JPH03482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a main body portion of a hydraulic valve used in a valve train of an overhead valve type internal heat engine.

In some overhead internal combustion machines, a hydraulic valve lifter is inserted between the cam and the pushrod to absorb thermal expansion of the valve train and compensate for component wear over time to maintain zero valve clearance. ing. An example of such a valve lifter is the
-43125 can be mentioned.
The valve lifter has a main body part that constitutes its outer shell, and this main body part consists of an outer sleeve part having a cylindrical inner hole and a bottom plate part integrated with the outer sleeve part, and the bottom plate part is connected to the cam of the camshaft. It constitutes a cam follower part that is brought into contact and driven. A plunger, a push rod seat, etc. are slidably housed in the inner hole of the outer sleeve portion. The valve lifter constructed in this manner is slidably inserted into a valve lifter mounting hole formed in the engine block between the cam and the push rod. During operation of the engine, the lower surface of the cam follower is subjected to wear and impact by the cam, and the outer peripheral surface of the outer sleeve portion is subjected to wear due to sliding with the valve lifter mounting hole. For this reason, it is desirable to use materials suitable for each of the outer sleeve portion and the cam follower portion, and to apply appropriate surface treatments to each.

The valve lister main body portion, which is an assembly of an outer sleeve portion and a cam follower portion, can be roughly classified into an integral casting type and a joining type depending on the manufacturing method.

In the former manufacturing process, both the outer sleeve part and the cam follower part are cast simultaneously and integrally in a single casting process, and the inner and outer diameters of the thus formed casting are ground to the desired dimensions and shape. ,
The final product is obtained by heat treatment and any necessary final polishing. However, in this method, since the outer sleeve part and the cam follower part are integrally cast from the same material, the material of the main body part is determined preferentially from the relationship with the cam, and is determined from the relationship with the valve lifter mounting hole. The material selection for the outer sleeve portion is secondary. As a result, alloy cast iron is mainly used as the material to obtain a cam follower sliding surface that has excellent wear resistance and bitting resistance against the cam. Alloy cast iron has poor machinability, and it is particularly difficult to process the inner diameter of the outer sleeve portion. Therefore, an integrally cast outer sleeve/cam follower assembly has poor quality and accuracy, is expensive, and is not suitable for mass production.

The latter joint type outer sleeve/cam follower assembly eliminates these drawbacks, and when manufacturing it, the outer sleeve part and the cam follower part can be manufactured separately in advance from materials that are suitable for each. That is, the cam follower part is manufactured by casting using alloyed cast iron, and the outer sleeve part is made of carbon steel or the like which has good machinability and fits the valve lifter mounting hole of the cylinder block. The outer sleeve portion and cam follower portion thus manufactured in advance are joined by brazing as shown in FIG. 1 to form an assembly, which is subjected to necessary machining and then subjected to appropriate surface treatment. This surface treatment involves hardening the cam follower to obtain a sliding surface with the desired wear resistance and pitting resistance, and carburizing and hardening the outer sleeve to give the outer peripheral surface the desired properties. The purpose is to impart wear resistance, etc. In the production of conventional bonded outer sleeve/cam follower assemblies, the entire assembly after brazing is first maintained at a predetermined carburizing temperature to carburize the outer sleeve, and then the temperature is increased to a predetermined quenching temperature. The outer sleeve portion and cam follower portion were hardened at this hardening temperature. However, in this method, the cam follower part is exposed to high temperatures for a long time during brazing and carburizing, so the cementite in the alloy cast iron base material of the cam follower part decomposes and graphite precipitates in the base material. Otherwise, graphite may grow, reducing the quality of the cam follower. In order to avoid this, the quenching time is set so that the cam follower part does not deteriorate.
When carburizing is carried out at high temperatures, it is difficult to get the carburizing atmosphere deep into the inner hole of the outer sleeve because it is done after brazing, which makes it impossible to obtain a satisfactory, uniform, and desired carburizing depth. , resulting in a decrease in quality. There is also the problem of corrosion due to insufficient cleaning of the flux used during brazing.

The present invention was devised in view of the problems mentioned above in the prior art, and it is possible to use materials suitable for each of the cam follower part and the outer sleeve part, and to perform surface treatments suitable for each. Another object of the present invention is to provide a method for manufacturing a joined type outer sleeve/cam follower assembly that is high in quality and suitable for mass production at low cost.

In order to achieve the above object, the method for manufacturing a joined type outer sleeve/cam follower assembly of the present invention includes:
By carburizing the pre-formed outer sleeve material at a predetermined temperature to form a carburized layer of uniform depth on the inner and outer circumferential surfaces, it is slowly cooled, and then the lower edge of the outer sleeve material is machined. At the same time, an annular protrusion is formed along the lower edge, and the carburized layer in the protrusion area that adversely affects welding is removed, and the preformed cam follower material and the outer sleeve material are bonded to each other. After welding the outer sleeve/cam follower assembly using condenser projection welding, which eliminates the need for brazing filler metal, flux, etc. and is suitable for mass production, the outer sleeve/cam follower assembly is then welded as a cam follower. It is characterized by quenching under quenching conditions that provide the necessary hardening to both materials without causing deterioration, or by quenching and tempering and then finishing. Here, carburizing treatment does not only include carburizing treatment in a narrow sense, but also broadly includes carbo-nitriding treatment in which nitriding progresses at the same time as carburizing, and similarly, carburized layer also means carbonitrided layer. do.

As described above, according to the method of the present invention, the outer sleeve part and the cam follower part are manufactured separately, and the outer sleeve part is carburized in advance before welding with the cam follower part, so that after welding, the joined body By simply quenching or quenching and tempering the outer sleeve portion and the cam follower portion at a predetermined quenching temperature, the quenching treatment suitable for each of the outer sleeve portion and the cam follower portion is completed at the same time. Therefore, since the cam follower part is not exposed to high-temperature carburizing treatment, graphite in the base material of the cam follower part does not precipitate or grow. However, since the outer sleeve part and the cam follower part are manufactured separately, it is possible to enjoy the advantage of the joint type in that materials suitable for each can be used, and the inner diameter of the outer sleeve can be easily machined. can.

The condenser projection welding method is known as a welding method suitable for welding dissimilar metals (Japanese Patent Publication No. 53-10935), and this welding method is particularly suitable for welding the outer sleeve and cam follower of the valve lifter according to the present invention. Are suitable. By applying the condenser projection welding method instead of conventional brazing, we can eliminate the problem of graphite precipitation and growth due to the heat during brazing the outer sleeve/cam follower assembly, and the problem of corrosion due to insufficient cleaning of flux. This makes it possible to mass produce in a shorter time. Further, the carburized layer of the welded part which is generated by carburizing before welding and which adversely affects the welded part can be removed at the same time by machining to form the projection, so there is no problem at all.

In the present invention, it is preferable to use alloy cast iron as the cam follower material, and to use cold forged steel or pipe material as the outer sleeve material.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. The outer sleeve material 10 is a cold forged product (for example, S15C) or a pipe material (for example,
From STKM12), form it by machining etc. as shown in Figure 2. Next, this outer sleeve material is subjected to carburizing treatment or carbo-nitriding treatment by a conventional method, and then slowly cooled by air cooling or furnace cooling. The carburizing temperature is approximately 900℃,
Preferably, the treatment time is about 3 to 4 hours. The reason for slow cooling was to facilitate the subsequent machining. Next, as shown in FIG. 3A, the lower edge of the outer sleeve material 10 is cut.
An annular projection 12 is formed along the lower edge, and a portion 16 of the carburized layer (or carbonitrided layer) 14 near the projection is removed.
The reason why the carburized layer 16 near the projection is removed is that the cam follower material to be welded also has a high carbon content, and if this remains, cracks will occur near the weld seam. The shape of the projection 12 is preferably such that the taper angle α of the tip is 30° to 60°, and the width W of the projection tip is 0.2 to 0.7 mm. In this way, the outer sleeve material 10 shown in FIG. 3B is obtained.

On the other hand, as shown in FIG. 4, the cam follower member material 18 is obtained by casting alloy cast iron into a desired shape and finishing the upper and lower surfaces. The concave portion of the cam follower material may be left as cast.

The previously formed outer sleeve material and cam follower material are brought into contact with each other, and while applying high pressure, a large current having a current waveform as shown in Figure 5 is instantaneously applied using a capacitor type resistance welding machine. energize and perform projection welding. Current rise time T ₁ is approximately 4 to 8 msec, energization time T ₂
is preferably about 10 to 20 msec.

After welding, the outer sleeve part is machined to form oil grooves and burrs are removed as necessary, and the entire joint is maintained at approximately 830 to 880°C for about 1 to 2 hours to remove the outer sleeve part and cam follower part. Both are quenched and tempered at the same time. Finally, finishing is performed to obtain the final product of the outer sleeve/cam follower assembly.

FIG. 6 is a sectional view illustrating the outline of the structure of a hydraulic valve lifter using an outer sleeve/cam follower assembly manufactured by the method of the present invention, where 20 is the outer sleeve/cam follower assembly, and 22 is a projection weld. 24 is a plunger, 26 is a check ball, 28 is a check ball retainer, 30 is a return spring,
32 is a push rod sheet.

As is clear from the above, according to the method of the present invention, the outer sleeve portion and the cam follower portion are manufactured separately and then joined by welding, so it is possible to use materials suitable for each. In addition, since the outer sleeve part is carburized before welding, the cam follower part will not be exposed to excessively high temperatures during subsequent processing, and graphite will precipitate or grow in the base material of the cam follower part. Therefore, it is possible to prevent the wear resistance and pitting resistance of the cam follower from deteriorating. Furthermore, since the outer sleeve portion is carburized before welding, it is possible to easily form a carburized layer on the inner hole wall with sufficient hardness for sliding and a uniform depth. Therefore, it is possible to obtain an inner peripheral surface having a sliding surface with excellent wear resistance against the plunger. Furthermore, a material that is easy to machine can be used for the outer sleeve, and since the outer sleeve is slowly cooled after being carburized, machining is easy. Furthermore, since the carburizing process is performed before quenching, the quenching conditions can be relaxed compared to when carburizing and quenching are performed simultaneously, and quench cracking of the cam follower member can be prevented. Therefore, according to the present invention, high quality outer sleeve/cam follower assemblies can be mass-produced at low cost. In addition, since condenser projection welding is used instead of conventional brazing, there is no need for brazing filler metal or flux, which is less expensive.There is also no possibility of corrosion caused by flux, and the cam follower is damaged by the heat during brazing. There is no problem with deterioration.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a bonded outer sleeve/cam follower assembly made by a conventional brazing method;
The figure is a sectional view of the outer sleeve material according to the method of the present invention, FIG. 3A is an enlarged sectional view of the projection of the outer sleeve material, and FIG. 3B is FIG. 3A.
FIG. 4 is a cross-sectional view of the cam follower material, FIG. 5 is a graph showing the energization waveform, and FIG. 6 is the outer sleeve manufactured by the method of the present invention. 1 is a schematic cross-sectional view of a hydraulic valve lifter using a cam follower assembly. DESCRIPTION OF SYMBOLS 10... Outer sleeve part material, 12... Projection extension, 14... Carburized layer, 16... Carburized layer in projection area, 18... Cam follower part material.

Claims (1)

[Claims] 1 A pre-formed outer sleeve material is carburized at a predetermined temperature to form a carburized layer on its inner and outer circumferential surfaces, then slowly cooled, and the lower edge of the outer sleeve material is machined to form a carburized layer along the lower edge. At the same time as forming an annular projection, the carburized layer in the projection area is removed, and the preformed cam follower material and the outer sleeve material are projection welded to form an outer sleeve/cam follower joint. A method for manufacturing a jointed outer sleeve/cam follower assembly for a hydraulic valve lifter for a medium combustion engine, which comprises quenching or quenching and tempering the entire outer sleeve/cam follower assembly and then finishing it.