JP2004034093A - Method for producing steering head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the complication of a sand core shape when a steering head is cast and to improve the productivity of the steering head and reduce production cost by making unnecessary the removing process of core sand etc., on the wall surface of a second hollow part into which a steering shaft rotatively supported on the steering head is inserted. <P>SOLUTION: The steering head for turnably supporting the steering shaft of a steering mechanism for supporting a front wheel in a motorcycle is produced by die casting wherein molten metal is poured into a cavity 60 formed of a mold 50 provided with a sand core 51 for forming a first hollow part and a metallic core 52 for forming a through-hole for inserting the steering shaft. The metallic core 52 is composed of a first core pin 52a and a second core pin 52b which can be pulled out from the mold in the mutually reverse directions in the center axis direction A of the through-hole. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a steering head constituting a body frame of a motorcycle by casting.
[0002]
[Prior art]
DESCRIPTION OF RELATED ART Conventionally, as a steering head which supports the steering shaft of the steering mechanism which supports the front wheel of a motorcycle, there exist some which were disclosed by patent 3,118,286, for example. This steering head is a hollow member that is cast into a substantially triangular prism shape by an upper plate, a lower plate, and a side plate that covers the entire periphery of the upper plate and the lower plate. Is formed in the vertical direction, and upper and lower bearings are formed surrounding the upper and lower openings of the shaft hole. The steering shaft inserted into the shaft hole is rotatably supported by a steering head via a bearing via a bearing mounted on the bearing portion.
[0003]
[Problems to be solved by the invention]
By the way, in the conventional steering head, the shaft hole is opened to the periphery between the upper and lower bearings in the steering head, and the internal space (corresponding to the hollow portion) of the steering head made of a hollow member as a whole. It forms one continuous space. In general, when such a steering head is formed by gravity casting, which is a type of die casting and is performed only by pressure based on the weight of the molten metal, the internal space including the shaft hole is formed by a sand core. When a sand core is used, since core sand adheres to the wall surface forming the internal space after casting, a removal operation for removing the adhered sand, for example, shot blast, air blast, or hydroblast is performed. .
[0004]
However, when the internal space has a complicated shape, it is extremely difficult to completely remove the sand attached to the steering head. There is also an attempt to apply a coating agent made of a release agent to the surface of the sand core to facilitate removal of sand, but in that case, it becomes difficult to remove the coating agent attached to the steering head. In particular, when a steering head is manufactured by die casting in which high-pressure molten metal is injected into a cavity formed by a mold having a sand core, it becomes more difficult to remove sand and a coating agent adhered to the steering head.
[0005]
Further, in a shaft hole through which a steering shaft that rotates with respect to the steering head is inserted, if core sand or a coating agent remains on a wall surface forming the shaft hole, the steering shaft is supported. During use, the sand or the coating agent detached from the wall surface may be caught in the support portion of the steering shaft, and the smooth rotation of the steering shaft may be hindered. Therefore, it is necessary to completely remove the sand and the coating agent adhering to the wall surface of the shaft hole, and the removal step increases the number of production steps of the steering head and increases the production cost.
[0006]
The present invention has been made in view of such circumstances, and the invention according to claims 1 and 2 suppresses the complexity of the shape of the sand core when casting the steering head. This eliminates the need for a step of removing core sand and the like from the wall surface of the second hollow portion through which the steering shaft rotatably supported by the steering head is inserted, thereby improving the productivity of the steering head and reducing manufacturing costs. The purpose is to do. The second object of the present invention is to further facilitate the formation of the second hollow portion by the metal core and to reduce the size and weight of the steering head.
[0007]
Means for Solving the Problems and Effects of the Invention
The invention according to claim 1 is a steering head for manufacturing a steering head that rotatably supports a steering shaft of a steering mechanism that supports a front wheel of a motorcycle by injecting molten metal into a cavity formed by a mold. In the manufacturing method, the steering head is formed with a first hollow portion for reducing the weight of the steering head, and a second hollow portion including a through hole through which the steering shaft is inserted. A method for manufacturing a steering head including a sand core forming a first hollow portion and a metal core forming the second hollow portion.
[0008]
Thus, in the steering head in which the first hollow portion and the second hollow portion are formed, only the first hollow portion is formed by the sand core, so that the first and second hollow portions are formed by the sand core. The complication of the shape of the sand core is alleviated as compared with the prior art. Further, since the second hollow portion is formed by the metal core, sand or the like does not adhere to the wall surface of the second hollow portion through which the steering shaft is inserted, so that a step of removing them is not required.
[0009]
As a result, according to the first aspect of the invention, the following effects can be obtained. That is, since only a part of the hollow portion of the steering head is formed of the sand core, the complexity of the sand core is reduced, and the second hollow portion does not require a step of removing sand or the like. And the manufacturing cost is reduced.
[0010]
According to a second aspect of the present invention, in the method of manufacturing a steering head according to the first aspect, the first core pin is configured such that the metal core can be die-cut in directions opposite to each other in a center axis direction of the second hollow portion. And a second core pin.
[0011]
Thus, the metal core is divided into two parts, so that the metal core can be easily die-cut, and the difference in area between the two openings of the second hollow portion due to the draft angle can be reduced.
[0012]
As a result, according to the second aspect of the invention, in addition to the effects of the first aspect of the invention, the following effects can be obtained. That is, since the metal core is composed of the first core and the second core that can be die-cut in directions opposite to each other in the center axis direction of the second hollow portion, each core pin after casting is easily pulled out. As a result, the formation of the second hollow portion formed of the through hole becomes easy, and the difference in the area between the two openings of the second hollow portion due to the draft angle can be reduced, so that the steering head is reduced in size and weight. .
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS.
Referring to FIG. 1, a body frame F of a motorcycle V including a steering head 3 manufactured by the manufacturing method of the present invention mainly includes a steering mechanism St, a power unit P including an internal combustion engine, and a main frame supporting a fuel tank T. 1 and a seat rail 2 mainly supporting the seat Se.
[0014]
2 and 3, the main frame 1 includes a steering head 3 forming a front end thereof, a pair of left and right front frames 4 coupled to a rear end of the steering head 3, and A pair of left and right upper intermediate frames 5 respectively connected to upper rear ends of the upper and lower frames 4, a pair of left and right lower intermediate frames 6 respectively connected to lower rear ends of both front frames 4, A pair of left and right rear frames 7 respectively connected to the rear ends of the upper and lower intermediate frames 5 and 6, a front cross member 8 connecting both front frames 4, and an upper rear cross connecting both rear frames 7. A member 9 and a lower rear cross member 10 are provided. Here, the front and rear frames 4, 7, the upper and lower intermediate frames 5, 6, and the three cross members 8 to 10 are all formed of aluminum pipe-shaped hollow members.
[0015]
In this embodiment, "front, rear, left and right" means front, rear, left and right with respect to the motorcycle V, unless otherwise specified. "Aluminum" means pure aluminum and aluminum alloys.
[0016]
The steering head 3 made of aluminum includes a front portion including a pivot portion 31 having a cylindrical peripheral wall 31w that rotatably supports the steering shaft 11, and a left and right portion 1 extending rearward while expanding in the left-right direction from the pivot portion 31. A pair of pipe-shaped mounting portions 32 and a rear portion between the mounting portions 32 and a connecting portion 33 as a reinforcing member for connecting the mounting portions 32 to each other are provided.
[0017]
A front end portion of the front frame 4 is a peripheral portion of the mounting portion 32 that defines an opening 34a1 of the side hollow portion 34a in a state where a part thereof is inserted and fitted into a side hollow portion 34a described later of the mounting portion 32. 32a. Similarly, the front frame 4 and the intermediate frames 5 and 6, the intermediate frames 5 and 6 and the rear frame 7, and the rear frame 7 and both rear cross members 9 and 10 are welded with their respective ends fitted. And are interconnected.
[0018]
The steering shaft 11 inserted into the through hole 35 as a second hollow portion formed in the pivot portion 31 is rotated by a pair of ball bearings 12 (see FIG. 2) which are support portions provided in the pivot portion 31. Supported as possible. As shown in FIG. 1, a top bridge 13 and a bottom bridge 14 are coupled to an upper end and a lower end of the steering shaft 11 projecting vertically from the through-hole 35. , The front wheel 17 is rotatably supported, and a pair of front forks 15 to which a bar handle 16 is coupled at an upper end portion are coupled. The steering shaft 11, the bridges 13, 14, the front forks 15, and the bar handle 16 constitute a steering mechanism St for supporting the front wheels 17 so as to be steerable.
[0019]
Referring to FIG. 1, each front frame 4 has a hanger portion 4 a that supports the power device P in cooperation with a support portion 7 a of each rear frame 7, and a support portion 7 a of each rear frame 7 includes: A pivot shaft 20 that rotatably supports a pair of left and right swing arms 19 that rotatably supports the rear wheel 18 at the rear end is fixed. The swing arms 19 are pivoted by a link type suspension mechanism including a link mechanism 21 connecting the support portions 7 a and the swing arms 19 and a damper 22 connecting the link mechanism 21 and the swing arms 19. It can swing vertically about the shaft 20. Further, the power of the internal combustion engine is transmitted to the output shaft 23 of the transmission, and further transmitted from the output shaft 23 to the rear wheel 18 via the endless chain 24 to rotate the rear wheel 18.
[0020]
Referring to FIGS. 4 to 7, the steering head 3 in which the pivot portion 31, the mounting portion 32, and the connecting portion 33 are integrally formed by die-casting as described later, forms a first hollow portion 34 that does not communicate with each other. And a hollow part H including a second hollow part constituting the through hole 35. The first hollow portion 34 is formed to reduce the weight of the steering head 3 by making the steering head 3 thin, and the through hole 35 is formed to rotatably support the steering shaft 11 on the pivotal support portion 31. It has a center axis L1 coinciding with the eleventh rotation axis.
[0021]
In the pivotal support portion 31, the inner peripheral wall surface 31c (also the wall surface forming the through hole 35) of the upper end portion 31a and the lower end portion 31b forming the upper opening 35a and the lower opening 35b of the through hole 35, respectively, is a double ball bearing. A pair of mounting portions 31d into which the 12 is press-fitted are formed by machining performed after casting (see also FIG. 2).
[0022]
Each mounting portion 32 is constituted by a peripheral wall 32w having a peripheral edge portion 32a defining an opening 34a1 at a rear end while being connected to the pivot support portion 31 over the entire periphery at a front end. Each peripheral wall 32w is an outer wall 32w1 far from the vehicle body center line L2 (see FIG. 5), which is a center line in the left-right direction, and is closer to the vehicle body center line L2 than the outer wall 32w1 and is more than the outer wall 32w1. And an inner wall 32w2 extending to the rear. Each mounting portion 32 has a side hollow portion 34a surrounded by the peripheral wall 32w.
[0023]
The connecting portion 33 is composed of upper and lower connecting walls 33w1 and 33w2 that connect the inner walls 32w2 to each other. The upper connecting wall 33w1 extends obliquely downward and rearward from the upper end portion 31a, and the lower connecting wall 33w2 extends obliquely downward and rearward from the lower end portion 31b with a gentler inclination than the upper connecting wall 33w1. , 33w2 are interconnected. The connecting portion 33 is surrounded by a peripheral wall 31w, both inner walls 32w2, and both connecting walls 33w1 and 33w2 of the pivot portion 31, and has a central hollow portion 34b having a substantially triangular pyramid shape. Further, a pair of plate-like reinforcing ribs connecting the connecting walls 33w1 and 33w2 at a position sandwiching the vehicle body center line L2 is provided at a rear portion of the connecting portion 33 where the distance between the mounting portions 32 in the left-right direction is increased. 33a (see FIGS. 4 and 5) is formed integrally with both connecting walls 33w1 and 33w2.
[0024]
Therefore, the first hollow portion 34 includes a pair of side hollow portions 34a and a central hollow portion 34b. Each side hollow portion 34a and the central hollow portion 34b communicate with each other through a communication port 34c. The communication port 34c serves as a sand hole for discharging the sand of the central core forming the central hollow portion 34b after casting.
[0025]
A mold for casting the steering head 3 will be described with reference to FIGS. The mold has an outer mold 40 and a core 50. The outer mold 40 includes first and second molds 41 and 42 which are divided into left and right by a dividing surface D1 (coinciding with the line VII-VII in FIG. 6) and first and second molds by dividing surfaces D2 and D3. The third mold 43 is divided rearward with respect to the second molds 41 and 42. On the other hand, the core 50 includes a sand core 51 that forms the first hollow portion 34 and the communication port 34c, and a metal core 52 that forms the through hole 35.
[0026]
The sand core 51 includes a pair of side cores 51a forming both side hollow portions 34a and a center core 51b forming the center hollow portion 34b. The sand core 51 is formed on the outer mold 40 by a skirting board (not shown) provided on each side core 51a and three skirting boards 51c1 to 51c3 (see FIG. 8) provided on the center core 51b. It is positioned and fixed with respect to.
[0027]
The metal core 52 is closer to the upper end 31a (see FIGS. 4 and 7) of the pivot portion 31 in the direction A of the center axis L1 of the through hole 35 (hereinafter, referred to as “center axis direction A”) (cavity described later). The first core pin 52a and the second core pin 52b are divided into two parts by using a plane orthogonal to the central axis L1 at a position (closer to the lower end of 60) as a division plane D4. Each of the core pins 52a and 52b has a frusto-conical surface, and is formed of a truncated cone-shaped pin having a central axis coinciding with the central axis L1 of the through hole 35, and penetrates the outer mold 40. Extending. Therefore, at the time of casting, the first core pin 52a is held so as to be able to be inserted into and removed from the outer mold 40 from below, which is one of the central axis directions A of the through holes 35, and the second core pin 52b is The first and second core pins 52a and 52b can be pulled out in the opposite direction in the center axis direction A because the first and second core pins 52a and 52b are held so as to be able to be inserted into and removed from the outer mold 40 from above, which is the other side in the center axis direction A. It is possible.
[0028]
The cavity 60 formed by the outer mold 40, the sand core 51, and the metal core 52 has an upper end 31a and a lower end 31b (see FIGS. 4 and 7) of the pivotal support 31, respectively. The steering head 3 is turned upside down so as to be formed at the upper end portion 60b.
[0029]
The mold is provided with a hot water supply system 61 for guiding a high-pressure molten metal of molten aluminum into the cavity 60. A hot water supply system 61 through which a molten metal from a heat retaining furnace (not shown) that stores the molten metal while keeping the temperature of the molten metal is pressurized by a plunger (not shown) flows. And a gate 63 located between them. The runner 62 formed in the first and second molds 41 and 42 communicates at its upstream end with a storage chamber formed by a hollow portion of a sleeve into which the plunger is slidably fitted, and has a downstream end. To communicate with the gate 63.
[0030]
The gate 63 formed over the entire circumference around the first core pin 52a by the first core pin 52a and the first to third molds 41 to 43 communicates with the runner 62 at the outer periphery thereof. At the downstream end, it comprises a cylindrical passage communicating with the lower end 60a of the cavity 60. Then, the flow rate of the molten metal at the outlet 63a of the gate 63 is set to be 5 m / s to 15 m / s, which is a value smaller than the flow rate in normal die casting and larger than the flow rate in gravity casting.
[0031]
Here, the reason for setting the flow velocity in this manner is that if the flow velocity of the molten metal at the outlet 63a of the gate 63 is less than 5 m / s, the molten metal in the cavity 60 becomes poor due to the poor running of the molten metal. When the flow rate of the molten metal exceeds 15 m / s, the pressurized molten metal injected into the cavity 60 comes into contact with the sand core 51 when it is cooled and solidified on the way to make the steering head 3 thinner and lighter. This is because the frequency of damage of the sand core 51 due to the inertia force of the molten metal increases, and the productivity of the steering head 3 is extremely reduced.
[0032]
The sand core 51 is located above the first core pin 52a with respect to the gate 63, and is located in a portion of the cavity 60 having a larger volume than the volume of the upper end portion adjacent to the gate 63. In addition, since the inner peripheral portion of the gate 63 is formed by using the first core pin 52a, the molten metal from the gate 63 moves upward in the cavity 60 while being in contact with the first core pin 52a. Since the molten metal flows toward the cavity 60 from the gate 63, the molten metal first contacts the first core pin 52a, and then flows through the cavity 60 to contact the sand core 51, The cavity 60 is filled while contacting the core 51 and the core pins 52a and 52b.
[0033]
Therefore, while the molten metal immediately after being injected from the gate 63 first flows while being in contact with the outer mold 40 and the first core pin 52a, the flow velocity is reduced due to flow resistance, and the flow velocity is reduced. Since the molten metal contacts the sand core 51 in this state, the inertia force (momentum) of the molten metal applied to the sand core 51 becomes smaller than the inertia force of the molten metal immediately after passing through the gate 63.
[0034]
As shown in FIG. 10, the first and third molds 41 and 43 and the second mold 41 are provided in the cavity 60 for forming the inner walls 33w2 (see FIG. 5) of the steering head 3. , The third molds 42 and 43 communicate with each other.
[0035]
Then, after the injection of the molten metal into the cavity 60 is completed and the molten aluminum is cooled and solidified, the core pins 52a and 52b and the outer mold 40 are removed. The sand of the sand core 51 is removed, and the core sand adhering to the wall surface forming the first hollow portion 34 of the steering head 3 immediately after casting is subjected to shot blast, air blast, hydroblast, or the like. It is removed in a removing step. Thereafter, as shown in FIG. 4, machining is performed to form the mounting portion 31 d and to form holes in the various bosses 36 a to 36 e formed in the pivot portion 31.
[0036]
Next, the operation and effect of the embodiment configured as described above will be described.
The molten metal pressurized by the plunger flows through the runner 62 and is injected into the cavity 60 through the gate 63, and the cavity 60 is filled with the molten metal from the lower end 60 a corresponding to the upper end 31 a of the pivot 31. . Then, the molten metal in the cavity 60 is solidified and the steering head 3 is cast.
[0037]
At this time, in the steering head 3 in which the first hollow portion 34 for reducing the thickness and weight of the steering head 3 and the through hole 35 through which the steering shaft 11 is inserted are formed, only the first hollow portion 34 is a sand core. Since it is formed by the 51, the complexity of the shape of the sand core 51 is suppressed as compared with the related art in which the entire hollow portion of the steering head is formed only by the sand core. In addition, since the through hole 35 is formed by the metal core 52, sand does not adhere to the wall surface of the through hole 35 through which the steering shaft 11 is inserted. And the manufacturing cost is reduced.
[0038]
Further, since the first hollow portion 34 and the through hole 35 of the steering head 3 do not communicate with each other, the rigidity of the pivot portion 31 can be increased, and this also contributes to the thinning and weight reduction of the steering head 3.
[0039]
The metal core 52 forming the through hole 35 is formed of the first core pin 52a and the second core pin 52b that can be die-cut in directions opposite to each other in the axial direction of the second hollow portion. The core pins 52a and 52b can be easily pulled out, and the difference in area between the two openings 35a and 35b of the through hole 35 due to the draft angle can be reduced, so that the diameter of the pivot portion 31 is prevented from increasing. Thus, the steering head 3 is reduced in size and weight.
[0040]
Further, the flow rate of the molten metal at the outlet 63a of the gate 63 is set in the range of 5 m / s to 15 m / s so as to be smaller than the flow rate in normal die casting and larger than the flow rate in gravity casting. The steering head 3 can be made thinner and lighter. In addition, the occurrence of breakage of the sand core 51 due to the molten metal is prevented or suppressed, so that the productivity of the steering head 3 can be improved and the manufacturing cost can be reduced. Further, since the strength of the sand core 51 can be reduced to avoid breakage by reducing the inertia force of the molten metal applied to the sand core 51, the core sand from the steering head 3 after casting can be reduced. Removal is facilitated, and also in this respect, the productivity of the steering head 3 is improved, and the manufacturing cost is reduced.
[0041]
Furthermore, the molten metal that has flowed into the cavity 60 from the gate 63 first contacts the first core pin 52a of the sand core 51 and the metal core 52, so that the molten metal contacts the first core pin 52a. During the flow, the flow velocity is reduced due to the flow resistance, and the sand core 51 contacts the sand core 51 in a state where the flow velocity is reduced, so that the inertia force (power) of the molten metal applied to the sand core 51 is reduced by the gate 63. Is smaller than the inertia force of the molten metal immediately after passing through, the occurrence of breakage of the sand core 51 due to the molten metal can be prevented or further suppressed, and the strength of the sand core 51 can be further reduced.
[0042]
Further, the flow rate of the molten metal at the outlet 63a of the gate 63 is set to a value smaller than the flow rate in normal die casting, that is, 5 m / s to 15 m / s. Has a cylindrical shape defined by the first core pin 52a, and is formed over the entire circumference of the first core pin 52a. The molten metal is rectified along the two core pins 52a and 52b while the cavity 60 is formed. By flowing inside, the turbulence of the flow of the molten metal in the cavity 60 is suppressed, and the gas is suppressed from being entrained. Therefore, the occurrence of blow holes at the opening edge 32 a which is also the welded portion of the mounting portion 32 is prevented. Is done.
[0043]
In addition, although the gate 63 is formed using the core forming the through hole 35, the core is constituted by the metal core 52, so that the first core adjacent to the gate 63 is formed. There is no breakage of the core due to the contact of the high-pressure molten metal with the pin 52a, for example, the breakage of the core such as peeling which can occur with a sand core.
[0044]
Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The sand core 51 may be provided with a coating agent composed of a segregation agent containing one or more layers of refractory fine particles. In addition, a resin binder, for example, acrylamide or phenol resin can be used for the sand core 51 in order to enhance the disintegration of the sand core 51 after casting. Further, in order to position the sand core 51 with respect to the outer die 40, pins protruding from the third die 43 into the cavity 60 are formed in the sand core 51 instead of the baseboards 51c1 to 51c3. May be inserted into the bottomed hole.
[0045]
In the embodiment, the first hollow portion 34 and the through hole 35 which are not communicated with each other are formed in the steering head 3. However, the first hollow portion 34 is formed on the condition that the through hole 35 is formed by the metal core 52. The hollow portion 34 and the through hole 35 may be partially communicated.
[0046]
In the above embodiment, the gate 63 is formed over the entire circumference around the first core pin 52a with the inner periphery formed by the first core pin 52a. May be formed on a part of the periphery of the object. Further, the gate 63 is located at a position away from the first core pin 52a, and the molten metal injected into the cavity 60 from the gate 63 first contacts the first core pin 52a, and the inertia force of the molten metal It may be formed at a position where it comes into contact with the sand core 51 after it has weakened slightly. Further, the metal core 52 may be constituted by a single core pin.
[0047]
In the above embodiment, the steering head 3 is manufactured by die casting. However, although it is slightly inferior to die casting in terms of productivity and thin-wall structure, the steering head 3 can be manufactured by gravity casting.
[Brief description of the drawings]
FIG. 1 is a schematic left side view of a motorcycle including a steering head which is a cast product manufactured according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part near a steering head of FIG. 1;
FIG. 3 is a view as viewed in the direction of the arrow III in FIG. 2;
FIG. 4 is a left side view of the steering head of FIG. 1;
FIG. 5 is a view taken in the direction of the arrow V in FIG. 4;
FIG. 6 is a view taken in the direction of arrow VI in FIG. 4, showing a main part of the steering head.
FIG. 7 is a sectional view taken along line VII-VII in FIG. 6;
8 is a view showing a cross section taken along line VIII-VIII of FIG. 10 of a casting mold for casting the steering head of FIG. 1 and a division surface of a first mold.
FIG. 9 is a sectional view taken along line IX-IX of FIG. 8;
FIG. 10 is a sectional view taken along line XX of FIG. 8;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Main frame, 2 ... Seat rail, 3 ... Steering head, 4 ... Front frame, 5, 6 ... Intermediate frame, 7 ... Rear frame, 8, 9, 10 ... Cross member, 11 ... Steering shaft, 12 ... Ball Bearings, 13 top bridge, 14 bottom bridge, 15 front fork, 16 bar handle, 17 front wheel, 18 rear wheel, 19 swing arm, 20 pivot shaft, 21 link mechanism, 22 damper, 23: main shaft, 24: chain,
31: pivot portion, 32: mounting portion, 33: connecting portion, 34: first hollow portion, 35: through hole, 36a to 36e: boss,
40 ... outer die, 41-43 ... die,
50: core, 51: sand core, 52: metal core, 52a, 52b: core pin,
60 ... cavity, 61 ... hot water supply system, 62 ... runner, 63 ... gate, 64 ... degassing passage,
V: motorcycle, F: body frame, St: steering mechanism, P: power unit, T: fuel tank, Se: seat, H: hollow part, L1: center axis, L2: body center line, D1 to D4: split Plane, A: Central axis direction.

Claims (2)

A steering head manufacturing method for manufacturing a steering head that rotatably supports a steering shaft of a steering mechanism that supports a front wheel of a motorcycle by injecting molten metal into a cavity formed by a mold,
The steering head is formed with a first hollow portion for reducing the weight of the steering head and a second hollow portion having a through hole through which the steering shaft is inserted, and the mold includes the first hollow portion. And a metal core forming the second hollow portion. 2. The steering head according to claim 1, wherein the metal core comprises a first core pin and a second core pin that can be die-cut in directions opposite to each other in a center axis direction of the second hollow portion. 3. Manufacturing method.

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