JPH082001Y2 - Master cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a master cylinder, and more particularly to a tandem master cylinder in which two pistons slide in a casing.

(Prior Art) Conventionally, in this type of tandem type master cylinder, for example, one shown in FIG. 2 is known as intended to improve the workability and assemblability of the casing. In FIG. 2, a casing 1 is closed at one end by a plug 2, and the casing 1 and the plug 2 are connected to a brake pedal via a push rod of a negative pressure booster (not shown). 4 is stored so as to be movable in the axial direction. These primary piston 3 and secondary piston 4 are casing 1 and plug 2
A first oil chamber 5 and a second oil chamber 6 are defined therein, and the first spring 7 and the second oil chamber 5 and 6 are formed in the first and second oil chambers 5, 6.
The spring 8 is contracted. A guide member 9 is interposed between the casing 1 and the plug 2 and the primary piston 3 and the secondary piston 4, and the primary piston 3 and the secondary piston 4 are included in the guide member 9 and the guide members 16 and 17. Guided by the peripheral part, it slides. Also, casing 1, plug 2
And a communication hole in the space partitioned by the guide member 9.
10 is formed, and the communication hole 10 is provided with a first reserve port 11a for brake fluid from a reservoir tank (not shown).
It is introduced into the first oil chamber via the suction hole 12 and the like. Further, the brake oil from the second reserve port 11b is introduced into the second oil chamber 6 via the suction hole 13 and the like. A primary cup 14 and a secondary cup 15 are provided between the primary piston 3 and the guide member 9 and between the secondary piston 4 and the casing 1. Slide around the circumference.

(Problem to be solved by the invention) However, in such a conventional master cylinder, since the primary piston 3 and the secondary piston 4 are guided by a common guide member 9, high concentricity is required. There are many parts that need to be set and a large clearance must be set to prevent twisting.
When the brake pedal is depressed, the primary piston 3
Is likely to fall or become eccentric, and the primary piston 3
That the primary piston 3 does not come into contact with the inner surface of the primary cup 14 evenly when sliding, or the sliding surface of the primary piston 3 becomes rough and the durability of the primary cup 14 deteriorates. There was a problem.

(Object of the Invention) Therefore, the present invention aims to improve the durability of the primary cup by surely guiding the shaft center portion of the primary piston by providing a guide member for each of the primary piston and the secondary piston. I am trying.

(Means for Solving the Problems) In order to achieve the above object, a master cylinder according to the present invention has a bottomed cylindrical casing, a primary piston and a secondary piston movably provided in the casing in an axial direction, and a casing. Between the bottom and the secondary piston, and between the secondary piston and the primary piston, the biasing member for biasing both pistons in one direction, and the casing and the primary piston are provided. A primary guide that is in sliding contact with the piston and guides only the piston, and a secondary guide that is provided between the casing and the secondary piston and that slides in contact with the secondary piston over the entire inner peripheral surface and guides only the piston, and a primary guide or a secondary guide. Next to the guide A seal ring that is provided in contact with and has an inner peripheral surface slidably abutting against the primary piston or the secondary piston.

(Operation) In the present invention, the primary guide and the secondary guide are respectively provided between the casing and the primary piston and the secondary piston, and these pistons are brought into sliding contact with the entire inner peripheral surfaces of both guides. Therefore, since there are few parts that require concentricity and there is no risk of twisting, the clearance of each part can be set to the necessary minimum, and the primary piston and secondary piston must slide securely on the entire inner peripheral surface of both guide members. The primary piston does not fall when the brake pedal is depressed. As a result, the primary cup is always brought into sliding contact with the primary piston with a uniform surface pressure, and the durability of the cup is improved.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

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

First, the configuration will be described. In FIG. 1, reference numeral 21 is a casing, and the casing 21 has a primary piston 22.
And the secondary piston 23 is housed so as to be movable in the axial direction. Fitting hole 22a in primary piston 22
Is formed, and a push rod of a negative pressure booster connected to a brake pedal (not shown) is fitted in the fitting hole 22a. The casing 21 has a cover 24 that closes one end and holds the primary piston 22.
And a plug 25 that closes the other end and constitutes the bottom of the casing 21, and in the casing 21, between the primary piston 22 and the secondary piston 23 and between the secondary piston 23 and the plug 25. A first oil chamber 26 and a second oil chamber 27 are defined. These first oil chamber 26,
The second oil chamber 27 is provided with a first spring member 28 and a second spring member 29 as biasing members, respectively, and the first spring member 28 can contract to the sliding member 31 via retainers 30a and 30b. When the retainer 30b is supported by the retainer 30b and is fitted in the recess 23a of the secondary piston 23, a reaction force is applied from the secondary piston 23 to the primary piston 22 via the sliding member 31. The second spring member 29 has one end abutting against the secondary piston 23 and the other end abutting against the plug 25 to urge the secondary piston 23 to the right in the figure.

On the other hand, a primary guide 32 is independently provided between the primary piston 22 and the cover 24, and the primary piston 22 slides while being guided by the entire inner peripheral surface of the primary guide 32. A communication hole 32a is formed in the primary guide 32, and the communication hole 32a is formed in the casing 21.
Communicates with the first supply hole 21a formed in. A secondary guide 33 is independently provided between the casing 21 and the secondary piston 23, and the secondary piston 23 slides while being guided by the entire inner peripheral surface of the secondary guide 33. The secondary guide 33 has a communication hole 33a.
Is formed, and the communication hole 33a communicates with the second supply hole 21b formed in the casing 21. Further, a reservoir tank 34 for storing brake oil is attached to the casing 21, and a first reserve port 34a and a second reserve port 34a communicating with the first supply hole 21a and the second supply hole 21b are provided below the reservoir tank 34, respectively. A reserve port 34b is formed. Then, the primary piston 22 and the secondary piston 23 are formed with communication holes 22b and 23b, respectively, and these communication holes 22b and 23b can communicate with the communication holes 32a and 33a. Therefore, the brake oil from the reservoir tank 34 is introduced into the first oil chamber 26 through the communication hole 22b, the communication hole 32a, the first supply hole 21a, and the first reserve port 34a, and the second oil chamber 27 is communicated with the brake oil. Hole 23b, communication hole 33a,
Brake fluid from the reservoir tank 34 is introduced through the second supply hole 21b and the second reserve port 34b. Also,
A first discharge hole 21c and a second discharge hole 21d are formed in the casing 21, and the first discharge hole 21c and the second discharge hole 21d are formed.
Is connected to front and rear wheel cylinders (not shown) to supply the brake hydraulic pressure in the first oil chamber 26 and the second oil chamber 27 to the wheel cylinders.

A primary cup 35 is provided between the primary piston 22 and the casing 21, and the primary cup 35 is adjacent to the primary guide 32 and is supported by a cup support member 36. In addition, a secondary cup 37 is provided between the secondary piston 23 and the casing 21, and this secondary cup 37 is adjacent to the secondary guide 33 and plugs.
It is supported by an annular protrusion 25a formed on 25.
The primary cup 35 and the secondary cup 37 are the primary piston 22 and the secondary piston 23.
When sliding on the inner circumference of the primary cup 35 and the secondary cup 37 and moving to the left in the figure, the communication hole 22
By closing b and 23b, the communication between the communication hole 32a and the first oil chamber 26 and the communication between the communication hole 33a and the second oil chamber 27 are blocked, and the first oil chamber 2
6. By closing the second oil chamber 27, the brake oil pressure in the oil chambers 26, 27 is supplied to the front and rear wheel cylinders via the first discharge holes 21c, 21d.

38 is a cup seal interposed between the casing 21 and the primary piston 22, and 39 is the casing 21.
It is an O-ring interposed between the secondary piston 23 and the secondary piston.

 Next, the operation will be described.

First, when the driver depresses the brake pedal to operate the brake, the push rod pushes the primary piston 22 leftward in the drawing. At this time, the primary piston 22 moves to the right in the figure against the biasing force of the first spring member 28, the communication hole 22b is closed by the primary cup 35, and the brake oil in the first oil chamber 26 is discharged into the first discharge hole. It is supplied to the wheel cylinder via 21c. The secondary piston 23 also moves to the right in the figure in communication with the primary piston 22, the recess 23a is closed by the secondary cup 37, and the brake oil in the second oil chamber 27 is transferred to the wheel cylinder via the second discharge hole 21d. Supplied. When you release the brake pedal,
Primary piston 22 and secondary piston 23
Is moved to the right in the figure by the urging force of the first spring member 28 and the second spring member 29, etc., to connect the first oil chamber 26 and the second oil chamber 27 to the reservoir tank 34.

During this period, the primary piston 22 and the secondary piston 23 move while being guided by the entire inner peripheral surfaces of the primary guide 32 and the secondary guide 33, respectively, but the primary piston 22 is moved to the primary guide 32 provided independently with the minimum required clearance. Since it is guided, the primary piston 22 and the secondary piston 23 can be reliably slid on the entire inner peripheral surface of both guides 32 and 33, and the primary piston 22 may fall when the brake pedal is depressed. Absent. For this reason, when the primary piston 22 slides, the primary piston 22 can always slide on the inner peripheral portion of the primary cup 35 with a uniform surface pressure, and the sliding surface of the primary piston 22 becomes rough. Without it, the durability of the primary cup 35 can be improved.

(Effect) According to the present invention, the primary guide and the secondary guide are independently provided between the casing and the primary piston and the secondary piston, and these pistons are slidably contacted with the entire inner peripheral surfaces of both guides. The guide can be guided to the primary piston with the minimum required clearance, and the primary piston and the secondary piston can be reliably slid on the entire inner peripheral surface of both guides, and the primary piston falls over when the brake pedal is depressed. Etc. can be prevented, and the durability of the primary cup can be improved by always sliding the primary cup against the primary piston with a uniform surface pressure.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a master cylinder according to the present invention, and FIG. 2 is a sectional view showing a conventional master cylinder. 21 ... Casing, 22 ... Primary piston, 23 ...
… Secondary piston, 25 …… Plug (casing), 28 …… First spring member (biasing member), 29 ……
2nd spring member (biasing member), 32 …… Primary guide, 33 …… Secondary guide, 35 …… Primary cup (cup seal), 37 …… Secondary cup (cup seal).

Claims (1)

[Scope of utility model registration request] 1. A cylindrical casing having a bottom, a primary piston and a secondary piston which are axially movable in the casing, a bottom portion of the casing and a secondary piston, and a secondary piston and the primary piston, respectively. A urging member that is provided to urge both pistons in one direction, a primary guide that is provided between the casing and the primary piston, and that guides only the piston by sliding contact with the primary piston over the entire inner peripheral surface, and the casing. A secondary guide that is provided between the secondary pistons and slides on the entire inner peripheral surface to guide only the secondary piston, and a primary guide or a secondary guide that is provided adjacent to the secondary guide and has an inner peripheral surface that is the primary piston or the secondary piston. Master cylinder, characterized in that it comprises a slidably contact with the seal ring, the.