Machine element or mechanism – Elements – Gear casings
Patent
1997-04-11
1999-03-09
Luong, Vinh T.
Machine element or mechanism
Elements
Gear casings
184 612, F16H 5702, F01M 900
Patent
active
058786325
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an automatic transmission, in particular for motor vehicles, with a positive displacement pump for supplying a hydrodynamic converter, a lubrication device and control and actuation devices of the automatic transmission via a number of control channels, wherein the positive displacement pump is driven at the rpm of the drive engine and wherein an excess flow of a pressure medium under pressure is fed to the positive displacement pump for charging it.
In such known automatic transmissions the pumps are so-called constant pumps, i.e. that a constant feed volume is supplied with every revolution of the drive engine and thus of the positive displacement pump. The feed flow of such a pump increases proportionally with its drive rpm. The design of the pump is generally based on its idle rpm. The feed flow supplied in this case already must meet the requirements of the transmission to be supplied.
At higher rpm, such a pump conveys a multiple of the required amount. A correspondingly large amount of pressure medium must be aspirated. Cavitation and pressure fluctuations therefore occur at higher rpm. Cavitation results in noise and pressure fluctuations cause steering problems.
An automatic transmission is known from DE-A1-42 00 910, wherein the pump is charged by an excess flow. The excess flow comes from a flow control valve or a pressure control valve. Here the excess flow emerges from a pressure bore of the flow or pressure control valve into a transverse bore, whereby it pressure control valve into a transverse bore, in the process pulls pressure medium out of a suction bore, which is connected with a reservoir, and flows from there into the suction nodule of the positive displacement pump.
Thus, a relatively large outlay is necessary for charging the positive displacement pump: a flow or pressure control valve must be installed in an additional bore cutout of the pump housing. The transverse bore must be cut very exactly, so that it is in a correct relationship with the control edges of the flow or pressure control valve. Furthermore, a certain amount of installation space for the flow or pressure control valve is required in the automatic transmission.
An automatic transmission is known from U.S. Pat. No. 3,620,646, in which an excess flow of a flow control valve is used for charging a positive displacement pump. In this case the excess flow is a function of the amount. The pressure in the automatic transmission is not taken into consideration.
Another arrangement of a stream feed of an internal gear pump is shown in FR-A-2443598. In this case a feed stream of an internal gear pump is introduced coaxially with a suction flow. This arrangement is very difficult to produce.
Furthermore, in this arrangement a very large distance in relation to the length of the injector is provided in between the feed nozzle and the suction nodule. This distance is preset because of a diffusor, which must be connected to the nozzle, and a mixing tube following this.
A similarly large distance in relation to the length of the feed nozzle is also provided in U.S. Pat. No. 3,620,646.
The invention is based on the object of creating an automatic transmission wherein charging of the positive displacement pump can be realized in a cost-effective manner by simple means and in the process requires as little space as possible.
SUMMARY OF THE INVENTION
This object is attained by the automatic transmission of the present invention. The object is attained in that in an automatic transmission in accordance with the present invention the feed nozzle terminates in the vicinity of the suction area of the positive displacement pump in a suction channel connected with a reservoir.
Advantageous and useful embodiments of the invention are recited in the description. The feed channel and the feed nozzle can be cast in the pump housing in a particularly simple manner by the lost-wax process. By means of this it is also possible to steadily reduce its cross section in a simple manner, so that the pressure medium can be f
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Hubler Wolfgang
Martin Gerhard
Tiesler Peter
Luong Vinh T.
ZF Friedrichshafen AG
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