MG2, based on the rotational positions θm1and θm2of the rotors of the motors MG1and MG2from the rotational position detection sensors43and44.

The battery50is configured, for example, as a lithium ion secondary battery or a nickel hydride secondary battery. This battery50as well as the inverters41and42is connected with the power lines54as described above. The battery50is under management of a battery electronic control unit (hereinafter referred to as “battery ECU”)52.

The battery ECU52is implemented by a CPU-based microprocessor and includes a ROM that stores processing programs, a RAM that temporarily stores data, input and output ports and a communication port other than the CPU, although not being illustrated. The battery ECU52inputs, via its input port, signals from various sensors required for management of the battery50. The signals from various sensors include, for example, a battery voltage Vb from a voltage sensor51aplaced between terminals of the battery50, a battery current Ib from a current sensor51bmounted to an output terminal of the battery50, and a battery temperature Tb from a temperature sensor51cmounted to the battery50. The battery ECU52is connected with the HVECU70via the respective communication ports. The battery ECU52outputs data regarding the conditions of the battery50to the HVECU70as appropriate. The battery ECU52computes a state of charge SOC, based on an integrated value of the battery current Ib from the current sensor51b. The state of charge SOC denotes a ratio of power capacity dischargeable from the battery50to the entire capacity of the battery50. The battery ECU52also computes input and output limits Win and Wout, based on the computed state of charge SOC and the battery temperature Tb from the temperature sensor51c. The input and output limits Win and Wout denote maximum allowable electric powers chargeable into and dischargeable from the battery50.

The HVECU70is implemented by a CPU-based microprocessor and includes a ROM that stores processing programs, a RAM that temporarily stores data, input and output ports and a communication port other than the CPU, although not being illustrated. The HVECU70inputs, via its input port, signals from various sensors. The signals from various sensors include, for example, an ignition signal from an ignition switch80, a shift position SP from a shift position sensor82configured to detect the operational position of a shift lever81, an accelerator position Acc from an accelerator pedal position sensor84configured to detect the depression amount of an accelerator pedal83, a brake pedal position BP from a brake pedal position sensor86configured to detect the depression amount of a brake pedal85, and a vehicle speed V from a vehicle speed sensor88. As described above, the HVECU70is connected with the engine ECU24, the motor ECU40and the battery ECU52via the communication ports. The HVECU70transmits various control signals and data to and from the engine ECU24, the motor ECU40and the battery ECU52.

The hybrid vehicle20of the embodiment having the above configuration runs in a drive mode, such as hybrid drive mode (HV drive mode) or an electric drive mode (EV drive mode). The HV drive mode denotes a drive mode in which the hybrid vehicle20is driven with operation of the engine22. The EV drive mode denotes a drive mode in which the hybrid vehicle20is driven with stopping operation of the engine22.

In the HV drive mode, the HVECU70first sets a required torque Tr* required for running (to be output to the driveshaft36), based on the accelerator position Acc from the accelerator pedal position sensor84and the vehicle speed V from the vehicle speed sensor88. The HVECU70subsequently multiplies the set required torque Tr* by a rotation speed Nr of the driveshaft36to calculate a driving power Pdrv* required for running. The rotation speed Nr of the driveshaft36used herein may be the rotation speed Nm2of the motor MG2or a rotation speed calculated by multiplying the vehicle speed V by a conversion efficiency. The HVECU70subtracts a charge-discharge power demand Pb* of the battery50(that takes a positive value in the case of discharging from the battery50) from the driving power Pdrv* to calculate a required power Pe* required for the vehicle. The HVECU70then sets a target rotation speed Ne* and a target torque Te* of the engine22and torque commands Tm1* and Tm2* of the motors MG1and MG2such as to cause the required power Pe* to be output from the engine22and cause the required torque Tr* to be output to the driveshaft36within the range of the input and output limits Win and Wout of the battery50. The HVECU70then sends the target rotation speed Ne* and the target torque Te* of the engine22to the engine ECU24, while sending the torque commands Tm1* and Tm2* of the motors MG1and MG2to the motor ECU40. When receiving the target rotation speed Ne* and the target torque Te* of the engine22, the engine ECU24performs intake air flow control, fuel injection control and ignition control of the engine22so as to operate the engine22based on the received target rotation speed Ne* and the received target torque Te*. When receiving the torque commands Tm1* and Tm2* of the motors MG1and MG2, the motor ECU40performs switching control of the switching elements of the inverters41and42so as to drive the motors MG1and MG2with the torque commands Tm1* and Tm2*. When a stop condition of the engine22is satisfied in the HV drive mode, for example, when the required power Pe* becomes equal to or less than a stop threshold value Pstop, the hybrid vehicle20stops operation of the engine22and shifts the drive mode to the EV drive mode.

In the EV drive mode, the HVECU70first sets the required torque Tr*, as in the case of the HV drive mode. The HVECU70subsequently sets the torque command Tm1* of the motor MG1to value 0. The HVECU70sets the torque command Tm2* of the motor MG2such as to output the required torque Tr* to the driveshaft36in the range of the input limit Win and the output limit Wout of the battery50. The HVECU70then sends the torque commands Tm1* and Tm2* of the motors MG1and MG2to the motor ECU40. When receiving the torque commands Tm1* and Tm2* of the motors MG1and MG2, the motor ECU40performs switching control of the switching elements of the inverters41and42so as to drive the motors MG1and MG2with the torque commands Tm1* and Tm2*. When a start condition of the engine22is satisfied in the EV drive mode, for example, when the required power Pe* calculated as in the HV drive mode becomes equal to or greater than a start threshold value Pstart that is larger than the stop threshold value Pstop, the hybrid vehicle20starts operation of the engine22and shifts the drive mode to the HV drive mode.

The following describes the operations of the hybrid vehicle20of the embodiment having the configuration described above or more specifically the operations to crank and start the engine22by the motor MG1.FIG. 2is a flowchart showing one example of a start-time control routine performed by the HVECU70of the embodiment. This routine is performed when the start condition of the engine22is satisfied during a run in the EV drive mode.

On start of the start-time control routine, the HVECU70first inputs data required for control, for example, the accelerator position Acc, the vehicle speed V, the rotation speed Ne of the engine22, the rotation speeds Nm1and Nm2of the motors MG1and MG2and the input and output limits Win and Wout of the battery50(step S100). The accelerator position Acc input here is the value detected by the accelerator pedal position sensor84. The vehicle speed V input here is the value detected by the vehicle speed sensor88. The rotation speed Ne of the engine22is the value that is computed based on the crank angle θcr of the engine22from the crank position sensor23and is input from the engine ECU24by communication. The rotation speeds Nm1and Nm2of the motors MG1and MG2are the values that are computed based on the rotational positions θm1and θm2of the rotors of the motors MG1and MG2from the rotational position detection sensors43and44and are input from the motor ECU40by communication. The input and output limits Win and Wout of the battery50are the values that are set based on the battery temperature Tb of the battery50from the temperature sensor51cand the state of charge SOC of the battery50based on the battery current Ib of the battery50from the current sensor51band are input from the battery ECU52by communication.

After inputting the data, the HVECU70sets a required torque Tr* required for driving (to be output to the driveshaft36), based on the input accelerator position Acc and the input vehicle speed V (step S110). According to this embodiment, a procedure of setting the required torque Tr* specifies and stores in advance a relationship between the vehicle speed V and the required torque Tr* with regard to various accelerator positions Acc in the form of a map in the ROM (not shown), and reads and sets the required torque Tr* corresponding to a given accelerator position Acc and a given vehicle speed V from this map. One example of the relationship between the vehicle speed V and the required torque Tr* with regard to various accelerator positions Acc is shown inFIG. 3.

The HVECU70subsequently sets a cranking torque Tst for cranking the engine22to a torque command Tm1* of the motor MG1(step S120). The cranking torque Tst used here is a value set by a cranking torque setting routine described later.

The HVECU70subtracts a torque that is output from the motor MG1and is applied to the driveshaft36via the planetary gear30in the state that the motor MG1is driven with the torque command Tm1*, from the required torque Tr*, so as to calculate a tentative torque Tm2tmp that is a provisional value of a torque command Tm2* of the motor MG2, according to Equation (1) given below (step S130). The HVECU70subsequently divides differences between the input and output limits Win and Wout of the battery50and power consumption (power generation) of the motor MG1, which is obtained by multiplying the torque command Tm1* of the motor MG1by the current rotation speed Nm1, by the rotation speed Nm2of the motor MG2, so as to calculate torque limits Tm2min and Tm2max as upper and lower limits of torque allowed to be output from the motor MG2, according to Equations (2) and (3) given below (step S140). The HVECU70then limits the tentative torque Tm2tmp with the torque limits Tm2min and Tm2max to set the torque command Tm2* of the motor MG2, according to Equation (4) given below (step S150).FIG. 4is a chart illustrating one example of a collinear diagram that shows a dynamic relationship between rotation speed and torque with regard to the rotational elements of the planetary gear30when the engine22is cranked and started by the motor MG1. In the diagram, axis S on the left side shows the rotation speed of the sun gear that is equal to the rotation speed Nm1of the motor MG1; axis C shows the rotation speed of the carrier that is equal to the rotation speed Ne of the engine22; and axis R shows the rotation speed Nr of the ring gear that is equal to the rotation speed Nm2of the motor MG2. Two thick arrows on the axis R indicate a torque that is output from the motor MG1and is applied to a ring gear shaft32avia the planetary gear30and a torque that is output from the motor MG2and is applied to the driveshaft36. Equation (1) is readily introduced from this collinear diagram.
Tm2tmp=Tr*+Tm1*/ρ  (1)
Tm2min=(Win−Tm1*·Nm1)/Nm2  (2)
Tm2max=(Wout−Tm1*˜Nm1)/Nm2  (3)
Tm2*=max(min(Tm2tmp,Tm2max),Tm2min)  (4)

After setting the torque commands Tm1* and Tm2* of the motors MG1an MG2, the HVECU70sends the set torque commands Tm1* and Tm2* of the motors MG1and MG2to the motor ECU40(step S160). When receiving the torque commands Tm1* and Tm2* of the motors MG1and MG2, the motor ECU40performs switching control of the switching elements of the inverters41and42to drive the motors MG1and MG2with the torque commands Tm1* and Tm2*.

The HVECU70subsequently compares the rotation speed Ne of the engine22with a drive start rotation speed Nsteg (step S170). The drive start rotation speed Nsteg denotes a rotation speed for starting the operation of the engine22(fuel injection control and ignition control) and may be, for example, 1000 rpm or 1200 rpm.

When the rotation speed Ne of the engine22is lower than the drive start rotation speed Nsteg, the HVECU70goes back to step S100and repeats the processing of steps S100to S170. When the rotation speed Ne of the engine22becomes equal to or higher than the drive start rotation speed Nsteg, the HVECU70sends start instructions of fuel injection control and ignition control of the engine22to the engine ECU24(step S180). When receiving the start instructions, the engine ECU24starts the fuel injection control and the ignition control of the engine22.

The HVECU70then determines whether the engine22falls into the state of complete explosion (step S190). When the engine22has not yet fallen into the state of complete explosion, the HVECU70goes back to step S100and repeats the processing of steps S100to S190. When the engine22falls into the state of complete explosion, this routine is terminated.

The following describes a process of setting the cranking torque Tst used at step S120in the above start-time control routine.FIG. 5is a flowchart showing one example of a cranking torque setting routine performed by the HVECU70according to the embodiment. This routine is performed concurrently with the start-time control routine ofFIG. 2when the start condition of the engine22is satisfied during a run in the EV drive mode.

On start of the cranking torque setting routine, the HVECU70first sets value 0 to the cranking torque Tst (step S200). The HVECU70subsequently limits the sum of a previously set cranking torque (previous Tst) and a rate value ΔTst1with a relatively large specified torque Tst1in a positive range (in the direction of increasing the rotation speed Ne of the engine22) (upper limit guarding) to set the cranking torque Tst, according to Equation (5) given below (step S210). The specified torque Tst1denotes a maximum value of the cranking torque Tst and is set to a torque for rapidly increasing the rotation speed Ne of the engine22. The rate value ΔTst1denotes a rate value for increasing the cranking torque Tst from the value 0.
Tst=min(previousTst+ΔTst1,Tst1)  (5)

The HVECU70subsequently inputs the rotation speed Ne and the crank angle θcr of the engine22(step S220). The crank angle θcr of the engine22is the value that is detected by the crank position sensor23and is input from the engine ECU24by communication. The rotation speed Ne of the engine22is the value that is computed based on the crank angle θcr of the engine22and is input from the engine ECU24by communication. The embodiment employs the four-cylinder engine22, so that the crank angle θcr is expressed in the range of −90° to 90° (repetitively changed in this range) on the assumption that the top dead center of the compression stroke in each cylinder of the engine22is set to 0°.

After inputting the rotation speed Ne and the crank angle θcr of the engine22, the HVECU70determines whether a predetermined condition is satisfied using the rotation speed and the crank angle θcr of the engine22(steps S230and S240). The predetermined condition denote a condition used to determine whether it is the timing to start decreasing the cranking torque Tst from the specified torque Tst1. According to this embodiment, the HVECU70determines that the predetermined condition is satisfied when both a rotation speed condition that the rotation speed Ne of the engine22is equal to or higher than a predetermined rotation speed Nstmg and a crank angle condition that the crank angle θcr of the engine22is in a predetermined range of θst1to θst2are met. The HVECU70determines that the predetermined condition is satisfied when at least one of the rotation speed condition and the crank angle condition is not met, and goes back to step S210.

The processing of steps S210to S240waits for satisfying the predetermined condition, while increasing the cranking torque Tat from the value 0 to the specified torque Tst1and keeping the cranking torque Tst at the specified torque Tst1by the rate process using the rate value ΔTst1. According to this embodiment, the predetermined range of θst1to θst2is a range specified in advance by experiment or by analysis such that the maximum vibration becomes equal to or lower than allowable upper limit vibration when the torque of the motor MG1(cranking torque Tst) starts decreasing in the state that the rotation speed Ne of the engine22is equal to or higher than the predetermined rotation speed Nstmg. The predetermined rotation speed Nstmg may be, for example, 300 rpm, 350 rpm or 400 rpm. The predetermined range of θst1to θst2may be for example, a range of 50°, 55° or 60° to 70°, 75° or 80°. The configuration of this embodiment determines whether the predetermined condition is satisfied using both the rotation speed condition and the crank angle condition. This configuration suppresses the occurrence of significantly large vibration when the torque of the motor MG1(cranking torque Tst) starts decreasing from the specified torque Tst1, compared with the configuration of determining whether the predetermined condition is satisfied using only the rotation speed condition.

When the predetermined condition is satisfied in the course of repeating the processing of steps S210to S240, the HVECU70sets the rotation speed Ne of the engine22at the time when the predetermined condition is satisfied to a satisfaction time rotation speed Neset (step S245). The HVECU70subsequently sets a rate value ΔTst2based on the satisfaction time rotation speed Neset (step S250). The rate value ΔTst2denotes a rate value for decreasing the cranking torque Tst from the specified torque Tst1. According to this embodiment, a procedure of setting the rate value ΔTst2specifies and stores in advance a relationship between the satisfaction time rotation speed Neset and the rate value ΔTst2in the form of a map in the ROM (not shown) and reads the rate value ΔTst2corresponding to a given satisfaction time rotation speed Neset from this map. One example of the relationship between the satisfaction time rotation speed Neset and the rate value ΔTst2is shown inFIG. 6. As illustrated, the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Neset. The reason of such setting will be described later.

The HVECU70subsequently limits the result of subtraction of the rate value ΔTst2from the previously set cranking torque (previous Tst) with a specified torque Tst2that is smaller than the specified torque Tst1in the positive range (lower limit guarding) to set the cranking torque Tst, according to Equation (6) given below (step S260). The specified torque Tst2denotes a torque for increasing the rotation speed Ne of the engine22to or above the drive start rotation speed Nsteg, while suppressing an increase in power consumption by the motor MG1.
Tst=max(previousTst−ΔTst2,Tst2)  (6)

The HVECU70subsequently inputs the rotation speed Ne of the engine22(step S270) and determines whether the rotation speed Ne of the engine22is equal to or higher than the drive start rotation speed Nsteg (step S280). When the rotation speed Ne of the engine22is lower than the drive start rotation speed Nsteg, the HVECU70goes back to step S260. The processing of steps S260to S280waits for increasing the rotation speed Ne of the engine22to or above the drive start rotation speed Nsteg, while decreasing the cranking torque Tst from the specified torque Tst1to the specified torque Tst2and keeping the cranking torque Tst at the specified torque Tst2by the rate process using the rate value ΔTst2.

When the rotation speed Ne of the engine22increases to or above the drive start rotation speed Nsteg in the course of repeating the processing of steps S260to S280, the HVECU70limits the result of subtraction of a rate value ΔTst3from the previously set cranking torque (previous Tst) with value 0 (lower limit guarding) to set the cranking torque Tst, according to Equation (7) given below (step S290). The rate value ΔTst3denotes a rate value for decreasing the cranking torque Tst from the specified torque Tst2.
Tst=max(previousTst−ΔTst3,0)  (7)

The HVECU70then determines whether the engine22falls into the state of complete explosion (step S300). When the engine22has not yet fallen into the state of complete explosion, the HVECU70goes back to step S290. The processing of steps S290and S300waits for the engine22falling into the state of complete explosion, while decreasing the cranking torque Tst from the specified torque Tst2to the value 0 and keeping the cranking torque Tst at the value 0 by the rate process using the rate value ΔTst3. When the engine22falls into the state of complete explosion in the course of repeating the processing of steps S290and S300, this routine is terminated.

The following describes the reason why the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Neset at step S250. In the process of cranking and starting the engine22by the motor MG1, the time period between start of cranking the engine22by the motor MG1and satisfaction of the predetermined condition (hereinafter referred to as early part of starting time period) and the rotation amount of the engine22(number of strokes of intake, compression, expansion and exhaust, i.e., total emission) in the early part of starting time period are varied according to the crank angle θcr and the temperature (friction) of the engine22at the start time of starting the engine22.

On the assumption that the rate value ΔTst2is a fixed value, the above variations in the early part of starting time period leads to variations of the time period between start of cranking the engine22by the motor MG1and completion of starting the engine22(hereinafter referred to as entire starting time period) and the rotation amount of the engine22in the entire starting time period. This is likely to cause deterioration of drivability (acceleration performance) and emission.

For example, it is assumed that a relatively small fixed value is used as the rate value ΔTst2(gradually decreasing the magnitude of the cranking torque Tst) and that the satisfaction time rotation speed Neset is a high rotation speed. The high satisfaction time rotation speed Neset basically provides the large rotation amount of the engine22in the early part of starting time period. Using the relatively small rate value ΔTst2results in further increasing the rotation amount of the engine22(total emission) in the entire starting time period and is likely to cause deterioration of emission.

In another example, it is assumed that a relatively large fixed value is used as the rate value ΔTst2(rapidly decreasing the magnitude of the cranking torque Tst) and that the satisfaction time rotation speed Neset is a low rotation speed. The low satisfaction time rotation speed Neset basically shortens the early part of starting time period. Using the relatively large rate value ΔTst2, however, requires a relatively long time duration for a subsequent increase of the rotation speed Ne of the engine22. This results in extending the entire starting time period and is likely to cause deterioration of drivability (acceleration performance).

Based on the above discussion, the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Neset according to the embodiment. This suppresses the variations of the entire starting time period and the rotation amount of the engine22(total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

FIG. 7is a diagram illustrating one example of time changes of the torque Tm1of the motor MG1and the rotation speed Ne and the crank angle θcr of the engine22in the process of cranking and starting the engine22by the motor MG1. In the diagram, solid line curves indicate case a (where the predetermined condition is satisfied at a time t12a), and broken line curves indicate case b (where the predetermined condition is satisfied at a time t12b). As shown by the solid line curves and the broken line curves, when the start condition of the engine22is satisfied at a time t11, the rate process using the rate value ΔTst1is performed to increase the torque Tm1of the motor MG1(cranking torque Tst) from the value 0 to the positive specified torque Tst1and keep the cranking torque Tst at the specified torque Tst1. This results in rapidly increasing the rotation speed Ne of the engine22. The predetermined condition is satisfied, i.e., the rotation speed Ne of the engine22is equal to or higher than the predetermined rotation speed Nstmg and the crank angle θcr of the engine22is in the predetermined range of θst1to θst2, at the time t12ain the case a and at the time t12bin the case b. The rate process using the rate value ΔTst2is then performed to decrease the torque Tm1of the motor MG1from the specified torque Tst1to the smaller specified torque Tst2and keep the torque Tm1at the smaller specified torque Tst2. This results in increasing the rotation speed Ne of the engine22, while reducing the power consumption of the motor MG1and decreasing the torque that is output from the motor MG1and is applied to the driveshaft36via the planetary gear30. When the rotation speed Ne of the engine22becomes equal to or higher than the drive start rotation speed Nsteg at a time t13, operations of the engine22(fuel injection control and ignition control) are started. Concurrently the rate process using the rate value ΔTst3is performed to decrease the torque Tm1of the motor MG1from the specified torque Tst2to the value 0 and keep the torque Tm1at the value 0. When the engine22falls into the state of complete explosion, the starting process of the engine22is completed and the hybrid vehicle20starts running in the HV drive mode. According to this embodiment, the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Nest (i.e., the rotation speed Ne of the engine22at the time t12aor at the time t12b). This suppresses variations of the entire starting time period (i.e., the time duration from the time t11to the time t13) and the rotation amount of the engine22(total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

The hybrid vehicle20of the embodiment described above controls the motor MG1in the following manner in the process of cranking and starting the engine22by the motor MG1. Until the predetermined condition is satisfied, i.e., until the rotation speed Ne of the engine22is equal to or higher than the predetermined rotation speed Nstmg and the crank angle θcr of the engine22is in the predetermined range of θst1to θst2, the motor MG1is controlled to increase the torque of the motor MG1from the value 0 to the positive specified torque Tst1and keep the torque of the motor MG1at the specified torque Tst1by the rate process using the rate value ΔTst1. After the predetermined condition is satisfied, the motor MG1is controlled to decrease the torque of the motor MG1from the specified torque Tst1by the rate process using the rate value ΔTst2. In this control of the motor MG1, the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Nest that denotes the rotation speed Ne of the engine22when the predetermined condition is satisfied. This suppresses variations of the entire starting time period and the rotation amount of the engine22(total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

The hybrid vehicle20of the embodiment performs the cranking torque setting routine ofFIG. 5to crank and start the engine22by the motor MG1. According to modifications, one of cranking torque setting routines ofFIG. 8toFIG. 10may be performed alternatively. The following sequentially describes these modified cranking torque setting routines.

The routine ofFIG. 8is described. The routine ofFIG. 8is similar to the routine ofFIG. 5except addition of step S242B and replacement of steps S245and S250in the routine ofFIG. 5with steps S245B and S250B. The like processes in the routine ofFIG. 8to those in the routine ofFIG. 5are expressed by the like step numbers and their detailed description is omitted.

In the routine ofFIG. 8, when the predetermined condition is satisfied in the course of repeating the processing of steps S210to S240after the processing of step S200, the HVECU70inputs a rotational acceleration αe of the engine22(step S242B) and sets the input rotational acceleration αe of the engine22(rotational acceleration αe of the engine22when the predetermined condition is satisfied) to a satisfaction time rotational acceleration αeset (step S245B). The HVECU70subsequently sets a rate value ΔTst2based on the satisfaction time rotational acceleration αeset (step S250B) and performs the processing of and after step S260. The rotational acceleration αe of the engine22is the value computed from the current value and the previous value of the rotation speed Ne of the engine22. According to this modification, a procedure of setting the rate value ΔTst2specifies and stores in advance a relationship between the satisfaction time rotational acceleration αeset and the rate value ΔTst2in the form of a map in the ROM (not shown) and reads the rate value ΔTst2corresponding to a given satisfaction time rotational acceleration αeset from this map. One example of the relationship between the satisfaction time rotational acceleration αeset and the rate value ΔTst2is shown inFIG. 11. As illustrated, the rate value ΔTst2is set to increase with an increase in satisfaction time rotational acceleration αeset. This is based on that the higher satisfaction time rotational acceleration αeset is likely to provide the higher satisfaction time rotation speed Neset and that the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Neset according to the above embodiment. Like the above embodiment, setting the rate value ΔTst2in this manner suppresses the variations of the entire starting time period and the rotation amount of the engine22(total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

The routine ofFIG. 9is described. The routine ofFIG. 9is similar to the routine ofFIG. 5except addition of step S202C and replacement of steps S245and S250in the routine ofFIG. 5with steps S245C and S250C. The like processes in the routine ofFIG. 9to those in the routine ofFIG. 5are expressed by the like step numbers and their detailed description is omitted.

In the routine ofFIG. 9, after setting the cranking torque Tst to the value 0 (step S200), the HVECU70starts counting a cranking time ta (step S202C). The cranking time ta denotes a time period since cranking the engine22by the motor MG1is started.

When the predetermined condition is satisfied in the course of repeating the processing of steps S210to S240, the HVECU70sets the cranking time ta on satisfaction of the predetermined condition to a satisfaction time cranking time taset (step S245C). The HVECU70subsequently sets a rate value ΔTst2based on the satisfaction time cranking time taset (step S250C) and performs the processing of and after step S260. According to this modification, a procedure of setting the rate value ΔTst2specifies and stores in advance a relationship between the satisfaction time cranking time taset and the rate value ΔTst2in the form of a map in the ROM (not shown) and reads the rate value ΔTst2corresponding to a given satisfaction time cranking time taset from this map. One example of the relationship between the satisfaction time cranking time taset and the rate value ΔTst2is shown inFIG. 12. As illustrated, the rate value ΔTst2is set to increase with an increase in satisfaction time cranking time taset. This is based on that the longer satisfaction time cranking time taset is likely to provide the higher satisfaction time rotation speed Neset and that the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Neset according to the above embodiment. Like the above embodiment, setting the rate value ΔTst2in this manner suppresses the variations of the entire starting time period and the rotation amount of the engine22(total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

The routine ofFIG. 10is described. The routine ofFIG. 10is similar to the routine ofFIG. 5except addition of step S212D to S216D and replacement of steps S245and S250in the routine ofFIG. 5with steps S245D and S250D. The like processes in the routine ofFIG. 10to those in the routine ofFIG. 5are expressed by the like step numbers and their detailed description is omitted.

In the routine ofFIG. 10, after setting the cranking torque Tst according to Equation (5) given above (step S210), the HVECU70determines whether the cranking torque Tst is equal to the specified torque Tst1and determines whether the previous cranking torque (previous Tst) is smaller than the specified torque Tst1(steps S212D and S214D). This determines whether it is immediately after the time when the cranking torque Tst reaches the specified torque Tst1.

When the cranking torque Tst is equal to the specified torque Tst1and the previous cranking torque (previous Tst) is smaller than the specified torque Tst1, the HVECU70determines that it is immediately after the time when the cranking torque Tst reaches the specified torque Tst1. The HVECU70then starts counting a maximum torque time tb (step S216D) and performs the processing of and after step S220. The maximum torque time tb denotes a time period since start of outputting the specified torque Tst1(maximum value of the cranking torque Tst) from the motor MG1.

When the cranking torque Tst is smaller than the specified torque Tst1at step S212D or when the cranking torque Tst is equal to the specified torque Tst1at step S212D and the previous cranking torque (previous Tst) is also equal to the specified torque Tst1at step S214D, the HVECU70determines that it is not immediately after the time when the cranking torque Tst reaches the specified torque Tst1. The HVECU70then skips the processing of step S216D and performs the processing of and after step S220.

When the predetermined condition is satisfied in the course of repeating the processing of steps S210to S240, the HVECU70sets the maximum torque time tb on satisfaction of the predetermined condition to a satisfaction time torque time tbset (step S245D). The HVECU70subsequently sets a rate value ΔTst2based on the satisfaction time torque time tbset (step S250D) and performs the processing of and after step S260. According to this modification, a procedure of setting the rate value ΔTst2specifies and stores in advance a relationship between the satisfaction time torque time tbset and the rate value ΔTst2in the form of a map in the ROM (not shown) and reads the rate value ΔTst2corresponding to a given satisfaction time torque time tbset from this map. One example of the relationship between the satisfaction time torque time tbset and the rate value ΔTst2is shown inFIG. 13. As illustrated, the rate value ΔTst2is set to increase with an increase in satisfaction time torque time tbset. This is based on that the longer satisfaction time torque time tbset is likely to provide the higher satisfaction time rotation speed Neset and that the rate value ΔTst2is set to increase with an increase in satisfaction time rotation speed Neset according to the above embodiment. Like the above embodiment, setting the rate value ΔTst2in this manner suppresses the variations of the entire starting time period and the rotation amount of the engine22(total emission) in the entire starting time period. This results in suppressing deterioration of drivability (acceleration performance) and emission.

In the hybrid vehicle20of the embodiment, the power from the motor MG2is output to the driveshaft36linked with the drive wheels38aand38b. As illustrated in a hybrid vehicle120according to one modification shown inFIG. 14, however, the power from the motor MG2may be output to another axle (axle linked with wheels39aand39bshown inFIG. 14) that is different from an axle connected with a driveshaft36(i.e., axle linked with drive wheels38aand38b).

In the hybrid vehicle20of the embodiment, the power from the engine22is output via the planetary gear30to the driveshaft36linked with the drive wheels38aand38b. As illustrated inFIG. 15, however, a hybrid vehicle220according to another modification may be equipped with a pair-rotor motor230that includes an inner rotor232connected with a crankshaft of the engine22via a damper28and an outer rotor234connected with a driveshaft36linked with drive wheels38aand38b. The pair-rotor motor230transmits part of the power from the engine22to the driveshaft36, while converting the remaining power to electric power.

In the hybrid vehicle20of the embodiment, the power from the engine22is output via the planetary gear30to the driveshaft36linked with the drive wheels38aand38b, while the power from the motor MG2is output to the driveshaft36. As illustrated in a hybrid vehicle320according to another modification shown inFIG. 16, however, a motor MG may be connected via a transmission330with a driveshaft36that is linked with drive wheels38aand38b, and an engine22may be connected via a damper28with a rotating shaft of the motor MG. This configuration causes the power from the engine22to be output to the driveshaft36via the rotating shaft of the motor MG and the transmission330, while causing the power from the motor MG to be output to the driveshaft36via the transmission330.

Any of the first, the second and the third hybrid vehicles of the invention may include a planetary gear including three rotational elements that are respectively connected with a driveshaft linked with an axle, an output shaft of the engine and a rotating shaft of the motor, and a second motor that is configured to transmit electric power to and from the battery and input and output power from and to the driveshaft.

The following describes the correspondence relationship between the primary components of the embodiment and the primary components of the invention described in Summary of Invention. The engine22of the embodiment corresponds to the “engine”; the motor MG1corresponds to the “motor”; and the battery50corresponds to the “battery”. The HVECU70performing the start-time control routine ofFIG. 2and the cranking torque setting routine ofFIG. 5and the motor ECU40controlling the motor MG1based on the torque command Tm1* from the HVECU70correspond to the “controller”.

The correspondence relationship between the primary components of the embodiment and the primary components of the invention, regarding which the problem is described in Summary of Invention, should not be considered to limit the components of the invention, regarding which the problem is described in Summary of Invention, since the embodiment is only illustrative to specifically describes the aspects of the invention, regarding which the problem is described in Summary of Invention. In other words, the invention, regarding which the problem is described in Summary of Invention, should be interpreted on the basis of the description in the Summary of Invention, and the embodiment is only a specific example of the invention, regarding which the problem is described in Summary of Invention.

The embodiment discussed above is to be considered in all aspects as illustrative and not restrictive. There may be many modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention. The scope and spirit of the present invention are indicated by the appended claims, rather than by the foregoing description.

INDUSTRIAL APPLICABILITY

The present invention is applicable to, for example, the manufacturing industries of hybrid vehicles.