JP2000034509A - Valve lifter and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve lifter excellent in joining strength between a compound layer and a valve lifter body made of Al or Al alloy, and its production. SOLUTION: The valve lifter is constituted by joining a valve lifter body composed of Al or Al alloy to a compound layer through a joining layer composed of mixed phases of Al or Al alloy and compound and having 50 to 1000 μm thickness. This valve lifter can be produced by placing a mixture of elemental powders mixed in a composition ratio capable of compound formation on the cam contact surface of the valve lifter body composed of Al or Al alloy to prepare a conjugated formed body and then pressurizing this conjugated formed body under a pressure of (30 to 1000) kgf/cm2 after direct electrification at (0.3 to 40) V/cm maximum voltage for 0.1 to 100 sec or simultaneously with the direct electrification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a valve lifter in which a compound layer of an intermetallic compound, carbide, boride, silicide, nitride or the like is firmly joined to a cam contact surface of a valve lifter main body made of an alloy, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, weight reduction has been demanded in order to cope with higher performance, higher fuel efficiency and lower pollution of automobiles.
There is a demand for further weight reduction of automobile engines and various parts around the engines. However, the conventional engine and various parts around the engine are generally made of low alloy steel, and since the weight reduction of low alloy steel is limited, Al or Al alloy which is lighter is used as a material. Production of various parts is being considered.

For example, Japanese Patent Application Laid-Open No. 4-33782 discloses a method of forming a compound layer on the surface of an Al or Al alloy substrate. One of the components manufactured by this method is a piston or valve system. Such engine parts are considered. This engine part is obtained by mixing a mixture of element powders having a composition ratio forming a compound layer with Al or A.
After preparing a composite molded body in contact with the engine component body made of an alloy, the composite molded body is charged into a resistance heating furnace together with ceramic powder or black smoke powder, and the composite molded body is heated indirectly. Or pressure while heating: 30k
Pressurized at gf / cm ² or more to form a compound layer on the surface of the engine component body by the reaction heat and pressure generated when the mixture of the element powders reacts to be synthesized into a compound layer, and manufacture by joining. are doing.

As a material system for forming the compound layer, gold is used.
There are intergeneric compounds, carbides, borides, silicides, nitrides,
Specifically, in the case of the intermetallic compound, TiAl, Ni_ThreeAl
For carbide, TiC, HfC, etc., and for boride, TiB
_TwoSuch as MoSi _TwoSuch as AlN
A wide variety of materials are known, such as
Materials of three or more elements are also known.

[0005] The valve lifter is also one of the engine parts, and is one of the valve system parts for contacting the cam to reciprocate the valve. Therefore, further reduction in weight is required. A valve lifter in which a valve lifter body is made of a suitable Al or Al alloy and the compound layer is joined to a cam contact surface thereof has been considered. Also in the case of manufacturing this valve lifter, a mixture of element powders having a composition ratio of forming a compound layer is brought into contact with a valve lifter main body made of Al or an Al alloy in the same manner as the engine parts to produce a composite molded body, The composite compact is charged together with the ceramic powder or black smoke powder into a resistance heating furnace, and after indirectly heating the composite compact or by applying a pressure of 30 kgf / cm ² or more while heating, the composite powder is cooled. The compound layer is formed on the surface of the valve lifter body by the reaction heat and pressure generated when the mixture reacts and is synthesized into the compound layer, and joined to manufacture a valve lifter.

[0006]

However, the conventional method of manufacturing a valve lifter involves indirectly heating a ceramic powder or graphite powder with a resistance heating element and pressing the heated ceramic powder or graphite powder. The mixture of the element powders is pressurized and, at the same time, the compound layer synthesis reaction heat is also applied to form a compound layer on the surface of the valve lifter main body made of Al or an Al alloy, and the heating time is at least 10 seconds. For example, if an attempt is made to form a TiAl compound layer over such a long period of time, an intermediate product such as TiAl ₂ is generated, and the crystal grains of the compound layer are coarsened. Cannot be obtained, and furthermore, indirectly heating by resistance heating for a long period of time, it is made of Al or Al alloy. If the lubricator body is heated above its melting point, the valve lifter body often melts or deforms, making it impossible to obtain a valve lifter of a predetermined shape, and even if a valve lifter of a predetermined shape is obtained, In addition, sufficient bonding strength between the compound layer of the valve lifter and the valve lifter main body could not be obtained, and the obtained compound layer had insufficient abrasion resistance.

[0007]

Means for Solving the Problems Accordingly, the present inventors have:
In view of the above, the bonding strength between the valve lifter main body made of Al or an Al alloy and the compound layer is more excellent,
Further, a valve in which a compound layer formed on a valve lifter main body made of Al or an Al alloy has fine crystal grains, a small amount of an intermediate product contained in the compound layer, and excellent wear resistance of the compound layer While conducting research to develop a lifter and a method for producing the same, a composite molded body in a state in which a mixture of element powders mixed at a composition ratio capable of forming a compound and a valve lifter body made of Al or an Al alloy are in contact with each other. The energizing condition for the maximum voltage: 0.3 to
After direct energization at 40 V / cm for 0.1 to 100 seconds or with direct energization, pressure: 30 to 1000 kgf / cm
^When the pressure of ² is performed, energy can be applied to the composite molded body in a shocking manner, so that the thickness of the bonding layer composed of a mixed phase of Al or an Al alloy and a compound is suppressed within a range of 50 to 1000 μm. Can further improve the bonding strength between the valve lifter body and the compound layer, further reduce the amount of intermediate products formed in the compound layer, and suppress the coarsening of the crystal grains of the compound layer to obtain uniform fine crystals. That a valve lifter having a compound layer having excellent wear resistance can be obtained by generating a compound layer having grains, minimizing diffusion of Al or an Al alloy in the valve lifter body into the compound layer. I got it.

The present invention has been made on the basis of this finding. (1) The thickness of a valve lifter main body made of Al or an Al alloy and a compound layer is made of Al or a mixed phase of an Al alloy and a compound. : A valve lifter joined through a joining layer of 50 to 1000 μm.

[0009] The compound layer comprises an intermetallic compound, a carbide,
It may be a compound layer obtained by laminating one or more of borides, silicides, and nitrides. Therefore, the present invention is characterized in that (2) the valve lifter according to (1), wherein the compound layer is one or more of an intermetallic compound, carbide, boride, silicide, and nitride. It has.

[0010] The valve lifter of the present invention, which is a valve lifter composed of a compound layer and an Al or Al alloy valve lifter body joined through a bonding layer having a thickness of 50 to 1000 µm comprising a mixed phase of Al or an Al alloy and a compound, is described above. As described above, a mixture of element powders mixed at a composition ratio capable of forming a compound is brought into contact with a valve lifter main body made of Al or an Al alloy to produce a composite molded body.
Maximum voltage: 0.3 to 40 V / cm after direct energization for 0.1 to 100 seconds or simultaneously with direct energization, pressure: 30 to
It can be obtained by pressurizing at 1000 kgf / cm ² . When the composite molded body is directly energized under the above-described conditions, a part of the mixture of element powders mixed at a composition ratio capable of forming a compound reacts, and self-heat is generated by reaction heat generated at this time, and the entire mixture of element powders is heated. Can be synthesized into a compound layer in a short time.

In addition, a mixture of element powders mixed in a composition ratio capable of forming the compound and a valve molded body made of Al or an Al alloy in contact with a valve lifter body are not preliminarily synthesized with a mixture of element powders. Preheated to the temperature range, and then the preheated composite compact was subjected to a maximum voltage of 0.3
After direct energization at ／ 40 V / cm for 0.1 to 100 seconds or simultaneously with direct energization, pressure: 30 to 1000 kgf / c
When pressurized at m ² , a compound layer having a small number of intermediate products and uniform fine crystal grains is formed through Al or a mixed phase of an Al alloy and a compound through a bonding layer having a thickness of 50 to 1000 μm. It is possible to obtain a more excellent valve lifter of the present invention joined to an Al alloy valve lifter body,

[0012] In the valve lifter of the present invention, Al
Alternatively, the thickness of the joining layer formed of Al or a mixed phase of the Al alloy and the compound formed between the valve lifter body made of the Al alloy and the compound layer is limited to 50 to 1000 μm because the thickness of the joining layer is If the thickness is less than 50 μm, sufficient bonding strength between the valve lifter main body and the compound layer cannot be obtained. On the other hand, if the thickness of the bonding layer exceeds 1000 μm, it is necessary to maintain a long heating time, and the Al or This is because the Al alloy diffuses into the compound layer, the crystal grains of the compound layer become coarse, the amount of intermediate products increases, the properties of the compound layer deteriorate, and the bonding strength also decreases, which is not preferable. is there.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As raw material powders, Ti powder, Fe powder, Ni powder, Al powder, Si powder, Co powder, Zr powder and B powder each having an average particle size of 1 to 7 μm
Powders were prepared, and these powders were blended at the ratios shown in Table 1, mixed, and molded to form a diameter: 30 mm and a height of 4 mm.
A mixture of element powders having the following dimensions was prepared.

On the other hand, pure Al and JISA2017 (C
u: 4.0%, Mn: 0.8%, Mg: 0.7%, S
i: 0.4%, Fe: 0.3%, the balance being Al alloy consisting of Al), outer diameter: 30 mm, height: 50
A valve lifter body having a size of mm was prepared.

Example 1 A mixture of these element powders and Al or JISA2017
A composite body A to L was prepared by contacting a valve lifter body made of an Al alloy in the combinations shown in Table 1,
These composite molded articles A to L were charged into a graphite mold, and
The composite moldings A to L are directly energized at the maximum voltage shown in Table 2 for the time shown in Tables 2 and 3 to cause a synthesis reaction, and the present invention is applied by applying pressure at the pressures shown in Tables 2 and 3 The valve lifters 1 to 12 were prepared, and the particle size contained in the compound layer constituting the valve lifters:
The area ratio of coarse particles of 20 μm or more was measured by microscopic observation, and the area ratio of the intermediate product was measured by microscopic observation after phase identification by X-ray diffraction. It was shown to.

Further, the thicknesses of the bonding layers of the valve lifters 1 to 12 of the present invention were measured by EPMA, and the measurement results are shown in Tables 2 and 3. Then, the valve lifter 1 of the present invention
-12 is built into a 6-cylinder, 12-valve, 8200 cc, 210 hp diesel engine with a rotational speed of 4000 rpm.
m., operating time: 200 hours of high-speed rotation conditions, test the actual machine, measure the maximum wear depth of the compound layer on the cam sliding surface, and evaluate the bonding strength of the compound layer to the valve lifter body Then, the joint surface of these two was observed along the outer periphery, and the number of cracks caused by peeling was measured. Further, for the purpose of evaluating the joining strength, the maximum breaking force of the joining portion was determined, and the value obtained by dividing the maximum breaking force by the joining area was determined to obtain the shear strength. The measurement results are shown in Tables 2 and 3.

Conventional Example 1 For further comparison, the composite molded articles A to L of Table 1 prepared in Example 1 were charged into a graphite mold, and graphite was pressed while applying a pressing force shown in Tables 4 and 5. The mold is heated to 20
Although the composite molded articles A to L were indirectly heated by heating for one minute to prepare the conventional valve lifters 1 to 12, the valve lifters having a predetermined shape in which the valve lifter body was melted or deformed were used. Could not be obtained.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

As is evident from the results shown in Tables 1 to 5, the valve lifters 1 to 12 of the present invention have a small compound layer with few coarse crystals, a small amount of intermediate products, and a small thickness of the bonding layer. Further, it can be seen that the joint strength between the valve lifter main body and the compound layer is excellent because of the excellent shear strength.

[0024]

As described above, the valve lifter of the present invention, which has excellent characteristics, can contribute to the improvement of the performance of automobiles, the reduction of fuel consumption and the reduction of weight in order to cope with low pollution. It provides a superior effect.

Continued on the front page F term (reference)

Claims (3)

[Claims] 1. A compound layer is formed on a cam contact surface of a valve lifter body made of Al or an Al alloy.
Thickness consisting of mixed phase of alloy and compound: 50-1000μ
A valve lifter characterized by being joined via an m joining layer. 2. The valve lifter according to claim 1, wherein the compound layer is made of one or more of an intermetallic compound, a carbide, a boride, a silicide, and a nitride. 3. A composite molded body is prepared by mounting a mixture of element powders mixed at a composition ratio capable of forming a compound on a cam contact surface of a valve lifter main body made of Al or an Al alloy. Maximum voltage on body: 0.3-40V / cm
The compound layer is formed on the cam contact surface of the valve lifter main body by applying a pressure of 30 to 1000 kgf / cm ² after directly applying electricity for 0.1 to 100 seconds or simultaneously with applying electricity. 3. The method for producing a valve lifter according to 1 or 2.