JP2812561B2 - Valve lifter and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight and highly wear-resistant valve lifter for use in a valve train of an internal combustion engine and a method of manufacturing the same.

[0002]

2. Description of the Related Art A valve lifter is used for a valve mechanism for fuel intake or exhaust of an internal combustion engine, and is disposed between a cam 90 provided at a fuel intake port 81 and a cam 88, as shown in FIG. Is what is done. The valve lifter 1 has a bottomed cylindrical structure having a bottom 11 and is located between the tip end surface 92 of the valve stem 91 and the cam 88. The concave shim contact surface 111 of the bottom outer wall has the cam 88 and the bottom. A shim 13 in sliding contact is mounted.
The stem contact surface 112 of the bottom inner wall abuts on the distal end surface 92 of the valve stem 91. In addition, valve lifter 1
The body outer wall surface 121 of the body 12 slides with the guide hole 82 of the cylinder head 8. In FIG. 5, reference numeral 94 denotes a valve spring, 93 denotes a cotter, and 95 denotes a spring retainer. By the way, the valve lifter has its body 1
2 moves in the axial direction along the guide hole 82, and at this time, the body 12 slides and rotates with the guide hole 82. Therefore, when the above-mentioned parts are abnormally worn, abnormal noise may be generated due to an increase in clearance, and damage may be caused due to an increase in impact force. Therefore, the body 12 of the valve lifter needs to have high wear resistance. Similarly, high wear resistance is required for the shim contact surface 111 and the stem contact surface 112. Therefore, conventionally, in general, cold forging is performed using case-hardened steel (such as SCM415), then carburizing and quenching, and then machining (mainly grinding) is performed to finish the product shape of the valve lifter. That is, the surface is hardened by carburizing and quenching to meet the demand for high wear resistance. As shown in FIG. 6, the valve lifter 1 manufactured in this manner is provided with a carburized quenching layer 4 on all surfaces such as a body outer wall surface 121, a body inner wall surface 122, a shim contact surface 111, and a stem contact surface 112. Are formed.

[0003]

However, the valve lifter made of the iron-based material has a high specific gravity, and therefore has a large inertial weight and is disadvantageous in terms of fuel consumption and noise. Further, in recent years, downsizing and high output of the engine are required, and the number of revolutions of the engine is increasing more and more. For this reason, recently, weight reduction of the valve lifter has been strongly desired. Therefore, it is conceivable to reduce the thickness of the body 12 of the valve lifter 1 to reduce the weight. However, since carburizing and quenching are performed from both the inner side and the outer side of the valve lifter, when the thickness of the body 12 is reduced, the entire body of the body 12 is also carburized and quenched to form a carburized structure (martensite structure). Become. According to the experiments performed by the inventors, when the thickness of the body 12 is set to 1 mm or less, the toughness of the body 12 is reduced, and there is a risk that the valve lifter may be damaged in the body when the engine rotates at high speed. Yes, it is not possible to further reduce the body thickness. In order to cope with such a problem, an example in which an alloy tool steel (such as SKD11) is used for a valve lifter main body (Japanese Patent Laid-Open No. 62-2539).
Japanese Patent Application Laid-Open No. Sho 63-75303) and an example in which the top and the body of a valve lifter are joined and fixed with different metals.
There is. However, the former uses an alloy tool steel having extremely large deformation resistance in cold forging, so that the life of the forming die during cold forging is extremely short. In addition, the productivity is low and the cost is high. In the latter case, it is necessary to bond and fix dissimilar metals, which is not suitable for mass production, resulting in poor productivity and high cost. The present invention has been made in view of the above problems, and an object of the present invention is to provide a valve lifter that is lightweight, has excellent wear resistance, and is excellent in productivity, and a method of manufacturing the same.

[0004]

The present invention relates to a cylindrical valve lifter having a bottom and made of case hardened steel, wherein the valve lifter has a thin body with a wall thickness of 0.5 to 1 mm and an outer wall surface of the body. The valve lifter is characterized by being carburized and hardened, while the inner wall surface of the body is not carburized. The most remarkable point of the present invention is that the thickness of the body is made thinner in the above range, the outer wall of the body is carburized and quenched, and the inner wall of the body is not carburized. The case hardening steel uses SCM415 or the like. The body of the valve lifter has a thin shape with a thickness of 0.5 to 1 mm. If the thickness is less than 0.5 mm, the body may be damaged when the engine rotates at a high speed. Also, 1m
If the thickness is larger than m, the purpose of reducing the weight of the valve lifter cannot be achieved. As described above, a method of manufacturing a valve lifter in which the outer wall surface of the body is carburized and quenched and the inner wall surface of the body is not carburized and quenched is a bottomed cylindrical body made of case-hardened steel processed into the shape of a valve lifter. Is prepared, a copper plating film is applied to the inner wall surface and the outer wall surface of the torso, then only the copper plating film on the outer wall of the torso is removed, and then the bottomed cylindrical body is carburized and quenched. There is a method of manufacturing a valve lifter characterized by performing a post-tempering treatment. In this method, prior to the carburizing and quenching process, a copper plating film is formed on the inner wall surface and the outer wall surface of the trunk,
The inner wall surface of the body that is not carburized and hardened leaves the copper plating film,
On the other hand, the body outer wall surface to be carburized and hardened removes the copper plating film to expose the surface of the case hardened steel. After that, carburizing and quenching is performed. As a result, the outer wall surface of the body is carburized and quenched, and a hard carburized and quenched layer having excellent wear resistance is formed on the surface. As a method of forming the copper plating film, for example, there is an electroplating method using a bronzing copper bath or a copper pyrophosphate bath. As a method of removing the copper plating film, there are centerless grinding, cutting with a lathe, and the like. The thickness of the copper plating film is 20μ to prevent carburizing and quenching.
m or more. The thickness of the carburized and quenched layer is preferably 200 to 400 μm. If the thickness of the carburized and quenched layer is less than 200 μm, it is difficult to obtain sufficient wear resistance, while if it exceeds 400 μm, the toughness of the body is impaired and the body may be damaged when the engine is running at high speed. After the carburizing and quenching treatment, a tempering treatment is performed, and a surface polishing finish is further performed.

[0005]

In the valve lifter of the present invention, the body is thin, having a wall thickness of 0.5 to 1 mm, so that it is lightweight. In addition, since the inner wall surface of the body does not have a hard carburized and quenched layer, the toughness of the body of the valve lifter is ensured by case hardened steel. Therefore, even when the body has a thin shape, there is no possibility that the body will be damaged during high-speed rotation of the engine. On the other hand, the outer wall surface of the body slides at high speed with the guide hole of the cylinder block. However, the carburized and quenched layer is formed on the surface of the outer surface and has a martensite structure with a hardness of Hv 700 or more, so it has excellent wear resistance. ing. Therefore, according to the present invention, a valve lifter that is lightweight and has excellent wear resistance can be provided. Further, according to the above manufacturing method, an excellent valve lifter as described above can be easily manufactured with high productivity.

[0006]

Embodiment 1 A valve lifter and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the valve lifter 2 of this embodiment is a bottomed cylindrical valve lifter made of case-hardened steel. The body 22 has a thin wall shape, and the body outer wall surface 221 is formed by carburizing and quenching. The inner wall surface of the body is not carburized and quenched. The body inner wall surface 222 has a copper plating film 3 on its surface. In addition, the valve lifter 2
Has a carburized and quenched layer 4 on the inner ceiling surface 241 and the stem contact surface 24. Further, the carburizing and quenching layer 4 is also provided on the shim contact surface 251 and the bank portion 252 of the valve lifter bottom 21. Reference numeral 25 denotes a shim mounting recess. The thickness t of the body is about 0.7 mm. Each of the carburized and quenched layers 4 has a thickness of about 3
It has a hard martensite layer of 00 μm. The copper plating film 3 has a thickness of about 20 μm. Next, in manufacturing the valve lifter 2, first, as shown in FIG. 2, a cylindrical body 20 with a bottom, which is processed into the shape of the valve lifter 2 and made of case hardened steel, is prepared. 222, a copper plating film 3 is formed on the outer wall surface 221 of the trunk. No copper plating film is formed on the other inner and upper surfaces. The formation of the copper plating film was performed by first preparing a copper blue plating bath, immersing only the body of the bottomed cylindrical body 20 in the bath, and performing electroplating. Therefore, the plating is not formed except on the inner and outer wall surfaces of the trunk. Thereafter, as shown in FIG.
Only the copper plating film 3 is cut and removed by a lathe. Next, the bottomed cylindrical body 20 is put into a carburizing and quenching apparatus,
Carburize and quench. Thereafter, tempering and surface polishing are performed to obtain a valve lifter 2 as shown in FIG. In the above manufacturing method, the bottomed cylindrical body 20 was obtained by cutting a case hardened steel plate (SCM415), upsetting, cold backward extrusion, and cutting. Carburizing and quenching were performed by treating at 880 ° C. for 180 minutes in an atmosphere of carburizing and quenching gas containing CO (carbon monoxide). The tempering was performed at 160 ° C. for 60 minutes. As described above, the valve lifter 2 of the present embodiment includes the body 22
Since it has a thin wall thickness of 0.7 mm, it is extremely light in weight as compared with the related art. In addition, the torso inner wall surface 22
As No. 2 does not have a hard carburized and quenched layer, the body of the valve lifter has a large toughness made of case hardened steel. Therefore, even when the body has a thin shape, the body is not likely to be damaged when the engine is rotated at a high speed. On the other hand, the outer wall surface of the body slides at high speed with the guide hole of the cylinder block, and the above-mentioned carburized and quenched layer is formed on the surface thereof.
Therefore, the surface has a hardness of Hv700 or more and is excellent in wear resistance. Therefore, according to this example, a valve lifter that is lightweight, has excellent wear resistance, and has excellent mass productivity can be easily manufactured.

Embodiment 2 This embodiment is, as shown in FIG. 4, a valve lifter in which an outer surface 23 of a bottom 21 is formed in a flat shape. The body outer wall surface 221 and the outer surface 23 have a carburized and quenched layer 4, and the body inner wall surface 222 has a copper plating film 3. Also,
The thickness of the body was 0.5 mm. Other structures and manufacturing methods are the same as in the first embodiment. Example 1 in this example as well
The same effect as described above can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a valve lifter according to a first embodiment.

FIG. 2 is an explanatory view of a copper plating film forming step in the method of manufacturing the valve lifter according to the first embodiment.

FIG. 3 is an explanatory view of a process before carburizing and quenching in the method of manufacturing the valve lifter according to the first embodiment.

FIG. 4 is a sectional view of a valve lifter according to a second embodiment.

FIG. 5 is a sectional view of a valve operating mechanism.

FIG. 6 is a sectional view of a conventional valve lifter.

[Explanation of symbols]

 1,2. . . Valve lifter, 22. . . Torso, 221. . . Outer wall surface of body, 222. . . 2. inner wall of the torso; . . 3. copper plating film; . . Carburizing and quenching layer,

Continuation of front page (56) References JP-A-62-63105 (JP, A) JP-A-64-106909 (JP, A) JP-A-56-112457 (JP, A) JP-A-63-109152 (JP, A) JP-A-62-253905 (JP, A) JP-A-63-75303 (JP, A) JP-A-3-271343 (JP, A) JP-A-62-196360 (JP, A) 63-303035 (JP, A) Japanese Utility Model Showa 62-18304 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 1/14

Claims (2)

(57) [Claims] 1. A bottomed cylindrical valve lifter made of case-hardened steel, said valve lifter having a body thickness of 0.5.
A valve lifter having a thin wall shape of about 1 mm and a carburized and quenched outer wall surface of the body, while a carburized and hardened inner wall surface of the body. 2. A bottomed cylindrical body made of case hardened steel and processed into a shape of a valve lifter is prepared, and a copper plating film is applied to the inner wall surface and the outer wall surface of the body. A method of manufacturing a valve lifter, comprising removing only a copper plating film, thereafter carburizing and quenching the bottomed cylindrical body, and then performing a tempering treatment.