JPH04314637A - Traction control device for vehicle - Google Patents

Abstract

PURPOSE:To contrive adequateness of traction control at the time of starting by independently estimating a friction coefficient respectively relating to right/ left drive wheels based on a relation between a preset engine speed and a road surface friction coefficient under a specified starting condition of a vehicle. CONSTITUTION:In a control unit 200, at the time of starting a vehicle, an engine speed, represented by a detection output signal Sn, is collated with a data map, determining a relation between an engine speed prestored in a built-in memory and a road surface friction coefficient, to individually estimate friction coefficients muR, muL of right/left rear wheels 20R, 20L at the time of starting. In the case of estimating the friction coefficient of only one of the right/left rear wheels, the control unit 200 estimates the coefficient with muX in a proportional relation to one of the estimated friction coefficients muR, muL. The value muX thus obtained is set to a value, for instance, 1.5 times one of the estimated road surface friction coefficients muR, muL. In this way, the estimated value is prevented from extremely separating.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention detects the slip of the drive wheels of a vehicle on the road surface, and performs torque control on the drive wheels to prevent the detected slip from exceeding a predetermined level. Regarding a control device.

0002

2. Description of the Related Art When a vehicle is running, for example, when the accelerator pedal is depressed to accelerate, the drive wheels slip on the road surface on a relatively large scale. In such a case, applying braking force to the driving wheels or reducing engine output will reduce the slippage of the driving wheels on the road surface. It is known that a vehicle is provided with a traction control device, that is, a traction control device that performs traction control to prevent the amount of traction from exceeding a predetermined level.

[0003] In such a traction control device, the traction control is normally performed by, for example, determining a target slip rate or a target slip amount (hereinafter, the target slip rate or the target slip amount is referred to as a target slip value) according to the road surface friction coefficient. Under the setting, the slip of the driving wheels of the vehicle on the road surface is greater than a predetermined slip rate or slip amount (hereinafter, the slip rate or slip amount is referred to as slip value), that is, the slip is greater than a predetermined magnitude. When this happens, in order to bring the slip on the road surface of the relevant driving wheel to the target slip value, the relevant driving wheel is controlled to apply a braking force to the driving wheel or to reduce the output of the engine installed in the vehicle. This is accomplished by performing a drive torque reduction operation that reduces the torque on the drive wheels.

[0004] When such traction control is performed, a brake device for the drive wheels installed in the vehicle is activated in order to apply braking force to the drive wheels, but the durability of the brake device for the drive wheels is taken into account. For example, as shown in Japanese Unexamined Patent Publication No. 63-166649, when the slip of the driving wheels on the road surface is relatively small, traction control is performed by reducing the engine output. In addition, when the slip of the driving wheels on the road surface is relatively large, traction control is performed by reducing the engine output and operating the driving wheel brake system. Devices have also been proposed. If the drive torque reduction operation for the drive wheels whose slip on the road surface exceeds a predetermined slip value is performed by controlling the output of the engine, the torque is normally supplied to the combustion chamber through the intake passage in the engine. The intake air amount is adjusted. Such adjustment of the amount of intake air can be achieved by, for example, providing a sub-throttle valve in the intake passage of the engine, separate from a main throttle valve that is disposed there and changes its opening degree in conjunction with depression of the accelerator pedal. The sub-throttle valve is driven by an actuator that is controlled by a control signal to adjust the slip at the driving wheels that has exceeded a predetermined slip value to a target slip value, and its opening degree is adjusted. It is done by.

[0005]

[Problems to be Solved by the Invention] Traction control in a vehicle as described above is desired to be performed not only when the vehicle is running, but also when the vehicle is started, in order to smoothly start the vehicle with good responsiveness. . However, when performing traction control, it is necessary to set a target slip value according to the road surface friction coefficient of the road surface that the wheels of the vehicle come into contact with. As disclosed in JP-A No. 60-99757, it is set based on the circumferential speed of the driven wheels of the vehicle, or is estimated based on the circumferential speed of the driven wheels of the vehicle and the circumferential acceleration of the driven wheels. There are, but
When the vehicle starts, it is not possible to determine the circumferential speed of the driven wheels of the vehicle, and therefore the situation is such that it is not possible to estimate the road surface friction coefficient of the road surface that the wheels of the vehicle come into contact with. Therefore, conventionally proposed traction control devices for vehicles have the disadvantage that traction control that appropriately corresponds to the road surface friction coefficient when the vehicle starts is not performed.

[0006] In view of the above, the present invention sets a target slip value according to the road surface friction coefficient of the road surface that the wheels of the vehicle come into contact with, and determines whether the slip of the driving wheels of the vehicle with respect to the road surface is greater than a predetermined magnitude. In performing traction control to set the slip of the driving wheels against the road surface to the target slip value when Vehicle traction can be determined appropriately even when the vehicle is starting, and therefore, in addition to traction control when the vehicle is running, it is also possible to appropriately control traction when the vehicle is starting. The purpose is to provide a control device.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, a traction control device for a vehicle according to the present invention, as shown in the basic configuration in FIG. a road surface friction coefficient estimating means for estimating a road surface friction coefficient; a target slip value setting means for setting a target slip value based on the estimated road surface friction coefficient; a slip detecting means for detecting slip of a driving wheel of a vehicle with respect to a road surface; A drive torque control means for controlling the torque of the drive wheels, and a target slip of the drive wheels with respect to the road surface when the slip detected by the slip detection means is greater than or equal to the target slip value set by the target slip value setting means. In order to obtain the slip value,
and an operation control means for activating the drive torque control means, and the road surface friction coefficient estimating means is configured to operate when the vehicle speed is, for example, 5.
km/h, or the difference between the driving wheel circumferential speed and the driven wheel circumferential speed of the vehicle is, for example, 5 km.
/h is less than the second predetermined value, and the driving wheel circumferential acceleration of the vehicle is, for example, greater than or equal to the third predetermined value of 2.0 Gal. a first estimation operation execution means that independently performs a road surface friction coefficient estimation operation for estimating a road surface friction coefficient based on the engine rotation speed for each of the left and right drive wheels of the vehicle;
In a state where the estimation operation execution means performs the road surface friction coefficient estimation operation only for one of the left and right driving wheels of the vehicle, the road surface friction coefficient for the other of the left and right driving wheels of the vehicle is A second estimating operation execution means for estimating using a value proportional to the road surface friction coefficient estimated for one of the left and right drive wheels.

[0008]

[Operation] In the vehicle traction control device according to the present invention configured as described above, when the vehicle speed of the vehicle is less than the first predetermined value, which is, for example, 5 km/h, or when the driving wheel of the vehicle If the difference between the circumferential speed and the driven wheel circumferential speed is, for example, 5
km/h is less than the second predetermined value, and the driving wheel circumferential acceleration of the vehicle is, for example, greater than or equal to the third predetermined value of 2.0 Gal. , the first estimation operation execution means in the road surface friction coefficient estimating means compares the rotational speed of the engine installed in the vehicle at that time with a preset relationship between the engine rotational speed and the road surface friction coefficient, and A road surface friction coefficient estimating operation in which the road surface friction coefficient is estimated by selecting the road surface friction coefficient corresponding to the rotation speed of the vehicle is performed independently for each of the left and right drive wheels of the vehicle, and In a state where the road surface friction coefficient estimation operation by the estimation operation execution means is performed for only one of the left and right drive wheels of the vehicle, the second estimation operation execution means in the road surface friction coefficient estimation means The road friction coefficient for the other of the left and right drive wheels of the vehicle is, for example, equivalent to 1.5 times the road friction coefficient estimated for one of the left and right drive wheels of the vehicle. It is estimated using a value that is proportional to the road surface friction coefficient estimated for one of the drive wheels.

[0009] Therefore, not only when the vehicle is running, but also when the vehicle is started, the road surface friction coefficient is appropriately estimated for each of the left and right drive wheels of the vehicle, and the target slip value is set based on the coefficient of road friction. When the slip of the drive wheels of the vehicle with respect to the road surface is equal to or greater than the target slip value, the drive torque control means is activated to bring the slip to the target slip value, and the vehicle is in a running state. In addition to traction control when the vehicle starts moving, traction control will also be performed appropriately when the vehicle starts moving. Moreover, in the case where the road surface friction coefficient is estimated by the road surface friction coefficient estimation operation only for one of the left and right driving wheels of the vehicle, the road surface friction coefficient for the other of the left and right driving wheels of the vehicle is Since the road surface friction coefficient is estimated with a value that is proportional to the road surface friction coefficient estimated for one of the left and right drive wheels, it is possible to avoid a situation where the road surface friction coefficient for the drive wheels is assumed to be extremely different. .

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 schematically shows an example of a vehicle traction control system according to the present invention, together with a vehicle to which it is applied.

In FIG. 2, an engine 12 is mounted at the front of a vehicle body 10. The engine 12 has, for example, four cylinders 11, each of which is supplied with a mixture formed by intake air through an intake passage 13 and fuel supplied from a fuel supply system, The air-fuel mixture supplied into each cylinder 11 is combusted by the operation of the ignition system and is discharged into the exhaust passage 18.

The intake passage 13 is provided with a main throttle valve 15 whose opening degree is changed in conjunction with an accelerator pedal 14, and a sub-throttle valve 17 which is driven to open and close by a throttle actuator 16. 17 and the main throttle valve 15, the amount of intake air flowing through the intake passage 13 is adjusted. Then, the fuel from the fuel supply system is mixed with the intake air whose amount is adjusted by the sub-throttle valve 17 and the main throttle valve 15 provided in the intake passage 13, and the resulting mixture is combusted in the cylinder 11. The engine 12 is activated and its output (torque) is transmitted to the hydraulic torque converter 22, automatic transmission 23,
The power is transmitted to the left rear wheel 20L and right rear wheel 20R via a power transmission path formed including the propeller shaft 24 and the differential mechanism 25, respectively. That is, the left rear wheel 20L and the right rear wheel 20R are the driving wheels.

Engine 12, hydraulic torque converter 2
2 and the automatic transmission 23 are combined to form one block, and the front left wheel 21L and the front right wheel 21 are connected to each other on both sides of the block.
R is arranged as a driven wheel. These left front wheels 21L
A brake control section 30 is provided in relation to the front right wheel 21R, the rear left wheel 20L, and the rear right wheel 20R. The brake control unit 30 includes a disc 32 attached to each of a left front wheel 21L, a right front wheel 21R, a left rear wheel 20L, and a right rear wheel 20R, and a caliper 34 provided with a brake pad that presses the disc 32. Brake 35A
, 35B, 35C and 35D. The caliper 34 of each of the disc brakes 35A to 35D is equipped with a wheel cylinder 36, and each wheel cylinder 36 has a conduit 37 extending from the hydraulic pressure adjustment section 40.
a, 37b, 37c and 37d are connected respectively. When brake fluid pressure is supplied to the wheel cylinder 36 from the fluid pressure adjustment unit 40 via conduits 37a to 37d, each caliper 34 applies a pressing force to the disc 32 according to the supplied brake fluid pressure. By pressing, the front left wheel 21L, the front right wheel 21R, the rear left wheel 20L, and the rear right wheel 20R are braked.

The hydraulic pressure adjustment section 40 includes a brake pedal 41.
Hydraulic pressure corresponding to the depression of the brake pedal 41 is supplied from a power cylinder 43 attached to the brake pedal 41 through conduits 42a and 42b, and the hydraulic pressure generated by the pump 44 and the pressure regulating valve 45 is conduit 46
Supplied through. The hydraulic pressure adjustment unit 40 forms brake hydraulic pressure according to the depression operation of the brake pedal 41 and supplies it to the disc brakes 35A to 35D through the conduits 37a to 37d. An operating state in which brake fluid pressures for the disc brakes 35C and 35D are individually formed and selectively supplied to the disc brakes 35C and 35D, respectively, according to the operating states of the electromagnetic on-off valves 51, 52, 53, and 54. Take etc.

The electromagnetic on-off valves 51 to 54 are divided into a set of an electromagnetic on-off valve 51 and an electromagnetic on-off valve 52, and a set of an electromagnetic on-off valve 53 and an electromagnetic on-off valve 54.
These sets are involved in adjusting the brake fluid pressure for the disc brakes 35C and 35D provided on the left rear wheel 20L and right rear wheel 20R, respectively. In each set, when one electromagnetic on-off valve 51 and 53 is closed and the other electromagnetic on-off valve 52 and 54 is opened, the brake fluid pressure supplied to the disc brakes 35C and 35D is reduced. and, on the contrary,
In each set, when one of the electromagnetic on-off valves 51 and 53 is opened and the other electromagnetic on-off valves 52 and 54 are closed, the disc brakes 35C and 35
When the brake fluid pressure supplied to D is increased and each set is closed, the disc brake 3
The brake fluid pressure supplied to 5C and 35D is maintained at the current state.

In addition to the above configuration, a control unit 200 is provided which controls the operation of the throttle actuator 16 and controls the opening and closing of the electromagnetic valves 51 to 54. The control unit 200 includes a left front wheel 21L and a right front wheel 21R.
, each of the left front wheel 21L, right front wheel 21R, left rear wheel 20L, and right rear wheel 20R obtained from speed sensors 61, 62, 63, and 64 provided in connection with the left rear wheel 20L and right rear wheel 20R, respectively. Detection output signal S representing the circumferential speed of
1, S2, S3, and S4, and a throttle opening sensor 65 provided in connection with the main throttle valve 15.
A detection output signal St representing the opening degree of the main throttle valve 15 obtained from the accelerator pedal sensor 66, a detection output signal Sa representing the depression amount of the accelerator pedal 14 obtained from the accelerator pedal sensor 66, and a left side signal obtained from the steering angle sensor 67. The detection output signal Sd representing the steering angle of the front wheel 21L and the right front wheel 21R and the vehicle running speed obtained from the vehicle speed sensor 68 (
A rotation speed sensor 69 that detects the detection output signal Sv representing the vehicle speed (vehicle speed) and the rotation speed of the engine 12 (engine rotation speed)
A detection output signal Sn representing the engine rotational speed obtained from the engine is supplied.

The control unit 200 outputs a detection output signal S1
~S4, St, Sa, Sd, Sv, and Sn are taken in at a predetermined period, and the peripheral speed of the left front wheel 21L represented by the detection output signal S1, the peripheral speed of the right front wheel 21R represented by the detection output signal S2, and the detection output signal S3 are determined. Based on the peripheral speed of the left rear wheel 20L represented by the left rear wheel 20L, the peripheral speed of the right rear wheel 20R represented by the detection output signal S4, the vehicle speed represented by the detection output signal Sv, the engine rotation speed represented by the detection output signal Sn, etc., when the vehicle starts and Each driving state of the vehicle is detected. When the vehicle starts, the detection output signal S
The engine speed represented by n is checked against a data map that defines the relationship between the engine speed and the road surface friction coefficient stored in advance in the built-in memory, and the road surface friction coefficient for the left rear wheel 20L when the vehicle starts is determined. μL and right rear wheel 20R
The road surface friction coefficient μR is estimated individually.

In this case, the engine speed represented by the detection output signal Sn is compared with a data map that defines the relationship between the engine speed and the road surface friction coefficient, and the estimated road surface friction coefficient is determined at the time when the vehicle starts. If only one of the road surface friction coefficient μL for the left rear wheel 20L and the road surface friction coefficient μR for the right rear wheel 20R is the same, the control unit 200 controls the left rear wheel 20 when the vehicle starts.
The other of the road surface friction coefficient μL for L and the road surface friction coefficient μR for the right rear wheel 20R is estimated using a value μX that is proportional to one of the estimated road surface friction coefficient μL and road surface friction coefficient μR. . Such value μ
X is, for example, a value corresponding to 1.5 times one of the estimated road surface friction coefficient μL and road surface friction coefficient μR.

When the vehicle is running, the average driven wheel circumferential speed is calculated by taking the average of the circumferential speed of the left front wheel 21L, which is indicated by the detection output signal S1, and the circumferential velocity of the right front wheel 21R, which is indicated by the detection output signal S2. At the same time, the average driven wheel circumferential speed is differentiated to determine the driven wheel circumferential acceleration, and the obtained average driven wheel circumferential speed and driven wheel circumferential acceleration are calculated from the average driven wheel circumferential speed and the driven wheel circumferential speed stored in the built-in memory in advance. The road surface friction coefficient μA for the left rear wheel 20L and right rear wheel 20R when the vehicle is in a running state is estimated by comparing with a data map that defines the relationship between the circumferential acceleration and the road surface friction coefficient.

In this way, the road surface friction coefficient μL and μ
In estimating R or μA, the control unit 200 determines that the vehicle speed represented by the detection output signal Sv is less than a predetermined value, for example, 5 km/h, the circumferential speed of the left rear wheel 20L and the detection output represented by the detection output signal S3. The difference between the peripheral speed of the left front wheel 21L represented by the signal S1, or the difference between the peripheral speed of the right rear wheel 20R represented by the detection output signal S4 and the peripheral speed of the right front wheel 21R represented by the detection output signal S2 is,
A predetermined value, for example, less than 5 km/h, and the peripheral acceleration of the left rear wheel 20L obtained by differentiating the peripheral speed of the left rear wheel 20L represented by the detection output signal S3, or the right rear wheel represented by the detection output signal S4. The circumferential acceleration of the right rear wheel 20R obtained by differentiating the circumferential velocity of the right rear wheel 20R is set to a predetermined value, for example, 2.
0Gal or more and the engine rotation speed represented by the detection output signal Sn is not in a reduced state, the time of starting the vehicle is detected, and if the engine 12 is in the operating state and the above-mentioned conditions are met. For example, if the vehicle speed indicated by the detection output signal Sv is 5 km/
h or more, or the difference between the circumferential speed of the left rear wheel 20L indicated by the detection output signal S3 and the circumferential velocity of the left front wheel 21L indicated by the detection output signal S1, or the difference between the circumferential velocity of the left rear wheel 20L indicated by the detection output signal S4, or the difference between the circumferential velocity of the left rear wheel 20L indicated by the detection output signal S4. The running state of the vehicle is detected when the difference between the circumferential speed of the front right wheel 21R and the circumferential speed of the right front wheel 21R represented by the detection output signal S2 is 5 km/h or more.

[0021]It should be noted that when the vehicle starts, different from the above,
The vehicle speed represented by the detection output signal Sv is a predetermined value, for example,
less than 5 km/h, or detection output signal S3
The circumferential speed of the left rear wheel 20L and the detection output signal S1 represented by
The difference between the circumferential speed of the left front wheel 21L represented by , or the difference between the circumferential speed of the right rear wheel 20R represented by the detection output signal S4 and the peripheral speed of the right front wheel 21R represented by the detection output signal S2 is set to a predetermined value, for example, 5 km/h and the circumferential acceleration of the left rear wheel 20L obtained by differentiating the circumferential speed of the left rear wheel 20L indicated by the detection output signal S3, or the circumference of the right rear wheel 20R indicated by the detection output signal S4. The condition that the circumferential acceleration of the right rear wheel 20R obtained by differentiating the speed is equal to or higher than a predetermined value, for example, 2.0 Gal, or the vehicle speed represented by the detection output signal Sv is a predetermined value, for example, 5 km/h and the difference between the peripheral speed of the left rear wheel 20L represented by the detection output signal S3 and the peripheral speed of the left front wheel 21L represented by the detection output signal S1, or the right rear wheel represented by the detection output signal S4. The difference between the peripheral speed of the front right wheel 20R and the peripheral speed of the right front wheel 21R represented by the detection output signal S2 is less than a predetermined value, for example, 5 km/h, and furthermore, the difference between the peripheral speed of the right front wheel 21R represented by the detection output signal S2 is less than
The circumferential acceleration of the left rear wheel 20L obtained by differentiating the circumferential velocity of
Or, the right rear wheel 20R indicated by the detection output signal S4
The detection may be performed when a condition is satisfied that the circumferential acceleration of the right rear wheel 20R obtained by differentiating the circumferential velocity of is equal to or greater than a predetermined value, for example, 2.0 Gal.

When the control unit 200 estimates the road surface friction coefficient μL and the road surface friction coefficient μR separately, the control unit 200 estimates the road surface friction coefficient μL and the road surface friction coefficient μR.
Based on this, the first basic target slip value for traction control by adjusting the opening of the auxiliary throttle valve when the vehicle starts, and the disc brake 35 when the vehicle starts.
A second basic target slip value for traction control with brake control by C and a third basic target slip value for traction control with brake control by disc brake 35D when the vehicle starts. In setting the first to third basic target slip values, the average value of the estimated road friction coefficient μL and the road friction coefficient μR is used as the average value of the estimated road friction coefficient μL and the sub-throttle coefficient stored in advance in the built-in memory. The first basic target slip value is set by comparing it with a data map that defines the relationship with the basic target slip value for traction control by adjusting the valve opening, and each of the road friction coefficient μL and the road friction coefficient μR is set. is compared with a data map that defines the relationship between the road surface friction coefficient and the basic target slip value for traction control by brake control, which is stored in advance in the built-in memory, to determine the second basic target slip value and the third basic target slip value. Set the target slip value.

Furthermore, the control unit 200 applies the vehicle speed represented by the detection output signal Sv, the accelerator depression amount represented by the detection output signal Sa, and the detection output signal to each of the set first to third basic target slip values. A first target slip value SST for traction control by adjusting the opening of the auxiliary throttle valve when the vehicle starts is multiplied by a correction coefficient based on each of the steering angles represented by Sd, and braking by the disc brake 35C when the vehicle starts. Second target slip value SS for traction control with control
BL and disc brake 3 when starting the vehicle
A third target slip value SSBR for traction control with brake control by 5D is set. Second target slip value SSBL and third target slip value SSB
Each of R is greater than the first target slip value SST.

Furthermore, when the control unit 200 estimates the road surface friction coefficient μA, the control unit 200 estimates the road surface friction coefficient μA.
Based on A, the fourth basic target slip value for traction control by adjusting the opening of the auxiliary throttle valve when the vehicle is in a running state, and by each of the disc brakes 35C and 35D when the vehicle is in a running state. A fifth basic target slip value for traction control with brake control is set. In setting the fourth and fifth basic target slip values, the estimated road friction coefficient μA is used as a road friction coefficient previously stored in the built-in memory and the traction control coefficient by adjusting the sub-throttle valve opening. The fourth basic target slip value is set by comparing it with a data map that defines the relationship with the basic target slip value, and the estimated road surface friction coefficient μA is
A fifth basic target slip value is set by comparing the relationship between the road surface friction coefficient stored in the built-in memory in advance and the basic target slip value for traction control by brake control against a data map.

Furthermore, the control unit 200 determines, for each of the set fourth and fifth basic target slip values,
The auxiliary throttle valve when the vehicle is in a running state is multiplied by a correction coefficient based on the vehicle speed represented by the detection output signal Sv, the accelerator depression amount represented by the detection output signal Sa, and the steering angle represented by the detection output signal Sd. Fourth target slip value S for traction control by opening adjustment
DT and a fifth basic target slip value SDBA for traction control with brake control by each of the disc brakes 35C and 35D when the vehicle is in a running state. Fifth target slip value SDB
A is greater than the fourth target slip value SDT.

Thereafter, the control unit 200 controls the left front wheel 21L, the right front wheel 21R, the left rear wheel 20L, and the right rear wheel 20R, which are respectively represented by the captured detection output signals S1 to S4.
Based on the circumferential speed of the left rear wheel 20L and the right rear wheel 20L,
From the difference between the larger circumferential speed of R and the average driven wheel circumferential speed obtained by taking the average of the circumferential speed of the left front wheel 21L and the right front wheel 21R, The system detects the "slip of the left rear wheel 20L on the road surface" and calculates its slip value SP, and also detects the "slip of the left rear wheel 20L on the road surface" from the difference between the circumferential speed of the left rear wheel 20L and the average driven wheel circumferential speed. Calculate the slip value SPL,
Further, from the difference between the circumferential speed of the right rear wheel 20R and the average driven wheel circumferential speed, the "slip of the right rear wheel 20R with respect to the road surface" is detected and its slip value SPR is calculated.

[0027] Then, the first to third target slip values SS
When T, SSBL and SSBR are set, the slip value SP of the calculated "slip of the driving wheels on the road surface"
is compared with the first target slip value SST, and the slip value S
When P changes from being less than the first target slip value SST to the first target slip value SST or more, the throttle actuator 16 is controlled to make the slip value SP match the first target slip value SST. By adjusting the opening degree of the sub-throttle valve 17, the engine 1
By reducing the output of 2, the left rear wheel 20L and right rear wheel 20R
Traction control is performed by adjusting the opening of the sub-throttle valve, which reduces the driving torque of the engine. In addition, the calculated slip value SPL of "slip of the left rear wheel 20L with respect to the road surface" is compared with the second target slip value SSBL, and when the slip value SPL is greater than or equal to the second target slip value SSBL, the left rear wheel In order to make the peripheral speed of 20L the target peripheral speed corresponding to the second target slip value SSBL, the electromagnetic on-off valves 51 and 52 are controlled to control the disc brake 3.
By activating 5C, the drive torque for the left rear wheel 20L is reduced, traction control is performed using brake control by the disc brake 35C, and the slip value SPR of the calculated "slip of the right rear wheel 20R on the road surface" is is the third target slip value SSBR
, the slip value SPR is the third target slip value S
When it is equal to or higher than SBR, the right rear wheel 20R is controlled to operate the disc brake 35D by controlling the electromagnetic on-off valves 53 and 54 to bring the circumferential speed of the right rear wheel 20R to the target circumferential speed corresponding to the third target slip value SSBR. Disc brake 35 reduces drive torque for rear wheel 20R
Traction control is performed using brake control by D.

On the other hand, the fourth and fifth target slip values SD
When T and SDBA are set, the slip value SP of the calculated "slip of the driving wheels on the road surface" is compared with the fourth target slip value SDT, and the slip value SP is determined as the fourth target slip value SDT.
When the slip value SP changes from less than the target slip value SDT to the fourth target slip value SDT or more, the throttle actuator 16 is controlled to cause the sub throttle valve 17 to match the slip value SP with the fourth target slip value SDT. Traction control is performed by adjusting the opening of the sub-throttle valve, which reduces the output of the engine 12 and reduces the drive torque for the rear left wheel 20L and the rear right wheel 20R. Also, the calculated “
Slip value S of the left rear wheel 20L's slip on the road surface
PL is compared with a fifth target slip value SDBA, and when the slip value SPL is greater than or equal to the fifth target slip value SDBA, the circumferential speed of the left rear wheel 20L is set to the fifth target slip value S.
Traction with brake control by the disc brake 35C, which reduces the drive torque for the left rear wheel 20L by controlling the electromagnetic on-off valves 51 and 52 and operating the disc brake 35C in order to achieve the target circumferential speed corresponding to DBA. control, and further compares the calculated slip value SPR of "slip of the right rear wheel 20R with respect to the road surface" with the fifth target slip value SDBA, and when the slip value SPR is greater than or equal to the fifth target slip value SDBA. , the disc brake 3 controls the electromagnetic on-off valves 53 and 54 in order to make the circumferential speed of the right rear wheel 20R a target circumferential speed corresponding to the fifth target slip value SDBA.
Traction control is performed using brake control using the disc brake 35D, which reduces the drive torque for the right rear wheel 20R by operating the brake 5D.

The first target slip value SST as described above
Alternatively, the control of the throttle actuator 16 for traction control by adjusting the opening of the auxiliary throttle valve under the setting of the fourth target slip value SDT causes the throttle actuator 16 to adjust the opening of the auxiliary throttle valve 17 to a slip value. This is done by supplying a drive signal Ct for adjusting SP to match the first target slip value SST or the fourth target slip value SDT. At this time, the opening degree of the sub-throttle valve 17 is adjusted so that the slip value SP of the "slip of the driving wheels with respect to the road surface" becomes the first target slip value SST.
Alternatively, by matching the fourth target slip value SDT, for example, the driving force torque increased when the accelerator pedal 14 is depressed is efficiently applied to the road surface from the left rear wheel 20L and right rear wheel 20R. It is assumed that the first target slip value SST or the fourth target slip value SDT is set so as to obtain the state that is transmitted. Note that the sub throttle valve 17 is maintained at its maximum opening, that is, in a fully open state, when traction control by adjusting the sub throttle valve opening is not performed.

[0030] Furthermore, traction control is performed using brake control using the disc brakes 35C and 35D with the second and third target slip values SSBL and SSBR or the fifth target slip value SDBA set as described above. The control of the electromagnetic on-off valves 51 and 52 and the electromagnetic on-off valves 53 and 54 is as follows:
Drive signals Ca and Cb are supplied to the electromagnetic on-off valves 51 and 52, respectively, for making the peripheral speed of the left rear wheel 20L a target peripheral speed corresponding to the second target slip value SSBL or the fifth target slip value SDBA. Furthermore, the peripheral speed of the right rear wheel 20R is set to the third target slip value SSBR or the fifth target slip value S to the electromagnetic on-off valves 53 and 54.
Drive signal Cc for achieving the target peripheral speed corresponding to DBA
This is done by supplying Cd and Cd, respectively.

Control unit 20 that operates as described above
0 is configured by, for example, a microcomputer, and an example of a program executed by such a microcomputer for traction control will be described with reference to the flowcharts shown in FIGS. 3 and 4.

In the program shown in the flowchart of FIG. 3, after the start, various detection output signals are fetched in step 70, and in the subsequent step 71, the driving wheels of the vehicle, that is, the left rear wheel 20L and the right rear wheel 20R are detected. The road surface friction coefficient of the contacting road surface is expressed as the road surface friction coefficient μL for the left rear wheel 20L when the vehicle starts.
and the road surface friction coefficient μR for the right rear wheel 20R, or the road surface friction coefficient μA for the left rear wheel 20L and right rear wheel 20R when the vehicle is in a running state, and the road surface friction coefficient μL and the road surface friction coefficient. First target slip value S for traction control by adjusting the auxiliary throttle valve opening when starting the vehicle based on μR
ST, the second brake for traction control with brake control by disc brake 35C when starting the vehicle.
and a third target slip value SSBR for traction control with brake control by the disc brake 35D when the vehicle starts.
, or the fourth target slip value SDT for traction control by adjusting the opening of the auxiliary throttle valve when the vehicle is in a running state based on the road surface friction coefficient μA, and the disc brake 35C and the fourth target slip value SDT when the vehicle is in a running state. Fifth target slip value SDBA for traction control with brake control by each of 35D
Set.

Next, in step 72, step 7
Based on the circumferential speeds of the left front wheel 21L, right front wheel 21R, left rear wheel 20L, and right rear wheel 20R, which are respectively represented by the detection output signals S1 to S4 captured at 0, the circumferential speed VWDL of the left rear wheel 20L and the right rear wheel 20R are determined. Of the circumferential speed VWDR of
If the two differ, the larger one is selected.
From the difference (VWD - VWN) between the average driven wheel circumferential speed VWN, which is the average of the circumferential speed of L and the circumferential speed of the right front wheel 21R,
It detects the "slip of the driving wheels on the road surface" and calculates the slip value SP. Also, the difference between the circumferential speed VWDL of the left rear wheel 20L and the average driven wheel circumferential speed VWN (VW
DL-VWN), the "slip of the left rear wheel 20L on the road surface" is detected and its slip value SPL is calculated, and the difference between the circumferential speed VWDR of the right rear wheel 20R and the average driven wheel circumferential speed VWN (VWDR- The "slip of the right rear wheel 20R on the road surface" is detected from the VWN) and its slip value SPR is calculated.

Thereafter, in step 73, based on the detection output signal St fetched in step 70, it is determined whether the opening degree MH of the main throttle valve 15 is 0 or not, that is, whether the main throttle valve 15 is in the fully closed state. to judge. As a result, if the main throttle valve 15 is in the fully closed state, it is determined in step 74 whether or not the traction flag FT is "0", and the traction flag F
If T is not "0", the traction flag FT is set to "0" in step 75, and then step 7
Return to 0. Furthermore, if the result of the determination at step 74 is that the traction flag FT is "0", the process returns directly to step 70. On the other hand, as a result of the determination in step 73, if the main throttle valve 15 is not in the fully closed state, step 7
In step 6, it is determined whether or not the traction flag FT is "1", and if the traction flag FT is not "1", in step 77, the slip of the "slip of the driving wheels on the road surface" calculated in step 72 is determined. It is determined whether or not the value SP is greater than or equal to the first target slip value SST set in step 71, or greater than or equal to the fourth target slip value SDT set in step 71.

As a result of the determination in step 77, if the slip value SP is greater than or equal to the first target slip value SST or greater than the fourth target slip value SDT, step 78 is performed.
At this point, the traction flag FT is set to "1" and the process proceeds to step 79. Furthermore, as a result of the determination in step 77, the slip value SP is equal to the first target slip value SST.
or if it is less than the fourth target slip value SDT, the process returns to step 70. Further, as a result of the determination in step 76, if the traction flag FT is "1", the process directly proceeds to step 79. In step 79, the slip value S of the "slip of the driving wheels on the road surface" is determined.
In order to adjust P to match the first target slip value SST or the fourth target slip value SDT, a drive signal Ct is sent to the throttle actuator 16 to adjust the opening of the sub-throttle valve. After traction control is performed, the process proceeds to step 80.

In step 80, the slip value SPL of the "slip of the left rear wheel 20L relative to the road surface" calculated in step 72 is greater than or equal to the second target slip value SSBL set in step 71, or It is determined whether or not the fifth target slip value SDBA is greater than or equal to the fifth target slip value SDBA. As a result, if the slip value SPL is greater than or equal to the second target slip value SSBL or greater than the fifth target slip value SDBA, in step 81, the slip value SPL of "the slip of the left rear wheel 20L with respect to the road surface" is set to the second target slip value SSBL. 2 target slip value SSBL, or
In order to adjust the disc brake 35 so that it matches the fifth target slip value SDBA, drive signals Ca and Cb are sent to the electromagnetic on-off valves 51 and 52, respectively.
After traction control with brake control by C is performed, the process proceeds to step 82. Further, as a result of the determination in step 80, if the slip value SPL is less than the second target slip value SSBL or less than the fifth target slip value SDBA, the process directly proceeds to step 82.

In step 82, the slip value SPR of the "slip of the right rear wheel 20R relative to the road surface" calculated in step 72 is greater than or equal to the third target slip value SSBR set in step 71, or It is determined whether or not the fifth target slip value SDBA is greater than or equal to the fifth target slip value SDBA. As a result, if the slip value SPR is greater than or equal to the third target slip value SSBR or greater than the fifth target slip value SDBA, in step 83, the slip value SPR of "the slip of the right rear wheel 20R on the road surface" is 3 target slip value SSBR, or
In order to adjust the disc brake 35 to match the fifth target slip value SDBA, drive signals Cc and Cd are sent to the electromagnetic on-off valves 53 and 54, respectively.
After traction control with brake control by D is performed, the process returns to step 70. Further, as a result of the determination in step 82, if the slip value SPR is less than the third target slip value SSBR or less than the fifth target slip value SDBA, the process directly returns to step 70.

FIG. 4 shows the driving wheels of the vehicle, that is, the left rear wheel 20L and the right rear wheel 20, which are performed in step 71 in the program shown in the flowchart of FIG.
A flowchart of processing executed when estimating the road surface friction coefficient of the road surface that R contacts and setting a target slip value based on the estimated road surface friction coefficient is shown.

In the process shown in the flowchart of FIG. 4, after starting, in step 90, the left friction coefficient estimation flag FLμ and the right friction coefficient estimation flag FRμ are each initialized to "0". Next, in step 91, it is determined whether the vehicle speed VV represented by the detection output signal Sv taken in in step 70 is less than 5 km/h. As a result, if the vehicle speed VV is less than 5 km/h, the detection output signal Sn
Whether the change AEN in the engine rotation speed EN obtained by differentiating the engine rotation speed EN expressed by is greater than or equal to 0,
That is, the engine rotation speed EN represented by the detection output signal Sn
Determine whether the value is constant or is increasing.

As a result of the judgment in step 92, if the change AEN in the engine speed EN is 0 or more, in step 93 the circumference of the left rear wheel 20L represented by the detection output signal S3 taken in in step 70 is determined. Speed VWDL
The difference between the peripheral speed VWNL of the left front wheel 21L and the detection output signal S1 taken in step 70 (VWDL
-VWNL) is less than 5 km/h. As a result, if the difference VWDL-VWNL is less than 5 km/h, in step 94, the circumferential acceleration A of the left rear wheel 20L obtained by differentiating the circumferential speed VWDL of the left rear wheel 20L
It is determined whether the WDL is 2.0 Gal or more.

As a result of the determination in step 94, the left rear wheel 20
If the circumferential acceleration AWDL of L is 2.0 Gal or more, in step 95, the left friction coefficient estimation flag F
After setting Lμ to "1", in step 96, the engine rotation speed EN represented by the detection output signal Sn is stored in advance in the memory built in the control unit 200.
For example, by comparing the data map showing the relationship between engine speed and road friction coefficient as shown in Table 1 below, find the corresponding road friction coefficient, and calculate it for the left rear wheel 20L when the vehicle starts. is set as the estimated value of the road surface friction coefficient μL, and the process proceeds to step 97.

On the other hand, as a result of the judgment in step 93, the difference V
If WDL-VWNL is 5 km/h or more, or as a result of the judgment in step 94, if the circumferential acceleration AWDL of the left rear wheel 20L is less than 2.0 Gal,
Proceed directly to step 97. Then, in step 97, the detection output signal S4 taken in in step 70 is
The difference between the peripheral speed VWDR of the right rear wheel 20R represented by and the peripheral speed VWNR of the right front wheel 21R represented by the detection output signal S2 taken in step 70 (VWDR - VWNR
) is less than 5 km/h. As a result, the difference V
If WDR-VWNR is less than 5 km/h, in step 98, the circumferential acceleration AWDR of the right rear wheel 20R obtained by differentiating the circumferential velocity VWDR of the right rear wheel 20R is 2.
．． It is determined whether or not it is 0Gal or more.

[0043]

[Table 1]

As a result of the determination in step 98, the right rear wheel 20
If the circumferential acceleration AWDR of R is 2.0 Gal or more, in step 99, the right friction coefficient estimation flag F
After setting Rμ to “1”, in step 100,
The engine speed EN represented by the detection output signal Sn is compared with the data map showing the relationship between the engine speed and the road surface friction coefficient as shown in Table 1 above, and the corresponding road surface friction coefficient is determined. The estimated value of the road surface friction coefficient μR for the right rear wheel 20R when the vehicle starts,
Proceed to step 101. In step 101, it is determined whether the left friction coefficient estimation flag FLμ is "1" or not. If the left friction coefficient estimation flag FLμ is not "1", in step 102, the left rear wheel The road surface friction coefficient μL for 20L is, for example, 1 of the estimated value of the road surface friction coefficient μR obtained in step 100.
．． A value μX that is proportional to the estimated value of the road surface friction coefficient μR obtained in step 100, which is equivalent to 5 times
After the estimation is performed, the process proceeds to step 103, and if the left friction coefficient estimation flag FLμ is "1", the process directly proceeds to step 103.

On the other hand, as a result of the judgment in step 97, the difference V
If WDR-VWNR is 5 km/h or more, or as a result of the judgment in step 98, if the circumferential acceleration AWDR of the right rear wheel 20R is less than 2.0 Gal,
In step 104, the left friction coefficient estimation flag FL
It is determined whether μ is "1" or not. As a result, if the left friction coefficient estimation flag FLμ is “1”, step 1
In step 96, the road surface friction coefficient μR for the right rear wheel 20R at the time of starting the vehicle is set to correspond to, for example, 1.5 times the estimated value of the road surface friction coefficient μL obtained in step 96. Obtained road surface friction coefficient μ
After estimating using a value μX that is proportional to the estimated value of L, the process proceeds to step 103.

In step 103, step 96
Or the road surface friction coefficient μL estimated in step 102
The average value of the road surface friction coefficient μR estimated in step 100 or step 105 is calculated based on the relationship between the road surface friction coefficient stored in advance in the built-in memory and the basic target slip value for traction control by adjusting the auxiliary throttle valve opening. A first basic target slip value for traction control by adjusting the opening of the auxiliary throttle valve at the time of starting the vehicle is set by comparing it with a data map that determines the road surface friction estimated in step 96 or step 102. The coefficient μL and the road surface friction coefficient μR estimated in step 100 or step 105 are data that defines the relationship between the road surface friction coefficient and the basic target slip value for traction control by brake control, which is stored in advance in a built-in memory. By comparing with the map, a second basic target slip value for traction control with brake control by the disc brake 35C when the vehicle starts, and a second basic target slip value for traction control with brake control by the disc brake 35D when the vehicle starts. A third basic target slip value is set.

Furthermore, in step 103, the values shown in FIG.
The detection output signal Sv taken in step 70 in
, Sa and Sd are multiplied by correction coefficients based on the vehicle speed, accelerator depression amount, and steering angle, respectively, to obtain a first target slip value SST for traction control by adjusting the auxiliary throttle valve opening when starting the vehicle, A second target slip value SSBL for traction control with brake control by the disc brake 35C when the vehicle starts, and a third target slip value for traction control with brake control by the disc brake 35D when the vehicle starts. Set SSBR and exit the program.

On the other hand, as a result of the determination in step 91, the vehicle speed VV is 5 km/h or more, as a result of the determination in step 92, the change in engine speed EN AEN is decreasing, or As a result of the determination in step 104, if the left friction coefficient estimation flag FLμ is not "1", the process proceeds to step 106. And step 10
6, the left front wheel 21 represented by the detection output signal S1
The average driven wheel circumferential speed VWN is calculated by taking the average of the circumferential speed VWNL of L and the circumferential speed VWNR of the right front wheel 21R represented by the detection output signal S2, and in the subsequent step 107, the average driven wheel circumferential speed VWN is differentiated. Driven wheel circumferential acceleration A
Find WN. Next, in step 108, the average driven wheel circumferential speed VWN and the driven wheel circumferential acceleration AWN calculated in steps 106 and 107 are combined with the average driven wheel circumferential speed and the driven wheel circumferential acceleration stored in the built-in memory in advance. By comparing it with a data map that determines the relationship with the road surface friction coefficient,
Step 109 calculates the corresponding road surface friction coefficient and uses it as the estimated value of the road surface friction coefficient μA for the left rear wheel 20L and right rear wheel 20R when the vehicle is in a running state.
Proceed to.

In step 109, step 10
The road surface friction coefficient μA estimated in step 8 is compared with a data map pre-stored in the built-in memory that defines the relationship between the road surface friction coefficient and the basic target slip value for traction control by adjusting the auxiliary throttle valve opening. , a fourth basic target slip value for traction control by adjusting the opening of the auxiliary throttle valve while the vehicle is in a running state is set, and the road surface friction coefficient μA estimated in step 108 is set.
is compared with a data map that defines the relationship between the road surface friction coefficient stored in the built-in memory in advance and the basic target slip value for traction control by brake control, and the disc brake is adjusted while the vehicle is running. A fifth basic target slip value for traction control with brake control by each of the disc brake 35C and the disc brake 35D is set.

Further, in step 109, the detection output signal S taken in in step 70 in FIG. 3 is applied to each of the set fourth and fifth basic target slip values.
Multiplying the correction coefficients based on the vehicle speed, the amount of accelerator depression, and the steering angle represented by v, Sa, and Sd, respectively, produces a fourth parameter for traction control by adjusting the opening of the sub-throttle valve while the vehicle is in a running state. target slip value SDT,
Then, a fifth target slip value SDBA for traction control with brake control by each of the disc brakes 35C and 35D while the vehicle is in a running state is set, and the program ends.

[0051]

Effects of the Invention As is clear from the above description, in the traction control device for a vehicle according to the present invention, a target slip value is set according to the road surface friction coefficient of the road surface that the wheels of the vehicle come into contact with. When the slip of the driving wheels on the road surface exceeds a predetermined level, when performing traction control to bring the slip of the driving wheels on the road surface to the target slip value, the vehicle speed is set to 5 km/h, for example. or the difference between the driving wheel circumferential speed and the driven wheel circumferential speed of the vehicle is less than a second predetermined value, which is, for example, 5 km/h, and the vehicle driving Under the starting state of the vehicle in which the circumferential acceleration is equal to or higher than a third predetermined value, for example, 2.0 Gal, the first estimation operation execution means in the road surface friction coefficient estimating means performs the operation of the vehicle at that time. The rotational speed of the engine installed in the vehicle is checked against a preset relationship between the engine rotational speed and the road friction coefficient, and the road friction coefficient corresponding to the engine rotational speed is selected to estimate the road friction coefficient. The road surface friction coefficient estimation operation is performed independently for each of the left and right drive wheels of the vehicle, and
In a state where the road surface friction coefficient estimation operation by the estimation operation execution means is performed for only one of the left and right drive wheels of the vehicle, the second estimation operation execution means in the road surface friction coefficient estimation means performs the estimation operation of the vehicle. The road surface friction coefficient for the other of the left and right drive wheels is, for example, 1 of the road surface friction coefficient estimated for one of the left and right drive wheels of the vehicle.
．． It is estimated using a value that is proportional to the road surface friction coefficient estimated for one of the left and right drive wheels of the vehicle, which is said to be equivalent to five times the coefficient of friction of the vehicle.

Therefore, according to the traction control device for a vehicle according to the present invention, the coefficient of road friction is determined for each of the left and right drive wheels of the vehicle not only when the vehicle is running but also when the vehicle is started. It is possible to appropriately estimate the slip value, and by setting a target slip value based on the estimation, traction control can be performed appropriately. Moreover, in this case, if the road surface friction coefficient is estimated based on the relationship between the preset engine speed and the road surface friction coefficient only for one of the left and right drive wheels of the vehicle, The road friction coefficient for the other drive wheel is
Since the estimated value is proportional to the road surface friction coefficient estimated for one of the left and right drive wheels of the vehicle, it is possible to avoid a situation where the road surface friction coefficient for the drive wheels is assumed to be extremely different. You will be able to do that.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram showing a traction control device for a vehicle according to the present invention in accordance with the claims.

FIG. 2 is a configuration diagram showing an example of a traction control device for a vehicle according to the present invention together with a vehicle to which it is applied.

FIG. 3 is a flowchart showing an example of a program executed by the microcomputer for traction control when the control unit in the example shown in FIG. 2 is configured by a microcomputer;

4 is a flowchart showing an example of a program executed by a microcomputer in estimating a road surface friction coefficient when the control unit in the example shown in FIG. 2 is configured by a microcomputer; FIG.

[Explanation of symbols]

10 Vehicle body 12 Engine 15 Main throttle valve 16 Throttle actuator 17 Sub-throttle valve 20L Left rear wheel 20R Right rear wheel 21L Left front wheel 21R Right front wheel 30 Brake control section 35A Disc brake 35B Disc brake 35C Disc brake 35D Disc brake 51 Electromagnetic opening/closing valve 52 Electromagnetic opening/closing valve 53 Electromagnetic opening/closing valve 54 Electromagnetic opening/closing valve 61 Speed sensor 62 Speed sensor 63 Speed sensor 64 Speed sensor 68 Vehicle speed sensor 69 Rotation speed sensor 200 Control unit

Claims (6)

[Claims] 1. Road surface friction coefficient estimating means for estimating a road surface friction coefficient on a road surface with which wheels of a vehicle come into contact; and a target slip ratio or a target slip amount based on the road surface friction coefficient estimated by the road surface friction coefficient estimating means. a target slip value setting means for setting a target slip value; a slip detection means for detecting the slip of the drive wheels of the vehicle with respect to the road surface; a drive torque control means for controlling the torque of the drive wheels of the vehicle; In order to make the slip of the driving wheels on the road surface equal to the target slip rate or target slip amount, and operation control means for operating the drive torque control means, and the road surface friction coefficient estimating means is configured to detect when the vehicle speed of the vehicle is less than a first predetermined value, or when the driving wheel circumferential speed and the driven wheel circumferential speed of the vehicle are detected. in a specific state in which the difference between a first estimation operation execution means that performs a road surface friction coefficient estimation operation for estimating a road surface friction coefficient independently for each of the left and right drive wheels of the vehicle; In a state where the estimation operation is performed only on one of the left and right drive wheels of the vehicle, the road surface friction coefficient for the other of the left and right drive wheels of the vehicle is 1. A traction control device for a vehicle, comprising: second estimation operation execution means for estimating with a value proportional to the estimated road surface friction coefficient. 2. The road surface friction coefficient estimating means is configured to determine whether the vehicle speed of the vehicle is equal to or greater than the first predetermined value, or the difference between the driving wheel circumferential speed and the driven wheel circumferential speed of the vehicle is greater than or equal to the second predetermined value. In a specific state different from the specific state described above, the operation of estimating the road surface friction coefficient based on the peripheral speed of the driven wheels of the vehicle is performed in common for left and right driving wheels of the vehicle. The traction control device for a vehicle according to claim 1, characterized in that: 3. Under the specific state in which the first estimation operation execution means in the road surface friction coefficient estimation means performs the road surface friction coefficient estimation operation, the vehicle speed of the vehicle is less than the first predetermined value. 3. The traction control device for a vehicle according to claim 1, wherein the difference between the driving wheel circumferential speed and the driven wheel circumferential speed of the vehicle is less than the second predetermined value. 4. Under the specific state in which the first estimation operation execution means in the road surface friction coefficient estimation means performs the road surface friction coefficient estimation operation, the rotational speed of the engine is not in a decreasing state. A traction control device for a vehicle according to claim 1, 2 or 3. 5. The second estimation operation execution means in the road friction coefficient estimating means calculates a value proportional to the road friction coefficient estimated for one of the left and right drive wheels.
5. The traction control device for a vehicle according to claim 1, wherein the value is selected to be equivalent to 1.5 times the coefficient of road friction estimated for one of the left and right drive wheels. 6. The vehicle, wherein the target slip value setting means estimates the road surface friction coefficient by performing the road surface friction coefficient estimation operation on at least one of the left and right drive wheels of the vehicle by the road surface friction coefficient estimating means. Claim 1, 2, 3, or 4, wherein the target slip rate or the target slip amount is set using an average road surface friction coefficient obtained by averaging road surface friction coefficients for left and right drive wheels. 5. The traction control device for a vehicle according to 5.