JP4222547B2 - Engine valve and manufacturing method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a poppet-type engine valve used in a combustion chamber of a four-stroke engine and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, the engine for automobiles and motorcycles has been further increased in speed, and accordingly, in order to reduce the weight of the engine valve, the diameter of the valve rod with respect to the valve diameter is designed to be narrower than the conventional one. (For example, see Reference 1). In addition, the production of engine valves has conventionally been done using a rod-shaped material slightly thicker than the diameter of the valve stem, and after cold or red hot, upset processing (upset forging) is added to one end to form a disk. The valve body and the valve rod are integrally formed by deformation.
[0003]
[Reference 1]
Japanese Patent Laid-Open No. 2002-168104
[Problems to be solved by the invention]
However, when a titanium alloy is used for the umbrella and stainless steel is used for the valve rod, the weight can be further reduced, but it is difficult to join the heterogeneous material with strength. In addition, it is difficult to cool a titanium alloy having a small thermal conductivity.
[0005]
[Means for Solving the Problems]
The problem described above is that a valve body member made of a substantially disc-shaped green compact made by compressing and solidifying titanium alloy powder and a stainless steel valve rod member have a peripheral edge. A coupling hole is provided in the inner surface of a cylindrical boss formed concentrically with the valve surface, a plurality of circumferential grooves are provided in a coupling portion of the valve rod member , and the valve rod member is formed in the coupling hole in the valve body member. This is solved by fitting the joint portion and firing the valve body member and the valve rod member at a sintering temperature and integrally joining them.
[0006]
As a manufacturing method, a valve rod member made of stainless steel and a valve body member made of a powder compact formed of titanium alloy powder and provided with a coupling hole are prepared, and the valve rod member is loosely fitted into the coupling hole. A hollow valve rod member is filled with a coolant, fired in a sintering furnace to sinter the valve body member, and sealed together with the sintering process due to the shrinkage of the valve body member accompanying the sintering. Can be solved by.
[0007]
[Action]
By making the valve body and the valve body separately and combining them later, the selection of the diameter of the valve body and the diameter of the valve body is not restricted by the manufacturing technology. The valve element is made by mixing a titanium alloy powder compact with a binder and then injecting it into a mold (MIM), just like plastic molding, and shrinks when the powder compact is sintered. In close contact with the outer peripheral surface of the valve rod member. Since the end portion of the valve rod that is hit by the rocker arm is partially quenched later, generally martensitic stainless steel is used, so that dissimilar materials must be joined.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
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 surface 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 green compact made by compressing and solidifying titanium alloy powder together with a valve rod member 21 described later. A valve face 11 is formed on the outer periphery of the valve body member 16, 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 has one end closed and the other end opened, and a large number in the circumferential direction is formed on the outer surface of the open end. The connecting portion 23 is formed of a plurality of grooves. The multiple grooves may be a single screw groove, but it is more preferable to provide multiple circumferential grooves at equal intervals.
Further, the cylindrical hole may be coupled to the taper shaft in order to allow the vertical contraction.
[0011]
The valve body 12 and the valve rod 13 formed as described above are sintered in a state in which the coupling hole 17 and the coupling portion 23 are fitted, and the valve body member 16 contracts due to heating accompanying the sintering. When the boss 18 strongly binds the connecting portion 23 from the outside, the sintering temperature is sufficiently high, so that metal molecules are diffused between the valve body 12 and the valve rod 13, and the metallurgical bonding is also high. Bond strength is obtained. Further, since the valve body 12 is made of a light titanium alloy and the valve rod 13 is made of hollow stainless steel, the engine valve 10 becomes lighter, and a weight reduction of about 56% is achieved with respect to 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 made by machining and rolling a steel material, and adding a binder (binder) to a titanium alloy powder and press-molding it to form a green compact (also called a green body). ) 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 initially made larger in diameter by about 0.5 mm to 1 mm than the coupling portion 23 provided in the valve rod member 21. Generally, the sintering temperature is 1000 ° C. to 1350 ° C. In this embodiment, about 1200 ° C. is used, and the contraction rate of the valve body member at this time is about 12%. It concludes with a bite. However, even if the valve rod member 21 is hollow, it is not deformed, and a great deal of stress does not remain, which is different from shrink fitting.
[0013]
As shown in FIG. 3, the material is pre-sintered, as shown in FIG. 3, with the closed side of the valve rod member 21 facing down in a vertical support hole 26 provided in a ceramic sintering mold 25 (joint portion). 23, with the valve body member 16 mounted on the valve rod member 21, the coupling hole 17 and the coupling portion 23 being fitted, and a nitrogen gas type continuous not shown. Sinter into a sintering furnace such as a furnace.
[0014]
When the constituent members of the engine valve 10 placed in the sintering furnace in this way are heated to a predetermined temperature, non-metallic members (such as PP resin of the binder) are gasified from the valve body member 16 forming the green compact. The outer shape, the inner diameter, and the height shrink in proportion to each other. Therefore, the coupling hole 17 contracts to a small diameter and comes into close contact with the outer surface of the coupling portion 23. In the case where 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% are obtained by sintering at 1200 ° C. Therefore, the solid material is not lost as the valve body member 16.
[0015]
Further, a cooling agent such as metallic sodium may be put in the hollow portion of the valve rod member 21 and sealed with the lid 19 to promote the cooling effect of the valve. In this case, the inner hole is stepped to support the stopper, and the copper brazed hermetic stopper is partially attached with copper having a melting point of 1080 ° C. and is allowed to flow to the outside air. And it is preferable that it becomes a sealed plug at 1200 ° C., and the inside is at a low pressure at room temperature.
[0016]
After the sintering is completed through such a process, the 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 quenched in a short time. It completes through the process of grinding the seating surface of the valve surface 11.
[0017]
【The invention's effect】
According to the above engine valve invention, the engine valve is connected by inserting the valve rod member into the coupling hole provided in the valve body member made of titanium alloy and utilizing the contraction accompanying the sintering of the valve body member. Therefore, a strong bond can be achieved without going through a welding or press-fitting process, and since the sintering process is also used, manufacturing is easy and inexpensive. Further, since the shrinkage during the sintering of the valve body member is utilized to couple with the groove of the valve rod member, the shearing strength of the member is added, and a slight metallurgical coupling is involved, so that the coupling is firmly performed. Furthermore, since an engine valve is manufactured by separately manufacturing a valve body and a valve stem, and connecting and integrating them in a later process, the valve body has a large diameter and a thin valve stem. However, it can be manufactured without being restricted by a manufacturing process or a material.
[0018]
According to the manufacturing method of the present invention, since the valve body member and the valve rod member are coupled using the sintering process of the valve body member, manufacturing is easy without requiring an independent process such as forging or welding. is there. In addition, the heat balance is improved by completing the connection and sealing at the same time during the sintering process.
There are effects such as.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an engine valve according to the present invention, in which the left half shows a state before sintering and the right half shows a state after sintering.
FIG. 2 is an exploded sectional view showing the structure of the engine valve before sintering separately.
FIG. 3 is a cross-sectional view showing a state in which engine valve components are supported by a sintered mold.
4 is a cross-sectional view corresponding to FIG. 3, showing a state in which a coolant is put in the hollow portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Engine valve 11 ... Valve surface 12 ... Valve body 13 ... Valve disc 14 ... Cotta groove 15 ... End surface 16 ... Valve body member 17 ·············································· Lid 21 ···· Valve member 23 ········· Connection portion 25 ···

Claims (2)

A valve body member made of a substantially disc-shaped green compact made by compressing and solidifying titanium alloy powder and a stainless steel valve rod member are used, and the valve body member is concentric with the valve surface forming the periphery. A coupling hole is provided in the inner surface of the cylindrical boss formed in the cylinder, a number of circumferential grooves are provided in the coupling portion of the valve rod member, and the coupling portion of the valve rod member is fitted in the coupling hole in the valve body member. An engine valve formed by integrally combining the valve body member and the valve rod member by firing at a sintering temperature. A valve guidance rod made of stainless steel, were prepared and a valve member made of a green compact having a coupling hole is formed using a titanium alloy powder, thereby loosely fitting the valve guidance rod to the coupling hole, a hollow Manufacture of an engine valve that puts a coolant into the valve rod member, sinters it in a sintering furnace to sinter the valve body member, and seals the valve body member simultaneously with the sintering process due to the shrinkage of the valve body member accompanying the sintering Method.

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