JPS5920504B2 - Anti-skid control method for brake mechanism - Google Patents

Description

[Detailed Description of the Invention] The present invention prevents the wheels from skidding on the road surface by controlling the braking torque even if an excessive braking input is applied to the brake mechanism during braking of a vehicle, thereby achieving efficient braking. The present invention relates to an anti-skid control method for such a brake mechanism.

Conventionally, anti-skid control methods include reducing the braking torque when the wheel angular deceleration caused by excessive braking operation increases to a predetermined value or more, and when the resulting wheel angular acceleration decreases to a predetermined value. In other words, there is a method of increasing the braking torque again when the circumferential speed of the wheels approaches the vehicle speed sufficiently. However, as the braking torque decreases, the angular deceleration of the wheel disappears, and the next time the angular acceleration occurs, there is no longer any danger of the wheel locking, so the angular acceleration of the wheel decreases below the predetermined value. Furthermore, reducing the dynamic torque causes the range of variation in the braking torque to increase. In addition, when increasing the braking torque when the circumferential speed of the wheels approaches the vehicle speed, it must be done quickly, otherwise the time required for the braking torque to reach the appropriate value will be extended, and the braking will be delayed. Efficiency is significantly reduced. However, the sudden increase in braking torque causes large vibrations in the vehicle.
This results in damage to the brakes that impairs braking sensation. An object of the present invention is to provide the above-mentioned anti-skid control method that eliminates the above-mentioned problems in the conventional method.

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
FIG. 1 shows an anti-skid brake device used to carry out the method of the present invention, which includes a brake hydraulic pressure generating device 1 and a brake mechanism installed on any wheel of a vehicle and operated by the output hydraulic pressure of the device 1. 2, and the device 1
The control device 3 controls the braking torque of the brake mechanism 2 by applying a hydraulic pressure that opposes the output hydraulic pressure of the brake mechanism 2 to the brake mechanism 2.The configuration of the control device 3 will be explained in sequence.

A known brake master cylinder is used as the brake hydraulic pressure generator 1, and it has a pressurizing chamber 6 filled with hydraulic oil.
By compressing the pressure with a pressurizing piston 5 connected to the brake pedal 4, an output hydraulic pressure can be generated.

The hydraulic brake mechanism 2 includes a brake drum 7 that rotates together with the wheels, and a pair of brake shoes 8 that are floatingly or swingably supported on a fixed panel (not shown) inside the drum 7.
8 and a wheel cylinder 9 interposed between the movable ends of both brake shoes 8, 8, and the wheel cylinder 9 has respective piston rods 10a, 10a connected to the movable ends of the brake shoes 8, 8. a pair of output pistons 10,
10 are slid together, and a first
A pressure receiving chamber 12 is formed, and a second pressure receiving chamber 13, 13 is formed between the output pistons 10, 10 and the end wall members 11, 11 of the wheel cylinder 9, and the first pressure receiving chamber 12 is connected to the pressurizing chamber 6. They are connected via a flow path 14.

The control device 3 has an oil sump 15, a hydraulic pump 16 serving as a hydraulic pressure source that communicates an inlet with the oil sump, a high-pressure flow path 17 extending from its discharge port, and a low-pressure flow path 18 that opens its end to the oil sump 15. The flow paths 17 and 18 are both connected to the second pressure receiving chambers 13 and 1.
Connected to 3.

Between both flow paths 17 and 18, they are connected to second pressure receiving chambers 13 and 1.
A first solenoid valve 20, which is a control valve that can be switched and communicated with the pressure receiving chamber 3, is interposed, and the solenoid valve 20 communicates the low pressure flow path 18 with the second pressure receiving chambers 13, 13 in a normal state. Furthermore, a normally open second solenoid valve 21 serving as a control valve is interposed in the low oil flow path 18, and a second pressure receiving chamber 13 is inserted by bypassing the first solenoid valve 20.
, 13, and the side passage 18a communicating with the side passage 18a is connected to
An orifice 19 is formed in the middle. Note that 22 in the figure is a pressure accumulator. FIG. 2 shows the first and second solenoid valves 20.
, 21, which connects the solenoid of the first electromagnetic valve 20 to the battery 29 via the contact 26 of the keep relay 25.

The keep relay 25 has a set coil 27 that can set the contact 26 to a closed position when energized, and a reset coil 28 that can reset the contact 26 to an open position when energized. the first in the circuit to be connected
A sensing switch 30 is inserted, and a second sensing switch 31 and a diode 24A are inserted in series in a circuit connecting the reset coil 28 and battery 29. Immediately after both sensing switches 30 and 31, the solenoid of the second solenoid valve 21 is connected via diodes 24B and 24C. The first sensing switch 30 senses an angular deceleration of a wheel braked by the brake mechanism 2 that is greater than a predetermined value a, and the second sensing switch 31 senses an angular acceleration of a wheel that is greater than a predetermined value b. Since a well-known inertial force sensing switch may be used for these, a description of the structure thereof will be omitted. Next, the operation of the above embodiment will be explained with reference to the characteristic diagram in FIG. 3. While the vehicle is running, . T
If the brake master cylinder 1 is actuated by depressing the brake pedal 4 at the time O, and the output hydraulic pressure is applied to the first pressure receiving chamber 12 of the wheel cylinder 9, the output pistons 10 and 10 of the saw pair are released by the hydraulic pressure. Since the brake shoes 8, 8 are pushed toward the inner surface of the brake drum 7, a braking torque corresponding to the oil pressure in the first pressure receiving chamber 12 acts on the wheels.

When the angular deceleration of the wheels increases as the braking torque increases and the wheels are in danger of locking, that is, when the angular deceleration of the wheels reaches the set value a, the first sensing switch 30 senses this. Since it is closed, the normally open second solenoid valve 21 is energized through the first sensing switch 30 and opens.

At the same time, the set coil 27 of the keep relay 25 is energized through the first sensing switch 30 and the contact 26 is closed, so that the first solenoid valve 20 is also energized through it and switched to the right side in FIG. The high pressure flow path 17 becomes conductive and the low pressure flow path 18 becomes disconnected, and the second pressure receiving chambers 13, 13 of the wheel cylinder 9 are supplied with pressure oil from the hydraulic pump 16 or the pressure accumulator 22, and the oil pressure is transferred to the first pressure receiving chamber. 12, the second pressure receiving chambers 13, 13
As the pressure increases, the braking torque applied to the wheels of the brake mechanism 2 is quickly reduced, and the risk of wheel locking is eliminated. When the angular deceleration generated in the wheel decreases to a predetermined value a as a result of the reduction in braking torque, the first sensing switch 30 opens again at T2, and the second solenoid valve 21 returns to its original state as shown in FIG.
Since the right side switching state of the solenoid valve 20 is connected by the keep relay 25, the second pressure receiving chambers 13, 13 are also communicated with the low pressure passage 18 via the side passage 18a having the orifice 19, and accordingly, the high pressure passage 17 is connected to the right side switching state of the solenoid valve 20. A part of the pressure oil supplied to the second pressure receiving chambers 13, 13 is appropriately restricted in flow rate by the orifice 19, leaks to the X low pressure flow path 17, and is supplied to the second pressure receiving chambers 13.
, 13 is reduced, and therefore the rate of decrease in braking torque can be reduced.

After that, the angular deceleration of the wheel disappears, and conversely, the angular acceleration occurs, and when it reaches the set value b, the second sensing switch 31 senses this state and closes, so the keep release. -25 reset coil 28 is energized and contact 26
is reset to the open position, so that the first solenoid valve 20
returns to its original state (left side) in Figure 1, and on the contrary, the second solenoid valve 2
1 is energized again and becomes closed.

As a result, both the high pressure and low pressure channels 17 and 18 are completely cut off, and the pressure in the second pressure receiving chambers 13 and 13 is maintained constant regardless of the output oil pressure of the brake master cylinder 1. Even if there is some time delay in the operation of the second solenoid valve 21, immediately before that, the pressure increase rate in the second pressure receiving chambers 13, 13 has decreased as described above, so the pressure in the second pressure receiving chambers 13, 13 This prevents the brake from rising too high, and thus allows a predetermined braking torque to continue to be applied within a range that does not cause the wheels to lock. After that, the angular speed increase of the wheel l@
．． When the circumferential speed of the wheels approaches the vehicle speed, it begins to decrease, and when the circumferential speed of the wheels approaches the vehicle speed sufficiently, T4, set value b.
, and as the second sensing switch 31 opens, the second sensing switch 31 opens.
Since the solenoid valve 21 returns to the open state and makes the low pressure flow path 18 conductive, the pressure reduction in the second pressure receiving chambers 13, 13 starts again, and the braking torque increases accordingly, and the braking torque reaches the above-mentioned constant value. The time required to reach the next peak value is relatively short, thus reducing the time wasted during braking when the circumferential speed of the wheels is sufficiently close to the vehicle speed.

Thereafter, the same operation is repeated, and the wheels are efficiently braked without skidding. However, when the vehicle stops due to the operation of the brake device 3, there is no guarantee that the second sensing switch 31 will close and the keep relay 25 will be reset.

If the keep relay 25 is set, that is, contact 2
If you stop at X with 6 closed, the second pressure receiving chamber 13,
Since the high pressure state 13 is maintained for a relatively long time due to the throttling effect of the orifice 19, it may interfere with the next braking operation.

In view of this, the command device 23 uses an off-delay timer 3 driven by the output signal of the first sensing switch 30.
The second contact 33 is connected to the reset coil 28 of the keep relay 25 in parallel with the second sensing switch 31.

The contact 33 of the off-delay timer 32 is in the open position in the reset state, and is closed only for a period from when the first sensing switch 30 closes until a certain period of time has elapsed after the first sensing switch 30 opens again (set state). It's becoming like that. Therefore, as long as the first sensing switch 30 opens, even if the second sensing switch 31 does not close, the off-delay timer 3 is always activated after a certain period of time has elapsed.
Since the keep relay 25 can be reset by the reset action in step 2, the above-mentioned problem is solved.

However, the delay time from when the first sensing switch 30 opens to when the contact 33 opens is such that the delay time from when the first sensing switch 30 opens to when the second sensing switch opens so as not to interfere with normal anti-skid control. Time until 31 closes (usually 0
．． Needless to say, it is necessary to set the value larger than 0.05 seconds or less. As described above, according to the present invention, when the angular acceleration of the wheel occurs and falls below a predetermined value during braking, the braking torque is promptly reduced, and as a result, the angular acceleration of the wheel increases above the predetermined value. In an anti-skid control method for a brake mechanism, which repeats the steps of maintaining a constant braking torque when the angular acceleration decreases below a predetermined value, and then increasing the braking torque when the angular acceleration decreases below a predetermined value, When the angular deceleration representing negative acceleration falls below a predetermined value, the rate of decrease of the braking torque is reduced, and then when the angular acceleration representing positive angular acceleration of the wheel occurs and exceeds the predetermined value, braking is applied. Since the reduction in torque is stopped and kept constant, in areas where the angular deceleration of the wheels is larger than a predetermined value, the braking torque is rapidly decreased to avoid wheel locking, and the angular deceleration of the wheels is In areas where the angular speed of the wheels has decreased below a predetermined value but has not yet increased by more than the predetermined value and there is a risk of wheel locking, the rate of decrease in braking torque is reduced to reduce the rate of decrease in wheel locking. This makes it possible to effectively prevent excessive reduction in braking torque while reliably avoiding wheel lock, and to limit the reduction in braking torque to the necessary limit. Therefore, when the braking torque is increased next time, the braking It is possible to shorten the fluctuation range and time required to reach the peak torque value, and it is possible to quickly obtain effective braking torque without causing large vibrations to the vehicle.As a result, it does not impede the driver's braking sensation. This improves braking efficiency and shortens the vehicle's rolling distance.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram of an anti-skid brake device used to carry out the method of the present invention, FIG. 2 is an electric circuit diagram of the command device, and FIG. 3 is a characteristic diagram of the command device.

Claims (1)

[Claims] 1. During braking, when the angular acceleration of the wheels decreases below a predetermined value, the braking torque is promptly reduced, and as a result, when the angular acceleration of the wheels increases beyond the predetermined value, the braking torque is kept constant. In an anti-skid control method for a brake mechanism, which repeats maintaining the angular acceleration and then increasing the braking torque when the angular acceleration decreases below a predetermined value, the negative angular acceleration of the wheel is expressed in the process of decreasing the braking torque. When the angular deceleration decreases below a predetermined value, the rate of reduction of the braking torque is reduced, and when an angular increase representing a positive angular acceleration of the wheel occurs and exceeds the predetermined value, the reduction of the braking torque is stopped. It is characterized in that it is kept constant. Anti-skid control method for brake mechanism.