JPH02212073A - Finishing method for hole internal face of work - Google Patents

Abstract

PURPOSE:To reduce working load and to generate no metal rise at the inlet port vicinity of the hole of a work by press-fitting the work part of a tool to the hole of the work while rotating it and performing a plastic working by the side contact. CONSTITUTION:A work part 12 is provided at the tip of a shaft part 11, a tool 10 made by locating at constant intervals on the concentric circle which is larger than the diameter of the shaft part the work face 13 in the specified shape of the work part 12, is used and while rotating the tool 10 the work part 12 is press-fitted to the hole 2 of a work 1. Thus the work part 12 is partially brought into contact with the hole 2 internal face of the work 1, the work load is reduced and this hole 2 is subjected to plastic working without accompanying the metal rise at the inlet port vicinity of the hole 2 of the work 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a processing method for finishing the inner surface of a hole in a workpiece by plastic working.

(Prior Art) Generally, an oil chamber 2 is provided in a crankshaft 1 for an automobile (see FIG. 5). This oil chamber 2 becomes a stress concentration area for the torsional force that occurs when driving a car.
It is the weakest part compared to other parts of the crankshaft 1. Particularly in high-output, high-speed crankshafts, there is a risk of breakage due to torsional resonance, and it is necessary to improve the strength of the material in order to prevent breakage. As an example of strength improvement measures, soft nitriding treatment using a gas or salt bath is often used. However, even if soft nitriding treatment is performed, there are cases where the strength is insufficient, and in this case, surface plastic processing It is known that it is effective to improve hardness (work hardening) by applying compressive residual stress. As this surface plastic processing method, there is a so-called ball threading method. In this ball threading method, as shown in FIG.
It is press-fitted into the oil chamber 2 to perform plastic working on the inner surface of the oil chamber 2 and improve the surface roughness.

(Problem to be Solved by the Invention) However, in the conventional finishing method described above, the ball 4 hits the inner surface of the oil chamber 2 all around, resulting in a high machining load, and machining is performed with such a high load. result,
For example, as shown in FIG. 6, the vicinity of the entrance of the oil chamber 2 may swell to form a raised portion 30 of meat.

There was also the problem that the crankshaft was bent and deformed.

The present invention has been made to solve the above-mentioned problems, and provides a method for finishing the inner surface of a hole in a workpiece by suppressing the machining load to a low level and preventing the formation of a raised portion of meat near the entrance of the hole. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a machined part at the tip of a shaft part, and forms a machined surface of a specific shape of the machined part on a concentric circle larger than the diameter of the shaft part. The method is characterized in that plastic working is performed by sliding contact by using tools positioned at regular intervals and press-fitting the machined part into the hole of the workpiece while rotating the tool.

(Function) According to the present invention, with the above-described configuration, the machining part comes into partial contact with the inner surface of the hole of the workpiece, and as a result, the machining load is reduced, so that no buildup of meat is generated near the entrance of the hole of the workpiece.

(Example) An example of the present invention will be described below with reference to the accompanying drawings. Note that the same parts as in FIG. 5 are indicated by the same reference numerals.

FIG. 1.2 shows a machining tool 10 used in an embodiment of the present invention. The machining tool 1O has a cylindrical shaft portion 11 with a diameter smaller than the inner diameter of the oil chamber 2 of the crankshaft 1. A processed portion 12 is connected to the tip of the shaft portion 11. The machining portion 12 has a substantially triangular shape when viewed from below the machining tool 10, and the machining surface 13 thereof has a spherical shape with a radius r+ when viewed from below. This machined surface 13 is arranged on a concentric circle centered on the axis G of the shaft portion 11 and has a radius r2 larger than the radius r0 of the shaft portion 11, and is intermittently in contact with the inner surface of the oil chamber 2. It has become. Note that when the processed portion 12 is viewed from the front, the processed surface 13 has a spherical shape with a radius r.

The operation of the machining tool IO configured in this way will be explained below. First, the machining part 13 of the machining tool IO is brought into contact with the oil chamber 2, and the tool 10 is pressed while being rotated. Then, the machining surface 13 of the machining section 12 comes into partial contact with the inner surface of the oil chamber 2, and the machining load is reduced. As a result, meat does not bulge near the entrance of the oil chamber 2.

Fig. 3.4 shows a machining tool 20 used in another embodiment. Unlike the previous embodiment in which the machining parts are provided in the same plane, the machining parts are provided in different cross sections along the axial direction. The feature is that it has been provided.

This tool 20 has a cylindrical shaft portion 21 having a diameter smaller than the inner diameter of the oil chamber 2 of the crankshaft 1.

A processed portion 22 is connected to the shaft portion 21 so as to wind the shaft portion 21 obliquely. The processed portion 22 has a portion between the upper and lower portions that protrudes compared to the diagonally upper and lower portions, and this portion forms a processed surface 23 . This processed surface 2
3 is arranged on a concentric circle centered on the axis G of the shaft portion 21 and having a radius r2 larger than the radius ro of the shaft portion 21, and is intermittently in contact with the inner surface of the oil chamber 2. There is.

Then, the machining portion 22 of the machining tool 20 is brought into contact with the oil chamber 2, and the tool 20 is pressed while being rotated. Then,
The processed surface 23 of the processed portion 22 partially contacts the inner surface of the oil chamber 2. Similarly to the processing tool IO described above, no buildup of meat occurs near the entrance of the oil chamber 2.

Note that in each of the embodiments described above, a crankshaft is used as an example of the workpiece, but the workpiece is not necessarily limited to this.

Further, the machined surface in each embodiment of the present invention is not limited to a perfect circle, but may be a curved surface made of a smooth curve such as an ellipse or a parabola.

Next, the results of comparison between the above-mentioned embodiment of the present invention and the conventional example will be shown. In this case, the crankshaft 1 is for a 4-cylinder, 4-cycle, 1600cc automobile, and the diameter of the armhole 2 is φ5.5. . Also, the bottle diameter is φ4.0
The sleeve hole 2 is formed perpendicular to the axial direction of the pin.

The material of the crankshaft l is general carbon steel S55,
In addition to being quenched and tempered, it is also treated with Tuftride. Note that the armhole 2 is reamed.

The data obtained by the machining method (hereinafter referred to as method A) using the pole burnish tool 5 shown in FIG.
8.9 Indicated by symbol A in the figure.

In this case, the machining allowance is set to 40 μm, and the standard dimension is φ5.5.
The ball 4 has a diameter 80 μm larger than that of the ball 4.

The data obtained by the machining method using the machining tool IO shown in FIGS. 1 and 2 (hereinafter referred to as method B) is shown in Section 7.8.
In this case, the radius r1 of the machined surface 13 is indicated by the symbol B in Figure 9.
is lI, and radius r is 2+++m. In addition, as in the case of method A, the processing allowance was set to 40 μm, and the standard dimension was φ5.5.
The processed surface 13 is formed so as to be 80 μm thicker than the other.

The data obtained by the machining method using the machining tool 20 shown in Fig. 3.4 (hereinafter referred to as method C) is shown in Section 7.8.
In this case, too, the machining allowance is 40 μm, and the machining surface 23 is formed to be 80 μm larger than the standard dimension φ5.5, which is indicated by the symbol C in FIG.

In the case of methods A, B, and C mentioned above, when investigating the machining load,
As shown in FIG. 7, it is clear that methods B and C can significantly reduce the machining load compared to method A.

The machining load in this case was the load when simply press-fitting in the axial direction without applying rotational torque.

In addition, the state of the swelling of the meat near the entrance of the sleeve hole 2 in the machining methods A, B, and C was examined and the machining accuracy was compared.

FIG. 8 shows the results of this comparison. In this case, method A resulted in an extremely large amount of meat buildup, whereas methods B and C eliminated the meat buildup, making it possible to improve processing accuracy.

Furthermore, when the accuracy of the runout of the crankshaft l obtained by methods A, B, and C was measured, the results shown in FIG. 9 were obtained. As a result, it has become clear that methods B and C can have a smaller effect on runout than method A.

Furthermore, when measuring the surface roughness, methods A, B, and C
It was found that data of 2 μm Rz or less could be obtained in any case.

(Effects of the Invention) As explained above, in the present invention, when a tool is brought into contact with a hole in a workpiece and rotated and pressed, only the machined surface that is formed so as to be intermittently in contact with the workpiece is turned into an inner surface of the hole in the workpiece. Since the machining load is reduced by sliding contact with the hole, it has the effect of preventing build-up of meat near the entrance of the hole in the workpiece. Further, since the machining load is reduced, the workpiece is not deformed, and the load on the machining tool itself is also reduced, so that breakage of the machining tool can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a processing tool used in one embodiment of the present invention, Fig. 2 is a bottom view showing the same processing tool, and Fig. 3 is a processing tool used in another embodiment of the invention. A front view showing the tool, Fig. 4 is a bottom view showing the same processing tool, Fig. 5 is a cross-sectional view showing an example of a conventional method for processing the inner surface of a hole in a workpiece, and Fig. 6 shows the thickness of the hole in the workpiece. Figures 7.8.9, 1, 2, 3, 4, and 5, showing the upward direction.
The test results obtained with the tools shown in the figures are shown, and FIG. 7 is a characteristic diagram showing the machining load, FIG. 8 is a characteristic diagram showing the amount of swelling, and FIG. 9 is a characteristic diagram showing the amount of change in runout. l...Crankshaft 2...Sleeve holes 10, 20...Machining tools 12, 22...Machining parts 13, 23...Machining surface Fig. 2 Fig. 3 Cause Fig. 4

Claims (1)

[Claims] A machining part is provided at the tip of the shaft part, and the machining surface of the particular shape of the machining part is positioned at regular intervals on a concentric circle larger than the diameter of the shaft part, using a tool, while rotating the tool. A method for finishing the inner surface of a hole in a workpiece, which is characterized by performing plastic working through sliding contact by press-fitting a processed part into the hole in the workpiece.