JPH0360968A - Finishing method for inner surface of inner cylinder - Google Patents

Abstract

PURPOSE:To cause a useful root part to be left in a rough machined state by a method wherein only the machining grain of the crest part of the machining grains of the crest part and a root part, produced by machining, is removed. CONSTITUTION:When a grinding stone layer 3 of a grinding stone body is brought into pressure contact with the inner surface of a work, for example, a cylinder bore, after rough machining, the surface of the grinding stone layer 3 at the crest part is apt to sink due to burrs and pluck, and the crest part is gradually scraped off from a top. When a grinding stone layer 3 surface is brought into contact with the flat work surface of a rhombic part surrounded with a cross batch, abrasive grains are brought into a state that they are pushed deep in the grinding layer from a surface layer by means of a work surface, and further grinding is suppressed, and the work surface is finished. In this case, the machining grain of the root part of a machining rough grain is left as it is and an oil pit action is prevented from damage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a finishing method for finishing the inner surface of a cylinder bore of, for example, an internal combustion engine.

(Prior Art) Conventionally, for example, the inner surface of a cylinder bore of an internal combustion engine has been surface-finished using a finishing method with relatively high surface accuracy, such as honing.

This honing uses a rotating tool called a honing head, which has several grinding stones attached around a rotating main shaft.While pressing the horn (grinding stones) attached to this honing head against the inner surface of the cylinder bore, the honing head itself rotates and reciprocates. It performs internal grinding by movement, and the processing order is usually such that pre-processing is performed by rough processing, followed by precision finishing.

(Problems to be Solved by the Invention) The horn (grindstone) of the honing head as described above usually uses abrasive grains such as diamond, and since the horn (grindstone) moves while rotating on the inner surface of the cylinder, it is difficult to sharpen the honing head. The locus of the grains follows a helical trajectory, and cross hatches peculiar to the honing process as shown in Fig. 1-(B) are formed on the inner surface of the inner cylinder as the honing head reciprocates. If you look at the crosshatch intersection 4 after rough machining with a microscope, you will notice that many of the diamond-shaped parts have a 4th cross section relative to the reference work surface.
- (A) As shown in the figure, peaks such as cracks and rips, and valleys such as grooves are seen, and in the conventional case, this surface is finished with a hard diamond grindstone 5.
- (B) The finished surface had a rough curved surface as shown in the figure. In other words, although the roughness became finer, fine peaks such as cracks and rips and valleys such as grooves still remained. Grooves and other troughs act as oil pits that help retain and spread lubricating oil, so they are preferable from the standpoint of wear resistance, but conversely, ridges such as cracks and welts can damage the engine. This was not desirable because it adversely affected the piston and piston rings in the initial stage of use.

Furthermore, in the conventional processing method, as shown in FIG. 4-(C), there was a high risk that the peaks folded during finishing processing would fill the valleys.

(Means for Solving the Problems) In order to solve this problem, the present invention uses a honing stone to remove only the peaks of the peaks and valleys on the inner surface of the inner cylinder of the rough-machined workpiece. .

In addition, the honing stone is constructed with a flexible grindstone body based on a flexible material, and is subjected to finishing processing.

(Operation) Only the peaks can be scraped off, leaving the valleys for oil pits.

By making the grinding wheel body that is pressed against the workpiece surface flexible,
The surface layer of the grindstone sinks into contact with the protruding peaks on the surface of the workpiece, allowing only the peaks to be gradually scraped off.

Furthermore, when grinding is performed to the workpiece surface, the abrasive grains on the surface of the grindstone layer are pushed deep into the grindstone layer by the workpiece surface, suppressing further grinding and smoothing the workpiece surface.

(Example) A method for finishing the inner surface of a cylinder according to the present invention will be explained based on the attached drawings.

Figure 1 shows the processing method by honing, (A) is an explanatory diagram of the processing method, (B) is a partially enlarged view of the finished surface,
FIG. 2 is a sectional view showing the structure of the grinding wheel of the present invention, and FIG. 3 shows the roughness curve, where (A) shows the roughness curve, and (B) shows the grindstone after rough processing.

As mentioned above, honing is a process in which multiple horns (grindstones) attached around the honing head are pressed against the inner surface of the inner cylinder while performing a grinding finish using rotational and reciprocating motion. The trajectory of the inner surface of the inner cylinder is as shown in FIG. 1-(A). That is, the locus of the grinding wheel 1 that moves while rotating is highly twisted, and furthermore, since this movement is a reciprocating motion, a loss hatch is generated on the machined surface as shown in Figure (B).

The honing finish of the present invention is applied to more precisely finish the cylinder bore of an engine that has been roughly machined by honing as described above.

For this reason, the horn (grindstone) of the present invention is made into a flexible body by using a cork base 2 as shown in FIG. 2, and providing a grindstone layer 3 on this base 2. This grindstone layer 3 is formed by mixing diamond powder as an abrasive grain into a cork material, hardening it, forming it, attaching it to the base 2 by adhesion or other means, and using it as a finishing grindstone body. Also, this whetstone layer 3
The front surface of the cylinder has an arc-shaped cross section in accordance with the cylinder bore diameter.

The action and roughness curve when honing is performed using such a flexible grindstone body are shown in FIG.

That is, when the grinding wheel layer 3 of the grinding wheel body of the present invention is pressed against the surface of the workpiece after rough machining as shown in Fig. 3-(A), the surface layer of the grinding wheel layer 3 will be damaged in the peaks caused by cracks, scuffs, etc. It tends to sink, and the mountain is gradually scraped away from the top.

Eventually, when the surface of the grinding wheel layer comes into contact with the flat work surface of the diamond-shaped part surrounded by the crosshatches, the abrasive grains are pushed deep from the surface layer by the work surface, suppressing further grinding, and the work surface becomes flat. 3- (B) Finished as shown in figure. At this time, the valley portion of the rough machining hole remains as it is, and the oil pit effect is not impaired.

(Effects of the Invention) As described above, the finishing method of the present invention can effectively remove only the peaks such as cracks and cracks on the surface of the workpiece, while leaving the useful valleys as they are in the rough-cut state. Therefore, it is particularly suitable for finishing the cylinder bore of an internal combustion engine, and is effective in protecting the piston part of the engine.

[Brief explanation of drawings]

Figure 1 shows the machining method by honing, (A) is an explanatory diagram of the machining method, (8) is a partially enlarged view of the finished surface,
Fig. 2 is a sectional view showing the structure of the grinding wheel of the present invention, Figs. Figure 4 shows the conventional example after rough machining (A), after finishing machining (B), and (C). In the figure, 1 is a grindstone, 2 is a base, 3 is a grindstone layer, 4 is a crosshatch intersection, and 5 is a grindstone.

Claims (2)

[Claims] (1) In a method of finishing the inner surface of an inner cylinder by finishing the inner surface of a rough-machined workpiece with a honing stone, this method removes only the peaks of the peaks and valleys created by rough machining. A method for finishing the inner surface of an inner cylinder, characterized by: (2) The method for finishing the inner surface of an inner cylinder according to claim 1, wherein the honing stone is a flexible grindstone body based on a flexible material.