Hydrodynamic torque converter

Details Hydrodynamic torque converter Hydrodynamic torque converter

2000-07-13

2002-08-13

Rodríguez, Saúl (Department: 3681)

192 clutches and power-stop control

Vortex-flow drive and clutch

Including drive-lockup clutch

C192S003330, C192S085060

Reexamination Certificate

active

06431335

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a hydrodynamic torque converter comprising a converter housing whose interior space is filled or can be filled with a converter work fluid, a turbine wheel which is arranged in the converter housing so as to be rotatable with respect to it, a lockup clutch by which the turbine wheel can be selectively coupled with the housing for common rotation, wherein the lockup clutch comprises a coupling element which is displaceable for producing the rotational coupling of the converter housing and turbine wheel, a first fluid channel arrangement for directing converter work fluid into the interior space of the converter housing, a second fluid channel arrangement for guiding converter work fluid out of the interior space of the converter housing, and a third fluid channel arrangement through which pressure fluid can be directed into or out of a pressure fluid space provided in the converter housing for the displacement of the coupling element, wherein there is no connection between the pressure fluid space and the interior space of the converter housing allowing an exchange of converter work fluid.
2. Description of the Related Art
A hydrodynamic torque converter in which a pressure fluid space is separated from the converter work fluid space is known. The pressure fluid space acts upon or displaces the coupling element, i.e., the pressure fluid space is sealed so as to prevent entry to converter work fluid. This is generally referred to as a converter with a closed three-line system. A hydrodynamic torque converter of this type is disclosed in WO 99/10663. A torque converter of this kind has an advantage over other types of converter in that the amount of converter work fluid in the interior of the converter housing is not affected by the supply of pressure fluid to the pressure fluid space. This is true regardless of whether the lockup clutch is in the engaged or disengaged state. In the hydrodynamic torque converter known from the prior art, the coupling element is displaced in a direction in which it acts upon friction linings through the supply of pressure fluid into the pressure fluid space, to produce rotational coupling of the turbine wheel and converter housing. For this purpose, the pressure fluid space is formed between the coupling element and an area of the converter housing, resulting in a very simple construction of a torque converter having relatively few parts.
A problem resulting from this construction and this manner of operation is that the coupling element must be displaced against the pressure of the converter work fluid prevailing in the converter interior in order to engage the lockup clutch. This means that if the coupling element is to generate a predetermined contact pressing pressure on the friction linings for producing the lockup state, it must be acted upon by a pressure in the pressure fluid space which appreciably exceeds the pressure of the converter work fluid prevailing in the converter interior. This requires a pump with a correspondingly high output. In the lockup state in which the torque converter does not perform its converter function, the pressure of the converter work fluid can be lowered, so that the pressure in the pressure fluid space can be lowered in a corresponding manner to save energy. However, if a spontaneous transition to the converter function occurs, the pressure of the converter work fluid prevailing in the interior of the converter housing in this operating state is often too low, so that cavitation problems can occur.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a hydrodynamic torque converter with increased output efficiency.
Briefly stated, the present invention is a hydrodynamic torque converter comprising a converter housing whose interior space is filled or can be filled with a converter work fluid, a turbine wheel which is arranged in the converter housing so as to be rotatable with respect to it, a lockup clutch by which the turbine wheel can be selectively coupled with the housing for common rotation, wherein the lockup clutch comprises a coupling element which is displaceable for producing the rotational coupling of the converter housing and turbine wheel, a first fluid channel arrangement for directing converter work fluid into the interior space of the converter housing, a second fluid channel arrangement for guiding converter work fluid out of the interior space of the converter housing, and a third fluid channel arrangement through which pressure fluid can be directed into or out of a pressure fluid space provided in the converter housing for the displacement of the coupling element, wherein there is no connection between the pressure fluid space and the interior space of the converter housing allowing an exchange of converter work fluid.
Further, according to the invention, the pressure fluid space can be filled with pressure fluid for displacing the coupling element for at least partial cancellation of the rotational coupling of the converter housing and turbine wheel.
In contrast to the prior art, the present invention accordingly displaces the coupling element for canceling the rotational coupling of the converter housing and turbine wheel, i.e., for disengaging the lockup clutch against the pressure of the converter work fluid prevailing in the interior space of the converter housing, by filling the pressure fluid space with pressure fluid. This results in some substantial advantages with respect to operation which have a positive effect on the efficiency of the converter operation in particular. First, the pressure fluid space need only be filled with pressure fluid when the lockup clutch is to be partially or fully disengaged. However, this operating state occurs only relatively briefly during normal driving, for example when starting or shifting gears. During normal driving, the converter does not perform its converter function, but rather is bypassed by the engagement of the lockup clutch. Therefore, the time period during which a pump must be put into operation for filling the pressure fluid space with pressure fluid is clearly reduced. Further, the pressure of the converter work fluid prevailing in the interior space of the converter housing in the engaged state of the lockup clutch acts upon the coupling element due to the reduction of fluid pressure in the pressure fluid space and presses the coupling element for engaging the lockup clutch. Consequently, it is not necessary to work against the pressure of the converter work fluid prevailing in the interior space of the converter housing for engaging the lockup clutch; rather, this pressure can be utilized in a positive fashion to produce the lockup state. This means that the fluid pressure in the interior space of the converter housing can be held at a normal or high level also in the lockup state, so that spontaneous transitions in converter operation also do not lead to cavitation problems or loss of output.
A further embodiment of the present invention is a hydrodynamic torque converter in which that the interior space of the converter housing is divided or can be divided into a first converter work fluid space and a second converter work fluid space by the coupling element.
According to another aspect of the present invention, the object stated above can be met by a hydrodynamic torque converter comprising a converter housing whose interior space is filled or can be filled with a converter work fluid, a turbine wheel which is arranged in the converter housing so as to be rotatable with respect to it, a lockup clutch by which the turbine wheel can be selectively coupled with the housing for common rotation, wherein the lockup clutch comprises a coupling element which is displaceable for producing the rotational coupling of the converter housing and turbine wheel, a first fluid channel arrangement for directing converter work fluid into the interior space of the converter housing, a second fluid channel arrangement for directin

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