Transmission air vent system

An automobile vehicle transmission air vent system includes a first component of a vehicle transmission having a resilient material seal member retained in a cavity created in the first component. A second component of a metal material includes a vent groove facing toward the seal member. A clutch pack of the vehicle transmission is actuated by one of the first component or the second component being displaced into engagement with the clutch pack. The vent groove receives a portion of the seal member in a first displaced position of the displaced one of the first component or the second component defining an air and oil flow path through the vent groove between the first component and the second component. The seal member is positioned outside of the vent groove in a second displaced position of the displaced one of the first component or the second component.

INTRODUCTION

The present disclosure relates to vehicle automatic transmission clutches and brakes.

Automobile vehicles including cars, sport utility vehicles and light duty trucks commonly include a multiple speed automatic transmission. Gear shifts are commonly accomplished using hydraulically actuated pistons that engage or disengage clutches and brakes. When vehicle operation ends and hydraulic pressure is no longer available in the transmission, hydraulic fluid settles to the bottom of the transmission and air in the transmission collects in the upper regions of the transmission. This volume of air in the area of the clutch or brake pistons effects initial operation of the transmission when the vehicle is restarted due to compression of the air by hydraulic fluid pressure flowing to the pistons, which can cause an incomplete gear shift or delay the gear shift.

Resilient material seals are commonly provided between the transmission pistons and structure such as the transmission housing. The seals minimize loss of hydraulic pressure past the pistons, and may prevent outflow of air trapped in the transmission past the pistons. Modifications to the seals have been made to allow air bleed past the pistons. The seals are provided with through holes or grooves which are sized to permit air passage during initiation of transmission operation, with minimal subsequent hydraulic fluid loss. It has been found that these through holes function at nominal operating conditions, but due to resilient material deflection limit air passage outside of the nominal design conditions, thereby preventing or slowing venting of air from the transmission to initiate shifting.

Thus, while current automatic transmission piston seal air vent holes achieve their intended purpose, there is a need for a new and improved system and method for venting air from an automatic transmission prior to an initial clutch engagement.

SUMMARY

According to several aspects, a transmission air vent system includes a first component of a vehicle transmission having a resilient material seal member positioned in a seal member cavity created in the first component. A second component of a metal material has a vent groove formed in the second component. One of the first component or the second component displaces with respect to the other one of the first component or the second component. The vent groove receives a portion of the seal member in a first displaced position of the displaced one of the first component or the second component defining an air and oil flow path through the vent groove between the first component and the second component. The seal member is positioned outside of the vent groove in a second displaced position of the displaced one of the first component or the second component.

In another aspect of the present disclosure, the first component defines a clutch piston; and the second component defines a transmission housing.

In another aspect of the present disclosure, when the seal member is positioned outside of the vent groove in the second displaced position the seal member sealingly engages with the transmission housing.

In another aspect of the present disclosure, the first component defines a dam; and the second component defines a longitudinal body portion of a clutch piston.

In another aspect of the present disclosure, when the seal member is positioned outside of the vent groove in the second displaced position the seal member sealingly engages with the longitudinal body portion of the clutch piston.

In another aspect of the present disclosure, the first component defines a stop; and the second component defines clutch piston.

In another aspect of the present disclosure, when the seal member is positioned outside of the vent groove in the second displaced position the seal member sealingly engages with the clutch piston.

In another aspect of the present disclosure, the vent groove includes a rounded first end and a rounded second end.

In another aspect of the present disclosure, a clearance gap is created between the portion of the seal member and a wall of the vent groove when the vent groove is in the first displaced position, the clearance gap defining the air and oil 13 flow path for air to bleed past the seal member.

In another aspect of the present disclosure, a length of the clearance gap is predefined as a distance between a return position and a stroked position of the displaced one of the first component or the second component.

According to several aspects, a transmission air vent system includes a first component of a vehicle transmission having a resilient material seal member retained in a seal member cavity created in the first component. A second component of a metal material has a vent groove formed in the second component facing toward the seal member. A clutch pack of the vehicle transmission is actuated by one of the first component or the second component being displaced into engagement with the clutch pack. The vent groove receives a portion of the seal member in a first displaced position of the displaced one of the first component or the second component defining an air and oil flow path through the vent groove between the first component and the second component. The seal member is positioned outside of the vent groove in a second displaced position of the displaced one of the first component or the second component.

In another aspect of the present disclosure, the vent groove includes a rounded first end and a rounded second end allowing unimpeded entrance of the seal member into the vent groove and exit of the seal member out of the vent groove between the first displaced position and the second displaced position.

In another aspect of the present disclosure, a length of the vent groove is predefined as a distance between a return position and a stroked position of the displaced one of the first component or the second component.

In another aspect of the present disclosure, a depth of the vent groove is predetermined to create a minimum clearance gap of the vent passage between a free end of the seal member and an inner wall of the vent groove when the seal member is positioned at least partially within the vent groove.

In another aspect of the present disclosure, the first component defines a clutch piston. The second component defines a transmission housing. When the seal member is positioned outside of the vent groove in the second displaced position the seal member elastically deflects to sealingly engage with the transmission housing.

In another aspect of the present disclosure, the first component defines a dam. The second component defines a longitudinal body portion of a clutch piston. When the seal member is positioned outside of the vent groove in the second displaced position the seal member elastically deflects to sealingly engage with the longitudinal body portion of the clutch piston.

In another aspect of the present disclosure, the first component defines a stop. The second component defines clutch piston. When the seal member is positioned outside of the vent groove in the second displaced position the seal member elastically deflects to sealingly engage with the clutch piston.

According to several aspects, a transmission air vent system includes a first component of a vehicle transmission has a resilient material seal member retained in a seal member cavity created in the first component. A second component of a metal material has multiple vent grooves formed at predetermined intervals about a perimeter of the second component, the multiple vent grooves facing toward the seal member. A clutch pack of the vehicle transmission actuated by one of the first component or the second component being displaced into engagement with the clutch pack. A flow passage communicates a pressurized fluid to one of the first component or the second component to displace the one of the first component or the second component. The vent groove receives a portion of the seal member in a first displaced position of the displaced one of the first component or the second component defining an air and oil flow path through the vent groove between the displaced one of the first component or the second component allowing air and oil flow from the flow passage through the air and oil flow path. The seal member is positioned outside of the vent groove in a second displaced position of the displaced one of the first component or the second component blocking flow through the air and oil flow path.

In another aspect of the present disclosure, the vent grooves are formed by removal of a portion of the metal material from a transmission housing, from a piston, from a stop member, or from a dam member.

In another aspect of the present disclosure, the vent grooves are in communication with an air flow passage venting out of the transmission via a transmission housing vent port.

DETAILED DESCRIPTION

Referring toFIG. 1, a transmission air vent system10is provided in an automatic transmission12of a vehicle. Air which collects in upper regions of the transmission12when the vehicle is not operating is automatically vented during vehicle and transmission startup using the transmission air vent system10. To vent air, multiple vent grooves are created across from and facing transmission shift clutch pistons which include at least a first vent groove14, a second vent groove16and a third vent groove18. The vent grooves define micro grooves which can be formed for example using laser cutting, machining, etching, or similar methods and are spaced at equal intervals about a perimeter of a transmission housing, as well as within the transmission12as will be discussed in greater detail in reference toFIGS. 2 through 6herein. Air within the transmission12is vented from internal cavities20of the transmission12out to atmosphere using air and oil flow paths which include the vent grooves. A quantity of the vent grooves in any single component is not limiting, and a minimum of three vent grooves is expected to provide adequate venting.

Referring toFIG. 2and again toFIG. 1, interior components of the transmission12are configured symmetrically about a longitudinal central axis22of the transmission, therefore only an upper half cross section of the transmission is presented, with the following components configured symmetrically about the longitudinal central axis22. A first clutch piston24of a metal material is slidably disposed with respect to an inner wall of the transmission12and when displaced actuates or de-actuates a clutch pack26having multiple clutch friction and reaction plates. A first dam28of a metal material is provided to guide and slidably support the first clutch piston24. A second clutch piston30of a metal material is also slidably disposed within the transmission12and is also actuates or de-actuates the clutch pack26. A stop32of a metal material is provided to act as a position stop for the second clutch piston30. A second dam34of a metal material is provided to guide and slidably support the second clutch piston30. With continuing reference toFIGS. 1 and 2, while the clutch pack26is commonly circumferentially configured about the transmission12and will be provided with multiple vent grooves equidistantly spaced about the perimeter of the body, pistons, stops or dams as discussed below, brake clutches which do not rotate may have only one or several vent grooves positioned at an elevated position, approximately at a 12 o'clock position as viewed inFIG. 1, to allow air venting.

Pressurized hydraulic fluid is provided to actuate the first clutch piston24via a fluid passage36. The fluid passage36communicates with and receives the pressurized hydraulic fluid via a fluid port38provided in a transmission shaft40. When the transmission12is idle, for example when the vehicle engine is not operating, air which is present throughout the internal cavities of the transmission12will rise within the transmission as the hydraulic fluid settles to a transmission sump (not shown). When the engine is started and a transmission gear shift is initiated, air which has accumulated for example in the fluid passage36will compress, interfering with flow of the substantially incompressible hydraulic fluid or oil to the first clutch piston24, thereby limiting rapid actuation of the first clutch piston24when initiating a clutch shift. It is therefore desirable to provide vent paths for the air and a portion of the hydraulic oil to bleed past the various clutch pistons and into an air flow passage42for venting out of the transmission12via a transmission housing vent port44.

Referring toFIG. 3and again toFIGS. 1 and 2, the first clutch piston24is slidably disposed with respect to an inner wall45of a transmission housing46. A fluid receiving cavity48upstream of the first clutch piston24provides exposure to a surface area of the first clutch piston24for the pressurized hydraulic fluid entering the fluid receiving cavity48from the fluid passage36to displace the first clutch piston24in a displacement direction50against an oppositely directed biasing force of a return spring52. Hydraulic fluid is normally prevented from bypassing the first clutch piston24by a seal member54positioned in a seal member cavity56of the first clutch piston24. The seal member54directly contacts and sealingly slides along the inner wall45during displacement of the first clutch piston24within a piston cavity58which opens into the air flow passage42. To provide a passage for air and oil to bleed past the seal member54of the first clutch piston24, a first vent groove60is created in the inner wall45which is described in greater detail in reference toFIGS. 4 and 5. According to further aspects, additional grooves can be provided across from and facing other seal members to promote venting of air within the transmission12which are not limited to clutch pistons. For example, a second vent groove62is created across from and facing a second seal member64of the first dam28, and a third vent groove66is created across from and facing a third seal member68of the stop32.

Referring toFIG. 4and again toFIGS. 2 and 3, a length70of the first vent groove60is predetermined based on a longitudinal displacement of the first clutch piston24in the displacement direction50between a first return position of the first clutch piston24shown inFIG. 4and a second stroked position of the first clutch piston24shown in reference toFIG. 6. The vent grooves such as the first vent groove60include a curved or rounded first end72and a curved or rounded second end74to provide smooth surfaces in contact with the seal member54as the seal member54slides into or out of the first vent groove60along the inner wall45of the transmission housing46. Other vent grooves are similarly configured and therefore are not further discussed herein.

In the first return position of the first clutch piston24a vent passage76is created between a free end78of the seal member54and an inner wall80of the first vent groove60. As hydraulic fluid enters the fluid receiving cavity air within the fluid receiving cavity48is displaced in an air and oil flow path82upstream of the seal member54and transitions to an air and oil flow path84within the vent passage76and will exit in an air and oil flow path86into the air flow passage42for discharge out of the transmission12. As air which may be combined with oil exit and hydraulic pressure builds within the fluid receiving cavity48pressure forces88acting against a face90of the first clutch piston24overcome the biasing force of the return spring52shown inFIG. 3, the first clutch piston24displaces in the displacement direction50.

Referring toFIG. 5and again toFIGS. 1 through 4, a total depth92of the first vent groove60is predetermined to allow for a minimum spacing or clearance gap94of the vent passage76to be maintained between the free end78of the seal member54and the inner wall80when the seal member54is positioned at least partially within the first vent groove60. Normal wear of the free end78of the seal member54is therefore provided for while maintaining air venting capability.

Referring toFIG. 6and again toFIGS. 1 through 4, the first clutch piston24is shown after displacement in the displacement direction50to a piston stroked position. At the piston stroked position, the free end78of the seal member54has exited from the first vent groove60and traversed the rounded second end74of the first vent groove60and compresses as it reaches frictional sealing contact with the inner wall45of the transmission housing46. This sealing contact thereafter blocks air or oil passage between the free end78and the inner wall45.

Referring toFIG. 7and again toFIGS. 1 through 6, vent grooves of the present disclosure are not formed in a seal member to avoid tolerance issues of creating and maintaining cavities in resilient materials. Vent grooves of the present disclosure are therefore formed by removal of metal material from a transmission housing, from a piston, from a stop member, or from a dam member. The first vent groove60provides the air and oil flow path84around the second seal member64. The second vent groove62is created in a longitudinal body portion96extending from the first clutch piston24and provides an air and oil flow path98around the second seal member64. The third vent groove66is created in a body portion100of the second clutch piston30and provides an air and oil flow path102around the third seal member68. A fourth vent groove104is created in a body portion106of the second clutch piston30and provides an air and oil flow path108around a fourth seal member110positioned in the second dam34. These are exemplary positions of vent grooves of the present disclosure, as the disclosure is not limited to the exemplary positions above, and it is noted the air and oil flow paths identified herein also allow for passage of a small volume of oil to pass until the seal members exit from the vent grooves and seat to seal off the air and oil flow paths.

A transmission air vent system of the present disclosure offers several advantages. These include provision of vent grooves in metal components in multiple transmission locations and in multiple different components including a transmission housing, a piston, a stop member, or a dam member. The vent grooves of the present disclosure provide more controlled paths for bleeding air from a transmission than provided from air paths extending directly through resilient material seal members. The vent grooves of the present disclosure can be applied in rotational clutches and in stationary clutches.