JPH1190736A - Shrink fitting fastening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a tooth part from softening caused by heating while shrink fitting. SOLUTION: A toothed gear 2, having a center hole 2a, a tooth part formed on its outer side surface, and a tooth bottom part, is fastened to a shaft member 1 by means of shrink fitting. The toothed gear 2 is heated while being held on a top surface of a middle diameter part 12 of the shaft member 1 by radiating a laser beam 3 onto the centripetal direction of the toothed gear 2 in the orthogonal direction to an axis line of the toothed gear 2 from outside to the outer side surface of the toothed gear 2. The laser beam 3 is radiated diagonally to the tooth part while being radiated orthogonally to the tooth bottom part, therefore, the tooth bottom part is actively heated and is expanded. At this time, as the tooth part is not so heated as the tooth bottom part, bad influence to heat treatment is avoided so as to surely ensure hardness and strength after performing heat treatment such as quench hardening treatment on the tooth part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrink fit fastening method, and more particularly, to a method of fastening a gear to a shaft member by laser shrink fitting.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
As a method of fastening the ring-shaped gear 90 having the above to the shaft member 91, a shrink fit fastening method is known. In this method, the gear 90 is heated to a predetermined temperature in a heating furnace and the center hole 90 is heated.
After the inner diameter of the gear 90a is expanded by heat expansion,
Is inserted and held in the fastening position of the shaft member 91. Then, the inner diameter of the center hole 90a of the gear 90 is reduced by cooling shrinkage, so that a fastening force is generated between the two members 90 and 91, and the two members 90 and 91 are fastened.

[0003]

However, the above-described conventional method using a heating furnace has the following problems. That is, the gear 90 is usually subjected to heat treatment such as quenching and hardening in order to improve the hardness and strength of the teeth and the like. However, when the entire gear 90 is uniformly heated in a heating furnace, the gears 90 have an annealing effect. Is softened.

[0004] The present invention has been made in view of the above circumstances, and a technique to solve the problem of providing a shrink fit fastening method that can solve the problem that the teeth are softened by heating during shrink fitting. It is an issue.

[0005]

According to the shrink-fit fastening method of the present invention for solving the above-mentioned problems, a gear having a center hole and a tooth portion and a tooth bottom formed on an outer peripheral side surface is shrink-fitted to a shaft member. Heating the gear by irradiating the outer peripheral surface of the gear with laser light traveling in the direction perpendicular to the axis of the gear and in the centripetal direction of the gear from the outer periphery of the gear, And a step of inserting and holding the heated gear at a fastening position of the shaft member to fasten the gear to the shaft member.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a shrink-fit fastening method according to the present invention, a gear having a center hole, a tooth portion and a tooth bottom formed on an outer peripheral side surface is shrink-fitted to a shaft member by using laser heating. To conclude. As for the type and size of the gear and the type of laser, the center hole of the gear is expanded by a predetermined amount by laser irradiation from the outer peripheral side so that the heated gear can be inserted into the fastening position of the shaft member. There is no particular limitation as long as it is possible.

[0007] Laser heating is performed by irradiating a laser beam traveling in a direction perpendicular to the axis of the gear and in the centripetal direction of the gear from the outer periphery of the gear to the outer peripheral side surface of the gear. This is, as shown in the example described later,
For example, the laser beam can be appropriately reflected by using a combination of a conical mirror having a conical side surface and a plurality of ring-shaped mirrors having a ring-shaped inclined surface inclined at a predetermined angle.

The heating condition by the laser is such that the center hole of the gear can be expanded by a predetermined amount by laser irradiation from the outer peripheral side so that the heated gear can be inserted into the fastening position of the shaft member. Can be set as appropriate according to the size, material, and the like. The holding of the gear during laser heating can be performed by bringing the axial end surface of the gear into contact with a fixing member, a holder, or the like.

The gear whose central hole has an inner diameter expanded by a predetermined amount by heating is inserted and held at the fastening position of the shaft member. Thereby, the center hole of the gear whose diameter has been increased by heating contracts by cooling, and the gear is fastened to the shaft member. Thus, in the shrink-fit fastening method of the present invention, the laser beam traveling in the direction perpendicular to the axis of the gear, and in the centripetal direction of the gear,
By irradiating the outer peripheral side of the gear from the outer periphery of the gear,
The gear is heated. According to such laser heating, while the laser beam irradiates the tooth bottom formed on the outer peripheral side surface of the gear at a right angle, and the laser beam irradiates the tooth obliquely, the energy of the tooth bottom is higher than that of the tooth. As the density increases, the degree of heating increases, and the tooth bottom is heated positively and expands. As a result, the inner diameter of the center hole of the gear is increased to such an extent that the heated gear can be inserted into the fastening position of the shaft member, and shrink fitting is possible.

At this time, since the degree of heating of the tooth portion is lower than that of the tooth bottom portion, adverse effects on the heat treatment can be avoided. Therefore, even if heat treatment such as quenching and hardening is performed to improve the hardness and strength of the tooth portion, the tooth portion is not softened by the annealing effect by heating at the time of shrink fitting, and heat treatment such as quench hardening is performed. Later hardness and strength can be reliably ensured.

In the shrink-fit fastening method according to the present invention,
From the viewpoint of maintaining good insertability between the heated gear and the shaft member, the laser heating is preferably performed in a state where the gear is brought as close as possible to the shaft member. Is preferably inserted into the fastening position. That is, in the conventional method of heating the entire gear in the furnace, when the heated gear is taken out of the furnace and transported to the shaft member, during the transport,
An oxide film may be formed on the entire outer surface of the gear that is entirely heated in the furnace. When an oxide film is formed on the inner peripheral surface of the center hole of the gear, the inner diameter of the center hole is reduced by the amount of the oxide film. In addition, during conveyance of the gear, the center hole of the gear may be reduced in diameter due to cooling and shrinkage under the influence of the environmental temperature. For this reason, the conventional method has a problem that the insertion of the heated gear is hindered.

On the other hand, in the method of the present invention utilizing laser heating, only the gear can be heated with the gear and the shaft member as close as possible, and the heated gear can be quickly moved to the fastening position of the shaft member. Can be inserted. According to this aspect, an oxide film is formed on the surface of the center hole of the gear, or the shrinkage due to the influence of the environmental temperature causes the center hole of the heated gear to be reduced in diameter. Good insertability of the gear into the shaft member can be maintained.

Further, in the shrink fit fastening method of the present invention,
The laser heating is preferably performed in a state where a laser light absorbing layer made of a material that more easily absorbs laser light is formed on the surface of the tooth bottom from the viewpoint of reducing the energy required for heating. According to this aspect, since the laser light applied to the gear tooth bottom can be more positively absorbed, the gear tooth bottom can be more selectively and more positively heated, It is possible to reduce the energy required for heating and shorten the heating time. Such a laser light absorbing layer can be formed, for example, by spraying and applying a carbon spray or the like to the tooth bottom.

Further, in the shrink fit fastening method of the present invention, the laser heating forms a laser light reflecting layer on the surface of the tooth portion and reduces the laser light reflection from the viewpoint of reducing energy required for heating. It is preferable that the reflection be performed in a state where a reflection mirror is appropriately arranged on the outer periphery of the gear so that the laser light reflected by the layer reaches the tooth bottom of the gear by reflection. According to this aspect, it is possible to irradiate the laser light applied to the gear tooth bottom to the gear tooth bottom by reflection, so that the gear tooth bottom can be more selectively used.
In addition, heating can be performed more positively, and it is possible to reduce the energy required for heating and shorten the heating time. Such a laser light reflecting layer can be formed by, for example, mirror-finishing the surface of the tooth portion, or applying a material that more easily reflects laser light.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the shrink-fit fastening method according to the present invention will be specifically described below. (Embodiment 1) In the method of this embodiment schematically shown in FIG. 1, a gear (ring gear) 2 having a center hole 2a is fastened to a shaft member 1 by shrink fitting using laser heating.

The shaft member 1 is made of carbon steel, has a large diameter portion 11 having an outer diameter substantially equal to the outer diameter of the gear 2, a smaller diameter than the outer diameter of the large diameter portion 11, and a center hole of the gear 2. An intermediate diameter portion 12 having an outer diameter equal to the inner diameter of 2a and a small diameter portion 13 having an outer diameter smaller than the outer diameter of the intermediate diameter portion 12 are integrally formed. The gear 2 is fastened to the base end of the middle diameter portion 12 (the lower end of the middle diameter portion 12 in FIG. 1).

The gear 2 is made of free-cutting steel.
As shown in FIG. 3, the outer peripheral side surface has tooth portions 21 and tooth bottom portions 22 alternately formed in the circumferential direction. The ratio occupied by the tooth portion 21 and the tooth bottom portion 22 is 3: 2 in the ratio of the circumferential length. That is, the circumferential length of the tooth bottom portion 22 is 40% of the entire circumference on the outer peripheral side surface of the gear 2.
Occupy.

In this embodiment, in the shaft member 1,
The outer diameter of the large diameter portion 11 is 128 mm, and the outer diameter of the middle diameter portion 12 is 1
The outer diameter of the small-diameter portion 13 is 50 mm. Also,
In the gear 2, the inner diameter of the center hole 2a is 120 mm, the axial thickness is 5 mm, the radial width from the surface of the tooth bottom 22 to the surface of the center hole 2a is 5 mm, and the radial width (height) of the tooth portion 21 is 3 mm. is there.

In this embodiment, first, the small diameter portion 13 of the shaft member 1 is
The center hole 2a of the gear 2 is inserted into the gear 2 and the gear 2 is placed on the front end surface of the middle diameter portion 12 (the upper surface of the middle diameter portion 12 in FIG. 1), thereby bringing the gear 2 as close as possible to the fastening position of the shaft member 1. (FIG. 1A). In addition,
As shown in FIG. 2, the axis of the shaft member 1 is perpendicular (see FIG. 2).
Up and down direction. The same applies hereinafter). Further, the gear 2 held by the middle diameter portion 12 of the shaft member 1
Are arranged such that the axis of the gear 2 coincides with the axis of the shaft member 1.

In this state, as shown in FIG. 1B, in a direction perpendicular to the axis of the gear 2, that is, in a horizontal direction (the left-right direction in FIG. 2; the same applies hereinafter) and the centering of the gear 2. The laser beam 3 traveling in the direction was uniformly irradiated in the circumferential direction from the outer periphery of the gear 2 to the outer peripheral side surface of the gear 2. this is,
As shown in FIG. 2, the laser irradiation apparatus 4 was used.

That is, the laser beam 3 emitted from the laser oscillator 41 in the horizontal direction is first applied to a flat mirror 42 arranged at an angle of 45 degrees so that the mirror surface faces obliquely downward, and the vertical direction (FIG. 2 downward). And, it has a conical inclined mirror surface which is disposed above the shaft member 1 so that its apex is located on the axis of the shaft member 1 and which is inclined at an angle of 45 degrees so that the mirror surface faces obliquely upward. The laser light 3 reflected by the flat mirror 42 was applied to the conical mirror 43, and the laser light 3 was reflected in the horizontal direction and in the centrifugal direction of the gear 2. The laser beam 3 reflected by the conical mirror 43 is uniformly distributed over the entire circumference. And it is arrange | positioned at the outer periphery of the conical mirror 43 so that the center may be located on the axis line of the shaft member 1,
A first ring-shaped mirror 4 having a ring-shaped inclined mirror surface inclined at an angle of 45 degrees so that the mirror surface faces obliquely downward;
4 was irradiated with the laser light 3 reflected by the conical mirror 43, and the laser light 3 was reflected in the vertical direction (downward in FIG. 2). Finally, a ring-shaped inclined mirror surface is provided on the outer periphery of the gear 2 so that its center is located on the axis of the shaft member 1, and is inclined at an angle of 45 degrees so that the mirror surface faces obliquely upward. The laser light 3 reflected by the first ring-shaped mirror 44 is applied to the second ring-shaped mirror 45, in a direction orthogonal to the axis of the gear 2, that is, in a horizontal direction, and
The laser beam 3 was reflected in the centripetal direction of the gear 2 and was uniformly irradiated in the circumferential direction from the outer periphery of the gear 2 to the outer peripheral side surface of the gear 2.

Here, the heating conditions by the laser irradiation device 4 are as follows. Laser: CO ₂ laser of 10 kW Irradiation time: about 6 seconds The above heating conditions were adjusted so that the inner diameter of the center hole 2a of the gear 2 was expanded by about 0.2 mm mainly due to the thermal expansion of the tooth bottom 22. It is. That is, in the present embodiment, on the outer peripheral side surface of the gear 2, the circumferential length of the tooth bottom 22 occupies 40% of the entire circumference. Here, when the entire gear 2 is heated and expanded, the inner diameter of the center hole 2a can be increased by about 0.2 mm by heating to about 140 ° C. On the other hand, in the present embodiment, it is necessary to increase the inner diameter of the center hole by a predetermined amount mainly due to the thermal expansion of the tooth bottom 22. When the inner diameter of the center hole 2a is increased by a predetermined amount by heating and expanding only the tooth bottom portion 22, the gear 2
The expansion amount of the tooth bottom portion 22 becomes about 2.5 times as compared with the case where the inner diameter of the center hole is expanded by a predetermined amount due to the overall thermal expansion. To expand the root 22 by about 2.5 times, it is necessary to heat the root 22 to about 320 ° C., and the amount of heat required for that is 42.7 kJ. Therefore, 10 kW
Irradiation was performed for about 6 seconds in consideration of the amount of reflection.

The gear 2 heated by the laser irradiator 4 as described above has a center hole 2a whose inner diameter is expanded by about 0.2 mm. To the middle diameter portion 12 of the shaft member 1.
(Fig. 1 (c))
State). By holding this state for about 10 seconds,
The gear 2 was fastened to the middle diameter portion 12 of the shaft member 1 by reducing the inner diameter of the center hole 2a due to cooling shrinkage.

In the shrink fit fastening method of the present embodiment described above,
As shown in FIG. 3, a laser beam 3 traveling in a direction orthogonal to the axis of the gear 2 and in a centripetal direction of the gear is
Irradiation is performed uniformly from the outer periphery of the gear 2 to the outer peripheral side surface of the gear 2 in the circumferential direction. For this reason, as shown in FIG. 4, the laser light 3 impinges on the tooth bottom 21 formed at the outer peripheral surface of the gear 2 at a right angle, while the laser light 3 impinges on the tooth 21 obliquely. Also, the energy density is higher in the tooth bottom 22 and the degree of heating is higher.
Are actively heated and expand. As the tooth bottom 22 is mainly heated and expanded in this way, the inner diameter of the center hole 2a is expanded to such an extent that the gear 2 can be inserted into the fastening position of the middle diameter portion 12, and shrink fit is possible. .

At this time, since the degree of heating of the tooth portion 21 is lower than that of the tooth bottom portion 22, adverse effects on the heat treatment can be avoided. Therefore, even if heat treatment such as quenching and hardening is performed in order to improve the hardness and strength of the tooth portion 21, the tooth portion 21 is not softened by the annealing effect due to the heating at the time of shrink fitting. Hardness and strength after heat treatment can be reliably ensured.

In the method of this embodiment, the gear 2 is inserted into the small diameter portion 13 of the shaft member 1 by inserting the center hole 2a of the gear 2 into the small diameter portion 13 and placing the gear 2 on the tip end surface of the medium diameter portion 12. Gear 2 is heated while being held as close as possible to the fastening position of the gear 2, and the gear 2 whose central hole 2a has an enlarged inner diameter due to thermal expansion immediately has the medium diameter portion 12 at the fastening position after the thermal expansion. Inserted and held at the base end of the For this reason, the center hole 2a of the heated gear 2 is less likely to be reduced in diameter due to the formation of an oxide film on the surface of the center hole 2a of the gear 2 or the cooling and shrinkage of the gear 2 under the influence of the environmental temperature. Thus, good insertability of the gear 2 into the middle diameter portion 12 can be maintained.

(Embodiment 2) In this embodiment, as shown in FIG. 5, a laser light absorbing layer 22a made of a material that more easily absorbs the laser light 3 is formed on the surface of the tooth bottom 22 of the gear 2. Specifically, the laser light absorbing layer 22a was formed by applying a carbon spray having a thickness of 10 μm as a material that more easily absorbs the laser light 3.

According to this embodiment, the laser beam 3 applied to the tooth bottom 22 of the gear 2 can be more positively absorbed by the laser light absorbing layer 22a, so that the tooth bottom 22 of the gear 2 can be selected more. The heating can be performed more actively and more positively, and the energy required for heating can be reduced and the heating time can be shortened. Note that the other configurations and operational effects are the same as those of the first embodiment.

(Embodiment 3) In this embodiment, as shown in FIG. 6, a laser light absorbing layer 22a is formed on the surface of the tooth bottom 22 of the gear 2 as in Embodiment 2, and the surface of the tooth 21 is formed. Was formed with a laser light reflecting layer 21a. The laser light reflecting layer 21a was formed by mirror-finishing the surface of the tooth portion 21. Due to the formation of the laser light reflecting layer 21a, the surface of the tooth portion 21 is made to reflect the laser light 3 more easily.

Further, a reflection mirror is appropriately arranged on the outer periphery of the gear 2 so that the laser light 3 reflected by the laser light reflection layer 21a reaches the tooth bottom 22 of the gear 2 by reflection. That is, as shown in FIG. 7, a ring-shaped semi-transmissive mirror 46 that can transmit all the laser light 3 entering from the back and reflect all the laser light 3 entering from the front is placed on the axis of the shaft member 1. It is arranged on the outer periphery of the gear 2 and on the inner periphery of the second ring-shaped mirror 45 so that its center is located at the center.

According to the present embodiment, the laser beam 3 applied to the tooth bottom 22 of the gear 2 can be more positively absorbed by the laser light absorbing layer 22a, and the laser beam 3 applied to the tooth 21 of the gear 2 can be absorbed. Laser light 3 to the laser light reflecting layer 2
After being reflected by 1a, the light can be reflected by the semi-transmissive mirror 46 and radiated to the tooth bottom 22, so that the tooth bottom 22 of the gear 2 can be more selectively and positively heated, It is possible to further reduce the energy required for heating and the heating time.

It should be noted that other structures, functions and effects are described in the first embodiment.
Is the same as

[0033]

As described in detail above, in the shrink-fit fastening method of the present invention, the gear is heated by irradiating the outer periphery of the gear with the laser beam in the centripetal direction. The bottom is selectively heat expanded to allow shrink fitting. For this reason, the tooth part has a lower heating degree than the tooth bottom part,
An adverse effect on the heat treatment can be avoided. Therefore,
Even if heat treatment such as quenching and hardening is performed to improve the hardness and strength of the teeth, the teeth are not softened by the annealing effect by heating at the time of shrink fitting, and after the heat treatment such as quench hardening. Hardness and strength can be reliably ensured.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating a shrink fit fastening method according to a first embodiment, where (a) shows a state in which a gear is held at a heating position, and (b) shows a state in which the gear is heated. State,
(C) shows a state where the heat-expanded gear is held at the fastening position.

FIG. 2 is a cross-sectional view illustrating a state in which a gear is heated by laser irradiation according to the first embodiment.

FIG. 3 is a partial plan view showing a state in which laser light is applied to a tooth portion and a tooth bottom portion of the gear according to the first embodiment.

FIG. 4 is a partial plan view illustrating a difference in the degree of heating between a tooth portion and a tooth bottom portion of the gear according to the first embodiment.

FIG. 5 is a partial cross-sectional view illustrating a state in which a laser light absorbing layer is formed on a tooth bottom of a gear according to the second embodiment.

FIG. 6 is a partial cross-sectional view illustrating a state in which a laser light absorbing layer is formed on a tooth bottom portion and a laser light reflecting layer is formed on a tooth portion according to the third embodiment.

FIG. 7 is a cross-sectional view illustrating how a gear is heated by laser irradiation according to the third embodiment.

FIG. 8 is a cross-sectional view illustrating a conventional shrink-fit fastening method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shaft member 2 ... Gear 3
... Laser light 4 ... Laser irradiation device 2a ... Center hole 21 ... Tooth part 22 ... Tooth bottom part

Claims (1)

[Claims] 1. A method of fastening a gear having a center hole and a tooth portion and a tooth bottom formed on an outer peripheral side surface to a shaft member by shrink fitting, the method comprising: A step of irradiating a laser beam traveling in a direction perpendicular to the direction of the gear and in the centripetal direction of the gear from the outer periphery of the gear to heat the gear, and inserting the heated gear into a fastening position of the shaft member; And holding the gear to the shaft member while holding the shaft.