JPH10169415A - Tappet for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve baking resistance of a tappet for an internal combustion engine by forming the tappet in nearly cup shape, forming a sliding contact face, brought into sliding contact with a cam, of Fe alloy steel containing Cr, and applying nitriding to the sliding contact face of the tappet. SOLUTION: A tappet 8 and a push rod 7 are elevated by the rotation of a cam 11. In association with this, a locker arm 2 is oscillated, and an exhaust valve 1 of a diesel engine is elevated at specified strokes through this oscillation. In this case, the tappet 8 is formed being provided with a shallow, circular recessed part at the bottom part of a steel body part of cup shape, and a disc member 12 made of Fe alloy steel containing Cr is fitted into this recessed part. The disc member 12 is provided in such a way that its bottom part is protruded slightly to the lower side than the original bottom part of a body part. The flat bottom face of the disc member 12 is made a sliding contact face 8A, and nitriding is applied to a bottom part to be the sliding contact face 8A. Frictional resistance of the sliding conact face 8A of the tappet 8 is thereby reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tappet for an internal combustion engine, for example, a tappet suitable for use in a diesel engine.

[0002]

2. Description of the Related Art Heretofore, there has been known a tappet for an internal combustion engine which is formed in a substantially cup shape and has a sliding contact surface which is in sliding contact with a cam, and is interlocked with a valve via a push rod and a rocker arm.

[0003]

However, the conventional general tappet has a drawback that seizure is liable to occur on the sliding contact surface due to a large frictional resistance of the sliding contact surface in sliding contact with the cam.

[0004]

[Means for Solving the Problems] In view of such circumstances,
The present invention provides a tappet for an internal combustion engine which has a sliding contact surface formed substantially in a cup shape and which slides on a cam, and which is interlocked with a valve via a push rod and a rocker arm, wherein the sliding contact surface contains Cr. It is made of ferrous alloy steel and has a sliding surface subjected to a nitriding treatment.

[0005]

According to this structure, the frictional resistance of the sliding contact surface can be reduced, and since the sliding contact surface is nitrided, seizure is less likely to occur than in the prior art.
Therefore, the seizure resistance of the tappet can be improved as compared with the related art.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, reference numeral 1 denotes an exhaust valve of a diesel engine. The exhaust valve 1 is slidably fitted to a cylinder (not shown), and the upper end of the exhaust valve 1 is protruded above a cylinder block (not shown) and is in contact with the tip of the rocker arm 2. A compression spring 3 is elastically mounted between the distal end of the rocker arm 2 and the upper surface of the cylinder block, whereby the distal end of the rocker arm 2 is constantly urged upward. At the other end of the rocker arm 2, an adjusting screw 5 is screwed through from below, and a tightening nut 6 is screwed to the upper end of the adjusting screw 5. A circular concave portion is formed at the lower end of the adjusting screw 5, and the upper end of the push rod 7 is brought into contact with the circular concave portion. On the other hand, the lower end of the push rod 7 is in contact with the inner part of the tappet 8 formed in a substantially cup shape. The lowermost portion of the tappet 8 is a flat sliding contact surface 8A, and the sliding contact surface 8A is in sliding contact with the cam 11 rotated below the sliding contact surface 8A. The rotation of the cam 11 causes the tappet 8 and the push rod 7 to move up and down, whereby the rocker arm 2 swings and the exhaust valve 1 moves up and down at a predetermined stroke. By loosening the nut 6 and then turning the adjusting screw 5 by a required amount, the amount of elevating stroke of the exhaust valve 1 can be finely adjusted. Then
The tappet 8 of this embodiment is provided with a cup-shaped steel main body 8B as shown in an enlarged view in FIG. 2, and a shallow circular recess 8a is formed at the bottom of the main body 8B. I have. The disc-shaped member 12 is fitted into the recess 8a, and the bottom surface of the disc-shaped member 12 is slightly exposed to the lower side than the original bottom of the main body 8B.
The flat bottom surface of the exposed disk-shaped member 12 is defined as a sliding surface 8A. The disc-shaped member 12 is fitted into the recess 8a after applying a lubricant in advance, so that the disc-shaped member 12 is
, And can be relatively rotated in the circumferential direction within the concave portion 8a. Further, the disk-shaped member 12 of the present embodiment is made of Fe alloy steel containing Cr, and further has a nitriding treatment on the bottom portion to be the sliding contact surface 8A. It is preferable to set the content of Cr in the Fe alloy steel constituting the disc-shaped member 12 to 5 to 25 wt% from the viewpoint of preventing adhesion. Since the tappet 8 of the present embodiment is configured as described above, the sliding contact surface 8 </ b> A
Frictional resistance can be reduced. And sliding surface 8
Since A is subjected to the nitriding treatment, seizure is less likely to occur than in the conventional art, and therefore, the seizure resistance of the tappet 8 can be significantly improved as compared with the conventional art. Further, the disk-shaped member 12 having the sliding contact surface 8A as described above can relatively rotate in the circumferential direction in the concave portion. In addition, the tappet 8 of the above embodiment is a disc-shaped member 1.
2 is fitted into the recess 8a of the main body 8B so that the disc-shaped member 12 can rotate relative to the main body 8B in the circumferential direction, but the disc-shaped member 12 is fitted into the recess 8a. Alternatively, it may be fixed. Further, the tappet 8 of the above embodiment is used.
Is composed of two members, the disk-shaped member 12 and the main body 8B. In that case, the sliding contact surface 8A
Needless to say, nitriding is performed in the same manner as in the above embodiment.

[0007]

As described above, according to the present invention, the effect that the frictional resistance of the sliding surface of the tappet can be reduced can be obtained. Further, an effect is obtained that the seizure resistance of the tappet can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a cross-sectional front view showing a main part of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the tappet 8 shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Exhaust valve 2 Rocker arm 7 Push rod 8 Tappet 8A Sliding contact surface 8B Main part 12 Disc member

Claims (4)

[Claims] 1. A tappet for an internal combustion engine which is formed in a substantially cup-like shape and has a sliding contact surface which is in sliding contact with a cam, and which is interlocked with a valve via a push rod and a rocker arm. A tappet for an internal combustion engine, wherein the tappet is made of an Fe alloy steel containing steel and has a sliding surface subjected to a nitriding treatment. 2. The tappet for an internal combustion engine according to claim 1, wherein the entire tappet including the sliding contact surface is integrally formed. 3. The internal combustion engine according to claim 1, wherein the tappet comprises a disk-shaped member serving as the sliding contact surface, and a cup-shaped main body fitted with the disk-shaped member. For tappets. 4. The tappet includes a disc-shaped member serving as the sliding contact surface and a cup-shaped main body having the disc-shaped member fitted in a recess, and the disc-shaped member is disposed in the recess. 2. The apparatus according to claim 1, wherein the apparatus is configured to be rotatable in a circumferential direction.
6. A tappet for an internal combustion engine according to claim 1.