Hydrokinetic torque converter with lockup clutch

Details Hydrokinetic torque converter with lockup clutch Hydrokinetic torque converter with lockup clutch

1998-07-20

2002-04-09

Lorence, Richard M. (Department: 3681)

192 clutches and power-stop control

Vortex-flow drive and clutch

Including drive-lockup clutch

C192S003310, C192S1030FA

Reexamination Certificate

active

06367605

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to improvements in torque transmitting apparatus in general, and more particularly to improvements in torque transmitting apparatus which employ hydrokinetic torque converters. Still more particularly, the invention relates to improvements in torque transmitting apparatus of the type wherein a hydrokinetic torque converter cooperates with or embodies a lockup clutch, also called bypass clutch.
It is known to utilize a hydrokinetic torque converter in the power train between the engine and the transmission in a motor vehicle. As a rule, the torque converter comprises a housing which defines a fluid-filled chamber and receives torque from the output element of the engine. The housing drives a pump which can transmit torque to the input element of the transmission by way of a turbine in the chamber of the housing. A stator can be interposed between the pump and the turbine as seen in the axial direction of the torque converter. The housing of the torque converter can accommodate a lockup clutch having a piston which is movable in the axial direction of the torque converter in response to the establishment of necessary pressure differential between a first compartment of the chamber at one side and a second compartment of the chamber at the other side of the piston. When the lockup clutch is engaged, it can transmit torque from the housing of the torque converter (i.e., from the output element of the engine) directly to the turbine in the chamber of the housing and hence directly to the input element of the transmission.
Torque transmitting apparatus of the above outlined character are disclosed, for example, in U.S. Pat. No. 4,618,041 (granted Oct. 21, 1986 to Sotoyama et al. for “Lockup control system for a torque converter for an automatic transmission”), in U.S. Pat. No. 4,619,350 (granted Oct. 28, 1986 to Maezono et al. for “Clutch operation control system for fluid torque converter of vehicular transmission”) and in U.S. Pat. No. 4,640,395 (granted Feb. 3, 1987 to Murasugi et al. for “Slip control mechanism for friction clutch in torque converter of automatic power transmission”). The disclosures of the above enumerated patents are incorporated herein by reference.
A drawback of heretofore known torque transmitting apparatus employing hydrokinetic torque converters and lockup clutches is that their operation is not entirely satisfactory under certain circumstances when such apparatus are in actual use, e.g., in the power trains between the engines and the transmissions of motor vehicles. For example, it is often desirable or plain necessary to disengage the lockup clutch, at least for a certain interval of time, during certain stages of operation of the motor vehicle. Such situation can develop, for example, when the temperature of surrounding air is relatively low or very low. The reason is that the hydraulic fluid which is utilized to fill the chamber defined by the housing of the torque converter is normally oil and the viscosity of such fluid increases in response to decreasing temperature. The pumping device which is utilized in conventional torque transmitting apparatus of the above outlined character is incapable of conveying the high-viscosity fluid at a required rate so that the pressure of fluid is too low or cannot be maintained at a desired value, namely at a value which is necessary to ensure that the lockup clutch remains disengaged or that the lockup clutch is disengaged to a desired degree. Such disengagement or partial disengagement of the lockup clutch is ensured if the pressure in one of the aforementioned compartments is maintained at or above a certain value. Many torque transmitting apparatus cannot ensure predictable disengagement or partial disengagement of the lockup clutch if the temperature of the surrounding atmosphere is close to or below 0° C.
Additional serious problems can arise when the transmission receiving torque from a standard torque converter is shifted in reverse gear. The reason is that, in many (actually in most) instances, the modulation pressure (namely the pressure which is necessary for proper operation of the gear transmission) increases with simultaneous drop of fluid pressure in the torque converter. This entails undesirable (at least partial) engagement of the lockup clutch. The reason for such at least partial engagement of the lockup clutch under the above outlined circumstances is the development of a force attributable to fluid pressure and arising as an integral effect of variations of fluid pressure at the opposite sides of the piston forming part of the lockup clutch. The variations of fluid pressure at opposite sides of the piston develop primarily as a result of the kinematic and/or dynamic relationships of fluid elements, namely essentially in dependency on their average peripheral speed and hence in dependency on the rotational speed of the parts (such as the housing and the turbine of the torque converter and the piston of the lockup clutch) which flank the aforementioned compartments of the chamber in the housing of the torque converter. Accordingly, the operation of the torque transmitting apparatus is dependent upon the RPM of the pump and turbine of the torque converter and upon the RPM of the piston of the lockup clutch. Reference may be had, for example, to U.S. Pat. No. 3,213,983 (granted Oct. 26, 1965 to Smirl et al. for “Fluid actuated transmission device”) which discusses the development and the effects of such forces and pressures. The disclosure of the patent to Smirl et al. is incorporated herein by reference.
An additional drawback of heretofore known torque transmitting apparatus which embody a hydrokinetic torque converter and a lockup clutch is that they are complex and expensive.
OBJECTS OF THE INVENTION
An object of the invention is to provide a torque transmitting apparatus which embodies a hydrokinetic torque converter and a lockup clutch and is constructed and assembled in such a way that its operation is satisfactory (or at least more satisfactory than that of heretofore known apparatus) under all circumstances which arise in actual use of such apparatus.
Another object of the invention is to provide a relatively simple, compact and inexpensive torque transmitting apparatus which can be utilized as a superior substitute for heretofore known apparatus employing a hydrokinetic torque converter and a lockup clutch.
A further object of the invention is to provide a novel and improved power train which employs a torque transmitting apparatus of the above outlined character.
An additional object of the invention is to provide a motor vehicle which embodies the improved torque transmitting apparatus.
Still another object of the invention is to provide a novel and improved lockup clutch which can be utilized in the above outlined torque transmitting apparatus.
A further object of the invention is to provide a novel and improved combination of a lockup clutch or bypass clutch and a hydrokinetic torque converter.
Another object of the invention is to provide a torque transmitting apparatus which can operate in a desired manner irrespective of pronounced variations of a number of different parameters such as the RPM of the housing of the torque converter, the temperature of the fluid in the housing of the torque converter and/or the viscosity of such fluid.
SUMMARY OF THE INVENTION
One feature of the present invention resides in the provision of a torque transmitting apparatus which comprises a hydrokinetic torque converter having a fluid-containing chamber and including a pump rotatable about a predetermined axis at a variable RPM by a rotary output element (e.g., a camshaft or a crankshaft) of a prime mover (such as the combustion engine or another engine of a motor vehicle). The torque converter further comprises a turbine which is disposed in the chamber and includes an output member which is rotatable about the predetermined axis (the output member can constitute the input element of an adjustable transmission in the power train between the engine

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