AUTOMOTIVE VARIABLE MECHANICAL LUBRICANT PUMP

Abstract

A mechanical lubricant pump includes a control ring which shifts between a maximum and a minimum eccentricity position, the control ring having a circumference with anti-spring and pro-spring hydraulic surfaces, a pump rotor having slidable vanes which rotate in the control ring, a preload spring which pushes the control ring into the maximum eccentricity position, a hydraulic pilot chamber which pushes the control ring into the minimum eccentricity position, a hydraulic pressure control circuit which controls a gallery pressure by regulating a pilot chamber pressure, and a hydraulic outlet chamber which surrounds a part of the circumference. The hydraulic pilot chamber is charged with a pump outlet pressure or with the gallery pressure of an engine. The hydraulic outlet chamber is charged with the pump outlet pressure and is connected to the pump outlet for a pressurized lubricant. The anti-spring hydraulic surface is larger than the counter-acting pro-spring hydraulic surface.

Claims

1-7. (canceled)

8. An automotive variable mechanical lubricant pump for providing a pressurized lubricant for an internal combustion engine, the automotive variable mechanical lubricant pump comprising: a control ring configured to be shiftable in a control ring sifting direction between a maximum eccentricity position and a minimum eccentricity position, the control ring comprising an outer control ring circumference which comprises an effective anti-spring hydraulic surface and a pro-spring hydraulic surface; a pump rotor comprising a plurality of slidable vanes which are configured to rotate in the control ring; a control ring preload spring configured to push the control ring into the maximum eccentricity position; a hydraulic pilot chamber configured to push the control ring into the minimum eccentricity position, the hydraulic pilot chamber being charged with a pump outlet pressure or with a gallery pressure of the internal combustion engine; a hydraulic pressure control circuit configured to control the gallery pressure by directly regulating a pilot chamber pressure; a pump outlet for the pressurized lubricant; and a dissymmetric hydraulic outlet chamber which is arranged to surround a part of the outer control ring circumference, the dissymmetric hydraulic outlet chamber being directly charged with the pump outlet pressure and being directly connected to the pump outlet for the pressurized lubricant, wherein, the effective anti-spring hydraulic surface in the dissymmetric hydraulic outlet chamber is larger than the pro-spring hydraulic surface which counter acts the effective anti-spring hydraulic surface.

9. The automotive variable mechanical lubricant pump as recited in claim 8, further comprising: an anti-spring hydraulic surface height arranged perpendicular to the control ring shifting direction; and a pro-spring hydraulic surface height arranged perpendicular to the control ring shifting direction, wherein, the anti-spring hydraulic surface height is larger than the pro-spring hydraulic surface height.

10. The automotive variable mechanical lubricant pump as recited in claim 8, wherein the effective anti-spring hydraulic surface is at least 10% larger than the pro-spring hydraulic surface.

11. The automotive variable mechanical lubricant pump as recited in claim 8, wherein the effective anti-spring hydraulic surface is at least 20% larger than the pro-spring hydraulic surface.

12. The automotive variable mechanical lubricant pump as recited in claim 8, further comprising: a hydraulic control circuit comprising a hydraulic control valve which is configured to control the gallery pressure of the internal combustion engine by directly regulating the pilot chamber pressure, the hydraulic control valve comprising an actual-pressure inlet which is charged with the remote gallery pressure of the internal combustion engine.

13. The automotive variable mechanical lubricant pump as recited in claim 12, wherein the hydraulic control valve further comprises a plunger which comprises a valve body for opening and closing a valve opening and a first active plunger surface which is charged with the gallery pressure of the actual-pressure inlet, and a valve preload spring which is configured to push the valve body into an open valve position.

14. The automotive variable mechanical lubricant pump as recited in claim 13, further comprising: a separate hydraulic switch which is configured to be electrically actuated, wherein, the valve plunger further comprises a second active plunger surface which is charged with the gallery pressure of the actual-pressure inlet via the separate hydraulic switch.

15. The automotive variable mechanical lubricant pump as recited in claim 8, further comprising: a hydraulic throttle arranged upstream of the hydraulic pilot chamber and downstream of a source of the pump outlet pressure.

Description

[0023] Three embodiments of the invention are described with reference to the enclosed drawings, wherein:

[0024] FIG. 1 shows schematically a first embodiment of a control circuit with an automotive variable mechanical lubricant pump, an engine which is supplied with pressurized lubricant coming from the lubricant pump, a pump control chamber being directly charged with the pump outlet pressure, and a hydraulic control valve, in a low set-pressure condition,

[0025] FIG. 2 shows the lubricant pump of FIG. 1 in a high set-pressure condition,

[0026] FIG. 3 shows a second embodiment of the control circuit with the pump control chamber being charged with the gallery pressure via the hydraulic control valve, and

[0027] FIG. 4 shows a third embodiment of the control circuit without a hydraulic control valve.

[0028] The figures show an arrangement 10 of an automotive variable mechanical lubricant pump 20, an internal combustion engine 12 and a lubricant tank 14 with a liquid lubricant 15, namely engine oil. The lubricant 15 in the lubricant tank 14 is sucked by the lubricant pump 20 and is delivered as pressurized lubricant to the engine 12 for lubrication and cooling of the engine 12.

[0029] The lubricant pump 20 of the first embodiment comprises a pumping unit 22, a hydraulic control valve 50 and a hydraulic switch 60 which all together can be integrated in one single lubricant pump device. The pumping unit 22 is provided with a rotatable pump rotor 26 with five radially slidable vanes 28 which are rotating in a linearly shiftable control ring 27. The pump rotor 26 is directly mechanically driven by the engine 12. The control ring 27 is linearly shiftable in a linear shifting direction 82. The control ring 27 encloses a pumping chamber which is divided into five pumping compartments by the rotor vanes 28. The pump rotor 26 rotates in the present embodiment in clockwise direction.

[0030] The control ring 27 is shiftable between a maximum eccentricity position as shown in FIGS. 1 and 2 providing a maximum compartment stroke, and a minimum eccentricity position providing a minimum compartment stroke. In the maximum eccentricity position of the control ring 27, the pumping performance is maximized, whereas in the minimum eccentricity position of the control ring 27, the pumping performance is minimized. The control ring 27 is arranged shiftable within a pumping unit housing 24 which supports the control ring 27 linearly shiftable. The control ring 27 is pushed by a control ring preload spring 34 into the maximum eccentricity position, as shown in the figures. The preload spring 34 is provided in a spring chamber 33 which is hydraulically connected to the lubricant tank 14 and which is generally under atmospheric pressure.

[0031] A pilot chamber 31 is provided opposite to the spring chamber 33. The pilot chamber 31 is defined by the pumping unit housing 24 and by a pilot chamber piston 30 which is a part of the body of the control ring 27. If the hydraulic pilot chamber 31 is charged with the pressurized lubricant, the control ring 27 is pushed into the minimum eccentricity position against the preload spring 34.

[0032] The lubricant which is pumped and pressurized in the pumping chamber and in the pumping compartments is directly discharged from the pumping chamber to a hydraulic outlet chamber 36 which is defined by a sector of the circular outside circumference 29 of the control ring 27 and by the pumping unit housing 24. The pressure of the lubricant in the hydraulic outlet chamber 36 is the outlet pressure PO of the lubricant pump 20 which is the lubricant pressure at a pump outlet port 90.

[0033] The hydraulic outlet chamber 36 is designed dissymmetric so that the effective anti-spring hydraulic surface 291 of the control ring circumference 29 in the hydraulic outlet chamber 36 is about 20% larger than the counter acting pro-spring hydraulic surface 292. The hydraulic surface 291, 292 is the projection of the control ring circumference surface within the outlet chamber 36 seen exactly in the control ring shifting direction 82. As can be seen in FIG. 1, the anti-spring hydraulic surface height H1 perpendicular to the control ring shifting direction 82 is larger than the pro-spring hydraulic surface height H2.

[0034] As a result, an anti-spring force is generated if the lubricant in the outlet chamber 36 is pressurized. The anti-spring force is the result of the hydraulic surface difference dA multiplied by the overpressure POPA with respect to atmospheric pressure. If the overpressure POPA is high enough, the control ring 27 is shifted into minimum eccentricity direction against the force of the control ring preload spring 34.

[0035] The hydraulic pilot chamber 31 is directly charged with lubricant having the pump's outlet-pressure PO via a hydraulic throttle 38. The hydraulic pilot chamber 31 is discharged via a valve inlet opening 57 and a valve outlet opening 58 of the hydraulic control valve 50 to atmospheric pressure. The hydraulic control valve 50 is provided with a valve housing 52 which is generally cylindrical inside. A complex valve plunger 59 comprising a cylindrical valve body 56 is provided axially shiftable within the valve housing 52. The valve plunger 59 is mechanically preloaded by a valve preload spring 51 pushing the valve plunger 59 into the open valve position in which the hydraulic pilot chamber 31 is connected without restriction or fluidic resistance to the lubricant tank 14 being under atmospheric pressure PA.

[0036] The valve plunger 59 is provided with a valve body 56 which steplessly completely covers, covers in part or leaves completely open the valve inlet opening 57 which is fluidically directly connected to the pilot chamber 31. The valve outlet opening 58 is fluidically directly connected to the lubricant tank under atmospheric pressure PA.

[0037] The valve plunger 59 is provided with a first circular active plunger surface 53 and a second ring-like active plunger surface 54. The first active plunger surface 53 is directly charged with the gallery pressure PG which is transferred from the engine 12 to the lubricant pump 20 through a pump gallery pressure inlet 80 and via an internal gallery pressure line 70. The second active plunger surface 54 is charged with the gallery pressure via a separate hydraulic switch 60 which is a valve and via a hydraulic line 72 between the hydraulic switch 60 and the control valve 50. The second active plunger surface 54 is charged with the gallery pressure PG or, alternatively, with atmospheric pressure PA via a hydraulic line 71, depending on the switching status of the hydraulic switch 60.

[0038] The hydraulic switch 60 is electronically controlled by an electronic pump control 92 which controls the switching state of the hydraulic switch 60 dependent on the lubricant temperature and the rotational pump speed. The hydraulic switch 60 hydraulically connects the second active plunger surface 54 to gallery pressure PG if the set-value of the gallery pressure PG should be low, as shown in FIG. 1. If the set-value of the gallery pressure PG should be relatively high, the hydraulic switch 60 is switched into the low pressure position to connect the second active plunger surface 54 to the atmospheric pressure PA of the lubricant tank 14, as shown in FIG. 2.

[0039] The position of the control ring 27 is the equilibrium position in which the spring force of the control ring preload spring 34 is more or less equal to the hydraulic force generated by the pilot chamber pressure PP in the pilot chamber 31 plus the hydraulic force in shifting direction 82 caused by the lubricant outlet pressure PO in the outlet chamber 36.

[0040] When the engine 12 is started after having stood still, the liquid lubricant 15 is sucked from the lubricant tank 14 into the pumping chamber where the lubricant is pumped by the pumping compartments to the hydraulic outlet chamber 36. If the lubricant is cold and has a relatively low viscosity, the lubricant's outlet pressure PO in the outlet chamber 36 can be relatively high. In that case, the total lubricant pressure outlet pressure PO generates a force at the control ring 26 which is directed against the spring force of the control ring preload spring 34 and thereby moves the control ring 27 into the low eccentricity direction so that the compartment stroke of the pump 20 is reduced, with the result, that the outlet pressure PO is reduced accordingly. As soon as the lubricant has arrived at the pilot chamber 31 and at the hydraulic control valve 50, the pump pressure control works properly.

[0041] The arrangement 10 according to the second embodiment as shown in FIG. 3 is similar to the first embodiment. But the control chamber 31 is charged with the gallery pressure (PG) via the control valve 50. The gallery pressure (PG) is directed by a hydraulic line 72 to a valve inlet of the control valve 50 depending on the position of the valve plunger 59. The control chamber 31 is charged with the gallery pressure (PG) or with the atmospheric pressure (PA). The hydraulic switch 60 has a similar function as in the arrangement according to the first embodiment. The hydraulic switch 60 charges the first circular active plungers surface 53 with the gallery pressure (PG) or alternatively with atmospheric pressure (PA) to thereby define a second set outlet pressure (PO).

[0042] The arrangement 10 according to the third embodiment shown in FIG. 4 is not provided with any hydraulic control valve anymore. The control chamber 31 is directly charged with the gallery pressure (PG) or with atmospheric pressure (PA) depending on the switching position of the hydraulic switch 60.

[0043] In all embodiments 10 no additional overpressure valve is provided.