Electric force transmission device

In an electric force transmission device employing two motor generators and a differential device having at least three rotating members and having two degrees of freedom, the first rotating member is coupled to the first motor generator, the second rotating member is coupled to the second motor generator, and the third rotating member is coupled to an output shaft and laid out to be located between the first and the second rotating members on an aligmnent chart. Also, a controller is configured to control the motor generators such that, when the output shaft is driven from its stopped state, before the driving is started, the first and second motor generators are rotated oppositely to each other, while keeping a rotational speed of the output shaft at the stopped state.

TECHNICAL FIELD

The present invention relates to an electric force transmission device, which is capable of driving an output system by only a power from two motor generators and which is useful for a hybrid transmission to have it built-in.

BACKGROUND ART

An electric force transmission device suitable for a hybrid vehicle employing an engine and a motor both serving as a driving power source and described in the following patent publication designated by “Document 1”, is generally known as a conventional electric force transmission device.

That is, this type of electric force transmission device is designed to command an electric force needed to merely achieve a required driving force to a motor without fully taking account of a state of a circuit provided to control the driving of the motor.

SUMMARY OF THE INVENTION

However, in the electric force transmission device disclosed in this document, the state of the circuit, provided to control the driving of the motor, is not taken into account. When electric force transmission is started (or during a starting period in case of on-vehicle electric force transmission device) from an output rotational speed of zero, there is a necessity of a torque rise from the state of the output rotational speed of zero. Larger torque is required, as compared to the electric force transmission under a condition where a certain output rotational speed has already been reached. Thus, there are some problems as described hereunder.

That is, the electric force transmission is started from the output rotational speed of zero, and therefore at the initial stage of the force transmission a component of direct current flows through the motor in a lock state where the motor does not yet rotate or the motor begins to rotate slowly. Thus, there is an increased tendency for the component of direct current to flow through a biased phase of phases of the motor.

Such a tendency becomes more remarkable, as the magnitude of transmitted torque increases. This is because the greater the transmitted torque, the greater the current value of direct current.

As a result of this, the heating value of a particular part of the motor-drive control circuit provided to control the driving of the motor, through which an electric current flows biasedly, tends to become large. Owing to the generated heat, a limitation on an electric current applied to the motor is made, and thus it is impossible to provide an adequate electric force, thereby resulting in a lack of output torque.

The present invention is premised on an electric force transmission device capable of driving an output system by an electric force from two motor generators. It is, therefore, an object of the invention to provide or propose an electric force transmission device capable of avoiding the previously-described disadvantages of the prior art, by dispersing a load into the motor-drive control circuits of these motor generators, during electric force transmission from the state of an output rotational speed of zero, during which the previously-discussed disadvantages may occur.

According to the present invention, an electric force transmission device comprises a differential device having three or more rotating members and having two degrees of freedom. An output to a drive system is transmitted or connected to the rotating member located on an inside on an alignment chart among these rotating members. Two motor generators are coupled to the rotating members located on both sides of the rotating member related to the output on the alignment chart, so that the drive system can be driven by only a power from the motor generators. The electric force transmission device is characterized in that when the driving achieved by only the power from the motor generators is equivalent to driving started from a state of an output rotational speed of zero, before the driving is started, the two motor generators are rotated oppositely to each other, while keeping the state of the output rotational speed of zero.

DETAILED DESCRIPTION

According to the electric force transmission device of the invention of the present application, when the driving achieved by only a power from two motor generators is equivalent to driving started from a state of an output rotational speed of zero, the two motor generators are rotated oppositely to each other, while keeping the state of the output rotational speed of zero. Therefore, when a driving force command is generated or issued and then the corresponding motor generator torques are generated, these motor generators are rotated oppositely to each other. That is, there is no risk that an electric current flows through a biased phase of phases of each of the motor generators, and thus it is possible to avoid the problem that the electric current flows biasedly through a particular part of the motor-drive control circuit provided to control the driving of each of the motor generators and as a result the heating value of the particular part becomes large. Additionally, it is possible to avoid the problem of a lack of output torque occurring owing to a limitation on the applied electric current to each of the motor generators.

Each of the embodiments of the electric force transmission device of the present invention will be hereinafter described in detail in reference to the drawings.

A drive system of a vehicle is constructed by a hybrid transmission1including two motor generators MG1and MG2, an engine2of the input side of hybrid transmission1, an engine clutch E/C interleaved between hybrid transmission1and engine2, a differential gear mechanism3of the output side of hybrid transmission1for dividing an output from hybrid transmission1into two components, and left and right drive wheels4L and4R to which the two components (two output components) divided by differential gear mechanism3are transmitted.

Hybrid transmission1has a construction as shown inFIG. 1, which is useful as a transaxle for the use of a front-engine front-wheel-drive vehicle (a FF vehicle), and involves therein differential gear mechanism3.

As can be seen from the detailed cross section ofFIG. 1, hybrid transmission1employs two single planetary gear sets (differential devices)21and22coaxially aligned with each other and arranged in the axial direction (the left-to-right direction in the drawing).

Planetary gear set21, located closer to engine2, is comprised of a ring gear R1, a sun gear S1, and a pinion P1, which is in meshed-engagement with these gears.

On the other hand, planetary gear set22, spaced apart from engine2, is comprised of the ring gear R1, a sun gear S2, and a pinion P2, which is in meshed-engagement with these gears.

Pinion P1of planetary gear set21is formed as a long pinion extending toward planetary gear set22. Pinion P2of planetary gear set22is formed as a large-diameter short pinion. Small-diameter long pinion P1is in meshed-engagement with large-diameter short pinion P2. These pinions P1and P2are rotatably supported on a common carrier C. That is, planetary gear sets21and22construct a so-called Ravigneaux planetary gear set.

The Ravigneaux planetary gear set corresponds to a differential device of the present invention. In the shown embodiment, the differential device includes four rotating members. However, in the case of a non-engine equipped vehicle, the differential device may be constructed only by three rotating members.

A compound current two-phase motor23is installed far away from engine2in such a manner as to be sandwiched between the engine and the Ravigneaux planetary gear set. The motor is accommodated in a transmission case24together with the Ravigneaux planetary gear set.

Compound current two-phase motor23is comprised of an inner rotor23riand an annular outer rotor23rosurrounding the inner rotor, such that these rotors are coaxially arranged with each other and rotatably supported in transmission case24. An annular stator23sis coaxially disposed in an annular space defined between inner rotor23riand outer rotor23ro. The annular stator is fixedly connected to transmission case24.

Compound current two-phase motor23is designed to construct a first motor generator MG1by outer rotor23roand annular stator23sand also to construct a second motor generator MG2by annular stator23sand inner rotor23ri.

The first motor generator MG1(outer rotor23ro) is connected to sun gear S1(corresponding to the first rotating member) of the Ravigneaux planetary gear set. The second motor generator MG2(inner rotor23ri) is connected to sun gear S2(corresponding to the second rotating member) of the Ravigneaux planetary gear set.

Ring gear R1(corresponding to the fourth rotating member) serves as an input element and is connectable via engine clutch E/C to engine2.

Carrier C (corresponding to the third rotating member) serves as an output element. An output gear25is coaxially arranged with and integrally connected to the carrier. A counter gear26is in meshed-engagement with output gear25. Counter gear26is fixedly connected to a counter shaft27. A final-drive pinion28is further connected to counter shaft27. Final-drive pinion28is in meshed-engagement with a final-drive ring gear29connected to differential gear mechanism3.

Hybrid transmission1discussed above in reference toFIG. 1can be represented by an alignment chart ofFIG. 2. In the alignment chart, symbol In denotes an input from engine2, a symbol Out denotes an output to drive wheels4L and4R, each of symbols α and β means a ratio of distances between the rotating members, determined by a ratio of the number of teeth of planetary gear set21and the number of teeth of planetary gear set22.

A lever HB ofFIG. 2shows a state of the lever during a hybrid running mode in which power from engine2is input into ring gear R1with engine clutch E/C engaged, power from motor generator MG1is input into sun gear S1and power from motor generator MG2is input into sun gear S2, and thus the power from engine2and the summed power from both of motor generators MG1-MG2are directed to the output Out in the drive system so as to generate or extract a normal rotation from the output Out. During the hybrid running mode, it is possible to steplessly vary the transmission ratio by way of motor generator control for motor generators MG1-MG2.

A lever EV ofFIG. 2shows a state of the lever during an electrical vehicle (EV) running mode in which engine2is uncoupled from hybrid transmission1with engine clutch E/C disengaged, only the power from motor generators MG1and MG2are directed through sun gears S1and S2of planetary gear sets21and22to the output Out in the drive system so as to generate or extract a normal rotation from the output Out. During the EV running mode as well as during the hybrid running mode, it is possible to steplessly vary the transmission ratio by way of motor generator control for motor generators MG1-MG2.

Furthermore, a lever REV ofFIG. 2shows a state of the lever during a reverse running mode in which engine2is uncoupled from hybrid transmission1with engine clutch E/C disengaged, motor generator MG1is driven in its normal-rotational direction and simultaneously motor generator MG2is driven in its reverse-rotational direction, while keeping the rotational speed of ring gear R1coupled to engine2at “0” as indicated by the lever REV inFIG. 2, so as to generate or extract a reverse rotation from the output Out, by using only the motor generators MG1and MG2as a power source.

The above-mentioned control for hybrid transmission1and the above-mentioned control for engine2(containing engine clutch E/C) are executed by a control system shown inFIG. 3.

Reference sign31denotes a hybrid controller capable of executing integrated control for the hybrid transmission as well as engine2. Hybrid controller31generates or supplies commands regarding a target torque tTe and a target speed tNe of engine2and commands regarding a target torque tTc and a target speed tNc of engine clutch E/C to an engine controller32.

Engine controller32controls operating conditions of engine2so that the target values tTe and tNe are both achieved, and also controls the engagement force of engine clutch E/C so that target torque tTc and target speed tNc are both achieved.

Hybrid controller31is further designed to generate or supply command signals regarding a target torque tT1and a target speed tN1of motor generator MG1and a target torque tT2and a target speed tN2of motor generator MG2to a motor controller33.

Motor controller33controls each of motor generators MG1-MG2by means of an inverter34and a battery35, so that target torques tT1and tT2and target speeds tN1and tN2are all achieved.

The present invention relates to a technique of power transmission of motor generators (MG1, MG2) during the electrical vehicle (EV) running mode as exemplified by the lever EV inFIG. 2. Specifically, the key point of the invention is to prevent an electric current from flowing biasedly through a particular part of a motor-drive control circuit provided to control the driving of each of the motor generators, and thus to avoid an inadequate electric force occurring due to a limitation on an electric current applied to each of the motor generators, arising from the generated heat, when electric force transmission is started so as to initiate the EV running mode by way of electric forces produced by motor generators MG1-MG2from the state (the standstill state or the stopped state) of the rotational speed of the output Out of zero.

In the system of the shown embodiment, in order to execute the ordinary control as well as the control that the present invention assumes an aim, hybrid controller31receives a signal from an accelerator opening sensor36that detects an accelerator opening APO in terms of an accelerator-pedal depression amount, a signal from a vehicle speed sensor37that detects vehicle speed VSP (proportional to an output rotational speed No), a signal from an engine speed sensor38that detects engine speed Ne, and a signal from a mode sensor39that detects a selected shift mode.

Hybrid controller31executes the control program shown inFIG. 4on the basis of input information from these sensors, when the driving or propelling is started from the state of the output rotational speed of zero (the state of No=0 is determined based on the signal from sensor37), and additionally the selected range mode (the selected range mode is determined based on the signal from sensor39) corresponds to a sporty mode at which there is an increased tendency for a low-speed side transmission ratio to be selected or the vehicle is conditioned in a state where a state of charge SOC (an electric power that can be carried out or delivered) of battery35is high and thus a large torque is required.

In contrast, when the driving or propelling is started from the state of the output rotational speed of zero (the state of No=0 is determined based on the signal from sensor37), and additionally the selected range mode (the selected range mode is determined based on the signal from sensor39) corresponds to an economy mode (a normal shift mode) at which there is an increased tendency for a high-speed side transmission ratio to be selected and thus a small or middle torque is required, the hybrid controller executes the control program shown inFIG. 6on the basis of input information from these sensors.

First, the control program ofFIG. 4is explained hereunder. This control program is executed under a condition where the driving is started from the state of the output rotational speed of zero (i.e., No=0), and additionally a large amount of torque is required.

At step S1, the following processing is repeatedly executed for a time period during which it is determined based on accelerator opening APO through step S2that there is no driving force command input.

That is, as shown inFIG. 5a, calculated are lever correction torques ΔT1and ΔT2for motor generators MG1and MG2, needed to provide a lever state that a rotational speed Ni of ring gear R1serving as the input element has been adjusted to a predetermined normal-rotational speed Niref (e.g., 3 rad/sec in the shown embodiment), while keeping a standstill state of the output rotational speed of zero (i.e., No=0) and the output torque of zero (i.e., To=0).

The reason for keeping rotational speed Ni of ring gear R1at predetermined normal-rotational speed Niref is that, in the system configuration of the embodiment, the state where rotational speed Ni is predetermined normal-rotational speed Niref (e.g., 3 rad/sec) and additionally the output rotational speed No is equal to zero (No=0) corresponds to a particular state where motor generators MG1-MG2can output motor torques rapidly, while enabling the most efficient rotational speed relationship. That is, predetermined normal-rotational speed Niref is different depending on the motor performance and the gear ratio. However, there is an innumerable combination of operating points of two motor generators MG1-MG2, satisfying the state of the output rotational speed of zero (No=0), and thus it is desirable to set the target speeds like this embodiment.

In calculating the above-mentioned lever correction torques ΔT1and ΔT2, a lever correction torque ΔTiref on ring gear R1, needed to bring the lever to the inclined state shown inFIG. 5a, is first calculated based on the actual rotational speed Ni and predetermined rotational speed Niref (e.g., 3 rad/sec). Second, this lever correction torque ΔTiref is converted into lever correction torques ΔT1and ΔT2on motor generators MG1-MG2by way of the following gear ratio (α, β) conversion.
ΔT1=(α+1)·J1·ΔTiref
ΔT2=−β·J2·ΔTiref
where J1denotes a rotational inertia including motor generator MG1, and J2denotes a rotational inertia including motor generator MG2.

Step S2determines based on accelerator opening APO that any driving force command has not yet been input, unless the driving force command is output due to an increase in accelerator opening APO from its lowest opening, caused by the driver's accelerator-pedal depression. In such a case, the routine returns to step S1, and the lever state shown inFIG. 5ais maintained.

Thus, the output rotational speed remains kept zero (i.e., No=0) and the output torque remains kept zero (i.e., To=0), and therefore the vehicle is kept in the standstill state.

When the driver depresses or pushes down the accelerator pedal for starting the vehicle and thus driving force command is generated or issued due to an increase in accelerator opening APO from the lowest opening, the control routine proceeds from step S2to step S3, at which driving force command achievement torques T1and T2for motor generators MG1-MG2, needed to achieve a target torque tTo (a driving force command value) on the output Out, which target torque is determined based on accelerator opening APO and vehicle speed VSP, are calculated from the following gear ratio (α, β) conversion.
T1=[β/(α+β+1)]·tTo
T2=[(α+1)/(α+β+1)]·tTo

As seen from the following expressions, the summed value of driving force command achievement torque T1and the previously-noted lever correction torque ΔT1is set as target torque tT1of motor generator MG1, whereas the summed value of driving force command achievement torque T2and the previously-noted lever correction torque ΔT2is set as target torque tT2of motor generator MG2. These target torques, i.e., the summed values, are output into motor controller33(see FIG.3).
tT1=ΔT1+T1
tT2=ΔT2+T2

Thus, as shown inFIG. 5b, for the same lever as shown inFIG. 5a, regarding both ends of the lever (that is, on motor generators MG1-MG2), the action of torques ΔT1and ΔT2shown inFIG. 5ais replaced by the action of torques ΔT1+T1and ΔT2+T2on the motor generators. Therefore, output torque To corresponding to target torque tTo is generated.

As a result of this, at step S4, as shown inFIG. 5c, it is possible to attain a lever translating operation that the lever on the alignment chart is translated while being kept at the same inclination as each of the levers shown inFIGS. 5a-5b. Thus, the vehicle can be started or propelled by driving the wheels.

According to the present embodiment, when the driving achieved by only the power from motor generators MG1-MG2is equivalent to driving started from a state of an output rotational speed of zero, before a driving force command is input, as seen inFIG. 5a, the two motor generators MG1-MG2are rotated oppositely to each other by respective torques ΔT1and ΔT2, while keeping the state of the output rotational speed of zero (i.e., No=0). Therefore, when the driving force command is generated or issued and then the corresponding motor generator torques T1and T2are generated, these motor generators MG1-MG2are rotated oppositely to each other.

Therefore, there is no risk that an electric current flows through a biased phase of phases of each of motor generators MG1-MG2, and thus it is possible to avoid the problem that the electric current flows biasedly through a particular part of the motor-generator-drive control circuit provided to control the driving of each of the motor generators and as a result the heating value of the particular part becomes large. Additionally, it is possible to avoid the problem of a lack of output torque occurring owing to a limitation on the applied electric current to each of the motor generators.

Furthermore, after the driving force command has been input, the summed value of driving force command achievement torque T1and lever correction torque ΔT1is set as target torque tT1of motor generator MG1, whereas the summed value of driving force command achievement torque T2and lever correction torque ΔT2is set as target torque tT2of motor generator MG2. Thus, as can be seen fromFIGS. 5b-5c, it is possible to initiate electric force transmission while keeping the inclined state of the lever shown inFIG. 5a, needed to achieve the previously-described operation and effects. There is no risk that motor generators MG1-MG2are loaded at the initial stage of electric force transmission so that the rotational speeds of the motor generators become zero, and thus it is possible to more certainly achieve the previously-described operation and effects.

Next, the control program ofFIG. 6is explained hereunder. This control program is executed under a condition where the driving is started from the state of the output rotational speed of zero, but a small or middle amount of torque is required. The former-half condition (i.e., No=0) is similar to that ofFIG. 4. However, the latter-half condition (i.e., the small or middle torque requirement) differs from the large torque requirement ofFIG. 4.

At step S11, in the same manner as step S1ofFIG. 4discussed above in reference to the alignment chart ofFIG. 5a, calculated are lever correction torques ΔT1and ΔT2for motor generators MG1and MG2, needed to provide a lever state that a rotational speed Ni of ring gear R1serving as the input element is brought or adjusted to a predetermined normal-rotational speed Niref (e.g., 3 rad/sec in the shown embodiment), while keeping a standstill state of the output rotational speed of zero (i.e., No=0) and the output torque of zero (i.e., To=0).

Thus, as can be seen fromFIG. 7a, lever correction torques ΔT1and ΔT2are applied to respective motor generators MG1-MG2. As shown inFIG. 7b, the lever on the alignment chart displaces with its rotary motion about the output Out, while keeping a standstill state of the output rotational speed of zero (i.e., No=0) and the output torque of zero (i.e., To=0).

As can be seen fromFIG. 7b, after the lever has been brought to a lever state or an inclined state that rotational speed Ni of ring gear R1serving as the input element has been adjusted to a set rotational speed (e.g., 1 rad/sec in the this embodiment) less than the predetermined normal-rotational speed Niref (3 rad/sec), the routine advances from step S12to step S13, without returning to step S11.

At step S13, driving force command achievement torques T1and T2for motor generators MG1-MG2, needed to achieve a target torque tTo (a driving force command value) on the output Out, which target torque is determined based on accelerator opening APO and vehicle speed VSP, are calculated in the same manner as the arithmetic processing of step3ofFIG. 4.

Thereafter, the summed value of driving force command achievement torque T1and the previously-noted lever correction torque ΔT1is set as target torque tT1of motor generator MG1, whereas the summed value of driving force command achievement torque T2and the previously-noted lever correction torque ΔT2is set as target torque tT2of motor generator MG2. These target torques, i.e., the summed values, are output into motor controller33(seeFIG. 3).

Thus, as shown inFIG. 7c, for the lever on the alignment chart, regarding both ends of the lever (that is, on motor generators MG1-MG2), the action of torques ΔT1and ΔT2shown inFIG. 7bis replaced by the action of torques ΔT1+T1and ΔT2+T2on the motor generators. Therefore, output torque To corresponding to target torque tTo is generated.

As a result of this, at step S14, as shown inFIG. 7d, it is possible to attain a lever translating operation that the lever on the alignment chart is translated while being kept at the inclination that rotational speed Ni of ring gear R1serving as the input element is brought or adjusted to predetermined normal-rotational speed Niref (3 rad/sec). Thus, the vehicle can be started or propelled by driving the wheels.

However, if a driving force command, created depending on accelerator opening APO, is input, target torque tTo (a driving force command value) on the output Out becomes “0” and thus driving force command achievement torques T1and T2of motor generators MG1-MG2become “0”. Therefore, target torques tT1and tT2for motor generators MG1-MG2become respective lever correction torques ΔT1and ΔT2, that is, tT1=ΔT1, tT2=ΔT2. And thus, the lever on the alignment chart is kept at the state as shown inFIG. 5a.

In the same manner as the first embodiment, in the second embodiment, when the driving achieved by only the power from motor generators MG1-MG2is equivalent to driving started from a state of an output rotational speed of zero, before a driving force command is input, as can be seen inFIG. 5a, the two motor generators MG1-MG2are rotated oppositely to each other by respective torques ΔT1and ΔT2, while keeping the state of the output rotational speed of zero (i.e., No=0). Therefore, when the driving force command is generated and then the corresponding motor generator torques T1and T2are generated, these motor generators MG1-MG2are rotated oppositely to each other.

Therefore, there is no risk that an electric current flows through a biased phase of phases of each of motor generators MG1-MG2, and thus it is possible to avoid the problem that the electric current flows biasedly through a particular part of the motor-generator-drive control circuit provided to control the driving of each of the motor generators and as a result the heating value of the particular part becomes large.

In particular, in the second embodiment, it is possible to suppress rotational speeds of motor generators MG1-MG2, produced before the driving force command is generated, at low values, and whereby an outputtable torque is limited but an electric power consumption rate can be suppressed at a low value.

When step S12determines that the inequality of Ni>1 rad/sec is satisfied, the routine proceeds to step S13, at which the summed value of driving force command achievement torque T1and lever correction torque ΔT1is set as target torque tT1of motor generator MG1, whereas the summed value of driving force command achievement torque T2and lever correction torque ΔT2is set as target torque tT2of motor generator MG2.

Thus, after the driving force command has been input, driving force command achievement torques T1and T2do not become “0”. Thus, as can be seen fromFIG. 7d, it is possible to initiate electric force transmission while keeping the inclined state of the lever shown inFIG. 5a, needed to achieve the previously-described operation and effects. There is no risk that motor generators MG1-MG2are loaded at the initial stage of electric force transmission so that the rotational speeds of the motor generators become zero, and thus it is possible to more certainly achieve the previously-described operation and effects.

In the shown embodiments, although the control program ofFIG. 4and the control program ofFIG. 6are explained as control routines separated from each other. It will be appreciated that these control routines may be combined with each other and executed as a single control program.