JPH046769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a moving hardening method for surface hardening the inner surface of a bush or other cylindrical body using induction heating means.

(Prior art) Cylindrical bodies used as bushes etc. are usually small 40mmφ/50mml, and large cylindrical bodies 120mm.
It is within the range of about φ・150 mml. When surface hardening the inner surface of this kind of cylindrical body using induction heating means, one-shot hardening is performed on a member with a narrow distance between both end faces, such as a race member of a ball bearing...The entire length between both end faces and the entire inner surface Heating and cooling at once cannot be applied, and as shown in Figure 3a, transfer quenching is usually used.

In the figure, reference numeral 1 denotes a fixed base having a through hole in the center, and a rotary table 2 is placed on the fixed base 1. The rotary table 2 can be forcibly rotated on a fixed base because a drive roll 22 rotatably driven by, for example, a ball bearing 21 and a drive source (not shown) contacts the circumferential surface of the rotary table 2. Further, a through hole is provided in the center of the rotating table 2, and a heating coil shown as C and a cooling jacket shown as J fixed below the heating coil pass through the respective through holes of the fixed base 1 and the rotating table 2. It is set up so that it can be raised and lowered freely. Cylindrical body W
is placed so that one end surface is in contact with the positioning member 23 provided at the periphery of the through hole of the rotary table 2, and the heating coil C vertically rises from below the rotary table 2 and the cooling jacket J follows it. The rotating cylindrical body W is hardened sequentially from the lower end surface to the upper end surface.

(Problems to be Solved by the Invention) When measuring the inner diameters of both end surfaces of the cylinder W on which the surface hardening layer h is formed on the inner surface according to the above-mentioned moving hardening method, the inner diameter S of the end surface at the start of hardening is always the inner diameter F of the end surface at the end of hardening. Although the difference is smaller, it is larger, and furthermore, the measurement of the inner diameter of the intermediate part shows a tendency of increasing and decreasing as shown in Fig. 3b from the quenching start end to the end quenching end, so the inner surface of the quenched cylinder is not polished. Therefore, a post-process to correct the inner diameter was required.

For example, although this is a means to prevent deformation of the diameter of both end faces during hardening of the intermediate part of the inner surface of the cylinder,
Even if the rotatable lid 3 equipped with the annular protrusion 31 that restrains the inner periphery of the end face is placed over the rotating cylinder W and hardened in place or in a moving manner as shown in FIG. Heating coil C
is obstructed by the lid and cannot be heated over the entire length of the inner surface, and the cooling range of the cooling jacket J that follows the heating coil C is shorter than the heating range, so the hardening result is surface hardening as shown in Figure 4b. Not only does the range stay within the range shown as h,
A constriction occurs near the end of the hardening range h, which does not solve the problem at all.

(Object of the Invention) The purpose of the present invention is to prevent the phenomenon, which occurs when the inner surface of the cylinder is surface hardened over the entire length, that the inner diameter is large at the end surface at the start of hardening, and the inner diameter gradually becomes smaller toward the end surface at the end of hardening. It has been done.

(Summary of the Invention) The gist of the present invention is as follows: (1) In the case of surface hardening the inner surface of a cylindrical body using a heating coil that moves from one end face to the other end face and a cooling jacket that follows the heating coil, (2) arranging a plurality of freely rotatable or rotatably driven rollers having a length spanning the entire length of the cylinder along the outer circumferential longitudinal direction of the cylinder; (3) quenching the cylinder while each roller is rotating; A method for moving the inner surface of a cylindrical body, characterized in that hardening is performed while applying a circumferential restraining force that gradually decreases from the start end face side to the end end face side.

In making the present invention, the inventor first investigated the cause of the difference in the diameter of the cylinder after quenching, and at the end face side S where quenching starts, the cylindrical body W has its surface layer rapidly heated from room temperature to a predetermined quenching temperature and then rapidly cooled. However, as the moving hardening progresses, the heat of the heated part propagates toward the unheated part by heat conduction, so that the hardened end face side F
As time progresses, thermal deposition increases not only in the surface layer but throughout the entire layer, and as a result, the heat mass increases sequentially from the quenching start end side S to the end end side F,
It was determined that the larger the heat mass, the greater the contraction, causing the above results.

Based on the above judgment, the present invention restrains the cylindrical body W from the outer circumferential direction with a large restraining force at the quenching start end side S where the heat mass is small, so that the expansion during heating and the contraction during cooling are all carried out within the cylindrical wall. At the end end F, the cylindrical body W is restrained from the outer circumferential direction with a small restraining force to allow thermal expansion to freely move in and out of the cylindrical wall...while being restrained to the extent that deformation of the circumferential shape does not occur. This is based on the technical concept of averaging the amount of shrinkage by allowing the shrinkage to occur freely in and out of the cylinder wall during quenching.

Embodiment 1 FIGS. 1a and 1b show the case where the present invention is applied to the hardening apparatus shown in FIG. 3, which is shown as the conventional method described above.

In the figure, 1 is a fixed base, 2 is a rotary table that can be rotated by a driving roller 22, and C and J are heating coils and cooling jackets, respectively, through holes provided in the fixed base 1 and the rotary table 2. As mentioned above, it can be raised and lowered through the hole. In the embodiment of the present invention, a plurality of shafts 41 are vertically fixed at predetermined positions on the rotary table 2, and each of the shafts 41 has a predetermined tapered shape having a large diameter on the lower end surface side and a small diameter on the upper end surface side. A roller 4 is mounted so as to be freely rotatable. The roller 4 has a length that is at least longer than the axial length of the cylindrical body W, and the circumference is assumed to be large or small due to hardening, or the start of hardening is confirmed by preliminary experiments. The lower circumferential diameter is made larger and the upper circumferential diameter is made smaller depending on the difference between the inner diameter of the end face and the inner diameter of the end end face. The plurality of rollers 4 are disposed so that the lower periphery of each roller 4 tightly contacts the side periphery of the lower end surface of the unhardened cylindrical body W, which is placed at a predetermined quenching position on the periphery of the through hole of the rotary table 2. Ru.

The case where the cylindrical body W is hardened using the embodiment apparatus having the above configuration will be described below.

If the cylindrical body W is pushed between a plurality of upright rollers 4 and placed on the rotary table 2, the positioning will be determined automatically. Next, when the drive roller 22 is rotationally driven to rotate the rotary table, the rotary table 2 rotates with the cylindrical body W placed thereon, and at the same time, the shaft 41 vertically fixed on the rotary table 2 also rotates. Since it rotates with the axis of the cylinder W as the center of rotation,
The roller group 4, which is freely rotatably attached to the shaft 41 and has its lower periphery in contact with the lower end surface periphery of the cylindrical body W, is in a rotating state. Under this condition, the heating coil C and the cooling jacket J are raised to harden the inner surface of the cylindrical body W from its lower end surface to its upper end surface. On the lower end surface side of the cylinder W, that is, on the quenching start end S, the expansion of the cylinder wall heated by the heating coil C is regulated at the outer periphery by the lower periphery of the roller group 4, so that the axis of the cylinder W ie, toward the inner circumferential wall, and contraction due to rapid cooling also occurs toward the inner circumferential wall. In addition, on the upper end surface side of the cylinder W, that is, on the quenching end side F, the temperature of the cylindrical wall increases due to the heat conducted from the quenching start end direction and expands. Since the outer periphery in the side F direction is in a non-contact state with the upper periphery of the roller group 4 disposed around it before quenching, the expansion freely occurs in the inner and outer directions of the cylindrical wall, and at least The shape expands toward the outer periphery to the extent that no deformation occurs, and contraction due to rapid cooling also causes centripetal contraction toward the center of free expansion. The amount of expansion and contraction of the cylindrical wall occurs gradually from the quenching start end to the quenching end, and the restraining force from the outer circumferential direction is large at the quenching start end and small at the end. Since the taper is set gently, the inner periphery of the quenched cylinder W is balanced between the expansion/contraction and the restraining force from the outer periphery.
It is possible to finish the inner surface with a hardened layer that maintains a substantially uniform inner diameter from the end to the end face side F.

Embodiment 2 A second embodiment of the present invention will be described with reference to FIGS. 2a and 2b.

In the figure, 5 is a shaft 5 fixed at a predetermined inclination so as to be close to the axis Ow of the cylindrical body W placed on the rotary table 2 at the bottom and separated from the axis at the top.
1 is a parallel circumferential roller mounted so as to be freely rotatable. The outward inclination of the rotating shaft of the roller group 5 is made in accordance with the difference between the inner diameter of the end surface at the start of hardening and the inner diameter at the end end surface, which is assumed to be caused by hardening. The function of the roller 5 is exactly the same as that of the tapered roller 4 shown in the first embodiment.

(Other Embodiments) The above two embodiments are cases in which the present invention is implemented on a cylindrical body W placed on a rotary table 2 that is forcibly rotated by a drive roller 22, but the present invention is not limited to this, and is capable of freely rotating. A group of rollers may be used in which the cylindrical body placed on a rotary table is pivoted to a rotating shaft, each of which is rotationally driven by a drive source. In other words, a cylindrical body in which a tapered roller pivoted on a rotating shaft parallel to the axis of the cylindrical body or a roller with a parallel circumferential diameter pivoted on a rotating shaft inclined to the axis of the cylindrical body is mounted on a rotary table. In addition, the restraining force is arranged around the periphery so that it is large on the end surface side where quenching starts and small on the end surface side where quenching ends, and quenching is performed while rotating the cylindrical body together with the rotary table by the rotation of each roller. Good too.

In the device of the embodiment, the heating/cooling mechanism is inserted under the rotary table or into the cylindrical body to harden it while it is rising, but of course it can be inserted from the top to the bottom of the cylinder and quenched while it is rising. The same applies to the above case.

(Effects of the Invention) By implementing the present invention, the problem of the hardening finish that existed in the conventional moving hardening of the inner surface of the cylinder, in which the inner diameter at the start end of the hardening is large and the inner diameter at the end end of the hardening is small, is solved, and the overall length is reduced. Since the inner diameter can be finished in parallel across the length, the process of correcting the diameter difference by polishing, which was required after hardening, can be omitted, and the cylinder can be automatically positioned during the hardening process without a positioning member. The effect of uniformity is remarkable.

[Brief explanation of drawings]

1A and 1B are respectively a top view and a partially sectional front view of an apparatus according to an embodiment of the present invention, and FIGS. Figure 3a is a cross-sectional front view of the apparatus according to the conventional method, and Figure 3b is a cross-sectional front view of the cylinder to explain the problems that exist when the inner surface of the cylinder is moved and hardened using the apparatus shown in Figure 3a. FIG. 4a is a partially sectional front view of another conventional device, and FIG. 4b is a sectional front view of a cylindrical body for explaining that the device shown in FIG. 4a is unsuitable. 4, 5...roller, 41,51...rotating shaft, W
...Cylinder, C...Heating coil, J...Cooling jacket.

Claims (1)

[Scope of Claims] 1. When surface hardening the inner surface of a cylindrical body using a heating coil that moves from one end face to the other end face and a cooling jacket that follows the heating coil, the inner surface of the cylindrical body is A plurality of freely rotatable or rotatably driven rollers having a length spanning the entire length of the body are arranged, and each roller applies a circumferential restraining force that decreases the rotating cylindrical body from the quenching start end face side to the end face side. A method for moving and hardening an inner surface of a cylindrical body, characterized in that the inner surface of a cylinder is hardened while imparting the same. 2. A circumferential restraining force that gradually decreases from the quenching start end surface side to the end quenching end surface side makes the rotation axis parallel to the axis of the cylinder, and the quenching is performed according to the difference between the quenching start end surface inner diameter and the end end inner diameter caused by quenching. The inner surface of the cylindrical body according to claim 1 is applied by a tapered roller having a large outer circumferential diameter in the direction of the starting end face and a small outer circumferential diameter in the direction of the ending end face. Transfer quenching method. 3. A circumferential restraining force that gradually decreases from the quenching start end surface side to the end quenching end surface side causes the rotating shaft to start quenching with respect to the axis of the cylinder according to the difference between the quenching start end surface inner diameter and the end quenching end surface inner diameter caused by quenching. The method of moving the inner surface of a cylindrical body according to claim 1, characterized in that the hardening is applied by parallel circumferential rollers set so as to be inclined outward from the opposite end toward the end end. .