JPH0445973Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tandem master cylinder used in a brake circuit of a vehicle or the like. [Prior art and its problems] For example, the master cylinder described in Japanese Utility Model Publication No. 1637/1983 includes a cylinder body having a cylinder hole formed therein, a pair of pistons slidably fitted into the cylinder hole, A tandem master cylinder is disclosed that includes a main pressure chamber defined in the cylinder hole between the pair of pistons, and a subordinate pressure chamber defined between one of the pair of pistons and the bottom of the cylinder hole. ing. In this master cylinder, in order to shorten the entire piston, a portion of the piston protrudes to the outside, and the inside thereof slides on the inner wall of the cylinder hole. However, although this piston is stepped and guided at two locations with different diameters within the cylinder hole, the sliding movement is unstable, and the distance between the cup seal attached to the piston and the connection hole to the wheel cylinder is , in the non-operating position of the piston, the cup seal connects the connecting hole during the stroke of the piston,
Since it must be made sufficiently large so that it does not pass through, it is difficult to shorten it further. In order to solve this problem,
As shown in Publication No. 219468, a guide member for slidingly guiding the other piston of the pair of pistons is provided at the opening of the cylinder hole, and the other piston is a plunger type piston whose sliding portion has the same outer diameter. It is possible to do so. However, in this case, if the pair of pistons have the same outer diameter, even when the other piston, which is a plunger type, strokes beyond the connection hole, the piston is Since it is necessary to form a gap between the outer periphery of the other piston and the inner wall of the cylinder hole over the stroke range of , it is necessary to insert a sleeve into the cylinder hole. In order to provide a recess that serves as a liquid passage, the cylinder hole must be machined into a stepped shape with a step formed deep within the cylinder hole, which poses a problem of complicating the cylinder body. [Problems to be solved by the invention] The present invention has been made in view of the above problems, and aims to provide a master cylinder that can stabilize the piston guide while shortening the entire master cylinder without complicating the cylinder body. purpose. [Means for solving the problem] The above object is to provide a cylinder body having a cylinder hole with one end open, a pair of pistons movably fitted into the cylinder holes, and a cylinder body between the pair of pistons. a main pressure chamber defined within the cylinder hole, and a subordinate pressure chamber defined between the bottom of the cylinder hole and one of the pair of pistons;
a guide member provided at the opening of the cylinder hole for slidingly guiding the other piston of the pair of pistons, the other piston being a plunger-type piston whose sliding portion has the same outer diameter; This is achieved by using a master cylinder in which the outer diameter of the other piston is smaller than the outer diameter of the sliding portion of the one piston. [Operation] The sliding parts of the pistons located on the opening side of the inner cylinder holes of the pair of pistons are not stepped like in the past, but have the same outer diameter, so the guide mechanism can be simplified, and Since the inner end side can be moved beyond the pressure fluid discharge port formed on the inner wall of the cylinder hole, the length of the entire master cylinder can be reduced accordingly. In addition, since the sliding parts have the same outer diameter, there is no need to slide the inner cylinder hole wall, so even if there is a slight error in the concentricity between the cylinder hole and the inner hole of the guide mechanism, the piston guide can be performed stably without causing twisting. This ensures stable operation. In addition, since the outer diameter of the piston located on the opening side is smaller than the outer diameter of the sliding part of the piston located on the bottom side of the cylinder hole, there is a gap between the piston on the opening side and the cylinder hole. The main pressure chamber and the pressure fluid discharge port are communicated with each other without inserting a sleeve that covers the stroke range of the piston, or without performing processing such as forming a step at a deep position from the opening of the cylinder hole. A gap serving as a liquid passage is secured. [Embodiment] Hereinafter, a tandem master cylinder according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a tandem master cylinder according to a first embodiment. In the figure, the tandem master cylinder is indicated as a whole by 1, and a cylinder body 2 is formed with boss portions 2a and 2b, which are not shown in the figure. Reservoir installed. Further, the cylinder body 2 is formed with a stepped hole 3 that communicates with the inner holes of the boss portions 2a and 2b and extends in the axial direction. It consists of a medium diameter hole section 5 and a large diameter hole section 6.
A floating piston 7 is attached to the small diameter hole 4 with a cup seal 1.
A slit 12 extending in the axial direction is formed between the cup seals 10 and 11 to define a liquid supply chamber 13 . Further, a stopper bolt 14 is screwed and fixed to the lower wall of the cylinder body 2, and this shaft normally comes into contact with the left end wall of the slit 12 as shown in the figure to restrict the return position of the floating piston 7. ing. A first hydraulic pressure chamber 15 is defined between the closed end wall of the cylinder body 2 and the floating piston 7, and a return spring 9 disposed in this chamber urges the floating piston 7 to the right in the figure. are doing. Further, a liquid replenishment hole 16 is formed in the upper wall portion of the cylinder body 2 so as to communicate with the inner hole of one boss portion 2a, and this is always in communication with the above-mentioned liquid replenishment chamber 13 . Connection holes 17 and 39 for connecting the wheels to the wheel cylinders are further formed in the lower wall portion of the cylinder body 2, and one of the connection holes 17 is always in communication with the first hydraulic pressure chamber 15 . The left part of the floating piston 7 is formed as a cylindrical part 18, and a spring receiver 19 is fitted and fixed to the open end of this part, and between this and a valve rubber 20 attached to the tip of the valve rod 21 A spring 24 is tensioned and urges the valve rod 21 to the right in the figure. The valve rod 21 is slidably fitted into an axial through hole 23 formed on the right side of the floating piston 7, and its right end abuts against the stopper bolt 14. Further, a hole 22 is formed in the peripheral wall of the cylindrical portion 18, thereby facilitating fluid communication between the inner hole in the cylindrical portion 18 and the hydraulic pressure generating chamber 15. The inner hole also communicates through a center hole 19a formed in the spring receiver 19. Further, a portion of the cylindrical portion 18 corresponding to the bottom wall functions as a valve seat 18a, and normally faces the end surface of the above-mentioned valve rubber 20 with a predetermined gap as shown in the figure. As will be described later, when the floating piston 7 moves to the left, the valve rubber 20 moves toward the valve seat 1.
In this state, the valve rubber 20, valve seat 18a, spring 24, etc. function as a check valve whose forward direction is toward the hydraulic pressure chamber 15. A guide member 26 equipped with a seal ring 27 is fitted and fixed at the open end of the cylinder body 2, and a cup seal 26 is attached to the right inner peripheral wall.
9 is attached to the main piston 8, and slides on the peripheral wall surface of the main piston 8 guided by the guide member 26 to perform a sealing action. Further, a support ring 28 is screwed and fixed to the open end, and between this and the guide member 26, the cup seal 29 is stably held at the position shown in the figure. In addition, the cup seal 3 is also
1 is fitted and fixed, and this is supported by a support ring 32.
The support ring 32 has a notch 32a to facilitate fluid communication.
is formed. A small hole 38 is formed near the inner end of the main piston 8 and faces the left end of the cup seal 31 in the illustrated return position. Further, a through hole 26a is formed in the guide member 26, which is similar to the through hole 3 formed in the cylinder body 2.
3, it is constantly in communication with the inner hole of the boss portion 2b. The main piston 8 has the same diameter over its entire length, but this outer diameter is smaller than the outer diameter of the portion of the floating piston 7 that slides into the small diameter hole 4. Further, this left part is formed into a cylindrical shape like the above-mentioned floating piston 7, and a spring receiving member 34 having a T-shaped cross section is provided in this inner hole.
A locking member 36 is attached to this shaft-shaped portion, and is engaged with a hole formed in the bottom wall of a substantially spring-shaped spring receiving member 37.
A spring 35 is stretched between the flange portion of the spring receiving member 37 and the spring receiving member 34. The spring force of this spring 35 is applied to the first hydraulic pressure generating chamber 1.
It is larger than the spring force of the return spring 9 disposed at 5.
A second hydraulic pressure generating chamber 25 is defined between the main piston 8 and the floating piston 7, and is always in communication with a connecting hole 39 formed in the lower wall of the cylinder body 2. Note that the recess 3 formed at the outer end of the main piston 8
0 is engaged with a push rod of a brake pedal (not shown). The tandem master cylinder according to the embodiment of the present invention is constructed as described above, and its operation will be explained next. When a brake pedal (not shown) is depressed, the main piston 8 is pushed to the left in the figure, and through the spring force of the strong spring 35, the floating piston 7 is pushed to the left. The floating piston 7 moves to the left in the figure against the spring force of the return spring 9. As a result, it comes into contact with the left end wall of the slit 12. When the stopper bolt 14 is separated from this, the valve rod 21 is moved to the right by the force of the spring 24, and the valve rubber 20 is seated on the valve seat 18a. Therefore, the first hydraulic pressure generating chamber 15 and the liquid replenishing chamber 13 are cut off. Thereafter, as the floating piston 7 moves to the left, hydraulic pressure is generated in the first hydraulic pressure generating chamber 15 , and this is transmitted to the wheel cylinder of the wheel via the connecting hole 17. Also, the main piston 8 and the idle piston 7
By resisting the spring force of the spring 35 and reducing the distance between the two, hydraulic pressure is also generated in the second hydraulic pressure generating chamber 25 , and this is applied to the wheel cylinder of the other wheel via the connecting hole 39. is transmitted to. Brakes are then applied to each wheel. Note that the leftward pushing of the main piston 8 causes the inner circumferential wall surface of the small diameter hole 4 to move because its outer diameter is smaller than the outer diameter of the portion of the floating piston 7 that slides into the small diameter hole 4. This is done without sliding, and even if the left end of the main piston 8 moves beyond the position of the connection hole 39, the second
A gap is secured that serves as a liquid passage that communicates the liquid pressure generation chamber 25 and the connection hole 39. When the pedal force on the brake pedal is released, the spring force of the return spring 9 and the spring 35 causes the main piston 8 and the floating piston 7 to move to the right in the figure.
As a result, negative pressure is generated in the second hydraulic pressure generating chamber 25 , but the liquid from the reservoir (not shown) is transferred to the boss portion 2b.
The lip portion of the cup seal 31 is bent through the inner hole 33, the through hole 26a formed in the guide member 26, and the gap between the guide member 26 and the peripheral wall of the main piston 8, and the notch of the support ring 32 is bent. Liquid is replenished through 32a. Therefore, the main piston 8 is quickly moved to the return position, and when the small hole 38 formed in this cylindrical portion moves further to the right beyond the lip of the cup seal 31, liquid flows from the reservoir through this hole 38. The main piston 8 is quickly refilled to the hydraulic pressure chamber 25 , and the main piston 8 is quickly moved back to the return position shown in the figure. On the other hand, negative pressure is generated in the liquid pressure generation chamber 15 due to the movement of the floating piston 7 to the right .
The liquid from the valve causes the valve rubber 20 to open and the liquid pressure generation chamber 1
5 to ensure rapid movement of the piston 7. When the piston 7 moves further, the valve rod 21
When the right end of the valve comes into contact with the stopper bolt 14, the valve rubber 20 is separated from the valve seat 18a as shown in the figure, and thus the hydraulic pressure generation chamber 15 and the liquid replenishment chamber 13 are separated from each other.
The brake fluid from the reservoir is in free communication with the fluid replenishing chamber 13 , the through hole 23 through which the valve rod 21 is inserted, the inner hole 22 in the cylindrical portion 18, and the spring receiver 19.
The liquid is replenished through the center hole 19a. Therefore, the liquid is quickly replenished from the liquid supply chamber 13 without generating negative pressure in the liquid pressure generation chamber 15 , and like the main piston 8, it can be quickly moved to the return position. As a result of the above, the pressure fluid in the wheel cylinder returns to the fluid pressure generation chambers 15 and 40 . This releases the brakes. The above is the operation of the first embodiment of the present invention, and the following effects are achieved. That is, according to this embodiment, the main piston 8 has the same diameter over its entire length, is guided by the guide member 26, and moves to the left from the position shown in FIG. 1 when the brake is applied. Since the outer diameter of 8 is smaller than the outer diameter of the portion of the floating piston 7 that slides in the small diameter hole 4, the main piston 8 does not slide in this small diameter hole 4, but moves with a gap. Therefore, even if the left end portion of the main piston 8 moves further to the left beyond the position of the connection hole 39, a gap is secured that will serve as a liquid passage that communicates the hydraulic pressure generation chamber 25 and the connection hole 39. In other words, according to this embodiment, the cylinder body can be easily made without complicating the cylinder body by inserting a sleeve into the cylinder hole or forming a step deep in the cylinder hole as in the conventional case. Despite the simple construction of 2, the main piston 8 can move within the cylinder body 2 beyond the connecting hole 39. Therefore, since there is no need to provide a sleeve or difficult machining, productivity can be improved and costs can be reduced. Further, since it is cylindrical and most of the length of the spring 35 is located within the cylinder, the entire length of the tandem master cylinder 1 can be shortened. Furthermore, according to this embodiment, the main piston 8 has the same diameter as a whole (plunger type piston), so the guide member 26 only needs to be provided at one location, and if it is a stepped piston like the conventional one, the guide member 26 is required at at least two locations. This embodiment has a much simpler configuration. Furthermore, since the main piston 8 only needs to move with a gap in the small diameter hole 4 of the stepped hole 3 of the cylinder body 2, it is easy to obtain concentricity between them during machining. do. That is, the concentricity of the main piston 8 with respect to the small-diameter hole 4 of the cylinder 2 can be machined without requiring much precision, so that production costs can be further reduced than in the past. FIG. 2 shows a tandem master cylinder according to a second embodiment of the present invention, generally designated 41. Also, parts corresponding to those in the first embodiment are given the same reference numerals, and detailed explanation thereof will be omitted. A stepped hole 43 is formed in the cylinder body 42 . From the left, a small diameter hole 44, a medium diameter hole 45,
It consists of a first large diameter hole 49a and a second large diameter hole 49b, and a floating piston 46 is slidably fitted into the small diameter hole 44 with cup seals 50, 51 attached thereto. A piston 46 is formed into a cylindrical shape between the cup seals 50 and 51, and a spring 48 is returned to the inner hole of the cylindrical portion 47 and is stretched between the inner end wall of the cylinder body 42 and the inner end wall of the cylinder body 42. A boss portion 42a is formed on the upper wall portion of the cylinder body 42, and a liquid supply hole 53 and a return hole 54 are formed in communication with this inner hole. Further, the annular liquid chamber between the cup seals 50 and 51 of the floating piston 46 is used as a liquid replenishment chamber 58 , and the cylinder body 42
A first hydraulic pressure generating chamber 52 is defined between the inner end wall of the piston 46 and the floating piston 46 . This is in constant communication with the connection hole 55 connected to the wheel cylinder.
A ring-shaped stopper member 56 is fitted and fixed at the end of the medium-diameter hole 45 on the right side of the floating piston 46, and is held in the illustrated position by a stopper bolt 57. The stopper member 56 normally abuts the end surface of the floating piston 46 as shown. Although only one stopper bolt 57 is shown in the figure, two or three stopper bolts 57 may actually be screwed and fixed at equal angular intervals.
This allows the stopper member 56 to be held more stably. Note that if the outer diameter of the floating piston 46 is _D2 , the inner diameter of _the stopper member 56 is D1, and the outer diameter of the main piston 8 is _D3 , the following relationship is given: _D3 < _D1 < _D2 . That is, when the main piston 8 moves to the left from the illustrated position, its front end portion can move further to the left through the opening of the stopper member 56. It is assumed that the connection hole communicating with the second hydraulic pressure generating chamber 25 (corresponding to the connection hole 39 in the first embodiment) is formed at a position angularly offset from the stopper bolt 57. For example 90°
It may be formed at an offset position. The present embodiment is configured as described above, and its operation will be explained. The function of the main piston 8 is the same as that in the first embodiment, so the function of the floating piston 46 will be mainly explained. When the brake pedal (not shown) is depressed, the first
Similarly to the embodiment, the floating piston 46 resists the spring force of the return spring 48 and moves to the left in the figure. When the cup seal 50 passes through the return hole 54, hydraulic pressure is generated in the first hydraulic pressure generating chamber 52 , and this is transmitted to the wheel cylinder of the wheel via the connecting hole 55, thereby applying the brake. Next, when the pressure on the brake pedal is released, the floating piston 46 moves to the right. At this time, when negative pressure is generated in the fluid pressure generation chamber 52 , brake fluid is drawn from the reservoir via the fluid supply chamber 58 . The lip of the cup seal 50 is bent to replenish the liquid. Therefore, even if negative pressure is generated, by replenishing the liquid, the floating piston 46 can quickly move to the return position shown in the figure. By contacting the stopper member 56, its return position is regulated. Other functions and effects are the same as those in the first embodiment, so their explanation will be omitted. FIG. 3 shows a tandem master cylinder according to a third embodiment of the present invention. In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted. That is, according to this embodiment, the floating piston is fitted in the cylinder hole at an angular position deviated by 90° from that of the first embodiment. Also, the main piston 8
The guide mechanism is different from that of the first embodiment. A stepped hole 63 extending in the axial direction is formed in the cylinder body 62, and this consists of a small diameter hole 64 and a large diameter hole 65, and the floating piston 7 is fitted into the small diameter hole 64. . In the guide mechanism, a support ring 67 and a cup seal 66 are provided in the large diameter hole 65 as in the first embodiment.
Although the guide member 68 has a stepped shape, its small diameter portion fits into the open end of the cylinder body 62. The large diameter portion is in contact with the right end surface of the cylinder body 62. Also, unlike the first embodiment, this embodiment does not include a seal ring. A through hole 68a is formed in the guide member 68. Further, on the right side, a cup seal 70 is supported by a bottom wall portion of a lid member 69 that is screwed and fixed to an annular space formed at the end of the cylinder body 62. The cup seals 66 and 70 slide against the peripheral wall of the main piston 8 for sealing, and the bottom wall of the lid member 69 has an opening through which the main piston 8 is inserted. Furthermore, a seal ring 70' is installed between the peripheral wall of the lid member 69 and the end wall of the cylinder body 62 to seal the outside and the inside of the cylinder body 62. According to the example, a vacuum booster is disposed on the right side even though it is not shown, and its main body consists of a front shell and a rear shell, and the front shell is disposed in contact with the right end surface of the cylinder body 62. The seal ring 70 also provides a seal between this and the master cylinder 61. Therefore, the portions of the lid member 69 and the main piston 8 that protrude in the figure are inserted into the front shell (not shown). The third embodiment is constructed as described above, but its operation is the same as that of the above embodiment, so a description thereof will be omitted. Although the same effects as in the above embodiment are achieved, this embodiment also has the effect that the overall length of the rear shell can be shortened, especially in combination with the rear shell, that is, the vacuum booster. Each embodiment of the present invention has been described above, but
Of course, the present invention is not limited to the above, and various modifications can be made based on the technical idea of the present invention. For example, in the above embodiment, the guide member 26 has a reduced diameter part on the inner circumferential wall part, and the main piston 8 is stably guided on both sides of the part. A large number of grooves extending in the axial direction may be formed to facilitate liquid communication between the second hydraulic pressure generating chamber 25 and the reservoir side. Further, in the third embodiment, a case where the vacuum booster (not shown) is combined has been described, but the vacuum booster may also be integrally combined with the master cylinder of the first and second embodiments. . Further, in the above embodiments, the main piston 8 has the same outer diameter over its entire area, but the diameter may be increased or decreased in the portion that does not protrude into the cylinder body even when the main piston 8 makes a full stroke. [Effects of the invention] As described above, according to the master cylinder of the invention, the piston of the pair of pistons located on the opening side of the cylinder hole is a plunger type piston whose sliding part has the same outer diameter, and The outer diameter of this piston is smaller than the outer diameter of the part of the piston located at the bottom of the cylinder hole that slides against the cylinder hole, so the overall length of the master cylinder can be shortened with a simple structure. easy to process,
Production costs can be reduced.

[Brief explanation of the drawing]

1 to 3 are side sectional views of tandem master cylinders according to first, second, and third embodiments of the present invention, respectively. In the figure, 8...main piston, 3, 4
3, 63...Stepped hole (cylinder hole), 7, 46...
...Floating piston, 26...Guide member.

Claims (1)

[Scope of utility model registration request] a cylinder body having a cylinder hole with one end open; a pair of pistons movably fitted into the cylinder hole; a main pressure chamber defined within the cylinder hole between the pair of pistons; A slave pressure chamber defined between a bottom portion and one of the pair of pistons, and a guide member provided at an opening of the cylinder hole and slidably guiding the other piston of the pair of pistons. and a master cylinder in which the other piston is a plunger-type piston whose sliding portion has the same outer diameter, wherein the outer diameter of the other piston is smaller than the outer diameter of the sliding portion of the one piston. Cylinder.