JP4420853B2 - Titanium alloy valve lifter and manufacturing method thereof - Google Patents

Description

The present invention relates to an improved structure of a titanium alloy valve lifter and a method of manufacturing a titanium alloy valve lifter .

The valve lifter in the valve operating device of the internal combustion engine is generally made of steel. Some examples are made of aluminum alloy from the viewpoint of sound. On the other hand, from the viewpoint of reducing the weight of the internal combustion engine valve system, aluminum alloy valve lifters cannot be used without reinforcing the ceiling surface and shim surface because they have difficulties in wear resistance and strength . Titanium alloys have high strength and high specific strength, which is a value obtained by dividing strength by specific gravity, and are effective for weight reduction. However, the titanium alloy has insufficient wear resistance as it is, and therefore, the sliding portion needs to have a wear-resistant surface treatment. Therefore, titanium alloys valve lifter, the surface layer portion the entire surface of the body of the valve lifter has been known one which is hardened in order to improve the sliding properties and wear resistance, the valve lifter, the inner surface of the valve lifter body In other words, a portion that does not require slidability and wear resistance is also cured (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-139314 (pages 2 to 3 and FIG. 1)

  Patent Document 1 describes a valve lifter made of a titanium alloy, and this valve lifter is designed to improve the slidability and wear resistance of a sliding portion with a valve cam or a lifter guide on the surface layer portion thereof. The surface layer portion of the lifter body is subjected to a cured layer treatment as an oxygen diffusion layer by oxidation treatment at a high temperature, and this cured layer extends over the entire surface layer portion of the lifter body. Since the oxidation treatment of the titanium alloy is performed at a high temperature and masking is difficult, the hardened layer extends to the inner surface layer portion of the valve lifter main body, which originally does not require slidability and wear resistance.

  Since the fatigue strength of the oxidized titanium alloy surface portion is reduced, it is necessary to cope with a shape such as an increase in thickness in order to obtain the same strength as that of the untreated one. The part of the valve lifter that requires the most strength is the ceiling. For this reason, a titanium alloy valve lifter that has been subjected to an overall oxidation treatment is required to cope with an increase in the thickness of the ceiling. The increase in the ceiling thickness increases the distance between the valve face and the camshaft, and as a result, it is difficult to keep the height of the cylinder head low. This causes an increase in engine weight.

  In the situation as described above, the inner surface of the ceiling of the valve lifter body is not a sliding part, that is, wear resistance is not required, and therefore surface treatment for removing the oxygen diffusion layer in this part is performed. This eliminates the adverse effects of fatigue strength reduction associated with the oxidation treatment of the valve lifter described above, and allows the ceiling thickness to be reduced. Therefore, the distance between the valve face and the camshaft can be increased without increasing the height of the cylinder head. Provided is a valve lifter made of a titanium alloy capable of keeping the thickness low.

The present invention relates to an improved structure of a titanium alloy valve lifter for solving the above-described problems and a method for manufacturing the same, and the invention according to claim 1 includes a ceiling part, a cylindrical part connected to the ceiling part, In a titanium alloy valve lifter in which an oxygen diffusion layer is formed by subjecting the entire valve lifter body , which is located at the center of the inner surface of the ceiling portion and has a protruding portion that receives contact with the upper end of the valve stem , to the valve lifter ceiling portion By processing the inner surface, the oxygen diffusion layer on the inner surface of the ceiling portion is removed so that the oxygen diffusion layer remains on the protruding upper surface and side surfaces of the protruding portion, and a part of the inner surface of the ceiling portion is removed . The material is also removed .

The invention according to claim 2 is the titanium alloy valve lifter according to claim 1, wherein the valve lifter ceiling portion is processed so as to become thinner toward the outer periphery.
Further, in the invention described in claim 3, the flat surface parallel to the top surface of the valve lifter ceiling part is formed on at least a part of the inner surface of the valve lifter ceiling part. It is a valve lifter.
The invention described in claim 4 is the titanium alloy valve lifter according to claim 3, wherein the flat surface is formed closer to the outer periphery of the inner surface of the valve lifter ceiling.
The invention according to claim 5 is the titanium alloy valve lifter according to any one of claims 1 to 4, wherein a recess is provided on the upper surface of the protrusion.

The invention according to claim 6 is a titanium alloy valve lifter having a ceiling portion, a cylindrical portion connected to the ceiling portion, and a protruding portion that is located at the center of the inner surface of the ceiling portion and receives the contact of the upper end of the valve stem. An oxygen diffusion layer is formed on the inner surface of the ceiling portion by subjecting the entire outer surface and inner surface of the titanium alloy valve lifter to an oxidation treatment to form an oxygen diffusion layer and machining the inner surface of the ceiling portion. The titanium alloy valve lifter manufacturing method is characterized in that the layer is removed and a part of the material of the inner surface of the ceiling part is also removed.

The invention according to claim 7 is the titanium according to claim 6, wherein the oxygen diffusion layer on the inner surface of the ceiling is removed by machining so that the oxygen diffusion layer remains on the upper and side surfaces of the protrusion. This is a method of manufacturing an alloy valve lifter.
In the invention according to claim 8, the oxygen diffusion layer remaining on the projecting upper surface of the projecting portion is removed by machining the oxygen diffusion layer on the inner surface of the ceiling portion. 8. The titanium alloy valve lifter manufacturing method according to claim 7, wherein the end portion of the portion not removed by machining of the layer and the central axial direction of the cylindrical portion are positioned so as to substantially coincide with each other. is there.
According to the ninth aspect of the present invention, the machining of a part of the material of the inner surface of the ceiling portion is performed by cutting a flat surface parallel to the top surface of the valve lifter ceiling portion, so that the thickness of the ceiling portion is substantially halved. The method for manufacturing a valve lifter made of titanium alloy according to any one of claims 6 to 8, wherein

  In the invention according to claim 1 of the present invention, the oxygen diffusion layer is removed by processing the inner surface of the valve lifter ceiling portion in the titanium alloy valve lifter in which the entire valve lifter body is oxidized. The removal of the diffusion layer eliminates the negative effects of reduced fatigue strength and allows the ceiling thickness to be reduced. Therefore, without increasing the distance between the valve face and the camshaft, that is, reducing the height of the cylinder head. Can be suppressed. Furthermore, the removal of the oxygen diffusion layer accompanying the processing of the inner surface of the ceiling portion described above reduces the weight of the valve lifter, thereby reducing the weight and improving the followability of the valve during high speed operation.

In the invention according to claim 2 of the present invention, in the invention according to claim 1, since the valve lifter ceiling portion is processed so as to become thinner toward the outer periphery, the valve lifter top surface on which the cam slides by the processing is provided. Since the outer peripheral part away from the vicinity of the center is thinned and the vicinity of the center of the top surface is formed thick, this processing does not reduce the strength of the cam sliding portion of the valve lifter top surface.
The invention according to claim 3 of the present invention is the invention according to claim 2, wherein a flat surface parallel to the top surface of the valve lifter ceiling portion is formed on at least a part of the inner surface of the valve lifter ceiling portion. The thickness of the valve lifter ceiling can be easily inspected using the flat surface.

  In the invention according to claim 4 of the present invention, in the invention according to claim 3, the flat surface is formed closer to the outer periphery of the inner surface of the valve lifter ceiling, so that it is flat compared to the case where it is formed closer to the inner periphery. Since a large surface area can be secured, the number of inspection points for the thickness inspection of the valve lifter ceiling can be increased, and a more accurate inspection can be performed.

The invention according to claim 6 has substantially the same effect as the invention according to claim 1.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a peripheral structure portion of a cylinder head 1 of a DOHC type internal combustion engine E having a valve operating mechanism in which the valve lifter of the present invention is used.
In the figure, reference numeral 2 denotes a valve lifter. The valve lifter 2 is pushed down by sliding with the cam 3 and pushes down the upper end 6 of the valve stem 5 via the inner shim 4.

  The finished valve lifter 2 has a predetermined length, as described above and as shown in enlarged view in FIG. 2, a cylindrical portion 22 having a predetermined diameter, and one end of the cylindrical portion 22. It has a substantially cylindrical shape with one end closed and a ceiling portion 21 that forms an end wall that closes the opening.

  The outer surface (top surface) 21a of the ceiling portion 21 is substantially flat, and the inner surface 21b is a protruding portion 21b1 whose central portion protrudes slightly higher, and this protruding portion 21b1 is interposed via the inner shim 4 described above. Or, it is a structure part that is directly subjected to contact with the upper end 6 of the valve stem (see FIG. 1).

  The valve lifter 2 is made of a titanium alloy in order to satisfy the requirements for weight reduction and strength. For example, Ti-6Al-4V, which is an α + β type titanium alloy, and other α type and β type alloys are used. Various titanium alloys can be employed.

  In the operation, the valve lifter 2 is in sliding contact with the valve cam 3 on the outer surface (top surface) 21a of the ceiling portion 21 as described above, and the lifter of the cylinder head 1 on the outer periphery of the cylindrical portion 22. Since the sliding portions 21a1 and 22a1 are in reciprocal sliding contact within the guide hole and are exposed to particularly severe sliding friction conditions, high wear resistance and excellent sliding properties are required. Therefore, the titanium alloy valve lifter 2 is subjected to an oxidation treatment at a high temperature described later for this purpose, and a hardened layer which is an oxygen diffusion layer 20 </ b> B is formed on the surface of the valve lifter 2.

  After the oxidation treatment under high temperature, the sliding surface 21a1 of the ceiling portion outer surface (top surface) 21a with the valve cam 3 which is the outer surface 20A1 of the valve lifter 2 may be subjected to surface polishing treatment for improving the surface roughness. is there. On the other hand, the ceiling inner surface 21b is subjected to surface grinding or cutting for removing the oxygen diffusion layer 20B for the purpose of eliminating a decrease in fatigue strength accompanying the oxidation treatment.

  The surface layer surface 20A (20A1, 20A2) of the valve lifter 2 has been subjected to surface processing such as the above-described surface polishing, surface grinding, cutting, etc., but the oxygen diffusion layer of the ceiling portion inner surface 21b of the valve lifter 2 of the present embodiment. The surface processed part for removing 20B is characteristic, and the surface processed part from which the oxygen diffusion layer is entirely ground or cut and removed is shown in FIG. 2 (b) which is a partially enlarged view thereof. Explained.

  Referring to FIG. 2 (b), the inner surface 21b of the ceiling portion 21 has a projecting base portion 21b2 at the center in the radial direction and protrudes at a predetermined height, and the protruding portion 21b1 protrudes in a substantially columnar shape. The protruding upper surface 21b3 of the protruding portion 21b1 has a small recess at the center, but is formed flat as a whole. The projecting upper surface 21b3 is in contact with the stem upper end 6 directly or via the inner shim 4 as described above, so that wear resistance and slidability are required, and machining is not performed after the oxidation treatment.

  The ceiling portion inner surface 21b is entirely machined except for the projecting upper surface 21b3, and the base portion 21b4 of the projecting base portion 21b2 of the central projecting portion 21b1 of the inner surface 21b faces the radially outer side of the inner surface 21b. While forming the wall surface, it smoothly connects to a wide processed wall surface 21b5 that expands in an annular shape. The wide processed wall surface 21b5 extending in an annular shape is a machined surface from which the oxygen diffusion layer 20B, which is a cured layer on the entire surface, is completely or substantially completely removed.

  A wide processing wall surface 21b5 extending in an annular shape is smoothly connected to the bottom portion 21b4 of the protruding base portion 21b2 and smoothly connected to the bottom portion 21b4, and is directed to the outer side in the radial direction and toward the outer side in the radial direction. A tapered surface 21b6 that is obliquely expanded so as to gradually approach the top surface 21a, and is smoothly connected to the tapered surface 21b6, and is directed radially outward and further radially outward of the surface 21b6. Moreover, it comprises a flat processed surface 21b7 that expands parallel to the outer surface (top surface) 21a of the ceiling. Therefore, the cross-sectional shape of the ceiling portion 21 that forms the end wall of the lifter 2 by the processed wall surface 21b5 of the inner surface 21b is a shape that gradually decreases from the central portion toward the radially outer side.

The tapered processing surface 21b6 extends from a smooth connection portion with the skirt portion 21b4 of the protruding base portion 21b2 to a substantially central portion in the radial direction of the wide processing wall surface 21b5.
Needless to say, the substantially central portion in the radial direction of the processed wall surface 21b5 is a continuous smooth connection portion of the tapered processing surface 21b6 with the flat processing surface 21b7, and the flat processing surface 21b7 extends from the continuous smooth connection portion to the ceiling. It reaches the outside in the radial direction of the wide processed wall surface 21b5 that extends over the entire inner surface 21b of the part, and here is the circular surface processed arc surface 21b8 that is the connection part between the annular outer part of the ceiling part inner surface 21b and the inner periphery 22b of the cylindrical part 22 Connected smoothly.

  The inner surface 21b of the ceiling portion 21 which has been subjected to the above-described surface processing and has improved dimensional accuracy is directly or via the inner shim 4 between the upper surface 21b3 of the inner surface central projection 21b1 and the stem upper end 6 shown in FIG. In this contact, the clearance X between the spring retainer 7 and the inner surface 21b of the stem upper end 6 is ensured, so that the spring retainer 7 and the inner surface 21b can be disposed close to each other using the clearance X. The contact position is lowered, so that the height of the cylinder head 1 is kept low, and the use of a thin inner shim 4 is also possible.

  Referring to FIG. 2 again, the outer surface (top surface) 21a of the ceiling portion 21 slides with the valve cam 3 as described above with respect to the inner surface 21b of the ceiling portion 21 subjected to the above-described processing. Since the surface 21a1 is used, the surface layer 20A1 of the oxygen diffusion layer 20B, which is the cured layer, is surface-treated so as to have a high surface roughness. The polishing process is for ensuring cam slidability, and this polishing process is performed using a barrel polishing machine or the like.

  Next, the above-mentioned structure is provided, and the outer surface 20A1 is formed on the entire surface or substantially the entire surface, and the inner surface 20A2 is provided with the oxygen diffusion layer 20B that is partially removed by machining. The manufacture of the valve lifter 2 will be described.

First Step As shown in FIG. 4A, first, as a material for forming the valve lifter 2, a titanium alloy rod, for example, a Ti-6Al-4V α + β titanium alloy round rod is prepared. Then, a disk-shaped billet 201 is cut out, and then the billet 201 is lubricated.

Second Step The billet 201 is heated to the forging temperature Tf, and then the billet 201 is hot forged, and the lifter primary workpiece 202 shown in FIG. 4B, for example, the outer diameter is 26 mm, the height is A 21 mm lifter primary processed body 202 is manufactured.
The primary workpiece 202 includes a cylindrical portion 222 that forms a cylindrical portion that is inserted into the lifter guide hole of the cylinder head 1, and an end portion that opposes the valve cam 3 by closing one end of the cylindrical portion 222. It has a substantially cylindrical shape with one end closed and a ceiling portion 212 that forms a wall. A projecting portion 212b1 projecting at a predetermined height in a columnar shape is formed at the center of the inner surface 212b of the ceiling portion 212 forming the end wall.

Third step: Machining is performed on the outer peripheral surface of the cylindrical portion 222 that forms the cylindrical portion of the primary lifter body 202, the outer surface (top surface) of the ceiling portion 212 that forms the end wall, and the annular end surface of the cylindrical portion 222. Then, the lifter secondary processed body 203 finished to a predetermined dimension shown in FIG. 4C is manufactured, and then the lifter secondary processed body 203 is subjected to a cleaning process.

Fourth Step The lifter secondary processed body 203 is placed in a heating furnace in an air atmosphere, and the processed body 203 is subjected to an oxidation treatment in which the heating temperature T1 is set to T1 ≧ 600 ° C. As shown in FIG. 5 (d), the lifter tertiary processed body 204, which is an intermediate body in which the oxidized oxygen diffusion layer 204B is formed on the entire surface of the lifter secondary processed body 203, is obtained.

  The lifter tertiary processed body 204 in which the oxygen diffusion layer 204B is formed on the entire surface layer 204A by being heated to T1 ≧ 600 ° C. in a heating furnace in an air atmosphere and subjected to oxidation treatment, It is cooled in the furnace or outside the furnace.

Fifth Step The cooled lifter tertiary processed body 204 is then subjected to processing by a machine such as a polishing machine or a grinding machine at the required location and finishing of the surface layer as required.

  In this embodiment, barrel polishing was performed to improve the surface roughness of the surface portion, particularly the outer surface (top surface) 214a of the upper surface portion 214.

Further, in addition to the above-described processing, processing is performed based on the removal of the oxygen diffusion layer 204B over the entire wall surface excluding the central protrusion upper surface 214b3 of the ceiling inner surface 214b forming the end wall (FIG. 2). (See also the enlarged view of the processed surface of the inner surface 21b in (b)).
The processing for removing the oxygen diffusion layer 204B over substantially the entire wall surface of the ceiling portion inner surface 214b partially overlaps with the above description, but is the following processing.

  That is, the processing for forming a smooth surface of the skirt portion 214b4 of the projecting base 214b2 of the central projecting portion 214b1 of the ceiling inner surface 214b, and the wall surface of the inner surface 214b substantially toward the radially outer side smoothly connected to the surface. This is the processing of the wide processing wall 214b5 that is formed in a radial direction and expands in an annular shape toward the outside in the radial direction.

  The processing of the wide processing wall 214b5 is performed on the taper processing surface 214b6 that smoothly connects to the skirt portion 214b4 of the protruding base 214b2, and on the radially outer side of the processing surface 214b6 that smoothly connects to the taper processing surface 214b6. This is a process for flattening a flat processed surface 214b7 that has a flat surface parallel to the outer surface (top surface) 214a of the upper surface portion 214 and expands outwardly in the radial direction. Further, in addition to the above-described processing, processing of a processing surface that is a circular arc surface 214b8 that is smoothly connected to the flat processing surface 214b7 is performed. These surface processing is usually performed by a polishing grinder or grinding machine using a polishing machine. It is made by polishing or cutting using a grinding wheel.

  The lifter tertiary processed body 204 obtained by performing the above processing on the outer surface 204A1 and the inner surface 204A2 is the finished valve lifter 2 illustrated in FIG. 5E (see also FIG. 2).

  The finished valve lifter 2 has an oxygen diffusion layer 20B in which the entire outer surface 20A1 of the lifter 2 is a hardened layer. Therefore, the sliding surface 21a1 of the valve lifter 2 with the valve cam 3 and the lifter guide of the cylinder head 1 are used. The reciprocating sliding surface 22a1 with the hole is provided as a valve lifter 2 in which the wear resistance and slidability of the sliding surfaces 21a1, 22a1 are sufficiently enhanced.

  Since the valve lifter 2 according to the embodiment of the present invention has the above-described structure, the following effects can be obtained.

  In the valve lifter 2 of the present invention, the oxygen diffusion layer 20B is removed by processing the inner surface 21b of the valve lifter ceiling portion 21 in the valve lifter 2 made of titanium alloy in which the entire valve lifter body is oxidized. By removing the diffusion layer 20B, it is possible to reduce the ceiling thickness by eliminating the adverse effect of fatigue strength reduction. Therefore, the height of the cylinder head 1 can be increased without increasing the distance between the valve face and the camshaft. It can be kept low. Furthermore, the removal of the oxygen diffusion layer 20B associated with the above-described inner surface processing of the ceiling portion reduces the weight of the valve lifter 2, thereby reducing the weight and improving the follow-up performance of the valve during high-speed operation. .

  The ceiling 21 that forms the end wall of the valve lifter 2 is processed so that its cross-sectional shape becomes thinner toward the outer periphery, so that it is separated from the vicinity of the center of the ceiling 21 of the valve lifter 2 on which the valve cam 3 slides. Although the outer peripheral portion is thin, the substantial sliding surface 21a1 with the valve cam 3 near the center of the ceiling 21 is formed thick, so the strength of the sliding surface 21a1 with the valve cam 3 is It is hardly affected by the processing, and the strength of the sliding surface 21a1 does not decrease.

  Further, at least a part of the processed surface of the ceiling portion inner wall 21b of the valve lifter 2 is formed as a flat processed surface 21b7 parallel to the outer surface (top surface) 21a of the ceiling portion. The thickness inspection can be easily performed using the flat processed surface 21b7.

  Further, since the flat processed surface 21b7 that is the processed surface of the ceiling portion inner surface 21b is a processed surface formed near the outer periphery of the inner surface 21b of the ceiling portion 21, the processed surface is the inner periphery of the ceiling inner wall 21b. Compared with the case where it is formed closer, the area of the flat processed surface 21b7 becomes larger, and the number of portions used for the thickness inspection can be increased accordingly, so that the thickness of the ceiling portion 21 can be more accurately inspected. It becomes possible.

  The titanium alloy valve lifter according to the present invention is not limited to the above-described embodiment, and can of course take various shapes without departing from the gist of the present invention. For example, processing is performed on the entire wall surface including the upper surface 21b3 of the central protrusion, or the wall surface only on a portion requiring particularly fatigue strength, not the entire inner surface 21b of the ceiling portion 21 excluding the central protrusion, as in the embodiment. The part may be processed.

It is a longitudinal cross-sectional view which shows the main structure part of the internal combustion engine in which the valve lifter of this invention was used. It is a figure which shows the valve lifter of this invention, (a) is a sectional side view, (b) is an enlarged view which expands and shows a part of (a). It is an expanded structure sectional view of the valve lifter mounting part of the present invention. It is a figure which shows the manufacturing process of the valve lifter of this invention. It is a figure which shows the manufacturing process of the valve lifter of this invention.

Explanation of symbols

1 .... Cylinder head, 2 .... Valve lifter, 3 .... Cam, 4 .... Inner shim, 5 .... Valve stem, 6 .... Valve stem upper end, 7 .... Spring retainer, 20A1 .. -Outer surface layer, 20A2 ... Inner surface layer, 20B ... Oxygen diffusion layer, 21 ... Ceiling part, 21a ... Ceiling part outer surface (top surface), 21a1 ... Sliding surface, 21b ..Inner surface of the ceiling part, 22 ... cylindrical part, 22a1 ... sliding surface, 201 ... billette, 202 ... primary workpiece for lifter, 203 ... secondary workpiece for lifter, 204 ... Tertiary processed bodies for lifters.

Claims (9)

An oxygen diffusion layer is formed by subjecting the entire valve lifter body having a ceiling portion, a cylindrical portion connected to the ceiling portion, and a protruding portion located at the center of the inner surface of the ceiling portion to receive contact of the upper end of the valve stem to an oxidation treatment. In the formed titanium alloy valve lifter, by processing the inner surface of the valve lifter ceiling portion, the oxygen diffusion layer on the inner surface of the ceiling portion is formed so that the oxygen diffusion layer remains on the upper and side surfaces of the protrusion. A titanium alloy valve lifter characterized in that it is removed and part of the material on the inner surface of the ceiling part is also removed .   The valve lifter made of titanium alloy according to claim 1, wherein the valve lifter ceiling portion is processed so as to become thinner toward the outer periphery.   3. The titanium alloy valve lifter according to claim 2, wherein a flat surface parallel to the top surface of the valve lifter ceiling is formed on at least a part of the inner surface of the valve lifter ceiling.   4. The titanium alloy valve lifter according to claim 3, wherein the flat surface is formed near the outer periphery of the inner surface of the valve lifter ceiling. The titanium alloy valve lifter according to any one of claims 1 to 4, wherein a recess is provided on the upper surface of the protrusion . A manufacturing method of a titanium alloy valve lifter having a ceiling part, a cylindrical part connected to the ceiling part, and a protruding part located at the center part of the inner surface of the ceiling part and receiving the contact of the upper end of the valve stem,
Oxygen treatment is performed on the entire outer surface and inner surface of the titanium alloy valve lifter to form an oxygen diffusion layer,
By machining the inner surface of the ceiling portion, the oxygen diffusion layer on the inner surface of the ceiling portion is removed, and further, part of the material on the inner surface of the ceiling portion is also removed.
A method for manufacturing a titanium alloy valve lifter. 7. The titanium alloy valve lifter according to claim 6, wherein the oxygen diffusion layer on the inner surface of the ceiling portion is removed by machining so that the oxygen diffusion layer remains on the upper and side surfaces of the protrusion. Production method. The removal of the oxygen diffusion layer on the inner surface of the ceiling by machining, the end of the portion where the oxygen diffusion layer remaining on the upper surface of the projection is not removed by machining of the oxygen diffusion layer on the inner surface of the cylindrical portion The titanium alloy valve lifter manufacturing method according to claim 7, wherein the valve lifter is positioned so as to substantially coincide with the center axis direction of the cylindrical portion. The machining of a part of the material of the inner surface of the ceiling part is performed until a flat surface parallel to the top surface of the valve lifter ceiling part is cut and the thickness of the ceiling part is substantially halved. A method for producing a valve lifter made of titanium alloy according to any one of 6 to 8.

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