Controllable Screw Spindle Pump

Abstract

A controllable screw spindle pump for the lubricating oil supply of an internal combustion engine comprises a pump housing (1), in which a throttle chamber (13) and a control chamber (14) are configured which are in contact with the lubricating oil to be conveyed; wherein the throttle chamber (13) is arranged between the pump inlet (10) and the spindle chamber (12), and the throttle chamber (13) comprises a throttle valve (3), by way of which a throughflow cross section of a conveying stream can be set; and the control chamber (14) comprises a hydraulic control valve (4) with a piston (40) which responds to a hydraulic control pressure (p1, p2) in the control chamber (14), and the control chamber (14) is oriented parallel to the spindle chamber (12) in relation to an actuating travel of the piston (40); and a valve body (30) of the throttle valve (3) is coupled to the piston (40) of the hydraulic control valve (4).

Claims

1-7. (canceled)

8. A controllable screw pump for supplying lubrication oil to a combustion engine, comprising: a pump housing with a spindle chamber as well as a pump inlet and a pump outlet communicating with the spindle chamber; at least two screw spindles rotatably accommodated in the spindle chamber, the screw spindles being driven by the combustion engine; wherein inside the pump housing, a throttle chamber and a control chamber are provided, which are in contact with the lubrication oil to be conveyed; wherein the throttle chamber is situated between the pump inlet and the spindle chamber, and the throttle chamber includes a throttle valve, via which a flow cross-section of a delivery flow is settable; the control chamber includes a hydraulic regulating valve with a piston that responds to a hydraulic control pressure inside the control chamber, and the control chamber is arranged in parallel to the spindle chamber with reference to a displacement of the piston; and a valve body of the throttle valve is coupled with the piston of the hydraulic regulating valve.

9. The controllable screw pump according to claim 8, wherein a displacement of the valve body of the throttle valve is arranged in parallel to the spindle chamber, and a valve seat of the throttle valve is provided at a mouth of the pump inlet into the throttle chamber.

10. The controllable screw pump according to claim 8, wherein the valve body of the throttle valve and the piston of the hydraulic regulating valve are seated on a common valve stem.

11. The controllable screw pump according to claim 8, wherein the screw pump comprises two screw spindles, wherein a cross-section of the spindle chamber is formed by two overlapping circle radii, and a cross-section of the control chamber is situated in the area of an intersection axis of an overlap of the circle radii next to the spindle chamber.

12. The controllable screw pump according to claim 8, wherein the control chamber comprises two hydraulic connections for introducing two hydraulic control pressures that act on opposing sides of the piston of the hydraulic regulating valve.

13. The controllable screw pump according to claim 8, wherein a compression spring is situated inside the control chamber on one side of the piston of the hydraulic regulating valve.

14. The controllable screw pump according to claim 8, wherein the pump housing comprises at one end face of the spindle chamber a collar portion that includes a passage for the housing and a shaft bearing for a drive shaft, and a gear rim that is seated on the drive shaft comprises a radial cut-out for the collar portion so that a toothing of the gear rim and the shaft bearing overlap axially.

Description

[0025] The invention will be explained hereinafter with the aid of an embodiment and with reference to the accompanying drawing,

[0026] FIG. 1 shows a simplified schematic sectional view through the design of one embodiment of the controllable screw pump in accordance with the invention.

[0027] In the embodiment of the schematic illustration of FIG. 1, a relative dimension of a hydraulic regulating valve 4 has been selected in favour of improved perception.

[0028] However, the hydraulic regulating valve 4 can likewise be smaller. Furthermore, to avoid a superimposed illustration of the hydraulic regulating valve 4 with a spindle chamber 12, in FIG. 1 a position of the hydraulic regulating valve 4 is shown offset with respect to the spindle chamber 12. However, a position and distance of the hydraulic regulating valve 4 with respect to the spindle chamber 12 can likewise vary in favour of a more compact arrangement.

[0029] In terms of this disclosure, the term ‘screw pump’ is understood to mean skew rotary piston pumps with a thread pitch for displacement of the delivery medium. Such types of pump generally comprise a driven screw spindle 2a and at least one further screw spindle 2b which is dragged via engagement of the toothing.

[0030] The screw pump of the illustrated embodiment has one driven screw spindle 2a and one dragged screw spindle 2b which are rotatably accommodated in a spindle chamber 12 of a pump housing 10. The driven screw spindle 2a communicates with a drive shaft 5 which is driven by a combustion engine via a gear rim 50. The drive shaft 5 exits the pump housing 1 in a collar portion 15. A shaft bearing 51 in the form of a compact bearing having two rows of ball bearings is fitted in the collar portion 15. The gear rim 50 is seated on the free end of the drive shaft 5, protruding therefrom, and has a bulge for the collar portion 15, and so a radial outer toothing axially overlaps with the shaft bearing 51.

[0031] A pressure side of the spindle chamber 12 which communicates with a pump outlet 11 in the form of a pressure connection is located on the drive side of the screw spindles 2a, 2b. A suction side of the spindle chamber 12 is located on the side of the screw spindles 2a, 2b opposite the drive. The suction side of the spindle chamber 12 communicates with a pump inlet 10 in the form of a suction connection via a throttle chamber 3. In consideration of the delivery direction, lubrication oil is sucked through by a negative pressure on the suction side of the spindle chamber 12, which is generated by a screw pitch of the rotating screw spindles 2a, 2b, via the pump inlet 10 and the throttle chamber 3, is conveyed through the spindle chamber 12 and ejected out of the spindle chamber 12 on the pressure side via the pump outlet 11.

[0032] A suction path upstream of the screw pump leads to an oil sump of the combustion engine. Downstream of the screw pump, a feed path of a lubrication oil delivery system, not illustrated, is provided. The feed path leads to branches of a lubrication oil supply of the combustion engine which serves to lubricate sliding surfaces between moving parts in a crank drive, a valve drive and cylinder barrels and the like under a required oil pressure.

[0033] The throttle chamber 13 of the pump housing 1 forms an inlet chamber at an end face of the spindle chamber 12. An annular valve seat 31 of a throttle valve 3 is formed at a mouth, at which the suction connection of the pump inlet 10 enters the throttle chamber 3. A valve body 30 of the throttle valve 3 is guided at a valve stem 34 axially opposite the suction connection of the pump inlet 10 and has a spherical sealing surface. By way of an opening position along a displacement of the valve body 30 with respect to the valve seat 31, a flow cross-section of the delivery flow of the lubrication oil between the pump inlet 10 and the spindle chamber 12 is set or limited, whereby a suction throttling of the screw pump is performed. On the other side of the valve stem 34 opposite the valve body 30, there is arranged a piston 40 which is accommodated in a cylindrical control chamber 14 of the pump housing 1. The piston 40 and the control chamber 14 form a hydraulic regulating valve 4 which sets an opening position of the throttle valve 3 by a controlled supply of pressure of the lubrication oil.

[0034] The spindle chamber 12 has a cross-sectional contour in the form of a so-called Figure-of-eight housing, i.e. it is formed by two bores in the pump housing 1 with overlapping radii in order to ensure engagement of the screw spindles 2a, 2b. The cylindrical control chamber 14 of the hydraulic regulating valve 4 is likewise formed by a bore in the pump housing 1 which extends in parallel to the bores of the spindle chamber 12. In a preferred compact embodiment which differs from the schematic illustration in FIG. 1, the cylindrical control chamber 14 is arranged close to a bulge of the Figure-of-eight housing, i.e. between the axes of the bores of the spindle chamber 12 close to a chamber wall of the spindle chamber 12, and so a tight packing of cylindrical cavities and thus a compact bounding geometry of the pump housing 1 is created.

[0035] The integrated arrangement of the hydraulic regulating valve 4 and of the throttle valve 3 is separated by a common stem guide 43 which is formed between the control chamber 14 and the throttle chamber 13. The stem guide 43 provides an axial guide for the common valve stem 34. A position of the piston 40 along a displacement of the hydraulic regulating valve 4 is set by two hydraulic control pressures p1 and p2 which prevail on both sides of the piston 40 in the control chamber 14. The control pressure p1 is generated via a hydraulic connection 41 on one side of the piston 40 in the control chamber 14. The control pressure p2 is generated via a hydraulic connection 42 on the other side of the piston 40 in the control chamber 14. An actuating movement of the piston 40 is responsive to a pressure difference between the two control pressures p1, p2 and retains a position in the event of an equilibrium of forces on both sides of the piston 40.

[0036] On the side of the control pressure p1, a compression spring, not shown, is preferably arranged which intervenes in the force ratio of the control pressures p1, p2. The length of the compression spring is selected such that without the two control pressures p1, p2 a closed position of the throttle valve 3 is prevented. The use of a compression spring ensures a fail-safe function, and so in the event of a failure in the hydraulic adjustment, stopping of the lubrication oil supply whilst the combustion engine is running is prevented by a closed throttle valve 3. Likewise, a complete opening position of the throttle valve 3 can optionally be prevented by a further compression spring on the opposite side. Depending upon the configuration of the lubrication oil system, a critical delivery pressure will not be exceeded in the event of a failure in the hydraulic adjustment.

[0037] A hydraulic actuation of the two control pressures p1, p2 occurs in a lubrication oil system, not illustrated, via an electric-hydraulic regulating device which is fed from the lubrication oil circuit of the combustion engine and by the delivery pressure of the screw pump. Such an electric-hydraulic regulating device has an electromagnetic 4/3 proportional valve. The 4/3 proportional valve comprises four connections, including an input connection for the supply of oil from an oil gate of the combustion engine and three output connections, two output connections of which provide the two control pressures p1, p2 with a controlled pressure difference and one output connection of which returns oil having an excess differential pressure from the adjustment into the oil sump. The output connections of the two control pressures p1, p2 are adjusted by means of a valve body which sets a respective hydraulic resistance and thus a respective pressure difference between the input connection and the three output connections. The valve body is adjusted by an electromagnetic actuating member having a coil and an anchor, and by a compression spring. The electromagnetic actuating member is actuated by a pulse width modulation of a supplied electrical power. A control of the control pressures p1, p2 of the hydraulic regulating valve 4 for adjusting the delivery volume of a lubrication oil circuit via the suction throttling of the throttle valve 3 in the screw pump can be effected by a control device in dependence upon a load, a rotational speed and a temperature of the combustion engine.

LIST OF REFERENCE NUMERALS

[0038] 1 Pump housing [0039] 2a Driven screw spindle [0040] 2b Dragged screw spindle [0041] 3 Throttle valve [0042] 4 Hydraulic regulating valve [0043] 5 Drive shaft [0044] 10 Pump inlet [0045] 11 Pump outlet [0046] 12 Spindle chamber [0047] 13 Throttle chamber [0048] 14 Control chamber [0049] 15 Collar portion [0050] 30 Valve body [0051] 31 Valve seat [0052] 34 Valve stem [0053] 40 Piston [0054] 41 Hydraulic connection with control pressure p1 [0055] 42 Hydraulic connection with control pressure p2 [0056] 43 Stem guide [0057] 50 Gear rim [0058] 51 Shaft bearing