JPS6328821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a master cylinder used in a hydraulic brake system of an automobile, etc., and in particular to a so-called fast-fill master cylinder that rapidly supplies hydraulic fluid to a pressure chamber for the purpose of reducing the piston stroke during operation.
This relates to improvements to the fill-type master cylinder.

In disc brakes, when reducing the distance between the brake disc and the brake pads that pinch it, the brake pads are dragged by the brake disc, causing abnormal wear of the pads, power loss, and even abnormal noise, which can lead to the worst case scenario. In this case, vapor lock may cause braking failure. Therefore, it is necessary to increase the above-mentioned interval to some extent, but in this case, the loss stroke of the brake system becomes large, and the brake pedal's pedal travel increases, which inevitably deteriorates the operating feeling.

A first-fill type master cylinder is used, for example, in such a brake system, and is useful for offsetting the above-mentioned large stroke loss with the reduction in piston stroke, and as a result, keeping the brake pedal travel small.

This type of master cylinder is known, for example, from US Pat.
It is well known as described in the specification of No. 4133178. A conventional master cylinder of this kind, typified by the one disclosed in this U.S. patent specification, includes a stepped piston defining a supply chamber between a large diameter portion and a small diameter portion thereof, and a stepped piston defining a supply chamber between a large diameter portion and a small diameter portion of the stepped piston. The end face of the small diameter part faces the pressure chamber, and a differential pressure valve is installed between the reservoir tank and the supply chamber that opens in response to a pressure above a certain level in the supply chamber, and the hydraulic fluid flow from the supply chamber to the reservoir tank is A check valve is provided to prevent the stepped piston from
During the piston pushing stroke in which the small diameter portion of the piston is pushed toward the pressure chamber to close the relief port communicating between the reservoir tank and the pressure chamber and generate output hydraulic pressure within the pressure chamber, the stepped piston moves into the supply chamber. The hydraulic fluid is supplied from the supply chamber to the pressure chamber by generating a set pressure in the supply chamber under the action of the differential pressure valve and opening a piston cup on the small diameter portion of the stepped piston. Ru. Further, in the return process of the stepped piston, the hydraulic fluid in the reservoir tank is supplied to the supply chamber whose volume increases through the check valve to correct the amount of hydraulic fluid in the supply chamber. According to this configuration, the piston stroke, that is, the master cylinder operating amount can be reduced by the amount of hydraulic fluid supplied to the pressure chamber during the pushing stroke of the stepped piston.

In the conventional first-fill type master cylinder, after the brake system has been assembled, hydraulic fluid is injected into the cylinder from the reservoir tank, and the above-mentioned U.S. patent specification shows that the cylinder can be filled while removing air by repeatedly pushing the stepped piston. As shown in the figure, the differential pressure valve was kept open when the master cylinder was not in operation, and was configured as a normally open type from which air could be vented. However, if the differential pressure valve is opened in this way, the hydraulic fluid in the supply chamber escapes from the normally open differential pressure valve to the reservoir tank at the beginning of the pushing stroke of the stepped piston until the differential pressure valve closes, and the pressure increases from the supply chamber. Since the hydraulic fluid cannot be delivered to the chamber and the first fill function cannot be obtained during this time, the operational feeling is adversely affected. Therefore, it is preferable that the differential pressure valve is kept closed except when it is opened in response to the internal pressure of the supply chamber.

Therefore, conventionally, a so-called normally closed master cylinder has been proposed, as in Japanese Utility Model Application Publication No. 56-40062, in which the differential pressure valve is closed even when the master cylinder is not in operation, except when it is opened in response to the internal pressure in the supply chamber. It was done. In this master cylinder, in order to solve the problem of air bleed caused by the normally closed type, the check valve is opened by the negative pressure generated in the supply chamber during the return stroke of the stepped piston, and the check valve is then supplied from the reservoir tank. Hydraulic fluid can be supplied to the chamber, and mixed air can be removed from an air bleed valve at the end of the brake system by progressively feeding the hydraulic fluid through the pushing stroke of the stepped piston.

However, with the conventional normally closed master cylinder,
When the stepped piston is pushed in, the relief port, which is blocked by its small diameter portion, allows direct communication between the reservoir tank and the pressure chamber when the master cylinder is inactive, so the pressure chamber is brought to atmospheric pressure when the master cylinder is inactive. On the other hand, during the return stroke of the stepped piston, when hydraulic fluid is supplied from the reservoir tank via the check valve, the supply chamber is brought to a negative pressure lower than atmospheric pressure by the amount of the check valve's opening pressure, and the master cylinder's Maintain this negative pressure during operation. Therefore, at the beginning of the next pushing stroke of the stepped piston, during the piston stroke from the negative pressure in the supply chamber to a positive pressure higher than atmospheric pressure in the pressure chamber, the pressure from the supply chamber passes through the piston cup to the pressure chamber. No hydraulic fluid flow occurs and first fill function cannot be obtained. Correspondingly, the pedal stroke becomes longer, resulting in deterioration of the operational feeling, and the efficiency of filling the hydraulic fluid with respect to the piston pushing stroke, and therefore the efficiency of air removal, is poor, and it takes a long time to remove the air.

In order to solve this problem in normally closed type master cylinders, the present invention is configured such that the relief port is connected to the supply chamber and the relief port communicates between the reservoir tank and the pressure chamber via a check valve.

According to the configuration of the present application, the relief port makes the pressure chamber and the supply chamber the same pressure when the master cylinder is in the inactive state, and a pressure difference is generated in both spaces at the same time as the stepped piston starts to be pushed. A flow of hydraulic fluid can be generated from the chamber through the piston cup to the pressure chamber. For this reason,
The first-fill function starts at the same time as the stepped piston starts pushing, so the pedal stroke does not become long and the operation feeling deteriorates, and the filling efficiency of the hydraulic fluid and therefore the air removal efficiency with respect to the piston pushing stroke are improved. It doesn't get worse and the time it takes to bleed the air becomes longer.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an example of the master cylinder of the present invention configured as a tandem master cylinder, in which 1 is a cylinder body, 2 is a reservoir tank, 3 is a primary piston fitted into the cylinder body 1, and 4 is also a cylinder body 1. It is a secondary piston fitted inside.

The primary piston 3 is stepped, the large diameter part 3a is fitted into the large diameter hole 1a near the open end of the cylinder body 1 under liquid-tight sealing by the lip seal 5, and the small diameter part 3b is fitted into the closed end of the cylinder body 1. It fits into the small diameter hole 1b nearby to define a supply chamber 10 between the large diameter part 3a and the small diameter part 3b, and also forms a communication hole 6 in the small diameter part 3b. A recess 3c is formed on the right end surface of the stepped primary piston 3 in the figure, into which the tip of a push rod 8, which moves to the left in the figure when depressed in conjunction with the brake pedal, enters.

A piston cup 9 is provided at the end of the primary piston 3 far from the push rod 8, and its outer circumferential lip portion slides against the inner circumferential surface of the small diameter hole 1b to close the communication hole 6.
0 through the communication hole 6, and is arranged in a direction that allows the flow of hydraulic fluid to flow out from the hole 6 and blocks the flow of hydraulic fluid in the opposite direction. A screw 11 is installed on the end face of the primary piston 3 far from the push rod 8, and its shaft guides a pair of spring seats 12 and 13, and a spring 14 is compressed between these spring seats.
The spring seats 12, 13 are kept in the illustrated position where they are furthest apart from each other. Further, the stopper pin 7 is screwed into the cylinder body 1 so as to engage with the spring seat 13, thereby preventing the primary piston 3 from coming off via the spring seat 13 and the screw 11.

The secondary piston 4 has land portions 4a, 4 at both ends.
b is fitted into the small diameter hole 1b, and a lip seal 15 is provided between the land portion 4a and the inner peripheral surface of the small diameter hole 1b to perform a seal between the two, and the land portion 4b
A communicating hole 21 is formed in the secondary piston 4, and a piston cup 22 for closing the communicating hole 21 is provided in the secondary piston 4. Thus, a pressure chamber 16 is defined between the primary piston 3 and the secondary piston 4, and a pressure chamber 17 is defined between the secondary piston 4 and the closed end of the cylinder body 1. These pressure chambers 1
Hydraulic pressure outlet ports 18, 19 communicating with the cylinders 6, 17 are formed in the cylinder body 1, allowing output hydraulic pressure to be taken out through these ports. Note that the piston cup 22 has its outer circumferential lip portion slidably in contact with the inner circumferential surface of the small diameter portion 1b to close the communication hole 21, but this piston cup allows the flow of hydraulic fluid from the communication hole 21 toward the pressure chamber 17. Oriented to prevent reverse hydraulic fluid flow.

A return spring 20 is compressed between the secondary piston 4 and the closed end of the cylinder body 1, and thereby the secondary piston 4 is brought into contact with the spring seat 13 in its original position as shown, and the primary piston 3 is brought into contact with the spring seat 13. It is held in its original position as shown in the figure, where it engages with the stopper pin 7.

The cylinder body 1 is provided with a supply port 23 and a relief port 24 for the secondary piston 4, which are arranged on both sides of the land portion 4b and the piston cup 22, and a hydraulic fluid inlet portion 25 that communicates with these ports. Small diameter part 3
A supply port 26 and a relief port 27 for the primary piston 3 are formed on both sides of the piston cup 9, and a hydraulic fluid inlet portion 28 communicating with these ports is provided. A corresponding hydraulic outlet 2 of the reservoir tank 2 is inserted into the hydraulic fluid inlet 25, 28 via grommets 29, 30.
a and 2b, respectively, thereby making it possible to supply hydraulic fluid from the reservoir tank 2 to the cylinder body 1.

In the present invention, the relief port 27 that opens into the pressure chamber 16 when the stepped piston 3 is not pushed in is communicated with the supply chamber 10 via the inlet portion 28 and the supply port 26.

A valve outer casing 31 is integrally formed at the hydraulic fluid outlet portion 2b of the reservoir tank 2, and this valve outer casing 31 is connected to the port 2.
In addition to having a bottomed cylindrical shape with openings toward 6 and 27,
A valve seat 32 is provided at the open end, and a slit 31a for passage of hydraulic fluid is formed at the bottom. A duckbill-shaped valve 33 is disposed inside the valve casing 31, and a spring 34 is compressed between the valve and the bottom of the valve casing 31 to restrain the valve 33 in the position where it is seated on the valve seat 32. do.

The Duckbill type valve 33 is well known, but in this example, it is configured so that liquid flows only in one direction with almost no resistance (valve opening pressure 0 to 0.05 Kg/cm ² ), and in the opposite direction. A check valve is used to prevent liquid flow as usual, and the duck-bill type valve 33 is arranged in a direction that allows the hydraulic liquid to flow from the reservoir tank 2 to the supply port 26, as shown by arrow a in the figure. do. Thus, since the duckbill type valve 33 is seated on the valve seat 32 by the spring 34 as described above, it constitutes a normally closed check valve that allows only the liquid flow shown by arrow a. In addition, the outer diameter of the valve 33 is made slightly smaller than the inner diameter of the valve outer casing 31, and an annular passage 35 is set between the two, so that the duck-bill type valve 33 as a check valve is normally closed together with the valve seat 32 and the spring 34. A differential pressure valve 36 can be configured.

The operation of the above embodiment will be explained next.

In the inoperative state shown in FIG.
When the primary piston 3 is moved to the left in the figure and the primary piston 3 is pushed in, the piston cup 9 closes the relief port 27, isolating this port from the pressure chamber 16 and sealing the pressure chamber 16. Also, primary piston 3
The leftward movement causes a volume reduction in the supply chamber 10, and the working fluid in the supply chamber 10 is transferred to the outside lip of the piston cup 9 inside the small diameter hole 1b while the differential pressure valve 36 is closed as described above. It is fed into the pressure chamber 16 while being elastically deformed in a direction away from the peripheral surface.

The hydraulic fluid sent into the pressure chamber 16 is supplied from the pressure chamber 16 through the port 18 to the brake system connected thereto, thereby absorbing the loss stroke of the brake unit of this system. After absorbing this loss stroke, the hydraulic fluid sent into the pressure chamber 16 causes the secondary piston 4 to move to the left in FIG. Hydraulic fluid is sent to the brake system connected to this, absorbing the loss stroke of the brake unit in this system.

By the way, since this loss stroke absorption operation is performed while feeding the hydraulic fluid from the supply chamber 10 into the pressure chamber 16 as described above, the amount of pushing of the primary piston 3, that is, the amount of pedal operation is reduced accordingly, and the operation feeling is improved. improves. In addition, prior to this action, since the relief port 27 communicates the pressure chamber 16 and the supply chamber 10 and makes them at the same pressure when the master cylinder is in the non-operating state, both chambers 10, 16 are in contact with each other from the beginning of the pushing stroke of the stepped piston 3. A pressure difference is generated between the two, allowing the hydraulic fluid to be fed from the supply chamber 10 to the pressure chamber 16, and a first-fill function can be achieved simultaneously with the depression of the stepped piston, thereby preventing the pedal stroke from becoming too long. When the pressure inside the supply chamber 10 becomes high during the operation, this pressure is applied to the Duckbill type valve 3.
3 against the spring 34 to release it from the valve seat 32,
In order to open the normally closed differential pressure valve 36 composed of these, a portion is released into the reservoir tank 2 through the supply port 26, the valve hole of the valve seat 32, the annular passage 33 and the slit 31a, and is released into the supply chamber 10. is maintained at a set pressure determined by the spring force of the spring 34.

When absorption of the loss stroke of the brake units of both systems is completed, the same value of hydraulic pressure is generated in the pressure chambers 16 and 17 at the same time, and these are applied to the ports 18 and 1.
9 to the corresponding brake systems, and braking is started by actuation of the brake devices.

When the pedal depression force is released, both pistons 3 and 4 are returned by the return spring 20 from the above-mentioned pushed-in position to the original position shown in FIG. At this time, the hydraulic fluid is replenished into the pressure chamber 17 by allowing the hydraulic fluid that has reached the communication hole 21 from the reservoir tank 2 through the inlet 25 and the supply port 23 to pass through the outer circumferential lip of the piston cup 22 from the circumferential surface of the small diameter hole 1b. This is done by deforming it so as to separate it and flowing into the pressure chamber 17. Further, the supply chamber 10 is replenished with the hydraulic fluid by allowing the hydraulic fluid to flow in the direction shown by the arrow a, as the duck-bill type valve 33, which constitutes the valve body of the differential pressure valve 36, which is self-closing as shown in the figure. This is possible because the hydraulic fluid in the reservoir tank 2 flows into the supply chamber 10 through the slit 31a, the duckbill type valve 33, and the supply port 26. Furthermore, the hydraulic fluid replenished into the supply chamber 10 deforms the outer peripheral lip of the piston cup 9 in a direction away from the inner peripheral surface of the small diameter hole 1b, reaches the pressure chamber 16, and flows into this pressure chamber. Hydraulic fluid replenishment is also possible. In this way, the hydraulic fluid is supplied to each chamber 10, 1.
6, 17, the master cylinder returns to the non-operating state shown in the figure, and each pressure chamber 16, 1
7, the reservoir tank 2, and the supply chamber 10 communicate with each other via the relief ports 24 and 27, so that the hydraulic pressure in each pressure chamber can be returned to the non-operating state, respectively, in preparation for the next operation.

By the way, in this example, since the check valve is configured with a duckbill type valve 33 whose opening pressure is almost zero, the duckbill type valve 33 is opened by the negative pressure generated in the supply chamber 10 during the return stroke of the primary piston 3, and the reservoir is opened. The hydraulic fluid in the tank can be supplied to the supply chamber. Therefore, by repeatedly pushing the primary piston 3, the hydraulic fluid can be fed sequentially, and the hydraulic fluid can be filled while removing air from the air bleed nipple. This operation is possible without the use of formula or pressure-feed filling equipment. Further, due to the arrangement of the relief port 27, there is no delay in starting the first fill function as described above, so filling of the hydraulic fluid while removing the air can be completed promptly.

Furthermore, for the same reason, the supply chamber 10 and the pressure chamber 16 are smoothly replenished with the hydraulic fluid, which should be carried out during the operation when the pedal depression force is released. Even when the brake pedal is depressed, sufficient braking force cannot be obtained, so when the brake pedal is depressed again to perform braking, the braking effect can be ensured and sufficient.

Note that in the above example, the check valve was configured with a duckbill type valve 33, but any configuration can be used as long as it reliably performs the check valve function and the opening pressure is almost zero. It is possible. Figures 2 to 4 show another example of the structure of the check valve. In this example, the check valve 40 is used as the valve body of the differential pressure valve 36 as in the previous example as shown in Figure 2, and both valves are integrated. However, the check valve 40 has a special construction as shown in FIGS. 3 and 4.

That is, the check valve 40 is composed of one plate-shaped valve body 41 and a valve seat body 42. Valve body 41
is made into a plate shape made of a material such as resin having a specific gravity lighter than the hydraulic fluid used in the master cylinder so that it floats in the hydraulic fluid, and a pair of valve seats are placed on both sides of the valve seat body 42. 42a and 42b are formed. The distance between the valve seats 42a and 42b is made larger than the thickness of the valve body 41 so that the valve body can be seated on either one of the valve seats 42a or 42b, and the outer peripheral edge of the valve body 41 and the valve seat body are 42, an annular passage 43 is set between the two. Further, the valve seat 42b is formed with a slit 42b' that opens on the valve seat surface.

In the configuration of this example, normally the valve body 41 floats and seats on the valve seat 42a as shown in FIG. 3, and the valve seat body 42 receives the spring force of the spring 34 as shown in FIGS. 2 and 4. Since the check valve 40 is seated on the valve seat 32, it functions as a normally closed check valve similar to the above-described example, and when the pressure in the supply chamber 10 becomes high, the hydraulic fluid flows from the supply chamber 10 toward the reservoir tank 2. It prevents this and performs the specified check function. Thus, the pressure within supply chamber 10 can be moved away from valve seat 32 by moving check valve 40 against spring 34 as shown in FIG. 3, thereby opening differential pressure valve 36. Also, from reservoir tank 2 to supply chamber 1
When the hydraulic fluid is supplied to the valve 0, even if the valve body 41 is seated on the valve seat 42b as shown in FIG.
b' does not cut off the supply path of the hydraulic fluid, and the supply chamber 10
It is possible to replenish hydraulic fluid to. Moreover, at this time, the valve element 41 is light enough to float in the hydraulic fluid and can be moved without any resistance, so the opening pressure of the check valve 40 becomes zero, and the same effect as in the example described above occurs. It can be effective.

Thus, the master cylinder of the present invention is configured such that the relief port 27 is connected to the supply chamber 10 and the relief port 27 communicates between the reservoir tank 2 and the pressure chamber 16 via the check valves 33 and 40, so that the master cylinder is not in operation. At this time, the pressure chamber 16 and the supply chamber 10 are brought to the same pressure, and at the same time as the stepped piston 3 is pushed in, a pressure difference is generated between the two chambers 10 and 16, and the working fluid flow is caused to flow from the supply chamber 10 to the piston cup 9. It can be supplied to the pressure chamber 16 via the air. Therefore, there is no delay in the first fill function, and problems such as deterioration of operation feeling such as a long pedal stroke, and deterioration of the efficiency of filling the hydraulic fluid while bleeding air, which causes air bleeding to take a long time, can be eliminated. can.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional side view showing one embodiment of the master cylinder of the present invention, FIG. 2 is a sectional view of essential parts showing another example of the present invention, and FIGS. 3 and 4 are the main parts shown in FIG. FIG. 3 is an explanatory diagram of the operation of the invention master cylinder. 1...Cylinder body, 2...Reservoir tank,
3...Stepped primary piston, 3a...Large diameter portion, 3b...Small diameter portion, 4...Secondary piston, 5, 15...Lip seal, 6, 21...Communication hole, 7...Stopper pin, 8... Push rod, 9, 22... Piston cup, 10... Supply chamber, 11... Screw, 12, 13... Spring seat,
14... Spring, 16, 17... Pressure chamber, 18, 1
9... Output hydraulic pressure outlet port, 20... Return spring, 23, 26... Supply port, 2
4, 27... Relief port, 29, 30... Grommet, 31... Valve casing, 31a... Slit, 32... Valve seat, 33... Duckbill type check valve, 34... Spring, 35... Annular aisle, 3
6...Differential pressure valve, 40...Check valve, 4
1... Plate floating valve body, 42... Valve seat body, 42
a, 42b...Valve seat, 42b'...Slit, 43
...A circular passage.

Claims (1)

[Scope of Claims] 1. A stepped piston is provided, a supply chamber is defined between a large diameter portion and a small diameter portion thereof, and an end face of the small diameter portion far from the supply chamber faces a pressure chamber;
Provided between the reservoir tank and the supply chamber is a normally closed differential pressure valve that opens in response to a pressure above a certain level in the supply chamber, as well as a check valve that prevents the flow of working fluid from the supply chamber to the reservoir tank. During a piston stroke for generating output hydraulic pressure in the pressure chamber by pushing the stepped piston toward the pressure chamber so that its small diameter portion closes the relief port communicating between the reservoir tank and the pressure chamber, the stepped piston The piston generates a set pressure in the supply chamber by reducing the volume of the supply chamber under the action of the differential pressure valve, and opens a piston cup on the small diameter portion of the stepped piston, thereby sending hydraulic fluid from the supply chamber to the pressure chamber. By opening the check valve with the negative pressure generated in the supply chamber during the return stroke of the stepped piston, hydraulic fluid can be supplied from the reservoir tank to the supply chamber, and the hydraulic fluid can be filled while air is removed by repeatedly pushing the piston. The master cylinder is characterized in that the relief port is connected to the supply chamber so that the relief port communicates between the supply chamber and the pressure chamber during non-operation of the master cylinder. 2. The master cylinder according to claim 1, wherein the check valve is a duckbill type valve. 3. The master cylinder according to claim 2, wherein the duckbill type valve is used as a valve body of the differential pressure valve, and the check valve and the differential pressure valve are integrated. 4. The check valve consists of one floating valve body and a pair of valve seats arranged on both sides of the floating valve body, and the valve body seats on one valve seat in response to the flow of hydraulic fluid from the supply chamber toward the reservoir tank. The valve hole is closed when the valve body is seated on the other valve seat in response to the flow of hydraulic fluid from the reservoir tank toward the supply chamber, and the valve hole remains open when the valve body is seated on the other valve seat. The master cylinder described in item 1. 5. The master cylinder according to claim 4, wherein the valve seat body constituting the pair of valve seats is used as a valve body of the differential pressure valve, and the check valve and the differential pressure valve are integrated.