WO1993013338A1

WO1993013338A1 - Damper and bypass clutch for hydrodynamic torque converter

Info

Publication number: WO1993013338A1
Application number: PCT/EP1992/002479
Authority: WO
Inventors: Fraser John Macdonald
Original assignee: Ford Motor Company Limited; Ford Werke A.G.; Ford France S.A.; Ford Motor Company
Priority date: 1991-12-23
Filing date: 1992-10-30
Publication date: 1993-07-08
Also published as: JPH07502325A

Abstract

A bypass clutch damper for an automatic transmission torque converter includes a support plate (91) and a turbine rotor (26), both fixed to the transmission input shaft. The support ring defines annular spring pockets (92, 100) about the axis of rotation containing coiled helical springs (102), each spring (102) having one end contacting the support plate (91). The opposite end of each of the damper springs (102) contacts a drive ring of a torque converter clutch. A clutch plate (70) is fixed to an impeller cover (12), and a clutch piston (60), fixed to the cover (14), is hydraulically actuated to move toward the drive ring (74) and the clutch plate (70). Friction surfaces on the drive ring (74) are forced into frictional contact with the clutch plate (70) and piston (60) in accordance with differential pressure across the clutch piston. The drive ring (74), when engaged, compresses the springs and causes functional contact as the springs move in frictional contact with the surfaces of the spring pockets.

Description

DAMPER AND BYPASS CLUTCH FOR HYDRODYNAMIC TORQUE CONVERTER

This invention relates to the field of torque converters for automatic transmissions. The invention pertains particularly to a damper and associated bypass clutch, which mechanically connects and disconnects selectively the turbine and impeller of the torque converter.

The present invention relates to improvements in damper assemblies of the kind shown in U.S. Patents 4,143,561; 4,422,535, 4,027,757 and 4,138,003. Each of these references shows a damper assembly that includes compound springs located in a clutch plate situated in an impeller housing of a torque converter. The springs cushion the application of a direct drive friction clutch, which locks together the impeller and the turbine of the converter to establish a mechanical torque delivery path arranged in parallel with the hydrokinetic torque delivery path provided by the converter.

A typical gearset adapted to accommodate a torque converter and damper assembly of the kind herein disclosed is described in U.S. Patents 3,314,307 and 3,491,617. Each of these patents describes compound planetary gearsets, with a hydrokinetic torque converter located between the gearset torque input elements and an internal combustion engine in a vehicle driveline. An overdrive clutch is adapted to connect directly the engine crankshaft or converter impeller to the compound carrier of the gear unit, thereby establishing an overdrive ratio. Upon engagement of the overdrive clutch, the hydrokinetic torque delivery path through the gearing and converter is interrupted and a fully mechanical torque delivery path is substituted. The converter damper assembly of the invention cushions the engagement of the overdrive clutch and prevents undesirable resonant frequencies from developing due to the inertia forces on the torque delivery elements in the transmission itself and due to forced vibrations in the driveline normally associated with an internal combustion engine.

In drivelines of this type, it is usual practice to provide an inertia flywheel to cushion engagement of the clutches and brakes of the transmission and to absorb transient torque variations and torsional vibrations. Although a flywheel may be required in a driveline incorporating the improved damper mechanism of the present invention, the mass of the flywheel may be reduced greatly without impairing drivability. The resonant vibrations normally absorbed by a larger flywheel can be accommodated instead by the damper assembly of the invention, which has a substantially smaller mass.

According to the present invention, there is provided a torque converter adapted to deliver driving torque from an internal combustion engine to a transmission drive shaft. The torque converter has an impeller connected to the engine, a turbine connected to torque input elements of a gear system, and a mechanical torque delivery path in parallel relationship with respect to the torque converter that is independent of the torque converter. A damper assembly, located in the torque flow path includes a clutch plate connected to the impeller; a torque input shaft connected to the gear system; a piston; a drive ring located between the piston and clutch plate; and damper springs establishing a damped resilient connection between the drive ring and the turbine wheel.

Conventional prior art torque converter clutch dampers are mounted on the clutch piston, and torque is applied to the damper from tangs carried on the turbine. In the prior art, the drive plate that carries torque to the damper is driven radially. In the clutch/damper assembly of this invention, the damper is mounted on the turbine wheel, and the drive ring that carries torque to the damper is driven angularly, is permitted to move axially as the bypass clutch and is engaged by differential pressure across the clutch piston. A support plate pilots movement of the drive ring and limits its angular movement, the range of compressive displacement of the damper springs, by providing stop surfaces at several angularly spaced locations♦

Annular pockets of circular cross-section formed by complementary arcuate flanges on the support plate contain the damper springs and hold those springs in correct position against the effect of forces tending to urge the springs radially outward as the springs are compressed. Due to the modular form inherent in the design, the number of damper springs can vary with kinematic requirements without changing the principle of operation. The damper springs are located at the radially outermost location within the torque converter casing, thereby minimising the damper-spring force needed to attenuate torsional vibration. Because the spring pockets closely conform to the outer surface of the coiled springs, as the springs compress they move in contact on the inner surface of the pockets, which are hardened by heat treatment to withstand wear due to this. The resulting frictional contact produces coulomb damping in parallel with the spring force between the drive ring and the turbine wheel. When the clutch is engaged, the drive ring is drivably connected to the impeller casing and engine; therefore, the parallel arrangement of dampers and springs is active between the engine and turbine wheel.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a side view of a torque converter, partially in cross section, showing a bypass clutch and damper according to the invention.

Figure 2 is an end view taken in direction A of a damper assembly shown in Figure 1.

Figure 3 is a cross section taken at plane 3-3 of Figure 7 showing a detail of the spring retainer within the damper assembly.

Figure 4 is an axial view of the drive ring showing details of the friction surface.

Figure 5 is a side view of the drive ring. Figure 6 is a top view of a detail in the drive ring.

Figure 7 is an axial view of the retainer and damper springs.

Referring first to Figure 1, a torque converter 10 includes an impeller cover 12, which is welded to an impeller shell 14 having recesses 16, which receive tabs 18 located on the outer surface of impeller blades 20. The impeller blades are retained between shell 14 and an inner impeller shroud 22.

Impeller cover 12 supports a circular pattern of threaded studs 24 to which a flywheel, rotatably supported on the engine crankshaft, is bolted, thereby drivably connect the cover to an engine.

Turbine blades 26 are spaced mutually about the axis of rotation and are located with respect to the impeller blades so that a toroidal fluid flow within the torque converter exits the impeller and enters the turbine at the radially outer area and leaves the turbine at the radially inner area. The outer periphery of the turbine blades is fixed mechanically or by welding or brazing to a turbine shell 28, which has openings 29 that receive tabs 30 formed on the turbine blades. The inner periphery of the turbine blades is connected to an inner turbine shroud 32 by locating tabs 34 within slots formed in shroud 32 and bending the tabs over on the inner surface of the shroud, thereby fixing the position of blades 26 between shell 28 and shroud 32. Turbine shell 28 is secured by rivets 36 to a turbine hub 38 having an internally splined surface 40 adapted to engage an externally splined surface on a transmission input shaft. Located between the flow exit section of the turbine and the flow entrance section of the impeller is a stator assembly comprising stator blades 46, spaced mutually around the axis of rotation, a hub 48 supporting blades 46, an inner shroud 50 connecting the radially inner tips of the blades, and an outer shroud 52 connecting the radially inner ends of the stator blades. An overrunning brake 54, fixed by splines 56 to a stationary sleeve shaft, provides one-way braking between the stator blades and the sleeve shaft.

A bypass clutch includes a piston assembly 58, which includes a piston 60, slidably mounted in an axially directed surface 62 formed on turbine hub 38 and sealed against the passage of hydraulic fluid by an O-ring 64, located in a recess formed in surface 62. A clutch plate 20 drivably connects cover 12 to the rotor of a hydraulic pump, the pressure source from which the torque converter and an automatic transmission are pressurised, controlled and actuated.

A ring 66, riveted at 67 to the piston, carries a splined surface 68 that is engaged by the splines formed on the radially inner surface of clutch plate 70. The clutch plate is fixed to the inner surface of cover 12 by a spot weld 72, which provides a seal against the passage of hydraulic fluid between the axially outer surface of disc 64 and the adjacent inner surface of the cover. Therefore, clutch plate 70 and piston 60 are drivably connected through cover 12 to the engine.

Drive ring 74 includes a radial leg 76 (shown in Figure 5) located between the inner face of clutch plate 70 and the outer face of piston 60, and six axial legs 76 (shown in Figure 6) , spaced mutually angularly about the axis of rotation and directed from leg 76 toward the turbine wheel. The surfaces of leg 76 that face plate 70 and piston 60 carry friction material 80, commonly referred to as "paper face" material, which is bonded to axially opposite radial surfaces of drive ring 74 by a bonding technique described by Frosbie, Milek and Smith in SAE Design Practices, Volume 5, (1962).

As seen in Figures 4 and 5, the friction material 80 has formed two concentric annular grooves, 82, 84, which can be machined by turning or formed by pressing a die on the face of the plate during formation of the disc as the friction material is pressure bonded to the steel drive ring 74. The friction material 80 is formed also with two sets of radial grooves 86, 80, members of each radial groove set spaced at 90° intervals from other members of the set and at 45° intervals from members of the other set. Radial grooves 86 do not communicate with the radially outer region but they do communicate with the radially inner region of the drive ring. They also interconnect each of the annular grooves. Radial grooves 88, which communicate with the radially outer region, do not communicate with the radially inner region.

Fluid in the torus cavity of the torque converter has a pressure that is higher than pressure in chamber 90, located between friction plate 70 and piston 60. Therefore, hydraulic fluid tends to flow radially inward through grooves 88 where it is transferred to the circumferential or annular grooves. The fluid then travels circumferentially to the adjacent radial grooves 86, from which the fluid is transferred to the radially inward region of the pressure chamber 90.

Fluid circulates continuously across the friction surfaces during operation of the clutch as the clutch slips, and fluid is transferred circumferentially through the grooves thereby creating the maximum cooling effect. Heat is dissipated to the fluid and carried to chamber 90 in the control system, where it is transferred to a cooler and then recirculated to the inlet side of a pump, which pressurised the entire hydraulic system of the transmission. The pump supplies pressure to the control system, which establishes regulated pressure levels in the torus circuit of the torque converter and in chamber 90.

Because the friction material does not engage directly with cover 12, transfer of heat generated during slipping of the clutch, the speed difference between that of drive ring 74 and that of the engine crankshaft, is minimised.

Referring now to Figures 1 and 2, the turbine shroud 28 and a torque converter damper support 91 are joined to a radially extending flange of turbine hub 38 at a riveted connection 36. At the radially outer end of support 91, several arcuate flanges 92, spaced angularly about the axis at 60° intervals, are formed. A spring retainer ring 94 includes a radially inwardly extending web 96, riveted to support plate 91 at angularly spaced locations 98, and an arcuate flange 100 substantially complimentary to flange 92 of the support plate. Flanges 92 and 102 define between them a substantially circular tubular cavity, in which are located six angularly spaced, helically-coiled damper springs 102. At six equally spaced angular locations spaced mutually about the axis of rotation, flange 100 of the retainer ring is formed with a local bead extending approximately 16.4 degrees between radially directed relief recesses 106 that permit formation of bead 104 in the arcuate flange 100. Similar relief slots 108, formed in the support 91, permit arcuate flanges 92 to extend outwardly from the planar radially directed web of the support ring and the radially outer end of support plate 91 to extend into the spring pockets over the same intervals and lengths as the local beads 104.

Drive ring 74 is supported on several arcuate surfaces 105 that coincide with the angularly spaced beads 104 and the radial ends of the support plate. Surfaces 105 guide the drive ring as it moves axially toward clutch plate 70 due to contact with the piston 60 and away from the clutch plate as pressure within control chamber 90 falls in rela¬ tion to pressure on the axially opposite side of the piston. Contact between the arcuate flanges 92 and the drive ring limits the extent to which the springs are compressed. Contact between the beads and radial ends of the support plate limit the extent to which the springs can expand.

Referring now to Figure 7 the damper assembly includes six angularly-spaced, helically-coiled damper springs 102, the coil of each spring being closed at each end by a plug 110. Each damper spring is located between a bead 104 of the arcuate flange 100 formed on retainer 94 and a radial end of support plate 91. The damper springs move from the fully extended position shown in Figure 7 to a fully stroked position shown in the upper right-hand quadrant of Figure 7 at 114. When the damper springs are compressed, the radially outer surface of the spring coils move in frictional contact on the inner surface 116 of the arcuate flange 100 of the retainer. Beads 104 and the radial ends of support plate 91 limit movement of compression damper springs 102. The springs may be arcuate as formed or straight and then bent to conform to the annular spring pockets.

Each of the six axially directed legs 78 of the drive ring 74 is located within the space between angularly opposite ends of each of the damper springs. Engine torque is transmitted through drive ring 74 to the damper assembly by bearing contact between axial flanges 78 and the adjacent ends of the damper spring.

Chamber 90, defined by piston 60, cover 12, clutch plate 70 and the friction material on drive ring 74, is a control pressure chamber, which communicates with the control pressure source in a matter described in U.S. Patent No. 4,633,738, which is assigned to the assignor of this invention. By controlling pressure in chamber 90, a pressure differential across piston 60 can be controlled. The pressure in the torus flow cavity on the left-hand side of piston 60 causes the friction surfaces on clutch plate 70 and piston 60 to become frictionally engaged with the friction material 80 on the inner and outer axial surfaces of radially extending leg 76 of drive ring 74. By appropriately modulating the pressure in chamber 90, controlled slipping will occur between the drive ring and the cover and piston, whereby torque fluctuation developed in the driveline due to engine torque perturbations and other torque transmitting irregularities can be absorbed. When pressure in chamber 90 is less than pressure in the torus cavity, piston 60 is forced to the right against the drive, and the drive ring is carried to the right into contact with clutch plate 70. The cover, clutch plate and piston turn at the speed of the engine. The drive ring is connected through the damper assembly resiliently through the damper springs to support 91, and via the attachment at rivets 36 to the torus rotor, and through hub 38 to the transmission input shaft.

Claims

1. A damper assembly for attenuating vibration in a torque converter having an impeller (22) and a turbine (26,28,32,38) hydrodynamically connectable to the impeller (22), comprising: a drive ring (74) alternately drivably connectable to and releasable from the impeller (22); a support plate (91) fixed to the turbine, defining an annular spring pocket (92,100) substantially concentric with the axis of rotation of the torque converter; and helical coiled springs (102) located in the spring pockets (92,100), spaced mutually about the axis of the damper, a first surface of each spring contacting the drive ring (74) and a second surface of each spring contacting the support plate (91), the springs (102) adapted to expand and contract as the drive ring (74) moves relative to the support plate (91).

2. In a torque converter adapted to deliver torque hydrodynamically between an impeller and a turbine, a damper assembly providing a mechanical torque path in parallel with the torque converter, comprising: a drive ring alternately drivably connectable to and releasable from the impeller; a support plate fixed to the turbine defining a spring retaining surface thereon; and spring means adapted for movement on said spring retaining surface, for providing a resilient connection between said drive ring and the support plate and a damped connection between said drive ring and the support plate, the damped connection arranged in parallel with the resilient connection.

3. An assembly according to claim 2, wherein the spring retaining surface comprise an annular spring pockets substantially concentric with the axis of rotation of the torque converter and the spring means includes coiled springs located in the spring pockets, spaced mutually about the axis of the damper, a first surface of each spring contacting the drive ring and a second surface of each spring contacting the support plate, the springs adapted to expand and contract in contact with the spring pockets as the drive ring moves relative to the support plate.

4. An assembly according to claim 1 or 3, wherein the spring pockets are arcuate and the springs are arcuate as formed, conforming substantially to the arcuate shape of the spring pockets.

5. An assembly according to claim 1 or 3, wherein the spring pockets are arcuate and the springs are straight as formed and are bent upon installation in the spring pockets to conform substantially to the arcuate shape of the spring pockets.

6. An assembly according to claim 1 or 2, wherein the support plate comprises: first partially circular flanges, each partially surrounding a spring, spaced mutually angularly about the damper axis and extending angularly about said axis; second partially circular flanges, each partially surrounding a spring, aligned and extending angularly with a first flange, pairs of first and second flanges defining spring pockets located between them, each pocket spaced mutually angularly about the damper axis.

7. An assembly according to claim 6, wherein the first flanges include first stop surfaces located within the spring pockets, extending angularly between the springs, the first surface of each spring located adjacent said stop surfaces.

8. An assembly according to claim 6, wherein the support plate further comprises second stop surfaces located within the spring pockets, extending angularly between the springs, the first surface of each spring located adjacent said stop surfaces, the first and second stop surfaces contacting the springs at diametrically opposite sides the first surface of each spring.

9. An assembly according to claim 1 or 2, wherein the support plate includes pilot surface means for slidably supporting the drive ring and permitting axial and angular movement of the drive ring relative to the support plate.

10. In a torque converter adapted to deliver torque hydrodynamically between an impeller and a turbine, a damper assembly providing a mechanical torque path in parallel with the torque converter, comprising: drive ring means movable axially for alternately drivably connecting and releasing the impeller and movably circumferentially with the turbine; a support plate fixed to the turbine defining a spring retaining surface thereon, supporting the drive ring for movement axially and circumferentially; and spring means adapted for movement on said spring retaining surface, for providing a resilient connection between said drive ring and the support plate and a damped connection between said drive ring and the support plate, the damped connection arranged in parallel with the resilient connection.