DE102010051610A1 - Vacuum pump for under pressure power brake of motor vehicle, has impeller's front side and inner wall aligned within section plane and parallel to each other at operating temperature, where plane holds rotation axis of rotor - Google Patents

Abstract

The vacuum pump has a rotor (13) rotating around a rotation axis (A) in a housing (11), and an impeller (21) guided in the rotor and cooperated with an inner wall (19) of the housing. The impeller is made of fiber reinforced plastic and lies against to an end with a front side (23) on an inner wall (19) of the housing. The front side of the impeller and the inner wall of the housing are aligned within a section plane and parallel or nearly parallel to each other at operating temperature of pump, which is higher than room temperature, where the plane holds the rotation axis of the rotor.

Description

The invention relates to a vacuum pump, which is used for example in a motor vehicle in conjunction with a vacuum brake booster. Such a vacuum pump comprises a housing, a rotor rotatable in the housing about a rotation axis, and at least one wing displaceable in the rotor, which at at least one end rests with an end face on an inner wall of the housing.

The wing divides the interior of the pump housing at least temporarily into a suction chamber and a pressure chamber. By rotationally driving the rotor about the axis of rotation, which is typically eccentric relative to the housing, the rotor-guided wing is also driven to rotate. As the respective face of the wing sweeps along the inner wall of the housing, the volume of the suction space of the pump is increased and the volume of the pressure space is reduced so that air (or other fluid) is drawn through an inlet opening of the housing and expelled through an outlet opening of the housing The respective wing may abut only one end or both ends on the housing inner wall, and a single or a plurality of wings may be provided. Such a pump is also referred to as a vane pump.

From the WO 2009/052929 A1 Such a vacuum pump is known, in which the longitudinal displacement of the blade within the rotor is controlled by an eccentric device.

In the DE 10 2005 031 718 A1 a vacuum pump of the type mentioned is described in which the respective wing is pressed during a rotational movement of the rotor by the centrifugal force against the inner wall of the pump housing.

In such a vacuum pump, an important requirement is that said end face of the wing on the inner wall of the housing as possible to attack slidably and sealingly. However, this often causes unwanted wear, especially if the wing is to be made of a lightweight and inexpensive material, such as plastic.

It is an object of the invention to provide a vacuum pump with at least one wing, which is guided displaceably in a rotor and cooperates with an inner wall of the pump housing, wherein wear of the housing inner wall contacting end face of the wing should be as effectively avoided or at least reduced.

This object is achieved by a vacuum pump with the features of claim 1, and in particular by the fact that the end face of the wing and the inner wall of the housing within a cutting plane containing the axis of rotation of the rotor are not aligned parallel to each other at room temperature.

In the case of the vacuum pump according to the invention, the face of the wing facing the inner wall of the housing at room temperature (typically about 23 ° C.) does not lie along the entire height of the wing (that is to say along the axis of rotation of the rotor) against the inner wall of the housing. Instead, the face of the wing and the inner wall of the housing are intentionally not parallel to each other, but the face of the wing and the inner wall of the housing assume an angle relative to each other which is typically very small but different from 0 ° (zero degrees). This angle between the end face of the wing and the inner wall of the housing is provided within a cutting plane which extends through the axis of rotation of the rotor and which corresponds in particular to the plane of extent of the typically flat-shaped wing.

By this particular mutual coordination of the respective shape of the wing and the inner wall of the housing is achieved that the end face of the wing and the inner wall of the housing at an operating temperature of the pump, which is higher than said room temperature, parallel (ie flush) or nearly parallel abut each other , In other words, said angle at the operating temperature of the pump is about 0 ° (zero degrees). As a result, at the operating temperature of the pump, so at the relevant speeds of the rotor, a minimal wear of the wing achieved. The wing can thus be easily made of a lightweight and inexpensive material.

In the context of the invention, it has been recognized that, depending on the material used and the manufacturing process, the blade has a thermal expansion characteristic which varies for different regions of said face of the blade. This uneven thermal expansion of the blade is attributed in particular to an inhomogeneous distribution of fillers, if the wing is formed of a filled material, or to an inhomogeneous density distribution when using a non-filled material. In particular, it can be observed that when the wing is manufactured by injection molding a fiber-reinforced plastic, the orientation of the fibers (eg carbon fiber or glass fiber) is inhomogeneous, ie for different areas is different. The resulting inhomogeneous thermal expansion upon reaching the operating temperature is compensated by the explained special shape of the wing and the housing inner wall.

If reference is made in the context of the invention to a parallel or non-parallel orientation of the end face of the wing and the inner wall of the housing or to corresponding angle specifications, these definitions relate to the nominal dimensions of the vacuum pump and its components, with manufacturing tolerances come into application , as is usual with conventional vacuum pumps.

Advantageous embodiments of the invention are mentioned in the following description and in the subclaims.

Preferably, the inner wall of the housing is aligned within said sectional plane parallel to the axis of rotation of the rotor, while the end face of the wing is intentionally disposed within said sectional plane at room temperature not parallel to the axis of rotation of the rotor, d. H. the face of the wing assumes an angle different from 0 ° (zero degrees) to the axis of rotation of the rotor. In other words, the housing inner wall facing the front side of the wing at room temperature preferably has an inclined course relative to the axis of rotation of the rotor. The two long sides of the wing thus have a trapezoidal contour at room temperature. In this embodiment, the manufacture of the vacuum pump is particularly simple, since the inner wall of the typically made of metal housing may have a parallel to the axis of rotation contour, while the wing can be manufactured as an injection molded plastic with inclined surfaces and this cost-effective multiple tools can be used , Alternatively, however, it is also possible in principle that the respective end face of the wing is aligned parallel with respect to the axis of rotation of the rotor, while instead the inner wall of the housing within the said cutting plane is intentionally not arranged parallel to the axis of rotation of the rotor, d. H. is inclined at an angle different from 0 ° to the axis of rotation of the rotor.

The housing inner wall facing the front side of the wing can rest flat at the operating temperature of the pump or only linearly on the inner wall of the housing. In other words, the respective end of the wing within a plane that is perpendicular to the axis of rotation of the rotor, have a triangular cross-section or a trapezoidal or rectangular cross-section. It is only important that at the operating temperature of the pump, the respective end face of the wing substantially uniformly along the entire height of the wing rests evenly against the inner wall of the housing.

The invention will now be described by way of example only with reference to the drawings.

1 shows a plan view of an open vacuum pump.

2 shows a cross-sectional view along the section plane II-II according to 1 at room temperature.

In 1 FIG. 12 is a plan view of a vacuum pump with the housing cover removed, such that within a housing. FIG 11 a rotor 13 it is obvious that on a ground 15 of the housing 11 rests. By means of an in 2 only schematically illustrated drive shaft 17 can the rotor 13 be driven to a rotational movement about a rotation axis A. The rotor 13 and the rotation axis A are relative to the housing 11 eccentrically arranged, wherein the rotor 13 with its outer circumference on the inner wall 19 (ie, the inner peripheral surface) of the housing 11 is applied. It should be noted that the inner wall 19 of the housing 11 in the plan view according to 1 not exactly circular, but in the area of the rotor 13 flattened.

In the rotor 13 is a grand piano 21 arranged longitudinally displaceable, with both ends of the wing 21 from the rotor 13 protrude. The extension plane of the wing 21 passes through the axis of rotation A of the rotor 13 , At both ends of the wing lies with a respective end face 23 on the inner wall 19 of the housing 11 Alternatively, it is also possible that the two end faces 23 only alternating on the inner wall 19 issue. The wing 21 and the rotor 13 divide the interior of the housing 11 in a suction room 25 which has an inlet opening 27 of the housing 11 is assigned, and in a pressure room 29 which has an outlet opening 31 of the housing 11 assigned.

The housing 11 is made of metal. The wing 21 By contrast, for example, it is formed from a filled material, namely from a fiber-reinforced or particle-reinforced plastic (eg thermoset or thermoplastic). This is the wing 21 to a one-piece injection-molded part, but alternatively, a multi-component injection molded part can be used. As a filler, for example, glass fiber, carbon fiber, Kevlar or metal may be provided.

Depending on the exact material composition, the density distribution and the selected manufacturing process, the wing 21 show a non-uniform thermal expansion behavior. This means that the wing 21 When heated from room temperature to operating temperature in different areas along the axis of rotation A varies greatly (in a direction perpendicular to the axis of rotation A). This can lead to a punctual overload on the wing tips, ie between the respective end face 23 of the grand piano 21 and the inner wall 19 of the housing 11 come. The uneven load on the faces 23 can damage the grand piano 21 to lead.

To avoid this effect, the shape of the wing 21 with the shape of the inner wall 19 of the housing 11 adjusted so that the respective end face 23 of the grand piano 21 and the inner wall 19 of the housing 11 within a section plane II-II, which is the axis of rotation A of the rotor 13 contains, at room temperature limit an angle α different from 0 ° with each other. This angle α can be very small and, for example, have the value 0.05 ° or 0.1 °. In other words, the front side 23 and the inner wall 19 intentionally not parallel to each other within the section plane II-II at room temperature.

This special shape of the grand piano 21 (at room temperature) is exaggerated in 2 shown. The wing 21 has a trapezoidal shape in this cross-sectional view.

Once during operation of the vacuum pump, the rotor 13 and the wing 21 rotate with the typically occurring high speeds, the wing reaches 21 an operating temperature that is significantly higher than the room temperature according to 2 , Due to the explained non-uniform thermal expansion is thereby achieved that the end faces 23 of the grand piano 21 flush and with uniform surface load on the inner wall 19 of the housing 11 abut and in this case the suction chamber 25 or the pressure chamber 29 close tightly. At the same time, excessive wear of the wing 21 avoided, allowing for the manufacture of the grand piano 21 comparable cost-effective materials and manufacturing technologies can be used.

Alternative to the orientation of the grand piano 21 according to 2 can be at room temperature between the end faces 23 and the inner wall 19 formed gap also in the lower part of the wing 21 be provided (corresponding to a negative angle α).

LIST OF REFERENCE NUMBERS

11

casing

13

rotor

15

ground

17

drive shaft

19

inner wall

21

wing

23

front

25

suction

27

inlet port

29

pressure chamber

31

outlet

A

axis of rotation

α

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/052929 A1 [0003]
• DE 102005031718 A1 [0004]

Claims (7)

Vacuum pump, with a housing ( 11 ), in the housing about a rotation axis (A) rotatable rotor ( 13 ) and at least one wing displaceable in the rotor ( 21 ), which at at least one end with a front side ( 23 ) on an inner wall ( 19 ) of the housing ( 11 ) is applied, characterized in that the end face ( 23 ) of the wing ( 21 ) and the inner wall ( 19 ) of the housing ( 11 ) within a sectional plane which is the axis of rotation (A) of the rotor ( 13 ), are not aligned parallel to each other at room temperature. Vacuum pump according to claim 1, characterized in that the wing ( 21 ) and the housing ( 11 ) are matched to one another such that the end face ( 23 ) of the wing ( 21 ) and the inner wall ( 19 ) of the housing ( 11 ) at an operating temperature of the pump, which is higher than said room temperature, parallel or nearly parallel abut each other. Vacuum pump according to claim 1 or 2, characterized in that the inner wall ( 19 ) of the housing ( 11 ) within said section plane parallel to the axis of rotation (A) of the rotor ( 13 ), wherein the end face ( 23 ) of the wing ( 21 ) within said sectional plane at room temperature not parallel to the axis of rotation (A) of the rotor ( 13 ) is aligned. Vacuum pump according to one of the preceding claims, characterized in that the end face ( 23 ) of the wing ( 21 ) is adapted to lie flat or linearly on the inner wall of the housing at an operating temperature of the pump. Vacuum pump according to one of the preceding claims, characterized in that the wing ( 21 ) is formed from a filled material or from a non-filled material with inhomogeneous density distribution. Vacuum pump according to one of the preceding claims, characterized in that the wing ( 21 ) is formed of a fiber-reinforced plastic. Vacuum pump according to one of the preceding claims, characterized in that the wing ( 21 ) is formed as a one-piece injection molded part or as a multi-component injection molded part.

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