JPH0321815Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a mold for obtaining a rocker arm made of a light alloy for use in an overhead camshaft valve mechanism of an internal combustion engine by die-casting.

Prior art and its problems In structural members for internal combustion engines, efforts are being made to reduce the weight by adopting light alloy materials, and moving parts such as rocker arms used in valve mechanisms are made of light alloy materials. This is also effective in reducing inertial force. In particular, it is effective to form the rocker arm used in an overhead camshaft valve mechanism suitable for high-speed engines from a light alloy material.

FIG. 1 shows a known rocker arm 01 made of light alloy for an overhead camshaft type valve mechanism as a front view with main parts cut away. The light alloy Rotsuka arm 01
has a shaft hole 02 in the middle part in the longitudinal direction that fits with the rocker arm shaft, and has a shaft hole 02 at one end that is made of chilled cast iron, quenched carburized steel, iron-based sintered material, etc., and is integrated with the rocker arm body by a casting. The other end is provided with a threaded hole 0 into which a gap adjustment screw that contacts the valve shaft end during valve opening is screwed.
5 is provided.

Such light alloy rocker arms are generally formed by die casting using a mold made of heat-treated low alloy steel. FIG. 2 shows a die-casting mold 06 as an example for obtaining the rocker arm 01. Mold 06 is fixed mold 07
and a movable mold 08, whose dividing surface (butting surface of both molds) is located at the center of the width of the circumferential surface (arrow A), which is smaller in width than the wider side surface that can be seen in Figure 1. (It does not necessarily have to be at the center in the strict sense).

When performing casting using the mold 06, after setting the anti-cam sliding contact piece 03 at a predetermined position in the cavity 010 of the fixed mold 07, the movable mold 08 is pushed against the fixed mold 07. Then, the molten metal is injected under pressure into the cavity defined by both molds 07 and 08.

However, the upper half of the anti-cam sliding contact piece 03 set in the cavity 010 is
10, when the mold 06 is closed, the anti-cam sliding contact piece 03 is likely to hit the cavity peripheral wall of the movable mold 08, causing jamming, which will only shorten the life of the mold. Instead, the cam sliding contact piece 03 was damaged, resulting in defective products.

Means for Solving the Problems An object of the present invention is to improve the life of a die-casting mold for manufacturing a rocker arm made of light alloy.

The purpose of this is to have both relatively wide side surfaces and a relatively small circumferential surface, as well as a rocker arm shaft fitting hole that penetrates from one side to the other side, and a part of the circumferential surface to be molded. In a die-casting mold for casting a light alloy rocker arm for an internal combustion engine, which has a sliding contact piece for a cam that is integrated with the main body by a wrapper, the die-casting mold is divided into a fixed mold having a cavity and a fixed mold having a cavity. and a movable type having a movable type, at least in the vicinity of the anti-cam sliding contact piece, the cavity depth of the fixed type is approximately equal to the full width of the plate-like portion having the sliding surface of the anti-cam sliding contact piece, and A split surface in which the depth of the cavity of the movable type near the anti-cam sliding contact piece disappears and becomes a surface that substantially coincides with the bottom surface of the cavity, and the depths of the cavities of the fixed type and the movable type in other parts become approximately equal depths. This is achieved by forming it into a shape.

Embodiment Hereinafter, an embodiment of the present invention shown in FIGS. 3 to 5 will be described.

FIG. 3 shows a perspective view of the rocker arm 10, which is the intended die-cast product. The rocker arm 10 is composed of a rocker arm main body 12 made of an aluminum alloy, and a cam sliding contact piece 22 which is integrated with the rocker arm main body 12 by casting and has excellent wear resistance. A locker arm shaft fitting hole 14 penetrating from one side to the other is formed in the longitudinally intermediate portion of the locker arm main body 12, and the end opposite to the end to which the anti-cam sliding contact piece 22 is attached. The valve driving portion 16 has a screw hole 20 into which a gap adjustment screw 26 that contacts the end of the valve shaft is screwed.

For reference, the top of the head of an overhead valve type four-stroke internal combustion engine incorporating the rocker arm 10 is shown in the fourth section.
As shown in the figure. The locker arm 10 is swingably supported by the locker arm shaft 30, and its anti-cam sliding contact piece 22 contacts the cam of the camshaft 32, and the gap adjustment screw 26 attached to the valve drive unit 16 is connected to the intake valve 3.
It faces the end of the valve stem of No. 4 with a small distance therebetween.

A die casting mold for obtaining rocker arm 10 is shown in FIG. The mold 40 includes a fixed mold 42 having a cavity 44 and a movable mold 46 having a cavity 48. The split surface of the mold 40 is basically located at the width center (not necessarily the center in the strict sense) of the circumferential surface C of the rocker arm 10, which is smaller in width than the side surface B, and is in sliding contact with the cam. The D portion of the fixed cavity 44 for setting the piece 22 has a deep shape that can completely accommodate the plate-like main body portion having the sliding surface of the anti-cam sliding contact piece 22. The E section of the fixed cavity 44 forming the drive section 16 is
It has a deep shape equal to the full width of the valve driving portion 16 (the two-dot chain line in FIG. 3 corresponds to the mold splitting surface).

Therefore, the fixed mold 42 is low in the center and high on both sides.

Note that the mold 40 has a sprue, but it is omitted in the figure.

Casting work using the mold 40 is performed by loading the anti-cam sliding contact piece 22 into the D portion of the cavity 44 with the movable mold 46 open, and then moving the movable mold 46 to the fixed mold 42.
Butt against the cavity 4 through the sprue.
This can be carried out by press-fitting the molten metal into the holes 4 and 48.

The functions and effects of using the mold 40 are as follows.

Since the plate-shaped main body portion of the anti-cam sliding contact piece 22 is completely housed in the D portion of the cavity 44, when the movable mold 46 is butted against the fixed mold 42,
The anti-cam sliding contact piece 22 and the movable mold 46 do not bite into each other, preventing damage to the mold 40 and the anti-cam sliding contact piece 22, improving the life of the mold 40, and producing defective products. Incidence rate decreases.

The seat surface 18 of the valve drive section 16 of the rocker arm body 12 is formed only by the cavity 44 of the fixed mold 42, and the step that tends to occur when a split surface is placed in the seat surface 18 portion does not occur on the seat surface 18. , it is possible to use the seat surface 18 (for the lock nut 28) with its cast surface as a reference surface, and it is possible to reduce manufacturing costs.

If there is a step on the seat surface 18 due to the split surface, the step will easily become a point of failure due to the notch effect, but there is no need to worry about this, and the rocker arm 10
The durability of the material is improved.

Note that the Rotsuka arm main body 12 is, for example, JIS
The anti-cam sliding contact piece 22 is made of AC12 material.
is made of, for example, a sintered material made of an iron-based alloy.

Effects of the invention As is clear from the above explanation, in the die-casting mold for the rocker arm of the present invention, the split surface of the two-split mold consisting of the fixed mold and the movable mold is positioned at the center of the width of the circumferential surface of the product rocker arm. As a basic rule, the setting part of the cam-to-cam sliding contact part of the fixed cavity has a split surface shape that allows the plate-like main body part with the sliding contact surface of the cam-to-cam sliding contact part to be completely housed within the fixed cavity. Therefore, there is no interference between the sliding contact piece for the cam, which is set in the fixed mold cavity prior to pouring, and the movable mold, which extends the life of the mold and reduces the incidence of defective products.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a known light alloy rocker arm, FIG. 2 is a perspective view showing a die-casting mold for obtaining the rocker arm, and FIG. 3 is a light alloy rocker arm according to an embodiment of the present invention. A perspective view of an alloy rocker arm, FIG. 4 is a sectional view showing the top of an internal combustion engine incorporating the light alloy rocker arm, and FIG. It is a perspective view of a die-casting mold. 10...Rotsuka arm, 12...Rotsuka arm body, 14...Rotsuka arm shaft fitting hole, 16...
Valve drive unit, 18... Seat surface, 20... Screw hole, 22
...Sliding contact piece for cam, 24...Protrusion, 26...Gap adjustment screw, 28...Lock nut, 30...
Rocker arm shaft, 32...camshaft, 34...intake valve, 40...mold, 42...fixed type, 44...cavity, 46...movable type, 48...cavity.

Claims (1)

[Claims for Utility Model Registration] It has both relatively wide side surfaces and a relatively small circumferential surface, and a rocker arm shaft fitting hole is formed that penetrates from one side to the other side. A die-casting mold for casting a light alloy rocker arm for an internal combustion engine, which includes an anti-cam sliding contact piece that is partially integrated with the main body by a casting, the die-casting mold having a cavity. A movable mold having a mold and a cavity, the depth of the cavity of the fixed mold at least in the vicinity of the anti-cam sliding contact piece being approximately equal to the full width of the plate-like portion having the sliding surface of the anti-cam sliding contact piece. At the same time, the depth of the cavity of the movable type in the vicinity of the sliding contact piece for the cam disappears, and a surface substantially coincides with the bottom surface of the cavity, and the depths of the cavities of the fixed type and the movable type in other parts are approximately equal. A die-casting mold for a rock arm that is characterized by being formed into a split surface shape.