US20150098804A1

US20150098804A1 - External actuator for an impeller shroud of a variable water pump

Info

Publication number: US20150098804A1
Application number: US14/508,361
Authority: US
Inventors: Vigel Russalian; Alexander Joseph Morein
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2013-10-07
Filing date: 2014-10-07
Publication date: 2015-04-09
Also published as: DE102014219565A1; DE102014219565B4

Abstract

An external actuator for a variable water pump is provided having an actuator housing with an outer wall with a plurality of radially inwardly directed projections, and a drive ring rotatably mounted in the housing. The drive ring has an internal thread. The projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers that are divided by vanes extending from the drive ring into first and second chamber portions. A control valve controls a flow of pressurized hydraulic fluid to the chambers to rotate the drive ring in both directions or hold it in position. A drive nut having external threads is located within the drive ring and rotation of the drive ring causes an axial displacement of the drive nut. An actuator pin connected to the drive nut extends into the water pump housing to actuate the variable flow impeller.

Description

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Application No. 61/887,497, filed Oct. 7, 2013.

FIELD OF INVENTION

The present invention relates to a drive mechanism suitable for use in variable actuation of an impeller assembly of a variable flow water pump for an internal combustion engine.

BACKGROUND

In automotive applications, there is a push for energy efficiency. Efficiencies can be gained for example, by having a water pump which is deactivated upon cold starting of an engine so that the engine can come up to the running temperature more quickly. Known systems for deactivating a water pump include an impeller assembly with a moveable cover or shroud which covers the vanes of the pump impeller when the water pump is not required. However, in such known systems, an internal actuator has been typically used, requiring the water pump to be substantially re-designed to include special seals for the actuator fluid, and or a separate pump for the actuator if the coolant being moved by the water pump is also used as the drive fluid for the actuator. These are complex mechanisms that require major modifications to the water pump as well as additional space requirements.
Additionally, as the water pump speed is directly correlated to the speed of the engine, the flow from a standard water pump is proportional to the engine speed. However, coolant requirements in an engine vary greatly based on many factors during regular operation. With the known variable water pumps, the controls do not always allow for specific flow control levels so that the coolant flow can be optimized for efficient engine performance during the various operating conditions, and instead are generally designed for “off” or “on” operation.
It would be desirable to provide a less complex and more reliable actuator arrangement, and in particular an actuator arrangement that limits the modifications required to an existing water pump housing and bearings, that can be simply controlled and allow variable actuation. The arrangement should also allow more precise flow control, while also maintaining a small space requirement, low weight, and low cost.

SUMMARY

Briefly stated, an external actuator is provided for a variable water pump which includes a housing and variable flow impeller located in the housing that is connected to a drive shaft. The external actuator includes an actuator housing having an outer wall with a plurality of radially inwardly directed projections. A drive ring is rotatably mounted in the housing and has an internal thread. The radially inwardly directed projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers. A plurality of radially outwardly extending vanes are located on the drive ring, with one of the vanes extending into each of the hydraulic chambers and contacting an inner surface of the outer wall to divide each of the hydraulic chambers into first and second chamber portions. A control valve is provided to control a flow of pressurized hydraulic fluid from a pressurized hydraulic fluid source so that (a) pressurized hydraulic fluid flows to the first chamber portions while hydraulic fluid in the second chamber portions is allowed to drain, causing the drive ring to rotate in a first direction, (b) pressurized hydraulic fluid flows to the second chamber portions while hydraulic fluid in the first chamber portions is allowed to drain, causing the drive ring to rotate in a second direction, opposite the first direction, or (c) hydraulic fluid in the first and second chamber portions is held in both of the chamber portions, fixing the drive ring in position. A drive nut having external threads is located within the drive ring, with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut. At least one actuator pin is connected to the drive nut and is adapted to extend into the water pump housing to actuate the variable flow impeller.
Using this arrangement, modifications to the existing water pump housing are limited due to the external actuator arrangement located outside of the housing, with only limited modifications to the water pump being required for attachment of the actuator housing and for one or more actuator pins to extend into the housing and actuate the variable flow impeller.
In another aspect, the internal and external threads are multi-lead threads, and the drive ring is adapted to rotate less than 180°. More preferably, there are four of the hydraulic chambers provided, and four of the vanes extend from the drive ring into the hydraulic chambers, and the drive ring is adapted to rotate less than 90° in order to actuate the variable flow impeller.
In one preferred embodiment, the actuator housing is mounted to the front of the water pump housing and has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft. Alternatively, it can be located on the back side of the water pump housing.
Preferably there are a plurality of actuator pins connected to the drive nut. In order to provide for a fail-safe operation of the water pump, a return spring is preferably located around each of the actuator pins so that the drive nut is biased to a position in which the variable flow impeller provides for full flow of coolant through the water pump.
Preferably, the internal and external threads on the drive ring and the drive nut are not self-locking.
Preferably, the variable flow impeller includes an impeller fixed to the drive shaft and an axially displaceable shroud, and the at least one actuator pin is adapted to be connected to the shroud for axial movement of the shroud in order to vary an output of the water pump. In one preferred arrangement, the pins extend through the housing into the pump chamber and are connected to the shroud and the shroud does not rotate within the water pump. In an alternate arrangement, the shroud is rotatable with the impeller, and the at least one actuator pin is connected to a contact ring that presses against the shroud in order to move the shroud to a deactivated position. Preferably a return spring is provided in order to move the shroud to a position allowing the water pump to provide a full flow of coolant. Preferably, a slide bearing or coating is provided on at least one of the contact ring or the shroud in a contact region between the contact ring and the shroud in order to prevent wear and increase the life of the variable water pump.
In another aspect, a variably actuatable water pump is provided having a pump housing with a pump chamber. A drive shaft extends through the pump housing from a drive side of the water pump to the pump chamber, with a drive wheel connected to a drive side end of the drive shaft. A variable flow impeller is located in the pump chamber, including an axially fixed impeller part connected to the drive shaft and an axially movable shroud, movable relative to the axially fixed impeller part from a first position in which blades connected to the impeller part are exposed in order to pump coolant, to a second position in which the blades are covered in order to prevent pumping of the coolant. An external actuator is connected to the pump housing. The external actuator includes an actuator housing having an outer wall with a plurality of radially inwardly directed projections. A drive ring is rotatably mounted in the housing and has an internal thread. The radially inwardly directed projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers. A plurality of radially outwardly extending vanes are located on the drive ring, with one of the vanes extending into each of the hydraulic chambers and contacting an inner surface of the outer wall to divide each of the hydraulic chambers into first and second chamber portions. A control valve is provided to control a flow of pressurized hydraulic fluid from a pressurized hydraulic fluid source so that (a) pressurized hydraulic fluid flows to the first chamber portions while hydraulic fluid in the second chamber portions is allowed to drain, causing the drive ring to rotate in a first direction, (b) pressurized hydraulic fluid flows to the second chamber portions while hydraulic fluid in the first chamber portions is allowed to drain, causing the drive ring to rotate in a second direction, opposite the first direction, or (c) hydraulic fluid in the first and second chamber portions is held in both of the chamber portions, fixing the drive ring in position. A drive nut having external threads is located within the drive ring with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut. At least one actuator pin is connected to the drive nut and extends into the water pump housing to axially move the shroud between the first and second positions.
Preferably, the variable water pump is provided on an internal combustion engine, and the actuator assembly has a hollow center and is adapted to be fastened to the water pump housing about the drive shaft in a space between the drive wheel and the pump housing. This space is typically open in internal combustion engines and thus an actuator can be provided without increasing an axial length of the internal combustion engine arrangement.
Preferably, one or more seals are located between the actuator pin(s) and the pump housing at the areas where the pins enter the pump housing.
Preferably, the control valve is connected to a pressurized hydraulic fluid source which can be the engine oil lubrication system of the internal combustion engine in order to provide pressurized hydraulic fluid to the first chamber portions or the second chamber portions in order to move the drive ring in the desired direction so that the drive nut axially shifts the actuator pin(s) in order to move the shroud between the fully covered and fully uncovered positions of the water pump impeller. The control valve preferably allows the position of the shroud to be held by preventing the flow of hydraulic fluid from either the first or second chamber portions, and thus allows the shroud to be maintained in any desired position between the fully uncovered and the fully covered positions of the impeller vanes so that the volume flow of coolant through the water pump can be regulated depending upon various running conditions of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings:

FIG. 1 is cross-sectional view through a first embodiment of a variable water pump having an external actuator.

FIG. 2 is a front view, partially in cross-section, through the actuator housing of FIG. 1.

FIG. 3 is a detailed elevational view, in cross-section, of the drive ring used in the external actuator shown in FIG. 1.

FIG. 4 is a perspective detailed view of the drive nut and actuator pins used in the external actuator shown in FIG. 1.

FIG. 5 is a partially exploded schematic view showing an alternate arrangement of the drive nut, actuator pins and a contact ring used to actuate the impeller shroud in a variable water pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. “Axially” refers to a direction along the axis of a shaft or rotating part. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import.
Referring to FIG. 1, a cross-section view through a variable water pump 12 having an external actuator assembly 10 is shown. The variable water pump 12 includes a housing 14 with a pump chamber 15 defined therein. A variable flow impeller assembly is provided having an impeller 16 as well as a shroud 18 which can be shifted axially to expose more or less of the vanes of the impeller 16 in order to control the flow of coolant through the water pump 12. The shroud 18 may or may not form a seal with the water pump housing 14 or possibly a volute element (not shown) opposite of the impeller 16, fully cutting off fluid flow to the impeller blades. The impeller 16 is mounted on a drive shaft 22 of the an integral shaft bearing assembly 20, which is provided as a unit including the shaft 22 and the bearings 24 that can then be assembled into the water pump housing 14. A seal 26 is preferably provided around the drive shaft 22 to prevent coolant from escaping from the pump chamber 15 along the drive shaft 22. A drive wheel 28 is preferably connected to a drive side of the drive shaft 22.
The external actuator 10 is preferably mounted to the water pump 12 in an area between the drive wheel 28 and the water pump housing 14. The actuator 10 includes a housing 30 having a base plate 32 and a cover plate 34. The base plate 32 can optionally be formed on the front of the water pump housing 14 as an integral part. As shown in FIG. 2, the base plate 32 preferably has a generally circular outer wall 35 with a plurality of radially inwardly directed projections 36 extending from an inside surface of the outer wall 35. A drive ring 40 is rotatably mounted in the actuator housing 30. The drive ring 40 has an internal thread 42, shown in detail in FIG. 3, located on the inner surface. As shown in FIG. 2, the radially inwardly directed projections 36 from the actuator housing outer wall 35 contact an outer surface of the drive ring 40 to define a plurality of hydraulic chambers 38. Seals can be located at the ends of the projections 36 in order to provide sealing contact. A plurality of radially outwardly extending vanes 44 are located on the drive ring 40, with one of the vanes 44 extending into each of the hydraulic chambers 38 and contacting an inner surface of the outer wall 35 to divide each of the hydraulic chambers 38 into first and second chamber portions 46, 48, as shown in FIG. 2. The side edges of the vanes 44 preferably sealingly engage the inner facing side surfaces of the base plate 32 and cover plate 34, and the radially outer edges of the vanes 44 contact the inner surface of the outer wall 35 in a sealing manner via seals or optionally by providing the vanes 44 as movable parts on the drive ring 44 which are biased outwardly from the drive ring 40 and against the inner surface of the outer wall 35. While four chambers 38 are shown, this number can be varied along with the number of vanes 44 that divide the chambers 38 into the first and second chamber portions 46 and 48
A drive nut 60 having external threads 62 is located within the drive ring 40, with the external threads 62, for example as shown in FIG. 4, engaging the internal threads 42 of the drive ring 40 as shown in FIG. 3 so that rotation of the drive ring 40 causes an axial displacement of the drive nut 60. As shown in FIG. 1, at least one actuator pin 64 is connected to the drive nut 60 and extends through openings 65 in the water pump housing 14 to actuate the variable flow impeller, preferably via being connected to the shroud 18 as shown. In the arrangement of FIG. 1, the shroud 18 is axially movable as indicated by the arrow, but is rotationally fixed. Seals 68 are arranged around the actuator pins 64 in the pump housing 14.
Preferably, the internal and external threads 42, 62 are multi-lead threads, as illustrated for example in FIG. 3, and the drive ring 40 is adapted to rotate less than 180°. In the preferred embodiment shown in FIGS. 1-4, there are four of the hydraulic chambers 38 and four of the vanes 44 located on the drive ring 40. Using this arrangement, the drive ring 40 is adapted to rotate less than 90° in order to shift the drive nut 60 and the attached actuator pin(s) 64 a sufficient axial distance so that the shroud 18 can be moved between a fully covered position, as shown in FIG. 1, in which the variable water pump flow is restricted due to the vanes of the impeller 16 being covered by the shroud 18, to an uncovered position which the shroud 18 is shifted (to the left from the position shown in FIG. 1) by movement of the drive ring 40 in the clockwise direction when viewed in connection with FIG. 2 so that the drive nut 60 is shifted axially and raises the shroud 18.
Return springs 66 are preferably provided around the actuator pins 64 so that in the event of failure of hydraulic fluid being delivered to the chamber portions 46, 48, the drive nut 60 is shifted (to the left in FIG. 1) and the shroud 18 uncovers the vanes of the impeller 16 so that the water pump 12 is placed in a fail-safe operating position.
Referring to FIG. 2, a control valve 54 is provided to control a flow of pressurized hydraulic fluid from a pressurized hydraulic fluid source, preferably an engine oil lubrication circuit, in order to control the external actuator 10. The control valve 54 includes an inlet I, two control connections A, B and a tank outlet T, as indicated. The control valve 54 can be adjusted to a first state to provide a flow of pressurized hydraulic fluid to the first chamber portions 46 while hydraulic fluid in the second chamber portions 48 is allowed to drain via the drain T, causing the drive ring 40 to rotate in a first direction, here represented as a clockwise direction in FIG. 2. The valve 54 is adjustable to a second state wherein pressurized hydraulic fluid flows to the second chamber portions 48 while hydraulic fluid in the first chamber portions 46 is allowed to drain to tank T, causing the drive ring to rotate in a second direction, opposite the first direction, illustrated in FIG. 2 as the counter clockwise direction. The control valve 54 is also adjustable to a third state such that hydraulic fluid in the first and second chamber portions 46, 48 is held in the chamber portions 46, 48, fixing the drive ring in position. A controller, which can be the ECM or a separate controller adjusts the position of the control valve 54 to allow a variable positioning of the shroud 18 in the water pump in order to control or regulate the flow of coolant from the water pump 12 based on engine operating conditions. A drain connection, not shown, can also be provided from the actuator housing 30 so that any seepage of oil from the actuator assembly 10 can be directed back to the engine oil lubricant reservoir.
In order to allow the return springs 66 to return the drive nut 60 to the fail-safe position, the internal and external threads 42, 62, are not self-locking threads. Accordingly, during a low pressure or failure of delivery of pressurized hydraulic fluid to the control valve 54, the return springs 66 can move the drive nut 60 to a position in which the shroud 18 does not cover the vanes on the impeller 16.
In the first preferred embodiment, the variable flow impeller assembly includes the impeller 16 which is fixed to the drive shaft 22 and the shroud 18 is axially displaceable via the actuator pin(s) 64 connected to the drive nut 60. This allows axial movement of the shroud 18 in order to control an output flow from the water pump 12. This arrangement is preferably used in connection with an on/off operation of the variable water pump 12.
For a flow regulating arrangement, one preferred alternate arrangement of the water pump and the connection of the actuator 10 to the variable flow impeller assembly is shown in FIG. 5. Only the differences from the arrangement shown in FIG. 1 are shown in detail. Here the drive nut 60′ is shown with actuator pins 64 connected to a contact ring 74. The water pump housing is schematically represented by the dashed line 14, with the seals 68 also being represented around the actuator pins 64 where they extend through the water pump housing 14. The contact ring 74 is adapted to contact the shroud 18′ which is arranged facing away from the drive wheel side of the water pump 12 for axial movement over the impeller 16 which is connected to the drive shaft (not shown in FIG. 5). Preferably, a slide bearing or anti-friction coating indicated at 78 is provided on the contact ring 74. This can be in the form of a PTFE coating or layer. This reduces wear and friction in a contact region between the contact ring 74 and the shroud 18.
A return spring 79 is preferably provided so that the shroud 18′ is biased toward the left in FIG. 5 to a fail-safe position so the vanes of the impeller 16 are exposed in order to pump coolant in the event that the actuator 10 cannot operate. While the spring 79 is shown in one end position, those of ordinary skill in the art will appreciate from the present disclosure that the spring could be located at other axial positions to provide the same effect of biasing the shroud 18′ to the fail-safe position. When a lower coolant flow or no coolant flow is desired, the drive nut 60′ is axially displaced via the actuator assembly 10 so that the shroud 18′ is moved to the right in FIG. 5 against the pressure of the spring 79 partially or fully covering the vanes of the impeller 16 to either regulate or stop the flow of coolant through the water pump 12.
The actuator assembly 10 can be provided separately or in conjunction with a water pump 12 providing a variably actuatable water pump assembly including the features of the water pump 12 and the actuator assembly 10. This arrangement provides the ability to have a variable water pump 12 in approximately the same envelope as an existing water pump by utilizing a portion of the space between the drive wheel and the water pump housing. This allows for improvements in engine efficiency and performance while maintaining a small space requirement and low cost.
Having thus described a preferred embodiment in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.

Claims

What is claimed is:

1. An external actuator for a variable water pump which includes a housing and variable flow impeller located in the housing that is connected to a drive shaft, the external actuator comprising:

an actuator housing having an outer wall with a plurality of radially inwardly directed projections;

a drive ring rotatably mounted in the housing, the drive ring having an internal thread, the radially inwardly directed projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers, a plurality of radially outwardly extending vanes are located on the drive ring, one of the vanes extending into each of the hydraulic chambers and contacting an inner surface of the outer wall to divide each of the hydraulic chambers into first and second chamber portions;

a control valve adapted to control a flow of pressurized hydraulic fluid from a pressurized hydraulic fluid source so that (a) pressurized hydraulic fluid flows to the first chamber portions while hydraulic fluid in the second chamber portions is allowed to drain, causing the drive ring to rotate in a first direction, (b) pressurized hydraulic fluid flows to the second chamber portions while hydraulic fluid in the first chamber portions is allowed to drain, causing the drive ring to rotate in a second direction opposite the first direction, or (c) hydraulic fluid in the first and second chamber portions is held in the chamber portions, fixing the drive ring in position; and

a drive nut having external threads located within the drive ring with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut, and at least one actuator pin connected to the drive nut that is adapted to extend into the water pump housing to actuate the variable flow impeller.

2. The external actuator for a variable water pump of claim 1, wherein the internal and external threads are multi-lead threads, and the drive ring is adapted to rotate less than 180°.

3. The external actuator for a variable water pump of claim 2, wherein there are four of the hydraulic chambers and four of the vanes located on the drive ring, and the drive ring is adapted to rotate less than 90°.

4. The external actuator for a variable water pump of claim 1, wherein the actuator housing has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft.

5. The external actuator for a variable water pump of claim 1, wherein there are a plurality of the actuator pins, and a return spring is located around each of the actuator pins that are adapted to move the drive nut to a failsafe position.

6. The external actuator for a variable water pump of claim 1, wherein the internal and external threads are not self-locking.

7. The external actuator for a variable water pump of claim 1, wherein the variable flow impeller includes an impeller fixed to the drive shaft and an axially displaceable shroud, and the at least one actuator pin is adapted to be connected to the shroud for axial movement of the shroud in order to vary an output of the water pump.

8. The external actuator for a variable water pump of claim 7, wherein the shroud is rotatable with the impeller, and the at least one actuator pin is connected to a contact ring that presses against the shroud.

9. The external actuator for a variable water pump of claim 8, further comprising a slide bearing or coating on at least one of the contact ring or the shroud in a contact region between the contact ring and the shroud.

10. A variably actuatable water pump, comprising:

a pump housing having a pump chamber;

a drive shaft extending through the pump housing from a drive side of the water pump to the pump chamber, with a drive wheel connected to a drive side end of the drive shaft;

a variable flow impeller located in the pump chamber, including an axially fixed impeller part connected to the drive shaft and an axially movable shroud, movable relative to the axially fixed impeller part from a first position in which blades connected to the impeller part are exposed in order to pump coolant, to a second position in which the blades are covered in order to prevent pumping of the coolant;

an external actuator connected to the pump housing, including:

a drive ring rotatably mounted in the housing, the drive ring having an internal thread, the radially inwardly directed projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers, a plurality of radially outwardly extending vanes are located on the drive ring, one of the vanes extending into each of the hydraulic chambers and contacting an inner surface if the outer wall to divide each of the hydraulic chambers into first and second chamber portions;

a drive nut having external threads located within the drive ring, with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut, and at least one actuator pin connected to the drive nut that extends into the water pump housing to axially move the shroud between the first and second positions.

11. The variable water pump of claim 10, wherein the actuator housing has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft in a space between the drive wheel and the pump housing.

12. The variable water pump of claim 10, further comprising a seal located between the at least one actuator pin and the pump housing.

13. The variable water pump of claim 10, further comprising a return spring located around the at least one actuator pin that presses against the pump housing and the drive nut to move the drive nut and the shroud to the first position as a failsafe.