JPH0558874B2 - - Google Patents

Description

[Detailed description of the invention]

【0001】

[Field of Industrial Application] The present invention relates to cylinder bodies used in master cylinders for brakes of automobiles and motorcycles, particularly cylinder bodies having a cylinder hole into which a piston is slidably fitted via a seal member. The present invention relates to a method for forming a small hole in a cylinder body, in which a small hole is formed in the inner peripheral surface of a cylinder hole.

【0002】

[Prior Art] Generally, the cylinder body of a master cylinder for brake operation has a relief as a small hole that communicates between the cylinder hole and an external oil reservoir, as shown in Japanese Utility Model Publication No. 59-9967, for example. A port (about 0.5 mm in diameter) is bored in the side wall, and the piston reciprocates on the inner peripheral surface of the cylinder hole via a seal member so as to cross the opening of this relief port.

[0003] By the way, in the cylinder body of the conventional master cylinder, the opening edge of the relief port on the cylinder hole side is formed into an edge shape. this is,
When manufacturing the cylinder body, a relief port is drilled from the outside of the cylinder body using a drill or punch, and then the inner peripheral surface of the cylinder hole is honed to remove any burrs that have formed at the opening of the port on the cylinder hole side. This is due to the results of finishing operations such as
That is, although the burrs on the opening edge of the relief port on the cylinder hole side are removed by finishing, the opening edge is formed into a sharp edge shape.

【0004】

[Problems to be Solved by the Invention] When inspecting conventional master cylinders that have been used for a long period of time, damage to the sealing member of the piston is often found. It has been determined that the seal member is cut into the relief port by the edge-like opening edge.

[0005] The present invention was made in view of such circumstances, and can prevent damage to the sealing member of the piston that slides in the cylinder hole, and can easily and accurately form small holes such as relief ports on the cylinder side wall. It is an object of the present invention to provide a method for forming a small hole in a cylinder body, which enables the formation of small holes in a cylinder body.

【0006】

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a cylinder body having a cylinder hole into which a piston is slidably fitted via a sealing member. In a method for forming a small hole in a cylinder body, in which a small hole is formed in a cylinder body, a small hole is formed in a thin wall portion formed in advance on the side wall of the cylinder body in correspondence with a recess provided on the outer surface of the side wall of the cylinder body from inside the cylinder hole. Drill a punch to make the small hole with the tip of the punch, and then press the funnel-shaped neck connected to the tip of the punch against the opening edge of the small hole on the cylinder hole side to make the opening edge into the cylinder hole. It is characterized by being formed in the shape of a tsupa whose diameter increases toward the end.

【0007】

[Examples] Examples of the present invention will be described below with reference to the drawings.

[0008] First, in FIG. 1, a cylinder body 1 made of Al alloy used in a brake master cylinder is shown.
has a bag-shaped cylinder hole 2 in the center,
Further, a mounting flange 3 is integrally formed on the outer periphery of the open end of the cylinder hole 2 of the cylinder body 1.

[0009] Furthermore, a thin wall portion 5 is formed in the side wall of the cylinder body 1 by forming a recess 4 on the outer surface thereof, and a relief port 6 as a small hole is bored in this thin wall portion 5, and the port 6 is opened. Hydraulic oil can flow between the cylinder bore 2 and an external oil reservoir (not shown) through the cylinder hole 2 . The opening edge 7 of the relief port 6 on the cylinder hole 2 side is shown in FIG.
The cross section is formed into an arc shape as shown in the figure.

[0010] A piston 8 having a seal member 9 attached to its outer periphery is slidably fitted into the cylinder hole 2.

[0011] Next, a method for forming the relief port 6 and its opening edge 7 will be described with reference to FIG. A punch 10 used to carry out this method has a relatively large-diameter shank portion 11 and a piercing needle portion 12 as a tip portion, which are integrally connected by a funnel-shaped neck portion 13, as shown in FIG. 4, for example. . The punch 10 is inserted into the cylinder hole 2 against the thin wall portion 5 of the cylinder body 1.
When you drive from the inside to the outside, first punch 10
The relief port 6 is bored by the piercing needle part 12 as the tip of the hole. Next, the funnel-shaped neck 13 of the punch 10 presses against the opening edge 7 of the relief port 6 on the cylinder hole 2 side, so that the opening edge 7 drips down toward the center of the port 6 as the punch 10 is driven. , the cross section will have an arcuate shape as described above.

[0012] Therefore, when the opening edge 7 of the relief port 6 on the cylinder hole 2 side is formed to have an arc shape in cross section as described above, the seal member 9 closes the opening of the relief port 6 as the piston 8 reciprocates. when crossing the
Since you can slide smoothly on the opening edge 7,
No damage will occur.

【0013】

[Effects of the Invention] As described above, according to the present invention,
In a method for forming a small hole in a cylinder body, the small hole opening in the inner peripheral surface of the cylinder hole is formed in the cylinder body having a cylinder hole into which a piston is slidably fitted via a sealing member. , a punch is driven from inside the cylinder hole into a thin wall portion previously formed on the side wall corresponding to the recess provided on the outer surface of the side wall of the cylinder body, and the small hole is bored with the tip of the punch; The funnel-shaped neck connected to the cylinder hole is pressed against the opening edge of the small hole on the cylinder hole side, and the opening edge is formed into a flap shape that expands in diameter toward the cylinder hole. By simply driving the hole, it is possible to make a small hole and expand the diameter of the opening edge of the hole in a concave manner, which greatly contributes to improving work efficiency. Moreover, when the piston slides in the cylinder hole, the seal member smoothly slides on the flared diameter portion of the opening edge, thereby extending the life of the seal member.

[0014] In addition, since the small hole is formed in a thin part of the side wall that is formed in correspondence with the recess provided on the outer surface of the side wall of the cylinder body, the small hole can also be formed by driving with the punch. The drilling work can be carried out easily and with high precision, which can further contribute to improving work efficiency and extend the life of the punch.

[Brief explanation of drawings]

[Fig. 1] A vertical side view showing an example of a cylinder body obtained by the method of the present invention.

[Figure 2] Enlarged view of the 2nd arrow view in Figure 1

[Figure 3] Process explanatory diagram of the method for forming the relief port and its opening edge

[Figure 4] Side view of the punch used to carry out the above forming method

[Explanation of symbols]

1 Cylinder body 2 Cylinder hole 4 Recess 5 Thin wall part 6 Relief port as a small hole 7 Opening edge 8 Piston 9 Seal member 10 punch 12 Punching needle part as tip part 13 Funnel neck

Claims (1)

[Claims] Claim 1: Piston 8 via seal member 9
In the method for forming a small hole in a cylinder body, the small hole 6 opening in the inner peripheral surface of the cylinder hole 2 is formed in the cylinder body 1 having a cylinder hole 2 into which the cylinder hole 2 is slidably fitted. A punch 10 is driven from inside the cylinder hole 2 into a thin wall portion 5 formed in advance on the side wall corresponding to the recess 4 provided on the outer surface of the side wall of the cylinder body 1, and the small hole 6 is punched with the tip 12 of the punch 10. The funnel-shaped neck 13 connected to the tip 12 of the punch 10 is pressed against the opening edge 7 of the small hole 6 on the cylinder hole 2 side.
A method for forming a small hole in a cylinder body, the method comprising: forming a small hole in a cylinder body in the form of a bumper whose diameter increases toward the cylinder hole 2.