JPS6239346A - Automatic car parking brake device - Google Patents

Abstract

PURPOSE:To make it possible to operate a parking brake automatically, by detecting whether the variation rate of the wheel speed is more than a specific value or not when the wheel is braked, and distinguishing securely whether the wheel rotation is stopped by a wheel lock or not. CONSTITUTION:Rotation sensors 22 and 23 are furnished to output pulse line signals P1 and P2 to show the rotating condition of wheel at the front and the rear wheels 3 and 5, and the pulse line signals P1 and P2 are input to the first and the second sped computing units 32 and 36 and to speed variation rate computing units 33 and 37. The speed computing units 32 and 36 are composed to output H signals S1 and S2 when the wheel rotation speed is zero, and the speed variation rate computing units 33 and 37 are composed to output H signals S3 and S4 when the absolute value of the negative variation rate of wheel rotation speed comes down below a specific value. When these signals are all at H level and, at the same time, the H signal showing the unoperating condition of the accelerator pedal 41 is output from an accelerator sensor 42, the first and the second electromagnetic valves 20 and 21 are closed to make a parking brake condition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic parking brake device for a vehicle.

(Prior art) In order to maintain the brake pressure required to keep the vehicle stopped even after the brake pedal is released, brake fluid pressure is applied between the star cylinder and the wheel cylinder. An automatic parking brake device has been proposed in which a solenoid valve is provided for holding and releasing the brake, and the solenoid valve is operated to maintain the operating state of the brake when the wheel rotation speed of the vehicle becomes zero ( Unexamined Japanese Patent Publication 1987-
137246). However, with this device, even in wheel lock situations where only the wheels come to a stop before the vehicle comes to a stop due to frozen road surfaces or sudden braking operations, the hydraulic pressure is maintained and the brake pedal cannot be pressed. Even if the brake is released, the brake state will not be released, and there is a possibility that the brake will fall into an extremely dangerous situation. Therefore, conventionally, for example, in the case of a four-wheeled vehicle, the hydraulic pressure of the brake fluid was limited to the two wheels that were easy to lock, and no hydraulic pressure retention mechanism was provided for the remaining two wheels that were difficult to lock. A device is being considered in which, when the speed of two wheels that are not equipped with a hydraulic pressure holding mechanism becomes zero, the hydraulic pressure holding mechanism of the other two wheels is activated, thereby locking the brakes. .

(Problems to be Solved by the Invention) However, since the conditions of the driving road surface vary, the following problems will occur even in the device configured as described above. In other words, when only a portion of the road surface is frozen, the wheels that are not equipped with a hydraulic pressure retention mechanism will lock up first, and this will cause the vehicle speed to remain at a predetermined level even though it is not zero. There was a risk that the two wheels of the vehicle would be locked, making it impossible to control the vehicle. Furthermore, since the hydraulic pressure holding mechanism is provided only for some of the wheels, there is also the problem that the braking force in the brake holding state is insufficient.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an automatic parking brake system for a vehicle that can control brake retention for all wheels without causing a wheel lock state. be.

(Means for Solving the Problem) The configuration of the present invention is such that the hydraulic pressure of the brake fluid can be maintained between the master cylinder and the wheel cylinder when the vehicle is stopped, even after the brake pedal is released. An automatic parking brake system for a vehicle comprising a solenoid valve for maintaining and releasing hydraulic pressure, comprising: at least one sensor that outputs a pulse train signal whose period changes according to the rotational speed of a wheel; a first detection means for detecting whether or not the rotational speed of the wheel has become zero in response to the Noculus train signal; a second detecting means for detecting, and in response to the detection results of the first and second detecting means, when the rotational speed of the wheel becomes zero without the rate of change of the rotational speed of the wheel becoming equal to or higher than a predetermined value; The present invention is characterized in that it includes means for operating the solenoid valve so that the hydraulic pressure is maintained.

(Operation) When the master cylinder is actuated by operating the brake pedal, thereby applying braking to the wheels, the second detection means detects whether the rate of change in wheel speed has exceeded a predetermined value. The predetermined value is set to a rate of change value that causes wheel lock, and when the second detection means detects that the rate of change in wheel speed has exceeded the predetermined value, the solenoid valve is not activated. First, hydraulic pressure is not maintained. If it is detected that the rate of change in the wheel speed is below a predetermined value, the solenoid valve is activated when the first detection means detects that the wheel rotation speed has become zero, and the The pressure is maintained and the parking brake is automatically applied.

In this way, if a wheel braking operation is performed that may cause a wheel lock, the solenoid valve will not maintain fluid pressure even if the wheel rotation speed becomes zero, so the brake pedal The brake state of the wheels can be released by loosening the pedal pressure. On the other hand, when there is no risk of wheel leakage occurring, the hydraulic pressure is maintained by the electromagnetic valve when the rotational speed of the wheel becomes zero.

(Embodiment) FIG. 1 shows a control system diagram showing an embodiment of an automatic parking brake device for a vehicle according to the present invention. The automatic parking brake device 1 is a device that locks the brakes on the front wheels 3.4 and rear wheels 5 and 6 when the vehicle is stopped by operating the brake pedal 2.
, 4 and rear wheels 5.6, respectively, and a control unit 31 for electrically controlling the brake mechanism 11. .

First, the brake mechanism 11 will be explained. The brake devices 7 to 10 provided corresponding to each wheel include wheel cylinders 12 to 15, respectively, and the wheel cylinders 12 and 13 for the front wheels have a brake pipe 16. The wheel cylinders 14 , 15 for the rear wheels are connected to the mask cylinder 17 via another brake pipe 18 . The operating rod 19 of the mask cylinder 17 is connected to the brake pedal 2, and by depressing the brake pedal 2, the mask cylinder 17 is activated.
The brake fluid entering each brake pipe 16, 18 and four wheel cylinders 12 to 15 is pressurized to operate the brake devices 7 to 10, thereby braking each wheel.

The wheel cylinder 12 is activated by operating the brake pedal 2.
．． The hydraulic pressure of the brake fluid acting on brake pedal 13 is transferred to brake pedal 2.
A first solenoid valve 20 is provided in the middle of the brake pipe 16 so that the hydraulic pressure of the brake fluid acting on the wheel cylinder 14.15 can be maintained even when the operation is released. In order to be able to hold the brake pedal 2 even when the brake pedal 2 is released, the brake pipe 18 is provided with a 21st brake valve in the middle of the brake pipe 18. A magnetic valve 21 is provided. The first and second electromagnetic valves 20, 21 are controlled to open and close by a control unit 31, which will be described later, and can apply a parking brake to each wheel according to predetermined conditions. In the illustrated embodiment, both the first and second solenoid valves 20.21 are configured to be open when their excitation coils are demagnetized and closed when their excitation coils are energized.

The front wheel 3 is equipped with a rotation sensor 22 that outputs a pulse train signal indicating the rotational state of the front wheel 3.The rotation sensor 22 outputs a pulse every time the wheel 3 rotates by a predetermined rotation angle. A first pulse train signal P1 consisting of these pulses is input to the control unit 31. As can be seen from the above description, the period of the first pulse train signal P1 changes depending on the rotational speed of the wheels 3. It turns out. Similarly, a rotation sensor 23 is attached to the rear wheel 5 in order to obtain a second pulse train signal P indicating the rotational state of the rear wheel 5.

The rotation sensor 23 outputs a pulse every time the rear wheel 5 rotates by a predetermined rotation angle, and a pulse train signal consisting of these /4' pulses is a second pulse train whose period changes according to the rotational speed of the wheel 5. It is output as a column signal P. The second/# pulse train signal P is also input to the control unit 31. The first pulse train signal P1 is input to the first speed calculation unit 32 and the first speed change rate calculation unit 33,
The first speed calculation unit 32 determines whether the rotational speed of the wheel 3 has become zero or not. The first speed calculation unit 32 outputs a first signal S1 which is detected from the period of the pulse train signal P□ and becomes "H" level when it is detected that the rotational speed of the wheel 3 is zero. The first speed change rate calculation unit 33 detects whether the feed value of the negative change rate of the rotational speed of the wheels 3 is equal to or greater than a predetermined value from a change in the period of the first pulse train signal P, When it is detected that the feed value of the rate of change of is equal to or higher than a predetermined value, the second signal S2 held at the rLJ level is output from the first speed change rate calculation unit 33. First speed change rate calculation unit 3
3 is applied with an accelerator signal S& from an accelerator sensor 42 that detects whether or not the accelerator pedal 41 is being operated, and the level of this accelerator signal Sm is rHJ indicating that the accelerator pedal 41 is not being operated. In response to the change from the level to the rLJ level at which the accelerator pedal 41 is being operated, the first speed change rate calculation unit 33 is reset, and the level of the zth (Nth st) becomes rHJ.
becomes.

First signal S1, second signal S! and the accelerator signal Sa are input to the AND gate 34, and only when the levels of these signals are all rHJ, the level of the output signal 01 of the AND gate 34 becomes rHJ. That is, if the rotational speed of the wheel 3 becomes zero due to the operation of the brake pedal 2, etc.
At this time, if the rate of decrease in the rotational speed of the wheels 30 does not exceed a predetermined value and the accelerator pedal 41 is not operated, the level of the output signal 0□ becomes rHJ. This is a normal vehicle stop state in which no wheel lock state occurs, and the output signal 01 is amplified by the amplifier 35, and the amplified output signal obtained as a result is the first control signal C.
1 is applied to the first solenoid valve 20. As a result, when the vehicle stops, the first solenoid valve 20 is closed and the brake fluid pressure acting on the wheel cylinder 12. Brake states 3 and 4 are maintained.

In other words, the parking brake is automatically applied.

If the brake pedal 2 is operated suddenly, and therefore the rate of decrease in the rotational speed of the wheel 3 is large, and the level of the second signal S2 reaches rLJ, the rotational speed of the wheel 30 becomes low and the first signal S1 Even if the level of the output signal 01 reaches rHJ, the level of the output signal 01 does not become "H" and the 11th X magnetic valve 20 is not closed.

Therefore, by reducing the amount by which the brake pedal 2 is depressed, it is possible to weaken the braking force.

The second pulse train signal P is input to the second speed calculation unit 36 and the second speed change rate calculation unit 37 to which the accelerator signal Sm is input.

The second speed calculation unit 36 is the first speed calculation unit 32
The third signal S3, which is at the rHJ level when the wheel 50 rotational speed is zero, is the first signal S3.
It is output from the speed calculation unit 32. On the other hand, the second speed change rate calculation unit 37 is configured in the same manner as the first speed change rate calculation unit 33, and is set to the rLJ level in response to the deceleration rate of the rotational speed of the wheels 5 exceeding a predetermined value. In response to the held accelerator signal S& reaching the "L" level, the second speed change rate calculating unit 37 outputs a fourth signal S4 which returns to the rHJ level.

The third signal S1, the fourth signal S4, and the accelerator signal Sa are input to the AND gate 38, and when the brake pedal 2 is operated, etc., the rotational speed of the rear wheel 50 becomes zero, and at this time, the rate of decrease in the rotational speed of the wheel 5 becomes a predetermined rate. rHJ when it is not larger than the value and the accelerator pebble 41 is not operated.
An output signal O1 is output from the ANDFF-) 38. This output signal O! is input to the amplifier 39, and its amplified output is applied to the second solenoid valve 21 as the second control signal C2. Therefore, in this case as well, when the level of the output signal 02 becomes "H", the second solenoid valve 21 is closed and the parking brake is automatically applied.

Note that the value of the predetermined rate of change determined in the first speed change rate calculation unit 33 and the value of the predetermined rate of change determined in the second speed change rate calculation unit 37 are generally different. This is because each value is appropriately set depending on the degree of braking of the corresponding wheel, but depending on the case, the two values may be the same.

According to the above configuration, the rate of decrease in the rotational speed of each wheel when the brake pedal is operated is checked, and if the rate of decrease reaches a value that causes wheel lock, the parking Since the brakes do not lock, driving safety is ensured, and since the parking brake works on all four wheels, there is no lack of braking force, making it possible to securely hold the vehicle even on steep slopes. It can be parked at.

The functions of control 22) 31 shown in FIG. 1 can also be realized using a microcomputer.

FIG. 2 shows a flowchart of an example of a control program executed by a microcomputer when the functions of the control unit 310 shown in FIG. 1 are implemented by the microcomputer. Next, to explain this flowchart, after initialization is performed in step 51, the rotational speed V of the wheel 3 is calculated based on the first and second pulse train signals P, , P, GC in the stellar f52!
and the rotational speed V of the wheels 5 are calculated. Thereafter, in step 53, each deceleration rate R,
,R, is performed using the values of the rotational speeds,v,,v,. Next, the process proceeds to step 54, where it is determined whether or not the deceleration rate 81 is equal to or greater than a predetermined value A. If the result of this determination is No, the process proceeds to step 55, where the wheel speed V
, is zero or not. If V, =O, the first solenoid valve 20 is closed in step 56, the parking brake is applied to the wheel 3.4, and the process proceeds to step 57. If the deceleration rate R0 of the wheel 3 is smaller than the predetermined value (the determination result of Stella 7° 54 is YES) or if the speed of the wheel 3 is not zero (the determination result of step 55 is No), step 56 is executed. step 5 without being
Proceed to step 7. Therefore, in this case, the parking brake is not applied, and by adjusting the operation of the brake pedal 2, the braking force applied to the wheels 3 and 4 can be adjusted.

In Stella f57, it is determined whether the deceleration rate R8 is greater than or equal to the predetermined value A2, and the determination result is N.

In this case, it is further determined in step 58 whether the wheel speed v2 is zero. In the case of Vz=Q, the second solenoid valve 21 is closed in the Stella f56, and the wheels 5,
The parking brake is applied at step 6, and the process proceeds to step 60. The deceleration rate R1 of the wheel 5 is smaller than the predetermined value A2 (Stella f5
If the determination result of Step 7 is YES) or if the speed of the wheel 5 is not zero (the determination result of Stella f58 is No), Stella f59 is not executed and the process proceeds to Stella f60.

The Stella f60 determines whether the depression amount θ of the accelerator pedal 41 is zero or not, and if the accelerator pedal 41 is being operated (θ>0), the determination result of the Stella f60 is YES. In step 61, the first and second
Solenoid valves 20, 21. Open together. As a result, even if the parking brake is applied, the accelerator pedal 41
When is depressed, the parking brake by the first and second solenoid valves 20.21 is released. After the execution of step 7'61ρ is completed, the process returns to Stella f52.

In addition, in the above embodiment, the front wheel brake system and the rear wheel brake system are each provided with a parking brake device according to the present invention independently, but the structure of the present invention is limited to this embodiment. Instead, modifications can be made as appropriate, such as using one or more wheels for vehicle speed detection.

(Effect) According to the present invention, as described above, in addition to stopping the rotation of the wheels, the configuration takes into consideration the negative rate of change in the rotational speed of the wheels, so the rotation of the vehicle stops due to the wheel locking of the wheels. To provide an excellent effect in which parking brakes can be automatically applied to all desired wheels without compromising safety by reliably distinguishing between cases in which parking brakes are applied and cases in which they are not.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of an automatic parking brake device according to the present invention, and Fig. 2 is an example of a control unit used when a microcomputer is used to realize the same function as the control unit shown in Fig. 1. It is a flowchart which shows. DESCRIPTION OF SYMBOLS 1... Automatic parking brake device, 2... Brake pedal, 3, 4... Front wheel, 5, 6... Rear wheel, 7-10.
... Brake group [,17... Master cylinder, 20...
... first solenoid valve, 21 ... second solenoid valve, 31 ... control unit, 32 ... first speed calculation unit, 33.
...First speed change rate calculation unit, 36...Second speed calculation unit, 37...Second speed change rate calculation unit, 34.38...And gate, 41...Accelerator pedal, 42. ...Accelerator sensor. Patent applicant: Diesel Kiki Co., Ltd. Representative Patent attorney: Masaru Takano Died 11- (
＾7γl し7

Claims (1)

[Claims] 1. In order to maintain the hydraulic pressure of the brake fluid when the vehicle is stopped even after the brake pedal is released, a solenoid valve for maintaining and releasing the hydraulic pressure is provided between the master cylinder and the wheel cylinder. An automatic parking brake device for a vehicle includes at least one sensor that outputs a pulse train signal whose period changes depending on the rotational speed of a wheel, and a sensor that detects whether the rotational speed of the wheel has become zero in response to the pulse train signal. a first detection means for detecting; a second detection means for detecting whether the rate of change in the rotational speed of the wheel has exceeded a predetermined value in response to the pulse train signal;
In response to the detection result of the detection means, the solenoid valve is operated so that the hydraulic pressure is maintained only when the rotational speed of the wheel becomes zero without the rate of change of the rotational speed of the wheel exceeding a predetermined value. An automatic parking brake device for a vehicle, characterized in that it is equipped with a means for