JP2002316547A - Four-wheel drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a burden of a user, by making generation of a four-wheel drive selectable. SOLUTION: This four-wheel drive device has a first power source 3 driving a first wheel drive shaft 1 rotated, a second power source 14 driving a second wheel drive shaft 2 rotated when a four-wheel drive is selected, a first power source control means 5, and a second power source control means 16, the first power source control means 5 is provided with a reduction amount calculation means 43 calculating a reduction amount relating to output shaft torque of the first power source 3 or drive torque of the first wheel drive shaft 1 at ordinary control time, and this reduction amount is transmitted to the second power source control means 16 through a communication means 11 when the four-wheel drive is selected, and the second power source control means 16, for controlling output shaft torque of the second power source 14 to be related to the received reduction amount, determines target drive torque of the second wheel drive shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a four-wheel drive device for a vehicle.

[0002]

2. Description of the Related Art In a conventional four-wheel drive system, a drive shaft using a gear called a transfer, a propeller shaft, a differential control device, and a final drive are driven from a drive shaft on a drive wheel driven by an internal combustion engine. There is a mechanical type that transmits power to the other drive shaft.

[0003] Further, for example, there is a configuration in which a front wheel is driven by an internal combustion engine, and a rear wheel is driven by operating an electric motor using a large-capacity battery mounted on a vehicle.

[0004] Also, Japanese Utility Model Laid-Open No. 4-76527
One of the axles is driven by an engine, the other is driven by a motor, and the drive by the motor can be selected by a changeover switch.

Japanese Patent Application Laid-Open No. 7-231508 has an internal combustion engine, a generator driven by the internal combustion engine, a motor driven by electric energy generated by the generator, and drive control means. The four-wheel drive device is configured by sharing the internal combustion engine and the motor.

[0006]

However, a vehicle provided with such a four-wheel drive device is designed in advance as a four-wheel drive vehicle, and the device required for four-wheel drive is always mounted. Because of this condition, the vehicle owner has to bear the cost for the four-wheel drive even if there are rarely running conditions that require four-wheel drive.

Further, the control of the four-wheel drive is complicated, and the device for the four-wheel drive cannot be removed from the vehicle.

Further, since the four-wheel drive device is heavy and increases friction loss, there is a problem that when four-wheel drive is not required, the expected fuel consumption rate is difficult to obtain even when traveling with two-wheel drive. Was.

An object of the present invention is to solve the problems of such a four-wheel drive device.

[0010]

According to a first aspect of the present invention, there is provided a first wheel drive shaft and a second wheel drive shaft, wherein the first wheel drive shaft and the second wheel drive shaft constantly rotate during traveling to rotationally drive the first wheel drive shaft. Power source, a second power source that rotationally drives the second wheel drive shaft when four-wheel drive is selected, a first power source control unit that controls an output shaft torque of the first power source, A four-wheeled vehicle having second power source control means for controlling the output shaft torque of the second power source; and communication means for communicating information between the first power source control means and the second power source control means In the drive,
The first power source control unit includes a reduction amount calculation unit that calculates a reduction amount with respect to the output shaft torque of the first power source or the drive torque of the first wheel drive shaft at the time of normal control. Sometimes the reduction amount is transmitted to the second power source control means through the communication means, and the second power source control means controls the output shaft torque of the second power source in relation to the received reduction amount. Is determined for the wheel drive shaft.

A second invention provides a first wheel drive shaft and a second wheel drive shaft, a motor for driving the first wheel drive shaft to rotate, and an electric motor for rotating the second wheel drive shaft. A motor control means capable of controlling an output shaft torque of the motor independently of a driver's accelerator operation; a power storage device for operating the motor; and a motor control means for controlling an output shaft torque of the motor. Communication means for communicating information between the prime mover control means and the motor control means,
In the four-wheel drive device having the above, the electric motor, the power storage device, and the electric motor control means are integrated to constitute a second wheel drive shaft drive unit which is detachable from the vehicle.

In a third aspect based on the second aspect, the prime mover control means is configured to calculate a decrease amount with respect to the output shaft torque of the prime mover or the drive torque of the first wheel drive shaft during normal control. Along with, during four-wheel drive traveling equipped with the second wheel drive shaft drive unit transmits the reduction amount to the motor control means through the communication means,
The motor control means determines a second wheel drive shaft target drive torque to control the output shaft torque of the motor in relation to the received reduction amount.

According to a fourth aspect of the present invention, in the third aspect, there is provided a wheel slip detecting means of the first wheel drive shaft, and the motor control means has a large wheel slip amount of the first wheel drive shaft. Thus, the traction control for reducing the driving torque of the first wheel drive shaft is performed, and the reduction amount calculating means calculates the reduction amount based on the torque reduction by the traction control.

According to a fifth aspect of the present invention, in the third aspect, a traveling mode selecting means capable of selecting a first traveling mode for normal use and a second traveling mode in which the driving force is reduced as compared with the first traveling mode. Wherein the reduction amount calculating means calculates the reduction amount based on a difference in driving force between when the second traveling mode is selected and when the first traveling mode is selected.

[0015]

According to the first aspect of the present invention, the first power source control means only has to perform common control at all times irrespective of whether it is four-wheel drive or not, thereby simplifying the control. Therefore, the device for four-wheel drive can be configured to be easily detachable from the vehicle.

According to the second aspect, when the second wheel drive shaft drive unit is not mounted, a two-wheel drive vehicle that drives only the first wheel drive shaft can be provided. , A four-wheel drive vehicle that drives both the first wheel drive shaft and the second wheel drive shaft. Further, it is easy to change the structure of the unit when used as a two-wheel drive vehicle and when used as a four-wheel drive vehicle.
In other words, it is possible to make the four-wheel drive option optional, retrofit, and even lease and rental business,
The burden on the user can be reduced. In addition, when the vehicle is used as a two-wheel drive vehicle, by removing the second wheel drive shaft drive unit, it is possible to improve fuel economy when four-wheel drive is unnecessary by reducing weight, reducing friction loss, and the like.

According to the third invention, the control of the prime mover control means can be simplified. Further, it is possible to provide a system with less adverse effects such as a cost increase for the base system device and an excessive occupation of the memory of the control means because only the potential for four-wheel drive is prepared.

According to the fourth aspect, control during four-wheel drive can be performed by utilizing control logic for reducing drive slip in a two-wheel drive vehicle.

According to the fifth aspect, control during four-wheel drive can be performed by utilizing the control logic of driving force control according to the traveling mode in a two-wheel drive vehicle.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show the system configuration of the first embodiment, and FIG. 1 shows the second wheel drive shaft drive unit 1.
FIG. 2 shows a state where the “second wheel drive shaft drive unit 13” is not mounted.

1 is a first wheel drive shaft (front wheel) of the vehicle, 2
Is the second wheel drive shaft (rear wheel), 3 is the first wheel drive shaft 1
Are automatic transmissions that reduce or increase the driving torque of the internal combustion engine 3 and transmit it to the first wheel drive shaft 1.

An engine control unit 5 controls the operating state of the internal combustion engine 3, an accelerator pedal sensor unit 6 converts an acceleration / deceleration intention of the driver into an electric signal,
7 is an electronic control throttle, 8 is a wheel, 9 and 10 are rotational speed sensors for detecting the rotational speeds of the first and second wheel drive shafts 1 and 2, respectively, and 11 is an engine control unit 5 and a motor control unit 16 (described later). A control communication line in the vehicle for connecting the motor drive shaft 12 to the second wheel drive shaft 2 converts the rotation of a motor 14 (described later) orthogonal to the second wheel drive shaft 2 into wheel drive shaft rotation,
This is a differential gear for transmitting torque.

The internal combustion engine 3 may be a gasoline engine or a diesel engine. In the case of a diesel engine, there is a type in which the torque control is performed only by the fuel injection amount and the intake air amount control is not necessary, and in that case, the electronic control throttle 7 is unnecessary. The automatic transmission 4 may be a stepped automatic transmission, or may be a stepless automatic transmission capable of steplessly controlling the gear ratio.

The second wheel drive shaft drive unit 13 includes a motor 14, a battery 15, a motor control unit 16 for the second wheel drive shaft drive unit 13, and an inverter 1
7. Consisting of components such as a connector 18 for connecting the control communication line 11 to the motor control unit 16 and a unit housing 13A for assembling these components integrally.

FIG. 3 is a view for explaining an example of connection between the differential gear 12 and the output shaft of the motor 14 of the second wheel drive shaft drive unit 13.

In the figure, reference numeral 19 denotes the differential gear 12
, 20 is provided on the upper part of the gear box 19, a flange having a hole through which the output shaft of the motor 14 is formed at the center, 22 is a shock absorber, 23
Denotes a suspension member, 24 denotes a drum brake back plate, and 25 denotes a wheel hub.

The flange 20 is formed so as to communicate with a hole formed in the floor of a trunk (not shown). The second wheel drive shaft drive unit 13 is detachably attached to the trunk via bolts and the like, and the motor 14 is detachably fastened to the flange 20 via bolts and the like. Is connected to the rotating shaft of the differential gear 12 through a hole in the center of the flange 20 and the motor 1
4 can be transmitted to the rotational torque of the differential gear 12.

FIG. 4 is a control block diagram of the motor control unit 16 for the engine control unit 5 and the second wheel drive shaft drive unit 13.

Reference numeral 26 denotes an input portion of an accelerator opening signal (APO) from the accelerator pedal sensor unit 6, 27 denotes an input portion of a vehicle speed signal (VSP) based on a signal from the rotational speed sensor 9 and the like.
Reference numeral 28 denotes an input unit of a mode switch signal (MODE) from a mode switch (not shown) for selecting a normal mode or a snow mode by a driver, and 29 denotes a rotation signal of the first wheel drive shaft 1 from the rotation speed sensor 9 ( Front wheel rotation signal FRREV)
An input unit 30 for inputting a rotation signal (rear wheel rotation signal RRREV) of the second wheel drive shaft 2 from the rotation speed sensor 10;
Reference numeral 31 denotes an input portion of a transmission ratio signal of the automatic transmission 4 from a transmission control device (not shown), and reference numeral 32 denotes an output torque of the torque converter (not shown) of the automatic transmission 4 ÷ input torque (output shaft rotation speed ÷ input shaft rotation speed). ) Shows the input section of the torque converter torque ratio signal.

Reference numeral 33 denotes a normal mode target driving force calculation block for obtaining a target driving force A in a normal mode of the vehicle based on the accelerator opening signal and the vehicle speed signal. Reference numeral 34 denotes a vehicle snow based on the accelerator opening signal and the vehicle speed signal. This is a snow mode target driving force calculation block for obtaining a target driving force B in the mode. The snow mode target driving force B is set smaller than the normal mode target driving force A at the same vehicle speed and the same accelerator opening.

Reference numeral 35 denotes a slip-time target driving force calculation block for detecting a slip state of the wheel 8 from the front wheel rotation signal and the rear wheel rotation signal and obtaining a target driving force D for suppressing the slip of the wheel 8. A mode switching block that switches the normal mode target driving force A calculated as a result of the calculation and the snow mode target driving force B calculated as a result of the calculation based on the mode switch signal. Force C) and the output of 35 (the target driving force D at the time of slip), whichever is smaller, selects a final target driving force E to determine the final target driving force E. Reference numeral 43 denotes a normal mode target driving force A and a final target driving force. A reduced driving force calculation block for calculating a reduced driving force F which is a difference between the forces E;
4 selects the optimal engine torque based on the final target driving force E, the gear ratio, and the torque converter torque ratio, and selects the optimal gear ratio in accordance with the final target driving force E, and electronically controls the signal G for engine torque control. A first wheel drive shaft driving force control block that outputs a signal H for speed ratio control to the automatic transmission 4 to the throttle 7.

A target motor torque calculation block 48 for calculating a target motor torque I based on the reduced driving force F received from the engine control unit 5 via the control communication line 11;
50 is the motor 14 for realizing the target motor torque I.
This is a motor control block for controlling the current of the motor.

The calculation content of the slip-time target driving force calculation block 35 is the same as that of a well-known traction control system (the driving force decreases as the slip ratio increases).

FIG. 5 shows an example of a control flow of the engine control unit 5. This flowchart shows the calculation order of a portion of the engine control unit 5 excluding the first wheel drive shaft driving force control block 44.

In step # 1, the accelerator opening signal APO, vehicle speed signal VSP, mode switch signal MODE, front wheel rotation signal FRREV,
The rear wheel rotation signal RRREV is input.

In step # 2, a normal mode target driving force map and a snow mode target driving force map as shown in FIG. 4 are searched based on the accelerator opening signal APO and the vehicle speed signal VSP, respectively. The force A and the target driving force B in the snow mode are calculated.

In step # 3, a slip-time target driving force D is calculated based on the front wheel rotation signal FRREV and the rear wheel rotation signal RRREV.

In step # 4, the flow branches to step # 5 when MODE is 1, ie, the snow mode, and to step # 6 when the MODE is other than that, ie, in the normal mode.

In # 5, it is calculated that [target driving force after switching C] = [target driving force B in snow mode], and in # 6, [target driving force C after switching] = [target driving force A in normal mode]. ] Is calculated.

In step # 7, the process branches when the post-switching target driving force C calculated in step # 5 or # 6 is larger than the slipping-time target driving force D, and when it is less than #.
8. In the following cases, proceed to # 9.

In # 8, [final target driving force E] = [slip target driving force D], and in # 9, [final target driving force E] =
[Target driving force after switching C].

In step # 10, the difference obtained by subtracting the final target driving force E calculated in step # 8 or # 9 from the normal mode target driving force A calculated in step # 2 is calculated as the reduced driving force F.

In # 11, the final target driving force E calculated in # 8 or # 9 is output to the first wheel driving shaft driving force control block 44.

In # 12, the reduced driving force F calculated in # 10 is output to the control communication line 11.

This is the end of the control flow.

With this configuration, when the driver has selected the normal mode and the wheels 8 are not slipping, the final target driving force E is the normal mode target driving force A.
Is equal to Therefore, while the vehicle travels by the engine torque control (normal control) of the normal mode target driving force A, the reduced driving force F becomes zero, and the output to the motor 14 becomes zero.

When the driver has selected the normal mode,
When the wheel 8 slips, the slip-time target driving force D becomes lower than the normal target driving force A, so that the final target driving force E becomes smaller than the normal mode target driving force A. Accordingly, while the difference engine torque is reduced, the reduced driving force F is generated by the difference, the output to the motor 14 becomes positive, and the motor 14 is driven based on the reduced driving force F.

When the driver has selected the snow mode and the wheels 8 are not slipping, the final target driving force E
Is equal to the snow mode target driving force B. Since the snow mode target driving force B is set to be smaller than the normal mode target driving force A, the final target driving force E becomes smaller than the normal mode target driving force A. Therefore, the engine torque control of the snow mode target driving force B is performed. While traveling, the reduced driving force F is generated by the difference, and the motor 14
And the motor 14 is driven based on the reduced driving force F.

If the driver has selected the snow mode and the wheels 8 are slipping, the slip-time target driving force D may be smaller than the snow mode target driving force B. While the torque is further reduced, the reduced driving force F is further increased, and the output to the motor 14 is further increased.
Drive.

As described above, the engine torque is controlled in each of the normal and snow running modes and in the slip mode, and the driving force during the normal control (when there is no slip in the normal mode) in the snow mode and in the slip mode. The four-wheel drive is performed by driving the motor 14 based on the reduced driving force.

That is, irrespective of the four-wheel drive or not, the engine control unit 5 performs the engine torque control in each of the normal and snow running modes and the slip, and performs the normal control (there is no slip in the normal mode). The motor control unit 16 drives the motor 14 to perform four-wheel drive on the basis of the reduced driving force with respect to the driving force of (time).

For this reason, the engine control unit 5 only has to always perform common control for four-wheel drive and two-wheel drive, and can simplify the control.

Therefore, the motor 14, the battery 15,
When the second wheel drive shaft drive unit 13 including the motor control unit 16 and the like is detachable from the vehicle and the second wheel drive shaft drive unit 13 is not mounted,
It can be a two-wheel drive vehicle that drives only the first wheel drive shaft 1, and when mounted, a four-wheel drive vehicle that drives both the first wheel drive shaft 1 and the second wheel drive shaft 2. It can be.

Further, by the control at the time of slip (traction control) and the control of the snow mode, the slip can be avoided and the snowy road can be stably driven.

That is, the control by the engine control unit 5 can exert its effect not only for four-wheel drive but also for two-wheel drive.

On the other hand, control logic for reducing drive slip in a two-wheel drive vehicle and control logic for driving force control according to the traveling mode in a two-wheel drive vehicle (for example,
In the snow mode, control at the time of four-wheel drive can be performed by utilizing a control logic (e.g., reducing the driving force to the accelerator than in the normal mode).

[0058] Therefore, it is necessary to provide a system that does not have any adverse effects such as the cost of the base system device and the excessive occupation of the memory of the control unit, because only the potential of "four-wheel drive" can be prepared. it can.

Further, the motor 14, the battery 15, the motor control unit 16 and the like are connected to the second wheel drive shaft drive unit 1.
3, the structure can be easily attached to and detached from the vehicle, so that the structure can be easily changed between the case of using the vehicle as a two-wheel drive vehicle and the case of using the vehicle as a four-wheel drive vehicle.

That is, it is possible to make the four-wheel drive optional business, retrofitting, and also business such as leasing and rental. Therefore, instead of imposing the full cost of four-wheel drive on users, unlike conventional products, `` rarely, four-wheel drive function is rarely needed, but four-wheel drive function is needed in case of emergency '' Only when necessary, the cost can be paid to the user according to the degree of benefit.

On the other hand, when the vehicle is used as a two-wheel drive vehicle, by removing the second wheel drive shaft drive unit 13, it is possible to improve fuel economy when four-wheel drive is unnecessary by reducing weight, reducing frictional loss, and the like.

FIGS. 6 and 7 show a second embodiment of the present invention. This is such that the actual driving torque K of the first wheel drive shaft 1 is estimated to obtain the reduced driving force F. The mechanical structure is the same as in the first embodiment.

FIG. 6 is a control block diagram of the motor control unit 16 for the engine control unit 5 and the second wheel drive shaft drive unit 13.

In the drawing, reference numeral 52 denotes an input portion of an engine speed signal from an engine speed sensor (not shown), and reference numeral 53 denotes an actual value from a throttle opening (not shown) for detecting the actual throttle opening of the electronic control throttle 7. An input unit 54 for the throttle opening signal is an actual driving torque estimating unit for estimating the actual driving torque from the gear ratio, the torque converter torque ratio, the engine rotation signal, and the actual throttle opening.

The actual drive torque estimating section 54 stores, for example, the relationship between the engine torque and the engine speed and the throttle opening as a map.
When the actual throttle opening is input, the engine torque is estimated by map interpolation calculation. Then, by multiplying the engine torque by the torque converter torque ratio, the gear ratio, and the final gear ratio stored as a fixed value, and dividing by the radius of the wheel 8, the driving torque of the vehicle obtained as a friction reaction force on the outer periphery of the wheel 8 is obtained. Estimate the sum. This is output to the reduced driving force calculation block 43 as the actual driving torque estimated value K. In the reduced driving force calculation block 43, the reduced driving force F is obtained by subtracting the actual driving force estimated value (based on the actual driving torque estimated value K) from the target driving force A in the normal mode.

The other structure is the same as that of the first embodiment.

FIG. 7 shows an example of the control flow of the engine control unit 5. This flowchart shows the calculation order of the normal mode target driving force calculation block 33, the actual driving torque estimation unit 54, and the reduced driving force calculation block 43 in the engine control unit 5.

In step # 1, the accelerator opening signal APO, the vehicle speed signal VSP, and the mode switch signal MODE are input.

In step # 2, a normal mode target driving force map as shown in FIG. 6 is searched based on the accelerator opening signal APO and the vehicle speed signal VSP.
Is calculated.

In step # 3, the gear ratio, torque converter torque ratio, engine rotation signal, and actual throttle opening are detected and input.

In step # 4, the actual drive torque estimating section 54 estimates the actual drive torque K based on the gear ratio, torque converter torque ratio, engine rotation signal and actual throttle opening input in # 3.

In step # 5, the difference obtained by subtracting the estimated actual driving force (based on the estimated actual driving torque K) calculated in step # 4 from the target driving force A in the normal mode calculated in step # 2 is reduced. Calculate as F.

In # 6, the reduced driving force F calculated in # 5
Is output to the control communication line 11. This ends the control flow.

When the actual driving force torque of the first wheel driving shaft 1 is estimated to obtain the reduced driving force F, the motor 14 can be controlled with higher accuracy, and four-wheel drive can be performed.

In each of the embodiments, the normal mode target driving force, the snow mode target driving force, and the slip-time target driving force are obtained. However, the respective driving torques may be obtained and used.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a first embodiment of a second wheel drive shaft drive unit in a mounted state.

FIG. 2 is a system configuration diagram of a state in which a second wheel drive shaft drive unit is not mounted.

FIG. 3 is an explanatory view of assembling a second wheel drive shaft drive unit.

FIG. 4 is a control block diagram.

FIG. 5 is a control flowchart.

FIG. 6 is a control block diagram according to a second embodiment.

FIG. 7 is a control flowchart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st wheel drive shaft 2 2nd wheel drive shaft 3 Engine 4 Automatic transmission 5 Engine control unit 6 Accelerator pedal sensor unit 7 Electronic control throttle 8 Wheels 9 and 10 Rotation speed sensor 11 In-vehicle control communication line 13 Second Wheel drive shaft drive unit 14 Motor 15 Battery 16 Motor control unit 33 Normal mode target drive force calculation block 34 Snow mode target drive force calculation block 35 Target drive force calculation block during slip 43 Reduced drive force calculation block 44 First wheel drive shaft Driving force control block 48 Target motor torque calculation block 54 Actual driving torque estimation unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) RE05 RE12 SE03 SE05 TB01 TE02 TE03 TO21 UI13

Claims (5)

[Claims] 1. A first wheel drive shaft and a second wheel drive shaft, a first power source that constantly rotates during traveling and rotationally drives the first wheel drive shaft, and the second wheel A second power source that rotationally drives the drive shaft when four-wheel drive is selected; a first power source control unit that controls an output shaft torque of the first power source; and an output shaft torque of the second power source. A four-wheel drive device comprising: a second power source control means for controlling; and a communication means for communicating information between the first power source control means and the second power source control means. The means includes a reduction amount calculating means for calculating a reduction amount with respect to the output shaft torque of the first power source or the driving torque of the first wheel drive shaft at the time of the normal control. Transmitting the amount to the second power source control means, the second power source Control means associated with the second to control the output shaft torque of the power source a second four-wheel drive system, characterized in that to determine the wheel drive shaft target drive torque decrease amount received. 2. A first wheel drive shaft and a second wheel drive shaft, a motor driving the first wheel drive shaft to rotate, an electric motor rotating the second wheel drive shaft to rotate, and the motor Motor control means capable of controlling the output shaft torque of the motor independently of the accelerator operation of the driver; a power storage device for operating the motor; a motor control means for controlling the output shaft torque of the motor; and a motor control means. A communication means for communicating information between the motor and the motor control means, wherein the motor, the power storage device, and the motor control means are integrally detachable from the vehicle. A four-wheel drive device comprising the above-mentioned wheel drive shaft drive unit. 3. The motor drive control means includes a reduction amount calculation means for calculating a reduction amount with respect to an output shaft torque of the prime mover or a drive torque of the first wheel drive shaft during normal control, and a second wheel drive shaft. At the time of four-wheel drive traveling with the drive unit mounted, the reduction amount is transmitted to the motor control means through the communication means, and the motor control means controls the output shaft torque of the motor in relation to the received reduction amount. The four-wheel drive device according to claim 2, wherein the second wheel drive shaft target drive torque is determined. 4. The vehicle according to claim 1, further comprising: means for detecting the slip of the wheel of the first wheel drive shaft, wherein the motor control means drives the first wheel drive shaft as the slip amount of the wheel of the first wheel drive shaft increases. The four-wheel drive device according to claim 3, wherein traction control for reducing torque is performed, and the reduction amount calculating means calculates the reduction amount based on a torque reduction amount due to the traction control. 5. A travel mode selection means which can select a first travel mode for normal time and a second travel mode in which the driving force is reduced more than the first travel mode, wherein the decrease amount calculating means comprises: 4. The four-wheel drive device according to claim 3, wherein when the second traveling mode is selected, the reduction amount is calculated based on a difference in driving force from when the first traveling mode is selected.