JPH1034312A - Manufacture of worm wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a worm wheel by a simple process and to prevent the development of abnormality on a tooth caused by bending stress on the root of tooth, etc., at the time of engaging the tooth with a rim. SOLUTION: A formed boss 1 in advance is charged into a forming mold, and the rim 3 is cast into the outer periphery of the boss 1 in the forming mold and the work wheel 6 composed of the boss 1 and the cast rim 3 is cooled. Thus, a plastic deformation is developed caused by cooling shrinkage to the joined part of the rim 3 and the boss 1, and a tensile residual stress of the rim 3 at the time of room temp. is reduced. By this method, in the case of being large tensile residual stress of the rim 3 developed to combine the rim 3 with the boss 1, the development of such trouble as to break, etc., at the time of engaging the worked tooth with the rim 1 is prevented from happening. Further, the development of abnormality of the tooth caused by the residual stress of the rim 3 is prevented by the manufacturing treatment with the simple process at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a worm wheel used as a reduction gear provided in an elevator hoist.

[0002]

2. Description of the Related Art FIG. 17 is a view showing a conventional worm wheel, and is a cross-sectional view along a rotation axis direction. In the drawing, 1 is a boss fixed to a shaft (not shown), 2 is a flange portion provided on the outer peripheral portion of the boss 1 and formed by retreating from a side surface, and 3 is a portion for processing a worm wheel gear. The rim has a fitting portion 4 facing the outer periphery and side surface of the flange portion 2 of the boss 1.

[0005] Reference numeral 5 denotes a fastener comprising a bolt inserted from the side surface of the rim 3 into the flange portion 2 of the boss 1 and a nut screwed into the insertion end of the bolt. Reference numeral 6 denotes a rim 3 fitted to the boss 1 for fastening. Boss 1 and rim 3
Is a worm wheel configured as a main part.

[0004] The conventional worm wheel is configured as described above, and the rim 3 is processed with teeth to produce a worm gear. Since the worm gear requires high strength and high wear resistance, for example, phosphor bronze is used as a material. However, since phosphor bronze is expensive, if the entire worm wheel 6 is made of phosphor bronze, the worm wheel 6 becomes expensive. In addition, phosphor bronze has a higher specific gravity than iron-based materials such as cast iron, so that the weight increases.

[0005] By forming the worm wheel 6 from the boss 1 made of cast iron and the rim 3 made of phosphor bronze for the above-described reason, the worm wheel 6 which is inexpensive and has high strength and abrasion resistance is manufactured.

FIG. 18 is a view showing another conventional worm wheel, and is a cross-sectional view taken along the rotation axis direction. In the figure, reference numeral 1 denotes a boss fixed to a shaft (not shown), and 3 denotes a rim which is cast on the outer periphery of the boss 1 formed in advance and constitutes a portion for processing a worm wheel gear. Reference numeral 6 denotes a worm wheel having the boss 1 and the rim 3 as main parts.

The other conventional worm wheel shown in FIG. 18 is constructed as described above, and the rim 3 is processed with teeth to produce a worm gear. Since the worm gear requires high strength and high wear resistance, for example, phosphor bronze is used as a material. However, since phosphor bronze is expensive, if the entire worm wheel 6 is made of phosphor bronze, the worm wheel 6 becomes expensive. In addition, phosphor bronze has a higher specific gravity than iron-based materials such as cast iron, so that the weight increases.

The worm wheel 6 is composed of the boss 1 made of cast iron and the rim 3 made of phosphor bronze for the above-described reason, so that the worm wheel 6 which is inexpensive and has high strength and abrasion resistance can be manufactured. Further, the fastener 5 in the worm wheel shown in FIG. 17 can be omitted, and machining and assembling operations of the flange portion 2 and the fitting portion 4 can be omitted, so that the worm wheel can be manufactured at low cost.

As a construction similar to the worm wheel shown in FIG. 18, as shown in Japanese Patent Application Laid-Open No. 58-128562, a portion corresponding to a rim in which a steel plate is pressed to form an annular ring and gear teeth is formed. There is a toothed transmission pulley having a boss formed by casting a light alloy therein.

[0010]

In the conventional worm wheel as described above, the construction shown in FIG. 17 requires an assembling operation in which the boss 1 and the rim 3 are separately manufactured, machined and fastened. There was a problem that the cost increased.

Also, in the configuration of FIG. 18 described above, the interference is generated by utilizing the fact that the rim 3 has a larger linear expansion coefficient of the material than the material of the boss 1, so that both the boss 1 and the rim 3 are connected. Are combined. For this reason, due to the influence of the tensile residual stress generated in the rim 3 due to an excessively increased interference, the tooth is damaged by the bending stress at the root of the tooth at the time of meshing of the teeth, and the processing is performed by the tensile residual stress of the rim 3. There has been a problem that the tooth may be deformed.

The present invention has been made to solve such a problem, and can be manufactured by a simple process.
It is another object of the present invention to provide a method of manufacturing a worm wheel in which an abnormality due to a bending stress of a root at the time of tooth engagement does not occur in a tooth.

[0013]

In a method for manufacturing a worm wheel according to the present invention, a boss formed in advance is placed in a molding die, and a rim is cast on the outer periphery of the boss by the molding die. The worm wheel formed by the rim is cooled to generate plastic deformation due to cooling shrinkage at the joint of the rim and the boss, thereby reducing the tensile residual stress of the rim at room temperature.

In the method for manufacturing a worm wheel according to the present invention, only the rim portion of the worm wheel formed by the boss and the cast rim is cooled,
Plastic deformation due to cooling shrinkage is generated at the joint portion of the rim with the boss, and the tensile residual stress of the rim at room temperature is reduced.

Further, in the method of manufacturing a worm wheel according to the present invention, the boss portion of the worm wheel formed by the boss and the cast rim is covered with heat insulating means, and the worm wheel is cooled to form the boss of the rim. Plastic deformation due to cooling shrinkage at the joints of the rims, reducing the tensile residual stress of the rim at room temperature.

In the method of manufacturing a worm wheel according to the present invention, a boss formed in advance is put into a molding die, and a rim is cast around the boss by the molding die while the boss is heated, so that the boss and the casting And reducing the tensile residual stress of the rim at room temperature of the worm wheel formed by the rim.

In the method of manufacturing a worm wheel according to the present invention, a boss formed in advance is put in a forming die, and the inner diameter of the boss is pressed to the outer periphery of the boss by the forming die in a state where the outer diameter is enlarged. The rim is cast and the boss pressure is released after casting to reduce the tensile residual stress of the rim in the worm wheel formed by the boss and the cast rim.

In the method for manufacturing a worm wheel according to the present invention, a boss formed in advance is put into a forming die, and a rim is cast on the outer periphery of the boss by the forming die, and the rim is formed by the boss and the cast rim. To reduce the tensile residual stress of the rim in a warm worm wheel.

In the method of manufacturing a worm wheel according to the present invention, the rim is provided with a holding portion projecting from the inner peripheral surface in the direction of the center of rotation and having a tip formed wider than the base. The boss is cast inside the rim by the mold around the holding portion of the rim, and the holding portion is pinched by the shrinkage of the boss after casting in the worm wheel formed by the rim and the cast boss. The pressure holds the rim to the boss.

Further, in the worm wheel manufacturing method according to the present invention, the rim is cooled during casting of the boss by the cooling mold provided on the molding die and arranged on the outer periphery of the rim.

Further, in the method for manufacturing a worm wheel according to the present invention, a boss is cast inside the rim by forming a heat insulating coating on the holding portion of the rim.

In the method for manufacturing a worm wheel according to the present invention, a heat insulating coating is formed on a holding portion of the rim, a boss is cast inside the rim, and the boss is provided on a molding die and disposed on the outer periphery of the rim. The rim is cooled at the time of casting the boss by the cooled cooling mold.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 and 2 are views showing an example of an embodiment of the present invention. FIG. 1 is a cross-sectional view along a rotation axis direction for explaining a worm wheel manufacturing state. FIG. 2 is a manufacturing process of the worm wheel in FIG. FIG. 3 is a stress-strain diagram of a rim material in FIG. In the drawing, reference numeral 1 denotes a boss made of cast iron fixed to a shaft (not shown), and 3 denotes a rim constituting a portion for processing a worm wheel gear, which is formed in advance from phosphor bronze having a larger linear expansion coefficient than the boss 1. The boss 1 is formed on the outer periphery of the boss 1 by casting through a molding die (not shown).

Reference numeral 6 denotes a worm wheel having the boss 1 and the rim 3 as main parts, 7 denotes a container containing the worm wheel 6, 8 denotes a cooling liquid contained in the container 7, containing liquid nitrogen and dry ice. It is made of a substance such as alcohol, which is inexpensive and has the ability to be easily cooled to room temperature or lower.

In the worm wheel manufacturing method described above, since the rim 3 has a larger linear expansion coefficient than the boss 1, after casting, the elasticity of the rim 3 is reduced by the difference in shrinkage between the boss 1 and the rim 3 during cooling. Deformation is hindered and interference occurs, and the boss 1 and the rim 3 are connected. However, since the elastic deformation of the rim 3 is prevented, a tensile residual stress is generated in the circumferential direction of the rim 3. For this reason, when the tensile residual stress is large, the teeth may be damaged or the teeth may be deformed due to the residual tensile stress when the teeth processed on the rim 3 are engaged.

The following cooling process is performed to prevent the occurrence of abnormalities in the teeth processed on the rim 3 as described above. That is, the worm wheel 6 on which the rim 3 is cast is immersed in the cooling liquid 8 of the container 7 after casting and cooled to about -180 ° C. As a result, the elastic deformation of the rim 3 is further increased due to a further increase in the interference, and when the proof strength of the material of the rim 3 is exceeded, a part of the joint between the boss 1 and the rim 3 is plastically deformed. When the temperature of the worm wheel 6 becomes room temperature, the tensile residual stress generated in the circumferential direction of the rim 3 decreases.

The effect of reducing the tensile residual stress will be described with reference to the diagram shown in FIG. That is, at the rim 3 portion of the worm wheel 6 manufactured by casting the rim 3, a tensile residual stress σ _a near the yield stress σ _y at a point A shown in FIG.
And the residual strain ε _a occur. Further, by further cooling the worm wheel 6 from room temperature, the interference increases, so that the distortion generated in the rim 3 also increases. From this state, the rim 3 material is cooled to a point B shown in FIG. 2 where a strain ε _b larger than a strain ε _y at which plastic deformation starts is generated.

Thereafter, when the temperature returns to the normal temperature shown at point C in FIG. 2, the tensile residual stress generated in the rim 3 becomes σ _c and the residual stress decreases. For this reason, when the tensile residual stress of the rim 3 generated due to the connection between the boss 1 and the rim 3 is large, it is possible to prevent problems such as breakage of the teeth machined on the rim 3 at the time of engagement. In addition, the effect of preventing the occurrence of abnormal teeth due to the residual tensile stress of the rim 3 can be obtained by an inexpensive manufacturing method using a simple process.

Embodiment 2 FIG. 3 is a view showing an example of another embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis for explaining a manufacturing state of the worm wheel. In the figures, the same reference numerals as those in FIGS. 1 and 2 denote corresponding parts, and 9 denotes a shaft fitted and fixed to the boss 1.

In the worm wheel manufacturing method as described above, the worm wheel 6 is
As shown in (1), only the rim 3 is immersed in the cooling liquid 8 stored in the container 7 and cooled to about -180 ° C.
Therefore, although detailed description is omitted, the same operation as the embodiment of FIGS. 1 and 2 can be obtained in the embodiment of FIG.

In the embodiment shown in FIG. 3, only the rim 3 is cooled, so that the difference in the amount of contraction between the boss 1 and the rim 3 is further increased. As a result, the distortion generated in the rim 3 is likely to increase, and a more effective residual stress reducing action after cooling can be obtained.

Embodiment 3 FIG. FIG. 4 is also a view showing an example of another embodiment of the present invention, and is a cross-sectional view along a rotation axis direction for explaining a worm wheel manufacturing state. In the figures, the same reference numerals as those in FIGS. 1 and 2 denote corresponding parts, and 10 is a heat insulating means which can be used under extremely low temperature conditions, for example, a heat insulating sheet formed by impregnating a glass cloth with an epoxy resin into a prepreg shape. It is attached to the outer surface of the boss 1 excluding the contact surface with the rim 3.

In the worm wheel manufacturing method as described above, the boss 1 is covered by the heat insulating means 10 and the worm wheel 6 is cooled by the cooling liquid 8 in the container 7 as shown in FIG.
And cooled to about -180 ° C. Therefore, although detailed description is omitted, the same operation as the embodiment of FIGS. 1 and 2 can be obtained in the embodiment of FIG.

In the embodiment shown in FIG.
Is covered by the heat insulating means 10, the cooling effect is larger at the rim 3 than at the boss 1. For this reason, the difference between the contraction amounts of the boss 1 and the rim 3 is further increased. As a result, the distortion generated in the rim 3 is likely to increase, and a more effective residual stress reducing action after cooling can be obtained.

Embodiment 4 FIG. FIG. 5 is also a view showing an example of another embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis for explaining a manufacturing state of the worm wheel. In the drawings, the same reference numerals as those in FIGS. 1 and 2 denote corresponding parts, 11 is a molding die made of a sand mold in which a preformed boss 1 is housed, 12 is a casting frame provided around the molding die 11, 13 Is a heater comprising a ceramic fiber heater or the like fitted in the shaft hole of the boss 1.

In the worm wheel manufacturing method as described above, the rim 3 is cast on the outer periphery of the boss 1 while the boss 1 formed in advance and arranged in the mold 11 is heated by the heater 13. Shown in described below in the circumferential direction of the tensile residual relationship stress sigma _theta and interference δ occurring tooth bottom position of the gear in the rim 3 when the formula (1) to (3).

[0037]

(Equation 1)

From the equation of the yakisame cylinder

[0039]

(Equation 2)

[0040]

(Equation 3)

Here, a: boss inner diameter b: radius of joint (outer diameter of boss = inner diameter of rim) c: rim outer diameter α _R : linear expansion coefficient of rim α _B : linear expansion coefficient of boss p: junction Pressure in the radial direction ΔT _R : T _RE -room temperature

[0042] [Delta] T _B :( rim of the boss at the time T _RE Temperature) - unheated A: constant determined by the shape of the boss and the rim r: tooth bottom position of the gear E ₁ =: modulus of longitudinal elasticity of the boss material E ₂ =: Longitudinal modulus of rim material ν ₁ =: Poisson's ratio of boss material ν ₂ =: Poisson's ratio of boss material

For example, the material of the rim 3 is phosphor bronze, the boss 1
Is cast iron, the temperature at which plastic deformation changes to elastic deformation in the cooling process after casting is higher than that of the boss 1 in the rim 3.
Is lower. Therefore, when the rim 3 material is a temperature change in the elastic deformation and T _RE from the plastic deformation in the cooling process,
The interference is determined by the difference in the amount of shrinkage between the boss 1 and the rim 3 from the time when the temperature of the rim 3 is _TRE to room temperature.

Then, at the temperature T _RE , the boss 1 and the rim 3
At the same temperature, the rim 3 has a larger linear expansion coefficient than the boss 1, so that the contraction amount of the rim 3> the contraction amount of the boss 1, and the tensile residual stress in the circumferential direction increases. On the other hand, the boss 1 is heated by the heater 13 to increase the temperature of the boss 1 when the temperature of the rim 3 reaches _TRE , whereby the tensile residual stress can be reduced.

Therefore, when the tensile residual stress of the rim 3 generated for connecting the boss 1 and the rim 3 is large, problems such as breakage of the teeth processed on the rim 3 at the time of engagement are prevented. can do. Then, such an effect of preventing abnormalities of the teeth due to the residual tensile stress of the rim 3 can be obtained by an inexpensive manufacturing method using a simple process. The heating temperature of the boss 1 is determined by the equations (1) to (3) to determine the difference in the coefficient of linear expansion between the boss 1 material and the rim 3 material, the allowable residual stress when the teeth mesh with each other, and the joint portion between the boss 1 and the rim 3 Is determined based on the required holding force.

Embodiment 5 FIG. FIG. 6 is also a view showing an example of another embodiment of the present invention, and is a cross-sectional view taken along the direction of a rotation axis for explaining a manufacturing state of a worm wheel. In the figures, the same reference numerals as in FIGS. 1 and 2 denote corresponding parts, 14 is a tapered hole formed in the shaft hole of the boss 1, and 15 is a punch having a tapered portion 16 corresponding to the tapered hole 14.

In the worm wheel manufacturing method described above, the preformed boss 1 is put into a forming die, and the tapered portion 16 of the punch 15 is press-fitted into the tapered hole 14. Then, the rim 3 is cast on the outer periphery of the boss 1 in a state where the inner periphery of the boss 1 is pressed by the punch 15, and the punch 15 is removed after cooling.

That is, pressure is applied to the inner periphery of the boss 1 to widen the outer periphery of the boss 1, and the punch 15 is removed after casting to reduce the pressure on the inner periphery of the boss 1 so that the interference is not excessively large. That is, the worm wheel 6 with reduced residual stress can be obtained. Therefore, although detailed description is omitted, the same operation as the embodiment of FIGS. 1 and 2 can be obtained in the embodiment of FIG.

The pressure p _Q applied to the inner periphery of the boss 1 is determined by the following equation (4) and the above-mentioned equations (1) to (3) to determine the coefficient of linear expansion of the material and the allowable residual when the teeth mesh. It is determined based on the stress and the required holding force of the joint between the boss 1 and the rim 3.

[0050]

(Equation 4)

Here, δ ': interference generated by applying pressure to the inside of the boss δ: interference generated when no pressure is applied to the inside of the boss (Equation (1)) E ₁ : elastic modulus of the boss material a : Boss inner diameter b: Radius of joint (boss outer diameter = rim inner diameter) p _Q : Radial pressure applied to boss inside

Embodiment 6 FIG. FIG. 7 is also a view showing an example of another embodiment of the present invention, and is a cross-sectional view along a rotation axis direction for explaining a worm wheel manufacturing state. In the drawings, the same reference numerals as those in FIGS. 1 and 2 denote corresponding parts, and 3 denotes a rim having a T-shaped cross section in the radial direction, a thickness in the radial direction set to a dimension M shown in FIG. The thickness in the direction along the axis is formed to the dimension N shown in FIG.

In the worm wheel manufacturing method described above, the boss 1 formed in advance is put into a mold, and the rim 3 is cast on the outer periphery of the boss 1. And rim 3
In the radial cross section, the ratio of the radial thickness M of the rim 3 is increased, and the thickness N of the rim 3 in the direction along the rotation axis is reduced except for portions necessary for the function and strength as a gear.

That is, the thickness M of the rim 3 in the radial direction is changed as described below. That is, the above equation
In equations (1) to (3), E ₁ = E ₂ , ν ₁ =
Assuming that ν ₂ and a term determined by the casting conditions and the materials of the rim 3 and the boss 1 are A = (α _R ΔT _R −α _B ΔT _B ), the following equation (5) is obtained.

[0055]

(Equation 5)

In equation (5), the inner diameter a of the boss 1 and the outer diameter c of the rim are kept constant, and the inner diameter M of the rim 3 in the radial direction is changed by changing the inner diameter b of the rim 3 (outer diameter of the boss 1). . Then, in equation (5), b is small, that is, the rim 3
When the thickness M in the radial direction is increased, the residual stress generated in the circumferential direction at the tooth bottom position can be reduced. Thus, it is possible to prevent the occurrence of abnormalities in the teeth due to the residual tensile stress at the bottom of the tooth, and it is possible to obtain the effect of preventing the occurrence of abnormalities by an inexpensive manufacturing method using simple steps.

For example, as shown in FIG. 7, the rim 3 has a T-shaped cross section in the radial direction, the radial thickness M of the rim 3 is increased, and the thickness N in the direction along the rotation axis is more than necessary. Do not increase. As a result, the amount of material generated in the rim 3 made of phosphor bronze is substantially the same as that of the rim 3 in the case where the rim 3 is fastened to the boss 1 shown in FIG. Can be reduced.

The material cost of the rim 3 can be reduced, and the worm wheel 6 can be manufactured at low cost. As a matter of course, by applying the method in the embodiment of FIG. 7 and changing the cross-sectional shape of the rim 3 in the radial direction to a cross-sectional shape other than the T-shape shown in FIG. A similar effect can be obtained.

Embodiment 7 FIG. 8 and 9 also show an example of another embodiment of the present invention. FIG. 8 is a perspective view showing a main part of the rim cut away, and FIG. 9 is an enlarged sectional view of the rim shown in FIG. FIG. Reference numeral 3 denotes a rim, and 17 denotes a plurality of holding portions projecting from the inner peripheral surface of the rim 3 toward the center of rotation.
It is arranged at the center of the wall thickness in the direction along the rotation axis, and in the cross section along the radial direction, the rotation center side is formed in a tapered shape that is formed wide, and at the corner of the base and the corner of the protrusion. Is provided with a chamfered portion 18. 19
Is a locking portion constituted by mutually opposed side walls of the holding portion 17.

In the worm wheel manufacturing method as described above, a boss (not shown) corresponding to the boss 1 in FIG. Cast to surround. And
Since the shrinkage of the boss is larger than the shrinkage of the rim 3 in the cooling process after casting, a gap is generated between the boss and the rim 3. However, the tapered surface of the rim 3 holding portion 17 is pressed by the boss. Thereby, the boss and the rim 3 are mutually held by the frictional force, and oppose the torque acting on the worm wheel similar to that of FIG. 1 described above.

Even if the holding force between the boss and the rim 3 is insufficient for the torque acting on the worm wheel, the boss is formed by the boss fitting portion (not shown) formed between the locking portions 19. Relative displacement between the and the rim 3 can be prevented. In the worm wheel in which the boss is cast, the residual stress of the rim 3 is small, and it is possible to prevent problems such as breakage of the teeth formed on the rim 3 at the time of meshing, and to prevent the rim 3 from remaining in tension. The effect of preventing abnormalities in teeth due to stress can be obtained by an inexpensive manufacturing method using a simple process.

Embodiment 8 FIG. FIG. 10 is also a view showing an example of another embodiment of the present invention. FIG. 10 is a perspective view showing a main part of the rim in a cutaway view. A worm wheel is configured in the same manner as in the above embodiment. In the figure, the same reference numerals as those in FIGS. 8 and 9 denote corresponding parts.

Reference numeral 17 denotes a ring-shaped holding portion which protrudes from the inner peripheral surface of the rim 3 in the direction of the rotation center and is arranged at the center of the thickness of the rim 3 in the direction along the rotation axis and extends along the radial direction. In the cross section, the center of rotation is formed in a tapered shape with a wide width. Reference numeral 19 denotes a locking portion formed by inner surfaces of holes provided apart from each other on the inner peripheral surface of the holding portion 17.

In the worm wheel manufacturing method as described above, the worm wheel is manufactured in the same manner as in the above-described embodiment of FIGS. 8 and 9, and the engaging portion 19 is formed with the boss fitting portion. Therefore, although detailed description is omitted, the same operation as the embodiment of FIGS. 8 and 9 can be obtained in the embodiment of FIG.

Embodiment 9 FIG. FIG. 11 also shows an example of another embodiment of the present invention. FIG. 11 is a front view showing a main part of the rim, and the other parts of FIG. A worm wheel is similarly configured. In the figure, the same reference numerals as those in FIGS. 8 and 9 denote corresponding parts.

Reference numeral 19 denotes a locking portion formed by opposing side walls of the holding portion 17. The rotation center side in the radial direction of the rim 3 is formed in a tapered shape closer to the protruding base portion of the holding portion 17. .

In the worm wheel manufacturing method as described above, the worm wheel is manufactured in the same manner as in the above-described embodiment of FIGS. 8 and 9, and the engaging portion 19 is formed with the boss fitting portion. Therefore, although detailed description is omitted, the same operation as the embodiment of FIGS. 8 and 9 can be obtained in the embodiment of FIG.

Also, in the embodiment shown in FIG. 11, a clamping action is generated between the tapered surface of the holding portion 17 of the rim 3 and the boss between the locking portions 19 facing each other. For this reason, it is possible to obtain a better mutual retaining action between the boss and the rim 3, and it is possible to effectively counter the torque acting on the worm wheel.

Embodiment 10 FIG. 12 and 13 also show an example of another embodiment of the present invention. FIG. 12 is a cross-sectional view along a rotation axis direction for explaining a manufacturing state of a worm wheel, and FIG. 13 is a cooling mold of FIG. FIG.
In the figure, reference numeral 11 denotes a molding die made of a sand mold in which a preformed rim 3 is accommodated, and 12 denotes a casting frame provided around the outer periphery of the molding die 11.

Reference numeral 20 denotes a core provided on the molding die 11 and arranged at the center of rotation of the rim 3. Reference numeral 1 denotes a boss cast by the molding die 11, and the boss 1 in the embodiment shown in FIGS. It is formed similarly to Reference numeral 21 denotes a runner provided in the molding die 11, and a gate 22 is formed. Reference numeral 23 denotes a cooling die provided on the molding die 11 and disposed on the outer periphery of the rim 3. The cooling die 23 has an annular shape, is provided with cuts 24 in a plane, and has a cooling water passage 25 provided therein.

In the worm wheel manufacturing method as described above, the cooling mold 23 is arranged on the outer periphery of the rim 3 formed in advance and arranged in the mold 11, and the boss 1 is cast at the center of the rim 3. You. Then, at the time of casting, the cooling mold 23 is used.
The rim 3 is cooled by passing through the cooling water passage 25 of the
Temperature rise is suppressed. As a result, the difference in the amount of shrinkage between the rim 3 and the boss 1 becomes larger than when the rim 3 is not cooled during casting, and the rim 3 and the boss 1 can be more effectively connected.

In the worm wheel 6 in which the boss 1 is cast, the residual stress of the rim 3 is small, and it is possible to prevent occurrence of problems such as breakage of teeth processed on the rim 3 at the time of engagement. Further, the effect of preventing the abnormalities of the teeth due to the residual tensile stress of the rim 3 can be obtained by a simple and inexpensive manufacturing method. Further, since the cuts 24 are provided in the cooling mold 23, the ability to follow the rim 3 during casting is increased, and a more effective cooling action can be obtained.

Embodiment 11 FIG. FIG. 14 is also a view showing an example of another embodiment of the present invention, and is a plan view of a cooling mold. In the drawings, the same reference numerals as those in FIGS. 12 and 13 denote corresponding parts, 25 is a cooling water channel provided on the cooling mold 23 and divided into two planes, and 26 is at both ends of each cooling water channel 25. It is a cooling water inlet / outlet provided.

In the worm wheel manufacturing method as described above, the cooling die 23 is arranged on the outer periphery of the rim 3 and the boss 1 is cast in the same manner as in the embodiment of FIGS. Therefore, although detailed description is omitted, the same operation as the embodiment of FIGS. 12 and 13 can be obtained in the embodiment of FIG.

Further, in the embodiment shown in FIG. 14, since a plurality of cooling water passages 25 are provided in the cooling mold 23, the cooling efficiency can be improved when there is a possibility that the cooling water flowing through the cooling water passage 25 will evaporate. it can.

Embodiment 12 FIG. FIG. 15 also shows an example of another embodiment of the present invention, and is a view corresponding to the portion X in FIG. 12 described above. In the drawings, the same reference numerals as those in FIGS. 12 and 13 denote corresponding parts, and 27 denotes a heat insulating coating, which is made of, for example, grease-like molybdenum disulfide, and is applied to the surface of the rim 3 facing the boss 1 at 17 holding portions. Have been.

In the worm wheel manufacturing method as described above, the rim 3 formed in advance is put into a forming die, and the boss 1 is cast around the inner periphery of the holding portion 17. At this time, since the heat insulating coating 27 is formed on the rim 3, it is possible to suppress a temperature rise of the rim 3 during casting. Therefore, the difference in the amount of contraction between the rim 3 and the boss 1 increases, and the rim 3 and the boss 1 can be more effectively coupled.

As a result, in the worm wheel 6 in which the boss 1 is cast, the residual stress of the rim 3 is small, and it is possible to prevent problems such as breakage of the teeth formed on the rim 3 at the time of meshing. Further, the effect of preventing the abnormalities of the teeth due to the residual tensile stress of the rim 3 can be obtained by a simple and inexpensive manufacturing method.

Embodiment 13 FIG. 16 is also a view showing an example of another embodiment of the present invention. FIG. 16 is a cross-sectional view taken along the direction of the rotation axis for explaining the state of production of the worm wheel. 12, the same reference numerals as those in FIGS. 12, 13, and 15 denote corresponding parts.

In the worm wheel manufacturing method as described above, the cooling mold 23 is arranged on the outer periphery of the rim 3 which has been formed in advance and arranged in the mold 11, and the boss 1 is cast at the center of the rim 3. You. The boss 1 is cast around the holding portion 17 of the rim 3, and a heat insulating coating 27 is formed on the surface of the rim 3 facing the boss 1 at the 17 holding portion.

Accordingly, although detailed description is omitted, FIG.
8 and 9 in the sixth embodiment,
The same operation as the embodiment of FIGS. 12 and 13 and the embodiment of FIG. 15 can be obtained.

[0082]

As described above, according to the present invention, a preformed boss is put into a molding die, a rim is cast on the outer periphery of the boss by the molding die, and a worm wheel formed by the boss and the cast rim is formed. To cause plastic deformation due to cooling shrinkage at the joint of the rim and the boss, thereby reducing the tensile residual stress of the rim at room temperature.

Thus, when the tensile residual stress of the rim generated for connecting the boss and the rim is large, it is possible to prevent a problem such as breakage of the tooth of the rim engaged with the rim. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using simple steps.

As described above, according to the present invention, only the rim portion of the worm wheel formed by the boss and the cast rim is cooled, and plastic deformation due to cooling shrinkage occurs at the joint portion of the rim with the boss. This reduces the tensile residual stress of the rim at room temperature.

As a result, there is an effect of preventing the occurrence of problems such as breakage of the teeth of the meshed rim when the tensile residual stress of the rim generated for connecting the boss and the rim is large. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using simple steps. Further, since only the rim portion is cooled, the difference in the amount of contraction between the boss and the rim is further increased, so that the distortion generated on the rim is likely to increase, and there is an effect of obtaining a more effective residual stress reducing action after cooling. .

As described above, according to the present invention, the boss portion of the worm wheel formed by the boss and the cast rim is covered with the heat insulating means, and the worm wheel is cooled and the rim of the rim is joined to the boss portion. This is to cause plastic deformation due to cooling shrinkage and reduce the tensile residual stress of the rim at room temperature.

Thus, when the tensile residual stress of the rim generated for connecting the boss and the rim is large, it is possible to prevent the occurrence of problems such as breakage of the teeth of the engaged rim. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using simple steps. Further, since the boss portion is cooled while being covered by the heat insulating means, the difference in the amount of shrinkage between the boss and the rim is further increased, and the distortion generated on the rim is likely to increase, so that the more effective residual after cooling. There is an effect of obtaining a stress reducing action.

As described above, according to the present invention, a preformed boss is placed in a molding die, and a rim is cast on the outer periphery of the boss by the molding die in a state where the boss is heated. Reduces the tensile residual stress of the rim of the worm wheel at room temperature.

Thus, when the tensile residual stress of the rim generated for connecting the boss and the rim is large, there is an effect of preventing a problem such as breakage of the tooth of the meshed rim or the like beforehand. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using simple steps.

Further, as described above, according to the present invention, the rim is formed on the outer periphery of the boss by the molding die in a state where the preformed boss is put into the molding die, the inner diameter of the boss is increased and the outer diameter is enlarged. Casting and releasing the pressure of the boss after casting to reduce the tensile residual stress of the rim in the worm wheel formed by the boss and the cast rim.

[0091] This has the effect of preventing the occurrence of inconveniences such as breakage of the teeth of the engaged rim when the tensile residual stress of the rim generated for coupling the boss and the rim is large. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using simple steps.

Further, as described above, according to the present invention, a boss formed in advance is placed in a molding die, and a rim is cast on the outer periphery of the boss by the molding die, thereby forming a worm wheel formed by the boss and the cast rim. In this case, the tensile residual stress of the rim is reduced.

[0093] This has the effect of preventing the occurrence of inconveniences such as breakage of the teeth of the engaged rim when the tensile residual stress of the rim generated for coupling the boss and the rim is large. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using simple steps.

Further, as described above, the present invention is provided with a holding portion projecting from the inner peripheral surface in the direction of the center of rotation and having a tip formed wider than the base portion. The rim is wrapped around the rim, and a boss is cast inside the rim by a molding die. The rim is pressed by the holding portion due to the shrinkage of the boss after casting in the worm wheel formed by the rim and the cast boss. Is held by the boss.

As a result, in the worm wheel in which the boss is cast, the residual stress of the rim is small, and it is possible to prevent problems such as breakage of the teeth formed on the rim when the rim is engaged with the rim. Has an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim.

Further, as described above, the rim is cooled at the time of casting the boss by the cooling mold provided on the molding die and arranged on the outer periphery of the rim.

Thus, in the worm wheel in which the boss is cast, the residual stress of the rim is small, and it is possible to prevent occurrence of problems such as breakage of the teeth formed on the rim at the time of meshing. In addition, an inexpensive manufacturing method using a simple process has an effect of preventing abnormal occurrence of teeth due to residual stress of the rim. Further, the rim is cooled by the cooling mold at the time of casting the boss, and a rise in the temperature of the rim is suppressed, so that the difference in the amount of shrinkage between the rim and the boss is increased, and there is an effect of improving the coupling action between the rim and the boss.

Further, as described above, according to the present invention, a heat insulating film is formed on the holding portion of the rim, and a boss is cast inside the rim.

Thus, in the worm wheel in which the boss is cast, the residual stress of the rim is small, and it is possible to prevent problems such as breakage of the teeth processed on the rim at the time of meshing. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using a simple process. Further, since the temperature rise of the rim is suppressed by the heat insulating coating at the time of casting the boss, the difference in the amount of shrinkage between the rim and the boss increases, and there is an effect of improving the coupling action between the rim and the boss.

As described above, according to the present invention, a heat insulating coating is formed on the holding portion of the rim, the boss is cast inside the rim, and the cooling boss provided on the molding die and arranged on the outer periphery of the rim is provided. The rim is cooled by the die when casting the boss.

Thus, the residual stress of the rim is small in the worm wheel in which the boss is cast, and it is possible to prevent the occurrence of problems such as breakage of the teeth formed on the rim at the time of meshing. In addition, there is an effect of preventing the occurrence of abnormal teeth due to the residual stress of the rim by an inexpensive manufacturing method using a simple process. Furthermore, the rim is cooled by the cooling mold during casting of the boss, and the temperature rise of the rim is suppressed by the heat-insulating coating, so that the difference in the amount of shrinkage between the rim and the boss is further increased. The effect is further improved.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention and is a cross-sectional view along a rotation axis direction for explaining a manufacturing state of a worm wheel.

FIG. 2 is a stress-strain diagram of a rim material in a process of manufacturing the worm wheel of FIG. 1;

FIG. 3 is a view showing the second embodiment of the present invention, and is a cross-sectional view along a rotation axis direction for explaining a manufacturing state of the worm wheel.

FIG. 4 is a view showing the third embodiment of the present invention, and is a cross-sectional view along the direction of the rotation axis for explaining the manufacturing state of the worm wheel.

FIG. 5 is a view showing the fourth embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis for explaining the manufacturing state of the worm wheel.

FIG. 6 is a view showing the fifth embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis, for explaining the manufacturing state of the worm wheel.

FIG. 7 is a view showing the sixth embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis for explaining the manufacturing state of the worm wheel.

FIG. 8 is a view showing the seventh embodiment of the present invention, and is a perspective view in which main parts of the rim are cut away.

9 is an enlarged radial cross-sectional view of the rim of FIG. 8;

FIG. 10 is a view showing the eighth embodiment of the present invention, and is a perspective view in which main parts of the rim are cut away.

FIG. 11 is a view showing a ninth embodiment of the present invention;
The front view which shows the principal part of a rim.

FIG. 12 shows the tenth embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis for explaining the manufacturing state of the worm wheel.

FIG. 13 is a plan view of the cooling mold of FIG.

FIG. 14 shows the eleventh embodiment of the present invention, and is a plan view of a cooling mold.

FIG. 15 is a view showing a twelfth embodiment of the present invention, and is a view corresponding to a portion X in FIG. 12 described above.

FIG. 16 is a view showing the thirteenth embodiment of the present invention, and is a cross-sectional view taken along the direction of the rotation axis for explaining the manufacturing state of the worm wheel.

FIG. 17 is a view showing a conventional worm wheel, and is a cross-sectional view along a rotation axis direction.

FIG. 18 is a view showing another conventional worm wheel;
Sectional drawing along a rotation axis direction.

[Explanation of symbols]

Reference Signs List 1 boss, 3 rim, 6 worm wheel, 10 heat insulating means, 11 molding die, 17 holding part, 23 cooling die, 27 heat insulating coating.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeki Maekawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Mikio Yamashita 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd.

Claims (10)

[Claims] 1. A boss formed beforehand is put into a molding form, a rim is cast on the outer periphery of the boss by the molding die, and a worm wheel formed by the boss and the cast rim is cooled. A method for producing a worm wheel, wherein plastic deformation due to cooling shrinkage is generated in a joint portion of a rim with the boss to reduce tensile residual stress of the rim at room temperature. 2. A method for manufacturing a worm wheel according to claim 1, wherein only the rim portion of the worm wheel formed by the boss and the cast rim is cooled. 3. The method for manufacturing a worm wheel according to claim 1, wherein the boss portion of the worm wheel formed by the boss and the cast rim is covered with heat insulating means to cool the worm wheel. . 4. A preformed boss is placed in a mold, and a rim is cast around the boss with the mold while the boss is being heated. The rim is formed by the boss and the cast rim. A method of manufacturing a worm wheel for reducing the tensile residual stress of the rim at normal temperature of the worm wheel. 5. A boss formed in advance is placed in a molding die, and a rim is cast on the outer periphery of the boss by the molding die in a state where the inner diameter of the boss is increased by applying pressure to the inner periphery of the boss. A method of manufacturing a worm wheel that releases pressure to reduce the tensile residual stress of the rim in the worm wheel formed by the boss and the cast rim. 6. A preformed boss is placed in a mold, and a rim is cast on the outer periphery of the boss by the mold, and the rim is pulled on a worm wheel formed by the boss and the cast rim. A method for manufacturing a worm wheel that reduces residual stress. 7. A holding portion which is provided from the inner peripheral surface in the direction of the center of rotation and whose tip is formed wider than the base portion is provided, and a preformed rim is put into a molding die, and the holding is performed by the molding die. A boss is cast inside the rim surrounding the rim, and the rim is pressed by the holding portion due to the shrinkage of the boss after casting in the worm wheel formed by the rim and the cast boss. Of manufacturing a worm wheel held in a tank. 8. The method for manufacturing a worm wheel according to claim 7, wherein said rim is cooled at the time of casting of the boss by a cooling die provided on a molding die and arranged on the outer periphery of the rim. 9. The method for manufacturing a worm wheel according to claim 7, wherein a heat insulating coating is formed on a holding portion of the rim, and a boss is cast inside the rim. 10. A boss is cast inside the rim by forming a heat-insulating coating on a holding portion of the rim, and the boss is cast by a cooling mold provided on a molding die and arranged on an outer periphery of the rim. 8. The method for manufacturing a worm wheel according to claim 7, wherein said rim is sometimes cooled.