The present invention relates to a mechanical automotive variable lubricant pump for pumping pressurized lubricant to a lubricant target like e.g. the internal combustion engine, gearboxes or other automotive components.

An automotive variable lubricant pump is commonly used to provide lubricant to the internal combustion engine or other automotive components to provide for sufficient lubrication of the engine or of the components.

DE 20 2005 021 925 Ul describes a variable lubricant pump which comprises a pump rotor with radially slidable vanes which rotate inside a circular control ring which is pivotable with respect to the rotor axis between a high pumping volume position and a low pumping volume position.

At a high rotational speed of the rotor, the pressure at the lubricant suction port at the beginning of the suction phase falls under the vapour pressure of the lubricant so that a cavitation in the lubricant is generated. The noise generated therefore significantly increases whereas the efficiency decreases. EP 0 652 370 Bl describes a variable displacement vane pump with an inlet arc and a smaller discharge arc to balance the pressure. This is achieved by so called undercut slots. These slots are difficult to produce and lead to a volatile change fom discharge/seal arc to the inlet arc.

The object of the present invention is to provide an automotive variable lubricant pump with reduced noise and an improved efficiency without the foregoing disadvantages. This object is solved with an automotive variable lubricant pump having the features of claim 1.

According to the present invention, the automotive variable lubricant pump for pumping a pressurized lubricant to an internal combustion engine is mechanically driven by the engine and comprises a pump rotor with radially slidable vanes which rotate in a shiftable or pivotable control ring defining a pump chamber and being radially shiftable or pivotable with respect to the rotor axis between a high pumping volume position and a low pumping volume position. The vanes are alternatively not provided to be exactly radially shiftable, but inclined in the radial direction. According to the present invention, an inner contour of the control ring comprises at least one portion that deviates from a circular shape with a radius r of the control ring so that an angular distance from the low volume commutation point to the high volume commutation point is larger than 180° so that the suction porting sector is larger than the outlet porting sector. Therefore, the suction increases and the pump can be filled with a lower pressure drop in comparison to a circular shape of the control ring. Pulsating of the pressure course is consequently decreased so that the pressure course is smoother. The angle interval, where the pressure at the lubricant suction port is below the vapour pressure, is further decreased. Noise of the variable lubricant pump which is generated by a pulsating of the pressure course and by the angle interval, where the pressure at the lubricant suction port is below the vapour pressure, is therefore reduced. The efficiency of the variable lubricant pump is thus also improved.

In an embodiment of the present invention, the control ring schematically is divided in four quadrants wherein the low volume commutation point is located in an area of the intersection of the III. and IV. quadrant and the high volume commutation point is located in an area of the intersection of the I. and II. quadrant wherein a radius Riv of a portion of the control ring located in the IV. quadrant is at least larger than a radius r of portions of the control ring located in the II. and III. quadrant. Alternatively or additionally the high volume commutation point is located in an area of the intersection of the I. and II. quadrant wherein a radius R (only shown as radius Riv)of a portion of the control ring located in the I. quadrant is at least larger than a radius r of portions of the control ring located in the II. and III. quadrant.

In an embodiment of the present invention, a lubricant suction port and a lubricant ejection port can, for example, both be provided in a front wall of the pump chamber. The lubricant suction port through which the lubricant is sucked, and the lubricant ejection port through which the lubricant is ejected, are therefore not provided in a radial wall of the control ring. Both ports are provided in the front wall arranged axially adjacent to the rotor.

The contour of the lubricant suction port can, for example, be restricted in a radial direction by the control ring. The lubricant suction port in a radial direction accordingly does not extend beyond the control ring.

Further advantages will become evident by the following detailed description of an embodiment of the present invention in combination with the drawings, which show:

Figure 1 shows a schematic drawing of a lubricating system comprising an automotive variable lubricant pump according to the present invention; and

Figure 2 shows an enlarged view of an embodiment of the automotive variable lubricant pump of Figure 1.

Figure 1 shows a schematic drawing of a lubricating system 5 comprising an embodiment of an automotive variable lubricant pump 10 according to the present invention. The variable lubricant pump 10 is mechanically driven by an internal combustion engine 12 and pumps lubricant from a lubricant reservoir 14 via a lubricant suction conduit 18 and a lubricant supply conduit 22 to the internal combustion engine 12 defining a lubricant target to lubricate components of the internal combustion engine 12. The lubricant is fed back from the internal combustion engine 12 to the lubricant reservoir 14 via a discharge conduit 30.

Figure 2 shows an enlarged view of an embodiment of the automotive variable lubricant pump 10 of Figure 1. The variable lubricant pump 10 comprises a pump rotor 34 with five radially slidable vanes 38 which rotate in a rotation direction 40 within a control ring 42. The control ring 42 is radially shiftable with respect to a static rotor axis 46. The control ring 42 and two front walls 50 (only one front wall shown) provided on axial sides of the variable lubricant pump 10 define a pump chamber 54 of the variable lubricant pump 10. The control ring 42 is shiftable between a high pumping volume position, shown in Figure 2, and a low pumping volume position. The pump rotor 34 provides a maximum eccentricity to the control ring 42 in the high pumping volume position so that the ejected lubricant volume is maximal. The pump rotor 34 provides an eccentricity to the control ring 42 which is almost zero in the low pumping volume position so that the ejected lubricant volume is minimal. The pump rotor 34 is shown in a high pumping volume position in Figure 2.

The pump chamber 54 is provided with a lubricant suction sector 56 and a lubricant ejection sector 58. The lubrication suction sector 56 is defined by a suction porting sector 60 and the lubricant ejection sector 58 is defined by an outlet porting sector 62. At the end of the suction porting sector 60 is indicated a low volume commutation point 64 and at the end of the outlet porting sector 62 is indicated a high volume commutation point 66. The boundary between both sectors 56, 58 respectively the two shapes 62, 64 are indicated by separation line 68. A lubricant suction port 69, through which lubricant is sucked from the lubricant suction conduit 18, is arranged in the lubricant suction sector 56 in the front wall 50. A respective lubricant ejection port 70, through which lubricant is ejected to the lubricant supply conduit 22, is arranged in the lubricant ejection sector 58 in the front wall 50.

The position where the separation line 68 crosses the control ring 42 defines the commutation points 64, 66, namely, the points where the lubricant suction sector 56 changes to the lubricant ejection sector 58 or vice versa. The respective position where the pumping volume is the lowest therefore defines a low volume commutation point 64, whereas the radially opposite position where the pumping volume is the highest defines a high volume commutation point 66.

To give a description of the invention, the control ring 42 is schematically divided in four quadrants I, II, III, IV, defined by a coordinate plane 67. The high volume commutation point is located in an area of the intersection of the I. and II. quadrants and the low volume commutation point is located in an area of the intersection of the III. and IV. quadrant. To provide a suction porting sector 60 which is larger than the outlet porting sector 62 a portion 72 of an inner contour 74 of the control ring 42 in the IV. quadrant has a radius Riv which is larger than a radius r of a circular shape 76 of the inner contour 74 of the control ring 42 in the other quadrants I., II. and III.. Therefore, the low volume commutation point 64 moves to the IV. quadrant of the control ring 42 so that an angular distance from the low volume commutation point to the high volume commutation point is larger than 180°. However the inner contour 74 of the control ring 42 has a constant cross section over the whole circumference. There are no slots or other passages formed in the inner contour.

The volume of the suction porting sector 60 is increased. The pressure course is therefore smoother and the angle interval, where the pressure at the lubricant suction port 69 is below the vapour pressure, is decreased. The noise of the variable lubricant pump 10 according to the present invention is therefore reduced.

It should be clear from the above that the automotive variable lubricant pump is not limited to the above described embodiment. Other designs of the pump are in particular possible. The variable lubricant pump is also not limited to five vanes. The radius Riv could be only applied to a part of the IV. quadrant. Reference should also be had to the appended claims.

Reference Numerals

5 lubricating system

10 variable lubricant pump

12 internal combustion engine

5 14 lubricant reservoir

18 lubricant suction conduit

22 lubricant supply conduit

30 discharge conduit

34 pump rotor

10 38 vane

40 rotation direction

42 control ring

46 rotor axis

50 front wall

15 54 pump chamber

56 lubricant suction sector

58 lubricant ejection sector

60 suction porting sector

62 outlet porting sector

20 64 low volume commutation point

66 high volume commutation point

67 coordinate plane

68 separation line

69 lubricant suction port

25 70 lubricant ejection port

72 portion of control ring in the IV. quadrant

74 inner contour

76 circular shape

a angular distance

30 r radius of the circular shape of the control ring in the quadrants I,

II, III

Riv radius of the portion of the control ring in the IV. quadrant