JPS643698B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a hydraulic braking device for an automobile, which includes a hydraulic main cylinder having a replenishment container and a relief hole, and hydraulic wheels to which braking fluid is supplied from the main cylinder. This invention relates to a brake cylinder and an anti-skid device. Publication of this kind (Federal Republic of Germany Patent Application Publication No.
2705467) in the hydraulic braking device,
If the braking device has a high stiffness, i.e. a small volume capacity, a high system pressure is created during braking before the piston cup of the piston of the main brake cylinder passes through the cylinder relief hole and into the cylinder; The piston cup may be damaged. In brake systems with anti-skid devices, the risk of piston cup breakage is doubled. That is, the piston of the brake main cylinder is pushed back in the direction of the starting position during the anti-skid action, and the primary cup of the piston cup of the piston passes through the relief hole again while the system pressure remains high. Broken primary cups often occur.

In contrast, the braking device having the features set forth in claim 1 of the present invention bypasses the throttling portion that causes the throttling action during emergency braking of the anti-skid device, thereby reducing excessive pressure during emergency braking. This has the advantage that damage to the piston cup due to excessive pressure rise can be avoided.

Next, embodiments of the present invention will be specifically described using the drawings.

A hydraulic braking system for a motor vehicle has a two-circuit tandem main cylinder 1 with supplementary containers 2 or 3 which are combined in a common casing, each of which has one supplementary hole. 4 or 5 and in each case one relief hole 6 or 7 to the corresponding primary and secondary chambers in the main cylinder 1. A brake circuit leads from the main cylinder 1 to a pair of wheel cylinders 8 and 9 and 10 and 11, respectively. An anti-skid device 12 or 13 is arranged in each brake circuit and in each anti-skid device, and within these anti-skid devices each brake circuit and a separate brake circuit 14 for each wheel cylinder 8 and 9 and 10 and 11 are arranged. It is divided into 15, 16, and 17. Furthermore, the antiskid device 12 includes one pressure accumulator 18, which can optionally be configured as an absorption device, one pressure accumulator 20, two solenoid valves 22 and 2.
3, one suction valve 26, one discharge valve 28 and 1
The antiskid device 13 has one pressure accumulator 19, one pressure accumulator 21, which may optionally be configured as an absorption device;
Two solenoid valves 24 and 25, one suction valve 27, 1
It has two discharge valves 29 and one return conveyance pump 31, and both conveyance pumps are driven by a common motor 3.
2.

Furthermore, in one or both braking circuits, a bypass channel 33 is provided between the main cylinder and the wheel cylinder, by means of which the antiskid device 12 or the antiskid devices 12 and 13 can be bypassed. An absorption device 35 is arranged within the bypass passage 33 . This absorption device 35 essentially consists of a piston 39 which is slidable in a housing 37 against the force of a spring 38.

The absorption devices optionally installed in the pressure accumulators 18 and 19 are combined with the pressure accumulation chamber of the return pump, which is necessary for the antiskid system.
Such an absorption device is shown in FIG. 5, and includes a piston 40 which is initially subjected to the spring force of a spring 41 during the working stroke. Next, the piston 40
After a predetermined stroke of 0, another spring 42 with a predetermined initial tension comes into play.

The absorption chamber 43 is connected via a suction valve 26 or 27 to a return pump 30 or 31 and via check valves 44, 44' to a branch channel 48 or 48' leading to the main cylinder.
If an anti-skid effect is to be produced, the absorption chamber (pressure accumulator 18 or 19) is connected to the solenoid valves 22 and 2.
3 or via 24 and 25 wheel cylinder 8
and 9 or 10 and 11.

The absorption chamber built into the pressure accumulator 20 or 21 is connected to the pump outlet valve (discharge valve 28 or 29).
is connected via a return pump 30 or 31 to a branch channel 48 or 48' which returns to the main cylinder 1, if appropriate via a check valve 49. The absorption devices in the pressure accumulators 20 and 21 are constructed in the same way as the absorption device 35. In the inactive state, the piston of this absorption device rests against a stop and has a predetermined working stroke by means of a prestressed spring.

A conduit 50 with a check valve 51 is shown between the low-pressure side and the high-pressure side, which can optionally be used if pressure compensation needs to be performed due to temperature changes.

During normal braking, brake fluid is pumped from the foot-operated main cylinder 1 through the opened solenoid valves 22, 23, 24 and 25 of the anti-skid device to the wheel cylinders 8, 9, 10 and 11;
The brakes are applied. When the operating pressure is reduced, the brake fluid is directed toward the main cylinder 1 again and is released. During a normal braking process, main cylinder 1
The piston cups of both pistons in the piston are not damaged when moving past the relief holes 6 and 7. This is because the pressure created in the brake system when the piston cup of the piston passes over the relief hole is not particularly high.

However, if emergency braking is required,
The driver quickly depresses the brake pedal fully. In this case, especially if the elasticity of the brake system is low, already excessively high pressures can suddenly build up when the piston cup of the piston passes over the relief holes 6 and 7, especially the relief hole 7 of the brake circuit opposite to the pedal. , the piston cup of the piston may therefore be damaged.

However, in such an emergency braking event, according to the invention, the absorption device 35 is activated and this piston 39 moves against the spring force of the spring 38. Therefore, the brake fluid bypasses the throttling points of the anti-skid device, which cause the device-specific throttling, and is fed directly into the brake cylinders 8 and 9 or 10 and 11, which conventionally already occurs when the piston cup passes through the relief hole. The sudden pressure increase that occurred can be avoided.

If one or more of the wheels locks up during a braking process, the anti-skid device 12 or 13 is activated and the brake fluid is removed from the wheel cylinders 8, 9, 10 and 11 and transferred to the return pumps 30 and 31. is returned to the main cylinder 1 by. In this case, in the known brake system, the piston cup of the main cylinder 1 is forced to pass through the relief holes 6 and 7 again under high pressure in the brake fluid conduit, which may also damage the piston cup. .

This is avoided according to the invention because the brake fluid is not returned directly to the main cylinder by means of the return pump 30 or 31, but is instead sent into the absorption device. For this purpose, the discharge side of the return pump 30 or 31 is shut off from the main cylinder 1 by means of a check valve 49, which is necessary in order to keep the piston cup on the discharge side of the return pump away from the area of the relief holes 6 and 7. A storage volume corresponding to the volume at a piston stroke distance of 1 cm ³ to 2 cm ³ is created. The transfer of the received brake fluid from the absorption device (pressure accumulators 20 and 21) to the main cylinder 1 takes place only after the main cylinder 1 is depressurized and the check valve 49 is then opened.

FIG. 4 shows a diagram of another embodiment combined with a damping device.

Also, in order to avoid high conduit pressure when the piston cup passes through the relief hole, instead of providing a similar device on the outlet side of the return pump,
It is also possible to provide it on the inlet side of the return conveyance pump. For this purpose, the pressure accumulators 18 and 19 are provided with an absorption volume which receives the required amount of brake fluid in a pressure range that is smaller than the pressure range of the opening pressure of the absorption valve 26 or 27 of the pump. In this way, during the antiskid process, ie when the pressure drops in the wheel cylinders, the brake fluid from the wheel cylinders fills the absorption volume and is subsequently returned to the main cylinder.

The reference P ₂ in FIGS. 3, 4 and 6 designates the starting point of the device which allows the volume variation of the brake fluid.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, in which FIG. 1 is a schematic diagram of a two-circuit brake system with two types of devices for bypassing the throttling point of the anti-skid device, and FIG. A sectional view of the absorption device of the transfer pump, FIG. 3 is a characteristic curve diagram of the embodiment shown in FIG. 2, FIG. 4 is a characteristic curve diagram of the combination of the absorption device and a buffer device, and FIG. FIG. 6 is a characteristic curve diagram of the embodiment of FIG. 5. 1... Main cylinder, 2 and 3... Compensation container, 4 and 5... Compensation hole, 6 and 7... Relief hole, 8, 9, 10 and 11... Wheel cylinder, 12 and 13... Anti-skid device, 14, 15, 16 and 17... Brake passage, 18, 19, 20 and 21... Pressure accumulator, 22,
23, 24 and 25...Solenoid valve, 26 and 27...Suction valve, 28 and 29...Discharge valve, 30 and 31...Return conveyance pump, 32...Motor, 33...Bypass passage, 35...Absorption device, 37...Casing, 38 …
Spring, 39... Piston, 40... Piston, 41...
Spring, 42... Spring, 43... Absorption chamber, 44 and 4
4'...Check valve, 48 and 48'...Branch passage, 49...
Check valve, 50... Conduit, 51... Check valve, and...
Braking circuit.

Claims (1)

[Scope of Claims] 1. A hydraulic braking device for an automobile, comprising a hydraulic main cylinder having a replenishment container and a relief hole, and a hydraulic wheel brake cylinder supplied with braking fluid from the main cylinder. In the type equipped with an anti-skid device, a passage bypassing the throttling points of the anti-skid devices 12 and 13 between the main cylinder 1 and the wheel brake cylinder in order to prevent the pressure in the main cylinder from increasing excessively. 1. A hydraulic braking device for an automobile, characterized in that a device is provided therein to enable unrestricted volume variation of a braking fluid. 2. Braking device according to claim 1, wherein the device for making it possible to change the volume of the braking fluid consists of a connectable and disconnectable absorption device for absorbing the volume changes of the braking fluid. 3 Return pump 3 for the brake fluid removed from the wheel cylinders during the anti-skid process
0, 31, an absorption device is arranged in the region of the return pumps 30, 31, and the absorption volume chamber of this absorption device is closed to the main cylinder 1 by a check valve 49. 3. The braking device according to claim 2, wherein the braking fluid in the absorption volume chamber is discharged toward the main cylinder only when the main cylinder is depressurized. 4. The braking device according to claim 3, wherein the absorption device is arranged on the discharge side of the return conveyance pumps 30, 31. 5. The braking device according to claim 3, wherein the absorption device is arranged on the suction side of the return conveyance pumps 30, 31. 6. The braking device according to claim 5, wherein the check valve is adjusted to an opening pressure that is lower than the opening pressure of the inlet valves of the return conveyance pumps 30 and 31. 7 The absorption volume chamber of the suction device returns to the transfer pump 3
6. The braking device according to claim 5, wherein the braking device is filled with a pressure lower than the opening pressure of the inlet valve of 0.31. 8 from the main cylinder 1 to the brake cylinders 8, 9, 10, 1 in parallel to the brake passages 14, 15, 16 and 17 with anti-skid devices 12, 13;
A bypass passage 33 leading to 1 is provided,
The braking device according to claim 1, wherein an absorption device 35 is incorporated in the bypass passage. 9. The braking device according to claim 8, wherein the absorption device 35 has a piston 39 that performs a stroke corresponding to a displacement amount of 1 cm ³ to 2 cm ³ .