JPH11198791A - Tandem master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem master cylinder capable of obtaining an excellent brake feeling irrespective of the fact that a double seal and a cup seal are used for a secondary side and a primary side, respectively. SOLUTION: A pressing force of a double seal 52 on a secondary side against a peripheral wall of a cylinder hole 14 is set smaller than that of a cup seal 51 on a primary side against a peripheral wall of the cylinder hole 14. For this purpose, an interference between the double seal 52 and the cylinder hole 14 is set to 0.1 to 0.4 mm or, in particular, to 0.1 to 0.35 mm, whereas the interference between the cup seal 51 and the cylinder hole 14 is set to 0.6 to 10 mm. With this setting, a piston 32 on the secondary side using the double seal 52 can be returned smoothly in the same manner as in a piston 31 on the primary side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a cup-type seal including a lip portion as a sealing means for a primary piston, and furthermore, as a sealing means for a secondary piston, an inner peripheral seal ring made of an elastic member, and the like. The present invention relates to a tandem master cylinder using a double seal including an outer peripheral seal ring that fits on the outer periphery.

[0002]

BACKGROUND OF THE INVENTION It is already known to use such a double seal as a sealing means for a master cylinder for a brake. For example, Japanese Patent Application Laid-Open No. Hei 9-136439
And Japanese Patent Application Laid-Open No. 9-136641 show a double seal in which an inner peripheral seal ring is formed by an O-ring and an outer peripheral seal ring is formed by a resin ring. The O-ring on the inner periphery is rich in elasticity, and presses the resin ring on the outer periphery against the peripheral wall of the cylinder hole of the cylinder body by the elastic force due to its elastic deformation. The outer resin ring has a higher hardness than the O-ring,
It does not elastically deform like a ring. However, the inner O-
The required sealing force can be obtained based on the elastic force of the ring. For this reason, the double seal has a seal erosion (that is, a phenomenon in which the lip of the seal is damaged by the opening of the communication hole provided in the cylinder body) as compared with a general cup-type seal including the lip. It has the advantage of being difficult.

Therefore, in a tandem master cylinder having two systems, a primary side and a secondary side, it is conceivable to apply a double seal only to the secondary side where the seal is easily damaged. Of course, the double seal can be applied not only to the secondary side but also to the primary side. However, the double seal has the above-mentioned advantages, but has a drawback that it is harder to mount than the cup-type seal. Therefore, it is practically advantageous to form a double seal only on the secondary side.

[0004]

A double seal is provided on the secondary side.
Various studies were conducted on tandem master cylinders using cup-type seals on the primary side, and during the return stroke to release the hydraulic pressure, the braking force on the secondary side, including the double seal, was unlikely to loosen and residual pressure was reduced. It has been found that there is a tendency to remain, which may deteriorate the brake feeling. This problem seems to arise from the difference between the construction of the double seal and the cup seal. From a design point of view, it is customary to make the seals for the pistons on the secondary side and the primary side and the cylinder bores substantially the same. The designer will set the interference of the double seal on the secondary side and the cup-shaped seal on the primary side to be substantially the same based on the general concept of such a design.

However, the double seal on the secondary side is
Even during the forward stroke of closing the communication hole to generate hydraulic pressure, or during the return stroke of opening the communication hole and releasing hydraulic pressure,
While the sliding resistance of substantially the same magnitude is generated, the cup-type seal on the primary side has a smaller sliding resistance in the return stroke than the sliding resistance in the forward stroke. This is because the lip portion of the cup-type seal easily falls down to the hydraulic pressure chamber side due to its structure during the return stroke, and reduces the sliding resistance to the peripheral wall of the cylinder body. As a result, no problem occurs during the forward stroke, but a difference in the magnitude of each sliding resistance between the secondary side and the primary side becomes apparent during the return stroke, causing the above-described problem.

In view of the above, the present invention provides a tandem master cylinder that can obtain a good brake feeling despite the use of a double seal on the secondary side and a cup-type seal on the primary side. The purpose is to do. More specifically, it is an object of the present invention to provide a technique capable of smoothly returning a secondary piston using a double seal in the same manner as a primary piston.

[0007]

A tandem master cylinder according to the present invention uses a double seal on the secondary side and a cup-type seal on the primary side, and applies a pressing force against the peripheral wall of the cylinder hole of the double seal to the cup-type seal. Is set smaller than the pressing force against the peripheral wall of the cylinder hole. As a method of setting such a pressing force, a method of changing seal materials while keeping the same interference (that is, a method of using a material having higher hardness as one seal material than the other seal material), or There is a method of changing the interference of each seal. The latter method of changing the interference is most preferable because it can be easily handled. A typical interference is between 0.1 mm and 0.2 mm between the double seal and the cylinder bore.
In contrast to 0.4 mm, especially 0.1 mm to 0.35 mm, the interference between the cup-shaped seal and the cylinder hole is 0.1 mm.
6 mm to 1.0 mm.

The reason why the seals on the secondary side and the primary side are specified in such a manner is that the secondary piston and the primary piston have a double seal on the secondary piston side during a return stroke in which the primary piston moves to one open end of the cylinder body. The point is that the sliding resistance and the sliding resistance by the cup type seal on the primary piston side are made substantially the same. As a result, the brake on the secondary side can be loosened as quickly as on the primary side, and the brake feeling as a whole can be improved.

[0009]

FIG. 1 is a sectional view showing a tandem master cylinder 10 for a brake to which the present invention is applied.
FIG. 3 is an enlarged view showing each part of a secondary side double seal and a primary side cup type seal. The tandem master cylinder 10 includes a cylinder main body 12 having a cylinder hole 14 along the axial direction inside. The cylinder body 12 is made of an aluminum alloy, and a corrosion-resistant anodic oxide film is formed on the inner peripheral surface of the cylinder hole 14. The anodic oxide film may be formed over the entire inner peripheral surface, or may be partially formed on the seal sliding surface on which the primary piston 31 and the secondary piston 32 slide. Such a cylinder body 12 includes connection holes 161 and 162 for connection to an external brake circuit, a primary communication hole 71 and a secondary communication hole 72 that communicate with a reservoir, and supply holes 196 and 296.
Have each. The cylinder hole 14 inside the cylinder body 12 is closed on the left side of the cylinder bottom 12b in the figure and is open on the side of the right cylinder head 12h. In such a cylinder hole 14, the cylinder bottom 12b
The components on the secondary side are inserted and set on the side near the cylinder head 12h, and the components on the primary side are inserted and set on the side near the cylinder head 12h.

In the tandem master cylinder 10, a secondary return spring 22, a secondary piston 32, a caged primary return spring 21, and a primary piston 31 are arranged in this order from the back of the cylinder hole 14 toward the opening side. Looking at each of the secondary and primary pistons 32, 31, two seal rings 52, 62;
1,61 are supported. The seal at the outer peripheral end of the secondary piston 32 facing the cylinder bottom 12b side is a double seal 52, and the seal at the outer peripheral end on the opposite side is a cup-shaped seal 62. In contrast, primary piston 3
Reference numeral 1 denotes a cup-shaped seal 51 including a lip portion 51a directed to the secondary side, wherein the seal at the outer peripheral end facing the cup-shaped seal 62 is an O-ring at the outer peripheral end near the cylinder head 12h. 61.

The cup-shaped seal 62 of the secondary piston 32 is connected to the cup-shaped seal 51 of the primary piston 31.
Together with this, the primary hydraulic chamber 41 is partitioned, and the double seal 52 of the secondary piston 32 partitions the secondary hydraulic chamber 42 together with the cylinder bottom 12b. The two separate seals or seal rings 52, 62; 51, 61 of the secondary and primary pistons 32, 31 define supply chambers 290, 190 on the side circumference of each piston 32, 31. The supply chambers 290 and 190 are chambers for communicating the hydraulic chambers 42 and 41 with the reservoir. Supply room 290 on the secondary side
Communicates with the reservoir through the supply hole 296,
The secondary hydraulic chamber 42 is communicated through a passage 92 provided inside the secondary piston 32 and a supply valve 65 provided at an opening of the passage 92. The supply valve 65 is a double seal 5
2 is a one-way valve for obtaining the function of replenishing the liquid to the secondary hydraulic chamber 42 because it does not have the function of replenishing the liquid.
On the other hand, the supply chamber 190 on the primary side is provided with the supply hole 1.
The reservoir can be connected to the reservoir through 96, and the primary hydraulic chamber 41 can be replenished while the lip portion 51a of the cup-shaped seal 51 is tilted.

The seals 52 and 62; 51 and 61 are set in mounting grooves provided in the secondary piston 32 and the primary piston 31. Since the seal 61 made of an O-ring and the cup-shaped seals 62 and 51 are made of a material that is easily elastically deformed, the setting thereof can be performed easily. In that respect, the inner peripheral seal ring 53 of the double seal 52 is also made of an O-ring, and its material is either a resilient polymer elastomer based on ethylene-propylene trimer or ethylene-propylene rubber. . Therefore, the set is easy. However, since the outer peripheral seal ring 55 of the double seal 52 is made of tetrafluoroethylene resin and has a higher hardness than the inner peripheral seal ring 53, it is not easily deformed, so that setting is not easy. For this reason, a conical tapered portion 320 is formed between the end face of the secondary piston 32 facing the secondary hydraulic chamber 42 and the mounting groove 300, thereby facilitating the setting (especially, see FIG. 2).

Now, the seals 62, 5 made of one part
2, the closing margin L of the cup-shaped seal 51 on the primary side is in the range of 0.6 mm to 1.0 mm similarly to the other seals 62, 61, as shown in FIG. Value. On the other hand, the interference M of the double seal 52 on the secondary side is a value of 0.1 mm to 0.4 mm, preferably 0.35 mm or less. By setting the interference M of the double seal 52 to 0.1 mm or more, an effective sealing function can be obtained.
By setting the thickness to 4 mm or less, it is possible to set so as to generate a sliding resistance substantially equal to that of the cup-shaped seal 51 having a larger interference L. As a result, the problem of the release delay of the brake on the secondary side can be effectively solved.

In the embodiment shown in FIG.
The liquid supply to the secondary hydraulic chamber 42 is ensured by, for example, but a small piston is movably provided inside the secondary piston 32 instead of the supply valve 65, and the secondary hydraulic chamber 42 When a pressure difference is generated between the pressure and the atmospheric pressure on the reservoir side, the small piston can be moved by the pressure difference to reduce the volume of the secondary hydraulic chamber 42.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing each part of a double seal and a cup type seal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tandem master cylinder 12 Cylinder main body 14 Cylinder hole 31 Primary piston 32 Secondary piston 41 Primary hydraulic chamber 42 Secondary hydraulic chamber 51 Cup type seal 51a Lip part 52 Double seal L Closing allowance of cup type seal M Tightening of double seal Teens

Claims (5)

[Claims] 1. A cylinder opening having one end open to the outside and a cylinder end closed at the other end, and a primary communication hole and a secondary communication hole which open to a peripheral wall of the cylinder hole and communicate with a reservoir. And a secondary piston inserted slidably into the cylinder hole and defining a secondary hydraulic chamber at the other end of the cylinder hole, and one end of the secondary piston inserted into the cylinder hole. And a primary piston defining a primary hydraulic chamber between the primary piston and the outer peripheral end of the primary piston on the primary hydraulic chamber side is a cup-type seal including a lip portion. The sealing means at the outer peripheral end of the secondary piston on the side of the secondary hydraulic chamber is made of an elastic member and has an inner peripheral seal fitted to the secondary piston. A tandem master cylinder, which is a double seal including a ring and an outer seal ring made of a material having a higher hardness than the inner seal ring thereof, and fitted into the outer periphery of the inner seal ring and in contact with the peripheral wall of the cylinder hole. The pressing force against the peripheral wall of the cylinder hole of the double seal,
A tandem master cylinder characterized in that the pressure is set smaller than a pressing force of the cup-shaped seal against a peripheral wall of a cylinder hole. 2. The magnitude of each of the two pressing forces is such that when the secondary piston and the primary piston return to the open end of the cylinder body in a return stroke, sliding by the double seal on the secondary piston side is performed. 2. The resistance is set so that the resistance is substantially the same as the sliding resistance of the cup seal on the primary piston side. 3.
Tandem master cylinder. 3. The pressing force of the double seal against the peripheral wall of the cylinder hole is obtained by the interference between the double seal and the cylinder hole, and furthermore, the pressing force of the cup type seal against the peripheral wall of the cylinder hole. 3. The tandem master cylinder according to claim 1, wherein the pressure is obtained by interference between the cup-shaped seal and the cylinder hole. 4. The interference between the double seal and the cylinder hole is 0.1 mm to 0.4 mm, and the interference between the cup type seal and the cylinder hole is 0.6 mm to 1.0 mm.
The tandem master cylinder of claim 3, wherein the diameter is in mm. 5. A sealing means at an outer peripheral end of a portion of the primary piston facing one end side of the cylinder body which is open, and a sealing means at an outer peripheral end of the secondary piston on a primary hydraulic pressure chamber side, respectively. 5. The tandem master cylinder according to claim 4, wherein the cylinder hole is a ring or a cup-shaped seal, and the interference between the O-ring and the cup-shaped seal and the cylinder hole is 0.6 mm to 1.0 mm.