JPH0230441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the thickness of an oil film on the inner peripheral surface of a cylinder and the outer peripheral surface of a piston ring.

In order to reduce piston ring friction loss and reduce lubricant consumption, the lubrication properties of piston rings must be clarified. To do this, it is necessary to accurately measure the thickness of the oil film between the outer peripheral surface of the piston ring and the inner peripheral surface of the cylinder. The piston ring oil film thickness is measured by the capacitance method, but the measurement methods published so far are
Since the surface of the pick-up electrode was not insulated, when the oil film became thin, the pick-up electrode came into direct contact with the other side, making it impossible to accurately measure the thickness of the oil film. Further, since the oil film thickness is measured by installing a large number of pick-up electrodes on the cylinder side, only intermittent measured values can be obtained, but it is desirable that the measured values during one cycle be continuous.

An object of the present invention is to provide a method for measuring the oil film thickness of a piston ring. This method is characterized in that the oil film between the outer circumferential surface of the piston ring and the inner circumferential surface of the cylinder is measured using the insulated coated electrode. The electrode can continuously measure the thickness of the oil film between the outer peripheral surface of the piston ring and the inner peripheral surface of the cylinder without contacting the other cylinder. The insulating coating applied to the surface of the pick-up electrode is created by anodizing the surface of the electrode.
Alternatively, it is formed by applying an insulating heat-resistant resin to the surface of the electrode.

Since the measuring method of the present invention does not allow the pick-up electrode to come into direct contact with the other cylinder, the thickness of the oil film near the top dead center and bottom dead center can be accurately measured, which was difficult to measure accurately due to the thin thickness of the oil film in the past. Furthermore, since a pick-up is provided on the piston ring side, it has the advantage that continuous oil film thickness measurement values can be obtained during one cycle. moreover,
If the insulating coating on the surface of the pick-up electrode is made of a material with a higher dielectric constant than lubricating oil, there is also the advantage that the sensitivity will be better than the conventional one without an insulating coating.

A pick-up electrode used in the measurement method of the present invention will be explained based on an embodiment shown in the drawings. As shown in Figures 1 and 2, the first piston ring 1 for a diesel engine without chrome plating
(width 3.8 mm, thickness 5.25 mm) A groove 2 (length 1.2 mm, width 11 mm, depth 0.6 mm) is carved on the outer circumferential surface at a position 90 degrees from the abutment, and a hole 3 passes through the groove to the back side. wear it. An aluminum pick-up electrode 5 whose surface is provided with an insulating coating 4 by anodizing is fitted into the groove 2, and a shield wire 6 is connected to the pick-up electrode 5 through the hole 3. A heat-resistant thermosetting resin 7 is filled in the gap between the groove 2 and the pick-up electrode 5 and between the hole 3 and the shield wire 6.
Fill it. In order to match the sliding surface of the anodized insulation coating 4 with the sliding surface of the piston ring 1, a break-in operation or the like is performed, if necessary. In the case of an aluminum anodic oxide film, the thickness of the insulating coating 4 is approximately 20 μm, but since the dielectric constant is greater than that of lubricating oil, the sensitivity of measurement by capacitance method is improved.

A method for measuring oil film thickness using the piston ring 1 to which the pick-up electrode 5 is attached will be explained based on an example. The test engine is an experimental single-cylinder diesel engine with bore x stroke = 139.7 x
It is 152.4mm, water-cooled, and direct injection. As shown in FIG. 2, the measured value of the capacitance detected by the electrode 5 is shown on an oscillograph 9. By applying this oscillograph reading to a calibration curve prepared in advance, the piston ring oil film thickness between the inner circumferential surface of the cylinder 8 and the outer circumferential surface of the piston ring during one cycle can be obtained.

Figures 3 and 4 are graphs showing the measurement results obtained in this way, and Figure 3 shows the piston ring oil film thickness during one cycle with one piston ring, rotation speed 1300 rpm, and no load. Figure 4 shows the change in the piston ring oil film thickness during one cycle with four piston rings, 1300 rpm, and full load. This figure shows that the piston ring oil film thickness becomes thinner just after the vertical dead center, which is consistent with lubrication theory, that it becomes thick near the middle of the stroke where the piston speed is high, and that the piston ring oil film becomes thinner just after the vertical dead center. It was confirmed that the thickness becomes the minimum immediately after the piston ring, and that it becomes thinner when there are four piston rings, but this is thought to be due to insufficient supply of lubricating oil. Also, although a graph is not shown, the measurement results showed that the piston ring oil film is thicker when the cooling water temperature is lower and the engine speed is higher when there is no load, and there is little change due to load.

As mentioned above, since the measurement method of the present invention uses a pick-up electrode with an insulating coating on its surface,
It is possible to accurately measure the thickness of thin oil films, which was difficult to measure conventionally, and since the electrode is attached to the piston ring side, continuous measurement values can be obtained.

[Brief explanation of drawings]

1 and 2 are an enlarged perspective view and a cross-sectional view of the main parts of a piston ring to which a pick-up electrode is attached, which is used in the measurement method of the present invention. 3 and 4 illustrate the piston ring oil film thickness during one cycle of a diesel engine measured by the method of the present invention. 1: Piston ring, 4: Insulating coating, 5: Pick-up electrode, 8: Cylinder.

Claims (1)

[Claims] 1. In the method of measuring the oil film thickness of a piston ring using the capacitance method, a pick-up electrode is embedded in the piston ring so that the insulated surface is exposed on the outer peripheral surface of the piston ring, and the pick-up electrode is made of aluminum. A method for measuring the oil film thickness on the inner circumferential surface of a cylinder and the outer circumferential surface of a piston ring, characterized in that the surface insulation coating is an anodized coating.