JP2007237899A - Anti-lock brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-lock brake control device hard to extend a braking distance even when a wheel is in a locking tendency in a fading state. <P>SOLUTION: Correction S<SB>8</SB>, S<SB>9</SB>in a direction where hydraulic pressure increases is carried out against control of the hydraulic pressure of wheel cylinders 7RL, 7FR, 7FL, 7RR by an anti-lock control means S<SB>10</SB>in detecting the fading state by a fading state detection means S<SB>7</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an anti-lock brake control device that prevents a wheel from being locked by controlling a hydraulic pressure of a wheel cylinder when the wheel tends to be locked.

  When the wheel cylinder presses the friction member against the rotating member and brakes the wheel (disk brake, drum brake, etc.) overuses on a long downhill, the friction surface of the friction member becomes hot and gas flows from the friction surface. The generated gas may reduce the friction coefficient of the friction surface. If the wheel tends to lock in such a fade state, the pressure reduction amount of the wheel cylinder by the antilock control becomes excessive, and the braking distance may be extended. The cause is considered as follows.

  When the friction member is in a fade state, the friction coefficient of the friction surface decreases. Therefore, as shown in FIG. 5, the hydraulic pressure of the wheel cylinder when the wheel tends to lock is higher in the fade state than in the fade state (broken line in the figure). When the hydraulic pressure of the wheel cylinder is high, the pressure reduction speed when the wheel cylinder is decompressed increases, so that the amount of pressure reduction of the wheel cylinder by the antilock control is greater in the fade state than in the fade state. For this reason, if the wheel tends to lock while in the fade state, the pressure reduction amount of the wheel cylinder by the antilock control is likely to be excessive, and the braking distance is considered to increase.

  Moreover, since the wheel cylinder is difficult to increase when the hydraulic pressure of the wheel cylinder is high, the pressure increasing speed when the wheel cylinder is increased is as shown in FIG. 5 when the fade state is not the fade state. It becomes smaller than (broken line in the figure). For this reason, the amount of pressure increase of the wheel cylinder due to the antilock control is likely to be insufficient, and the braking distance is more likely to be extended.

  If the braking distance increases due to such a cause, a serious accident may occur in a fade state in which the braking distance tends to be particularly long.

  Therefore, an antilock brake control device that does not increase the braking distance even in the fade state is desired, but an antilock brake control device that supports the fade state has not yet been proposed.

  The problem to be solved by the present invention is to provide an anti-lock brake control device in which the braking distance is not easily extended even if the wheel tends to lock when in a fade state.

  In order to solve the above problems, the wheel cylinder presses the friction member against the rotating member that rotates integrally with the wheel and brakes the lock tendency detecting means for detecting the lock tendency of the wheel, and the lock tendency detecting means locks it. Anti-lock control means for controlling the hydraulic pressure of the wheel cylinder to prevent the wheel from being locked when a tendency is detected, fade state detection means for detecting a fade state of the friction member, and detection of the fade state And an anti-lock correction unit that corrects the hydraulic pressure in a direction to increase the hydraulic pressure control by the anti-lock control unit when the friction member detects a faded state. Adopted for anti-lock brake control device.

  When the anti-lock control unit controls the hydraulic pressure by controlling the pressure-reducing control valve and the pressure-increasing control valve, as the anti-lock correcting unit, with respect to the pressure reduction speed of the hydraulic pressure by the pressure-reducing control valve, A configuration in which the fluid pressure is corrected in the increasing direction can be employed. In this case, the correction in the direction of increasing the hydraulic pressure is correction for decreasing the pressure reduction rate of the hydraulic pressure. Further, when the anti-lock control means inputs a pulse voltage to control the pressure reducing control valve, the anti-lock control means adopts a configuration that performs the correction on the duty ratio of the pulse voltage. Can do.

  Similarly, when the anti-lock control means controls the hydraulic pressure by controlling the pressure-reducing control valve and the pressure-increasing control valve, the anti-lock correcting means is configured to increase the hydraulic pressure by the pressure-increasing control valve. A configuration in which the fluid pressure is corrected in the direction of increasing the hydraulic pressure can be employed. In this case, the correction in the direction to increase the hydraulic pressure is correction to increase the pressure increase rate of the hydraulic pressure. Furthermore, when the anti-lock control means controls the pressure increase control valve by inputting a pulse voltage, the anti-lock correction means adopts a configuration for performing the correction on the duty ratio of the pulse voltage. be able to.

  Further, in the case where the control of the hydraulic pressure by the antilock control means includes a control for ending the pressure reduction when a preset pressure reduction time has elapsed after starting the pressure reduction of the fluid pressure, the antilock correction means As the above, it is possible to adopt a configuration in which the pressure in the direction of increasing the hydraulic pressure is corrected with respect to the pressure reduction time. In this case, the correction in the direction of increasing the hydraulic pressure is correction for shortening the pressure reduction time.

  Further, when the control of the hydraulic pressure by the anti-lock control means includes a control to end the pressure reduction of the hydraulic pressure when the acceleration of the wheel becomes larger than a preset pressure reduction end threshold, As the anti-lock correction means, it is possible to adopt a configuration in which the hydraulic pressure is corrected in the direction of increasing the pressure reduction end threshold. In this case, the correction in the direction of increasing the hydraulic pressure is correction for increasing the depressurization end threshold value.

  Further, it is preferable that the fade state detection means detects the degree of fade, and the antilock correction means performs the correction with a magnitude corresponding to the degree of fade detected by the fade state detection means.

  In the antilock brake control device according to the present invention, when the fade state is detected by the fade state detection means, the antilock correction means increases the hydraulic pressure relative to the control of the hydraulic pressure of the wheel cylinder by the antilock control means. Make corrections. Therefore, even if the wheels tend to lock when in a fade state, the braking distance is difficult to increase.

  In the case where the anti-lock correction means corrects the pressure reduction speed of the hydraulic pressure by the pressure reduction control valve, when the fade state is detected by the fade state detection means, the pressure reduction speed of the wheel cylinder decreases. . Therefore, even if the wheel tends to lock when in a fade state, the amount of pressure reduction of the wheel cylinder by anti-lock control is unlikely to be excessive, and the braking distance is not easily extended.

  The anti-lock correction means corrects the hydraulic pressure increase speed by the pressure increase control valve. When the fade state is detected by the fade state detection means, the wheel cylinder pressure increase speed is detected. Becomes larger. For this reason, even if the wheel tends to lock when it is in a fade state, the amount of pressure increase of the wheel cylinder by the antilock control is ensured, and the braking distance is not easily extended.

  In the case where the anti-lock correction means corrects the pressure reduction time, when the fade state is detected by the fade state detection means, the pressure reduction time of the wheel cylinder is shortened. Therefore, even if the wheel tends to lock when in a fade state, the amount of pressure reduction of the wheel cylinder by anti-lock control is unlikely to be excessive, and the braking distance is not easily extended.

  Further, the anti-lock correction means that performs the correction with respect to the decompression end threshold value, when the fade state is detected by the fade state detection means, the decompression end threshold value increases, and the wheel cylinder The timing to end the decompression is advanced. Therefore, even if the wheel tends to lock when in a fade state, the amount of pressure reduction of the wheel cylinder by anti-lock control is unlikely to be excessive, and the braking distance is not easily extended.

  In addition, the anti-lock correction means that performs the correction with a magnitude corresponding to the degree of fading detected by the fade state detection means is more reliable even when the degree of fading is large. Can be suppressed.

  FIG. 1 shows a piping system diagram of a brake system that employs an antilock brake control device according to an embodiment of the present invention. This brake system has a master cylinder 2 that converts the depression force of the brake pedal 1 into hydraulic pressure, and a master reservoir 3 that stores brake fluid is attached to the master cylinder 2. The master reservoir 3 supplies brake fluid to the master cylinder 2 and collects excess brake fluid from the master cylinder 2.

  The master cylinder 2 has pressure chambers 2A and 2B inside. The pressure chamber 2A is connected to the wheel cylinder 7RL through the master cylinder side pipe line 4A, the pressure increase control valve 5RL, and the wheel cylinder side pipe line 6RL in this order, and the wheel cylinder side pipe line 6RL is connected to the pressure reduction control valve 8RL. To the decompression line 9A. The master cylinder side pipe line 4A is connected to the wheel cylinder 7FR via a pressure increase control valve 5FR and a wheel cylinder side pipe line 6FR, and the wheel cylinder side pipe line 6FR is depressurized via a pressure reduction control valve 8FR. It is connected to the conduit 9A. The pressure increase control valves 5RL and 5FR are normally open solenoid valves, and the pressure reduction control valves 8RL and 8FR are normally closed solenoid valves.

  The wheel cylinder 7RL is operated by the hydraulic pressure supplied from the wheel cylinder side pipe line 6RL, and presses the pad 11RL against the disc 10RL rotating integrally with the left rear wheel to apply a braking force to the left rear wheel. Similarly, the wheel cylinder 7FR also operates with the hydraulic pressure supplied from the wheel cylinder side pipe line 6FR, and presses the pad 11FR against the disk 10FR that rotates integrally with the right front wheel.

  The master cylinder side pipe line 4A and the pressure reducing line 9A are connected via a pump 12A. When the pump 12A is driven by the motor 13, the brake fluid is sent from the pressure reducing line 9A to the master cylinder side pipe 4A. A check valve 14A is provided on the discharge side of the pump 12A, and the check valve 14A prevents the backflow of brake fluid from the master cylinder side pipe line 4A to the pump 12A.

  An auxiliary reservoir 15A is attached to the pressure reducing line 9A. The auxiliary reservoir 15A stores brake fluid that flows into the pressure reducing line 9A from the wheel cylinder side pipe lines 6RL and 6FR when the pressure reducing control valves 8RL and 8FR are opened.

  A fluid pressure system similar to the fluid pressure system connected to the pressure chamber 2A is also connected to the other pressure chamber 2B.

  Each wheel is provided with a wheel speed sensor 16RL, 16FR, 16FL, 16RR that detects the rotational speed of the wheel. Further, temperature sensors 17RL, 17FR, 17FL, and 17RR that detect the temperature of the pads are attached to the pads 11RL, 11FR, 11FL, and 11RR, respectively. Detection signals of these sensors 16RL to 16RR and 17RL to 17RR are input to a brake electronic control unit (hereinafter referred to as “brake ECU”) 18 shown in FIG. The brake ECU 18 outputs control signals for the pressure increase control valves 5RL to 5RR, the pressure reduction control valves 8RL to 8RR, and the motor 13 for driving the pump.

  In this brake system, normally, the pressure increase control valves 5RL to 5RR are opened and the pressure reduction control valves 8RL to 8RR are closed, so that the hydraulic pressure generated in the pressure chambers 2A and 2B of the master cylinder 2 remains as it is. 7RL to 7RR. Further, when one of the wheels tends to be locked during braking, the pressure reduction control valves 8RL to 8RR and the pressure increase control valves 5RL to 5RR corresponding to the wheels are controlled by the brake ECU 18, and the liquid in the wheel cylinders 7RL to 7RR is controlled. Control pressure and prevent wheel lock.

  The antilock control by the brake ECU 18 will be described with reference to FIG.

First, to calculate the wheel speed Vw of each wheel based on the detection signal of the wheel speed sensors 16RL～16RR (Step _S 1), calculates the vehicle speed V based on the calculated wheel speed Vw (step _S 2). The vehicle body speed V is calculated, for example, by selecting the fastest wheel speed from the wheel speed Vw of each wheel. Further, the slip amount S of each wheel is calculated based on the wheel speed Vw and the vehicle body speed V of each wheel (step S ₃ ). The slip amount S is a difference between the wheel speed Vw and the vehicle body speed V.

Next, when the anti-lock control has not yet started (step S ₄ ), it is determined whether or not the anti-lock control start condition is satisfied (step S ₅ ). The anti-lock control start condition is, for example, when the slip amount S is greater than a preset decompression start threshold A and the vehicle body speed V is greater than a preset reference speed (eg, 5 km / h). is there.

When the condition for starting the anti-lock control is determined to be satisfied (step S _5), sets the pressure reduction rate R _DOWN and pressure increase rate R _UP of the wheel cylinders by anti-lock control (step S _6). The decompression rate R _DOWN corresponds to the decompression speed when decompressing the wheel cylinders 7RL to 7RR, and is, for example, the duty ratio (ratio of energization time) of the pulse voltage input to the decompression control valves 8RL to 8RR. Similarly, the pressure increase rate R _UP corresponds to the pressure increase speed when the wheel cylinders 7RL to 7RR are increased. For example, the duty ratio of the pulse voltage input to the pressure increase control valves 5RL to 5RR is subtracted from 100%. It is a thing.

Furthermore, based on the temperature of the pad 11RL~11RR detected by the temperature sensor 17RL～17RR, it determines whether the pads 11RL~11RR is in a fade condition (step _S 7). If it is determined that the fade state has occurred, a correction value ΔR _DOWN of the decompression rate is set with a magnitude corresponding to the temperature of the pad (step S ₈ ), and an amount corresponding to the correction value ΔR _DOWN is determined from the decompression rate R _DOWN. Correction for subtraction is performed (step S ₉ ). Similarly, to set the correction value [Delta] R _UP intensifier rates in a size corresponding to the temperature of the pad (Step S _8), performs a correction to be added to the pressure increase rate R _UP the amount corresponding to the correction value [Delta] R _UP (step _S 9). On the other hand, when it is determined not to be in the fade state (step S ₇ ), the pressure reduction rate R _DOWN and the pressure increase rate R _UP are not corrected. Thereafter, anti-lock control is started based on the pressure reduction rate R _DOWN and the pressure increase rate R _UP (step S ₁₀ ).

After the antilock control is started (step S ₄ ), until the antilock control end condition is satisfied (step S ₁₁ ), the decompression rate R _DOWN and the pressure increase rate R _UP are set (step S ₆ ). Detection of fade state (step S ₇ ), correction of pressure reduction rate R _DOWN and pressure increase rate R _UP (step S ₈ , S ₉ ) when the fade state is detected, based on pressure reduction rate R _DOWN and pressure increase rate R _UP The execution of the antilock control (step S ₁₀ ) is repeated, and if the antilock control end condition is satisfied (step S ₁₁ ), the antilock control is ended (step S ₁₂ ). The antilock control end condition is, for example, when the vehicle stops.

An example of hydraulic pressure control of the wheel cylinders 7RL to 7RR by antilock control will be described with reference to FIG. When executing an anti-lock control for the left rear wheel, first inputs a pulse voltage to the pressure reduction control valve 8RL closes the pressure increase control valves 5RL, to decompress the wheel cylinder 7RL at a speed corresponding to the pressure reduction rate R _DOWN (vacuum mode). When a preset decompression time T elapses from the start of decompression, the decompression control valve 8RL is closed and the hydraulic pressure of the wheel cylinder 7RL is retained (holding mode). Thereafter, when the slip amount S becomes smaller than a preset pressure increase start threshold B, a pulse voltage is input to the pressure increase control valve 5RL with the pressure reduction control valve 8RL closed, and the pressure increase rate R _UP is supported. The wheel cylinder 7RL is increased at the increased speed (pressure increase mode). Again, when the slip amount S is greater than the pressure-decrease start threshold A, to decompress the wheel cylinder 7RL at a speed corresponding to the pressure reduction rate R _DOWN (pressure decrease mode). Thus, the lock of the wheel is prevented by repeating the pressure reduction mode, the holding mode, and the pressure increase mode. The pumps 12A and 12B are driven during execution of the antilock control.

In the antilock brake control device, the friction coefficient of the friction surfaces of the pads 11RL to 11RR is lowered in the fade state. Therefore, the hydraulic pressure of the wheel cylinders 7RL to 7RR when the wheels tend to lock and the antilock control is started is higher in the fade state than in the fade state. Therefore, in the fade state, as shown in FIG. 5, is larger than (dashed line in the figure) when depressurization rate of the wheel cylinder 7RL~7RR by the anti-lock control is not fade state, decompression rate _{R DOWN,} the pressure increase rate _{R UP} If this correction is not performed, the pressure reduction amount of the wheel cylinders 7RL to 7RR tends to be excessive.

However, since this anti-lock brake control device corrects and reduces the pressure reduction rate R _DOWN in the fade state, as shown in FIG. 6, the pressure reduction speed when the wheel cylinders 7RL to 7RR are decompressed is the pressure reduction rate. It becomes smaller than the case where _RDOWN is not corrected (broken line in the figure). Therefore, even if the wheel tends to lock when in the fade state, the pressure reduction amount of the wheel cylinders 7RL to 7RR by the antilock control does not become too large, and the braking distance is not easily extended.

Further, when the anti-lock brake control device is in a fade state, the pressure increasing rate R _UP is corrected and increased, so that the pressure increasing speed when the wheel cylinders 7RL to 7RR are increased as shown in FIG. The pressure increase rate R _UP is larger than when the pressure increase rate R _UP is not corrected (broken line in the figure). Therefore, even if the wheel tends to lock when in a fade state, the pressure increase amount of the wheel cylinders 7RL to 7RR by the antilock control is ensured, and the braking distance is not easily extended.

In addition, since the pressure reduction rate R _DOWN and the pressure increase rate R _UP are set in accordance with the temperature of the pads 11RL to 11RR, even when the degree of fading is large, the elongation of the braking distance can be more reliably suppressed. .

In the above embodiment, when it is determined that the fade state is established, the pressure reduction rate R _DOWN and the pressure increase rate R _UP are corrected. However, other control parameters of the antilock control may be corrected. For example, as shown in FIG. 7, the pressure reduction time T may be corrected and shortened when it is determined that the vehicle is in a fade state. If anti-lock control is configured to end the decompression mode when the wheel acceleration becomes greater than a preset deceleration end threshold, the deceleration end threshold is determined when it is determined that the vehicle is in a fade state. The value may be corrected and increased. Even in this case, since the timing for ending the pressure reduction mode is earlier than when the deceleration end threshold value is not corrected, the pressure reduction amount of the wheel cylinders 7RL to 7RR by the antilock control does not become too large, and the braking distance is increased. Hateful. In short, when the fade state is detected, correction in the direction of increasing the hydraulic pressure of the wheel cylinders 7RL to 7RR may be performed with respect to the hydraulic pressure control of the wheel cylinders 7RL to 7RR by the antilock control.

  In the above embodiment, the pressure reducing speed and the pressure increasing speed of the wheel cylinders 7RL to 7RR are adjusted by duty control that changes the energizing time of the pulse voltage input to the pressure reducing control valves 8RL to 8RR and the pressure increasing control valves 5RL to 5RR. However, the pressure reduction speed and the pressure increase speed may be adjusted by other methods. For example, a proportional control valve is used as the pressure increase control valve or the pressure reduction control valve, and the magnitude of the current input to the proportional control valve The pressure reduction speed and pressure increase speed of the wheel cylinders 7RL to 7RR may be adjusted by changing.

  In the above embodiment, a brake system using a disc brake as an example of a braking force generation device has been described as an example. However, the antilock brake control device of the present invention is a brake using another type of braking force generation device. For example, the disc brake of the above embodiment may be applied to a brake system in which the wheel cylinder is replaced with a drum brake that brakes the wheel by pressing the brake lining against the drum.

Piping system diagram of brake system adopting antilock brake control device of embodiment of this invention Block diagram of anti-lock brake control device The flowchart which shows the control which brake ECU of FIG. 2 performs The figure which shows an example of the change of the vehicle body speed, the change of a wheel speed, and the hydraulic pressure change of a wheel cylinder when antilock control is performed by the antilock brake control device of the embodiment of the present invention when not in a fade state The figure which shows an example of the change of the vehicle body speed, the change of a wheel speed, and the change of the hydraulic pressure of a wheel cylinder when anti-lock control is performed without correcting the control parameter in the fade state The figure which shows an example of the change of the vehicle body speed, the change of a wheel speed, and the hydraulic pressure change of a wheel cylinder when antilock control is performed by the antilock brake control device of the embodiment of the present invention in the fade state The figure which shows the change of the vehicle body speed, the change of wheel speed, and the hydraulic pressure change of a wheel cylinder when antilock control is performed in the modification of the antilock brake control device of the embodiment of the present invention in the fade state

Explanation of symbols

5RL, 5FR, 5FL, 5RR Pressure increase control valve 7RL, 7FR, 7FL, 7RR Wheel cylinder 8RL, 8FR, 8FL, 8RR Pressure reduction control valve 10RL, 10FR, 10FL, 10RR Disc 11RL, 11FR, 11FL, 11RR Pad R _DOWN Pressure reduction rate R _UP pressure increase rate T Pressure reduction time

Claims (8)

The wheel cylinder (7RL, 7FR, 7FL, 7RR) presses the friction member (11RL, 11FR, 11FL, 11RR) against the rotating member (10RL, 10FR, 10FL, 10RR) rotating integrally with the wheel to brake the wheel. Lock tendency detecting means (S ₃ ) for detecting the lock tendency;
Anti-lock control means for controlling the hydraulic pressure of the wheel cylinders (7RL, 7FR, 7FL, 7RR) to prevent the wheels from being locked when the lock tendency is detected by the lock tendency detection means (S ₃ ). S ₁₀ ),
Fade state detection means (S ₇ ) for detecting a fade state of the friction member (11RL, 11FR, 11FL, 11RR);
Said friction member at its fade condition detecting means _{(S 7) (11RL, 11FR} , 11FL, 11RR) when the fading condition has been detected, the control of the fluid pressure by the anti-lock control unit _{(S 10)} Anti-lock correcting means (S ₈ , S ₉ ) for correcting in the direction of increasing the hydraulic pressure;
Anti-lock brake control device. The anti-lock control means (S ₁₀ ) controls the hydraulic pressure by controlling the pressure reducing control valve (8RL, 8FR, 8FL, 8RR) and the pressure increasing control valve (5RL, 5FR, 5FL, 5RR),
The anti-lock correction means (S ₈ , S ₉ ) performs the correction on the pressure reduction speed of the hydraulic pressure by the pressure reduction control valves (8RL, 8FR, 8FL, 8RR).
The antilock brake control device according to claim 1. The anti-lock control means (S ₁₀ ) inputs a pulse voltage to control the pressure reducing control valves (8RL, 8FR, 8FL, 8RR),
The antilock correcting means (S ₈ , S ₉ ) performs the correction on the duty ratio of the pulse voltage.
The antilock brake control device according to claim 2. The anti-lock control means (S ₁₀ ) controls the hydraulic pressure by controlling the pressure reducing control valve (8RL, 8FR, 8FL, 8RR) and the pressure increasing control valve (5RL, 5FR, 5FL, 5RR),
The antilock correction means (S ₈ , S ₉ ) performs the correction on the pressure increase rate of the hydraulic pressure by the pressure increase control valves (5RL, 5FR, 5FL, 5RR).
The antilock brake control device according to claim 1. The antilock control means (S ₁₀ ) inputs a pulse voltage to control the pressure increase control valves (5RL, 5FR, 5FL, 5RR),
The antilock correcting means (S ₈ , S ₉ ) performs the correction on the duty ratio of the pulse voltage.
The anti-lock brake control device according to claim 4. The control of the hydraulic pressure by the anti-lock control means (S ₁₀ ) includes a control for ending the pressure reduction when a preset pressure reduction time (T) has elapsed since the pressure reduction of the fluid pressure was started,
The anti-lock correction means performs the correction for the decompression time (T);
The antilock brake control device according to claim 1. The control of the hydraulic pressure by the anti-lock control means (S ₁₀ ) includes a control for ending the reduction of the hydraulic pressure when the acceleration of the wheel becomes larger than a preset pressure reduction end threshold. ,
The anti-lock correction means performs the correction on the decompression end threshold;
The antilock brake control device according to claim 1. The fade state detection means (S ₇ ) detects the degree of fade,
The anti-lock correction means (S ₈ , S ₉ ) performs the correction with a magnitude corresponding to the degree of fade detected by the fade state detection means (S ₇ );
The antilock brake control device according to any one of claims 1 to 7.

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