GB2176537A - Adjusting the vanes in a vane pump between operative and idle positions - Google Patents

Abstract

A vane pump, in particular a vacuum vane pump, comprises two or more vanes 4,5 which are movable in vane slots in a rotor 3. Each vane has on one of its lateral faces 11 a strip 7 which is parallel to the axis. The strip 7 slides with the vane and thereby varies the volume of a sealed chamber 10 which communicates at least intermittently in the course of a revolution of the rotor with a preferably substantially central pressure medium connection 9. The connection 9 may be communicated with a pressure or a vacuum via valve 19 to cause the vanes 4,5 to move to their operative position or to both be retracted within the rotor. <IMAGE>

Description

SPECIFICATION A vane pump with hook-shaped vanes The invention relates to a vane pump, in particular a vacuum vane pump, comprising two or more vanes which are movable in vane slots of a rotor and devices for restricting the radial vane movement.

With vane pumps which are coupled, for example, in a motor vehicle with the engine in such a way that they run continuously with it and whose object is to keep an accumulator, for example a servo brake, continuously at a predetermined operating pressure or vacuum, there have been many attemps to interrupt or to throttle the output of the pump when not required. The possibility of switching the pump on and off demands a considerable additional expense and also increases the unit's liability to failure.

Attempts have been made to render the vane pump ineffective when not required by pulling or pivoting the vanes away from the housing wall under certain conditions. Thus, for example, DE-OS 30 15 409 describes a rotating vacuum pump with a rotor rotating eccentrically in a housing bore and at least one vane with a device for holding the vane in a position which switches off the pump action. This device consists of a mass which is coupled to each vane and which moves the end faces of the vanes away from the internal housing wall at elevated speeds.

DE-OS 30 14 520 describes a vane pump with vanes which are pivotally fixed on the rotor periphery about their joints lying in the rotor surface and which rests on the internal housing wall either due to the effective contrifugal forces or due to restraint. For pivoting the vanes into a position in which the pressure supply is interrupted, some substantially radially directed, radially movable pins are provided in the region of the pivotal vanes, one end of each of which engages in a recess in the curved end portion of one vane and the other end of which lies on the surface of a cone which is axially movable in a central bore of the shaft of the rotary piston. The vanes are folded if or opened by axial movement.

Both designs are unsatisfactory. Whereas the first design cannot have its operating behaviour influenced from the exterior and is only effective, owing to its design, in the low speed range, which greatly restricts its usefulness, the other design is expensive, susceptible to mechanical breakdown and can also only be used with the particular design of pivotal vanes.

An object of the invention is therefore to enable vane pumps to bring the pump vanes into the operating position or idling position as required, optionaly as a function of a predetermined final pressure in the outlet or inlet of the pump which may be greater or smaller than atmospheric air pressure.

Accordingly, the inventiion provides a vane pump, in particular a vacuum vane pump, comprising two or more vanes which are movable in vane slots in a rotor and devices for restricitng the radial movement of the vanes, wherein each vane has on one of its lateral faces a strip which is parallel to the axis, the laterial face having the said strip sliding with its radially outer region on an opposing strip whereby the strip and the said opposing strip form a sealed chamber of variable volume which communicates at least intermittently in the course of a revolution of the rotor with a preferably substantially central pressure medium connection, which pressure medium connection may be charged with a pressure medium.

It is preferable if the vane "strip" is arranged in each case on the end of the vane lying in the rotor and the vane end is hookshaped in design. The pressure medium connection can be chargeable, in particular, as a function of the vacuum or super pressure generated.

Inaparticular embodiment, in particular as a vacuum vane pump which is arranged in a motor vehicle and is driven by the vehicle engine, for example a petrol injection or diesel engine, the pressure medium connection designed as a pressure medium duct can be connected to the lubricant circuit of the vehicle engine for charging with pressure medium.

The opposing strip provided in the vane slot is preferably arranged parallel to the axis.

In a further embodiment, two vanes lying against one another in a common vane slot are provided in the rotor, the two vanes having a respective strip in the region of their parts located in the rotor. The strips of the two vanes face one another, the respective strip of one vane sliding on the side facing it of the other vane and two strips forming a pressure chamber between themselves (hereinafter also called "hook chamber"). The strips of the two vanes can be formed by a hookshaped design of the vane ends located in the rotor, the hook heads forming between themselves the pressure chamber whose length varies continuously between two limit values during rotation of the rotor.

In a particular embodiment, the two pump vanes are also provided at their ends pointing towards the internal wall of the housing with hook heads. The radial dimentions thereof can be calculated such that the outer vane limits lie at the surface of the rotor when the vanes are driven completely in and the inner hook head of a respective vane rests approximatley on the internal face of the outer hook head of the other vane.

When the vanes are driven in, it may be advantageous to throttle the supply of lubricant to the interior of the pump. For this pur pose, it is proposed that the lubricant passages normally provided in one or both lateral housing walls be arranged inside the region covered by the rotor in such a way that they are constantly covered when the vanes are drawn in.

The hook chamber can be charged in various ways with a pressure causing the vanes to travel inwards. One simple possibility involves connecting the hook chamber to the pump outlet, i.e. the pressure chamber or, when arraning the pump in a motor vehicle and driving it by the vehicle engine, by connecting it to the lubricant circuit thereof. In this arrangement, for example, a non-return valve is incorporated into the connection to act as a pressure relief valve, the non-return valve being sealed against the pressure chamber by the action of a compression spring which is preferably adjustable and being open only once a specific pressure which overcomes the spring force is attained in the pressure chamber. The vane movements can possibly be affected, for example, also as a function of the pump speed.

Preferred embodiments of the invention are explained in more detail below, by example only, with reference to the accompanying drawings, wherein: Figure 1 shows a vane pump with vane control by a two-way valve.

Figures 2 to 5 show the relative position of hook chamber and connecting passage.

Figure 6 shows the pump with the vanes driven in the rotor.

Figure 7 shows the pump with four individual vanes.

Figure 8 shows the pump with an S-shaped or Z-shaped vane cross-section.

The rotor 3 is arranged eccentrically in the interior of a pump housing 1 so that it is at a minimum distance from the internal housing wall 2. The vanes 4 and 5 are arranged so as to be easily movable relative to one another and relative to the slotted walls 14 of the vane slot 6 in the rotor 3. In the embodiment illustrated, the vanes 4, 5 have in cross-section hook heads 8 at their ends facing the internal housing wall 2 in addition to the internal hook heads 7, and these are explained in detail below, On the rotor axis there is a connecting passage 9 for the supply of pressure medium to the hook chamber or chambers 10, which opens into the vane slot 6. If the rotor shaft is reported at both ends, the passage 9 can be arranged in the journal remote from the driven end.If the shaft has a cantilevered mounting, the passage 9 can be in the end wall of the housing 1 remote from the driven side. To ensure that the hook chamber 10 is connected in any position of the rotor, the mouth of the passage 9 can have a prefeably circular widened area 13, particularly if it lies in the remote internal housing wall. As shown clearly in Fig. 1, it is possible if suitable dimensions are selected, also to supply the hook chamber in the extreme position illustrated without the space between the end of the vane 4 lying in the rotor and the outer hook 8 of the vane 5 being connected to the passage 9.

In a particular embodiment, the lateral walls 14 of the vane slot 6, the sliding faces 11 and 12 of the vanes and the contact surfaces of the hook heads 7 and 8 with the faces 11 and optionally also 14 can be provided with highly abrasion-resistant wearing plates or a metallic, ceramic, mineral, glass or plastics coating in order thus considerably to reduce the wear. For example, chromium, chromium alloys, hard enamel, glass, ceramic materials, plastics such as polytetrafluoroethylene and others may be used as coverings.

Fig. 1 schematically shows a particular embodiment of the control means for the vane movement, namely a two-way valve 19 which can be actuated by a control means 22 with a membrane and ram. A line 24 leads from the valve 19 to the connecting passage 9, and a second line 25 to the lubricant connection 15 which is arranged such that it is covered by the rotor 3. The valve inlet is connected to two supply lines, a pressure connection 16, marked with a (+) in this case, and a vacuum connection 17, marked with a (-). The valve position illustrated, in which the pressure connection is connected via the line 24 to the connecting passage 9 and the vacuum connection to the lubricant connection 15, is designated as valve position 1 which causes the vanes 4, 5 to retract into the rotor.If the connection is produced by the valve member 21 (switching position 2), a vacuum is applied to the hook chamber 10 and the vanes are driven out again while the oil connection 15 is supplied with oil again. The two-way valve 19 is controlled via the control connection 23.

The control connection is connected to the inlet (not shown) of the vane pump. If the vacuum in the inlet falls below a predetermined value, the membrane (in Fig. 1) bulges to the right and drives the ram. The valve is thus switched over. Figs. 2 to 5 show various rotor positions during one revolution of the rotor, which reveal the rotor positions in which the hook chamber communicates with the connecting passage 9 or the widened area 13, even at extreme positions. It has however been found that the overlap, for example, which begin at a rotor position in front of that shown in Fig. 5 and ends at a rotor position after that illustrated in Fig. 2 is definitely sufficient for allowing the vanes to be driven in because the overlapping region increases as they are drawn in.

Fig. 6 shows the situation with the vanes drawn in. In this position the vanes 4, 5 are held securely while the connection to the pressure connection lasts.

Fig. 7 shows an embodiment of the vane pump according to the invention in which four vanes 43 guided individually in associated slots 42 are provided. The strips 7 of the vanes 43 each lying inside the vane slots 42 form, together with the opposing strips 44 of the vane slots 42 the pressure or hook chambers 10. The changes in length during one rotation of the rotar are shown clearly in the four vane positions illustrated.

The slots 42 in the rotor 3 end at a depth which should be no smaller than the radial vane length. The two values are preferably approximately equal so that the outer ends of the vanes 43 lie at the surface of the rotor 3 in the fully driven in state. In the rotor 3 there is provided a central passage 32 whose axis preferably coincides with the rotor axis and to which the vane slots 42 are connected via connecting ducts 33.

The pressure or hook chambers 10 are supplied with pressure fluid in the pump illustrated by means of a groove 31 provided either in one end face of the rotor 3 or in the adjacent end housing wall, the groove running concentrically to the rotor surface and the pressure medium duct 9 opening into the groove 31 at any point. The groove 31 is preferably positioned such that its outer limit in the radial direction coincides substantially with the edges of the rotor strips 44 pointing toward the rotor axis. This ensures that the pressure chambers 10 remain connected to the pressure medium duct 9 even at their smallest length.

Operation of the vane pump will now be described with reference to the illustrated embodiment, a multiple way valve being designated by 19, a pump by 34, for example the lubricant pump of a motor vehicle, the tank or oil sump by 35. The multiple way valve has two switching positions 20 and 21. For movement between positions 20 and 21, one side of the multiple way valve is connected via a control means 22, the line 37 and the connection 39 to the suction inlet of the pump and the other side is loaded by a spring 36. In the illustrated switched position 20 of the valve 19, the central passage 32 is placed under pressure via the line 40 through the pump 34 while the line 41 connects the annular groove 31 via the pressure medium duct 9 to the tank 35.The pump pressure thus acts via the connecting ducts 33 on the radially inwardly pointing foot surfaces of the vanes 42 and presses them outwards against the internal wall of the housing 2. Once the pressure or vacuum in the consumer, for example the servo brake 38, has attained its set value the valve 19 is switched into position 21. The central passage 32 is now connected to the tank while the groove 31 is charged with pressure via the pressure medium duct 9. The pressure or hook chambers 10 are thus placed under pressure and the vanes 42 driven in. The pumping action therefore ceases until the valve 19 is switched over again.

Finally, Fig. 8 shows a vane pump according to the invention with a vane cross-section which is modified relative to the embodiment in Fig. 1 and has an S-shape for the two vanes 4, 5 guided in their common vane slot 27. As shown in the drawings, the central region of the slot is symmetrical about an axial plane while the widened slot portions 27 opening the rotor periphery are laterially offset relative to one another. The opposing strips 26 form the transition between the symetrical and offset portion of the slot and form the pressure or hook chambers 10 with the strips or hook heads 7 of the vanes 4, 5 lying in the rotor. During their movement in the slot, the vanes 4, 5 slide towards one another with their facing vane surfaces 28, 29 while the internal strips or hook heads 7 of the vanes 4, 5 slide on the lateral walls of the slot 30.

Corresponding to the position and size of the pressure chamber 10 when the vane 5 is driven fully out, the circular groove 51 connected to the pressure medium duct 9 has a very small external diameter so that the circular recess 13 in Fig. 1 can be used instead of it. As nothing is changed from the described mode of operation, the vanes 4, 5 can also have a Z-shaped cross section instead of the S-shape illustrated. As described for Fig. 1, care must be taken in the dimensioning of the vanes that the vane length measured diametrically together with the thickness of the hook head 8 measured in the same direction is not greater than the rotor diameter.

The present invention affords the possibility of switching the pumping function on or off according to random operating parameters, the valve being switched on for charging the hook chamber with pressure as a function of this operating parameter. If the pump is used for producing a high pressure, protection against impermissibly high pressure can be provided. If the pump is used for producing a vacuum, the pump can be switched off at a predetermined vacuum.

Claims (15)

1. A vane pump, in particular a vacuum vane pump, comprising two or more vanes which are movable in vane slots in a rotor and devices for restricting the radial movement of the vanes, wherein each vane has on one of its lateral faces a strip which is parallel to the axis, the lateral face having the said strip sliding with its radially outer region on an opposing strip whereby the strip and the said opposing strip form a sealed chamber of variable volume which communicates at least intermittently in the course of a revolution of the rotor with a preferably substantially central pressure medium connection, which pressure medium connection may be charged with a pressure medium.

2. A pump according to Claim 1, wherein the strip is arranged in each case on the end of the vane lying in the rotor.

3. A pump according to Claim 1 or 2, wherein in the pressure medium connection can be charged with pressure medium as a function of the vacuum or super pressure produced.

4. A pump according to any of Claims 1 to 3, wherein two or more, preferably four slots each receiving a vane are provided, each slot terminating before a central bore, and wherein the vanes have strips at their inner ends and the slots have opposing strips, the vane slots communicating via connecting ducts with the central bore.

5. A pump according to any of Claims 1 to 3, wherein two vanes superimposed in a common vane slot are provided in the rotor, wherein the strip is arranged in each case on the vane end sliding in the rotor at the side turned away from the other vane, and wherein the rotor slot comprises the said opposing strip (26) in the vicinity of the rotor centre.

6. A pump according to any of Claims 1 to 3, wherein in that two vanes superimposed in a common vane slot are provided in the rotor, wherein the two vanes each have a strip in the region of their parts placed in the rotor and the strips of both vanes face one another, and wherein the respective strip of one vane slides on the side facing it of the other vane and the two strips form a pressure chamber or hook chamber between them.

7. A pump according to Claim 6, wherein the strips of the two vanes are formed by the hook-shaped design of the vane ends placed in the rotor and the hook heads form between themselves a pressure chamber or hook chamber of which the length varies continuously between two limit values during rotation of the rotor.

8. A pump according to Claim 5 or 6, wherein the pressure medium duct opens at one end face of the pump housing into a recess and is in alignment with the pressure chamber between the hook heads of the two pump vanes.

9. A pump according to Claim 8, wherein the bore(s) and the recess(es) are arranged concentrically to the rotor axis.

10. A pump according to any of Claims 5 to 9, wherein the pump vanes are also provided with hook heads at their ends pointing towards the internal housing wall, the two vanes having a substantially identical S- or Zshape in cross-section.

11. A pump according to any of Claims 5 to 9, wherein the pressure medium duct is provided in the rotor shaft as an axial passage.

12. A pump according to any of the preceding Claims, wherein the rotor has a central bore, and connections to the vane slot(s) are provided.

13. A pump according to any of the preceding Claims, wherein the hook chamber can be charged by means of a device, controlled by known means, alternately with oil under pressure for driving in the vanes and with the tank or a vacuum for driving them out into the operating position.

14. A pump according to Claim 13, wherein a pressure-actuated change-over valve connects the hook chamber as a function of the generated pump vacuum alternately to the pressure connection for driving in the vanes and/or to the tank or the vacuum connection for attaining the operating position.

15. A vane pump substantially as herein described and as illustrated in the accompanying drawings.