192 clutches and power-stop control – Clutches – Fluent material
Patent
1996-01-23
1998-01-06
Ta, Khoi Q.
192 clutches and power-stop control
Clutches
Fluent material
475 93, 475108, F16D 3104
Patent
active
057044597
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a positive displacement coupling device, of the type in which the release or blockage of the delivery of a hydraulic pump is controlled in order selectively to prevent or enable relative rotation between two elements of the pump.
The present invention also concerns a transmission device with at least two ratios and in which the gradual starting function is ensured by a coupling device of the type described above.
FR-A-1 191 526 and U.S. Pat. No. 3,130,607, for example, disclose positive displacement coupling devices comprising a common toothed member meshing with several planet gears supported in rotation in a cage, thereby to provide as many hydraulic individual pumps as there are planet gears. In fact, in numerous applications it is necessary to make use of several individual pumps for the pressure generated in the delivery area of each pump when the delivery is blocked not to reach prohibitive levels.
In known coupling devices, delivery ways connect the delivery area of the various individual pumps to a valve that controls the release or blockage of the individual pumps' deliveries. When the delivery is blocked the common toothed member can no longer turn in relation to the cage and coupling therefore occurs between them.
There are two reasons why in practice the common toothed member has a relatively large diameter. On the one hand, the common toothed member must mesh with several planet gears, which means that the former has a longer perimeter; on the other hand, the greater the diameter of the common toothed member, the greater the torque of the force produced by each individual pump when its delivery is blocked.
Consequently, the higher the coupling torque to be achieved, the greater the number of planet gears and diameter of the common toothed member. When the delivery of the individual pumps is released, the flow of hydraulic fluid produced by the pumps is proportional to the number of planet gears and diameter of the common toothed member. In conclusion, obtaining a given coupling torque necessarily results in a given flow of hydraulic fluid when the device is in the uncoupled state.
It has been found that in most situations, these flow rates reach extremely high levels, corresponding to very high speeds of circulation of oil in the channels that form the link between the delivery areas, control valve, oil reservoir and then from the latter to the inlet areas. In the vast majority of cases, these speeds are totally prohibitive whatever the design envisaged for the channels and the valve. This results in noisy operation, overheating and loss of pressure, and makes it impossible to achieve perfect uncoupling.
The object of the present invention is therefore to provide a positive displacement coupling device which can be used in numerous practical situations, particularly for gradual coupling between the driving wheels of a vehicle and a thermal engine on starting, which is technically simple and offers good uncoupling qualities without the pressure of the hydraulic fluid during the coupled state being excessive.
According to the invention, the positive displacement coupling device comprising a common toothed member meshing with at least one planet gear mounted in rotation in a housing to form with each planet gear and the housing an individual hydraulic pump comprising an hydraulic fluid inlet area and an hydraulic fluid delivery area on either side of a meshing area between the common toothed member and each planet gear, and distribution means selectively to enable and prevent the flow of hydraulic fluid from the delivery area of each pump, is characterised in that the distribution means comprise a cutaway movable organ adjacent to one of the faces of each planet gear, and in that the movable organ can be moved between a release position in which it establishes, due to its cutaway structure, direct communication between the inlet and delivery areas, and a coupling position in which it blocks off at least one of the two inlet and delivery areas associated with each planet ge
REFERENCES:
patent: 1599345 (1926-09-01), Pike
patent: 1903714 (1933-04-01), Frias et al.
patent: 2730218 (1956-01-01), Wickman
patent: 3130607 (1964-04-01), Kraemer
patent: 3623584 (1971-11-01), Hill
patent: 5456642 (1995-10-01), Frost
Antonov Automotive Technologies B.V.
Ta Khoi Q.
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