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 plvotable 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.

The object of the present invention is to provide an automotive variable lubricant pump with reduced noise and an improved efficiency.

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 slldable vanes which rotate in a shiftable 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. An inner contour of the control ring comprises a concave portion In a lubricant suction sector of the control ring so that the Inner contour of the control ring deviates from a circular shape. The vanes are alternatively not provided to be exactly radially shiftable, but inclined in the radial direction. According to the present invention, the inner contour of the control ring is the inner circumferential shape of the control ring defining the pump chamber. The control ring generally defines a circular pump chamber. The inner circular contour In the region of the concave portion is, however, changed to higher radii of the control ring so that the total volume of the pump chamber compared to a circular shape is increased In this sector. The concave portion Is arranged at a lubricant suction sector. The lubricant suction sector is defined as the rotor rotation angle Interval in which, as seen in the direction of rotation of the rotor, the volume of a vane chamber defined by two adjacent vanes increases so that lubricant Is sucked into the vane chamber. In the lubricant suction sector, the concave portion has the effect that the volume of the vane chamber quickly Increases at the very beginning of the suction phase i.e. within the first part of the concave zone. Therefore, the vane chamber volume in the subsequent part of the concave zone 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 concave portion can, for example, be arranged between a low volume commutation point located between a lubricant ejection sector and the lubricant suction sector, and an angle of 90° behind the low volume commutation point. The lubricant ejection sector is defined as the rotation angle interval of the rotor, as seen In a direction of rotation of the rotor, where the volume of the vane chamber decreases so that lubricant is ejected from the vane chamber. A point on the control ring between the lubricant suction sector and the lubricant ejection sector Is thereby defined as the commutation point. TWo commutation points exist because the control ring comprises two points between the lubricant suction sector and the lubricant ejection sector, namely, a low volume commutation point and a high volume commutation point. The high volume commutation point is located, where the volume of the vane chamber is maximal. The low volume commutation point Is therefore located where the volume of the vane chamber is minimal. The concave portion Is arranged within an angle section of 90° starting at the low volume commutation point according to the present Invention. The vane chamber volume is thereby Increased, especially in a range of a low volume of the vane chamber. Cavitation is reduced by increasing the vane chamber volume because cavitation mainly occurs at a low volume of the vane chamber. Noise caused by cavitation is thus reduced. In an embodiment of the present Invention, the concave portion can, for example, open at the low volume commutation point. The cavitation can effectively be reduced by increasing the volume of the vane chambers directly behind the low volume commutation point. Noise caused by cavitation is accordingly reduced. The efficiency of the variable lubricant pump Is improved by reducing cavitation. 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.

In an embodiment of the present invention, the inner contour of the control ring before and behind the concave portion can, for example, be circular. The inner contour of the control ring before and behind the concave portion therefore has the same radius.

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;

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

Figure 3 shows a diagram which compares a pressure curve of a control ring according to the present Invention with a pressure curve of a standard circular control ring.

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 58 and a lubricant ejection sector 62. The boundary between both sectors 58, 62 Is indicated by separation line 66. A lubricant suction port 69, through which lubricant is sucked from the lubricant suction conduit 18, Is arranged in the lubricant suction sector 58 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 62 In the front wall 50.

The position where the separation line 66 crosses the control ring 42 defines the commutation points 72, 76, namely, the points where the lubricant suction sector 58 changes to the lubricant ejection sector 62 or vice versa. The respective position where the pumping volume Is the lowest therefore defines a low volume commutation point 72, whereas the radially opposite position where the pumping volume Is the highest defines a high volume commutation point 76. The control ring 42 comprises a concave portion 80 so that an Inner contour 82 of the control ring 42 deviates from a circular shape 84. The Inner contour 82 of the control ring 42 is shifted to higher radii In a region of the concave portion 80. The concave portion 80 Is arranged in a segment of the lubricant suction sector 58 starting at the low volume commutation point 72, whereas the segment encloses an angle a of 90°. The concave portion 80 directly starts at the low volume commutation point 72 in the shown embodiment. The volume of a vane chamber 88, defined by two adjacent vanes 38, compared to the circular shape 84 of the control ring 42, Is Increased in the region of the concave portion 80. The volume of the vane chamber 88 quickly Increases at the very beginning of the suction phase I.e. within the first part of the concave portion 80. Therefore, the vane chamber volume In the subsequent part of the concave portion 80 can be filled with a lower pressure drop In comparison to a circular shape 84 of the control ring 42. 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.

Figure 3 shows a diagram of the pressure in the vane chambers 88 during a rotation of the pump rotor 34 in the lubricant suction sector 58. In this diagram, the pressure curve of a control ring 42 according to the present invention is compared to a pressure curve of a standard circular control ring. The pressure curve of the standard circular control ring shows that the pressure in the vane chamber 88 from the beginning of the suction phase to approximately 70° is very low. This pressure is below the vapour pressure so that cavitation occurs. Noise caused by cavitation is consequently generated in this angle interval. The pressure increases behind this angle Interval so that cavitation does not occur further.

In comparison thereto, the pressure In the vane chambers 88 of the variable lubricant pump 10 according to the present invention increases at a smaller angle. The pressure in the vane chambers 88 already increases behind an angle of approximately 35°. The angle interval having a low pressure in the vane chambers 88 is thereby significantly decreased. Cavitation generated during the suction process is consequently decreased so that noise caused by cavitation is likewise decreased.

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 concave portion are in particular possible. The variable lubricant pump Is also not limited to five vanes. Reference should also be had to the appended claims.

Reference Numerals

5 lubricating system

10 variable lubricant pump

12 Internal combustion engine

14 lubricant reservoir

18 lubricant suction conduit

22 lubricant supply conduit

30 discharge conduit

34 pump rotor

38 vane

40 rotation direction

42 control ring

46 rotor axis

50 front wall

54 pump chamber

58 lubricant suction sector

62 lubricant ejection sector

66 separation line

69 lubricant suction port

70 lubricant ejection port

72 low volume commutation point

76 high volume commutation point

80 concave portion

82 inner contour

84 circular shape

88 vane chamber

a angle