JPH03121968A - Driving force control device for vehicle - Google Patents

Abstract

PURPOSE:To ensure the stability of a vehicle and the like by inhibiting driving shaft output torque reducing control at the time of detecting the failure of a driving shaft output torque reducing means, as well as performing braking liquid pressure intensifying control in case of the accelerator stepping-in speed being more than the specified value, and stopping braking control in case of less than the specified value. CONSTITUTION:At the time of a slip being generated to a vehicle due to acceleration, the output torque of a driving shaft is reduced at a means (a), as well as braking liquid pressure is enlarged at a means (b) to avoid the slip. Hereupon, when the partial failure of the driving shaft output torque reducing means (a) is detected by a failure detecting means (e), the braking control means (b) executes pressure intensifying control to driving wheels only in case accelerator pedal stepping-in speed obtained from a detecting means (c) and an arithmetic means (d) is larger than the specified value. In case of being less than the specified value, that is, at the time of the vehicle being in low acceleration or running at constant speed, braking control is stopped. The generation of the fading phenomenon of a brake shoe can be thereby prevented while preventing the acceleration slip of the vehicle as well as ensuring the stability of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vehicle driving force control device that performs braking control and drive shaft output torque control, for example, internal combustion engine output control, in accordance with the acceleration slip state of the vehicle. It is related to.

Conventional technology In general, when a vehicle accelerates, the friction force between the drive wheels and the road surface is optimized to obtain sufficient acceleration while preventing the wheels from slipping and causing the vehicle body to skid or other unstable conditions. Are there any known driving force control devices that do this? In this type of control device, drive shaft output torque reduction means such as means for reducing fuel consumption or delaying ignition timing, or means for controlling the amount of intake air to the internal combustion engine are known. Also known are braking control means for controlling brake hydraulic pressure.

For example, JP-A-61-85248 and JP-A-6]-
Publication No. 85249 discloses that in order to prevent the acceleration slip of the drive wheels that occurs when the vehicle accelerates, a first throttle/nottle valve that is provided in the intake passage and linked to the accelerator pedal as a drive shaft output torque reducing means is disclosed. Alternatively, a configuration is disclosed that includes opening/closing control means for a second throttle valve provided on the downstream side and braking control means for controlling brake fluid pressure of drive wheels.

With this configuration, when acceleration slip occurs, the driving force transmitted from the internal combustion engine to the drive wheels via the drive shaft is reduced to the output of the drive shaft! - Control is performed by a drive shaft output torque reducing means that reduces torque, and the brake fluid pressure of the drive wheels is increased. That is, by performing braking control, the rotation of the drive wheels can be suppressed, and slips caused by acceleration can be prevented.

Problems to be Solved by the Invention However, such conventional vehicle driving force control devices,
In particular, in the configuration described in JP-A-61-85248, when a failure occurs in the means for reducing the output torque of the drive shaft, control by the drive shaft output torque reducing means is prohibited. For example, in a vehicle that uses the second throttle valve described above, the valve is fully opened or held at the same opening to prevent unexpected deceleration or stopping of the vehicle. In order to suppress the slip of the driving wheels in such a state, the slip must be reduced only by the braking control means that increases the pressure of the brake fluid supplied to the driving wheels. For example, if the vehicle is When driving on roads where driving slips occur frequently, such as snowy roads,
Due to excessive braking operation to compensate for the inoperation of the drive shaft output torque reducing means, a pre-knee fade phenomenon is likely to occur, and normal foot brake operation may become ineffective. There were some issues of concern.

Therefore, the present invention solves the problems that such conventional vehicle driving force control devices have, and when acceleration slip occurs in the vehicle, the driving force is reduced by a drive shaft output torque reducing means, and the driving force is reduced. The brake control means can prevent the slip by increasing the brake fluid pressure to the drive wheels, and when a failure occurs in the drive shaft output torque reduction means and control of the drive shaft output torque is prohibited. Another object of the present invention is to provide a vehicle driving force control device that can prevent the occurrence of a brake shoe fade phenomenon.

Means for Solving the Problems In order to achieve the above object, the present invention reduces the output torque of the drive shaft when the vehicle accelerates and slips, as shown in the diagram corresponding to the claims in FIG. In a vehicle driving force control device which prevents slippage of the drive wheels by a torque reduction means a and a brake control means for braking the drive wheels, the accelerator pedal operation amount detection means C detects the operation amount of the accelerator pedal. and an accelerator pedal depression speed calculation means d for calculating the depression speed of the accelerator pedal from the detected accelerator pedal operation amount, and a failure detection means C for detecting a failure of the drive shaft output torque reduction means, When the detection means e detects a failure in the drive shaft output torque reduction means a, the drive shaft output torque reduction means is prohibited from controlling the output torque of the drive shaft, and the accelerator pedal depression speed calculation means d According to the present invention, the vehicle driving force control device is configured to prohibit braking control by the braking control means, except when the depression speed of the accelerator pedal is greater than a predetermined value.

According to this configuration, when the vehicle accelerates and slips, the output torque of the drive shaft is reduced and the rotation of the drive wheels is reduced, and the brake fluid whose pressure is regulated by the brake control means is supplied to the drive wheels. The braking force of the vehicle increases and the slip can be avoided.

``During the operation described in item 1 above, when it is detected by the failure detection means that a part of the drive shaft output torque reduction means has failed, the accelerator pedal is adjusted based on the signal obtained from the accelerator pedal depression speed calculation means. Only when the accelerator pedal depression speed is greater than a predetermined value, the braking control for the driving wheels is carried out, and when the accelerator pedal depression velocity is smaller than the predetermined value, the above braking control is stopped.

Therefore, when the vehicle suddenly accelerates, where excessive engine torque is generated due to a sudden increase in engine torque, which is likely to cause a decrease in vehicle stability, pressure increase control of the brake fluid to the drive wheels is carried out to stop the vehicle from accelerating slip. , during low acceleration and constant speed driving, where the decline in vehicle stability due to acceleration slip is relatively less likely to occur, by not implementing the control described in "-", the frequency of braking control operation can be reduced while ensuring vehicle stability. Even when driving on a high road surface, the pre-knee fade phenomenon does not occur.

Embodiments Hereinafter, embodiments of the vehicle driving force control device according to the present invention will be described in detail based on the drawings.

In the schematic diagram shown in FIG. 2, an engine 2L is a left front wheel, 2R is a right front wheel, and the left front wheel 2I- and the right front wheel 2R are driven wheels. On the other hand, 3L is a left rear wheel, 3R is a right rear wheel, and the left rear wheel 3L and right rear wheel 3R are drive wheels driven by the engine 1. Said engine 1
The driving force is transmitted to the axle 7 on the rear wheel side via the transmission 4, propeller shirt l-5, and differential gear 6.

A propeller shaft rotation speed sensor 8 is attached to the differential gear 6 as drive wheel speed detection means. That is, the left rear wheel 3L and the right rear wheel 3, which are the driving wheels.
The average rotation speed of R is detected by the propeller shaft rotation speed sensor 8 as a pulse (g M ).

10 is an intake passage that supplies fuel to the engine 1,
Inside the intake passage 1, a first throttle valve 11 and a second throttle valve 12 are arranged in parallel. 2. The second throttle valve 12 may be located either upstream or downstream of the first throttle valve 11.

Reference numeral 13 denotes an accelerator pedal operated by the driver, and the opening degree of the first throttle valve 11 is controlled by the accelerator pedal 13.

An accelerator sensor 14 is attached to the accelerator pedal 13 as means for detecting the amount of operation of the accelerator pedal 13.

15 is a step motor for opening and closing the second throttle valve 12; 16 is a second throttle valve 1;
This is an opening sensor as the opening detection means of No. 2. The opening sensor 16 constitutes a part of a throttle valve operation control means as a drive shaft output torque reduction means, as will be described later.

Furthermore, the left front wheel 2L and right front wheel 2R, which are driven wheels, are equipped with a rotation speed sensor 1 that detects the rotation speed of each wheel as a pulse signal.
．． 8.19 is installed. The propeller shaft rotation speed sensor 8 and the rotation speed sensor 1.8.
19 and a control circuit to be described later constitute a slip state amount calculation means for calculating the slip state amount of the vehicle.

In addition to the normal brake fluid that is supplied to each wheel cylinder 2OL, 2OR of the left rear wheel 3L and right rear wheel 3R, which are drive wheels, in response to the depression force of a brake pedal (not shown), a braking control means (to be described later) is provided. Brake fluid is supplied through a pipe 22 and a pipe 23 branched from the pipe 22.

30 determines the opening degree of the second throttle valve 12, and also indicates the supply state of brake fluid supplied to each wheel cylinder 2OL, 2OR of the left rear wheel 3L and right rear wheel 3R via the pipeline 22.23. This control circuit 30 is configured by a microcomputer, and includes an A/D conversion circuit 31 . Central processing unit 32 (CPU), motor drive circuit 33. The main components are an F/V conversion circuit 34 and a read-only memory circuit 35 (ROM).

On the other hand, 40 is a hydraulic pump that generates brake fluid to be supplied to the drive wheels, 41 is an accumulator, and 42 is a normally closed hydraulic control valve as a braking control means. A predetermined hydraulic pressure constantly supplied from the hydraulic pump 40 via the check valve 43 is stored in the accumulator 41 . 44 is a drain pipe connecting the hydraulic pressure control valve 42 and the hydraulic fluid tank 46.

Reference numeral 45 denotes a check valve arranged in a pipeline between the hydraulic pump 40 and the tank 46.

The signal line 18a output from the rotation speed sensor 18 of the left front wheel 2L, the signal line 19a output from the rotation speed sensor 19 of the right front wheel 2R, and the signal line 8a output from the propeller shaft rotation speed sensor 8 Each is input to the F/V conversion circuit 34 of the control circuit 30,
The signal line +68 output from the opening sensor 16 that detects the opening of the second throttle valve 12 and the signal line 14a output from the accelerator sensor 14 are connected to the A/I) conversion circuit 31 of the control circuit 30. It has been entered.

Further, a signal line 33a output from a motor drive circuit 33 in the control circuit 30 is input to the step motor 15.

Further, a signal line 32a outputted from CI) U 32 of the control circuit 30 is connected to a slide/id 42a attached to the hydraulic pressure control valve 42. Therefore, based on the signal from the signal line 32a, the hydraulic control valve 42
It operates to switch the hydraulic pressure supplied to 2 to the pressure increasing side or the pressure reducing side.

According to this circuit configuration, as a basic operation, first, the rotation speed sensor I provided on the left front wheel 2L and the right front wheel 2R
819 and each signal obtained from the propeller shaft rotation speed sensor 8 provided in the differential gear 6 is input to the F/V conversion circuit 34 that constitutes the control circuit 30, and the F/V conversion circuit After each signal is converted into a voltage signal by 34, it is input to the A/D conversion circuit 31, while the opening sensor 16 of the second throttle valve 12
A signal obtained from the A/D conversion circuit 31 is input to the A/D conversion circuit 31. Then, the A/D conversion circuit 31 converts each of the above input signals into digital values, and then inputs the digital values to the CPU 32.

The CPU 32 calculates a target opening value for the second throttle valve 12 based on the human input signals described in 1 above and the storage information stored in advance in the ROM 35, and outputs the calculated opening value to the motor drive circuit 33. Then, the motor drive circuit 33 becomes C
The step motor 15 is driven by outputting a drive signal corresponding to the opening target value inputted from the PU 32. The driving force of the step motor 15 drives the second throttle valve 12 disposed in the intake passage 10 to open and close, thereby controlling the output of the engine.

Therefore, when the slip state quantity calculating means detects that the vehicle is slipping, the rotational output of the engine I is reduced by setting the opening target value of the second throttle valve 12 to be fully closed. At the same time, the hydraulic pressure control valve 42 is switched to the pressure increasing side based on the action of the control circuit 30, and the brake fluid accumulated in the accumulator 41 is delivered to the left rear wheel 3L and the right rear wheel 3R, which are the driving wheels. be provided. Therefore, when the vehicle slips, opening/closing control is carried out to reduce the opening degree of the second throttle valve 12, and the increased pressure of brake fluid is supplied to the driving wheels 3L, 3R from the hydraulic pressure control valve 42 as a braking control means. Since the rotation of the driving wheels 3L and 3R is reduced, the braking force of the old vehicle is increased, and the slip can be avoided.

2. If the throttle valve operation control means 2 serving as the drive shaft output torque reduction means, for example, the opening sensor 16 of the second throttle valve 12, fails during the operation described in 1.
The opening/closing control of the second throttle valve 12 is prohibited, and the operation amount of the accelerator pedal I3 is detected by the accelerator sensor 14, and based on this detection signal, the CP
The accelerator pedal depression speed is calculated by U32,
The braking control for the driving wheels 3L and 3R is carried out only when the accelerator pedal depression speed is greater than a predetermined value, and the braking control is stopped when the accelerator pedal depression velocity is smaller than the predetermined value. be done.

Therefore, when the vehicle accelerates rapidly, which is likely to cause excessive torque to be generated due to a sudden increase in engine torque and result in a decrease in vehicle stability, pressure increase control of the brake fluid to the drive wheels is carried out to prevent the vehicle from accelerating and slipping. By not implementing the above control during low acceleration and constant speed driving, where the decline in vehicle stability due to acceleration slip is relatively less likely to occur, the vehicle stability can be ensured while the braking control is activated more frequently on road surfaces. This provides an effect that the brake shoe fae-1 phenomenon does not occur even when the vehicle is traveling on the road.

Next, referring to FIG. 3, the actual driving force control by the control circuit 30 will be explained in detail using flowchart i. still,
The processing within the main routine shown here is a fixed-time interrupt processing driven at a predetermined cycle (for example, 20 IIlsec) by an operating system (not shown).

In the same figure, when the engine key is inserted into the key cylinder and the ignition switch is turned from off to on, the microcomputer's power is turned on and the interrupt starts for a fixed period of time.・In step 100), it is determined in step 101 whether or not this is the first flow after power-on, and if it is the first, a start signal is added to step 102, and initialization processing such as clearing the ROM 35 is performed. will be done. In addition, if it is not the first flow,
The initialization processing described in - is omitted and the process immediately proceeds to step 103.

In step 103, the wheel speed VF+ is calculated based on the rotational speed detected by the rotational speed sensor I8 of the left front wheel 2L as the slip state amount calculating means, and the wheel speed VF+ is calculated based on the rotational speed detected by the right front wheel rotational speed sensor 19. The average wheel speed V of the rear wheels is calculated based on the wheel speed VFR calculated by 11, and the accelerator pedal operation amount current value 1.1 detected by the accelerator sensor 14. N is read.

Next, in step 104, it is determined whether the voltage value Vlo detected by the opening sensor 16 attached to the second throttle valve 12 is within a preset standard. In the case of this example, the above standards are 0.5V to 4.
It is set to 5V.

In step 104, if Vl6 is within the specification 1, it is determined that the operation of the opening sensor 16 is normal, and step 1
If the opening sensor 16 is outside the standard, it is determined that the opening sensor 16 is malfunctioning, and the process advances to step 2015.

VI [+ or outside the standard means that the opening sensor 16
Since the power supply line may be short-circuited or disconnected, feedback control of the step motor 15, which will be described later, becomes impossible. Therefore, in step 201, the current value of the accelerator pedal operation amount N and the past value of the accelerator pedal operation amount stored in the ROM 35 ■74. From the accelerator pedal engagement speed L'+,' = L, t-1,.

In the next step 202, it is determined whether the accelerator pedal depression speed L' is greater than a predetermined value l. (2) If L' or L' is larger than a predetermined value, the process proceeds to the control routine from step 105; if L' is smaller than the predetermined value, the process proceeds to step 203;
In step 20, energization to the solenoid 42a of the hydraulic pressure control valve 42 is stopped and the hydraulic pressure control valve 42 is maintained at the reduced pressure position.
4 Current value of accelerator pedal operation amount 1. Rewrite N to accelerator pedal operation amount past value LD and store it, drive wheel 3L,
Subsequent driving force control for 3R and 6 is not performed.

Next, in step 105, VFl read in step 103, Vl, and the average wheel speed of the left front wheel 2L and right front wheel 2R, which are driven wheels, are calculated as v, - (V FL + V FR) / 2. In other words, it is calculated as the average value of both wheel speeds VFR and VFL.

Here, it is generally known that the average wheel speed VF of the driven wheels described above coincides with the vehicle body speed of the vehicle.

Next, in step 106, the slip rate S as the amount of slip between the tire and the road surface is calculated from the average wheel speed V in 1 and the average wheel speed VR of the left rear wheel 3L and right rear wheel 3R, which are the drive wheels. , 5-(VR-VF)/vn.

Next, in step 107, the slip ratio S obtained in step 106 is set to the set value S. (For example, S.

01), and if it is larger, it is assumed that a slip has occurred and the process proceeds to step 110, whereas if it is smaller, it is assumed that a slip has not occurred and the process proceeds to step 108.

In step 108, the target opening value 5TEP' of the second throttle valve 12 is set to full open, and in the next step 109
Then, the hydraulic pressure control valve 42 is set to the pressure reducing position and the process proceeds to step 112.

Further, if a slip has occurred, step 110
The opening degree of the second throttle valve 12 is 1" target value 5TEP.
" is fully closed, and in the next step III, the hydraulic pressure control valve 42 is closed.
is switched to the pressure increasing position and the process proceeds to step 112. By switching the hydraulic pressure control valve 42 to the pressure increasing position, the hydraulic fluid accumulated in the accumulator 41 is supplied to the left rear wheel 3I- and the right rear wheel 3R via the hydraulic pressure control valve 42 and the pipes 22, 23. Therefore, the braking force of the left rear wheel 3L and right rear wheel 3R is increased.

Next, in step 112, the deviation Dir between the actual opening value 5TEP of the second throttle valve 12 detected by the opening sensor 16 and the opening target value STIΣI)1 is calculated as Dir=STEP'-5TEP. Then, in step 113, the motor speed is calculated based on the deviation level 1.Furthermore, in step 114, it is determined whether the motor rotates forward/reversely/maintains.

Step ], l If forward rotation is determined in step 4, 1 is added to the actual opening value 5TE11 of the second throttle valve 12 in step 115, and if reverse rotation is determined, step 115 is performed. , step 116 causes the second slot y
1 is subtracted from the actual opening value 5TEP of the I-le valve 12. In addition, when a determination is made to hold, the actual opening value 5TEP remains unchanged.

In step 117, in response to the command in step 114], a motor rotation signal corresponding to 5 TEP is output to the motor drive circuit 33, and the step motor 1 is
5 to rotate the second throttle valve 12 in the intake passage 10 shown in FIG. 1 by an angle corresponding to l5TEP. In step 11.8, the accelerator pedal operation amount current value LN is rewritten and stored as the accelerator pedal operation amount current value LII, and the control for one operation cycle is completed.

By repeating this interrupt flowchart 1.9, the second throttle valve 12 is rotated to the target angle.

Although it is not shown in the flowchart, if it is determined in step 104 that the opening sensor 16 attached to the second throttle valve 12 is malfunctioning, the opening sensor 16 attached to the second throttle valve 12 naturally step motor 1
5 is prohibited, that is, the closing operation of the second throttle valve 12 is not performed, and the left rear wheel 3, which is the driving wheel, is prohibited.
Only brake fluid pressure increase control for L and right rear wheel 3R is performed.

According to this embodiment, even when the vehicle is not slipping, there is no loss of intake air amount due to the second throttle valve, and therefore the acceleration response of the vehicle is maintained well. can do. Furthermore, even during anti-slip control, the first throttle valve opens and closes to a certain extent depending on the amount of accelerator pedal operation, so there remains a correspondence between accelerator pedal operation and engine driving force. There is also the effect that there is no major discomfort.

'', the second throttle valve 1 installed in parallel with the first throttle valve 11 serves as a drive shaft output torque reducing means for reducing the output torque of the axle 7 of the rear wheel.
Although the means for reducing the output of engine I using No. 2 has been shown, it is also possible to use means for controlling the amount of fuel supplied to engine I or controlling the ignition timing in addition to such means. In this case, the fuel supply amount control or the ignition timing control returns to the normal state when the failure is detected.

In addition, ``2S'' is used as a reference value for determining the slip rate S.

-0 and -1, but this slip rate is determined by the vehicle, engine, etc., and can be changed freely.

Furthermore, as a means for detecting a failure of the throttle valve operation control means, the determination is made based on whether the opening sensor 16 is out of specification, but it is also possible to use, for example, the opening target value and actual opening of the second throttle valve. If the deviation from the threshold value is greater than a predetermined value, it can be determined that the throttle valve has a failure due to foreign matter getting stuck or freezing.

Further, the failure detection means may be one that detects not only a failure of the opening sensor but also a failure of an actuator such as the step motor 15, and furthermore, a failure of a part of the control circuit for fuel supply control or ignition timing control. It may also be something that detects.

Further, although the step motor 15 is used as a means for opening and closing the second throttle valve 12, the step motor 1
5, a DC motor or a servo motor may be used.

Furthermore, in order to reduce the drive shaft output torque in order to prevent slips when driving the vehicle, θ is used in combination with either the slot I/reparve opening/closing means and the engine's ignition timing or fuel supply amount control mechanism. You can also do that.

In the embodiment described in -1- below, the slip rate S was used as the slip state quantity that cuts the degree of slip by 1, or instead of this, the slip ff1v, v was used, and each setting was adjusted accordingly. A similar control may be performed by determining a value.

Incidentally, by attaching a spring to the second throttle valve 12 that biases the second throttle valve 12 toward the fully open side during normal times, if the control circuit 30 or the step motor 15 etc. Even if a failure occurs and control of the second throttle valve 12 is prohibited,
The second throttle valve 12 can be held at the fully open position by the spring, and the normal running state by the first throttle valve 11 can be maintained.

In this embodiment, whether the braking control is prohibited except when the depression speed of the accelerator pedal 13 is greater than a predetermined value, or whether there is a need to reduce the driving speed knob or a relatively small predetermined vehicle speed. Braking control may also be prohibited when the vehicle is in a non-turning state or when the vehicle is not turning.

In addition, if the drive shaft output torque reduction means is to prohibit the control of the drive shaft output torque, or if a second throttle valve is used, the second throttle valve opening should be set to full open or malfunction. It means to hold the detection period for a certain period of time, and for those that use fuel supply amount control or ignition timing control, it means to return to normal control without performing control to prevent slippage. Needless to say.

Effects of the Invention As described above in detail, the vehicle driving force control device according to the present invention provides the following effects.

That is, when the vehicle slips, control is performed such that the torque transmitted to the drive shaft of the drive wheel is reduced by the drive shaft output torque reducing means according to the slip state, and furthermore, the brake fluid increased in pressure from the braking control means is Since it is supplied to the drive wheels, the drive torque of the drive wheels can be reduced and the braking force of the vehicle can be increased, making it possible to avoid slipping of the vehicle. During such an operation, if the failure detection means detects that the drive shaft output torque reduction means has failed, control by the drive shaft output torque reduction means is prohibited and the signal obtained from the accelerator pedal depression speed calculation means is According to The above control can be stopped when the vehicle is accelerating at low speeds or traveling at a constant speed. In other words, when the vehicle is rapidly accelerating, which is likely to cause a drop in vehicle stability due to a sudden increase in engine torque, pressure increase control of the brake fluid to the drive wheels is carried out to prevent the vehicle from accelerating slip, and to reduce the acceleration slip. By disabling the control described in -1- during low acceleration and constant speed driving where vehicle stability is less likely to deteriorate due to Even if there is such an effect, the stability of the vehicle is ensured and the fade phenomenon of prekinny does not occur.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to claims of the vehicle driving force control device according to the present invention, Fig. 2 is a schematic diagram showing an embodiment of the same driving force control device, and Fig. 3 is an actual example of the same driving force control. It is a flowchart. 1... En7in, 2 L... Left front wheel, 2R right front wheel, 3
L... Left rear wheel, 3 feet... Right rear wheel, 8 Propeller shaft rotation speed sensor, 10... Intake vent FIL] 1... First throttle valve, 12 - Second throttle valve, 13 ... Accelerator sensor, 1/I... Accelerator sensor, 15... Step motor, 16... Opening sensor,
18.19... Rotation speed sensor, 20L, 2OR... Wheel cylinder, 30... Control circuit, 31... A/D conversion circuit, 32... CPU, 3
3... Motor drive circuit, 34... F/V conversion circuit, 35... Read-only memory circuit, 40... Hydraulic pressure pump, 41... Accumulator, 42... Hydraulic pressure control valve ( Braking control means) 27~

Claims (1)

[Claims] (1) Drive force control for a vehicle that prevents the slip of the drive wheels when the vehicle accelerates and slips using a drive shaft output torque reduction means that reduces the output torque of the drive shaft and a brake control means that brakes the drive wheels. In the device, an accelerator pedal operation amount detection means for detecting the operation amount of the accelerator pedal, an accelerator pedal depression speed calculation means for calculating the accelerator pedal depression speed from the detected accelerator pedal operation amount, and the drive shaft output torque reduction means. and a failure detection means for detecting a failure of the drive shaft output torque reduction means, and when the failure detection means detects a failure of the drive shaft output torque reduction means, the control of the output torque of the drive shaft by the drive shaft output torque reduction means is prohibited. In addition, the vehicle is characterized in that a signal obtained from the accelerator pedal depression speed calculating means prohibits braking control by the braking control means unless the accelerator pedal depression speed is greater than a predetermined value. driving force control device.