JP2009257880A - Oil film thickness measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil film thickness measuring apparatus and a method for preventing accuracy degradation in measuring oil film thickness due to changes in the temperature of oil films. <P>SOLUTION: The oil film thickness measuring apparatus is provided with: a film thickness measuring electrode 12 embedded in a piston ring sliding surface 1a of a cylinder liner 1 in such a way as to be in the same plane and electrically insulated; a temperature detection device 14 for detecting the temperature T of an oil film 3 between the electrode and a piston ring; an electrostatic capacitance detector 16 for detecting the electrostatic capacitance C of the oil film between the electrode and the piston ring; and a film thickness computing device 18 for computing the oil film thickness (d) on the basis of a detected temperature of the oil film and a detected electrostatic capacitance. The film thickness computing device stores temperature characteristics of oil film dielectric constants and performs temperature compensation on oil thickness dielectric constants on the basis of these characteristics. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an oil film thickness measuring device and method in an engine.

  Patent Documents 1 and 2 have already been proposed as means for measuring the oil film thickness inside the cylinder during engine operation.

  The oil film thickness measurement method of Patent Document 1 uses a pickup electrode embedded in the piston ring so that the surface on which the insulating coating is applied is exposed to the outer peripheral surface of the piston ring in the method of measuring the piston ring oil film thickness by the capacitance method. The pickup electrode is made of aluminum, and the insulating film on the surface thereof is an anodized film.

  The “film thickness measuring apparatus and method” of Patent Document 2 is intended to accurately and inexpensively measure the film thickness of an oil film on a piston ring sliding surface inside an engine cylinder.

  Therefore, as shown in FIG. 6, this device is formed in the gap by measuring the capacitance C of the gap between the electrode 51 and the piston ring 52 provided flush with the piston ring sliding surface of the cylinder liner. Is a film thickness measuring device that measures the film thickness d of the lubricating oil film, and charges the capacitance C by supplying a constant current to the electrode 51, and changes the charging voltage associated with the charging. A capacitance C based on the capacitance indicated by the detection signal input from the capacitance detection unit 53, and a capacitance detection unit 53 that detects the capacitance C based on the capacitance and outputs a detection signal indicating the capacitance. And a film thickness calculator for calculating the film thickness d.

Japanese Patent Publication No. 02-30441, “Method for Measuring Oil Film Thickness of Cylinder Inner Surface and Piston Ring Outer Surface” JP 2007-107947 A, “Film thickness measuring apparatus and method”

  As described above, the conventional oil film thickness measuring means using the electrostatic capacitance method measures the capacitance of the oil film, and calculates the oil film thickness from this. Further, when calculating the oil film thickness, the oil film thickness was calculated with the dielectric constant of the oil film being constant.

  However, in the conventional measuring means, when the temperature of the oil film changes, the dielectric constant of the oil film changes. Therefore, there is a problem that the accuracy of the oil film thickness measurement is lowered due to the temperature change of the oil film.

  The present invention has been developed to solve the above-described conventional problems. That is, an object of the present invention is to provide an oil film thickness measuring device and method that can prevent a decrease in measurement accuracy of the oil film thickness due to a temperature change of the oil film.

According to the present invention, the electrode for film thickness measurement embedded in the piston ring sliding surface of the cylinder liner flush and electrically insulated,
A temperature detecting device for detecting the temperature of the oil film between the electrode and the piston ring;
A capacitance detector for detecting the capacitance of the oil film between the electrode and the piston ring;
A film thickness calculator that calculates the oil film thickness from the detected oil film temperature and capacitance;
The film thickness calculation apparatus stores an oil film dielectric constant temperature characteristic, and provides an oil film dielectric constant temperature compensation based on the temperature characteristic.

  According to a preferred embodiment of the present invention, when the electrode faces the piston ring, the temperature detection device faces the same piston ring and is flush with the piston ring sliding surface of the cylinder liner. This is a temperature sensor for temperature detection that is embedded in an insulated state.

  According to still another preferred embodiment of the present invention, the temperature detection device is installed so as to be switchable with the capacitance detector, and detects resistance of an oil film between the electrode and the piston ring. Circuit.

Further, according to the present invention, the temperature of the oil film between the piston ring and the electrode for measuring the film thickness, which is flush with and electrically insulated from the piston ring sliding surface of the cylinder liner,
Detecting the capacitance of the oil film between the electrode and the piston ring;
Stores temperature characteristics of oil film dielectric constant and performs temperature compensation of oil film dielectric constant based on this.
An oil film thickness measuring method is provided, wherein the oil film thickness is calculated from the detected oil film temperature and capacitance.

  According to a preferred embodiment of the present invention, when the electrode faces the piston ring, the temperature of the oil film is detected by the temperature sensor for temperature detection facing the same piston ring.

  According to another preferred embodiment of the present invention, an electric resistance of an oil film between the electrode and the piston ring is detected by a resistance detection circuit that is installed so as to be switchable with the capacitance detector. The oil film temperature is calculated from the resistance and capacitance.

  According to the apparatus and method of the present invention, the temperature of the oil film is detected by the temperature detection device, the temperature characteristic of the oil film dielectric constant is stored by the film thickness calculation device, and the temperature compensation of the oil film dielectric constant is performed based on this. Since the oil film thickness is calculated from the detected oil film temperature and the capacitance, it is possible to prevent the measurement accuracy of the oil film thickness from being lowered due to the temperature change of the oil film.

Further, the temperature detection device is a temperature sensor for temperature detection (for example, a thermocouple), and when the electrode for film thickness measurement is opposed to the piston ring, the temperature detection device is opposed to the same piston ring (that is, It is possible to measure the oil film temperature more accurately by disposing the film at the same height as the electrode) and in the vicinity of the electrode for film thickness measurement and measuring the oil film temperature at the oil film thickness measurement position.
Moreover, the oil film thickness can be accurately measured by performing temperature compensation of the dielectric constant based on the temperature characteristics of the dielectric constant of the oil film stored in advance.

  In addition, when the temperature detection device is a switch that can be switched with the capacitance detector and detects an electric resistance of an oil film between the electrode and the piston ring, an electrode for film thickness measurement The temperature of the oil film is calculated from this by detecting the electric resistance of the oil film using the, so there is no need for a temperature sensor for temperature detection, and both the oil film temperature and the capacitance can be accurately detected at the same position. .

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

FIG. 1 is a first embodiment of an oil film thickness measuring device (partially sectional view) according to the present invention.
In this figure, an oil film thickness measuring device 10 of the present invention includes an electrode 12 for film thickness measurement, a temperature detecting device 14, a capacitance detector 16, and a film thickness calculating device 18.

  The electrode 12 for measuring the film thickness is embedded in the piston ring sliding surface 1a of the cylinder liner 1 so as to be flush with and electrically insulated.

  The temperature detection device 14 detects the temperature T of the oil film 3 between the electrode 12 and the piston ring 2. When the electrode 12 faces the piston ring 2, the temperature detection device 14 faces the same piston ring 2 and is embedded in the piston ring sliding surface 1 a of the cylinder liner 1 so as to be flush and electrically insulated. This is a temperature sensor for temperature detection. The temperature sensor 14 includes a thermocouple 14 a and a bridge circuit 14 b and outputs the detected temperature T to the film thickness calculation device 18.

  The capacitance detector 16 detects the capacitance C of the oil film 3 between the electrode 12 and the piston ring 2, and outputs the detected capacitance C to the film thickness calculation device 18.

  The film thickness calculation device 18 is, for example, a computer (PC), stores the temperature characteristics of the oil film dielectric constant, and based on the oil film dielectric constant temperature compensation, the oil film temperature T and the capacitance C are detected. The oil film thickness d is calculated and output to an output device (not shown).

FIG. 2 is a detailed view of the vicinity of the electrode portion for film thickness measurement in FIG.
In this figure, a film thickness measuring electrode 12 is formed by concentrically covering a cylindrical sensor electrode 12a with an insulating material 12b and further concentrically covering the outer periphery of the insulating material 12b with a sensor case 12c of a conductor. It has a structure. Such an electrode 12 is press-fitted into the sensor mounting hole so as to be flush with the piston sliding surface 1a.
When facing the piston ring 2, the sensor electrode 12a forms a capacitor (measurement capacitor) having the piston ring 2 as a counter electrode and the oil film 3 as a dielectric.

  The sensor electrode 12 a is connected to the capacitance detector 16 through the coaxial cable 13. Also, as shown in the figure, one end of the braided wire forming the shield layer of the coaxial cable 13 is connected to the conductor sensor case 12c, and the other end is connected to the grounding portion (GND: ground) of the capacitance detector 16. It is connected. Thereby, the sensor case 12c and the electrostatic capacitance detector 16 are commonly grounded.

FIG. 3 is a detailed view of the vicinity of the capacitance detector of FIG.
In this figure, the sensor electrode 12a, the oil film 3, and the piston ring 2 constitute an equivalent circuit in which a capacitor having a capacitance C using the oil film 3 as a dielectric is formed. The capacitance detector 16 includes a power supply voltage V1, a negative voltage (−V2), resistors R1 and R2, a reset switch 16a, and a C / V conversion board 16b.
The power supply voltage V1 and the resistor R1 are connected in series to the sensor electrode 12a as a constant current circuit. The resistor R2, the negative voltage (−V2), and the reset switch 16a that supplies a constant current constitute a discharge circuit. The C / V conversion board 16b detects the capacitance C from the voltage change.

The principle of the capacitance detector will be described below.
As shown in FIG. 3, a constant current is supplied from a constant current circuit including a power supply voltage V1 and a resistor R1 to the sensor electrode 1a to charge a capacitor having a capacitance C. With the C / V conversion board 16b, the capacitance C of the measuring capacitor can be obtained from the charging time until the charging voltage during charging rises from 0V to a predetermined voltage value. In order to continuously measure the capacitance C, it is necessary to discharge the charged charge. Therefore, the reset switch 16a is turned on at a predetermined cycle, and a negative voltage (-Vr) is applied to the measurement capacitor from the reset power source to discharge the electric charge.

2 has a capacitance C1 (described in FIG. 3) unique to the electrode between the sensor electrode 12a and the sensor case 12c. This capacitance C1 can be obtained in advance by calibrating the capacitance detector 16 in the absence of an oil film.
Therefore, in actual measurement, the capacitance C + C1 is obtained by the capacitance detector 16 described above, and the capacitance C1 unique to the electrode is removed from the capacitance C + C1.

Using the apparatus described above, according to the method of the present invention, first, the electrode 12 for measuring the film thickness and the piston ring embedded in the piston ring sliding surface 1a of the cylinder liner 1 so as to be flush with each other and electrically insulated. 2 is detected by the temperature detector 14 and output to the film thickness calculator 18.
In parallel, the electrostatic capacity C of the oil film 3 between the electrode 12 and the piston ring 2 is detected by the electrostatic capacity detector 16 and output to the film thickness calculation device 18.
The film thickness calculation device 18 stores the temperature characteristic of the dielectric constant of the oil film 3 in advance, performs temperature compensation of the oil film dielectric constant based on this, and calculates the oil film thickness d from the detected oil film temperature T and capacitance C. Calculate and output.

The temperature compensation and calculation means in the film thickness calculation device 18 will be described below.
In the present invention, the dielectric constant of the oil film is treated as a function of the temperature T.
The electrostatic capacity C of the oil film 3 can be expressed by equation (1).

C = ε (T) × S / d (1)
Here, S is the electrode area of the sensor electrode 12a, d is the oil film thickness, ε (T) is the dielectric constant (temperature-dependent function), and T: the temperature of the oil film (obtained by the temperature sensor).

The oil film thickness can be calculated by equation (2).
d = ε (T) × S / C (2)

4 is a second embodiment of the oil film thickness measuring device (partial sectional view) according to the present invention, and FIG. 5 is a detailed view (partly equivalent) of the temperature detecting device and the capacitance detector of FIG. Circuit).
In this example, the temperature detection device 14 is a resistance detection circuit installed so as to be switchable with the capacitance detector 16, or detects the electric resistance R of the oil film 3 between the electrode 12 and the piston ring 2, The temperature T of the oil film is calculated from the electric resistance, the capacitance, and the film thickness / temperature characteristics of both.

  In FIG. 3, the sensor electrode 12a, the oil film 3, and the piston ring 2 constitute a capacitor having a capacitance C using the oil film 3 as a dielectric. C1 is a capacitance inherent to the electrode between the sensor electrode 12a and the sensor case 12c, and R is an electric resistance between them.

In this example, the temperature detection device 14 includes a power supply voltage V3 and a resistor R3. Further, the temperature detection device 14 and the capacitance detector 16 are switched by a switching relay 19.
The temperature detector 14 detects an intermediate voltage Vr between the resistor R3 and the resistor R, and from this, the electric resistance R of the oil film 3 can be obtained by the following equation (3).

  R = (R3 × Vr) / (V3-Vr) (3)

  Furthermore, since the electric resistance R of the oil film 3 has a certain relationship with the temperature T of the oil film 3 and the oil film thickness d, by storing this relationship (R = R (T, d)) in advance, The temperature T can be obtained from the temperature characteristics of the resistance R and the capacitance.

  According to the above-described apparatus and method of the present invention, the temperature T of the oil film 3 is detected by the temperature detection device 14, the temperature characteristic of the oil film dielectric constant is stored by the film thickness calculation device 18, and the oil film dielectric constant is based on this. Since the oil film thickness d is calculated from the oil film temperature T detected by performing the temperature compensation and the capacitance C, it is possible to prevent the measurement accuracy of the oil film thickness from being lowered due to the temperature change of the oil film.

Further, when the temperature detection device 14 is a temperature sensor for temperature detection (for example, a thermocouple), and the electrode 12 for film thickness measurement faces the piston ring 2, the temperature detection device 14 faces the same piston ring 2. The oil film temperature can be measured more accurately by arranging it at the same height as the electrode 12 and measuring the oil film temperature at the oil film thickness measurement position.
Moreover, the oil film thickness can be accurately measured by performing temperature compensation of the dielectric constant based on the temperature characteristics of the dielectric constant of the oil film stored in advance.

  When the temperature detector 14 is a switch that can be switched with the capacitance detector 16 and is a resistance detection circuit that detects the electrical resistance R of the oil film 3 between the electrode 12 and the piston ring 2, the film thickness measurement is performed. Because the oil film electrical resistance R is detected using the electrode 12 and the oil film temperature T is calculated from this, the temperature sensor for detecting the temperature is not required, and both the oil film temperature and the capacitance are accurately located at the same position. Can be detected.

  In addition, this invention is not limited to embodiment mentioned above, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

1 is a diagram (cross-sectional view) of a first embodiment of an oil film thickness measuring device according to the present invention. FIG. 2 is a detailed view of an electrode for film thickness measurement in FIG. 1. FIG. 2 is a detailed view of the capacitance detector of FIG. 1. It is 2nd Embodiment figure (sectional drawing) of the oil film thickness measuring apparatus by this invention. FIG. 5 is a detailed view of the temperature detection device and the capacitance detector of FIG. 4. 10 is a schematic diagram of “film thickness measuring apparatus and method” in Patent Document 2. FIG.

Explanation of symbols

1 Cylinder liner, 1a Piston ring sliding surface,
2 piston ring, 3 oil film,
10 Oil film thickness measuring device, 12 Electrode for film thickness measurement,
12a sensor electrode, 12b insulating material, 12c sensor case,
13 coaxial cable, 14 temperature detector,
14a thermocouple, 14b bridge circuit, 16 capacitance detector,
16a reset switch, 16b C / V conversion board,
18 Film thickness calculator (PC), 19 switching relay

Claims (6)

An electrode for film thickness measurement embedded in a cylinder liner with a piston ring sliding surface flush and electrically insulated;
A temperature detecting device for detecting the temperature of the oil film between the electrode and the piston ring;
A capacitance detector for detecting the capacitance of the oil film between the electrode and the piston ring;
A film thickness calculator that calculates the oil film thickness from the detected oil film temperature and capacitance;
The film thickness calculation device stores the temperature characteristic of the oil film dielectric constant, and performs temperature compensation of the oil film dielectric constant based on the temperature characteristic.   The temperature detection device is for temperature detection that is embedded in the piston ring sliding surface of the cylinder liner that is flush with and electrically insulated when the electrode is opposed to the piston ring. The oil film thickness measuring apparatus according to claim 1, wherein the oil film thickness measuring apparatus is a temperature sensor.   The temperature detection device is a resistance detection circuit that is switchably installed with the capacitance detector and detects an electric resistance of an oil film between the electrode and the piston ring. The oil film thickness measuring device described. Detects the temperature of the oil film between the piston ring and the electrode for film thickness measurement, which is embedded in the piston ring sliding surface of the cylinder liner in a flush and electrically insulated manner,
Detecting the capacitance of the oil film between the electrode and the piston ring;
Stores temperature characteristics of oil film dielectric constant and performs temperature compensation of oil film dielectric constant based on this.
An oil film thickness measuring method, wherein the oil film thickness is calculated from the detected oil film temperature and capacitance.   5. The oil film thickness measuring method according to claim 4, wherein when the electrode faces the piston ring, the temperature of the oil film is detected by a temperature sensor for temperature detection facing the same piston ring.   By detecting the electric resistance of the oil film between the electrode and the piston ring by a resistance detection circuit installed so as to be switchable with the capacitance detector, the temperature of the oil film is calculated from the electric resistance and the capacitance. The oil film thickness measuring method according to claim 4.

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