JPS58102818A - Processing of crank shaft - Google Patents

Abstract

PURPOSE:To enable the providing of remaining stress for improving mechanical strength easily by a method wherein a bending moment is given to a crank pin, and after a plastic deformation occurs in a crank corner fillet part on the journal axis side, the bending moment is released. CONSTITUTION:With one end 2a of the journal 2 of the crank shaft 1 fixed unmovably, the other end 2b of the journal 2 is pulled to exert a tension load P1 in the axial direction of the crank shaft 1. At this time opposing crank arms 3 are connected to the journal 2 by crank pins 4 at eccentric positions from the journal 2. Accordingly, the bending moment M1 to generate the tension stress onto the journal axis side of the crank pin 4 is given to the crank pin 4, and after the crank pin corner fillet part 4a on the journal 2 axis side is plastically deformed, the bending moment M1 is released to provide the corner fillet part 4 with the remaining stress.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a processing method for pre-applying compressive residual stress to the inside of a corner of a crankshaft to prevent stress concentration from occurring during use in rounding to increase fatigue strength.

As the above processing method, conventionally, the crank bin fillet Ws
A method of applying pressure and heat treatment has been adopted, but in these cases, the crank pin fillet part is difficult to machine due to both shape and space considerations, making the device complex in structure. However, it had the disadvantage that processing was time-consuming.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that can easily apply compressive residual stress to improve strength in terms of both equipment and labor.

Next, an embodiment of the present invention will be explained based on the drawings.
As shown in Figure 2, the crankshaft has a journal (2)
Fix one end (gm) so that it does not move, and journal (
2) Pull the other end (2b) 9 Apply a tensile load (Pθ) in the centrifugal direction to the crankshaft (11) At this time, the crankshaft (1) has its crank arms (3) facing each other on the journal (2). The structure is such that the crank pin (4) connects the crank pin (4) at an eccentric position.
) is applied to the crank pin (4) by a bending moment (MO) that causes a tensile stress on the journal (2) axis side.
Journal (2) Crank pin fillet on the shaft center side (4m)
Tensile stress concentrates on the crank pin (4c).
) is within the elastic deformation limit when plastic deformation occurs in the 2nd ink pin fillet (4 pins) on the 69 journal axis side, the application of tensile load (PR) is stopped and the application of bending moment (Ml) is canceled. do. Then, the crank pin parallel part (4c)
Since it is within the elastic deformation limit, it returns to its original undeformed state, but at this time, compressive force is applied to the crank bin fillet (mu), which is plastically deformed and elongated, so that the inside of the crank bin corner (4 m) A compressive residual stress remains.

In addition, a residual stress of tensile strength 9 remains in the crankshaft fillet (center) of the journal (2) other than on the axial center side.

The parallel part of the crank pin (4C) is within the elastic deformation limit, and the magnitude of the tensile load (Pt) that causes plastic deformation in the fillet part of the crank pin (4m) depends on the material 9 dimensions and shape of the crankshaft (1). Although it varies, as an example, Figure 8,
The test piece shown in FIG. 4 will be explained.

(1) Test piece material Material: FCD 90 Dimensions: (2) Residual compressive stress in crank pin fillet (4aL) after tension load P1 is released Residual compressive stress at crank pin fillet (4aL) when tensile load P1 is applied 2 inch pin fillet ζ- (The stress strain diagram of 4aJ and the parallel part of the crank pin (4c3) is shown in Figure 2.

In Figure 6, it can be seen that stress is concentrated at the crank pin fillet (4 m) and large strain is generated on the crank pin parallel part (4 ct) K. @6 tons of tensile load P1 is applied. FIG. 6 shows the distribution of residual compressive stress in the axial direction of the crank pin inside the corner of the 2nd link bin (4at) after release.

In Fig. 6, the two-dot chain line indicates the crank bin fillet (4a1
) indicates the R part, and the number 1 for residual stress indicates compressive residual stress. A tensile load P1 of 10 tons was applied, and the residual compressive stress distribution state in the crankpin radial direction at the crankpin fillet (411) K after the application was removed is shown in FIG.

In Fig. 7, the 8-dot chain line indicates the crank bin fillet (411
) is shown, and the residual stress symbol indicates the compressive residual stress.

Next, a tensile load of 6) was applied to the test piece shown in Fig. 8, and after the application was released, the test piece was cut at the gsaaoa-a position. Figure 8 shows the results of a strength test conducted using a journal Kt-Bopparner testing machine (5) K with a reverse shear load applied.

That is, the vertical axis shows the bending load (Ps), and the horizontal axis shows the number of times of repeated load application (b). The range indicated by the pair of solid lines is where the crankshaft to which compressive residual stress is applied is located, and is the range indicated by the pair of broken lines (B).
Fi, the crankshaft to which no compressive residual stress was applied is located. It can be seen from this that by applying compressive residual stress, the fatigue strength improved from α8- to 1.25-, or more than 60-.

In the above embodiment, a tensile load (Pl) in the axial direction is applied to bend the bending point (Ml) into a bending point (Ml).
However, as shown by symbol P2 in FIG. 1, a radial suppressing load (PI) may be applied to one end (8 m) of the crank arm to apply a bending moment to the second link pin (4).

To apply a tensile load to the second link shaft, fix the other end of the journal (8b) to the other end of the journal (gb) instead of pulling the other end of the journal (gb).

(Ba) may be pulled, or both the journal one end (gm) and the other end (2b) may be pulled.

In summary, the crankshaft processing method according to the present invention is as follows:
The bending moment that causes tensile stress on the journal (2) axis side of the two-ink pin (4) is within the elastic deformation limit.
) is characterized in that the application of the bending moment is canceled when plastic deformation occurs in the bending moment.

In other words, since it is only necessary to apply a bending moment to the crank pin (4), the necessary equipment can be installed with a simpler structure than in the past, and the processing time can be simplified.
Crankshafts with high fatigue strength can now be provided at low cost.

[Brief explanation of drawings]

FIG. 5 is a stress strain diagram when a tensile load is applied, FIGS. 6 and 7 are explanatory diagrams showing the residual stress distribution, and FIG. 8 is an explanatory diagram of the test results. (1)...Crankshaft, (21...Journal, (4)...Rip)/Kupin, (
4m)...Crank pin fillet on the journal axis side, (4c)...Crank pin parallel part. Fig. 5 Fig. 6 Oval 471 Butt power (弼M) Fig. 7

Claims (1)

[Claims] The bending moment that causes tensile stress on the axis of the journal (2) of the crank pin (4) is applied to the crank pin (4) K.
The parallel part of the crank pin (4c) is within the elastic deformation limit of the fillet part of the crank pin on the axis side of the foot journal (2).
4a) A method for processing a crankshaft, characterized in that the application of the bending moment is canceled when plastic deformation occurs in the crankshaft.