JPH0573203U - Valve rocker shaft - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To reduce wear of valve rocker shaft in severe corrosive wear environment. [Structure] A hard ion plating film (10) having a thickness of 1 to 10 μm is formed on a sliding surface of a valve rocker shaft (1) which is an engine valve system component.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a valve rocker shaft used in a valve train of an internal combustion engine, and more specifically to a valve blocker shaft having improved wear resistance of an iron-based valve rocker shaft.

In recent years, as the output power and rotation speed of the valve train of internal combustion engines have increased, the rotational speed of camshafts used in valve trains has increased, and in OHC / valve rocker arm type internal combustion engines, the valve rocker arms have valve valves. The rotation speed that swings around the rocker shaft increases, and the sliding speed between the outer surface of the valve rocker shaft and the inner surface of the shaft hole of the valve rocker arm increases, resulting in rapid wear of the valve rocker shaft and durability. I'm having problems with sex.

FIG. 1 is a diagram showing a part of an OHC type four-cycle engine. In the drawings, reference numeral 3 is a camshaft which is rotated in synchronization with the crankshaft by rotation of a crankshaft transmitted by a drive system (not shown), and reference numeral 1 is a valve rocker shaft to which the present invention is directed. ..

While the camshaft 3 is rotating, the cam of the camshaft pushes the cam follower surface 2 a at the tip of the valve rocker arm 2, so that the valve rocker arm 2 makes a seesaw motion about the valve rocker shaft 1 as a shaft, thereby inhaling and exhausting air. Open and close valve 4. The intake and exhaust valves 4 are normally urged upward by a spring 5 arranged on the outer circumference.

Therefore, the opening operation of the valve is performed when the protruding portion 3 a of the cam piece of the cam shaft 3 presses the cam follower surface 2 of the valve rocker arm 2. When the rotational speed of the camshaft 3 increases from the above valve actuating mechanism, the seesaw motion of the valve rocker arm 2 becomes faster, and the outer peripheral surface of the valve rocker shaft 1 and the inner circumference of the shaft hole of the valve rocker arm 2 which are the swing centers of the valve rocker arm 2 become faster. It can be understood that the sliding conditions become severe.

[0006]

[Prior Art]

 In order to cope with the severe operating conditions described above, carbon steel, chrome steel, and chromolybdenum steel that have been nitrided or carburized as a means of improving sliding characteristics have been conventionally used, or surface treatment such as induction hardening only on the sliding part. These iron-based valve rocker shafts are used.

[0007]

[Problems to be solved by the device]

 However, in the internal combustion engines of recent years, the surface treatment as described above cannot be said to have sufficient sliding characteristics, and problems such as wear have occurred. In addition, there are regions in Africa, Southeast Asia, etc. where poor gasoline, a mixture of lead and alcohol, is used as fuel. The use of such poor gasoline accelerates the increase of combustion products and the deterioration of the lubricating oil.As a result, the lubrication environment of the valve blocker shaft deteriorates. When the valve rocker shaft is worn due to wear due to a decrease in viscosity, noise will be generated from the valve train and the valve opening / closing timing will be misaligned, causing serious problems. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a valve rocker shaft having sufficient wear resistance even under more severe conditions.

[0008]

[Means for Solving the Problems]

 The valve rocker shaft according to the present invention forms an ion plating film on the sliding surface with the valve rocker arm, which has superior wear resistance and adhesion compared to other films.

That is, the present invention is a valve rocker shaft, characterized in that the valve rocker shaft main body is made of steel, and the sliding surface of the valve rocker shaft is covered with a hard ion plating film having a thickness of 1 to 10 μm. .. As the main body of the valve rocker shaft, that is, the base material, carbon steel, alloy steel, or other steel material or a material obtained by subjecting these steel materials to nitriding treatment, carburizing treatment, induction hardening treatment, or the like is used. That is, the steel material coated with the hard ion plating film provides sufficient wear resistance, but the hardening treatment applied to the steel material in advance further enhances this performance. The surface on which the hard ion plating film is formed must be a sliding surface, but it may be formed on other parts of the valve blocker shaft. Considering the possibility that the surface layer may disappear due to wear in the initial familiarization, the film thickness of ion plating should be 1 μm or more to leave the film after the familiarization, and the film surface should have no cracks or cracks. It is necessary to set the thickness to 10 μm or less in order to maintain a good adhesion without causing the occurrence of

The constituent material of the hard ion plating film is a metal compound such as a nitride, a carbide, or a boride, which has a micro Vickers hardness of 1200 HmV or more. However, from the viewpoint of adhesion, it is desirable that the ion plating film is a nitride composed of chromium and nitrogen, titanium and nitrogen, or titanium, aluminum and nitrogen. In the case of a film composed of titanium, aluminum, and nitrogen, aluminum is limited to 80% or less in atomic% with respect to titanium from the viewpoint that the adhesive force decreases as the ratio of aluminum to titanium increases. The lower limit of aluminum is preferably 5% in atomic% with respect to titanium.

Ion plating is a method whose principle is as described in “Handbook of Metals” (Revised 5th Edition), pages 902 to 903. Among these, the reactive ion plating method is preferable. The ratio of metal to nitrogen in the film is preferably 45 to 95 atom% of metal and the balance is nitrogen. Although the present description has been given for the OHC type valve rocker shaft, it is obvious that the present invention can be applied to the OHC type valve rocker shaft.

[0012]

[Action]

 The hard ion plating film having the above-described thickness has excellent wear resistance because it has high hardness and good adhesion to the base material. In addition, the hard ion plating film is ceramics, so it has high chemical stability, good corrosion resistance, and excellent corrosion wear. Hereinafter, the present invention will be described in detail with reference to examples.

[0013]

【Example】

 A hard ion plating film 10 having a thickness of 5 μm was formed on the sliding surface of the valve rocker shaft shown in FIG. The valve rocker shaft used in this example was made of carbon steel having a diameter of 18 mm and a sliding width (w) with the valve rocker arm of 22 mm. A carbon steel material was processed as shown in FIG. 2 (a), and only the curved surface of the outer peripheral portion that slides on the valve rocker arm was induction hardened.

By lapping and polishing the sliding surface of the valve rocker shaft, oxides on the surface are removed and chlorofluorocarbon cleaning is performed to remove dirt adhering to the surface, and the surface is thoroughly cleaned to remove the vacuum of the ion plating device. Inserted into chamber. Evacuate until the pressure in the chamber reaches 1.3 x 10 ^-2 Pa, then release the internal gas of the valve rocker shaft heated to 300-500 ° C by the heater built into the ion plating device. Then, it cooled to 200 degreeC. When the pressure in the chamber became 4 × 10 ⁻³ Pa or less, a target made of chromium, titanium, or titanium-aluminum was used as a cathode, and arc discharge was generated on the surface of the target to eject desired metal ions. At this time, a bias voltage of -700 to -900 V is applied to the valve rocker shaft, and the metal ions ejected from the target are made to collide with the coating surface of the valve rocker shaft with high energy. By so-called bombard cleaning, the valve rocker shaft is Surface oxide removal and activation treatment were performed. After that, while lowering the bias voltage and depositing metal ions on the surface of the valve rocker shaft, nitrogen gas was introduced into the chamber, and nitrogen was ionized by passing through the plasma, and in the case of chromium-nitrogen based coating, 1. In the case of 3 × 10 ⁻¹ Pa and titanium-aluminum-nitrogen, a pressure of about 1.3 Pa was applied and a bias voltage of −20 to −100 V was applied to form an ion plating film on the valve rocker shaft. . After forming a predetermined film thickness, the valve rocker shaft was taken out of the chamber after cooling in a vacuum chamber to 200 ° C. or lower.

The valve rocker shaft thus obtained was installed in a 4-cycle engine having a displacement of 2000 cc, a water-cooled 6-cylinder, and an engine speed of 6000 rpm, an oil temperature of 120 ° C., a cooling water temperature of 90 ° C., and a full load condition. A bench test was performed for 200 hours. The ball blocker arm incorporates an aluminum die cast product. The fuel used was gasoline containing 3 grams of lead and 1 deciliter of alcohol per 1 liter of gasoline. Table 1 shows the results of measuring the amount of wear of the valve rocker shaft after the test, together with the results of measuring the amount of wear of the valve rocker shaft that was not subjected to ion plating treatment.

[0016]

[Table 1] The ratio of titanium to aluminum in the coating type column of Nos. 3, 4, and 5 represents atomic%.

As shown in Table 1, the valve rocker shafts having the chromium-nitrogen based, titanium-nitrogen based, and titanium-aluminum-nitride based coatings ion-plated are all compared with the uncoated valve rocker shafts. It has excellent wear resistance.

[0018]

[Effect of the device]

 As described above, the conventional valve rocker shaft had a problem in wear resistance, but by providing a hard ion plating film, it is possible to provide a ball blocker shaft with excellent wear resistance, and to improve internal combustion. Higher engine output and higher engine speed have become possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an OHC type valve mechanism for explaining a valve rocker shaft and a peripheral mechanism.

FIG. 2 is a perspective view and a sectional view of a valve rocker shaft according to the present invention.

[Explanation of symbols]

 1 valve rocker shaft 2 valve rocker arm 3 camshaft 4 valve 5 valve spring 6 spring retainer 7 cotter 10 hard ion plating film

Claims (4)

[Scope of utility model registration request] 1. A valve rocker shaft (1) as an engine valve system component, characterized in that a hard ion plating film (10) having a thickness of 1 to 10 μm is formed on a sliding surface of a steel valve rocker shaft. Valve rocker shaft to be. 2. A hard ion plating film (10)
2. The valve rocker shaft according to claim 1, wherein the valve rocker shaft comprises chromium and nitrogen. 3. A hard ion plating film (10)
2. The valve rocker shaft according to claim 1, wherein the valve rocker shaft comprises titanium and nitrogen. 4. A hard ion plating film (10)
2. The valve rocker shaft according to claim 1, wherein said valve rocker shaft comprises titanium, aluminum and nitrogen, and the ratio of aluminum to the total amount of titanium and aluminum in the coating is at most 80% in atomic%.