Method and apparatus for measuring oil level

• US 4,782,698 A
• Filed: 12/29/1986
• Issued: 11/08/1988
• Est. Priority Date: 12/29/1986
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Wilson, Thomas H.
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US06/947,297
• Time in Patent Office: 680 Days
• Field of Search: 73/304 C, 364/509, 374/144
• US Class Current: 73/304.00C
• CPC Class Codes: F16N 19/003 Indicating oil level measuring liquid level in general G01F
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors

Abstract

A single capacitor is used to measure the oil level in an engine or transmission and compensate the sensed capacitance for changes in dielectric constant. Measurements are made for two different running conditions, one giving a capacitance reading dependent only on dielectric constant and one giving a capacitance dependent on oil level as well as dielectric constant. The transmission application uses a capacitor that is fully immersed in oil when the engine is off and partly immersed when the engine is idling, so that both types of measurements can be obtained. The engine application uses a capacitor having an upper section spaced from a lower section. Only the lower section is immersed during engine idle to render dielectric constant information, while the upper section is partly immersed when the engine is off.

Claims

1. Means for measuring oil level in an automotive vehicle subject to change of oil level according to engine running conditions, comprising an oil reservoir containing oil the level of which is to be measured, a single capacitor in the reservoir positioned for immersion in said oil to a predictable amount during a reference measuring period and for immersion in said oil to a variable level during a level measuring period, and means controlled by engine running conditions for measuring the capacitances of said capacitor respectively during the reference and level measuring periods and for comparing the two capacitances to determine the level of oil in said reservoir.

2. Means for measuring oil level in an automotive vehicle subject to change of oil level according to engine running conditions, comprising an oil reservoir containing oil the level of which is to be measured, a single capacitor in the reservoir positioned for immersion in said oil to a predictable amount during a reference measuring period and for immersion in said oil to a variable level during a level measuring period, means for enabling said reference measuring period and said level measuring period in a predetermined sequence in response to running conditions of said engine, means for measuring the capacitance of said capacitor during each of said measuring periods, means effective during one of the measuring periods for storing the measured capacitance, and means effective during the other of the measuring periods for comparing the stored capacitance and the current capacitance, whereby the effective oil level is determined independently of changes in the oil dielectric constant.

3. Means for measuring oil level in an automotive engine comprising, a reservoir containing oil the level of which is to be measured, a single capacitor having a pair of opposed plates divided into two spaced sections, a lower section positioned for total immersion in the oil when the engine is idling and an upper section positioned in the range of oil level to be measured only when the engine is off, means for measuring the level capacitance of said capacitor when the engine is off and the reference capacitance of said capacitor when the engine is idling, and means for determining the ratio of the level capacitance to the reference capacitance to yield a compensated level capacitance whereby the effective oil level is determined independently of changes in the oil dielectric constant.

4. Means for measuring oil level in an automotive transmission comprising, a transmission driven by an engine, the transmission having a reservoir that contains oil and which is filled with oil when the engine is off and partially filled with oil when the engine is idling, a capacitor in the reservoir for complete immersion in said oil when the engine is off and for spanning the range of oil level to be measured when the engine is idling, means for measuring the level capacitance of said capacitor when the engine is idling and the reference capacitance of said capacitor when the engine is off, and means for determining the ratio of the level capacitance to the reference capacitance to yield a compensated level capacitance whereby the effective oil level is determined independently of changes in the oil dielectric constant.

5. The method of measuring oil level in a reservoir of an automotive vehicle wherein the reservoir contains oil and wherein the oil level is subject to vehicle engine operation, comprising the steps of;

measuring the capacitance of a capacitor while it is immersed in oil to a predetermined extent during one engine condition, thereby establishing a reference capacitance, measuring the capacitance of the same capacitor while it is partially immersed in oil to an unknown extent during another engine condition, thereby establishing an uncompensated level capacitance, storing at least one of the measured capacitances for comparison to the other capacitance, and determining the ratio of the capacitances to obtain a value of oil level independently of the oil dielectric constant.

6. The method of measuring oil level in a reservoir of an automotive vehicle engine wherein the reservoir contains oil and wherein the oil level is subject to vehicle engine operation, comprising the steps of;

measuring the capacitance of a capacitor while it is partially immersed in oil to an extent dependent on oil level when the engine is off, thereby establishing a level capacitance, measuring the capacitance of the same capacitor during engine idling while it is immersed in oil to a predetermined extent, storing at least one of the measured capacitances, determining the ratio of the capacitances to obtain a value of oil level independently of the oil dielectric constant, and producing an output signal bearing oil level information.

7. The method of measuring oil level as defined in claim 6 including the steps of measuring the oil temperature and compensating the oil level value for temperature.

8. The method of measuring oil level in a reservoir of an automotive vehicle transmission wherein the reservoir contains oil and wherein the oil level is subject to vehicle engine operation, comprising the steps of;

measuring the capacitance of a capacitor when the engine is idling and the capacitor is partially immersed in oil to an unknown extent dependent on oil level, thereby establishing a level capacitance, measuring the capacitance of the same capacitor when the engine is off and the capacitor is immersed in oil to a predetermined extent, storing at least one of the measured capacitances, determining the ratio of the capacitances to obtain a value of oil level independently of the oil dielectric constant, and producing an output signal bearing oil level information.

9. The method of measuring oil level as defined in claim 8 including the steps of measuring the oil temperature and compensating the oil level value for temperature.