ELECTRIC GEROTOR PUMP AND METHOD FOR PRODUCING SAME

Abstract

An electrically driven gerotor pump has a gerotor which comprises a stationary outer gerotor element with an inner toothing that is axially delimited by two chamber walls, wherein each chamber-forming root section of the inner toothing is paired with a pressure valve which is connected to the outlet. The gerotor also comprises an inner gerotor element with an outer toothing which is guided in the outer gerotor element in a circumferential manner on an eccentric section of the shaft and is mounted in a rotatable manner so as to mesh with the inner toothing.

Claims

1. An electrically driven gerotor pump comprising: a pump housing in which a shaft is rotatably mounted and in which a gerotor, an inlet and an outlet are included; an electric drive with a motor stator and a motor rotor, which is connected to the shaft and which rotationally drives the gerotor; wherein the gerotor comprises a stationary outer gerotor element with a plurality of internal teeth which is axially delimited by two chamber walls, each chamber-forming root portion of the internal teeth having associated therewith a pressure valve communicating with the outlet; and an inner gerotor element with a plurality of external teeth which is circumferentially guided and rotatably mounted on an eccentric portion of the shaft in the outer gerotor element so as to meshingly engage the internal teeth.

2. The electrically driven gerotor pump according to 1, wherein the eccentric portion of the shaft on which the inner gerotor element is circumferentially guided and rotatably mounted is formed as an eccentric extension on a free end of the shaft.

3. The electrically driven gerotor pump according to 2, wherein a bearing of the shaft is arranged in the housing in a single axial shaft portion and comprises at least two rows of roller bodies.

4. The electrically driven gerotor pump according to claim 1, wherein a link between the inlet and the chamber-forming root portions of the internal teeth of the outer gerotor element extends through the free end of the shaft, a control slot in the eccentric extension and a radial branch to root portions of the external teeth (33b) in the inner gerotor element.

5. The electrically driven gerotor pump according to claim 1, wherein a chamber wall closes an open axial end of the pump housing and includes orifices of the inlet and outlet.

6. The electrically driven gerotor pump according to claim 1, wherein the pressure valves are formed by radial opening slots in the outer gerotor element which are covered with respect to an annular outlet chamber around the outer gerotor element by clasp-like bent sheet-metal parts with a turnaround section.

7. The electrically driven gerotor pump according to claim 1, wherein the chamber walls have a surface structure with a regular or irregular pattern applied at a depth of preferably 1 to 2 m on the front faces facing the gerotor.

8. The electrically driven gerotor pump according to claim 1, wherein on inner faces the pump housing has axial portions with cylindrical lateral surfaces, which fit in a fixing manner to a cylindrical outer circumferential portion of a shaft seal, a bearing of the shaft, at least one of the two chamber walls and the outer gerotor element.

9. A method for producing the electrically driven gerotor pump according to claim 8, comprising the steps of: press-fitting, in this axial order, the shaft seal, the shaft bearing including the shaft, a first front-face chamber wall and the stationary outer gerotor element into the pump housing; intermediately or subsequently sliding an eccentric extension of the shaft into a press-fitted bearing of the inner gerotor element; fixing a second front-face chamber wall in the pump housing by press-fitting or welding; intermediately or subsequently press-fitting the other end of the shaft into the motor rotor; and inserting and fixing the motor stator with motor electronics as well as a motor cover.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention is described below in detail based on two embodiments with reference to the accompanying drawings. They show:

[0039] FIG. 1 is a longitudinal section through the electrically driven gerotor pump according to the present invention; and

[0040] FIG. 2 is a cross-section of the gerotor taken from a cutting plane A of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

[0041] The assembly of the electrically driven gerotor pump according to the present invention is described below with reference to FIGS. 1 and 2.

[0042] As may be seen in FIG. 1, the pump housing 1 includes a radially internal housing portion open to one axial side, and a radially exterior housing portion open to the other axial side. A shaft seal 12, a shaft 2 with a bearing 21, as well as the gerotor 3, and the chamber walls 13a, 13b are accommodated in the internal housing portion. The electric drive 5 is accommodated with the stator 51, motor electronics 50 and the motor rotor 52 in the exterior housing portion.

[0043] The motor rotor is connected with an end section of the shaft 2, situated opposite of the gerotor 3, and radially surrounds the internal housing portion or axially reaches across it towards the shaft center. The motor stator 51 is fixed around the motor rotor 52 against an inner surface of the outer wall of the exterior housing portion at the pump housing 1. An open drive-side end of the pump housing 1 is closed by a motor cover 15 in which motor electronics 50 with a circuit board, power electronics with power supply terminals, and a pump ECU are embedded.

[0044] A shaft bearing 21 is arranged between the shaft circumference and an inner lateral surface i.e., shell surface, of the internal housing portion at an axial portion of the shaft 2 accommodated in the pump housing 1. The shaft bearing 21 corresponds to the type of water pump bearing known from its use in centrifugal pumps. The shaft bearing 21 includes two axially adjacent rows of roller bodies 20a and 20b. A row of roller bodies 20a with spherical roller bodies, circumferentially guided between two opposing rounded grooves in the shaft 2 and the shell of the bearing 21, absorbs radial and axial forces at the shaft 2. A row of roller bodies 20b with cylindrical roller bodies, corresponding to a needle bearing, absorbs radial forces and ensures a sufficient absorption of breakdown torque at the shaft axis despite a low axial distance between the bearing positions.

[0045] At a free end of the shaft 2 behind the shaft bearing 21, an eccentric shaft extension 23, which has a smaller circumference than the shaft circumference and whose central axis of the circle circumference is eccentrically displaced towards a shaft axis, extends in an axial direction further into the pump housing 1. The assembly of the gerotor 3 is accommodated in an axial extension portion of the shaft extension 23 between the same and the pump housing 1.

[0046] The gerotor 3 includes an outer gerotor element 31 and an inner gerotor element 30. The outer gerotor element 31 is stationarily fixed in an internal lateral surface, i.e., shell surface, of a flange portion of the pump housing 1 and comprises internal teeth 33a. Within the outer gerotor element 31, the inner gerotor element 30 comprising external teeth 33b is arranged on the eccentric shaft extension 23. The inner gerotor element 30 is rotatably mounted on the eccentric shaft extension 23 with a sliding bearing 32 and is circumferentially guided, when the shaft 2 rotates, by the eccentric displacement of the shaft extension 23 to the shaft axis, i.e., the axis of rotation of the shaft 2, on a circular path within the stationary outer gerotor element 31. Meanwhile, the inner gerotor element 30 and the outer gerotor element 31 meshingly engages in a way that is characteristic for gerotor types.

[0047] The gerotor 3 is axially delimited by two chamber walls 13a and 13b as shown in FIG. 1. In a radial area of the stationary outer gerotor element 31, in which the crescent-shaped working chambers of the internal teeth 33a are located, the chamber walls 13a and 13b are in stationary surface contact with the front faces of the outer gerotor element 31. At the same time, the chamber walls 13a and 13b are in sliding contact with the front faces of the inner gerotor element 30 in the same radial area. In this way, the pumping medium is enclosed between the internal teeth 33a and the external teeth 33b at the axial delimitation.

[0048] On the eccentrically guided circular path of the inner gerotor element 30, the latter rolls off the external teeth 33b. At the same time, a circumferential, endless series of gradually engaging and releasing displacement actions takes place in the area of the meshing engagement in the crescent-shaped working chambers formed in the root portions of the internal teeth 33a of the outer gerotor element 31. An entry and an exit, described below, are provided for the pumping medium into and out of each working chamber, and the principle of operation of a circumferential displacement device is created.

[0049] An inlet bore, extending as a blind hole through the chamber wall 13b in the eccentric extension 23 of the shaft 2, extends along a rotation axis of shaft 2 and simultaneously forms the inlet 14 of the pump. As illustrated in FIGS. 1 and 2 from different perspectives, the eccentric extension 23 has a control slot 24 that, within an axial portion of the inner gerotor element 30, takes up an arc segment of the circumference of the eccentric extension 23 stretching into the inlet bore. A radial branch of entry ducts 34 is formed in the inner gerotor element 30, extending between an intersection of the circumferential control slot 24 and the root portions of the external teeth 33b.

[0050] A rotational angle range, to which the control slot 24 is cut out or opened, is directed, in the eccentric extension 23, to the side of the meshing engagement where the volumes of the crescent-shaped working chambers in the internal teeth 33a increase, i.e., on a rearward side with respect to the circumferential direction of the eccentric extension 23. The control slot 24 thereby controls a filling of the working chambers such that always those working chambers, of which the volumes increase again after the meshing engagement, are connected with the inlet 14 of the pump via an allocated entry duct 34. In contrast, an extension of the rotational angle range of the control slot 24 is selected such that a connection between the inlet 14 and such entry ducts 34 allocated to working chambers with decreasing volumes before and during the meshing engagement is blocked.

[0051] Exit ducts, which exit from the root points of the internal teeth 33a, are formed towards the radially opposite side of the working chambers as radial opening slots 41 in the stationary outer gerotor element 31. The opening slots 41 are part of a plurality of back pressure valves or pressure valves 4, the number of which corresponds to the working chambers of the internal teeth 33a. The pressure valves 4 are formed by the radial opening slots 41 and several elastic bent sheet-metal parts 40. A bent sheet-metal part 40 covers the outlet-side orifice of the opening slots 41 and can thereby be pushed back from a covering position over the orifice by a pre-determined pressure in each opening slot 41.

[0052] As shown in FIG. 2, the bent sheet-metal parts 40 have a cross-section with a turnaround section for forming a double-layer clasp shape. To be more precise, the bent sheet-metal parts 40 furthermore comprise, in the cross-section, a bulge in a sheet-metal layer in order to create a gap between the free ends of the double-layer clasp shape, which effects an elastic bias corresponding to a bending beam or a cantilever against the exit orifice of an opening slot 41. In the area of the free ends, i.e., opposite of the turnaround section, each bent sheet-metal part 40 respectively covers one opening slot 41 and is furthermore spread into an annular exit chamber 17 in a pre-stressed manner. In addition, the bent sheet-metal parts 40 are fixed using an interlocking engagement between an elevation of the turnaround section and a corresponding cutout in the circumference of the outer gerotor element 31, in order to resist the hydraulic medium bypassing in a circumferential direction.

[0053] The annular exit chamber 17 is formed by an outer circumference or a circumferential step of the outer gerotor element 31 and an inner shell portion of the pump housing 1 or a ring section of the outer gerotor element 31 allocated for this purpose and serves to gather the circumferentially exiting displacement flows and deliver them to an opening of the pump outlet 16. The chamber wall 13b accommodates both the pump outlet 16 and the pump inlet 14.

[0054] As is apparent from FIGS. 1 and 2, the entire pump assembly may be implemented without any screw connections. To this end, the individual elements are press-fitted through the two opposite open sides of the pump housing 1 in an axial order from the shaft seal 12 via the shaft 2 together with the shaft bearing 21, the chamber wall 13a, and the outer gerotor element 31 with the bent sheet-metal parts 40, into the internal housing portion of the pump housing 1 that makes corresponding, dimensionally stable press fittings available as staggered cylindrical inner lateral surfaces. Furthermore, the inner gerotor element 30 is slid onto the eccentric shaft extension 23 together with the press-fitted sliding bearing 32. Then, the chamber wall 13b is either press-fitted or welded, depending on the pressure range the pump is designed for. In the meantime or afterwards, a portion, protruding from the internal housing portion, of the shaft 2 is press-fitted into the motor rotor 52 on the opposite side, and the motor stator 51, together with the motor electronics 50, as well as the motor cover 15, are pushed into the exterior housing portion of the pump housing 1 and fixed.

[0055] The embodiments above are intended to be illustrative and not limiting. Additional embodiments may be within the claims. Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

[0056] Various modifications to the invention may be apparent to one of skill in the art upon reading this disclosure. For example, persons of ordinary skill in the relevant art will recognize that the various features described for the different embodiments of the invention can be suitably combined, un-combined, and re-combined with other features, alone, or in different combinations, within the spirit of the invention. Likewise, the various features described above should all be regarded as example embodiments, rather than limitations to the scope or spirit of the invention. Therefore, the above is not contemplated to limit the scope of the present invention.