JPH0694804B2 - Valve retainer for internal combustion engine valve system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve retainer (valve spring retainer) used in a valve train of an internal combustion engine such as an automobile engine.

2. Description of the Related Art A typical example of a direct drive type valve train in a conventional automobile engine is shown in FIG. In FIG. 2, a valve seat 3 is provided at an opening end on the combustion chamber side of an exhaust or intake port 2 formed in a cylinder head 1, and this valve seat 3 has a face portion 4a of a valve 4. Are in contact with each other. Shaft of valve 4,
That is, a valve retainer (hereinafter simply referred to as “retainer”) 6 is attached near the tip of the valve stem 4b via a cotter 5 having a split structure, and this retainer 6 serves as a spring seat on the valve stem side for the valve spring 7. Has become. Furthermore, a valve lifter 8 is covered on the tip of the valve stem 4b, and a shim 9 on the upper surface of the valve lifter 8 contacts the cam 10.

In such a valve system, the retainer 6 has its tapered inner surface 6a pressed against the tapered outer surface 5a of the cotter 5 by the elastic force of the valve spring 7. With the vertical movement of the cotter, repeated impact force is applied through the cotter 5, and the cotter 5
Since the shocking friction acts on the contact surface with the retainer 6,
The inner surface of the slab has enough strength (proof strength) to withstand repeated impacts, and has sufficient abrasion resistance against sliding with the cotter 5, and at the same time, has an attacking ability against the cotter 5. Is also required to be small.

By the way, in recent valve trains, in order to reduce the weight, it is common to replace the conventional steel with valve lifters, retainers, etc., and use aluminum alloy. However, if the retainer is simply made of aluminum, the following problems occur. That is, aluminum alloys are generally lower in strength and proof stress than steels, and when the retainer is an aluminum alloy, it is usually made by casting.
Since aluminum alloy castings often do not have sufficient strength and yield strength due to the presence of casting defects such as pinholes, there is a problem in applying the aluminum alloy castings to the retainer as they are. Also, when an aluminum alloy is used for the retainer, there is a problem that the contact surface of the cotter is likely to wear due to sliding with the steel cotter, and also in order to secure the surface roughness to prevent the mating material from being scratched. There was a problem.

On the other hand, regarding a retainer made of an aluminum alloy, as a method for strengthening the surface of the retainer made of aluminum alloy, which is in contact with the valve spring, that is, the spring seat surface 6b in FIG.
No. 90907, it is proposed to form a reinforcing layer on the spring seat surface. As a concrete strengthening layer, a steel sheet is formed on the spring seat surface by cast iron, or a TIG remelting treatment layer is formed on the spring seat surface, and further, a wear-resistant material is surface-treated on the spring seat surface. It has been proposed to perform (eg Fe-P plating) or thermal spraying. In the case of this proposal, it is only the spring seat surface that is satisfactorily reinforced that is in contact with the valve spring, so that the problems with the surface on the contact side with the cotter as described above are not solved. It is also conceivable to apply the reinforcing layer forming means on the spring seat surface as proposed above to the contact surface with the cotter, but even in that case there was the following problem.

That is, when the steel plate is arranged on the side of the contact surface with the cotter by cast iron or the like, the merit of weight reduction using the aluminum alloy for the retainer is lost. Further, when the TIG remelting treatment is applied to the contact surface with the cotter, it is effective in improving the strength and proof stress, but the wear resistance is not so improved. Furthermore, simply by spraying or plating the wear resistant material on the contact surface with the cotter, the wear resistance is not improved, but the strength and proof strength are not improved, and the spray is applied to the inner surface of the small hole for inserting the cotter. It is difficult to do.

Problems to be Solved by the Invention As described above, the spring seat surface strengthening means for the valve spring in the aluminum alloy retainer described in JP-A-62-90907 is used as a contact surface with the cotter of the aluminum alloy retainer. Even when applied to, it was difficult to secure strength, proof strength and wear resistance at the same time, and not to impair the lightness.

The present invention has been made in view of the above circumstances, and the strength, the proof strength and the wear resistance of the surface of the aluminum alloy retainer on the side in contact with the cotter are sufficiently secured at the same time, and the lightness is not impaired, and the cotter is used. It is an object of the present invention to provide a retainer made of an aluminum alloy, which has an appropriate surface roughness so as to reduce the opponent attacking property against.

Means for Solving the Problems This invention relates to a valve retainer, which is attached to an end of a valve stem via a cotter and receives one end of a valve spring in a valve train of an internal combustion engine, in which a base material is made of an aluminum alloy, In addition, a remelting treatment layer is formed on the surface of the base material that is in contact with the cotter, and a TiN layer is formed on the surface of the remelting treatment layer.

In addition, here, the remelting treatment layer, TIG arc or laser,
It means a layer obtained by heating the surface of the base material by using a high-density heating energy source such as plasma arc or electron beam to rapidly remelt the surface layer and subsequently performing rapid resolidification.

The working remelting treatment layer is formed by blown holes, pinholes, shrinkage cavities, etc. contained in the surface layer of the base aluminum alloy due to rapid remelting by applying high-density heating energy and subsequent rapid resolidification. Casting defects have been removed, and the structure has been refined by rapid resolidification. Therefore, the remelted layer has markedly improved strength and yield strength as compared with the aluminum alloy as the base material. The hardness of the TiN (titanium nitride) layer is Hv2000.
The strength is significantly higher than that of the base metal and the wear resistance is excellent.

Therefore, in the retainer of the present invention in which the remelting treatment layer is formed on the surface in contact with the cotter and the TiN layer is further formed on the surface, the strength and proof strength at the portion in contact with the cotter are excellent and at the same time wear resistance is improved. Are better.

Here, the TiN layer is preferably formed by a PVD method such as sputtering or ion plating, and its thickness is preferably about 3 to 10 μm.
When a thin TiN layer formed by the D method is directly formed on the aluminum alloy base material, that is, when a thin TiN layer formed by the PVD method without the remelting treatment layer, the surface roughness of the TiN layer increases. However, the retainer of the present invention in which the TiN layer is formed on the remelted layer can prevent such a problem. That is, in the base material made of an aluminum alloy, particularly in the base material made of casting, there are many defects such as pinholes in the surface layer as described above, the porosity reaches about 0.5 to 0.8%, and the outermost surface layer after processing is Since the concave portions due to pores also appear, if a thin TiN layer is directly formed on the surface by the PVD method, irregularities due to pores on the inner base metal surface will also appear on the TiN layer surface, and the surface of the TiN layer surface will appear. Roughness increases and the TiN layer is hard, which increases the opponent's aggressiveness when sliding against the cotter. On the other hand, in the retainer of the present invention, the remelting treatment layer is formed on the surface of the base material on the cotter side, and the remelting treatment layer has almost no defects such as pores as described above, so that the surface roughness is small. Therefore, even when a thin TiN layer on the remelted layer is formed by the PVD method, the surface roughness of the TiN layer can be significantly reduced without being affected by pores, and Opponent aggression can be reduced. Here, in order to sufficiently reduce the attacking property against the cotter, it is preferable that the surface roughness of the remelted layer after the undercoating (surface roughness before forming the TiN layer) is 0.8 μmRz or less.

Example [Example 1] As a retainer 6 having a shape as shown in FIG. 2, a remelting treatment layer and a TiN layer were formed from the base metal side to the surface on the contact surface 6a side with the cotter 5. An aluminum alloy retainer formed in order was prepared as follows.

That is, the diameter of the center part of a disk-shaped material made of JIS AC2B aluminum alloy casting with an outer diameter of 30 mm and a height of 10 mm.
Current 200A, voltage 30V, Ar gas flow 25 /
Remelting treatment was performed with a TIG torch for 5 minutes and a treatment time of 5 seconds. By this treatment, the tensile strength at the remelted portion is 25
From kgf / mm ² to 40kgf / mm ^2, 20kgf / m Strength from 13 kgf / mm ²
improved each m ^2, also defects (porosity) was confirmed to be almost zero from 0.8 percent.

Then, the material that had been subjected to the remelting treatment as described above was subjected to machining to complete the shape of the retainer. At this time, the surface roughness on the contact surface side with the cotter (roughness of the surface of the remelted layer) was set to 0.6 μmRz. Then, a TiN layer having a thickness of 5 μm was formed on the contact surface with the cotter at a temperature of 100 ° C. or less by PVD treatment. At this time, the surface roughness was 0.6 μmRz like the surface of the remelted layer before PVD treatment.

The cross-sectional structure of the thus obtained retainer on the side of contact with the cotter is schematically shown in FIG. In FIG. 1, reference numeral 11 is an aluminum alloy base material, and this base material 11
In Example 1, primary crystal Si particles 12 are dispersed and crystallized in the matrix, and pores 13 are present as casting defects. Further, in FIG. 1, reference numeral 14 is a remelting processed layer, and the remelting processed layer 14 has a fine structure. Further code 15
Is the TiN layer by PVD method.

[Comparative Example 1] A retainer was produced in the same manner as in Example 1 except that the TiN layer was not formed by the PVD method.

[Comparative Example 2] A retainer was produced in the same manner as in Example 1 except that the remelting treatment by the TIG arc was not performed.

[Performance Evaluation Test 1] Each retainer according to Example 1 and Comparative Examples 1 and 2 has 28
Built into the valve train of a 00cc gasoline engine, 10,000 rpm
A 100-hour over-rotation endurance evaluation test using rpm was performed.

As a result, the amount of sinking of the cotter (difference from the initial position) due to wear in the sliding portion with the cotter reached 30 μm at the end of the test when the retainer of Comparative Example 1 was used. Further, when the retainer of Comparative Example 2 was used, the retainer was cracked 50 hours after the start of the test, and the continuation of the test had to be stopped. On the other hand, in the retainer of Example 1 according to the present invention, no abnormality occurred until the end of the test, and the sinking amount of the cotter was 5 μm or less, which was almost the same as the initial position. From these results, it is clear that the retainer according to the present invention has sufficiently high wear resistance at the contact portion with the cotter and high resistance to impact.

Example 2 When manufacturing a retainer in the same manner as in Example 1, TIG
By changing the finishing degree of the surface of the contact part with the cotter in machining after remelting by arc, the surface roughness of that surface is 0.6 μmRz, 0.8 μmRz, 1.0 μmR
It was adjusted to four levels of z and 1.2 μmRz. PVD method
The roughness of the TiN layer surface after forming the TiN layer is 0.6 as above.
There were four levels of μmRz, 0.8 μmRz, 1.0 μmRz, and 1.2 μmRz.

[Performance Evaluation Test 2] With respect to each retainer according to Example 2, the same test as in Performance Evaluation Test 1 was performed to examine the wear depth of the contact surface (sliding surface) of the cotter with respect to the retainer.

As a result, the surface roughness of the cotter and the sliding surface are each 0.6 μm.
When the retainers of Rz and 0.8 μmRz were used, wear of the cotter did not occur at all. On the other hand, the surface roughness
When each retainer of 1.0 μmRz and 1.2 μmRz was used, the cotter was worn by 10 μm and 15 μm, respectively, and the cotter was depressed. From such test results, it is understood that the surface roughness of the contact surface with the cotter is 0.8 μmRz or less.

If the TiN layer is formed directly on the finished surface of the aluminum alloy base material by the PVD method without forming a remelted layer, the surface roughness of the TiN layer will be the same as that of the base material when the finished surface has no defects. Although it is equivalent to the surface roughness of the machined surface, irregularities of about 1 to 2 μmRz are generated on the TiN layer surface in the part where the pores are exposed. Therefore, in this case, as is clear from the above test results, the cotter Will be worn out. Therefore, it is clear that forming the remelting treatment layer is effective also in improving the surface properties of the TiN layer when the TiN layer is formed by the PVD method and reducing the opponent attacking property.

Advantageous Effects of Invention The valve retainer of the present invention is made of an aluminum alloy as a base material, and has a remelting treatment layer and Ti
The N layer is formed in that order, and in such a valve retainer, high strength and proof strength are given to the part in contact with the cotter by the remelting treatment layer and at the same time excellent wear resistance is provided by the TiN layer. Therefore, it is less likely that cracks will be generated by the impact applied through the cotter, and at the same time less likely to be worn by sliding with the cotter.
Even if it is formed by the VD method, the surface roughness can be suppressed appropriately, so it is possible to reduce the attacking force against the cotter, and therefore the reliability and durability of the valve train using the aluminum alloy retainer. It can be significantly increased compared to the past. In addition, the valve retainer of the present invention has almost no increase in weight as compared with the valve retainer that is made of the aluminum alloy as a whole, and therefore, the merit of weight reduction by using the aluminum alloy for the valve retainer is not impaired.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a sectional structure of a portion of the valve retainer of the present invention which comes into contact with a cotter, and FIG. 2 is a longitudinal sectional view showing an example of a general internal combustion engine valve system. 5 ... cotter, 6 ... retainer, 6a ... face contacting the cotter, 11 ... aluminum alloy base material, 14 ... remelting treatment layer, 15 ... TiN layer.

Claims (1)

[Claims] 1. A valve retainer, which is attached to an end of a valve stem via a cotter and receives one end of a valve spring in an internal combustion engine valve system, wherein a base material is made of an aluminum alloy, and the base material is a cotter. A valve retainer for a valve operating system of an internal combustion engine, wherein a remelting treatment layer is formed on a surface of the contacting side, and a TiN layer is formed on a surface of the remelting treatment layer.