Measuring and testing – Fluid pressure gauge – Combined
Reexamination Certificate
1999-06-04
2001-11-20
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Combined
Reexamination Certificate
active
06318182
ABSTRACT:
TECHNICAL FIELD
The present invention relates to measurement of hydraulic pressure, and more particularly to a device that monitors solenoid current to measure hydraulic pressure without using a separate pressure sensor.
BACKGROUND ART
Automotive transmissions require adequate hydraulic pressure for reliable operation. Currently, solenoid valves are the most common way for regulating hydraulic pressure in transmissions, such as in a clutch control valve, and the pressure is measured using a pressure transducer or some other external pressure sensor attached to the solenoid valve. In a clutch control valve, for example, the hydraulic pressure indicates the force at which the clutch is engaging. The additional sensing circuitry, however, adds complexity to the automotive transmission control system. Further, adding sensors and connecting circuitry to the solenoid valves require extra parts and extra wiring, increasing the cost and complexity of the automotive transmission system.
Therefore, there is a need for a device that measures the hydraulic pressure of a solenoid valve while minimizing the extra circuitry needed to conduct the pressure measurement.
SUMMARY OF THE INVENTION
Accordingly, the present invention measures hydraulic pressure of a solenoid valve by monitoring the change in the valve's inductive characteristics as the solenoid moves. Because changes in the inductive characteristics of the solenoid valve affect the current rise profile of the solenoid, the current rise profile of the solenoid valve itself can be monitored to determine the hydraulic pressure, without using a separate pressure sensor. In one embodiment, an input voltage source is coupled to the solenoid valve, and the current rise for a given input voltage is measured over time to detect any movement in the solenoid. The solenoid will tend to move at an earlier time and reach a lower maximum current under low hydraulic pressure and at a later time and higher maximum current under high hydraulic pressure. Alternatively, or in addition, the pressure can be calculated directly from the maximum current reading. As a result, the solenoid valve itself provides information about the hydraulic pressure, without requiring the use of an additional pressure transducer or other sensor attached to the solenoid valve.
REFERENCES:
patent: 3691821 (1972-09-01), Davey
patent: 5165448 (1992-11-01), Handte
Eaton Corporation
Oen William
Rader & Fishman & Grauer, PLLC
LandOfFree
Measurement of transmission oil pressure by monitoring... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measurement of transmission oil pressure by monitoring..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measurement of transmission oil pressure by monitoring... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2601576