JPH05466Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a brake pressure control device for a vehicle.

[Prior art] Large vehicles have large axle loads, so brake boosters that use pneumatic pressure are installed, but since the axle load when an empty vehicle is much smaller than when it is loaded, the braking force is reduced when the vehicle is empty. It may become too large and the wheels may lock. If the wheels lock up while the vehicle is running, the vehicle body may turn, creating a dangerous situation.

In the brake pressure control device disclosed in JP-A-52-122775 (Fig. 4), a hollow rod having an exhaust port is connected to an upper membrane supported by a case, and a supply valve surrounding the upper end of the hollow rod is connected to an upper membrane supported by a case. The upper chamber of the bulkhead having an air port communicates with a source of air pressure, and the vacuum chamber below the bulkhead is provided with an outlet communicating with the brake. The valve is brought into contact with the air supply and exhaust ports by spring force. At the lower end of the case, a chamber partitioned by a lower membrane is provided with a passage communicating with the air spring. A spring is accommodated in the atmospheric chamber between the pair of upper and lower membranes. The air pressure of the air spring acting on the lower membrane acts through the spring on the upper membrane, pushing up the hollow rod,
The air intake is open.

When the brakes are applied, pressurized air from the air pressure source enters the inlet,
It is supplied to the brakes via the air supply port, decompression chamber, and outlet. At this time, the brake pressure acts on the upper surface of the upper membrane, so the hollow rod is pushed down, the exhaust port opens, and the air supply port closes. Brake pressure is released from the inner space of the hollow rod to the atmosphere through the atmospheric chamber, and eventually the hollow rod is pushed back, closing both the air supply and exhaust ports. By repeating the above-described operations, the pressurized air from the air pressure source is reduced in pressure in accordance with the air pressure of the air spring, and is supplied to the brake.

However, in the brake pressure control device described above, when the air pressure in the decompression chamber acts on the upper membrane against the spring force, the hollow rod is pushed down excessively and the exhaust port opens, causing the air pressure (brake pressure) in the decompression chamber to decrease. When the brake pressure becomes low, the hollow rod is pushed up excessively by the spring together with the upper membrane, causing the air supply port to open repeatedly, which tends to cause brake pressure to pulsate, which may impede smooth braking action. .

[Problems to be solved by the invention] The purpose of the invention is to properly control the brake pressure according to the shaft load, that is, the air pressure of the air spring, and in particular to obtain smooth braking action without pulsating the brake pressure. An object of the present invention is to provide a brake pressure control device for a vehicle.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention is such that a hollow piston is inserted into a small diameter cylinder formed on the upper end wall of a cylindrical case, and a pressurized air introduction chamber is defined on the upper side. , a flange having a conical surface is integrally provided at the lower end of the hollow piston, an annular membrane is connected to and away from the conical surface between the center side of the flange and the inner peripheral wall of the case, and an atmospheric chamber is formed above the membrane. Decompression chambers are divided under the membrane, an air supply port is provided in the hollow part of the hollow piston to communicate the pressurized air introduction chamber to the decompression chamber, and the piston is fitted into a small diameter cylinder connected to the lower end wall of the case. An atmospheric chamber is partitioned on the upper side, and an operating chamber communicating with the air spring is partitioned on the lower side, and a rod connected to the piston protrudes from the air supply port of the hollow piston with a gap, and connects to the exhaust port at the upper end of the rod. A passage communicating with the atmospheric chamber is provided inside the rod, and a pressure reducing valve which is urged into engagement with the air supply port and the exhaust port by a spring force is supported by a hollow piston.

[Operation] The hollow piston is provided with an air supply port in its hollow portion, through which the pressure reducing valve is biased by a spring force. The air pressure of the air spring acts on the piston from the lower working chamber of the small diameter cylinder at the lower end of the case, bringing the rod into contact with the pressure reducing valve. The rod has an exhaust port in contact with the pressure reducing valve, and the exhaust port communicates with an atmospheric chamber above the small diameter cylinder.

During braking, pressurized air is supplied to a small diameter cylinder at the top of the case, which pushes down the hollow piston. Since the pressure reducing valve is regulated by the rod, the air supply port of the hollow piston opens, and pressurized air enters the pressure reducing chamber through the hollow part of the hollow piston and is supplied to the brake.

At this time, the air pressure in the pressure reduction chamber acts on the conical surface of the flange through the membrane, pushing up the hollow piston and bringing the air supply port of the hollow piston closer to the pressure reduction valve. The contact area between the membrane and the conical surface of the flange changes depending on the air pressure in the decompression chamber, and the hollow piston changes depending on the force exerted on the upper end surface by the air pressure of the small diameter cylinder at the upper end of the case.
It is statically fixed at a position where the force exerted by the air pressure in the decompression chamber on the conical surface of the flange is balanced. In this way, the pressurized air in the small diameter cylinder at the upper end of the case is reduced in pressure to a value corresponding to the air pressure in the air spring between the air supply port of the hollow piston and the pressure reducing valve.

[Embodiment of the invention] As shown in FIG. 1, the cylindrical case 45 of the brake pressure control device has a divided body 45 that is approximately cup-shaped.
The periphery of the membrane 64 is sandwiched between the membrane 64 and the divided body 45b. A hollow piston 69 connected to the inner edge of the annular membrane 64 is fitted with a seal 60 and slidably fitted into a small diameter cylinder 70 formed at the upper end of the divided body 45a. The upper chamber of the small diameter cylinder 70 forms a pressurized air introduction chamber 42a, and the inlet 42
is connected to the air tank via the brake valve.

The inside of the case 45 has an air port 57 formed by a membrane 64.
It is divided into an atmospheric chamber 46 having an outlet 51 and a decompression chamber 63 having an outlet 51. The flange 68, which is integral with the lower end of the hollow piston 69, is formed with a conical surface 68a on its lower surface that contacts and separates from the membrane 64. The divided body 45b has a cylindrical portion 48a formed on the cylindrical wall 48 of the axis, and a small diameter cylinder 48b formed on the lower end wall. Cylindrical part 4
8a is the large diameter portion 50a of the rod 50, and the small diameter cylinder 48b is the piston 50b that connects the rod 50.
are slidably fitted through seals 80a and 80b, respectively, thereby configuring the actuator 71.

The inner space of the rod 50, that is, the exhaust passage 58 is
An exhaust port 58a is opened at the upper end, and the piston 50
It communicates with the atmospheric chamber 59a through a radial passage 59 provided in a portion adjacent to b. Small diameter cylinder 48b
The piston 50b connects an atmospheric chamber 59a that accommodates the spring 47 and an operating chamber 90a that communicates with the air spring.
It is divided into That is, the lower working chamber 90a communicates with the inside of the air spring of the suspension system (not shown) through the passage 90 and the entrance/exit 91.

The lower end of the small diameter cylinder 48b is a cylindrical portion 53a.
It is closed by a plug 53 having a diameter. Cylindrical part 5
3a fits the lower end 50c of the rod 50 with the eel 80c attached. The cylindrical portion 53a communicates with the pressurized air introduction chamber 42a through a pipe 67, and the rod 5
This cancels out the air pressure acting on the top and bottom ends of 0. The upper end of the rod 50 is brought into contact with the pressure reducing valve 61 by the force of the spring 47 in the atmospheric chamber 59a.

The pressure reducing valve 61 includes a hollow portion 55 of a hollow piston 69;
In detail, the valve chamber 41 formed at the upper end of the hollow part 55
supported inside. The pressure reducing valve 61 is biased and engaged by the spring 44 to a hollow portion 55 connecting the pressurized air introduction chamber 42a and the pressure reducing chamber 63, that is, an air supply port 56 (FIGS. 2 and 3).

Next, the operation of the device of the present invention will be explained. When the load of the vehicle is large, the air pressure of the air spring is high and the pressure reducing valve 61 is in the state shown in the figure. now,
When the brake pedal is pressed, the brake valve opens and pressurized air from the air tank flows from the inlet 42 to the small diameter cylinder 70.
and press down the hollow piston 69. Since the pressure reducing valve 61 is held down by the rod 50, the air supply port 56 of the hollow piston 69 opens. The pressurized air in the pressurized air introduction chamber 42a of the small diameter cylinder 70 enters the decompression chamber 63 via the air supply port 56 and the hollow portion 55 (FIG. 2).

When the air pressure in the pressure reduction chamber 63 becomes high, the hollow piston 69 is pushed up and comes into contact with the pressure reduction valve 61, blocking the inflow of pressurized air and achieving an equilibrium state. The pressurized air in the vacuum chamber 63 is sent to the brake via the outlet 51. The pressure reduction ratio of the air pressure at the outlet 51 to the air pressure at the inlet 42 is inversely proportional to the effective pressure receiving area of the upper and lower end surfaces of the hollow piston 69.

The pressure receiving area of the upper end surface of the hollow piston 69 is equal to the cross-sectional area of the small diameter cylinder 70;
The pressure receiving area of the lower end surface of 9 is the membrane 64 and the hollow piston 6.
This is the contact area of the flange 68 of No. 9 with the conical surface 68a. The contact area of the membrane 64 is determined by the equilibrium position of the hollow piston 69, ie the position of the pressure reducing valve 61, which in turn is determined by the position of the rod 50.

When the carrying load of the vehicle is small, the air pressure of the air spring acting from the entrance/exit 91 to the small diameter cylinder 48b is low, and the piston 50b and rod 50 are at a lower position than shown. When you press the brake pedal,
The brake valve opens and pressurized air from the air tank enters the inlet 42.
enters the small diameter cylinder 70 from the hollow piston 69
Press down. The pressurized air of the small diameter cylinder 70 enters the decompression chamber 63 through the air supply port 56 and the hollow part 55.
Push up the hollow piston 69. hollow piston 6
9 is lower than the illustrated position, and the pressure reduction ratio becomes smaller as shown by the broken line in FIG.

In the loaded state, the decompression ratio is almost 1, but
When the vehicle is empty, the air pressure is halved, and even if you press the brake pedal hard, the high air pressure that occurs when the vehicle is loaded does not affect the brakes. In other words, a braking force corresponding to the axle load is obtained, and there is no fear that the wheels will lock even when the axle load is small, ensuring safe driving.

Since the small diameter cylinder 70 and the cylindrical portion 53a in which the lower end brake 50c of the rod 50 is fitted are connected through the pipe 67, the rod 50 is stably held in a predetermined position by the air pressure of the air spring, and when the brake is applied, the small diameter cylinder 70 The rod 50 is not swayed by the air pressure of the pressurized air supplied to the rod 50, and maintains a stable pressure reduction ratio corresponding to the air pressure of the air spring.

When the brake is released, the small diameter cylinder 70 becomes atmospheric pressure, the air pressure in the pressure reducing chamber 63 pushes up the hollow piston 69, and the pressure reducing valve 61 closes to the rod 5.
Since the exhaust port 58a at the upper end of the brake is opened, the air pressure of the brake is released to the atmospheric chamber 59a through the outlet 51, the decompression chamber 63, the hollow part 55, the exhaust port 58a of the rod 50, the passage 58, and the passage 59.

[Effect of the invention] In the brake pressure control device according to the invention, the membrane is pushed up by the air pressure in the decompression chamber, and as the piston rises, the contact area between the membrane and the flange gradually decreases, so the force pushing up the hollow piston becomes weaker. , the air supply port of the hollow piston will come into contact with the pressure reducing valve slowly, and the hollow piston will not move too far upward and the pressure reducing valve will be separated from the exhaust port at the upper end of the rod.

In other words, when the brakes are applied, pressurized air from the air pressure source is initially supplied to the brakes as is, but
The air pressure supplied to the brakes gradually decreases,
The air pressure is statically determined to be reduced in accordance with the air pressure of the air spring. Therefore, the air pressure supplied to the brake does not pulsate and cause the brake to become jerky, and extremely smooth braking can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of the brake pressure control device for a vehicle according to the present invention, Figs. 2 and 3 are front sectional views showing the opposite operating states of the pressure reducing valve, and Fig. 4 is the brake pressure control device for the same vehicle. FIG. 42a...pressurized air introduction chamber, 44...spring, 4
5...Case, 46...Atmospheric chamber, 48b, 70...
...Small diameter cylinder, 50...Rod, 50b...Piston, 55...Hollow part, 56...Air supply port, 58
... Passage, 58a... Exhaust port, 59a... Atmospheric chamber, 61... Pressure reducing valve, 63... Pressure reducing chamber, 64...
Membrane, 68...flange, 68a...conical surface, 69
...Hollow piston, 90a... Working chamber.

Claims (1)

[Scope of utility model registration request] A hollow piston is fitted into a small-diameter cylinder formed on the upper end wall of the cylindrical case to define a pressurized air introduction chamber on the upper side, and a flange with a conical surface is integrally provided at the lower end of the hollow piston. An annular membrane is connected to the inner circumferential wall and separates from the conical surface, and an atmospheric chamber is defined above the membrane, a decompression chamber is defined below the membrane, and a pressurized air introduction chamber is formed in the hollow part of the hollow piston. The piston is fitted into a small-diameter cylinder connected to the lower end wall of the case, and the atmospheric chamber is divided into the upper side and the working chamber which communicates with the air spring is divided into the lower side. The connected rod projects into the air supply port of the hollow piston with a gap, and a passage is provided inside the rod that communicates the exhaust port at the upper end of the rod with the atmospheric chamber, and a spring force is applied between the air supply port and the exhaust port. A brake pressure control device for a vehicle, characterized in that a pressure reducing valve that is biased and engaged by a hollow piston is supported by a hollow piston.