JPH0724564Y2 - Tappet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a tappet installed in a valve mechanism of an engine.

(Prior Art) As is well known in the art, in an overhead valve engine, lifts of an intake cam and an exhaust cam are transmitted to a push rod via a cylindrical tappet with a bottom, and further via a rocker arm. Is transmitted to the air supply valve and the exhaust valve. In the case of a vehicle diesel engine, the tappet is generally made of special cast iron.

(Problems to be solved by the invention) Due to EGR, which is widely adopted as a part of engine exhaust gas purification measures in recent years, sludge contained in oil increases and wear of various components in the valve train mechanism increases. The tendency is to increase, and improvement in wear resistance of the tappet is required. On the other hand, from the viewpoint of fuel efficiency and acceleration performance, it is desired to reduce the weight of tappets as a technical requirement common to all engine parts.

In view of the above circumstances, a ceramic chip having excellent wear resistance, that is, a tappet bottom plate is integrally cast on the bottom of a tappet body made of an aluminum alloy, particularly a hypereutectic aluminum-silicon alloy having excellent wear resistance. The tappets that have been made have already been proposed.

An example of the structure of the previously proposed tappet will be described with reference to FIG. 3. In the figure, reference numeral 10 generally indicates a bottomed cylindrical tappet, and the tappet 10 is a ceramic having excellent wear resistance, such as silicon nitride. A disk-shaped or short cylinder-shaped tappet bottom plate 16 and a tappet bottom plate 16 which are made of a raw material, sialon, etc., and which are surrounded by a groove 12 on the outer peripheral surface and have a recess 14 in the center of the upper surface. A hollow cylindrical tappet body made of an aluminum alloy cast in the lower end part, for example, a hypereutectic aluminum-silicon alloy having good castability and excellent wear resistance.
It is composed of 18 and. The recess 14 provided on the upper surface of the tappet bottom plate 16 is for receiving the lower end spherical surface portion 22 of the push rod 20 which is schematically shown by a chain double-dashed line in the figure, and is also a recess groove surrounded by the outer peripheral surface. Needless to say, 12 is provided to increase the bonding strength between the tappet bottom plate 16 and the tappet body 18.

Furthermore, in order to further increase the coupling strength between the tappet bottom plate 16 and the tappet body 18 in cooperation with the recessed groove 12, (in particular, the coupling strength against the push-up force of the valve cam acting on the lower surface of the tappet bottom plate 16 is increased). Hollow hole 24 in tappet body 18 (to ensure)
The inner diameter of the lower end portion adjacent to the tappet bottom plate is set sufficiently smaller than the outer diameter of the top surface of the tappet bottom plate 16, in other words, as shown on the right side of the center line 0-0, A configuration has been proposed in which the peripheral portion is largely overhung on the outer peripheral portion of the upper surface of the tappet bottom plate 16.

As a result of conducting various test studies on the tappet 10 having the above-mentioned structure, the coefficient of thermal expansion of the aluminum alloy is extremely large as compared with the coefficient of thermal expansion of the ceramics forming the tappet bottom plate 16, so that it is surrounded by the outer peripheral surface of the tappet bottom plate 16. It was found that cracks and fractures often occurred in the upper throat portion 26 of the formed recessed groove 12. The cause of the defects such as the cracks is, as shown in the right part of the figure, as shown by the arrow a in the figure due to the contraction of the aluminum alloy tappet body 18 having a large thermal expansion coefficient during solidification. A large compressive force acts on the throat portion 26 of the concave groove 12 and the lower end portion of the tappet body 18 is suppressed from shrinking in the radial direction by the tappet bottom plate 16 having a remarkably small coefficient of thermal expansion, whereas the tappet body 18 is Since the portion above the tappet bottom plate is allowed to freely contract, a bending moment as shown by an arrow M is generated in the throat portion 26 due to an inclined deformation as shown by a dashed line in the figure. It is presumed that, due to the action, as a result, a large stress is generated in the throat portion 26, which eventually develops into a crack and further progresses to fracture.

Therefore, as a measure for preventing damage to the throat portion 26, as shown on the left side of the center line 0-0 in FIG. 3, the inner diameter of the lower end portion of the hollow hole 24 of the tappet body 18 is set to the tappet bottom plate 16. By setting it slightly smaller than the outer diameter of the upper surface to reduce the amount of overhang on the upper surface of the tappet bottom plate at the inner peripheral portion of the tappet body, the compressive force a acting on the throat portion 26 is reduced and the influence of the bending moment M is reduced. Attempts were made to reduce it. By adopting this measure, it was confirmed that damage to the throat portion 26 of the tappet bottom plate 16 can be effectively avoided.
When the engine is assembled, the lower spherical surface of the push rod 20 is increased because the flat flat surface 28 on the upper surface of 16 is widened.
As a result, there is often a problem that 22 is erroneously assembled while being placed on the flat flat surface 28 as shown. The push rod 20 does not fit properly into the recess 14 of the tappet bottom plate 14 and has a flat flat surface.
If the engine is assembled in the state of being mounted on the 28, there is a risk that the valve train member may be seriously damaged in the subsequent trial operation and the like, and there is a problem that disassembling and reassembling the engine requires a lot of trouble.

The present invention was devised in view of the above circumstances, and improves the durability and reliability by solving the problems of the previously proposed tappet formed by casting and encapsulating a ceramic tappet bottom plate with an aluminum alloy, An object of the present invention is to provide a tappet in which a push rod can be assembled in a correct position when an engine is assembled.

(Means for Solving the Problems) In order to achieve the above object, a tappet according to the present invention is made of ceramics having excellent wear resistance, and a groove is provided around the outer peripheral surface of the tappet and at the center of the upper surface. A disk-shaped tappet bottom plate provided with a recess for receiving the spherical portion of the lower end of the push rod, and an aluminum alloy hollow cylindrical tappet body formed by integrally casting the tappet bottom plate, On the inner peripheral surface of the hollow hole adjacent to the tappet bottom plate of the tappet body, there are provided a plurality of fold-shaped projections each extending inward in the radial direction and guiding the spherical portion of the lower end of the push rod into the recess for fitting. It is characterized by being.

(Operation) According to the present invention, since the inner peripheral surface of the hollow hole adjacent to the tappet bottom plate of the tappet body is provided with a plurality of fold-shaped projections extending inward in the radial direction, it is possible to push at the time of assembling the engine. Since the lower end spherical surface of the rod slides along the surface of the fold-shaped protrusion and is guided and fitted into the recess on the upper surface of the tappet bottom plate, erroneous assembly is avoided. Further, by providing the fold-like protrusions, while avoiding an increase in stress acting on the throat portion of the concave groove formed on the outer peripheral surface of the tappet bottom plate, the coupling strength between the tappet body and the tappet bottom plate, especially the valve operating It is possible to sufficiently secure the coupling strength against the lift force of the cam.

(Embodiment) An embodiment of the present invention will be specifically described below with reference to FIGS. 1 and 2. (It should be noted that the same reference numerals are used for substantially the same members and parts as those of the above-mentioned proposed tappet.) As shown, a circle made of ceramics such as silicon nitride and sialon having excellent wear resistance. A groove 12 is surrounded on the outer peripheral surface of the plate-shaped or short cylinder tappet bottom plate 16, and a recess 14 for receiving the lower end spherical surface portion 22 of the push rod 20 is provided in the central portion of the upper surface. There is. Above tappet bottom plate 16
Is integrally cast by a hollow cylindrical tappet body 18 of a suitable aluminum alloy, preferably a hypereutectic aluminum-silicon alloy (e.g. American Aluminum Association Standard 390 alloy). A plurality of fold-shaped protrusions 30 extending in the radial direction are provided at the lower end portion of the hollow hole 24 of the tappet body 18 adjacent to the tappet bottom plate 16.

In the tappet 10 having the above-described structure, since a large number of fold-shaped projections 30 are provided on the inner peripheral surface of the lower end portion of the hollow hole 24 of the tappet body 18, the basic circle diameter d at the lower end of the hollow hole shown in FIG. Can be made sufficiently large to reduce the amount of overhang on the upper surface of the tappet bottom plate 16 (indicated by symbol c in FIG. 2). The aluminum alloy tappet body portion existing above the outer peripheral portion of the tappet bottom plate 16 is composed of a tubular or conical portion having the thickness of the above small overhang c and the fold-shaped projection 30, and the total volume thereof is sufficiently small. Therefore, at the time of solidification shrinkage of the aluminum alloy after casting, the compressive force a acting on the throat portion 26 above the concave groove 12 of the tappet bottom plate 16 and the compression force a based on the difference in coefficient of thermal expansion of wear between the aluminum alloy and the ceramics and Based on the bending moment M, the stress generated in the same portion can be sufficiently reduced to prevent the tappet bottom plate 16 from being damaged. Further, by the cooperative operation of the fold-shaped projections 30 and the groove 12 on the outer peripheral surface of the tappet bottom plate, it is possible to sufficiently secure the coupling strength between the tappet body 18 and the tappet bottom plate 16, and particularly to contact the lower surface of the tappet bottom plate. The fold-shaped projection 30 effectively acts on the pushing force of the valve operating cam. Furthermore, by providing the fold-shaped projection 30, the lower end spherical surface of the push rod 20 slides along the surface of the projection 30 during engine assembly and is guided into the recess 14 provided in the central portion of the upper surface of the tappet bottom plate 16. The push rod 20 and the tappet 10 can be easily and correctly assembled because they are fitted and fitted.

(Effect of the Invention) As described above, the tappet according to the present invention is made of ceramics having excellent wear resistance, and has a groove on the outer peripheral surface thereof and a spherical surface at the lower end of the push rod at the center of the upper surface. A disk-shaped tappet bottom plate provided with a recess for receiving the portion,
It consists of a hollow cylindrical tappet body made of aluminum alloy integrally formed by casting the tappet bottom plate.The tappet bottom plate of the tappet body extends radially inward on the inner peripheral surface of the hollow hole adjacent to the tappet bottom plate. The present invention is characterized in that a plurality of fold-shaped projections for guiding and fitting the spherical portion of the lower end of the push rod into the recess are provided, which is lighter in weight than conventional cast iron tappets, and has wear resistance and It is practically useful because it is possible to provide a tappet that has excellent durability and that can properly hold the relative position with the push rod when assembling the engine.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, FIG. 2 is a horizontal sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a vertical sectional view similar to FIG. It is a figure. 10 …… Tappet, 12 …… Recessed groove, 14 …… Recess, 16 …… Tappet bottom plate, 18 …… Tappet body, 30 …… Folded protrusion.

Claims (1)

[Scope of utility model registration request] 1. A ceramic material having excellent wear resistance,
Formed by integrally casting and encapsulating a disk-shaped tappet bottom plate having a concave groove on its outer peripheral surface and a recess for receiving the spherical portion of the lower end of the push rod in the center of the upper surface. And a hollow cylindrical tappet body made of aluminum alloy, the inner peripheral surface of the hollow hole adjacent to the tappet bottom plate of the tappet body, each extending radially inward, the spherical portion of the lower end of the push rod A tappet, which is provided with a plurality of fold-shaped projections that are guided and fitted into the recess.