JPS6248043B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cast-in valve seat used in an internal combustion engine.

Aluminum alloys are used in the cylinder heads of internal combustion engines for reasons such as weight reduction and improved cooling performance, but since aluminum alloys cause significant wear on the contact surfaces with the valves, wear-resistant valve seats are usually used in cylinder heads. be assembled into. When assembling a valve seat, there is a difference in thermal expansion coefficient between aluminum alloy and valve seat material, and generally aluminum alloy has a higher coefficient of thermal expansion, so there is a risk that the valve seat will fall off from the cylinder head. For this reason, a normal valve seat is either press-fitted into a valve seat fitting hole provided in the cylinder head, or the valve seat is set in a mold and encased when the cylinder head is cast.

In the case of press-fitting, the number of steps is large because the valve seat fitting hole is machined, the valve seat is heated and press-fitted, and the valve seat surface is then finished. It is difficult to completely eliminate danger. On the other hand, in the case of casting, there is no risk of the valve seat falling out, and machining of the valve seat fitting hole is not required, but there are still some insufficiencies. This point will be explained below with reference to FIGS. 1 and 2.

As shown in FIG. 1, the valve seats 1 and 2 are supported by a core 3 forming an intake port hole 30, a core 4 forming an exhaust port hole 40, and a mold 5. An aluminum alloy is cast into the mold. All cavities except cores 3 and 4 are filled with this aluminum alloy. After casting, the mold is removed and the cores 3 and 4 are removed, producing a cylinder head with a valve seat cast inside, as shown in FIG. As is clear, the valve seats 1, 2 after being cast have an extra portion 10 shown by a dashed line in FIG. , required for fitting into the valve seat recesses 1', 2' of the mold and for assembly with the core. Therefore, when processing the valve seat after casting, it is necessary to shave off this excess portion 10. However,
Since this machining allowance is extremely large, not only does the machining time become longer, but it also has the drawback that it is difficult to process a product with an increased number of valves.

The present invention seeks to provide a valve seat useful in overcoming all of the above-mentioned drawbacks. According to the present invention, this valve seat, as shown in FIG.
A valve seat main body 11 having substantially the same dimensions and shape after processing, and an insert piece 12 having an annular portion 13 that fits into the recesses 1' and 2' of the mold shown in FIG. 1 and a cylindrical portion 14 for assembling with the core. It is formed as a result. When the insert piece 12 is fitted into the valve seat body 11 via the cylindrical portion 14 as shown, the insert piece 1
The annular portion 13 of No. 2 covers the combustion chamber side end surface 111 of the valve seat body 11, and also covers the insert piece 12.
The cylindrical portion 14 covers the inner peripheral surface 112 of the valve seat body 11.

Valve seat body 11 and insert piece 12
The valve seat 1 formed by assembling as described above is supported by a mold and core in the same manner as the embodiment shown in FIG. 1, and then cast with an aluminum alloy. In this case, the annular portion or umbrella portion 13 of the insert piece 12 is fitted into the recesses 1', 2' of the mold, and the cylindrical portion 14 is opposed to the core. After casting, the insert piece 12 is pulled out toward the combustion chamber side,
Thus, the inner circumferential surface 112 of the valve seat body 11 is continuous with the inner surface of the port hole 30 or 40, and the combustion chamber side end surface 111 of the valve seat body 11 is continuous with the combustion chamber side surface of the cylinder head 6.

In a preferred embodiment of the present invention, as shown in FIG. 4, an axial slit 120 is provided at one location in the circumferential direction of the insert piece 12, so that the insert piece 12 has radial contractility by itself. Do it like this. In this configuration, the valve seat body 1
The ease of assembling and removing the insert piece 12 from the insert piece 1 can be improved.

In another aspect, in order to ensure reliable coupling between the valve seat body 11 and the insert piece 12, as shown in FIG.
A knurled surface 123 may be provided on the outer peripheral surface 122 of the cylindrical portion 14. Furthermore, if consideration is given to making it easier to remove the insert piece from the valve seat body after casting, the outer peripheral surface 12 of the cylindrical portion 14 of the insert piece 12 should be
2 can be provided with a number of axially extending grooves 124.

As shown in FIG. 4, providing a slit that extends completely in the axial direction across the insert piece facilitates assembly and removal of the valve seat body and the insert piece, but on the other hand,
Hot water may enter between the valve seat body 11 and the insert piece 12 through the slit. To overcome this drawback, one or more slits 120 may be provided in the cylindrical portion 14, leaving a lower portion 125, as shown in FIG. It goes without saying that the embodiments shown in FIGS. 4 to 7 can be combined as appropriate.

Since the present invention has the above-described configuration, after the insert piece is removed, only the valve contact surface of the cast valve seat body is required to be finished. As a result, productivity is significantly improved compared to conventional methods. Furthermore, the material weight of the valve seat can be significantly reduced, resulting in excellent economic efficiency, and the insert piece can be used repeatedly, so the practical effect is extremely large.

Although the above embodiment shows the case where the insert piece is made of metal material, the insert piece may also be made of casting sand, or the insert piece may be made of a combination of metal material and casting sand for reinforcement. You may also create

In this case, if the insert piece is made only of casting sand, it will be disposable, but if the insert piece is partially made of metal material, the metal part can be used again.

As mentioned above, the weight of the valve seat material can be significantly reduced, making it highly economical.
This has the effect of reducing the number of man-hours required to process the valve seat.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view showing how a valve seat is cast into a cylinder head using a conventional method, Figure 2 is a sectional view showing a valve seat cast in a cylinder head using the method shown in Figure 1, and Figure 3 is a schematic sectional view showing a valve seat cast in a cylinder head using the conventional method. FIGS. 4 to 7 are diagrams illustrating modes of using the valve seat according to the present invention, and are diagrams showing various modifications of an insert piece that is one of the components of the valve seat according to the present invention. DESCRIPTION OF SYMBOLS 1... Valve seat, 11... Valve seat body, 12... Insert piece, 13... Annular part, 14... Cylindrical part, 5... Mold, 1', 2'...
...Concavity, 3, 4...core.

Claims (1)

[Claims] 1. A valve seat is formed by a valve seat main body having approximately the dimensions and shape after processing, and an insert piece having an annular part that fits into a recess of a mold and a cylindrical part for assembly with a core, and the insert piece is A cast-in valve seat characterized by being fitted into a valve seat body through the cylindrical portion.