JP2002195178A - Rotary vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively ensure a proper clearance between a rotor 80 and a casing without reducing the productivity, of a pump. SOLUTION: Ring-shaped spacer members 500, 500' are arranged between each side wall face 331s and 70s of the rotor 80, a base 331, and a lid member 70. A thickness of the spacer members 500, 500' is about 50 μm, and polyimide resin having a self-lubricating property and high heat resistance is preferable as their material. When the rotor 80 rotates, each spacer member 500, 500' becomes a stopper in the direction of axial line of the rotor 80, prevents the rotor 80 from falling down, and keeps a proper clearance in an outer peripheral part in the radial direction of the rotor 80 at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary vacuum pump for obtaining a vacuum by rotating a rotor in a casing, and for example, relates to a technology of a vacuum pump effective as a negative pressure source for a brake booster or the like. .

[0002]

BACKGROUND OF THE INVENTION In this type of rotary vacuum pump, a pump working chamber (that is, a suction chamber and an exhaust chamber) is defined in a casing by a rotor and a vane, and the inside of the pump working chamber is rotated as the rotor rotates. In this case, a pump action is performed in which external air (for example, air in a negative pressure chamber of a brake booster, ie, a variable pressure chamber) is sucked, compressed, and then exhausted to the outside. The number of vanes is one or more. The single vane is supported on the casing side, and the plural vanes are supported on the rotor side. JP-A-61-164094
And the publications of Japanese Patent No. 2722445 show a first type of vacuum pump including a single vane of the former type. In the first type, the axis of a rotary drive shaft of a rotary drive such as an electric motor is disclosed. And the center of rotation of the rotor is eccentric,
Therefore, the rotor, when it is rotated to move the internal space in the casing in the radial direction.

On the other hand, the latter second type including a plurality of vanes is disclosed in Japanese Patent Application Laid-Open Nos.
Each publication of JP 0-108582 indicates, in the second type, the axis of the rotary drive shaft of the rotary drive unit, the rotation center of the rotor is positioned on the same axis. Thus, the second type of vacuum pump has a lower rotor-casing relationship than the first type, since the rotor does not move radially within the casing but rotates at the same position. Galling or seizing hardly occurs. Therefore, the second type has an advantage that the rotor can be of a cantilever type (a type having a bearing on only one side of the rotor).

Meanwhile, in such rotary vacuum pump, while smoothly rotating the rotor within the casing, in order to obtain an effective pumping action, it must be properly maintained the clearance between the rotor and the casing.
For example, the clearance is a value of about several tens of μm, and is a size that is affected by an assembly error of the pump, a difference in thermal expansion between the rotor and the casing, an axial play of the rotor, and the like. In particular, in the case of a cantilever type rotor, the rotor falls down in a direction crossing the axial center due to rattling between the rotary drive shaft that supports the rotor, and the end face (the outer peripheral portion) of the rotor is formed in the casing. unnecessarily contact with the side wall surface, which may cause galling.

[0005]

Therefore, in the prior art, a proper clearance is ensured by assembling with a shim or a sheet sandwiched between a rotor and a casing and removing the shim or the sheet after assembling. Japanese Unexamined Patent Publication (KOKAI) Showa No. 60-1085), or at least one surface of a rotor or a casing is coated with a special material.
No. 82 and JP-A-61-164094). But,
With these conventional methods, assembly work is troublesome,
Alternatively, more extra steps involved in coating, there is a difficulty in terms of pumping productivity. Furthermore, if the rotor is cantilevered (the cantilevered type has the advantage that the pump is lower in cost because one bearing can be omitted compared to the double-sided type), It is inevitable that there is a backlash between the rotating shaft and the supporting shaft, and it is much more difficult to stably secure an appropriate clearance for a long period of time.

Accordingly, an object of the present invention is to provide a technique capable of effectively ensuring an appropriate clearance between a rotor and a casing without reducing the productivity of a pump. It is another object of the present invention to provide a technique that can be effectively applied to a cantilever type rotor. Other objects of the present invention will become clear from the following description.

[0007]

According to the present invention, a concept is adopted in which a specific spacer member is disposed between the rotor and the casing, particularly, at both end surfaces of the rotor. That is, the present invention has basic features in the following points. A. A spacer member separate from the rotor and the casing is provided between each of the two side walls of the casing and both end portions of the rotor facing the side walls. B. The spacer member is thin enough not to impair the pumping action of the rotary vacuum pump, and occupies only the central region of the rotor.

If the thickness of the spacer member is too large, the required degree of vacuum cannot be obtained. Conversely, if the thickness is too small, handling during assembly becomes difficult. According to experiments, for example, even with a thickness of about 50 μm, the same degree of vacuum (or required pumping action) as that of 10 to 25 μm can be obtained. Therefore, considering the handleability, the thickness of the spacer member is preferably as large as possible, for example, about 50 μm, as long as the required degree of vacuum can be obtained. When the spacer member is made of a self-lubricating material, the spacer member can be brought into close contact with the rotor and the casing.
It is good to have a clearance of about m.
Thereby, the resistance associated with the contact can be further reduced.

Since the spacer member is selectively located at the center of the rotor, a predetermined clearance (for example, a constant clearance) is always provided between the radially outer portion of the rotor and the side wall surface of the casing.
(A clearance of 50 to 60 μm). When the rotor is provided with a vane groove, the spacer member should be large enough not to cover the vane groove. One spacer member facing the end of the rotary drive shaft can be fitted and supported in the recess on the casing side, so it can be in any shape such as a disk or ring,
The other spacer member has a ring shape because it has to be supported on the rotary drive shaft. From the viewpoint of sharing both spacer members, it is preferable that both spacer members have the same ring shape.

The rotor and the casing are generally made of metal, and are preferably made of the same material, for example, aluminum or an alloy thereof in order to eliminate the difference in thermal expansion between the two. In contrast, the material of the spacer member is non-metal,
Preferably, a synthetic resin material having high heat resistance, for example, polyacetal or polyimide is used. In particular, a material having good self-lubricating property is preferable.

Here, the rotor is connected to a rotary drive shaft of a rotary drive and driven to rotate, and the rotor is keyed to the rotary drive shaft. Therefore, the rotor is integrated with the rotary drive shaft around the axis of the rotary drive shaft, and no relative movement occurs between the two. However, the rotor can move relatively slightly in the axial direction of the rotary drive shaft. The spacer member functions as a stopper for the rotor that moves in the axial direction. In addition, the spacer member selectively positioned at the center of the rotor also has a function of supporting the rotor when the rotor is about to fall from the axial direction. The function of the spacer member is particularly effective when the rotor is cantilevered. In a more preferred embodiment, by devising the flow of fluid to the pump working chamber, the force acting on both end surfaces portions of the rotor to the left the same based on the pressure of the fluid flowing. If the force acts on the left and right identical on both end surfaces portions of the rotor, the rotor will be rotated at a substantially constant part of the rotary drive shaft, more stably and smoothly rotate from and.

[0012]

FIG. 1 is a side view of a rotary vacuum pump according to an embodiment of the present invention. FIG. The rotary vacuum pump 10 is used for a brake booster of a vehicle, and has an arm 20 having a U-shaped cross section for attachment to the vehicle. The rotary vacuum pump 10 in a horizontal position is mounted on the arm 20 fixed to the frame of the vehicle by the damper 22a,
It is supported so as to be hung via 22b. This support forms, also in the sense to lower the center of gravity of the vehicle, preferable in the sense that facilitates operation of the rotary vacuum pump 10.

A rotary vacuum pump 10 with an arm 20
Includes a rotary drive 30 composed of an electric motor, and a pump unit 50 driven by the rotary drive 30. The rotary drive 30 includes a rotary drive shaft 32 that is electrically driven to rotate.
including. The casing of the rotary driving device 30 includes a flat base 331 and a cup-shaped cover 332 located on one surface side of the base 331. The rotation drive shaft 32 penetrates through the cover 332 and the base 331, and one end is supported by a bearing in the auxiliary cover 332a.
The other end is supported by a bearing 33 inside the base 331. The other end of the rotary drive shaft 32 penetrates the base 331 and enters the inside of the pump unit 50.

The base 331 of the rotary drive 30 also functions as a component of the casing of the pump unit 50. The casing of the pump unit 50 has a flat base 331.
And the cylinder member 60 located on the other surface side of the base 331
And a lid member 70 that sandwiches the cylinder member 60 together with the base 331. The cylinder member 60 has a cylindrical shape with an internal hole having a uniform diameter, and forms an inner peripheral wall surface 60s surrounding the center line. The base 331 and the lid member 70 are each provided between the seal ring 6 and the cylinder member 60.
The two bolts 2a and 62b are sandwiched therebetween and are airtightly connected to each other by a support bolt 72. Therefore, the pump unit 50
The inner peripheral wall surface 60s of the cylinder member 60 and the base 33
1 and the side wall surfaces 331 s and 70 s of the lid member 70 (these side wall surfaces are orthogonal to the center line) to define an internal space. The axis of the rotary drive shaft 32 is slightly eccentric with respect to the center of the inner peripheral wall surface 60s of this internal space,
End portion 32 of rotary drive shaft 32 that has entered the interior space
0 supports the rotor 80. Therefore, the rotor 8
The rotation center of 0 coincides with the axis of the rotation drive shaft 32 and is located on the same axis. Here, the casing parts of the rotor 80 and the pump unit 50 are formed of the same system of metal material (aluminum or aluminum alloy) in order to eliminate a change in clearance due to a difference in thermal expansion.

[0015] The rotor 80, such as a vane groove 810 for housing the vane 90 consisting of carbon (here, four) are provided. The plurality of vane grooves 810 are arranged at equal intervals around the center of the rotor 80, and each vane groove 810 extends from the outer peripheral surface of the rotor 80 to a radially intermediate portion. Each vane 90 in each vane groove 810
Receives the action of centrifugal force with the rotation of the rotor 80,
The radial end portion is the inner peripheral wall surface 60s of the cylinder member 60.
And rotates together with the rotor 80. Therefore,
Each vane 90 includes a rotor 80 and casing components (cylinder member 60, base 331, and lid member 70).
At the same time, a pump working chamber 200 is defined around the rotor 80. FIG. 2 showing the cross-sectional structure along the line 2-2 in FIG. 1 clarifies the configuration of each pump working chamber 200 in the pump section 50. Further, FIG. Can be. As shown in FIG. 2, the cylinder member 60 includes an inlet 110 and an outlet 12.
0 are provided at symmetrical positions. Rotor 80
Since the center of rotation of the pump member 80 and the center of the cylinder member 60 are eccentric, the volume of the pump working chamber 200 around the rotor 80 changes as the rotor 80 rotates. For example, when the rotor 80 rotates in the direction of the arrow P in FIG. 2, the pump working chamber 200 facing the suction port 110 increases in volume with rotation and then decreases in volume.
The pump working chamber 200 that increases in volume with rotation functions as a suction chamber, and the pump working chamber 2 that reduces in volume with rotation.
00 functions as an exhaust chamber. In addition, the suction port 110 is
Located axially center of the internal space, the inlet 1
The suction groove 110d (which extends in the rotation direction of the rotor 80) communicates with a suction groove 110d provided on the inner peripheral wall surface 60s of the cylinder member 60 having the ten. The suction groove 110d smoothes the suction of the air from the suction port 110 and prevents the rotation of the rotor 80 from being impaired by the suction air. Also, although not shown in the drawing, when viewed from the circumferential position, it is located at the same position as the suction groove 110d.
Side walls 331s, 70 of the base 331 and the lid member 70
s may be provided with a suction assist groove.

Attention is now directed to the end portion 320 of the rotary drive shaft 32 that supports the rotor 80. End portion 320
Has a D-shaped cross section, and the partially cut one surface portion 320k serves as a key, and is keyed to a central hole 80t of the rotor 80 which fits the key. Therefore, the rotor 80 can move in the axial direction on the rotation drive shaft 32, but is integral with the rotation drive shaft 32 in the rotation direction.

Next, FIG.
Please refer to. As described above, the rotor 80, the base 331, and the side walls 331s, 70
Each between the s, for example, important to impart a predetermined clearance of 50-60. In the rotary vacuum pump 10, ring-shaped spacer members 500 and 500 ′ are arranged between the rotor 80 and the side walls 331 s and 70 s of the base 331 and the lid member 70. The diameter of the spacer members 500 and 500 ′ is, for example, about 15 mm, and is a size that does not cover the vane grooves 810 of the rotor 80. Incidentally, the diameter of the rotor 80 is, for example, about 40 to 45 mm, and the length of the vane groove 810 is 15 mm or smaller. Base 331 side of the spacer member 500 fits to the rotary drive shaft 32, also a spacer member 500 of the lid member 70 side '
Is a projection 70 provided on the side wall surface 70 s of the lid member 70.
It fits into 0 and is supported respectively. Each of the spacer members 500 and 500 'is made of polyimide, has a self-lubricating property, and has sufficient heat resistance to heat accompanying rotation. The spacer members 500 and 500 ′ can be disposed so as to be completely in contact with and sandwiched between adjacent members, but preferably, the spacer members 50 and 500 ′ are preferably sandwiched.
It is preferable to provide an extra clearance of about 5 to 10 μm for every 0,500 ′. Each spacer member 5
00, 500 'are provided when the rotor 80 rotates.
0 is a stopper in the axial direction.
The function of preventing the inclination of the rotor 80 from falling down and always maintaining an appropriate clearance at the radially outer peripheral portion of the rotor 80 is achieved. As a result, despite the fact that the rotor 80 is cantilevered, the rotor 80 rotates smoothly and a good pump action is produced. In addition,
When the rotor 80 rotates, each spacer member 500, 50
0 'appears to rotate integrally with the rotor 80. Therefore, each of the spacer members on both sides of the rotor 80 is not one but two, and one of the overlapping spacer members is self-lubricating, the other is non-lubricating, and the two spacer members overlap each other. The surface may be a sliding surface.

[Brief description of the drawings]

FIG. 1 is a side view of an embodiment of the present invention, and a partial cross-sectional view.

FIG. 2 is a view for clarifying a pump action of the apparatus of FIG. 1, and is a schematic sectional view taken along line 2-2 of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of FIG.

DESCRIPTION OF SYMBOLS 10 rotary vacuum pump 30 rotary drive 32 rotary drive shaft 331 base 50 pump section 500, 500 'spacer member 60 cylinder member 60s inner peripheral wall surface 70 lid member 331s, 70s side wall surface 80 rotor 810 vane groove 90 vane 110 suction port 120 exhaust port 200 pump working chamber

Claims (8)

[Claims] 1. A casing which defines an internal space by an inner peripheral wall surrounding a center line and two side walls orthogonal to the center line, a rotary drive located outside the casing and having a rotary drive shaft, A rotor that is located in the internal space of the casing and that is connected to a rotary drive shaft of the rotary drive and that is driven to rotate; and a pump that is supported by one of the rotor and the casing and that is pumped around the rotor together with the rotor and the casing. A rotary vacuum pump including a vane for partitioning a chamber, and further having the following features. A. A spacer member separate from the rotor and the casing is provided between each of the two side walls of the casing and both end portions of the rotor facing the side walls. B. The spacer member is only thin does not impair the pumping action of the rotary vacuum pump, moreover, occupy only the area of the center of the rotor. Wherein said spacer member always maintain the predetermined clearance between the side wall surface of the the radially outer portion of the rotor casing, rotary vacuum pump according to claim 1. 3. An axial center of said rotary drive shaft is located at an eccentric position with respect to a center of an inner peripheral wall surface of said casing, and an axial center of said eccentric rotary drive shaft and a rotational center of said rotor are on the same axis. The rotary vacuum pump according to claim 1, wherein 4. The rotor is cantilevered,
A rotary vacuum pump according to claim 3. 5. The rotor has a vane groove extending from an outer peripheral surface of the rotor to an intermediate portion in the radial direction and accommodating the vane therein, and the spacer member has such a size that does not cover the vane groove. The rotary vacuum pump according to claim 3, wherein 6. The spacer member has a ring shape,
The fits to the rotary drive shaft, or is supported fit in the convex portion provided on the side wall surface of the casing, rotary vacuum pump according to claim 3. 7. The rotary vacuum pump according to claim 3, wherein said spacer member is made of a self-lubricating synthetic resin material. 8. The rotor is movable in the axial direction of the rotary drive shaft, but is located at a substantially constant portion on the rotary drive shaft by a stopper function of the spacer member. The rotary vacuum pump according to claim 2, wherein the rotary vacuum pump is maintained in a non-contact state with the side wall surface of the casing by a fall prevention function.