JP2008088815A - Hollow poppet valve and manufacturing method thereof - Google Patents

Abstract

【Task】
In the technology to plastically process the main part of the hollow poppet valve from the valve part through the flare part to the stem by plastic processing of the steel plate, facilitating the plastic forming of the thick valve part and the finishing of the seating part, and The point is to obtain an end structure for reliably connecting the small diameter end of the stem and the mandrel closing the small diameter end.
[Solution]
Connects the valve section formed in a shallow conical shape with a thick plate thickness and the stem section formed in a circular tube shape from the valve section to the stem section via an arc-shaped flare section that continuously reduces the plate thickness. A seating portion was formed on the outer surface of the large-diameter end forming the valve portion of the deep drawn base material.
[Selection] Figure 1

Description

  The present invention relates to a hollow poppet valve suitable as an intake / exhaust valve for an engine. In particular, the present invention is to obtain a manufacturing method with excellent productivity that can achieve further weight reduction and produce it with high efficiency.

  In general, a so-called hollow poppet valve is known in which a shaft hole in the axial direction is formed in the stem core to be hollow for the purpose of reducing the mass of the poppet valve. In addition, in order to further reduce the weight and improve the productivity of the hollow poppet valve, a technique has been proposed in which a steel plate is formed into a hollow shape without being machined from the stem to the valve portion by plastic working (for example, Patent Document 1).

  However, since the poppet valve shown in this document is a process in which the thickness from the stem to the valve portion through the flare portion is formed with the same thickness, the poppet valve formed thereby has a strong combustion pressure. The strength of the valve part to receive was apt to be insufficient. Therefore, it was considered to reinforce the flare formed by expanding one end of the stem by friction welding a thick valve plate molded separately (see Patent Document 2), but a series of thinning steps A separate process is required, which complicates the process and dramatically reduces the weight reduction effect of the valve.

  In addition, since the hollow poppet valve is formed into a thin cylindrical shape, there is a step of adding a cotter groove that receives the elasticity of the valve spring or reinforcing the end that receives the pressing force of the cam. It is necessary. Therefore, in order to perform the process rationally, a technique for fixing a hard mandrel to the small-diameter end of the stem has been known (see, for example, Patent Document 3).

However, the stem end treatment method shown in this document supports a steel ball in a cotter groove provided at the end of the stem and reduces the diameter of the stem from the outer periphery to prevent the stem from falling out. Even if tightened tightly, there is a limit to the tightening strength, and when the stem is thin, fixing is likely to be incomplete.
JP 2000-45730 A JP 2001-221348 A JP 2001-317315 A

  The problem to be solved is the plastic forming of the main part of the hollow poppet valve from the valve part to the stem through the flare part through plastic processing of the steel plate, plastic forming of the thick valve part and finishing of the seating part And an end structure for ensuring the connection between the small diameter end of the stem and the mandrel closing the small diameter end.

  The invention of the object according to the present application is a relatively thick-walled valve portion made of a shallow cone having one end made large in diameter and an inner end made small in diameter, and a circle made relatively thin. The tubular stem portion is connected in series by a flare portion formed by an arcuate curved surface that protrudes in the axial direction, and the flare portion is connected to the stem portion from the thick portion that is connected to the valve portion. While the thickness of the thin wall portion gradually decreases, the partition plate is welded to the inner surface opening formed by the valve portion and the flare portion, and the outer periphery of the opening portion of the circular tube forming the stem portion is welded. A mandrel provided with a groove is fitted, and the back surface of the cotter groove provided outside the mandrel is locked to the outer circumferential groove to block the inside and outside, and is seated on the outer surface of the large diameter end forming the valve portion It is characterized by cutting parts.

  In addition, the invention of the method according to the present application is a material for forming a deep-drawn base material having a series of valve portions, cylindrical stems, and flare portions that connect the two, by drawing a steel plate into a substantially frustoconical shape. Machining step for forming a seating portion on the valve portion, a welding step for welding and closing a partition plate to the opening on the valve portion side, and an insertion step for inserting a mandrel with an outer peripheral groove provided at the small diameter end of the stem And reducing the diameter of the outer surface of the stem in the axial direction to form a cotter groove, and reducing the diameter of the cotter groove to engage the outer peripheral groove.

  According to the invention of the product according to the present application, although the thickness of the valve portion of the poppet valve and the flare portion is reduced to reduce the weight, the space from the periphery of the valve portion to the flare portion is Since it is formed in a thin conical shape with a large plate thickness, it can withstand strong combustion pressure and strong impact when the poppet valve is seated.

  The inner surface of the stem that opens to the combustion chamber side is closed by a partition plate welded to the inside of the large-diameter end, so the pressure of the combustion chamber acting on the partition plate is reduced, and a thinner material is sufficient, making it even lighter Can be realized.

  The flare portion interposed between the thick valve portion and the thin tubular stem portion connects the two at a relatively short distance, so that the plate thickness can be changed smoothly. Therefore, the stress of the valve spring transmitted from the stem part to the valve part can be converted without any unnecessary stress from the pulling direction to the bending direction, so there is no waste in the material of this part and the weight of the valve part Can be reduced.

  According to the invention of the method according to the present application, when the hollow poppet valve material is produced by cold plastic processing, the valve portion is formed into a shallow conical shape. Since the large cross-sectional shape is not changed, the moldability of the valve portion is not impaired even if the thickness of the valve portion is increased. In addition, since the flare portion where the cross-sectional area shape is greatly reduced can be made relatively short, the range for changing the cross-sectional area of the flare portion can be reduced, and there is an advantage that it is easy to manufacture and modify the mold .

  Furthermore, the end portion of the thin cylindrical stem is closed by a mandrel, but the mandrel has an outer peripheral groove, so that the back surface is engaged when the cotter groove is provided on the outer periphery of the stem. . At this time, since the cotter groove is relatively narrow and deep, it has high rigidity and is less likely to be restored to its original shape by elasticity, so that it can be reliably locked and the axial movement of the mandrel is reliably prevented.

  The purpose of further reducing the weight of the hollow poppet valve was achieved without satisfying the required functions of the poppet valve and the ease of cold plastic working and without reducing the mechanical strength.

  FIG. 1 is a cross-sectional view along the axis of a hollow poppet valve 10 according to the present invention. The hollow poppet valve 10 is a relatively short flare portion that reduces the thickness of one of the thick conical valve portion 20 and the thin tubular stem portion 30 from one to the other in the axial direction. 40, which are connected together by a series and metallurgically.

  The valve part 20 is formed in a conical shape with a substantially constant thickness, the apex angle α is set to 130 °, and is formed in a so-called shallow conical shape whose height is lower than the diameter. ing. Therefore, the strong combustion pressure in the combustion chamber acts strongly on the valve portion 20 having a wide apex angle, but this portion has a large thickness and withstands the pressure with sufficient strength. The apex angle β is the apex angle of the seating portion 22 and is set to approximately 90 ° as in the conventional case. The seating portion 22 cuts or grinds the outer side of the end portion (hereinafter referred to as a large diameter end) of the valve portion 20 to form a combustion chamber surface 22a, an outer peripheral surface 22b, and a seating surface 22c. is there. Since this processing only cuts the end portion of the large diameter end that has been plastic processed into a plate shape, it can be efficiently performed with less machining allowance.

  The stem portion 30 has a thin tubular shape as a whole, is inserted into the inner surface of the valve guide 12 indicated by reference numeral 12 in FIG. 1 and is slidably supported. The opposite end receives the elasticity of the valve spring and the pressing force of the valve cam (not shown) to cause the valve 20 to open and close, while the valve opening means 14 such as a valve lifter or a rocker arm. Affected. That is, the stem portion 30 is constantly subjected to the action of an alternating load in the axial direction.

  A cotter groove 32 for locking the valve spring and a hard end face 34 that receives the action of the valve opening means 14 are provided at an end portion (hereinafter referred to as a small diameter end) of the stem portion 30 that is not connected to the flare portion 40. Is formed. The hard end face 34 is press-fitted with a mandrel 36 made of a bearing steel ball or roller near the end of the cotter groove 32. The end face 34 is formed by grinding the mandrel 36 after press-fitting.

  Thus, since the mandrel 36 is once press-fitted into the small-diameter end of the stem portion 30, the mandrel 36 is not loosened even if the outer diameter of the stem portion 30 is processed in a subsequent process. Therefore, even if it is an exhaust valve in which sodium is sealed in the stem portion 30, leakage from the portion of the mandrel 36 can be prevented.

  The flare portion 40 is formed by connecting a large-diameter end connected to the valve portion 20 and a small-diameter end continuous to the stem portion 30 with two smooth arcs, and the outer surface has the shape of a conventional poppet valve. The inner surface is drawn by an arc R2 having a slightly different center and radius from the outer surface. On the inner surface of the flare portion 40 formed in this way, a partition plate 42 made by pressing a steel plate on the large diameter end side is fixed by projection welding, and the front and back sides are sealed. As in this example, when the partition plate 42 is hemispherical and the combustion chamber side is convex and welded, high strength can be maintained against the combustion pressure, so the thickness of the partition plate 42 can be reduced, This greatly contributes to the weight reduction of the hollow poppet valve 10.

  Next, a method for manufacturing the hollow poppet valve 10 will be described. The entire process will be briefly described with reference to FIG. 2. First, a material process for manufacturing the deep-drawn base material A including the valve part 20, the stem part 30, and the flare part 40 by drawing with a press machine, which will be described later. Done.

  As shown in FIG. 3, the raw material process is obtained by punching the deep-drawn base material A into a circular shape of a deep-drawn cold-rolled steel having substantially the same thickness as the valve portion 20. The first material 60 shown is drawn by a not-shown pressing machine, and as shown in FIG. 2B, the side wall and the bottom part are formed into a bowl shape connected by a relatively large arc R. The material 61 is molded.

  The second material 61 is applied with a drawing process as shown in FIGS. 3C, 3D, and 3E to reduce the outer diameter. At the same time, the valve is formed in a conical shape at the opening of the bowl-shaped second material 61. A third material 62 obtained by narrowing the outer diameter of the straight pipe part 20b while leaving a conical ear part 20a corresponding to the part 20, and a fourth material obtained by further narrowing the straight pipe part 20b and expanding the ear part 20a. Deformation progresses to 63 and the fifth material 64.

  In the middle thereof, as shown in FIG. 6F, the angle and shape of the ear portion 20a expanded in a conical shape and the arc-shaped portion 20c corresponding to the flare portion 40 are corrected to make a sixth material 65. Then, the straight pipe portion 20b is further elongated to form the seventh material 66, and finally the outer diameter of the ear portion 20a corresponding to the valve portion 20 is reduced. Trimming to make a deep drawn base material A.

  The deep-drawn base material A thus obtained is processed with a small diameter end as shown in FIGS. Details will be described with reference to FIG. In processing the small-diameter end, first, as shown in FIG. 3A, the portion 70 whose shape is unstable by drawing is cut off. As a result, a round stem portion 30 with a stable thickness is obtained at the remaining portion. Then, the mandrel 36 is relatively press-fitted into the opening 72 formed so that the airtightness of the front and back surfaces is maintained.

  Thereafter, the stem 30 is positioned on both axial sides of the mandrel 36 and the outer diameter is clamped by the rolling roller 50 shown in FIG. That is, in the diameter reducing process, the cotter groove 32 is formed, and simultaneously, the caulking process in which the opening 72 is bent in the axial direction is simultaneously performed. As a result, the small-diameter end has a so-called circular chamfered shape that protrudes outward. As a result, the press-fitted material B in which the small diameter end of the stem portion 30 is closed is completed.

  Next, the press-fitted material B is closed to the welded material C by opening the opening opened on the combustion chamber side surface (hereinafter, simply referred to as the inner surface) of the flare 40 using the partition plate 42 by a welding process. In this example, the partition plate 42 is formed in a hemispherical shape, and projection welding (a kind of electric resistance welding) is performed with its concave surface facing the inner surface of the flare portion 40. As a result, in addition to the effect of reducing the weight described above, there is an effect on the process that facilitates projection welding. Further, when projection welding is used to weld the partition plate 42, the welding time is short and the melting range is narrow, so that reliable welding can be obtained. When the hollow poppet valve 10 is an exhaust valve, before the partition plate 42 is welded, a predetermined amount of powdered sodium is put inside, and then the partition plate 42 is welded.

  Thereafter, as shown in FIG. 2 and FIG. 4 (b), the welded material C is a series of machines including an outer surface 30a of the stem portion 30, a hard end surface 34, and a grinding process as necessary, as well as cutting. A processing step is performed, and then a heat treatment step for performing a soft nitriding process or the like is performed to complete the process. The grinding process and the heat treatment process are not significantly different from the finishing process of the conventional hollow poppet valve.

  In FIG. 4, a steel ball is used as the mandrel 36. However, the structure of the invention is not limited to this, and as shown in FIG. 5, a shaft-like member having a circumferential groove 38 provided on the outer periphery is used. Can be used. When the shaft-shaped mandrel 36 is fixed to the stem portion 30, the back surface of the cotter groove 32 may be engaged with the outer peripheral groove 38, thereby preventing it from coming off.

It is sectional drawing along the axis line of the hollow poppet valve which concerns on this invention. It is process drawing which shows the manufacturing process of a hollow poppet valve. It is process drawing which shows the manufacturing process of a deep drawing base material. It is process drawing which shows the process of closing the small diameter end of a stem part. It is process drawing which shows the other process of closing the small diameter end of a stem part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hollow poppet valve 12 Valve guide 14 Valve opening means 20 Valve part 22 Seating part 22a Combustion chamber surface 22b Outer peripheral surface 22c Seating surface 30 Stem part 30a Stem part ground outer surface 32 Cotta groove 34 Hard end face 36 Steel ball (core metal )
38 Peripheral groove 40 Flare portion 42 Partition plate 50 Rolling roller 60, 61, 62 First material, second material, third material 63, 64, 65, 66 Fourth material, fifth material, sixth material, seventh Material 70 Unstable part 72 Opening
A Deep drawing substrate
B Press-fitted material
C Welded material R1, R2 Arc

Claims (4)

  There is a gap between a relatively thick-walled valve portion made of a shallow cone having one end made of a large diameter and an inner end made of a small diameter, and a tubular stem portion made of a relatively thin wall. The flared portion formed by an arcuate curved surface projecting in the axial direction is integrally connected, and the flared portion gradually extends from the thick portion connected to the valve portion to the thin portion connected to the stem portion. While reducing the plate thickness, a spherical shell is welded to the inner surface of the opening formed by the valve portion and the flare portion, and a mandrel is fitted into the opening portion of the circular tube forming the stem portion to block the inside and outside. A hollow poppet valve in which a seating portion is formed on the outer surface of the large-diameter end forming the valve portion.   2. The hollow poppet valve according to claim 1, wherein a conical angle of the valve portion is set to be wider than a conical angle of the seating portion.   In Claim 1, while providing an outer periphery groove | channel in the mandrel fitted by the opening part of the circular pipe which makes the said stem part, reducing the outer surface of the opening part of the said circular pipe, providing a cotter groove | channel, A hollow poppet valve having a back surface engaged with an outer peripheral groove of the mandrel.   A material process for forming a deep drawn base material having a series of a valve part that is made by drawing a steel plate into a substantially frustoconical shape, a cylindrical stem, and a flare part that connects the two, and a seating part on the valve part Machining process to be formed, welding process in which the partition plate is welded and closed to the valve side opening, insertion process in which a mandrel is inserted into the small diameter end of the stem, and the outer surface of the stem is reduced in the axial direction. Method of manufacturing a hollow poppet valve including a diameter reducing step of locking the mandrel to the stem

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