JP2004340050A - Engine valve and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that it is difficult to rigidly join different kinds of light-weight material like titanium system alloy to each other in order to satisfy a demand for a thinner valve stem which is recently required to reduce the weight while the diameter of an engine valve tends to increase for improvement of the engine performance. <P>SOLUTION: The engine valve includes a valve element member which is made of green compact and which has a coupling hole formed concentrically with a conical valve surface, and a valve stem member. The coupling hole of the valve element member is fitted on a connecting portion of the valve stem member comprising multiple grooves extending in the circumferential direction, and the valve element member and the valve stem member are baked at the sintering temperature so as to be united with each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a poppet type engine valve used in a combustion chamber of a four-stroke engine and a method of manufacturing the same.
[0002]
[Prior art]
In recent years, engines for automobiles and motorcycles have become even faster, and the weight of engine valves has been reduced accordingly. (For example, see Reference Document 1). Conventionally, engine valves are manufactured using a rod-shaped material that is slightly thicker than the diameter of the valve rod, cold or red hot, and then upset at one end (upsetting forging) to form a disk. By deforming, the valve body and the valve rod are integrally formed.
[0003]
[Reference 1]
Japanese Patent Application Laid-Open No. 2002-168104
[Problems to be solved by the invention]
However, if a titanium alloy is used for the umbrella portion and stainless steel is used for the valve rod, the weight can be further reduced, but strong joining of the different materials is difficult. Also, it was difficult to cool a titanium-based alloy having low heat conductivity.
[0005]
[Means for Solving the Problems]
The above object is to use a valve member made of a substantially disk-shaped compact formed by compressing and solidifying a titanium alloy powder, and a valve rod member made of stainless steel, and the valve member has a peripheral edge. A coupling hole is provided concentrically with the valve surface, a coupling portion of the valve rod member is fitted into the coupling hole, and the valve body member and the valve rod member are integrally sintered by firing at a sintering temperature. Solved by
Further, the connecting portion of the valve rod member preferably has a large number of circumferential grooves.
[0006]
As a manufacturing method, a valve rod member and a valve body member made of a green compact formed using titanium alloy powder and provided with a coupling hole are prepared, and the valve rod member is loosely fitted into the coupling hole, and these are fired. This can be solved by firing in a furnace and sintering the valve member, and by simultaneously contracting the valve member with the sintering, connecting the valve member and the valve rod member.
Further, a coolant may be put in the hollow portion of the valve body member, a brazing material may be put on the lid member, and the valve may be hermetically sealed at the same time as the sintering process.
[0007]
[Action]
By forming the valve body and the valve rod separately and combining them later, the selection of the diameter of the valve body and the diameter of the valve rod is not restricted by the manufacturing technology. The valve body member is made by a method of mixing a titanium alloy compact with a binder and injecting it into a mold (MIM) as in the case of plastic molding, and shrinks when the compact is sintered. And is tightly integrated with the outer peripheral surface of the valve rod member. Since the end of the valve rod that is hit by the rocker arm is partially hardened later, martensitic stainless steel is generally used, so that joining of dissimilar materials is required.
[0008]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, an embodiment of the present invention will be described. 1 and 2, reference numeral 10 denotes an engine valve according to the present invention. The engine valve 10 has a valve body 12 having a valve face 11 and a valve rod 13 attached to a central portion of the valve body 12 and extending to one side therefrom. Reference numeral 14 denotes a cotter groove for locking the cotter, and 15 denotes an end surface that comes into contact with a rocker arm that presses and drives the valve rod 13 in the axial direction.
[0009]
The valve body 12 is made by heating and sintering a valve body member 16 made of a compact formed by compressing and solidifying a titanium alloy powder together with a valve rod member 21 described later. The valve member 16 has a valve surface 11 formed on the outer periphery, and a boss 18 and a coupling hole 17 provided in the boss 18 are formed concentrically at the center.
[0010]
The valve rod 13 is made of stainless steel or heat-resistant steel, and the hollow valve rod member 21 is closed at one end and open at the other end. Is formed. Although the plurality of grooves may be a single screw groove, it is more preferable to provide a plurality of circumferential grooves at equal intervals.
In addition, a cylindrical hole may be connected to the tapered shaft to allow free contraction in the vertical direction.
[0011]
The valve element 12 and the valve rod 13 formed as described above are sintered in a state where the coupling hole 17 and the coupling portion 23 are fitted, and the valve element member 16 contracts due to heating accompanying the sintering. At this time, the boss 18 strongly binds the connecting portion 23 from the outside, and since the sintering temperature is sufficiently high, metal molecules are diffused between the valve body 12 and the valve rod 13 and metallurgical bonding is high. A bond strength is obtained. Further, since the valve body 12 is made of a lightweight titanium alloy and the valve rod 13 is made of hollow stainless steel, the engine valve 10 is lightened, a weight reduction of about 56% is achieved for a solid stainless steel valve, and the weight is 44. %.
[0012]
Next, a sintering method for manufacturing the engine valve 10 will be described. First, as a material, a valve rod member 21 formed by machining and rolling a steel material, and a binder (binder) added to a powder of a titanium alloy to form a green compact (also referred to as a green body). ) Is prepared, and a ceramic (unfired) sintering mold 25 for holding them in a sintering furnace is prepared. Here, the coupling hole 17 provided in the valve body member 16 is made larger in diameter than the coupling portion 23 provided in the valve rod member 21 by about 0.5 mm to 1 mm at first. Generally, the sintering temperature is from 1000 ° C. to 1350 ° C. In this embodiment, about 1200 ° C. is used, and the shrinkage rate of the valve member at this time is about 12%. It is concluded by biting. However, even if the valve rod member 21 is hollow, it is not deformed, and a large stress does not remain, which is different from shrink fit.
[0013]
As a pre-process of sintering, the material is inserted into a vertical support hole 26 provided in a ceramic sintering mold 25 with the closed side of the valve rod member 21 facing downward as shown in FIG. 23 with the valve body member 16 mounted on the valve rod member 21 and the coupling hole 17 and the coupling portion 23 fitted together. It is put into a sintering furnace such as a furnace and sintered.
[0014]
When the constituent members of the engine valve 10 placed in the sintering furnace are heated to a predetermined temperature in this manner, the non-metallic members (such as a PP resin as a binder) are gasified from the valve member 16 forming the compact. And its outer shape, inner diameter and height shrink almost proportionally. Therefore, the coupling hole 17 contracts to a small diameter and comes into close contact with the outer surface of the coupling portion 23. When the titanium alloy powder is Ti-6Al-4V, there is a report that a density of 95%, a tensile strength of 830 MPa and an elongation of 13.4% can be obtained by sintering at 1200 ° C., so that the valve member 16 is as good as solid material.
[0015]
In some cases, a coolant such as metallic sodium is put in the hollow portion of the valve rod member 21 and sealed with the lid 19 to enhance the cooling effect of the valve. In this case, the inner hole supports the plug as a step, and in the case of a copper brazed hermetic plug, a copper paste having a melting point of 1080 ° C. is partially applied to allow the air to flow to the outside air. It is preferable that the inside of the container is sealed at 1200 ° C. and the inside thereof is kept at a low pressure at room temperature.
[0016]
After sintering is completed through such a process, a cotter groove 14 is formed on the outer peripheral surface of the valve rod member 21, the end surface 15 is rapidly heated by a flame burner, and the surface is hardened in a short time. The process is completed through the step of grinding the seating surface of the valve surface 11.
[0017]
【The invention's effect】
According to the above-mentioned invention of the engine valve, the engine valve is configured such that the valve rod member is inserted into the coupling hole provided in the valve body member made of titanium alloy, and is connected using shrinkage accompanying sintering of the valve body member. As a result, it is possible to form a strong connection without performing a welding or press-fitting step, and also to use the sintering step, so that the production is easy and inexpensive. In addition, since the valve member is combined with the groove of the valve rod member by utilizing shrinkage at the time of sintering, the shear strength of the member is added, and a slight metallurgical connection is involved, so that the connection is firmly performed. Further, since the engine valve is manufactured by separately manufacturing the valve body and the valve rod, and connecting them in a later step, the valve body is large in diameter and the valve rod is thin. However, the device can be manufactured without being restricted by the manufacturing process or the material.
[0018]
According to the invention of the manufacturing method, since the valve body member and the valve rod member are joined using the sintering process of the valve body member, the manufacturing is easy without requiring an independent process such as forging or welding. is there. In addition, the heat account can be improved by completing the connection and sealing at once in the sintering process.
And so on.
[Brief description of the drawings]
FIG. 1 is a sectional view of an engine valve according to the present invention, in which a left half shows a state before sintering and a right half shows a state after sintering.
FIG. 2 is an exploded sectional view showing a structure of an engine valve before sintering separately.
FIG. 3 is a cross-sectional view showing a state in which components of the engine valve are supported on a sintered mold.
FIG. 4 is a sectional view corresponding to FIG. 3 and showing a state in which a coolant is filled in a hollow portion.
[Explanation of symbols]
10, engine valve 11, valve face 12, valve body 13, valve rod 14, cotter groove 15, end face 16, valve body member 17 ····························································································································· Supporting-holes

Claims (4)

A valve body member made of a substantially disk-shaped compact formed by compressing and solidifying a titanium alloy powder, and a stainless steel valve rod member are used, and the valve body member is concentric with a peripheral valve surface. An engine valve comprising: a coupling hole provided in the coupling member; a coupling portion of the valve rod member is fitted into the coupling hole; and the valve body member and the valve rod member are integrally sintered by firing at a sintering temperature. 2. The engine valve according to claim 1, wherein the connecting portion of the valve rod member has a number of circumferential grooves. A valve rod member and a valve body member formed of a compact formed with titanium alloy powder and provided with a coupling hole are prepared, and the valve rod member is loosely fitted into the coupling hole, and these are placed in a sintering furnace. And sintering the valve body member, and simultaneously contracting the valve body member with the sintering to simultaneously couple the valve body member and the valve rod member. 4. The method for manufacturing an engine valve according to claim 3, wherein a coolant is filled in a hollow portion of the valve body member, a brazing material is attached to the lid member, and the plug is sealed at the same time as the sintering process.

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