JPH0215736Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a brake fluid that controls the rear wheel cylinder fluid pressure to a value that is reduced by a substantially constant ratio of the master cylinder fluid pressure when the rear wheel cylinder fluid pressure of an automobile's hydraulic brake is higher than a predetermined value. This relates to pressure control valves.

Various configurations of this type of brake fluid pressure control valve are known, but the rear wheel cylinder hydraulic pressure control characteristics have small hysteresis when the fluid pressure rises and falls, and the structure is simple and can be made small. One example is the one described in Japanese Patent Publication No. 50-9949. This brake fluid pressure control valve includes a housing having a stepped cylinder chamber, a master cylinder connection port and a rear wheel cylinder connection port communicating with a large diameter portion and a small diameter portion of the stepped cylinder chamber, respectively, and The stepped cylinder chamber is arranged within the large diameter part, and is formed by a large number of radial protrusions with a cross-sectional radius formed at one end and a large number of axial protrusions with a semicircular cross-section formed on the outer periphery. an annular base part that abuts the end wall and peripheral wall of the diameter part and forms a valve seat at a portion of the inner periphery of the stepped cylinder chamber near the small diameter part; The large stepped cylinder chamber allows brake fluid to flow from the small diameter side of the stepped cylinder chamber to the large diameter side of the stepped cylinder chamber between the peripheral wall and end wall of the diameter section, but prevents it from flowing in the opposite direction. An elastic seal consists of an annular lip that abuts the circumferential wall of the diameter part, and a gap passes through the inside of the annular base of the elastic seal, and one end of the seal is connected to the rear wheel cylinder hydraulic pressure. a piston, the other end of which is exposed to air, and which has a valve head that seats on and leaves the valve seat from the small diameter side of the stepped cylinder chamber; and the piston is attached so that the valve head leaves the valve seat. It consists of a spring that exerts force.

In a brake fluid pressure control valve with such a configuration, during braking, the piston is held in a fixed position with its valve head disengaged from the valve seat of the seal until the rear wheel cylinder fluid pressure reaches a predetermined value, and the rear wheel cylinder fluid is The pressure becomes equal to the master cylinder hydraulic pressure.
When the rear wheel cylinder hydraulic pressure exceeds a predetermined value, the piston moves to the other end and its valve head seats on the valve seat of the seal.Then, as the master cylinder hydraulic pressure increases, the piston reciprocates and the valve head is repeatedly seated and removed from the valve seat, and the rear wheel cylinder hydraulic pressure is controlled as shown by the following equation.

PW=(1-SS/SL)PM+F/SL However, PW: Rear wheel cylinder hydraulic pressure PM: Master cylinder hydraulic pressure SS: Cross-sectional area of the other end of the piston SL: Seal between the two when the valve head is seated on the valve seat Area surrounded by the diameter F: Spring load when the valve head is seated on the valve seat By the way, when the rear wheel cylinder hydraulic pressure is controlled to be lower than the master cylinder hydraulic pressure, the rear wheel cylinder hydraulic pressure and the master cylinder hydraulic pressure are The seal is pressed against the peripheral wall and end wall of the large diameter portion of the stepped cylinder chamber due to the pressure difference, and the axial and radial ridges of the seal are compressed and deformed. This compressive deformation of the axial protrusion increases the inner diameter of the base portion of the seal, and the diameter of the valve seat formed on the inner periphery of the base portion increases. This increase in the diameter of the valve seat causes a change in SL in the above equation, which hinders the stability of the performance of the brake fluid pressure control valve, so it is preferable that the axial protrusion undergoes as little deformation as possible under compressive load. Furthermore, if permanent deformation occurs in the axial protrusions and the radial protrusions due to the repeated application of the differential pressure, the permanent deformation of the axial protrusions promotes the deformation of SL in the above equation, and also the radial protrusions The permanent deformation of the strip causes the seal to displace to the end wall side of the large diameter portion of the stepped cylinder chamber, resulting in a decrease in the amount of displacement of the piston from the rest position to the position where the valve head seats on the valve seat, and the above equation This results in a decrease in F, which also hinders the performance stability of the brake fluid pressure control valve.

However, in the conventional brake fluid pressure control valve described above, a large number of radial protrusions each having a semicircular cross section and a plurality of radial protrusions each having a semicircular cross section are formed on one end surface and the outer peripheral surface of the annular base portion of the seal made of an elastic body. Since a large number of axial protrusions are in contact with the end wall and peripheral wall of the large diameter portion of the stepped cylinder chamber, the above differential pressure acts on the elastic seal, causing each radial protrusion and each axial protrusion to is pressed against the end wall and peripheral wall of the large diameter portion of the stepped cylinder chamber, a large surface pressure acts on each radial protrusion and each axial protrusion, causing each radial protrusion and each axial protrusion to deforms greatly in its initial stage, and the amount of overall deformation increases. As a result, the performance of the brake fluid pressure control valve becomes unstable, and the amount of deformation of each radial ridge and each axial ridge of the elastic seal is large. There is a problem in that the amount of permanent deformation of the protrusion is large, and the performance of the brake fluid pressure control valve changes greatly over time.

The present invention reduces the amount of deformation due to compressive loads and prevents permanent deformation by making the transverse shapes of the axial and radial protrusions of the seal substantially trapezoidal, compared to conventional products whose cross sections were semicircular. This makes the brake fluid pressure control valve more stable in performance than the conventional brake fluid pressure control valve.

Hereinafter, the present invention will be further clarified by describing one embodiment of the present invention based on the drawings.

In FIG. 1, 10 is a brake pedal, 12
is a brake booster, 14 is a tandem master cylinder, 16 and 18 are front wheel cylinders,
20 and 22 are rear wheel cylinders, 24 and 2
6 is a brake fluid pressure control valve.

The front wheel cylinder 18 and the rear wheel cylinder 22 are actuated by pressure fluid from one outlet of the tandem master cylinder 14, and the front wheel cylinder 16 and the rear wheel cylinder 20
The brake hydraulic pressure control valves 24 and 26 control the hydraulic pressure of the rear wheel cylinders 22 and 20, respectively.

The housing 28 of the brake fluid pressure control valve 24 includes a stepped cylinder chamber 36 formed by fitting a plug 32 into the opening of a stepped cylinder bore 30 and preventing it from coming off; a large diameter portion of the stepped cylinder chamber 36; It has a master cylinder connection port 38 and a rear wheel cylinder connection port 40 that communicate with the small diameter portion, respectively, and further has a front wheel cylinder connection port 42 that communicates with the master cylinder connection port 38. A rubber seal 44 is disposed within the large diameter portion of the stepped cylinder chamber 36. The details of this seal 44 are as shown in FIGS. 2 to 4, and its annular base portion 46 is formed at one end thereof and has a plurality of radial protrusions 48 having a substantially trapezoidal cross section. A plurality of axial protrusions 50 having a substantially trapezoidal cross section formed on the outer periphery are in contact with the end wall and peripheral wall of the large diameter portion of the stepped cylinder chamber 36 on the short side surfaces of the outer periphery, and the steps on the inner periphery thereof are A valve seat 52 is formed in a portion of the attached cylinder chamber 36 closer to the small diameter portion. and sticker 4
4, the brake fluid flows between the outer periphery and one end of the annular base portion 46 and the peripheral wall and end wall of the large diameter portion of the stepped cylinder chamber 36 from the small diameter portion side of the stepped cylinder chamber 36 to the large diameter portion side of the stepped cylinder chamber 36. The stepped cylinder chamber 36 has an annular lip portion 54 that abuts against the circumferential wall of the large diameter portion of the stepped cylinder chamber 36 in order to allow the fluid to flow toward the outside but prevent it from flowing in the opposite direction. A piston 56 within the stepped cylinder chamber 36 has one end slidably fitted into the small diameter portion of the stepped cylinder chamber 36 and the other end slidably fitted within the plug 32 to form an air chamber 58. are doing. The piston 56 passes through the inside of the annular base portion 46 of the seal 44 with a gap formed therein, and has a valve head 60 that seats on and leaves the valve seat 52 of the seal 44 from the small diameter side of the stepped cylinder chamber 36. It has an internal passage 62 that communicates the outer peripheral gap of the valve head 60 with the rear wheel cylinder connection port 40. The piston 56 is biased in the direction in which the valve head 60 separates from the valve seat 52 by a spring 68 interposed between the flange 64 and the spring retainer 66, and when not in operation, the piston 56 has one end in a stepped cylinder chamber. 36 occupies the position shown in FIG. 1 in contact with the end wall of the small diameter section. A large number of protrusions 70 are formed at the other end of the annular base portion 46 of the seal 44 to ensure a gap for passage of brake fluid between the annular base portion 46 and the flange 64 of the piston 56 and for positioning the seal 44. In the figure, 72 is a seal that prevents brake fluid from entering the air chamber 58, and 74 is a seal that prevents the brake fluid from entering the air chamber 58.
76 is a snap ring that prevents the plug 32 from coming off, and 78 is a cover that prevents water etc. from entering the housing 28. The master cylinder connection port 38 is connected to one outlet of the tandem type master cylinder 14, and the rear wheel cylinder connection port 40 is connected to the rear wheel cylinder 2.
2 and is connected to the front wheel cylinder connection port 4.
2 is connected to the front wheel cylinder 18.

The brake fluid pressure control valve 24 having such a configuration is manufactured by Tokukosho.
It operates as described in Publication No. 50-9949. When the brake fluid pressure control valve 24 controls the rear wheel cylinder fluid pressure to be lower than the master cylinder fluid pressure, the axial protrusion 5 of the seal 44 is caused by the differential pressure between the rear wheel cylinder fluid pressure and the master cylinder fluid pressure.
A compressive load is applied to the 0 and radial protrusions 48,
The surface of each outer periphery short side of a large number of radial protrusions 48 with a trapezoidal cross section and a large number of axial protrusions 50 with a trapezoidal cross section.
Since the surfaces on the short sides of the outer circumference are in contact with the end wall and peripheral wall of the large diameter portion of the stepped cylinder chamber 36, the surface pressure acting on each radial protrusion 48 and each axial protrusion 50 is Since it is smaller than the conventional one having a semicircular cross section, the amount of deformation of each radial protrusion 48 and each axial protrusion 50 of the seal 44 can be reduced compared to the conventional one. Therefore, according to this embodiment, the valve seat 52 due to the deformation of each axial protrusion 50
Changes in the stroke of the piston 56 and changes in the load of the spring 68 due to changes in the diameter of the valve and the deformation of each radial protrusion 48 can be reduced, and the performance of the brake fluid pressure control valve can be made more stable than in the past. . Furthermore, since the amount of deformation of each radial protrusion 48 and each axial protrusion 50 of the seal 44 can be reduced, the amount of permanent deformation of each protrusion 48, 50 due to the repeated action of the differential pressure can be reduced. This makes it possible to reduce changes in the performance of the brake fluid pressure control valve over time and to improve the durability of the seal 44. In addition, FIG. 5 shows the axial protrusion 50.
and the amount of compressive deformation (amount of reduction in protrusion height of each protrusion) in response to compressive load when the cross-sectional shape of the radial protrusion 48 is semicircular as in the past and trapezoidal as in the present application. It is. Further, according to this embodiment, the surface of each short side of the outer periphery of the large number of radial protrusions 48 having a trapezoidal cross section and the surface of each short side of the outer circumference of the large number of axial protrusions 50 having a trapezoidal cross section are stepped. Since the attached cylinder chamber 36 comes into contact with the end wall and peripheral wall of the large diameter portion, a large number of protrusions can be provided without interference between adjacent protrusions during deformation. Each protrusion 48, 50 can be deformed uniformly and smoothly without large local deformation. Therefore, the durability of each protrusion 48, 50 can be improved, and the performance of the brake fluid pressure control valve can be stabilized. Furthermore, according to this embodiment, the cross-sectional shapes of the many radial protrusions 48 and the many axial protrusions 50 are such that straight lines forming the outer surfaces connect the bases of the respective protrusions 48 and 50. Since it is formed into a trapezoid that is parallel to a straight line and shorter than the straight line, softened rubber easily wraps around the outer edge of the outer surface during molding of the seal 44, resulting in poor molding of each protrusion 48, 50 due to insufficient wrapping. can be reduced,
Its productivity can be improved.

Since the brake fluid pressure control valve 26 is substantially the same as the brake fluid pressure control valve 24, a description thereof will be omitted.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a partial cross-sectional view of a seal, Fig. 3 is a cross-sectional view taken along the - line in Fig. 2, Fig. 4 is a cross-sectional view taken along the - line in Fig. 2, Fifth
The figure is a diagram showing the relationship between the compressive load and the amount of compressive deformation of the axial protrusions and radial protrusions of the seal. 28... Housing, 36... Stepped cylinder chamber, 44... Seal, 46... Annular base portion, 4
8... Radial protrusion, 50... Axial protrusion, 54
...Annular lip portion, 68...Spring.

Claims (1)

[Scope of Claim for Utility Model Registration] A housing having a stepped cylinder chamber, a master cylinder connection port and a rear wheel cylinder connection port communicating with the large diameter portion and the small diameter portion of the stepped cylinder chamber, respectively; A large number of radial protrusions with a trapezoidal cross section formed on one end surface of the large diameter part, and each short side of the outer periphery of a large number of axial protrusions with a trapezoidal cross section formed on the outer peripheral surface of the large diameter part. an annular base portion that abuts the end wall and peripheral wall of the large diameter portion of the stepped cylinder chamber on its side surfaces, and forms a valve seat at a portion of its inner periphery on the side of the small diameter portion of the stepped cylinder chamber; Brake fluid is allowed to flow from the stepped cylinder chamber small diameter section to the stepped cylinder large diameter section between the outer peripheral surface and one end surface and the circumferential wall and end wall of the stepped cylinder chamber large diameter section, but vice versa. an annular lip that abuts against a peripheral wall of a large diameter portion of a stepped cylinder chamber to prevent flow; and an annular lip that penetrates the inner side of the annular base portion of the elastic seal with a gap formed therein. , a piston having one end receiving rear wheel cylinder hydraulic pressure and the other end being exposed to air, and having a valve head that seats on and leaves the valve seat from the small diameter side of the stepped cylinder chamber; A brake fluid pressure control valve comprising a spring that urges the piston to disengage from the valve seat.