JPS646977B2 - - 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 first-filter (first-filter) which rapidly supplies a large amount of hydraulic fluid to a pressure chamber for the purpose of reducing the piston stroke during operation. This invention relates to an improvement of a master cylinder known as a fast fill type or quick take-up type.

In disc brakes, if the distance between the brake disc and the brake pads that clamp it is made smaller, the brake pads will be dragged by the brake disc, causing abnormal wear of the pads, loss of power, and even abnormal noise. In this case, there is a risk that the brake cannot be braked due to vapor lock.
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 pedal travel is increased, which inevitably deteriorates the operation feeling.

A first-fill master cylinder is useful, for example, in such a brake system to keep the brake pedal travel small by sending a large amount of fluid into the pressure chamber during the initial stroke of the piston in the stepped cylinder. .

This type of master cylinder is known, for example, from US Pat.
It is well known as described in the specification of No. 4208881.

However, in the master cylinder disclosed in this U.S. patent specification, the reservoir chamber and the cylinder side are connected to send a large amount of low pressure hydraulic fluid to the brake side during the initial stroke of the piston, and the cylinder side is under negative pressure. The valve unit 88, which functions to supply hydraulic fluid from the reservoir chamber to the cylinder side, connects the metal valve seal member 102 and the valve body 104 with a passage 114,
126, orifices 144, 108, etc. are formed by complicated machining, etc., and therefore have the drawbacks of high manufacturing cost and increased overall weight.

Conventionally, in order to overcome these drawbacks, the part of the valve unit mentioned above where the passage and orifice are provided is made of synthetic resin, and this is press-fitted into one end of the spring retainer that constitutes the other part of the valve unit. The present applicant has previously filed U.S. Pat.
is proposed.

However, in such a conventional valve unit, a portion made of synthetic resin deforms due to heat or the like, and the pressing force between this portion and the other portion of the spring retainer into which it is press-fitted is reduced, making it easier to separate. If one part of the valve unit is separated from the other in this way, the spring force applied to the valve body housed inside the valve unit will be reduced, resulting in a first-fill function (a large amount of actuation occurs during the initial stroke of the piston). The upper limit hydraulic pressure that can be obtained (sending fluid to the brake side) becomes smaller. Therefore, there is a problem in that a sufficient amount of hydraulic fluid cannot be discharged to the brake side, resulting in a large stroke loss of the brake pedal, making quick braking operations difficult.

This invention was made by focusing on such conventional problems, and includes a cylinder body having a small diameter hole and a large diameter hole, a reservoir tank attached to the cylinder body, and a cylinder body having a small diameter hole and a large diameter hole in the cylinder body. A stepped piston is slidably inserted into both holes of the diameter hole to define a pressure chamber in the small diameter hole and a supply chamber in the large diameter hole, and a reservoir tank and a supply chamber. A check valve is provided in a passage communicating between the supply chamber and the reservoir tank to prevent the flow of working fluid from the supply chamber to the reservoir tank, and allows flow in the opposite direction. a valve seat body having a predetermined length in the axial direction from one end to the other end;
a valve body that can come into contact with and separate from the valve seat body on one end side of the valve seat body; a spring that biases the valve body toward the valve seat body; The spring retainer has one end fitted to the outer periphery of the valve seat body for a predetermined length and the other end abuts the spring, and the valve body moves against the spring when the pressure inside the supply chamber exceeds a certain level. and separate from the valve seat body.
A master cylinder is provided with a differential pressure valve that allows the flow of working fluid from a supply chamber to a reservoir tank, and a valve seat body of the differential pressure valve is formed of synthetic resin, and a predetermined protrusion is provided at one end of the spring retainer. The above-mentioned problem is solved by providing a protrusion part, making the protruding part protrude toward the valve seat body at a position separated by a predetermined distance from one end of the valve seat body, and biting into the valve seat body. It is an object.

The present invention will be explained below based on the drawings.

1, 2, and 3 are diagrams showing an embodiment in which the present invention is applied to a tandem master cylinder.

First, the configuration will be explained. 1 is a cylinder body having a large diameter hole 1a and a small diameter hole 1b; 2 is a reservoir tank; 3 is a primary piston fitted into both the large diameter hole 1a and the small diameter hole 1b of the cylinder body 1;
4 is a secondary piston fitted into the small diameter hole 1b of the cylinder body 1.

The primary piston 3 constitutes a stepped piston, and its large diameter portion 3a is connected to a large diameter hole 1 near the open end of the cylinder body 1 under liquid-tight sealing by a cup seal 5.
a, the small diameter part 3b is fitted into the small diameter hole 1b near the closed end of the cylinder body 1, and the large diameter part 3
A supply chamber 6 is defined between the small diameter portion 3b and the small diameter portion 3b, and a communication hole 7 is formed in the small diameter portion 3b. The stepped primary piston 3 is prevented from coming off by a cover 8 attached to the open end of the cylinder body 1 so as to abut against the end face of the large diameter part 3a, and a recess 3c is formed in the end face of the large diameter part 3a. The tip of a push rod 9, which moves to the left in the figure when the brake pedal is depressed in conjunction with the brake pedal, is inserted into the recess 3c.

A piston cup 10 is provided at the end of the primary piston 3 far from the push rod 9, and its outer circumferential lip portion slides against the inner circumferential surface of the small diameter hole 1b to close the communication hole 7, but this piston cup communicates with the supply chamber 6. It is oriented to allow the flow of hydraulic fluid to flow out through the hole 7 and to block the flow of hydraulic fluid in the opposite direction. Install a screw 11 on the end face of the primary piston 3 on the side far from the push rod 9,
The shaft portion guides the spring seat 12, and
This spring seat is prevented from coming off by the head portion 11a. Also, the spring seat 12 and the primary piston 3
A return spring 13 is installed in between. A pressure chamber 14 is defined between the primary piston 3 and the secondary piston 4, and this pressure chamber 14 faces an end surface of the primary piston 3. A hydraulic pressure outlet port 15 communicating with this pressure chamber 14 is formed in the cylinder body 1, and output hydraulic pressure can be taken out to a brake side (not shown) through this port. A return spring 23 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 12 in its original position as shown, and the primary piston 3 is brought into engagement with the cover 8. and restrain it in its original position as shown. As shown in detail in FIG. 2, the cylinder body 1 has a hydraulic fluid inlet portion 16 connected to the reservoir tank 2, and a passage 17 communicating with the reservoir tank 2 is formed in the hydraulic fluid inlet portion 16. There is. Furthermore, a supply port 18 communicating with the supply chamber 6 on the large diameter side and a relief port 19 communicating with the pressure chamber 14 on the small diameter side are formed in the cylinder body 1, sandwiching the boundary between the small diameter portion 1b and the large diameter portion 1a. , the supply port 18 and the relief port 19 open at the bottom of the passage 17, respectively. A valve unit 20 is accommodated in the passage 17, and this valve unit 20 has a differential pressure valve 21 and a check valve 22 as usual. Reference numeral 25 denotes a valve seat body made of synthetic resin, and the valve seat body 25 has a predetermined length in the axial direction from one end to the other end. Further, the valve seat body 25 is housed in the passage 17, and a seal 24 is provided to maintain liquid tightness between the valve seat body 25 and the passage. This valve seat body 25 has a through hole 2 along the axis.
6 is formed. The inner surface of the upper end of the through hole 26 in FIG. A plurality of holes 28 surrounding the through hole 26 are formed in the valve seat body 25, and the lower ends of the holes 28 are connected to the valve seat body 25 and the screw 3.
It is normally closed by a valve body 29 made of an elastic material held between the valve body 8 and the valve body 29 . The valve body 29 allows the hydraulic fluid to flow from the reservoir tank 2 to the supply chamber 6 and blocks the hydraulic fluid from flowing from the supply chamber 6 to the reservoir tank 2. The aforementioned hole 28 and valve body 29 constitute the check valve 22 as a whole. 30 is the valve seat body 2 on one end side of the valve seat body 25;
The valve body 30 is a valve body that can come into contact with and separate from the valve seat 27 . This valve body 30 closes the through hole 26 by seating on the valve seat 27. Reference numeral 31 denotes a spring whose lower end is in contact with the valve body 30, and this spring 31 urges the valve body 30 toward the valve seat body 25, that is, in the valve closing direction.
A spring retainer 32 is made of, for example, press-molded metal and has a cap-shaped cross-section. One end of the spring retainer 32 on the opening side press-fits the outer periphery of the valve seat body 25 by a predetermined length from one end of the valve seat body 25 to the other end. As shown in detail in FIG. 3, the fitting portion which is one end of the spring retainer 32 has a predetermined projection 3.
3 is provided, and this protrusion 33 is connected to the valve seat body 2.
The valve seat body 2 is located at a predetermined distance from one end of the valve seat body 5.
This protruding portion 33 forms a recess in the valve seat body 25 and engages with the valve seat body 25. A through hole 34 is provided along the axis at the other end of the spring retainer 32, and the upper end of the spring 31 is in contact therewith. In this way, the valve seat body 25
The above-mentioned valve body 30 and spring 31 are housed inside surrounded by the spring retainer 32 and the valve body 30 . The aforementioned valve seat body 25, valve body 30, spring 31, and spring retainer 32 constitute the differential pressure valve 21 as a whole. 35 is an orifice provided in the valve seat body 25, and the orifice 35 connects the reservoir tank 2, the supply chamber 6, and the pressure chamber 14, and directs the air bubbles accumulated in the supply chamber 6 and the pressure chamber 14 to the reservoir tank 2 side. It forms a passageway for escape. In this way, the valve unit 20 consisting of the valve seat body 25 and the spring retainer 32 is connected to the passage 1.
It is held between a step 36 provided at 7 and a snap spring 37. Note that there is a slight gap between the valve unit 20, the step 36, and the snap spring 37 in order to absorb manufacturing errors.

Next, the action will be explained.

In the inoperative state shown in FIG.
When moved to the left in the figure and pushed in the stepped primary piston 3, the supply chamber 6 is moved to the left of the primary piston 3.
However, the volume is reduced due to the tiering. Due to this volume reduction, the hydraulic fluid in the supply chamber 6 flows into the pressure chamber 14 via the supply port 18 and the relief port 19, and flows out from the hydraulic outlet port 15. The piston cup 10 passes through the relief port 19,
When this port is isolated from the pressure chamber 14, the hydraulic fluid in the supply chamber 6 passes through the communication hole 7, elastically deforms the outer peripheral lip of the piston cup 10 in the direction away from the inner peripheral surface of the small diameter hole 1b, and 14 and flows out from the outlet port 15. During this time, the valve body 30 is in the closed position pressed against the valve seat 27 by the spring 31, and the hole 28 is in the closed position.
, the hydraulic fluid in the supply chamber 6 will not flow into the reservoir tank 2.

The hydraulic fluid flowing out from the port 15 after flowing into the pressure chamber 14 is supplied to the hydraulic brake system connected to this port, and strokes the actuating unit (brake unit) of this system until the pad hits the disk.

This loss stroke is performed while feeding a large amount of hydraulic fluid from the supply chamber 6 to the pressure chamber 14 as described above, so the primary piston 3
The amount of depression, that is, the amount of pedal operation is reduced, and the intended purpose of the first fill function is achieved. During this loss stroke, the internal pressure within the supply chamber 6 gradually increases, and this pressure acts on the valve body 30 via the passage 17. When the brake unit finishes its loss stroke and the hydraulic pressure in the supply chamber 6 exceeds the set pressure determined by the spring force of the spring 31, the valve body 30 moves upward in FIGS. 1 and 2 against the spring 31. It is pushed up and the differential pressure valve 21 is opened. As a result, the supply chamber 6 communicates with the reservoir tank 2 and becomes atmospheric pressure. Therefore, the pressure within the supply chamber 6 does not generate a force that presses the primary piston 3 to the right, and the brake pedal depression force is transmitted from the end surface of the small diameter portion 36 of the primary piston 3 to the pressure chamber 3 through the push rod 9.
4 and generates high pressure. Therefore, a small amount of high pressure hydraulic fluid is delivered from port 15 to the corresponding hydraulic system. Note that the secondary piston 4 is moved by the hydraulic pressure in the pressure chamber 14, generates the same hydraulic pressure in the corresponding pressure chamber, and supplies the hydraulic pressure to the corresponding hydraulic system.

Next, when the pedal depression force is released, the primary piston 3 and the secondary piston 4 move from the position shown in FIG. 1 where they are pushed to the left in FIG. It is directed back to its original position. At this time, the hydraulic fluid is supplied to the pressure chamber 14 by allowing the hydraulic fluid in the supply chamber 6 to pass through the communication hole 7 and deform the outer peripheral lip of the piston cup 10 in a direction away from the inner peripheral surface of the small diameter hole 1b. This is done by flowing into the pressure chamber 14. Furthermore, the supply chamber 6 is replenished with the hydraulic fluid. At this time, the primary piston 3 is stepped and causes an increase in the internal volume of the supply chamber 6, so the supply chamber 6 becomes negative pressure, and the valve body 29 is elastically deformed. In order to open the hole 28, the hydraulic fluid in the reservoir tank 2 flows into the supply chamber 6.
This is done by flowing into the

By replenishing the hydraulic fluid in this way, the master cylinder returns to the non-operating state shown in Figure 1.
It can prepare for the next operation.

By the way, the protruding portion 33 of the spring retainer 32 of the valve unit 20 protrudes toward the valve seat body 25 at a position separated by a predetermined distance from one end of the valve seat body 25 at the fitting portion with the valve seat body 25. ,
A portion is created in which the contact surface pressure between the valve seat body 25 and the spring retainer 32 is locally larger than in other portions other than the protruding portion 33. For this reason, the valve seat body 25 made of synthetic resin absorbs moisture contained in the hydraulic fluid, or receives heat from the engine or the like or due to a rise in the temperature of the hydraulic fluid during braking, or the spring retainer 32 If the valve seat body 2 deforms over time due to pressure contact force from
The portion of the spring retainer 32 in No. 5 that contacts the protruding portion 33 forms a recessed portion because the contact surface pressure is large.
The part of the valve seat body 25 that contacts other parts of the spring retainer 32 has a lower contact surface pressure than the part that contacts the protrusion 33, so the part of the valve seat body 25 that contacts other parts of the spring retainer 32 is designed to form a convex part compared to the part that contacts the protrusion 33. transforms into
Therefore, as time passes, the valve seat body 25 deforms to form a larger recess at the part where it contacts the protrusion 33 of the spring retainer 32, and naturally forms a reliable retainer against the spring retainer 32. . For this reason, a force is always acting on the spring retainer 32 and the valve seat body 25 in the direction of separating them from each other due to the elastic force of the spring 31. Since the retainer is naturally formed over time, the valve seat body 25 and the spring retainer 32 are prevented from separating and separating. As a result, since the length of the spring 31 does not change, the biasing force of the spring 31 in the valve closing direction applied to the valve body 30 of the differential pressure valve 21 does not change, and the valve body 30
The valve opens only when the supply chamber 6 reaches a predetermined pressure, and connects the reservoir tank 2 and the supply chamber 6. Therefore, like in a conventional valve unit, the valve seat body and spring retainer separate and become spaced apart, and the spring housed therein stretches, causing the valve body, which is biased by this spring, to When the setting force becomes small and the fluid pressure in the supply chamber is low, that is, before the loss stroke is completed, the valve body opens and connects the reservoir tank and the supply chamber, making it impossible to obtain sufficient first fill function. This situation is avoided.

FIG. 4 shows another embodiment of the invention. In this embodiment, the tip of the spring retainer 32 is bent into a hook shape to form a protrusion 33 toward the valve seat body 25 side. The operation is similar to that of the previous embodiment.

As explained above, according to this invention,
A cylinder body having a small diameter hole and a large diameter hole, a reservoir tank attached to the cylinder body, and a reservoir tank that is slidably inserted into both the small diameter hole and the large diameter hole of the cylinder body. A stepped piston defines a pressure chamber in the large diameter hole and a supply chamber in the large diameter hole, and a passage connecting the reservoir tank and the supply chamber is provided to allow the flow of working fluid from the supply chamber to the reservoir tank. A check valve is provided in the passage connecting the reservoir tank and the supply chamber, and has a predetermined length in the axial direction from one end to the other end. a valve seat body; a valve body that can come into contact with and separate from the valve seat body on one end side of the valve seat body; a spring that biases the valve body toward the valve seat body; and a spring retainer which is fitted to the outer periphery of the valve seat body for a predetermined length toward the other end, and whose other end abuts the spring. In the master cylinder, the valve seat body of the differential pressure valve is made of synthetic resin. A predetermined protrusion is provided at one end of the spring retainer, and the protrusion is made to protrude toward the valve seat body at a position spaced a predetermined distance from the one end of the valve seat body, and to bite into the valve seat body. Therefore, a retainer is formed during press-fitting, and a more reliable retainer for the spring retainer can be naturally formed as the valve seat body deforms over time. Therefore, it is possible to securely fit the valve seat body and spring retainer with an inexpensive and simple structure, and as a result, the valve seat body and spring retainer are separated, the spring is stretched, and the valve is closed. This has the effect of avoiding a situation where the valve body opens with low hydraulic pressure due to weakening of the body force, and the first fill function cannot be sufficiently obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a master cylinder according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of main parts of this master cylinder, FIG. 3 is an enlarged sectional view of section A in FIG. 2, and FIG. 3 is an enlarged sectional view of a master cylinder according to another embodiment of the invention, corresponding to FIG. 3. FIG. 1...Cylinder body, 1a...Large diameter part, 1b...
...Small diameter hole, 2...Reservoir tank, 3...Primary piston, 4...Secondary piston, 6...
... Supply chamber, 7 ... Communication hole, 10 ... Piston cup, 14 ... Pressure chamber, 17 ... Passage, 18 ...
...Supply port, 19...Relief port, 2
0... Valve unit, 21... Differential pressure valve, 2
2...Check valve, 25...Valve seat body, 26...
...Through hole, 27... Valve seat, 30... Valve body, 31...
... Spring, 32 ... Spring retainer, 3
3... Protrusion.

Claims (1)

[Claims] 1. A cylinder body having a small diameter hole and a large diameter hole,
A reservoir tank attached to the cylinder body is slidably inserted into both the small diameter hole and the large diameter hole of the cylinder body, thereby defining a pressure chamber in the small diameter hole and supplying it to the large diameter hole. Provided in a passage connecting the stepped piston that defines the chamber, the reservoir tank, and the supply chamber, it prevents the flow of hydraulic fluid from the supply chamber to the reservoir tank, and allows flow in the opposite direction to pass through. A check valve and a valve seat body, which is also provided in a passage connecting the reservoir tank and the supply chamber and has a predetermined length in the axial direction from one end to the other end, and one end side of the valve seat body. a valve body that can come into contact with and separate from the valve seat body; a spring that biases the valve body toward the valve seat body; and a spring that biases the valve body toward the valve seat body; a spring retainer that is fitted to the spring for a predetermined length and whose other end abuts the spring, and when the pressure inside the supply chamber reaches a certain level, the valve body moves against the spring and separates from the valve seat body; A master cylinder is provided with a differential pressure valve that allows the flow of working fluid from a supply chamber to a reservoir tank, and a valve seat body of the differential pressure valve is formed of synthetic resin, and a predetermined protrusion is provided at one end of the spring retainer. 1. A master cylinder, wherein the protrusion protrudes toward the valve seat body at a position spaced a predetermined distance from one end of the valve seat body and bites into the valve seat body.