JP2001097194A - Brake intensity judging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure brake intensity whether a brake pedal stepped on by a driver is strongly stepped on or gently stepped on by a simple method. SOLUTION: A wheel deceleration detecting means detecting the deceleration of wheels is provided and as the deceleration of the wheels is less, the brake pedal is judged to be stepped on more gently. A means measuring a time from starting the stepping-on of the brake pedal to generating the lock inclination of the wheels is provided and as the measuring time is longer, the brake pedal is judged to be stepped on more gently. Whether the brake pedal is strongly stepped on or gently stepped on can be judged by the extent of a master cylinder pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the degree of depression of a brake pedal by a driver, for example, used in an anti-skid control device.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Publication No. 51-6308, an anti-skid control device for controlling a brake hydraulic pressure by controlling a duty ratio of a control valve has been proposed. In this device, during control, the duty ratio is changed according to the slip ratio of the wheels, and the brake oil pressure is controlled so that the wheels do not lock.

[0003]

As described above, it is necessary to change the drive duty ratio of the control valve in accordance with the slip ratio of the wheel, and immediately after the start of the anti-skid control, to obtain the optimum wheel cylinder brake oil pressure. . However,
The adjustment of the duty ratio is preferably varied by the driver's depression of the brake pedal.In particular, when the duty ratio at the start of the anti-skid control is varied by the driver's depression of the brake pedal, the anti-skid control starts. Immediately afterwards, good anti-skid control becomes possible.

Accordingly, an object of the present invention is to make it possible to measure the braking strength by a simple method.

[0005]

According to the present invention, there is provided a brake strength determining method according to the present invention.
And a wheel deceleration detecting means for detecting the deceleration of the wheel, and it is determined that the brake pedal is depressed more slowly as the deceleration of the wheel is smaller.

[0006] That is, when the brake is depressed strongly, the wheel deceleration drops significantly, and when the brake pedal is depressed gently, the wheel deceleration does not drop much. The present application is characterized in that such a phenomenon can be simply used for determining the brake strength.

[0007] According to a second aspect of the present invention, there is provided a measuring means for measuring a time from when the brake pedal is depressed until the wheel tends to lock, and the longer the time measured by the measuring means, the more the brake pedal. May be determined to be depressed loosely.

In this case, when the brake is depressed strongly, the locking limit of the wheels is reached, and the tendency to lock appears quickly,
On the other hand, if you step on the pedal slowly,
Over time, a tendency to rock appears. Using such a phenomenon, it is also possible to easily determine the brake strength.

According to a third aspect of the present invention, it is determined that the brake pedal is depressed more slowly as the deceleration of the wheel is smaller and the time from when the brake is depressed until the tendency to lock the wheel is longer. You may.

In this case, for example, on a low μ road, extremely accurate braking strength can be determined. That is, when the brake is strongly depressed on a low μ road, the wheel deceleration rapidly decreases and the vehicle tends to lock. Therefore, other than this state, it can be simply determined that the brake pedal is depressed loosely.

Also, it is possible to determine whether the brake pedal is depressed strongly or slowly based on the master cylinder pressure itself.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described. In FIG. 1, which shows a hydraulic brake system with two X pipes for a wheel-driven vehicle, 1 is a master cylinder, and 2 is a brake pedal. Each wheel (front right wheel 11, front left wheel 2
1, the right rear wheel 31 and the left rear wheel 41) have brake wheel cylinders 12, 22, 32, 42, respectively.
Further, wheel speed sensors 13 and 2 for detecting the speed of each wheel.
3, 33 and 43 are installed. Further, a brake switch 53 for detecting depression of the brake pedal 2 is provided.

The master cylinder 1 is a tandem type for the first and second hydraulic systems. In the first hydraulic system, a brake hydraulic pressure is applied to the wheel cylinder 12 of the right front wheel 11 via a two-position valve 15. The brake hydraulic pressure is applied to the wheel cylinder 42 of the left rear wheel 41 via a proportioning valve (referred to as a P valve) 44 and a two-position valve 45.
In the second hydraulic system, hydraulic pressure is similarly applied to the wheel cylinder 22 of the left front wheel 21 via the two-position valve 25, and hydraulic pressure is applied to the wheel cylinder 32 of the right rear wheel 31 via the P-valve 34 and the two-position valve 35. Add. Each two-position valve 15, 25,
Numerals 35 and 45 denote electromagnetic three-port two-position valves,
The ports are connected to the master cylinder side hydraulic piping, and each B port is connected to the wheel cylinder side. The C ports of the two-position valves 15 and 45 are connected to the suction side of the pump 51 via check valves 16 and 46, respectively.
The C ports 5 and 35 are connected to the suction side of the pump 52 via check valves 26 and 36, respectively.

The pumps 51 and 52 are structurally integrated, are commonly driven by one electric motor, and have their discharge sides connected to the A-port side piping of the two-position valves 15 and 25. , Is controlled by an electronic control unit (ECU) 60.

The ECU 60 controls each of the wheel speed sensors 13 and 2
Output signals from 3, 33, and 43 are input, and wheel speed, wheel acceleration, and the like are calculated based on these signals, and the two-position valves 15, 25, 35, and 4 are calculated based on the calculated values and the like.
5 is duty-controlled, and the driving of the pumps 51 and 52 is commanded.

The ECU 60 is connected to the brake switch 5
3 is input, and the strength of the brake is determined using this signal.

The ECU 60 is of a microcomputer type, and includes a CPU, a ROM for storing control programs and data, a RAM for temporarily storing operation data, and an I / O unit connected to each sensor, valve, and pump. And so on.

FIG. 2 shows an extracted structure of one wheel in FIG. 1, and FIG. 3 shows a drive signal waveform and a brake pressure waveform. The operation will be described with reference to FIGS. (I) During Normal Braking The two-position valve 15 is in the position shown in FIG. 2A in a non-energized state, and the pump 51 is also in a non-driven state. For this reason, the brake pressure of the master cylinder 1 generated when the brake pedal 2 is depressed acts directly on the wheel cylinder 12 via the two-position valve 15, and a braking force is generated on the right front wheel 11. (Ii) At the time of anti-lock control When the locking tendency of the right front wheel 11 is increased by the braking operation during traveling, the anti-lock control is started. When the antilock control is started, the ECU 60 outputs an ON command signal to drive the pump 51 as shown in FIG. As a result, the pump 51 is always driven continuously during the antilock control. 3 (B), (C)
ECU60 as shown in the two position valve 15 by duty control to adjust the brake pressure P _w of the wheel cylinder 12.

Here, when the two-position valve 15 is not energized (first
Position) between the A-B port as shown in FIG. 2 (A) is communicated, as a result, the brake hydraulic pressure P _W of the wheel cylinder 12 by the master cylinder side of the brake hydraulic pressure is boosted.

On the other hand, when energized (second position), the two-position valve 15 communicates between the B and C ports as shown in FIG. 2B. As a result, the pump 51 drives the brake in the wheel cylinder 12. The hydraulic pressure P _W is reduced.

The period T in FIG. 3 is constant (for example, 20 to
50 msec), and the decompression time T_R(2
Average by changing the ON time of the position valve 15)
Slow pressure increase and slow pressure reduction are performed by controlling the change of the hydraulic pressure. Since then,
Decompression time T for the cycle T of _RRatio (T_R/ T) × 100
(%) Is called a duty ratio D.

In the duty control of the two-position valve 15, the tendency to decrease the pressure increases as the duty ratio D increases, and the tendency to increase the pressure increases as the duty ratio D decreases.

An example of the anti-skid control process executed by the ECU 60 is shown in a flowchart of FIG. 4 and will be described in detail below with reference to this flowchart.

In step 100, each wheel speed sensor 1
The respective wheel speeds (front right wheel speed V _FR , front left wheel speed V _FL , rear right wheel speed V _RR , rear left wheel speed V _RL ) are calculated based on the wheel speed signals detected by 3, 23, 33, 43. Is done. In step 101, the accelerations G _FR , G _FL , G _RR , G _{RL of} each wheel are calculated from the changes in the wheel speeds V _FR , V _FL , V _RR , V _RL calculated in step 100. Step 102 the estimated vehicle body speed V _B, is estimated vehicle acceleration G _B is calculated by the following equation.

[0025]

[Number 1] _{V B (n) = MED (} V B (n-1) -α 1 · t C, V Wmax, V B (n-1) + α 2 · t C) ...... (a)

[0026]

## EQU2 ## V _Wmax = MAX (V _FR , V _FL , V _RR , V _RL ) (b)

[0027]

[Equation 3] G_B= (V_{B (n)}-V_{B (n-1)}) / T_C(C) where MED is an operator for selecting an intermediate value, and MAX is
Means the operator that selects the maximum value. Equation (a)
V_{B (n)}Subscript of_(n)Is the value calculated this time,_{(n- 1)}Is the last
Indicates a calculated value. And α₁, Α_TwoIs the body
Upper limit of deceleration and upper limit of acceleration.
Body speed V_{B (n-1)}And the vehicle speed V calculated this time_{B (n)}Speed with
It limits the difference. Note that t_CPlays body speed
Cycle (for example, 4 to 10 msec).

[0028] At step 103, based on the estimated vehicle speed V _B computed at step 102, to create a reference speed V _S for determining the locking tendency of the wheel. That is, the estimated vehicle speed V _B is multiplied by K _O (K _O = 0.7 to 0.9).
5) Then, find the speed corresponding to the target slip ratio,
A value obtained by subtracting the offset speed V _O from the speed is set as a reference speed V _S.

[0029]

Equation 4] -V _O ...... (d) where _{V S = K O · V B} , to the estimated vehicle speed V _B catching K _O multiplied by the speed K _O · V offset velocity V _O from _B is estimated This is because even when the vehicle body speed V _B becomes small to have a large velocity difference than the offset speed V _O to the estimated vehicle body speed V _B and the reference speed V _S.

In step 104, steps 102, 1
03 estimated based on the vehicle acceleration G _B and the reference velocity V _S determined, the parameters representing the locking tendency of each wheel (hereinafter,
Wheel parameters) W _FR , W _FL , W _RR , and W _RL are calculated by the following equations.

[0031]

[Number 5] _{W ** = A · (V **} -V S) + B · (G ** -G B) ...... (e) here, the formula W _** and V _**, etc. of the (e) Symbol _** is FR, F
Represents any of L, RR, and RL.

Wheel parameter W calculated by equation (e)_**
Is W_**When> 0, there is no tendency to lock the wheel.
_**When ≤0, it means that there is a tendency to lock._**|
Represents the strength of the lock tendency. And anti-skidding
W_**If> 0, the wheel cylinder 12,
22, 32, 42 brake hydraulic pressure P_WIs increased and W_{* *}
If ≦ 0, it is held or reduced.

At step 105, it is determined whether or not the anti-skid control has already been started. If the control has been started, the routine proceeds to step 111, and if not, the routine proceeds to step 106.

At step 106, the locking tendency of each wheel is determined. That is, the wheel parameter W _{** of} each wheel obtained in step 104 and the control start level −K _W (K _W :
(Positive constant). As a result, if it is determined that any of even one level -K _W is smaller than the wheel parameter W _**, starts antiskid control proceeds to step 107. On the other hand, if it is determined in step 106 that all the wheel parameters W _FR , W _FL , W _RR , and W _RL are equal to or higher than the level −K _W, it is determined that none of the wheels has a locking tendency, and the process returns to step 100. .

In step 107, the pumps 51 and 52 are driven (ON state) to start anti-skid control.

In step 108, it is determined whether the driver is stepping on the brake pedal 2 strongly or slowly. During slow braking, the deceleration of the wheel speed is small, and there is a long time from when the brake is started to when the wheels tend to lock up. For example, if the following conditions are satisfied, it is determined that the braking is slow. .

Condition: G _** > K _S and T _ST > K _ST where G _** is the wheel acceleration when W _** <-K _W is satisfied in step 106, and K _S is a constant of -3 to The value is about -5G. T _ST is the time from when the brake switch 53 is turned on until the start of the anti-skid control, and K _ST is a constant value of about 0.1 to 0.5 seconds. The time T _ST is shown in FIG.
It is measured by the software timer method not shown in the figure.

If it is determined in step 108 that the braking is slow, the process proceeds to step 110. If it is determined that the braking is not slow (strong braking), the process proceeds to step 10.
Go to 9.

In steps 109 and 110, the duty ratio D for driving the two-position valves 15, 25, 35 and 45 of each wheel is set.
_** set the initial value D _{O **} of. Here, step 109
In D _{O **} = D _1, step _{110 D O ** = D 2 (} D 1
> D ₂ ). In step 111, it is determined whether or not all the wheel parameters W _FR , W _FL , W _RR , W _RL have been greater than 0 for more than Te seconds (for example, 0.5 to 2 seconds). If the result of this determination is affirmative, it is determined that the locking tendency of the wheels has been completely suppressed, and the routine proceeds to step 116. In step 116, the pumps 51 and 52 are brought into the non-driving state (OFF state), and the two positions 15, 25,
The energization to 35 and 45 is stopped (OFF state), the anti-skid control ends, and the process returns to step 100. On the other hand, if the determination result in step 111 is negative, the locking tendency of the wheels has not yet been completely suppressed.
The anti-skid control is executed for.

In steps 112 to 115, each car
Depending on the strength of the locking tendency of the wheels 11, 21, 31, 41
Duty to drive 2-position valves 15, 25, 35, 45
Ratio D _**Is the wheel parameter W as shown in the following equation (f).
_**And the initial value D_{O **}Is calculated from

[0041]

[6] _{D ** = D O ** -∫K D} · W ** dt ...... (f) where, K _D is a positive constant.

Then, the two-position valves 15, 25, 35, 4 of the respective wheels are determined by the duty ratio D _** calculated by the equation (f).
5 and drive returns to step 100.

According to the equation (f), the locking tendency of the wheels is large.
At the time (W_**<0) is the duty ratio D_**Is bigger
Pressure of the wheel cylinder_{W **}Is small
(Decompression), and when the locking tendency of the wheel is small (W_**
> 0) is the duty ratio D _**Is smaller because
Brake pressure P_{W **}Is larger (increased pressure
Is).

That is, during the anti-skid control, the duty ratio D _** changes according to the equation (f) according to the tendency of the wheels to lock, and the brake pressure P _{W **} of the wheel cylinder is controlled to a pressure adapted to the road surface. .

Incidentally, the relationship between the duty ratio D and the brake oil pressure _PW of the wheel cylinder changes according to the brake oil pressure of the master cylinder 1 (the driver's brake pedal pressing force) as shown in FIG. In the wheel cylinder 5, when the master cylinder pressure P _M is higher in value _{P A (P M = P A} ) the equilibrium pressure P _W of the duty ratio D and the wheel cylinder becomes a characteristic as shown by curve a, the master cylinder hydraulic pressure when P _M is lower in value _{P B (P M = P B} ) is a characteristic as shown by curve b.

[0046] For example, assuming the optimum value of the brake hydraulic pressure (equilibrium pressure) P W _** of the wheel cylinder at a road and P _O, when the master cylinder pressure P _M is higher (P _M = P _A) in FIG. 5 is duty ratio corresponding to the optimum value P _O is D _1.

[0047] In the present invention, at the time of the master cylinder pressure P _M is higher strengths brakes has the initial value D _{O **} duty ratio D to D _1, the wheel cylinder braking oil pressure P _{W **}
Quickly reaches the optimum value P _O after the start of the anti-skid control.

When the master cylinder oil pressure P _M is low (P _M = P _B ) on the same road surface, the duty ratio with respect to the optimum value P _O is D ₂ . In the present invention, the master cylinder pressure P _M
When the brake is low, the initial value D _{O **} of the duty ratio D
The has a D _2, in this case the brake hydraulic pressure P _W also wheel cylinder _** promptly become the optimum value P _O after anti-skid control is started.

As described above, the strong brake and the slow brake are determined, and the initial value D _{O **} of the duty ratio is changed. Therefore, regardless of how the driver depresses the brake pedal 2,
Immediately after the start of the anti-skid control, good anti-skid control becomes possible, the tendency of locking the wheels is suppressed, and the stability and maneuverability of the vehicle are improved.

In the first embodiment, the initial value of the duty ratio is switched between two values by judging the strong brake and the slow brake. However, the initial value is switched by three or more values by judging how to depress the brake in detail. You may do. Of course the initial value of the duty ratio as a function of time T _ST from the wheel acceleration G _W and the brake switch 530N during anti-skid control is started to control the start, it may be changed steplessly.

In the first embodiment, the same initial values D ₁ and D ₂ of the duty ratio are used for the front wheels and the rear wheels, but different values may be used for the front wheels and the rear wheels.

[0052] Also, the target brake pressure of the anti-skid control at the start of the wheel cylinders as a specific pressure P _O in the above example, to switch in the strong braking and slow braking the initial value of the duty ratio corresponding to a specific pressure P _O The value of the specific pressure P _O was changed according to the road surface condition.
The initial value of the duty ratio may be changed according to the road surface condition. This will be described as a second embodiment. Since the processing of the anti-skid control executed by the ECU 60 in the second embodiment is the same except for step 200 in FIG. 4, the processing performed in step 200 in the second embodiment will be described in detail with reference to the flowchart of FIG. Will be described. Step 200 is executed only when the anti-skid control is started. Estimated vehicle acceleration G calculated in step 201
_B is a reference value _KT (for example, _KT = -0.2G to -0.5G).
Compared to the case of G _B> K _T in Step 201 Step 2
Advances to 02, whereas when G _B ≦ K _T in step 201, the process proceeds to step 203.

In steps 202 and 203, it is determined whether the braking is gentle or strong in the same manner as in step 108 of FIG. 4. If it is determined in step 202 or 203 that the braking is gentle, the process proceeds to step 205 or step 207. At 205, the initial value of the duty ratio is set to D _{O **} =
D ₂ (<D ₁ ) or D _{O **} = D ₄ (<
The process proceeds to step 111 as D ₃ ). On the other hand, step 2
If it is determined in step 02 or step 203 that the braking is not gentle braking (strong braking), the process proceeds to step 204 or step 206 to set the initial value of the duty ratio to step 20.
4 proceeds to D _{O **} = D ₃ as step 111 in D _{O **} = D ₁ or step 205. Here, D ₁ , D ₂ , D ₃ , D ₄
Are set as D ₁ > D ₂ , D ₃ > D ₄ , D ₁ > D ₃ , and D ₂ > D ₄ . Step 201 is to determine the magnitude of the road surface friction coefficient by determining a magnitude of the estimated vehicle acceleration G _B. In other words, low μ
When the vehicle deceleration during braking is road is small, can determine the magnitude of the road surface friction coefficient μ depending on the size of the reverse on the road surface friction coefficient larger high μ road surface estimated vehicle acceleration G _B because large vehicle deceleration during control .

In the first embodiment, the initial value of the duty ratio is changed only depending on whether the brake is gentle or strong.
In the present embodiment, the initial value of the duty ratio is further changed according to the road surface friction coefficient μ, so that the initial value of the duty ratio can be set to a more appropriate value.

That is, on a road surface having a large road surface friction coefficient,
Wheel cylinder brake pressure P_{W * *}The optimal value of
Since the friction coefficient μ is larger than the optimum value on a road surface having a small friction coefficient μ, FIG.
Of the brake pressure on a road surface with a large coefficient of road friction
Appropriate value is P_H, Brake pressure on a road surface with a low coefficient of friction
The optimal value of_LThe road surface with a small road friction coefficient μ
Now, the initial value of the duty ratio D
_{O **}To D₁Or D_TwoRoad surface with a large friction coefficient μ
Then D_{O **}To D_ThreeOr D _FourNasu
This makes it possible to control the road surface conditions and how the driver applies the brakes.
Switch the initial value of the duty ratio to an appropriate value
Good anti-skid control immediately after the start
Chiskid control can be performed.

In the second embodiment, the road surface condition is discriminated into two according to the estimated vehicle acceleration. However, the road condition may be discriminated more finely than three. It is also possible in the manner infinitely varied the initial value of the duty ratio as a function of time T _ST and the estimated vehicle speed G _B as in the previous examples.

Further, the initial value of the duty ratio may be switched only by the estimated vehicle body acceleration without determining whether the braking is slow or strong.

[0058] In this embodiment, although judged road surface condition by the estimated vehicle acceleration, determines the road surface condition by the sagging amount of the wheel speed (difference between the estimated vehicle body speed V _B and the wheel speed V _**) You may do.

In the above embodiment, only the pressure increase and the pressure reduction are the second.
Regarding the method for calculating the initial value of the duty ratio for valve placement
But the pressure control valve is not a two-position valve,
For example, a system that continuously adjusts the pressure according to the drive current
If it is a control valve, calculate the drive current using the following formula.
In the same manner as in the above embodiment, the driving current I_**Initial value I of_{O *
*}Is changed according to how to depress the brake and road surface conditions
Just do it.

[0060]

Equation 7] where _{I ** = I O ** -∫K I} · W ** dt, K I is a positive constant.

In the above embodiment, the time _TST is used from the time when the brake switch 53 is turned on until the start of the anti-skid control to determine whether the brake is slow or strong.
Since 3 ON / OFF switch position of some variation, by detecting the time from the brake switch 53 on until the vehicle acceleration changes, it may be corrected a comparison value K _ST with T _ST.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of the device of the present invention.

2A is a configuration diagram showing one wheel of the device shown in FIG. 1, and FIG. 2B is a configuration diagram showing one wheel of the device shown in FIG.

FIG. 3 is a time chart for explaining the operation.

FIG. 4 is a flowchart for explaining the operation.

FIG. 5 is a characteristic diagram for explaining the operation.

FIG. 6 is a flowchart for explaining the operation of a second embodiment of the device of the present invention.

FIG. 7 is a characteristic diagram used to explain the operation of the second embodiment of the device of the present invention.

[Explanation of symbols]

2 ... brake pedal, 11, 21, 31, 41 ... wheels,
13, 23, 33, 43 ... wheel speed sensor, 15, 2
5, 35, 45 ... control valve, 53 ... brake switch, 6
0: Electronic control circuit.

Claims (5)

[Claims] 1. A method of determining whether a brake pedal operated by a driver is strongly depressed or loosely depressed, comprising: a wheel deceleration detecting means for detecting a wheel deceleration. A brake strength determining method for determining that the brake pedal is depressed more loosely as the deceleration of the wheel is smaller. 2. A method for judging whether the brake pedal operated by the driver is strongly depressed or depressed loosely, comprising: a lock tendency judging means for judging a locking tendency of a wheel; Measuring means for measuring the time from the start of pressing the brake pedal until the tendency to lock the wheels appears, and it is determined that the longer the time measured by the measuring means, the more the brake pedal is depressed. Brake strength judgment method. 3. A method for determining a braking strength of whether a brake pedal operated by a driver is depressed hard or depressed, comprising: wheel deceleration detecting means for detecting deceleration of a wheel; Measuring means for measuring the time from the start of depressing the brake pedal to the time when the tendency to lock appears on the wheel; and the smaller the deceleration of the wheel and the longer the time from the start of depressing the brake until the tendency to lock the wheel, the more the brake A brake strength determination method that determines that the pedal is depressed loosely. 4. A vehicle body acceleration detecting means for detecting a vehicle body acceleration of a vehicle, wherein a time from when the brake pedal is depressed until the vehicle body acceleration changes is detected. The method according to claim 2 or 3, wherein the time measured by the measuring means is corrected. 5. A method for judging whether the brake pedal depressed by a driver is strongly depressed or loosely depressed, wherein the master cylinder pressure is low when the master cylinder pressure is high. It is characterized in that it is determined that the brake is strong compared to the case.