JP2001099779A - Road surface condition detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road surface condition detecting device capable of exactly detecting road surface conditions such as slipperiness of the road in running at a constant speed. SOLUTION: When a determining circuit 16, as a determining means of the road surface condition, detects a water film based on a detection signal from a water film sensor 12, as a wafer film detecting means for detecting a water film between the tire and the road surface, and from a wheel speed sensor 14 for detecting the wheel speed, it is determined that the road surface is more slippery when roughness of the road surface is less and the vehicle speed is greater, an alarm device 18 provided on the outside of the device provides an alarm, and a vehicle control device 20 slows down the vehicle automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface state detecting device, and more particularly, to a road surface state detecting device for detecting a road surface state such as slipperiness (road surface μ maximum value) of a road surface traveling without large acceleration / deceleration. It relates to a detection device.

[0002]

2. Description of the Related Art As shown in FIG. 14, a braking force acting between a tire and a road surface increases with an increase in the slip ratio until the slip ratio reaches a predetermined value. ) Also increases, but when the slip ratio reaches a predetermined value, the road surface μ takes a maximum value, and thereafter decreases as the slip ratio increases. That is, the wheels are locked.
Therefore, in order to apply the brake safely, it is important to estimate the maximum value of the traveling road surface μ and apply a braking force to the wheels according to the road surface condition.

Conventionally, various methods for estimating the road surface μ have been proposed. However, μ can be estimated in a constant speed running state (near a slip ratio of zero) without large acceleration / deceleration.
Except in the case where the tire is completely lifted by the water film due to the hydroplane phenomenon and the μ characteristics change near the slip rate of zero, the road surface μ maximum value reduces the slip rate by accelerating and decelerating. It could not be estimated unless it was increased and did not reach the region where μ was saturated.

[0004] As can be seen from the fact that the maximum value of the road surface μ is greatly reduced by the hydroplane phenomenon, the water film existing between the tire and the road surface is the largest factor in reducing the maximum value of the road surface μ.

Japanese Patent Application Laid-Open No. HEI 7-179108 discloses an apparatus for detecting a water film between a tire and a road surface by detecting a water film between the tire and the road surface by an electrode type sensor embedded in the tire. There has been proposed a tire condition detecting device that warns that the danger of slip has increased due to the plane phenomenon. Japanese Patent Application Laid-Open No. 7-83827 proposes a road surface condition detecting device that irradiates light to the tire surface, detects the wet / dry condition of the tire surface from the reflected light, and determines the dry / wet condition of the road surface.

[0006]

However, even on a wet road where a water film is present between the tire and the road surface, if the road surface roughness is large, a high road surface μ maximum value substantially equal to that of a dry road can be obtained. Even when the amount of the water film is extremely small, the road surface μ maximum value is greatly reduced when the road surface is smooth. Therefore, the above-described device that only detects the water film between the tire and the road surface has a problem that it is not possible to accurately determine the road surface condition such as whether the running road surface is slippery at a constant speed running state. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a road surface state detecting device for accurately detecting a road surface state such as slipperiness of a running road surface at a constant speed running state. To provide.

[0008]

According to a first aspect of the present invention, there is provided a road surface condition detecting apparatus for detecting the presence or absence of a water film existing between a tire and a road surface. Detecting means, road surface roughness detecting means for detecting road surface roughness of the traveling road surface, vehicle speed detecting means for detecting the traveling speed of the vehicle body,
When the presence of a water film is detected based on the detection signals of the water film detection means, the road surface roughness detection means, and the vehicle speed detection means, the road surface slips as the road surface roughness decreases and the vehicle speed increases. And road surface state determination means for determining that the road surface is easy to use.

According to a second aspect of the present invention, there is provided a road surface condition detecting device for detecting a water film amount existing between a tire and a road surface, and a road surface roughness detecting device for detecting a road surface roughness of a running road surface. And a vehicle speed detecting means for detecting a traveling speed of the vehicle body, based on detection signals of the water film detecting means, the road surface roughness detecting means, and the vehicle speed detecting means, the water film amount is large and the road surface roughness is small. And road surface state determination means for determining that the road surface is more slippery as the vehicle speed is higher.

According to the first aspect of the present invention, the presence / absence of a water film existing between the tire and the road surface is determined by the water film detection means, and the road surface roughness of the running road surface is determined by the road surface roughness detection means. Are respectively detected by the vehicle speed detecting means. Then, the road surface state determination means determines the ease of road surface slippage based on detection signals from the water film detection means, the road surface roughness detection means, and the vehicle speed detection means.

The slipperiness of the road surface, that is, the degree of reduction of the maximum value of the road surface μ changes depending on the presence or absence of a water film, road surface roughness, and vehicle speed. When there is no water film between the tire and the road surface, the road surface μ maximum value does not decrease, but when the water film exists, the road surface μ maximum value decreases. As shown in FIG. 15, when a water film is present, the road surface μ maximum value decreases as the road surface roughness decreases. Further, as shown in FIG. 16, when a water film is present, the higher the vehicle speed, the higher the road surface μ.
The maximum value is lower.

On ice, as shown in FIG. 17, when the ice temperature is low, the decrease in the road surface μ maximum value is small, but when the ice temperature is around 0 ° C., the decrease in the road surface μ maximum value becomes large.
This is considered to be because when the ice temperature is high, the ice is easily melted due to frictional heat or the like, and a water film is present between the tire and the road surface. Further, even on ice, when the road surface roughness is large, the degree of reduction of the road surface μ maximum value is small.

When the presence of a water film is detected based on the above correlation, it is determined that the road surface is more likely to slip as the road surface roughness is smaller and the vehicle speed is higher. As described above, it is possible to predict the slipperiness of the road surface during braking by using the information obtained in a constant speed traveling state. Therefore, the braking characteristics (maximum deceleration, etc.) or the turning performance (maximum skidding) of the vehicle during traveling It is possible to predict a frictional force or the like, and to warn the driver based on the prediction, and to automatically decelerate to a safe state by the vehicle control device.

According to the second aspect of the present invention, the amount of water film present between the tire and the road surface is determined by the water film detecting means, the road surface roughness of the running road surface is determined by the road surface roughness detecting means, and the running speed of the vehicle body is reduced. Each is detected by the vehicle speed detecting means. Then, the road surface state determination means determines the ease of road surface slippage based on detection signals from the water film detection means, the road surface roughness detection means, and the vehicle speed detection means.

The slipperiness of the road surface, that is, the degree of reduction of the maximum value of the road surface μ changes depending on the amount of water film, the road surface roughness, and the vehicle speed. When a water film exists between the tire and the road surface, the road surface μ maximum value decreases. The degree of the decrease is larger as the water film is thicker, that is, as the amount of the water film is larger. Therefore, when the water film amount can be detected, the road surface is more likely to slip as the water film amount is larger, the road surface roughness is smaller, and the vehicle speed is higher, based on the detected water film amount, road surface roughness, and vehicle speed. Is determined.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a road surface state detecting device according to the present invention will be described in detail based on an embodiment.

As shown in FIG. 1, a road surface condition detecting device according to a first embodiment includes a water film sensor 12 as water film detecting means for detecting the presence or absence of a water film, and a wheel speed detecting wheel speed. It comprises a sensor 14 and a determination circuit 16 as road surface state determination means, and is mounted on a vehicle. The water film sensor 12 and the wheel speed sensor 14 are connected to a judgment circuit 16, and the judgment circuit 16 is provided with an alarm device 18 provided outside the device.
And the vehicle control device 20.

The judgment circuit 16 includes a CPU 22 and a ROM 2
4 and a RAM 26, and the CPU 22
Various arithmetic processing is performed based on a determination program stored in the OM 24 and described below.

As shown in FIG. 2, the wheel speed sensor 14 has a signal rotor 28 which rotates with wheels (not shown).
The signal rotor 28 is made of a magnetic material, and is configured as a gear having a number of teeth (for example, 48 teeth) arranged at equal intervals around the periphery. An electromagnetic pickup 30 is fixedly arranged so as to approach the outer periphery of the signal rotor 28. The electromagnetic pickup 30 detects a change in the magnetic field caused by the passage of one tooth of the signal rotor 28 that rotates with the wheel, and outputs a sinusoidal detection signal that vibrates every time one tooth passes. This sine wave detection signal is converted into a pulse signal train by a pulse generator 32 arranged at the subsequent stage, and is input to the determination circuit 16 as a wheel speed signal.

The water film sensor 12 is constituted by arranging a plurality of electrode pairs 34 each consisting of a pair of positive and negative electrodes arranged close to each other. As shown in FIGS. It is embedded in the tire tread so that the part is exposed on the tire surface. As shown in FIG. 3A, the water film sensor 12 couples, for example, two electrode pairs 34 arranged at predetermined intervals in the tire axial direction, as shown in FIG. Are arranged at predetermined intervals in a large number of rows. When the tread portion in which the water film sensor 12 is embedded is grounded, if a water film exists between the tire and the road surface, a certain amount of current flows between the positive and negative electrodes to detect the presence of the water film. be able to.

The control routine executed by the determination circuit 16 will be described with reference to FIGS.

In step 100, the decision circuit 16 fetches a signal from the water film sensor 12 and
At 02, it is determined whether or not a water film exists between the tire and the road surface. If there is a water film, the signal from the wheel speed sensor 14 is fetched in step 104, and the wheel speed _Vw is calculated in step 106. Then detected road surface roughness C based on the variation of the wheel speed V _w at step 108. That is, when the vehicle is traveling at a constant speed, the fluctuation of the wheel speed increases as the road surface becomes rougher, so that the road surface roughness can be detected from the wheel speed. Detecting a vehicle speed V _r, based on the step 110 in the wheel speed V _w.

The reduction amount G of the maximum road surface μ shows a larger characteristic according decreases as road surface roughness, as shown in FIG. 5 with respect to the road surface roughness C, and the vehicle speed V _r is increased, the vehicle speed is increased things from, in step 112, using the map or the function shown in FIG. 5 which has been stored in the ROM, based on the road surface roughness was detected C and the vehicle speed V _r to detect the reduction amount G of the maximum road surface mu. Step 10
If it is determined in step 2 that there is no water film, the amount of decrease G of the road surface μ maximum value is set to zero in step 114.

Next, the detected decrease amount G of the road surface μ maximum value G
Using, slipperiness of the road surface makes a decision as to whether or not greater than the threshold G ₀ in step 116. That is, lowering the amount G of the maximum road surface μ is determined whether or not greater than the threshold G _0, if out of limits G _0, an alarm from the alarm device 18 at step 118, the vehicle control at step 120 The vehicle speed is automatically controlled by the device 20. For example, by controlling the throttle valve that adjusts the amount of intake air supplied to the combustion chamber to close regardless of the amount of depression of the accelerator pedal, the drive torque of the engine is adjusted, and the engine is automatically controlled to decelerate. I do. On the other hand, when the value is equal to or less than the limit value G ₀ ,
The next signal is fetched and the determination is repeated again.

As described above, in this embodiment, it is possible to predict the slipperiness of the road surface during braking from a running condition at a constant speed based on the presence or absence of a water film, the road surface roughness, and the vehicle speed. It can predict the braking characteristics (maximum deceleration, etc.) or turning performance (maximum skid friction force, etc.) of the vehicle, warn the driver based on this prediction, and automatically control the safety by the vehicle control device. It becomes possible to decelerate to a proper state. In the present embodiment, the determination in step 116 is performed in one step, but it is also possible to determine the state of the road surface in multiple steps and finely. In this embodiment, the road surface roughness is detected by using the wheel speed sensor 14. However, it is also possible to mount a vertical acceleration sensor on the vehicle and detect the road surface roughness by using this.

The road surface condition detecting apparatus according to the second embodiment can detect not only the presence or absence of a water film but also the magnitude of the amount of a water film, instead of the water film sensor 12 of the first embodiment. The same components as those of the road surface state detecting device according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The water film sensor 12a is composed of a plurality of pressure sensors 36 embedded in the tire axial direction and arranged in the tire circumferential direction.
As shown in FIG. 6 (B), the pressure sensor 36 is arranged on each of the surface portion 38 and the groove portion 40 of the tire tread along the axial direction of the tire, and five pressure sensors 36 are arranged in the axial direction of the tire. Let A, B, C, D, and E be pressure sensors of A, C, and E respectively.
B and D are provided in the groove 40. FIG. 6A
As shown in the figure, a large number of pressure sensor 36 rows are arranged at predetermined intervals along the circumferential direction of the tire.
6 is connected to a movable contact 42 provided for each of the five pressure sensors arranged in the axial direction. On the vehicle body side, a fixed contact 44 is arranged at a position facing the movable contact 42 connected to the pressure sensor, and the fixed contact 44 is connected to an arithmetic unit of the determination circuit 16 provided on the vehicle body side.

In the water film sensor 12a, when a large amount of water film exists between the tire and the road surface, as shown in FIG. 6C, the amount of water entering the groove 40 increases. Therefore, the pressure in the groove increases, and the difference between the pressure acting on the pressure sensor A or the pressure sensor C disposed on the surface portion 38 of the tire and the pressure acting on the pressure sensor B disposed on the groove 40 becomes a predetermined pressure. Since the difference ΔP or less, the pressure acting on the pressure sensor B is compared with the difference between ΔP and the average value of the pressure acting on the pressure sensor A and the pressure acting on the pressure sensor C. The presence can be detected.

When the amount of water film existing between the tire and the road surface is medium, the amount of water entering the groove 40 is also medium, but air is mixed in the groove 40. And
This air is compressed by the water film, and a pressure equal to or more than a predetermined value acts on the pressure sensor B disposed in the groove 40. By comparing the pressure acting on the pressure sensor B with the reference pressure P ₀ , Can be detected. On the other hand, when a water film hardly exists between the tire and the road surface or when the amount of the existing water film is small, water does not normally enter the groove 40 and the air in the groove 40 is almost compressed. Pressure sensor B disposed in the groove 40
Pressure on the so less than reference pressure P _0, by comparing the reference pressure P ₀ the pressure acting on the pressure sensor B, it is possible to detect that water film amount is small.

The connection between the movable contact 42 and the fixed contact 44 is
As shown in FIG. 7A, a metal connection portion 42A provided on the movable contact 42 and a metal connection portion 44A provided on the fixed contact 44
In addition to the method of directly transmitting an electric signal by contacting
7B, a light emitting element 42B is provided on the movable contact 42 and a light receiving element 44B is provided on the fixed contact 44, and a signal is transmitted by light. As shown in FIG.
2C, a coil 44C may be provided on the fixed contact 44, and the contact may be performed in a non-contact manner, such as a method of transmitting a signal by electromagnetic induction by magnetic force. Further, a method of transmitting an electric signal based on a change in capacitance can be adopted.

FIG. 8 is a flowchart showing a control routine executed by the determination circuit 16 of this embodiment. Parts corresponding to those in FIG. 4 are described with the same reference numerals.

In step 124, a procedure described later is used.
The water film amount W is detected. Then, steps 104, 10
In step 6, the signal from the wheel speed sensor 14 is fetched, and the wheel speed
Degree V _wIs calculated. In the next step 108, this wheel speed
Degree V_wRoad surface roughness C is detected based on the variation of
Wheel speed V at 110_wVehicle speed V based on_rIs detected.

The decrease of the road surface μ maximum, for the road surface roughness C, and the vehicle speed V _r, in the same manner as described in FIG. 5, FIG. 9
The characteristics shown in FIG. Further, the amount of decrease in the maximum road surface μ in accordance with the amount of water film increases as shown in FIG. 10 becomes large relative to the water film weight W and the vehicle speed V _r, the amount of decrease in the maximum road surface μ in accordance with the vehicle speed increases reduction of road surface μ maximum value based because they exhibit characteristics that increase, using the map or the function shown in FIGS. 9 and 10 which are stored in the ROM in step 126, the road surface roughness was detected C and the vehicle speed V _r determine the amount g _1, obtains a reduction amount g ₂ of maximum road surface μ based on the detected water film weight W and the vehicle speed V _r, then the product of the g ₁ and g ₂ (g ₁ × g ₂₎ and the road surface μ using the map of FIG. 11 showing the relation between the reduction amount G of the maximum value, the detected road surface roughness C, water film weight W, and detects the reduction amount G of the road surface μ maximum at the vehicle speed V _r.

Next, the detected amount of decrease G of the road surface μ maximum value G
, The slipperiness of the road surface is set to the limit value G in step 116.
_It is determined whether or not the number has exceeded ₀ . That is, lowering the amount G of the maximum road surface μ is determined whether or not greater than the threshold G _0, if out of limits G _0, the alarm device in step 118 1
8, an alarm is issued, and in step 120, the vehicle control device 20
Automatically controls the vehicle speed. If the value is equal to or less than the limit value G ₀ , the next signal is fetched and the determination is repeated again.

FIG. 12 is a flowchart showing the details of the routine for detecting the amount of water film in step 124. In step 124a, the signals from the pressure sensors A, B, C, D, and E are fetched, and in step 124b, the pressure P _B of the sensor _B is
Is greater than or equal to the difference between the average value (P _A + P _C ) / 2 obtained from the pressure P _A of the sensor _A and the pressure P _{C of the} sensor C and the constant ΔP;
Alternatively, the pressure P _D of the sensor _D is the average value (P _C + P _E ) / 2 obtained from the pressure P _C of the sensor _C and the pressure P _{E of the} sensor E.
Is determined to be greater than or equal to the constant ΔP, and if the requirement is satisfied, it is determined that the water film amount is large, and the fact that the water film amount is large is stored in the RAM in step 124c. If the requirement is not satisfied, it is determined in step 124d whether the pressure P _B of the sensor B is equal to or more than the reference value P ₀ or the pressure P _{D of the} sensor _D is equal to or more than the reference value P _0. If the condition is satisfied, it is determined that the amount of the water film is being measured, and the fact that the amount of the water film is being measured is stored in the RAM in step 124e. If the requirement is not satisfied, it is determined at step 124f that the water film amount is small.
Store in AM.

In the present embodiment, the water film sensor 12a composed of a pressure sensor is used as the water film amount detecting means, but the water film sensor 12 composed of a large number of electrode pairs used in the first embodiment is used.
Can be used to detect the amount of water film. FIG. 13 is a flowchart showing a routine for detecting the amount of water film by the determination circuit 16 in this case. In this case, the determination circuit 16
At step 130, a signal from the connected water film sensor is fetched, and at step 132, the number C of water film sensors that have detected a water film is counted. In step 134, the count value C is determined whether a predetermined value C ₀ or more, in the case of more than the predetermined value C _0, it is determined that the water film amount large stores water film Large amount at step 136. If the count value is less than the predetermined value C ₀ , it is determined in step 138 whether or not the count value C is 0. If the count value is 0, zero water film amount is stored in step 140 and the count value is not 0 In this case, in step 142, the small amount of water film is stored.

As described above, in the present embodiment, the slipperiness of the road surface during braking can be predicted from the running state at a constant speed based on the water film amount, the road surface roughness, and the vehicle speed. It is possible to predict the vehicle's braking characteristics (maximum deceleration, etc.) or turning performance (maximum skid friction force, etc.). It becomes possible to decelerate to the state.

In the above embodiment, the water film amount is calculated by the determination circuit 16 provided on the vehicle side. However, as shown in FIGS. 7D to 7F, the water film amount on the water film sensor side is calculated. An arithmetic unit may be provided at the movable contact 44 to calculate the amount of water film based on the input pressure signal, and the calculated amount of water film may be input to the determination circuit via the contact.

Further, in the above embodiment, the example in which the alarm and the vehicle control are performed has been described. However, either one may be performed, or only the display may be performed instead.

[0040]

According to the road surface condition detecting device of the present invention, it is possible to accurately detect a road surface condition such as whether the traveling road surface is slippery from a constant speed traveling condition.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a road surface state detection device according to a first embodiment.

FIG. 2 is a schematic diagram of a wheel speed sensor in the road surface condition detection device according to the first embodiment.

FIGS. 3A and 3B are schematic diagrams of a water film sensor in the road surface condition detecting device according to the first embodiment.

FIG. 4 is a flowchart illustrating a control routine performed by the road surface condition detection device according to the first embodiment.

FIG. 5 is a diagram showing a map showing characteristics of a decrease amount of a road surface μ maximum value with respect to road surface roughness and vehicle speed.

FIGS. 6A and 6B are schematic diagrams of a water film sensor in a road surface condition detection device according to a second embodiment. (C)
FIGS. 4A and 4B are explanatory diagrams illustrating the principle of detecting a water film amount by the water film sensor shown in FIGS.

FIGS. 7A, 7B, and 7C are schematic diagrams showing a method in which the water film sensor shown in FIG. 6 transmits signals, and FIGS.
(E) (F) is a schematic diagram showing an application example in which the arithmetic unit is provided on the water film sensor side.

FIG. 8 is a flowchart illustrating a control procedure performed by the road surface condition detection device according to the second embodiment.

FIG. 9 is a diagram showing a map showing characteristics of a decrease amount of the road surface μ maximum value with respect to road surface roughness and vehicle speed.

FIG. 10 is a diagram showing a map showing characteristics of a reduction amount of a road surface μ maximum value with respect to a water film amount and a vehicle speed.

11 is a road surface μ obtained from a diagram showing the map of FIG. 9;
Diagram showing a map showing the relationship between the decrease amount G of the product and the road surface μ maximum value of the decrease amount g ₁ and decrease g ₂ of the road surface μ maximum value obtained by diagram showing a map of FIG. 10 of the maximum value It is.

FIG. 12 is a flowchart showing details of step 124 in FIG. 8;

FIG. 13 is a flowchart showing details of another example of step 124 in FIG. 8;

FIG. 14 is a graph showing a relationship between a braking friction coefficient μ of a road surface and a slip ratio.

FIG. 15 is a graph showing a relationship between a road surface friction coefficient μ and road surface roughness.

FIG. 16 is a graph showing a relationship between a braking friction coefficient μ of a road surface and a vehicle speed.

FIG. 17 is a graph showing a relationship between a braking friction coefficient μ of a road surface and an ice temperature.

[Explanation of symbols]

 12, 12a Water film sensor 14 Wheel speed sensor 16 Judgment circuit 18 Alarm device 20 Vehicle control device 22 CPU 24 ROM 26 RAM 28 Signal rotor 30 Electromagnetic pickup 32 Pulse generator 34 Electrode 36 Pressure sensor 38 Surface portion 40 Groove portion 42 Movable contact 44 Fixed contact

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Shu Asami, 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. (72) Inventor, Koji Umeno 41F Yokomichi No. 1 Toyota Central Research Laboratory Co., Ltd. F-term (reference) 2F069 AA57 AA83 BB24 GG06 GG20 HH09 HH15 HH30 NN05 3D046 BB01 BB22 BB27 EE01 HH22 HH45 HH46 HH50 MM08

Claims (2)

[Claims] 1. A water film detecting means for detecting the presence or absence of a water film existing between a tire and a road surface, a road surface roughness detecting means for detecting a road surface roughness of a running road surface, and a running speed of a vehicle body. Vehicle speed detection means, based on the detection signal of the water film detection means, the road surface roughness detection means, and the vehicle speed detection means, when the presence of a water film is detected, the road surface roughness is small and the vehicle speed A road surface state determining device that determines that the larger the road surface, the easier the road surface is to slip. 2. A water film amount detecting means for detecting a water film amount existing between a tire and a road surface; a road surface roughness detecting means for detecting a road surface roughness of a traveling road surface; and a traveling speed of a vehicle body. Based on the detection signals from the vehicle speed detection means, the water film detection means, the road surface roughness detection means, and the vehicle speed detection means, the road surface slips as the water film amount increases, the road surface roughness decreases, and the vehicle speed increases. A road surface state detection device, comprising: a road surface state determination unit that determines that the road surface state is easy.