JPS6338565B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a crankshaft, and more particularly to a crankshaft in which a pin portion and a journal portion are surface hardened so that the depth of the hardened layer is continuously changed along the cylindrical direction of each bearing cylindrical portion. Generally, when surface hardening the bearing parts of the pin part and journal part of a crankshaft, a surface hardening method using high frequency induction heating is adopted as a means to minimize the distortion caused by heat treatment. Conventionally, as seen in the axial cross-sectional view of the crankshaft 10 shown in FIG.
14 and journal parts 21, 22, 23, 2
Surface hardening was applied only to the cylindrical bearing portions 30 and the hardened layer 40 of the bearings Nos. 4 and 25. On the other hand, in order to improve the strength of the crankshaft of the same size in response to the increase in horsepower of internal combustion engines, not only the bearing cylindrical portion 30 but also the curved portion continuing to the cylindrical portion 30 are A method of forming the surface hardening layer 50 on the portion including the portion 31 and the fillet portion 32 following it has come to be practiced. However, since the pin part and journal part of the crankshaft are not on the same axis and have a complicated curved shape, distortion occurs after surface hardening, which causes a great deal of trouble in the subsequent manufacturing process. The current situation is that, especially when a hardened layer pattern is formed over a wide area as shown in Figure 2 above, the distortion increases even more, and the amount of distortion that occurs makes it impossible to use the crankshaft. It often happens. When straightening distortion after surface hardening, if a hardened layer pattern as shown in Figure 2 is formed, there is a risk that the stress during straightening will be concentrated near the curved part 31, causing cracking, damage, etc. If the strain is extremely high and the strain generated during hardening is large, straightening work is almost impossible. The present invention has been made in view of the above points, and includes surface hardening of the bearing cylindrical portion of the hinge portion and the journal portion, and subsequent curved portions and fillet portions, and minimizes the amount of distortion generated. The object of the present invention is to provide a crankshaft that does not require straightening work after hardening. In order to prevent the occurrence of distortion, it is necessary to predict the amount and direction of distortion that will occur after quenching, and to form a hardened layer pattern that cancels out the internal residual stress that causes distortion. One method is to form a deviated hardened layer pattern whose depth varies in the circumferential direction, as opposed to the conventional uniform hardened layer pattern which has a uniform hardened layer depth in the circumferential direction as shown in FIG. Conceivable. However, the factors that determine the amount of distortion generated by hardening down to the curved and fillet parts of the crankshaft and the direction in which it shows its maximum value are complex, and the mutual interference effects of each factor have been recognized, so it is necessary to systematize them. It is extremely difficult to analyze it. Therefore, in order to determine these values experimentally, we repeated various experiments on crankshafts that had no residual internal stress due to processing that would promote distortion due to heating, and found that the maximum strain It was found that the following factors can be cited as factors that influence the amount and direction. (1) Material, pre-heat treatment, shape and dimensions of the crankshaft itself. (2) When surface hardening is performed on cylindrical parts, curved parts, and fillet parts by induction heating, (2,1) Effective hardened layer pattern and its depth. (2, 2) Quenching order of pin part and journal part. (2, 3) Tempering treatment method. Examples of the present invention carried out based on the above experiments will be described below. Figure 3 shows the surfaces of pin parts 11, 12, 13, 14 and journal parts 21, 22, 23, 24, 25 of a crankshaft used in a four-cylinder internal combustion engine in the order and conditions shown in Table 1. After quenching and tempering, hold both ends of the crankshaft at the center each time, and then tighten the journal parts 22 and 23.
and 24, which shows a polygonal line plotting the reading of the dial gauge in contact with 24. The broken lines in the figure show the state before quenching, and the orders 5' and 6' indicate the order 4 for separate test pieces.
In the next step, the journal part 2 is
The hardening method in No. 3 was changed from uniform hardening to deviation hardening. Further, deviation hardening and uniform hardening will be described later.

[Table] Furthermore, considering the above experimental results, the broken line in Figure 3 shows the state of the journal part 23 before quenching, and the journal part 23 is displaced by 0.63 mm in the direction shown in the figure, but it is evenly distributed in the journal part 23. In the case of hardening, there is a displacement of 0.42 mm in the opposite direction to the above, as shown by the broken line. This is because the mass near the fillet on the side shown in Figure 3 is smaller, so there is less heat conduction loss, and as a result, the accumulated heat affects the depth of the hardened layer in the fillet and curved parts, and This is thought to be because the axial elongation in the direction is considerably larger than the axial elongation in the direction. In contrast, as a result of applying deviation hardening to the journal portion 23, it is believed that by reducing the difference in elongation, good results as shown in FIG. 3 were obtained. FIG. 4 shows the formation of the hardened layer in the pin portion and journal portion in accordance with an embodiment of the present invention. That is, the total length is approximately 500 mm, and the pin half stroke is approximately
This is a crankshaft used in a 45mm four-cylinder internal combustion engine, and the bearing cylindrical part and the following curved part and fillet part are surface hardened, and all pin parts and journal parts 2.
3 has been subjected to deviation hardening, and the other journal parts have been uniformly hardened. In addition, in Figure 4, 10
1, 102, 103 and 104 are counterweights. The depth of the hardened layer of the pin parts 11, 12, 13, and 14 due to deviation hardening is approximately 50 mm in diameter.
The minimum value in the cylindrical part on the side far from the central axis of the crankshaft, that is, the top side t, is 3.2 mm,
The maximum value is 4.2 mm on the opposite web side w, which is 2.2 mm in the 45-degree direction of the curved portion, and 6.2 mm in the 45-degree direction of the curved portion. Regarding the journal part 23, for a cylindrical part with a diameter of 60 mm, the maximum value is 4.0 mm at the upper side of the figure, that is, the u part,
The minimum value is 3.3 mm on the lower side, that is, the d part, and the other journal parts other than 23 are 21, 22, and 2.
Nos. 4 and 25 are uniformly hardened to the same depth within the range of 3.3 to 3.5 mm. As explained above, in all pin parts and journal parts 23, the depth of the hardened surface layer when viewed from the circumferential direction is the same as the depth of the counterweight adjacent to each pin part or journal part 23 when viewed from the axial direction of the crankshaft. The plane that divides left and right symmetrically is each pin part or journal part 2
Among the ends of the diameter of each pin part or journal part 23 that intersect with 3, the maximum is at the end near the counterweight, the minimum is at the other end, and the maximum is at the intermediate part between both ends. A deviated hardened layer pattern is formed that gradually changes from the minimum to the maximum or from the minimum to the maximum. In the surface hardening, the optimum coil bodies are used for the pin part and the journal part, respectively.
The processing was performed one by one in the order of 1, 22, 24, 25, 21, and 23. Next, FIG. 5 is an explanatory diagram for explaining a surface hardening method for forming a hardened layer pattern with deviation. 80 is a high frequency coil body, which is the surface to be hardened, that is, the pin portion 11 of the crankshaft 10 in the figure.
The cylindrical part 30 is in contact with the part to be quenched via an insulating spacer 81, and during heating, as the part to be quenched revolves and rotates, the spacer 81 maintains a constant gap from the part to be quenched by means of a known pantograph mechanism. However, it follows the rotation of the crankshaft. On the other hand, when the crankshaft 10 is rotated, the pin part 11 rotates around its axis as shown by the arrow, and the coil body 80 slides with a constant gap maintained over the entire circumference of the cylindrical part of the pin part 11. During this time, a high frequency current is applied to the coil body 80. Here, a small current is passed in the section shown as θ in the figure at approximately 120 degrees, and a large current is passed in the other sections to heat it. After heating for an appropriate time, the surface of the surface to be hardened is rapidly cooled with a coolant. Then, the hardened layer is thick in the section where a large current is passed, and becomes gradually thinner in other sections, and the hardened layer with the minimum depth is obtained in the middle of the small current section. The above method is the same for the journal part, and by setting a limit switch or the like at the time of change of the high frequency current, surface hardening with deviation can be automatically performed. In this embodiment, a crankshaft for a four-cylinder internal combustion engine has been described, but the crankshaft is not limited to this, and a crankshaft for a six-cylinder or more cylinder engine can be manufactured in the same manner. In this case, it can be easily determined by a few experiments which journal and in which direction the deviation should be hardened. As described above, the present invention applies surface hardening not only to the cylindrical portions of the pin portions and journal portions of the crankshaft, but also to the curved portions and fillet portions formed at the ends of the cylindrical portions. In this case, the depth of the hardened surface layer of all the pin parts and one or more journal parts when viewed from the circumferential direction is the same as the depth of the counterweight adjacent to each pin part or journal part when viewed from the axial direction of the crankshaft. Among the ends of the diameter of each pin part or journal part, which are generated when the symmetrically dividing plane intersects with each pin part or journal part, the diameter is maximum at the end near the counterweight, and the diameter is maximum at the other end. It has a deviated hardening layer pattern that gradually changes from the maximum to the minimum or from the minimum to the maximum in the middle part of both ends, so it can respond to the increase in horsepower of the internal combustion engine and the amount of quenching distortion. This has the advantage of omitting press straightening after quenching and reducing the number of polishing steps.

[Brief explanation of the drawing]

Fig. 1 is an axial cross-sectional view of a crankshaft showing the hardening situation in a conventional example, Fig. 2 is a cross-sectional view when the range of surface hardening is expanded, and Fig. 3 is a graph plotting the amount of strain during hardening. FIG. 4 is a sectional view showing the hardening state of the product of the present invention, and FIG. 5 is an explanatory view of the deviation hardening method. 10...Crankshaft, 11, 12, 1
3, 14...pin part, 21, 22, 23, 24,
25...Shank portion, 80...Coil body, 10
1,102,103,104...Counterweight.

Claims (1)

[Claims] 1. In a crankshaft in which not only the cylindrical part of the pin part and journal part of the crankshaft, but also the curved part of the end that follows the same part and the fillet part that follows this curved part, are surface hardened, all pin parts and The depth of the surface hardened layer of one or more journal parts when viewed from the circumferential direction is such that the plane that symmetrically divides the counterweight adjacent to each of the pin parts or journal parts when viewed from the axial direction of the crankshaft is the same. Among the ends of the diameter of each of the pin parts or journal parts that intersect with the pin parts or journal parts, the diameter is maximum at the end near the counterweight, minimum at the other end, and both ends A crankshaft characterized in that the crankshaft has a deviated hardening layer pattern that gradually changes from the largest to the smallest or from the smallest to the largest in the middle part of the crankshaft.