JP2792932B2 - Manufacturing method of valve lifter - Google Patents

Description

The present invention relates to a method for manufacturing a valve lifter.

2. Description of the Related Art In general, in an internal combustion engine, a valve lifter is interposed between a valve operating cam and a valve shaft of the valve operating valve, and the valve lifter is substantially coaxially arranged near an upper end portion of the valve shaft. The main body has a cylindrical main body portion, and a cam sliding portion that closes the upper end portion of the main body portion in the axial direction and has an upper surface slidably in contact with the valve operating cam. It can be opened and closed.

By the way, despite the tendency that the valve train tends to be heavier with the increase in the number of valves in recent years, the weight of the valve train has been required to increase the engine rotation limit or to improve fuel efficiency. ing. Therefore, there is a strong demand for a significant reduction in the weight of a valve lifter that occupies a large weight in the inertial mass of a valve train (for example, about 1/3 of an iron valve lifter with an HLA).

As a measure for reducing the weight of the valve lifter, for example, a method of forming the valve lifter conventionally formed of iron with an aluminum alloy can be considered, but since the aluminum alloy has low wear resistance, the cam sliding contact portion is formed of an aluminum alloy. It is not possible. Therefore, a valve lifter in which only the main body portion is formed of an aluminum alloy and the cam sliding contact portion is formed of iron has been proposed, but the weight of this valve lifter has not been thoroughly reduced.

In addition, a method of forming the valve lifter with a lightweight and highly wear-resistant ceramic is conceivable.However, since the ceramic has a low toughness, if the entire valve lifter is formed of ceramic, sufficient strength cannot be obtained and the manufacturing cost is low. There is a problem that it becomes expensive.

Therefore, while the main body is formed of an aluminum alloy,
A valve lifter has been proposed in which a cam sliding contact portion is formed of ceramic to reduce the weight, improve wear resistance, and reduce manufacturing cost.

[Problems to be Solved by the Invention] However, in a valve lifter in which the main body is formed of an aluminum alloy and the cam sliding contact portion is formed of a ceramic, the coefficient of thermal expansion between the aluminum alloy and the ceramic is greatly different. It is very difficult to connect to the cam sliding part. For example, when the main body and the cam sliding contact portion are simply connected using an adhesive or the like, when the temperature changes, the two may be separated due to a difference in expansion coefficient. For this reason, in the valve lifter, an important point is a method of connecting the main body portion and the cam sliding contact portion. In this regard, for example, the following proposal has been made.

A recess is formed in the upper end surface of the tappet (valve lifter)
A ceramic plate having high wear resistance has been proposed to be fitted in the recess (Japanese Patent Application Laid-Open No. 59-1984).
190412). However, in this valve lifter, since the outer diameter of the bucket portion (main body portion) is large, the weight is not thoroughly reduced.

The main body is formed by an outer cylinder having an upper end opened and a flange formed on a peripheral edge thereof, and an inner cylinder having an upper end surface closing the upper end, between the inner cylinder upper end surface and the flange of the outer cylinder. There has been proposed a valve lifter in which a ceramic cam sliding contact portion is interposed (see Japanese Utility Model Laid-Open No. 61-173704). However, in this case, since the main body has a double structure, weight reduction is not sufficient.

In addition to forming a shaft hole in the upper end surface of the tappet (valve lifter), a ceramic follower with a shaft is made, and the shaft is fitted into the shaft hole so that the follower can rotate freely around its axis. There has been proposed a valve lifter for preventing occurrence of uneven wear or chipping (see Japanese Patent Application Laid-Open No. 60-219407). However, since the main body and the follower (cam sliding part) are not joined to each other, the cam sliding part is damaged when jumping (momentary separation of the valve cam and the cam sliding part) occurs. There is a problem that sometimes.

A ceramic circular pellet is placed above the upper end surface of a cylindrical valve lifter having a closed upper end, and a metal ring member for pressing the circular pellet downward (on the valve shaft side) is provided. A device that is fixed to the outside has been proposed (see JP-A-62-174510). However, when the ring member is not joined to the pellet, the pellet may be damaged when jumping occurs. Further, when the ring member is joined to the pellet, breakage of the pellet due to jumping can be prevented, but such joining is technically difficult and increases the production cost.

A proposal has been made in which a ceramic circular member is fitted to a ring formed at the upper end of a valve lifter (see Japanese Utility Model Application Laid-Open No. 61-160202). However, in such a joining method, the circular member cannot withstand sliding between the valve cam and the cam.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has high wear resistance of a cam sliding contact portion with respect to a valve operating cam, is sufficiently lightweight, and has an improved engine rotation limit or improved fuel efficiency. It is an object of the present invention to provide an inexpensive manufacturing method of a valve lifter capable of improving performance.

Means for Solving the Problems A first invention of the present application made to achieve the above object includes a cylindrical main body and a cam sliding contact portion that closes one end of the main body, Manufacture of a valve lifter for an internal combustion engine in which a main body shares an axis with a valve shaft and a cam sliding portion slides on the valve operating cam between a valve operating cam and a valve shaft of the valve operating. (A) a disk-shaped sliding contact body,
A fitting portion formed along the peripheral edge portion of the sliding contact portion main body to form a groove between the sliding contact portion main portion, and a dish-shaped space formed inside the fitting portion; And (b) forming an outer peripheral surface which is formed separately from the cam sliding contact portion and which coincides with the outer peripheral surface of the cam sliding contact portion when combined with the cam sliding contact portion. Preparing a main body having a connecting portion that projects inward from the front end of the main body and engages with the groove; (c) engaging the disc-shaped pressure receiving plate member with the peripheral edge of the pressure receiving plate member; The cam sliding contact part is fitted into the cylindrical space part of the fixing means composed of a die having an inner peripheral surface
(D) combining the main body portion with the cam sliding contact portion in the columnar space portion, and heating the main body portion before or after the combination so as to increase the distortion rate, and (e) coupling the main body portion kept at a high temperature. The material forming the main body is plastically flowed by applying a pressing force by a pressing means to a portion not engaged with the fitting portion of the portion, and the main body and the cam sliding contact portion are joined by this plastic flow. It is characterized in that it is made to be.

According to a second invention of the present application, in the method for manufacturing a valve lifter according to the first invention, the main body is formed of an aluminum alloy, and the cam sliding contact portion is formed of ceramic. Things.

According to the first aspect of the present invention, when the valve lifter is manufactured, the main body is preheated and plastic flow of the main body is easily generated, so that the caulking force is reduced and the stress concentration is suppressed, Damage to the cam sliding portion is prevented.

According to the second aspect of the present invention, the main body portion and the cam sliding contact portion are
Both are made of materials with low density (aluminum alloy, ceramic), so the valve lifter can be reduced in weight sufficiently, the inertial mass of the valve train is reduced, the responsiveness is improved and the engine rotation limit is reduced. It is possible to improve the fuel efficiency and the fuel efficiency.

In addition, since the ceramic has high wear resistance, the wear resistance of the cam sliding contact portion with respect to the valve cam can be sufficiently increased,
The reliability of the valve lifter can be improved.

Further, since the main body and the cam sliding contact portion are joined by the plastic flow of the aluminum alloy forming the main body, the joining strength between the main body and the cam sliding contact portion is greatly increased, And the reliability of the connection between the cam and the sliding contact portion can be improved.

In addition, relatively expensive ceramics are used only for the cam sliding contact portion, and plastic flow machining only applies an appropriate pressing force or impact force in the vicinity of the joint portion of the main body portion with the cam sliding contact portion. Since the operation can be performed with a simple operation, the manufacturing cost of the valve lifter can be reduced.

By the way, when manufacturing the valve lifter, the cam sliding contact portion made of ceramic is fixed to the fixing means, and the main body portion made of aluminum alloy is placed on the cam sliding contact portion, and the pressing force or the impact force is applied to the main body portion using a punch or the like. When plastic flow is performed by an ordinary method such as applying pressure, if an attempt is made to apply a relatively large pressing force that causes sufficient plastic flow to the aluminum alloy, the line of action of the pressing force locally, particularly in the cam sliding contact part A sudden change in stress occurs around the extension line of the cam, and the cam sliding portion (ceramic) may be broken.

However, in the present invention, the body is heated in advance before plastic flow is performed, and the body is in a high temperature state when a pressing force is applied. In general, as the temperature of the aluminum alloy increases, the strain rate (plasticity) increases. Therefore, at this time, the deformation resistance of the aluminum alloy forming the main body becomes very small. For this reason, a plastic flow is easily generated only by applying a relatively small pressing force or impact force to the main body using a punch or the like. Therefore, the stress induced in the cam sliding portion (ceramic) at the time of performing the plastic flow is greatly reduced, no sudden stress change portion is generated, and it is possible to effectively prevent the cam sliding portion from being broken.

[Examples] Examples of the present invention will be specifically described below.

As shown in FIG. 1, a cylindrical main body 1 made of an aluminum alloy is heated to a temperature (approx. (For example, 300 ° C.).

Then, as shown in FIG.
And a die 3 having an inner peripheral surface that engages with the peripheral edge of the pressure receiving plate member 2. The cam sliding contact part 5 made of ceramic is fitted. The cam sliding portion 5 is arranged such that a surface located on the cam side when mounted on the valve train (hereinafter, this surface is referred to as a cam side surface) is in close contact with the upper surface of the pressure receiving plate member 2. You. A fitting portion 5a is formed along a surface of the cam sliding contact portion 5 on the side to be connected to the main body 1 (hereinafter, this surface is referred to as a valve operating surface) slightly inside the peripheral portion thereof. I have. In addition, a dish-shaped space portion 6 is formed in a portion surrounded by the fitting portion 5a in order to reduce the weight of the valve lifter V as much as possible.

Next, the heated main body 1 is mounted on the valve-side surface of the cam sliding contact portion 5. The end of the main body 1 on the side connected to the cam sliding contact portion 5 has an outer peripheral surface of the fitting portion 5a and a valve-acting-side surface of the cam sliding contact portion 5 outside the fitting portion 5a. A coupling portion 1a having an engaging shape (reversed surface) is formed.
The inner peripheral surface of the coupling portion 1a is in close contact with the outer peripheral surface of the fitting portion 5a, and the bottom surface of the coupling portion 1a is the cam sliding contact portion 5 outside the fitting portion 5a.
Close to the valve side surface of

At this time, the main body 1 is of course maintained at a temperature (for example, 300 ° C.) at which the strain rate of the aluminum alloy is sufficiently large. In addition, instead of setting the main body 1 preheated by the external heating means (not shown) to the fixing means F, a heating means for heating the main body 1 is built in the fixing means F, Room temperature body 1
May be heated after it is set on the fixing means F.

Next, as shown in FIG. 3, a pressing means 9 having a punch 8 having an annular pressing surface slightly larger in diameter than the inner peripheral surface of the connecting portion 1a presses the pressing force P ( Impact force) is applied in the axial direction of the valve lifter V. Due to this pressing force P, the aluminum alloy forming the connecting portion 1a causes plastic flow, and is pushed into the annular groove 11 formed on the outer peripheral surface of the fitting portion 5a, whereby the cam sliding contact portion 5 and the main body are moved. The part 1 is connected.

Here, the main body 1 is kept at a high temperature (for example, 300 ° C.), but as shown in FIG. 4, the strain rate (plasticity) of the aluminum alloy progressively increases as the temperature increases. For this reason, the strain rate (plasticity) of the aluminum alloy forming the main body 1 becomes very high, and the deformation resistance becomes very small.
Plastic flow can easily occur by applying a relatively small pressing force or impact force to 1a. Therefore, the stress generated in the cam sliding contact portion 5 is greatly reduced, the occurrence of a sudden stress change portion is prevented, and the destruction of the cam sliding contact portion 5 is effectively prevented.

In addition, since both the cam sliding contact part 5 and the main body part 1 are formed of a material having a low density, it is possible to sufficiently reduce the weight of the valve lifter V. Therefore, the rotation limit of the engine can be increased, and the fuel efficiency can be improved. Table 1 shows valve lifters made of iron only.
A valve lifter according to the present invention in which the main body is formed of an aluminum alloy and the cam sliding contact portion is formed of iron, and the valve lifter according to the present invention in which the main body portion is formed of the aluminum alloy and the cam sliding contact portion is formed of ceramic The following shows examples of the weight, the weight of the valve train when these are mounted, and the rotation limit of the engine.

Further, since the cam sliding contact portion 5 is formed of ceramic having high wear resistance, the reliability of the valve lifter V can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view of a main body of a valve lifter according to the present invention. FIG. 2 is an explanatory longitudinal sectional view of an assembly composed of a valve lifter and a fixing means in a state where a cam sliding portion and a main body shown in FIG. 1 are arranged in a cylindrical space of the fixing means. FIG. 3 is an explanatory longitudinal sectional view of an assembly composed of a valve lifter, a fixing means, and a pressing means in a state where a plastic flow is generated in the main body by the pressing means. FIG. 4 is a diagram showing the characteristics of the strain rate (plasticity) of an aluminum alloy with respect to temperature. V ... valve lifter, F ... fixing means, 1 ... body part,
1a: joint, 2 ... pressure receiving plate member, 3 ... die, 4 ...
Cylindrical space, 4a ... opening, 5 ... cam sliding contact part, 5a ...
... fitting part, 8 ... punch, 9 ... pressing means, 11 ... groove.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshishi Kamioka 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-61-42443 (JP, A) JP-A-Hei 1 -141882 (JP, A) JP-A-64-87037 (JP, A) JP-A-61-159605 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 1/14 B21D 39/00

Claims (2)

(57) [Claims] The present invention further comprises a cylindrical main body and a cam sliding portion for closing one end of the main body, wherein the main body is connected to a valve shaft between a valve operating cam and a valve shaft of the valve operating valve. A method of manufacturing a valve lifter for an internal combustion engine, wherein an axis is shared and a cam sliding portion is disposed so as to be in sliding contact with a valve operating cam, comprising: a disk-shaped sliding contact portion main body; A cam having a fitting portion formed along the peripheral portion slightly inside the peripheral portion and forming a groove between the sliding contact body and a dish-shaped space formed inside the fitting portion. A sliding contact portion is prepared, is formed separately from the cam sliding contact portion, has an outer peripheral surface that matches the outer peripheral surface of the cam sliding contact portion when combined with the cam sliding contact portion, and faces inward from the tip of the main body portion. A main body having a connecting portion that projects to the groove and engages with the groove is prepared, and a disc-shaped pressure receiving plate member and an inner portion that engages with a peripheral portion of the pressure receiving plate member are prepared. A cam sliding part is fitted into a cylindrical space part of a fixing means constituted by a die having a surface, and the main body part is combined with the cam sliding part in the cylindrical space part, and before or after the combination. Is heated so that the distortion rate is increased, and a material that forms a main body by applying a pressing force by pressing means to a portion of the main body kept at a high temperature and not engaging with the fitting part of the connecting part. Wherein the main body and the cam sliding contact portion are joined by the plastic flow. 2. The method according to claim 1, wherein the main body is formed of an aluminum alloy.
2. The method according to claim 1, wherein the cam sliding contact portion is formed of ceramic.