JPH0329587Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a vacuum pump used as a negative pressure source in automobiles, etc. In particular, the invention relates to a vacuum pump that is used as a negative pressure source in automobiles, etc. In particular, the piston pull rod is moved in the axial direction by the rotational movement of the rocker arm. This invention relates to an improvement in a piston pull rod in a rocker arm type vacuum pump that is reciprocated to actuate a piston connected to the piston pull rod.

Conventional technology This type of vacuum pump, for example,
-Described in Publication No. 14786. In this vacuum pump, the end of the piston pull rod opposite to the side connected to the piston is fitted into the casing of the vacuum pump so as to be slidable in the axial direction, and a flange is provided in the middle part. A retainer portion having a shape is provided. Further, the rocker arm is rotatably supported by the casing via a pivot shaft at its longitudinally intermediate portion, and has one end engaged with the cam and the other end engaged with the retainer portion. As a result, as the cam rotates, the rocker arm is reciprocated within a certain angle range, causing the piston pull rod and the piston to reciprocate linearly.

If the retainer part of this piston pull rod is to be formed integrally with the main body part, it will be necessary to forge or cast the material, which will increase the cost, so it should be manufactured separately from the main body part. It is desirable to fix it to Also, the piston pull rod,
It is desirable that the end that is slidably fitted into the casing be as large in diameter as possible to prevent wear.

In view of this, an attempt was made to fit a cylindrical member into a rod main body having a relatively small diameter, and to form a large-diameter portion for preventing the rod from coming off at the end of the rod main body protruding from the cylindrical member. In this way, it becomes possible to slidably fit the cylindrical member having a large diameter into the casing, and to use the end surface of the cylindrical member on the piston side as the retainer surface.

Problems that the invention aims to solve: However, when tested, it was found that the cylindrical member of this piston pull rod rotates around the rod body during pump operation, causing wear on the contact surface between the two. Alternatively, if the locker arm fails to follow the cam and an impact load is applied to the cylindrical member in the axial direction, the retaining portion formed at the tip of the rod body is deformed by this load. It has become clear that there is a problem in that the relative position in the axial direction between the cylindrical member and the rod body changes. If the relative positions of the two change, the top dead center position of the piston changes, which may cause the piston to collide with the casing and generate abnormal noise. In order to avoid the occurrence of this abnormal noise, it is necessary to set a large gap between the piston and the casing at the top dead center, which increases the volume at the top dead center and lowers the ultimate vacuum. This is because the degree of vacuum that can be achieved by the vacuum pump is determined by the ratio of the volume at the top dead center and the volume at the bottom dead center.

Means for solving the problem The present invention was made to solve this problem, and its gist is that the piston pull rod is
It consists of a rod body and a cylindrical member, one end of the rod body is connected to a piston, a cylindrical member is fitted to the opposite end of the rod body, and the tip of the rod body protrudes from the cylindrical member. A large-diameter retaining portion is formed by upsetting the rod body, and at least a portion of the portion of the rod body located inside the cylindrical member is expanded in the diametrical direction to tightly adhere to the inner circumferential surface of the cylindrical member. The piston-side end surface of the cylindrical member is the retainer surface.

If a serration is formed on the inner peripheral surface of the cylindrical member to which the diametrical bulge of the rod body is brought into close contact, the cylindrical member can be more securely fixed to the rod body.

Functions and Effects If the retaining portion is formed by upsetting as described above, and the rod body is inflated in the diametrical direction to make it tightly adhere to the inner peripheral surface of the cylindrical member, the cylindrical member can be attached to the rod body. This prevents the contact surface between the two from being worn out.

In addition, even if the rocker arm has poor tracking and an axial impact load is applied to the cylindrical member, the impact load will be received by the frictional resistance between the outer circumferential surface of the rod body and the inner circumferential surface of the cylindrical member, and the rod will come out. The load applied to the stopper is reduced or eliminated, and deformation of the stopper is effectively prevented.

This prevents the top dead center position of the piston from changing, making it possible to improve the ultimate vacuum of the vacuum pump while using an inexpensive piston pull rod consisting of a rod body and a cylindrical member.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 2 is a diagram showing a vacuum pump used as a negative pressure source for a vacuum booster that drives a brake master cylinder of an automobile. The casing 10 of this vacuum pump consists of a lower casing 12 and an upper casing 14.
The lower casing 12 is a container-shaped member having an upwardly open cylinder bore 16, and is provided with a mounting flange 18 fixed to the engine at its lower part. On the other hand, the Atsupa casing 14 is a substantially flat member, and the lower casing 12 and Atsupa casing 14 are fitted together at flat mating surfaces 20 and 22, and are fixed together with an appropriate number of bolts 24. casing 1
It constitutes 0.

The inner peripheral surface of the cylinder bore 16 is covered with a lining 30 made of synthetic resin, and a disk-shaped piston 32 is fitted inside the lining 30 in an airtight and slidable manner. As a result, a pump chamber 3 having a variable volume is provided between the piston 32 and the Atsupa casing 14.
4 is formed. This pump chamber 34 is connected to a vacuum tank (not shown) through a suction valve and a suction port 36 (not shown), while a passage 40 formed in the upper casing 14, a check valve 42 for discharge, and a passage 40 formed in the lower casing 12 The cam chamber of the engine is communicated with the cam chamber of the engine through a passage 44 formed by the cam chamber.

One end of a piston pull rod 50 is fixed to the center of the piston. This piston pull rod 50 has a generally rod-shaped rod body 52.
and a cylindrical member 54 fixed to its lower end. The cylindrical member 54 is provided with a flange 56 as a retainer at the end near the piston 32, and a locking arm is attached to the retainer surface 57, which is the surface of the flange 56 on the piston 32 side, via a washer 58 as a sliding member. One end of 70 is engaged. The rocker arm 70 is a longitudinal member, and its middle portion is rotatably supported by the lower casing 12 via a pivot shaft 72. Piston pull rod 5 of Rocker arm 70
The end on the side that engages with the rod body 52 is a bifurcated yoke portion 74, which abuts against the washers 58 on both sides of the rod body 52 while straddling the rod body 52. This Rotsuka Arm 7
The other end of the yoke 76 is also bifurcated, and a roller 80 as a cam follower is rotatably attached to this yoke 76 by a shaft 78. The rocker arm 70 is biased clockwise in FIG. 2 by a spring 82 disposed between it and the lower casing 12.
As a result, the outer circumferential surface 84 of the roller 80
is pressed against the cam surface 92 of. Further, the piston 32 is urged upward by a spring 94, that is, in a direction that reduces the volume of the pump chamber 34, so that the flange 56 of the piston pull rod 50 is pushed through the washer 58 to the rocker arm 70. It is pressed against the yoke portion 74. Therefore, as the cam 90 rotates, the rocker arm 70 reciprocates within a certain angle range, causing the piston pull rod 50 to reciprocate linearly in the axial direction, thereby causing the piston 32 to reciprocate, thereby opening the pump chamber. By changing the volume of 34, air is taken in and discharged.

The cylindrical member 54 is completely fixed to the rod body 52. That is, as shown in FIG. 1, the protruding end of the rod main body 52 from the cylindrical member 54 is used as a large diameter part 60 for preventing the rod from coming off, but not only that, but also the large diameter part of the rod main body 52 Expanded diameter portion 6 in which a portion of a constant length close to 60 bulges in the diameter direction
2, and by bringing the outer circumferential surface of the enlarged diameter portion 62 into tight contact with the inner circumferential surface of the cylindrical member 54, relative movement of the cylindrical member 54 with respect to the rod main body 52 is prevented.

The large diameter portion 60 and the enlarged diameter portion 62 are formed, for example, on the rod main body 52 and the cylindrical member 5.
4 is prevented from moving backward by stopper jigs 64 and 65, respectively, and an outer periphery restraining jig 66 is fitted on the outside of the cylindrical member 54 to prevent an increase in the outer diameter. This can be done by upsetting the protruding end of the upsetting punch 68. At this time, if you do not harden the parts of the rod body 52 that are to become the large diameter part 60 and the enlarged diameter part 62 to prevent them from coming off, or you can reduce the degree of hardening and harden other parts, the desired length can be expanded. Thus, the diameter portion 62 can be obtained.

Note that if serrations 69 shown in FIG. 3 are formed on the inner circumferential surface of the cylindrical member 54, the two can be fixed even more securely.

The surface of the yoke portion 74 on the washer 58 side is formed as a partial circumferential surface 100 so that rotation of the rocker arm 70 is smoothly converted into linear motion of the piston pull rod 50 and the piston 32. Since the yoke portion 74 performs circular arc movement, relative movement in a direction perpendicular to the axis of the piston pull rod 50 is unavoidable between the yoke portion 74 and the flange 56 serving as a retainer portion that receives the yoke portion. but,
In this vacuum pump, the washer 58 can be moved in the diametrical direction by a distance greater than the relative movement amount of the washer 58 with respect to the flange 56.
This relative movement is absorbed by the washer 58 sliding on the retainer surface 7 of the flange 56, and almost no slippage occurs between the washer 58 and the yoke portion 74, effectively preventing wear thereof. . Further, the washer 58 slides on the retainer surface of the flange 56, but since these are in contact over a wide surface, there is little wear. Therefore, there is less change in the top dead center position of the piston 32 due to wear, and the gap between the piston 32 and the adpa casing 14 at the top dead center can be set small, reducing the top dead center volume. This makes it possible to improve the ultimate degree of vacuum.

Furthermore, in this vacuum pump, since the cylindrical member 54 is completely fixed to the rod main body 52 as described above, a change in the position of the piston top dead center due to rotation of the cylindrical member 54 is also prevented. That is, if the cylindrical member 54 is not fixed to the rod main body 52, the cylindrical member 54 is
rotates around the rod body 52, and sliding occurs between the end face of the cylindrical member 54 and the shoulder surface 61 of the large-diameter portion 60 for retaining the cylindrical member 54, which wears out and the rod of the cylindrical member 54 The position relative to the main body 52 will be lowered, and the top dead center position of the piston 32 will be raised accordingly. However, in this vacuum pump, the cylindrical member 54 is fixed to the rod main body 52, so this Such inconvenience will not occur. In addition, if the locker arm 70 does not completely follow the cam 90 for some reason, or if the piston pull rod 50 does not completely follow the locker arm 70, the yoke portion 74 will move through the washer 58. It collides with the flange 56 , and an axial impact load is applied to the cylinder member 54 , and the large diameter part 60 for retaining deforms due to the impact load, thereby lowering the position of the cylinder member 54 and moving it above the piston 32 . There is a risk that the dead center position will rise, but the occurrence of such a situation is also caused by the cylinder member 5.
4 is fixed to the rod body 52, this can be prevented or reduced.

One embodiment of the present invention has been described in detail above, but
This is literally just an example, and it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art, such as omitting the washer 58.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a piston pull rod according to an embodiment of the present invention together with an apparatus for manufacturing the same. FIG. 2 is a front sectional view of a vacuum pump equipped with the piston pull rod. FIG. 3 is a front sectional view of a cylindrical member used in another embodiment of the present invention. 10...Casing, 32...Piston, 50
... Piston pull rod, 52 ... Rod body,
54... Cylindrical member, 56... Flange, 58... Washer, 60... Large diameter part for retaining, 62... Expanded diameter part, 64, 65... Stopper jig, 66... Outer circumference restraint jig, 68... Upsetting punch, 69... Serration, 70... Locker arm, 72... Pivot shaft, 74... Yoke section.

Claims (1)

[Claims for Utility Model Registration] (1) A locking arm that extends in the axial direction from the piston of the vacuum pump and is provided with a retainer portion, and rotates around one axis on the retainer surface that is the surface of the retainer portion on the piston side. In a piston pull rod that receives a yoke portion formed at one end and converts rotation of a rocker arm into linear reciprocating motion of a piston, the piston pull rod is composed of a rod body and a cylindrical member. , while one end of the rod body is connected to the piston, the cylindrical member is fitted to the opposite end of the rod body, and the tip of the rod body protruding from the cylindrical member is fitted with a large diameter rod by upsetting. At the same time, at least a part of the portion of the rod body located inside the cylindrical member is inflated in the diametrical direction to tightly adhere to the inner peripheral surface of the cylindrical member, and the end surface of the cylindrical member on the piston side is formed. A piston pull rod for a vacuum pump, characterized in that the retainer surface is a piston pull rod. (2) Utility model registration claim 1, wherein a serration is formed on the inner circumferential surface of the cylindrical member, to which the diametrical bulge of the rod body is brought into close contact.
Piston pull rod as described in section.