JPH0640051B2 - 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 likely to cause side skid, which causes a problem of impairing running stability.

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 driving force coefficient while the vehicle is traveling, and on the other hand, performs the experiment to determine the relationship between the slip ratio and the driving force coefficient. Preliminarily stored as at least one driving force coefficient characteristic having a road surface friction coefficient as a parameter, and the value of the detected driving force coefficient and the stored driving force coefficient characteristic,
By comparing the value of the driving force coefficient corresponding to the detected slip ratio, it is possible to determine whether the friction coefficient of the road surface is high or low. That is, a traveling road surface state determination device for determining the state of a road surface while the vehicle is traveling, a slip ratio detection means for detecting a slip ratio of a drive wheel with respect to the road surface, a driving force of a drive device of a vehicle and a wheel received by the drive wheel. A driving force coefficient detecting means for detecting a load ratio, a characteristic obtained in advance by an experiment or the like, which is a slip ratio of a driving wheel with respect to a road surface, and a ratio of a driving force of a driving device of a vehicle and an axle load received by the driving wheel. The storage means stores at least one driving force coefficient characteristic indicating the friction coefficient of the road surface as a parameter, and the value of the driving force coefficient obtained from the detection signal of the driving force coefficient detecting means. In the driving force coefficient characteristic stored in the means, the value of the driving force coefficient corresponding to the value of the slip ratio obtained from the detection signal of the slip ratio detecting means is compared with And it is characterized in that it comprises a determining means for determining the height of the friction coefficient of the surface.

The above-mentioned "axle load received by the drive wheels" means a vertical load that acts on each drive wheel in consideration of the vehicle load movement amount during driving.

Further, the driving force coefficient represented by the "ratio between the driving force of the vehicle drive device and the axle load received by the driving wheels" is obtained by calculating the values of the driving force coefficients for all the driving wheels and averaging these values. The driving force coefficient may be obtained for one specific driving 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 and 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 the left and right tie rods that transmit the operation of the rack and pinion mechanism 4 to the front wheels 2L and 2R and steer them left and right. 5, 5 and nuck arms 6, 6.

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

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 that are partitioned in the vehicle width direction by 18a.
18b and 18c communicate with a control valve 20 for controlling the oil supply direction to the power cylinder 18 and the hydraulic pressure via hydraulic passages 19a and 19b, respectively.
To the hydraulic pump via an oil supply passage 21 and an oil return passage 22.
23 is connected, and the hydraulic pump 23 is rotationally driven by a motor 24. The control valve 20 detects the rotation direction of the pinion shaft 17 and communicates the oil supply passage 21 with the counterclockwise hydraulic chamber 18b when the rear wheels 8L, 8R are steered to the left (steering counterclockwise in the figure). While the right-turning hydraulic chamber 18c is communicated with the oil return path 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, and at the same time, the hydraulic pump The hydraulic pressure from 23 is reduced to a pressure corresponding to the rotational force of the pinion shaft 17, and the pulse motor 14 causes the rear wheel operating rod 11 to move through the bevel gears 15, 16, the pinion shaft 17, the pinion 13 and the rack 12. When it is moved in the axial direction (vehicle width direction), pressure oil is supplied to the power cylinder 18 to assist the movement of the rear wheel operation rod 11.

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.
Basically, these two steering ratio characteristics A and B are basically the same as the steering ratio k in the negative phase (the front and rear wheels are steered in the opposite direction) as the vehicle speed increases from a low speed to a high speed. In the high speed range, the steering ratio k changes to the same phase in the positive direction (the front and rear wheels are steered in the same direction). The turning ratio k is set to increase with the phase. Of the two steering ratio characteristics A and B, the steering ratio characteristic B for low μ road traveling is wider than 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 becomes the value of the opposite phase in the negative direction. The steering ratio k is set to a larger value in the medium speed range or the high speed range where k has the same phase value in the positive direction.

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
It is connected to the S computer 37, and the ABS computer 37 receives the rotation speeds of the front wheels 2L and 2R, which are driving wheels, and the rear wheels 8L and 8R, which are driven wheels, from the wheel rotation sensors 38. . Then, the rotational speeds of the front wheels 2L and 2R, which are input to the ABS computer 37, are input to the traveling road surface state determination device 28 as driving wheel speed signals, and the rotational speeds of the rear wheels 8L and 8R are input to the traveling road surface state determination device 28, respectively. ing. In addition, the ABS computer 37
It is also connected to the vehicle speed sensor 27 and the ABS modulator 39, and outputs a vehicle speed signal to the vehicle speed sensor 27 on the basis of an input signal from the wheel rotation sensor 38 of the rear wheels 8L and 8R.
A control signal of the brake fluid pressure supplied to the braking device of each wheel 2L, 2R, 8L, 8R is output to the S modulator 39.

The traveling road surface state determination device 28 is further connected to an axle load sensor 40 and a braking force sensor 41, and detects from the axle load sensor 40 the axle load received by each of the front wheels 2L, 2R that are drive wheels. A signal is input, and from the driving force sensor 41, a detection signal for detecting the driving force of the drive device acting on each of the front wheels 2L, 2R 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 driving, and can be obtained as follows, for example.
That is, since there is a proportional relationship between the amount of displacement of the coil spring of the suspension and the vertical load, it can be detected by attaching a strain sensor (strain gauge) to the surface of the coil spring. 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 driving force is a tangential force acting between the driving wheel and the road surface during driving, and can be obtained as follows. That is, when the driving force is D, it can be expressed by D = a + bT _D a, b: constant: wheel rotation speed T _D : driving torque. Since the drive torque T _D corresponds to the twist amount of the drive shaft of the drive wheel, it can be detected by a sensor that detects the twist amount of the drive shaft. For example, as shown in Fig. 4a, 1
If a pair of pickups P ₁ and P ₂ are provided and, as shown in FIG. 4b, the amount of twist R of the drive shaft is obtained from the time displacement of the output pulse of these pickups P ₁ and P ₂ ,
The driving torque T _D can be represented by T _D = lR (l: constant). Therefore, the driving force D can be represented by D = α−βR.

FIG. 5 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 driving 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, the calculation processing of (V _D −V _O ) / V _D × 100 is performed based on the drive wheel speed V _D and the vehicle speed V _o obtained as the input signal from the ABS computer 37, and the slip is detected. The value of the rate S is detected.

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

The slip ratio S and the driving force coefficient μ _D 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. 7, the road surface state determination map includes a slip ratio S of the driving wheels with respect to the road surface and a driving force coefficient μ _D (that is, a ratio of the driving force D of the driving device and the axle load W received by the driving wheels). It is a graph showing the relationship, and at least one braking force coefficient characteristic curve with the friction coefficient μ of the road surface as a parameter is shown. The driving force coefficient characteristic curve is a characteristic curve that can be obtained by experiments or the like. In the figure,
Driving force coefficient characteristic curves E and F obtained by experiments on a dry concrete road surface with a friction coefficient μ of 0.6 and on ice with a μ of 0.15, and an interpolation method is used from these two characteristic curves E and F. The driving force coefficient characteristic curve G calculated by the above is shown. This characteristic curve G is a curve showing the driving 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. In FIG. 7, the values of the slip ratio S and the driving force coefficient μ _D input from the slip ratio detecting unit 42 and the driving 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 _D ) on the road surface state determination map stored in the storage unit 44, and this point X is above or below the reference driving 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, if the determination unit 45 has S = 30%, μ _D
= 0.4, the value of the driving force coefficient corresponding to S = 30% in the driving force coefficient characteristic curve G is 0.
35 and the above μ _D = 0.4, and μ _D = 0.
As 4> 0.35, it is determined that the point X (S = 30, μ _D = 0.4) is above the characteristic curve G. This reveals that the coefficient of friction of the road surface on which the vehicle is traveling is higher than the set value, that is, it is a high μ road.

In FIG. 7, the driving force coefficient characteristic curves stored in the storage unit 44 are three, E, F, and G, and the reference characteristic curve is G1, but the reference characteristic curve is shown. It is also possible to set a plurality of values to determine the level of the friction coefficient of the road surface finely by dividing into more stages instead of the two-stage determination of the high μ road and the low μ road. In this case, it is possible to obtain all the reference characteristic curves by interpolation,
It is also possible to use a plurality of characteristic curves obtained from actual measurement data obtained by running experiments on a road surface having various high and low friction coefficients as they are and use them as reference characteristic curves.

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 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 and 8R are controlled so that at low vehicle speeds, the front wheels 2L and 8R
The front wheels 2 are steered in the opposite phase of L and 2R, and at medium and high vehicle speeds.
It is steered in the same phase as L and 2R.

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, since 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, the rear wheels 8L, 8R are more than those in traveling normally. Front wheels 2L, 2
The steering wheel is steered in the same phase direction as R to increase the lateral gripping force of the wheels, and as a result, the wheels (the front wheels 2L, 2R and the rear wheels 8L, 8R) can be laterally slid even when traveling on a low μ road. Will be prevented. Therefore, traveling stability can be improved.

FIG. 8 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 driving force coefficient characteristics are set, and the slip ratio and the driving force detected during vehicle traveling 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. 9 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 modification 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.

Furthermore, FIG. 10 shows the overall construction 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. 1, the steering force of the front wheel steering mechanism 1 is used to mechanically drive the rear wheels 8L, 8R. It was designed to be steered.

That is, the rear wheel turning mechanism 7'includes a turning ratio changing device 46 including gears, and the turning ratio changing device 46 is connected to a rear end of a transmission rod 47 extending in the vehicle front-rear direction. 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 all ends 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 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.
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 driving force coefficient during traveling of the vehicle by the slip ratio detecting means and the driving force coefficient detecting means, while storing them. The means stores in advance the relationship between the slip ratio and the driving force coefficient as at least one driving force coefficient characteristic using the friction coefficient of the road surface as a parameter, and the determining means determines the value of the detected driving force coefficient. , The stored driving force coefficient characteristic is compared with the value of the driving 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. 4A and 4B are explanatory views for detecting drive torque, FIG. 5 is a block diagram showing a configuration of a traveling road surface state determination device, and FIG. FIG. 7 is a flow chart showing the operation of the traveling road surface state determination device, FIG. 7 is a graph showing the operation of the traveling road surface state determination device, FIG. 8 is a block diagram of a modified example of the controller of the four-wheel steering device, and FIG. 9 is the controller. FIG. 10 is a diagram showing a steering ratio characteristic when a steering ratio control is performed by a steering angle, and FIG. 10 is a schematic diagram showing another example of a four-wheel steering device for a vehicle provided with a traveling road surface state determination device according to the present invention. Is. 28 …… Running road surface condition discriminating device 42 …… Slip ratio detecting unit 43 …… Driving force coefficient detecting unit 44 …… Storage unit 45 …… Identifying unit

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 drive wheel with respect to the road surface; A driving force coefficient detecting means for detecting a ratio of an axle load received by the wheels, a characteristic obtained in advance by experiments, etc., that is, a slip ratio of the driving wheels with respect to a road surface, a driving force of a vehicle drive device and an axle received by the driving wheels. A storage unit that stores at least one driving force coefficient characteristic indicating a road ratio as a parameter, the relationship between the load ratio, and a value of the driving force coefficient obtained from the detection signal of the driving force coefficient detecting unit. Is compared with the value of the driving force coefficient corresponding to the value of the slip ratio obtained from the detection signal of the slip ratio detecting means in the driving 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.