JPH04365908A - Valve rocker arm - Google Patents

Abstract

PURPOSE:To improve abrasin resistance and seizure resistance by forming a rocker chip joined to the top end of a rocker arm with steel, while forming a hard ion plating membrane having specified thickness on the surface of the sliding surface thereof. CONSTITUTION:When a valve rocker arm 1 is rotated by the cam 2a of a cam shaft 2, it is perssure-pushed through a rocker chip 3. A rocker shaft 8 is oscilated along axis opposing to a spring 5 so as to open/close an intake/ exhaust valve 4. In such constitution, the rocker chip 3 is formed by using steel. A hard ion plating membrane having the thickness of 1 to 10 mum is formed on the obverse of the sliding surface in the rocker chip 3. A hard ion plating membrane is formed by employing either one bombination out of chrome and nitrogen combination, titanium and nitrogen combination, or titanium and nitrogen combination. It is thus possible to improve abrasion resistance and sizure resistance.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a valve rocker arm used in a valve train of an internal combustion engine, and more specifically, the present invention relates to a valve rocker arm used in a valve train of an internal combustion engine. Regarding valve rocker arms.

[0002] In recent years, with the increase in output and rotation speed of internal combustion engines, the rotational speed of the camshafts used in valve train mechanisms has increased, and in the OHC/valve rocker arm type, the sliding speed of the camshaft and valve rocker arm has increased. As a result, the sliding conditions for valve rocker arms are becoming more severe. Furthermore, since the rocker tip is struck by the cam nose of the cam piece, it is used under extremely harsh conditions with a combination of sliding and impact, resulting in rapid wear and the formation of large and/or sharp irregularities on the surface of the rocker tip. When this happens, the cam piece comes into contact with the metal, causing seizure, which has caused problems with durability.

FIG. 1 is a diagram showing a part of an OHC type four-stroke engine. In the figure, reference numeral 2 denotes a camshaft to which the rotation of the crankshaft is transmitted by a drive system (not shown) and rotates in synchronization with the crankshaft, and reference numeral 1 denotes a valve rocker arm to which the present invention is directed.

While being rotated by the cam of the camshaft 2, the valve rocker arm 1 is pushed by the rocker chip 3 connected to the tip of the valve rocker, and performs a seesaw movement around the rocker shaft 8. This opens and closes the intake and exhaust valves 4. The valve 4 is always urged upward by a spring 5 disposed around its outer periphery. Therefore, the valve opening operation is performed when the protrusion 2a of the cam piece of the camshaft 2 is connected to the rocker tip 3.
This is done when you press . As the rotational speed of the camshaft 2 increases, the sliding speed increases, the pressing force on the rocker tip 3 increases, and the nose portion 2 of the cam piece shaft 2 increases.
It can be seen that the impact caused by a increases, resulting in harsher operating conditions.

[0005]

[Prior Art] In order to cope with the harsh operating conditions mentioned above, rocker chips have been made of chromium molybdenum steel with surface treatments such as carburizing and quenching, induction hardening, and chrome plating, or wear-resistant sintered chips. A rocker arm made by casting a rocker chip made of material with aluminum alloy, press-fitting it into the tip of a rocker arm body made of aluminum alloy, or forging it from chrome steel or molybdenum chrome steel. The sliding characteristics are improved by composite means such as joining the above-mentioned rocker chip to the tip of the main body by brazing.

[0006]

[Problems to be Solved by the Invention] However, in recent internal combustion engines, the surface treatments or sintered materials described above do not have sufficient sliding properties, and problems such as seizure and wear have occurred. ing.

[0007] In view of the above, an object of the present invention is to solve the conventional problems and provide a valve rocker arm having sufficient seizure resistance and wear resistance even under more severe conditions.

[0008]

[Means for Solving the Problems] The valve rocker arm according to the present invention forms a hard ion plating film with excellent seizure resistance and wear resistance on the surface of the rocker chip that is joined to the tip of the valve rocker arm. .

That is, in the present invention, the rocker chip body is formed of steel, and the sliding surface thereof has a thickness of 1 to 10 μm.
This is a valve rocker arm characterized in that a rocker chip coated with a hard ion plating film of 100 mm is joined to the tip of the rocker arm. As the main body of the rocker chip, that is, the base material, a steel material such as carbon steel, alloy steel, or tool steel, or a material obtained by subjecting these steel materials to a hardening treatment such as nitriding treatment, carburizing treatment, or induction hardening is used.

[0010] That is, although sufficient seizure resistance and wear resistance can be obtained by the steel material provided with the hard ion plating film, the hardening treatment applied to the steel material further improves these performances. Note that during ion plating, the base material is heated to 500°C as described below, but the surface layer of the base material subjected to these hardening treatments is less softened, and as a result, the above performance is enhanced. .

[0011] 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 rocker chip. The film thickness of hard ion plating must be 1 μm or more, considering the possibility that the film will disappear due to wear during the initial break-in, so that the film remains even after the break-in, and chips and cracks do not occur on the film surface. To maintain good adhesion, the film thickness is increased to 10%.
It is necessary that the thickness be less than μm.

The constituent materials of the hard ion plating film are metal compounds such as nitrides, carbides, and borides, which have a micro-Vickers hardness of 1200 HmV or more. However, from the viewpoint of adhesion between the main body and the film, the hard ion plating film is preferably a nitride consisting of chromium and nitrogen, titanium and nitrogen, or titanium, aluminum and nitrogen. However, as the ratio of aluminum to titanium increases, the adhesion strength decreases, so the content of aluminum is limited to 80% or less in atomic percent relative to titanium. The lower limit of aluminum is preferably 5%.

The principle of ion plating is based on the Metal Handbook (
This is the method as shown in pages 902-903 (Revised 5th Edition). Among these, reactive ion plating is preferred. The ratio of metal to nitrogen in the film is 45
It is preferable that 95 atomic % is nitrogen, with the remainder being nitrogen.

The material of the valve rocker arm body can be cast iron, steel, or aluminum alloy without any problem. Additionally, the method of joining the coated rocker chip and the rocker arm body can be selected from a variety of methods, including press-fitting, casting, brazing, and caulking.

Although the present description has been made with respect to an OHC type valve rocker arm, it is clear that the present invention is also applicable to an OHV type valve rocker arm.

[0016]

[Action] The hard ion plating film with the thickness mentioned above has high hardness and good adhesion to the base material, which has excellent impact resistance, so it has excellent wear resistance. . In addition, hard ion plating films have excellent seizure resistance due to their low coefficient of dynamic friction and high thermal stability. Hereinafter, the present invention will be explained in detail with reference to Examples.

[0017]

EXAMPLE A hard ion plating film 10 having a thickness of 5 μm was formed on the sliding surface of a rocker chip shown in FIG. The rocker chip used in this example has a sliding surface size of 10
．． The size was 5 x 9.5 mm, and the material used was chromium molybdenum steel. Chrome molybdenum steel was forged, carburized and quenched, then tempered, and only the sliding surfaces were induction hardened.

The rocker chip sliding surface is lapped and polished to remove surface oxides.
It was also washed with Freon to remove dirt adhering to the surface, thoroughly cleaned, and then inserted into the vacuum chamber of the ion plating apparatus. After performing vacuum suction until the pressure inside the chamber reaches 1.3 x 10-2 Pa, the heater built into the ion plating device is heated to 300 to 500°C to release the gas contained in the rocker chip, and then Cool to 200°C. The pressure inside the chamber is 4×10−
When the pressure becomes 3 Pa or less, a target made of chromium, titanium, or titanium-aluminum is used as a cathode, and arc discharge is generated on the surface of the target to eject desired metal ions. At this time, apply a bias voltage of -70 to the rocker chip.
A voltage of 0 to -900 V was applied, and oxides on the surface of the rocker chip were removed and activated by so-called bombard cleaning, in which the metal ions themselves ejected from the target collided with the coated surface of the rocker chip with high energy. Thereafter, nitrogen gas is introduced into the chamber while metal ions are deposited on the sliding surface of the rocker chip, and the nitrogen is ionized by passing through the plasma.
In the case of -1 Pa, titanium-nitrogen, and titanium-aluminum-nitrogen, the pressure was set to about 1.3 Pa, and a bias voltage of -20 to -100 V was applied to form an ion plating film on the rocker chip. After forming a predetermined film thickness, the base material was cooled down to 200° C. or lower in a vacuum chamber, and then the rocker chip was taken out of the chamber.

The ion-plated rocker chip is press-fitted into the tip of a rocker arm body made of aluminum die-casting and which has a hole for press-fitting the tip at a predetermined position at the tip, thereby forming a valve rocker arm. I did it.

The valve rocker arm thus obtained was assembled into a 1600 cc, water-cooled, 4-cylinder, 4-stroke engine, and the engine speed was 6000 rpm, oil temperature 120°C, cooling water temperature 90°C, and under the conditions of full load. I did a time bench test. Table 1 shows the results of measuring the amount of wear on the rocker tip after the test, along with the results of measuring the amount of wear on the rocker tip that was not subjected to ion plating treatment.
It was shown to.

Table 1 also shows the results of evaluating the seizure resistance by a pin-on-disc scuff test. The test conditions were as follows. Load: 45MPa (maximum) Friction speed: 0.8m/sec Oil: 250mL/min Mating material: FC chill material

[0022]

[Table 1] Note: ○ indicates that the image was not burned in, × indicates that it was burned in.

0
[023] As shown in Table 1, chromium-nitrogen, titanium-
Both rocker tips with ion-plated nitrogen and titanium-aluminum-nitrogen coatings have better wear resistance than uncoated rocker tip steel shims.

[0024]

[Effects of the Invention] As explained above, conventional materials and surface treatments had problems with wear resistance and seizure resistance.
According to the present invention, a hard ion plating film made of chromium and nitrogen, titanium and nitrogen, titanium, aluminum and nitrogen is provided on the sliding surface of the rocker chip, thereby providing a valve rocker arm with excellent wear resistance and seizure resistance. This makes it possible to increase the output and speed of internal combustion engines.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an OHC type valve train for explaining a valve rocker arm and peripheral mechanisms.

FIG. 2 is a front view of the valve rocker arm.

FIG. 3 is a perspective view and a sectional view of a rocker chip joined to the tip of a valve rocker arm.

[Explanation of symbols]

1 Valve rocker arm 2 Camshaft 3 Rocker chip 4 Valve 5 Valve spring 6 Spring retainer 7 Cotter 8 Rocker shaft

Claims (4)

[Claims] Claim 1: In a valve rocker arm, which is an engine valve system component, in which a rocker chip is joined to the tip of the rocker arm, the rocker chip is made of steel, and the sliding surface of the rocker chip has a thickness of 1 to 10 μm on the sliding surface. A valve rocker arm formed by joining a rocker arm to a rocker chip characterized by the formation of a hard ion plating film. 2. The valve rocker arm according to claim 1, wherein the hard ion plating film on the surface of the rocker chip is made of chromium and nitrogen. 3. The valve rocker arm according to claim 1, wherein the hard ion plating film on the surface of the rocker chip is made of titanium and nitrogen. 4. The hard ion plating film on the surface of the rocker chip is made of titanium, aluminum, and nitrogen, and the ratio of aluminum to titanium in the film is at most 8 at %.
The valve rocker arm according to claim 1, wherein the valve rocker arm is 0%.