JPH1059161A - Plunger type master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger type master cylinder in which a dead stroke of a piston can be set small without deteriorating such characterics that a cup-shaped seal member naturally has, or without increasing slide resistance to the piston. SOLUTION: Contact pressure P of a base part 21 side (protruded part 21d) of a circular seal member 21 to a piston 19 is set to be smaller than contact pressure Q of an inner circumferential lip part 21a of it, so sealing action to a liquid supply hole at the time of a stroke of the piston 19 is performed on the base part 21c side for sufficiently obtaining natural functions of a cup seal when a brake is actuated. A dead stroke of the piston 19 can thus be set smaller without increasing slide resistance to the piston 19 while characteristics that the cup-shaped seal member 21 naturally has are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunger type master cylinder, and more particularly, to a sealing structure of an annular sealing member of a master cylinder.

[0002]

2. Description of the Related Art As a prior art of this kind, Japanese Utility Model 4-39 is used.
No. 090, this conventional plunger-type master cylinder will be described below with reference to the drawings.

FIG. 7 is a sectional view showing a primary piston side of a conventional plunger type master cylinder. A piston guide 2 is disposed in an opening of the cylinder housing 1, and a primary piston 6 is slidably fitted into the piston guide 2 so that the cylinder housing 1
A hydraulic pressure chamber 5 is defined inside. A hole 3 and a liquid supply hole 7 are formed in the piston guide 2 and the piston 6, respectively. When the valve 3 is not operated, the return force is applied to the hole 3 and the liquid supply hole 7 by the spring force of the return spring 10. The reservoir and the hydraulic chamber 5 communicate with each other via a passage 4 communicating with a reservoir (not shown). An annular seal member 8 is provided on the end surface of the piston guide 2 on the side of the hydraulic chamber 5. When the piston 6 is pushed into the hydraulic chamber 5 and the liquid supply hole 7 passes through the seal member 8, The communication between the supply hole 7 and the hole 3 is interrupted, and the hydraulic pressure is generated in the hydraulic pressure chamber 5 by the further movement of the piston 6. An annular sealing member 9 is provided on the end surface of the piston guide 2 on the opening side of the cylinder housing 1 to prevent leakage of the hydraulic fluid to the outside of the cylinder housing 1.

[0004] As shown in FIGS. 8 and 9, the seal member 8 has an inner peripheral lip portion 8 a elastically contacting the outer periphery of the piston 6.
And an outer peripheral lip portion 8b elastically contacting the sleeve 13, and a base portion 8c connecting the inner and outer peripheral lip portions 8a and 8b on the rear end side. Further, a piston 6 is provided on the inner peripheral side of the base portion 8c. A convex portion 8d protruding toward is formed. The seal member 8 has an annular recess 8e formed between the inner and outer lip portions 8a and 8b.
The base portion 8c is fitted to the cylinder housing 1 with the base portion 8c contacting the piston guide 2 toward the side.

When the seal member 8 is disposed in the cylinder housing 1 as shown in FIG. 9, the entire inner peripheral surface of the seal member 8 is in contact with the piston 6; As shown by the length of the arrow in the pressing force line diagram indicated by middle A, the pressing force on the base portion 8c side is
The pressure is greater than the pressure contact force a. As a result, the seal point of the piston 6 is shifted further rearward (to the right in the figure), and the distance between the seal point and the liquid replenishment hole 7 of the piston 6,
That is, the ineffective stroke of the piston 6 is to be reduced.

[0006]

Usually, a cup-shaped sealing member (also called a cup seal or a lip seal) such as the sealing member 8 has a sealing point at an inner peripheral lip portion and an outer peripheral lip portion. During the operation of the brake, these lip portions receive the hydraulic pressure generated in the hydraulic pressure chamber as back pressure and increase their own pressure contact force, so that a high sealing effect due to the structure can be obtained. doing.

However, since the base portion 8c of the seal member 8 of the conventional master cylinder communicates between the inner peripheral lip portion 8a and the outer peripheral lip portion 8b, the resultant force is high, and the pressure contact force of the base portion 8c is high. Is larger than the press-contact force of the inner peripheral lip portion 8a, and the seal point for the piston 6 is on the base portion 8c side. Therefore, there is a problem that it is difficult to obtain the inherent characteristics of the cup seal as described above. In short, the conventional sealing member 8 has a cup shape, but attempts to reduce the invalid stroke of the piston 6 at the expense of the inherent characteristics of the cup seal.

Further, the conventional sealing member 8 has a base portion 8c.
Since the pressure contact force on the side is further increased than before, there is a problem that the sliding resistance against the piston 6 is inevitably increased. In this case, the piston 6 cannot move smoothly, and a quick brake release operation due to a delay in returning the piston 6 cannot be performed.

The present invention has been made in view of the above-described problems, and it is an object of the present invention to reduce the invalid stroke of a piston without sacrificing the inherent characteristics of a cup-shaped seal member and without increasing the sliding resistance to the piston. It is an object to provide a plunger-type master cylinder that can be used.

[0010]

The above objects are attained by providing a cylinder body having a cylinder hole, a piston which is movably fitted in the cylinder hole in the axial direction to define a hydraulic chamber, and a piston formed in the piston. A fluid passage including a fluid supply hole that communicates with the reservoir, and a fluid passage that is held in the cylinder hole and moves the fluid supply hole toward the reservoir in response to movement of the piston toward the fluid pressure chamber. An annular seal member that blocks from the, the annular seal member,
An outer peripheral lip having a distal end facing the hydraulic chamber and elastically contacting the cylinder body side, an inner peripheral lip having a distal end facing the hydraulic chamber and elastically contacting the outer periphery of the piston, and a rear lip of each of these inner and outer peripheral portions. A plunger-type master cylinder having a base portion communicating with an end side, and a protrusion protruding toward the piston formed on the inner peripheral side of the base portion. A plunger-type master cylinder is characterized in that the inner peripheral lip portion has a pressure contact force smaller than that of the piston.

By making the pressure contact force of the convex portion projecting from the inner peripheral side of the base portion of the annular seal member to the piston smaller than the pressure contact force of the inner peripheral lip portion to the piston, liquid replenishment at the time of the piston stroke at the base portion side. The fluid communication between the reservoir and the hydraulic chamber through the hole is cut off, and the original characteristics of the seal member having the inner peripheral lip portion as the main pressure contact force with the piston during the brake operation are sufficiently exhibited. This makes it possible to reduce the invalid stroke of the piston while sufficiently obtaining the original characteristics of the cup seal. Further, since the pressure contact force of the seal member with respect to the piston is not increased at all as compared with the related art, the sliding resistance with respect to the piston does not increase, so that smooth movement of the piston can be ensured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plunger-type master cylinder according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a plunger-type master cylinder according to an embodiment of the present invention. A seal ring 2 is provided at one end opening of the cylinder body 16.
The primary piston 19 and the secondary piston 20 are slidably fitted to the piston guides 25 and 26 in the cylinder body 16, and the two pistons 19 are fitted therein. , 2
0, a primary hydraulic chamber 30 is defined, and between the secondary piston 20 and the lid member 17, a secondary hydraulic chamber 31 is defined.

The piston guide 25 includes a seal ring 27
Is supported by the cylindrical member 18 screwed and fixed to the opening of the cylinder hole 40. Piston guide 25
The cylinder body 16 is formed with a radial passage 51, and the cylinder body 16 is formed with a communication hole 57. These holes are formed through a nipple portion 45 of the reservoir fitted into the boss portion 41 of the cylinder body 16 together with the seal ring 43. It communicates with the inside. The annular seal member 21 according to the present invention is provided on the end surface of the piston guide 25 on the primary hydraulic pressure chamber 30 side.
Is provided, and details thereof will be described later. An annular sealing member 23 is provided on the side of the piston guide 25 on the opening side of the cylinder hole 40.

The primary piston 19 has a fluid supply hole 1 for communicating the primary hydraulic chamber 30 with the reservoir.
9a is formed, and in the illustrated inoperative position, the liquid supply hole 19a is formed through the radial passage 51 of the piston guide 25 and the inner peripheral surface of the piston guide 25 and the outer peripheral surface of the primary piston 19. It is in communication with the liquid supply hole 19a through the communication or between the cylinder hole 40 and the piston guide 25 and between the annular seal member 21 and the piston guide 25.

The other piston guide 26 is fitted in a cylinder hole 40 with a seal ring 29 attached to the outer peripheral portion, and is supported by the lid member 17. The piston guide 26 has a radial passage 52 and an axial passage 53 orthogonal thereto,
A communication hole 58 is formed in the cylinder body 16 and communicates with the inside of the reservoir via a nipple portion 46 of the reservoir fitted into the boss portion 42 of the cylinder body 16 together with the seal ring 44. The annular seal member 22 according to the present invention is also provided on the end surface of the piston guide 26 on the side of the secondary hydraulic chamber 31. An annular sealing member 24 that blocks fluid communication between the primary hydraulic chamber 30 and the secondary hydraulic chamber 31 is provided on an end face of the piston guide 26 on the primary hydraulic chamber 30 side.

Further, the secondary piston 20 is similarly formed with a fluid supply hole 20a for communicating the secondary hydraulic chamber 31 with the reservoir, and in a non-operating position shown in the drawing, a radial passage 52 of the piston guide 26 is provided. , And the inner peripheral surface of the piston guide 26 and the secondary piston 2
0, and communicates with the liquid supply hole 20a through the outer peripheral surface of the liquid supply hole 20a, or through the radial passage 52, the axial passage 53, and the liquid supply hole 20a through the space between the annular seal member 22 and the piston guide 26. Communicating.

The nipple portions 45 and 46 are held by a common nipple holder 47, and the nipple holder 47 is integrally fixed to the cylinder body 16 by screws 48 and 49.

A return spring 32 is stretched between the primary piston 19 and the secondary piston 20, one end of which is connected to the primary piston 19, and the other end of which is the retainer 3.
6 is supported. The retainer 36 is relatively movable with respect to a bolt member 34 as a connecting member screwed and fixed to the primary piston 19, and is engageable with a head 34 a of the bolt member 34. The bottom 36 </ b> A of the retainer 36 is in contact with the secondary piston 20 by the spring force of the return spring 32.

Further, the secondary piston 20 and the lid member 1
A return spring 33 is also stretched between the secondary piston 7 and one end, and one end is supported by the secondary piston 20 and the other end is supported by the retainer 37. The retainer 37 is a secondary piston 2
It is relatively movable with respect to a bolt member 35 as a connecting member screwed and fixed to 0, and is engageable with a head 35a of the bolt member 35. Retainer 37
Of the cover member 1 by the spring force of the return spring 33.
7 is in contact.

The return spring 33 on the secondary side has a slightly smaller spring force than the return spring 32 on the primary side, and is not shown at the rear end (right side in the figure) of the primary piston 19. Since the drive rod of the booster is engaged in a loaded state, the primary piston 19 is positioned in the illustrated stationary state (non-operating state). Further, the secondary piston 20 is performed by balancing the spring forces of the return springs 32 and 33. If the positioning of the primary piston 19 during non-operation cannot be performed correctly, the secondary piston 20 is brought into contact by the flange portion 20b of the secondary piston 20 abutting against the step portion 100 inside the cylinder hole 40.
Is performed.

Next, the annular sealing member 2 according to the present invention
1 and 22 will be described, but since they have exactly the same structure, only one seal member 21 will be typically described.

The seal member 21 is made of rubber and has a front end facing the primary hydraulic chamber 30, an inner peripheral lip portion 21 a elastically contacting the outer periphery of the primary piston 19, and a front end facing the primary hydraulic chamber 30. The outer peripheral lip portions 21b which are in elastic contact with the inner and outer peripheral lip portions 21a,
1b at the rear end side and a base portion 21c, which is a so-called cup seal. FIG.
As shown in the figure, a convex portion 21d projecting from the piston 19 is formed on the inner peripheral side of the base portion 21c. A plurality of (six in this embodiment) cutouts 21f are formed at equal intervals on the outer periphery of the base 21c of the seal member 21.

In the present embodiment, as shown by reference numeral g in FIG.
2, the space 55 is secured between the outer periphery of the base portion 21c and the cylinder body 16 so as to fit into the cylinder hole 40 as shown in FIG.
As a result, when the seal member 21 is mounted on the master cylinder 15, as shown in FIG. 6, the pressure contact force line segment P (with the length of the arrow from the reference line O) of the protrusion 21d on the base portion 21c side against the piston 19, as shown in FIG. ) Is made smaller than the pressing force Q of the inner peripheral lip portion 21a against the piston 19. The pressing force P of the projection 21d is large enough to perform a desired sealing action.

The pressure contact force Q is defined by a line A of the pressure contact force of the conventional seal member 8 with respect to the piston 6 shown in FIG.
The size is substantially equal to the size of the inner peripheral lip 8a. That is, the seal member 21 according to the present embodiment
The pressure contact force on the inner peripheral lip portion 21a side is predominant without increasing the pressure contact force on the rim 9 at all.

Further, in the present embodiment, the sealing member 21
When the inner peripheral surface of the rim abuts on the piston 19, a space S is formed between the inner peripheral lip portion 21a and the base portion 21c (convex portion 21d).
Are formed, and these inner peripheral lip portions 2 are formed.
The seal member 21 is supported at three points 1a, the convex portion 21d, and the outer peripheral lip portion 21b.

The seal member 21 is configured as described above, but the spacer 38 is disposed on the step portion 50 of the cylinder hole 40 so as to face the base portion 21c. The main body 38a of the spacer 38 enters a recess 21e formed between the lip portions 21a and 21b on the inner and outer circumferences of the annular seal member 21 (see FIG. 2). The spacer 39 disposed on the other seal member 22 also has the same structure, and is disposed on the step 17 a at the tip end of the lid member 17.

As shown in FIG. 4 and FIG.
Reference numeral 8 denotes an annular spacer body 38a and a plurality of (four in the present embodiment) enlarged diameter portions 38b integrally formed therewith.
These enlarged diameter portions 38 b are elastically deformed (reduced in diameter) so as to engage with the wall surface of the cylinder hole 40, and are disposed in the step portion 50 of the cylinder hole 40. The other spacer 39 also has the same configuration.

The plunger-type master cylinder 15 according to the present embodiment is configured as described above. Next, this operation will be described.

When a brake pedal (not shown) is depressed,
Also, the primary piston 19 moves from the inoperative position shown in FIG. 1 to the left through the booster (not shown). At the same time, the liquid supply hole 19a also moves, but the liquid supply hole 19a is
When reaching d), the fluid communication between the primary hydraulic chamber 30 and the reservoir is cut off. The hydraulic pressure is generated in the primary hydraulic chamber 30 by the further movement of the primary piston 19, and is supplied to a brake device (not shown). The secondary piston 20 also moves with the movement of the primary piston 19, and its liquid supply hole 20a is
When the secondary hydraulic chamber 31 reaches the base portion 22c (22d), the fluid communication between the secondary hydraulic chamber 31 and the reservoir is interrupted, and further movement of the secondary piston 20 generates hydraulic pressure in the secondary hydraulic chamber 31. Not supplied to the braking device. As a result, all the wheels (not shown) are braked.

At this time, the hydraulic pressure generated in both the primary and secondary hydraulic chambers 30, 31 acts on the recesses 21e, 22e of the seal members 21, 22 according to the present invention, and the inner peripheral lip portions 21a thereof. , 22a and outer lip 21
It works to increase the pressure contact force (sealing force) of b and 22b.
That is, the original characteristics of the cup-shaped seal member function.

As described above, according to the present embodiment, the sealing members 21 and 22 use the pressing force of the inner peripheral lip portions 21a and 22a as the main pressing force against the pistons 19 and 20, while the base member 21c does not. , 22c are also provided with a pressure contact force enough to obtain a sealing force, so that the liquid supply holes 19a, 20a of the pistons 19, 20 reach just below the base portions 21c, 22c of the sealing members 21, 22. At this point, the hydraulic chambers 30, 31 can be shut off from the reservoir side. That is, the invalid stroke of the pistons 19 and 20 can be reduced.

When the depression on the brake pedal is released to stop the brake operation, the primary piston 19 and the secondary piston 20 return to the inoperative positions shown in the drawing by the spring forces of the return springs 32 and 33.

At this time, in the present embodiment, the pistons 1 of the projections 21d and 22d of the seal members 21 and 22 are used.
As described above, the pressing force on the inner peripheral lip portion 2
Since the pressing force of the pistons 19, 20 against the pistons 19, 20 is smaller than that of the pistons 19, 20, the pistons 19, 20 can slide smoothly on the sealing members 21, 22, so that the pistons 19, 20 can be moved to the inoperative position shown in the drawing. You can return smoothly.

When the pistons 19, 20 return to the non-operating position due to the spring forces of the return springs 32, 33, the interiors of the primary and secondary hydraulic chambers 30, 31 tend to be under negative pressure. The liquid is applied to the sealing members 21 and 2
The outer peripheral lip portions 21b and 22b are bent inward in the radial direction and supplied to the two hydraulic pressure chambers 30 and 31 so that the pistons 19 and 20 return quickly. Therefore, in the present embodiment, as described above, the notches 21f, 2f are formed on the outer periphery of the bases 21c, 22c of the seal members 21, 22 at equal intervals.
2f is formed at each of six locations, so that the hydraulic pressure chamber 3
0, 31 can be easily replenished, and the piston 1
Return of 9 and 20 can be performed quickly. Therefore, a quick brake release operation can be performed.

Further, in this embodiment, the spacer 38,
By arranging 39, the sealing members 21 and 22 can be positioned, and the sealing members 21 and 22 are respectively positioned at three points of the inner peripheral lip portions 21a and 22a, the outer peripheral lip portions 21b and 22b, and the convex portions 21d and 22d. Because it is supported,
Movement of both pistons 19, 20 or both hydraulic chambers 3 for hydraulic fluid
The tilting of the seal members 21 and 22 at the time of replenishment into the insides 0 and 31 can be prevented, and a stable shutoff operation between the hydraulic chambers 30 and 31 and the reservoir can always be performed. In addition, the spacers 38 and 39 are used as the sealing members 21 and 22.
Are provided so as to abut only a part of the inner lip portions 21a and 22a of the outer lip portions 21a and 22a.
There is no hindrance to the bending deformation of b and 22b.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, the spacer 39 for positioning the seal member 22 on the secondary piston 20 side is provided as a separate member similarly to the spacer 38 on the primary piston 19 side, but is integrated with the lid member 17. May be formed.

In the above embodiment, the sealing member 2
The notches 21f and 22f formed on the outer circumferences of the base portions 21c and 22c of the first and second 22 are formed at six locations at equal intervals. However, the number of the notches 21f and 22f is not limited to this. Good.

In the above-described embodiment, as shown in FIG. 2, when the inner peripheral surface of the seal member 21 comes into contact with the piston 19, the inner peripheral lip portion 21a and the base portion 21c (the convex portion 21d) are formed. A space S is formed between
This may be omitted. Secondary side sealing member 22
Is the same.

[0041]

As described above, according to the plunger type master cylinder of the present invention, it is possible to reduce the invalid stroke of the piston while sufficiently exhibiting the characteristics inherent in the cup-shaped seal member. The piston can be moved smoothly.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an entire plunger type master cylinder according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part in FIG.

FIG. 3 is an enlarged sectional view showing a free state of an annular seal member according to the embodiment of the present invention.

FIG. 4 is an enlarged front view of a spacer according to the embodiment of the present invention.

FIG. 5 is a sectional view taken along line [5]-[5] in FIG.

FIG. 6 is a diagram showing a distribution of a pressing force applied to a piston on an inner peripheral surface of an annular seal member according to the embodiment of the present invention.

FIG. 7 is a sectional view showing a main part of a conventional plunger type master cylinder.

FIG. 8 is an enlarged sectional view showing a free state of an annular seal member in a conventional example.

FIG. 9 is a diagram showing a distribution of a pressing force on a piston on an inner peripheral surface of an annular seal member in a conventional example.

[Explanation of symbols]

 15 Plunger Master Cylinder 16 Cylinder Body 19 Primary Piston 19a Liquid Supply Hole 20 Secondary Piston 20a Liquid Supply Hole 21 Seal Member 21a Inner Peripheral Lip 21b Outer Peripheral Lip 21c Base 21d Convex 21e Concave 21f Notch 22 Seal 30 Primary hydraulic chamber 31 Secondary hydraulic chamber 38 Spacer 39 Spacer 40 Cylinder hole 55 Space

Claims (4)

[Claims] A cylinder body having a cylinder hole;
A piston which is movably fitted in the cylinder hole in the axial direction to define a hydraulic pressure chamber, a liquid passage including a liquid supply hole formed in the piston and which communicates the hydraulic pressure chamber with a reservoir; An annular seal member that shuts off the liquid supply hole from the reservoir side in response to the piston moving toward the hydraulic pressure chamber while being held at the hydraulic pressure chamber side. An outer peripheral lip portion facing the chamber and elastically contacting the cylinder body side, an inner peripheral lip portion having a front end facing the hydraulic pressure chamber and elastically contacting the outer periphery of the piston, and these inner and outer lip portions are connected at the rear end side. A plunger-type master cylinder having a base portion and a projection protruding toward the piston on an inner peripheral side of the base portion, wherein a pressing force of the convex portion against the piston is applied to the inner peripheral rib. A plunger-type master cylinder characterized in that a pressure of the tapping portion against the piston is smaller than that of the plunger. 2. The annular seal member is formed such that an inner diameter of a portion of the inner peripheral lip portion serving as a seal point with respect to the piston is smaller than an inner diameter of the protrusion.
The plunger-type master cylinder according to claim 1, wherein a space is secured in the cylinder body side on the outer periphery of the base portion, and the space is fitted into the cylinder hole. 3. A spacer, which enters a recess formed between both lip portions on the inner and outer circumferences and faces the base portion in the cylinder hole. Alternatively, the plunger-type master cylinder according to claim 2. 4. A plurality of notches are formed at equal intervals on an outer periphery of the base.
Plunger-type master cylinder described in 1.