Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Load responsive
Reexamination Certificate
2000-07-05
2002-12-17
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Load responsive
Reexamination Certificate
active
06494797
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to improvements in hydraulically operated automatic transmission assemblies, and to a method of supplying hydraulic fluid to the fluid-consuming or utilizing constituents of such transmission assemblies.
German patent No. 195 46 293 A1 discloses a hydraulically operated automatic transmission assembly which can be utilized in the power train of a motor vehicle to transmit torque between the engine and the wheels, normally in response to engagement of a friction clutch which serves to transmit torque between the rotary output element of the engine and the rotary input element of the variable speed or change speed transmission forming part of the automatic transmission assembly. The patented transmission assembly employs at least one static fluid consumer, a hydraulic transmission regulating component (e.g., a proportional and/or another valve), and at least one dynamic fluid consumer which is controlled by the transmission regulating component(s). The at least one static fluid consumer can include or constitute a fluid cooling unit, and the at least one dynamic fluid consumer can constitute a regulating arrangement for a continuously variable transmission (CVT). The speed ratio of such CVT is variable by the at least one transmission regulating component of the hydraulic transmission regulating unit. The patented transmission assembly further comprises a hydraulic resistor which is installed in a conduit serving to supply pressurized hydraulic fluid from the source to the static and dynamic fluid consumers. The source can include a pump which circulates transmission fluid in the automatic transmission assembly.
The aforementioned conduit receives hydraulic fluid from a fluid conveying unit which supplies fluid for the CVT and is located upstream of a volumetric flow regulator the regulating or adjusting function of which is influenced by the hydraulic resistor. In other words, the hydraulic resistor determines or controls the maximal volumetric flow of the working fluid because the quantity of conveyed fluid depends upon the RPM of the fluid conveying unit. Thus, when the RPM rises to a predetermined value, the fluid conveying unit delivers a volumetric flow of the working fluid which exceeds the fluid requirements of the automatic transmission assembly. The total or overall fluid flow which is supplied by the fluid conveying unit is divided into first and second flows for the static and dynamic fluid consumers, respectively.
As used herein, the term “dynamic fluid consumer” is intended to denote each consumer which, at least for a certain relatively short interval of time, requires a varying supply of hydraulic fluid. For example, an actuator in the hydraulic circuit of a prime mover is operated by receiving a variable supply of hydraulic fluid. In addition to the aforediscussed variable-RPM consumers (such as a CVT), dynamic fluid consumers further encompass, for example, various types of engageable and disengageable clutches including the so-called lockup or bypass clutches of torque converters. On the other hand, the term “static fluid consumer” is intended to denote those consumers of hydraulic fluid which, at least as a rule, receive fluid at a constant or substantially constant rate. Such static fluid consumers include cooling units for hydraulic fluid, the torque converter(s) and the lubricating means.
The patented automatic transmission assembly is operated in such a way that the conduit conveys the regulated volumetric flow into the transmission regulating unit. A portion of such flow is lost in the dynamic fluid consumers and as a result of leakage. The remainder of the flow is conveyed into the static fluid consumer or consumers. Any fluid that remains is caused to enter the suction side of the fluid conveying unit. The just described sequence of utilization of the fluid flow is considered to be necessary in order to ensure that a body of highly pressurized fluid reaches those consumers (normally or preferably including the dynamic consumer or consumers) which require a highly pressurized fluid, and that the working fluid thereupon reaches the low-pressure consumer or consumers normally encompassing the static fluid consumer(s). The fluid pressure is selected or regulated prior to admission into the consumer(s) requiring highly pressurized hydraulic fluid; however, the pressure of hydraulic fluid which is conveyed to the static fluid consumer(s) and/or to other consumers of lower-pressure fluid is normally determined by the quantity of fluid which is available for such purpose and by the geometry (a) of the piping which confines the low-pressure fluid and (b) the static fluid consumer(s). This results in the establishment, in the low-pressure region, of a specific “backwater” effect.
In an automatic transmission assembly for use in a motor vehicle, it is normally desirable or necessary to ensure that the operation be satisfactory while the temperature of transmission fluid fluctuates within a range of between about −30° C. and +140° C. When the fluid temperature (within the just mentioned range) is relatively high, the losses due to leakage increase (because the viscosity of the fluid is relatively high) well above average losses, and this applies especially for leakages in the transmission regulating unit. The fluid which escapes due to such increased temperature-induced reduction of viscosity is considered a lost fluid, i.e., a fluid which is not returned into the intake of the fluid conveying unit including the pump or another source of pressurized fluid.
It has been found that, if the temperature of the transmission fluid rises to a high or very high value (e.g., to a range of between +90° C. and +140° C.), the quantity of hydraulic fluid reaching the low pressure section (including the static fluid consumer or consumers) is too low. Thus, the operation of the lubricating system and/or of the cooling system of the automatic transmission assembly is likely to be unsatisfactory. Consequently, the temperature of fluid which has been caused to flow through the cooling unit or units is not sufficiently low (i.e., has not been sufficiently lowered) to ensure adequate cooling of the entire supply of transmission fluid because the percentage of fluid flowing through the cooling unit or units is too small. This entails a further rise of fluid temperature, i.e., a further drop of viscosity and additional leakage. Such chain reaction entails a progressively decreasing rate of fluid flow through the cooling system and a progressively increasing heating of the circulating transmission fluid. The result is an unstable condition of the automatic transmission assembly, and such condition is aggravated due to continuously increasing percentage of escaping leak fluid so that, if such situation persists, all consumers are likely to receive insufficient quantities of transmission fluid. Attempts to overcome such problems in presently known automatic transmission assemblies include an increase of the regulated volumetric flow.
If the temperature of the transmission fluid drops to a low or very low value (e.g., to between about −30° C. and 0° C.), the static fluid consumer or consumers receives or receive relatively large quantities of hydraulic fluid. Furthermore, as the viscosity of the transmission fluid increases, friction within the fluid also increases; this is particularly undesirable in connection with the flow of fluid through the conduits. Consequently, the pressure of fluid in the static consumer(s) is likely or bound to rise to an excessive value, namely to a value which can entail a destruction of a static fluid consumer (e.g., the fluid cooling unit or units). Moreover, the high pressure of fluid entering the low-pressure fluid consumer or consumers is bound to exert an adverse influence upon (such as an excessive rise of pressure of) fluid flowing in the dynamic consumer or consumers as well as of fluid flowing back into the fluid conveying or supplying unit. This can cause extensive damage t
Agner Ivo
Homm Manfred
Kemmner Benjamin
Bucci David A.
Darby & Darby
Johnson Vicky A.
LuK Lamellen und Kupplungsbau Beteiligungs KG
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