JPS644046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a valve spring seat that supports a valve spring, and in particular to a method for manufacturing a valve spring seat that supports a valve spring seat, and in particular, a method for forming a smooth connection between the inner circumferential surface and the corner of the valve spring seat. The present invention relates to a method for manufacturing a valve spring seat, which can prevent valves from falling off due to damage to the valve stem when attaching the valve spring seat to the valve stem, and which does not increase costs.

[Technical background of the invention and its problems] FIG. 1 shows a valve opening/closing mechanism of an internal combustion engine, and FIG. 2 shows an enlarged view of the upper part of the valve. In the figure, the valve 1 is driven by the vertical movement of a push rod 2, which is actuated by the rotation of a camshaft (not shown), transmitted to the valve stem 1a via a rocker arm 3. On the outside of the upper part of the valve stem 1a, there is a valve spring 5 for springing the valve head 1b in the direction of seating it on the valve seat 4, that is, in the upward direction.
6 is provided. The valve springs 5, 6 are supported below by a lower valve spring seat 8 supported on the cylinder head 7, and above them by an upper valve spring seat 9. The upper valve spring seat 9 is attached to the outside of the valve stem 1a, and is attached to the upper end of the valve stem 1a by a clasp 10 having a tapered outer peripheral surface. The inner circumferential surface 9a of the valve spring seat 9 is tapered so as to fit into the outer circumferential surface of the valve spring 10, and its diameter is gradually reduced downward. The kotta 10 has a cylindrical shape divided into two parts, and its donut-shaped upper end 10
It is fitted into a groove 11 formed on the upper end of the a-valve stem 1a.

Attach the valve spring seat 9 to the valve stem 1a.
When installing the valve spring seat 9
is compressed against the elastic force of the valve springs 5 and 6 and pushed down along the valve stem 1a. Then, with the valve spring seat 9 pressed down, attach the two-piece kotsuta 10 to the valve stem 1a, and then gently lift the valve spring seat 9, and the kotsuta 10 will be inserted between the valve stem 1a and the valve spring seat 9. 10 is fitted, and the valve spring seat 9 is attached to the valve stem 1.
a Attached to the upper end.

However, when pressing down the valve spring seat 9 which has been surface hardened and is harder than the valve stem 1a, the valve spring seat 9
tends to swing in the radial direction of the valve stem 1a, and the sharp edge of the corner 9b on the inner circumferential surface 9a side of the valve spring seat 9 has the disadvantage of damaging the fitting portion 10 of the valve stem 1a. If the attachment part of the valve stem 1a is damaged, the holding force of the valve stem 1a held by the valve stem 1a due to friction with the valve stem 1a will decrease, and as a result, during overrun movement of the internal combustion engine, etc. When an excessive load is applied to the kotta 10,
The valve spring seat 9 and the valve spring seat 9 may come off and the valve 1 may become disconnected, causing a serious accident such as damage to the internal combustion engine.

The valve spring seat 9 is required to have wear resistance, and therefore is subjected to surface hardening treatment such as carburizing treatment and nitriding treatment. In addition, the valve spring seat 9
The inner circumferential surface 9a of the valve spring seat 9 requires precision grinding in order to improve its adhesion with the socket 10. However, since the valve spring seat 9 is deformed when subjected to carburizing treatment, etc., the inner circumferential surface 9a is 9a is subjected to precision grinding. Furthermore, in order to prevent the valve stem 1a from being damaged by the corner 9b of the valve spring seat 9 as described above, the corner 9b is rounded by R-chamfering as shown in FIG. 3 before the carburizing treatment. Add. However, in FIG. 3, the inner circumferential surface 9c before the carburizing process shown by the chain line becomes the inner circumferential surface 9a by precision grinding after the carburizing process. For this reason, even if the R-chamfered portion 12 is provided, a sharp edge will be formed at the connecting portion B between the R-chamfered portion 12 and the final inner circumferential surface 9a, resulting in damage to the valve stem 1a.

Measures to prevent damage to the valve stem 1a include increasing the hardness of the valve 1, not carburizing only the corners 9b of the valve spring seat 9, and carburizing the valve spring seat 9 and grinding its inner peripheral surface. After that, it may be possible to round off the sharp edges of the connecting portion B with sandpaper or the like (see Fig. 4). However, both of the above methods have problems such as increased costs.

As a related technology, "Valve stem cap device for internal combustion engine" (Japanese Utility Model Publication No. 114115/1983)
is proposed.

[Object of the Invention] The present invention was devised to effectively solve the above-mentioned conventional problems, and an object of the present invention is to avoid damaging the valve spring seat when attaching it to the valve stem. To provide a method for manufacturing a valve spring seat that can smoothly connect the inner circumferential surface part and the corner part of the valve spring seat, can prevent damage to the valve stem, and does not increase costs.

[Embodiments of the Invention] Figures 5 and 6 show the vicinity of the corner 9b of the valve spring seat 9. Figure 5 shows the shape before carburization, and Figure 6 shows the shape before carburization. This figure shows the shape after the inner circumferential surface was ground.

As shown in FIG. 5, the tip of the corner portion 9b is chamfered with a small radius of curvature R to form a curved surface portion 13, and the inner circumferential surface 9 before carburizing treatment.
On the c side, there is a connecting part 1 that smoothly connects to the curved part 13.
4 is formed. The connecting portion 14 has a large radius of curvature so that it can be considered to be substantially planar.

After the valve spring seat 9 is carburized in the shape shown in Fig. 5, the inner circumferential surface 9c is precisely ground to the inner circumferential surface 9a and tapered by approximately 7 degrees. 14 is the inner peripheral surface 9 after this precision grinding
The connecting portion 14 is formed to be connected at an almost linear acute angle to a, and a portion of the connecting portion 14 remains after precision grinding.
The opening θ of the connecting portion C between the inner circumferential surface 9a and the inner circumferential surface 9a is 170° or more. Therefore, at the connection part C, the valve stem 1a
This was confirmed in actual machine tests. Furthermore, providing the connecting portion 14 before the carburizing treatment causes almost no substantial cost increase, and furthermore, damage to the valve stem 1a can be reliably prevented and the reliability of the valve mechanism can be improved.

[Effects of the Invention] In summary, according to the present invention, the corners of the valve spring seat and the inner circumferential surface can be smoothly connected with a substantially linear obtuse angle, and no sharp edges are formed. It is possible to reliably prevent engine damage, improve the reliability of the valve opening/closing mechanism, and exhibit excellent effects such as high practicality without increasing costs.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing an example of a valve opening/closing mechanism of an internal combustion engine, Fig. 2 is an enlarged sectional view of the same part, Fig. 3 is an enlarged sectional view of section A in Fig. 2, and Fig. 4 is an enlarged sectional view of part A in Fig. 3. B
FIG. 5 is a cross-sectional view showing the vicinity of the corner of the valve spring seat before carburizing treatment in the method of the present invention; FIG.
The figure is a sectional view showing the state after carburizing the sheet and grinding the inner peripheral surface. In the figure, 1 is a valve, 1a is a valve stem, 5,
6 is a valve spring, 9 is a valve spring seat, 9a is a final inner circumferential surface, 9b is a corner portion, 9c is an inner circumferential surface before carburizing treatment, 10 is a stud, 13 is a curved surface portion, and 14 is a connecting portion .

Claims (1)

[Claims] 1. At the corner of the inner peripheral surface of the valve spring seat,
The valve spring seat is formed by a curved surface with a small radius of curvature and a connecting part with a large radius of curvature that extends from this curved surface to the inner circumferential surface and smoothly connects to the curved surface and the inner circumferential surface, and then the valve spring seat is surface hardened. A method for manufacturing a valve spring seat, characterized in that the inner circumferential surface which has been treated and surface hardened is subjected to a grinding treatment, leaving a part of the connecting portion.