Motors: expansible chamber type – Plural relatively movable or rigidly interconnected working... – Condition responsive means for modifying working member...
Patent
1997-11-04
1999-08-17
Lopez, F. Daniel
Motors: expansible chamber type
Plural relatively movable or rigidly interconnected working...
Condition responsive means for modifying working member...
474 18, 474 28, 477 48, F16H 900
Patent
active
059377291
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
A hydraulic emergency control for an electronically controlled, continuously variable transmission (continuously variable transmission, CVT) is described in not prepublished P 44 10 311.5. The CVT transmission which is preferably employed in motor vehicles, has a control for emergency driving operations which, when the electrohydraulic control of normal driving operations fails, allows a tension of the transmission means with simple hydraulic means. These means are recited in the description of FIGS. 1, 2a and 2b. For one, they allow start-up under full load without slippage of the transmission means and, for another, allow a gear change following starting from a high starting gear ratio to a lower overdrive gear ratio.
ADVANTAGES OF THE INVENTION
The hydraulic emergency control in accordance with the invention is needed in order to make possible emergency operation of a continuously transmitting looped gear without the support of an electrohydraulic actuation means that is active under normal driving conditions. In this case, the emergency control is intended to allow starting under a full load, without exceeding the permissible slippage limit of the looped gear. A gear ratio control, which is a function of the rpm, furthermore is intended to permit a gear adjustment over the entire transmission range. Here, while assuring the required transmission means tension, the hydraulic emergency control is intended to charge the hydraulic axial adjustment devices of the beveled disks with fluid pressure in such a way that known maximum fluid pressures for emergency driving operations, which are partially maintained over the entire transmission range, are lowered outside of the start-up range. The load on the hydraulic components is reduced by lowering the individual fluid pressures, and the losses as well as the wear of the transmission means is reduced by lowering the surface pressures acting on the transmission means members.
To this end, by means of the hydraulic emergency control in accordance with the invention, a fluid pressure limitation for the piston chamber of a second beveled disk axial adjustment device is employed, which is controlled as a function of the fluid pressure in the piston chamber of the axial adjustment device of a first pair of beveled disks. With the further embodiments, the second beveled disk axial adjustment device corresponds to the beveled disk axial adjustment device on the power-take off or secondary side, while the axial adjustment device of the pair of beveled disks on the powered or primary side represents the first beveled disk axial adjustment device. Another arrangement is also in principle conceivable.
For controlling the fluid pressure of the beveled disk contact pressure as a function of the gear ratio, a remote-controlled pressure regulating valve, which is actuated with the aid of the fluid pressure from the piston chamber on the drive side, is arranged parallel with an already provided pressure relief valve. This pressure regulating valve is opened when the permissible fluid pressure in the piston chamber on the drive side has been reached and lowers the fluid pressure on the power take-off side. Alternatively to this separate pressure regulating valve it is also possible to combine the pressure regulating valve and the pressure relief valve in a remote-controlled pressure relief valve. Means are provided for this which permit remote control only during emergency driving operation. These means can be an additional valve which interrupts and blocks the remote control when the electrical actuator fails. For example, it can also be a valve expansion for the valve which switches in the throttle point for picking up the rpm-dependent pressure drop in case of emergency driving operations. All valves required for emergency driving operations can be actuated electrically or hydraulically.
With longer gear ratios in particular, the hydraulic circuit in accordance with the invention creates a fluid pressure which falls on the power take-off side and slightly rises
REFERENCES:
patent: 4400164 (1983-08-01), Cadee
patent: 4657522 (1987-04-01), Miyawaki
patent: 4861318 (1989-08-01), Van Beek et al.
Baeuerle Peter
Haecker Hans
Luh Joachim
Pelders Rine
Spiess Ewald
Lopez F. Daniel
Robert & Bosch GmbH
Striker Michael J.
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