JPH0324873Y2 - - 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., and in particular, a vacuum pump in which a piston pull rod extending from a piston rotates around a pivot axis. The present invention relates to a rocker arm type vacuum pump in which a piston is driven by reciprocating motion by a rocker arm.

Conventional technology This type of vacuum pump, for example,
It is already known from the publication No. 61-14786. In this vacuum pump, one end of the rocker arm is engaged with the retainer surface on the piston side of a flange-shaped retainer part provided on the piston pull rod, so that the reciprocating rotation of the rocker arm is controlled by the piston pull rod. is converted into a reciprocating linear motion. The end of the rocker arm has a convex curved surface that touches the retainer surface at one point when viewed from a direction parallel to the center line of rotation of the rocker arm, which allows the rocker arm to rotate smoothly due to the piston pull rod. It is now converted into linear motion.

Problems to be Solved by the Invention However, this vacuum pump had a problem in that the friction between the retainer surface and the convex curved surface of the rocker arm in contact with the retainer surface was severe. The locker arm and the piston pull rod are arranged so that the end of the locker arm that engages with the retainer moves mainly in a direction parallel to the axis of the piston pull rod as the locker arm rotates. , since the motion of this end is an arc motion,
A component of motion in a direction perpendicular to the axis of the piston pull rod is unavoidable, causing slippage and friction between the retainer and the end of the rocker arm. Since the end of the rocker arm has a convex curved surface as described above, the contact surface pressure with the retainer section is high, and since slippage occurs under this high surface pressure, friction is particularly likely to occur.

If these convex curved surfaces and the retainer surface rub, the top dead center position of the piston will rise, and the piston will collide with the casing at the top dead center, producing abnormal noise. In order to avoid this, 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 degree of vacuum achieved. 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 in a rocker arm type vacuum pump, the contact surface of the rocker arm with the retainer surface of the piston pull rod. is a convex curved surface that touches the retainer part at one point when viewed from a direction parallel to the axis of the pivot shaft of the rocker arm, and the radius of curvature of the convex curved surface, the center of curvature of the convex curved surface, and the axis of the pivot shaft are The length of the connecting straight lines and the relative position between the centers of curvature and the axis of the pivot shaft are calculated as
This is determined to be approximately equal to the amount of movement of the contact point between the convex curved surface and the retainer surface due to rolling of the convex curved surface on the retainer surface as the rocker arm rotates.

In a preferred embodiment of the present invention, a sliding member movable in a direction perpendicular to the axis of the piston pull rod is interposed between the retainer surface and the convex curved surface. If this sliding member can move in the above direction, a certain effect can be obtained, but it should be able to move by a distance greater than the difference between the motion component of the center of curvature and the amount of movement of the contact point. When it is complete, it becomes complete.

Function: In the vacuum pump of the present invention, slippage between the convex curved surface of the rocker arm and the retainer surface of the piston pull rod is significantly reduced. As the rocker arm rotates, a motion component in the direction perpendicular to the axis of the piston pull rod is generated at the center of curvature of the convex curved surface.
The point of contact between the convex curved surface and the retainer surface will also move in the same direction by the same distance, but at the same time, a phenomenon occurs in which the convex curved surface rolls on the retainer surface as the rocker arm rotates, and this causes the convex surface to roll on the retainer surface. The point of contact between the curved surface and the retainer surface moves in a direction perpendicular to the axis of the piston pull rod. In the vacuum pump of the present invention, the moving distance of the contact point between the convex curved surface and the retainer surface caused by the above two reasons is made to be approximately equal, so that the sliding between the retainer surface and the convex curved surface is prevented. rarely occurs. If the radius of curvature of the convex curved surface changes gradually, it is possible to completely eliminate slippage between the convex curved surface and the retainer surface, but even if it is a simple partial cylindrical surface, the dimensions and relative By choosing the position properly, it is possible to have very little slippage.

In a desirable embodiment in which a movable sliding member is interposed between the convex curved surface and the retainer surface, the difference in momentum between the convex curved surface and the retainer surface is mainly absorbed by the sliding of the sliding member on the retainer surface. Therefore, almost no slipping occurs at the contact portion between the convex curved surface with high surface pressure and the sliding member, and friction between the two is particularly effectively prevented.

Effects of the Invention As described above, according to the present invention, friction caused by slippage between the end of the rocker arm and the retainer of the piston pull rod is effectively prevented, and the durability of the vacuum pump is improved. Further, since it is possible to set a small distance between the piston and the casing at the top dead center, it is possible to reduce the volume at the top dead center and improve the ultimate degree of vacuum. Moreover,
For this purpose, it is only necessary to appropriately select the dimensions and relative positions of each part, so the cost of the vacuum pump does not increase.

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 have flat mating surfaces 20 and 2.
2 and fixed by an appropriate number of bolts 24 to form an integral casing 10.
It consists of

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 formed 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 engaging part for 0 is a yoke part 74 divided into two parts.
The rod body 52 is in contact with washers 58 on both sides of the rod body 52 while straddling the rod body 52. The other end of the rocker arm 70 is also a bifurcated yoke portion 76, and a roller 80 as a cam follower is rotatably attached to this yoke portion by a shaft 78. Rotsuka arm 70 is lower casing 1
A spring 82 disposed between the second
In the figure, the roller 80 is biased clockwise, thereby pressing the outer circumferential surface 84 of the roller 80 against the cam surface 92 of the cam 90. 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 locking arm 70
The piston 32 is reciprocated by reciprocating in a certain angle range, and the piston pull rod 50 is reciprocated linearly in the axial direction.
By changing the volume of 4, air is taken in and discharged.

The cylindrical member 54 is completely fixed to the rod body 52. That is, as shown in FIG. 3, 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; Expanded diameter part 6 where a part of 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 close 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 reason for this will be explained later.

In addition, the large diameter part 60 and the enlarged diameter part 62 for preventing slipping off are also provided.
For example, the retraction of the rod main body 52 and the cylindrical member 54 can be performed using stopper jigs 64 and 65, respectively.
The protruding end of the rod body 52 from the cylindrical member 54 is installed with an upsetting punch 68 while the outer circumferential restraint jig 66 is fitted to the outside of the cylindrical member 54 to prevent the outer diameter from increasing. This can be done by incorporating At this time, the rod body 52
By not hardening the parts that should become the large diameter part 60 and the enlarged diameter part 62 to prevent them from coming off, or by reducing the degree of quenching and hardening the other parts, the enlarged diameter part 62 of the desired length can be obtained. This is possible.

Note that if serrations 69 shown in FIG. 4 are formed on the inner circumferential surface of the cylindrical member 54, the two can be fixed even more securely.

Piston pull rod 5 of the rocker arm 70
The surface of the washer 58 side of the yoke portion 74 serving as an engaging portion for the pivot shaft 72 is a partial cylindrical surface 100 centered on a straight line parallel to the axis of the pivot shaft 72. _As shown _{in FIG} . , the radius r of the partial cylindrical surface 100, and the length of the straight line connecting the center O and the axis P are the yoke portion 74.
is determined so that the slippage is as small as possible. That is, when the piston 32 is at the center position of the entire stroke range, the axis P of the pivot shaft 72 is located a certain distance a above the plane H obtained by extending the surface of the washer 58 in contact with the yoke portion 74 toward the pivot shaft 72 side. It is located in
Moreover, the radius r is selected to be an appropriate value in relation to the length. If you explain in detail,
When the piston 32 moves from the top dead center to the bottom dead center, the center of curvature of the yoke portion 74 (partial cylindrical surface 100
The center of the piston pull rod 50 moves along an arc with a radius from O ₂ to O ₃ , but at this time, a motion component of a distance m is generated in a direction perpendicular to the axis C of the piston pull rod 50. Since the washer 58 and the yoke portion 74 always come into contact at a position directly below the center O, the contact point also moves by a distance m in the same direction. On the other hand, as the rocker arm 70 rotates, the partial cylindrical surface 100 of the yoke portion 74 rolls on the washer 58, and the contact point between the two is perpendicular to the axis C of the piston pull rod 50. This movement amount increases as the radius r of the partial cylindrical surface 100 increases. Therefore, by selecting the radius r to an appropriate value, the amount of movement of the contact point due to rolling is made approximately equal to the motion component of the center O in the direction perpendicular to the piston pull rod axis C. be able to.

However, while the amount of movement of the contact point due to rolling is proportional to the rotation angle of the rocker arm 70, the motion component of the center O is not exactly proportional to the rotation angle. When using a partially cylindrical surface as in this embodiment, both cannot be made completely equal. Therefore, in this embodiment, taking into consideration that the contact surface pressure between the yoke portion 74 and the washer 58 increases as the piston 32 approaches the bottom dead center, slippage is made to be zero near the bottom dead center. The dimensions and relative positions of each part are selected.

Therefore, on the top dead center side, the yoke portion 74
Although a relative movement corresponding to the difference between the above-mentioned motion component and the amount of movement will occur between and the flange 56, the washer 58 can move in the diametrical direction by a distance greater than the relative movement amount with respect to the flange 56. Therefore, the washer 58 is the flange 56.
This relative movement is absorbed by sliding on the retainer surface, and there is almost no slippage between the washer 58 and the yoke portion 74, and their wear is effectively prevented. Also, the washer 58 is attached to the flange 5.
It slides on the retainer surface of No. 6, but since these are in contact with each other over a wide surface, there is less 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 Atsupa 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 embodiment, since the cylindrical member 54 is completely fixed to the rod body 52 as described above, the position of the piston top dead center due to rotation of the cylindrical member 54 is prevented from changing. That is, if the cylindrical member 54 is not fixed to the rod main body 52, the cylindrical member 54 rotates around the rod main body 52 during operation of the pump, and the end face of the cylindrical member 54 and the retaining ring supporting it rotate. Sliding occurs between the diameter portion 60 and the shoulder surface 61, which wears out, lowering the position of the cylindrical member 54 relative to the rod body 52, and raising the top dead center position of the piston 32 by that amount. However, in this vacuum pump, since the cylindrical member 54 is fixed to the rod main body 52, such inconvenience does not occur.
In addition, for some reason, the Rotsuka arm 70 may not be connected to the cam 9.
0 or the piston pull rod 50 does not completely follow the rocker arm 70, the yoke portion 74 collides with the flange 56 via the washer 58, and the cylinder member 54 An axial impact load is applied to the cylindrical member 54, and the impact load deforms the retaining large diameter portion 60, thereby lowering the position of the cylindrical member 54, and the piston 3
There is a risk that the top dead center position of 2 will rise.
The occurrence of such a situation can be prevented or reduced by fixing the cylindrical member 54 to the rod main body 52.

One embodiment of the present invention has been described in detail above, but
This is literally an example, and the present invention can be modified and improved based on the knowledge of those skilled in the art, such as omitting the washer 58 or integrally forming the piston pull rod 50. Of course, the idea can be put into practice.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing how to determine the relative positions and dimensions of a piston pull rod, rocker arm, and pivot shaft in a vacuum pump that is an embodiment of the present invention. FIG. 2 is a front sectional view of the vacuum pump. FIG. 3 is a diagram schematically showing the piston pull rod of the vacuum pump together with an apparatus for manufacturing the same. FIG. 4 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, 57... Retainer surface, 58... Washer, 70... Locker arm, 72... Pivot shaft, 74... Yoke part,
90...Cam, 100...Partial cylindrical surface, O(O ₁ ,
O ₂ , O ₃ ) ... Center of the partial cylindrical surface, P ... Axis center of the pivot axis, r ... Radius of the partial cylindrical surface, ... Length of the straight line connecting the center O and the axis P.

Claims (1)

[Claims for Utility Model Registration] One end of a rocker arm whose intermediate portion is rotatably supported by a pivot shaft on a retainer of a piston pull rod that extends in the axial direction from a piston provided in a casing. In the vacuum pump, the retainer of the locker arm is engaged with the locker arm and the other end thereof is engaged with the cam, and the swinging motion of the locker arm due to rotation of the cam is converted into linear reciprocating motion of the piston. The contact surface with the retainer surface of the pivot shaft is a convex curved surface that touches the retainer surface at one point when viewed from a direction parallel to the axis of the pivot shaft, and the radius of curvature of the convex curved surface, the center of curvature of the convex curved surface, and the above-mentioned The length of the straight line connecting the axial center of the pivot shaft, and the relative position between the center of curvature and the axial center of the pivot shaft, are determined by determining whether the center of curvature is perpendicular to the axial center of the piston pull rod as the rocker arm swings. The motion component in the direction is determined to be approximately equal to the amount of movement of a contact point between the convex curved surface and the retainer surface due to rolling of the convex curved surface on the retainer surface as the rocker arm rotates. A low-friction vacuum pump. A sliding member is interposed between the retainer surface and the convex curved surface and is movable in the diametrical direction of the piston pull rod by a distance greater than the difference between the motion component of the center of curvature and the amount of movement of the contact point. A vacuum pump according to claim 1 of the registered utility model claim.