JPH02230983A - Piston slide type vacuum pump - Google Patents

Abstract

PURPOSE:To improve the ultimate vacuum and exhaust speed by providing a porous plate with the thickness to fill the top dead point gap of an operating piston on at least one of the head side end face of a piston section and the inner face of the head cover section of a pump housing, and impregnating a lubricant. CONSTITUTION:When an operating piston 20 reaches the top dead point in the reciprocating stroke of the operating piston 20, a pump chamber 31 is almost filled by a porous plate 29, a lubricant is impregnated in porous sections of the porous plate 29, thus most of the air in the pump chamber 31 is discharged through a discharging check valve 37. The downward stroke of the operating piston 20 is started from the top dead point position where the volume occupied by the air in the pump chamber 31 is very small, thus a vacuum pump 50 has an excellent vacuum characteristic, and the ultimate vacuum and exhaust speed can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston sliding vacuum pump that is installed in a vehicle such as an automobile and used as a negative pressure source for a brake system.

[Conventional technology]

In general, a piston sliding type vacuum pump has a piston part of an operating piston slidably inserted into a cylinder part provided in a bomb housing, and a suction check valve and a discharge check valve are provided on the head side of the operating piston. A bomb chamber is formed, and the actuating piston is reciprocated by a reciprocating drive mechanism, and the negative pressure generated in the pump chamber is applied to an actuator such as a brake booster or a reservoir connected to the actuator. As a drive mechanism for reciprocating the working piston, there is a mechanism using an electric motor as a prime mover as shown in Japanese Patent Application Laid-Open No. 62-60989,
As shown in Japanese Patent No. 4786, many use the camshaft of the engine as the driving shaft.

[Problem to be solved by the invention]

However, in the above-mentioned conventional piston sliding type vacuum pump, the top dead center clearance, which is the height of the bomb chamber when the working piston reaches the top dead center position, is due to manufacturing errors in the working piston, pump housing, etc., and the piston. In order to prevent the piston part from colliding with the head cover part of the bomb housing even if the piston position varies due to inclination, etc., it was necessary to set the piston part larger than a certain degree. As a result, the minimum volume of the pump chamber at the piston top dead center position is large, the vacuum bomb's ultimate vacuum level and pumping speed are low, and when used in a brake system, it takes time to recover negative pressure after using the brake. was there.

The present invention solves the above conventional problems, and provides a piston layered vacuum bomb that can reduce the minimum volume at the top dead center of the bomb chamber and improve the ultimate vacuum degree and pumping speed. With the goal.

[Means to solve the problem]

In order to achieve the above object, the vacuum bomb of the present invention has an operating piston slidably fitted into a cylinder section provided in a pump housing, and a suction check valve and a discharge check valve on the head side of the operating piston. In the piston sliding type vacuum bomb, which forms a bomb chamber equipped with a reciprocating drive mechanism for the operating piston, at least one of the head side end surface of the piston part and the inner surface of the head cover part of the pump housing. To,
The present invention is characterized in that a porous plate having a thickness that fills the top dead center gap of the operating piston is fixed, and this porous plate is impregnated with lubricating oil.

The porous plate in this invention is, for example, a metal porous plate made of metal such as Ni or copper and having an open-cell porous structure and whose thickness changes by plastic deformation or elastic deformation when compressed. In addition, a porous resin plate or a rubber porous plate having similar structure and characteristics can also be used.

[Effect]

In the piston sliding type vacuum bomb of the present invention, when the operating piston reaches the top dead center, the bomb chamber is almost filled with the porous plate, and the pores of this porous plate are impregnated with mm oil. The volume occupied by the air in the bomb chamber is extremely small.

In general, in piston-sliding type vacuum bombs, the ultimate vacuum can be increased by reducing the ratio of the minimum volume (air volume in the bomb chamber at top dead center) to the stroke volume of the pump chamber. As a result of the presence of the quality plate, the air volume within the bomb chamber is greatly reduced, resulting in improved ultimate vacuum and pumping speed, resulting in a vacuum pump with excellent pump characteristics.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In the figure, 1 is a pump housing, which includes a housing body 2 that accommodates an operating piston 20, a head force bar 3 that is airtightly attached to the diagonally upward opening of this housing body 2, and a head force bar 3 that extends horizontally through the housing body 2. A cover 5 is airtightly attached to one side opening of a communication chamber 4. The housing body 2 is attached to the side end of a cylinder head 6 of an engine in a vehicle with bolts 7, and the communication chamber 4 is connected to a camshaft of the cylinder head 6 through an opening 8 provided in an end wall of the cylinder head 6. (Overhead force shaft) Communicates with the storage chamber 9. 1
0 is a camshaft, 11 is a bearing that supports the camshaft 10, and 12 is a cylinder head force bar.

A cylinder liner 1 is disposed inside the cylindrical portion 2a of the housing body 2.
5 is fitted to form a cylinder portion 16, and a guide hole 17 is bored coaxially with this cylinder portion 16, and the lower end of this guide hole 17 opens into the communication chamber 4. The actuating piston 20 consists of a large-diameter piston part 21 and a small-diameter cylindrical rod part 22 connected to each other, and the piston part 21 is slidably fitted into the cylinder part 16 and the rod part 22 is fitted into the guide hole 17, respectively. It is inserted. An O-ring 24 is fitted into a groove 23 provided on the outer periphery of the piston portion 21, and the outer periphery of the O-ring 24 slides against the cylinder liner 15 to maintain airtightness. 25 is rod part 2
2 and the camshaft 10, one end of which is rotatably connected to the rod part 22 by a pin 26, and the other end of the connecting rod 25 is connected to the camshaft 10 extending into the communication chamber 4. It is rotatably connected via a bearing 28 to a crankshaft 27 fixedly protruding from the shaft end. Reference numeral 29 is a porous plate made of Ni-based metal having a spongy structure, which is adhered to the head side end surface 21a of the piston portion 21, and its pores are impregnated with lubricating oil. This porous plate 29 has an outer diameter approximately equal to the diameter of the piston portion 21, and as shown in FIG. When the dead center position is reached, the top dead center gap S has an initial thickness t that is slightly larger than the maximum value announced by each part. This thickness t. After the porous plate 29 is assembled into the pump housing 1 and the entire bomb is assembled to the cylinder head 6 of the vehicle, the porous plate 29 is actuated when the actuating piston 20 is first reciprocated by the rotation of the camshaft 10. When the piston 20 rises as shown in FIGS. 3(a) and 3'(b) and reaches the top dead center as shown in FIG. 3(C), the head side end surface 21a and the inner surface of the head force bar 3 3a and undergoes plastic deformation, and the thickness becomes approximately equal to the actual top dead center gap S for each product.
As shown in FIG. 1 and (d), the thickness is maintained to fill the top dead center gap S.

On the other hand, 31 is a pump chamber formed between the piston part 21 of the working piston 20 and the head force bar 3.
The opening on the bomb chamber 31 side of the intake port 32 protruding from the
A suction check valve 33 is incorporated. Intake port 3
2 is connected to the pump chamber 3 via this intake check valve 33.
1, and is connected to a brake booster reservoir tank via an intake pipe 34.

Further, an exhaust passage 35 that communicates with the communication chamber 4 is provided in the lower part of the housing body 2, and a discharge check valve is provided at the open end of the exhaust passage 35 opposite to the exhaust port 36 recessed in the head force bar 3. 37 are provided. Further, 41 is a variable volume chamber formed between the cylinder part 16 and the rod part 22,
It is provided on the opposite side of the bomb chamber 31 with respect to the piston portion 21 .

Reference numeral 42 denotes an intake passage connecting the variable volume chamber 41 and the communication chamber 4, and the exhaust passage 35 opens at a position of the intake passage 42 closer to the communication chamber 4.

In the vacuum bomb 50 configured as described above, the actuating piston 20 is reciprocated through the connecting rod 25 by the rotation of the camshaft 10. During the upward stroke of the working piston 20 (sliding in the direction of arrow X toward top dead center), the suction check valve 33 closes and the discharge check valve 37 opens, allowing air in the pump chamber 31 to communicate. It is discharged into the chamber 4. Further, when the operating piston 20 is in its downward stroke (sliding in the direction of arrow Y toward the bottom dead center), the suction check valve 33 opens and the discharge check valve 37 closes, conversely to the above, and the pump chamber is closed. 31 becomes negative pressure and the intake port 3
Air is sucked into the pump chamber 31 from the second side, and vacuum evacuation is performed.

When the working piston 20 reaches the top dead center during the reciprocating stroke of the working piston 20, the pump chamber 31 is closed to the porous plate 29.
Furthermore, since the pores of the porous plate 29 are impregnated with lubricating oil, most of the air in the bomb chamber 31 is discharged through the discharge check valve 37.

In this way, the downward stroke of the actuating piston 20 starts from the top dead center position where the volume occupied by the air in the pump chamber 31 is extremely small, so the vacuum pump 50 exhibits excellent vacuum characteristics and achieves the ultimate vacuum level. and pumping speed is improved.

Vacuum bomb 50 with the above configuration (stroke of operating piston 20 = 13 strokes, cylinder inner diameter -70 seconds)
The pump characteristics when the pump was operated at a camshaft rotation speed of 375 rpm were as shown in curve A in FIG. In contrast, the conventional same specification without the porous plate 29 (however, the operating piston 20 and the head force bar 3
The bomb characteristics of the vacuum bomb with a top dead center clearance of -1.3mgg) are as shown by curve C in the figure, and compared to the conventional product, the example product has a higher ultimate vacuum and pumping speed than the conventional product. It can be seen that there has been a significant improvement.

In addition, for the above example product, the cylinder inner diameter was set to 55 mm,
The bomb characteristics of the second embodiment product, in which the operating piston 20 and the porous plate 29 are also made smaller in diameter, are shown as curve B in FIG. ), bomb characteristics equivalent to or better than those obtained were obtained.

The present invention is not limited to the above-mentioned embodiments; for example, the reciprocating drive mechanism of the operating piston may include one using an hm shaft and a connecting rod as described above, one using an electric motor and a connecting rod, or one using a rocker arm and a biasing spring. Various drive mechanisms can be adopted, such as.

Further, in the above embodiment, the porous plate 29 was attached to the head side end surface 21a of the piston part, but instead, the porous plate 29 was attached to the inner surface of the head force bar 3, or to both the inner surface and the head side end surface 21a. You can.

Furthermore, the porous plate 29 may be made of an elastic material. In this case, when the working piston reaches the top dead center and the porous plate 29 is elastically deformed, some lubricating oil is released from the pores. However, this oil is reabsorbed into the pores of the porous plate that expands with the downward stroke of the operating piston, and is further absorbed into the bomb chamber 31 through the gap between the cylinder part 16 and the O-ring 24.
The lubricating oil that enters the side also reaches the porous plate 29 and is supplied as oil for pore impregnation.

〔Effect of the invention〕

As explained above, according to the present invention, the air volume in the bomb chamber when the operating piston reaches the top dead center is greatly reduced by the porous plate impregnated with lubricating oil, thereby increasing the ultimate vacuum level and pumping speed. When used in a brake system, the negative pressure recovery time after the brake is used can be shortened, and the vacuum bomb can be made smaller and lighter.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a piston sliding type vacuum bomb showing an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 3 (a) to (d) are multi-hole FIGS. 4 and 5 are longitudinal cross-sectional views of the working piston portion showing changes in dimensions of the quality plate, and are characteristic diagrams of the vacuum bomb shown in FIG. 1. 1...Bomb housing, 2...Housing body,
3°・° Head force bar, 3a...Inner surface, 16...Cylinder part, 20...Working piston, 21...Piston part, 21a...Head side end surface, 25...Conrod, 27 ... crankshaft, 29 ... porous plate, 31
...Bomb chamber, 33...Inhalation check valve, 3
7...Discharge check valve, 50...Vacuum bomb. salary 1 figure

Claims (1)

[Claims] 1. A working piston is slidably fitted into a cylinder part provided in a pump housing, a pump chamber equipped with a suction check valve and a discharge check valve is formed on the head side of the working piston, and the working piston In a piston sliding vacuum pump comprising a reciprocating drive mechanism, at least one of the head side end surface of the piston part and the inner surface of the head cover part of the pump housing,
A piston sliding type vacuum pump characterized in that a porous plate having a thickness that fills the top dead center gap of the operating piston is fixed, and this porous plate is impregnated with lubricating oil.