WO2001096759A2

WO2001096759A2 - Dual mass wet clutch

Info

Publication number: WO2001096759A2
Application number: PCT/IB2001/000977
Authority: WO
Inventors: Michael Lee Bassett; Daniel Vern Gochenour; Steven Duane Lepard; Kevin Francis Schlosser
Original assignee: Eaton Corporation
Priority date: 2000-06-15
Filing date: 2001-06-05
Publication date: 2001-12-20
Also published as: AU2001264153A1; WO2001096759A3

Abstract

Provided herein is a torsional vibration damping system (20) for damping torsional vibrations in a vehicle driveline. The system comprises a driving member (22) adapted to be connected to an engine crankshaft, a damper assembly (30) and a wet clutch assembly (40). The damper assembly has an input member (32), an output member (36) and at least one compliant member (34). The compliant member is operatively disposed between the input member and the output member. By axially spacing the wet clutch (50) from the driving member the wet clutch may be sealed in a housing (42) to provide the advantages of both a torsional vibration damping system and a wet clutch.

Description

DUAL MASS WET CLUTCH

Field of the Invention

The present invention relates to a torsional vibration damping system, more specifically, the invention relates to a torsional vibration damping system for damping torsional vibrations in a vehicle driveline driven by an internal combustion engine, such as a piston engine.

Background of the Invention Torsional vibrations are the rotational irregularities of a rotatingly driven component. In a vehicle drivetrain, torsional vibrations are caused by the forces generated within a combustion engine by the combustion of gases during the periodic combustion process. Torsional vibrations of the second or third order which originate from the engine, as a result of the ignition frequency of four or six cylinder engines, respectively, are predominant in the vehicle driveline. Torsional vibrations not only emanate from the engine power pulses but also from torque spikes and from abrupt changes in driveline torque due to rapid engine acceleration and deceleration.

Torsional vibrations cause premature wear to driveline components as well as audible noise. In a conventional driveline, the flywheel, which is rigidly connected to the crankshaft, will generate high reaction forces on the crankshaft. Furthermore, torque irregularities from a periodic combustion engine adds additional stress in the form of high frequency torques to the transmission. Furthermore, when a manual transmission is in neutral, gear rattle occurs, which is also an audible event, due to the teeth of meshing gears lifting away from another and then striking each other as a result of high frequency torque fluctuations.

Along with gear rattle, order based responses from the second or third engine order may be passed through the drivetrain and into the body structure. This sound can be greatly amplified if the components forming the sound are excited at their resonant frequencies. Torsional vibration issues are further compounded by efforts to improve vehicle efficiency. Reductions in vehicle size and weight as well as reductions in driveline component inertia, such as flywheel masses, as well as reductions in transmission oil viscosity have added to the existing torsional vibration challenges. Lower drivetrain inertia results in a higher natural frequency of the drivetrain. As the engine rotational speed passes through the drivetrain natural frequency, resonant frequency occurs. The input displacement of a system is amplified at resonant frequency.

It is well known in the art to incorporate torsional vibration damping mechanisms in a dry clutch. It is also well known to incorporate a two- mass flywheel where a first and second flywheel are separated by a torsional damping mechanism. Such an approach is disclosed in "The Two-Mass Flywheel - A Torsional Vibration Damper for the Power Train of Passenger Cars - State of the Art and Further Technical Development" by Arno Sebulke, SAE Technical Paper No. 870394. Disclosed therein is a method of producing a mechanical low-pass filter which decouples rotational irregularities before they reach the transmission. Sebulke teaches to tune a two-mass flywheel incorporating a spring and friction system, i.e. a damper, tuned to provide a natural frequency of 15 Hertz, which is below engine idle speed. Resonant frequency of the damping system is designed to be below the engine's idle speed in order to avoid excitation while driving. However, Sebulke admits that starting and stopping the engine is problematic since, in those situations, the fundamental firing frequency must pass through the nature frequency of the system. The typical target for the natural frequency of a torsional vibration damping system is 20 Hertz. However, a number of problems still exist with the torsional vibration damping system of the prior art. One such problem is the angle limitation between the two masses. More specifically, as the dual mass system dampens torsional vibrations, inputs from the first mass, are transferred through the damper to the second mass where the second mass will rotate with respect to the first mass. As this rotation occurs, the energy storage means within the damper, typically coil springs, provide the rotational compliance between the rotating elements. The amount of relative rotation between the two masses is therefore limited when using coil springs as energy absorption means. During startup, it is not unusual to measure torques in the range of 8,000 foot-pounds. When the coil springs completely compress, shock within the system can lead to catastrophic results, such as damper or shaft failure.

Another component of the damper is hysteresis, which is provided by friction producing elements. The hysteresis cooperates with the energy storage component of the damper to remove energy from the system.

The prior art is replete with the dual mass dampers for attenuating torsional vibrations. A variety of spring arrangements have been employed to solve startup departure issues, including combining two springs in series. Also, coil springs have been replaced by elastomers, where a number of diaphragms are arranged projecting radially inward. Also, a plurality of elastomeric rings have been employed, separated by metal rings, to permit long spring travel and retain a low spring stiffness rate. Furthermore, a variety of viscous damping mechanisms have also been employed.

In an effort to take advantage of a need to provide a second mass it is known to replace the second mass, which is typically a flywheel, with a component that has utility, such as a frictional dry clutch. Although replacing a flywheel, which would otherwise be a mass without additional utility, with a dry clutch, employing a wet clutch has several advantages. The advantages with a wet clutch include more consistent frictional engagement than available with a dry clutch as well as having cooling capacity. However, providing a wet clutch as the second mass of a dual mass torsional vibration damping system would have several complications.

Therefore, there is a need in the art to provide a dual mass wet clutch for damping torsional vibrations.

Summary of the Invention It is therefore a feature of the present invention to provide a torsional vibration damping system having a driving member and driven member where the driven member is a wet clutch. It is further a feature of the present invention to provide a modular torsional vibration damping system where the components of the system may be changed to provide various damping characteristics.

A torsional vibration damping system for damping torsional vibrations in a vehicle driveline comprises a driving member having an axis of rotation where the driving member is adapted to be connected to an engine crankshaft. A damper assembly comprises an input member which is coupled to the driving member. A compliant member having energy storage means is operatively disposed between the input member and an output member. A wet clutch assembly having a housing with a coupling shaft rotatably supported in the housing is provided. The coupling shaft is coupled to the damper assembly and the wet clutch. The wet clutch is disposed in the housing and is axially spaced from the driving member by the coupling shaft. The wet clutch is rotatable relative to the driving member. In a second embodiment, a transmission and clutch assembly for a motor vehicle is disclosed, which comprises a transmission case having an input shaft rotatably supported in the case, an output shaft rotatably supported in the case and gear ratio change means disposed within the case. A wet clutch assembly is provided, which comprises a housing coupled to the transmission case, a coupling shaft supported in the housing and coupled to a wet clutch disposed within the housing. The input shaft of the transmission is coupled to the wet clutch for frictional coupling. A torsional damping assembly which comprises an input member, an output member and at least one compliant member having energy storage means is interconnected between a driving member and a coupling shaft. The compliant member is operatively disposed between the input and output members, where the output member is coupled to the coupling shaft. The driving member has an axis of rotation and is connected to an engine output shaft. The driving member is also connected to the input member of the torsional damping assembly, whereby the wet clutch is axially spaced from and rotatable relative to the driving member via the damper assembly to dampen torsional vibrations from an engine to the transmission. Brief Description of the Drawings

FIG. 1 is a schematic view of a motor vehicle driveline.

FIG. 2 is a schematic view of a dual mass wet clutch damper. FIG. 3 is a perspective view of an automated manual transmission and a torsional vibration damping system.

FIG. 4 is a cross-sectional view of a dual mass torsional vibration damping system.

FIG. 5 is a perspective view of a damper assembly operatively coupled to a wet clutch assembly.

FIG. 6 is a perspective view of a damper assembly and wet clutch assembly.

FIG. 7 is a cross-sectional view of a dual mass torsional vibration system having an elastomeric damper operatively disposed between the driving member and the driven member.

FIG. 8 is a cross-sectional view of an elastomeric damper assembly.

Detailed Description of the Preferred Embodiment Although the term "wet clutch" is used herein, it is to be understood that the term "wet clutch" shall also apply to other friction devices including ball ramp clutches and dry clutches.

A schematic view of a motor vehicle driveline 10 is shown in FIG.

1 which includes an engine 12 and a transmission 60 coupled to a drive shaft 14 for transmitting torque to a differential gear assembly 16 to distribute torque to at least one ground engaging wheel 18. The engine 12 is preferably an internal, periodic combustion type, but may be any type of power plant having torque characteristics that are improved by a torsional vibration damping system.

Transmission 60 includes a transmission case 62 having an input shaft 64 shown in FIG. 2, rotatably supported in the transmission case 62, and an output shaft 66 rotatably supported in the transmission case 62, as shown in FIG. 3. A plurality of constant mesh ratio gears, for varying the torque or speed ratio between the input shaft 64 and output shaft 66, also referred to as gear ratio change means (not shown), are disposed within the case 62 and are interconnected between the input shaft 64 and the output shaft 66.

Referring now to FIG. 2, a dual mass torsional vibration damping system 20 is shown. The torsional vibration damping system 20 includes a driving member 22, a driven member 46 and a damper assembly 30 operatively disposed therebetween. In the immediate embodiment, a first mass of the dual mass system is a flywheel, or driving member 22 which is adapted to be attached to an output shaft (not shown), also known as a crankshaft, of a combustion power source. Driving member 22 rotates about an axis of rotation 24. An input member 32 of damper assembly 30 is coupled to the driving member 22. The damper assembly 30 further includes a compliant member 34 and an output member 36. In the present embodiment, the compliant member 34 is a coil spring, which is disposed between the input member 32 and output member 36. The output member 36 has a hub portion which is internally splined. A coupling shaft 44 has external splines for coupling to the output member 36 of damper assembly 30.

In the present embodiment driven member 46 is a wet clutch assembly 40, which comprises a housing 42, containing a wet clutch 50. The coupling shaft 44 is rotatably supported by a bearing 41 within housing 42. Wet clutch 50 is axially spaced from, and rotatably relative to the driving member 22 by the coupling shaft 44. The wet clutch 50 is coupled to the coupling shaft 44 at the clutch pack housing 54 having internal splines. The wet clutch 50 may be splined directly to coupling shaft 44 or indirectly by coupling to an intermediate component 49. Although splines are employed for coupling the damper assembly 30 and wet clutch 50 to coupling shaft 44, it should be understood by those skilled in the art that any suitable substitute for splines may be employed in the present invention. Relative rotation between the driving member 22 and the driven member 46 is achieved by the compliant member 34 of the damper assembly 30. The compliant member 34 provides energy storage means for angular departure between the driving member 22 and a driven member 46 as a function of torque. Referring now also to FIG. 3, wet clutch assembly 40 is shown operatively coupled to transmission 60. More specifically, wet clutch housing 42 is secured to transmission case 62. Wet clutch assembly 40 may be substituted for a conventional frictional clutch housing. The transmission input shaft 64, as shown in FIG. 2, is preferably coupled directly or indirectly to the wet clutch 50.

Referring to FIG. 2, wet clutch 50 has a plurality of stationary clutch plates 52 which are splined to the clutch pack housing 54. A plurality of rotating clutch plates 56 are splined to a hub 58. The rotating clutch plates 56 are interposed between the stationary clutch plates 52. In the preferred embodiment, hub 58 is internally splined to receive a transmission input shaft 64.

Housing 42 is sealed to prevent oil from leaking from the wet clutch assembly 40. Referring now to FIG. 4, a second embodiment of a dual mass torsional vibration damping system 20 is shown. A clutch pack 51 , which comprises interposed stationary clutch plates 52 and rotating clutch plates 56 is engaged by engaging actuation ring 59 against the clutch pack 51 , causing the stationary clutch plates 52 to contact the rotating clutch plates 56 to achieve frictional engagement. Oil pressure is provided to the wet clutch 50 by a pump 48, which in the present embodiment is a gerotor pump. The damper assembly 30, as shown in FIG. 4, includes a compliant member 34, having energy storage means which, in the present embodiment, is a plurality of coil springs. Hysteresis within the damper assembly 30 is provided by frictional element 38.

Referring now to FIG. 5, a perspective view of a damper assembly 30 operatively coupled to the wet clutch assembly 40 is shown. FIG. 5 reveals the modular aspect of the torsional vibration damping system 20. As can be seen, damper assembly 30 may be easily removed from coupling shaft 44, allowing either the wet clutch 50 or the damping assembly 30 to be changed. Referring now to FIG. 6, a perspective view of damper assembly 30 uncoupled from coupling shaft 44 is shown. A bulkhead 45 provides structural support to coupling shaft 44 and further serves to prevent leakage of oil from the wet clutch assembly 40. Referring now to FIG. 7, a cross-sectional view of another embodiment of a torsional vibration damping system 20 is shown. The dual mass torsional vibration damping system 20 of the present embodiment has a damper assembly 30 which includes a unitary compliant member 35. Referring now also to FIG. 8, damper assembly 30 further includes input member 32 and output member 36, where the input member 32 is adapted to be secured to the driving member 22. Unitary compliant member 35 has a first end 37 and a second end 39 operatively disposed between the input member 32 and the output member 36. The input member 32 is in contact with the compliant member 35 at the first end 37. The output member 36 is in contact with the compliant member 35 at the second end 39. In the preferred embodiment of damper assembly 30, the compliant member is attached to input member 32 and output member 36 by an adhesive. It should become apparent to those skilled in the art that any suitable substitute for an adhesive may be employed to permit compliant member 35 to operatively contact input member 32 and output member 36. The output member 36 is adapted to be coupled to a driven member 46. Coupling between the damper assembly 30 and driven member 46 is achieved by an internally splined hub portion 31.

In the preferred embodiment, the compliant member 35 is an elastomeric compliant member. The compliant member 35 has energy storage means for providing angular departure between the driving member 22 and driven member 46 as a function of torque. The compliant member 35 is substantially ring shaped. As can be seen in the cross-sectional view of damper assembly 30 of FIG. 8, the unitary compliant member 35 of the preferred embodiment has a trapezoidal cross-section. However, other geometric cross- sections for compliant member 35 are contemplated to be within the spirit and scope of the present invention, including a cross-section having one or more inclusions.

One material used for forming compliant member 35 which exhibited excellent performance results is a Silicone elastomer, due in part to its temperature range. Those skilled in the art should immediately recognize that any suitable material, including natural rubber, may be substituted for Silicone. The desired spring rate for compliant member 35 is between about 60,000 LB- IN/RAD to 150,000 LB-IN/RAD. A specific torsional rate would be determined by vehicle size and configuration. The unitary elastomeric compliant member 35 has intrinsic hysteresis. As the spring is an energy storage means, friction is an energy conversion means i.e., for converting rotational energy into heat energy, for example, thereby removing kinetic energy from the system. The damper 30 as shown in FIGs. 7 and 8 has no mechanical stops unlike a damper with coil springs. A damper with coil springs has inherent mechanical stops since the coil springs have a limitation on how far they can be compressed. Once that limit is reached compliance is no longer available and the damper acts as a solid member, transferring torque spikes through the damper instead of absorbing the torque spikes.

During startup torque spikes in the range of 8,000 foot-pounds have been measured. Dampers within the current state of the art do not provide adequate compliance to absorb these high startup torques. The design criteria for a dual mass torsional vibration damping system is typically to design the system so the natural frequency is at about 20 Hertz, which is below engine idle speed. However, during startup the engine speed will invariably pass through the dual mass system natural frequency causing a great deal of excitation within the system. A conventional dual mass system excited at its natural frequency during startup may experience a compliance limitation which would result in the torsional energy being transferred directly to the transmission input shaft.

The unitary elastomeric compliant member 35 provides for 10 degrees or more of angular departure between the driving member 22 and the driven member 46. The angular departure of the compliant member 35 is only limited by the material compliance as 10 degrees may be exceeded if required by the design criteria of the system. Damper assembly 30 may be used with a wet clutch assembly 40, as shown in FIG. 7, a dry clutch assembly, or in a conventional two-flywheel torsional vibration damping system. The damper assembly 30 provides a novel solution to startup torsional vibration damping issues which until the present invention have remained unsolved. The dual mass torsional vibration damping system 20 combines the advantages of damping torque spikes in a vehicle driveline while also providing the advantages of a wet clutch. By axially spacing the wet clutch 50 from the driving member 22, a dual mass wet clutch torsional vibration damping system 20 as shown in FIG. 7 may be provided. Coupling shaft 44 provides for torque transfer from the damper assembly 30 to the wet clutch assembly 40. Axially spacing the wet clutch 50 from the driving member 22 allows for the housing 42 to be provided in order to seal the wet clutch assembly 40. Furthermore, housing 42 also prevents contamination of frictional coupling devices, such as dry frictional clutches and ball ramp clutches.

The foregoing discussions discloses and describes the preferred embodiment of the present invention. However, one skilled in the art would readily recognize from the discussion and the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined in the following claims.

Claims

What is claimed is:

1. A torsional vibration damping system, said system for damping torsional vibrations in a vehicle driveline, comprising: a driving member having an axis of rotation, said driving member adapted to be connected to an engine crankshaft; a damper assembly comprising an input member, an output member and at least one compliant member having energy storage means and operatively disposed between said input and output members, said input member coupled to said driving member; and a wet clutch assembly comprising a housing, a coupling shaft rotatably supported in said housing and coupled to said output member of said damper assembly, a wet clutch disposed in said housing and coupled to said shaft, said wet clutch axially spaced from, and rotatable relative to, said driving member.

2. The torsional vibration damping system of claim 1 , wherein said housing of said wet clutch assembly is sealed.

3. The torsional vibration damping system of claim 1 , wherein said compliant member of said damper assembly comprises at least one spring element.

4. The torsional vibration damping system of claim 1 , wherein said damper assembly further includes at least one frictional element

5. The torsional vibration damping system of claim 1 , wherein said compliant member is an elastomeric member having an intrinsic hysteresis.

6. A transmission and clutch assembly for a motor vehicle, comprising: a transmission case having an input shaft rotatably supported in said case, an output shaft rotatably supported in said case and gear ratio change means disposed within said case; a wet clutch assembly comprising a housing coupled to said transmission case, a coupling shaft rotatably supported in said housing and coupled to a wet clutch disposed in said housing, said input shaft coupled to said wet clutch of said wet clutch assembly for frictional coupling thereto; a damper assembly comprising an input member, an output member and at least one compliant member having energy storage means and operatively disposed between said input and output members, said output member coupled to said coupling shaft; and a driving member having an axis of rotation, said driving member connected to an engine output shaft and to said input member of said damper assembly, whereby said wet clutch is axially spaced from, and rotatable relative to, said driving member via said damper assembly to dampen torsional vibrations from an engine to said transmission.

7. The assembly of claim 6, wherein said housing of said wet clutch assembly is sealed.

8. The assembly of claim 6, wherein said compliant member of said torsional damping assembly comprises at least one spring element.

9. The assembly of claim 6, wherein said torsional damping assembly further includes at least one frictional element

10. The assembly of claim 6, wherein said compliant member is an elastomeric member having an intrinsic hysteresis.

11. A friction clutch for a drive train of a motor vehicle, comprising: a driving member having an axis of rotation, said driving member adapted to be connected to an engine crankshaft; a damper assembly comprising an input member, an output member and at least one compliant member having a energy storage means and operatively disposed between said input and output members, said input member coupled to said driving member; and a wet clutch assembly comprising a housing, a coupling shaft rotatably supported in said housing and coupled to said output member of said damping component, a wet clutch disposed in said housing and coupled to said shaft, said wet clutch axially spaced from, and rotatable relative to, said driving member.

12. The friction clutch of claim 11 , wherein said housing of said wet clutch assembly is sealed.

13. The friction clutch of claim 11 , wherein said compliant member of said damper assembly comprises at least one spring element.

14. The friction clutch of claim 11 , wherein said damper assembly further includes at least one frictional element.

15. The friction clutch of claim 11 , wherein said compliant member is an elastomeric member having an intrinsic hysteresis.