JP2003328970A - Vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce gas leakage from a side seal portion of a vacuum pump in which side seal of a rotor is performed by lessening a side clearance, and to enhance vacuumizing performance of the pump. <P>SOLUTION: A thin plate 20 is inserted in at least one of between the rotor 5 and an end frame 2 and between the rotor 5 and a housing 1. The thin plate 20 is bent by negative pressure in a pump chamber 13 and is sucked on a rotor side. A clearance C between the rotor 5 and the thin plate 20 is thus lessened, and gas leakage from it is reduced. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump that moves a rotor in a casing to suck and exhaust air.

[0002]

2. Description of the Related Art Wankel type vacuum pumps, scroll type vacuum pumps, rolling piston type vacuum pumps, and vane type vacuum pumps have casings whose both ends are closed by side housings (housing and end frame), and an eccentric arrangement in the casings. Has a rotor to be housed therein, and the volume of the pump chamber (chamber) formed between the inner surface of the casing and the outer periphery of the rotor is changed by the rotation, revolution or revolution of the rotor to perform intake and exhaust. .

The vacuum performance of these vacuum pumps is greatly affected by the quality of the side seal (the seal between the rotor and the side housing).

As for the side seal, as in the Wankel type rotary engine, a side seal member is attached to the side surface of the rotor and the side seal member is pressed against the side housing by a spring, or a lubricating oil is used in a gap between the rotor and the side housing. It is possible to use a method such as encapsulating the oil and stopping the gas leakage due to the surface tension of the lubricating oil.However, since these methods complicate the pump, the side seal in the vacuum pump requires a clearance ( It is often done by a method that makes it difficult for gas to pass through by reducing the side clearance).

Unlike an engine, a vacuum pump does not involve high compression, so that it is possible to secure required performance by a method of reducing side clearance and reducing gas leakage. According to this method, a special seal member or a complicated mechanism is not required, and the pump can be simplified and the cost can be reduced.

[0006]

When the side seal of the rotor is performed without using the side seal member, the smaller the side clearance is, the less the amount of gas leaks and the more the vacuum performance of the pump is improved. If it is made too small, the rotor and the side housing interfere with each other to hinder the rotation of the rotor, causing problems such as wear and seizure of the sliding surface.

For this reason, it is regulated that the side clearance is sufficiently small, and the sealing performance of the side seal portion is limited by the method.

[0008] Therefore, an object of the present invention is to improve the sealing performance of the side seal portion as compared with the prior art by naturally reducing the side clearance with the operation of the vacuum pump.

If the rotor and the casing are made of materials having different coefficients of thermal expansion, the clearance changes due to the temperature change and the gap becomes large. The gap becomes large due to wear of the sliding surface, and therefore it is desired to prevent the deterioration of the sealing performance due to these factors as well. Therefore, a seal structure for a side seal that meets this requirement should be provided. provide.

[0010]

In order to solve the above problems, according to the present invention, a rotor is provided between a rotor for interlocking in the casing to cause a volume change in the pump chamber and a housing for closing one end of the casing. A thin plate that is attracted to the rotor side by the negative pressure of the pump chamber is inserted into at least one of the end frame that closes the other end of the casing.

The thin plate may be surface-treated to reduce friction with the rotor. The outer end of this thin plate may be arranged inside the seal between the casing and the housing and between the casing and the end frame. The thin plate can be held by sandwiching it between the casing and the housing and between the casing and the end frame.

[0012]

[Operation] When the pump is driven and the pump chamber becomes negative pressure,
The thin plate is attracted to the rotor side by the negative pressure of the pump chamber and bends, and the gap between the rotor and the thin plate becomes smaller. If there is a margin in the amount of bending of the thin plate, the amount of bending of the thin plate will increase in accordance with the expansion of the gap due to the difference in thermal expansion and the wear of the rotor side surface. Therefore, regardless of whether the gap fluctuates or not, The installation reduces the leakage of gas from the side seals and improves the vacuum performance of the pump.

Since the thin plate is appropriately pushed back when it receives a pushing-back force exceeding the suction force from the rotor, the suction of the thin plate does not significantly increase friction with the rotor or hinder the rotation of the rotor.

[0014]

1 to 3 show an embodiment of the present invention. The illustrated pump is a Wankel vacuum pump. In this Wankel type vacuum pump, as shown in FIG. 1, a casing 3 is sandwiched between left and right side housings, that is, a housing 1 and an end frame 2, and three members are connected by bolts 4.

A triangular rotor 5 is housed in the casing 3, and an internal gear 6 provided on the rotor 5 meshes with a pinion 7 fixed to the housing 1.

A crankshaft 9 supported by the housing 1 and the end frame 2 through a bearing 8 is passed inside the rotor 5, and the eccentric shaft 9a of the crankshaft is arranged concentrically with the internal gear 6. The bearing 10 assembled in the rotor 5.

The crankshaft 9 is connected to the output shaft of the motor 11. When the crankshaft 9 is rotated by the motor 11, the rotor 5 meshed with the pinion 7 revolves around the pinion 7 while rotating. Reference numeral 12 is a weight balancer attached to the crankshaft 9 for the purpose of reducing the vibration generated by the eccentric movement of the rotor 5.

The inner surface of the casing 3 has a bilobal shape slightly larger than the movement trajectory of the apex of the rotor 5, and the pump chamber 1 formed between the inner surface and the outer peripheral surface between the apexes of the rotor.
The rotational movement of the rotor 5 accompanied by the revolution of the rotor 3 causes a volume change, and intake and exhaust are repeated.

The housing 1 has an intake hole 14 and an exhaust hole 1.
The gas in the pump chamber 13 which has been provided with two pieces of gas 5 each and which has moved to the compression stroke is supplied from the exhaust hole 15 to the check valve 16 provided in each of the exhaust holes.
Exhausted through. In the illustrated pump, the exhaust gas passes from the internal space 17 of the housing 1 to the inside of the motor 11 and exits from the drain pipe 18 to the outside.

An apex seal 19 is incorporated in each apex of the rotor 5 so as to be slidable in the radial direction. The apex seal 19 is pressed against the inner surface of the casing 3 by the centrifugal force generated by the rotation of the rotor, and the outer circumference of the rotor and the inner surface of the casing. The seal between them is made.

The seal between the rotor 5 and the housing 1 and between the end frame 2 is made by the side clearance of the rotor.

The thickness of the casing 3 is made slightly thicker than the thickness of the rotor 5 so that a clearance C for rotating the rotor is created between the rotor 5 and the housing 1 and the end frame 2, and the clearance C is made as small as possible. Therefore, the side seal of the rotor is performed without using the side seal member.

In the illustrated pump, a thin plate 20 which is bent by the negative pressure of the pump chamber 13 is provided between the rotor 5 and the end frame 2, and the gap C on the end frame 2 side is between the thin plate 20 and the rotor 5. Occurs in

The thin plate 20 is preferably formed of a metal plate, a ceramic sheet, or the like, which is less worn and has good sliding characteristics. Examples of the material of the metal plate include, but are not limited to, carbon tool steel and high-strength carbon steel. It is also preferable that a surface treatment is performed to reduce friction with the rotor 5. As the surface treatment, it is conceivable to provide an amorphous carbon coating having a small friction coefficient or an alumite coating whose surface pores are sealed with molybdenum disulfide, but is not limited thereto.

As shown in FIGS. 1 and 3, the thin plate 20 is held at its outer peripheral portion between the casing 3 and the end frame 2.
It can be performed by sandwiching it between the casing 3 and the housing 1. Since the center side of the thin plate provided with the through hole 20 is inserted between the rotor 5 and the end frame 2, it is not necessary to fix the thin plate.

The vacuum pump of the present invention having the above-described structure is used for vacuum suction of a vehicle vacuum booster, for example. When this pump is activated,
The degree of vacuum of the equipment on the side of vacuum suction increases with time. As the degree of vacuum rises, the degree of vacuum in the pump chamber 13 in the suction stroke rises, and the thin plate 20 bends and is sucked to the rotor 5 side when the negative pressure in the pump chamber exceeds a certain value. For this reason, the gap between the rotor 5 and the thin plate 20 becomes smaller, and the negative pressure in the pump chamber 13 due to gas leakage from the side seal portion is prevented from decreasing, so that the vacuum performance of the pump is improved.

The thin plate 20 may be provided between the housing 1 and the rotor 5, or may be provided on both sides of the rotor 5 as shown in FIG. Further, as shown in FIG. 3, the outer end of the thin plate 20 is provided between the housing 1 and the casing 3,
It is preferable to dispose the inside of the seal portion between the end frame 2 and the casing 3 because the casing end can be sealed with one sealing member 21 (in the structure of FIG. 1, two sealing members are used to seal both surfaces of the thin plate 20). There is a need to).

FIG. 4 shows a Wankel type vacuum pump having a thickness t =
The comparison result of the vacuum performances of the pumps when the thin plate 20 of iron of 0.3 mm is provided (thin plates are arranged on both sides of the rotor as shown in FIG. 3) and when the thin plate is not provided is shown. In FIG. 4, a difference in the degree of vacuum of a device that has been vacuum-sucked due to the presence or absence of the thin plate 20 begins to immediately after the start of suction, and finally becomes -5 kPa.
There are differences in degree, and the effect of thin plate installation is clearly visible in this result.

[0029]

As described above, in the vacuum pump of the present invention, the thin plate is arranged on at least one side of the rotor, and the thin plate is bent by the negative pressure of the pump chamber to reduce the clearance between the thin plate and the rotor. By doing so, gas leakage from the side of the rotor is reduced and the vacuum performance of the pump is improved.

The effect of improving the vacuum performance is particularly remarkable when the present invention is applied to a pump in which inevitable clearance fluctuation occurs. That is, it is possible to cope with the clearance variation by changing the bending amount of the thin plate, and high vacuum performance can be secured even if a difference in thermal expansion between the rotor and the casing due to temperature change, wear of the sliding surface, and the like occur.

Further, in the pump of the present invention, the sealing performance is enhanced by the action of the thin plate even if the clearance on the rotor side portion is set to be slightly large, so that it is not necessary to strictly set the initial clearance, and the housing, casing, end It is possible to say that the processing accuracy of the frame is lowered.

Besides, in the case where the outer end of the thin plate is disposed inside the housing and the casing and inside the seal portion between the end frame and the casing, the sealing of the casing end is not complicated.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a vacuum pump of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a vertical cross-sectional view of another embodiment.

FIG. 4 is a chart showing a comparison result of vacuum performance with and without a thin plate.

[Explanation of symbols]

1 housing 2 end frame 3 casing 5 rotor 6 Internal gear 7 pinion 8, 10 bearings 9 crankshaft 11 motor 12 weight balancer 13 pump room 14 Intake hole 15 Exhaust hole 16 Check valve 19 Apex Seal 20 thin plate 20a through hole 21 Seal member

Claims (4)

[Claims] 1. At least one of a rotor that interlocks in a casing to cause a volume change in a pump chamber and a housing that closes one end of the casing, and at least one of a rotor and an end frame that closes the other end of the casing. The vacuum pump is characterized in that a thin plate that is attracted to the rotor side by the negative pressure of the pump chamber is inserted. 2. The vacuum pump according to claim 1, wherein the thin plate is surface-treated to reduce friction with the rotor. 3. The vacuum pump according to claim 1, wherein an outer end of the thin plate is arranged inside a seal portion between the casing and the housing and between the casing and the end frame. 4. The vacuum pump according to claim 1, wherein the thin plate is sandwiched and held between the casing and the housing and between the casing and the end frame.