JPH04255507A - Valve lifter - Google Patents

Abstract

PURPOSE:To improve the insert molding efficiency of a chip by disposing short fibers of a length specified times as large as the thickness of the chip in the periphery of an insert chip. CONSTITUTION:A fiber reinforced plastic valve lifter 12 is constructed so that a wear-resisting metal chip 13 is insert-molded in a surface contacting with the end surface of a valve stem. In this case, reinforced fiber is basically composed of long fibers, but short fibers of a length 0.5-3 times as large as the thickness of the chip 13 are disposed in the periphery of the chip 13. Thus, the percentage content of fibers in the peripheral portion of the chip 13 will not be lowered, and bending of long fibers are decreased so that the inserting strength of the chip 13 can be improved.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a valve lifter, and in particular to a fiber-reinforced plastic (F) for direct-acting valve-train engines.
Regarding valve lifters manufactured by RP).

0002

2. Description of the Related Art In internal combustion engines having a direct-acting valve system, a valve lifter is used to convert the rotational movement of a camshaft into vertical movement of a valve. FIG. 4 shows the structure near such a valve lifter. The upper ends of the intake and exhaust valves 1, which are urged upward by the valve spring 2, slide into contact with the valve lifter 3, and the valve lifter 3 has its upper surface pressed against the shim 5.
It is slidably driven by the cam 4 via the cam 4. The valve lifter 3 slides on the inner peripheral surface of a bore (valve lifter guide hole) 7 provided in the cylinder head 6 and is driven in the vertical direction, and can also rotate in the circumferential direction. Since such a valve lifter 3 transmits the drive from the cam 4 to the valve 1, it needs to be lightweight and strong, and since it slides on the stem end of the valve 1 and the valve lifter guide hole, it needs to have excellent wear resistance. . Therefore, conventionally, carburized steel is used for valve lifters.

[0003] In recent years, with the aim of reducing friction and increasing output by increasing engine speed, reducing the inertia weight of engine valve train systems has become an important issue, and there is a demand for reducing the weight of valve lifters. Therefore, the application of FRP, which has a higher specific strength than conventional steel materials, to valve lifters is being considered (
(Japanese Patent Application Laid-Open No. 62-128103). Simply configuring the valve lifter with FRP will result in damage to the valve lifter,
Valve damage may occur due to wear of the valve lifter, and the function of the engine valve system may be impaired, such as valve blow-through. In order to solve these problems,
41913, the strength of the valve lifter is increased by using plastic reinforced with relatively long fibers (FRP), and a wear-resistant metal tip (hereinafter also referred to as a tip) is cast in the part that contacts the end of the valve stem. A loose valve lifter is described.

0004

[Problem to be solved by the invention] JP-A-2-24191
The valve lifter described in Publication No. 3 is an effective method because the cast-in wear-resistant tip has a reverse tapered outer periphery, so the tip does not fall off due to the casting. However, because the fiber length is long, the lower edge of the tip In the narrow areas nearby, the fibers cannot go around during molding, leaving only the matrix resin. Also, in the area around the contact surface of the tip with the valve stem end surface, the fibers do not flow sufficiently to the lower surface, resulting in a decrease in the fiber volume ratio (
It was found that Vf) was significantly lowered and the casting strength was lowered. Further, when the fibers are oriented in this way to follow the chip shape, the fibers in this part are formed with a small curvature, so the internal stress in this part becomes significantly high. In addition, a boundary occurs around the chip between the area with a low fiber volume ratio and other areas with a high fiber volume ratio, and due to the difference in thermal expansion coefficient, molding shrinkage cracks occur during molding of the FRP valve lifter. becomes more likely to occur. Furthermore, a gap is created between the FRP body and the steel chip due to the difference in coefficient of thermal expansion, and loosening is likely to occur under high heat conditions. Therefore, the casting strength of the chip decreases. Therefore, an object of the present invention is to provide an FRP valve lifter with improved die casting properties.

[0005]

[Means for Solving the Problems] In order to achieve the above objects, the present invention provides a fiber-reinforced plastic valve lifter in which a wear-resistant insert tip is cast into the contact surface with the valve stem end surface. The fibers are basically long fibers, but around the chip there is a thickness of 0.
To provide a valve lifter characterized in that short fibers having a length of 5 to 3 times are arranged.

FIG. 1 shows a cross-sectional view of the entire FRP valve lifter according to the present invention, and FIG. 2 shows an enlarged cross-sectional view of the tip of the valve lifter and its surrounding area. In the FRP valve lifter of the present invention, a reverse tapered wear-resistant tip 13 is inserted into a portion 13a where the stem end of the valve comes into contact, a short fiber reinforced resin layer 12b surrounds this tip, and a long fiber reinforced resin layer covers the valve lifter body including the outside thereof. It is composed of two fiber-reinforced resin layers consisting of layer 12a.

The oil temperature of the valve lifter in an internal combustion engine increases during operation, and the valve lifter normally operates at a temperature of about 120 to 130°C. Further, since the outer circumferential surface of the valve lifter slides up and down by sliding with the lifter hole, abrasion heat is generated microscopically in the worn portion. From this point of view, heat-resistant grade polyimide or vinyl ester resins are suitable as resins used in the FRP valve lifter of the present invention, which exhibit less strength loss under high temperatures.

The tip is necessary to impart wear resistance to the valve, and is preferably made of steel, steel-based alloys (chromium steel, molybdenum steel, etc.) that have been conventionally used for valve lifters, but Vickers Hardness Hv is 500
Use the above. The thickness of the chip is preferably 50% or less of the thickness of the top surface of the valve lifter. If it exceeds 50%, the top surface strength will decrease. The outer diameter of the tip is 1.
It is preferable that it is 5 times or more and within 90% of the valve lifter inner diameter d3, but if it is too large, the mass will increase, so it is necessary to decide according to the required pull-out strength of the insert. If it is less than 1.5 times, the tapered part of the insert cannot be formed, and if it is more than 90% of the valve lifter diameter d3, the outer diameter of the short fiber reinforced portion will be larger than d3 and the skirt strength will decrease. By making the insert have a reversely tapered cross section, the casting effect can be enhanced. The reverse taper angle is preferably 30° to 75°.

[0009] The reinforcing fibers used in FRP can be fibers commonly used in FRP, such as carbon fibers, glass fibers, aramid fibers, etc. Since the FRP valve lifter according to the present invention has a two-layer structure, the surrounding layer of the chip and the outer layer, the two layers should be reliably bonded.
It is preferable that both layers have the same matrix resin, with the only difference being the fiber length and fiber type.

[0010] A suitable fiber content is 30 to 70% by weight;
Preferably it is 45 to 70% by weight. If the fiber content is less than 30% by weight, the effect of fiber reinforcement will not be sufficient, the wear resistance of the valve lifter will sharply decrease in the long fiber reinforced portion, and the casting effect will not be obtained in the short fiber reinforced portion. On the other hand, if the fiber content exceeds 70% by weight, the amount of resin, which is a fluid component, decreases, making molding almost impossible.

The fibers reinforcing the main portion of the FRP valve lifter are long fibers having a length substantially corresponding to the dimensions of the valve lifter. This allows the FRP valve lifter to have excellent strength, side wear resistance, and the like.

On the other hand, the fibers for reinforcing the chip periphery are short fibers having a length of 4 times or less, preferably 0.5 to 3 times the thickness of the chip. If the length of the short fibers around the chip is 5 times or more the thickness of the chip, the effect of shortening the fibers cannot be obtained, and the pull-out strength of the chip is significantly reduced. Further, from the viewpoint of manufacturing, it is preferable that the thickness be 0.5 times or more the thickness of the chip. Further, as for the dimensions of the portion around the chip reinforced with short fibers, it is desirable that the total thickness of the chip and the portion reinforced with short fibers covering the top thereof is 50% or less of the thickness of the top surface of the valve lifter. If this total thickness exceeds 50%, the strength of the top surface of the valve lifter will also decrease. Also, Figures 1 and 2
Referring to , the outer diameter dimension d0 of the short fiber reinforced portion is at least larger than the maximum outer diameter d1 of the inverted tapered tip, but smaller than the inner diameter d3 of the valve lifter. d
This is because if d0 is smaller than d1, the effect of short fiber reinforcement cannot be obtained, whereas if d0 is larger than d3, the strength of the skirt portion 14 of the valve lifter is reduced. Further, the short fiber reinforced portion has a natural slope from the top of the chip toward the lower surface of the top surface of the valve lifter so as not to disturb the arrangement of the long fibers.

[0013]

[Function] The valve lifter body is reinforced with long fibers for high strength.
In addition to increasing wear resistance, short fibers are placed in areas around the cast chip where the long fibers cannot go around, so the fiber content around the chip does not decrease and the bending of the long fibers is reduced. Therefore, the casting strength of the chip is improved.

[0014]

EXAMPLE A valve lifter as shown in FIGS. 1 and 2 was manufactured. As an FRP molding material, the short fiber reinforced portion 2b is made of a heat-resistant vinyl ester-based BMC material (a mixture of semi-hardened resin and carbon fibers, the fiber content of which is 3-dimensionally randomly oriented, fiber content 5).
0wt% molding material), the long fiber reinforced portion 2a is a molding material (semi-cured resin and fibers are mixed, and the long fiber reinforced part 2a is a two-dimensional A sheet-like molding material oriented in random directions with a fiber content of 50 wt% was used, and the length of the short fibers was varied with respect to the thickness t1 of the chip. The tip was made of bearing steel SUJ2, the outer diameter d1 was 1/2 of the inner diameter d3 of the valve lifter, the thickness t1 was 30% of the thickness t2 of the top surface of the valve lifter, and the reverse taper angle was 45°.

A short fiber-reinforced resin material was placed around this chip, and a long fiber-reinforced resin material for the valve lifter body was placed outside of the chip, followed by heat compression molding to form an FRP valve lifter. The maximum dimension d0 of the short fiber reinforced portion was set to 90% of the inner diameter d3 of the valve lifter.

In the molded product thus produced, the FRP portion of the thick top surface of the chip was counterbored with the outer diameter d1 of the chip, and a compressive load was applied from the top surface of the chip through this counterbore to measure the pull-out strength of the chip. did. In addition, after molding,
The fiber content of the FRP was 60 wt% in both layers. The above results are shown in FIG. From FIG. 3, it is recognized that when the length of the short fibers is 5 times or more the thickness t1 of the chip, the pull-out strength of the chip decreases significantly.

Next, the molded product was cut as shown in the cross section of FIG. 2, and the structure of the FRP around the chip was observed. As a result, the longer the fiber length in the short fiber portion around the chip, the lower the fiber content in the region 12b around the chip, and the more resin-rich the region 12b was. In particular, when the fiber length is more than 5 times the chip thickness t1, the orientation of the fibers around the chip is on the small diameter side of the chip (valve contact surface side) as in the conventional product (cross section of long fiber FRP valve lifter) shown in Figure 5. It is thought that the strength of the chip is low because the strength of the reinforcing fibers is limited to the strength of the resin. In addition, when the area around the chip becomes resin-rich, molding shrinkage is large due to the high coefficient of thermal expansion of the resin (60 For reinforced resin, the fiber direction is 5 to 8 x 10-6
Due to the difference in thermal expansion between the two, shrinkage cracks are likely to occur during molding near the boundary between the two. From the above, the reinforcing fiber length around the chip is preferably 4 times or less, more preferably 3 times or less the thickness of the chip. This molding material consists of chopped strand fibers (a large number, usually 1,000 to 12,000 fibers/
It uses a molding material in which a bundle of fibers is made into a single bundle with a resin-based restraint agent and matrix fat is cut into a predetermined length and made into a bulk or sheet shape. In order to obtain the characteristics (strength) of the fibers, it is effective to set the lower limit of the length of the fibers to a length that is longer than the diameter of one fiber bundle, but from a manufacturing standpoint, it is recommended that the length be at least 0.5 times the thickness of the insert chip. is desirable. Among the short fiber reinforced portions around the insert, the thickness of the upper layer of the chip may be sufficient to cover the chip. This is because the thickness of this portion becomes thick and if the thickness of the valve lifter at t3 exceeds 50% of the thickness at the top surface t2, the strength of the top surface decreases.

[0018]

[Effect of the invention] According to the present invention, FR reinforced with long fibers
In the valve lifter made of P, the strength of the peripheral part of the insert tip can be improved without impairing its durability (strength, wear resistance).

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a valve lifter according to an embodiment.

FIG. 2 is a partially enlarged schematic sectional view of the valve lifter of the embodiment.

FIG. 3 is a graph showing the relationship between the length of the fibers around the chip and the chip removal strength.

FIG. 4 is a schematic diagram showing the structure around the valve lifter.

[Explanation of symbols]

1...Valve 2...Valve spring 3...Valve lifter 4...Cam 5...Sim 6...Cylinder head 7...Bore (valve lifter guide hole) 12...Valve lifter 12a...Long fiber reinforcement 12b...Short fiber reinforcement 13...Wear-resistant metal tip 13a...Chip surface 14...Skirt

Claims (1)

[Claims] Claim 1: In a fiber-reinforced plastic valve lifter in which a wear-resistant insert tip is cast into the contact surface with the end face of the valve stem, the reinforcing fibers basically consist of long fibers; A bubble lifter characterized in that short fibers having a length of 0.5 to 3 times the thickness of the insert tip are arranged.