JP2008267466A - Case component manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a case component manufacturing method capable of preventing misalignment of the centers of shaft holes for rear wheels, shaft holes for front wheels and a plurality of pin holes between a pair of case parts even when there are restrictions on machining conditions. <P>SOLUTION: The pair of case parts 2A, 2B are secured to a machine 6 in such a state that mating surfaces 201 of the pair of case parts 2A, 2B to be joined to each other are arranged facing a main shaft of the machine 6. Subsequently, the main shaft of the machine 6 is moved to form the rear wheel shaft holes 31 and the front wheel shaft holes 32 in the pair of case parts 2A, 2B and the plurality of pin holes 34 for insertion of a plurality of positioning pins in the pair of case parts 2A, 2B. Thereafter, the pair of processed case parts 2A, 2B are combined and the positioning pins are inserted in the plurality of pin holes 34 so as to form a transfer case (case component) 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a case component formed by combining a pair of case portions.

For example, a transmission used in a four-wheel drive vehicle is configured to transmit the power of the output shaft portion to the rear wheels and front wheels of the vehicle via a differential device or the like. A transfer case that accommodates an output shaft portion of the transmission, a driven output shaft portion, a differential device, and the like is used as a portion that transmits this power to the rear wheels and the front wheels.
This transfer case is formed by combining a pair of case portions with each other, and a rear wheel shaft hole for rotating and supporting the output shaft portion, and a driven output that rotates following the rotation of the output shaft portion. Front wheel shaft holes for inserting and supporting the shaft portion through the shaft portion are formed in the same axial center over the respective case portions.

By the way, the shapes of the case portions are different, and conventionally, for each case portion, a rear wheel shaft hole, a front wheel shaft hole, and a pin hole for positioning the case portions are processed. Yes. And the center position of the shaft hole for rear wheels and the shaft hole for front wheels in a pair of case parts is managed with the positioning pin inserted in the pin hole provided in each case part.
For this reason, when the transfer case is formed by assembling the case part, the center positions of the rear wheel shaft hole and the front wheel shaft hole in each case part may be displaced. Further, the deviation of the center position that occurs between the case portions is caused by differences in conditions such as the temperature of the coolant, the thermal deformation of the processing machine, and the outside air temperature among the processing machines that perform the hole machining of the case portions. There is also a fear.

  Further, for example, Patent Document 1 discloses a transmission that includes an input shaft to which power from a prime mover is input and an output shaft that shifts and outputs power from the input shaft. In this transmission, a transmission shaft member for transmitting rotation of an output shaft to a drive shaft is rotatably held by bearings held in holding holes formed in a main case (mission case) and a sub case (extension case), respectively. Yes. And the technique which processes the holding hole in a main case and the holding hole in a subcase in the state which assembled | attached the main case and the subcase is disclosed. According to this, it is possible to prevent the displacement between the center of the holding hole in the main case and the center of the holding hole in the sub case, and it is possible to improve the assembly accuracy of the reduction driven gear.

However, the processing technique in Patent Document 1 is an effective processing technique only when a hole can be drilled from the outside of the main case or the sub case with the main case and the sub case assembled. Therefore, due to the structure of each case, it cannot be adopted when the hole cannot be drilled from the outside of the main case or the sub case.
In particular, when the distance between the portions that support the shaft portions in the pair of cases is shortened, the inclination of the shaft portions that are supported in the shaft holes is increased even if the shift amounts between the shaft centers of the shaft holes are the same. In this case, there is a risk that the noise of the gear provided on the shaft portion will increase. Therefore, a machining method that can prevent the displacement of the center of the shaft hole in the pair of cases is desired even when the machining conditions are particularly limited.

JP 2004-183800 A

  The present invention has been made in view of such a conventional problem, and even when processing conditions are limited, a rear wheel shaft hole, a front wheel shaft hole, and a plurality of pins are provided between a pair of case portions. An object of the present invention is to provide a method for manufacturing a transfer case that can prevent the center positions of the holes from shifting from each other.

The present invention is a method of manufacturing a case component comprising a pair of case portions in which shaft holes are formed in the same axis, and configured to position the pair of case portions with each other via a plurality of positioning pins. In
An arrangement step of fixing the pair of case parts to the processing machine and arranging each mating surface where the pair of case parts are combined with each other toward the main shaft side in the processing machine,
A processing step of moving the main shaft in the processing machine to process the shaft holes in the pair of case portions and the plurality of pin holes for inserting the plurality of positioning pins in the pair of case portions;
An assembly step of forming a case component by inserting the plurality of positioning pins into the plurality of pin holes using the pair of case portions subjected to the arrangement step and the processing step as a pair of sets. (Claim 1).

In the case component manufacturing method of the present invention, first, in the arranging step, the pair of case parts are fixed to the processing machine in a state where the mating surfaces of the pair of case parts are directed to the main shaft side of the processing machine.
Next, in the processing step, the spindle in the processing machine is moved to process the shaft hole and the plurality of pin holes for each case portion. At this time, the shaft hole and the plurality of pin holes can be continuously processed for each case portion.

Therefore, it is possible to almost match the processing conditions when processing the pair of case portions, and even if there are variations in various conditions such as coolant temperature, thermal deformation of the processing machine, outside temperature, etc. in the processing machine, The pair of case portions are affected almost equally.
Thereby, in the assembly process, when the case parts are formed by combining the pair of case parts that have been subjected to the arranging process and the processing process as a pair of sets via the plurality of positioning pins, between the pair of case parts. The center positions of the shaft hole and the plurality of pin holes can be prevented from shifting.

  In the present invention, drilling is performed in a state in which the mating surfaces of the pair of case portions are directed in the direction of the main shaft in the processing machine. Therefore, in the manufacturing method of the present invention, in particular, when the hole processing cannot be performed from the outer surface opposite to the mating surface in each case portion, that is, in the position corresponding to the shaft hole on the outer surface in each case portion, Etc. can also be employed.

  Therefore, according to the case component manufacturing method of the present invention, it is possible to prevent the center positions of the shaft hole and the plurality of pin holes from being shifted between the pair of case portions even when the processing conditions are limited. can do.

A preferred embodiment of the present invention described above will be described.
In the present invention, before performing the placement step, a preliminary processing step for processing a processing reference hole and a processing reference surface for fixing the pair of case portions to the processing machine is performed to form a pair of sets. It is preferable that the arrangement step, the processing step, and the assembly step are performed using a pair of case portions that have been subjected to the preliminary processing step.
In this case, the processing conditions for processing the processing reference hole and the processing reference surface can be almost matched to the pair of case portions. Therefore, when the hole is machined by fixing the pair of case parts to the processing machine using the machining reference hole and the machining reference surface, the center of the shaft hole and the plurality of pin holes is formed between the pair of case parts. It can suppress more effectively that position shifts.

Further, the processing machine has the main shaft arranged in a horizontal direction, and in the arranging step, the pair of case portions arranges the mating surfaces perpendicular to the direction of the main shaft and the processing. Assuming a virtual center line that passes through the original position, which is the horizontal center position of the main shaft in the machine, in the vertical direction, one case portion and the other case portion constituting the pair of case portions are connected to the shaft hole and It is preferable that the processing positions of the plurality of pin holes are arranged in a state of being symmetric with respect to the virtual center line.
In this case, when a processing machine having a main shaft in the horizontal direction is used, the pair of case portions are almost equally affected by the thermal deformation of the processing machine. Therefore, it can suppress more effectively that the center position of a shaft hole and a plurality of pin holes shifts between a pair of case parts.

Further, in the preliminary processing step, the processing reference hole is formed at two positions located on opposite sides of the shaft hole in the mating surfaces of the pair of case portions, and in the processing step, Preferably, the pin hole is formed in the vicinity of the processing reference hole on the mating surfaces of the pair of case portions.
In this case, it is possible to improve the accuracy of the formation positions of a plurality of pin holes that serve as a reference when assembling the pair of case portions. Therefore, when a reference pin is inserted into each pin hole of a pair of case parts to form a transfer case as a case part, the center positions of the shaft hole and the plurality of pin holes are between the pair of case parts. It is possible to more effectively suppress the shift.

Further, the case part is a transfer case used for a transmission for a four-wheel drive vehicle, and the shaft hole is at least a rear wheel shaft hole for rotatably supporting the output shaft portion of the transmission. And a shaft hole for a front wheel for inserting and supporting the driven output shaft portion that rotates following the rotation of the output shaft portion.
In this case, even when processing conditions are limited, transfer that prevents the center positions of the rear wheel shaft hole, the front wheel shaft hole, and the plurality of pin holes from shifting between the pair of case portions. A case can be manufactured.
In addition to the transfer case, the case part may be a case for an FF transmission. Further, the case component may be a case for another driving device in which the support distance of the shaft portion rotatably supported in the shaft hole is relatively short.

Hereinafter, embodiments of the method for manufacturing a case component according to the present invention will be described with reference to the drawings.
The case part of this example is a transfer case 1, and the transfer case 1 is a rear wheel for inserting and rotatingly supporting an output shaft portion 41 in a transmission for a four-wheel drive vehicle, as shown in FIGS. A pair of cases in which shaft holes 32 for front wheels for inserting and rotatingly supporting the shaft hole 31 for rotation and the driven output shaft portion 42 that rotates following the rotation of the output shaft portion 41 are formed in the same axial center. It consists of parts 2A and 2B. As shown in FIG. 2, the pair of case portions 2 </ b> A and 2 </ b> B are configured to be positioned with respect to each other via positioning pins inserted into the plurality of pin holes 34.

In this example, a transfer case 1 as a case part is manufactured by performing the following steps.
First, as a preliminary processing step, the processing reference hole 36 and the processing reference surface 37 for fixing the pair of case portions 2A and 2B to the processing machine 6 are processed (see FIG. 1). Next, as shown in FIG. 1 and FIG. 6, as a placement process, a pair of case portions 2A and 2B that have undergone the preliminary machining process are used as a set, and a pair of the case reference holes 36 and the machining reference surface 37 are used as a reference. Are fixed to the processing machine 6. At this time, the pair of case parts 2A and 2B are fixed bases in the processing machine 6 with the respective mating surfaces 201 where the pair of case parts 2A and 2B are combined with each other facing toward the front side (opposite side of the main shaft 61) in the processing machine 6. Fix to 61. Thereafter, the fixing base 61 is rotated by 180 ° so that the respective mating surfaces 201 face the spindle 61 side in the processing machine 6.

  Next, as shown in the figure, as a processing step, the main shaft 61 in the processing machine 6 is moved, the rear wheel shaft hole 31 and the front wheel shaft hole 32 in the pair of case portions 2A and 2B, and the pair of case portions 2A. In 2B, a plurality of pin holes 34 for inserting a plurality of positioning pins are processed. Thereafter, as shown in FIG. 2 and FIG. 5, as an assembling process, a pair of processed case portions 2 </ b> A and 2 </ b> B are used as a set, a plurality of positioning pins are inserted into a plurality of pin holes 34, and a transfer case 1 is formed.

Hereinafter, the manufacturing method of the transfer case (case part) 1 of this example will be described in detail with reference to FIGS.
As shown in FIG. 5, the transfer case 1 of the present example includes a rear wheel shaft hole 31 and a front wheel shaft hole 32, and a transmission shaft portion 43 that transmits a rotational force from the output shaft portion 41 to the driven output shaft portion 42. Auxiliary shaft hole 33 is provided for rotating and supporting. In the transfer case 1, three shaft holes, a rear wheel shaft hole 31, an auxiliary shaft hole 33, and a front wheel shaft hole 32 are formed.
As shown in FIGS. 3 to 5, the pair of case portions 2 </ b> A and 2 </ b> B includes a front case portion 2 </ b> A disposed on the front side F of the vehicle and a rear case portion disposed on the rear side R of the front case portion 2 </ b> A. 2B. The front case portion 2A is configured to be coupled to the transmission main body on the front side thereof, and the extension case portion 21 is configured to be coupled to the rear side R of the rear case portion 2B.

  Further, as shown in FIG. 5, the output shaft portion 41 is connected to a connection output shaft portion 41 for transmitting power to the rear wheels via a differential device 44. Projecting to the rear of the extension case portion 21. The transmission shaft portion 43 is connected to the output shaft portion 41 via a differential device 44, and power is transmitted to the transmission shaft portion 43 and the driven output shaft portion 42 via gears provided respectively. It is configured as follows.

  As shown in FIG. 5, the rear wheel shaft hole 31, auxiliary shaft hole 33, and front wheel shaft hole 32 that perform drilling in the machining process of this example are an output shaft portion 41, a transmission shaft portion 43, and a driven output shaft portion, respectively. It is a shaft hole for arranging a bearing 45 for allowing 42 to rotate. As the bearing 45, a bearing formed by arranging a plurality of cylindrical rollers (may be steel balls, conical rollers, etc.) between the inner ring and the outer ring can be used.

As shown in FIG. 3, the shaft holes 31, 32, 33 of the front case portion 2 </ b> A are processed from the mating surface 201 on the rear side R so as to guide the outer ring of the bearing 45 from the front side F. On the other hand, as shown in FIG. 4, the shaft holes 31, 32, 33 of the rear case part 2 </ b> B are processed from the mating surface 201 on the front side F so as to guide the outer ring of the bearing 45 from the rear side R.
As shown in FIG. 3, in the front case portion 2A, the shaft holes 31, 32, 33 cannot be machined from the front side F (the side opposite to the mating surface 201), and as shown in FIG. In the rear case portion 2B, the shaft holes 31, 32, and 33 cannot be processed from the rear side R (the side opposite to the mating surface 201).

  As shown in FIG. 6, the processing machine 6 used in the processing step of this example is a machining center 6 in which the main shaft 61 is disposed in the horizontal direction H. The processing machine 6 uses the linear motor 64 to move the main shaft 61 in the X-axis direction (left-right direction, horizontal direction) and the Y-axis direction (up-down direction, vertical direction) to perform processing. It is configured. Further, the processing machine 6 measures the movement of the main shaft 61 to the X axis and the Y axis by the linear scales 65 provided in parallel to the X axis and the Y axis, respectively, and feeds back the measurement values by the respective linear scales 65, The X-axis and Y-axis linear motors 64 are controlled.

Moreover, in the processing machine 6, the fixing stand 62 for fixing each case part 2A, 2B is arrange | positioned rotatably. The fixing table 62 is rotatably arranged so that a set surface 621 for fixing the case portions 2A and 2B is positioned on the main shaft 61 side and on the opposite side to the main shaft 61.
The fixed base 62 is movable in the axial direction of the main shaft 61 by a ball screw 66 and a motor that drives the ball screw 66. In this example, the axial direction of the main shaft 61 is the Z-axis direction (front-rear direction, depth direction). In FIG. 6, the X-axis direction, the Y-axis direction, and the Z-axis direction are indicated by arrows X, Y, and Z, respectively.
Instead of moving the fixed base 62 in the Z-axis direction, the main shaft 61 can also be moved in the Z-axis direction.

  The spindle 61 in the processing machine 6 is detachable by replacing a plurality of types of tools for drilling. In the processing step of this example, the rear wheel shaft hole 31, the auxiliary shaft hole 33, and the front wheel shaft hole 32 are processed by the same end mill 611 attached to the main shaft 61 (see FIGS. 3 and 4). Further, the plurality of pin holes 34 are processed using an end mill 611 having a smaller diameter than the end mill 611.

As shown in FIGS. 1 and 2, the pin hole 34 of this example includes a rear wheel shaft hole 31, an auxiliary shaft hole 33, and a front wheel shaft hole 32 on each mating surface 201 of the front case portion 2 </ b> A and the rear case portion 2 </ b> B. It is formed at two locations located on opposite sides of each other. The two pin holes 34 are formed in the vicinity of the positions farthest from each other in the case portions 2A and 2B.
Further, as shown in FIG. 1, the machining reference hole 36 of this example is formed in the vicinity of each pin hole 34, and the machining reference surface 37 is a portion where the machining reference hole 36 is formed and the two machining reference holes 36. It forms in the part located between. Thereby, the precision of the formation position of the several pin hole 34 used as the reference | standard at the time of assembling a pair of case part 2A, 2B can be improved.

As shown in FIG. 1, in the processing machine 6 of this example, the fixing base 62 for fixing the case portions 2 </ b> A and 2 </ b> B has its set surface 621 perpendicular to the axial direction (Z-axis direction) Z of the main shaft 61. Can be arranged. Then, the processing machine 6 clamps the three processing reference surfaces 37 with the clamp members 63 in a state where the two processing reference holes 36 are positioned, and fixes the case portions 2A and 2B to the fixing base 62. It is configured as follows. FIG. 1 shows a fixed base 62 to which the pair of case portions 2A and 2B are fixed as viewed from the direction of the main shaft 61 of the processing machine 6.
Further, the main shaft 61 of the processing machine 6 of this example is configured to process the rear wheel shaft hole 31, the auxiliary shaft hole 33, the front wheel shaft hole 32, and the plurality of pin holes 34 in the same direction. .

In the manufacturing method of the transfer case 1 of this example, first, in the preliminary processing step, two processing reference holes 36 and three processing reference surfaces 37 are respectively processed for the pair of case portions 2A and 2B (see FIG. 1).
Therefore, the processing conditions for processing the processing reference hole 36 and the processing reference surface 37 can be almost matched to the front case portion 2A and the rear case portion 2B.

  Next, as shown in FIG. 1, in the arranging step, the front case portion 2 </ b> A and the rear case portion 2 </ b> B in which the processing reference hole 36 and the processing reference surface 37 are processed in a pair of sets in the preliminary processing step are processed into a processing machine. Fix to 6. At this time, an operator or the like fixes the case portions 2A and 2B to the set surface 621 of the fixed base 62 facing away from the main shaft 61, and after fixing, the fixed base 62 is rotated to set the case. The surface 621 is directed toward the main shaft 61 (perpendicular to the axial direction of the main shaft 61).

Further, at the time of fixing, the case portions 2A and 2B are fixed to the fixing base 62 with reference to the two processing reference holes 36 and the three processing reference surfaces 37. Further, assuming a virtual center line C passing through the original position, which is the center position in the horizontal direction H, of the main shaft 61 in the processing machine 6 in the vertical direction V, the shaft holes 31 and 32 in the front case portion 2A and the rear case portion 2B. , 33 are fixed to the fixed base 62 with the front case portion 2A and the rear case portion 2B in a state where the processing positions of the, 33 are symmetrical with respect to the virtual center line C.
In FIG. 1, the distances from the virtual center line C to the centers of the rear wheel shaft hole 31, the auxiliary shaft hole 33, the front wheel shaft hole 32, and the plurality of pin holes 34 are indicated by two-dot chain lines.

Next, as shown in FIGS. 3 and 4, in the machining process, the main shaft 61 in the processing machine 6 is moved to cause the rear wheel shaft hole 31, the holding shaft hole, and the front wheel shaft to move to the case portions 2 </ b> A and 2 </ b> B. The hole 32 and the plurality of pin holes 34 are processed continuously. 3 and 4 show the case portions 2A and 2B as viewed from the side.
Therefore, it is possible to almost match the processing conditions when processing the front case portion 2A and the rear case portion 2B. In the processing machine 6, there are fluctuations in various conditions such as the temperature of the coolant, the thermal deformation of the processing machine 6, and the outside air temperature. Even if it exists, the influence by this fluctuation | variation will receive the front case part 2A and the rear case part 2B substantially equally.

  In this example, in the processing machine 6 having the main shaft 61 in the Z-axis direction (front-rear horizontal direction) Z, the distance from the virtual center line C to the X-axis direction (left-right horizontal direction) X of the processing machine 6 is large. Accordingly, even if the processing conditions such as thermal deformation of the processing machine 6 affect the accuracy of the processing position for drilling, the front case portion 2A and the rear case portion 2B are affected almost equally. It will be. Therefore, in the front case portion 2A and the rear case portion 2B, an error occurs in the machining positions from the virtual center line C of the rear wheel shaft hole 31, the auxiliary shaft hole 33, the front wheel shaft hole 32, and the plurality of pin holes 34. Can be minimized.

  As a result, as shown in FIGS. 2 and 5, the transfer case 1 is assembled using the front case portion 2A and the rear case portion 2B that have been subjected to the preliminary processing step, the placement step, and the processing step as a pair in the assembly step. When formed, the center positions of the rear wheel shaft hole 31, the front wheel shaft hole 32, and the plurality of pin holes 34 are effectively suppressed from being shifted between the front case portion 2A and the rear case portion 2B. it can.

Further, in this example, as shown in FIGS. 1, 3, and 4, drilling is performed with the mating surfaces 201 of the front case portion 2A and the rear case portion 2B facing the main shaft 61 in the processing machine 6. I do. 3 and 4, the direction of the main shaft 61 is indicated by an arrow S.
Therefore, the manufacturing method of the present example is particularly suitable when the hole cannot be drilled from the outer surface 202 opposite to the mating surface 201 in the front case portion 2A and the rear case portion 2B, that is, in the outer surface 202 in the front case portion 2A and the rear case portion 2B. The present invention can also be adopted when a part of the case portion or the like is present at a position corresponding to the rear wheel shaft hole 31 and the front wheel shaft hole 32.

  Therefore, according to the manufacturing method of the transfer case 1 of this example, the rear wheel shaft hole 31 and the auxiliary shaft hole 33 are provided between the front case portion 2A and the rear case portion 2B even when the processing conditions are limited. The center positions of the front wheel shaft hole 32 and the plurality of pin holes 34 can be prevented from shifting. When the output shaft portion 41, the transmission shaft portion 43 and the driven output shaft portion 42 are rotationally supported by the bearings 45 provided in the rear wheel shaft hole 31, the auxiliary shaft hole 33 and the front wheel shaft hole 32, respectively, Gear noise generated when the gears provided in the shaft portions 41, 42, 43 and the differential device 44 mesh with each other can be reduced.

Plane explanatory drawing which shows the state which fixed a pair of case part to the fixing stand in a processing machine in an Example. Plane explanatory drawing which shows a pair of case part in the state opened in the Example seen from the side of those mating surfaces. Sectional explanatory drawing which shows the front case part in an Example. Cross-sectional explanatory drawing which shows the rear case part in an Example. Sectional explanatory drawing which shows the transfer case in an Example. An explanatory perspective view showing a processing machine in an example.

Explanation of symbols

1 Case parts (transfer case)
2A Front case portion 2B Rear case portion 201 Matching surface 202 Outer surface 31 Rear wheel shaft hole 32 Front wheel shaft hole 33 Auxiliary shaft hole 34 Pin hole 36 Reference hole 37 Reference surface 41 Output shaft portion 411 Connection output portion 42 Driven output shaft portion 43 Transmission shaft portion 44 Differential device 45 Bearing 6 Processing machine 61 Main shaft 62 Fixed base C Virtual center line H Horizontal direction V Vertical direction F Front side R Back side

Claims (5)

In a method of manufacturing a case component comprising a pair of case portions in which shaft holes are formed in the same axial center, and configured to position the pair of case portions with each other via a plurality of positioning pins,
An arrangement step of fixing the pair of case parts to the processing machine and arranging each mating surface where the pair of case parts are combined with each other toward the main shaft side in the processing machine,
A processing step of moving the main shaft in the processing machine to process the shaft holes in the pair of case portions and the plurality of pin holes for inserting the plurality of positioning pins in the pair of case portions;
An assembly step of forming a case component by inserting the plurality of positioning pins into the plurality of pin holes using the pair of case portions subjected to the arrangement step and the processing step as a pair of sets. A method of manufacturing a case part characterized by In claim 1, before performing the placement step, a preliminary processing step of processing a processing reference hole and a processing reference surface for fixing the pair of case portions to the processing machine is performed,
A method of manufacturing a case part, wherein the placement step, the processing step, and the assembly step are performed using a pair of case portions that have been subjected to the preliminary processing step as a pair of sets. In Claim 1 or 2, the said processing machine arrange | positions the said spindle in a horizontal direction,
In the arranging step, the pair of case portions are arranged so that the mating surfaces thereof are arranged perpendicularly to the direction of the main shaft, and a virtual center that passes through the original position that is the horizontal center position of the main shaft in the processing machine in the vertical direction. Assuming a line, the processing position of the shaft hole and the plurality of pin holes is made symmetrical with respect to the virtual center line between the one case part and the other case part constituting the pair of case parts. A method of manufacturing a case part, characterized by being arranged in a state. In Claim 3, in the preliminary processing step, the processing reference holes are formed at two positions located on opposite sides of the shaft hole in the mating surfaces of the pair of case portions,
In the processing step, the pin holes are formed in the vicinity of the processing reference holes on the mating surfaces of the pair of case portions, respectively. In any one of Claims 1-4, the said case component is a transfer case used for the transmission for four-wheel drive vehicles,
The shaft hole is inserted and rotated through at least a rear wheel shaft hole for inserting and supporting the output shaft portion of the transmission to rotate, and a driven output shaft portion driven and rotated by the rotation of the output shaft portion. A method of manufacturing a case component, characterized by being a shaft hole for a front wheel for supporting.

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