JPH05156345A - High frequency induction quenching method to sprocket wheel segment for construction machine - Google Patents

Abstract

PURPOSE:To uniformly quench only positions to be quenched, such as tooth surface, tooth bottom in a sprocket wheel segment without overheat. CONSTITUTION:The sprocket wheel segment 2 of a construction machine is supplied and positioned in an induction heating coil 3 having cooling liquid spouting holes, and to the inner peripheral surface being unnecessary to quench, the cooling liquid is spouted during heating by the coil to restrain heating and only the outer peripheral surface having tooth part is heated to execute the quenching. The coil 3 is set so as to face at narrow interval to the outer peripheral surface side and face at comparatively wide interval to the inner peripheral surface being unnecessary to quench in the sprocket wheel segment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless track sprocket wheel for a construction machine, and more particularly to an induction hardening method for a sprocket wheel segment obtained by dividing the sprocket wheel into a plurality of segments.

[0002]

2. Description of the Related Art In a sprocket wheel for an endless track for a construction machine, a tooth surface or a tooth bottom portion (hereinafter referred to as a tooth portion) which is a contact surface with the endless track is required to have high hardness and wear resistance. The outer peripheral surface is quenched and hardened. As a quenching method, as shown in FIG. 6, a method is known in which a high-frequency induction coil 21 is arranged so as to face the outer peripheral surface of the sprocket wheel 20, and the stationary one-shot quenching is performed by induction hardening. Normally, the sprocket wheel is a single body as shown in FIG. 6, but in order to simplify the sprocket wheel replacement work that is performed at the construction site these days, as shown in FIG. 5, 4 to 6 sprocket wheels are used. The segment type sprocket wheel 23, which is obtained by assembling the divided segment 2, has been put to practical use. When the sprocket wheel segments 2 constituting such a segment type sprocket wheel are individually induction hardened as in the case of the integral type, not only the outer peripheral surface having teeth but also no need for hardening. There is a problem that the peripheral surface is hardened and it becomes difficult to machine the mounting portion of the inner peripheral surface after the quenching process. Therefore, in the conventional quenching of the sprocket wheel segment, only the tooth portion is quenched by single-tooth moving quenching.

[0003]

However, the one-tooth moving quenching has a very poor productivity, and in addition, an uncured portion is generated for each tooth, wear resistance is poor, and an overheated portion or the like is generated. There is a problem that a cured layer cannot be obtained and defective products are likely to occur. The present invention is intended to solve the above-mentioned problems of the prior art in the quenching of a sprocket wheel segment for an endless track for construction machinery, and to uniformly disperse only the tooth surface of the sprocket wheel segment, the bottom of the tooth, etc. It is an object of the present invention to provide an induction hardening method for a sprocket wheel segment that is hardened to a uniform depth and has a uniform hardened layer at a high depth without overheating and has excellent productivity.

[0004]

The induction hardening method for a sprocket wheel segment for a construction machine according to the present invention, which solves the above problems, sends a sprocket wheel segment for a construction machine into an induction heating coil having a coolant injection hole. The inner surface is heated and hardened by heating the inner peripheral surface by injecting a cooling liquid to the inner peripheral surface that does not require quench hardening during heating by the coil. Then, after heating, the outer peripheral surface is rapidly cooled for quenching. The coil faces the sprocket wheel segment on the outer peripheral surface side at an interval narrow enough to heat the outer peripheral surface, and on the inner peripheral surface that does not require quench hardening, about twice the interval on the outer peripheral surface. By arranging so as to face each other at a relatively wide interval, heat generation due to high frequency induction heating of the inner peripheral surface is effectively reduced.

[0005]

When the sprocket wheel segment is fed into the coil, the coil induces an induced current in the sprocket wheel segment, which is a conductive material, to heat the sprocket wheel segment, but at the same time, to the inner peripheral surface of the sprocket wheel segment. Since the cooling liquid is sprayed, the inner peripheral surface is always cooled during operation of the coil, and since the gap with the coil is large, the inner peripheral surface does not reach a high temperature and the cooling liquid is not supplied. Only the outer peripheral surface is heated to a predetermined quenching temperature. Therefore,
Even with stationary one-shot quenching, only the outer peripheral surface that needs to be hardened is hardened, and the inner peripheral surface that does not want to be hardened can be prevented, making it easy to machine in the subsequent process. You can get the product.

Further, since it is a one-time quench, the shape of the coil can be formed in conformity with the shape of the tooth portion, and the hardening of the outer peripheral surface which requires hardening can be performed under uniform conditions, and the sprocket wheel The tooth flanks / bottoms of the segments are hardened uniformly without overheating, resulting in a deep-hardened layer and a product with a long life. Further, since it is a one-time quenching, the work efficiency is very high and the productivity is improved as compared with the conventional one-tooth moving quenching. Therefore, even in the case of stationary one-shot quenching, only the outer peripheral surface that needs to be hardened is hardened, and the inner peripheral surface that does not want to be hardened can be prevented, which facilitates machining in the post process. We were able to obtain a good product.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an embodiment of an apparatus for carrying out the induction hardening method for sprocket wheel segments according to the present invention. In the drawing, reference numeral 1 is an induction hardening apparatus, and as shown in FIG. 5, a coil for induction heating having a structure for injecting a cooling liquid arranged so as to surround the outer peripheral portion of a sprocket wheel segment 2 into which a sprocket wheel is divided into four. Three
It has a stationary one-shot quenching structure. The coils 3 are arranged on the outer peripheral surface side of the tooth portion requiring quenching so as to face each other at a narrow interval enough to heat the outer peripheral surface according to the shape of the tooth portion, and do not require quenching other than the tooth portion. On the peripheral surface, they are arranged so as to face each other with a relatively wide interval. The distance between the inner peripheral surface of the sprocket wheel segment and the coil should be made as large as possible in order to suppress heating, but if it is too far away, power loss will occur, so about twice the distance on the outer peripheral surface is desirable. An outer peripheral facing surface 5 that faces the outer peripheral surface of the sprocket wheel segment 2,
2 and FIG. 3 on the inner peripheral facing surface 6 facing the inner peripheral surface.
Coolant injection holes 7 and 8 are respectively formed as shown in FIG. 4, but a cooling liquid passage 9 communicating with the cooling liquid injection hole 7 for injecting the cooling liquid on the outer peripheral surface and a cooling liquid injection hole for injecting the cooling liquid on the inner peripheral surface. The cooling liquid passages 10 communicating with the liquid injection holes 8 are respectively provided with the cooling liquid supply port 1
1, 1 and 12 are separately connected to a cooling liquid supply source via an electromagnetic valve (not shown) so that the cooling liquid injection timing can be controlled separately. The cooling liquid injection hole 7 for injecting the cooling liquid on the outer peripheral surface of the sprocket wheel segment 2 is
The sprocket wheel segment is provided with a high density so that the cooling liquid is sprayed uniformly and uniformly over the entire outer peripheral surface of the sprocket wheel segment to enhance the quenching effect. In the figure, 13 is a coil power source and 14 is a lead wire.

Hardening of the sprocket wheel segment is performed by the above induction hardening apparatus as follows. When the sprocket wheel segment 2 is supplied into the coil 3 by a work supply device (not shown), an induced current is induced in the sprocket wheel segment, which is a conductive material, by the coil 3, and the sprocket wheel segment However, at the same time, the cooling liquid is supplied into the cooling liquid supply passage 10, the cooling liquid is injected from the cooling liquid injection hole 8, and the cooling liquid is injected to the inner peripheral surface of the sprocket wheel segment.
Therefore, the inner peripheral surface of the sprocket wheel segment is always cooled during the operation of the coil, and since the gap between the coil and the coil is large, the inner peripheral surface does not reach a high temperature and the outer peripheral surface to which the cooling liquid is not supplied. Only is heated to a given quenching temperature. When the outer peripheral surface is heated to a predetermined temperature, the cooling liquid is supplied into the cooling liquid passage 9 and the cooling liquid is simultaneously ejected from the cooling liquid injection holes 7 to the outer peripheral surface, so that the teeth are rapidly cooled. As shown in FIG. 4, the quenching layer 15 with a high depth was formed only on the outer peripheral surface.

With respect to the thus-quenched endless track sprocket segment for construction machinery, a hardness test was conducted by selecting 5 points on the tooth surface and the tooth bottom. As a result, the surface hardness was HRC 56 to 58 at all measurement points. A uniform hardened layer was obtained. Further, the same measurement was performed on the inner peripheral surface other than the tooth portion, but the hardness of the inner peripheral surface was in the range of HRC18 to 20, and no hardened layer was observed.

[0010]

As is apparent from the above description, the present invention has the following special effects. Only the outer peripheral surface of the sprocket wheel segment, which requires hardening, can be hardened by stationary one-shot hardening, and a good product that can be easily machined in the subsequent process can be obtained. It was possible to dramatically improve the work efficiency of the quenching work of the sprocket wheel segment for the endless track of construction machinery, which was carried out. Also, since it is a one-time quenching, quenching of the outer peripheral surface that requires hardening is performed uniformly,
The tooth flanks and roots of the sprocket wheel segment are hardened uniformly without overheating, and a deep-hardened layer can be obtained, and the life of the sprocket wheel segment can be dramatically improved compared to conventional sprocket wheel segments. It was

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an induction hardening apparatus for carrying out the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a schematic diagram showing a quenched state of a sprocket segment.

FIG. 5 is a front view of a segmented sprocket wheel for an endless track of a construction machine.

FIG. 6 is a schematic view of a conventional induction hardening device for a sprocket wheel for an endless track of a construction machine.

[Explanation of symbols]

 1 Induction hardening device for sprocket wheel segment 2 Sprocket wheel segment 3 Coil 7, 8 Coolant injection hole 9, 10 Coolant passage

Claims (2)

[Claims] 1. A sprocket wheel segment for a construction machine is fed and positioned in an induction heating coil having a cooling water injection hole, and a cooling liquid is applied to an inner peripheral surface which does not require quench hardening during heating by the coil. To suppress the heating of the inner peripheral surface and heat only the outer peripheral surface having teeth to the quenching temperature,
A method for induction hardening a sprocket wheel segment for a construction machine, characterized by quenching by quenching the outer peripheral surface after heating. 2. The coil faces the sprocket wheel segment on the outer peripheral surface side at a narrow interval enough to heat the outer peripheral surface, and on the inner peripheral surface not requiring quench hardening at a relatively wide interval. The induction hardening method for a sprocket wheel segment for a construction machine according to claim 1, wherein the induction hardening is performed.