JPH0428577B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an air brake control device for preventing rear wheels from locking due to forward movement of the vehicle body load during braking in a vehicle equipped with an air spring type suspension system. be.

[Conventional technology] With a leaf spring type suspension system, the axle load can be detected from the deflection of the leaf spring, but with an air spring type suspension system, the vehicle height is automatically adjusted even if the axle load changes. The axle load cannot be detected from the relative displacement between the axle and the axle. Therefore, it is difficult to adjust the brake pressure using a load-sensitive proportional valve.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to provide an air brake control device that controls rear wheel brake pressure during braking based on the air pressure of an air spring of a rear wheel suspension system. It's about doing.

[Means for solving the problem] In order to achieve the above object, the configuration of the present invention is to provide a pressure reducing valve in the downstream part of the piping connecting the air tank and the rear wheel brake rather than the brake valve. A comparator compares the set value of the air pressure setting device, which sets the air pressure of the rear wheel air spring according to conditions, with the detected value of the air pressure sensor, which detects the air pressure of the rear wheel air spring. The pressure reducing valve is driven by the output of the control device based on the deviation between the set value and the detected value, and air pressure corresponding to changes in the air pressure of the rear wheel air spring is supplied to the rear wheel brake via the pressure reducing valve.

[Function] According to the present invention, reference values corresponding to specific conditions are set in advance for the air pressure of the front wheel air spring and the air pressure of the rear wheel air spring, and during braking, the air pressure of the front wheel air spring is adjusted by a separate comparator. The front wheel reference value and the air pressure of the rear wheel air spring are compared and determined with the rear wheel reference value, respectively, and the pressure reducing valve for the front wheel brake and the pressure reducing valve for the rear wheel brake are separately operated by the output of the control device based on the determination signal. control and supply high air pressure to the front brakes and low air pressure to the rear brakes.
It is possible to obtain a braking force according to the load borne by the front axle and the load borne by the rear axle.

The air pressure setting device stores and sets the air pressure of the air spring to a value suitable for various conditions such as load capacity and road conditions in the ROM of the memory of the microcomputer that acts as a control device, and when braking, it sets a value that corresponds to the various conditions. By reading, optimal brake control can be obtained.

[Embodiment of the Invention] As shown in the overall configuration in FIG. 1, air pressure sensors 14 for detecting the air pressure responsible for the shaft load are arranged on the air springs that support the front wheels and the air springs that support the rear wheels, respectively. Comparators 30 and 30a compare the detection signal of the air pressure sensor 14 and the setting signal of the air pressure setting device 21, which sets a reference value corresponding to changes in the friction coefficient of the road surface due to sunny or rainy weather.

Based on the change in the air pressure of the front wheel air spring and the rear wheel air spring due to the forward movement of the vehicle body load during braking, the control device 31 controls the air pressure between the air pressure source and the front wheel brake, and between the air pressure source and the rear wheel brake. To,
The respective pressure reducing valves 28 are operated separately,
Add air pressure commensurate with the front and rear wheel loads.

As shown in FIG. 2, the left and right front wheel suspension systems A and the left and right rear wheel suspension systems B are constructed in exactly the same manner. That is, a shock absorber 1 consisting of a cylinder 2 and a piston 3 is disposed between a known lower arm that supports wheels and a vehicle body.
is connected to the vehicle body, and the rod 3a of the piston 3 is connected to the lower arm. Both end chambers of the cylinder 2 partitioned by the piston 3 are communicated with each other by an electromagnetic variable throttle valve 4.

Air spring 5 is supported between the vehicle body and the lower arm. The air spring 5 communicates with the pressurized container 6 and the spring body 7, which moves up and down as the diaphragm deforms, through an electromagnetic throttle valve 8. The pressurized container 6 is communicated with an air tank 13 or released to the atmosphere via a conduit 9 and a vehicle height adjustment valve C consisting of electromagnetic on-off valves 10 and 26.

In the illustrated example, the pressurized containers 6 of the left and right air springs 5 of the rear wheel suspension system B are communicated with the air tank 13a or the atmosphere through separate vehicle height adjustment valves C, but a common vehicle height adjustment valve C may also be used.

In order to move the front wheel brake 17, the air tank 1
9 is a brake valve 27, a pressure reducing valve 28, a relay valve 18
It is communicated with the rear wheel brake 17 through the. Similarly,
The air tank 19 is communicated with the rear wheel brake 17a through a brake valve 27, a pressure reducing valve 28, and a relay valve 18.

As shown in FIG. 3, the pressure reducing valve 28 is provided with a housing 45 with the peripheral edge of the diaphragm 64 sandwiched between a substantially cup-shaped divided body 45a and a divided body 45b.
A piston 69 supporting a diaphragm 64 is fitted with a seal member 60 and slidably fitted into a cylinder 70 of the divided body 45a.

Inlet 42 of cylinder 70 communicates with air reservoir 19 (FIG. 2) through a brake valve. housing 4
The inside of 5 is provided with an atmospheric port 57 by a diaphragm 64.
An atmospheric chamber 46 connected to the air chamber 46 and a decompression chamber 6 connected to the outlet 51
3. The piston 69 is located inside the atmospheric chamber 46 and is integrally provided with a flange 68 that guides the diaphragm 64. The divided body 45b that partitions the decompression chamber 63 includes a conical body 66 that guides and supports the diaphragm 64.

The divided body 45b is provided with a cylindrical portion 48 at its axis,
A lower end flange of the guide cylinder 56 surrounding the inner cylinder part 48 is supported by a retaining ring 49 on the end wall part of the divided body 45b. The guide tube 56 is slidably fitted into a cylinder 62 provided at the lower end of a piston 69. The inside of the guide tube 56 is communicated with the front wheel brake or the rear wheel brake via the outlet 51. A hollow valve body 50 is slidably fitted into a cylindrical portion 48 that is integral with the divided body 45b, and the lower end of the cylindrical portion 48 is connected to an air port 59.

The air port 59 of the cylindrical portion 48 supports a control lever 55 via a rotation shaft 58 . control lever 55
The tip of the valve body 50 is engaged with a notch 47 provided in the valve body 50,
Moreover, it is held down by the piston 52 so that there is no play. The piston 52 is fitted into a cylinder 53 connected to an end of the divided body 45b. Air pressure at the inlet 42 is introduced into the cylinder 53 via a conduit 67, and the piston 52 is pressed against the tip of the control lever 55 by the air pressure and the force of the spring 54. A rotation shaft 58 supporting the control lever 55 is rotated by, for example, a servo motor in response to a signal from the microcomputer 20, and the rotation shaft 58 supports the control lever 55.
is displaced to control the pressure in the decompression chamber 63.

Normally, the upper end of the hollow portion of the valve body 50 is closed by the valve body 43 having a sealing member 61. The valve body 43 is a hollow space 41 formed at the upper end of the piston 69.
It is fitted into the inside of and is biased downward by a spring 44.

From the state shown in FIG.
5, the upper end of the valve body 50 separates from the sealing member 61 of the valve body 43, and the atmosphere enters the decompression chamber 63 from the atmosphere port 59 through the hollow part of the valve body 50, and the pressure in the decompression chamber 63 decreases. . At this time, based on the difference between the pressure acting on the upper end side of the piston 69 and the pressure acting on the diaphragm 64 of the decompression chamber 63, the diaphragm 64 moves toward the conical surface of the divided body 45b.
6, the pressure receiving area of the diaphragm 64 is reduced, and the piston 69 is displaced to a position where the pressure of the decompression chamber 63 acting on the diaphragm 64 and the air pressure of the inlet 42 acting on the piston 69 are balanced, and at this time the valve The upper end of the body 50 is closed by a sealing member 61 of the valve body 43.

Conversely, when the valve body 50 is pushed up by the control lever 55, the valve body 43 opens and the air pressure at the inlet 42 is applied to the decompression chamber 63 through the cylindrical portion 62, increasing the pressure receiving area of the diaphragm 64, and the piston 69
is pushed up, and the valve body 43 closes the space between the cylinder 70 and the cylindrical portion 62. In this way, the entrance 42
The pressure of the air is reduced in response to the tilting of the control lever 55, and the air is supplied from the outlet 51 to the relay valve 18 (FIG. 2).

As shown in FIG. 2, an air pressure sensor 14 for detecting the vehicle body load is provided on the spring body 7 of each wheel, and a detection signal from the air pressure sensor 14 is applied to a microcomputer 20 as a digital signal.
Further, in order to detect the vehicle height, a vehicle height sensor 15 is disposed between the spring body 7 and the pressurized container 6, and a detection signal from the vehicle height sensor 15 is applied to the microcomputer 20 as a digital signal.

Digital signals from an air pressure setting device 21 consisting of a potentiometer for setting the air pressure of the spring body 7 and a vehicle height setting device 22 consisting of a potentiometer are applied to the microcomputer 20. Further, an engine speed sensor 23, a vehicle speed sensor 24,
Each digital signal from the brake sensor 25 that detects the amount of operation of the brake pedal is applied to the microcomputer 20. Based on the signals from each sensor, the microcomputer 20 operates the servo motor 28a that drives the control lever 55 of the pressure reducing valve 28 described above, and controls the front wheel brake pressure and the rear wheel brake pressure in accordance with changes in the axle load. In addition, the solenoid 4a of the electromagnetic variable throttle valve 4, the solenoid 8a of the electromagnetic throttle valve 8, the solenoid 10a of the electromagnetic on-off valve 10, and the solenoid 26a of the electromagnetic on-off valve 26 are actuated to control the front wheel brake pressure, rear wheel brake pressure, and each shock absorber. 1. Control the damping force of the air spring 5.

Next, the operation when controlling the device of the present invention by a microcomputer will be explained. Fourth,
Figure 5 is a flowchart of the above control program,
p11 to p32 represent each step of the flowchart. When the engine starts, the calculation part p11 is used, and p12 automatically sets the reference value of the air pressure of the air spring.
In order to prevent abnormal operation of the control device, a calculation reference value P _IN is set on the program, and this is loaded as a temporary reference value Po. Read the signal of the vehicle speed sensor 24 at p13. Use p14 to determine whether the vehicle is stopped or not, and prohibit changing the air pressure setting while the vehicle is running.

If the vehicle is stopped at p14, it is determined at p15 whether t seconds have elapsed during which the signal from the vehicle speed sensor 24 is 0. This confirms whether the vehicle has come to a complete stop. If the vehicle is stationary, p16
Then, it is determined whether the switch for applying the reference signal set by the air pressure setting device 21 and the signal set by the vehicle height setting device 22 to the microcomputer 20 is closed.

If the driver wants to change the air spring air pressure and vehicle height, close the manual switch and then use the setting device 2.
Set 1 and 22 manually. This switch is preferably of an automatic reset type to prevent the reference value from changing regardless of the driver's will. Each setting device 21,
If the signal circuit 22 is closed, manually adjust the air pressure setting device 21 and vehicle height setting device 22 at p17, and read the air pressure setting value _PSN . Set the air pressure setting value _PSN input on p18 as the new air pressure reference value Po, and proceed to p19.

If the vehicle is running at p14, the brake sensor 25 determines whether the brake is in operation at p19. If the brake is in operation, input/output data for the front wheel suspension system A is selected in p20, and processed by a subroutine in p21. In other words, as shown in Figure 5, the subroutine is entered at p22, and the air pressure of the right front wheel air spring 5 is determined at p23.
P _R is detected by the air pressure sensor 14, and the air pressure P _L of the left front wheel is similarly detected by the air pressure sensor 14 at p24. In p25, the average air pressure P of the right front wheel and the left front wheel is calculated, and in p26, the difference between the average air pressure P and a reference value Po set according to the road surface condition is calculated. p27
It is determined whether the average air pressure P is larger than the reference value Po. If the average air pressure P of the front wheel air spring is greater than the standard value Po, set p29 to servo motor 2.
8a to gradually increase the opening degree of the pressure reducing valve 28. If the average air pressure P is smaller than the reference value Po, the servo motor 28a is energized at p28 to gradually reduce the opening degree of the pressure reducing valve 28. At p30, the subroutine processing ends and the program enters p31 shown in FIG.

Next, the input/output data for the rear wheel suspension system B is selected, and the subroutine shown in FIG. 5 is entered at p32, where the average air pressure P of the rear wheel air spring is set to the reference value Po.
If it is larger than , set the servo motor 28a in p29.
The opening degree of the pressure reducing valve 28 is gradually increased. If the average air pressure P is smaller than the reference value Po, the servo motor 28a is energized at p28 to gradually reduce the opening degree of the pressure reducing valve 28. After such processing is completed, the process returns to p13 and is repeated at predetermined intervals.

According to the embodiment described above, reference values are set in advance for the air pressure of the front wheel air spring and the air pressure of the rear wheel air spring, and when braking, the respective air pressures of the front wheel air spring and the rear wheel air spring are determined by the comparators 30 and 30a. is compared with each reference value, and based on the determination signal, the control device 31
The pressure reducing valve 28 for the front wheel brake and the pressure reducing valve 28 for the rear wheel brake are controlled separately, and high air pressure is supplied to the front wheel brake, and low air pressure is supplied to the rear wheel brake, so that the load burden ratio between the front and rear axles can be adjusted. You can get the appropriate braking force. The air pressure setting device 21 essentially sets the ratio between the front wheel brake pressure and the rear wheel brake pressure, and this ratio is determined by storing setting values suitable for various conditions in advance in the ROM of the memory of the microcomputer. Keep it
Optimal brake control can be obtained by reading out settings that correspond to the air pressure of the front and rear air springs, vehicle speed, etc.

In addition, in the above-mentioned embodiment, each air pressure of the front wheel air spring and the rear wheel air spring is detected, but the air pressure change during braking is detected only for the rear wheel air spring,
By simply reducing the air pressure applied to the rear brakes based on the difference between the detected value and the reference value, it is possible to obtain a braking force that corresponds to the forward movement of the vehicle body load during braking.

[Effects of the Invention] As described above, the present invention uses the air pressure of the rear wheel air spring as a reference, which is preset according to the load amount and road conditions, and adjusts the air pressure ( The air pressure in the rear wheel air spring gradually decreases as the vehicle load moves forward during braking), so it reduces the air pressure to the rear wheel brake, so the air pressure that is optimal for the various conditions that affect the effectiveness of the rear wheel brake can be obtained. It will be done.

In other words, the air pressure of the air springs and the vehicle height can be freely set according to the load capacity and road conditions, and the pressure is reduced by the output of the control device based on the deviation between the air pressure setting value and the actual air pressure of the rear wheel air springs. Since it drives the valve, even if the driver changes the air pressure of the air spring in response to road conditions or load capacity, the changed air pressure is used as the standard and the optimum air pressure is adjusted to accommodate the pressure difference between the actual air pressure and the actual air pressure. This system supplies air pressure to the rear brakes, preventing the rear wheels from locking up, maintaining vehicle stability, and safely stopping the vehicle in the shortest possible distance.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of an air brake control device according to the present invention, Fig. 2 is an overall configuration diagram of the device, Fig. 3 is a front sectional view of a pressure reducing valve, and Figs. 3 is a flowchart illustrating software for controlling each electromagnetic valve used in the invention device. 5: Air spring, 14: Air pressure sensor, 17a:
Rear wheel brake, 19: Air tank, 21: Air pressure setting device, 27: Brake valve, 28: Pressure reducing valve, 28a:
Servo motor, 30: comparator, 31: control device.

Claims (1)

[Claims] 1. A pressure reducing valve is installed downstream of the brake valve in the piping connecting the air tank and the rear wheel brake, and the setting value of the air pressure setting device is set to adjust the air pressure of the rear wheel air spring according to the load amount, road conditions, etc. A comparator compares the detected value of the air pressure sensor that detects the air pressure of the rear wheel air spring, and the output of the control device based on the deviation between the set value from the comparator and the detected value during braking drives the pressure reducing valve. An air brake control device for a vehicle, characterized in that air pressure corresponding to changes in air pressure in a wheel air spring is supplied to rear wheel brakes via a pressure reducing valve.