JP2732512B2 - Aluminum alloy valve lifter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve lifter used for a valve mechanism of an internal combustion engine. More specifically, the present invention relates to an intake valve that directly determines a cam lift amount due to rotation of a cam shaft. The present invention relates to a valve lifter of a direct drive type valve mechanism for transmitting to a valve or an exhaust valve.

[Prior Art] FIG. 3 is a vertical cross-sectional view of an outer shim type direct drive type valve operating mechanism often used in an internal combustion engine. In FIG. 3, 1 is a valve lifter, 2 is a cylinder head, and 3 is a valve. 4 is a stem of an intake / exhaust valve, 5 is an adjusting shim, and 6 is a cam.

Conventionally, as the valve lifter, those obtained by carburizing and quenching chromium steel or chromium molybdenum steel having excellent wear resistance and fatigue strength have been used in many cases. However, steel has a specific gravity of 7.
Since it is as large as 8 g / cm ³ , the inertia weight is large and the spring load must be increased in order to accurately transmit the cam lift amount to the valve under high-speed operation conditions of the internal combustion engine.
Increasing the spring load has the disadvantage of increasing friction loss and increasing fuel consumption. To improve fuel consumption, various proposals have been made to manufacture a valve lifter from a lightweight material for the purpose of reducing the valve spring load by reducing the weight of the valve lifter. In particular, many proposals have been made to make the valve lifter body an aluminum alloy. (JP-A-58-101204, JP-A-62-10721)
3, JP-A-62-63105, JP-A-62-183005, JP-A-1-10
No. 6909).

Particularly, the bulk (body) material in the embodiment of the valve lifter made of aluminum alloy conventionally proposed is disclosed in
No. 107213 is a JIS 2024BE alloy, and JP-A-62-63105
JIS ADC12 alloy and high silicon aluminum alloy (17
% Si-4.5% Cu-0.55% Mg-0.13% Fe-0.1% Mn-0.1% N
i-0.1% Zn-0.1% Sn-balance A1). In addition, Shokai 62
-183005 is a JIS A2017 alloy.

Also, it has been considered to devise the structure of the valve lifter by using techniques such as surface treatment, welding, and casting.
In No. 105, the disc in contact with the cam was carburized and quenched.
Constructed of CM415, the opposite disk part and body part are made by casting aluminum alloy, and the outer peripheral surface of the cylindrical part is Fe-P
It is shown that plating is to be performed, and in JP-A-62-107213,
It has been shown that an alloying layer of TIG or the like is provided on the contact surface of the valve. Further, Japanese Patent Application Laid-Open No. 1-106909 discloses that an aluminum alloy valve lifter is provided with Fe-P plating or
It is shown that iron-based alloy electroplating is performed on the plating.

[Problems to be solved by the invention]

In practical use of an aluminum alloy valve lifter, the following problems must be solved.

Destruction due to insufficient strength and toughness of aluminum alloy A normal outer shim type valve lifter uses the valve spring force and the cam force to act on the valve lifter when the cam operates the valve lifter.
The stress is concentrated on the portion indicated by the section and is repeatedly applied. In addition, during abnormal movement of the valve train, a large stress is impulsively applied to the portion 1a. For this reason, the valve lifter is easily broken from this portion 1a.

Conventionally studied aluminum alloys have a lower fatigue strength than steel, and therefore have to be made thicker to prevent the above-mentioned destruction. The Society of Automotive Engineers of Japan, Academic Lecture Preprint 892 1989-10, 97-10
In "Strength Study" on page 0 (hereinafter referred to as "Automotive Technology Society"), the necessity of increasing the thickness of the aluminum alloy lifter compared with steel is mentioned. Not only is the degree of weight reduction low due to the increase in wall thickness, but also the mounting position of the camshaft is shifted in the direction opposite to the combustion chamber by the thickness increase of the valve lifter, and the overall height of the engine is increased, and the engine This causes problems such as an increase in the weight of the device.

Further, in the internal combustion engine, lean combustion is performed in order to reduce fuel consumption, and the combustion temperature is rising. In such engines, the valve lifter temperature can be up to 150
It may rise to about ° C. If the aluminum alloy is used for a long time at such a temperature, an overaging phenomenon occurs in the above-mentioned aluminum alloy, resulting in a decrease in strength and hardness. In order to reduce the strength, the valve lifter must be designed to have a greater thickness. Further, the decrease in hardness causes wear of the sliding surface with the shim.

In Japanese Patent Application Laid-Open No. 62-63105, a valve lifter having a shape as shown in FIG. 5 has been proposed as a countermeasure against the problem of strength of an aluminum valve lifter. In the figure, 7 is an iron-based material having excellent wear resistance, 8 is an aluminum alloy, 9 is
Is a surface treatment layer provided for abrasion resistance and seizure resistance on the aluminum alloy.

However, in such a shape, although the stress applied to the aluminum alloy lifter main body portion is reduced by providing the iron-based material 7, when the valve lifter is assembled to the engine, the valve clearance needs to be adjusted. In order to perform this, it is necessary to change every valve lifter, and it takes more time to adjust the valve clearance as compared with a conventional outer shim type using an adjusting shim.

Wear of the sliding part of the adjusting shim The lifter of the part shown by 1b in FIG. 4 slides on the bottom surface of the adjusting shim, and the lifter of the part shown by 1c slides on the outer peripheral part of the adjusting shim. Adjusting shims are usually made of carburized and quenched steel, so that these parts can
Wear progresses at b and 1c. Since the wear of 1b increases the valve clearance, it leads to engine noise and changes the valve lift timing. In extreme cases, wear of the 1c part may cause the shim to come off the top of the valve lifter and damage the engine. Therefore, there is a need for an aluminum alloy that is not worn by the adjusting shim and does not wear the adjusting shim.
The above-mentioned collection of lectures by the Society of Automotive Engineers of Japan considers these wears and considers that iron-based thermal spraying on aluminum alloys is optimal.

The above-mentioned known alloys for lifters have a reduced hardness due to overaging when exposed for a long time even at a temperature of about 150 ° C. This further promotes wear. Such abrasion is hindered to some extent by thermal spraying. However, if overageing occurs, the thermal spraying base softens and wear tends to occur, and it is considered that prevention of softening of the base is a fundamental solution.

Troubles due to sliding with the cylinder head Since the valve lifter reciprocates in a hole provided in the cylinder head, abrasion and seizure troubles are likely to occur on the outer peripheral surface of the lifter shown in 1d of FIG. Almost all cylinder heads have been switched from cast iron to aluminum alloys for the purpose of weight reduction. Seizure is likely to occur in the combination of an aluminum alloy cylinder head and an aluminum alloy valve lifter. JP-A-62-63105 proposes to apply hard chrome plating, Ni-P plating, Fe-P plating, Ni-SiC plating to the outer periphery of a valve lifter, or to perform anodizing treatment or anodizing treatment with a lubricant. ing. Also, as an underlayer for Fe-P-based plating, it is proposed that anodization be performed and then Fe-P plating be performed thereon (Japanese Utility Model Application Laid-Open No. 62-18300).
5) Also, there is a proposal to similarly apply a thick Fe-P plating on a thin Ni-P plating (Japanese Utility Model Application Laid-Open No. 18303/1987). As can be seen from the background of these proposals, surface treatment of the sliding surface of the aluminum alloy with the cylinder is considered to be indispensable as a measure against wear. Therefore, features and disadvantages of various surface treatments will be considered.

Since the film formed by the anodizing treatment has a high coefficient of friction and is liable to cause seizure, there is a problem in application to a valve lifter. Even if a lubricant such as molybdenum disulfide or fluororesin is present in the anodic oxide film, a slight effect on the reduction of the friction coefficient is recognized, but there is no significant change in the property of high friction coefficient and easy seizure.

Hard chromium plating on aluminum alloys shows relatively good adhesion, but poor lubricity of the lubricating oil, and therefore poor seizure resistance. Also, because of its brittle nature,
It is easy to peel off at the cylindrical part with high stress

There is a problem that the adhesion of the Fe—P plating film to the aluminum alloy is poor. Regarding the control of the plating bath, Fe has the property of becoming divalent and trivalent ions,
There is a problem that pH management is very difficult and the defective rate is high.
In general, such plating is maintained at a temperature of 300 to 400 ° C. after plating to form a compound of phosphorus and Fe, thereby increasing hardness and exhibiting wear resistance and seizure resistance. However, the aluminum alloy body is overaged at this temperature, and the hardness and strength are significantly reduced. Therefore, the temperature after plating is 100
There is no choice but to hold at ~ 150 ° C for a short time. At such a temperature, the hardness of the plating layer is low, so that the plating layer is liable to wear and the seizure resistance is insufficient. When a thick plating film is used as a measure against abrasion, the plating film is easily peeled off due to plating stress.

As a countermeasure against such plating problems, it is expensive to provide two layers of coating such as Fe-P + anodizing for abrasion resistance. In addition, it is not a complete measure against peeling that accompanies a thick plating film. In addition, the iron-based plating applied to the outermost surface is easily rusted, and the rust generated partially causes the notch action, and due to stress concentration,
-P plating may peel off and cause seizure with the cylinder head.

As in the case of Fe-P plating, the Ni-P plating film on an aluminum alloy has a problem that it has poor adhesion and can only be kept at 100 to 150 ° C. for a short time. On the other hand, Ni plating does not easily rust, and the plating bath is easily managed. It is well known that conventional Ni-based plating contains 8 to 12% of P. However, a valve lifter obtained by simply plating a known aluminum alloy with Ni-P plating is easy to slide with a cylinder head material. Seizure occurs.

The method of forming a film of molybdenum, iron, or an iron-based alloy on the outer periphery of a valve lifter by thermal spraying is not only expensive, but also has low adhesion and poor dimensional accuracy. And Also, since fine holes are present in the thermal spray coating, if hard foreign matter enters the sliding surface between the valve lifter and the cylinder head with the intake of the internal combustion engine, the hard holes will The foreign matter is taken in as if inlaid, causing the surface of the cylinder head hole of the sliding partner to wear significantly, causing a phenomenon that eventually causes seizure.

Wear with Valve Stem The part 1e of the valve lifter shown in FIG. 4 is the contact surface with the valve stem, and this part comes into contact with the end of the valve stem having high hardness. Measures are needed. In the case where the load is relatively high and the aluminum alloy is soft, a thin film cannot be a countermeasure. In such a case, it is common practice to join a member which is partially excellent in wear resistance to the soft material by welding, press-fitting, caulking, casting, or the like and integrate them. Therefore, the same means is required for the valve lifter, but it is necessary to avoid stress concentration on the valve lifter and to integrate the valve lifter by economical means. In addition, in the above-mentioned lecture book of the Automotive Engineering Society, a steel pad is caulked and attached to the contact portion with the valve stem.

With respect to the above four points, an object of the present invention is to achieve the following items.

Improve the strength and toughness of aluminum alloy: Maintain high strength even under high temperature heat history that can be used in outer shim type shape, and withstand shocking stress applied during abnormal movement of valve train To provide an aluminum alloy with excellent toughness.

Abrasion of sliding parts with adjusting shims: To provide an aluminum alloy with excellent wear resistance when subjected to high temperature hitting and abrasion by steel.

Trouble due to sliding with the cylinder head: Select an inexpensive surface treatment with excellent sliding characteristics that can replace the plating film, anodic oxidation, and thermal spray coating that have been conventionally proposed. In other words, the temperature rise after film formation is only a temperature history of 100 to 150 ° C, and the dimensional accuracy of the film is high and the surface of the film is smooth, so that the barrel after processing or with little stress due to processing Finished to a degree of polishing, with a low coefficient of friction and excellent surface treatment against seizure and wear.

Wear with valve stem: Take appropriate measures to prevent this.

[Means for Solving the Problems] In order to solve the above technical problems, the valve lifter made of an aluminum alloy according to the present invention comprises Cu: 3 to 8%, Mg: 0.5 to 2.5%, Si: 0.2 to 1.5%, Mn. , Fe, Cr, Ni, Co, V, Zr, Ti, containing at least 3 to 10% in total amount of Mg ₂ Si in an atomized powder having a substantially aluminum composition. While being precipitated, the average particle size is 2 in the matrix composed of the atomized powder.
A base made of a composite material in which hard powder of about 30 μm is dispersed in a volume ratio of 2 to 10%, and a part which slides with the cylinder head contains P: 1 to 3% by weight, and the balance is made of Ni. And an outer peripheral surface provided with a plating layer in which Si ₃ N ₄ is dispersed at an area ratio of 10 to 25%, and a contact surface with a valve stem formed of an iron-based alloy piece bonded to the main body. It is characterized by the following.

The structure of the valve lifter of the present invention will be described in detail below with reference to FIG.

In the aluminum alloy valve lifter of the present invention, in order to prevent breakage of the lifter and to reduce the weight,
Is a new aluminum alloy with excellent high-temperature strength and toughness. The chemical composition is Cu: 3-8%, Mg: 0.5-2.5%, Si: 0.2-1.5%, one or more of Mn, Fe, Cr, Ni, Co, V, Zr, Ti A total of 3 to 10% is contained, and the balance is based on an alloy substantially consisting of aluminum. In order to prevent wear by the adjusting shim, the average particle size of the atomized aluminum alloy powder is 2 to 30 μm in the matrix. Hard particles of 10
a is dispersed in a volume ratio of 2 to 10%. The alloy composition of the matrix is determined as described above so that the strength and toughness do not decrease even when the hard particles different from the matrix are dispersed in the matrix.

In order to prevent seizure and abrasion that are likely to occur due to sliding with the cylinder head, a plating layer mainly composed of Ni with good adhesion is provided on the outer peripheral surface of the lifter 10b in FIG.

In order to prevent wear of the part that contacts the valve stem,
On the contact surface of the lifter with the valve stem, a chip 10d made of an iron-based alloy is attached to the aluminum alloy lifter body in a concave portion shown in 10c in FIG.

The manufacturing method of the aluminum alloy constituting the lifter body of the present invention is as follows. The powder having the above composition is passed through a 100-mesh or 150-mesh sieve to remove coarse powder having a slow cooling rate during atomization. A hard powder having an average particle size of 2 to 30 μm in a volume ratio of 2 to 30 is added to the alloy powder.
It is blended so as to be 10%, and sufficiently mixed so as to be in a uniform dispersion state. The mixed powder is filled in a rubber mold and formed into a billet for extrusion by cold isostatic pressing. Next, this billet is heated and held at 450 to 500 ° C. in a high-purity argon gas to remove physically and chemically adsorbed water on the surface of the aluminum alloy powder, and then inserted into a container of a hot extruder, and extruded at a specific ratio. Extrude into a round bar under 15 or more conditions. The extruded material is cut into a predetermined size and subjected to a softening treatment (O treatment) as necessary or forged cold or hot in a mold close to the shape of the lifter body as it is. Then, after heat treatment of T7, it is cut into the final lifter main body shape, set in a plating jig, and sequentially subjected to degreasing, pickling, base treatment, and plating treatment, and the outer peripheral surface is mainly composed of Ni, P, Si ₃ and ceramics such as N ₄ is subjected to a baking treatment is provided a plating layer dispersed.

A concave portion for inserting a chip made of an iron-based alloy may be provided in the sliding contact portion with the valve stem by machining, but it is desirable to form the concave portion by a forging process from the viewpoint of strength and reduction of manufacturing cost. A chip made of an iron-based alloy is integrated into the concave portion of the lifter main body by press-fitting or caulking, and then finished into a final lifter shape by machining.

[Action]

In the present invention, the base composition of the aluminum alloy constituting the lifter body is limited as described above for the following reason.

Hardness and strength of an aluminum alloy to which Cu is added increase due to age hardening. When such an Al-Cu alloy is kept at a high temperature for a long time, it tends to overage and its hardness and strength tend to decrease significantly, but at 150 ° C, the degree of decrease is small. C
If the u content is less than 3%, the strength and hardness are insufficient,
On the other hand, if it exceeds 8%, the intermetallic compound becomes extremely coarse, and the toughness of the material is extremely reduced. The intermetallic compound is a complex compound containing transition elements such as Fe and Mn in addition to Cu ₂ Al. Optimal from the balance of strength and toughness
The Cu content range is 4-6%.

Mg further increases the strength by age hardening when coexisting with Si. However, if it is kept at a temperature of 150 ° C. or more for a long time, it tends to be overaged, and the hardness and strength tend to be remarkably reduced. If Mg is less than 0.5%, the contribution to strength is low, and
If it exceeds 2.5%, the toughness decreases.

Si precipitates Mg ₂ Si in coexistence with Mg to increase the strength of the material, but if the amount is less than 0.2, the effect is small, and if it exceeds 1.5%, the toughness of the material is reduced.

When the elements of Mn, Fe, Cr, Ni, Co, V, Zr, and Ti are added in a large amount in a usual dissolution method, a coarse intermetallic compound is precipitated and the material becomes extremely brittle. However, when the molten alloy is solidified into fine droplets and solidified into powder, as in the atomization method, the cooling rate is extremely high, so these elements form supersaturated solid solutions or form fine intermetallic compounds. And disperse throughout the base. In aluminum alloys starting from such alloy powders, the addition of alloying elements is effective in increasing the strength, and the strengthening is independent of the overaging phenomenon. In the present invention, Mn, Fe, Cr, Ni, Co, V, Z
The strength is increased by adding one of r and Ti alone or in a total amount of 3 to 10% of a combination of two or more. In particular, the strength is less reduced even after being kept at 150 ° C. for a long time. The amount is one or two or more in total.
If it is less than 10%, the effect of improving the strength is small, and if it exceeds 10%, a coarse intermetallic compound is crystallized in the powder, and the material becomes extremely brittle. Therefore, the above range is set. In particular, among the above-mentioned alloy elements, elements that are easy to use because of their ease of dissolution in molten aluminum are Fe, Cr, Mn, Co, and Ni. But Co has the problem of high price. A particularly preferred range is 4 to 8%.
It is.

After sieving the powder, the average particle size is 2 to 30 μm
Is mixed in a volume ratio of 2 to 10%, and the mixture is sufficiently mixed so as to be in a uniform dispersion state. As the hard particles, powders of carbides, oxides, nitrides, silicides, borides and alloy powders having a hardness of Hv 600 to 2500 are most suitable.

When the average particle size is 2 μm or less, the abrasion resistance and seizure resistance with the shim are insufficient, and when the average particle size exceeds 30 μm, it acts as an internal notch, lowering the fatigue strength and toughness of the material, In addition, it hinders machinability during lifter finishing,
This hinders the adhesion of the plating to the outer periphery of the lifter. Therefore, the particle size is in the above range. Particularly good particle sizes are 5 to 10 μm.

The hard particles having the above particle diameter are set to a volume ratio of 2 to 10% in the aluminum alloy matrix, but if it is less than 2%, the abrasion resistance and seizure resistance with the shim are insufficient, and exceed 10%. In addition, the strength and elongation of the material are significantly reduced, and the machinability during lifter finishing is hindered, and the adhesion of the plating on the outer peripheral portion is hindered. A particularly preferred range is 3-5%.

 Next, the reasons for limiting the plating film will be described.

Ni as the main component of the plating layer is superior to iron-based plating in terms of rust prevention and stabilization in the manufacturing process, and is mainly made of Ni by improving the wear resistance of the lifter body This is because a known lifter can provide a lifter showing sufficient wear resistance to the cylinder.

If Ni-P plating is used, P
Preferably, the amount is between 1 and 4%. If the P content is less than 1%, the seizure resistance is insufficient, and if the P content is more than 3%, the toughness of the plating film is reduced, and it is easy to peel off at the cylindrical portion of the lifter having high stress. .

Conventionally, SiC with an average particle size of about 3 to 10 μm
Films dispersed in -P plating are also known, but they tend to wear the mating cylinder head material and have poor adhesion, so there is a problem when used in combination with conventional aluminum alloys. . Also, the plating surface becomes rough,
There is a disadvantage that finishing by mechanical processing such as centerless polishing is required. When the centerless polishing is performed, the Young's modulus of the aluminum alloy lifter is less than half of that of the steel material, and the elastic limit stress is low. Therefore, if the thickness of the cylindrical portion of the lifter is thin, deformation occurs, and the dimensional accuracy is deteriorated. For this reason, in the case of performing centerless polishing, it is necessary to increase the thickness of the cylindrical portion, and the advantage of using the bent aluminum alloy for the valve lifter main body cannot be utilized. This was also a cause that the weight reduction of the conventional aluminum alloy lifter had to be insufficient. In consideration of such circumstances, Si ₃ N ₄ is used as the best dispersing material in the present invention. Since Si ₃ N ₄ has a lower hardness than SiC, it is characterized by not abrading the mating cylinder head material and by being excellent in seizure resistance. The reason why the dispersion amount of Si ₃ N _{4 having} the above particle size is set to 10 to 25% in terms of area ratio is that if it is less than 10%, the performance in terms of seizure and wear is insufficient, and if it exceeds 25%, the film becomes This is because, in addition to being brittle, chipping and peeling are likely to occur, and the surface roughness after plating becomes extremely rough. Good results are obtained in the range of 15-20%.

Further, the Si ₃ N ₄ dispersed plating layer is formed by maintaining Ni at a high temperature (350 to 400 ° C.) like a conventionally known Ni—P—SiC film.
_Even if the hardness is not increased by precipitating ₃ P, sufficiently excellent sliding characteristics are exhibited by the dispersion of Si ₃ N ₄ . For this reason, sufficient performance can be obtained only by maintaining the temperature at 170 to 180 ° C. for a short time after the plating process. Therefore, the lifter body made of the aluminum alloy does not overage. Since the Si ₃ N ₄ dispersed plating layer has excellent sliding characteristics, the plating film thickness of 5 to 10 μm is sufficient. Therefore, the dimensional accuracy is extremely good, and the film surface may be smooth. Can be used as it is, or it can be used simply by subjecting the lifters to a group by a vibration barrel or the like and smoothing the surface. As a result, conventionally, a method of providing a thick surface coating such as thermal spraying or Fe plating, and then performing centerless grinding to improve dimensions and surface roughness was also performed, but the present invention does not require centerless grinding Therefore, it is not necessary to increase the thickness of the cylindrical portion of the lifter.

In claim 2 of the present invention, the grain size of Si ₃ N ₄ is set to 0.5 to 2 μm, in addition to preventing wear of the mating cylinder head material within this range, when thermal expansion or mechanical stress is applied. This is because the stress is dispersed in the film and the plating film is hardly peeled off. On the other hand, if the average particle size is smaller than 0.5 μm, the sliding characteristics are poor. On the other hand, if the average particle size is larger than 2 μm, the surface of the plating film becomes rough and requires finishing, and the stress dispersion effect is reduced. Tends to occur.

Further, if it is smaller than 0.5 μm, it is too fine and the sliding characteristics are not good, and the cost increases. On the other hand, if it is larger than 2 μm, uniform dispersion is difficult to obtain, and the surface of the film after plating is In some cases, the finish becomes coarse, and finishing by centerless polishing is required. Therefore, increasing the thickness of the cylindrical portion hinders weight reduction. The preferred particle size of Si ₃ N ₄ is 0.8 to 1.5 μm. Particularly good results are 0.5-1 μm
Was obtained with an average particle size of

The reason that the portion of the lifter that is in sliding contact with the valve stem is made of an iron-based material is that an aluminum alloy is deformed because its strength is lower than that of an iron-based material. Among iron-based materials, a material having a hardness of _HRC 50 or more is optimal. For example, a carburized and quenched material of SCM420 or a liquid phase sintered iron-based sintered material containing a large amount of chromium is most suitable.

〔Example〕

The aluminum alloy whose components were adjusted was melted and powdered by an atomizing method to obtain a powder having the composition shown in Table 1. This powder was passed through a 150 mesh sieve, under the sieve (-150
An Al ₂ O ₃ powder having an average particle size of 5 μm is blended with each powder of the mesh (mesh) so as to be 3.5% by volume, and mixed so as to be sufficiently uniform. Each mixed powder was made into a cylindrical billet of φ90 mm and 400 mm in length by a hydrostatic press, and the billet was heated to 450 ° C in an argon atmosphere and held for 1.5 hours to remove moisture adsorbed on the powder surface. After removal, insert into the container of hot extruder and perform hot extrusion φ20mm
Was obtained. First, for the purpose of investigating the mechanical properties, a round bar was cut into a predetermined shape of each test piece to form a tensile test piece and a fatigue test piece. Next, the test piece was kept at 490 ° C. for 2 hours and subjected to liquid cooling treatment with water cooling.
T7 treatment was carried out to maintain the temperature at ℃ and effect the aging effect.

The tensile test was conducted in two ways: a test at room temperature and a test performed at a temperature of 150 ° C. after giving a heat history of holding at 150 ° C. for 400 hours. The fatigue test was conducted at room temperature and at 150 ° C for 4 hours.
Two tests were conducted at a temperature of 150 ° C. after a heat history of holding for 00 hours was given. Table 3 shows the results.

For comparison, after continuously casting 2618 alloy, which is considered to be the most excellent in heat resistance among 2000 alloys, and 4032 alloy, which is excellent in sliding properties and heat resistance used for forged piston materials etc. A T7-treated material was prepared by hot extrusion.
Table 2 shows the chemical composition. Table 4 shows the results of similar strength tests.

Also, a forged material shape is made from each extruded material, and the forged material is forged into a lifter shape.
The lifter body shown in the figure was prepared by cutting.

Then, Si ₃ N ₄ having an average particle size of 0.8 μm is 16.5% in area ratio, P% is 2% in the outer peripheral portion, Ni is the remainder, and hardness is Hmv400.
500500 plating layers were provided in a thickness of 10 μm. The plating was performed at a bath temperature of 60 ° C. in a bath in which the above-mentioned Si ₃ N ₄ was uniformly suspended in a solution containing nickel sulfate and nickel chloride as a main component by using an electrolytic method, and after plating, the temperature was 130 ° C. For 1 hour. Thereafter, the surface was smoothed by vibrating with a polishing abrasive grain using a vibration barrel polishing machine. At this time, the outer diameter of the plated portion of the lifter was about 1 μm smaller than before processing. Next, 1.8% C-1.0% Si-18% Cr-
2% Mo-1% V-0.5% P-balance iron, hardness _HRC
At 58, a stem contact portion chip made of an iron-based sintered alloy having a true density ratio of 99% was attached by caulking to the concave portion of the lifter body.
Thereafter, the sliding contact portion of the lifter with the outer shim was turned and then the contact portion of the stem was finished by polishing with reference to the surface. The dimensions in FIG. 2 are as follows.

H = 24.1mm h1 = 2.3mm h2 = 3.6mm h3 = 1.2mm φD = 31mm φd = 27.5mm The lifter body is composed of the above materials. The sliding part with the cylinder head is subjected to surface treatment. Each lifter with an iron-based sintered alloy crimped in the contact part was installed in the actual machine, and the cooling water temperature was 105 ° C, the load was continuously operated for 250 hours under the condition of 7000 rpm, and the disassembly and investigation were performed after the test. There were no abrasion due to the outer shim, and no abrasion or seizure of the sliding surface with the cylinder head, which was a problem in the past. It was also confirmed that there was no wear at the stem contact portion. No cracks due to fatigue or impact were observed in the lifter body.

The lifter body is made of No.5, and a test piece for a baking test is created from the above-described plated lifter, and a test piece is similarly created from a lifter provided with an iron-sprayed film that is currently in practical use, An evaluation test for seizure resistance was performed with a pin-disk type friction tester against a disk made of a cylinder head material (AC4). The test conditions are
Speed 2m / sec, lubricating oil engine oil # 30, the lubricating oil temperature was 90 ° C., initially subjected to running-in 10 minutes at 20 Kg / cm ^2, increasing the load in the subsequent 5Kg / cm ² increments the load 3
In this test, the load point at which the friction coefficient sharply rises is determined as a seizure value in a test in which the friction coefficient is rapidly increased by 5 kg / cm ² .
In this test, the above-mentioned plating film did not cause seizure up to about 2 to 3 times the load as compared with the conventional iron sprayed film.

In addition, a test piece for torsion test was created from the cylindrical part of the lifter provided with the iron spray coating currently in practical use, the lift body was made of No. 5, and the same from the above-described plated lifter cylindrical part. A test piece having a shape was prepared, and a torsion test was performed to compare the torsion angles at which the surface treatment films began to peel off from the lifter body. As a result, even if a twist angle of twice or more of the compression allowance at which the peeling of the iron sprayed film started was given, the peeling of the plating did not occur.

〔The invention's effect〕

As described above, the lifter of the present invention has high fatigue strength of the aluminum alloy constituting the main body and has a small decrease in strength even when held at a high temperature for a long time. Becomes In the case of the same reliability, the weight can be further reduced by reducing the thickness of the main body. Also in sliding with the outer shim,
Since the hard particles dispersed in the alloy matrix and the strength of the matrix at a high temperature are high, a decrease in wear resistance even when exposed to a high temperature for a long time is small.

The plating layer in the sliding contact portion with the cylinder head has excellent seizure resistance and adhesion, and has an advantage in production that only requires a slight finishing after plating. Further, since the cetane-less polishing finish is not required, there is also an advantage that the thickness of the cylindrical portion of the lifter can be further reduced and the weight can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a lifter according to an embodiment of the present invention, FIG. 2 is a sectional view of a lifter showing dimensions of the embodiment of the present invention, FIG. 3 is a sectional view of a valve train of an internal combustion engine, The figure is a sectional view of a lifter, and FIG. 5 is a sectional view of a lifter using a known aluminum alloy. 1 ... Lifter 5 ... Outer shim 1a ... Parts that are easily broken by the lifter 1b, 1c ... Parts of the lifter that are easily worn by the outer shim 1d ... ... Outer peripheral surface of the lifter 1e ... ... Contact surface with the stem of the lifter 10: Base of the lifter body 10a: Hard particles dispersed in the base 10b: Plating layer 10c: Concavity of the lifter 10d: Chip of iron-based material

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-9607 (JP, A) JP-A-1-106909 (JP, A) JP-A-60-86250 (JP, A) JP-A 59-86 96295 (JP, A) JP-A-63-31901 (JP, A)

Claims (3)

(57) [Claims] (1) Cu: 3 to 8%, Mg: 0.5 to 2.5%, Si: 0.2 to 1.5%, and one or more of Mn, Fe, Cr, Ni, Co, V, Zr and Ti in total Hard powder having an average particle size of 2 to 30 μm in a matrix composed of the atomized powder, while precipitating Mg ₂ Si in the atomized powder having an amount of 3 to 10% with the balance being substantially aluminum. Of a composite material in which 2 to 10% is dispersed by volume, and a portion that slides with the cylinder head, contains P: 1 to 3% by weight, and the remainder is made of Si ₃ N ₄ in a matrix composed of Ni. Characterized by comprising an outer peripheral surface provided with a plating layer having an area ratio of 10 to 25% dispersed therein, and a valve stem contact surface composed of an iron-based alloy piece joined to the main body. Valve lifter. 2. The Si ₃ N ₄ dispersed in the plating layer on the outer peripheral surface.
The aluminum alloy valve lifter according to claim 1, wherein the average particle diameter of the aluminum alloy is 0.5 to 2 m. 3. The contact surface of the valve stem has a true density ratio.
3. The valve lifter made of an aluminum alloy according to claim 1, wherein the valve lifter is made of 95% or more of an iron-based sintered alloy.