Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Fluid pressure actuator for adjustment of member
Patent
1997-02-06
1999-03-23
Marmor, Charles A.
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Fluid pressure actuator for adjustment of member
477 50, 417 15, F16H 5900, B60K 4112, F04B 4900
Patent
active
058851780
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electro-hydraulic control means for controlling a continuously variable loop transmission and, more particularly, to an electro-hydraulic control means for controlling a hydraulic pressure in a continuously variable loop transmission including a hydraulic bevel disk axial displacement device provided with a secondary piston chamber and a pump for supplying the secondary piston chamber with hydraulic oil in order to provide a clamping force in the displacement device, wherein the control means includes several individual valves for adjusting the hydraulic pressure including a proportioning pressure relief valve and a flow control valve. The invention also relates to a loop transmission including the aforementioned control means.
2. Prior Art
A hydraulic control for an electronically controlled continuously variable transmission (continuously variable transmission: CVT) is described in EP 0 451 887 A1. The CVT transmission, which is preferably used in automobiles has, among other things, an electronic control which regulates the hydraulic oil pressure in the secondary side of the piston chamber in order to set the clamping force during normal driving operations in such a way that advantageous transmission effectiveness is achieved. For regulating the secondary oil pressure, the control requires the vicinity actual pressure value in the area of the secondary side piston chamber. A pressure sensor is disposed there for this purpose. The nominal pressure is adjusted as a function of the measured actual pressure via a directly controlled valve.
SUMMARY OF THE INVENTION
Among other things, the hydraulic transmission in accordance with the invention comprises a proportional pressure relief valve for regulating the secondary oil pressure, which is controlled by an electrically operated flow control valve. The electrical supply of the actuating device of the flow control valve is performed by a control unit which detects the control oil pressure of the control line leading to the proportional pressure relief valve by means of a pressure sensor. Among other things, the control unit contains, besides a sensor signal evaluating device and an electronic pressure control device, a multiplier device that multiplies by a ratio between the pressure working surfaces on the control oil pressure side and on the secondary oil pressure side of the proportional pressure relief valve slide. Since the hydraulic oil pressures acting on the proportional pressure relief valve slide are inversely proportional to the two pressure working surface areas, it is possible to calculate the secondary oil pressure from the respective control oil pressure. The flow control valve is supplied with current as a function of the calculated secondary oil pressure obtained from the pressure sensor signal using the multiplier.
Based on the invention, it is no longer necessary to connect the pressure sensor with or in a working line under high secondary oil pressure, or the piston chamber on the secondary side. Instead, only one pressure sensor is required, which is designed for the lower control oil pressure. It is therefore possible to employ a simpler and more cost-effective sensor, which can operate without its own oil feed.
Furthermore, the sensor detecting the control oil pressure can also be installed away from the respective control line, for example directly in the control unit.
In addition, the characteristics of the control path for the pressure regulator housed in the control unit becomes more advantageous, since at least two dynamic elements can be omitted. For example, these are, for one, the valve slide dynamics of a directly controlled pressure relief valve and, for another, the elasticity of the secondary side piston chamber including the associated working line sections.
BRIEF DESCRIPTION OF THE DRAWING
An exemplary embodiment, in addition to the prior art, is schematically represented in the drawings in the form of hydraulic circuit diagram
REFERENCES:
patent: 4764155 (1988-08-01), Kumura et al.
patent: 4869706 (1989-09-01), Miyata et al.
patent: 4875892 (1989-10-01), Sueda
patent: 5045028 (1991-09-01), Rattunde et al.
patent: 5049112 (1991-09-01), Gunsing
patent: 5098345 (1992-03-01), Van Vuuren
patent: 5173084 (1992-12-01), Lemieux
patent: 5378198 (1995-01-01), Moroto et al.
patent: 5431602 (1995-07-01), Hendricks et al.
Kaness Matthew A.
Marmor Charles A.
Robert & Bosch GmbH
Striker Michael J.
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