Torque converter

A torque converter includes a front cover connected to an engine with a set block, a pump impeller integrally connected to the front cover, a turbine runner facing to the pump impeller and connected to an input shaft of a transmission, a lock-up clutch for engaging/disengaging the front cover relative to the input shaft through a damper, an engaging hydraulic pressure chamber separated from a power transmission hydraulic chamber surrounded by the pump impeller and the front cover, and that engaging pressure of the lock-up clutch is provided into the engaging hydraulic pressure chamber, a front cover hub, a piston inserted so as to slide in the engaging hydraulic pressure chamber, a clutch engaging portion operated to be engaged/disengaged by the piston, plural projection portions being projecting by stamping and welded to the front cover, and an oil path formed between the front cover and the front cover hub among the projection portions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2003-331569, filed on Sep. 24, 2003, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention generally relates to a torque converter including a lock-up clutch. More particularly, the present invention pertains to the torque converter whose cost is reduced without lessening virtual function thereof.

BACKGROUND

Generally, a torque converter transmits engine torque to a transmission through fluid, and such fluid usually causes torque transmitting loss due to fluid friction. To avoid such fluid friction loss, a lock-up clutch provided at the torque converter is engaged for transmitting engine torque when a rotation speed of a pump impeller provided at the input side becomes similar to a rotation speed of a turbine runner provided at the output.

Recently, a locked up condition of the clutch has been expanded for improving fuel consumption. Corresponding to such trend, the torque converter also includes an engaging hydraulic pressure chamber (lock up chamber) between a front cover and a front cover hub for improving the lock up engaging accuracy and a durability of the torque converter, and the number of such torque converter having such chamber has been increased.

A known torque converter is disclosed in U.S. Pat. No. 5,533,602 and SAE 2002-01-0935, which includes a front cover hub processed by forging or grinding and an oil path formed by drilling the front cover hub for providing a hydraulic pressure to the engaging hydraulic pressure chamber. The front cover hub is fixed to a front cover by pressing or welding.

The cost of such torque converter having aforementioned configuration has been increased due to the forging or grinding process applied to the front cover hub.

Thus, a need exists for a torque converter to decrease the cost thereof without lessening the virtual function thereof.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, A torque converter comprises a front cover connected to an engine with a set block, a pump impeller integrally connected to the front cover, a turbine runner facing to the pump impeller and connected to an input shaft of a transmission, a lock-up clutch provided inside the front cover to be in line with a torus portion which is comprised of the pump impeller and the turbine runner in axial direction of the input shaft for engaging/disengaging the front cover relative to the input shaft through a damper, an engaging hydraulic pressure chamber separated from a power transmission hydraulic chamber surrounded by the pump impeller and the front cover integrated therewith, and that engaging pressure of the lock-up clutch is provided into the engaging hydraulic pressure chamber, a front cover hub provided between the front cover and the input shaft, a piston provided at the lock-up clutch and inserted so as to slide in the engaging hydraulic pressure chamber, a clutch engaging portion provided at the lock-up clutch and operated to be engaged/disengaged by the piston, plural projection portions provided at the front cover hub, formed to be projecting toward the front cover side by stamping, and welded to the front cover, and an oil path formed between the front cover and the front cover hub among the projection portions.

According to another aspect of the present invention, A torque converter comprises a front cover connected to an engine, a pump impeller provided at the front cover, a turbine runner facing to the pump impeller and connected to an input shaft of a transmission, a lock-up clutch provided inside the front cover for engaging/disengaging the front cover relative to the input shaft through a damper, a front cover hub provided between the front cover and the turbine runner, and forming an engaging hydraulic pressure chamber into which engaging pressure of the lock-up clutch is provided, a piston provided at the lock-up clutch and inserted so as to slide in the engaging hydraulic pressure chamber, a clutch engaging portion provided at the lock-up clutch and operated to be engaged/disengaged by the piston, and plural portions provided at the front cover hub, formed to be projecting toward the front cover side by stamping, and welded to the front cover.

DETAILED DESCRIPTION

An embodiment of the present invention will be explained hereinbelow referring to attached drawings.FIG. 1illustrates a cross sectional view of a pattern diagram of a torque converter related to the embodiment of the current invention.FIG. 2Aillustrates a plain view simply indicating a front cover hub of the torque converter according to the embodiment of the present invention.FIG. 2B illustrates a cross sectional view of the front cover hub along a line X–X′ inFIG. 2A.FIG. 3illustrates a plane view simply indicating an assembling unit including a front cover, the front cover hub and a drum member of the torque converter according to the present invention.FIG. 4A illustrates an outer plane view simply indicating an assembling unit including set blocks, the front cover, the front cover hub and the drum member.FIG. 4B illustrates a cross sectional view along Y–Y′ line inFIG. 4A.

As shown inFIG. 1, the torque converter10includes the set block20, the front cover30, a pump impeller40, a turbine runner50, a damper60, a lock-up clutch70, an engaging hydraulic pressure chamber80, the front cover hub90, a power transmission hydraulic chamber100, an input shaft110, an oil path120, a one-way clutch130and a stator140.

A plurality of the set block20is provided along the outer peripheral side of the engaging hydraulic pressure chamber80and at the outside of the front cover30as shown inFIG. 1andFIG. 4. A block portion21made of a plate is formed at each set block20including two arcs whose center point is identical to the center point of the front cover30. The set blocks20are provided in pairs relative to the aforementioned center point, in all three pairs of set blocks20are equally spaced on a circumference and welded to the front cover30from the inside of the set blocks20inFIG. 4A. Further, a drive plate (not shown) is screwed into each set block20with bolts, which is meshed with and driven by a pinion gear of a starter for starting the engine.

A configuration of the front cover30connected to the engine (not shown) with the set blocks20(FIG. 1andFIG. 4) will be explained as follows. As shown in the cross sectional view inFIG. 1, the front cover30includes a center portion30a, a front wall (30b,30cand30d), a peripheral wall portion30eand a connecting portion30f. A center piece31whose axis is identical to a crank shaft of the engine is welded to the center portion of the front cover30. The front wall includes a first depressed portion30b, a protuberant portion30cand a second depressed portion30d. The first depressed portion30bdepressed in the right direction inFIG. 4B is formed at outer peripheral side of the center portion30ato be free from a bolt head which is used to fix the drive plate to an edge portion of the crank shaft. The protuberant portion30cprojecting in the left direction inFIG. 4B is formed at outer peripheral side of the first depressed portion30b. The second depressed portion30dis depressed in the right direction inFIG. 4B to be approximately the same level as the fixing surface of the center piece31and formed at an outer peripheral side of the protuberant portion30c. The set block20is attached at the second depressed portion30d. The peripheral wall portion30eis extending in axial direction of the input shaft from the most outer peripheral portion of the front wall (30b,30cand30d). Further, the inner peripheral diameter of the front cover30is increased at the end of the peripheral wall portion30eto form the connecting portion30fat which the pump impeller40is engaged.

The front cover hub90being a ring shape is attached to inside of the front wall of the front cover30at the center portion thereof. The front cover hub90is fixed to the front wall of the front cover30by projection welding from inside thereof at three points on the circumference.

The pump impeller40is integrally connected to the front cover30as shown inFIG. 1. The pump impeller40includes an outer shell42at which plural blades41are implanted, an impeller hub43integrally welded to an inner peripheral of the outer shell42and connected to the oil pump gear (not shown) at an end of a shank of the impeller hub43, and inner core44attached at the inner edge of the blades41.

The turbine runner50is provided to be faced to the pump impeller40and connected to the input shaft110of the transmission (not shown) through the turbine hub51(shown inFIG. 1). The turbine runner50includes the outer shell53having plural blades52as the pump impeller40has. The turbine runner50also includes inner cores54attached at the inner edge side of the blades52. The outer shell53is bended and extending inwardly to be connected to the turbine hub51along with a driven plate63of the damper60. The turbine hub51is engaged with an outer spline of the input shaft at an inner spline of the turbine hub51so as to be connected to the input shaft110.

The damper60is provided at outer peripheral of the lock-up clutch70(shown inFIG. 1). The damper60includes a plurality of damper spring61made of coil spring, a drive plate62engaged with one side of each damper spring61and the driven plate63engaged with the other side of each damper spring61. The drive plate62includes a plate62bfor supporting friction discs62aand a plate62chaving notches for housing the damper springs61. The drive plate62is engaged with an end portion of each damper springs61. The plate62bis integrated with the plate62cby rivet. The driven plate63and the outer shell53are fixed to the turbine hub51by rivet at inner peripheral sides of the driven plate63and the outer shell53. The driven plate63including housing portions for housing the damper springs61is engaged with the other end of each damper spring61relative to the rotating direction of the drive plate62.

The lock-up clutch70is provided inside the front cover30to be aligned with a torus portion comprised of the pump impeller40and the turbine runner50in the shaft direction. The front cover30is engagable/disengagable relative to the input shaft110through the damper60. The lock-up clutch70includes a piston71which is able to be slide in the engaging hydraulic pressure chamber80and a clutch engaging portion72is engaged/disengaged by the slide of the piston71.

The piston71being a ring shape includes a first groove71a, spline portions71b, a second groove71c, a first protrude portion71dand a second protrude portion71eas shown inFIG. 1. The first groove71ainto which a first D ring74is fitted is formed on the inner peripheral surface of the piston71. The spline portions71bextending inwardly to be inserted into the notch portions90bof the front cover hub90for stopping the rotation of the piston71. The second groove71cinto which a second D ring73is fitted is formed on the outer peripheral surface of the piston71. The first protrude portion71dis provided at the inside of the piston71to be engagable with friction members72aof a clutch engaging portion72. The second protrude portion71eis provided to be engaged with the front cover30at inside thereof to secure a space between the front cover30and the piston71. The first D ring73is provided for sealing a space between the piston71and the drum member72b, and the second D ring74is provided for sealing a space between the piston71and the front cover hub90.

The clutch engaging portion72includes the friction members72abeing alternating layered with the friction discs62aand the drum member72bwelded to the front cover30for supporting the friction members72ato be slidably.

The engaging hydraulic pressure chamber80provided inside the power transmission hydraulic chamber100is surrounded by the front cover30and the pump impeller40so as to be separated from the power transmission hydraulic chamber100. An engaging hydraulic pressure of the lock-up clutch70is provided to the engaging hydraulic pressure chamber80. The engaging hydraulic pressure chamber80is surrounded by the front cover30, the piston71, the drum member72band the front cover hub90.

The front cover hub90is provided between the front cover30and the input shaft110(turbine hub51). The front cover hub90includes plural projection portions90a, notch portions90bformed at the outer peripheral portion thereof and an opening90c. As shown inFIG. 2A and 2B, the cross sectional shape of the projection portion90ais an arc shape or hemispherical shape. The projection portions90ais formed by stamping to be projecting in the left direction inFIG. 1in order that the projection portions90aare welded to the front cover30. The spline portion71bof the piston71is fitted and inserted into the notch portions90b. The hydraulic pressure is provided through an oil path of the input shaft110into the engaging hydraulic pressure chamber80through the opening90c(fromFIG. 1throughFIG. 4). The cylindrical inner peripheral surface of the piston71is slidable on the outer peripheral surface of the front cover hub90in axial direction of the input shaft110. The front cover hub90is welded to the front cover30by projection welding at the projection portion90afrom the front cover hub90side. The process for welding the front cover hub90is not limited to the aforementioned means. An electron beam welding may be applied alternatively. A space between the front cover hub90and the front cover30among of the projection portions90ais an oil path120.

The stator14provided between the pump impeller40and the turbine runner50is supported by the one-way clutch130. (shown inFIG. 1)

A lock up engaging pressure or a lock up slip pressure is first provided through an oil path formed inside the input shaft110, further the pressure is provided into the engaging hydraulic pressure chamber80through the oil path120formed between the front cover30and the front cover hub90.

In aforementioned configuration, the oil path formed at the front cover hub for providing the hydraulic pressure into the engaging hydraulic pressure chamber can be formed without grinding process, a result, the cost of the torque converter10can be reduced.