Bidirectional automotive positive-displacement pump

The invention is directed to a bidirectional automotive positivedisplacement pump for pumping oil within an oil circuit of a vehicle.

A positive-displacement pump, in particular a so-called gerotor pump can generate relatively large pressures within its pumping chamber, in particular within a high-pressure discharge zone. As a result, a relatively large driving torque can be required for rotating the pump rotor against the high counter-pressure from the discharge zone. Furthermore, the relatively large discharge pressures can cause damages to the pressure lines of a connected pressure circuit and to the connected consumer devices.

Therefore, a positive-displacement pump, in particular a gerotor pump can be provided with an overpressure-relief valve for releasing the overpressure from the high-pressure discharge zone to a low-pressure suction zone of the pumping chamber. The high-pressure discharge zone and the low-pressure suction zone are fluidically connected via a connection channel which is openable and closable by a simple unidirectional check valve. The check valve is spring-biased and is actuated purely mechanically by the overpressure. If the pressure exceeds a defined overpressure value, the valve opens the connection channel so that the pressure is released to the suction zone until the nominal discharge pressure is achieved within the discharge zone. The overpressure value thereby is substantially defined by the preload of the said spring.

Exemplary pumps are disclosed in the documents DE 10 2013 207 321 Al, US 9,909,715 B2 or EP 2 781 750 Bl. The rotational direction of the pump rotor can in some applications be reversed so that the pump rotor can rotate in both rotational directions. A valve system switches the flow direction within the connected pressure circuit to guarantee the unidirectional supply of the pressure circuit independently of the rotational direction of the pump. An example of such a bidirectional gerotor pump is disclosed in the US 6,017,202 A.

It is an object of the present invention to provide a bidirectional automotive positive-displacement pump with a bidirectional overpressure-relief valve that is releasing the overpressure from a high-pressure zone to a low- pressure zone independently of the rotational direction of the pump rotor.

This object is achieved by a bidirectional automotive positive-displacement pump according to the present invention with the features of main claim 1.

A bidirectional automotive positive displacement pump comprises a pump rotor which is rotatably arranged within a pumping chamber. The bidirectional automotive positive displacement pump further comprises a static pump housing which defines said pumping chamber. The pumping chamber comprises a pumping chamber inlet/outlet opening, a pumping chamber outlet/inlet opening which is arranged mirror symmetrically to the pumping chamber inlet/outlet opening and a neutral zone being arranged at the apoapsis of the pumping chamber between the pumping chamber inlet/outlet opening and the pumping chamber outlet/inlet opening.

The pump rotor is eccentrically arranged within the pump chamber, thereby several pumping compartments are defined that change their volume over one rotation of the pump rotor within the pumping chamber. Thereby, each pumping compartment sucks fluid depending on the rotational direction of the pump rotor either through the pumping chamber inlet/outlet opening or through the mirror symmetrical pumping chamber outlet/inlet opening into the pumping chamber. As the automotive positive displacement pump according to the invention is bidirectionally driveable, i.e., is able to pump fluid independently of the rotational direction of the pump rotor, the pumping chamber inlet/outlet opening is in a first rotational direction, for example, in a clockwise rotational direction an inlet opening and in the second rotational direction, for example, in a counterclockwise rotational direction an outlet opening. The rotational direction of the pump rotor defines a suction zone and a discharge zone. Within the suction zone, the volume of each pumping compartment increases during the rotation of the pump rotor, wherein the volume of each pumping compartment decreases during the rotation of the pump rotor within the discharge zone. The suction zone and the discharge zone are symmetrically separated by the eccentricity axis defined by the axis through the centre of the pump rotor and through the centre of the pumping chamber. In the first rotational direction, for example, the clockwise rotation, the pumping chamber inlet/outlet opening is an inlet opening through which the increasing pumping compartments suck fluid from a fluid source into the pumping chamber. Thereby, the low-pressure suction zone of the pumping chamber is defined at the pumping chamber inlet/outlet opening. The pumping chamber outlet/inlet opening then defines the outlet opening and thereby defines the high-pressure discharge zone of the pumping chamber. The decreasing pumping compartments discharge the fluid through the pumping chamber outlet/inlet opening out of the discharge zone into a connected pressure circuit.

A change of the rotational direction, i.e., referring to the said example, a counter-clockwise rotation of the pump rotor, causes the suction zone and the discharge zone to switch. As a result, the pumping chamber inlet/outlet opening then defines the outlet opening for discharging the pressurized fluid out of the pumping chamber and the pumping chamber outlet/inlet opening defines the inlet opening for sucking the fluid into the pumping chamber.

The neutral zone is arranged symmetrically with respect to the eccentricity axis of the pump rotor and extends between the pumping chamber inlet/outlet opening and the pumping chamber outlet/inlet opening at the apoapsis of the pumping chamber. The apoapsis defines, with respect to the eccentricity axis, that side of the pumping chamber being located at the larger distance from the centre of the pump rotor to the radial inside of the pumping chamber. The apoapsis is, as a result, located, seen from the centre of the pump rotor, that direction along the eccentricity axis where the centre of the pumping chamber is located. In the neutral zone, the suction zone and the discharge zone are fluidically separated to each other by the pump rotor.

The bidirectional automotive positive displacement pump further comprises an overpressure-relief channel which fluidically connects the pumping chamber inlet/outlet opening and the pumping chamber outlet/inlet opening. Via this overpressure-relief channel, the fluid can flow from the pumping chamber inlet/outlet opening to the pumping chamber outlet/inlet opening and vice versa. Accordingly, the overpressure-relief channel fluidically connects the suction zone and the discharge zone of the pumping chamber.

Furthermore, the bidirectional automotive positive displacement pump comprises an overpressure-relief valve for opening and closing said overpressure-relief channel. The overpressure-relief valve is arranged such that an overpressure is released from the pumping chamber inlet/outlet opening to the pumping chamber outlet/inlet opening or alternatively vice versa, i.e., from the pumping chamber outlet/inlet opening to the pumping chamber inlet/outlet opening, if the pressure is above a predefined overpressure value. As the location of the high-pressure discharge zone and the low-pressure suction zone depend on the rotational direction of the pump rotor, the overpressure-relief valve is arranged and defined such that a pressure relief from the discharge zone to the suction zone is possible independently of the rotational direction of the pump rotor. Thereby, an overpressure within the discharge zone can be reliably released to the suction zone in both rotational directions of the pump rotor.

In a preferred embodiment of the invention, the overpressure-relief valve is mechanically pressure actuated. Accordingly, the overpressure-relief valve is a passive switching valve which is automatically opened by the overpressure in the discharge zone. As a result, the overpressure-relief valve is relatively cost efficient and low in maintenance.

In a preferred embodiment of the invention, the overpressure-relief valve is a linear slide valve, i.e., the overpressure-relief valve performs a linear stroke-type movement for opening and closing the overpressure-relief channel. This stroke-type movement is initiated by the overpressure in the discharge zone. The sliding functionality can be realised, for example, by arranging an overpressure-relief valve body in a corresponding sliding bore.

In a preferred embodiment of the invention, the overpressure-relief valve is mechanically biased by a compression spring. The compression spring is arranged such that the overpressure-relief valve body is pushed into a closing position, where the overpressure-relief channel is completely closed. As the pressure force of the overpressure must exceed the spring force to open the overpressure-relief channel, the preload of the compression spring substantially defines the overpressure value for opening the overpressure-relief valve. The preload of the compression spring is therefore preferably adjustable.

In another preferred embodiment of the present invention, the overpressure-relief valve is arranged within the pump housing. The overpressure-relief valve can thereby be arranged relatively close to the pumping chamber so that the overpressure-relief channel, which is preferably arranged within the pump housing, can be relatively short allowing a fast and immediate opening of the overpressure-relief valve. Furthermore, the definition of the overpressure-relief channel within the pump housing can be realised relatively simply, for example, by using simple bore holes within the pump housing body.

In another preferred embodiment of the invention, the overpressure-relief valve is arranged such that an overpressure-relief valve actuating axis is oriented substantially perpendicularly to a flow direction of the overpressure-relief channel. The term perpendicularly means that the overpressure-relief valve actuating axis is, for example, perpendicularly arranged to the overpressure-relief channel itself, if the overpressure-relief channel is linear. The term perpendicularly can also mean that the overpressure-relief actuating direction axis is, for example perpendicularly arranged to an axis which directly connects the centres of each overpressure-relief channel opening in the pumping chamber, if the overpressure-relief channel itself is, for example, not linear.

In a preferred embodiment of the invention, the overpressure-relief valve actuating axis is arranged in a separating plane which symmetrically separates the pumping chamber inlet/outlet opening and the pumping chamber outlet/inlet opening. The separating plane preferably runs through the eccentricity axis of the pumping chamber and through the rotor axis of the pump rotor. Thereby, the overpressure-relief valve is arranged symmetrically to both the pumping chamber inlet/outlet opening and the pumping chamber outlet/inlet opening. As a result, the force application surface of the overpressure force at the overpressure-relief valve is identical for both flow directions within the overpressure-relief channel and is thereby independent of the rotational direction of the pump rotor.

In a preferred embodiment of the invention the overpressure-relief valve body is substantially cylindrical. A cylindrical overpressure-relief valve body allows a relatively simple manufacturing of the overpressure-relief valve body itself and of the corresponding overpressure-relief valve body support. For example, the overpressure-relief valve body support can be a simple bore hole within the pump housing. Furthermore, a cylindrical overpressure-relief valve body allows a relatively simple ceiling of the overpressure-relief valve body against the overpressure-relief valve body support. The sealing thereby guarantees that the fluid within the overpressure-relief channel does not pass the overpressure-relief valve body towards the overpressure-relief valve body support.

In another preferred embodiment of the invention the connection channel is bypassing the neutral zone. The overpressure-relief channel openings are preferably arranged, with respect to the eccentricity axis or the separating plane, symmetrically at both sides of the neutral zone, one overpressure-relief channel opening being arranged within the pumping chamber inlet/outlet opening and the other one within the pumping chamber outlet/inlet opening. The connection channel is thereby arranged remote to the pump's inlet and outlet ports which are preferably arranged at the periapsis of the pumping chamber, the periapsis being located, compared to the apoapsis, at the opposite end of the pumping chamber, with respect to the eccentricity axis. In a preferred embodiment of the invention, the bidirectional automotive positive displacement pump is an oil pump for pumping oil within an oil circuit of a vehicle.

In another preferred embodiment of the invention the bidirectional automotive positive displacement pump is a gerotor pump.

The bidirectional automotive positive displacement pump according to the invention allows a rotation of the pump rotor in both rotational directions, thereby guaranteeing an automatic release of the overpressure from the discharge zone to the suction zone independently of the rotational direction of the pump rotor and without any additional switching mechanisms or control units for switching or controlling the overpressure-relief valve.

One embodiment of the invention is described with reference to the enclosed drawings, wherein figure 1 shows a schematic longitudinal cross-sectional view of a bidirectional automotive positive displacement pump according to the invention, and figure 2 shows the bidirectional automotive positive displacement pump of figure 1 in a schematic transversal cross-sectional view through the overpressure-relief channel.

Figure 1 shows a bidirectional automotive gerotor oil pump 10 with a rotatable two-part pump rotor 15 comprising an inner rotor hub 151 and an outer rotor ring 152. The inner rotor hub 151 is an external geared wheel provided with six equiangularly arranged external teeth. The outer rotor ring 152 is an internal geared ring provided with seven equiangularly arranged internal teeth. The inner rotor hub 151 is co-rotatably connected to a driveshaft 11 which can be driven, for example, by an electric motor, by an internal combustion engine or any other suitable drive means.

The pump rotor 15 is arranged within a pumping chamber 13 which is substantially defined by a static pump housing 12. The inner rotor hub 151 is eccentrically arranged with respect to the outer rotor ring 152, wherein the external teeth of the inner rotor hub 151 mesh with the internal teeth of the outer rotor ring 152 so that the outer rotor ring 152 is mechanically driven by the inner rotor hub 151. Thereby, six pumping compartments 131 are defined within the pumping chamber 13. The rotational movement of the pump rotor 15 causes each pumping compartment 131 to continuously change its volume during one rotation.

The pumping chamber 13 comprises a crescent-shaped pumping chamber inlet/outlet opening 17 and a crescent-shaped pumping chamber outlet/inlet opening 18 which is arranged and defined mirror-symmetrically the to the pumping chamber inlet/outlet opening 17 with respect to an eccentricity axis E defining the eccentricity direction of the inner rotor hub 151 with respect to the outer rotor ring 152.

The bidirectional automotive gerotor oil pump 10 is driveable in both rotational directions. Depending on the rotational direction of the pump rotor 15 a suction zone SZ and a discharge zone DZ are defined, wherein the suction zone SZ is that zone within the pumping chamber 13, where the pumping compartments 131 increase their volume and wherein the discharge zone DZ is that zone within the pumping chamber 13, where the pumping compartments 131 decrease their volume. The increasing volume of the pumping compartments 131 within the suction zone SZ causes oil to be sucked into the pumping chamber 13, in particular into each pumping compartment 131, for example, from an external oil tank. The decreasing volume of the pumping compartments 131 within the discharge zone DZ causes the oil to be discharged from each pumping compartment 131 and thereby to be discharged from the pumping chamber 13. If the pump rotor 15 rotates clockwise, the suction zone SZ is with respect to figure 1, located in the right half of the pumping chamber 13, wherein the discharge zone DZ is located in the left half of the pumping chamber 13, the left half and the right half being symmetrically separated by the eccentricity axis E. The pumping chamber outlet/inlet opening 18 then defines the pumping chamber inlet opening through which the oil is sucked into the pumping chamber 13. Accordingly, the pumping chamber inlet/outlet opening 17 defines the pumping chamber outlet opening through which the oil is discharged into, for example, an oil circuit of a vehicle.

If the pump rotor 15 rotates counter-clockwise, the suction zone SZ is, with respect to figure 1, located in the left half of the pumping chamber 13, wherein the discharge zone DZ is located in the right half of the pumping chamber 13. Accordingly, the pumping chamber inlet/outlet opening 17 defines the inlet opening through which the oil is sucked into the pumping chamber 13, wherein the pumping chamber outlet/inlet opening 18 defines the outlet opening through which the oil is discharged into, for example, an oil circuit of a vehicle.

The pumping chamber inlet/outlet opening 17 is at the distal end of the periapsis P of the pumping chamber 13 fluidically connected to an inlet/outlet port Pl of the pumping chamber 13, wherein the pumping chamber outlet/inlet opening 18 is at the distal end of the periapsis P of the pumping chamber 13 fluidically connected to an outlet/inlet port P2 of the pumping chamber 13. Analogue to the pumping chamber inlet/outlet opening 17 and the pumping chamber outlet/inlet opening 18, the inlet/outlet port Pl and the outlet/inlet port P2 each define either an inlet or an outlet of the pumping chamber 13 depending on the rotational direction of the pump rotor 15. The pumping chamber 13 further comprises a neutral zone 19 which is a substantially rectangular bar 191 that is arranged between the pumping chamber inlet/outlet opening 17 and the pumping chamber outlet/inlet opening 18 at the distal end of the apoapsis A of the pumping chamber 13. The neutral zone 19 in coaction with the pump rotor 15 fluid ically separates the suction zone SZ from the discharge zone DZ.

The pumping chamber inlet/outlet opening 17 and the pumping chamber outlet/inlet opening 18 are fluidically connected by an overpressure-relief channel 20 which bypasses the neutral zone 19 at the apoapsis-sided end of both the pumping chamber inlet/outlet opening 17 and the pumping chamber outlet/inlet opening 18.

Figure 2 shows the routing of the overpressure-relief channel 20 within the pump housing 12. The overpressure-relief channel 20 is defined by two boreholes 201, 202, wherein the two boreholes 201, 202 extend in a borehole plane B being arranged orthogonally to an axial end surface 153 of the pump rotor 15 and orthogonally to the eccentricity axis E. The first borehole 201 extends from the pumping chamber inlet/outlet opening 17 under angle of about 35° with respect to the axial end surface 153 of the pump rotor 15 towards the inside of the pump housing 12 and towards a separating plane S which runs both through the eccentricity axis E and through the rotational axis of the pump rotor 15, the separating plane S thereby symmetrically separating the pumping chamber inlet/outlet opening 17 and the pumping chamber outlet/inlet opening 18. The second borehole 202 extends from the pumping chamber outlet/inlet opening 18 under an angle of about 35° with respect to the axial end surface 153 of the pump rotor 15 towards the inside of the pump housing 12 and towards the separating plane S. As a result, the angle between the first borehole 201 and the second borehole 202 is 110°. The borehole 201 comprises a first overpressure-relief channel opening 203 at the pumping chamber inlet/outlet opening 17. The borehole 202, accordingly, comprises a second overpressure-relief channel opening 204 at the pumping chamber outlet/inlet opening 18. Of course, the overpressure-relief channel 20 can alternatively be differently shaped or routed within the pump housing 12. For example, the overpressure-relief channel 20 can be defined by a linear channel being casted into the pump housing 12.

The bidirectional automotive gerotor oil pump 10 further comprises a pressure-actuated overpressure-relief valve 25 being arranged within the pump housing 12. The overpressure-relief valve 25 comprises a substantially cylindrical overpressure-relief valve body 26 being slidably arranged within a cylindrical overpressure-relief valve body supporting bore 28 which is defined within the pump housing 12. The fit of the overpressure-relief valve body 26 within the overpressure-relief valve body supporting bore 28 is relatively tight to avoid a leakage or to minimise the leakage of oil from the overpressure-relief channel 20 into the overpressure valve body supporting bore 28. The orientation of the overpressure-relief valve supporting bore 28 defines the sliding direction of the overpressure-relief valve body 26 along an overpressure-relief valve actuating axis D which is the centre axis of the overpressure-relief valve body supporting bore 28. The overpressure-relief valve actuating axis D is arranged within the separating plane S and is arranged parallel to the axial end surface 153 of the pump rotor 15, i.e., is arranged also rectangularly to the rotational axis of the pump rotor 15. Thereby, the overpressurerelief valve actuating axis D is arranged rectangularly with respect to a flow direction F of the pressure relief channel 20, the flow direction F being defined by a linear axis through the centres of each overpressure-relief channel opening 203, 204 and not by the boreholes 201, 202. The centre of the overpressure-relief valve body supporting bore 28 is arranged at the intersection point of the centrelines of the two boreholes 201, 202 at the separating plane S. The two boreholes 201, 202 extend into the overpressure-relief valve body supporting bore 28, so that the two boreholes 201, 202 are fluidically connected to each other via the overpressure-relief valve body supporting bore 28. Alternatively, the overpressure-relief valve actuating axis D can be differently orientated, for example, the overpressure-relief valve actuating axis D can be orientated under an angle between 0° and 90° with respect to the rotational axis of the pump rotor 15, unless the overpressure-relief valve actuating axis D is still rectangularly arranged with respect to the flow direction F.

As shown in figure 1, the overpressure-relief valve body 26 is mechanically biased by a helical compression spring 27 which is arranged within the overpressure-relief valve body supporting bore 28 at that side of the overpressure-relief valve body 26 which is remote to the overpressurerelief channel 20 so that the compression spring 27 pushes the overpressure-relief valve body 26 along the overpressure-relief valve actuating axis D into the overpressure-relief channel 25, the overpressurerelief valve body 26 thereby closing the overpressure-relief channel 25. The compression spring can alternatively be defined by any other compressible type of spring which is suitable for mechanically biasing the overpressure-relief valve body 26.

The axial end of the overpressure-relief valve body 26 which extends into the overpressure-relief channel 25 is provided with a conical tip 261 which defines a force application surface allowing the pressure force within the overpressure-relief channel 25 to push the overpressure-relief valve body 26 into the overpressure-relief valve body supporting bore 28 against the spring force of the compression spring 27. The conical shape of the tip 261 in combination with the orientation of the sliding direction of the overpressure-relief valve body 26 allow a substantially identical force application of the pressure force from each borehole 201, 202 and also allow a substantially identical force transfer to the overpressure-relief valve body 26. Thereby, the overpressure relief functionality from the pumping chamber inlet/outlet opening 17 to the pumping chamber outlet/inlet opening 18 or, alternatively, from the pumping chamber outlet/inlet opening 18 to the pumping chamber inlet/outlet opening 17 is guaranteed independently of the rotational direction of the pump rotor 15.

Alternatively, to a conical tip 261, the axial end of the overpressure-relief valve body 26 which extends into the overpressure-relief channel 25 can be provided with any shape which defines a suitable force application surface, for example, a convex or hemispherical shape or a concave shape.

The compression spring 27 is at its overpressure-relief valve body sided end centred by a cylindrical protrusion 262 extending from the overpressure-relief valve body 26 into the compression spring 27 at that side being remote to the overpressure-relief channel 25. At its other end, the compression spring 27 is biased by a cylindrical plug 29, which is screwed into thread within the overpressure-relief valve body supporting bore 28. Additionally, an o-ring 291 is arranged between the plug 29 and the pump housing 12 to seal the overpressure-relief valve body supporting bore 28. The axial position of the cylindrical plug 29 defines the preload of the compression spring 27 and thereby defines the overpressure value at which the overpressure-relief valve 25 opens the overpressure-relief channel 20. If the pressure within the pumping chamber 13, in particular within the discharge zone DZ is above the defined overpressure value, the pressure force pushes the overpressure-relief valve body 26 into the overpressure-relief valve body supporting bore 28, so that the pressure relief channel 20 is open. As a result, the oil flows from the high-pressure discharge zone DZ through the two boreholes 201, 202 to the low-pressure suction zone SZ until the pressure within the discharge zone DZ falls below the overpressure value. If the pressure within the discharge zone DZ is below the overpressure value, the spring force of the compression spring 27 pushes the overpressure-relief valve body 26 back into the closing the overpressure-relief channel 25 is closed.