Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Patent
1994-05-27
1997-07-08
Thorpe, Timothy
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
417490, 417295, 475 59, 747301, F04B 104
Patent
active
056454066
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a transmission, especially an automatic gear or a continuously variable gear for motor vehicles with a positive-displacement pump for supplying a lubricating device and the control and activation devices of the transmission wherein the positive-displacement pump is driven by the rotation of a drive motor.
In known gears of this kind, the pumps are so-called fixed displacement pumps whose supply flow increases in proportion to the speed rotation of the drive motor. The pump is generally designed for an idling speed of the drive motor. Thus the feed flow supplied to such a pump must meet the minimum requirements of the transmission that is to be supplied when the drive motor is running at idling speed.
Such a pump conveys more than the required volume when the drive motor is running at a higher rotating speed, the conveyed volume being proportional to the speed of rotation of the drive motor. The duct cross-sections of the pump therefore must be significantly larger than would be required by the minimum supply flow needed to supply the transmission. Besides, the attendant high power consumption of the pump results in a poor transmission efficiency.
The invention is based on the concept of improving the known transmission so that the pump will consume less power and the transmission efficiency will thus be improved. To that end, the pump should have a relatively short length in the axial direction and should contain simple parts that can be made at a reasonable cost.
This problem is solved by the transmission of the present invention. The solution consists above all in the fact that the positive-displacement pump is a pump with a suction throttle.
While the power consumption of pumps without suction throttles rises in proportion to the feed volume and thus increases with the rotation speed of the drive motor, in the case of a pump with a suction throttle, once a certain rotation speed is achieved, an almost constant supply flow is conveyed by the pump and that flow results in a substantially constant power consumption by the pump.
Advantages and practical features of the invention are described below. It is thus possible, for example, to use an internally-geared wheel pump or a radial piston pump. Here, the wheel pump, which has a suction throttle, has the same advantageous features as regards to the space required for mounting as a known internal-wheel pump without a suction throttle. A radial piston pump with a suction throttle, furthermore, offers the advantage of a better volumetric efficiency. the radial piston pump is a very reliable pump because of its very minor leakage even at high pressures.
To provide a simple drive for the pump, its drive means is practically connected with a part of a start-up device that is connected in front of the transmission. In the case of a radial piston pump, its eccentric is advantageously connected with the pump wheel of an hydrodynamic converter. Because the shaft passing through the interior of the positive-displacement pump is generally fixed in the housing, the eccentric of the radial piston pump is made as an eccentric slide bush that is driven via an axially directed projection of the pump shaft of the converter.
When the pistons of the radial piston pump are made as deep-drawn parts--whose radially outwardly directed piston ring cooperates with a suction ring groove arranged in a pump housing and the groove's intake openings--a pump is obtained that "sucks in on top."
This means that the intake space is not located in the interior within reach of the eccentric. In that way, the eccentric space is not impacted by the high under pressure generated in the piston chamber. In the case of a piston pump that "sucks in from below," this eccentric space would have to be filled with oil. On account of the large shaft diameter and the resultant large sealing diameter, air could be sucked in via the seal. This disadvantage can be avoided by the arrangement of the invention because, in this case, the eccentric space contains only an oil mist used to
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Kuhn Walter
Reichenmiller Michael
Rowe Gerald
Zippel Christof
Kim Ted
Thorpe Timothy
ZF Friedrichschafen AG
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