JPH09193604A - Road surface friction coefficient improving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge friction material only in the case of a travel road being a low μ road in a road surface friction coefficient improving device that discharges friction material in front of wheels in the case of the generation of slip quantity exceeding the specified value. SOLUTION: Injection nozzles 10L, 10R are disposed in front of wheels FL, FR. Friction material tanks 16L, 16R are connected to the injection nozzles 10L, 10R through discharge control valves 12L, 12R and pressure pipes 14L, 14R. The friction material tanks 16L, 16R are filled with sand. An ECU 30 opens the discharge control valves 12L, 12R in the case of a travel road being judged to be a low μ road and the execution conditions of ABS control being effected on the basis of the detection signals of an acceleration sensor 32, wheel speed sensors 38FL, 38FR, 38RL, 38RR, and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface friction coefficient improving device, and more particularly to a road surface friction coefficient improving device for discharging a friction material in front of a wheel when a slip amount exceeding a predetermined value occurs on the wheel. Regarding

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-3-20870.
As disclosed in No. 1, there is known a road surface friction coefficient improving device that discharges a friction material in front of a wheel when a slip amount exceeding a predetermined value occurs in the wheel. When the vehicle is traveling on a low friction coefficient road such as an icy road, an excessive slip amount is likely to occur on the wheels during braking. When the friction material is discharged to the front of the wheel as in the conventional device described above, the coefficient of friction between the wheel and a road having a low coefficient of friction such as a frozen road is improved. Therefore, according to the above conventional device, the braking ability of the vehicle on the low friction coefficient road can be enhanced.

[0003]

By the way, the wheels have
For example, a large slip amount may occur even when the vehicle is traveling on a dry paved road. According to the above-mentioned conventional device, the friction material is discharged in front of the wheel even when a slip amount exceeding a predetermined value occurs on the wheel on the high friction coefficient road.

The friction coefficient between the wheel and the road surface is improved by discharging the friction material when the vehicle is traveling on a low friction coefficient road such as an icy road. However, when the vehicle is traveling on a high-friction coefficient road such as a dry paved road, the friction material may be discharged, which may rather reduce the friction coefficient between the wheels and the road surface. In this respect, the above conventional device has a possibility of further promoting the slip amount when a large slip amount occurs on the wheel on the high friction coefficient road.

The present invention has been made in view of the above-mentioned points, and provides a road surface friction coefficient improving device which permits the release of friction material only when the vehicle is traveling on a low friction coefficient road. With the goal.

[0006]

The above object is achieved by the present invention.
As described above, a friction material discharging device for discharging the friction material is provided in front of the wheel, and when the slip amount of the wheel exceeds a predetermined value, the friction coefficient improving device for the road surface for discharging the friction material from the friction material discharging means. In the above, the road surface friction coefficient improving device is provided with: a road surface condition detecting means for detecting a road surface condition; and a discharge control means for permitting discharge of the friction material when the road surface is a predetermined low friction coefficient road.

According to the first aspect of the invention, the release control means permits the release of the friction material when it is determined that the road surface has a predetermined low friction coefficient road based on the detection result of the road surface state detection means. Therefore, the friction material is not discharged when the vehicle is traveling on a high friction coefficient road.

Further, as described in claim 2, the above object is to provide the friction coefficient improving device for a road surface according to claim 1, wherein at least one friction material discharging means is provided in front of each of the left and right wheels. Then, the road surface state detecting means,
Left and right road surface state detecting means for detecting a road surface state in contact with each of the left and right wheels is provided, and the emission control means is arranged in front of each of the left and right wheels in accordance with the state of the road surface in contact with each of the left and right wheels It is also achieved by a road surface friction coefficient improving device including independent control means for independently controlling the friction material discharging means.

In the present invention, the independent control means provided in the discharge control means independently controls the friction material discharge means arranged in front of the left and right wheels. The friction material discharging means arranged in front of the left and right wheels discharges the friction material only when the road surface contacting the wheels is a predetermined low friction coefficient road according to the detection result of the left and right road surface state detecting means. Tolerate. Therefore, when the vehicle is traveling on a straddle road, the friction material is discharged to the road surface portion having a low friction coefficient, while the friction material is not discharged to the road surface portion having a high friction coefficient.

Further, as described in claim 3, claim 1
In the road surface friction coefficient improving device described in (2) and (2) above, there is provided a turning state detecting means for detecting a turning state of the vehicle, and the friction material releasing means controls the friction material releasing means according to the turning state of the vehicle. The friction coefficient improving device is effective for stabilizing the turning behavior of the vehicle.

In the present invention, the friction material discharging means controls the friction material discharging means according to the detection result of the turning state detecting means. While the vehicle is turning, the behavior of the vehicle is likely to change. Therefore, when the release state of the friction material is controlled according to the turning state of the vehicle as in the present invention, the turning behavior of the vehicle is stably maintained.

[0012]

FIG. 1 shows a system configuration diagram of an embodiment of the present invention. FIG. 1 shows a front view of a road surface friction coefficient improving device when mounted on a vehicle. The friction coefficient improving device according to the present embodiment includes injection nozzles 10L and 10R arranged in front of the left and right front wheels FL and FR of the vehicle. Release control valves 12L and 12R are connected to the injection nozzles 10L and 10R, respectively. The release control valves 12L and 12R are electromagnetic opening / closing valves that maintain a closed state in a normal state.

The release control valves 12L and 12R are provided with friction material tanks 16L and 16R via pressure pipes 14L and 14R.
Are in communication. The friction material tanks 16L and 16R are filled with sand discharged as friction material on the road surface. The friction material tanks 16L and 16R are provided at their bottoms with residual sand sensors 18L and 18R that emit an ON output when the sand in the tank is consumed, respectively.

The pressure pipes 14L and 14R are provided with an electromagnetic opening / closing valve 2
The air tank 22 communicates with 0L and 20R.
A compressor 24 communicates with the air tank 22. When the pressure inside the air tank 22 becomes equal to or lower than a predetermined value, the compressor 24 pumps air into the air tank 22 until the internal pressure reaches a predetermined pressure.

The friction coefficient improving device of this embodiment includes an electronic control unit 30 (hereinafter referred to as ECU 30). The ECU 30 includes an acceleration sensor 32 for detecting a longitudinal acceleration G generated in the vehicle, a brake switch 36 for producing an ON output when the brake pedal 34 is depressed, wheel speeds of the left and right front wheels FL, FR and left and right rear wheels RL, RR. Wheel speed sensor 38FL, 38FR, 3 for detecting
8RL, 38RR (Hereinafter, when these are collectively referred to,
(Indicated by reference numeral 38), and an indicator lamp 40 arranged in the vehicle compartment are connected. ECU 30
Is based on the output signals of the acceleration sensor 32, the brake switch 36, and the wheel speed sensor 38, and the release control valves 12L, 12R and the electromagnetic opening / closing valves 20L, 20 described above are used.
Drive R. Further, the ECU 30 turns on the indicator lamp 40 when the remaining sand sensors 18R and 18L described above detect that the sand in the friction material tanks 16L and 16R has been consumed.

In FIG. 2, the ECU 30 controls the release control valve 12
The flowchart of an example of the control routine performed in order to drive L, 12R and the solenoid on-off valves 20L, 20R is shown. When the routine shown in FIG. 2 is started, first, at step 100, it is judged if a known antilock brake control (hereinafter referred to as ABS control) is being executed. The ABS control is executed when a slip ratio S that exceeds a predetermined value occurs in any of the wheels during the braking operation (while the ON signal is output from the brake switch 36). The slip ratio S is the estimated vehicle speed VS0 and the wheel speed V.
It is calculated as follows using w and. The estimated vehicle speed VS0 is calculated based on the wheel speed Vw of the wheel that is rotating at the highest speed during braking.

S = (VS0-Vw) × 100 / VS0 (1) If it is determined in the above step 100 that the ABS control is not in progress, all the wheels maintain the proper grip state. It is determined that it is not necessary to discharge the sand, which is the friction material, to the road surface, and thereafter, the routine of this time is ended without proceeding any processing. On the other hand, the above step 10
When it is determined that the ABS control is being performed at 0, it is determined at step 102 whether or not the road on which the vehicle is traveling is a predetermined low friction coefficient road (hereinafter, referred to as low μ road).

FIG. 3 shows a flowchart of an example of a subroutine executed by the ECU 30 to determine whether or not the road surface on which the vehicle is traveling is a low μ road. The routine shown in FIG. 3 is a regular interrupt routine that is executed every predetermined time. When the routine shown in FIG. 3 is started, first, at step 200, it is judged if the ABS control is being executed. If the ABS control is not in progress, the routine of this time is ended without proceeding any processing. On the other hand, if it is determined that the ABS control is being performed, the output signal of the acceleration sensor 32, that is, the longitudinal acceleration G acting on the vehicle is read in step 202.

When the reading of the acceleration G is completed, next, at step 204, it is judged if the acceleration G is smaller than a predetermined judgment value Ga. The ABS control is executed when the slip ratio of any wheel exceeds a predetermined value during braking as described above. In such a situation, deceleration corresponding to the friction coefficient μ between the road surface and the wheels acts on the vehicle. Therefore, when the vehicle is traveling on a high friction coefficient road (hereinafter referred to as a high μ road), a large deceleration acceleration is detected by the acceleration sensor 32 during the execution of the ABS control.
Further, when the vehicle is traveling on a low μ road, a small deceleration acceleration is detected by the acceleration sensor 32 during execution of the ABS control.

If it is determined in step 204 that G <Ga holds, it can be determined that the vehicle is traveling on a low μ road. Therefore, if the above determination is made, the low μ road flag is set to "1" in step 206, and then this routine is ended. On the other hand, if it is determined in step 204 that G <Ga does not hold, it can be determined that the vehicle is traveling on a high μ road. Therefore, if the above determination is made, the low μ road flag is set to "0" in step 208, and then this routine is ended. In this embodiment, the discriminant value Ga is set to a value that satisfies the condition of G <Ga when the traveling road is a low μ road such as an icy road.

At step 102 in the routine shown in FIG. 2, a low μ value in which "1" or "0" is set as described above.
Based on the state of the road flag, it is determined whether or not the road on which the vehicle is traveling is a low μ road. As a result, when it is determined that the road on which the vehicle is traveling is the low μ road, the routine for this time is terminated after the processing for discharging sand is executed in step 103.

In the system of this embodiment, the release of sand is controlled by the release control valves 12L and 12R and the electromagnetic opening / closing valve 2.
It is executed by opening 0L and 20R. When the solenoid on-off valves 20L, 20R are opened, the pressure pipes 14L, 1
High pressure air is introduced into the 4R. Pressure tube 14L, 1
When the discharge control valves 12L and 12R are opened under the condition that high pressure air is introduced into the 4R, the pressure pipes 14L and 14L
Sand inside R is discharged in front of the left and right front wheels FL, FR.
Wheels F when the vehicle is traveling on a low μ road such as an icy road
When sand is discharged in front of L and FR, the road surface and wheels FL and F
The coefficient of friction with R is improved. As a result, a higher braking ability can be obtained as compared with the case where sand is not discharged.

When the road on which the vehicle is traveling is a road having different friction coefficients at the contact portions of the left and right wheels, that is, a so-called "crossover road", the road on which the vehicle is traveling at step 102 is a low μ road. May not be determined.
When the vehicle is traveling on a straddle road, if the sand is discharged to the side having a lower friction coefficient, both the left and right wheels can obtain a high braking force. For this reason, in the system of the present embodiment, as will be described later, when the traveling road is a bridging road, even if the traveling road is not determined to be a low μ road in step 102, the sand It is supposed to be released.

However, if the sand is discharged only in front of one of the left and right wheels while the vehicle is turning, the turning behavior of the vehicle may become unstable. From this perspective,
In the system of the present embodiment, even when the vehicle is traveling on a straddle road, the release of sand is prohibited when the vehicle is turning.

In order to realize the above function, step 102
If it is determined that the road on which the vehicle is traveling is not a low μ road, then in step 104, it is determined whether or not the vehicle is turning. As a result, when it is determined that the vehicle is turning, the sand discharge is stopped in step 106 and then the routine shown in FIG. 2 is ended.

A method for determining whether or not the vehicle is turning in the system of this embodiment will be described below with reference to FIGS. 4 and 5. FIG. 4 shows a μ-S characteristic diagram of a wheel, that is, a characteristic diagram showing a relationship between a wheel slip ratio and a friction coefficient μ. As shown in FIG. 4, in a region where the wheel slip ratio S is smaller than the predetermined value S ₀ , the friction coefficient μ and the slip ratio S have a substantially proportional relationship. Further, in the region where the slip ratio S exceeds the predetermined value S ₀ , the friction coefficient becomes a value smaller than the peak value μ ₀ .

The above-described ABS control monitors the slip ratio S of each wheel, if S is the case of more than S _0, or S is detected can exceed S _0, suppress excessive braking force It should be started. Therefore, when the ABS control is started, more specifically, when the wheel cylinder pressure is reduced by the ABS control, the slip ratio S of the wheel to be controlled becomes a predetermined value S ₀ , or It matches another predetermined value near the predetermined value S ₀ .

The slip ratio S _{OUT of the} turning outer wheel and the slip ratio S _IN of the turning inner wheel are respectively the wheel speed V of the turning outer wheel.
_{By substituting WOUT} and V _WIN into the above equation (1), the following equation can be obtained. S _OUT = (VS0-V _WOUT ) × 100 / VS0 (2) S _IN = (VS0-V _WIN ) × 100 / VS0 (3) While the vehicle is turning, Due to the difference from the running locus of the turning outer wheel, a larger wheel speed is generated in the turning outer wheel than in the turning inner wheel. In addition, since the load of the vehicle shifts to the outer wheel side of the turn while the vehicle is turning, the wheel speed V _{WIN of the} inner wheel turns
Is easily decelerated compared to the wheel speed V _{WOUT of the} outer turning wheel. Therefore, at the time of turning braking, after the braking operation is started, the slip ratio S _IN of the turning inner wheel reaches S ₀ prior to the slip ratio S _OUT of the turning outer wheel. Therefore, at the time of turning braking of the vehicle, the turning outer wheel is preceded by the AB turning wheel side.
Execution of S control is started.

If the braking operation is continued after S _IN reaches S ₀ , S _0UT may reach S ₀ .
In the above process, S _IN is the estimated vehicle speed VS0 of when it reaches the S ₀ VS0 _IN, the estimated vehicle speed VS0 at the time the S _0ut has reached S ₀ is assumed to be VS0 _OUT, VS0 _IN> VS0 _OUT is established. Therefore, ABS
When the control execution condition is satisfied, that is, S _IN = S
₀ or S _OUT = S _0, the slip amount ΔVSN _IN = (VS0-V _WIN );
_{When OUT} = (VS0- _VWOUT ) is compared, ΔVSN _IN >
ΔVSN _OUT is established. In the present embodiment, in consideration of the above characteristics, the slip amounts ΔVSN of the left and right wheels are compared at the time when the ABS control is started, and if there is a difference exceeding the predetermined value, the vehicle is turning. It is decided to determine that there is.

FIG. 5 is a flowchart of an example of a subroutine executed by the ECU 30 to determine whether the vehicle is turning in the system of this embodiment. The routine shown in FIG. 5 is a periodic interruption routine that is started every predetermined time. When the routine shown in FIG. 5 is started,
First, at step 300, it is judged if the variation | ΔV _WFL | of the wheel speed V _WFL of the left front wheel exceeds a predetermined value. Immediately after the ABS control is started for the left front wheel FL, that is, the slip ratio S of the left front wheel FL is the upper limit value S _0.
The vehicle speed was gradually reduced immediately after the vehicle reached V _WFL
Is decelerated rapidly. Therefore, when | ΔV _WFL |> α is satisfied, it is determined that the ABS control start condition is satisfied for the left front wheel.

If it is determined in step 300 that | ΔV _WFL |> α holds, then in step 302,
The slip amount ΔVSN _{FL of the} left front wheel is calculated. The slip amount ΔVSN _FL is calculated by subtracting the wheel speed V _WFL of the left front wheel from the estimated vehicle speed VS0 calculated by a known method in another routine. On the other hand, if the above conditions are not satisfied, the process of step 302 is jumped, and then the process of step 304 is executed.

In step 304, the wheel speed V of the right front wheel
It is determined whether or not the amount of change in _WFR | ΔV _WFR | exceeds a predetermined value. If | ΔV _WFR |> α is satisfied, it is determined that the ABS control start condition is satisfied for the right front wheel. If such a determination is made, then step 30 is performed.
At 6, the slip amount ΔVSN _FR of the right front wheel is calculated. The slip amount ΔVSN _FR is calculated by subtracting the wheel speed V _WFR of the right front wheel from the estimated vehicle speed VS0. On the other hand, if the above conditions are not satisfied, step 306
Processing is jumped, and then the processing of step 308 is executed.

At step 308, it is judged if the difference between the slip amounts of the left and right front wheels | ΔVSN _FL −ΔVSN _FR | exceeds a predetermined value β. As a result, | ΔVSN _FL −Δ
If VSN _FR |> β is satisfied, then step 310 is performed.
After the turning flag is set to "1", the routine of this time is ended. On the other hand, | ΔVSN _FL −ΔVSN _FR |
If> β is not satisfied, the turning flag is subsequently set to "0" in step 312, and then this routine is ended. In the routine shown in FIG. 2, in step 104, it is determined whether or not the vehicle is turning based on the state of the turning flag in which "1" or "0" is set as described above.

Next, the processing when it is determined in step 104 shown in FIG. 2 that the vehicle is not turning is described. In the system of the present embodiment, if the above determination is made, then in step 108, it is determined whether or not the road on which the vehicle is traveling is a cross road.
As a result, when it is determined that the traveling road is not a straddling road, the routine of this time is ended after the processing of step 106 is executed next. On the other hand, when it is determined that the road is a straddle road, the routine for this time is ended after the process for discharging sand from the injection nozzle 10L or 10R disposed on the low μ road side is executed in step 110. It

A method for determining whether or not the road on which the vehicle is traveling is a crossing road will be described below with reference to FIGS. 6 to 9. FIG. 6 shows the left and right rear wheels RL and RR when the ABS control execution conditions are satisfied.
The flowchart of an example of the control routine which ECU30 performs in order to determine the mode which should be set with respect to each of L and RR is shown.

The routine shown in FIG. 6 is executed for each of the left and right rear wheels RL and RR at predetermined time intervals. When the routine shown in FIG. 6 is started, first, at step 400, it is judged if the condition of the pressure reduction mode is satisfied for the wheel to be controlled. If the condition of the pressure reduction mode is satisfied, in step 402,
After the setting mode for the wheels to be controlled is set to the pressure reducing mode, this routine is ended.

In step 400, if the pressure reducing mode condition is not satisfied for the wheels to be controlled,
At step 404, it is judged if the condition of the holding mode is satisfied. If the condition of the holding mode is satisfied, the setting mode of the wheel to be controlled is set to the holding mode in step 406, and then the routine of this time is ended.

If it is determined in step 404 that the condition of the holding mode is not satisfied, then in step 408, the setting mode for the wheel to be controlled is set to the pressure increasing mode, and then this routine is executed. Will be terminated. By executing the above routine for each of the left and right rear wheels RL, RR, the setting modes of the left and right rear wheels RL, RR are set independently of each other during the execution of the ABS control.

FIG. 7 shows a flowchart of an example of a control routine executed by the ECU 30 to control the hydraulic circuits communicating with the wheel cylinders of the left and right rear wheels RL and RR based on the mode set as described above. The routine shown in FIG. 7 is executed at predetermined time intervals with both the left and right rear wheels RL and RR as control target wheels.

When the routine shown in FIG. 7 is started, first, at step 500, it is judged if the ABS control is being executed. If ABS control is not being executed,
Since there is no real benefit of advancing the subsequent processing, this processing is ended as it is. On the other hand, if the ABS control is being executed, the process of step 502 is executed.

In step 502, the left and right rear wheels RL, RR
It is determined whether or not any of the above is set to the pressure reduction mode. As a result, if the setting mode of any of the wheels is the pressure reducing mode, in step 504, the left and right rear wheels R
After both the hydraulic circuits corresponding to L and RR are pressure-reduced,
This routine ends.

In the above step 502, the left and right rear wheels R
If it is determined that neither L nor RR is in the pressure reduction mode, then in step 506, the left and right rear wheels RL and RR are determined.
It is determined whether any of the above is set to the holding mode. As a result, if the setting mode of any of the wheels is the holding mode, in step 508, the left and right rear wheels R
After the hydraulic circuits corresponding to L and RR are both held and controlled,
This routine ends.

In step 506, the left and right rear wheels R
If it is determined that neither L nor RR is in the holding mode, that is, if the setting modes of the left and right rear wheels L and RR are both pressure increasing modes, then in step 510, the left and right rear wheels RL and RR are set. After the fluid pressure circuits corresponding to are both pressure-increased, the routine of this time is ended. According to the above-described processing, the control in which the wheel cylinder pressures of the left and right rear wheels RL, RR are unified to the low pressure side, that is, so-called low select control is realized.

FIG. 8 shows a flowchart of an example of a control routine executed by the ECU 30 so as to determine the time period during which the pressure reduction control is executed for the left and right rear wheels RL and RR during execution of the ABS control. The routine shown in FIG. 8 is executed for each of the left and right rear wheels RL and RR at predetermined time intervals.

When the routine shown in FIG. 8 is started, first, at step 600, it is judged if the ABS control is being executed. If it is determined that the ABS control is not being executed, the counter C is determined in step 602.
After t and Cr are both reset to "0", the routine of this time is ended. The counter Ct is set to A as described later.
It is a counter for counting the execution time of the BS control.
The counter Cr is a counter for counting the time when the pressure reduction mode is set for the wheel to be controlled as described later.

If it is determined in step 600 that the ABS control is being executed, then step 60 is performed.
4 is executed. At step 604, it is judged if the ABS control is being executed for the rear wheels. When it is determined that the rear wheels are not the target of the ABS control, the routine of this time is ended without any further processing. On the other hand, if it is determined that the rear wheels are the target of the ABS control, then the process of step 606 is executed.

At step 606, it is judged if the setting mode for the wheel to be controlled is the pressure reducing mode. As a result, when it is determined that the setting mode is the pressure reducing mode, the counter Cr is incremented in step 608. On the other hand, if it is determined that the setting mode is not the pressure reducing mode, step 608 is jumped, the counter Ct is incremented in step 610, and then the routine of this time is ended. By performing the above-described processing for each of the left and right rear wheels RL, RR, it is possible to individually obtain the cumulative value of the time in which the pressure reduction mode is set for the left and right rear wheels RL, RR.

FIG. 9 shows a flowchart of an example of a control routine executed by the ECU 30 to determine whether or not the road on which the vehicle is traveling is a crossing road based on the counters Ct and Cr described above. The routine shown in FIG. 9 is a periodic interruption routine that is started every predetermined time.

When the routine shown in FIG. 9 is started, first, at step 700, from a time point before the predetermined time T ₂ ,
The coefficient values that have been coefficientd by the counters Ct and Cr are read until the present time. Next, at step 702, it is judged if the coefficient value of the counter Ct, that is, the cumulative value of the ABS control execution time exceeds the predetermined time T ₁ . Ct
When> T ₁ is not established, it is determined that the amount of information necessary for accurately executing the crossing road determination is insufficient, and this routine is terminated without any further processing. .

In step 702, Ct> T ₁
If it is determined that the condition is satisfied, then in step 704, the value of the counter Cr for the right rear wheel RR (hereinafter, referred to as Cr (RR)), that is, the time when the pressure reducing mode is set for the right rear wheel RR. The cumulative value of is the left rear wheel R
A value obtained by multiplying the value of the counter Cr for L (hereinafter referred to as Cr (RL)) by a predetermined value K, that is, a cumulative value of the time when the pressure reduction mode is set for the right rear wheel RL and the predetermined value K.
It is determined whether or not it is larger than the multiplication value with (K> 1).

If the traveling road is a road showing a uniform friction coefficient, that is, a uniform road, the time for which the pressure reduction mode is set for the left rear wheel RL and the time for which the pressure reduction mode is set for the right rear wheel RR. There is no significant difference between and. Therefore, when the condition of step 704 is satisfied (when the pressure reducing mode is set so as to be significantly biased to the right rear wheel RR side), the road surface on which the right rear wheel RR is in contact is the left rear wheel RL. It can be determined that the μ is lower than that of the running road surface. Therefore, if the condition of step 704 is satisfied,
Next, at step 706, the current road is memorized as a straddling road in which the friction coefficient on the right rear wheel RR side is lower than the friction coefficient on the left rear wheel RL side, and then this routine is ended. It

On the other hand, in step 704, Cr (R
If it is determined that R)> K · Cr (RL) is not established, then in step 708, Cr (RL)> K.
-It is determined whether or not Cr (RR) is established. When the above conditions are satisfied (when the pressure reduction mode is set so as to be significantly deviated to the left rear wheel RL side), the road surface with which the left rear wheel RL is in contact is the road surface with which the right rear wheel RR is in contact. It can be judged that it is low μ compared to. Therefore, the above step 70
If the condition of No. 8 is satisfied, then in step 710, the traveling road of the vehicle is stored as a straddling road in which the friction coefficient on the right rear wheel RR side is lower than the friction coefficient on the left rear wheel RL side. After this, this routine ends.

In step 110 shown in FIG. 2, it is judged whether or not the traveling road of the vehicle is a straddle road based on the information on the road condition stored as described above, and the traveling road is a straddle road. In this case, it is determined which of the left and right sides is the low μ side. Thereafter, as described above, the sand, which is the friction material, is discharged only to the low μ side, and a state where both the left and right wheels can exert a high braking force is formed in the straddling road.

FIG. 10 is a diagram for explaining the effect obtained by discharging sand only on the low μ side in the straddling road. In FIG. 10 (A), when sand is not discharged to the low μ side of the straddle, front, rear, left and right FL, FR, RL,
The braking force generated by the RR wheels is displayed as a vector. Further, in FIG. 10B, the braking force generated by the front, rear, left and right FL, FR, RL, and RR wheels when the sand is discharged to the low μ side of the straddle road is displayed as a vector.

As shown in FIGS. 10 (A) and 10 (B), when the braking operation is performed on the straddle road, the left and right front wheels FL,
A relatively large deviation occurs in the braking force of FR. The braking force of the left and right rear wheels RL and RR is controlled substantially uniformly by the above-described low select control. The deviation that occurs in the braking force of the left and right front wheels FL, FR generates a moment that tends to rotate the vehicle around the center of gravity. Therefore, in order to stabilize the vehicle behavior, it is desirable that the braking force difference between the left and right front wheels FL, FR is small. As shown in FIGS. 10A and 10B, when sand is discharged to the low μ road side, the left and right front wheels FL, FR
The braking force difference is reduced. Therefore, according to the system of the present embodiment, it is possible to stabilize the behavior of the vehicle on the straddle road.

Next, a second method for determining whether or not the traveling road is a low μ road will be described. As mentioned above,
In the system of this embodiment, the ECU 30 determines whether or not the traveling road is a low μ road by executing the routine shown in FIG. In the routine shown in FIG. 3, the acceleration sensor 32 detects the deceleration acceleration G, and A
The deceleration G detected during execution of the BS control is a predetermined value G
When it is smaller than a, it is determined that the traveling road is a low μ road.

The deceleration acceleration G of the vehicle is the rate of change of the vehicle body speed. Therefore, the deceleration G can be measured not only by the acceleration sensor 32 but also as a rate of change of the actually measured vehicle speed V measured by using the ground vehicle speed sensor or the like or the above-mentioned estimated vehicle speed VS0. Therefore, whether or not the traveling road is the low μ road is determined by dividing the measured vehicle body speed V or the estimated vehicle body speed VS0 by the predetermined time ΔT and V / ΔT or VS0 / ΔT smaller than the predetermined value Gb. You may judge based on whether or not.

Next, a third method for determining whether or not the traveling road is a low μ road will be described. FIG. 11 shows a flowchart of an example of a control routine executed by the ECU 30 to realize the third method. In FIG. 11, the same steps as those shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. In the routine shown in FIG. 11, when it is determined in step 200 that the ABS control is being executed, next step 21
At 0, it is determined whether or not the pressure reduction time continuously executed for the control target wheel exceeds the predetermined time Tr.

As a result of the above determination, when it is determined that the depressurization time does not exceed Tr, the routine of this time is ended without proceeding any further processing. On the other hand, if it is determined that the depressurization time exceeds Tr, then the process of step 212 is executed. At step 212, it is judged if the variation amount ΔVw of the wheel speed Vw of the control target wheel is smaller than a predetermined value Gc.

When the pressure reduction control is continuously executed for a predetermined time Tr or longer, the wheel cylinder pressure of the wheel to be controlled is greatly reduced. Therefore, if the traveling road of the vehicle is a high μ road, a relatively large acceleration occurs in the wheel speed Vw of the controlled wheel. On the other hand, if the traveling road of the vehicle is a low μ road, a large acceleration does not occur in the wheel speed Vw of the controlled wheel.

Therefore, in step 212, ΔVw <
When it is determined that Gc is established, it can be determined that the traveling road is a low μ road. If such a determination is made, thereafter, at step 206, the low μ road flag is set to "1" and then this routine is ended. When it is determined in step 212 that ΔVw <Gc is not satisfied, it can be determined that the traveling road is a high μ road. If such a determination is made, step 20 is performed thereafter.
After the low μ road flag is set to "0" at 8, the routine of this time is ended. According to the above processing, it is possible to accurately determine whether or not the traveling road is a low μ road, as in the case of executing the routine shown in FIG.

In the above embodiment, the sand is added to the friction material according to the first aspect of the invention by the injection nozzles 10L, 10R; the discharge control valves 12L, 12R; the pressure pipes 14L, 14R;
Friction material tanks 16L, 16R; solenoid valves 20L, 20
R; the air tank 22; and the compressor 24 correspond to the friction material discharging means according to claim 1 respectively. Further, in the above embodiment, the ECU 30 executes the process of step 102 (subroutine shown in FIG. 3 or FIG. 11) so that the road surface state detecting means according to claim 1 executes the process of step 103. As a result, the release control means according to claim 1 is realized.

Further, in the above embodiment, the ECU 3
0 executes the processing of the step 108 (subroutine shown in FIGS. 6 to 9), and the left and right road surface state detecting means according to claim 2 executes the processing of the step 110. Independent control means executes the processing of step 104 (subroutine shown in FIG. 5), whereby the turning state detecting means of claim 3 performs the processing of step 106 or 108 based on the determination result of step 104. By executing the above, the friction material discharging means according to claim 3 is realized.

Next, a second embodiment of the present invention will be described. The system of this embodiment is realized by adding a throttle sensor to the system configuration shown in FIG. 1 and causing the ECU 30 to execute the control routine shown in FIG. The present embodiment is a system for a front-wheel drive vehicle, and the left and right front wheels FL and FR, on which the injection nozzles 10L and 10R are arranged, are the drive wheels of the vehicle.

FIG. 12 shows that the ECU 30 executes the known traction control control (hereinafter referred to as TRC control) while the release control valves 12L and 12R and the electromagnetic opening / closing valve 2 are operated.
The flowchart of an example of the control routine performed in order to drive 0L and 20R is shown. When the routine shown in FIG. 12 is started, first, at step 800, it is judged if the TRC control is being executed. The TRC control is executed when it is detected that the vehicle is accelerating based on the output signal of the throttle sensor and the slip ratio S that exceeds a predetermined value is generated in any of the wheels. The slip ratio S is calculated by the following equation using the estimated vehicle body speed VS0 and the wheel speed Vw. The estimated vehicle speed VS0 during acceleration is calculated based on the wheel speed Vw of the driven wheels.

S = (VS0-Vw) × 100 / Vw (4) If it is determined in step 800 that the TRC control is not in progress, all the wheels maintain the proper grip state. It is determined that it is not necessary to discharge the sand, which is the friction material, to the road surface, and thereafter, the discharge of the sand is stopped in step 806, and then the routine shown in FIG. 12 is ended. on the other hand,
When it is determined in step 800 that the TRC control is being performed, it is determined in step 802 whether the traveling road is a low μ road.

FIG. 13 shows a flowchart of an example of a subroutine executed by the ECU 30 to determine whether or not the road surface on which the vehicle is traveling is a low μ road in this embodiment. still,
The routine shown in FIG. 13 is a scheduled interrupt routine that is executed every predetermined time. When the routine shown in FIG. 13 is started, first, at step 900, it is judged if TRC control is in progress. If TRC control is not in progress,
This routine is ended without any processing. On the other hand, when it is determined that the TRC control is in progress,
In step 902, the output signal of the acceleration sensor 32,
That is, the longitudinal acceleration G acting on the vehicle is read.

When the reading of the acceleration G is completed, next, at step 904, it is judged if the acceleration G is smaller than a predetermined judgment value Gd. The TRC control is executed when the slip ratio of any wheel exceeds a predetermined value during acceleration as described above. In such a situation, the acceleration acts on the vehicle according to the friction coefficient μ between the road surface and the wheels. Therefore, when the traveling road is a high μ road, a large acceleration is detected during the TRC control. Further, when the traveling road is a low μ road, a small acceleration is detected during the TRC control.

Therefore, in step 904, G
If it is determined that <Gd holds, it can be determined that the vehicle is traveling on a low μ road. In this case, thereafter, in step 906, the low μ road flag is set to "1", and then this routine is ended. On the other hand, if it is determined in step 904 that G <Gd is not established, it can be determined that the vehicle is traveling on a high μ road. In this case, after that, in step 208, the low μ road flag is set to "0", and then this routine is ended. In the present embodiment, the discriminant value Gd
Is G <when the road being driven is a low μ road such as an icy road.
It is set to a value that satisfies the condition of Gd.

At step 802 in the routine shown in FIG. 12, it is determined whether or not the traveling road is a low μ road, based on the state of the low μ road flag described above. As a result, when it is determined that the vehicle is running on a low μ road, step 80
After the processing for discharging sand is executed in 4, the routine of this time is ended. On the other hand, if it is determined that the traveling road is not the low μ road, the routine for this time is ended after the processing for stopping the release of the sand is executed in step 806.

As described above, according to the system of this embodiment, when the vehicle is traveling on a low μ road such as an icy road, the T
With the execution of RC control, sand can be discharged in front of the drive wheels. The release of sand in front of the drive wheels improves the coefficient of friction between the road surface and the drive wheels. Therefore, according to the system of the present embodiment, a higher driving force can be obtained on a road having a low coefficient of friction such as a frozen road, as compared with the case where sand is not discharged.

By the way, in the second embodiment described above,
Although the sand release control on the straddle road and the sand release prohibition control during turning braking are not executed, the present invention is not limited to this, and is the same as in the case of the first embodiment described above. Alternatively, these controls may be executed. Further, in the above-described second embodiment, it is determined whether or not the traveling road is a low μ road based on the output signal of the acceleration sensor 32, but the present invention is not limited to this. Alternatively, it may be determined whether or not the traveling road is a low μ road based on the acceleration G calculated from the change rate of the actually measured vehicle speed V or the estimated vehicle speed VS0.

In the above embodiment, the ECU 30
By executing the process of step 802 (subroutine shown in FIG. 13) by the road surface state detecting means of claim 1, and by executing the process of step 804, the release control means of claim 1 respectively. Will be realized.

[0074]

As described above, according to the first aspect of the present invention, the friction material can be discharged to the front of the wheel only when the vehicle is traveling on the low friction coefficient road. Therefore,
According to the road surface friction coefficient improving device of the present invention, it is possible to avoid the inconvenience of lowering the friction coefficient between the road surface and the wheels due to the release of the friction material on the high friction coefficient road.

According to the second aspect of the present invention, when the vehicle is traveling on a straddle road, the friction material is discharged to the side having a low friction coefficient and the friction material is not discharged to the side having a high friction coefficient. be able to. Therefore, according to the road surface friction coefficient improving device of the present invention, stable vehicle behavior can be obtained on a straddling road.

According to the third aspect of the invention, the release of the friction material can be controlled according to the turning state of the vehicle. Therefore, according to the road surface friction coefficient improving device of the present invention,
It is possible to prevent the turning behavior of the vehicle from becoming unstable due to the friction material being released during the turning of the vehicle.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a first embodiment of the present invention.

2 is a flowchart of an example of a control routine executed in the electronic control unit shown in FIG.

3 is a flowchart of an example of a low μ road determination routine executed in the electronic control unit shown in FIG.

FIG. 4 is a characteristic diagram showing a relationship between a wheel slip ratio and a friction coefficient.

5 is a flowchart of an example of a during-turning determination routine executed in the electronic control unit shown in FIG.

6 is a flowchart of an example of a mode setting routine executed in the electronic control unit shown in FIG.

7 is a flowchart of an example of a control content determination routine executed in the electronic control unit shown in FIG.

8 is a flowchart of an example of a straddle road determination routine (No. 1) executed in the electronic control unit shown in FIG.

9 is a flowchart of an example of a straddle road determination routine (No. 2) executed in the electronic control unit shown in FIG.

FIG. 10A is a diagram showing a braking force distribution generated when slip prevention control is not executed. FIG.
FIG. 6B is a diagram showing a braking force distribution generated when the slip prevention control is executed.

11 is a flowchart of another example of the straddling low μ road determination routine executed in the electronic control unit shown in FIG.

FIG. 12 is a flowchart of an example of a control routine executed in the second embodiment of the present invention.

FIG. 13 is a low μ implemented in the second embodiment of the present invention.
It is a flowchart of an example of a road determination routine.

[Explanation of symbols]

10L, 10R Injection nozzle 12L, 12R Release control valve 14L, 14R Pressure pipe 16L, 16R Friction material tank 18L, 18R Residual sand sensor 20L, 20R Electromagnetic on-off valve 22 Air tank 24 Compressor 30 Electronic control unit (ECU) 32 Acceleration sensor 36 Brake switch 38FL, 38FR, 38RL, 38RR Wheel speed sensor 40 Indicator light

Claims (3)

[Claims] 1. A friction coefficient improving device for a road surface, comprising friction material discharging means for discharging a friction material in front of a wheel, and discharging the friction material from the friction material discharging means when the slip amount of the wheel exceeds a predetermined value. A road surface friction coefficient improving device, comprising: a road surface condition detecting means for detecting a road surface condition; and a discharge control means for permitting discharge of a friction material when the road surface has a predetermined low friction coefficient road. . 2. The road surface friction coefficient improving device according to claim 1, wherein at least one of the friction material discharging means is disposed in front of each of the left and right wheels, and the road surface state detecting means includes each of the left and right wheels. The friction material is provided in front of each of the left and right wheels according to the state of the road surface with which the left and right wheels are in contact, the left and right road surface state detecting means for detecting the state of the road surface with which the left and right wheels are in contact. An apparatus for improving a friction coefficient of a road surface, comprising independent control means for independently controlling the discharging means. 3. The road surface friction coefficient improving device according to claim 1, further comprising a turning state detecting means for detecting a turning state of the vehicle, wherein the friction material releasing means is provided in accordance with a turning state of the vehicle. An apparatus for improving a friction coefficient of a road surface, characterized by controlling a friction material discharging means.