JPH09109706A - Hybrid vehicle - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To always start an engine without increasing a capacity of a generator and limiting traveling conditions. An engine 11, a generator 16, and an output shaft 1
4 is connected via the planetary gear unit 13 and the torque of the electric motor 25 is output to the output shaft 14, the rotation of the generator 16 is controlled during low speed traveling in which the generator 16 can output the engine starting torque. Engine 1
1 is started, and during high speed traveling, the generator 16 is fixed by the brake 28, and the engine 11 is rotated by the rotation of the output shaft 14 to start.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid vehicle, and more specifically, it connects an engine, a generator and a drive output system via a differential gear device, and transfers a part of the output of the engine to the generator. However, the present invention relates to a hybrid vehicle in which the rest is transmitted to a drive output system and an electric motor is connected to the drive output system.

[0002]

2. Description of the Related Art Conventionally, a hybrid vehicle having a drive device using both an engine and a motor has been provided in order to achieve low pollution and low fuel consumption. Various types of hybrid vehicles of this type are provided, for example, the rotation generated by driving an engine is transmitted to a generator to drive the generator, and the electric power obtained by the generator is converted into a direct current. A series (series) hybrid vehicle in which the electric power of the battery is converted and sent to a battery for charging, and the electric power of the battery is exchanged with an alternating current to drive the electric motor, or the driving force of the engine and the electric motor is output to the output shaft. There is a parallel type hybrid vehicle in which the output of the electric motor is driven to control the output of the electric motor to accelerate and decelerate.

In the above-mentioned parallel type hybrid vehicle, a hybrid vehicle having a structure in which an engine, a generator and a drive output shaft are connected through a differential gear unit and an electric motor is connected to the drive output shaft is proposed. Has been done. In hybrid vehicles of this structure, it is possible to switch to engine / motor drive mode, motor drive mode, etc., and also to charge the battery with regenerative power and to start the engine by driving the generator as a motor. It can be carried out.

[0004]

On the other hand, in the parallel type hybrid vehicle having the differential gear device,
An engine, a generator, and an electric motor are connected via a differential gear device, and the rotational speeds and torques of them are mutually related. As a result, for example, when the vehicle runs at high speed with the engine stopped, the number of revolutions of the generator increases, making it difficult to secure the generator torque necessary for starting the engine, which makes it difficult to start the engine. It may be possible. Therefore, when the motor is traveling alone with the engine stopped, an upper limit is set for the vehicle speed, or when the engine is started, the number of rotations that allows the generator to generate the required generator torque and Therefore, there is a problem that it becomes necessary to reduce the vehicle speed. On the other hand, although the above problem can be solved by increasing the capacity of the generator, it causes an increase in the size and weight of the generator,
Not preferred.

An object of the present invention is to provide a hybrid vehicle in which the engine can be started without lowering the vehicle speed even when the vehicle is traveling at high speed.

[0006]

This and other objects are attained by the present invention described below.

(1) In a hybrid vehicle including an engine, a generator capable of controlling the number of revolutions, a drive output shaft for transmitting a driving force for driving the drive wheels, and an electric motor connected to the drive output shaft, A differential gearing in which a first gear element is connected to the output shaft of the engine, a second gear element is connected to the rotor of the generator, and a third gear element is connected to the drive output shaft; The engine speed control unit controls the rotation speed of the generator to start the engine, the fixing unit fixes the rotation of the generator, and the vehicle speed detection unit detects the vehicle speed of the vehicle. When the detected vehicle speed is low speed, the engine is started by controlling the rotation speed of the generator by the engine starting means, and during high speed running, the fixing means of the generator is used. A hybrid vehicle in which the engine is started by fixing rotation.

(2) The low speed running means a time when the generator is rotating in a rotation speed region where a generator torque necessary for starting the engine can be secured, and the high speed running means a power generation. Hybrid vehicle according to (1) above, when the machine is rotating at a rotational speed higher than the rotational speed range.

(3) The hybrid vehicle according to (1) or (2), wherein the fixing means is a wet brake.

[0010]

When the engine is stopped and the vehicle is driven by the electric motor alone, the rotation of the drive output shaft driven by the electric motor is input to the generator via the differential gear device. When the vehicle speed increases and the vehicle travels at high speed, the number of revolutions input to the generator also increases as the vehicle speed increases, and the generator cannot secure the torque required to start the engine. Therefore, during high speed traveling in which the generator cannot output the starting torque of the engine, the rotation of the generator is fixed by the fixing means, and the engine is rotated by the reaction force of the torque received by the fixing means to start the engine.

During low speed traveling in which the generator can output the starting torque of the engine, the engine is started by controlling the rotation of the generator. At this time, the generator can generate power at the same time, and the amount of power generation can be increased.

Further, in the engine speed range in which the engine can be started by controlling the engine speed, the engine can always be started by controlling the engine speed to maximize the power generation capacity of the generator. It is possible to further increase the amount of power generation.

Further, when a wet brake is used as the fixing means, the rotation of the generator is fixed while sliding the engagement surface of the brake, so that the load on the engine and the differential gear device is suppressed and the life of the parts is extended. be able to.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a hybrid vehicle of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing a drive device for a hybrid vehicle according to an embodiment of the present invention. In the figure, an engine 11 and an engine output shaft 12 that outputs rotation generated by driving the engine 11 are provided on a first axis.
A planetary gear unit 13 that is a differential gear device that performs a speed change with respect to the rotation input through the engine output shaft 12, and a unit output shaft that is a drive output shaft that outputs the rotation after the speed change in the planetary gear unit 13. 1
4, a first counter drive gear 15 fixed to the unit output shaft 14, a generator 16 that mainly acts as a generator in a normal traveling state, and a transmission shaft 17 that connects the generator 16 and the planetary gear unit 13. And are arranged. The unit output shaft 14 has a sleeve shape and is disposed so as to surround the engine output shaft 12. The first counter drive gear 15 is disposed closer to the engine 11 than the planetary gear unit 13.

The planetary gear unit 13 includes a sun gear S which is a second gear element, a pinion P which meshes with the sun gear S, a ring gear R which is a third gear element which meshes with the pinion P, and a pinion P which are rotatable. And a carrier CR that is a first gear element that is supported by. The sun gear S is connected to the generator 16 via the transmission shaft 17,
The ring gear R is connected to the first counter drive gear 15 via the unit output shaft 14, and the carrier CR is connected to the engine 11 via the engine output shaft 12.

Further, the generator 16 is fixed to the transmission shaft 17 and is rotatably disposed.
And a coil 23 wound around the stator 22. The generator 16 is
Electric power is generated by the rotation transmitted via the transmission shaft 17. The coil 23 is connected to the battery 19 (FIG. 2) and supplies electric power to the battery to charge the battery.

In the generator 16, the other end of the transmission shaft 17 is
A brake 28 is connected as a fixing means, and by bringing the brake 28 into an engaged state, the rotor 21 is fixed and the rotation of the generator 16 and the rotation of the sun gear S are stopped. Brake 28 of the present embodiment
Is a wet brake and is operated by hydraulic pressure supplied from a pressure oil source. The pressure oil source is, for example, an electric hydraulic pump, a transmission shaft 17 of the generator 16 and an engine output shaft 12
Among them, a hydraulic pump or the like driven by the faster rotation can be used.

On the second axis parallel to the first axis, the electric motor 25, the motor output shaft 26 for outputting the rotation of the electric motor 25, and the second counter drive gear 27 fixed to the motor output shaft 26. And are arranged. The electric motor 25 is fixed to the motor output shaft 26 and is rotatably disposed on a rotor 37, a stator 38 disposed around the rotor 37, and a coil 3 wound around the stator 38.
9 and 9. The electric motor 25 generates torque by the current supplied to the coil 39. For that purpose, the coil 39 is connected to the battery 19 (FIG. 2) and is configured to be supplied with current from the battery.
When the hybrid vehicle of the present invention is in a decelerating state, the electric motor 25 receives rotation from drive wheels (not shown) to generate regenerative electric power, and supplies the regenerative electric power to the battery 19 for charging.

In order to rotate a drive wheel (not shown) in the same direction as the rotation of the engine 11, a counter shaft 31 is arranged as a drive output shaft on a third axis parallel to the first axis and the second axis. It is set up. A counter driven gear 32 is fixed to the counter shaft 31. Further, the counter driven gear 32 and the first counter drive gear 15, and the counter driven gear 3
2 and the second counter drive gear 27 are meshed,
The rotation of the first counter drive gear 15 and the rotation of the second counter drive gear 27 are reversed and transmitted to the counter driven gear 32. Further, a differential pinion gear 33 having a smaller number of teeth than the counter driven gear 32 is fixed to the counter shaft 31.

The differential ring gear 35 is disposed on the fourth axis which is parallel to the first axis, the second axis and the third axis.
The differential ring gear 35 and the differential pinion gear 33 are meshed with each other. Further, the differential device 36 is fixed to the differential ring gear 35, and the differential ring gear 3
The rotation transmitted to the differential gear 36 is transmitted to the differential device 36.
And transmitted to the drive wheels. In the above configuration, the drive output system is the planetary gear unit 13
, A generator 16, a first counter drive gear 15,
The counter driven gear 32, the second counter drive gear 27, the counter shaft 31, the differential pinion gear 33, the differential ring gear 35, and the differential device 36 are included.

Thus, not only the rotation generated by the engine 11 can be transmitted to the counter driven gear 32, but also the rotation generated by the electric motor 25 can be transmitted to the counter driven gear 32. The hybrid vehicle can be run in an engine drive mode that drives only 11, a motor drive mode that drives only the electric motor 25, and an engine-motor drive mode that drives the engine 11 and the electric motor 25. Further, by controlling the electric power generated in the generator 16, the rotation speed of the transmission shaft 17 can be controlled. Further, as a result, the engine 16 can be started by the generator 16. Also, when stopping the rotation of the generator,
The rotor 28 of the generator 16 can be fixed by engaging the brake 28.

Next, the control system of the hybrid vehicle of the present invention will be described in detail with reference to the block diagram of FIG. The control means constituting the control system of the present embodiment includes a vehicle control device 41, an engine control device 42, a motor control device 43, and a generator control device 44. These control devices 41, 42, 43, 44 are, for example, CPUs.
(Central processing unit), ROM (read-on memory) in which various programs and data are stored, RAM (random access memory) used as a working area, and the like can be configured by a microcomputer.

Further, this control system is provided with an accelerator sensor 45 for detecting an accelerator opening α, a vehicle speed sensor 46 as a vehicle speed detecting means for detecting a vehicle speed V, and a brake sensor 47 for detecting a brake depression amount β. ing. The detection values detected by these sensors 45, 46, 47 are supplied to the vehicle control device 41.

The vehicle controller 41 operates as follows. The motor torque TM ₁ is determined according to the accelerator opening α from the accelerator sensor 45 and the vehicle speed V from the vehicle speed sensor 46, and this is normally supplied to the motor control device 43 as a motor torque command value TM ₀ . Further, an engine ON / OFF signal is supplied to the engine control device 42. Specifically, for example, when the brake is depressed and the brake depression amount β is supplied from the brake sensor 47, the engine 11 is brought into a non-driving state and the engine is turned off.
A signal is supplied, and when the brake is released, an engine ON signal that drives the engine 11 is supplied.

Further, a solenoid ON / O is applied to an electromagnetic valve 54 for operating the brake 28 provided in the generator 16.
Supply an FF signal. The electromagnetic valve 54 is supplied with O
Based on the N / OFF signal, the solenoid built in the electromagnetic valve 54 operates, and for example, in the case of an ON signal,
The solenoid is actuated to open the valve, supply pressure oil to the brake 28, put the brake 28 in the engaged state, and turn it off.
In the case of a signal, the valve is closed to disengage the brake 28.

In particular, in the embodiment of the present invention, the vehicle control device 41 detects the vehicle speed through the vehicle speed sensor 46 when the engine is stopped, and the generator 16 causes the engine 1 to operate.
If the vehicle speed is such that the torque TGE required to start 1 is generated, the engine 11 is started by controlling the rotation speed of the generator 16. If the vehicle speed is so high that it is difficult to generate the starting torque, the brake 28 as described above is engaged to start the engine 11.
When the engine 11 is started by the engagement of the brake 28, the torque variation when the brake 28 is engaged is detected, and the variation torque Δ from the motor torque TM ₁ during normal traveling is detected.
The motor torque command value TM ₀ obtained by correcting TM is supplied to the motor control device 43.

The engine control unit 42 is the vehicle control unit 4
Engine 1 based on a selection command signal input from
1 is switched between a drive state in which engine torque is output (ON state) and a non-drive state in which engine torque is not generated (OFF state). Further, by controlling the throttle opening θ according to the actual engine speed NE input from the speed sensor provided in the engine 11,
It controls the output of the engine 11.

The motor control device 43 controls the electric current (torque) IM of the electric motor 25 so that the supplied motor torque command value TM ₀ is output from the electric motor 25.

The generator control device 44 controls the rotation speed NG of the generator 16 and controls the current (torque) IG so that the control target rotation speed NG ₀ input from the vehicle control device 41 is reached. The generator control device 44 and the vehicle control device 4
The engine starting means is constituted by 1 and.

Next, the operation of the hybrid vehicle having the above structure will be described. FIG. 3A is a conceptual diagram of the planetary gear unit 13 (FIG. 1) according to the first embodiment of the present invention, and FIG. 3B is a speed of the planetary gear unit 13 according to the first embodiment of the present invention during normal traveling. 4 and FIG. 4 show the planetary gear unit 1 according to the first embodiment of the present invention.
FIG. 3 is a torque diagram of No. 3 during normal traveling.

In this embodiment, as shown in FIG. 3A, the number of teeth of the ring gear R of the planetary gear unit 13 is twice the number of teeth of the sun gear S.
Therefore, the unit output shaft 14 connected to the ring gear R
NR is the number of rotations of the
And NE is the number of revolutions of the engine output shaft 12 connected to the carrier CR (hereinafter referred to as “engine number of revolutions”), the NR, NE and the number of revolutions NG of the generator connected to the sun gear S are The relationship is as shown in FIG.

NG = 3.NE-2.NR. Further, the torque output from the ring gear R to the unit output shaft 14 (hereinafter referred to as "ring gear torque") is TR, the torque of the engine 11 (hereinafter referred to as "engine torque") is TE, and the generator torque is T.
Assuming G, the relationship between TR, TE and TG is as shown in FIG.

TE: TR: TG = 3: 2: 1. Then, during normal traveling of the hybrid vehicle, ring gear R, carrier CR and sun gear S
Are all rotated in the positive direction, and as shown in FIG. 3B, the ring gear rotation speed NR, the engine rotation speed NE, and the generator rotation speed NG all take positive values.

Then, the engine torque TE is input to the carrier CR, and the engine torque TE is received by the reaction force of the first counter drive gear 15 and the generator 16 shown in FIG. As a result, as shown in FIG. 4, from the ring gear R to the unit output shaft 14
The ring gear torque TR from the sun gear S to the transmission shaft 17
The generator torque TG is output to. The ring gear torque TR and the generator torque TG are obtained by apportioning the engine torque TE by a torque ratio determined by the number of teeth of the planetary gear unit 13, and on the torque diagram, the ring gear torque TR and the generator torque TG.
The engine torque TE is obtained by adding and.

FIG. 5 is a velocity diagram of the planetary gear unit 13 when the engine 11 is stopped. From this state, when the brake 28 of the generator 16 is engaged, the rotation of the sun gear S becomes 0, the engine 11 is rotated and the engine is started as shown in the speed diagram of FIG. 6 (A). Can be made. Also, if torque can be generated in the generator 16, FIG.
As shown in the velocity diagram of FIG. 1, the engine 11 is rotated while the generator 16 is generating power, and the engine 11 is rotated.
Can be started.

Next, the control operation of the vehicle control device 41 will be described with reference to the flow chart shown in FIG. In the present embodiment, when starting the engine while the vehicle is running and selecting the start by engaging the brake 28 and the start by the generator 16, the determination is made based on the value of the vehicle speed V. That is, when the vehicle speed V input from the vehicle speed sensor 46 is higher than a preset value V *, the engine is started by engaging the brake 28, and when the vehicle speed V is lower than the preset value V *, the generator 16 is used.
Start by.

The value of V * is obtained as follows.
The generator torque TG * required for starting the engine 11 (hereinafter referred to as “starting required torque”) is known, and from the rotational speed / torque diagram of the generator shown in FIG. The number of revolutions NG * whose maximum value is the required torque TG * for starting is determined.

With the engine 11 stopped, the output speed NOUT * when the generator speed is NG * is determined. From the gear ratio of the planetary gear unit 13, the output speed NOUT * (= NR) is NOUT * = NG * / 2.
Is required. Then, from NOUT *, the vehicle speed V at that time
* Is required.

Based on such a vehicle speed V *, the following control operation is performed. The selected traveling mode is determined (step S101), and when the engine / motor drive mode is selected, the vehicle speed V is detected by the vehicle speed sensor 46 (step S102). The engine / motor drive mode may be selected, for example, by the driver manually, when the braking brake is released, or when transitioning from low speed to high speed.

It is determined whether the input vehicle speed V is equal to or higher than the above-mentioned vehicle speed V * (step S103). Vehicle speed V
If not, the torque is generated in the generator 16 so as to rotate the engine 11 to reduce the rotation speed, and the engine 11 is started (step S104).
Specifically, the target rotation speed NG ₀ whose value is determined as the rotation speed at which the required start torque TG * is output is the generator control device 4.
4. Planetary gear unit 13 at this time
The velocity diagram of is as shown in FIG. 6 (B). At the same time, the generator 16 also generates electric power and can generate electric power.

When the input vehicle speed V is equal to or higher than the above-mentioned vehicle speed V *, the vehicle control device 41 turns on the solenoid.
A signal is transmitted to the electromagnetic valve 54 to bring the brake 28 into the engaged state (step S105). As a result, FIG.
As shown in (A), the rotation of the generator 16 is fixed, the engine 11 is rotated, and the engine 11 can be started.

Next, a subroutine for correcting the torque fluctuation caused by fixing the generator 16 is executed (step S
106) Finish. A subroutine for correcting the torque fluctuation will be described based on the flowchart shown in FIG. The engine controller 42 detects the angular acceleration αBE when the rotation speed of the engine 11 changes due to the engagement of the brake 28 (step S201). Next, the deceleration torque TBR generated on the unit output shaft 14 when the engine is started is calculated (step S202). The deceleration torque TBR is the gear ratio from the carrier CR of the planetary gear unit 13 to the unit output shaft 14a, the engine brake torque TEL, and the engine inertia I.
Let E be obtained by the following equation.

TBR = a × TEL + a × IE × αBE The fluctuation torque ΔTM at the output portion of the electric motor 25 is calculated from the obtained deceleration torque TBR and counter gear ratio i (step S203). That is, the fluctuation torque ΔTM is
It is obtained by the following formula.

ΔTM = TBR × i The motor torque command value TM ₀ is corrected by the following equation, and the corrected motor torque command value TM ₀ is output to the motor control device 43 (step S204).

TM ₀ = TM ₁ + ΔTM It is judged whether or not the starting operation of the engine 11 is completed (step S205). If not completed, the operations from step S201 to step S205 are repeated.
When the starting operation is finished, this subroutine is finished.

Next, FIG. 10 shows the operating state of each part when the hybrid vehicle of the present invention is controlled to start the engine 11 when the hybrid vehicle accelerates and shifts from the low speed range to the high speed range. The description will be given based on the time charts. When traveling is started from the stopped state (t in FIG. 10)
₁ ), vehicle speed gradually increases from 0. When driving at low speed,
The vehicle runs only by the motor torque of the electric motor 25, and the rotation speed of the generator 16 increases due to the torque transmitted from the unit output 14 via the planetary gear unit 13 as the vehicle speed increases. At this time, as shown in FIG. 5, in the velocity diagram of the planetary gear unit 13, the rotation speed of the engine 11 is 0.

When the vehicle speed reaches V * (t in FIG. 10)
₂ ), the vehicle control device 41 turns on the switch in the engine / motor drive mode and supplies a solenoid ON signal to the electromagnetic valve 54 in order to engage the brake 28. By this operation, the brake 28 starts the engaging operation. The wet pressure of the brake 28 gradually increases while sliding the engagement surface of the brake, and when the brake 28 is completely engaged, the rotation of the generator 16 is stopped (t _{3 in} FIG. 10).
From the time when the brake 28 starts the engaging operation to the time when the brake 28 is completely engaged (between t _{2 and} t _{3 in} FIG. 10), the rotation speed of the generator 16 decreases with the passage of time t.

On the other hand, the engine speed NE is equal to the brake 2
It increases with the passage of time t due to the reaction force of the torque that 8 receives. During this time, although the output torque fluctuates due to the engagement of the brake 28, the motor torque TM ₀ is controlled to a value corrected by the fluctuation torque ΔTM, so a shock due to a drop in the output torque is prevented. When the rotation of the engine 11 is started, the engine 11 can be started and the brake 28 is completely engaged (t _{3 in} FIG. 10) (FIG. 6).
In (A)), the engine control unit 42 (EG ECU) is activated (ON state), and engine torque is output. After that (after t _{3 in} FIG. 10), the engine torque from the engine 11 is obtained, so the motor torque is set smaller by that amount.

In the present embodiment, the brake 28 provided on the generator 16 is a wet brake, and the braking operation is performed while sliding the engaging surface of the brake 28, so that the generator 28 is completely compared with the dry brake. There is a time until 16 is stopped, and abrupt fluctuations in output torque are suppressed. As a result, control of torque correction and the like during that time is facilitated, so that the traveling speed can be stabilized more reliably by torque correction. Further, since the impact applied to the output shaft of the planetary gear unit 13 and the engine 11 when the brake is engaged is smaller than that in the case of the dry brake, the life of parts of the power transmission system such as the engine 11 and the planetary gear unit 13 is reduced. It can be postponed.

In addition to the above embodiment, the present invention is directed to a power generator 1
The actual rotation speed NG of 6 is detected, and the rotation speed NG is compared with the maximum generator rotation speed NG * that can output the required torque for starting. If NG *> NG, the generator rotation speed is NG. Control the number to start the engine 11, and if NG * ≦ NG,
Control for engaging the brake 28 may be performed.

[0051]

As described above, according to the first aspect of the present invention, by fixing the rotation of the generator, the engine can be started without reducing the vehicle speed even when the electric motor drives at high speed. Is possible, and
Since the engine is started by controlling the rotation of the generator when traveling at a low speed, it is possible to start the engine while generating electricity, and it is possible to improve efficiency.

According to the second aspect of the present invention, since the engine is started by the rotation control of the generator within the maximum range in which the engine can be started by the rotation control of the generator, the power generation of the generator is performed. It is possible to make maximum use of the functions and further improve efficiency. Further, it is possible to use a generator having a smaller capacity, and it is possible to reduce the size and weight of the entire vehicle.

According to the third aspect of the invention, since the wet brake is used as the fixing means, abrupt torque fluctuation when the rotation of the generator is fixed is suppressed, and the life of the engine, the differential gear device, etc. is extended. You can

[Brief description of the drawings]

FIG. 1 shows a hybrid vehicle according to an embodiment of the present invention, and is a conceptual diagram of a drive device mounted on the hybrid vehicle.

FIG. 2 illustrates a hybrid vehicle according to an embodiment of the present invention, and is a conceptual diagram of a control system mounted on the hybrid vehicle.

FIG. 3 is a conceptual diagram and velocity diagram of a planetary gear unit.

FIG. 4 is a torque diagram during normal traveling of the planetary gear unit.

FIG. 5 is a velocity diagram of the planetary gear unit.

FIG. 6 is a velocity diagram of the planetary gear unit.

FIG. 7 is a flowchart showing a control operation of the vehicle control device.

FIG. 8 is a rotational speed-torque diagram showing a controllable region of the generator.

FIG. 9 is a flowchart showing a control operation of the vehicle control device.

FIG. 10 is a time chart showing a control operation of the vehicle control device.

[Explanation of symbols]

 11 Engine 13 Planetary Gear Unit 16 Generator 25 Electric Motor 28 Brake 41 Vehicle Control Device 42 Engine Control Device 43 Motor Control Device 44 Generator Control Device 46 Vehicle Speed Sensor 54 Electromagnetic Valve

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshikazu Yamauchi Aisin AW Inc. 10 Takane, Fujii-cho Aisin AW Co., Ltd.

Claims (3)

[Claims] 1. An engine, a generator whose rotation speed is controllable, a drive output shaft for transmitting a driving force for driving a drive wheel, an electric motor connected to the drive output shaft, and a first gear element. A differential gear unit connected to an output shaft of an engine, a second gear element connected to a rotor of the generator, and a third gear element connected to the drive output shaft; and a rotation speed of the generator. It has an engine starting means for controlling and starting the engine, a fixing means for fixing the rotation of the generator, and a vehicle speed detecting means for detecting the vehicle speed of the vehicle, and the vehicle speed detected by the vehicle speed detecting means is low. At the time of traveling, the engine is started by controlling the number of revolutions of the generator by the engine starting means, and at the time of high speed traveling, the rotation of the generator is fixed by the fixing means. Hybrid vehicle, characterized in that to start the engine. 2. The low-speed traveling is a time when the generator is rotating in a rotation speed region in which a generator torque required for starting an engine can be secured, and the high-speed traveling is a generator. 2. The hybrid vehicle according to claim 1, wherein the vehicle is rotating at a rotational speed higher than the rotational speed region. 3. The hybrid vehicle according to claim 1, wherein the fixing means is a wet brake.