JPH044048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a port for an engine cylinder by punching out a scavenging or exhaust port in a cylinder sleeve that forms a cylinder hole of a two-stroke engine.

[Conventional technology]

Conventionally, in cylinders used in high-output engines such as motorcycles, cylinder sleeves made of high-phosphorus cast iron that are centrifugally cast into aluminum cylinder bodies are press-fitted or encapsulated by casting. It is not easy to form ventilation holes for air intake, scavenging air, exhaust air, etc., that is, ports in the sleeve, and it is difficult to obtain high precision.

[Problem to be solved by the invention]

Traditionally, the most common method for forming ports is to form them simultaneously when the cylinder sleeve is cast, but this method involves adjusting the relative positions of several ports,
It was not possible to accurately form the size of each port, and it took a lot of effort to make corrections, which lowered productivity. This was also formed by punching with a press machine, but due to the low toughness of the high cast iron material, if you tried to punch out several port holes at the same time, it would be difficult to Cracks or damage often occur, which also lowers productivity. Furthermore, in order to improve this drawback, it is also known to use a steel plate as a material, punch out port holes in it using a press machine, and then wind it into a cylindrical shape (for example, Japanese Utility Model Publication No. 54-29365). However, since the rigidity is non-uniform over the entire circumference, it is difficult to form the cylinder into a cylinder with high precision, the yield of machining is low, and gas leaks easily occur from the joints.

[Means to solve the problem]

The purpose of this invention is to solve the above-mentioned problems, and a plurality of punches having substantially the same shape as ports are provided on a boss having a diameter slightly smaller than the inner diameter of the cylinder sleeve so as to be able to protrude and retract in the radial direction. The material of the cylinder sleeve is fitted onto the cylinder sleeve, and then each punch is sequentially projected along the circumferential direction while the material is pressed and compressed toward the shaft center to punch out a port hole. be.

[Effect]

The cylinder sleeve material is punched while compressive stress (hoop stress) is generated in the circumferential direction. Therefore, the tensile stress generated around the processed portion during punching is offset by the hoop stress and reduced.

〔Example〕

The present invention will be explained with reference to illustrated embodiments.
In the figure, reference numeral 1 denotes a cylinder sleeve port punching device used for carrying out the engine cylinder port machining method according to the present invention. A punch 4, which will be described later, is provided inside the boss 3 so as to be protrusive and retractable, and four sets of reverse push units 5 of the same shape extending from all sides toward the punch 4 are arranged outside the boss 3. (However, three sets are omitted in the drawing).

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 a collar 3a provided at the lower end. It is fixed. 3b is provided on the collar 3a, and has a washer protrusion that supports 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 vertically slidable, 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,
The port hole w is located at a relatively low position in Fig. 3,
In other words, the exhaust port w on the cylinder head side
1 and the intake port w2 located at a higher position are shown. Furthermore, in FIG. 4, a pair of scavenging ports W3 are provided at left-right symmetrical positions, and an intake port w2 is located closer to the cylinder head than these scavenging ports w3 and is adjacent to the intake port w2 in FIG. It is shown. Reference numeral 5 denotes a reverse push unit which is a reverse push means that cooperates with the punch 4. Cam member 6
A downward slope 6a is provided at a position corresponding to the punch 4, so that when the cam member 6 moves downward, the punch 4 advances outward. That is, five punches 4 for punching one exhaust port w1, two intake ports w2, and two scavenge ports w3 are provided on the boss 3 in a radial direction so as to be protrusive and retractable in four different directions. The downward slopes 6a of the cam member 6 are provided corresponding to the positions of the port holes w, but their phases are sequentially biased upward in the circumferential direction with one of them as a reference. When the punches 6 move downward, the several punches 4 disposed outside of the punches 4 successively protrude along the circumferential direction.

The main body of the reverse push unit 5 includes a die 7 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, an inverted mold 8, and a slider 9 supporting them. It is configured to be movable back and forth on a rail 10 fixed to the upper surface of the bed 2 by the action of a piston cylinder mechanism 11 for the slider on the rear surface. 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. Note that 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 and the reverse mold 8
Two reverse-pushing piston-cylinder mechanisms 12 are provided.

Next, a method of processing the cylinder sleeve W will be explained. First, the slider piston cylinder mechanism 11
The reverse pushing piston cylinder mechanism 12 is moved backward, and the cam member 6 is returned to the upper end. Next, a material is prepared by machining the inner and outer diameters and end faces of a cast product obtained by centrifugal casting, and this material is fitted onto the outer periphery of the boss 3 and supported by a washer 3b. Thereafter, the specific slider piston cylinder mechanism 11 and the reverse push piston cylinder mechanism 12 are advanced, and a part of the cylinder sleeve W is pressed against the outer periphery of the boss 3 and fixed. At this time, the material of the cylinder sleeve W is pressurized along the radial direction toward the axis by the five dies 7, and 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. In this state, when the cam member 6 is pulled down by a hydraulic piston cylinder (not shown), its punch 4 protrudes and punches out the port hole w while pushing back the inverted mold 8. At this time, the cylinder sleeve W is punched out with its periphery closed by the outer periphery of the boss 3, the die 7, and the inverted mold 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.

According to the experiments repeatedly conducted by the inventor in creating the present invention, the pressing force necessary to generate the hoop stress is influenced by the shearing force necessary to open the port hole w.
Reverse push piston cylinder mechanism 12 that pushes the die 7
It was found that the pressure at 196 kN or more is sufficient. In addition, the cylinder sleeve W is made of alloy cast iron material for cylinder liners, and its dimensions are as follows:
70mm, inner diameter 64mm. Further, the maximum shear stress applied to the material during punching was approximately 300 MPa as a result of measuring the punching load by attaching a resistance wire strain gauge to the punch 4.

After punching, the punched waste material remains in the die 7, but after the punching is completed, the slider piston cylinder mechanism 11 is activated to move the reverse push unit 5 backward, and the reverse die 8 is moved from the die 7 to the original position. The waste material is discharged to the outside by advancing it to the position.

When the cam member 6 is further lowered, adjacent port holes w are punched out in the same manner, and the machining of the port holes w proceeds sequentially along the circumferential direction. When all the port holes w have been formed, the cam member 6 is returned to the upper end, and the reverse push unit 5, which has been once retreated, is moved forward again, and the punch 4 that remains protruding is pushed into the boss 3. Finish the process. However, the method for pushing the punch 4 into the boss 3 is not limited to this embodiment, and any method can be used.

Note that if hoop stress is not generated, cracks are likely to occur in the punched part, so this method could not be adopted for industrial production due to yield issues. By punching in the generated state, it has become possible to perform shear drilling on cylinder sleeves on a mass production scale.

〔Effect of the invention〕

As described above, in this invention, the material of the cylinder sleeve is formed of a cast tube cast by the centrifugal casting method, and the material of the cylinder sleeve can be freely protruded and retracted in the radial direction by a plurality of punches having substantially the same shape as the port hole. Then, the material is pressed and compressed toward the axial center by a reverse push unit that is in contact with the outer circumference over almost the entire circumference, and in this state, each punch is pressed around the circumference. Since the port holes are punched by sequentially protruding along the direction, the material of the cylinder sleeve is punched in a state where compressive stress (hoop stress) is generated in the circumferential direction. Therefore, the tensile stress generated around the punched part can be offset and reduced by the hoop stress, so that a port hole can be reliably bored in a brittle and easily cracked cast pipe by punching. . Also,
The punch does not cut into adjacent port holes at the same time, and when one port hole is punched and the next port hole is punched, the material of the cylinder sleeve is allowed to move slightly, so there is no strain. This has the effect of eliminating defects that could damage the material. In addition, high accuracy can be maintained between adjacent port holes.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a plan view of the main part of a port punching device used for carrying out the engine cylinder port processing method according to the present invention, FIG. 2 is a cross-sectional view thereof, and FIG. Figure 3 is an enlarged cross-sectional view, and figure 4 is the same.
FIG. 1...port punching device, 3...boss, 4...
Punch, 6...cam member, 6a...downward slope,
7...Dice, 11...Piston cylinder mechanism for slider, 12...Piston cylinder mechanism for reverse push, 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 with a diameter slightly smaller than the inner diameter of the cylinder sleeve and a port hole W. A plurality of punches 4 having substantially the same shape are fitted into bosses 3 provided so as to be able to protrude and retract in the radial direction, and then this material is pushed by a reverse push unit 5 that is in contact with the outer circumference of the material over substantially the entire circumference. A method for machining a port in an engine cylinder, characterized in that the punches 4 are pressed toward the shaft center and compressed, and in this state, each punch 4 is sequentially projected along the circumferential direction to punch a port hole W. 2 The material of the cylinder sleeve W has a cylindrical shape,
2. A method for machining a port in an engine cylinder according to claim 1, wherein at least one end surface is machined.