PUMP ASSEMBLY FOR SYNCHRONOUS PRESSURIZATION OF TWO FLUID CIRCUITS

Abstract

The invention relates to a pump assembly for the synchronous pressurization of two fluid circuits. Two internal gear pumps are disposed together in a pump housing and rotationally driven by drive shafts thereof. Pinions of the pumps are located in an associated pump chamber and engage in an internal gear thereof. The pump chambers of the internal gear pumps are separated from each other by a common separating wall or partition, which is designed as a separate housing part and engages in a hollow cross-section of a housing part forming the circumferential wall of one of the internal gear pumps. Suction channels and pressure channels associated with the internal gear pumps transition into a radially extending longitudinal section in the pump housing following an axial longitudinal section in the lateral boundary wall of the associated pump chamber. According to the invention, a suction channel and a pressure channel of one of the internal gear pumps are integrated in the separating wall.

Description

PRIOR ART

The invention is based on a pump assembly for synchronous pressurization of two fluid circuits as generically defined by the preamble to independent claim 1.

One such pump assembly is known for instance from German Patent Disclosure DE 10053991 A1 as a so-called pump insert for a hydraulic, wheel slip control vehicle brake system; different brake circuits of the brake system, with diagonal brake circuit distribution, are supplied by the two internal gear pumps of the pump insert. The two internal gear pumps are partitioned off from one another by a separately embodied partition of the multi-piece housing and a common drive shaft passes transversely through them. The pinions of the two gear pumps are slipped onto this drive shaft and joined to it in a manner fixed against relative rotation via a slaving connection. To seal off the pump chambers of the adjacent gear pumps from one another, two shaft sealing rings are inserted, spaced apart from one another, into adapted annular chambers of the partition bore. If some brake fluid passes through the shaft passage that is thus sealed off at both ends, then the fluid is carried away via a ventilation bore that is disposed between the shaft sealing rings with radial extension in the partition. For inclusion of the two internal gear pumps in the respective associated brake circuit, each internal gear pump is also assigned one suction channel and one pressure channel, which viewed in the axial direction are located on opposite end regions of the pump assembly, extend essentially radially, and with angling of their end region open into the suction side and compression side, respectively, of the associated pump chamber. The pairs of channels belonging to the internal gear pumps, because of their lateral disposition next to the face ends of the pump assembly, have a considerable spacing from one another, which must also be taken into account in the engineering design and dimensioning of the pump housing.

DISCLOSURE OF THE INVENTION

The pump assembly of the invention having the characteristics of independent claim 1 has the advantage over the prior art that the axial spacing of the pairs each of a suction channel and a pressure channel of the internal gear pumps from one another can be reduced markedly. As a result, a more-compact structure of the pump assembly can be attained and may be associated with a simplified embodiment of the line system for the two fluid circuits. The suction channel and the pressure channel can furthermore be disposed in a technically simpler manner with accurate positioning in the partition, since the partition acts as an axial runup disk for the wheel sets of the pumps. Hence the partition before installation in the pump housing is accessible from all sides, which for instance makes metal-cutting machining for creating or machining the hollow channels markedly easier. The surrounding housing parts furthermore no longer need to be joined at a distance of their face ends from one another on the circumference of the partition by means of rolled-in regions or the like; instead, the dividing plane can extend next to the partition, and the annular face ends of the housing parts to be joined together can be butt-joined. As a result, the connection intensity of the hollow-cylindrical housing parts can be improved substantially, so that the pump assembly does not have to be slid into a pump housing that stabilizes it.

By the provisions and refinements recited in the dependent claims, advantageous embodiments of and improvements to the pump assembly defined by independent claim 1 are possible.

Especially advantageously, the suction channels and the pressure channels of both internal gear pumps are integrated with the partition. As a result, the pressure channels and suction channels of both internal gear pumps are located quite close together, which makes a correspondingly compact structure of the pump assembly possible. If in addition the leakage channel is integrated with the partition, then the leakage channel can be shortened considerably and requires no outlet opening of its own, if it discharges into an outflow bore of one or both suction channels of the partition. If all the fluid channels of the pump assembly that are immediately adjacent to the pump chambers or fluidically communicate with them are located, inside the partition along with the leakage channel, then the fluid channels can be introduced with a precise fit into the “partition” workpiece with little production effort or expense and in the case of integrally cast fluid channels can be easily machined.

Despite the integration of two suction channels and two pressure channels, the partition can have a relatively slight thickness, if the four fluid channels are disposed essentially in the same cross-sectional region of the partition. So that this is possible, the fluid channels can each be offset from one another by 90° in the partition, as a result of the fact that the internal gear pumps of the pump assembly are rotated by 180° from one another. This has the positive side effect that compressive forces acting in opposite directions in the internal gear pumps largely cancel one another out.

If a valve assembly is provided in the line system of one of the fluid circuits to be supplied, then this valve assembly can be integrated directly with the associated fluid channel of the partition. This valve assembly can include one valve or even two valves in one or both of the fluid circuits to be supplied. Equipping the fluid circuit or circuits with two valves each, which is technically especially appropriate, happens if a pressure reduction valve is disposed in the suction channel or channels of the partition and an overpressure valve is disposed in the pressure channel or channels of the partition. For this valve assembly, space that is already present anyway inside the partition is thus utilized, so that an external disposition of the valves in the system of the associated fluid circuit can be dispensed with. This saves a corresponding amount of space outside the pump assembly and may simplify the line system connected to it.

In a preferred embodiment, the partition comprises a cylindrical disk with plane-parallel face ends that extend at a right angle to the center longitudinal axis of the disk and parallel to one another, and it is pressed into a cylindrical hollow cross section of the associated housing part. If the plane face ends are polished which because of the disk shape can be done inexpensively with high surface quality, then they can serve directly as runup faces for the gear wheel sets. By pressing the disk into a cylindrical hollow cross section, for instance with a press fit, a position-securing installed position of the disk in the housing can be ensured without additional fastening means. The pressing-in operation must be done such that the radial ends of the fluid channels of the disk, after the pressing-in operation, are aligned with corresponding fluid channels in the housing. By the selection of a suitable press fit, a connection that is fluid-tight without additional sealing means can optionally be created between the outer circumference of the disk and the inner circumference of the housing.

The pressed-in partition can advantageously be braced axially between opposed annular face ends of two housing parts, and the outside diameter of one of the housing parts is largely equivalent to the outside diameter of the partition. The tubular end region adapted in diameter to the partition can then, similarly to the partition, be pressed or thrust into the larger tubular end region of the other housing part, after which the tube ends overlap longitudinally in telescoping fashion. Given adequate axial securing, a very stable combination is obtained by putting together the hollow housing parts and the partition.

To ensure that the tooth gaps of the wheel sets in the internal gear pumps will be reliably sealed off on their face ends remote from the partition, one thrust pad, of a plastic material that is usual for thrust pads, can be disposed on each of the ends of the pump assembly; it is axially braced on the face ends of the associated wheel set on the one hand and on the opposed bore wall of the pump chamber on the other. Preferably, each of the thrust pads is structurally united with an associated bearing sleeve for the drive shaft, which leads to a desirable reduction in the number of parts in the pump assembly. The bearing sleeve itself may be embodied in one piece with the thrust pad and can itself form a slide bearing. However, the bearing sleeve may alternatively receive or surround either a roller bearing or bearing shells of a slide bearing.

An advantageous embodiment of the invention is shown in the drawings and described below in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic center longitudinal section through a pump assembly of the invention.

FIG. 2 shows a pump chamber of the pump assembly of FIG. 1 in a side view.

FIG. 3 shows a vertical section through a partition of the pump assembly, taken along the section line in FIG. 1.

EMBODIMENT OF THE INVENTION

As can be seen from FIG. 1, a pump assembly 10 includes two internal gear pumps 11 and 11′, which are located laterally directly beside one another and are disposed in a common pump housing 12. In the installed state, the pump assembly 10 is component of a pressure control unit, not shown, for a vehicle brake system that has diagonally distributed brake circuits, and the internal gear pumps 11 and 11′ are each responsible for supplying pressure to one of the brake circuits in the course of brake interventions, known per se, for ABS or ESP applications. The common pump housing 12 is composed on the outside of two cuplike hollow housing parts 13 and 14, which each define one pump chamber of the internal gear pump 11 and 11′, respectively, on three sides and are joined together with their end regions overlapping longitudinally. Between these housing parts 13 and 14, a partition 15 is fitted in as an internal housing part, which defines the pump chambers of the two internal gear pumps 11 and 11′ on the fourth side with its face ends. The partition 15 comprises a cylindrical disk with plane-parallel face ends, which is pressed into a cylindrical hollow cross section of the associated housing part 13.

The drive of the two internal gear pumps 11 and 11′ is effected via a common drive shaft 16, which is driven to rotate by a direct current motor flanged to the outside; via a sealed-off shaft passage, the drive shaft 16 is introduced into the housing 12 and passes through coaxial bearing bores, which are recessed out of the face ends of the housing parts 13 and 14 as well as out of the partition 15. At the middle bearing point, the drive shaft 16 is slidingly supported rotatably directly in the bore of the partition 15, while at the lateral bearing points the drive shaft 16 is slidingly rotationally supported via a bearing sleeve 17 and a bearing sleeve 17′ of plastic. The bearing sleeves 17 and 17′ are each embodied hollow-cylindrically and rest by positive engagement between the circumference of the drive shaft 16 and the associated bore wall of the respective housing part 13 and 14.

Between the bearing points, the drive shaft 16, adjacent to the bearing sleeve 17 and 17′, respectively, passes through a respective thrust pad 18 and 18′, which is embodied in one piece with the associated bearing sleeve 17 and 17′, and after that passes through a central insertion opening in the associated pinion 19 and 19′ of the internal gear pumps 11 and 11′, and finally passes through an associated shaft seal ring 20 and 20′, which is pressed into an associated, stepped widened portion of the bearing bore for the drive shaft 16 in the partition 15.

As can be seen in conjunction with the side view of the pump chamber of the internal gear pump 11 in FIG. 2, the drive shaft 16, with an approximately hexagonal cross section that has gently rounded edges, passes through a hollow cross section, fitting it, of the pinion 19, thus providing a slaved connection secure against relative rotation between the pinion 19 and the drive shaft 16. The outer toothing of the pinion 19 meshes with the inner toothing of an internal gear 21, which in turn is supported by its round outer circumference rotatably in a bore portion of the associated housing part 13. The valve assembly is located exactly in the center in the upper region of the inner toothing internal gear 21, as a result of which the tip circles of the pinion 19 and internal gear 21 define an overall crescent-shaped annular chamber. This annular chamber is designed mirror-symmetrically with respect to the vertical center plane of the wheel set in which plane the axes of rotation of the pinion 19 and internal gear 21 extend. In the crescent-shaped annular chamber, a filler piece 22 is supported pivotably in the center by means of a centrally disposed axle bolt 23. However, the pivotability is limited to a minimum, since the outer circumferential side of the filler piece 22 is in contact with little play with the covered tooth tips of the inner toothing of the internal gear 21, and the inner circumferential side of the filler piece 22 rests with little play on the covered tooth tips of the pinion 19. In the partition 15, a suction channel 24 can also be seen on the right-hand suction side of the internal gear pump 11, and an associated pressure channel 25 for the brake fluid can be seen on the left-hand compression side.

Now, if with an internal gear pump 11 that is completely filled with brake fluid and is vented, the drive shaft 16 rotates clockwise, for instance by means of an electric geared motor, then the pinion 19 rotates synchronously with it, as does the internal gear 21 in the same direction because of the valve assembly with the pinion 19. Since the tooth gaps covered by the filler piece 22 are sealed off on one face end by the thrust pad 18 subjected to corresponding axial force and on the opposite face end by running up against the partition 15, the hollow volumes of brake fluid received by the tooth gaps can be transported, given adequate sealing of the tooth tips from the filler piece 22, can be transported, with a corresponding pressure increase, from the suction channel 24 to the pressure channel 25 of the internal gear pump 11. The sealing required for this between the tooth tips and the filler piece 22 comes about solely because of a defined circumferential play of the filler piece 22, by which play, in operation, a pressure distribution over the circumferential length of the filler piece 22 is brought about, which leads to an adequate rotational force of the filler piece 22 about the center longitudinal axis of the axle bolt 23. Upon clockwise rotation of the pinion 19, the result is accordingly also a clockwise rotational force on the filler piece 22, as a result of which the inner circumferential side of the filler piece 22 is pressed down by the lever arm on the left of the axle bolt 23 onto the covered tooth tips of the pinion 19, and the outer circumferential side is pressed down by the lever arm on the right of the axle bolt 23 onto the tooth tips of the internal gear 21. As a consequence of the forcing of the lever ends of the filler piece 22 between the toothing of the pinion 19 and the toothing of the internal gear 21, there is a contrary equal contact pressure of the filler piece 22, as is required for adequate sealing between the covered tooth tips and the filler piece 22.

As has already been explained, the internal gear pump 11′ is jointly driven by the drive shaft 16, since the pinion 19′ is also penetrated by the drive shaft 16 and is connected to it in a manner fixed against relative rotation via a slaved connection corresponding to the pinion 19. The geometry of the internal gear pump 11′ per se is also largely the same as that of the internal gear pump 11, and the wheel set comprising the pinion 19′ and the internal gear 21′ is disposed in a manner rotated by 180° relative to the wheel set comprising the pinion 19 and the internal gear 21. Because of this 180° relative rotation of the wheel set arrangement in the internal gear pumps 11 and 11′, or in other words an oppositely eccentric disposition, the resultants of the pressure forces on the compression side of the internal gear pump 11 and 11′ act in opposite radial directions, as indicated in FIG. 1 by thick arrows. Thus these resultant radial forces largely cancel one another out, making more-favorable dimensioning of the pump housing 12 possible, since in its dimensioning, now essentially only the torques acting as a result of the axial offset of the resultants have to be taken into account in terms of engineering.

It is understood that with the oppositely eccentrically disposed internal gear pumps 11 and 11′, the thrust pads 18 and 18′ and the filler pieces 22 and 22′, respectively, must also be rotated 180° relative to one another. The same is true for the suction channel 24′ and the pressure channel 25′, which are also integrated with the partition 15 and are open toward the pump chamber of the internal gear pump 11′.

As can be seen in the sectional view through the partition 15 in FIG. 3, the suction channel 24 discharging into the pump chamber of the internal gear pump 11 and the associated pressure channel 25 are located essentially in the same cross-sectional plane as the suction channel 24′, discharging into the pump chamber of the internal gear pump 11′, and the associated pressure channel 25′. Moreover, they are disposed radially so far in the direction of the outer circumference that they can be in axial overlap with the pressed-in shaft seal rings 20 and 20′ without impairing the function. As a result, the partition 15 overall needs only a slightly greater thickness than is necessary anyway for the integration of the axial and radial channel portion of the respective suction channel 24 and 24′. In the same cross-sectional region, there is additionally a leakage channel 26 as well, for carrying away brake fluid that has forced its way into the bearing bore of the partition 15; the leakage channel begins at the bearing bore of the partition 15 between the shaft seal rings 20 and 20′, extends diagonally through the partition 15, and discharges into the two suction channels 24 and 24′. It can also be seen that a respective pressure reduction valve 27 and 27′ is disposed in the suction channels 24 and 24′, and a respective overpressure valve 28 and 28′ is disposed in the pressure channels 25 and 25′, and the arrangement is made such that all the valves 27, 27′, 28 and 28′ received by the partition 15 are located inside voids in the partition in every switching state.

The overpressure valves 28 and 28′ are structurally identical, oppositely disposed overpressure valves of conventional construction, in which a ball is located in the flow path of the pressure channel and is pressed against its sealing seat by the force of a restoring spring. As soon as the fluid pressure at the sealing seat is greater than the spring force, the ball is positively displaced, and the flow path of the pressure channel is thus opened up. The pressure channels 25 and 25′, which with their radial longitudinal portion are integrated with the partition 15 diametrically to one another and near the circumference, are thus, given corresponding pressure, moved radially outward counter to the spring loading and as a result communicate fluidically with the associated brake circuit, or given a corresponding change in pressure conditions are closed again by spring force and as a result fluidically disconnected from the brake system.

By comparison, the pressure reduction valves 27 and 27′ are embodied as linear slide valves, which pass transversely through the radial flow path of the suction channel 24 and 24′, respectively, with a tapered control portion and are likewise inserted in the opposite direction. The slide directions of the pressure reduction valves 27 and 27′ are parallel to one another and to the radial longitudinal portions of the pressure channels 25 and 25′. The slides of the pressure reduction valves 27 and 27′ are also each kept in an axial outset position by the spring force of an associated helical compression spring, but this outset position corresponds to the open position of the pressure reduction valve 27 and 27′. The helical compression spring is braced here on the respective annular end face of a piston portion adjoining the control portion, which piston portion is guided in sliding fashion, with sealing occurring, in its bore of the partition 15, and the control portion, with an end region that has a middle bore, engages an associated blind bore in the partition 15. If the fluid pressure in the suction channel 24 and 24′ now rises above a predetermined limit value, then the fluid that has flowed into the blind bore presses against the annular face end of the control portion and thus displaces the piston of the pressure reduction valve 27 and 27′ counter to the force of the restoring spring; and the flow path of the suction channel 24 and 24′ is increasingly shifted by the advancing control portion and brings about a corresponding throttling of the fluid flow. In the present case in which the internal gear pumps 11 and 11′ are associated with brake circuits of a brake system, the components of the pressure reduction valves 27 and 27′ are adapted to one another in such a way that a pressure limit value of approximately 10 bar on the suction side of the internal gear pumps 11 and 11′ cannot be exceeded. As a result, unnecessary frictional forces in the internal gear pumps 11 and 11′, which would have an adverse effect both on the efficiency of the pump assembly 10 and in terms of its wear, can be avoided. If fluid from the suction channel 24 and 24′ flows past the sealing plane of the pressure reduction valve 27 and 27′ into the guide bore thereof, then it can flow away jointly with fluid from the leakage channel 26, since the guide bore is open toward the circumference of the partition 15 and thus acts additionally as an outflow opening.

Claims

1-10. (canceled)

11. A pump assembly for synchronous pressurization of two fluid circuits, which pump assembly includes two internal gear pumps, disposed together in a pump housing and driven to rotate via a respective drive shaft thereof, pinions of the pumps are located in an associated pump chamber and are in toothed engagement with a respective internal gear, and the pump chambers of the internal gear pumps are partitioned off from one another by a common partition which is embodied as a separate housing part and which engages a hollow cross section of a housing part that forms the circumferential wall of one of the internal gear pumps, and suction channels and pressure channels associated with the internal gear pumps transition, after an axial longitudinal portion in a lateral boundary wall of the associated pump chamber, into a longitudinal portion that extends radially in the pump housing, the suction channel and the pressure channel of one of the internal gear pumps being integrated with the partition.

12. The pump assembly as defined by claim 11, wherein the suction channels and the pressure channels of both internal gear pumps are integrated with the partition.

13. The pump assembly as defined by claim 11, wherein a leakage channel, which is in fluidic communication with an outflow opening of a suction channel in the partition, is integrated with the partition.

14. The pump assembly as defined by claim 12, wherein a leakage channel, which is in fluidic communication with an outflow opening of a suction channel in the partition, is integrated with the partition.

15. The pump assembly as defined by claim 11, wherein each suction channel and each pressure channel of the partition is disposed in a same cross-sectional region thereof.

16. The pump assembly as defined by claim 12, wherein each suction channel and each pressure channel of the partition is disposed in a same cross-sectional region thereof.

17. The pump assembly as defined by claim 13, wherein each suction channel and each pressure channel of the partition is disposed in a same cross-sectional region thereof.

18. The pump assembly as defined by claim 11, wherein a valve assembly is provided in at least one suction channel or pressure channel of the partition.

19. The pump assembly as defined by claim 12, wherein a valve assembly is provided in at least one suction channel or pressure channel of the partition.

20. The pump assembly as defined by claim 13, wherein a valve assembly is provided in at least one suction channel or pressure channel of the partition.

21. The pump assembly as defined by claim 18, wherein a pressure reduction valve is disposed in each suction channel of the partition, and an overpressure valve is disposed in each pressure channel of the partition.

22. The pump assembly as defined by claim 19, wherein a pressure reduction valve is disposed in each suction channel of the partition, and an overpressure valve is disposed in each pressure channel of the partition.

23. The pump assembly as defined by claim 11, wherein the partition is a cylindrical disk with plane-parallel face ends, which is pressed into a cylindrical hollow cross section of an associated housing part.

24. The pump assembly as defined by claim 12, wherein the partition is a cylindrical disk with plane-parallel face ends, which is pressed into a cylindrical hollow cross section of an associated housing part.

25. The pump assembly as defined by claim 23, wherein the pressed-in partition is braced axially on an annular face end of the associated housing part, and on the face end thereof opposite it, an annular face end of the housing part adjoining the associated housing part is braced, and tubular end regions of the housing parts are joined together in telescoping fashion, overlapping longitudinally.

26. The pump assembly as defined by claim 24, wherein the pressed-in partition is braced axially on an annular face end of the associated housing part, and on the face end thereof opposite it, an annular face end of the housing part adjoining the associated housing part is braced, and tubular end regions of the housing parts are joined together in telescoping fashion, overlapping longitudinally.

27. The pump assembly as defined by claim 11, wherein wheel sets of the internal gear pumps comprised of the pinion and internal gear, on their end faces oriented toward the ends of the pump assembly, are axially acted upon by an associated thrust pad, which also includes a bearing sleeve for the drive shaft.

28. The pump assembly as defined by claim 12, wherein wheel sets of the internal gear pumps comprised of the pinion and internal gear, on their end faces oriented toward the ends of the pump assembly, are axially acted upon by an associated thrust pad, which also includes a bearing sleeve for the drive shaft.

29. The pump assembly as defined by claim 27, wherein the thrust pad and the bearing sleeve are plastic and are embodied in one piece.

30. The pump assembly as defined by claim 28, wherein the thrust pad and the bearing sleeve are plastic and are embodied in one piece.