JPH0679905B2 - Road condition determination device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling road surface state determination device, and more particularly to a device for determining the level of friction coefficient of a road surface while a vehicle is traveling.

(Prior Art) Conventionally, as a four-wheel steering device for a vehicle in which the rear wheels are also steered in accordance with the steering of the front wheels, for example, JP-A-55-91457.
As disclosed in the publication, a front wheel steering mechanism that steers the front wheels and a rear wheel steering mechanism that steers the rear wheels are provided. The steering angle of the rear wheels depends on the steering angle of the front wheels and the vehicle speed. The front and rear wheels have opposite phases at low speeds and the same phase at high speeds to prevent side slippage of the vehicle and improve running stability. It is known that it can be improved.

However, when the rear wheels are steered in the same way as during normal driving when the tire grip is low, such as when driving on low μ roads such as snowy roads and frozen roads, the front and rear wheels are out of phase. At such low speeds, the vehicle is apt to skid, and running stability is impaired.

For such a problem, by appropriately changing the steering ratio of the rear wheels to the front wheels in accordance with the condition of the friction coefficient of the road surface while the vehicle is traveling, not only during normal traveling but also during traveling on a low μ road. It is also possible to suppress the side slip of the wheels to the minimum and improve the running stability.

(Problems to be Solved by the Invention) In order to prevent the wheels from slipping by the above-described method, it is an important prerequisite that the friction coefficient of the road surface can be accurately determined at any time.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a traveling road surface state determination device capable of discriminating whether the friction coefficient of a road surface during traveling of a vehicle is high or low.

(Means for Solving Problems) The traveling road surface state determination device according to the present invention detects the slip ratio and the braking force coefficient while the vehicle is traveling, and on the other hand, the relationship between the slip ratio and the braking force coefficient is determined by experiments or the like. Preliminarily stored as at least one braking force coefficient characteristic having a friction coefficient of the road surface as a parameter, and the value of the detected braking force coefficient and the stored braking force coefficient characteristic,
By comparing the value after the braking force coefficient corresponding to the detected slip ratio, whether the friction coefficient of the road surface is high or low is determined. That is, a traveling road surface state determination device for determining a state of a road surface while the vehicle is traveling, a slip ratio detection means for detecting a slip ratio of a braking wheel with respect to the road surface, a braking force of a vehicle braking device, and an axle received by the braking wheel. A braking force coefficient detecting means for detecting a load ratio, a characteristic obtained in advance by an experiment or the like, and a slip ratio of a braking wheel with respect to a road surface, a braking force of a braking device of a vehicle and an axle load received by the braking wheel. The storage means stores at least one braking force coefficient characteristic indicating the friction coefficient of the road surface as a parameter, and the value of the braking force coefficient obtained from the detection signal of the braking force coefficient detecting means. The braking force coefficient characteristic stored in the means is compared with the value of the braking force coefficient corresponding to the value of the slip rate obtained from the detection signal of the slip rate detecting means, and the And it is characterized in that it comprises a determining means for determining the height of the friction coefficient of the surface.

The "axle load received by the braking wheel" means a vertical load that acts on each braking wheel in consideration of the amount of vehicle load movement during braking.

The braking force coefficient represented by the "ratio between the braking force of the vehicle braking device and the axle load received by the braking wheel" is obtained by obtaining the values of the braking force coefficient for all the braking wheels and averaging these values. Alternatively, the braking force coefficient may be obtained for one specific braking wheel.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 shows the overall configuration of a four-wheel steering system for a vehicle provided with a traveling road surface condition determining apparatus according to a first embodiment of the present invention.
Reference numeral 1 denotes a front wheel steering mechanism that steers left and right front wheels 2L, 2R. The front wheel steering mechanism 1 includes a steering handle 3 and
A rack and pinion mechanism 4 that converts the rotational movement of the steering handle 3 into a linear movement, and left and right tie rods 5 that transmit the operation of the rack and pinion mechanism 4 to the front wheels 2L, 2R to steer them left and right. 5 and knuckle arm 6,6
Consists of.

Reference numeral 7 denotes a rear wheel steering mechanism that steers left and right rear wheels 8L, 8R. The rear wheel steering mechanism 7 has tie rods 9, 9 and knuckle arms 10, 10 on the left and right rear wheels 8L, 8R. A rear wheel operation rod 11 connected in the vehicle width direction and extending in the vehicle width direction is provided.
A rack 12 is formed on the rear wheel operation rod 11, and the rack 12 is
The pinion 13 meshing with 12 is rotated by the pulse motor 14 via the pair of bevel gears 15 and 16 and the pinion shaft 17, so that the rear wheels 8L and 8R correspond to the rotation direction and the rotation amount of the pulse motor 14. It is configured to be steered left and right.

A power cylinder 18 having the rod 11 as an operating rod is connected to the rear wheel operating rod 11. The power cylinder 18 is a piston fixed to the rear wheel operation rod 11.
It has a left-turning hydraulic chamber 18b and a right-turning hydraulic chamber 18c partitioned in the vehicle width direction by 18a.
b and 18c communicate with a control valve 20 for controlling the oil supply direction and hydraulic pressure to the power cylinder 18 via hydraulic passages 19a and 19b, respectively, and the control valve 20 is provided with an oil supply passage 21 and an oil return passage 22. A hydraulic pump 23 is connected via the hydraulic pump 23, and the hydraulic pump 23 is rotationally driven by a motor 24. The control valve 20 has a pinion shaft 17
When the rear wheels 8L and 8R are steered to the left (steering in the counterclockwise direction in the figure) by detecting the rotational direction of the oil supply passage 21, the oil supply passage 21 is moved to the left turning hydraulic chamber.
While communicating with 18b and communicating the right-turning hydraulic chamber 18c with the oil return passage 22, when the rear wheels 8L, 8R are steered to the right (steering in the clockwise direction in the figure), the communication state opposite to the above is established. At the same time, the hydraulic pressure from the hydraulic pump 23 is reduced to a pressure corresponding to the rotational force of the pinion shaft 17, and the bevel gears 15, 1 are driven by the pulse motor 14.
6, when the rear wheel operation rod 11 is moved in the axial direction (vehicle width direction) via the pinion shaft 17, the pinion 13 and the rack 12, the rear wheel operation rod 11 is moved by supplying pressure oil to the power cylinder 18. I am trying to help.

The operation of the pulse motor 14 and the drive motor 24 of the hydraulic pump 23 is controlled by a control signal output from the controller 25 that is the control unit of the rear wheel steering mechanism 7.
The controller 25 receives a steering angle signal from a steering angle sensor 26 that detects a front wheel steering angle from the steering amount of the steering wheel 3 in the front wheel steering mechanism 1 and a vehicle speed signal from a vehicle speed sensor 27 that detects a vehicle speed. A road surface friction coefficient determination signal from a traveling road surface state determination device 28 that determines whether the friction coefficient of the road surface during traveling of the vehicle is high or low is input, and a battery power source 29 is connected.

Inside the controller 25, as shown in FIG.
A characteristic storage unit 30 that stores two types of steering ratio characteristics of the front wheels and the rear wheels with respect to the vehicle speed as shown in FIG. 3, a steering angle signal from the steering angle sensor 26, and a vehicle speed signal from the vehicle speed sensor 27 are received. From the turning ratio characteristics stored in the storage unit 30, a target turning angle calculation unit 31 that calculates a target turning angle of the rear wheels corresponding to the front wheel turning angle and the vehicle speed, and the target turning angle calculation unit 31 A pulse generator 32 that outputs a pulse signal corresponding to the target turning angle calculated in step S1, and a drive pulse signal that receives the pulse signal from the pulse generator 32 and drives the pulse motor 14 and the drive motor 24 of the hydraulic pump 23. Driver to convert
And a pulse motor so that the ratio of the rear wheel steering angle to the front wheel steering angle (steering ratio) can be varied according to a predetermined steering ratio characteristic so that the rear wheel steering angle becomes a target steering angle.
A turning ratio varying means 34 for controlling the driving motor 24 of the hydraulic pump 23 and the hydraulic pump 23 is configured.

Here, as shown in FIG. 3, the steering ratio characteristic stored in advance in the characteristic storage unit 30 is a steering ratio characteristic A for normal running in a state where the friction coefficient of the road surface is high such as in fine weather. And 2 of the steering ratio characteristic B for running on low μ roads such as in the rain or on unpaved roads.
Both types of steering ratio characteristics A and B are basically
As the vehicle speed increases from a low speed to a high speed, the steering ratio K shifts from a large value to zero in a negative phase opposite (phase where the front and rear wheels are steered in the opposite direction), and the steering ratio K changes in the medium speed range. Steering ratio K
Are in the same phase in the positive direction (the front and rear wheels are steered in the same direction)
In the high speed range, the steering ratio K is set to be large in the same phase. Of the two steering ratio characteristics A and B, the steering ratio characteristic B for low μ road traveling is compared to the steering ratio characteristic A for normal traveling over the entire vehicle speed range from low speed to high speed. The steering ratio K tends to shift to the same phase side, and the steering ratio K approaches zero or changes to the same phase in the positive direction in the low speed range where the steering ratio K has the value of the opposite phase in the negative direction. In the medium speed range or high speed range where K has the same phase value in the positive direction, the steering ratio K
Is set to a larger value.

Further, inside the controller 25, there is further provided a characteristic selection unit 35 which receives a road surface friction coefficient determination signal from the traveling road surface state determination device 28. The characteristic selection unit 35
When the determination signal from the traveling road surface state determination device 28 obtains a determination result that the road surface is a high μ road having a friction coefficient of a set value or more, the steering for normal traveling from the characteristic storage unit 30 is obtained. While selecting the ratio characteristic A, the steering ratio characteristic B for traveling on the low μ road is selected when the determination result that the road surface is the low μ road having the friction coefficient less than the set value is obtained. The target turning angle calculation unit 31 calculates the target turning angle according to the turning ratio characteristic of the characteristic storage unit 30 selected by the characteristic selecting unit 35.

As shown in FIG. 1, the traveling road surface state determination device 28 is
Connected to computer 37, said ABS computer 3
7 includes front wheels 2L and 2R that are drive wheels and rear wheels 8L and 8 that are driven wheels.
The rotation speed of R is input from each wheel rotation sensor 38. Then, the rotational speeds of the rear wheels 8L, 8R input to the ABS computer 37 are input to the traveling road surface state determination device 28 as a vehicle speed signal. Also ABS
The computer 37 is also connected to the vehicle speed sensor 27 and the ABS modulator 39, and the wheel rotation sensors 3 for the rear wheels 8L and 8R are also connected to the computer 37.
The vehicle speed signal is output to the vehicle speed sensor 27 based on the input signal from 8, and the ABS modulator 39 outputs the control signal of the brake fluid pressure supplied to the control device of each wheel 2L, 2R, 8L, 8R. ing.

At the time of vehicle braking, the wheels 2L, 2
R, 8L, 8R is braked, but when this braking causes the vehicle to decelerate above a predetermined level causing slip between the road surface and the brake wheels, a control signal is output from the ABS computer 37 to the ABS modulator 39. As a result, predetermined brake fluid pressure control for avoiding the skid state is performed. As described above, the road surface condition determination device 28
Although a vehicle speed signal is input to, the rear wheels 8L, 8R are also braked when the vehicle is being braked, so the rotation speeds of the rear wheels 8L, 8R do not always correspond to the vehicle speed. Therefore, the ABS computer 37 performs an operation of regarding the rotation speed of the wheel having the highest rotation speed among the four wheels, which is considered to be closer to the vehicle speed, as the vehicle speed. The pseudo vehicle speed V _R thus obtained is input to the traveling road surface state determination device 28 and the vehicle speed sensor 27. At the same time, the braking wheel speed V is also input to the traveling road surface state determination device 28. Braking wheel speed V, the average value of the rotational speed of the other three wheels excluding the target is the wheel of detection of the pseudo vehicle speed V _R is employed.

The traveling road surface state determination device 28 is further connected to the axle load sensor 40 and the braking force sensor 41, from the axle load sensor 40, the axle load received by each of the wheels 2L, 2R, 8L, 8R. The detected detection signal is input, and from the braking force sensor 41, a detection signal that detects the braking force of the braking device acting on each of the wheels 2L, 2R, 8L, 8R is input.

The axle load is a vertical load that acts on each of the front wheels 2L and 2R in consideration of the vehicle load movement amount during braking, and can be obtained as follows, for example. That is, since there is a proportional relationship between the displacement amount of the coil spring of the suspension and the vertical load, a strain sensor (strain gauge) is attached to the surface of the coil spring.
It can be detected by attaching. Therefore, if the axle load is W and the output value of the strain sensor is Q, it can be expressed by W = rQ (r: constant).

On the other hand, the braking force is a tangential force that acts between the braking wheel and the road surface during braking, and can be obtained as follows. That is, if the braking force is B, Can be expressed as

Here the brake torque T _{B is, T B = 2μ P · B} R · A · P W μ: coefficient of friction between the brake disc and pad B _R: effective brake radius A: cross-sectional area of the brake cylinder R _W: wheel cylinders It can be expressed by the brake fluid pressure inside. In this formula, 2 μ _P · B _R · A can be treated as a constant, and thus can be expressed as T _B = kP _W (k: constant). After all, the braking force B can be expressed as B = α + β P _W (α, β: constant). Therefore, the braking force B can be obtained by detecting P _W from the wheel rotation speed sensor and P _W from the pressure sensor.

FIG. 4 is a block diagram showing the configuration of the traveling road surface state determination device 28.

The traveling road surface state determination device 28 includes a slip ratio detection unit 42, a braking force coefficient detection unit 43, a storage unit 44, and a determination unit 45, and detects the road surface on which the vehicle is traveling according to the flow shown in FIG. It is designed to determine whether the friction coefficient is high or low.

That is, in the slip ratio detecting unit 42, based on the braking wheel speed V and the pseudo vehicle speed V _R obtained as the input signal from the ABS computer 37, the calculation process of (V _R −V) / V _R × 100 is performed, and the slip ratio is calculated. The value of S is detected.

On the other hand, in the braking force coefficient detection unit 43, the axle load sensor 40
Based on the axle load W input from the vehicle and the braking force B input from the braking force sensor 41, B / W is calculated and the value of the braking force coefficient μ _B is detected.

The slip ratio S and the braking force coefficient μ _B thus detected
The value of is input to the discriminating unit 45, and in the discriminating unit 45, the value is compared with the road surface state discrimination map stored in the storage unit 44, so that whether the friction coefficient of the road surface is high or low is determined. Has become.

As shown in FIG. 6, the road surface state determination map is such that the slip ratio S of the braking wheel with respect to the road surface and the braking force coefficient μ _B (that is, the ratio between the braking force B of the braking device and the axle load W received by the braking wheel).
FIG. 3 is a graph showing the relationship between and, and at least one braking force coefficient characteristic curve with the road friction coefficient μ as a parameter is shown. The above braking force coefficient characteristic curve is
This is a characteristic curve that can be obtained by experiments or the like. In the figure, braking force coefficient characteristic curves E and F obtained by experiments on dry concrete road surface with friction coefficient μ of 0.6 and on ice with μ of 0.15 and interpolation method from these two characteristic curves E and F are used. The calculated braking force coefficient characteristic curve G is shown. The characteristic curve G is a curve showing the braking force coefficient characteristic corresponding to the friction coefficient of the road surface which serves as a reference when determining whether the road surface on which the vehicle is traveling is a high μ road or a low μ road.

4 and 5, the values of the slip ratio S and the driving force coefficient μ _B input from the slip ratio detecting unit 42 and the braking force coefficient detecting unit 43 to the discriminating unit 45 are as shown in FIG.
It is represented as a coordinate point X (S, μ _B ) in the road surface state determination map stored in the storage unit 44, and this point X is above or below the reference braking force coefficient characteristic curve G. Whether or not the friction coefficient of the road surface during traveling of the vehicle is high or low is determined. For example, in the discrimination unit 45, S = 30%, μ _B =
When a detection signal of 0.4 is input, the value 0.35 of the braking force coefficient corresponding to S = 30% in the braking force coefficient characteristic curve G and the above μ _B = 0.4 are compared, and μ _B = 0.4> 0.35
It is determined that the point X (S = 30, μ _B = 0.4) is above the characteristic curve G. As a result, it is determined that the friction coefficient of the road surface on which the vehicle is traveling is higher than the set value, that is, the road is a high μ road.

In FIG. 6, there are three braking force coefficient characteristic curves E, F, and G stored in the storage unit 44, and the reference characteristic curve is G.
Although it is shown as one, it is not a two-step judgment of high μ road and low μ road by setting a plurality of reference characteristic curves, but the high and low of the friction coefficient of the road surface is finely divided by more steps. You may do it. In this case, all the characteristic curves to be the reference may be obtained by the interpolation method, but it is possible to use the multiple characteristic curves obtained from the actual measurement data obtained by the running experiment on the road surface having various high and low friction coefficients as the reference. The characteristic curve may be as follows.

In this way, when the discriminating unit 45 discriminates whether the friction coefficient μ of the road surface during traveling of the vehicle is high or low, the discriminating signal is inputted to the four-wheel steering controller 25, and the steering ratio characteristic is variably controlled. The Rukoto.

Next, the operation and effect of the above-described first embodiment will be described. When the road surface friction coefficient is equal to or greater than the set value during normal running, the controller 25 of the rear wheel steering mechanism 7 uses the characteristic selection unit 35. The steering ratio characteristic A for normal traveling is selected from the two types of steering ratio characteristics A and B stored in the characteristic storage unit 30, and the steering ratio is based on the selected steering ratio characteristic A. Since the target turning angle is calculated by the target turning angle calculation unit 31 of the variable means 34, the turning ratio of the rear wheel turning angle to the front wheel turning angle is changed according to the turning ratio characteristic A for the normal running. As a result, the rear wheels 8L, 8R are steered in the opposite phase to the front wheels 2L, 2R at low vehicle speeds, and in the same phase as the front wheels 2L, 2R at medium and high vehicle speeds.

On the other hand, when the road surface friction coefficient is less than the set value in rainy weather, unpaved roads, or snowy roads, the characteristic selection unit 35 receives the road surface friction coefficient determination signal from the traveling road surface state determination device 28. Then, instead of the steering ratio characteristic A for normal traveling described above, the steering ratio characteristic B for traveling on a low μ road is selected from the characteristic storage unit 30, and the selected steering characteristic for traveling on a low μ road is selected. The turning ratio is variably controlled by the turning ratio changing means 34 in accordance with the turning ratio characteristic B.

In this case, the steering ratio characteristic B for traveling on the low μ road is deviated to the same phase side as compared with the steering ratio characteristic A for traveling normally, so that the rear wheels 8L, 8R are more Also steered in the same phase as the front wheels 2L, 2R, increasing the lateral gripping force of the wheels, and as a result, the side slip of the wheels (front wheels 2L, 2R and rear wheels 8L, 8R) is increased even when traveling on low μ roads. It will be prevented as much as possible. Therefore, traveling stability can be improved.

FIG. 7 shows a modified example of the controller 25 of the rear wheel steering mechanism 7 in the first embodiment. This controller 25 includes a target steering angle calculation unit 31 'and a pulse generator.
A predetermined steering ratio characteristic (a characteristic storage unit 30 in the first embodiment, which includes a steering ratio of a rear wheel steering angle to a front wheel steering angle and is stored in a characteristic storage unit 30 ', is constituted by a driver 32' and a driver 33 '.
The steering ratio varying means 34 'is variably controlled in accordance with the steering ratio characteristic A for normal traveling stored in (4), and receives the road surface friction coefficient discrimination signal from the traveling road surface state discrimination device 28. In accordance with the decrease in the road surface friction coefficient, the corrected steered angle in the positive direction is gradually added to the target steered angle calculated by the target steered angle calculation unit 31 'of the steered ratio varying means 34', and the steered ratio is changed. The correction unit 36 is provided as a correction unit that gradually and largely corrects the steering ratio in the same phase direction. That is, in this modified example, in the determination of the level of the friction coefficient of the road surface in the traveling road surface state determination device 28, a plurality of reference braking force coefficient characteristics are set, and the slip ratio and the braking force detected during traveling of the vehicle are set. It will be done by matching the values of the coefficients with these properties.

Therefore, in the case of the modified example, the steering ratio characteristic for normal traveling is gradually corrected in the same phase direction as the friction coefficient of the road surface decreases, so that the road surface friction coefficient as in the first embodiment is increased. When the value becomes less than the set value, the steering ratio control accuracy becomes finer and the running stability is improved compared to the case where the steering ratio characteristics are switched from those for normal driving to those for low μ road driving. Can be further improved.

Further, FIG. 8 shows a steering ratio characteristic when the steering ratio is controlled by calculating the rear-wheel steering angle θ _R according to the magnitude of the front-wheel steering angle θ _F as a modified example of the first embodiment. It is shown. The steering ratio control by the steering angle, the front wheel turning angle theta _F is smaller than at high vehicle speed, steering of the rear wheel steering angle theta _R for the front wheel turning angle theta _F based on the actual situation that becomes large at the time of low vehicle speed The steering ratio characteristic is basically the same as in the case of steering ratio control by vehicle speed, in which the front wheel and the rear wheel are in opposite phases at low vehicle speeds and at the same phase at high vehicle speeds. Is set to.

Then, even in the case of the steering ratio control by the steering angle,
As the steering ratio characteristic, the steering ratio characteristic C for normal traveling is used.
And a steering ratio characteristic D for traveling on a low μ road. Low μ
Compared with the steering ratio characteristic C for normal traveling, the steering ratio characteristic D for road traveling has a positive in-phase side of the rear wheel steering angle θ _R over the entire range of the front wheel steering angle θ _F. When the road surface friction coefficient is less than the set value, the steering ratio characteristic D
Accordingly, the rear wheels are steered in the same phase direction as the front wheels as compared with the case of normal traveling, as in the case of the first embodiment. In the case of the steering ratio control by the steering angle, the vehicle speed sensor 27 for detecting the vehicle speed as in the first embodiment is unnecessary.

Further, FIG. 9 shows the overall structure of a four-wheel steering system for a vehicle according to a second embodiment of the present invention. The rear wheel steering mechanism 7'in this four-wheel steering system is the four-wheel steering system of the first embodiment. Instead of electrically steering the rear wheels 8L, 8R by operating the pulse motor 14 as in the rear wheel steering mechanism 7 in FIG.
The rear wheels 8L and 8R are mechanically steered by utilizing the steering force of.

That is, the rear wheel steering mechanism 7'includes a steering ratio changing device 46 including gears and the like, and a rear end of a transmission rod 47 extending in the vehicle front-rear direction is connected to the steering ratio changing device 46 and A pinion 49 that meshes with a rack 48 formed on the rack shaft 4a of the rack and pinion mechanism 4 of the front wheel steering mechanism 1 is provided at the front end of the rod 47. A sliding member 50 extends from the steering ratio changing device 46, and a rack 51 formed on the sliding member 50 is attached to the rear wheel operation rod 11 via the rack 12 and the pinion 13. Articulated pinion shaft 17
The pinion 52 provided at the front end of the is meshed. Then, the steering force of the front wheel steering mechanism 1 is equal to the rack and pinion mechanism 4
Steering ratio changing device from the rack shaft 4a of the vehicle through the transmission rod 47
The steering force is transmitted to the rear wheel operation rod 11 via the sliding member 50 and the pinion shaft 17 after the steering ratio is changed under the control of the controller 25 in the steering ratio changing device 46.
The rear wheels 8L and 8R are configured to be steered to the left and right by being transmitted to. The other configurations of the four-wheel steering system are the same as those of the four-wheel steering system of the first embodiment, and the same members are designated by the same reference numerals and the description thereof will be omitted.

And a controller for controlling the turning ratio changing device 46.
Of course, 25 itself is the same as that of the first embodiment, and of course, the same action and effect can be obtained.

(Effects of the Invention) As described in detail above, the traveling road surface state determination device according to the present invention detects the slip ratio and the braking force coefficient during traveling of the vehicle by the slip ratio detecting means and the control force coefficient detecting means, while storing them. By means of the means, the relationship between the slip ratio and the braking force coefficient is stored in advance as at least one braking force coefficient characteristic with the friction coefficient of the road surface as a parameter. , The stored braking force coefficient characteristic is compared with the value of the braking force coefficient corresponding to the detected slip ratio to determine whether the friction coefficient of the road surface is high or low. In addition, it is possible to accurately determine the road surface condition.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a four-wheel steering system for a vehicle provided with a traveling road surface condition determining apparatus according to the present invention, FIG. 2 is a block diagram of a controller of the four-wheel steering system, and FIG. FIG. 4 is a block diagram showing a configuration of a traveling road surface condition determining device, FIG. 5 is a flowchart showing an operation of the traveling road surface condition determining device, and FIG. FIG. 7 is a graph showing the operation of the traveling road surface state determination device, FIG. 7 is a block diagram of a modified example of the controller of the four-wheel steering system, and FIG. 8 is a steering ratio when the controller controls the steering ratio by the steering angle. FIG. 9 is a schematic diagram showing another example of the four-wheel steering system for a vehicle provided with the traveling road surface condition determining apparatus according to the present invention. 28 …… Running road surface condition discriminating device 42 …… Slip ratio detecting unit 43 …… Braking force coefficient detecting unit 44 …… Memory unit 45 …… Discriminating unit

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Claims (1)

[Claims] 1. A traveling road surface condition determining device for determining a condition of a road surface during traveling of a vehicle, comprising: slip ratio detecting means for detecting a slip ratio of a braking wheel with respect to the road surface; braking force of a braking device for a vehicle; Braking force coefficient detecting means for detecting the ratio of the axle load received on the wheels, and characteristics obtained by experiments in advance, such as the slip ratio of the braking wheels with respect to the road surface, the braking force of the vehicle braking system and the axles received by the braking wheels. A storage unit that stores at least one braking force coefficient characteristic that indicates a relationship between the load ratio and a friction coefficient of the road surface as a parameter, and a value of the braking force coefficient obtained from a detection signal of the braking force coefficient detection unit. Is compared with the value of the braking force coefficient corresponding to the value of the slip ratio obtained from the detection signal of the slip ratio detecting means in the braking force coefficient characteristic stored in the storage means, A traveling road surface state determination device, comprising: a determination unit that determines whether the friction coefficient of the road surface during traveling is high or low.