JPH0212131Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a brake device for a vehicle.

In a vehicle's brake system, there is a space between the brake pedal and the master cylinder in order to always obtain sufficient braking force for the maximum speed and weight of the vehicle, and to reduce driver fatigue by reducing the force applied to the brake pedal. Some models are equipped with a booster that amplifies the pedal effort. In boosters that have been commonly used in the past, the output of the booster that is amplified is in a constant relationship with the pedal depression force. However, especially for commercial vehicles such as trucks, the vehicle weight varies greatly between when it is fully loaded and when it is empty.
In order to obtain the same deceleration rate, it is necessary to change the pedal depression force according to the increase or decrease in weight. If the output of the booster is set so that sufficient braking force can be obtained even when the vehicle weight is large,
If the weight is light, there is a risk that the wheels will lock with a small pedal force, impairing braking stability. Further, since the pedal depression force and its reaction force are proportional, if the weight of the vehicle is large, the driver will receive a large reaction force, increasing the driver's fatigue level.

In addition, in the brake system, in order to prevent the rear wheels from locking up before the front wheels due to load transfer during braking, a pressure control valve is installed in the brake circuit connected to the rear wheel brakes. It is already known that when the force exceeds a certain predetermined value, its rate of increase is lower than the rate of increase of the front wheel braking force. Pressure control valves that have been generally employed have a structure in which the transition point at which the rate of increase in rear wheel braking force begins to decrease is fixed. However, in order to always maintain high braking efficiency without causing the rear wheels to lock, regardless of the vehicle weight, it is necessary to change the front and rear wheel brake force distribution in accordance with the vehicle weight.

The present invention has been developed in view of the above, and includes an air pressure source for supplying compressed air, an inlet for supplying the compressed air, and a pedal force applied to the brake pedal according to the pressure of the compressed air supplied to the inlet. A booster that amplifies the output, a master cylinder that operates based on the output of the booster to generate brake fluid pressure, front and rear brakes that are operated by the same brake fluid pressure, and the pressing force of the brake pedal mentioned above. a pedal displacement meter that detects the vehicle weight and outputs a pedal force signal that is an electrical signal corresponding to the same pedal force; a vehicle weight sensor that detects the vehicle weight and outputs a weight signal that is an electrical signal corresponding to the same weight; and a vehicle weight sensor that communicates with the air pressure source. an inlet passage, an outlet passage communicating with the inlet of the booster, a pilot chamber into which the pressure in the inlet passage is introduced, a pressure chamber into which the pressure in the outlet passage is introduced, and a pressure chamber in the pilot chamber. and a second acting force depending on the pressure in the pressure chamber, and when the first acting force is greater than the second acting force, the inlet passage and the outlet passage communication means that communicates between the inlet passage and the outlet passage and blocks the inlet passage and the outlet passage when the second acting force is greater than the first acting force; a pressure reducing means for reducing the pressure in the outlet passage when the passage is cut off from the outlet passage; and a pressure reducing means for reducing the pressure in the exit passage when the depression force on the brake pedal increases based on the depression force signal, and increasing the pressure in the pilot chamber to reduce the pressure in the pilot chamber. an electro-pneumatic converter comprising a pressure changing means for reducing the pressure in the pilot chamber when the weight of the vehicle decreases based on a signal; a pressure control valve that responds to the pressure and reduces brake fluid pressure supplied to the rear wheel brake when the pressure exceeds a predetermined pressure value; and a pressure control valve that responds to a change in the vehicle weight based on the weight signal; The gist of the present invention is a brake device comprising means for controlling the operation of the pressure control valve so as to change the pressure value at which the brake fluid pressure starts to decrease.

According to the above configuration, in response to a change in vehicle weight, the relationship between the brake pedal depression force and the front wheel braking force and the rear wheel braking force is changed, and the output of the booster and the rate of increase in the rear wheel braking force are changed. The transition point at which it begins to drop will be changed, thus
Even if the weight of the vehicle changes, it is possible to obtain a constant deceleration with a constant pedal force, and even when the weight is light, the rear wheels can be prevented from locking with a small pedal force, resulting in braking stability and high braking efficiency. can be maintained at all times.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of an air servo brake device according to an embodiment of the present invention. Compressed air is generated by an air pressure source 1 such as an air pump, and is stored in an accumulator 2. It is also supplied to the electro-pneumatic converter 3. During braking, the electro-pneumatic converter 3 adjusts the pressure of compressed air from the pneumatic source 1 according to the force on the brake pedal and the weight of the vehicle, and then supplies it to the pneumatic booster 4 to operate the device. The master cylinder 5 is actuated by the amplified output from the booster. The brake hydraulic pressure generated by the master cylinder 5 is directly supplied to the front wheel brakes 6, and after the pressure is controlled by a variable pressure control valve 7 according to the weight of the vehicle, it is supplied to the rear wheel brakes 8. The brake pedal has a predetermined displacement amount in response to an input pedal depression force, and the pedal displacement meter 9 generates an electrical depression force signal in accordance with the displacement amount of the brake pedal. The pedal force signal detected by the pedal displacement meter 9 and the weight signal detected by the vehicle weight sensor 10 are input to the current generator 11, and the current generator converts the electro-pneumatic converter 3 based on both signals. Activate. The weight signal is also input to the controller 12, and the controller operates the drive device 13 for controlling the pressure of the variable pressure control valve 7 based on this signal.

Next, each component will be explained in detail.

In FIG. 2, the electro-pneumatic converter 3 is connected to the pneumatic source 1
a housing 22 comprising an inlet passage 20 connected to the booster 4 and an outlet passage 21 connected to the booster 4;
The valve seat 23 is movably arranged in the same housing.
A valve member 24 cooperates with the valve member 24 to control communication between the inlet passage 20 and the outlet passage 21, a spring 25 biases the valve member to the closed position shown in FIG. Two diaphragms 29 delimiting the exhaust chamber 27 and the pressure chamber 28
and 30 are fixed to the support body 31 of the diaphragm, and one end thereof faces the valve member 24 and is connected to the outlet passage 21.
It has a tubular member 32 that protrudes inward and communicates the passage with the exhaust chamber 27. The pilot chamber 26 communicates with the inlet passage 20 through an orifice 33 and a pilot passage 34, and is open to the atmosphere through a nozzle 35 and an atmosphere opening chamber 36, and the exhaust chamber 27 is connected to the atmosphere through an exhaust port 37. opened,
Furthermore, the pressure chamber 28 is connected to the outlet passage 21 via a passage 38.
is communicated with. Moreover, inside the housing 22,
A flapper 39 is disposed opposite the nozzle 35, and the flapper is attached to a movable plate 40 and holds an air-core movable coil 41. The moving coil 41 extends in and is guided and supported in a support 42 fixed to the housing 22, which also carries a permanent magnet 43. The movable coil 41 is connected to the current generator 11, and when it is not energized, it is attracted by the attractive force of the permanent magnet 43 and moves the movable plate 40 upward, and when it is energized, it generates electromagnetic force and moves the movable plate 40 upward.
A repulsive force is generated between the movable plate 40 and the movable plate 40 to move the movable plate 40 downward.

Note that in this embodiment, the diaphragm 29,
30, the tubular member 32, the valve member 24, the valve seat 23, and the spring 25 act as communication means in the scope of the utility model registration claim, and the exhaust port 37 and the exhaust chamber 2
7 and the tubular member 32 act as a pressure reduction means in the scope of the utility model registration claims. Further, the movable coil 41, the permanent magnet 43, the flapper 39, the movable plate 40, the support body 42, and the nozzle 35 operate as pressure changing means within the scope of the utility model registration claims.

In FIG. 3, the booster 4 includes a housing 5
A piston 53 is slidably fitted into the interior of the housing 50 and defines a pressure chamber 51 and an atmosphere open chamber 52; Closed cylindrical member 56
and the stepped hole 57 of the same cylindrical member and the hole 58 of the lid 55.
A plunger 60 is slidably supported within the plunger 60 and is connected to a rod 59 that engages the brake pedal.
and an inlet chamber 63 which is disposed sealingly and slidably within the bore 57 by an annular support 61 and is connected to the outlet passage 21 of the electropneumatic converter 3 via an inlet 62 .
A valve member 64 is interposed between the housing 50 and the piston 53, and urges the piston to the right to abut against the housing 50, while also forcing the stopper 65 of the cylindrical member 56 against the housing. A spring 66 that is brought into contact with the plunger 60, and two springs 67 and 68 that are interposed between the bottom wall of the hole 57 and the plunger 60 and bias the plunger to the right.
, a spring 70 that is interposed between a spring retainer 69 fixed to the plunger 60 and the valve member 64 and biases the valve member to the left; and a support 6
1 and the spring retainer 69,
It has a spring 71 that holds the support in a fixed position relative to the cylindrical member 56 and biases the plunger 60 to the right, and the spring 68 has a shorter natural length than the spring 67. piston 5
3 has a protruding rod 72 connected to the master cylinder 5. Further, the cylindrical member 56 includes
A radially stepped hole 73 communicating with the hole 57 is provided in which a locking pin 74 is slidably fitted to engage a hole 75 drilled in the housing 50. and is biased downward by a spring 76. Boost device 4 shown in Figure 3
In the brake release position, the valve member 64 engages a valve seat 77 provided on the plunger 60 while being separated from a valve seat 78 provided on the housing 50, so that the pressure chamber 51 is in contact with the cylindrical member 56. It is opened to the atmosphere through a passage 79 provided and an exhaust port 80 provided in the housing 50, and the inlet chamber 63 is closed.

In FIG. 4, the variable pressure control valve 7 controls the rear wheel brake oil pressure according to the brake oil pressure from the master cylinder 5 and the oil pressure to the rear wheel brake 8, and according to the vehicle weight. Hole 9
0, an inlet 91 connected to the oil outlet of the master cylinder 5 and an outlet 92 connected to the rear wheel brake 8
a housing 93 having a housing 93 slidably disposed within the bore 90 to bound an inlet pressure chamber 94 and an outlet pressure chamber 95 and cooperating with an annular seal 97 mounted on a step 96 of the bore 90; Both pressure chambers 94 and 9
A piston-shaped valve member 98 that controls communication between 5 and 5.
, the large diameter left end portion 99 of the valve member and the housing 9
The spring 101 is interposed between the valve member 98 and the adjusting screw 100 screwed into the valve member 3 and urges the valve member 98 rightward to the open position shown in FIG. In this open position, the small diameter right end 102 of the valve member 98
is away from seal 97 and land 10
3 is in contact with a plurality of protrusions 104 provided at intervals in the circumferential direction on the seal 97, and the annular lip 105 of the seal 97 is in pressure contact with the inner surface of the hole 90, so that the inlet pressure chamber 94 is land 1
It communicates with the outlet pressure chamber 95 through a plurality of grooves 106 provided on the outer periphery of the valve 03 and a gap between the seal 97 and the valve member 98. The seal 97 is provided with a groove 107 on its bottom and outer circumference that allows oil to flow from the outlet pressure chamber 95 to the inlet pressure chamber 94 when the brake is released. The adjusting screw 100 has an end (not shown) rotatably connected to a drive device 13 such as a motor, and when rotated in one direction, moves toward the valve member 98 to adjust the setting force of the spring 101. When rotated in the opposite direction, it moves away from the valve member 98 and decreases the setting force.

First, the basic operation of the above-mentioned brake device will be explained.

When no pedal force is applied to the brake pedal, the current generator 11 controls the movable coil 4 of the electro-pneumatic converter 3 based on the pedal force signal from the pedal displacement meter 9.
1 is not energized, and the electro-pneumatic converter 3 is in the brake release position shown in FIG. In this position, the valve member 24
is seated on the valve seat 23 and connects the inlet passage 20 and the outlet passage 2.
1, the tubular member 32 is separated from the valve member 24 and opens the outlet passage 21 to the atmosphere via the exhaust chamber 27. In addition, the booster 4 is also the third one.
In the brake release position shown in the figure, the inlet chamber 63 is closed and opened to the atmosphere via the electro-pneumatic converter 3, and the pressure chamber 51 is also opened to the atmosphere, so the booster 4 is No output is given to master cylinder 5.

When applying force to the pedal during braking, current generator 1
1 generates electromagnetic force by energizing the movable coil 41 of the electro-pneumatic converter 3 based on the pedal force signal from the pedal displacement meter 9, and the repulsive force generated between the coil and the permanent magnet 43 causes The flapper 39 and the movable plate 40 are moved downward. Compressed air from the air pressure source 1 flows into the pilot chamber 26 via the inlet passage 20, the pilot passage 34 and the orifice 33;
Furthermore, the air flows out from the atmosphere opening chamber 36 to the atmosphere through the nozzle 35, and as the flapper 39 moves downward and approaches the nozzle 35, nozzle back pressure, that is, pressure is generated in the pilot chamber 26. As a result,
Diaphragms 29 and 30 are pushed downwardly, causing tubular member 32 to engage valve member 24 and interrupt communication between outlet passage 21 and exhaust chamber 27. At the same time, the plunger 60 is moved relative to the cylindrical member 56 via the rod 59 of the booster 4, which is interlocked with the pedal, while first compressing the springs 67 and 71.
4 is seated on the valve seat 78 and connects the pressure chamber 51 and the exhaust port 8.
Cut off communication with 0.

When the pedal force is further applied, the current flowing through the movable coil 41 increases and the repulsive force increases, so that the amount of downward movement of the movable plate 40 increases and the flapper 39 approaches the nozzle 35 further, causing the pilot chamber 26 to move closer to the nozzle 35. The pressure inside increases. As a result, the diaphragms 29 and 30 and the tubular member 32 are pushed downward, pushing the valve member 24 against the spring 25 against the valve seat 2.
3, the compressed air in the inlet passage 20 is made to flow through the outlet passage 21 and is supplied to the inlet chamber 63 of the booster 4. At the same time, rod 59 and plunger 60
However, the spring 68, which has a short natural length, moves further relative to the cylindrical member 56 while compressing the spring 68, and the valve seat 77
is separated from the valve member 64, and the pressure chamber 51 is communicated with the inlet chamber 63 via the passage 79 and the gap between the plunger 60 and the valve member 64. Therefore, the compressed air supplied from the electro-pneumatic converter 3 to the inlet chamber 63 flows into the pressure chamber 51, the pressure in the same chamber begins to rise, and the piston 53 moves to the left against the force of the spring 66. The rod 72 transmits the power to actuate the master cylinder 5 through the rod 72. The compressed air also flows into the hole 73, causing the locking pin 74 to move upwardly against the force of the spring 76 into engagement with the hole 75, so that the cylindrical member 56 is immovably locked relative to the housing 50. Therefore, the only reaction force applied to the pedal is the force of the springs 67, 68, and 71.

The compressed air in the outlet passage 21 of the electropneumatic converter 3 communicating with the pressure chamber 51 of the booster 4 also flows through the passage 3
8 into the pressure chamber 28, and the pressure within the chamber increases. This pressure is acting on the diaphragm 30, and when it increases until it balances with the force due to the pressure in the pilot chamber 26, the spring 25 causes the valve member 24 to sit on the valve seat 23, and the inlet passage 2
0 to the outlet passage 21 is blocked.

In this way, the value of the current flowing through the movable coil 41, the amount of downward displacement of the movable plate 40, and the nozzle back pressure are determined according to the pedal depression force, and therefore
The pressure within the pressure chamber 51 and the output transmitted to the master cylinder 5 are determined.

The brake hydraulic pressure generated by the operation of the master cylinder 5 is supplied directly to the front wheel brake 6 and also to the inlet pressure chamber 94 of the variable pressure control valve 7. Since the valve member 98 is normally in the open position shown in FIG. 4, hydraulic pressure is communicated through the gap between the seal 97 and the valve member 98 to the outlet pressure chamber 95 and is supplied to the rear brake 8, which is equal to the front brake. power and rear wheel braking force.

The valve member 98 has a biasing force to the left due to the outlet pressure in the outlet pressure chamber 95 that acts on a large pressure-receiving area of the right end portion 102, and an inlet pressure chamber that acts on a small pressure-receiving area of the left peripheral edge of the land 103. A biasing force to the right is exerted due to the inlet pressure in 94 and the force of spring 101. Therefore, as the oil pressure from the master cylinder 5 rises, the inlet pressure and the outlet pressure equally rise, and when the above two biasing forces exceed a balanced value (hereinafter referred to as the transition point), the biasing force to the left will shift to the right. The biasing force toward the valve member 9 becomes larger than the biasing force toward the valve member 9.
8 is moved to the left so that the right end 102 is the seal 9
7, communication between the inlet pressure chamber 94 and the outlet pressure chamber 95 is restricted. After the transition point, the outlet pressure is maintained at a value lower than the inlet pressure, corresponding to the ratio between the two pressure-receiving areas of the valve member 98. the result,
After the transition point, the rate of increase in the rear wheel brake force is kept lower than the rate of increase in the front wheel brake force, preventing the rear wheels from locking up.

When the pedal pressure is released when the brake is released, the current from the current generator 11 to the moving coil 41 is stopped.
The movable coil 41 is attracted by the permanent magnet 43 and the movable plate 40 is moved upward, thereby increasing the gap between the nozzle 35 and the flapper 39 and reducing the pressure in the pilot chamber 26. As a result, the diaphragms 29 and 30 are pushed upward, the tubular member 32 is separated from the valve member 24, and the air pressure in the inlet chamber 63 and outlet passage 21 of the booster 4 is reduced to the exhaust chamber 27.
and is exhausted to the atmosphere through the exhaust port 37. Also, springs 67, 68 and 71 push plunger 60 back to the position shown in FIG.
As a result, the air pressure in the pressure chamber 51 is discharged to the atmosphere through the passage 79 and the exhaust port 80 and decreases, the piston 53 is pushed back by the spring 66, and the output to the master cylinder 5 is released.

At the same time, as the oil pressure from the master cylinder 5 decreases, the oil pressure supplied to the front wheel brakes 6 and the variable pressure control valve 7 also decreases. As the inlet pressure in the inlet pressure chamber 94 decreases, the biasing force to the left increases, and the right end 10 of the valve member 98
2 is engaged with the seal 97 to open both pressure chambers 94.
and 95, but the outlet pressure, which is higher than the inlet pressure, flows through the groove 107 to the lip 105.
Since the lip is separated from the surface of the hole 90, the hydraulic pressure in the rear wheel brake 8 is transferred to the outlet pressure chamber 9.
5. Master cylinder 5 through the gap between seal lip 105 and hole 90 and inlet pressure chamber 94.
is discharged to. When the rightward biasing force becomes greater than the leftward biasing force due to the decrease in outlet pressure, the valve member 98 is moved again to the open position shown in FIG.
The oil pressure inside the rear wheel brake 8 is controlled by the seal 97 and the valve member 9.
It is discharged to the master cylinder 5 through the gap between the cylinder 8 and the cylinder 8.

The above operation is performed when the weight of the vehicle is constant. However, if the weight changes, the maximum air pressure that can be generated in the booster 4 is adjusted by the electro-pneumatic converter 3. By adjusting the maximum output of the booster 4 and the maximum brake oil pressure of the master cylinder 5 by adjusting the above, a desired braking deceleration can be obtained regardless of changes in weight. In addition, in the variable pressure control valve 7, the outlet pressure is a constant ratio between the pressure receiving areas and the inlet pressure, and since the pressure receiving area is a constant, the outlet pressure and the force of the spring 101 are proportional to each other. As the spring force increases or decreases, the outlet pressure also increases or decreases, so if the spring force is changed in response to changes in vehicle weight, the transition point of the rear wheel braking force will also change, and the desired front and rear wheel braking force will be adjusted. Brake force distribution can be obtained.

Therefore, the vehicle weight W is detected by the vehicle weight sensor 10, and a weight signal corresponding to this weight W is input to the current generator 11 and the controller 12. Based on this weight signal, the current generator 11 is set in advance to generate the maximum air pressure required in the pressure chamber 51 of the booster 4 in order to generate the optimum maximum braking force according to the vehicle weight. The current flowing through the moving coil 41 of the electro-pneumatic converter 3 is controlled according to the characteristics. Further, based on the weight signal, the controller 12 determines the spring force of the variable pressure control valve 7 suitable for the weight W from preset characteristic data, and adjusts the adjustment screw 10.
0 displacement amount is determined to drive a motor (not shown) of the drive device 13, and the actual displacement amount detected by a tachometer or displacement meter (not shown) is compared with the predetermined displacement amount to provide feedback. It controls.

To explain this control mode, in the electro-pneumatic converter 3, for example, the vehicle weight is set to a value like when the vehicle is empty.
In the case of W ₁ , the current generator 11 applies a small current to the moving coil 41 in accordance with this value, causing the flapper 39 and the moving plate 40 to move downward a relatively small amount.
As a result, the gap between the flapper 39 and the nozzle 35 is relatively large and the nozzle back pressure is small, so that the maximum air pressure generated in the outlet passage 21 and the pressure chamber 51 of the booster is a certain low value. Conversely, when the vehicle weight W is the value W ₃ as at the time of maximum loading, the current generator 11 sends a large current to the coil 41 according to this value, moves the movable plate 40 further downward, and closes the flapper 39. The nozzle 35 is brought very close to the nozzle 35 or completely occluded to increase the nozzle back pressure. Therefore, the maximum air pressure that can be generated within the pressure chamber 51 becomes a certain large value, and the maximum output of the booster 4 increases. If the vehicle weight lies between the values W ₁ and W ₂ , a predetermined intermediate value W ₂ , for example at 1/2 load.
In this case, the current flowing through the coil 41 is controlled by the current generator 11 to a predetermined value according to this value, the nozzle back pressure becomes an intermediate value, and the maximum air pressure in the pressure chamber 51 and the maximum of the booster are controlled. The output is set to a predetermined intermediate value.

By the way, the reaction force when the pedal is depressed is determined by the reaction forces of the springs 67, 68, and 71, and this spring force is determined by the amount of displacement of the plunger 60 with respect to the cylindrical member 56. That is, if the amount of displacement is the same, the pedal effort is the same.

As a result, the value of the current flowing through the movable coil 41 of the electro-pneumatic converter 3 is changed in response to changes in vehicle weight, thereby changing the output of the booster 4 even with the same pedal depression force, and Since the booster is mechanically connected to the master cylinder 5,
The brake hydraulic pressure generated in the master cylinder can also be varied accordingly.

The characteristic of brake force with respect to pedal depression force obtained in this way is shown in FIG.

Next, in the variable pressure control valve 7, the vehicle weight W is set to a value
In the case of W ₁ , the controller 12 rotates the motor of the drive device 13 in accordance with this value, rotates the adjustment screw 100 in one direction and moves it to a predetermined left end position, and therefore moves the valve member 98 to the right. The setting force of the spring 101 that biases the position becomes a predetermined minimum value. As a result, the outlet pressure at the transition point will be at a certain low value. Conversely, when the vehicle weight W is the value _W3 , the controller 12 drives the motor in accordance with this value to rotate the adjusting screw 100 in the opposite direction and move it to a predetermined right end position. As a result,
The setting force of spring 101 is at a predetermined maximum value, and the outlet pressure at the transition point is at a certain high value. The vehicle weight W is an intermediate value W ₂ between the values W ₁ and W ₃
In the case of
1 set force and outlet pressure are set at predetermined intermediate values.

The operation of this variable pressure control valve 7 is controlled by the electro-pneumatic converter 3.
This is done in synchronization with the operation of As a result, even with the same pedal depression force, the brake oil pressure in the master cylinder 5 is continuously changed in response to changes in vehicle weight and is directly supplied to the front wheel brakes 6, resulting in an increase in front wheel brake force as shown in FIG. At the same time, this brake oil pressure is supplied to the rear wheel brake 8 after being lowered to a different pressure value or more, and the front and rear wheel brake force distribution characteristics as shown by the solid line in FIG. 6 are obtained. be.

Therefore, according to the present invention, even if the weight of the vehicle changes, it is possible to obtain a constant deceleration with a constant pedal force, and even when the vehicle weight is light, the rear wheels can be prevented from locking with a small pedal force. Therefore, braking stability and high braking efficiency can be maintained at all times.

In Fig. 6, the dashed line represents the front and rear brake force distribution characteristics by the variable pressure control valve in the case where the front wheel brake force, that is, the brake oil pressure of the master cylinder does not change even if the vehicle weight changes, and the dashed line represents the ideal brake force distribution characteristic. It represents the force distribution characteristics.

In the above embodiment, the spring 101 of the variable pressure control valve 7 is
Although the setting force of the valve member 98 is continuously adjusted, air pressure may be used to continuously change the biasing force that biases the valve member 98 toward the open position.
That is, in a vehicle equipped with an air spring type suspension, the weight of the vehicle and the air pressure of the air spring are proportional. Therefore, this air pressure can be used as a weight signal and as a means for changing the setting force of the spring or a means for changing the urging force of the valve member 98 to the open position.

A modification of the above embodiment shown in FIG. 7 shows an example using pneumatic means, and the same components as those in FIG. 4 will be described with the same reference numerals.

In the variable pressure control valve 7 shown in FIG.
01 is the land 103 of the valve member 98 and the inlet pressure chamber 9
4, and biases the valve member 98 to the open position with a predetermined setting force. Further, the left end portion 99 of the valve member 98 is sealingly and slidably engaged with the inner surface of the hole 90 so that the end wall of the hole 90 limits the control pressure chamber 109 . This control pressure chamber 109 is directly connected to the air spring via an inlet 110. Other structures are the same as those in FIG.

The operation of this variable pressure control valve 7 is substantially the same as that shown in FIG. A biasing force to the right is exerted by the air pressure inside the vehicle, and since this air pressure is proportional to the weight of the vehicle, the valve member 98 is biased to the right to the open position in response to the change in weight. The biasing force changes, and the transition point of the rear wheel braking force changes.

Therefore, this modification can also achieve the same effects as the above embodiment.

Although the preferred embodiments of the present invention have been illustrated and described, the present invention is not limited thereto, and can be modified in many ways.

For example, the valve member 98 of the variable pressure control valve 7 may respond only to the pressure in the outlet pressure chamber instead of responding to the pressure in the inlet pressure chamber and the outlet pressure chamber as in the above embodiment. In this case,
The valve member has a biasing force due to the outlet pressure acting on its pressure-receiving area, a biasing force due to a variable force of a spring as shown in FIG. 4, or a constant force of a spring and added thereto as shown in FIG. This structure controls the outlet pressure by balancing the biasing force generated by the variable air pressure.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an overview of an air servo brake device showing an embodiment of the present invention, and Fig.
Fig. 3 is a detailed sectional view of the booster shown in Fig. 1, Fig. 4 is a detailed sectional view of the variable pressure control valve, and Fig. 5 is a detailed sectional view of the brake force relative to the pedal depression force. FIG. 6 is a distribution characteristic diagram of front and rear wheel brake force, and FIG. 7 is a detailed sectional view of a variable pressure control valve showing a modification of the present invention. 1...Air pressure source, 2...Accumulator, 3...
...Electro-pneumatic converter, 4... Booster, 5... Master cylinder, 6... Front wheel brake, 7... Variable pressure control valve, 8... Rear wheel brake, 9... Pedal displacement meter, 10... Vehicle weight sensor, 11... Current generator, 12... Controller, 13... Drive device.

Claims (1)

[Claims for Utility Model Registration] An air pressure source that supplies compressed air, and a booster that has an inlet for supplying compressed air and amplifies and outputs the force applied to the brake pedal according to the pressure of the compressed air supplied to the inlet. A master cylinder that is activated by the output of the booster to generate brake fluid pressure, a front wheel brake and a rear wheel brake that are activated by the same brake fluid pressure, and detects the pressing force of the brake pedal and responds to the pressing force. a pedal displacement meter that outputs a pedal force signal that is an electrical signal; a vehicle weight sensor that detects the vehicle weight and outputs a weight signal that is an electrical signal corresponding to the same weight; an inlet passage that communicates with the air pressure source; and the booster. an outlet passage communicating with the inlet of the device; a pilot chamber into which the pressure in the inlet passage is introduced; a pressure chamber into which the pressure in the outlet passage is introduced; and a first action responsive to the pressure in the pilot chamber. When the first acting force is larger than the second acting force, the inlet passage and the outlet passage are communicated with each other, and the above-mentioned If the second acting force is larger than the first acting force, the communication means blocks the inlet passage and the outlet passage, and the communication means connects the inlet passage and the outlet passage. pressure reducing means for reducing the pressure in the exit passage when the brake pedal is shut off; and pressure reduction means for increasing the pressure in the pilot chamber when the depression force on the brake pedal increases based on the depression force signal, and reducing the vehicle weight based on the weight signal. an electro-pneumatic converter comprising a pressure changing means for reducing the pressure in the pilot chamber when the pressure decreases; a pressure control valve that reduces the brake fluid pressure supplied to the rear wheel brakes when the pressure exceeds a predetermined pressure value; and a pressure control valve that starts reducing the brake fluid pressure in response to a change in the vehicle weight based on the weight signal. A brake device comprising means for controlling the operation of the pressure control valve so as to change the pressure value.