Seal assembly for torque converter

A seal assembly includes a seal carrier configured to be coupled to and rotate with a shaft. The seal carrier defines at least three annular recesses configured to receive annular seals. The seal assembly further includes at least three annular seals configured to provide a seal between the seal carrier and a non-rotating housing defining an inner surface having a circular cross-section. One of the at least three seals is received in each of the at least three annular recesses, and one of the at least three seals has a smaller cross-sectional area than a cross-sectional area of at least one of the other seals.

TECHNICAL FIELD

The present disclosure relates to a seal assembly and, more particularly, to a seal assembly for a torque converter.

BACKGROUND

It is often desirable to provide a coupling between the rotating output of a prime mover and the rotating input of a driven load that permits a disparity between the rotational speed of the rotating output of the prime mover and the rotating input of the driven load. For example, in order to permit continuous rotation of the output of the prime mover even when it is desirable to stop rotation of the input of the driven load, it is desirable to provide a coupling that permits the rotational output of the prime mover to continue despite the input of the driven load being stopped.

An example of such a coupling is a torque converter, which provides a hydrodynamic fluid coupling between the rotating output of a prime mover and the rotating input of a driven load. For example, a machine such as a vehicle may include an internal combustion engine and a transmission, with the output of the internal combustion engine coupled to an input of the transmission by the torque converter.

A torque converter generally includes an input coupling for coupling the output of a prime mover to the input of the torque converter, and an output shaft for coupling the output of the torque converter to a driven load, such as a transmission. The torque converter further includes a housing containing fluid, such as hydraulic fluid. Within the housing, the input coupling is coupled to a pump including an impeller for pumping the fluid in the housing. The torque converter further includes a turbine coupled to the output shaft of the torque converter. The impeller of the pump, driven by the input coupling, pumps fluid through the turbine, thereby causing the turbine to rotate and drive the output shaft of the torque converter and the input of, for example, a transmission. By virtue of the fluid coupling provided by the interaction between the impeller and the turbine, the output of the prime mover may continue to rotate the input coupling of the torque converter, even when the output shaft of the torque converter is stopped.

The output shaft of the torque converter extends generally through the center of the impeller and the turbine, which rotate about the longitudinal axis of the output shaft. As a result, it is desirable to provide a fluid seal between the output shaft of the torque converter and the housing of the torque converter to prevent leakage of the fluid from the housing at the interface between the output shaft and the housing. However, such seals are subjected to high levels of stress as a result of rotation of the output shaft relative to the non-rotating portion of the housing. In addition, such seals are subjected to high levels of stress due to high fluid pressure on one side of the seal, resulting from high fluid pressure in the torque converter housing relative to the low pressure on the opposite side of the seal. As a result, such seals may tend to degrade over time, and possibly leak fluid, which is undesirable. Therefore, it may be desirable to develop a seal for a torque converter output shaft that improves the seal at the interface between the output shaft and housing.

One attempt to provide a seal for a torque converter is described in U.S. Pat. No. 6,145,842 to Zellers et al. (“the '842 patent”). The '842 patent discloses a torque converter having a lip seal abutting the torque converter impeller control pump drive hub. The drive hub is rotatably supported in a transmission housing. The '842 patent discloses that oil from the drive hub side of the bushing passes through the bushing into a chamber sealed from atmosphere by the lip seal. The bushing has a control passage for exhausting a portion of the oil from the control pump side prior to reaching the chamber.

Although the lip seal arrangement disclosed in the '842 patent may provide a seal for preventing oil from leaking between the torque converter housing and the impeller control pump drive hub, it may suffer from a number of possible drawbacks. For example, the seal disclosed in the '842 patent does not provide a seal between the torque converter output shaft and the housing of the torque converter. The seal assembly and method disclosed herein may be directed to mitigating or overcoming the possible drawback set forth above.

SUMMARY

In one aspect, the present disclosure includes a seal assembly including a seal carrier configured to be coupled to and rotate with a shaft. The seal carrier defines at least three annular recesses configured to receive annular seals. The seal assembly further includes at least three annular seals configured to provide a seal between the seal carrier and a non-rotating housing defining an inner surface having a circular cross-section. One of the at least three seals is received in each of the at least three annular recesses, and one of the at least three seals has a smaller cross-sectional area than a cross-sectional area of at least one of the other seals.

In another aspect, the present disclosure includes torque converter including a housing configured to be rotated by a prime mover, and an impeller coupled to the housing and configured to rotate with the housing and pump fluid. The torque converter further includes a turbine configured to rotate as a result of fluid pumped by the impeller, and a stator associated with the impeller and the turbine. The stator is configured to direct fluid flow between the turbine and the impeller. The torque converter further includes an output shaft coupled to the turbine and configured to be rotated by the turbine, and a non-rotating housing coupled to the stator and configured to receive the output shaft, wherein the non-rotating housing defines an inner surface having a circular cross-section. The torque converter further includes a seal assembly coupled to the output shaft. The seal assembly includes a seal carrier coupled to and configured to rotate with the output shaft, the seal carrier defining at least first and second annular recesses configured to receive annular seals, and an annular groove between the first and second annular recesses. The seal assembly further includes a first annular seal and a second annular seal configured to provide a seal between the seal carrier and the non-rotating housing, wherein the first and second annular seals are received respectively in the first and second annular recesses. The non-rotating housing defines a fluid passage configured to provide flow communication between the annular groove of the seal carrier and a location exterior with respect to the non-rotating housing, such that the first annular seal is exposed to a lower fluid pressure than the second annular seal, wherein the first annular seal has a smaller cross-sectional area than a cross-sectional area of the second annular seal.

In still a further aspect, the present disclosure includes a method for providing reduced fluid pressure between a seal assembly and a lip seal, wherein the seal assembly is coupled to a shaft configured to rotate within a non-rotating housing. The method includes providing a seal assembly including a seal carrier defining at least three annular recesses having at least three annular seals received respectively therein, wherein the seal carrier is coupled to and rotates with the shaft, and the annular seals provide a seal between the seal carrier and the non-rotating housing. The method includes supplying fluid to the seal assembly at a first pressure to provide lubrication between the annular seals and the seal carrier. The method further includes providing a fluid passage in the non-rotating housing in flow communication with an annular groove between two of the at least three annular seals, such that fluid pressure between the two annular seals is at a second pressure that is less than the first pressure, wherein the lip seal is coupled to the non-rotating housing at a position opposite at least one other annular seal with respect to the two annular seals, and wherein one of the two annular seals has a smaller cross-sectional area than a cross-sectional area of another of the two annular seals.

DETAILED DESCRIPTION

FIG. 1is a partial section view of an exemplary embodiment of a torque converter10configured to couple an output12of a prime mover14to an input member16of a driven mechanism18. For example, prime mover14may be an internal combustion engine or an electric motor having an output shaft20configured to be coupled to an input coupling22of exemplary torque converter10. As shown inFIG. 1, for example, output shaft20is coupled to a flywheel24, which, in turn, is coupled to a rotating housing26of exemplary torque converter10. In the exemplary embodiment shown, flywheel24, driven by prime mover14, is coupled to and drives rotating housing26. Exemplary torque converter10includes an output shaft28coupled to input member16of driven mechanism18via an output yoke30. Driven mechanism18may be an input of a machine such as, for example, a transmission of a machine such as a vehicle, pump, compressor, or generator, or any other machine configured to be driven by a prime mover.

In the exemplary embodiment shown inFIG. 1, torque converter10includes a housing32configured to house the moving parts of torque converter10, as well as fluid used to provide a fluid coupling between input member16and output shaft28of torque converter10. Housing32contains rotating housing26, which is coupled to a pump34having an impeller36configured to pump fluid within rotating housing26. Torque converter10further includes a turbine38opposite impeller36. Turbine38is coupled to output shaft28, for example, via a splined coupling, such that as turbine38rotates, output shaft28also rotates. Exemplary torque converter10shown inFIG. 1further includes a stator40configured to re-direct fluid exiting turbine38back to impeller36of pump34to improve efficiency. Output shaft28rotates about longitudinal axis X on a pair of bearings42located at opposite ends of output shaft28, with bearings42being mounted in a fixed manner relative to housing32of torque converter10.

During operation, prime mover14rotates flywheel24, which is coupled to rotating housing26of torque converter10, thereby driving rotating housing26. Impeller36of pump34, being coupled to rotating housing26, rotates about longitudinal axis X and pumps fluid through turbine38. Turbine38includes a plurality of vanes43configured to rotate turbine38about longitudinal axis X as fluid flows through vanes43. Turbine38, by virtue of being coupled to output shaft28of torque converter10, drives output shaft28, which is coupled to driven mechanism18by output yoke30. Thus, the interaction of the fluid being pumped through turbine38by impeller36provides a hydrodynamic fluid coupling between prime mover14and driven mechanism18.

The hydrodynamic fluid coupling permits output12of prime mover14to rotate at a different speed than input member16of driven mechanism18. For example, for machines such as vehicles, prime mover14may operate at a relatively low speed while input member16of the transmission is held in a stopped condition (e.g., by operation of brakes of the vehicle). Pump34of torque converter10pumps fluid through turbine38, but by holding input member16in a stopped condition, the energy of the pumped fluid can be absorbed by heating of the fluid rather than turning turbine38. However, if input member is no longer held in a stopped condition, fluid pumped through turbine38causes it to rotate, thereby rotating output shaft28of torque converter10. As the speed of output12of prime mover14is increased, pump34of torque converter pumps fluid through turbine38at an increasing rate, thereby causing turbine38and output shaft28to rotate at an increasing rate.

In the exemplary embodiment shown, output shaft28rotates about longitudinal axis X on bearings42. Housing32includes a lubricating passage44configured to supply the bearing42located at the end of output shaft28adjacent output yoke30of torque converter10. Lubricant may be provided under pressure to ensure sufficient lubrication and cooling of bearing42. For example, lubricant may be supplied to bearing42at about 70 pounds per square inch.

In order to prevent leakage of lubricant associated with bearing42, exemplary torque converter10includes a seal assembly46configured to provide a fluid seal between output shaft28and an inner surface48of a non-rotating housing50, which is coupled to housing32of torque converter10. In the exemplary embodiment shown, inner surface48of non-rotating housing50defines a circular cross-section.

As shown inFIGS. 1,2A, and2B, exemplary seal assembly46is positioned between bearing42and a longitudinal end of output yoke30. Exemplary seal assembly46includes a seal carrier52configured to be coupled to and rotate with output shaft28. As shown inFIG. 3, seal carrier52defines, for example, at least three annular recesses (e.g., first annular recess54a, second annular recess54b, and third annular recess54c), each configured to receive an annular seal (e.g., first annular seal56a, second annular seal56b, and third annular seal56c, respectively). Seal carrier52may be formed of metal or other materials known to those skilled in the art, and the annular seals may be formed of an elastomeric seal material or other materials known to those skilled in the art. As output shaft28rotates, seal carrier52rotates with the output shaft28, but the annular seals do not rotate with seal carrier52. Rather, they remain stationary and provide a seal between seal carrier52and inner surface48of non-rotating housing50. As a result, the annular seals rotate with respect to respective annular recesses of seal carrier52. Because the annular seals abut and slide against the annular recesses of seal carrier52, the annular seals are lubricated to prevent overheating and/or degradation.

As shown inFIGS. 1,2A, and2B, in order to provide lubricant to the annular seals, exemplary output shaft28includes a lubricating passage58extending along longitudinal axis X. Lubricating passage58terminates at an end wall, and one or more radially extending passages60extend outwardly from lubricating passage58to the external surface of output shaft28at a longitudinal position corresponding to seal assembly46. Lubricant may be supplied to seal assembly46via lubricating passage58and radially extending passage(s)60. For example, according to some embodiments, lubricant may be supplied to seal assembly46at a pressure of as much as about 300-450 pounds per square inch due the pressure in the fluid being pumped through turbine38by pump34.

Referring toFIGS. 2A,2B, and3, exemplary seal carrier52defines an outer cylindrical surface defining an annular groove62located between first annular recess54aand second annular recess54b. In addition, outer cylindrical surface of exemplary seal carrier52defines an annular cavity64located between second annular recess54band a third annular recess54c. Annular cavity64provides an annular lubricating passage between seal carrier52and inner surface48of non-rotating housing50.

As shown inFIGS. 2A,2B, and3, exemplary seal carrier52further defines an inner cylindrical surface defining an inner annular recess66. Inner annular recess66is configured to provide flow communication between radially extending passage(s)60of output shaft28and seal carrier52. Seal carrier52further defines one or more radially extending passages68extending from annular cavity64, thereby permitting lubricant to flow from passage(s)60of output shaft28, into inner annular recess66, through passage(s)68and into annular cavity64. Lubricant in annular cavity64lubricates and cools second and third annular seals56band56cin second and third annular recesses54band54c, respectively.

Lubricant in annular cavity64may be highly pressurized, for example, at a pressure as high as about 300-450 pounds per square inch or more. In contrast, lubricant supplied to bearing42may be at about 70 pounds per square inch. Thus, the pressure drop across third annular seal56cin third annular recess54cmay be about 230 pounds per square inch or more. As a result, lubricant may flow from annular cavity64, across third annular seal54c, to bearing42. In addition, second annular seal56breceived in second annular recess54bis exposed on one side to the pressure in annular cavity64. As a result, a significant amount of lubricant may leak past second annular seal56bto provide lubricant to first annular seal56a.

As shown inFIGS. 2A and 2B, non-rotating housing50may include one or more fluid passages70in flow communication with annular groove62of seal carrier52. Fluid passage(s)70may provide flow communication between annular groove62and a fluid reservoir (not shown) of torque converter10. As a result of flow communication between annular groove62and relief passage(s)70, the fluid pressure of the lubricant between second annular seal56band first annular seal56amay be reduced substantially, for example, to about 90 pounds per square inch. As a result, leakage of lubricant across first annular seal56a, from annular groove62to the opposite side of first annular seal56amay be greatly reduced. According to some embodiments, fluid passage(s)70provide relatively cleaner lubricant to first and second annular seals56aand56bthan lubricant supplied to second and third annular seals56band56cby lubricating passage58and radially extending passage(s)60, which may include debris from other portions of torque converter10.

As shown inFIGS. 2A,2B, and3, in addition to seal assembly46, a lip seal72may be provided between output yoke30and non-rotating housing50at a longitudinal position spaced from first annular seal56a. According to some embodiments, lip seal72may be provided between output shaft28and non-rotating housing50. Lip seal72is received in non-rotating housing50(e.g., and fixed therein via adhesive) and does not rotate with output shaft28or output yoke30. Exemplary lip seal72includes a retainer portion74and a seal portion76, with retainer portion74being received in non-rotating housing50and seal portion76being pressed against output yoke30to prevent lubricant that passes first annular seal56afrom leaking from torque converter10. According to some embodiments, it is intended that a relatively small amount of lubricant pass across first annular seal56afrom annular groove62to the opposite side of first annular seal56ato provide lubricant for seal portion76of lip seal72to prevent overheating and/or degradation.

The exemplary embodiments shown inFIGS. 1-3may result in reduced leakage of lubricant past lip seal72. In particular, the one or more fluid passages70provide reduced the pressure between first and second annular seals56aand56b. As a result, the pressure drop across first annular seal56ais significantly reduced, resulting in less leakage of lubricant past first annular seal56a. As a result, lip seal72, although still receiving a small amount of lubricant (e.g., an amount sufficient to prevent lip seal72from overheating and/or degrading) is able to substantially prevent leakage of lubricant past lip seal72and from torque converter10. In addition, first annular seal56amay result in a reduced likelihood of damage to lip seal72due, for example, to a failure of second annular seal56bthat could result in lubricant under high pressure (e.g., 300-450 psi) spraying directly against lip seal72. According to some embodiments, a relatively less costly seal material may be used for first annular seal56arelative to the seal material used for second annular seal56bas a result of the reduced pressure drop across first annular seal56a.

FIG. 4shows another exemplary embodiment of seal assembly46. Due to the reduced pressure drop across first annular seal56a, it may be possible to reduce the size of first annular seal56arelative to the size of second annular seal56bas shown inFIG. 4. For example, the cross-sectional area of first annular seal56aand/or first annular recess54amay be smaller than the cross-sectional area of second annular seal56band/or second annular recess54b, respectively. For example, the cross-sectional area of first annular seal56aand/or first annular recess54amay be, for example, less than about 90% of the cross-sectional area of second annular seal56band/or second annular recess54b, respectively. For example, according to some embodiments, the cross-sectional area of first annular seal56aand/or first annular recess54amay be less than about 80%, 70%, 60%, 50%, or 40% of the cross-sectional area of second annular seal56band/or second annular recess54b, respectively. This may result in reducing the cost of seal assembly46.

INDUSTRIAL APPLICABILITY

Exemplary seal assembly46disclosed herein may be used, for example, to reduce or prevent leakage of fluid from a torque converter at the interface between the housing and the output shaft of the torque converter. For example, some conventional torque converters may include a seal between the housing and the output shaft, but such seals may result in more fluid leaking from the torque converter than desired. The exemplary seal assembly disclosed herein may mitigate or overcome this drawback,

Exemplary seal assembly46disclosed herein includes at least three annular seals. As a result, annular cavity64between two of the at least three annular seals may be provided with lubricant at a first pressure, and annular groove62between one of the two annular seals and a third of the at least three annular seals may be provided with lubricant at a second pressure that is lower than the first pressure. The lower second pressure is provided by one or more fluid passages70in non-rotating housing50, which serve(s) to provide a lubricant having a relatively reduced pressure to annular groove62. As a result, the third annular seal allows less lubricant to flow to a space between the third annular seal and lip seal72, which serves to reduce the amount of (or prevent) lubricant from leaking from torque converter10. Further, a relatively less costly seal material may be used for first annular seal56arelative to the seal material used for second annular seal56bas a result of the reduced pressure drop across first annular seal56a. In addition, due to the reduced pressure drop across first annular seal56a, it may be possible to reduce the size of first annular seal56arelative to the size of second annular seal56b. As a result, the cost of seal assembly46may be reduced.