阅读说明：本技术 空心发动机气门 (Hollow engine valve ) 是由 森井宏和 西尾秀信 平尾健一郎 于 2015-07-24 设计创作，主要内容包括：本发明提供一种抑制制造成本的增大且耐久性高的空心发动机气门。空心发动机气门具备气门主体,该气门主体遍及气门头部和与该气门头部连接的气门轴部而形成有有底的空心孔,其特征在于,上述气门头部的底面为平面或凹面,上述空心孔的底面是形成为顶角为140°以上且178°以下的倒圆锥状的凹面,且上述空心孔的底面的内径比上述空心孔的上述阀轴部的内径大。(The invention provides a hollow engine valve with high durability, which can restrain the increase of manufacturing cost. A hollow engine valve is provided with a valve body having a bottomed hollow hole formed over a valve disc and a valve shaft portion connected to the valve disc, wherein the bottom surface of the valve disc is a flat surface or a concave surface, the bottom surface of the hollow hole is a concave surface formed in an inverted conical shape having an apex angle of 140 DEG or more and 178 DEG or less, and the inner diameter of the bottom surface of the hollow hole is larger than the inner diameter of the valve shaft portion of the hollow hole.)

1. A hollow engine valve comprising a valve body having a bottomed hollow hole formed over a valve disc and a valve shaft portion connected to the valve disc,

the bottom surface of the valve head is a plane or a concave surface,

the bottom surface of the hollow hole is a concave surface formed in an inverted conical shape having an apex angle of 140 ° or more and 178 ° or less, and the inner diameter of the bottom surface of the hollow hole is larger than the inner diameter of the valve shaft portion of the hollow hole.

Technical Field

The present invention relates to a hollow engine valve, and more particularly to a hollow engine valve including a valve body having a bottomed hollow hole formed in a valve disc and a valve shaft portion connected to the valve disc.

Background

In recent years, with the increase in output and performance of engines, there has been an increasing demand for engine valves capable of performing highly accurate valve opening and closing operations. Therefore, a hollow engine valve is provided in which the interior is hollow and weight reduction is achieved. A method for manufacturing such a hollow engine valve is disclosed in patent document 1, for example.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2010-094732

Disclosure of Invention

Problems to be solved by the invention

In the conventional method for manufacturing a hollow engine valve disclosed in patent document 1, a solid round bar as a raw material of the hollow engine valve is forged to form an intermediate member having an enlarged diameter portion corresponding to a valve head portion and a solid body portion, and then a bottomed hollow hole is formed in an upper surface of the intermediate member by punching, thereby obtaining a semi-finished product of the hollow engine valve. Further, the diameter-enlarged portion and the body portion of the semi-finished product are pressed by forging, thereby forming a finished product of the hollow engine valve.

However, when the hollow engine valve is used as an exhaust valve, the hollow engine valve is subjected to a use environment in which the hollow engine valve is exposed to high-temperature exhaust gas, and therefore, it is necessary to manufacture the hollow engine valve from heat-resistant steel or heat-resistant alloy having high heat resistance. However, such a material having high heat resistance is generally a difficult-to-cut material, and a reduction in tool life often occurs.

In particular, as shown in patent document 1, in the step of obtaining a semifinished product of a hollow engine valve, when a bottomed hollow hole is formed by punching the upper surface of an intermediate member of a difficult-to-cut material, a tool (punch) used for punching has to be replaced several times, which causes a problem of an increase in manufacturing cost.

In addition, although a case may be considered in which a hollow hole is formed in the shaft portion of a solid semifinished product by cutting after the semifinished product is molded to have a solid outer shape similar to that of a finished product of a hollow engine valve, in this case, an elongated hole having a very large ratio of length to diameter has to be processed by a drill, and thus the processing itself is difficult and the tool life becomes very short.

In the conventional manufacturing method disclosed in patent document 1, the bottom surface of the hollow hole of the semifinished hollow engine valve is a flat surface, and the angle formed between the bottom surface of the hollow hole and the inner peripheral surface is substantially 90 °. In this case, if the enlarged diameter portion and the body portion of the semi-finished product are pressed by forging, corner portions between the bottom surface and the inner peripheral surface of the hollow hole are folded and R of the corner portions is decreased. As a result, stress concentration is likely to occur at the corner portions when the hollow engine valve is used, and the durability of the hollow engine valve may be reduced.

The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a highly durable hollow engine valve and a method for manufacturing the same, in which an increase in manufacturing cost is suppressed.

Means for solving the problems

In order to achieve the above object, a method of manufacturing a hollow engine valve according to the present invention is a method of manufacturing a hollow engine valve including a valve body having a bottomed hollow hole formed in a valve disc portion and a valve shaft portion connected to the valve disc portion, the method including: forming a valve body intermediate member by forging a solid round bar as a material of a valve body, the valve body intermediate member including a semifinished valve disc portion corresponding to a valve disc portion and a solid shaft portion corresponding to a valve shaft portion; forming a valve body intermediate member into a valve body semifinished product by performing cutting work of forming a bottomed semifinished hollow hole corresponding to the hollow hole throughout the solid shaft portion and the semifinished valve stem portion, the valve body intermediate member being provided with a semifinished valve stem portion and a semifinished valve stem portion corresponding to the valve stem portion; and necking the semi-finished product of the valve main body by gradually extruding the shaft part of the semi-finished product valve, so that the diameter of the shaft part of the semi-finished product valve is reduced, the axial length of the shaft part of the semi-finished product valve is prolonged, and the semi-finished product of the valve main body is formed into the valve main body.

In the present invention thus constituted, the valve body intermediate member is formed as a valve body semifinished product having a semifinished product valve stem portion and a semifinished product valve stem portion by forging a solid round bar as a material of the valve body into a valve body intermediate member having a semifinished product valve stem portion and a solid shaft portion and then cutting a semifinished product hollow hole having a bottom formed over the solid shaft portion and the semifinished product valve stem portion, whereby the semifinished product hollow hole can be formed by using a cutting tool (drill) suitable for the processing of a difficult-to-cut material even when the difficult-to-cut material is used as a material of the hollow engine valve, whereby the semifinished product hollow hole can be formed by cutting a solid semifinished product having the same outer shape as that of a finished product of the hollow engine valve as compared with the case where the semifinished product hollow hole is formed by punching a material of the valve body intermediate member The cost required for the tool can be reduced and the processing cycle time can be shortened as compared with the case where the elongated hollow hole is processed and formed. Therefore, an increase in the manufacturing cost of the hollow engine valve can be suppressed.

In the present invention, it is preferable that the semi-finished hollow hole is formed by a drill having an inclined tip in the step of forming the semi-finished hollow hole corresponding to the hollow hole.

In the present invention thus constituted, the bottom surface of the semi-finished hollow hole can be formed in an inverted conical shape, whereby it is possible to suppress a corner portion between the bottom surface and the inner peripheral surface of the hollow hole from being folded and R of the corner portion from decreasing when necking is performed on the semi-finished valve stem portion, as compared to a case where the bottom surface of the semi-finished hollow hole is a flat surface. Therefore, when the hollow engine valve is used, the stress concentration generated at the corner portion can be reduced, and the hollow engine valve with high durability can be manufactured.

In the present invention, it is preferable that the tip angle of the cutting edge of the drill is 140 ° or more and 178 ° or less.

In the present invention thus constituted, the bottom surface of the semi-finished hollow hole can be formed in an inverted conical shape having an apex angle of 140 ° or more and 178 ° or less, whereby the inside diameter of the bottom surface of the hollow hole can be maintained at an appropriate size, and reduction in R at the corner portion between the bottom surface and the inner peripheral surface of the hollow hole when necking is performed on the semi-finished valve stem portion can be suppressed. Therefore, it is possible to manufacture a hollow engine valve having high durability in which both light weight and high cooling performance are achieved by forming a hollow hole having an appropriate size, and stress concentration at a corner portion between the bottom surface and the inner peripheral surface of the hollow hole is reduced.

Further, the hollow engine valve according to the present invention is a hollow engine valve including a valve body having a bottomed hollow hole formed over a valve disc and a valve stem portion connected to the valve disc, wherein a bottom surface of the valve disc is a flat surface or a concave surface, and a bottom surface of the hollow hole is a concave surface.

In the present invention thus constituted, in comparison with the case where the bottom surface of the hollow hole is flat, it is possible to suppress the corner portion between the bottom surface and the inner peripheral surface of the hollow hole from being folded and the R of the corner portion from decreasing when the hollow engine valve is manufactured. Therefore, when the hollow engine valve is used, the stress concentration generated at the corner portion can be reduced, and the hollow engine valve with high durability can be obtained.

In the present invention, it is preferable that the bottom surface of the hollow hole is formed in an inverted conical shape.

In the present invention thus constituted, in comparison with the case where the bottom surface of the hollow hole is flat, it is possible to suppress the corner portion between the bottom surface and the inner peripheral surface of the hollow hole from being folded and the R of the corner portion from decreasing when the hollow engine valve is manufactured. Therefore, when the hollow engine valve is used, the stress concentration generated at the corner portion can be reduced, and the hollow engine valve with high durability can be obtained.

In the present invention, it is preferable that the bottom surface of the hollow hole is formed in an inverted conical shape having an apex angle of 140 ° or more and 178 ° or less.

In the present invention thus constituted, the inner diameter of the bottom surface of the hollow hole can be maintained at an appropriate size, and the corner portion between the bottom surface and the inner peripheral surface of the hollow hole can be prevented from being folded and the R of the corner portion from being reduced when the hollow engine valve is manufactured. Therefore, it is possible to obtain a hollow engine valve having both light weight and high cooling performance by forming a hollow hole of an appropriate size and high durability by reducing stress concentration generated at a corner portion between the bottom surface and the inner peripheral surface of the hollow hole when the hollow engine valve is used.

Effects of the invention

According to the hollow engine valve and the method for manufacturing the same of the present invention, a highly durable hollow engine valve can be obtained while suppressing an increase in manufacturing cost.

Drawings

FIG. 1 is a cross-sectional view of a finished hollow engine valve according to an embodiment of the present invention.

Fig. 2 is a process diagram showing a manufacturing process of a hollow engine valve according to an embodiment of the present invention.

Fig. 3A is a cross-sectional view of a valve body semi-finished product of a hollow engine valve according to an embodiment of the present invention.

Fig. 3B is an enlarged cross-sectional view of a semi-finished valve head of a valve body semi-finished product of a hollow engine valve according to an embodiment of the present invention.

Fig. 4A is a cross-sectional view of a valve body of a hollow engine valve according to an embodiment of the present invention.

Fig. 4B is an enlarged cross-sectional view of the valve disc of the valve body of the hollow engine valve according to the embodiment of the present invention.

Detailed Description

Hereinafter, a hollow engine valve and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings.

First, a hollow engine valve according to an embodiment of the present invention will be described with reference to fig. 1. FIG. 1 is a cross-sectional view of a finished hollow engine valve according to an embodiment of the present invention.

First, in fig. 1, reference numeral 1 denotes a hollow engine valve according to an embodiment of the present invention. The hollow engine valve 1 is used as an intake valve or an exhaust valve in an internal combustion engine of a vehicle or the like.

The hollow engine valve 1 has a hollow valve body 2 and a solid shaft end closure member 4.

The valve body 2 has an umbrella-shaped valve disc portion 6 and a valve shaft portion 8 extending from the valve disc portion 6 in the axial direction. For example, the bottom surface 6a of the valve disc 6 has an outer diameter of 30mm, and the valve stem 8 has an outer diameter of 6 mm. A bottomed hollow hole 10 is formed in the valve disc portion 6 and the valve stem portion 8 so as to follow the outer shapes of the valve disc portion 6 and the valve stem portion 8. The inner diameter of the bottom surface 10a of the hollow hole 10 is larger than the inner diameter of the valve shaft portion 8, and for example, the inner diameter of the bottom surface 10a of the hollow hole 10 is 10mm, and the inner diameter of the hollow hole 10 of the valve shaft portion 8 is 3 mm. For example, sodium metal for a coolant can be sealed in the hollow hole 10. In the following description, a direction from the valve stem portion 8 to the valve disc portion 6 along the axial direction of the hollow engine valve 1 is defined as a lower direction, and a direction from the valve disc portion 6 to the valve stem portion 8 is defined as an upper direction.

The shaft-end closing member 4 has the same outer diameter as the valve shaft portion 8 of the valve body 2, and the upper end of the valve shaft portion 8 and the lower end of the shaft-end closing member 4 are engaged with each other.

As shown in fig. 1, the bottom surface 6a of the valve disc 6 of the valve body 2 is a flat surface, while the bottom surface 10a of the hollow hole 10 of the valve disc 6 is a concave surface. More specifically, the bottom surface 10a of the hollow hole 10 is formed in an inverted conical shape, and the apex angle thereof is formed in a range of 140 ° to 178 °.

As the material of the valve body 2 and the shaft-end closing member 4, a high-tensile steel equivalent to HT80 and a heat-resistant material (for example, SUH-based heat-resistant steel or NCF-based heat-resistant alloy) having a tensile strength of 300MPa or more at 800 ℃ are used.

Next, a method for manufacturing the hollow engine valve 1 according to the embodiment of the present invention will be described with reference to fig. 2 to 4. Fig. 2 is a process diagram showing a manufacturing process of the hollow engine valve 1 according to the embodiment of the present invention. Fig. 3A is a cross-sectional view of the valve body semifinished product 24 of the hollow engine valve 1 according to the embodiment of the present invention, and fig. 3B is an enlarged cross-sectional view of the semifinished product valve head 14 of the valve body semifinished product 24. Fig. 4A is a cross-sectional view of the valve body 2 of the hollow engine valve 1 according to the embodiment of the present invention, and fig. 4B is an enlarged cross-sectional view of the valve disc 6 of the valve body 2.

First, as shown in fig. 2 (a), a solid round bar 12 processed to have a predetermined length and an outer diameter is prepared.

Next, as shown in fig. 2 (b), the solid round bar 12 is forged 1 or more times to form the valve body intermediate member 18 including the semi-finished valve disc 14 corresponding to the valve disc 6 and the solid shaft 16 corresponding to the valve shaft 8. The outer diameter D of the bottom surface 14a of the semifinished valve disc 14 formed at this time₁Is slightly larger than the outer diameter of the bottom surface 6a of the valve disc 6 of the completed product, for example, 32 mm. Further, the outer diameter D of the solid shaft portion 16₂The outer diameter of the valve shaft 8 is larger than that of the finished product, for example, 14 to 20 mm. In the forging process in this step, any of cold forging, warm forging, and hot forging may be used.

Next, as shown in fig. 2 (c), the valve body intermediate member 18 is subjected to a cutting process for forming a bottomed semi-finished hollow hole 20 corresponding to the hollow hole 10 over the solid shaft portion 16 and the semi-finished valve disc portion 14. The valve body intermediate member 18 is thereby formed into a valve body semifinished product 24 including the semifinished valve disc 14 and the semifinished valve stem 22 corresponding to the valve stem 8.

As shown in fig. 3A, in the cutting process for forming the semi-finished hollow hole 20, the semi-finished hollow hole 20 having a bottom is formed over the solid shaft portion 16 and the semi-finished valve disc 14. The cutting is performed by using a hole drilling machine having a shaft core cooling function. Specifically, the drilling machine is provided with a superhard drill having a coolant passage hole, and the coolant is supplied to the drill by a pressure of 2MPa or more. The drilling machine performs drilling by cutting from the upper end of the solid shaft portion 16 to the semi-finished valve disc 14 while holding the outer peripheral portion of the semi-finished valve disc 14. The internal diameter of the semi-finished hollow bore 20 thus formedIs slightly larger than the inner diameter of the bottom surface 10a of the finished hollow hole 10, for example

The tip angle of the cutting edge of the drill used for this cutting work is 140 ° or more and 178 ° or less. Therefore, as shown in fig. 3A, the bottom surface 20a of the semi-finished hollow hole 20 is formed at an apex angle θ₁Is in the shape of an inverted cone of 140 DEG or more and 178 DEG or less. That is, as shown in FIG. 3B, the bottom surface 20a of the semi-finished hollow bore 20 is inclined at an angle θ with respect to the bottom surface 14a of the semi-finished valve disc 14₂Is formed to be 1 DEG to 20 deg. As shown in fig. 3B, a predetermined round R is formed at a corner portion between the bottom surface 20a and the inner peripheral surface 20B of the semi-finished hollow hole 20 formed by the cutting process₁(e.g. R)₁＝1.0mm)。

In the case where the tip angle of the tip of the drill is less than 140 ° (i.e., the inclination angle θ of the bottom surface 20a of the semi-finished hollow hole 20)₂Greater than 20 deg.), if the wall thickness of the bottom surface 14a of the semi-finished valve disc 14 is constant, the volume of the semi-finished hollow bore 20 of the semi-finished valve disc 14 is reduced, thereby resulting in a reduction in weight and an improvement in cooling performance due to the formation of the hollow bore 10The effect is reduced. When the tip angle of the cutting edge of the drill is greater than 178 ° (that is, the inclination angle θ of the bottom surface 20a of the semi-finished hollow hole 20)₂Less than 1 °), when necking is performed on the half-finished valve shaft portion 22, which will be described later, a corner portion between the bottom surface 10a and the inner peripheral surface 10b of the hollow hole 10 is folded and R of the corner portion is reduced, so that stress concentration is likely to occur at the corner portion during use of the hollow engine valve, and the durability of the hollow engine valve 1 may be reduced. Therefore, as described above, the tip angle of the cutting edge of the drill is preferably 140 ° or more and 178 ° or less (that is, the inclination angle θ of the bottom surface 20a of the semi-finished hollow hole 20)₂1 ° or more and 20 ° or less).

After the cutting process for forming the semi-finished hollow hole 20 described above, as shown in fig. 2 (d), the semi-finished valve body 24 is subjected to necking (reduction) for a plurality of times (for example, 8 to 15 times) for gradually pressing the semi-finished valve shaft 22, thereby reducing the diameter of the semi-finished valve shaft 22 and extending the axial length of the semi-finished valve shaft 22. Thereby, the valve body semi-finished product 24 is formed into the valve body 2 including the valve disc portion 6 and the valve shaft portion 8.

The semi-finished valve stem portion 22 is necked down to the outer diameter (for example, 6mm) of the valve stem portion 8 by necking, and the length in the axial direction is extended. In this necking, the lower end portion of the semi-finished valve stem portion 22 (the connecting portion to the semi-finished valve stem portion 14) is pushed in so as to be inclined toward the central axis. Accompanying this, as shown in fig. 4B, R at the corner portion between the bottom surface 10a and the inner peripheral surface 10B of the hollow hole 10 is₂Is larger than R of a corner portion between the bottom surface 20a and the inner peripheral surface 20B of the semi-finished hollow hole 20 shown in FIG. 3B₁Decrease (e.g. R)₂0.2 mm). Further, the inner diameter of the bottom surface 10a of the hollow hole 10Internal diameter of hollow bore 20 of a less than semi-finished productSlightly smaller (e.g. of)。

Next, the shaft end closing member 4 is joined to the upper end of the valve shaft portion 8 of the valve body 2, and the outer periphery of the bottom surface 6a of the valve disc portion 6 is chamfered, thereby forming the hollow engine valve 1 as a finished product.

Next, a further modification of the embodiment of the present invention will be described.

In the above-described embodiment, the case where the bottom surface 6a of the valve disc 6 of the valve body 2 is a flat surface was described, but the bottom surface 6a of the valve disc 6 may be a concave surface.

Next, the operational effects of the vehicle interior structure according to the embodiment of the present invention and the modifications of the embodiment of the present invention will be described.

First, after a solid round bar 12 as a material of the valve body 2 is forged to form a valve body intermediate member 18 having a semifinished valve disc 14 and a solid shaft 16, the valve body intermediate member 18 is subjected to a cutting process for forming a bottomed semifinished hollow hole 20 over the solid shaft 16 and the semifinished valve disc 14, thereby forming the valve body intermediate member 18 into a valve body semifinished product 24 having the semifinished valve disc 14 and the semifinished valve shaft 22, and therefore, even when a difficult-to-cut material is used as the material of the hollow engine valve 1, the semifinished hollow hole 20 can be formed using a cutting tool (drill) suitable for the processing of the difficult-to-cut material, whereby compared to a case where the semifinished hollow hole 20 is formed by punching process for the valve body intermediate member 18, Or, in the case where the shaft portion of the solid semi-finished product having the same outer shape as the finished product of the hollow engine valve 1 is formed into the elongated hollow hole by the cutting process, the cost required for the tool can be reduced and the processing cycle time can be shortened. Therefore, an increase in the manufacturing cost of the hollow engine valve 1 can be suppressed.

Further, since the semi-finished hollow hole 20 is formed by the drill with the inclined tip, the bottom surface 20a of the semi-finished hollow hole 20 can be formed in an inverted conical shape, and thus, in comparison with the case where the bottom surface 20a of the semi-finished hollow hole 20 is a flat surface, it is possible to suppress a corner portion between the bottom surface 10a and the inner peripheral surface 10b of the hollow hole 10 from being folded and R of the corner portion from being reduced when the necking is performed on the semi-finished valve shaft portion 22. Therefore, when the hollow engine valve is used, the stress concentration generated at the corner portion can be reduced, and the hollow engine valve 1 having high durability can be manufactured.

In particular, since the tip angle of the cutting edge of the drill is 140 ° or more and 178 ° or less, the bottom surface 20a of the semi-finished hollow hole 20 can be formed in an inverted conical shape having an apex angle of 140 ° or more and 178 ° or less, and thus the inner diameter of the bottom surface 10a of the hollow hole 10 can be maintained at an appropriate size, and reduction in R at the corner portion between the bottom surface 10a and the inner peripheral surface 10b of the hollow hole 10 can be suppressed when the semi-finished valve stem portion 22 is subjected to necking. Therefore, the hollow engine valve 1 having both light weight and high cooling performance by forming the hollow hole 10 of an appropriate size and high durability by reducing stress concentration at the corner portion between the bottom surface 10a and the inner peripheral surface 10b of the hollow hole 10 can be manufactured.

Description of the reference symbols

1 hollow engine valve

2 valve body

6 valve head

8 valve shaft part

10 hollow hole

12 solid round bar

14 semi-finished product valve head

16 solid shaft part

18 valve body intermediate member

20 semi-finished product hollow hole

22 semi-finished valve stem

Semi-finished product of 24-valve main body