JPS5938317B2 - Method of plating the flat parts of the upper and lower surfaces of thin piston rings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of plating the upper and lower surfaces of a thin piston ring.

Modern engines are changing to specifications that require high revolutions, high speeds, high loads, and high outputs, and the parts used, especially the piston rings, which are sliding parts, are being operated under increasingly harsh conditions.

On the other hand, as output increases, the cross-sectional area of piston rings, which are sliding parts, tends to be made as small as possible in order to reduce inertia and frictional resistance. In particular, the width dimension is being set to smaller and smaller values. FIG. 1 shows a schematic diagram of a piston ring, and many piston rings having a width W of about 0.8 to 1.5 WIR are mass-produced in engines currently in operation. On the other hand, higher engine loads and higher outputs have led to new and different piston ring quality requirements. One of them is that if the upper and lower piston ring surfaces A and B (see Figure 1) are made of iron, they will wear heavily due to the high heat and rotation of the engine and reduce output, so these upper and lower surfaces have anti-wear properties. It became necessary to take measures such as electrodepositing or thermal spraying a resistant material, or heat-treating the upper and lower surfaces to harden the material. Among these methods, the thermal spraying method is expensive and not suitable for mass production, and the heat treatment method requires high-temperature treatment and unless special materials are used, the performance of the piston ring will deteriorate in other aspects.Currently, the electrodeposition method, That is, plating processing is usually performed. The method of plating the upper and lower surfaces of the piston ring is as shown in Figure 2, by attaching the piston ring 1 itself to the cathode and immersing it in a pre-adjusted plating liquid 5, facing the anode 4, for a certain period of time. This is done by applying electricity from the power source 2.

However, the piston ring has a small cross-sectional area, and the outer peripheral surface C (
(see Figure 1) is an important surface that slides on the inner circumferential surface of the cylinder or cylinder liner during engine operation, and it is impossible to provide a cathode electrical contact on this outer circumferential surface from the viewpoint of piston ring function. . Furthermore, since the piston ring's upper and lower surfaces A and B are to be plated in the future, they cannot naturally serve as cathode contacts. The only remaining surface is the inner circumferential surface D of the piston ring (see Figure 1), and currently, when plating piston rings of the same type, for example, with Cr plating, this inner circumferential surface is used as shown in Figure 2. D is used to conduct electricity as a cathode electrical contact E for production. However, since this contact is not fixed, the piston ring 1 is attached using the tip of the cathode contact tool 3 as a fulcrum. As shown in FIG. 3, this cathode current-carrying portion is simply supported by a thin width portion W of the piston ring in contact with the tip E of the cathode contact at a point or a line. On the other hand, in order to obtain a specified plating thickness, the piston ring 1 must be immersed and held in a plating tank for a long time, and the plating liquid 5 must be about 45 to 60 mm thick.
Since the temperature is set at 0°C, there is circulation and convection inside the tank, so the piston ring installed may come off the cathode fixture 3 during the plating process and fall into the plating tank 6, or return to the plating tank. There have been many accidents in which the piston ring falls off from the cathode contact 3 before or after the plating process is carried out. The present invention relates to a method for preventing piston rings from falling off, and has great industrial advantages along with improved productivity. The present invention provides a concave groove on the inner circumferential surface D of the piston ring, and furthermore, the tip of the cathode contact tool is shaped to fit into the concave groove on the inner circumferential surface of the piston ring. This is based on the knowledge that the piston ring can be prevented from falling off when it is taken into and out of the plating tank and during the plating process. That is, the present invention is a method of plating the upper and lower surfaces of a piston ring, which is characterized in that a groove is formed on the inner circumferential surface of the piston ring, and a plated current-carrying contact is brought into contact with the groove and energized. , relates to a method of plating the upper and lower surfaces of a thin piston ring. FIG. 4 shows an enlarged view of the pole-mounted current-carrying part in the method of the present invention. A groove 7 is provided on the inner circumferential surface D of the piston ring, and the tip 8 of the cathode contact 3 fits into the groove 7. A contact point is formed in the piston ring, completely preventing the piston ring from falling off.

The size and shape of the concave groove 7 cannot be determined unconditionally because it is correlated with the cross-sectional shape and cross-sectional area of the piston ring, as well as the depth of the ring groove of the piston, but it can be semicircular, triangular, or square. It may have any shape, and its depth may be within a range that does not allow the tip of the cathode fixture to come off, but it is preferable from the viewpoint of engine function that it is not very deep. It goes without saying that the contact point between the tip 8 of the contact tool 3 and the groove 7 may be a point contact or a line contact. In forming the grooves, it is possible to form grooves on the inner peripheral surface of a cast iron piston ring by turning the inner peripheral surface, and to form the grooves on the inner peripheral surface of a steel piston ring during wire forming.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a piston ring, Fig. 2 is a schematic diagram of the case where the upper and lower surfaces of the piston ring are plated, Fig. 3 is an enlarged cross-sectional view of the cathode energized part in the conventional method, and Fig. FIG. 4 is an enlarged cross-sectional view of the cathode current-carrying portion in the method of the present invention.

Claims (1)

[Claims] 1. A method of plating the upper and lower surfaces of a piston ring, characterized in that a groove is formed on the inner circumferential surface of the piston ring, and a plated current-carrying contact contacts the groove and is energized. A method of plating the top and bottom surfaces of a ring.