JPH07158503A - Manufacture of cylinder liner - Google Patents

Abstract

PURPOSE:To provide the manufacture of a cylinder liner in which the upper part of the cylinder liner is nitrided and its lower part is not nitrided. CONSTITUTION:A cylinder liner perform material 1a in which the inner diameter d of the lower part of the cylinder liner without nitriding is smaller than the inner diameter D of the inner surface of the cylinder liner 1 to be nitrided is prepared, and the cylinder liner preform material 1a is nitrided in a nitriding furnace, then the nitrided lower part of the cylinder liner 1 is machined so as to remove the nitrided surface layer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing a cylinder liner.

[0002]

2. Description of the Related Art In a cylinder liner of an internal combustion engine, a piston and a piston ring slide on the inside of the cylinder liner. Therefore, oil lubrication occurs, but wear occurs under severe lubrication conditions. Various surface treatments are known for their composition.

[0003]

However, in the above technique, there is a problem of wear of the top dead center portion above the oil ring which can be placed at the top dead center of the piston. There's a problem.

[0004]

[Knowledge] It has been found that when the cylinder liner has a higher hardness at the top dead center of the upper part and a softer lower part than the top dead center, the wear resistance is excellent over the entire area of the liner.

Further, it is known that the nitriding treatment increases the matrix hardness.

However, since the nitriding treatment is usually carried out in a furnace, it is difficult to perform the nitriding treatment only on the upper part of the cylinder liner, and the whole is nitrided. For this reason, a technique of partially performing nitriding treatment is known, but when it is applied to a cylinder liner, various difficulties are involved.

Therefore, an object of the present invention is to provide a method of manufacturing a cylinder liner in which the upper portion of the cylinder liner is nitrided and the lower portion is not nitrided.

[0008]

According to the present invention, a cylinder liner material is prepared in which the inner diameter of the inner surface portion of the cylinder liner subjected to the nitriding treatment is smaller than the inner diameter of the lower portion not subjected to the nitriding treatment. Provided is a method for manufacturing a cylinder liner, which comprises nitriding a cylinder liner material in a nitriding furnace and cutting the inner surface lower part of the nitrided cylinder liner to remove the nitrided surface layer. ing.

[0009]

[Description of Operation and Effect] In the method of manufacturing a cylinder liner configured as described above, the top dead center portion, which is the upper portion of the cylinder liner, is nitrided and the lower portion thereof is not nitrided.

Therefore, the upper portion of the liner is resistant to thermal deformation and has a high hardness, so that it is resistant to abrasion against reciprocating motion.

Further, since the portion not subjected to the nitriding treatment is relatively soft, it is resistant to abrasion in one direction and is effective in extending the life of the liner.

Further, no special member such as chromium or molybdenum is required, and the manufacturing control is easy.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, at the position of the top dead center of the piston 3 on the inner circumference of the cylinder liner 1, the 1st ring 4,
2nd ring 5 and oil ring 6 contact top dead center 2
Has undergone nitriding treatment 2b.

With reference to FIG. 2, the liner material 1a before the nitriding treatment has an inner diameter in a range 2a corresponding to the fulcrum portion 2 on the piston ring.
The inner diameter D is smaller than that of g) by the finishing margin g such that the nitriding portion remains after finishing.

Further, the inner diameter of the lower portion is set to an inner diameter d having a sufficient finishing allowance h so that the portion subjected to the nitriding treatment at the time of finishing does not remain. Therefore, if the material liner having the above dimensions is nitrided in the nitriding furnace and then finished, the nitriding portion 2b remains only at the top dead center portion 2 of the inner circumference of the liner.

Further, referring to FIGS. 3 and 4, the wear of the top dead center portion 2 of the cylinder liner is smaller when the matrix hardness is larger, and the matrix hardness of the lower liner bore is relatively small. As described above, it is found that the wear is smaller in the above case.

It is well known that the nitriding treatment increases the matrix hardness.

Therefore, in the cylinder liner 1 in which the top dead center portion 2 is subjected to the nitriding treatment and the lower portion thereof is pearlite ground, the wear resistance is improved over the entire inner circumference of the liner.

[0020]

Since the present invention is configured as described above, the wear resistance is improved over the entire area of the cylinder liner, the combustion gas sealability, the piston ring, and the liner durability are improved. Improves engine reliability and durability.

[Brief description of drawings]

FIG. 1 is a side sectional view of a cylinder liner showing an embodiment of the present invention.

FIG. 2 is a side sectional view showing a material shape of the liner of FIG. 1 before nitriding treatment.

FIG. 3 is a diagram showing a relationship between a liner top dead center wear amount and matrix hardness.

FIG. 4 is a diagram showing a relationship between a liner bore wear amount and matrix hardness.

[Explanation of symbols]

 1 ... Cylinder liner 2 ... Top dead center part 3 ... Piston 4 ... 1st ring 5 ... 2nd ring 6 ... Oil ring

Claims (1)

[Claims] 1. A cylinder liner material is prepared in which the inner diameter of the inner surface of the cylinder liner that is subjected to nitriding treatment is smaller than the inner diameter of the lower portion that is not subjected to nitriding treatment, and the cylinder liner material is nitrided in a nitriding treatment furnace. The method for producing a cylinder liner is characterized in that the inner surface lower part of the cylinder liner subjected to the nitriding treatment is cut to remove the surface layer subjected to the nitriding treatment.