JPH0249174B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an engine cylinder in which a port for scavenging, exhaust, etc. is punched out in a cylinder sleeve that forms a cylinder hole of a two-stroke engine.

[Conventional technology]

BACKGROUND ART Conventionally, in cylinders used in high-output engines such as motorcycles, a centrifugally cast cylinder sleeve is press-fitted into an aluminum cylinder body, or the cylinder sleeve is encapsulated by casting. By the way, the cylinder of a two-stroke engine has several port holes in the cylinder sleeve for intake, exhaust, and scavenging air, but the positions and sizes of these have a great effect on engine performance, so high precision is required. has been done.

[Problems to be solved by the invention]

By the way, the general method for forming port holes in the cylinder sleeve is to simultaneously form them by casting when the cylinder sleeve is cast, but in this method, the mutual position of several ports and the position of each port are It was not possible to accurately form the size, and manual corrections required a great deal of effort, lowering productivity.

In addition, drilling port holes in the cylinder sleeve using a press machine was considered, but the cylinder sleeve is cylindrical and difficult to machine, and the wall thickness is thin, and the material, cast iron, is brittle, so it has no crush strength. was considered difficult.

Therefore, in order to improve this drawback, it is also known to use a steel plate as a material, punch out port holes with a press machine, and then wind it into a cylindrical shape. (For example, Japanese Utility Model Publication No. 54-29365) However, the bending rigidity of a flat plate punched with port holes becomes uneven, and when it is wound into a cylindrical shape, it becomes a polygon. In addition, gas leakage was likely to occur from the joints.

[Means for solving problems]

In order to solve the above problems, this invention aims to punch out port holes from the inside to the outside of the cylinder sleeve by press working, and to further facilitate the process. The material of the cylinder sleeve is formed from a cast tube cast by centrifugal casting, and the material of this cylinder sleeve is fitted into a boss in which a plurality of punches having approximately the same shape as the port hole are provided so as to be freely projectable and retractable in the radial direction. [Embodiment] The present invention will be explained with reference to the illustrated embodiment, in which the punch is projected outward in the circumferential direction to punch out the port hole.
In the figure, reference numeral 1 denotes a cylinder sleeve port punching device used for carrying out the method of manufacturing an engine cylinder according to the present invention, and a boss 3 with a diameter slightly smaller than the inner diameter of the cylinder sleeve W, which is the workpiece, is located at the center of the upper surface of the bed 2. A punch 4, which will be described later, is provided inside the boss 3 so as to be protrusive and retractable, and four pairs of reverse push units 5 are arranged outwardly from the boss 3 and extend from all sides toward the punch 4 ( (3 pairs are omitted in the figure).

First, the structure of the punch 4 will be explained with reference to FIGS. 3 and 4. The boss 3 that supports the punch 4 has a cylindrical shape and is attached to the center of the upper surface of the bed 2 by four bolts at the collar 3a provided at the lower end. It is fixed. 3b is a washer provided on the collar 3a and supporting the end surface of the cylinder sleeve W on the cylinder head side. A cam member 6 is fitted into the center hole 3c of the boss 3 so as to be slidable up and down, and several holes provided on the outer surface are provided with port holes w at positions corresponding to the port holes w of the cylinder sleeve W. A punch 4 having the same size and the same cross-sectional shape is slidably supported. In addition,
In FIG. 3, an exhaust port w1 located at a relatively low position and an intake port w2 located at a high position are shown as port holes w, and in FIG. 4, a pair of scavenging ports w3 provided symmetrically are shown. .
The cam member 6 is provided with a downward slope 6a at a position corresponding to the punch 4, so that when the cam member 6 moves downward, the punch 4 advances outward. In other words, the five punches 4 are the bosses 3
It is provided in a radial direction so that it can be projected and retracted in four different directions. The cam member 6 is provided corresponding to the port hole w, but the space between the port holes is sequentially biased upward in the circumferential direction with one of the port holes as a reference, and the cam member 6 moves downward. and when,
Several punches 4 arranged outside of these punches protrude sequentially along the circumferential direction.

The main body of the reverse push unit 5 is composed of a die 7 and an inverted die 8 having a curved surface substantially the same as the outer surface of the cylinder sleeve W so as to support the outer surface of the cylinder sleeve W, and a slider 9 that supports them.
The slider 9 has a rail 10 fixed to the top surface of the bed 2.
Piston cylinder mechanism 11 for slider with top on back
It is configured to be able to move forward and backward by the action of. The die 7 is fixed to the outer surface of the slider 9, and the reverse mold 8 is connected to a piston of a reverse-pressing piston-cylinder mechanism 12 provided on the slider 9. In addition, in this cross section, the cylinder sleeve W is provided with two port holes W on the upper and lower sides, so the die 7, the reverse mold 8, and the reverse pressing piston cylinder mechanism 12 each have two port holes W.
A pair is provided.

Next, a method for manufacturing an engine cylinder will be explained. First, the piston cylinder mechanism 11 for the slider
and the reverse push piston cylinder mechanism 12 are moved back, and the cam member 6 is returned to the upper end. Next, a cylinder sleeve W made of a cast tube obtained by centrifugal casting and machined on the inner and outer diameters and end faces is prepared, and this is fitted onto the outer periphery of the boss 3.
Support with washer 3b. Thereafter, the slider piston cylinder mechanism 11 and the reverse push piston cylinder mechanism 12 are moved forward to press a portion of the cylinder sleeve W against the outer periphery of the boss 3 and fix it locally. At this time, the material of the cylinder sleeve W is pressurized along the radial direction toward the axis by the four dies 7,
Hoop stress is generated within the material. This hoop stress is stress generated in the circumferential direction when pressure parallel to the radial direction is applied to the annular ring, and the hoop stress generated in this embodiment is compressive stress in the circumferential direction. Then, in this state, the punch 4 protrudes and punches out the port hole w while pushing back the inverted die 8. At this time, the cylinder sleeve W is punched out with its circumference closed by the outer periphery of the boss 3, the die 7, and the inverted die 8. During punching, tensile stress is generated around the hole punched by the punch 4, but this tensile stress is offset and significantly reduced by the hoop stress described above. The waste material punched out at this time remains in the die 7, but when the punching is finished,
After the slider piston cylinder mechanism 11 is operated to move the reverse push unit 5 backward, the reverse die 8 is advanced relative to the die 7 and the waste material is discharged to the outside.

When the cam member 6 is further lowered, adjacent port holes w are punched out in the same manner as described above, and port holes w to be sequentially arranged around the entire circumference of the cylinder are formed.

〔Effect of the invention〕

As described above, in this invention, the material of the cylinder sleeve is formed from a cast tube cast by the centrifugal casting method, and the material of the cylinder sleeve is radially protruded and retracted by a plurality of punches having substantially the same shape as the port hole. This material is then fitted into the provided boss.
The cylinder sleeve material is pressed and compressed toward the shaft center by a reverse push unit that is in contact with the outer periphery over almost the entire circumference, and in this state each punch is projected to punch out the port hole. Therefore, the material of the cylinder sleeve is The punching process is performed in a state where compressive stress (hoop stress) is generated. Therefore, the tensile stress generated around the machined part during punching can be offset and reduced by the hoop stress, making it possible to reliably punch a port hole in a cast pipe that is brittle and prone to breakage. . In addition, since the port hole can be formed by cutting the material of the cylinder sleeve from the inside, the punch cuts into a relatively soft part of the inner surface, so the cutting edge will not be damaged.
Furthermore, as the depth of cut progresses and the crack reaches the hard outer surface, it breaks all at once, eliminating the need to cut through the hard part with the cutting edge, extending the life of the tool and allowing accurate port hole machining over a long period of time. There is an effect that can be achieved. Incidentally, at this time, a fracture surface is generated at the corner of the outer diameter portion, but it is so small that the effect on the performance of the engine can be ignored.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a plan view of the main parts of a port punching device used for carrying out the method of manufacturing an engine cylinder according to the present invention;
FIG. 2 is a sectional view thereof, FIG. 3 is an enlarged sectional view thereof, and FIG. 4 is a sectional view thereof. 1...port punching device, 3...boss, 4...
Punch, 5... Reverse push unit, 6... Cam member, W... Cylinder sleeve, w... Port hole.

Claims (1)

[Claims] 1. The material of the cylinder sleeve W is formed from a cast tube cast by a centrifugal casting method, and the material of the cylinder sleeve W is formed to have a diameter slightly smaller than the inner diameter of the cylinder sleeve, and is abbreviated as a port hole w. A boss 3 in which a plurality of punches 4 of the same shape are provided so as to be freely protrusive and retractable in the radial direction.
Then, this material is pressed and compressed toward the shaft center by the reverse push unit 5 that is in contact with the outer periphery of the material over almost the entire circumference, and in this state, each punch 4 is made to protrude to open the port. A method for manufacturing an engine cylinder, characterized by punching out a hole w. 2 The material of the cylinder sleeve W has a cylindrical shape,
2. The method of manufacturing an engine cylinder according to claim 1, wherein at least the inner surface and one end surface are machined. 3. The method of manufacturing an engine cylinder according to claim 1, wherein the cast pipe cast by the centrifugal casting method is obtained by cutting a long cast pipe into lengths for each cylinder.