JPH04246212A - Valve lifter and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a valve lifter of light weight and excellent in anti-wear property and mass-productivity. CONSTITUTION:In a valve lifter 2 for an internal combustion engine, its body is made of casehardened steel, an wall thickness of its skirt 22 is made small to 0.5 to 1mm, and anti-wear film such as hard chromium plating layer, etc., is provided on the external wall surfaces 221 of the skirt. Also, the skirt 22 is not cemented nor quenched. To manufacture the valve lifter above, a cylindrical body with bottom made of casehardened steel and formed into a shape of valve lifter is prepared, the external and internal wall surfaces of its skirt are plated, cemented and quenched, and the external wall surfaces of the skirt only are coated with anti-wear film 5.

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 used in a valve train of an internal combustion engine, and a method for manufacturing the same.

0002

[Prior Art] A valve lifter is used in the fuel intake or exhaust valve mechanism of an internal combustion engine, and as shown in FIG. It is something that will be done. The valve lifter 1 has a bottomed cylindrical structure with a bottom portion 11, and is located between the distal end surface 92 of the valve stem 91 and the cam 88, and the concave shim contact surface 111 on the outer wall of the bottom portion has the cam 88 and the cam 88. A shim 13 is mounted in sliding contact. Further, the stem abutting surface 112 of the bottom inner wall abuts the tip end surface 92 of the valve stem 91. Also, valve lifter 1
The body outer wall surface 121 of the body 12 slides on the guide hole 82 of the cylinder head 8. In addition, in FIG. 6, 94 is a valve spring, 93 is a cotter, and 95 is a spring retainer.

By the way, the valve lifter 1 has a body portion 1.
2 moves along the guide hole 82 in its axial direction, and at this time the body 12 slides on the guide hole 82 and rotates. Therefore, if the above-mentioned parts are abnormally worn, abnormal noise may be generated due to the increased clearance, and damage may occur due to increased impact force. Therefore, the body 12 of the valve lifter 1 is required to have high wear resistance. Furthermore, the shim contact surface 111 and the stem contact surface 112 are repeatedly subjected to the pressing force of the cam 88 and the pressure of the valve spring 94, and therefore require strength and high wear resistance. Therefore, in the past, case hardening steel (SCM415 etc.) was generally used.
The product was cold forged using steel, then carburized and quenched, and then machined (mainly grinding) into the product shape of a valve lifter. That is, the above-mentioned carburizing and quenching is used to harden the surface and meet the demand for high wear resistance. As shown in FIG. 7, the valve lifter 1 manufactured in this manner has a body portion 12.
Body outer wall surface 121, body inner wall surface 122, shim contact surface 1
11, a carburized and hardened layer 4 is formed on the entire surface such as the stem contact surface 112.

0004

[Problem to be Solved] However, the above-mentioned valve lifter made of iron-based material has a high specific gravity and therefore has a large inertial weight, which is disadvantageous in terms of fuel consumption and noise. In addition, in recent years, there has been a need for smaller engines and higher output, and the number of engine revolutions has been increasing. Therefore, there has recently been a strong desire to reduce the weight of valve lifters. Therefore, it is conceivable to reduce the thickness of the body portion 12 of the valve lifter 1 to reduce the weight. However, since carburizing and quenching is performed from both the inner and outer surfaces of the valve lifter, when the wall thickness of the body 12 is made thinner, the entire core of the body 12 is also carburized and quenched, resulting in a carburized structure (martensitic structure). Become.

[0005] Also, according to the inventors' experiments, the trunk 12
If the wall thickness of the body is less than 1 mm, the toughness of the body 12 will decrease, and there is a risk that the valve lifter will be damaged in the body when the engine rotates at high speed. That is impossible. In addition, in order to deal with this problem, an example of using alloy tool steel (SKD11, etc.) for the valve lifter body (Japanese Patent Laid-Open No. 62-2
53905) and an example in which the top and body of a valve lifter are bonded and fixed using dissimilar metals (Japanese Patent Application Laid-open No. 75303/1983). However, because the former uses alloy tool steel that has extremely high deformation resistance during cold forging, the life of the forming die during cold forging is extremely short. In addition, this results in poor productivity and high costs. In addition, in the latter case, it is not suitable for mass production because it is necessary to bond and fix dissimilar metals.
Productivity is poor and costs are high. In view of the above problems, the present invention aims to provide a valve lifter that is lightweight, has excellent wear resistance, and has excellent productivity, and a method for manufacturing the same.

[0006]

The present invention provides a bottomed cylindrical valve lifter made of case-hardened steel, the valve lifter having 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 in that a wear-resistant film is formed on the surface, and the outer wall surface and inner wall surface of the body are not carburized and quenched, while other parts are carburized and quenched. The most noteworthy feature of the present invention is that the thickness of the body is made into a thin shape within the above range, and the outer wall surface and inner wall surface of the body are not carburized and quenched, while other parts are carburized and quenched. A wear-resistant film is formed on the outer wall surface. As the case hardening steel, SCM415 or the like is used. The body of the valve lifter has a thin shape with a thickness of 0.5 to 1 mm. If it is thinner than 0.5 mm, there is a risk of damage to the body when the engine rotates at high speed. Furthermore, if the thickness is thicker than 1 mm, the purpose of reducing the weight of the valve lifter cannot be achieved.

[0007] Examples of the wear-resistant coating include hard chrome plating, solid lubricant baking coating, and phosphate coating. Examples of the solid lubricants include molybdenum disulfide, graphite, and tungsten disulfide. Further, as a method for manufacturing the above-mentioned valve lifter, there are the following methods. That is, a bottomed cylindrical body processed into the shape of a valve lifter and made of case hardening steel is prepared, a copper plating film is applied to the inner wall surface and the outer wall surface of the body, and then the bottomed cylindrical body is carburized. There is a method for manufacturing a valve lifter which is characterized by performing a quenching treatment, further performing a tempering treatment, then polishing the outer wall surface of the body, and forming a wear-resistant film on the surface of the outer wall surface of the rear body.

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 body, and then a carburizing and quenching process is performed, and after tempering, a copper plating film is formed on the surface of the outer wall surface of the body. Forms a wear-resistant film. In addition, as a method for forming the above-mentioned copper plating film, for example, a copper bronze bath,
There is an electroplating method using a copper pyrophosphate bath.

The thickness of the copper plating film is preferably 20 μm or more to prevent carburization and quenching. Further, the thickness of the carburized and quenched layer is preferably 200 to 400 μm. When the thickness of the carburized and quenched layer is less than 200 μm, it is difficult to obtain sufficient wear resistance, while when it exceeds 400 μm, the toughness is impaired and there is a risk of damage when the engine is operated at high speed. Further, the formation of the wear-resistant film is performed by plating, solution coating, etc. using the various wear-resistant film materials described above. Further, the thickness of these wear-resistant coatings is preferably 10 to 100 μm in order to ensure wear resistance.

0010

[Operations and Effects] The valve lifter of the present invention has a thin body with a wall thickness of 0.5 to 1 mm, so it is lightweight. Furthermore, since the body does not have a hard carburized and quenched layer, the body of the valve lifter has the toughness of case-hardened steel. Therefore, even if the body is thin, there is no risk of damage to the body when the engine rotates at high speed. On the other hand, the outer wall surface of the body slides at high speed on the guide hole of the cylinder block, and a wear-resistant coating is formed on that surface. Therefore, it has excellent wear resistance. In addition, other parts of the valve lifter, such as the shim contact surface and stem contact surface, are carburized and quenched as in the past, so that the strength and wear resistance of these parts are also ensured. therefore,
According to the present invention, it is possible to provide a valve lifter that is lightweight and has excellent wear resistance. Moreover, according to the above manufacturing method, the excellent valve lifter described above can be easily manufactured with high productivity.

[0011]

Embodiments Embodiment 1 A valve lifter and a manufacturing method thereof according to an embodiment of the present invention will be explained with reference to FIGS. 1 to 4. As shown in FIGS. 1 and 4, the valve lifter 2 of this example is a bottomed cylindrical valve lifter made of case-hardened steel, and the body 22 is thin-walled, and the body outer wall surface 221 is the surface of the valve lifter 2. A wear-resistant film 5 is formed on the surface. In addition, the body outer wall surface 221
The inner wall surface 222 of the body is not carburized and hardened. Also,
The valve lifter 2 has a ceiling surface 241 and a stem contact surface 24.
has a carburized and hardened layer 4. Furthermore, the carburized and hardened layer 4 is also provided on the surfaces of the shim contact surface 251 and the bank portion 252 of the valve lifter bottom portion 21. Note that the reference numeral 25 is a concave portion for attaching a shim. Further, the inner wall surface 222 of the body has a copper plating film 3 on its surface.

[0012] The wall thickness t of the body is approximately 0.7
It is mm. In addition, the above-mentioned carburized and quenched layer 4 is
It has a hard martensite layer with a thickness of about 300 μm. Further, the copper plating film 3 has a thickness of about 20 μm. The wear-resistant coating 5 is a hard chrome plating layer with a thickness of about 20 μm. Next, in manufacturing the above-mentioned valve lifter 2, first, as shown in FIG.
Prepare. Next, a copper bronze plating bath is prepared, and only the body of the bottomed inner cylindrical body 20 is immersed in the bath, and electroplating is performed to form a copper plating film on the body inner wall surface 222 and the body outer wall surface 221. form 3. Therefore, no copper plating is formed on anything other than the inner and outer walls of the body.

[0013] Thereafter, the bottomed cylindrical upper body 20 is placed in a carburizing and quenching device, and carburizing and quenching is performed. As a result, as shown in FIG. 3, a carburized and hardened layer 4 is formed on the entire surface other than the body 22. After that, tempering and surface polishing of the outer wall of the body are performed. As a result, most of the copper plating film 3 on the surface of the body outer wall surface 221 is removed. Note that this surface polishing of the outer wall surface of the body is a surface treatment for forming the wear-resistant film 5. Therefore, some copper plating film 3 may remain. Next, a hard chrome plating layer 5 is further formed on the outer wall surface 221 of the body, as shown in FIG. As a result, the valve lifter 2 as shown in FIG. 1 is obtained. In the above manufacturing method, the bottomed cylindrical body 20 is made of case hardened steel plate (SCM41
5) by cutting, upsetting, cold backward extrusion, and cutting. In addition, carburizing and quenching is performed using CO (
In an atmosphere of carburizing gas containing carbon monoxide),
This was carried out by processing at 880°C for 180 minutes. Further, tempering was performed at 160°C for 60 minutes.

The hard chrome plating layer 5 was formed by immersing the bottomed cylindrical body in a chromium plating bath and using a conventional plating method. As mentioned above, the valve lifter 2 of this example has a thin body section 22 with a wall thickness of 0.7 mm, so it is extremely lightweight compared to the conventional valve lifter 2. Furthermore, since the body 22 does not have a hard carburized and quenched layer, the body of the valve lifter has great toughness due to the case hardening steel. Therefore, even if the body is thin, there is no risk of damage to the body when the engine rotates at high speed.

On the other hand, the outer wall surface of the body slides at high speed on the guide hole of the cylinder block, and the hard chrome plating layer 5 is formed on that surface. Therefore, the surface has excellent wear resistance. In addition, other parts of the valve lifter, such as the shim contact surface 251 and the stem contact surface 24, are
Since it has carburized and quenched 4, this part has excellent strength and wear resistance. Therefore, according to this example, it is lightweight and
It is possible to easily manufacture a valve lifter that has excellent wear resistance and is also suitable for mass production.

Embodiment 2 This embodiment is a valve lifter in which the outer surface 23 of the bottom surface 21 is formed into a planar shape, as shown in FIG. The parts other than the body 22 have a carburized and quenched layer 4, and the body outer wall surface 221 has a hard chrome plating layer 5. On the other hand, a copper plating film 3 is provided on the inner wall surface 222 of the body. Further, the wall thickness of the body was 0.5 mm. Other structures and manufacturing methods are the same as in Example 1. In this example as well, the same effects as in Example 1 can be obtained.

Example 3 In this example, in place of the hard chrome plating layer in Example 1, a wear-resistant film was formed by baking a solid lubricant. In this example, after the dipping treatment and tempering in Example 1, the surface of the outer wall surface 221 of the body was polished, a solid lubricant was sprayed on it, and it was fired to form a wear-resistant film made of the solid lubricant. Molybdenum disulfide was used as the solid lubricant. In forming the above film, degreasing, cleaning, preheating, spraying of solid lubricant, and baking in a drying oven were performed. As a method for forming a solid lubricant film, for example, Asahi Chiyoda Kogyo Co., Ltd.'s "Defrick Coating Method" is used.
There is. The above wear-resistant film was formed to have a thickness of about 10 μm. The above solid lubricant was sprayed while rotating the bottomed cylindrical body. In this example as well, the same effects as in Example 1 can be obtained.

Example 4 In this example, in place of the solid lubricant in Example 3,
It was treated with a phosphoric acid coating. That is, as described above, after the surface of the body outer wall surface 221 is polished, the degreasing treatment is performed. Then, with a manganese monophosphate solution (for example, Nippon Parkerizing Co., Ltd., trade name, Lubrite),
The surface of the body outer wall surface 221 of the bottomed cylindrical body is treated. This forms a phosphate coating on the surface. In this example as well, the same effects as in Example 1 can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a valve lifter of Example 1.

FIG. 2 is an explanatory diagram of a step of forming a copper plating film in the method of manufacturing a valve lifter of Example 1.

FIG. 3 is an explanatory diagram after carburizing and quenching in Example 1.

FIG. 4 is an explanatory diagram of the hard chrome plating layer of the valve lifter of Example 1.

FIG. 5 is a sectional view of a valve lifter according to a second embodiment.

FIG. 6 is a sectional view of the valve mechanism.

FIG. 7 is a sectional view of a conventional valve lifter.

[Explanation of symbols]

1, 2. ．． ．． Valve lifter, 22. ．． ．． Torso, 221.
．． ．． Body outer wall surface, 222. ．． ．． Body inner wall surface, 3. ．． ．． Copper plating film, 4. ．． ．． Carburized and quenched layer, 5. ．． ．． Hard chrome plating layer,

Claims (3)

[Claims] Claims: 1. A valve lifter having a bottomed cylindrical shape made of case-hardened steel, the valve lifter having a body having a wall thickness of 0.
It has a thin wall shape of 5 to 1 mm, and a wear-resistant film is formed on the surface of the outer wall of the body.The outer wall of the body and the inner wall of the body are not carburized and quenched, and the other parts are not carburized and hardened. A valve lifter characterized by being carburized and quenched. [Claim 2] Prepare a bottomed cylindrical body processed into the shape of a valve lifter and made of case-hardened steel, apply a copper plating film to the inner wall surface and outer wall surface of the body, and then attach the bottomed cylindrical body to the shape of a valve lifter. 1. A method for manufacturing a valve lifter, which comprises carburizing and quenching the body, then tempering the body, polishing the outer wall surface of the body, and forming a wear-resistant film on the outer wall surface of the rear body. 3. The method of manufacturing a valve lifter according to claim 2, wherein the formation of the wear-resistant film is performed by plating with hard chromium, baking with a solid lubricant, or treating with a phosphate film.