JP2018114534A - Hub and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture by cold forging unnecessary in post-treatment after molding, excellent in a material yield and shape accuracy, without causing reduction in fatigue strength by cutting of a flow line on a surface of meeting parts 14 and 15 between a flange 12 and bosses 8 and 13, while realizing a low processing load in a large-sized hub 7.SOLUTION: A hub 7 is integrally provided with a flange 12, a first boss 8 and a second boss 13. In a cross section including an axial direction, inclination angles θ, θformed by respective outer walls 8b and 13b of the first and second bosses 8 and 13 and the axial direction are a critical angle or more expressed by 200×arctan[H/{R×(1-cos(arcsin(H/R)))}]/π[deg.]. A diameter of the flange 12 is 1.5 times or more and 70 mm or more of a diameter of the outer walls 8b and 13b of the boss large in a diameter among the first boss 8 and the second boss 13. H: a height [mm] of the boss large in a diameter among the first boss 8 and the second boss 13, R: a distance [mm] of an outer wall to the product center of the boss large in a diameter among the first boss 8 and the second boss 13SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hub and a method for manufacturing the hub, and more specifically to a hub used for a rotating part such as an automobile or a construction machine and a method for manufacturing the hub.

  The hub is generally a hollow cylindrical part provided in the vicinity of a rotation shaft in a circular or radial rotation component, and the rotation shaft is disposed therethrough along with a bearing. The hub has a substantially substantially axisymmetric shape, and includes a flange projecting in a part of the axial direction in the axial radial direction and a boss projecting in the axial direction from both or one surface of the flange. As the hub, for example, a wheel hub that supports a rotating automobile wheel, a clutch hub that is incorporated in a constantly meshing manual transmission of an automobile, and the like are known.

  So far, relatively large hubs (flange diameter 70 to 180 mm) such as wheel hubs and clutch hubs have been manufactured by hot forging. That is, round steel, which is a material having a C content of about 0.5% by mass, is cut into a predetermined size, heated to a processing temperature of about 1200 ° C., and formed into a predetermined shape having a flange and a boss by hot forging. However, it has been manufactured by performing post-processing such as cutting or shot blasting to remove surface scale and improving shape accuracy, and then induction hardening and curing.

  However, when hubs are manufactured by hot forging, post-processing for scale removal, shape accuracy finishing, etc. is necessary after molding, which increases the manufacturing cost. Since a part of the forging line is inevitably cut by post-processing, a decrease in the fatigue strength of this meeting part is inevitable.

  On the other hand, if a large hub is to be manufactured by cold forging which is excellent in material yield and shape accuracy, a very high processing load is required in the molding for extending the flange. For this reason, since a large-scale and expensive forging processing facility must be used, the facility cost is remarkably increased and cannot be implemented in practice. Therefore, it is difficult to manufacture a large hub by ordinary cold forging.

  On the other hand, instead of ordinary cold forging, there has been known an invention that reduces the processing load by sequentially processing a part of a product by cold rotary forging.

  For example, in Patent Document 1, a wheel hub made of a metal having a malleability and having a flange at one end of a shaft, a friction coefficient μ between a mold contacting a flange and a workpiece is set to 0.10 or more, Sequential cold working by rotary forging reduces the push-in amount and suppresses the processing load, thereby suppressing the occurrence of local deformation while extending the life of the mold and reducing the size of the rotary forging machine. Thus, an invention has been disclosed in which the diameter expansion ratio (diameter of the expanded portion after rotational forging / material diameter before rotational forging) is stably increased as compared with the prior art.

  Patent Document 2 discloses a rotary forging device that suppresses a phase shift between upper and lower rotary molds.

  Furthermore, Non-Patent Document 1 points out that as a disadvantage of rotary forging, the deformation mode of the material by rotary forging is mainly compressive deformation in the axial direction of the material, so that the shape of products that can be manufactured is limited. Yes.

Japanese Patent Laid-Open No. 2006-159337 JP-A-2-30350

Edited by the Japan Society for Technology of Plasticity, “Plastic Processing Technology Series“ Rotating Machining-Rolling and Spinning ”” p. 100, issued by Corona, 1990

  According to the invention disclosed in Patent Document 1, it is possible to reduce the processing load by reducing the indentation amount as compared with normal cold forging, but the degree of reduction of the processing load is large. It is not sufficient for cold forging the hub of this type, and further suppression of the processing load is desired.

  Patent Document 2 does not disclose a technique for reducing a processing load in cold rotary forging.

  Further, Non-Patent Document 1 discloses that the shape of the product is limited, but does not disclose any specific shape restrictions or solving means thereof.

  The above-described large hub has not been actually formed by cold rotary forging or cold swing forging. This is because it is difficult in practice to form the hub boss by cold rotary forging or cold swing forging because the formability is insufficient and the material is cracked or the required shape accuracy cannot be obtained. This is because it has been considered.

  The present invention has been made in view of the above-described problems of the prior art. A large-sized hub such as a wheel hub or a clutch hub can be formed at a meeting portion between a flange and a boss while realizing a low processing load. It aims at providing the technique manufactured by cold forging, without producing the fall of the fatigue strength by the cutting | disconnection of the forging line in the surface.

  The present invention is listed below.

(1) A hollow cylindrical body having a hollow flange provided in a part of the axial direction so as to project in a direction substantially orthogonal to the axial direction, and an outer wall projecting in the axial direction from one surface of the flange. A metal cold rotation integrally including a first boss and a second boss which is a hollow cylindrical body having an outer wall protruding in the axial direction from the other surface of the flange in the axial direction A hub which is a forged product or a cold swing forged product,
In a cross section including the axial direction, an inclination angle that is an inferior angle formed by the outer wall of the first boss and the axial direction that is inclined toward the inside of the first boss is expressed by the following equation (1). Is greater than the critical angle
In the cross section, an inclination angle that is an inferior angle formed by the outer wall of the second boss inclined toward the inside of the second boss and the axial direction is less than the critical angle,
The hub has a diameter of 1.5 or more times a diameter of an outer wall of a boss having a larger diameter among the first boss and the second boss, and 70 mm or more, preferably 70 to 180 mm. .

Critical angle [deg.] = 200 × arctan [H / {R × (1-cos (arcsin (H / R)))}] / π (1)
In the formula (1),
H: Height of a boss having a large diameter among the first boss and the second boss [mm]
R: Distance from the outer wall of the boss having a large diameter to the center of the product [mm] among the first boss and the second boss
It is.

  (2) The forging stream line on the surface of the meeting part between the flange and the first boss is continuous, and the forging line on the surface of the meeting part between the flange and the second boss is continued. Hub described in.

  (3) After forming the first boss by performing cold forging by forward extrusion on a metal material, the flange and the second boss are formed by performing cold rotary forging or cold swing forging. The manufacturing method of the hub according to 1 or 2, wherein the forming is performed.

(4) A hollow cylindrical body having a hollow flange provided in a part of the axial direction so as to project in a direction substantially orthogonal to the axial direction, and an outer wall projecting in the axial direction from one surface of the flange. A metal cold rotation integrally including a first boss and a second boss which is a hollow cylindrical body having an outer wall protruding in the axial direction from the other surface of the flange in the axial direction A hub which is a forged product or a cold swing forged product,
In a cross section including the axial direction, an inclination angle that is an inferior angle formed by the outer wall of the first boss and the axial direction that is inclined toward the inside of the first boss is expressed by the following equation (1). Is greater than the critical angle
In the cross section, an inclination angle that is an inferior angle formed by the outer wall of the second boss and the axial direction inclined toward the inside of the second boss is a critical angle represented by the following equation (1): That's it,
The hub has a diameter of 1.5 or more times a diameter of an outer wall of a boss having a larger diameter among the first boss and the second boss, and 70 mm or more, preferably 70 to 180 mm. .

Critical angle [deg.] = 200 × arctan [H / {R × (1-cos (arcsin (H / R)))}] / π (1)
In the formula (1),
H: Height of a boss having a large diameter among the first boss and the second boss [mm]
R: Distance from the outer wall of the boss having a large diameter to the center of the product [mm] among the first boss and the second boss
It is.

  (5) The forged streamline on the surface of the meeting portion between the flange and the first boss is continuous, and the forged streamline on the surface of the meeting portion between the flange and the second boss is continued. Hub described in.

(6) Pre-processing for forming a first intermediate formed product having the second boss by performing cold forging by forward extrusion on a metal material;
Cold rotating forging or cold swing forging is performed on the first intermediate molded product, and the flange and the cross section including the axial direction are inclined toward the inside of the portion formed on the first boss. A second portion provided with a portion formed on the first boss, wherein an inclination angle which is an inferior angle formed by the outer wall of the portion and the axial direction is less than a critical angle represented by the following equation (1): A first process for forming an intermediate molded product;
Cold forging by forward extrusion is performed by a punch die, and a portion formed on the first boss of the second intermediate molded product is pressed, thereby causing the portion formed on the first boss to be outside. 6. The method for manufacturing a hub according to 4 or 5, including a second process of performing a widening process of bending and bending.

  (7) The manufacturing method of the hub according to item 6, wherein the inclination angle of the outer wall of the portion formed on the first boss of the second intermediate molded product by the second processing is 65 ° or more. .

  That is, the difference between the inclination angle of the outer wall of the portion formed on the first boss and the inclination angle of the outer wall of the first boss of the hub is set to 25 ° or less.

  (8) In the second processing, before the partial pressing of the second intermediate molded product to be molded to the first boss by the mold, the outer wall of the portion molded to the first boss is The hub manufacturing method according to claim 6 or 7, wherein a mold having an inner surface shape that coincides with an outer surface shape of the first boss of the hub is disposed outside.

  According to the present invention, a large hub having a diameter of 70 mm or more, such as a wheel hub or a clutch hub, is utilized by using sequential molding (cold rotary forging or cold swing forging) to achieve a low work load while cooling. It can be manufactured by hot forging.

  For this reason, according to the present invention, since no post-processing after molding is required, the large hub is prevented while preventing a decrease in fatigue strength due to the cutting of the streamline at the surface of the large hub flange and the boss. Can be molded with good shape accuracy and a high material yield, and the amount of capital investment can be suppressed, and the cost can be reduced.

Fig.1 (a) is explanatory drawing which shows typically the forging used by the prior process of this invention, FIG.1 (b) is explanatory drawing which shows typically the rotary forging used by the 1st process of this invention. FIG.1 (c) is explanatory drawing which shows typically the forging used by the 2nd process of this invention. FIG. 2A to FIG. 2E are explanatory views schematically and chronologically showing the swing forging used in the first processing of the present invention. FIG. 3 is an explanatory view showing a deformation state of a material at the time of rotary forging. 4 (a) is a cross-sectional view showing a hub according to the present invention, FIG. 4 (b) is an explanatory view showing an enlarged portion A of FIG. 4 (a), and FIG. It is explanatory drawing which expands and shows the site | part corresponded to the said A part in the conventional hub manufactured by the hot forging.

  The present invention will be described with reference to the accompanying drawings.

In the present invention, the above-described cold forging of the large hub is applied with sequential processing that performs partial sequential processing, specifically, rotary forging or swing forging, thereby reducing the processing load and Realize cold forging with excellent yield and shape accuracy. Hereinafter, the hub and the manufacturing method thereof according to the present invention will be sequentially described.
1. Hub 7 according to the present invention
Fig.1 (a) is explanatory drawing which shows typically the forging used by the prior process of this invention, FIG.1 (b) is explanatory drawing which shows typically the rotary forging used by the 1st process of this invention. FIG.1 (c) is explanatory drawing which shows typically the forging used by the 2nd process of this invention.

  FIG. 2A to FIG. 2E are explanatory views schematically and chronologically showing the swing forging used in the first processing of the present invention. FIG. 3 is an explanatory view showing a deformation state of a material at the time of rotary forging.

  Further, FIG. 4A is a cross-sectional view showing the hub 7 according to the present invention, and FIG. 4B is an explanatory view showing an enlarged portion A of FIG. 4A. c) It is explanatory drawing which expands and shows the site | part corresponded to the said A part in the conventional hub 7 manufactured by the hot forging.

  As shown in FIGS. 1 (c) and 4 (a), the hub 7 has a flange 12, a first boss 8 and a second boss 13 in the axial direction (the one-dot chain line in FIG. (In the extending direction). The hub 7 is a cold rotating forged product or a cold swing forged product made of metal (for example, steel or aluminum alloy).

  The hollow flange 12 is provided so as to protrude in a direction orthogonal to the axial direction in a part of the axial direction. The first boss 8 has an inner wall 8 a and an outer wall 8 b that protrude in the axial direction from one surface 12 a of the flange 12. The first boss 8 is provided in a hollow and cylindrical shape.

  Further, the second boss 13 has an inner wall 13 a and an outer wall 13 b that protrude in the axial direction from the other surface 12 b of the flange 12. The second boss 13 is provided in a hollow and cylindrical shape.

  Since the present invention provides two types of hubs 7 having different shapes, these will be described sequentially.

(1-1) First hub 7
As shown in FIG. 1B, in the cross section including the axial direction, an inclination angle θ that is an inferior angle formed by the outer wall 8b of the first boss 8 that inclines toward the inside of the first boss 8 and the axial direction. ₁ is not less than the critical angle represented by the following formula (1).

Further, in the cross section, the inclined angle theta ₂ is a minor angle to the outer wall 13b and the axial direction forms a second boss 13 which is inclined towards the inside of the second boss 13 is less than the critical angle.

  Further, the diameter of the flange 12 is set to 1... Of the diameter of the outer wall 8b of the boss having the larger diameter among the first boss 8 and the second boss 13 (the first boss 8 in the hub 7 shown in FIGS. 1 and 4). 5 times or more and 70 mm or more, preferably 70 to 180 mm.

Critical angle [deg.] = 200 × arctan [H / {R × (1-cos (arcsin (H / R)))}] / π (1)
In the formula (1), H is the height [mm] of the boss having a large diameter among the first boss 8 and the second boss 13, and R is the first boss 8 and the second boss 13. The distance from the outer wall of the boss having a large diameter to the center of the product [mm].

(1-2) Second hub 7
In a cross section including the axial direction, inclination angles θ ₁ and θ ₂ that are inferior angles formed between the outer walls 8b and 13b of the first bosses 8 and 13 inclined toward the inside of the first bosses 8 and 13 and the axial direction. Are both above the critical angle.

  The diameter of the flange 12 is 1.5 times or more the diameter of the outer wall 8b of the boss having the larger diameter among the first boss 8 and the second boss 13, and is 70 mm or more, preferably 70 to 180 mm. is there.

  Furthermore, since the first and second hubs 7 are both manufactured by cold rotary forging or cold swing forging as will be described later, post-processing (such as scale removal and shape accuracy finishing after molding). There is no need to perform cutting or shot blasting.

  For this reason, in both the first and second hubs 7, the forging lines 16 on the surface of the meeting portion 14 between the flange 12 and the first boss 8 are continuous, and the flange 12 and the second boss 13 are connected to each other. A forge line (not shown) on the surface of the meeting part 15 continues. Therefore, in both the first and second hubs 7, a decrease in fatigue strength due to the cutting of the forging lines 16 on the surfaces of the meeting portions 14 and 15 is prevented.

On the other hand, in the conventional hub manufactured by hot forging, as shown in FIG. 4 (c), the forged lines 17 on the surfaces of the meeting portions 14 and 15 are cut by post-processing after molding, A decrease in fatigue strength is inevitable.

2. Production Method According to the Present Invention As shown in FIG. 1 (a), in the pre-processing of the present invention, the second boss is formed by performing cold forging by forward extrusion on the cylindrical material 3 using the upper mold 1 and the lower mold 2. First intermediate molded product 4 having 13 is molded.

  As shown in FIG. 1B, in the first processing (rotational forging) of the present invention, the first intermediate molded product 4 is processed while the upper die 5 and the lower die 6 are rotated, and the second processing is performed. This is a rotary forging process for forming the intermediate molded product 18.

The lower mold 6 performs only rotation, and the first intermediate molded product 4 supported by the lower mold 6 rotates together with the lower mold 6. The upper mold 5 is moved downward toward the lower mold 6 while rotating at a predetermined angle θ _{3 with} respect to the vertical line.

  By the first processing, the first intermediate molded product 4 is deformed as shown in FIG. 3, and the second intermediate molded product 18 is manufactured without causing a crack defect.

  As shown in FIG. 1 (c), in the second processing of the present invention, after the second intermediate molded product 18 is placed on the lower mold 2, a mold having an outer wall 19a having a shape that matches the final product shape. The (upper mold) 19 is arranged on the outer side of the outer wall of the portion 18a formed on the first boss 8 in the second intermediate molded product 18 so as to press the flange 18b of the second intermediate molded product 18.

  Thereafter, the punch die 20 having a truncated cone shape is lowered to perform a squeezing process for squeezing the inner wall of the portion 18a formed in the first boss 8 in the second intermediate molded product 18 outward. In this way, the hub 7 is manufactured.

  In the above description, the case where the large hub 7 is formed by cold rotary forging is taken as an example. However, the situation is the same even in the case of cold swing forging shown in FIG. 2 instead of cold rotary forging. . That is, in the cold rotary forging, as shown in FIG. 1B, the upper mold 5 rotates in an inclined manner and the first intermediate molded article 4 rotates horizontally with the lower mold 6 to thereby form the first intermediate molded article. 4 is sequentially processed.

  On the other hand, in the cold swing forging, as shown in FIG. 2, the upper die 21 is lowered while performing a swinging motion for turning the rotating shaft. The first intermediate molded product 4 does not move with the lower mold 6. In this way, the first intermediate molded product 4 is sequentially processed. For this reason, the processing load on which the material is loaded from the upper molds 5, 21 and the lower mold 2 is the same for both rotary forging and swing forging.

  By manufacturing the large hub 7 by cold rotary forging or cold swing forging, the processing load is greatly reduced to about 1/3 to 1/10 of the normal cold forging.

  However, when the large hub 7 to be manufactured by the present invention is manufactured by cold rotary forging or cold swing forging, depending on the shape of the first boss 8 of the hub 7, In some cases, the portion 4a formed in the first boss 8 is broken or has a remarkable shape accuracy, and cannot be manufactured.

  The non-working region 11 (the upper die 5 is the first one) opposite to the working region 10 (the region where the upper die 5 contacts and presses the first intermediate molded product 4) by cold rotary forging or cold swing forging. In the region away from the intermediate molded product 4), the upper die 5 generates a force in a direction in which the outer wall of the portion 4a formed on the first boss 8 of the first intermediate molded product 4 is bent inward. . When the degree of contact between the upper mold 5 and the first intermediate molded product 4 in the non-working region 11 is severe, the first intermediate molded product 4 is broken or has a remarkable shape accuracy failure.

The requirement of the shape of the outer wall 8b of the first boss 8 of the hub 7 that is the product, which causes the above-described first intermediate molded product 4 to break or the remarkable poor shape accuracy, is expressed by the above equation (1). . That is, (1) is than the critical angle is, less gentle shape shape of the outer wall 8b of the first boss 8, i.e. the inclined angle theta ₁ is critical angle of the outer wall 8b of the first boss 8 defined by the formula In this case, it is possible to avoid a shape accuracy defect due to the first processing that is cold forging.

  Next, the first boss 8 whose shape outside the range of the expression (1), that is, the shape of the outer wall 8b is steep, cannot be processed by rotary forging. Therefore, in the present invention, the first intermediate molded product 4 having the second boss 13 is formed by pre-processing for performing cold forging by forward extrusion on the material 4.

  Next, the second intermediate molded product 18 having a shape that can be processed by the first processing that is rotary forging is formed.

  Finally, the second intermediate molded product 18 is subjected to the second process which is a bending process that does not require rotary forging, in other words, a low processing load is required. The hub 7 having a steep shape on the outer wall 8b of the boss 8 is formed.

  Briefly, after the shape satisfying the shape of the outer wall represented by the formula (1) is processed by cold rotary forging (first processing), the second intermediate forming is performed by squeezing as the second processing. By bending the root portion 8c of the first boss 8 in the product 18, the first boss 8 having the steep outer wall 8b is finished.

  The processing of the flange 12 of the hub 7 requires a large processing load corresponding to a wide processing site. On the other hand, the 2nd process (cold forging by normal forward extrusion) with respect to the root part 8c of the 1st boss | hub 8 of the hub 7 mainly becomes a bending process (mouth expansion process) with respect to the root part 8c. For this reason, a processing load can be restrained small, without resorting to rotary forging.

  Furthermore, even when the shape of the outer wall 8b of the first boss 8 of the hub 7 satisfies the shape of the outer wall represented by the expression (1), if the shape is excessively gentle, specifically, the hub 7 when the difference between the inclination angle of the outer wall 8b of the first boss 8 and the inclination angle of the outer wall of the portion 18a formed on the first boss 8 in the second intermediate molded product 18 is greater than 25 °. In the second processing, the shape of the outer wall of the first boss 8 cannot be processed with high precision, or the processing load becomes excessive, and the processing cannot be performed.

  For this reason, the hub 7 to which the present invention is applied is processed by cold rotary forging or cold swing forging when the shape of the outer wall 8b represented by the expression (1) is satisfied, When the shape of the outer wall 8b represented is not satisfied, the shape of the outer wall represented by the expression (1) is satisfied by cold rotary forging or cold swing forging (first processing), and the hub 7 The difference between the inclination angle of the outer wall 8b of the first boss 8 and the angle of the outer wall of the portion 18a formed on the first boss 8 in the second intermediate molded product 18 was processed within 25 °. Thereafter, the hub 7 having a desired shape can be formed by processing into a shape including the steep outer wall 8b outside the range of the expression (1) by the second processing.

  As a raw material, carbon steel for mechanical structure S55C (C: 0.52-0.58 mass%, Si: 0.15-0.35 mass%, Mn: 0.60-0.90 mass%, P: 0.00. A spheroidizing annealing material of 030 mass% or less, S: 0.035 mass% or less) was used.

  As shown in FIG. 1 (a), a first intermediate molded product 4 having a second boss 13 was formed by pre-working the material 3 by cold forging by forward extrusion.

Next, as shown in FIG. 1B, in the first processing, the first intermediate molded product 4 is processed into the second intermediate molded product 18 while rotating the upper mold 5 and the lower mold 6. A cold rotary forging process for forming was adopted. The lowering speed of the upper mold 5 was set to 0.4 mm / sec, the rotation speeds of the upper mold 5 and the lower mold 6 were set to about 50 rpm, and the inclination angle θ ₃ of the upper mold 1 was set to 4 °.

  As shown in FIG. 1 (c), in the second processing, after the second intermediate molded product 18 is installed in the lower mold 6, the mold (upper mold) 19 is replaced with the second intermediate molded product 18. The portion formed on the flange 12 is arranged outside the outer wall of the portion 18a formed on the first boss 8 so as to press the portion formed on the flange 12.

  Then, by lowering the punch die 20, the second intermediate molded product 18 is squeezed, and the diameter of the first boss 8 is 35 or 40 mm, and the diameter of the second boss 13 is 30. Alternatively, the hub 7 having a diameter of 40 mm and a flange 12 of 80 mm was manufactured.

  Table 1 summarizes the molds and component shapes in the first processing and the second processing together with the experimental results. Table 1 shows the experimental results of steel material cracking and shape accuracy defects. The results of the first processing in Table 1 are based on experiments, and the results of the second processing are based on FEM analysis.

  In Table 1, “x” as a result of the first processing indicates that a part formed on the first boss 8 is broken during the forming. In addition, “x” as a result of the second machining indicates that an excessive machining load is required in order to accurately machine the outer wall shape to a desired shape along the mold after raising the steep angle. Therefore, it shows that forging processing equipment becomes expensive.

  From the results shown in Table 1, according to the present invention, a large hub 7 such as a wheel hub or a clutch hub having a diameter of the flange 12 of 70 mm or more can be reduced by cold forging or cold swing forging. While realizing, high material yield with good shape accuracy without causing deterioration of fatigue strength due to cutting of the forged wire 16 at the surface of the meeting portion 14, 15 between the flange 12 and the first and second bosses 8, 13. It can be seen that the cost can be reduced by reducing the capital investment amount.

DESCRIPTION OF SYMBOLS 1 Upper mold | type 2 Lower mold | type 3 Cylindrical raw material 4 1st intermediate molded product 4a The part 5 shape | molded by the 1st boss | hub 5 Upper mold | type 6 Lower mold | type 7 Hub 8 1st boss | hub 8a Inner wall 8b Outer wall 8c Root part 10 Processing area 11 Non-processed region 12 Flange 12a, 12b Surface 13 Second boss 13a Inner wall 13b Outer wall 14, 15 Meeting portion 16, 17 Forging line 18 Second intermediate molded product 18a Portion 18b molded to first boss of hub 19 Mold (Upper mold)
19a outer wall 20 punch mold 21 upper mold

Claims (8)

A hollow cylindrical body having a hollow flange projecting in a direction substantially perpendicular to the axial direction in a part of the axial direction, and an outer wall protruding from one surface of the flange toward the axial direction. A cold rotating forging made of metal, which is integrally provided in the axial direction, and a second boss which is a hollow cylindrical body having an outer wall protruding in the axial direction from the other surface of the flange, or A hub that is a cold rocking forging,
In a cross section including the axial direction, an inclination angle that is an inferior angle formed by the outer wall of the first boss and the axial direction that is inclined toward the inside of the first boss is expressed by the following equation (1). Is greater than the critical angle
In the cross section, an inclination angle that is an inferior angle formed by the outer wall of the second boss inclined toward the inside of the second boss and the axial direction is less than the critical angle,
The hub has a diameter that is 1.5 times or more of an outer wall diameter of a boss having a larger diameter among the first boss and the second boss, and is 70 mm or more.
Critical angle [deg.] = 200 × arctan [H / {R × (1-cos (arcsin (H / R)))}] / π (1)
In the formula (1),
H: Height of a boss having a large diameter among the first boss and the second boss [mm]
R: Distance from the outer wall of the boss having a large diameter to the center of the product [mm] among the first boss and the second boss
It is.   The forged streamline at the surface of the meeting portion between the flange and the first boss is continuous, and the forged streamline at the surface of the meeting portion between the flange and the second boss is continuous. Hub.   After forming the first boss by performing cold forging by forward extrusion on a metal material, forming the flange and the second boss by performing cold rotary forging or cold swing forging, The manufacturing method of the hub according to claim 1 or 2. A hollow cylindrical body having a hollow flange projecting in a direction substantially perpendicular to the axial direction in a part of the axial direction, and an outer wall protruding from one surface of the flange toward the axial direction. A cold rotating forging made of metal, which is integrally provided in the axial direction, and a second boss which is a hollow cylindrical body having an outer wall protruding in the axial direction from the other surface of the flange, or A hub that is a cold rocking forging,
In a cross section including the axial direction, an inclination angle that is an inferior angle formed by the outer wall of the first boss and the axial direction that is inclined toward the inside of the first boss is expressed by the following equation (1). Is greater than the critical angle
In the cross section, an inclination angle that is an inferior angle formed by the outer wall of the second boss and the axial direction inclined toward the inside of the second boss is a critical angle represented by the following equation (1): That's it,
The hub has a diameter that is 1.5 times or more of an outer wall diameter of a boss having a larger diameter among the first boss and the second boss, and is 70 mm or more.
Critical angle [deg.] = 200 × arctan [H / {R × (1-cos (arcsin (H / R)))}] / π (1)
In the formula (1),
H: Height of a boss having a large diameter among the first boss and the second boss [mm]
R: Distance from the outer wall of the boss having a large diameter to the center of the product [mm] among the first boss and the second boss
It is.   The forged streamline on the surface of the meeting part of the said flange and the said 1st boss | hub continues, and the forged streamline on the surface of the meeting part of the said flange and the said 2nd boss | hub continues. Hub. Pre-processing to form a first intermediate molded product having the second boss by performing cold forging by forward extrusion on a metal material;
Cold rotating forging or cold swing forging is performed on the first intermediate molded product, and the flange and the cross section including the axial direction are inclined toward the inside of the portion formed on the first boss. A second portion provided with a portion formed on the first boss, wherein an inclination angle which is an inferior angle formed by the outer wall of the portion and the axial direction is less than a critical angle represented by the following equation (1): A first process for forming an intermediate molded product;
Cold forging by forward extrusion is performed by a punch die, and a portion formed on the first boss of the second intermediate molded product is pressed, thereby causing the portion formed on the first boss to be outside. The manufacturing method of the hub according to claim 4 or 5 including the 2nd processing which carries out mouth widening processing bent down.   The hub manufacturing method according to claim 6, wherein the inclination angle of the outer wall of the portion formed on the first boss of the second intermediate molded product by the second processing is 65 ° or more.   In the second processing, before the partial pressing to the first boss of the second intermediate molded product by the mold, on the outside of the outer wall of the portion to be molded to the first boss, The hub manufacturing method according to claim 6 or 7, wherein a mold having an inner surface shape that matches an outer surface shape of the first boss of the hub is disposed.

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