JP2000033454A - Manufacture of flywheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength of a fitting part and a ring gear and to reduce the manufacturing cost of a flywheel. SOLUTION: A round bar of carbon steel for a mechanical structure is cut in a specified length to cut out a metallic stock (S1) and after being squeezed in the axial direction through the hot forging into a disk shape (S2), an intermediate product of a shape similar to that of an intended flywheel is hot-forged (S3). The intermediate product is hot-forged using a die having a gap between the butting surfaces and since burrs projected to the gap are left behind on the intermediate product, after the burrs are cut and removed (S4), cooled to the normal temperature, annealed and performed to a bonderizing processing (S5) and after putting a shape in order approximate to that of the flywheel (S6) by cold-forging, a ring gear is formed on its outer circumferential surface (S6) by cold-forging. The wear resistance is improved by performing shot-peening work or the like to a friction surface against which a clutch disk is pressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flywheel, and more particularly to a flywheel manufacturing method in which a ring gear is integrally provided on an outer peripheral portion.

[0002]

2. Description of the Related Art Engines that operate by burning fuel are frequently used in automobiles and the like. However, such engines are inevitably subject to periodic rotation fluctuations (torque fluctuations) due to explosions. Usually, a flywheel is attached to a crankshaft or the like to suppress the fluctuation. In addition to the engine, a flywheel is used for a rotating member that causes periodic rotation fluctuation to suppress the rotation fluctuation.

[0003] As shown in FIG. 12, a flywheel for a vehicle is generally a ring gear made of carbon steel for mechanical structure, for example, S48C, provided with a large number of teeth on the outer peripheral portion by cutting using a hob cutter or a pinion cutter. In addition, a main body made of gray cast iron, for example, FC230, provided with a mounting portion for mounting a crankshaft at a central portion, is integrally fixed by press-fitting, shrink fitting, or the like. The ring gear rotates the crankshaft when the engine is started, and is rotated by being engaged with a pinion of a starter motor.

[0004]

However, in the flywheel, since the main body is made of gray cast iron, the tensile strength of the mounting portion is insufficient, and it is necessary to make the mounting portion thick in order to compensate for the insufficient strength. As a result, the weight of the main body increases, and the weight ratio of the outer periphery of the flywheel to the total weight of the flywheel decreases, so that the moment of inertia of the flywheel decreases, the rotation fluctuation of the crankshaft increases, and the fuel efficiency decreases. There was an inconvenience. Further, since the flywheel is composed of two parts, the ring gear and the main body, the number of steps is increased, and there is a limit in reducing the manufacturing cost. Further, the flywheel is rotated at a high speed (high-speed rotation) with the improvement of the engine performance, and the pinion of the starter motor meshes with the ring gear at a higher pressure and a higher rotation with a higher engine startability (high compression). Therefore, the flywheel and the ring gear are required to have sufficient resistance. However, since the meshing teeth of the ring gear are formed by cutting, the metal flow is cut and the starter motor is moved in the same direction as the cut metal flow. However, sufficient mechanical strength (toughness, etc.) could not be obtained because of a load from the steel, and it was necessary to set a large module.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flywheel in which the strength of a mounting portion and a ring gear is improved and the manufacturing cost is reduced. .

[0006]

In order to achieve the above object, a first aspect of the present invention is directed to a disk portion having a substantially disk shape and a cylinder integrally provided on an outer peripheral edge of the disk portion. And a central portion of the disk portion is a mounting portion integrally fixed to a predetermined rotating member, and one of the outer peripheral portions of the disk portion with respect to the mounting portion. A method of manufacturing a flywheel, wherein a friction surface is provided on an end surface of the flywheel, and a ring gear including a large number of meshing teeth parallel to an axis is provided on an outer peripheral surface of the cylindrical portion. Hot forging the material to form an intermediate product integrally having a shape similar to the disk portion and the cylindrical portion, and a butt surface of a pair of molds forging the intermediate product. Is set at a position different from the portion forming the ring gear, and A hot forging step in which a predetermined gap is provided in the contact surface to allow the excess thickness to protrude, and (b) the outer peripheral surface of the intermediate product is generated by the excess thickness protruding in the gap. A cutting step of cutting the flange-shaped burrs, and (c) performing cold forging from the axial direction on the intermediate product from which the burrs have been cut so as to have a shape substantially equal to the disk portion and the cylindrical portion. A shaping step of compressing and shaping, and (d) performing a cold forging process on the cylindrical portion of the shaped intermediate product, thereby forming an outer peripheral surface of the cylindrical portion and not including the cut portion of the burr. A ring gear forming step of forming the ring gear at one end in the direction.

According to a second aspect of the present invention, in the method for manufacturing a flywheel according to the first aspect, (a) the metal coarse material is obtained by cutting a round bar-shaped steel material having a metal flow aligned in an axial direction at a predetermined length. (B) in the hot forging step, the cylindrical metal coarse material has an axial length of 3 /
It is characterized in that the intermediate product is processed by crushing it to 10 or less.

A third invention is the method of manufacturing a flywheel according to the second invention, wherein the hot forging step comprises the steps of: (a) subjecting the cylindrical metal rough to hot forging to have an axial length of 3 mm; And (b) pressing the disc-shaped coarse material from the axial direction by hot forging to form the intermediate product. And an intermediate product forming step.

According to a fourth aspect of the present invention, there is provided the method of manufacturing a flywheel according to any one of the first to third aspects, wherein the friction surface of the disk portion is subjected to quenching and hardening treatment, followed by shot peening to form a large number of fine particles. It is characterized by having a friction surface treatment step of forming a concave portion.

[0010]

According to such a method of manufacturing a flywheel, the flywheel is integrally formed by subjecting a predetermined metal coarse material such as carbon steel for machine structure to hot forging and cold forging. Since it is formed, the tensile strength of the mounting portion is improved and the thickness can be reduced, the weight ratio of the outer periphery of the flywheel to the total weight of the flywheel can be increased, and the moment of inertia of the flywheel increases. Further, as compared with the case where a large number of teeth are provided on the ring gear by cutting, the metal structure (metal flow) is continuously connected without cutting in the forging, so that the mechanical strength is improved. In particular, since such a ring gear is formed on the outer peripheral surface of the cylindrical portion and at one end in the axial direction not including the cut portion of the burr, the other end portions of the plurality of meshing teeth are connected to each other, so that high-speed rotation is achieved. Sufficient toughness is obtained even for high compression and high compression, and the mechanical strength is further improved. Since such high mechanical strength is obtained, it is possible to reduce the size of the ring gear module, and the outer peripheral portion (gear portion) has a larger mass than the ring gear having the same outer diameter and a larger module, thereby reducing the moment of inertia. Increase. Furthermore, since the number of steps is reduced by performing integral molding, manufacturing costs are reduced.

On the other hand, in the present invention, a predetermined gap is provided in the butting surfaces of a pair of dies for forging and forming an intermediate product in the hot forging step, so that the excess thickness is allowed to protrude. The load on the mold is reduced, and the life of the mold is improved. The excess material that has protruded into the gap remains as a flange-shaped burr on the outer peripheral surface of the intermediate product, and since the burr is removed in the cutting process, the metal flow is cut off accordingly, but in the subsequent shaping process, Since the disk portion and the cylindrical portion are compression-shaped with high dimensional accuracy by cold forging, the reduction in strength due to cutting of the metal flow due to the compression at that time is improved. Also, since the disk portion and the cylindrical portion are shaped to high dimensional accuracy by cold forging prior to the processing of the ring gear, the processing accuracy when the ring gear is cold forged is improved, and The dimensional accuracy is improved.

In the second invention, a columnar metal coarse material obtained by cutting a round bar-shaped steel material having a metal flow aligned in the axial direction at a predetermined length is used, and crushing it in the axial direction to obtain a predetermined shape. Therefore, the connection of the metal flow is maintained well. In the hot forging step, the cylindrical metal coarse material is crushed until the axial length is reduced to 3/10 or less to process the intermediate product, so that a portion where the material density is low is generated. Therefore, a local decrease in mechanical strength is avoided. The length of metal coarse material in the axial direction is 3/1
Since the metal coarse material is crushed until it becomes 0 or less, the diameter of the metal coarse material is reduced, and the material cost is reduced as compared with the case where a large-diameter metal coarse material is used.

According to the third aspect of the present invention, the cylindrical metal material is first crushed in the axial direction by hot forging to form a flat disk shape. In this disk shape, the metal flow is substantially radial. Extends to the outer peripheral side and in the thickness direction 18
The light is converged toward the center by being turned by 0 °, and a substantially homogeneous state is obtained around the axis. That is, if a large and complicated deformation is applied at once, the flow state of the metal may become uneven or the metal flow may be interrupted, but in the present invention, a simple disk-shaped coarse material is first forged. As a result, a good connection between the metal core and the homogeneous state around the shaft center can be obtained, and in subsequent hot forging and cold forging,
The homogenous state around the axis and the connection of the metal flow are maintained well.

According to the fourth aspect of the present invention, since a large number of micro concave portions (micro holes) are formed by performing shot peening on the friction surface of the disk portion, the friction surface such as a clutch disc pressed against the friction surface is formed between the friction portions. An air layer is formed, and an increase in friction coefficient at a high temperature is suppressed, thereby preventing a reduction in life due to wear of the friction surface. In other words, the friction surface of the flywheel becomes hot due to sliding friction with the friction material, but in the case of a conventional cast iron product, the graphite contained as a component melts out and performs a lubricating action, so that even at high temperatures, the friction coefficient increases. However, in the case of the product of the present invention made of a predetermined metal material such as carbon steel for mechanical structure, the coefficient of friction increases as the temperature rises as it is.

When the friction coefficient of the friction surface increases, the connection of the clutch is sharpened. For example, in the case of a flywheel for a vehicle, the following problems occur. (a) The clutch operation becomes difficult and the engine is easily stopped. (b) The shock load torque generated in a transmission system such as a transmission increases, which causes a reduction in service life. (c) The judder phenomenon that vibrates violently at low rotation is likely to occur. (d) Wear becomes severe, and the life of the clutch disk (friction material) is shortened.

On the other hand, even when the fine irregularities are provided, when the friction surface is worn and the surface roughness is reduced, the air layer is reduced and the friction coefficient is increased. In addition, the generation of heat causes the material of the clutch disk to thermally decompose and soften, and the frictional force increases, and the friction coefficient further increases.However, in the present invention, quenching and hardening is performed prior to shot peening, The surface hardness is, for example, HRC 45 to 47
Since it is hardened to the extent, the same durability (life) as that of a conventional cast iron product can be secured.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention is preferably applied to a flywheel for a vehicle which is coaxially mounted on an engine crankshaft, but is also applicable to a flywheel which is mounted on another rotating member. Can be done. A flywheel for a vehicle is driven to rotate when an engine is started by a drive pinion of a starter meshing with a ring gear.

As the metal rough material, a round bar-shaped steel material of carbon steel for machine structure is suitably used. As for the steel material immediately after casting and rolling, the metal flow is aligned in the axial direction as in the second invention, but it is also possible to use a steel material that has been subjected to a drawing process after rolling in order to further enhance roundness. In the disk processing step of crushing a cylindrical metal coarse material into a flat disk shape until the axial length dimension becomes 3/10 or less, the thickness of the crushed disk shape is determined by the purpose. It is desirable that the thickness is set to be approximately the same as the axial dimension of the flywheel, specifically, the axial thickness of the cylindrical portion of the outer peripheral portion.

Hot forging and cold forging are performed by using a die 1
Forging may be performed in a reciprocating manner into a target shape, but forging may be performed in multiple stages using a plurality of dies, or may be performed by repeatedly pressing the same dies a plurality of times. The gap between the butting surfaces of a pair of molds forged into an intermediate product is small, and if the load on the mold is large, the molding accuracy of the intermediate product will be impaired if the load is large. For example, about 4 mm within a range of about 2 to 6 mm Is desirable.

Hot forging process and shaping process in the hot forging process,
It is desirable that the cold forging in the ring gear processing or the cutting of the burrs in the cutting step be performed by press working using a press machine.

The friction surface treatment step of the fourth invention is desirably performed after the ring gear processing step by cold forging, but may be performed between the shaping step and the ring gear processing step. In addition to the friction surface treatment, it is also possible to perform finish cutting, predetermined drilling, quenching and hardening of a ring gear, and the like.

In the shot peening process (WPC process) in the friction surface treatment step, shots (steel grains, etc.) of about φ40 to 200 μm having hardness equal to or higher than that of the object are compressed to 100 m / cm by compressed air or centrifugal force. At a speed of about sec, the flywheel is hit against the surface of the flywheel to form a hardened layer having a depth of about 10 to 20 μm and a large number of microholes on the surface. The depth of the microhole is several μm.

In the quenching and hardening treatment in the friction surface treatment step, for example, induction hardening by high frequency induction heating or the like is preferably used, and the surface hardness of the friction surface is set to, for example, about HRC 45 to 47 prior to shot peening.

In the above-described friction surface treatment step, quenching and hardening treatment by induction hardening or the like is performed prior to shot peening. However, in practicing other inventions, only shot peening may be performed. Depending on the use conditions and materials, such a friction surface treatment may be omitted, or a completely different surface treatment may be performed.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The flywheel 10 in FIG. 1 is an example of a vehicle flywheel manufactured according to the manufacturing method of the present invention, wherein (a) is a perspective view and (b) is a cross-sectional view including an axis S. The flywheel 10 includes a disk portion 12 having a substantially disk shape, and a cylindrical portion 14 provided integrally with an outer peripheral edge of the disk portion 12.
4 is provided so as to protrude from the disk portion 12 in one axial direction. A central portion of the disk portion 12 is a mounting portion 16, which is swelled about half in the same direction as the cylindrical portion 14, and is bolted to a predetermined rotating member, that is, an engine crankshaft (not shown) through a plurality of mounting holes 18. It is fixed concentrically and integrally. A center hole 17 is provided at the center of the mounting portion 18. A friction surface 20 is provided on one end surface of a portion of the disk portion 12 closer to the outer periphery than the mounting portion 16, that is, a lower end surface in the figure, and a clutch disk of a clutch (not shown) is pressed. In addition, at one axial end of the outer peripheral surface of the cylindrical portion 14, that is, at the tip end portion in the protruding direction, a large number of meshing teeth 22 are provided in parallel with the axis S over the entire circumference to form a ring gear 24. The rotation is driven by being engaged with a drive pinion of a starter (not shown).

FIG. 2 is a flowchart for explaining the manufacturing process of the flywheel 10. In step S1, a round bar-shaped steel material (rolled steel material) of carbon steel for machine structure such as S35C is cut into a predetermined size with a sawing machine or the like to obtain a cylindrical metal rough as shown in FIG. The material 30 is cut out. The diameter dimension d ₁ and the height dimension t ₁ of the metal coarse material 30 have slightly larger volumes than the target volume of the flywheel 10 in consideration of drilling and burrs, and at the time of hot forging in step S2. For example, d ₁ ≒ about 100 mm and t ₁ ≒ 100 so that the axial dimension is 3/10 or less.
mm. The rolled steel material in the shape of a round bar has a metal structure of 30 mm because the metal structure is elongated in the axial direction.
The metal flows F are aligned in the axial direction as shown in FIG. 3B, and are connected from one end face 32 to the other end face. 3A is a perspective view of the rough metal member 30, and FIG. 3B is a diagram illustrating a metal flow F in a cross section including the axis S.

In step S2, the cylindrical metal blank 30 is crushed in the axial direction by hot forging of a press, and a flat disk-shaped blank 36 as shown in FIG. Mold into The height t ₂ of the disk coarse material 36 is substantially the same as the axial dimension of the intended flywheel 10, specifically, approximately the same as the axial dimension of the cylindrical portion 14 in the outer peripheral portion. In the example, t ₂ is about 28 mm, and the diameter dimension d _{2 is} about 185 mm. Disk material 36
The metal flow F extends substantially radially to the outer peripheral side as shown in FIG. 4 (b), and is bent 180 ° in the thickness direction at the outer peripheral portion to converge toward the center side, and is substantially rotated around the axis S. Become homogeneous. That is, if a large and complicated deformation is applied at once, the flow state of the metal may be uneven or the metal flow F may be interrupted. However, in this case, the metal flow F is simply forged into a simple disk shape. In addition, the uniform state around the axis S and the connection of the metal flow F are maintained favorably. This step S2 is a hot forging step, and particularly corresponds to a disk processing step. 4 (a) is a perspective view of the disk material 36, and FIG. 4 (b) is a view for explaining the metal flow F in a cross section including the axis S.

In step S3, the disk coarse material 36 is pressed in the axial direction, that is, in the thickness direction by hot forging of a press, so as to be similar to the disk portion 12 and the cylindrical portion 14 as shown in FIG. An intermediate product 38 integrally having a shape portion to be formed, that is, a disk equivalent portion 38a and a cylindrical equivalent portion 38b is formed. This intermediate product 38 is different from the intended flywheel 10 in that the center hole 17, the mounting hole 18, the ring gear 24 are not provided, and the disk equivalent portion 38 a
Although the thickness of the connecting portion between the outer peripheral edge or cylindrical corresponding portion 38b of is gradually increased, diameter d _3, the height t ₃ is substantially the same as the flywheel 10, d ₃ ≒ 225 mm approximately, t ₃
It is about 30 mm. FIG. 7 shows an example of a pair of a fixed mold 40 and a movable mold 42 forged on the intermediate product 38, and molding surfaces 44 and 46 corresponding to the intermediate product 38, respectively.
The target intermediate product 38 is obtained by moving the movable mold 42 up and down a plurality of times.

The butting surfaces 48 and 50 of the pair of fixed mold 40 and movable mold 42 are, for example, 4 mm in a mold closed state where movable mold 42 is located at the bottom dead center as shown on the right side of center line O. It is formed so as to have a predetermined gap g of about a degree, and a flange-shaped burr 52 is formed on the outer peripheral surface of the intermediate product 38 by the excess thickness of the disk coarse material 36 protruding into the gap g. The gap g is formed only on a part of the inner peripheral side of the butting surfaces 48 and 50 that is continuous with the molding surfaces 44 and 46.
A step may be provided on one or both of the butting surfaces 48 and 50. Also, the butting surfaces 48 and 50 are
Each forming surface 44 is formed such that a burr 52 is formed at a position on the outer peripheral surface of the intermediate product 38 which is different from the portion where the ring gear 24 is provided, specifically, at a portion near the side where the friction surface 20 is provided. The position relative to 46 is determined. Even in the state of the intermediate product 38, the disk coarse material 36
And the homogenous state around the axis S and the connection of the metal flows are favorably maintained. This step S3 is a hot forging process, and particularly corresponds to an intermediate product forming process. 5A is a perspective view of the intermediate product 38, and FIG. 5B is a cross-sectional view including the axis S. The left side from the center line O in FIG. 7 is a state before forging, and the right side is movable. The mold 42 has been lowered to the bottom dead center.

In step S4, as shown in FIG. 8, the ring-shaped cutting blade 56 and the punch 58 are lowered by the press on the intermediate product 38 placed on the fixed die 54, so that the cutting blade 56 By the said burr 5
2 is cut and removed, and the center hole 1 is
7 is drilled. This cutting press is performed while the intermediate product 38 is heated in the previous step. This step S4 is a cutting step. The left side of the center line O in FIG. 8 is a state before the cutting press, and the right side is a state after the cutting press.

In step S5, the intermediate product 38 in which the burr 52 has been cut and removed and the center hole 17 has been formed is left to cool to room temperature, and thereafter dust and the like adhering to the surface are removed, followed by annealing and bonding. I do. Annealing is for homogenizing and softening the material, and is performed by reheating and heat treatment. The hot forging (S2, S3)
Since the same effect can be obtained by controlling the cooling rate after cutting and cutting (S4), the temperature may be controlled by placing the intermediate product 38 in a furnace during cooling. Bonding process is intermediate product 3
8 is coated with zinc phosphate or the like, and cold forging is performed by lubricating the intermediate product 38 with the fixed dies 60 and 70 and the movable dies 62 and 72 in the next step (S6, S7). This is to make it easier to do.

In step S6, as shown in FIG. 9, for example, the movable mold 62 is moved closer to the fixed mold 60, whereby the intermediate product 38 is pressed from the axial direction to perform cold forging. The compression molding is performed so as to have substantially the same shape as the plate portion 12 and the cylindrical portion 14, in other words, to have substantially the same shape as the state where the ring gear 22 is not provided in the flywheel 10. By the compression shaping (coining, facing) by the cold forging, the intermediate product 38 is shaped into a target shape with high dimensional accuracy, and the portion where the burr 52 is cut by compressing the outer peripheral portion in the axial direction. , The density of the metal flow becomes honey, and a decrease in strength due to cutting of the metal flow is suppressed. FIG. 6 is a view showing the intermediate shaped product 64 after compression-shaping in step S6.
2 and the cylindrical portion 14 are integrally provided. Step S6
Corresponds to a shaping step. FIG. 6A is a perspective view.
9B is a cross-sectional view including the axis S. The left side of the center line O in FIG. 9 is a state before compression shaping, and the right side is a state after compression shaping in which the movable mold 62 is lowered to the bottom dead center. It is.

In step S7, as shown in FIG. 10, a fixed die 70 having a ring-shaped die 68 provided with processing teeth 66 corresponding to the meshing teeth 22 of the ring gear 24.
Then, the intermediate shaped product 64 with the cylindrical portion 14 protruding downward.
Is set, and the movable mold 72 is lowered to make the intermediate shaped product 64.
The ring gear 24 is formed by cold forging on the outer peripheral surface of the cylindrical portion 14 and on the tip side of the cut portion of the burr 52. Intermediate shaped products 6
The ring gear 2 is formed with high dimensional accuracy.
4 is also cold forged, so that the ring gear 24 is formed with high dimensional accuracy, and because it is forged in the axial direction, the metal flow is not cut, so that the ring gear 2
The mechanical strength of each meshing tooth 22 of No. 4 is sufficiently ensured. Step S7 corresponds to a ring gear machining process. The left side of the center line O in FIG. 10 is a state before forging,
The right side is a state after forging in which the movable mold 72 has been lowered to the bottom dead center.

Thereafter, in step S8, the friction surface 2
A surface modification treatment for improving the abrasion resistance is performed. That is, first, the friction surface 20 is hardened to a hardness of approximately HRC 45 to 47 by performing induction hardening on the friction surface 20. Next, φ40 ~
By performing a shot peening process of hitting a 200 μm shot (steel grain or the like) at 100 m / sec by compressed air or centrifugal force, a number of micrometers having a depth of several μm as shown in FIG. A hardened layer having a depth of about 20 μm deeper than the holes 74 and the micro holes 74 is formed. The micro holes 74 correspond to minute concave portions. The hardness of the cured layer is, for example, HRC7
It is about 0 to 90. This step S8 corresponds to a friction surface processing step. Before or after step S8, the mounting hole 18 is cut by a drill or the like, and the surface of the ring gear 24 is subjected to a hardening process such as induction hardening.

As described above, according to this embodiment, since the flywheel 10 is integrally formed by forging from the metal coarse material 30 of carbon steel for machine structure, the tensile strength of the mounting portion 16 is improved and the thickness is reduced. And the weight ratio of the outer peripheral portion (cylindrical portion 14) of the flywheel to the total weight of the flywheel 10 increases, and the flywheel 10
Has a large moment of inertia. As a result, it is possible to reduce fluctuations in the rotation of the crankshaft, thereby improving fuel efficiency. Further, in comparison with the case where a large number of meshing teeth 22 are provided in the cylindrical portion 14 by cutting, the strength is improved because the metal flow is continuously connected in the forging, and the number of meshing teeth 22 is one end in the axial direction. That is, FIG.
Are connected to each other, sufficient toughness can be obtained even for high-speed rotation and high compression, and the mechanical strength is further improved. Since such high mechanical strength is obtained, the size of the module of the ring gear 24 can be reduced, and the mass of the outer peripheral portion (gear portion) becomes larger than that of a ring gear having the same outer diameter and a larger module, so that the moment of inertia is increased. Increase. Furthermore, since the number of steps is reduced by performing integral molding, manufacturing costs are reduced.

On the other hand, in the present embodiment, a predetermined gap g is provided in the butting surfaces 48 and 50 of the pair of dies 40 and 42 forged into the intermediate product 38 in step S3, and the excess thickness is allowed to protrude. So that the mold 4
The load applied to 0 and 42 is reduced, and the mold life is improved.
The excess material that has protruded into the gap g remains on the outer peripheral surface of the intermediate product 38 as a flange-like burr 52. Since the burr 52 is removed in the cutting step of step S4, the metal flow is cut accordingly. However, by compressing in the axial direction in the subsequent shaping step (step S6), reduction in strength due to cutting of the metal flow is improved. Also,
In this way, prior to the processing of the ring gear 24, the intermediate product 38
Since the disk equivalent portion 38a and the cylindrical equivalent portion 38b are shaped with high dimensional accuracy by cold forging, the ring gear 24
Of the ring gear 24 is improved, and the dimensional accuracy of the ring gear 24 is improved.

Further, since a cylindrical metal coarse material 30 obtained by cutting a round bar-shaped rolled steel material at a predetermined length t ₁ is used, the metal flow is aligned in the axial direction, and the metal flow is crushed in the axial direction. Therefore, the connection of the metal flows is favorably maintained. In the hot forging process of steps S2 and S3, the cylindrical metal coarse material 30 is crushed until the axial length becomes 3/10 or less, and the intermediate product 3 is crushed.
Since the material 8 is formed, a portion where the material density is low does not occur, and a local decrease in mechanical strength is avoided.

In particular, in this embodiment, the columnar metal coarse material 3 is used.
First, in step S2, the metal flow is extended substantially radially to the outer peripheral side while being crushed in the axial direction by hot forging to form a flat disk shape in step S2, and 180 It turns and converges to the center side, and a substantially homogeneous state is obtained around the axis. That is, if a large and complicated deformation is applied at once, the flow state of the metal may become uneven or the metal flow may be interrupted. In this embodiment, first, in step S2, the simple disk coarse material 36 is formed. Because of the forging, a homogeneous state around the axis and the connection of the metal flow are obtained well, and the subsequent hot forging (step S3) and cold forging (step S6,
Also in S7), the uniform state around the axis S and the connection of the metal flows are maintained well.

Further, since the metal coarse material 30 is crushed until the axial length becomes 3/10 or less,
Diameter d ₁ of the metal coarse material 30 is reduced, the material cost is reduced compared with the case of using a metal coarse material having a larger diameter.

In this embodiment, since a large number of microholes 74 are provided by subjecting the surface of the friction surface 20 to shot peening, a friction material such as a clutch disk pressed against the friction surface 20 is provided. An air layer is formed between them, and an increase in the friction coefficient at a high temperature is suppressed, and a reduction in the life due to wear of the friction surface 20 and the like are prevented. That is, the flywheel 10 is driven by sliding friction with the friction material.
Although the friction surface 20 becomes high in temperature, in the case of a conventional cast iron product, the graphite contained as a component melts out and performs a lubricating action, so that even at high temperatures, the friction coefficient increases little and wear hardly occurs. On the other hand, in the case of the product of the present embodiment made of carbon steel for machine structural use, the coefficient of friction increases as the temperature rises as it is.

On the other hand, even if the micro holes 74 are provided, if the friction surface 20 is worn and the surface roughness is reduced,
The air layer becomes smaller and the coefficient of friction increases. Further, the generation of heat causes the material of the clutch disk to be thermally decomposed and softened, the frictional force increases, and the friction coefficient further increases. For this reason, a quenching and hardening treatment is performed prior to the shot peening to reduce the surface hardness to, for example, HRC.
By curing to about 45 to 47, the same durability (life) as that of a conventional cast iron product is secured.

Although the embodiment of the present invention has been described in detail with reference to the drawings, this is merely an embodiment,
The present invention can be implemented in various modified and improved aspects based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a flywheel for a vehicle manufactured according to the manufacturing method of the present invention, where (a) is a perspective view and (b)
Is a sectional view including the axis S.

FIG. 2 is a flowchart illustrating a manufacturing procedure of the flywheel of FIG.

3A and 3B are views for explaining a metal rough cut out in step S1 of FIG. 2, wherein FIG. 3A is a perspective view and FIG. 3B is a view for explaining a metal flow F having a cross section including an axis S;

4A and 4B are views for explaining a flat metal coarse material (disc coarse material) hot-forged in step S2 of FIG. 2, wherein FIG. 4A is a perspective view and FIG. It is a figure explaining metal flow F of a section.

5A and 5B are diagrams showing an intermediate product hot forged in step S3 of FIG. 2, wherein FIG. 5A is a perspective view and FIG. 5B is a cross-sectional view including an axis S.

FIGS. 6A and 6B are views showing an intermediate product (intermediate shaped product) compression-formed by cold forging in step S6 of FIG. 2, wherein FIG. 6A is a perspective view, and FIG. is there.

7 is a cross-sectional view of a mold when hot forging an intermediate product in step S3 of FIG. 2;

FIG. 8 is a cross-sectional view of a mold when cutting is performed in step S4 of FIG.

FIG. 9 is a cross-sectional view of a mold when compression-shaping is performed by cold forging in step S6 of FIG.

FIG. 10 is a cross-sectional view of a die when processing a ring gear by cold forging in step S7 of FIG. 2;

11 is a diagram showing a cross-sectional shape of a friction surface of the flywheel of FIG.

FIG. 12 is a diagram illustrating a configuration of a conventional flywheel.

[Explanation of symbols]

 10: Flywheel 12: Disk portion 14: Cylindrical portion 16: Mounting portion 20: Friction surface 24: Ring gear 30: Metal coarse material 36: Disk coarse material (metal coarse material crushed into a disk shape) 38: Middle Products 48, 50: Butt surfaces 52: Burrs 64: Intermediate shaped products (Compressed shaped intermediate products) 74: Micro holes (micro concave portions) Step S2: Hot forging process, disk working process Step S3: Hot forging process , Intermediate product molding process Step S4: Cutting process Step S6: Shaping process Step S7: Ring gear machining process Step S8: Friction surface treatment process

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C21D 9/00 C21D 9/00 A F term (reference) 4E087 AA02 BA15 BA17 BA19 CA13 CA14 CA33 CA51 CB01 CB03 DA04 DA05 DB02 DB03 DB11 DB15 DB16 DB18 EC12 EC22 EC46 HA02 HA11 HA12 4K042 AA18 AA23 AA25 BA01 BA02 BA03 BA13 DA01 DA03 DB01

Claims (4)

[Claims] 1. A disk portion having a substantially disk shape and a cylindrical portion provided integrally with an outer peripheral edge of the disk portion, and a central portion of the disk portion is provided. A mounting portion integrally fixed to a predetermined rotating member, and a friction surface is provided on one end surface of a portion of the disk portion on an outer peripheral side of the mounting portion, while an outer peripheral surface of the cylindrical portion is provided. A method of manufacturing a flywheel in which a ring gear comprising a large number of meshing teeth parallel to an axis is provided, wherein a hot forging process is performed on a predetermined metal rough material, and the disc portion and the cylindrical portion are formed. In the step of molding an intermediate product integrally having a similar shape portion, the butting surfaces of a pair of molds forged with the intermediate product are set at positions different from a portion forming the ring gear, and A predetermined gap is provided in the abutment surface to allow the excess thickness to protrude. A hot forging step, and a cutting step of cutting off a flange-shaped burr generated on the outer peripheral surface of the intermediate product by protruding excess material into the gap; and a shaft on the intermediate product from which the burr has been cut. A shaping step of performing cold forging from a direction and compressing and shaping so as to have a shape substantially equal to the disk portion and the cylindrical portion; and performing a cold forging process on the cylindrical portion of the shaped intermediate product. A ring gear forming step of forming the ring gear at one end in the axial direction not including the cut portion of the burr on the outer peripheral surface of the cylindrical portion. 2. The metal rough material has a cylindrical shape obtained by cutting a round bar-shaped steel material having a metal flow aligned in an axial direction at a predetermined length, and the hot forging step comprises: The method for manufacturing a flywheel according to claim 1, wherein the intermediate product is processed by crushing the metal coarse material of (1) until the length in the axial direction becomes 3/10 or less. 3. The hot forging step is characterized in that the columnar metal rough material is subjected to hot forging to have an axial length of 3/1.
A disk processing step of crushing to a flat disk shape until it becomes 0 or less, and an intermediate product forming step of pressing the disk-shaped coarse material from the axial direction by hot forging to form the intermediate product The method for manufacturing a flywheel according to claim 2, comprising: 4. The method according to claim 1, further comprising a friction surface treatment step of forming a plurality of minute concave portions by performing shot peening after quenching and hardening the friction surface of the disk portion. A method for manufacturing a flywheel according to any one of the preceding claims.