JPS6156062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-precision machining method for crankshafts.

It is an object of the present invention to particularly prevent distortion of a crankshaft after grinding, and to prevent occurrence of journal runout and deterioration of stroke accuracy.

A further object of the present invention is to prevent the occurrence of grinding burns, grinding cracks, notches, etc. on the fillet portions of crank pins and journals.

It is well known that a crankshaft 1 of an internal combustion engine, etc., is composed of a crank journal 2 supported by a bearing and a crank pin 3 to which a connecting rod is attached, as shown in FIG.

Conventionally, the crank journal 2 and crank pin 3 have been ground by a plunge cut method using a grindstone 6 shaped into a general shape including a fillet portion 11 and an R portion 5, as shown in FIG.

Such conventional processing methods have the following disadvantages. That is, especially when induction hardening is applied to the fillet portion 11 and R portion 5, residual stress is released during grinding, causing bending of the crankshaft, deterioration of stroke accuracy, and journal runout.

In addition, since the fillet portion 11 and the R portion 5 have a large amount of machining allowance, the grindability is extremely poor, which requires a lot of machining time, and since both sides of the grindstone 6 cannot be dressed, grinding burn and grinding cracks are likely to occur. Ta. Furthermore, if both sides of the grindstone 6 are damaged due to wear or the like, a large amount of dressing is required in the radial direction, resulting in severe wear of the grindstone and shortening the usable life of the grindstone. In addition, in the case of a dressing method other than the full-form dress, the shaping accuracy of the joint between the fillet part 11 and the R part 5 is poor, and as a result, there is a gap between the ground fillet part 11 and the R part 5 as shown in FIG. There was a problem that such notches 7 were likely to occur and the strength of the R portion 5 was reduced.

The present invention provides a crankshaft grinding method that eliminates the various problems caused by the conventional plunge cut method using a grindstone. This method is characterized in that the outer diameter that remains is ground using a general grindstone.

A specific example of the processing method of the present invention will be described below with reference to FIG. In FIG. 5A, 2 is a crank journal, and its outer diameter fillet portion 11 and R
The portion 5 has a surface hardening layer 4 formed by induction hardening, and has a machining allowance 10 for grinding.

First, both fillet portions 11 and the R portion 5 of the crank journal 2 are simultaneously ground using a grindstone 8 by angular grinding. Through this first step of angular grinding, the surface of the fillet portion 11 and the concave curved portion 9 continuous to the surface of the fillet portion 11 of the R portion are formed at the same time, and a machining allowance 1 is formed on the outer diameter portion.
0 remains.

Next, as shown in FIG. 5B, the machining allowance 10 of the remaining outer diameter portion is removed using a general grindstone 6 having a width slightly smaller than the face-to-face dimension of the left and right fillet portions 11 after grinding in the first step. The second step is to grind the material.

As described above, in the first step, the fillet portion and the R portion are angularly ground in advance, and then in the second step, the outer diameter is ground using a general grindstone having a width smaller than the face-to-face dimension of the fillet portion that does not contact the surface of the fillet portion. Since it grinds the fillet part on both sides of the full-form grindstone, it eliminates the problem of grinding burn and grinding cracks on the fillet part, and reduces the grinding resistance of the full-form grindstone. However, the outer diameter part can be ground with high accuracy. It also has the effect of preventing wear on both sides of the full-form grindstone, which cannot be dressed.

Although the above embodiment describes the grinding of the crank journal 2, the crank pin 3 is also ground by the same method, and the same effect can be obtained.

As described above, the present invention solves all the drawbacks of conventional crankshaft processing methods and makes it possible to manufacture a crankshaft with very high precision.

[Brief explanation of the drawing]

Fig. 1 is a side view of the crankshaft, Fig. 2 is an enlarged sectional view taken along the lines of Fig. 1, Fig. 3 is a sectional view explaining the conventional processing method, and Fig. 4 is a sectional view of the fillet portion using the conventional processing method. , FIG. 5 shows an embodiment of the method of the present invention, FIG. 5A is a sectional view of the first step, and FIG.
Figure B is a cross-sectional view of the second step. 1... Crankshaft, 2... Crank journal, 3... Crank pin, 4... Hardened surface layer, 5... R part, 66... General grindstone, 8... Grinding wheel for angular grinding, 9... Concave Curved part, 10... Grinding allowance, 11... Fillet part.

Claims (1)

[Claims] 1. In a crankshaft in which a surface hardening layer is applied with a grinding allowance over the fillet portion, R portion, and outer diameter portion of the crankpin and crankshaft of the crankshaft, an angular grinding wheel is used to grind the fillet portion against the crankshaft axis. A first grinding step of simultaneously grinding the right-angled surface and the concave curved surface of the R portion, and a grinding process in which both sides of the grindstone have a width smaller than the face-to-face dimension of the fillet portion, in which a gap is formed between the surfaces of the fillet portion. A method for high-precision machining of a crankshaft, comprising: a second grinding step of grinding the outer diameter portion using a full-form grindstone.