JPWO2013038709A1 - Joint assist device and method for adjusting joint assist device - Google Patents

Abstract

The joint assist device of the present invention includes an inner support plate 1b disposed inside a joint, an outer support plate 1a disposed outside the joint, an inner support plate 1b, and an outer support plate 1a on the rear knee side. A connecting member 30 to be connected, a first inner arm 10b rotatably provided on the upper end side of the inner support plate 1b, and a second inner arm 20b rotatably provided on the lower end side of the inner support plate 1b. A first outer arm 10a rotatably provided on the upper end side of the outer support plate 1a, and a second outer arm 20a rotatably provided on the lower end side of the outer support plate 1a. The inner arm 10b, the first outer arm 10a, the second inner arm 20b, and the second outer arm 20a are made of thermoplastic resin and can be adjusted to fit the body shape of the user. Improved visibility of wearing It can be.

Description

  The present invention relates to a joint assist device used by being mounted on a joint, and a method for adjusting the joint assist device.

As shown in Patent Document 1, the present inventor has put into practical use an appliance in which the main structural member of the appliance is made of an aluminum alloy. The present invention is intended to solve the problems of the orthosis and realize dramatic improvements in the performance of the orthosis, stabilization of quality, and improvement of wearability.
The first problem with aluminum alloy braces is that even if the shape of the brace arm is finally adjusted according to the patient's symptoms, the brace arm is plastically deformed by repeated loading due to use, and therefore the It means that the corrective power is not exhibited continuously. The second problem is that aluminum corrodes due to the salt content of sweat and causes damage. The third problem is that when a patient wears a metal brace and gets on an aircraft, the metal must be detected by a metal detector and subjected to a confirmation test.
There is a need to improve the above-mentioned problems and to provide a brace that is lighter than conventional braces and has improved performance and feel.

Japanese Patent No. 2903509 JP 2000-31694 A

In the aluminum orthosis according to Patent Document 1 or Patent Document 2, the arm shape and the connecting member can be adjusted according to the patient's symptoms using the plasticity of aluminum. However, the shape of the aluminum arm is changed by the repeated load during use, and the initial correction force cannot be maintained. Therefore, the arm shape can be adjusted according to the patient's body shape and symptom, and the practical use of the brace which does not undergo plastic deformation with respect to the repeated load during use has been expected.
An orthosis in which the arm portion of a joint orthosis is made of resin has already been put into practical use. The brace structure is often rugged and does not worry about shape changes during use, but is not intended to adjust the shape of the arm or the connecting member to the patient's symptoms.

  Therefore, an object of the present invention is to provide a joint assist device that can be adjusted to fit the user's body shape and can improve the visibility of the wearing of the brace and a method for adjusting the joint assist device.

According to a first aspect of the present invention, there is provided the joint assist device according to the first aspect, wherein the inner support plate disposed inside the joint, the outer support plate disposed outside the joint, the inner support plate, and the outer support plate are moved backward. A connecting member connected on the knee side, a first inner arm rotatably provided on the upper end side of the inner support plate, and a second inner arm rotatably provided on the lower end side of the inner support plate A joint assisting device comprising: a first outer arm rotatably provided on an upper end side of the outer support plate; and a second outer arm rotatably provided on a lower end side of the outer support plate. The first inner arm, the first outer arm, the second inner arm, and the second outer arm are made of a thermoplastic resin.
According to a second aspect of the present invention, in the joint assist device according to the first aspect, the connecting member is made of a thermoplastic resin.
According to a third aspect of the present invention, in the joint assist device according to the second aspect, the first inner arm, the first outer arm, the second inner arm, and the second outer arm are shortened. A fiber reinforced thermoplastic resin is used, and the connecting member is a long fiber reinforced thermoplastic resin or a cloth reinforced thermoplastic resin.
According to a fourth aspect of the present invention, in the joint assist device according to the first or second aspect, the thermoplastic resin may be polyamide, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide polyethersulfone, polyphenylene. One of ether, polysulfone, and liquid crystal polymer is used.
According to a fifth aspect of the present invention, in the joint assist device according to the third or fourth aspect, the short fiber reinforced thermoplastic resin, the long fiber reinforced thermoplastic resin, and the cloth reinforced thermoplastic resin may include carbon. One or more of fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, zylon, and liquid crystal polymer are used.
The present invention described in claim 6 is a method for adjusting a joint assist device according to any one of claims 1 to 5, wherein a determination step for determining the necessity of deformation and the necessity for deformation in the determination step are provided. A measuring step for measuring the amount of deformation when it is determined that there is a possibility, and softening for heating at least the first inner arm, the first outer arm, the second inner arm, and the second outer arm A processing step, a deformation processing step for performing a deformation processing on the softened first inner arm, the first outer arm, the second inner arm, and the second outer arm, and at least the first And a curing process step for cooling the inner arm, the first outer arm, the second inner arm, and the second outer arm.

According to the joint assist device of the present invention, adjustment that fits the wearer's body shape is possible.
The first function required in the joint assist device is the correction force or support force of knee osteoarthritis. By adopting a carbon fiber reinforced resin, which is much more rigid than aluminum, for the brace arm, the orthodontic arm undergoes plastic deformation under repeated loads, so that the correction force adjusted for the patient does not drop. Furthermore, according to the experience of the inventors, although depending on the level of symptoms of the patient, there is a strong tendency to avoid being recognized by other people that the visibility of the wearing of the brace, that is, wearing the brace. I understood. However, the joint assist device of the present invention can improve visibility of wearing of the brace.
Aluminum structural materials are prone to corrosion damage due to the salt content of sweat, etc., but the problem of corrosion damage can be solved by using resin.
Further, when a user wears a metal knee brace to board an aircraft, the metal detector detects the metal, and troubles such as receiving a confirmation inspection occur. An all-plastic device will not be detected by a metal detector, and the weight of the device can be reduced. As a result, it is possible to provide a knee brace that allows the wearer to spend daily life without hindrance.

The perspective view seen from one side of the joint assistant device by one example of the present invention. Perspective view seen from the other side of the device Side view showing the extended state of the device The figure which shows the orthosis frame of the apparatus Side view showing the same device installed Front view showing the same device installed The flowchart which shows the adjustment method of the joint assistance apparatus by a present Example. Front view showing the orthosis frame with the device temporarily mounted Front view showing the appliance frame in a state in which the device after adjustment is mounted

1a outer support plate 1b inner support plate 10a first outer arm 10b first inner arm 11a, 11b upper end side rotation fulcrum 12a, 12b pin 20a second outer arm 20b second inner arm 21a, 21b lower end side turn Moving fulcrum 22a, 22b Pin 30 Connecting member 41 First band 42 Second band 43 Third band 50a Outer pad 50b Inner pad 60a Connection part 60b Elastic connection part 70a, 70b Cover member

  In the joint assist device according to the first embodiment of the present invention, the first inner arm, the first outer arm, the second inner arm, and the second outer arm are made of thermoplastic resin. . According to the present embodiment, since these arms are made of the thermoplastic resin, it is possible to provide a joint assist device that can be adjusted according to the wearer and that is not deformed at the time of wearing.

  According to a second embodiment of the present invention, in the joint assist device according to the first embodiment, the connecting member is made of a thermoplastic resin. According to the present embodiment, the connecting member can be adjusted, and the distance between the inner support plate and the outer support plate can be adjusted to the wearer.

  According to a third embodiment of the present invention, in the joint assist device according to the second embodiment, the first inner arm, the first outer arm, the second inner arm, and the second outer arm are short fibers. A reinforced thermoplastic resin is used, and the connecting member is a long fiber reinforced thermoplastic resin or a cloth reinforced thermoplastic resin. According to the present embodiment, the amount of deformation of these arms can be increased as compared with the connecting member, and the strength of the connecting member can be higher than that of these arms.

  In the joint assist device according to the first or second embodiment, the fourth embodiment of the present invention includes, as the thermoplastic resin, polyamide, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide polyethersulfone, Any of polyphenylene ether, polysulfone, and liquid crystal polymer can be used.

  According to a fifth embodiment of the present invention, in the joint assist device according to the third or fourth embodiment, carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, xylon, and liquid crystal are used as the thermoplastic resin. By impregnating any one kind or plural kinds of polymers, a short fiber reinforced thermoplastic resin, a long fiber reinforced thermoplastic resin, or a cloth reinforced thermoplastic resin can be obtained.

  The sixth embodiment of the present invention is a method for adjusting a joint assist device according to any one of the first to fifth aspects, wherein a determination step for determining the necessity of deformation, and the necessity for deformation at the determination step A measurement step of measuring a deformation amount when it is determined that there is a softening treatment step of heating at least the first inner arm, the first outer arm, the second inner arm, and the second outer arm, and softening A deformation process step for performing a deformation process on the first inner arm, the first outer arm, the second inner arm, and the second outer arm, and at least the first inner arm, the first outer arm, And a curing step for cooling the second outer arm. According to the present embodiment, adjustment according to the wearer is possible.

Hereinafter, a joint assist device according to an embodiment of the present invention will be described with reference to the drawings.
1 is a perspective view as seen from one side of the joint assist device according to the present embodiment, FIG. 2 is a perspective view as seen from the other side of the device, FIG. 3 is a side view showing the extended state of the device, and FIG. It is a figure which shows the orthosis frame of an apparatus.
The joint assist device according to the present embodiment includes an outer support plate 1a arranged outside the joint, an inner support plate 1b arranged inside the joint, an outer support plate 1a, and an inner support plate 1b on the rear knee side. And a connecting member 30 to be connected. The lateral support plate 1a is disposed above the femoral lateral epicondyle, and the medial support plate 1b is disposed above the femoral medial epicondyle.

The outer support plate 1a is provided with an upper end side rotation fulcrum 11a and a lower end side rotation fulcrum 21a. One end of the first outer arm 10a is rotatably provided at the upper end side rotation fulcrum 11a, and one end of the second outer arm 20a is rotatably provided at the lower end side rotation fulcrum 21a.
The outer support plate 1a is composed of two plate-like members, and one end of the first outer arm 10a and one end of the second outer arm 20a are sandwiched between the two plate-like members.
The inner support plate 1b is provided with an upper end side rotation fulcrum 11b and a lower end side rotation fulcrum 21b. One end of the first inner arm 10b is rotatably provided at the upper end side rotation fulcrum 11b, and one end of the second inner arm 20b is rotatably provided at the lower end side rotation fulcrum 21b.
The inner support plate 1b is composed of two plate-like members, and one end of the first inner arm 10b and one end of the second inner arm 20b are sandwiched between the two plate-like members.

The second outer arm 20a is longer than the first outer arm 10a, and the second inner arm 20b is longer than the first inner arm 10b.
Although slightly different depending on the wearer's body shape and leg length, for example, the following effects are obtained. When the dimension from the upper end side rotation fulcrum 11a of the first outer arm 10a to the pin 12a is 83 mm, the dimension from the lower end side rotation fulcrum 21a of the second outer arm 20a to the pin 22a is 140 mm. When the dimension from the upper end side rotation fulcrum 11b of the first inner arm 10b to the pin 12b is 83 mm, the dimension from the lower end side rotation fulcrum 21b of the second inner arm 20b to the pin 22b is 155 mm. According to the experimental results, the following dimensions are preferable. The dimension from the upper end side rotation fulcrum 11a of the first outer arm 10a to the pin 12a is 1.05 to 0.95 times the dimension from the upper end side rotation fulcrum 11b to the pin 12b of the first inner arm 10b. The dimension from the lower end side rotation fulcrum 21a of the second outer arm 20a to the pin 22a is 1. The dimension from the lower end side rotation fulcrum 21b of the second inner arm 20b to the pin 22b. The length is from 05 times to 0.85 times, and the dimension from the lower end side rotation fulcrum 21a of the second outer arm 20a to the pin 22a is from the upper end side rotation fulcrum 11a of the first outer arm 10a to the pin. The length from 1.5 times to 2 times the dimension up to 12a, and the dimension from the lower end side rotation fulcrum 21b of the second inner arm 20b to the pin 22b is the upper end side rotation fulcrum 11b of the first inner arm 10b. From From 1.5 times the dimension of up emissions 12b and the length of the doubled.

The first outer arm 10a, the first inner arm 10b, the second outer arm 20a, and the second inner arm 20b are made of a thermoplastic resin.
The first outer arm 10a, the first inner arm 10b, the second outer arm 20a, and the second inner arm 20b are preferably made of short fiber reinforced thermoplastic resin.
As the thermoplastic resin, polyamide, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide polyethersulfone, polyphenylene ether, polysulfone, or liquid crystal polymer is used, and short fibers are carbon fiber, glass fiber Boron fiber, aramid fiber, polyethylene fiber, xylon, and liquid crystal polymer are used.

The connecting member 30 is also made of a thermoplastic resin.
The connecting member 30 is preferably a long fiber reinforced thermoplastic resin or a cloth reinforced thermoplastic resin.
As the thermoplastic resin, any one of polyamide, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide polyethersulfone, polyphenylene ether, polysulfone, and liquid crystal polymer is used. As the long fiber, one or more of carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, xylon, and liquid crystal polymer are used. The fabric includes carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, xylon, and liquid crystal polymer, or carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene. A nonwoven fabric made of one or more of fiber, xylon, and liquid crystal polymer is used.
In addition, a short fiber and a long fiber are used as a reinforcing material of a thermoplastic resin. When the short fiber reinforced thermoplastic resin is used, it is suitable for a large deformation treatment as compared with the long fiber reinforced thermoplastic resin or the cloth reinforced thermoplastic resin. On the other hand, when a long fiber reinforced thermoplastic resin or a cloth reinforced thermoplastic resin is used, it is more resistant to deformation than a short fiber reinforced thermoplastic resin, does not require a large deformation treatment, and has a strength against deformation during use. Can be secured.

The outer support plate 1a and the inner support plate 1b can be made of resin. The outer support plate 1a and the inner support plate 1b are not members that adjust the shape in the first place. The outer support plate 1a and the inner support plate 1b are composed of two plate-like members, and are provided with upper end side rotation fulcrums 11a and 11b and lower end side rotation fulcrums 21a and 21b. Therefore, since it does not plastically deform with respect to repeated loads, it may be made of an aluminum alloy as in the conventional case. However, by configuring the outer support plate 1a and the inner support plate 1b with a thermoplastic resin, there is an effect that the influence of sweat is eliminated and the detection by the metal detector is not performed.
In addition, when making the outer side support plate 1a and the inner side support plate 1b into resin, it is preferable to use resin with big intensity | strength, such as fiber reinforced resin or cloth reinforced resin.

The first band 41 wound around the thigh is attached to the end of the first inner arm 10b and the end of the first outer arm 10a. Moreover, the 2nd band 42 wound around a leg part is attached to the edge part of the 2nd inner side arm 20b, and the edge part of the 2nd outer side arm 20a. In particular, the lengths of the first outer arm 10a and the second outer arm 20a, and the first inner arm 10b and the second inner arm 20b are set so that the second band 42 is disposed on the upper part of the gastrocnemius. It is preferable that it is set.
The first outer arm 10a has a pin 12a for attaching the first band 41 to the other end side, and the first inner arm 10b has a pin 12b for attaching the first band 41 to the other end side. Yes. The second outer arm 20a has a pin 22a for attaching the second band 42 on the other end side, and the second inner arm 20b has a pin 22b for attaching the second band 42 on the other end side. doing.
The end portion of the second outer arm 20a is rotatably provided by a pin 22a, and the end portion of the second inner arm 20b is rotatably provided by a pin 22b.
A covering member 70a that covers a part of the other end of the second outer arm 20a is provided at the end of the second outer arm 20a, and a second inner arm is provided at the end of the second inner arm 20b. A covering member 70b is provided to cover a part on the other end side of the arm 20b. The covering members 70a and 70b and the second band 42 are stitched except for the openings 71a and 71b, and the rotation ranges of the second outer arm 20a and the second inner arm 20b are restricted by the openings 71a and 71b. ing. Therefore, the second outer arm 20a and the second inner arm 20b can be operated by a predetermined angle by the openings 71a and 71b.

The third band 43 is disposed so as to be wound between the first band 41 and the knee joint. The third band 43 holds an inner pad 50b disposed inside the knee joint. The inner pad 50b is provided with an elastic connecting portion 60b. One end of the elastic connecting portion 60b is connected to the first inner arm 10b by a pin 12b, and the other end is connected to the inner pad 50b. The elastic connection portion 60b is made of a spring material such as a leaf spring, and is provided so as to be elastically deformed between the first inner arm 10b and the body.
The third band 43 is connected to the first outer arm 10a via the connection portion 60a at a position outside the knee joint. An outer pad 50a is provided inside the outer support plate 1a.

Next, a method for mounting the joint assist device according to the present embodiment will be described with reference to FIGS.
FIG. 5 is a side view showing a state where the joint assist device according to the present embodiment is mounted, and FIG. 6 is a front view showing a state where the device is mounted.
The lateral support plate 1a is disposed above the femoral lateral epicondyle 101, and the medial support plate 1b is disposed above the femoral medial epicondyle 102. Accordingly, the outer pad 50 a is located at the lower part of the biceps femoris 103 and the inner pad 50 b is located at the lower part of the semitendon-like muscle 104. The inner pad 50b is suspended from the first inner arm 10b by an elastic connecting portion 60b, and the third band 43 is connected to the first outer arm 10a by a connecting portion 60a. Therefore, the inner pad 50 b comes into close contact with the semi-tendon-like muscle 104 by tightening with the third band 43. Further, since the force is applied to the first outer arm 10a in the direction of the femur 105 by the tightening by the third band 43, the force is also applied to the outer support plate 1a in the direction of the femur 105, and the outer pad 50a is Close contact with the head muscle 103. Thus, since the inner pad 50b is disposed at the position of the semi-tendon-like muscle 104 and the outer pad 50a is disposed at the position of the biceps femoris 103, adhesion by pressing is high. As a result, the medial pad 50b can be prevented from slipping by the femoral medial epicondyle 102, and the lateral pad 50a can be prevented from slipping by the femur lateral epicondyle 101.

Further, the second band 42 is disposed above the gastrocnemius muscle 106, that is, above the largest position of the gastrocnemius muscle 106, so that the second band 42 can be prevented from slipping off.
The pin 22b of the second inner arm 20b is close to the position of the inner support plate 1b by the dimension w3 in the direction of the tibia 107 except for an extreme varus knee, although it depends on the posture of the lower limbs. At this time, since the second inner arm 20b must rotate with respect to the inner support plate 1b and also with respect to the pin 22b within a predetermined range, the second inner arm 20b is inclined at an intermediate portion of the second inner arm 20b. It is necessary to configure the surface 20x. However, by placing the inclined surface 20x along the femoral medial condyle 108 and the upper part of the tibia 107, the medial support plate 1b and the second medial arm 20b are brought into a state along the crus 110 from the femur 109. Can be arranged.
Accordingly, the second outer arm 20a and the second inner arm 20b are positioned on both sides of the patella 111.

Next, a method for adjusting the joint assist device according to the present embodiment will be described with reference to FIG.
FIG. 7 is a flowchart showing the adjustment method of the joint assist device according to the present embodiment, FIG. 8 is a front view showing the orthosis frame in a state where the joint assist device is temporarily mounted, and FIG. 9 shows the adjusted joint assist device. It is a front view which shows the appliance frame of the state which was made.
First, a joint assist device as a standard product is produced (step 1). In the standard product, the first outer arm 10a, the first inner arm 10b, the second outer arm 20a, the second inner arm 20b, and the connecting member 30 are each formed by injection molding, and thereafter from FIG. It is assembled in the state shown in FIG. The standard product is manufactured in advance in several sizes according to the body shape.
In step 2, a joint assist device having a size most suitable for the user is selected from these standard products.
Then, the joint assist device selected in step 2 is temporarily mounted (step 3), and the necessity for deformation is determined (step 4).

FIG. 8 shows a provisional wearing state of the joint assist device in step 3.
If there is a need for deformation in step 4, the amount of deformation is measured (step 5).
After the deformation amount is measured in step 5, the joint assist device is removed (step 6), and the joint assist device is softened (step 7). The softening process of the joint assist device is performed by heating. For example, hot air is blown to a necessary member or a necessary part in the first outer arm 10a, the first inner arm 10b, the second outer arm 20a, the second inner arm 20b, and the connecting member 30.
After the softening treatment in Step 7, the necessary members or necessary portions of the first outer arm 10a, the first inner arm 10b, the second outer arm 20a, the second inner arm 20b, and the connecting member 30 are deformed. Processing is performed (step 8).
After the deformation process in step 8, in particular, the deformation process member or the deformation process part is cooled to perform the curing process (step 9). The curing process is not limited to the case where cooling is forcedly performed by blowing cold air or cooling gas, and natural cooling may be used.
After the curing process in step 9, temporary mounting is performed again (step 3), and the necessity for deformation is determined (step 4).
If it is determined in step 4 that there is no need for deformation, the adjustment of the joint assist device is completed (step 10).

FIG. 9 shows a mounted state of the joint assist device that has been adjusted in Step 10.
The processing flow in FIG. 7 has been described including the step of producing a joint assist device as a standard product and then selecting the standard product. However, the present invention can also be applied to a case where a user who has already worn the joint assist device readjusts the joint assist device after a predetermined period has elapsed. In the readjustment of the joint assist device, the processing flow from step 3 is performed.
In the description of this embodiment, the adjustment method after the joint assist device is completed in the state shown in FIGS. 1 to 3 has been described. However, the adjustment can also be performed in the state of the appliance frame shown in FIG. When the adjustment is performed in the state of the appliance frame, the appliance frame is temporarily attached using a member other than the appliance frame as a jig.
As another method, the processes from step 3 to step 5 can be performed by simulation using data. In the case of simulation, dimension data relating to the user's wearing part is measured and input in advance. Image data may be used as the dimension data. In that case, the three-dimensional model is simulated, and the selected equipment (member) is applied to the simulated three-dimensional model, thereby determining the necessity of deformation and calculating the amount of deformation.

  The joint assist device of the present invention is used not only for reflexive knee rehabilitation and polio knees, for deformable joints such as O-legs, X-legs and rheumatoid arthritis, and for sports such as ligament damage and meniscal damage. It can also be widely used by workers who place a burden on joints such as knees and elbows.

Claims (6)

  An inner support plate arranged inside the joint, an outer support plate arranged outside the joint, a connecting member for connecting the inner support plate and the outer support plate on the rear knee side, and the inner support A first inner arm rotatably provided on the upper end side of the plate, a second inner arm rotatably provided on the lower end side of the inner support plate, and a rotatable upper end side of the outer support plate A joint assisting device comprising: a first outer arm provided on a lower end of the outer support plate; and a second outer arm rotatably provided on a lower end side of the outer support plate, wherein the first inner arm, the first A joint assist device, wherein the outer arm, the second inner arm, and the second outer arm are made of thermoplastic resin.   The joint assist device according to claim 1, wherein the connecting member is made of a thermoplastic resin.   The first inner arm, the first outer arm, the second inner arm, and the second outer arm are made of short fiber reinforced thermoplastic resin, and the connecting member is made of long fiber reinforced thermoplastic resin or cloth reinforced. The joint assist device according to claim 2, wherein the joint assist device is a thermoplastic resin.   The thermoplastic resin is any one of polyamide, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide polyethersulfone, polyphenylene ether, polysulfone, and liquid crystal polymer. 2. The joint assist device according to 2.   The short fiber reinforced thermoplastic resin, the long fiber reinforced thermoplastic resin, and the cloth reinforced thermoplastic resin are any one of carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, zylon, and liquid crystal polymer, or The joint assist device according to claim 3 or 4, wherein a plurality of types are used.   6. The method for adjusting a joint assist device according to claim 1, wherein a determination step for determining the necessity of deformation and a deformation when it is determined that the deformation is necessary in the determination step. A measuring step for measuring the amount, a softening treatment step for heating at least the first inner arm, the first outer arm, the second inner arm, and the second outer arm, and the softened first step A deformation processing step for performing a deformation processing on one inner arm, the first outer arm, the second inner arm, and the second outer arm, and at least the first inner arm and the first outer arm. And a hardening processing step for cooling the second inner arm and the second outer arm.