JPS6039573B2 - master cylinder device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is for vehicles in which the ratio of hydraulic pressure output to brake operating force, that is, the boost ratio, automatically changes from the smallest at the beginning of the braking operation, to the largest thereafter, and finally to a medium level. This invention relates to a master cylinder device for hydraulic brakes.

The master cylinder device, which sends a large amount of low-pressure hydraulic fluid at the beginning of the brake action, and then increases the power ratio midway through and sends a small amount of high-pressure hydraulic fluid to the brake output section, allows for quick braking effect and doubles the vacuum. Although it is possible to obtain a high brake output almost equivalent to that of a master cylinder device having a power device, the stroke of the piston during the high-pressure pumping stroke becomes long, which is undesirable because a considerable amount of brake pedal depression is required.

The present invention proposes a master cylinder device that quickly obtains a high braking force with a smaller piston stroke by reducing the boost ratio at the end of the braking action. The structure of the present invention will be explained based on the illustrated embodiment. As shown in FIG. 1, the master cylinder device consists of a cylinder body 10, a large-diameter drive piston 39, and a small-diameter piston 42. A large diameter cylinder 41 is formed on the base end side of the cylinder body 10, and a middle cylinder 1 is formed on the closed tip side, and these are connected to a seal ring 2.
are connected to each other by small diameter cylinders supporting 8. A reservoir 8 is attached to the upper circumferential wall of the cylinder body 10, and the inside thereof is connected to the proximal end of the Nakayo cylinder via a passage 5, and to the proximal end of the Oyo cylinder 41 via a passage 15. . A valve seat 6 integrally equipped with a valve body 7 biased by a spring 3 and an elastic body opened and closed by the valve body 7 is housed in a large diameter chamber formed in the middle of the passage 5, and is locked by a stop mechanism 4. be done. The stem portion of the valve body 7 protrudes into the interior of the proximal end of the inner cylinder, and operates by engaging with the weave of the inner cylinder piston 42a, which will be described later.
The drive piston 39 is provided with a wide circular groove 19 on the outer periphery of the central portion, and is constantly connected to the passage 15 described above.

Seal rings 23 and 18 are attached to the outer periphery of both ends to seal the sliding portion with the cylinder 41. In the brake released state, the spring accommodated in the liquid chamber 9 partitioned by the drive piston 39, that is, the inner end wall of the cylinder 41 and the drive piston 3
The drive piston 39 is biased against the retaining ring 17 which is engaged with the open end of the cylinder 41 by the force of the return counter 27 interposed between the left end of the cylinder 41 and the left end of the cylinder 41 . Drive piston 3
9 is provided with a cylindrical part on the left end side of the inside thereof, which locks the end of the small-diameter piston 42 through a stopper 11 so as to be able to slide slightly. It is connected to room 9. an axial passage 26 abutting the inner end wall of the cylindrical portion and passing through the passage 12 and the small diameter piston 42;
A high-pressure operating valve is constituted by an elastic seat 24 that blocks the driving piston 39 and the small diameter piston 4.
It is normally separated from the inner end by the force of a spring 25 interposed between the inner end and the inner end. A stem portion of the check valve 20 is guided in a small-diameter cylindrical portion 14 that is an extension of the passage 26, and this sliding portion is sealed by a seal ring 13. The right end side of the cylindrical portion 14 is connected to the liquid chamber 9 via an inclined passage 22, passes through a valve chamber formed on the right end side of the cylindrical portion 14, and is further connected to the reservoir 8 via a passage 16, a circular groove 19, and a passage 15. It is connected to. The check valve 2 is provided with an elastic seat 21 that comes into contact with and separates from the right end surface of the cylindrical portion 14 to open and close it, and the normal passage 22 and the passage 1 are closed by the force of a spring 38.
6.

Due to the machining of the valve chamber, the driving piston 39 is divided into left and right parts from the passage 16 so that they abut each other and move integrally. According to the present invention, a medium-diameter piston 42a that is iron-fitted to the center cylinder 1 is integrally formed at the tip of the small-diameter piston 42.

A seal ring 31 is attached to the outer periphery of the medium-diameter piston 42a, and a cylindrical portion for encasing a stepped piston 33 is continuous with the passage 26. The force urges a retaining ring 34 secured to the end of the cylindrical portion. Seal rings 2 and 32 are attached to the large and small portions of the stepped piston, respectively, and a passage 37 passing through the shaft center is provided inside. The medium-diameter cylinder 1 is partitioned by the medium-sized piston 42a into a liquid chamber 36 having an outlet passage 35 and a chamber 29 from which the aforementioned valve 7 projects. However, the normal passage 50
(FIG. 2), the chambers 29 and 36 are flush with each other via the passage 26 of the small diameter piston 42 and the passage 37 of the stepped piston. Next, the operation of the master cylinder device according to the present invention will be explained. When the brake is released, the drive piston 39 and the small diameter piston 42 are in the state shown in FIG. 1, the valve 20 is closed, the valve 7 is open, and the elastic seat 24
The high pressure operating valve constituted by the stepped piston 33 is open, and the pressure reducing valve constituted by the stepped piston 33 is open.

Now, when the brake is operated, the drive piston 39 is pushed to the left, and the small diameter piston 42 is also moved to the left together with the high pressure operating valve 24 being kept open by the force of the spring 25.

Therefore, when the valve 7 is disengaged from the medium piston 42a and closes the passage 5, the liquid in the liquid chamber 9 of the Oyo cylinder 41 is sent to the liquid chamber 36 via the passages 12, 26, 27, and the outlet 35 to the brake output. The liquid amount in this case is the product of the cross-sectional area of the drive piston 39 and its operating amount. In this manner, the brake output wheel cylinder is operated by a large amount of low-pressure hydraulic fluid, and in the case of a drum brake, the braking gap between the brake shoe and the brake drum is quickly eliminated. After the brake shoes engage with the brake drum, the hydraulic pressure in the hydraulic chamber 36 increases due to the reaction force of the brake output section, and when it exceeds the operating force FI shown in FIG. Applying a rightward pushing force against the force of the spring 25, the high-pressure actuated valve constituted by the resilient seat 24 isolates the passage 12 from the passage 26, while also exerting pressure on the stem end of the check valve 20. The lever is pushed open against the force of the spring 38, and the liquid in the liquid chamber 9 is transferred to the passage 22 and the cylindrical portion 14.
, passage 16, groove 19 and passage 15 to the reservoir 8.

Sufficient clearance is provided between the cylindrical portion 14 and the stem portion of the valve 20. In this state, the drive piston 39
When continues to be pushed leftward, the Nakayo piston 42a
The fluid in the chamber 36 is pressurized and supplied from the outlet 35 to the brake output. However, some of the liquid is in the passages 37, 50
(Fig. 2) and flows to the chamber 29, so the amount of fluid supplied to the brake output section is the product of the cross-sectional area of the small diameter piston 42 and its operating amount, and the fluid pressure increases by the change in the cross-sectional area. , increases along the solid line 52 in FIG. 3 in proportion to the brake operating force applied to the drive piston 39. When the brake operating force exceeds F2, the pressure reducing valve constituted by the stepped piston 33 moves to the right against the force of the spring 30, closing the passage 50.

At this time, the liquid chamber 36 is pressurized by the medium-diameter piston 42a, and the liquid volume is the product of the cross-sectional area of the medium-diameter piston and its operating amount, and the pressure transmitted to the brake output section is relative to the operating force of the brake pedal. increases along line 53 in FIG.
In this decompression stroke, the valve 7 opens as the volume of the chamber 29 increases, and the liquid is replenished from the reservoir 8. In addition, the gap between the stepped piston 33 and the cylindrical portion that joins it will be pressurized, but if this volume is found to be sufficiently large compared to the operating amount of the stepped piston, it will hardly be able to operate the pressure reducing valve. It does not affect. When the brake operating force is released, the large-diameter piston 39 is returned to the position where it abuts against the retaining ring 17 by the force of the spring 27, and the 4-flea piston 42, which is locked by the retainer 11, is also pulled back, and the medium-diameter piston 42a The valve 7 is tilted open.

As explained above, the present invention provides a master cylinder device in which a high-pressure operating valve switches between a low-pressure pressure feeding stroke by a large-diameter drive piston and a high-pressure pressure feeding stroke by a small-diameter piston. This is because the medium-diameter piston part is integrally constructed, and a pressure reducing valve consisting of a stepped piston is provided inside the bracket, so that both end chambers of the medium-diameter cylinder partitioned by the central piston can be opened and closed. , When the operating force of the brake pedal exceeds a certain value F2, the pressure reducing valve is activated and the Nakayo piston is effectively activated to reduce the boost ratio and shorten the stroke of the brake pedal by the amount of the decrease. It is possible. Then, as the brake operating force is gradually increased, the boost ratio changes over three stages, so at the beginning of braking, a large amount of low-pressure hydraulic fluid is supplied to the brake output section, and the brake shoes are quickly engaged with the brake drum. After that, high-pressure braking force is applied using a small amount of high-pressure fluid, and when the brake operating force exceeds a certain value, the boost ratio is reduced to maintain high braking force with less brake pedal operation. As shown by the broken line in Fig. 3, it is possible to obtain almost the same performance as a normal master cylinder device equipped with a vacuum booster. It is also extremely advantageous in that the installation space for the vehicle can be significantly reduced.
In the embodiment, it goes without saying that the present invention can also be directly applied to a tandem master cylinder' device if the second liquid chamber in which the floating piston is fitted is constructed at the end of the intermediate cylinder 1.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a master cylinder device according to the present invention;
FIG. 2 is a longitudinal sectional view showing the operating state of the pressure reducing valve when the brake operating force of the device is at its maximum, and FIG. 3 is a diagram showing the operating characteristics of the device. 1: Nakayo cylinder, 7: Valve body, 8: Reservoir, 9: Liquid chamber, 10: Cylinder body, 20: Check valve, 21: Elastic seat,
24: Elastic seat, 25: Spring, 27: Tuft imitation, 29: Liquid chamber, 33: Stepped piston, 35: Outlet passage, 36: Liquid chamber, 39: Drive piston, 41: Large diameter cylinder, 42: Small Light piston, 42a: middle law piston. Figure 2 Figure 3 Figure 1

Claims (1)

[Claims] 1. In a master cylinder device of a type in which a high-pressure operating valve provided at a joint between a large-diameter piston and a small-diameter piston switches from a low-pressure pressure feeding stroke by a large-diameter driving piston to a high-pressure pressure feeding stroke by a small-diameter piston, the small-diameter piston A medium-diameter piston portion that fits into a medium-diameter cylinder is integrally formed at the tip of the medium-diameter piston, and a pressure reducing valve consisting of a stepped piston having a large diameter on the tip side is provided inside the medium-diameter piston, and the pressure reducing valve is provided inside the medium-diameter piston. A one-way valve that allows flow from the reservoir to the chamber is provided between the proximal chamber of the medium-diameter cylinder and the reservoir, which are partitioned by the medium-diameter cylinder. A master cylinder device characterized in that a passage passing through the pressure reducing valve midway and connecting both end chambers of the medium diameter cylinder is blocked by the operation of the pressure reducing valve.