JPS6311687A - Masking jig for plating piston - Google Patents

Abstract

PURPOSE:To prevent a plating soln. from entering the pin hole of a piston by increasing the internal pressure of a hermetically sealed elastic tubular body inserted in the pin hole so that the tubular body can be closely adhered to the inside of the pin hole. CONSTITUTION:A hermetically sealed elastic tubular body 4 whose outside is closely adhered to the inside of the pin hole 2 of a piston 1 is inserted in the pin hole 2. A fluid is introduced into the tubular body 4 from a fluid introducing pipe 3 fitted to the body 4 to closely adhere the outside of the body 4 to the inside of the pin hole 2 and then plating is carried out. Thus, the piston 1 is plated except for the inside of the pin hole 2.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a masking jig for piston plating.

(Conventional technology) Conventionally, the pistons in all-aluminum engines have been electroplated to improve various performances such as wear resistance, low friction, and corrosion resistance, but the inner surface of the pin hole does not require plating. It is a part. In this case, as a method for preventing plating precipitation at the pin hole site that occurs during piston plating work, a method of pasting masking tape on the inner surface of the pin hole is known.

(Problems to be Solved by the Invention) This method of applying masking tape generally requires manual work, requires strong force, and requires a great deal of effort to remove the masking tape. It takes time. In addition, from a quality perspective, high masking accuracy is required,
In order to make products uniform, a large number of man-hours are required and productivity is low. Furthermore, this method did not provide sufficiently satisfactory quality. On the other hand, there is also a known method in which the entire surface of the piston, including the pin hole, is plated without the masking process, and then the inner surface of the pin hole is machined, but this method complicates the process and increases costs. There was a drawback.

The present invention has been made in view of the above points, and an object thereof is to provide a masking jig for piston plating that can reliably and easily prevent plating by masking.

(Means for Solving the Problems) As a means for solving the above-mentioned problems, the present invention provides a sealed cylinder having an outer circumferential surface that closely contacts the inner surface of the pin hole of the piston, and a sealed cylinder that is attached to the sealed cylinder and has a It consists of a fluid introduction pipe that introduces fluid into a sealed cylinder.

In the present invention, the sealed cylinder is made of an elastic material such as rubber, and its functional part is formed into a cylindrical shape that fits into the pin hole. The inside of the sealed cylinder is a sealed chamber filled with fluid, and the number of sealed chambers can be divided into one or two or more depending on the size of the sealed cylinder. can. In this case, it is preferable that the thickness of the partition wall be set larger than the thickness of the outer circumferential portion of the sealed cylinder to ensure the required strength. The outer periphery of the sealed cylinder is so thick that it bulges outward with some elasticity when it is filled with fluid and reaches a predetermined pressure.

The fluid introduction tube is attached to the end face of the sealed cylinder. The fluid introduction tube is usually connected to a fluid supply source via a flexible tube. The fluid introduction pipe is provided with a number of fluid communication ports corresponding to at least the number of sealed chambers of the sealed cylinder. The length of the fluid introduction tube can be determined independently of the length of the pin hole, and by having the fluid introduction tube penetrate in the axial direction of the closed cylinder, the fluid introduction tube itself can be attached to the supporting member of the closed cylinder. It is possible to give the function of

Although the closed cylinder requires a pipe for discharging fluid, this pipe can serve the same function as, for example, a fluid introduction pipe.

The fluid that can be used in the present invention is mainly air, but it is also possible to use liquids such as oil.

(Function) When using the masking jig of the present invention, insert the sealed cylinder into the pin hole of the piston, and then introduce fluid into the sealed cylinder from the fluid introduction pipe to reduce the internal pressure of the sealed cylinder. to a predetermined value.

Then, the sealed cylinder expands in volume to a thickness corresponding to the pin hole, and the outer peripheral surface of the sealed cylinder comes into close contact with the entire inner surface of the pin hole with a predetermined pressure.

Thereafter, the entire piston is put into a plating bath with the outer surface of the sealed cylinder kept in close contact with the inner surface of the pin hole, and plating is performed.

Therefore, the piston is plated except for the inner surface of the pin hole. In this case, since the outer surface of the sealed cylinder is in close contact with the inner surface of the pin hole with a predetermined pressing force, airtightness between the two is ensured, and an excellent masking effect can be obtained over the entire area of the inner surface of the pin hole. Ru.

After finishing the plating process, the sealed cylinder can be easily taken out from the pin hole by simply discharging the fluid inside the sealed cylinder and causing the closed cylinder to shrink.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing the state when the masking jig is inserted into the pin hole of the piston.

In this figure, 1 is a piston, and 2 is a pin hole. The masking jig inserted into this pin hole 2 consists of a flexible masking member 4 made of rubber and a support pipe 3 arranged in the direction of the center thereof. This masking member 4 is
It is formed into a cylindrical shape that fits the pin hole 2, and its interior is defined by a partition wall 13, and two sealed chambers 5 and 6 are provided on both sides of the partition wall 13. The support pipe 3 includes
A pipe 9 is provided with a communicating lower pipe 8 for introducing and discharging pressurized air into the sealed chambers 5 and 6 of the masking member 4, and communicates with an air source 14 via an openable pulp 10. Therefore, by opening and closing the opening/closing pulp 10, it is possible to freely stop the supply of pressurized air to the masking member 4. Both ends of the masking member 4 and the support pipe 3 A cap-like fastener 11, 12 is attached to the overlapping portion with the masking member 4, so that no air leakage occurs even if the internal pressure of the masking member 4 becomes high.

Next, the operation of the masking jig according to the present invention will be explained. First, the piston 1 is mounted on a plating hanger (not shown), and then the masking member 4 is inserted and set at a predetermined position inside the pin hole 2 of the piston 1. In this case, since the support pipe 3 has been previously opened to the atmosphere by operating the opening/closing pulp 10, the pressurized air in the masking member 4 is exhausted and is in a contracted state.

Next, by switching the opening/closing pulp 10 connected to the air source 14, a predetermined amount of pressurized air is supplied to the communication lower, 8, and into the closed chambers 5, 6 through the lexical pipe 9 and the support pipe 3. As a result, the masking member 4 is expanded, and the masking member 4 is formed on the inner surface of the pin hole 2.
The outer surface of the As a result, the entire inner surface of the pin hole 2 is masked by the masking member 4. In this manner, the piston 1 is inserted into a plating tank (not shown) with the pin hole 2 of the piston 1 masked, and plating is performed by energizing the tank. After plating, the piston 1 is taken out from the plating tank, the masking member 4 is contracted again by operating the opening/closing pulp 10, and the masking member 4 is pulled out from the pin hole 2.

In the embodiment, one support pipe 3 is provided as both an air introduction pipe and an air discharge pipe, but a plurality of air introduction pipes and air discharge pipes may be provided separately. Further, although two masking members 4 are defined by the partition wall 13 in a direction perpendicular to the longitudinal direction, the present invention also includes a masking member 4 partitioned in the same direction as the longitudinal direction. .

(Effects of the Invention) As described above, according to the present invention, the sealed cylindrical body of the masking jig tightly contacts and masks the entire inner surface of the pin hole of the piston with a predetermined pressing force. The plating does not penetrate into the inner surface of the pin hole, and as a result, plating precipitation and corrosion are reliably prevented, and the quality of the piston is improved compared to conventional pistons.

Furthermore, since the masking jig can be easily loaded and unloaded in a short time, the masking workability is significantly improved, the conventional machining is no longer required, and the number of man-hours is reduced. Therefore, it is possible to reduce costs, improve productivity, and further contribute to promoting automation of masking. Figure 1 is a sectional view of one embodiment of the present invention, and Figure 2 is an overview of the present invention. FIG.

3... Support pipe (fluid introduction pipe) 4...
・Flexible masking member (sealed cylinder) 5.6... Sealed chamber 7, 8... Communication port 9... Flexible masking member (7' Patent applicant Toyota Motor Corporation 7.8. ...Fugaku Exit 9...1L4>1' Luha 1ia Fang 2 figure

Claims (1)

[Claims] (1) A piston body characterized by comprising a sealed cylinder having an outer circumferential surface that comes into close contact with the inner surface of a pin hole of the piston, and a fluid introduction tube attached to the sealed cylinder and introducing fluid into the sealed cylinder. Masking jig.