JPH0228064A - Steering control device - Google Patents

Abstract

PURPOSE:To prevent an uncontrolled steering phenomenon in a split mu road by steering front and rear wheels respectively in specific directions in accordance with a degree of drive torque difference between the right and left drive wheels, when a car speed is not more than a predetermined value further when a rotary speed difference between the right and left drive wheels is not less than a predetermined value. CONSTITUTION:In an automobile, for instance, rear wheel-drive vehicle, pressure oil from an external hydraulic power source 30 is introduced to a power cylinder 27 through a control valve 39, thus right and left front wheels 24, 25 are steered independently of handle control action. The control valve 39 is controlled by a controller 33. Here the controller 33 provides respectively a car speed detecting part 331, drive wheel speed difference detecting part 332 and a drive torque difference detecting part 333 while a front wheel steering control part 334 controlling the control valve 39 in accordance with a detecting result of these detecting parts 331, 332, 333. When a car speed is not more than a predetermined value further when a rotary speed difference is not less than a predetermined value, in accordance with a degree of drive torque difference, for instance, each front wheel 24, 25 is steered in a direction of larger drive torque.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a steering control device for a vehicle, and particularly to a technology for reducing a steering phenomenon when traveling on a split μ road.

(Prior Art) Conventionally, a differential device (conventional differential) was used in ``Automotive Engineering Complete Book Vol. 9 Power Transmission Devices''.
The apparatus described on pages 309 to 321 of the publication published by Sankaido Co., Ltd., November 1980 is known.

Furthermore, as a differential device equipped with a viscous clutch that is interposed between relatively rotatable members and limits the differential motion between the two members, for example, the device described in Japanese Patent Application Laid-Open No. 60-227024, etc. Are known.

Further, as a differential device equipped with a differential limiting force variable device that controls the differential limiting force by varying the engagement force from the outside using a hydraulic clutch, for example, Japanese Patent Application Laid-Open No. 62-103226
Devices described in Japanese Patent Application Laid-open No. 103227/1983 are known.

(Problem to be Solved by the Invention) However, when driving on a split road with a vehicle equipped with such a differential, the drive is divided between the left and right wheels via the differential due to the influence of the road surface μ. As shown in Fig. 9, the torque is high on the high μ road side torque (■2), which causes low wheel speeds, and the low μ road side torque (μ+11), which causes high wheel speeds, becomes low, and a yaw moment M acts on the vehicle in the direction of the arrow. Therefore, there was a problem in that the rudder was steered in the direction of the moment even though the vehicle was traveling straight ahead.

In particular, in a differential gear equipped with a viscous clutch for limiting the differential or a variable differential limiting force device, the yaw moment M
In particular, if the latter differential device is configured to strengthen the differential limiting force when the accelerator is on in order to improve starting performance, high drive torque can be obtained when driving on a split μ road, but the The drive torque difference also becomes significant, leading to a noticeable steering phenomenon.

In addition, in the case of a conventional differential,
Theoretically, the transfer ratio (drive torque distribution ratio) is 1.
However, in reality, the value is 1.2 to 1.5 due to the influence of friction and the like.

As a result, the left and right drive torque distribution ratios are different, and when traveling on a split μ road, a yaw moment is generated in the vehicle, similar to a differential device in which the differential limiting force is variable, although the value is small.

The present invention was made with attention to such problems, and
A steering control device that effectively prevents the steering phenomenon when traveling on split μ roads in vehicles equipped with a normal differential device, a differential device with a viscous clutch, or a differential device with differential limiting force or a variable differential device. development as a common issue.

(Means for Solving the Problems) It is an object of the present invention to solve the above problems, and to achieve this object, the steering control device according to claim 1 is provided with predetermined detection means and control means, The steering control device is capable of controlling at least one of the steering angles by an external command, and the detection means includes vehicle speed detection means for detecting vehicle speed, and rotation of left and right drive wheels distributed via a differential device. It has a rotational speed difference detection means for detecting a speed difference, and a drive torque difference detection means for detecting a drive torque difference between the left and right drive wheels, and the control means is configured to control the speed of the left and right drive wheels when the vehicle speed is equal to or lower than a predetermined vehicle speed. When the rotational speed difference is greater than a predetermined value, the front wheels are steered in a direction with a larger drive torque or the rear furnace is steered in a direction with a smaller drive torque depending on the magnitude of the drive torque difference. It has a steering control section that performs
The method is characterized by ≠.

The steering control device according to claim 2 is a steering control device comprising a predetermined detection means and a control means and capable of controlling the steering angle of at least one of the front wheels and the rear wheels by an external command, The detection means includes a vehicle speed detection means for detecting the vehicle speed, a rotation speed difference detection means for detecting the rotation speed difference between the left and right drive wheels distributed via a differential device equipped with a variable differential limiting force device, and and drive torque difference detection means for detecting a drive torque difference between the drive wheels, and the control means includes:
a differential limiting force control section that performs control to increase the differential limiting force when the vehicle speed is less than a predetermined vehicle speed and the rotational speed difference between the left and right drive wheels is greater than or equal to a predetermined value; The vehicle is characterized by having a steering control section that controls at least one of steering the front wheels in a direction with a larger driving torque or steering the rear wheels in a direction with a smaller driving torque depending on the magnitude of the torque difference. It was a means to do so.

The drive torque difference detection means may be a means for determining the drive torque difference from the difference between the respective drive torques of the left and right drive wheels detected by a torque sensor, or the drive torque difference may be a means for determining the drive torque difference from the difference between the drive torques of the left and right drive wheels detected by a torque sensor, or the drive torque difference between the left and right drive wheels detected by the rotational speed difference detection means The drive torque difference may be estimated based on the value of the rotational speed difference between the two rotational speeds.

(for production) The operation of the steering control device according to the first aspect will be described.

It is detected that the vehicle is running on a split μ road based on the judgment conditions that the vehicle speed is less than a predetermined vehicle speed and the rotational speed difference between the left and right drive wheels is greater than a predetermined value. In the wholesale section, depending on the magnitude of the drive torque difference detected by the drive torque difference detection means, at least one of steering the front wheels in a direction with a larger drive torque and steering the rear wheels in a direction with a smaller drive torque is performed. Control takes place.

Therefore, a yaw moment around the center of gravity is generated due to the cornering force based on the steering of at least one of the front wheels or the rear wheels, and this yaw moment is approximately the same in the opposite direction as the yaw moment generated due to the drive torque difference between the left and right drive wheels. Because of the size, both yaw moments cancel each other out around the center of gravity.

The operation of the steering control device according to the second aspect will be described.

Based on the judgment conditions that the vehicle speed is below a predetermined vehicle speed and the rotational speed difference between the left and right drive wheels is greater than or equal to a predetermined value, it is detected that the vehicle is running on a split μ road. In the limiting force control section, control is performed to increase the differential limiting force, and at the same time, in the steering control section, the front wheels are steered in a direction of greater drive torque in accordance with the magnitude of the drive torque difference detected by the drive torque difference detection means. At least one of the following steering control is performed: steering the rear wheels in a direction with a smaller drive torque.

Therefore, by controlling to increase the differential limiting force, the left and right wheel drive torque is increased, and the drivability on the split μ road is improved.

On the other hand, control to increase the differential limiting force generates a large yaw moment due to the drive torque difference between the left and right drive wheels. is canceled by the yaw moment of

(Example) Embodiments of the present invention will be described below based on the drawings.

First, a rear wheel drive vehicle to which the steering control device A1 of the first embodiment is applied, which is characterized by a configuration, and more specifically corresponds to the invention described in claim 3, is shown in FIG. As shown in
, a transmission 11, a propeller shaft 12, a differential 13 (differential device), a drive shaft 14, 15, rear wheels +6.17, front wheels 24, 25, and a power cylinder 27 for steering the front wheels.

In addition to the mechanical front wheel steering by the driver's steering wheel operation, the front wheel steering power cylinder 27
Steering control that controls the steering direction of the front wheels 24 and 25 is performed by applying pressurized oil from an external hydraulic source 30 to the front wheel steering power cylinder 2 through a front wheel steering control valve 39.
This is done by leading to 7.

Further, a controller 33 (control means) that outputs a drive signal to the front wheel steering control valve 39 is an electronic control circuit including a valve drive circuit, and this controller 33 includes a vehicle speed detection section 331 (vehicle speed detection means); It includes a drive wheel rotation speed difference detection section 332 (rotation speed difference detection means), a drive torque difference detection section 333 (drive torque difference detection means), and a front wheel steering control section 334 (steering control section).

The vehicle speed detection unit 331 receives a right front wheel speed NFn and a left front wheel speed NFn from a right front wheel speed sensor 35 and a left front wheel speed sensor 36.
A detection signal of L is input.

Detection signals of the right rear wheel speed NIIR and the left rear wheel speed NRL are inputted to the drive wheel rotational speed difference detection section 332 from the right rear wheel speed sensor 37 and the left rear wheel speed sensor 38 .

The drive torque difference detection section 333 receives detection signals of the right rear wheel drive torque TR and the left rear wheel drive torque TL from the right rear wheel drive torque sensor 40 and the left rear wheel drive torque sensor 41.

Next, the operation of the first embodiment will be explained.

Controller 3 based on the flowchart shown in FIG.
The flow of control operation in 3 will be described.

In step 100, the right front wheel speed NFn and the left front wheel speed N, L are determined.
, right rear wheel speed N1IR, left rear wheel speed NnL, right rear wheel drive torque T, and left rear wheel drive torque T1- are read.

In step 101, the vehicle speed V is calculated from the average speed of the front wheels 24.25, which are non-driving wheels, using the equation shown below.

-% (NFR+NrL) In step 102, the vehicle speed V is the set vehicle speed V. It is determined whether the vehicle speed is as low as below.

In step 103, it is determined whether the rotational speed difference 1Nnn Nn,l between the left and right rear wheels 16,17 is greater than or equal to a set value ε.

That is, the vehicle speed condition in step 102 and step 103
It is determined whether or not the vehicle is running on a split μ road based on the rotational speed difference condition, and if V≦Vo and lNl1□−
When Nn, l≧ε, it is assumed that the vehicle is running on a split μ road, and the process proceeds to step 104, where the magnitude relationship between the right rear wheel drive torque TR and the left rear wheel drive torque lower is determined, and further, T
When n>TL, the process advances to step 105, and when T,<
When it is TL, the process proceeds to step 106, and in each step, the front wheel turning angle of 6F is determined.

Here, a method for determining the front wheel turning angle δ when T n > T t will be described based on FIG. 3.

When there is a torque difference between the left and right rear wheels16.17, the yaw moment M around the center of gravity acting on the vehicle is tr TRT
L M = −(−−−) ・・・■r
r However, tr is the tread width.

The front wheel steering angle δ required to generate the yaw moment M° to cancel this is calculated as follows: YL=Cp-WL・δ, if the tire characteristics are approximated by assuming that the standard value of cornering power with respect to the load is approximately CP.

YR=Cp-Wn・δ.

M' ``a ・(Y L + Y R) '''
■However, YL and Y are cornering forces, and a is the distance from the center of gravity position to the front wheel axle position.

In order to satisfy M=M'', the front wheel turning angle δ is calculated using the above equation (■=■), and becomes a constant of 2K·(TR-TL)K.

In step 107 and step 108, the front wheel 24.2
5 is the large steering direction of the rear wheel drive torque (T n > T
When L, the steering is to the right; when T, <T, the steering is to the left), and the steering command signal (i) that provides the front wheel steering angle 61 obtained in step 105 or step 106 is the front wheel steering control valve. 39.

Then, in steps 109 and 110, FLAG-3=1 is set, which indicates control to prevent the steering phenomenon.

Further, if even one of the control conditions in steps 102 and 103 is not satisfied, the process proceeds to step 111, and the FLAG
It is determined whether -S=1, and when FLAG-5=1, a command signal is output in step 112 to return the front wheels to their original positions.

In addition, in slap 113, FLAG-5 = 1 is FLAG
-3 = rewritten to 0.

As explained above, the steering control device A1 of the first embodiment provides the following effects.

■Vehicle speed V is the set vehicle speed V. When traveling on a split μ road where the rotational speed difference between the left and right drive wheels is greater than or equal to the set value ε, the controller 33 performs steering control to steer the front wheels 24, 25 in the direction of greater drive torque. The yaw moment M due to the drive torque difference (road surface transmission torque difference) between the rear wheels 16.17 is the cornering force Y R, Y generated based on the steering of the front wheels 24.25.
It is canceled by the yaw moment M around the center of gravity due to L,
It is possible to prevent the steering phenomenon caused by traveling on a split μ road.

■ When performing steering control, drive torque difference TR-
Since TLl is calculated and control is performed to obtain a front wheel steering angle according to this value, the yaw moment due to front wheel steering is neither too large nor too small compared to the yaw moment due to the drive torque difference, and is effective. Moreover, the steering phenomenon caused by traveling on a split μ road can be reliably prevented.

Next, with reference to FIGS. 4 to 6, a steering control device A2 according to a second embodiment of the present invention will be described. .

The basic structure and operation are the same as the first embodiment described above. Here, the same numbers are given to the same components as in the first embodiment, and the explanation thereof will be omitted.

First, the configuration will be explained.

In FIG. 4, the differential 13 has a known viscous clutch 50 therein that limits the differential movement between the left and right drive wheels.

Here, the characteristics of the viscous clutch 50 are as shown in FIG.
It is known experimentally that TLI has a certain relationship.

The present embodiment utilizes this known characteristic, and uses the value of the rotation speed difference 1Nnn NnLl between the left and right drive wheels detected by the rotation speed difference detection unit 332 instead of the drive torque difference detection unit 333 of the first embodiment. Drive torque difference 1Tn based on
- A driving torque difference estimation and detection section 335 is provided to estimate T and l.

Next, the flow of control operations in the controller 33 will be described based on the flowchart shown in FIG.

Similar to the configuration, steps that are common to those in the first embodiment are given the same numbers and their explanations will be omitted.

In step 150, the right front wheel speed NFR and the left front wheel speed N, L are determined.
and right rear wheel speed N. R and left rear wheel speed N8. - is read.

In step 154, the right rear wheel speed NRR and the left rear wheel speed NnL are determined.
It is determined which wheel is slipping, that is, which wheel has a lower road surface μ, the left or right.

If it is determined that the road surface μ on the left rear wheel side is low, step 155. Proceeding to step 107, the front wheels are steered to the right according to the drive torque difference ITLI-TL+ estimated in step 151.

Similarly, if it is determined in step 154 that the road surface μ on the right rear wheel side is low, step 156. Proceed to step 10B and steer the front wheels to the left.

Note that even if 13 is a conventional one, the characteristics of the drive torque difference 1TR-T,l with respect to the rotational speed difference lNnnNRLl can be determined experimentally, so this characteristic is dataed to the drive torque difference estimation detection unit 335. By initially setting as , it is possible to perform steering control similar to that of the second embodiment.

Next, with reference to FIGS. 7 and 8, a steering control device A3 according to a third embodiment of the present invention will be described.

First, the configuration will be explained.

As shown in FIG. 4, a rear wheel drive vehicle to which the steering control device A3 of the third embodiment is applied includes an engine 10, a transmission 11, a propeller shaft 12, a differential 13, a drive shaft 14. +5, rear wheel 16.17
, rear wheel steering power cylinder 19 (rear wheel steering actuator), side rods 20, 2+, knuckles 22, 2
3, front wheels 24, 25, a differential limiting clutch 26, and a front wheel steering power cylinder 27 (front wheel steering actuator) are provided.

Then, the rear wheel 1 is controlled by hydraulic control to the rear wheel steering power cylinder 19 and the front wheel steering power cylinder 27
6.17 and the front wheels 24.25, and the engagement force control of the differential limiting clutch 26 built into the differential 13 (type 13 multi-disc friction clutch, etc.) controls the left and right rear wheels. 16.17 differential side eye power control that variably controls the differential side eye power Δt refers to the differential side eye power control that variably controls the differential side eye power Δt. This is performed by guiding the rear wheel steering power cylinder 19 and the front wheel steering power cylinder 27 to the differential limiting clutch 26 via the dynamic limiting control valve 32, respectively.

That is, the controller 33 that outputs drive signals to the rear wheel steering control valve 31, the front wheel steering control valve 39, and the differential limiting control valve 32 also functions as a four-wheel steering control section and a differential side eye power control section. 4-wheel steering and differential limiting force control section 336
Or is provided.

Next, the operation of the third embodiment will be explained.

Controller 3 based on the flow chart shown in FIG.
The flow of control operation in 3 will be described.

In step 200, the right front wheel speed NFR and the left front wheel speed N, L are determined.
, right rear wheel speed NRR, and left rear wheel speed NRL are read.

In step 201, the average speed of the front wheels 24.25, which are non-driving wheels, and the vehicle speed V are calculated using the following calculation formula.

■2% (NFR+NFL) In step 202, the vehicle speed V is the set vehicle speed V. It is determined whether the vehicle is running at the following low vehicle speeds.

In step 203, the wheel speed difference between the left and right rear wheels is 16.17!
It is determined whether NRp NRL+ is greater than or equal to the set value ε.

Then, when V≦Vo and NRRNRL+≧ε, that is, when traveling on a split μ road, the process proceeds to step 204, and a command signal (i,) for increasing the four differential limiting forces is output to the differential limiting control valve 32. be done.

In step 205, the magnitude relationship between the right rear wheel torque TR and the left rear wheel torque TL is determined, and when TL>TR, the process proceeds to step 206, and when TR>TL, the process proceeds to step 207.

In step 206, the front wheels 24 and 25 are steered to the left, where the rear wheel drive torque is large, and the front wheels are steered to a predetermined front wheel steering angle F that is preset based on TR and TL. A steering command signal (i3) that obtains is output to the front wheel steering control valve 39, and the rear wheels 16.17 are steered to the right with a large rear wheel drive torque, in a predetermined direction based on TR and TL. A steering command signal (i,) from which the front wheel turning angle δRO is obtained is output to the rear wheel turning control valve 31.

In step 207, the front wheels 24, 25 are steered to the right direction with a large rear wheel drive torque, and the steering command signal (13) obtained from the predetermined front wheel steering angle 6 FD, which is preset based on TR and TL, is sent to the right. A steering command signal outputted to the wheel steering control valve 39 to steer the rear wheels 16.17 to the left with a large rear wheel drive torque and to obtain a predetermined front wheel steering angle δRO set in advance based on TR and TL. (12) is output to the rear wheel steering control valve 31.

Next, in steps 208 and 209, FLAG-S=1 is set indicating control to prevent the steering phenomenon.

Further, if even one of the control conditions in steps 202 and 203 is not satisfied, the process proceeds to step 210, and the FLAG
-S=1 is determined, and when FLAG-3=1, a command to cancel the four differential limiting forces is output in step 211, and furthermore, in step 212, the front wheel two
A command signal is output to return the rear wheels 4.25 and 16.17 to their original positions.

Then, in step 213, FLAG-3=1 is FL
It is rewritten to AG-3=0.

As explained above, in the steering control device A3 of the third embodiment, the vehicle speed V is the set vehicle speed V. below, and the wheel speed difference between the left and right rear wheels is greater than or equal to the set value ε.
When driving on a road, the controller 33 performs differential restriction control to strengthen the differential eye power Δ, and also controls the front wheels 2.
Since steering control is performed to steer the rear wheels 16.17 in the direction of lower wheel speeds and the rear wheels 16.17 in the direction of higher wheel speeds, the drive to the rear wheels 16.17 is performed by applying the differential eye power Δt. The increased torque ensures drivability on split μ roads, and the increased drive torque increases the power of the left and right rear wheels.
．． Even if a high yaw moment occurs due to the difference in drive torque of 17, it is canceled out by the high yaw moment around the center of gravity due to the cornering force generated based on the steering of the front and rear wheels, preventing the steering phenomenon caused by split μ road driving. You can get the effect that you can.

That is, when traveling on a split μ road, running performance can be improved without causing vehicle spin.

Although the embodiments have been described above based on the drawings, the specific configuration is not limited to these embodiments, and any changes or additions that do not depart from the gist of the present invention are included in the present invention. .

For example, in the embodiment, examples of front wheel control and front and rear wheel control are shown as steering control. It may also be possible to control only the rear wheels.

In addition, in the embodiment, an example was shown in which both the steering and the differential limiting force are controlled by hydraulic pressure, but there are also cases where wheel steering is controlled by an electric motor, or where the differential limiting force is obtained by an external electromagnetic force. , even by other means.

Furthermore, in the embodiment, the vehicle speed detection section, rotational speed difference detection section, drive torque difference detection section, etc. are provided in the controller, but these detection means may be provided separately outside the controller. Needless to say.

(Effects of the Invention) As described above, in the steering control device of the present invention according to claims 1 and 2, the vehicle speed is equal to or lower than the predetermined vehicle speed, and the rotational speed difference between the left and right driving wheels is a predetermined value. At the above time,
The means has a steering control unit that controls at least one of steering the front wheels in a direction with a larger drive torque and steering the rear wheels in a direction with a smaller drive torque depending on the magnitude of the drive torque difference. Therefore, it is possible to obtain the effect of preventing the steering phenomenon when traveling on a split μ road.

In addition to the above-mentioned effects, the steering control device according to claim 2 has a means for simultaneously performing control to increase the differential limiting force and steering control when traveling on a split μ road, thereby improving vehicle drive torque and steering control. An effect can be obtained that can achieve both the prevention of the phenomenon of being removed.

[Brief explanation of the drawing]

FIG. 1 is an overall diagram showing a steering control device according to a first embodiment of the present invention, FIG. 2 is a flowchart showing the flow of control operations in the controller of the first embodiment, and FIG. 3 is a diagram showing the first embodiment. Fig. 4 is an overall view showing the steering control device according to the second embodiment of the present invention, and Fig. 5 is a flowchart of the control operation in the controller of the device according to the second embodiment. FIG. 6 is an explanatory diagram showing the relationship between the rotational speed difference and the drive torque difference in a differential device using a viscous clutch, and FIG. 7 is a steering control illumination diagram according to a third embodiment of the present invention.
FIG. 8 is a general view showing the device; FIG. 8 is a flowchart showing the flow of control operations in the controller of the device of the third embodiment; FIG.
The figure is an explanatory diagram of the steering phenomenon when traveling on a split μ road. AI, A2. A3... Steering control device 0... Engine... Transmission 2... Propeller shaft 3... Differential (differential device) 4.15...
・Drive shaft 6.17...Rear wheel 9...Power cylinder for steering wheel contact 24.25...Front wheel 26...Differential limiting clutch 27...Power cylinder for steering front wheel 31... Rear wheel steering control valve 32...differential limit control valve 33...controller (control means) 331...vehicle speed detection section (vehicle speed detection means) 332...
Rotational speed difference detection section (rotational speed difference detection means) 333... Drive torque difference detection section (drive torque difference detection means) 334...-Front wheel steering control section (steering control section) 335...
- Drive torque difference estimation detection unit (drive torque difference detection means) 336... Four-wheel steering and differential limiting force control unit (steering control unit, differential side eye power control unit) 39... Front wheel steering control valve 50.・Viscous clutch

Claims (1)

[Scope of Claims] 1) A steering control device comprising predetermined detection means and control means and capable of controlling the steering angle of at least one of front wheels or rear wheels by an external command, the detection means comprising: Vehicle speed detection means for detecting vehicle speed; rotational speed difference detection means for detecting a rotational speed difference between left and right drive wheels distributed via a differential; and drive torque difference detection means for detecting a drive torque difference between the left and right drive wheels. means, the control means is configured to move the front wheels in a direction with greater drive torque according to the magnitude of the drive torque difference when the vehicle speed is less than or equal to a predetermined vehicle speed and the rotational speed difference between the left and right drive wheels is greater than or equal to a predetermined value. 1. A steering control device comprising a steering control section that controls at least one of steering the rear wheels in a direction with a smaller drive torque. 2) A steering control device that includes predetermined detection means and control means and is capable of controlling the steering angle of at least one of the front wheels or the rear wheels by an external command, and the detection means includes a vehicle speed detection device that detects the vehicle speed. a rotational speed difference detection means for detecting a rotational speed difference between left and right drive wheels distributed via a differential device having a variable differential limiting force device; and a drive for detecting a drive torque difference between the left and right drive wheels. torque difference detection means, and the control means performs differential limiting force control to increase the differential limiting force when the vehicle speed is below a predetermined vehicle speed and the rotational speed difference between the left and right drive wheels is above a predetermined value. and simultaneously with this differential limiting force control, depending on the magnitude of the drive torque difference, the front wheels are steered in the direction of greater drive torque, or the rear wheels are steered in the direction of smaller drive torque. A steering control device characterized by having a steering control section that performs one control. 3) The steering control device according to claim 1 or 2, wherein the drive torque difference detection means is a means for determining the drive torque difference from the difference between the respective drive torques of the left and right drive wheels detected by a torque sensor. . 4) The drive torque difference detection means is a means for estimating the drive torque difference based on the value of the rotational speed difference between the left and right drive wheels detected by the rotational speed difference detection means. 2. The steering control device according to 2.