JPH022653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a piston ring for an internal combustion engine, particularly a tapered face type piston ring (hereinafter abbreviated as a taper ring).

(Prior Art) In recent years, high-speed internal combustion engines have come to require a tapered ring with a slight inclination on the sliding surface with the cylinder for reasons of performance.

In other words, by tapering the outer circumferential surface and reducing the contact area of the sliding surface with the cylinder, surface pressure is increased, improving conformability at the beginning of operation, and stabilizing oil consumption and blow-by in a short time. Now I can do it. Furthermore, the tapered ring facilitates the formation of an appropriate oil film on the sliding surface during the piston's upward stroke, and has the effect of sweeping away excess oil during the downward stroke.

In addition, if the taper starting point, i.e., the bottom corner of the outer peripheral surface, is left at an acute angle, the taper ring will cause corner chipping or scratches on the inner wall of the cylinder, which is undesirable. In order to create deeper scratches, corners are usually chamfered to a depth of about 0.2 mm.

In order to further reduce blow-by, the chamfer dimensions of this lower end corner part need to be minute, but in particular, manufacturing is required to form a minute chamfer of 0.1 mm or less on the outer peripheral surface and bottom surface that sandwich the corner part. The following methods were used.

) After chamfering the outer circumferential surface by cutting with a cutting tool or the like, a wear-resistant layer such as plating is formed, and then grinding is performed to form a tapered surface (FIG. 1 A to C).

) If a sufficiently small chamfer cannot be obtained by the above-mentioned method, the lower surface of the ring is further ground to form a minute chamfer following the step of ).

) After forming a wear-resistant layer such as plating, taper grinding is performed to make the lower corner part an acute angle, and then fine chamfering is performed (Fig. 2
c).

(Problems to be Solved by the Invention) The conventional methods described above have the following problems. That is, in the method (), it is difficult to keep the formation thickness of the wear-resistant layer and the amount of taper grinding constant, and the final finished dimensions tend to vary. ) method requires a lot of man-hours and is not suitable for mass production. In addition, with the method (2), it is difficult to achieve the target minute chamfer size only by the final chamfer grinding, and the number of man-hours increases.

In view of the above, an object of the present invention is to provide an effective manufacturing method for forming a minute chamfer, particularly a chamfer of 0.1 mm or less, at the corner portion of the lower end of a tapered ring.

(Means for Solving the Problems) A method for manufacturing a piston ring according to the present invention that enables the above-mentioned object is such that the outer peripheral surface of the ring is vertically asymmetrical at the corner portions of the upper end and the lower end, and the lower end is smaller than the upper end. A first step of performing machining such as cutting to form a chamfer, a second step of forming a wear-resistant layer on the outer peripheral surface, and forming the outer peripheral surface into a tapered shape and making the bottom corner part an acute angle. The present invention is characterized by comprising a third step in which a grinding process is performed as shown in FIG.

Further, wrapping finishing is further performed after buffing if necessary.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

First, as shown in FIG.
Cutting is performed using a cutting tool 18 or the like to form a chamfer that is vertically asymmetrical and smaller at the lower end corner 16 than at the upper end corner 14, but this chamfering is done by applying a wear-resistant layer such as hard chrome plating in a subsequent process. This is to improve the adhesion state when forming the plating and to facilitate the removal after plating. The amount of vertically asymmetrical chamfering is carefully set in consideration of the thickness of the wear-resistant layer, the subsequent taper grinding, and the size of the micro chamfer, but in general, the lower end corner 16 is 1/3 to 1/3 of the upper end corner 14. It is appropriate to make it 1/2 the size.

Next, as shown in FIG. 4, after forming a wear-resistant layer 20 such as hard chrome plating, the corner portion 16 at the lower end of the outer peripheral surface is ground to an acute angle to form a tapered shape.

Finally, as shown in FIG. 5, by polishing the outer circumferential surface 12 with a buff 22, a minute chamfer is formed at the corner portion 16 at the lower end of the outer circumferential surface. By applying the buff 22, which is elastic and has a precision polishing ability, the buff 22 wraps around the bottom surface of the ring as shown in the figure, and the buff 22 wraps around the bottom surface of the ring as shown in the figure, and removes microscopic particles of 0.1 mm or less from the acute angle points on the outer peripheral surface and the bottom surface that sandwich the corner portion 16. A rounded chamfer is formed.

If necessary, after buffing, a normal wrapping finish is performed to improve the perfect circularity of the ring.

(Example) By the method shown in Fig. 3, a ring diameter of 137 mm,
A cast iron piston ring material with an axial width of 3.5 mm and a radial width of 5.4 mm was cut with a cutting tool to form a chamfer with a radius of curvature of 0.35 mm at the upper end and a curvature radius of 0.15 mm at the lower end of the outer peripheral surface of the ring.

Next, after forming a hard chrome plating layer with a thickness of 0.23 mm on the outer peripheral surface, the upper end of the outer peripheral surface is cut by 0.13 mm and the lower end is cut by 0.09 mm using the method shown in Figure 4.
A 50-minute tapered surface was formed, and the bottom corner was made at an acute angle.

Next, as shown in Fig. 6, a set of 20 rings 10, 10, . At the same time, by applying the buff 22 and rotating both in the opposite direction, and moving the buff 22 in the direction of the rotation axis, the corner of the lower end of the outer circumferential surface of the ring is made with an acute angle of 0.07 mm from the acute angle point on the outer circumferential surface, and an acute angle on the lower surface. A curved chamfer was formed by removing 0.05mm from the point.

Finally, by finishing polishing by wrapping, the removed portion on the outer peripheral surface was chamfered 0.04 mm from the intersection corner point, and the lower surface was chamfered 0.03 mm from the intersection corner point.

The conditions for buffing were as follows.

Work rotation speed: 330 rpm Buff rotation speed: 1500 rpm Buff feed movement speed: 10 mm/s Buffing material: Commercially available nonwoven fabric impregnated with aluminum oxide (effects of the invention) As described above, the method of the present invention When chamfering the bottom corner of the surface, buffing, which has elasticity and has precise polishing ability, is used to enable minute chamfering, and is a method suitable for mass production. The tapered ring manufactured by the present invention can particularly reduce blow-by of combustion gas from the chamfered portion at the lower end of the outer periphery.

[Brief explanation of drawings]

FIGS. 1 and 2 show a conventional method for manufacturing a taper ring. FIGS. 3 to 6 show the manufacturing method of the present invention in the order of steps. Explanation of symbols 10...piston ring, 12...
...outer circumferential surface, 16...lower corner portion, 22...buff.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a piston ring having a tapered contact surface, such that chamfers are formed at the corners of the upper and lower ends of the outer circumferential surface, which are vertically asymmetrical and smaller at the lower end than at the upper end. A first step of performing machining such as cutting, a second step of forming a wear-resistant layer on the outer circumferential surface, and a second step of grinding so that the outer circumferential surface is tapered and the bottom corner is made at an acute angle. A method for manufacturing a piston ring, comprising three steps and a fourth step of forming a minute chamfer at the lower end corner by buffing the outer circumferential surface. 2. The method for manufacturing a piston ring according to claim 1, wherein after the fourth step, the outer circumferential surface is further lapped. 3. In the fourth step, the minute chamfers formed on the corners of the lower end of the outer peripheral surface are each 0.1 mm from the acute angle points on the outer peripheral surface and the lower surface that sandwich the corner parts.
The method for manufacturing a piston ring according to claim 1, characterized in that the piston ring is chamfered as follows.