EP1055823A1

EP1055823A1 - Vane type vacuum pump for automobiles

Info

Publication number: EP1055823A1
Application number: EP98959196A
Authority: EP
Inventors: Shigeru Onoue; Tsuyoshi Yano; Tomoki Takahashi; Takashi Kinoshita
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1998-12-14
Filing date: 1998-12-14
Publication date: 2000-11-29
Anticipated expiration: 2018-12-14
Also published as: KR100385683B1; EP1055823B1; WO2000036303A1; DE69839159T2; EP1055823A4; DE69839159D1; KR20010040678A; TW414837B

Abstract

In order to provide a vehicular vane-type vacuum pump in which the weight can be reduced, no abnormal wearing between shafts occurs and in which the manufacturing cost is low, the present invention resides in a vehicular vane-type vacuum pump comprising a cylindrical housing having a suction port and a discharge port, a rotor eccentrically housed within the housing, a shaft for rotationally driving the rotor and a vane rotatable in a sliding contact with an inner circumferential surface of the housing, whereby a fluid is pumped from the suction port to the discharge port and characterized in that the shaft is provided at its outer circumference with a projection or a groove and the shaft and the rotor are integrally secured together. The rotor may be formed by aluminum die-casting, plastic molding or by metal sintering. The projection or the groove on the outer circumference of the shaft may be integrally formed during cold forging of the shaft or manufacturing of the shaft by sintering or by weld-attaching a metal plate-formed product on an outer circumference of the shaft. Also, the housing and the shaft may be made of the same kind of material.

Description

TECHNICAL FIELD

This invention relates to improvements in a vehicular vane-type vacuum pump.

BACKGROUND ART

Fig. 9 is a sectional side view showing one example of a conventional vehicular vane-type vacuum pump, and Fig. 10 is a sectional view showing a spline coupling between a rotor and a shaft of the conventional vehicular vane-type vacuum pump shown in Fig. 9. As shown in Figs. 9 and 10, the conventional vehicular vane-type vacuum pump defines a hermetic space by a cylindrical housing 4 having a suction port 1 and a discharge port 2 and bracket 5 connected together by bolts 3. The bracket 5 rotatably supports a shaft 7 by a bearing 8, and the shaft 7 has provided thereon a rotor 9 eccentrically housed within the housing 4 and rotatable within the housing 4. The rotor 9 is provided with vanes 11 disposed in radial vane slots 10 as shown in Fig. 10 and rotate together with the rotor 9 while sliding at their outer edges along the inner circumferential surface of the housing 4, whereby the fluid is suctioned from the suction port 1 and is discharged under pressure from the discharge pod 2 by the rotation of the rotor 9.
The shaft 7 is provided with a coupling 13 so that a rotational force may be inputted from the vehicle side. The shaft 7 is also provided with splines 14 which mesh with splines 15 in the rotor 9 so that a torque may be transmitted therebetween.
In such the vehicular vane-type vacuum pump, when a rotational force is transmitted to the shaft 7 from the coupling 13, the rotor 9 eccentrically rotates within the housing 4. This eccentric rotation causes the vanes 11 on the rotor 9 to rotate and slide along the inner circumferential surface of the housing 4 while being urged to project in the radially outward direction from the rotor 9 due to the centrifugal force, whereby the fluid is suctioned from the suction port 1 and is discharged under pressure from the discharge port 2 by the rotation of the rotor 9.
In such the vehicular vane-type vacuum pump, the shaft 7 and the rotor 9 are fitted together by the splines 14 and 15 to constitute a spline coupling, which is high in machining cost and results in a high product price. Also, while the spline coupling portion by the splines 14 and 15 are lubricated by oil, an abnormal wearing may occur depending upon the oil property. The spline coupling is a loose connection, pausing a difficulty in obtaining a required precision. Also, since the spline coupling needs a strength in splines with respect to torque, a strong material, such as an iron-based sintered product for the rotor 9 and steel material for the shaft 7, must be used in the conventional design, impossible to make the product light weight. Also, the rotor 9 and the housing 4 are conventionally made of materials having different coefficients of thermal expansion, requiring that a large clearance be provided between the rotor and the housing for absorbing the difference in thermal expansion.
This invention has been made in order to solve the above discussed problems and has as its object the provision of a vehicular vane-type vacuum pump in which the weight can be reduced, no abnormal wearing between the shafts occurs and the manufacturing cost can be reduced.

DISCLOSURE OF INVENTION

In order to achieve the above object, the present invention resides in a vehicular vane-type vacuum pump comprising a cylindrical housing having a suction port and a discharge port, a rotor eccentrically housed within the housing, a shaft for rotationally driving the rotor and a vane rotatable in a sliding contact with an inner circumferential surface of the housing, whereby a fluid is pumped from the suction port to the discharge port and characterized in that the shaft is provided at its outer circumference with a projection or a groove and the shaft and the rotor are integrally secured together.
The shaft may be insert-formed into an integral forged structure during forging of the rotor, and the rotor may be formed by aluminum die-casting, integrally formed by plastic molding or by sintered aluminum powder.
Also, the projection or the groove on the outer circumference of the shaft may be integrally formed during cold forging of the shaft or the projection or the groove of the shaft may be integrally formed at the time of manufacturing of the shaft by sintering.
Further, the projection of the shaft may be formed by weld-attaching an iron-based metal plate product on an outer circumference of the shaft or the housing and the shaft may be made of the same kind of material.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a sectional side view illustrating one embodiment of the vehicular vane-type vacuum pump of the present invention;
Fig. 2 is a sectional view taken along line A - A of Fig. 1;
Fig. 3 is a sectional side view illustrating a second embodiment of the vehicular vane-type vacuum pump of the present invention;
Fig. 4 is a sectional view taken along line B - B of Fig. 3;
Fig. 5 is a sectional side view illustrating a third embodiment of the vehicular vane-type vacuum pump of the present invention;
Fig. 6 is a sectional view taken along line C - C of Fig. 5;
Fig. 7 is a sectional side view illustrating a fourth embodiment of the vehicular vane-type vacuum pump of the present invention;
Fig. 8 is a sectional view taken along line D - D of Fig. 7;
Fig. 9 is a sectional side view of a conventional vehicular vane-type vacuum pump; and
Fig. 10 is a sectional view illustrating a spline coupling between the rotor and the shaft of the conventional vehicular vane-type vacuum pump shown in Fig. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

For more detailed description of the present invention, embodiments of the present invention will be described in conjunction with the accompanying drawings. In the following description, the component parts identical to those of the conventional example are designated by the same reference characters and their description may be omitted.
Fig. 1 is a sectional side view showing an embodiment of the vehicular vane-type vacuum pump of the present invention, and Fig. 2 is a sectional view taken along line A - A of Fig. 1 and showing a coupling between a rotor and a shaft.
The vehicular vane-type vacuum pump of the present invention, which has an overall structure similar to the vehicular vane-type vacuum pump shown in Figs. 9 and 10, defines a hermetic space by a cylindrical housing 4 having a suction port 1 and a discharge port 2 and bracket 5 connected together by bolts 3. The bracket 5 rotatably supports a shaft 21 by a bearing 8, and the shaft 21 has provided thereon a rotor 24 eccentrically housed within the housing 4 and rotatable within the housing 4. The rotor 24 is provided with vanes 11 disposed in radial vane slots 10 and rotated together with the rotor 24 while sliding at their outer edges along the inner circumferential surface of the housing 4, whereby the fluid is suctioned from the suction port 1 and is discharged under pressure from the discharge port 2 by the rotation of the rotor 24. The shaft 21 is provided with a coupling 13 so that a rotational force may be inputted from the vehicle side.
According to this invention, the shaft 21 is provided at a shaft portion of the shaft main body 22 corresponding to the entire axial length of the housing 4 with two fin-shaped projections 23 extending in the axial direction and projecting in the radial direction at radially opposite positions. The rotor 24 has formed therein two axial grooves 25 corresponding to and engaging with two fin-shaped projections 23 so that a torque may be transmitted through these fin-shaped projections 23 and the axial grooves 25. As for the fin-shaped projections 23, one or more projections may be used and the axial length may be freely set as long as a sufficient torque transmission and ease of manufacture may be ensured.
The fin-shaped projections 23 shown in Figs. 1 and 2 may be formed integrally with the shaft main body 22 at the time of cold forging of the shaft 21, may be formed at the time of manufacturing by sintering when the shaft 21 is made of a sintered material, or may be formed by attaching by welding an iron-based metal plate product to the circular rod-shaped shaft main body 22. The metal plate product used may have a flat end portion and a bent portion at the other end bent to extend along the circumferential surface of the shaft main body 22.
The rotor 24 is formed and integrally attached with respect to such the shaft 21 by integral casting or integral molding. With such the structure, the clearance in the conventional spline coupling is eliminated to provide no play between the shaft main body 22 of the shaft 21 and the rotor 24. The shaft may also be integrally casted by insert molding during casting of the rotor.
The rotor may be integrally formed by aluminum die-casting or plastic molding, or may be formed by sintering after aluminum powder molding.
In such the vehicular vane-type vacuum pump, when a rotational force is transmitted to the shaft 21 from the coupling 13, the rotor 24 eccentrically rotates within the housing 4. This eccentric rotation causes the vanes 11 on the rotor 24 to rotate and slide along the inner circumferential surface of the housing 4 while being urged to project in the radially outward direction from the rotor 24 due to the centrifugal force, whereby the fluid is suctioned from the suction port 1 and is discharged under pressure from the discharge port 2 by the rotation of the rotor 24.
In such the vehicular vane-type vacuum pump, it is possible to provide the fin-shaped projections 23 disposed on the shaft main body 22 with a required and sufficient torque transmitting area, allowing a large torque transmission. Therefore, an aluminum alloy or plastic material of a small strength which have not been used as a rotor material can be used as a rotor material, allowing the product to be light-weighted. Also, when the housing 4 and the rotor 24 are made of the same kind of material, no difference of thermal expansion generates therebetween.
Also, since the splines are not used, the manufacturing cost can be reduced, and since there is no play due to the clearance in the spline coupling, the abnormal wear does not occur.
Fig. 3 illustrates a second embodiment of another shaft 26 that can be used in the vehicular vane-type vacuum pump of the present invention, and Fig. 4 illustrates a section taken along line B - B of Fig. 3. This shaft 26 is different from the shaft 21 shown in Figs. 1 and 2 in that it has three fin-shaped projections 23, but in other respects the structure is the same. This shaft 26 may be formed by the cold forging or sintering forming by integrally forming the shaft main body 22 and the fin-shaped projections 23.
Fig. 5 is a side view illustrating a third embodiment of a shaft of the vehicular vane-type vacuum pump of the present invention, and Fig. 6 is a sectional view taken along line C - C of Fig. 5. This shaft 28 comprises a circular rod-shaped shaft main body 29 and two fin-shaped projections 30 radially outwardly extending from the shaft main body 29. The fin-shaped projections 30 is made of two bent metal plates 31, with a semi-circular cylindrical portion 32 of the metal plate 31 attached by welds 27 to the shaft main body 29, and two fin portions 33 extend radially opposite direction of the shaft main body 29 from both ends of the semi-circular cylindrical portion 32 are overlapped to each other. The number of fin-shaped projections 30 is arbitrary.
Fig. 7 is a side view illustrating a fourth embodiment of the shaft of the vehicular vane-type vacuum pump of the present invention, and Fig. 8 is a sectional view taken along line D - D of Fig. 7. This shaft 34 has formed in the surface of the shaft main body 35 axially extending grooves 36 for defining projections 37 therebetween. This shaft 34 may be formed by machining, cold forging or sintering forming.

INDUSTRIAL APPLICABILITY

As has been described, the vehicular vane-type vacuum pump of the present invention comprises a cylindrical housing having a suction port and a discharge port, a rotor eccentrically housed within the housing, a shaft for rotationally driving the rotor and a vane rotatable in sliding contact with an inner circumferential surface of the housing, whereby a fluid is pumped from the suction port to the discharge port, and the shaft is provided at its outer circumference with a projection or a groove and the shaft and the rotor are integrally secured together, so that a vehicular vane-type vacuum pump is provided in which the weight can be reduced, no abnormal wearing in the spline coupling occurs and in which the manufacturing cost is low.

Claims

A vehicular vane-type vacuum pump comprising a cylindrical housing having a suction port and a discharge port, a rotor eccentrically housed within said housing, a shaft for rotationally driving said rotor and a vane rotatable in sliding contact with an inner circumferential surface of said housing, whereby a fluid is pumped from said suction port to said discharge port, characterized in that;
said shaft is provided at its outer circumference with a projection or a groove and said shaft and said rotor are integrally secured together.
A vehicular vane-type vacuum pump as claimed in claim 1 wherein said shaft is insert-formed into an integral forged structure during forging of said rotor.
A vehicular vane-type vacuum pump as claimed in claim 2 wherein said rotor is formed by aluminum die-casting.
A vehicular vane-type vacuum pump as claimed in claim 2 wherein said rotor is integrally formed by plastic molding.
A vehicular vane-type vacuum pump as claimed in claim 2 wherein said rotor is formed by sintered aluminum powder.
A vehicular vane-type vacuum pump as claimed in any one of claims 1 to 5 wherein said projection or said groove of said shaft is integrally formed during cold forging of said shaft.
A vehicular vane-type vacuum pump as claimed in any one of claims 1 to 5 wherein said projection or said groove of said shaft is integrally formed at the time of manufacturing of said shaft by sintering.
A vehicular vane-type vacuum pump as claimed in any one of claims 1 to 5 wherein said projection of said shaft is formed by weld-attaching an iron-based metal plate product on an outer circumference of said shaft.
A vehicular vane-type vacuum pump as claimed in any one of claims 1 to 8 wherein said housing and said shaft are made of the same kind of material.