JP6853452B2 - Shaft member - Google Patents

Description

The present invention relates to a shaft member that generates vibration in a vibration test, an acceleration test, or the like.

Conventionally, a vibration generator has been used in various situations. Typical examples are a vibration test device that inspects the durability of the vibrating body against vibration, an electrical property inspection device that inspects the electrical output by vibrating an acceleration sensor, and a buffer that inspects the compression durability of the spring. There are test devices, test devices that test durability by repeatedly hitting the operation buttons of the device, and the like. For example, when measuring the durability of a screw fastener to be a vibrated body, the screw fastener to be a vibrated body is fixed to a jig arranged for a vibration test device and applied. By shaking, the degree of looseness and fatigue of the screw fasteners are tested.

However, in the conventional vibration generator, since the vibration table vibrates violently, in order to resist the inertial force and the moment, the base is enlarged to secure the weight, and the base is further increased by anchor bolts or the like. There was a problem that it had to be firmly fixed to the ground or the like. Further, there is a problem that a noise component is superimposed on the original vibration due to the vibration of the entire vibration generator.

Further, in the vibration test, a plurality of vibrated bodies may be compared, but in the conventional vibration generator, it is necessary to separately perform a vibration test on the plurality of vibrated bodies. As a result, it tends to be ambiguous whether or not vibration was performed under exactly the same conditions between the two. In particular, when the weights of the objects to be vibrated are different from each other, the vibration mode is likely to fluctuate due to their own weight, so that the vibration conditions may be different.

On the other hand, if a plurality of vibrating bodies are installed on a common vibration table and a vibration test is to be performed collectively, the weight of the vibrating bodies increases, making it difficult to achieve correct vibration, and a plurality of vibrating bodies. There is a problem that the vibrations of the vibrated bodies of the above are superimposed as noise components on each other and have an adverse effect.

The present invention has been made by the inventor of the present inventor in view of the above problems, and can be fixed to a floor or the like while being able to generate high-precision, high-efficiency and high-output vibration. It is not essential, and an object of the present invention is to provide a shaft member that can be transported and can be operated without being fixed to the floor.

The present invention that achieves the above object is a shaft member that can be connected to a plurality of vibrating parts, each of which reciprocates in a predetermined direction, and is a first drive mechanism that can displace the first vibrating part among the plurality of vibrating parts. The first driving shaft including the first driving shaft constituting the above and the second driving shaft constituting the second driving mechanism that displaces the second vibrating portion, the first driving shaft has a coaxial rotation shaft and is centered on the axis. and orthogonal cross-section a round first large diameter portion and a first small diameter portion of the, forms a cylindrical shape, one end of which is fixed directly to the first large-diameter portion, the other end is fixed directly to the first small-diameter portion It has a first crank portion that can be connected to the first vibrating portion, and the first driving shaft has no portion hidden by the first small diameter portion or the first crank portion in an axial view, and the first The axis of one crank portion is eccentric with respect to the axis of the first large diameter portion, and is arranged within the contour range of the first large diameter portion in an axial view. The second driving shaft is a second large-diameter portion having a coaxial rotation axis and a perfect circular cross section perpendicular to the axis, which is arranged within the contour range of the first crank portion in the axial direction. and a second small diameter portion forms a cylindrical shape, one end of which is fixed directly to the second large-diameter portion, the second other end is connectable to the second vibrating portion are directly fixed to the second small-diameter portion The second driving shaft has a crank portion, and the second driving shaft has no portion hidden by the second small diameter portion or the second crank portion in an axial direction, and the axis of the second crank portion is the second. It is eccentric with respect to the axial center of the large-diameter portion and is arranged within the range of the contour of the second large-diameter portion in the axial view, and the second small-diameter portion is the contour of the second crank portion in the axial view. The first driving shaft and the second driving shaft are shaft members arranged within the range of the above, and the center of gravity is set to the center of rotation in the axial view.

In relation to the shaft member , the first large diameter portion and the second large diameter portion have the same diameter and are integrated to form a single cylindrical member .

In relation to the shaft member , the first small diameter portion and the second large diameter portion have the same diameter and are integrated to form a single cylindrical member .

In relation to the shaft member, the first large diameter portion, the first crank portion , the first small diameter portion, and the above so that the outer diameter gradually decreases from one side along the axial direction toward the other side. It is characterized in that the second large diameter portion, the second crank portion , and the second small diameter portion are arranged in this order.

According to the present invention, it is possible to generate high-output vibration in a compact manner with high accuracy and high efficiency by a simple structure, but the vibration generator itself swings without being fixed to a floor or the like. It is possible to obtain a highly durable vibration generator without self-excitation.

It is a top view of the vibration generator which concerns on embodiment of this invention. It is (A) front view and (B) front sectional view of the vibration generator. It is a side view of the vibration generator. It is a side sectional view of the vibration generator. (A) to (C) are partial side views showing the operation of the drive mechanism of the vibration generator. (A) to (C) are front sectional views showing a modified example of the vibration generator. It is a side view which shows typically the modification of the vibration generator. (A) is a front view, a right side view, and a left side view showing a common axis of a modified example of the vibration generator, (B) is a front sectional view of the common axis, and (C) is a vibration generator. It is a front sectional view of. It is a front view, the right side view, and the left side view which show the common shaft (crankshaft) of the modification of the vibration generator.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a vibration generator 1 according to an embodiment of the present invention. The vibration generator 1 includes a base 10 and a first vibration unit 120 that is reciprocally arranged in a predetermined direction (here, a vertical direction, hereinafter referred to as a vibration direction) with respect to the base 10. The first drive mechanism 130 that moves the first vibrating unit 120, the second vibrating unit 220 that is reciprocated with respect to the base 10 in the vibration direction, and the second driving mechanism that moves the second vibrating unit 220. 230 and. Further, the first vibration phase of the first vibration unit 120 by the first drive mechanism 130 and the second vibration phase of the second vibration unit 220 by the second drive mechanism 230 are the vibration directions of the vibration generator 1 or its vibration system. The phase difference is set so that the position of the center of gravity in the above is constant regardless of the phase of the first vibrating portion 120 and the second vibrating portion 220.

The first vibrating unit 120 has a pair of first guides 160 that reciprocately guide in the vibration direction, and the second vibrating unit 220 has a pair of second guides 260 that reciprocately guide in the vibration direction. ..

As shown in FIGS. 3 and 4, the first guide 160 is installed on the first guide shaft 162 which is erected on the base 10 and extends toward the first vibrating portion 120 and the first vibrating portion 120. , The first guided portion 164 for slidably accommodating a part (the tip in this case) of the first vibrating portion 120 and the first urging portion 164 for urging the first vibrating portion 120 side. It has a part 168.

The first guide shaft 162 has a columnar base end portion 162A and a columnar tip portion 162B arranged on the first vibrating portion 120 side of the base end portion 162A, with respect to the base end portion 162A. As the tip portion 162B becomes thinner, the step portion 162C is formed at the boundary thereof.

The first guided portion 164 is a cylindrical sleeve member, and is press-fitted into a bottomed accommodating hole 122 formed on the back surface side (the side facing the base 10) of the first vibrating portion 120. A part of the tip end side 162B is slidably accommodated on the inner peripheral side of the first guided portion 164. The first guided portion 164 is removed from the first vibrating portion 120 so that it can be easily replaced when wear or the like occurs.

The first urging portion 168 is a so-called cylindrical coil spring, and is installed on the outer peripheral surface of the tip portion 162B. One end face of the first urged portion 168 is in contact with the step portion 162C, and the other end face is in contact with the first guided portion 164. As a result, the first urged portion 168 can always urge the first guided portion 164 toward the first vibrating portion 120 with the base 10 or the first guide shaft 162 as a reference. Here, the first urging portion 168 is not indispensable, and even if it is adopted, it is not limited to the cylindrical coil spring, and for example, one having continuous elasticity can be used. is there.

With the above configuration, the first vibrating portion 120 is linearly guided in the vibrating direction by the pair of first guides 160. Further, even if the first guided portion 164 tries to separate from the accommodating hole 122 due to the vibration of the first vibrating portion 120, it can be prevented by the first urging portion 168.

Since the second guide 260 of the second vibrating unit 220 has exactly the same configuration as the first guide 160, the description will be omitted by matching the last two digits of the symbols of the parts or members in the drawings.

As shown in FIG. 4, the first drive mechanism 130 connects the first driving shaft 132, the first crank 134 rotating together with the first driving shaft 132, the first crank 134, and the first vibrating portion 120. It has a connecting portion 136, which constitutes a so-called slider crank mechanism. As a result, the rotation of the first driving shaft 132 can be converted into a reciprocating linear motion in the vibration direction.

The first driving shaft 132 is rotatably held by a pair of bearing portions 140, 140 installed on the base 10 (see FIG. 2). Here, the bearing portions 140, 140 are composed of bearing members such as so-called bearings (not shown) and bearing plate portions for holding the bearing members and fixing them to the base 10. The structure and the like are not particularly limited as long as the one driving shaft 132 and the second driving shaft 232 can be pivotally supported, and for example, a plastic sliding sleeve can be used. Further, a pulley 50 is installed on the first driving shaft 132, and a belt 52 is wound between the pulley 50 and the pulley M1 on the motor M side. As a result, the first driving shaft 132 rotates using the motor M as a power source.

The first crank 134 is a cylindrical member fixed to the first driving shaft 132 between the pair of bearing portions 140, 140, and is in a state of being eccentric from the first driving shaft 132. Therefore, when the first driving shaft 132 rotates, the eccentric center HC of the first crank 134 rotates eccentrically with respect to the axial center SC of the first driving shaft 132 (see FIG. 5).

The first series contact portion 136 is a member that extends between the rotating shaft 126 installed on the back surface of the first vibrating portion 120 and the first crank 134 and rotatably holds both of them. That is, the first series contact portion 136 has a vibrating portion side hole 136A into which the rotating shaft 126 is inserted, and a crank side hole 136B into which the first crank 134 is inserted. The rotating shaft 126 is a member of the first vibrating portion 120 that extends parallel to the axis of the first driving shaft 132, and here, so-called bolts and nuts are used.

Therefore, as shown in FIG. 5 (A), when the first driving shaft 132 is rotated by 90 ° in one direction while the first vibrating portion 120 is located at the top dead center, as shown in FIG. 5 (B). The first crank 134 rotates eccentrically, and the first series contact portion 136 serves as a link to move the rotation shaft 126 (first vibrating portion 120) downward. Further, when the first driving shaft 132 is rotated by 90 °, as shown in FIG. 5C, the eccentric center HC of the first crank 134 reaches the lowest point, and the first series tangent portion 136 becomes a link. The rotating shaft 126 (first vibrating portion 120) is moved to the bottom dead center. After that, although not particularly shown, the first driving shaft 132 further rotates in one direction to return to the top dead center in FIG. 5 (A). Since the first vibrating portion 120 is linearly guided in the vertical direction by the pair of first guides 160, the first vibrating portion 120 has a perfect linear motion. Although not shown, the first vibrating portion 120 is provided with a ventilation path that allows the space surrounded by the first vibrating portion 120, the first guide 160, and the first guided portion 164 to be ventilated to the outside. It is possible to provide it, and by providing this ventilation path, it is possible to eliminate the repeated compression and expansion of the gas in this space and the energy loss associated therewith.

Since the second drive mechanism 230 has exactly the same configuration as the first drive mechanism 130, the description thereof will be omitted by matching the last two digits of the symbols of the parts or members in the drawings.

In the present embodiment, as shown in FIG. 2, the first driving shaft 132 of the first driving mechanism 130 and the second driving shaft 232 of the second driving mechanism 230 are configured by a single common shaft 30. As a result, the first driving shaft 132 and the second driving shaft 232 are arranged coaxially. Further, the pulley 50 is arranged and shared between the first driving shaft 132 and the second driving shaft 232, and the rotation of the motor M is passed through the single pulley 50 to the first driving shaft 132 and the second driving shaft 132. It is transmitted to the drive shaft 232. The common shaft 30 is not limited to the case where the whole is integrally integrated, and includes the concept that the first driving shaft 132 and the second driving shaft 232 are connected by a coupling or a gear and rotate integrally.

Further, the eccentric direction of the first crank 134 and the eccentric direction of the second crank 234 are different from each other with respect to the common shaft 30. Specifically, the first crank 134 and the second crank 234 are fixed to the common shaft 30 with a phase difference of 180 °. As a result, the first rotation phase of the first crank 134 (the rotation phase of the eccentric center HC) and the second rotation phase of the second crank 234 (the rotation phase of the eccentric center HC) are different from each other with a phase difference of 180 °. As a result, in the vibration system composed of the first vibration unit 120 and the second vibration unit 220, and the first crank 134 and the second crank 234, the vibration direction and the center of gravity in the horizontal direction are always constant, and vibration is generated. The first vibrating section 120 and the second vibrating section 220 can be alternately reciprocated in a stable state without the device 1 itself vibrating, swinging, or self-exciting. There is.

As described above, according to the vibration generator 1 of the present embodiment, the first vibration phase of the first vibration unit 120 by the first drive mechanism 130 and the second vibration phase of the second vibration unit 220 by the second drive mechanism 230 are , Are set to be different. As a result, the timing of generation of the inertial force in the vibration direction of the first vibrating unit 120 and the first drive mechanism 130 and the inertial force in the vibration direction of the second vibrating unit 220 and the second drive mechanism 230 can be shifted, and the inertial forces of each other can be shifted. It is possible to offset the force. That is, the vibration of one of the first vibrating unit 120 and the second vibrating unit 220 can function as a counterweight of the other vibration. As a result, the inertial force generated in the entire vibration generator 1 can be reduced, and the weight of the base 10 can be reduced by that amount. Further, the fastening force when fixing the base 10 to the floor surface can be reduced, and depending on the setting of the vibration generation system using the vibration generator 1, it may be used without being fixed to the floor surface or the like, or vibration. The generator 1 can also be carried and used freely.

Further, according to the vibration generator 1, the vibration of the first vibration unit 120 and the vibration of the second vibration unit 220 can be effectively utilized at the same time. For example, when inspecting the durability against vibration, the two vibrating bodies can be fixed to the vibration of the first vibrating portion 120 and the second vibrating portion 220, and the vibration durability test can be performed at the same time. The test efficiency can be improved. In particular, when comparing and verifying the durability of two vibrated bodies, according to the vibration generator 1, the vibration conditions can be matched with each other, so that the verification accuracy can be improved.

In particular, according to the vibration generator 1, since the phase difference between the first vibration phase of the first vibration unit 120 and the second vibration phase of the second vibration unit 220 is set to 180 °, the inertial force in the vibration direction Can be completely offset. As a result, the rotational load of the motor M is also reduced, and the entire device can be compactly configured.

Further, according to the first and second guides 160 and 260 of the vibration generator 1, the first and second guided portions 164 and 264, which are abused by sliding, can be easily replaced, but during vibration. , The first and second urging portions 168,268 can prevent the first and second guided portions 164,264 from falling off. Even if the first and second guided portions 164 and 264 are fixed by screws or pins, in this type of vibration generator 1, a shearing force is repeatedly applied to the screws and pins during vibration. It breaks easily. Therefore, in the present embodiment, the first and second urging portions 168,268 using springs, rubber, etc., cause the first and second guided portions 164,264 to be the first and second vibrating portions 120,220. Stable operation is realized for a long period of time by suppressing the complete dropout while allowing some slide from the rubber.

In the above embodiment, the case where the number of vibrating parts is two is illustrated, but the present invention is not limited to this, and the number may be three or more, or four or more. In the case of three, for example, the phase of the eccentric center of each vibrating portion is shifted by 120 ° from each other, so that the total inertial force can be offset. For example, in the case of four, as shown in FIG. 6A, of the first to fourth vibrating parts 120, 220, 320, 420 driven by the first to fourth drive mechanisms 130, 230, 330, 430. By shifting the phases of the eccentric centers by 90 ° from each other, the total inertial force can be offset.

Further, in the above embodiment, the case where the driving shaft is the common shaft 30 among the plurality of drive mechanisms has been illustrated, but the present invention is not limited to this. For example, as shown in FIG. 6B, by using a plurality of driving shafts 30A and 30B rotated by a plurality of pulleys 50A and 50B and rotating each of them by a motor or the like, a plurality of vibrating portions ( Here, the first to fourth vibrating parts 120, 220, 320, 420) may be vibrated. At this time, the present invention is not limited to the case where the plurality of driving shafts 30A and 30B are arranged coaxially, and the plurality of driving shafts 30A and 30B may be arranged in a different axis shape (offset shape) in a state parallel to each other. The driving shafts 30A and 30B may be arranged in a non-parallel state. At this time, by connecting the driving shafts to each other with gears, pulleys, or the like, the motors can be rotated by a drive source such as a single motor.

Further, in the above embodiment, the case where the first and second drive mechanisms convert the rotary motion into the linear motion by the so-called slider crank mechanism is illustrated, but the present invention is not limited to this, and other motion conversion mechanisms are used. Can be adopted.

Further, for example, as in the vibration generator 1 shown in FIG. 6C, as the first and second drive mechanisms 130 and 230, for example, a linear motion mechanism (solenoid mechanism) using a magnetic force of a coil is used. And the second vibrating parts 120 and 220 can be vibrated. In addition to magnetic force, it can be vibrated by hydraulic pressure or pneumatic pressure.

Further, in the above embodiment, the case where the rotation directions of the plurality of driving shafts are matched has been illustrated, but the present invention is not limited to this, and the rotation directions can be opposite to each other. For example, as schematically shown in the vibration generator 1 of FIG. 7, with respect to the first to fourth vibrating parts 120, 220, 320, 420, one of the two vibrating parts (first and third vibrating parts 120, 320). ), And the driving shaft 30B that drives the remaining two vibrating portions (second and fourth vibrating portions 220, 420) are preferably reversed in the rotational direction. In this way, in the system system, in addition to the inertial force at the time of vibration, the rotational moments can cancel each other out, so that a more compact configuration can be realized and more stable operation can be realized.

Further, in the above embodiment, the case where the first and second cranks 134 and 234 are integrated with the first and second driving shafts 132 and 232 by a key or the like (not shown) is illustrated. However, the present invention is not limited to this. For example, a single metal rod-shaped material is integrally formed by cutting or the like, such as the crankshaft for motion conversion between rotational motion and reciprocating motion shown in FIGS. 8A and 8B. By doing so, the first and second cranks 134 and 234 can be integrally formed with respect to the first and second driving shafts 132 and 232. At this time, for example, the first driving shaft 132 includes a first large-diameter portion 132A and a first small-diameter portion 132B that form a cylinder in a coaxial state, and a first crank 134 that becomes a cylinder in an eccentric state between them. Is integrally formed. The diameter of the first large diameter portion 132A is set to be equal to or larger than the diameter of the outermost contour circle of the movement locus of the eccentric motion of the first crank 134. That is, it is designed so that the first crank 134 does not protrude outward from the first large diameter portion 132A when viewed from the axial direction. On the other hand, the first small diameter portion 132B is designed so as not to protrude outward from the first crank 134 when viewed from the axial direction.

The second driving shaft 232 and the second crank 234 have the same design as described above. When the second large-diameter portion 232A of the second driving shaft 232 and the first large-diameter portion 132A of the first driving shaft 132 come close to each other, a single cylindrical member is formed.

In this way, as shown in FIG. 8C, the first series contact portion 136 can be easily inserted from the first small diameter portion 132B side and positioned on the first crank 134. Further, the second connecting portion 236 can be easily inserted from the second small diameter portion 232B side and positioned on the second crank 234. Further, since the diameter of the common shaft (crankshaft) 30 is gradually reduced from the center in the axial direction toward the shaft end, the cutting process at the time of manufacturing becomes easy. Of the pair of bearing portions 140, 140, a large diameter holding hole corresponding to the first large diameter portion 132A is formed on the side holding the first large diameter portion 132A to hold the first small diameter portion 132B. A small diameter holding hole corresponding to the first small diameter portion 132B is formed on the side.

As a result of the above, the rattling of the first and second driving shafts 132, 232 and the first and second cranks 134 and 234 is eliminated, and the first and second driving shafts 132, 232 and the first and second cranks 134, Factors that reduce durability such as fatigue failure of the key that binds 234 are eliminated, and stable operation can be performed for a long period of time. In addition, the first and second drive mechanisms 130 and 230 can be assembled and disassembled extremely easily, and maintainability can be improved.

In FIG. 8, for example, the first driving shaft 132 has a first large diameter portion 132A and a first small diameter portion 132B, and has a double-sided structure that is rotatably held by a pair of bearing portions 140 and 140. Although illustrated, the present invention is not limited to this, and a cantilever structure can be used. In this case, it is preferable to omit the first small diameter portion 132B and 232B from the viewpoint of rigidity.

Further, as in the crankshaft 30 shown in FIG. 9, when the first driving shaft 132 and the second driving shaft 232 are integrated, the shaft gradually becomes thinner from one direction to the other. The first large diameter portion 132A, the first crank 134, the first small diameter portion 132B, and / or the second large diameter portion 232A, the second crank 234, and the second small diameter portion 232B can be arranged in this order. At this time, the eccentric amounts of the first crank 134 and the second crank 234 are matched with each other with respect to the center of gravity of the crankshaft 30 (of course, it is not always necessary to match the eccentric amounts, but this eccentric amount is used. By matching, the position of the center of gravity of the vibration system, the inertial force acting on the first vibrating portion 120 and the second vibrating portion 220, the first series connecting portion 136 and the second connecting portion 236, and the first crank 134 and the second crank 234. It is possible to cancel out the moments and the like generated with respect to the above, and it is possible to prevent the vibration generator 1 from self-exciting and stabilize the posture.) When the crankshaft 30 is viewed from the axial direction, the first crank 134 does not protrude from the first large diameter portion 132A, and the first small diameter portion 132B protrudes from the first crank 134. The second large diameter portion 232A does not protrude from the first small diameter portion 132B (the same diameter here), and the second crank 234 with respect to the second large diameter portion 232A. The second small diameter portion 232B does not protrude from the second crank 234. In this way, the first series contact portion can be easily inserted from the second small diameter portion 232B and positioned on the first crank 134. Further, although not particularly shown in FIG. 9, it is also possible to integrally connect the third driving shaft and the fourth driving shaft to the crankshaft.

The crankshafts shown in FIGS. 8 and 9 can be used for various purposes of converting rotational motion and reciprocating motion, in addition to the vibration generator.

The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

1 Vibration generator 10 Base 30 Common shaft 50 Pulley 52 Belt 120 First vibration part 122 Accommodating hole 126 Rotating shaft 130 First drive mechanism 132 First driving shaft 134 First crank 136 First series contact part 136A Vibration part side hole 136B Crank side hole 140 Bearing part 160 First guide 162 First guide shaft 162A Base end part 162B Tip part 162C Step part 164 First guided part 168 First urging part 220 Second vibrating part 230 Second drive mechanism 232 No. Two driving shaft 232 Second drive shaft 234 Second crank 236 Second connecting part 236A Vibration part side hole 236B Crank side hole 240 Bearing part 260 Second guide 262 Second guide shaft 262A Base end part 262B Tip part 262C Step part 264 First (2) Guided part 268 Second urging part HC Eccentric center SC Axle center M Motor M1 Pulley

Claims (4)

A shaft member that can be connected to a plurality of vibrating parts, each of which reciprocates in a predetermined direction.
Among the plurality of the above-mentioned vibrating parts, the first driving shaft constituting the first driving mechanism capable of displacementing the first vibrating part and the second driving shaft constituting the second driving mechanism for displaceting the second vibrating part are provided. ,
The first driving axis is
The first large-diameter part and the first small-diameter part whose rotation axis is coaxial and whose cross section orthogonal to the axis is a perfect circle,
Forms a cylindrical shape, one end of which is fixed directly to the first large-diameter portion, the other end having a a first crank portion connectable to directly fixed to the first small-diameter portion the first vibrating portion ,
The first driving shaft has no portion hidden by the first small diameter portion or the first crank portion in the axial direction.
The axis of the first crank portion is eccentric with respect to the axis of the first large diameter portion, and the first crank portion is arranged within the contour range of the first large diameter portion in the axial direction.
The first small diameter portion is arranged within the range of the contour of the first crank portion in the axial direction.
The second driving axis is
The second large-diameter part and the second small-diameter part whose rotation axis is coaxial and whose cross section orthogonal to the axis is a perfect circle,
Forms a cylindrical shape, one end of which is fixed directly to the second large-diameter portion, the other end anda second crank portion connectable to directly fixed to the second small-diameter portion the second vibrating portion ,
The second driving shaft has no portion hidden by the second small diameter portion or the second crank portion in the axial direction.
The axis of the second crank portion is eccentric with respect to the axis of the second large diameter portion, and the second crank portion is arranged within the contour range of the second large diameter portion in the axial direction.
The second small diameter portion is arranged within the contour range of the second crank portion in the axial direction.
The first driving shaft and the second driving shaft are shaft members characterized in that the center of gravity is set at the center of rotation in the axial direction. The shaft member according to claim 1, wherein the first large-diameter portion and the second large-diameter portion have the same diameter and are integrated to form a single cylindrical member. The shaft member according to claim 1, wherein the first small diameter portion and the second large diameter portion have the same diameter and are integrated to form a single cylindrical member. The first large diameter portion, the first crank portion , the first small diameter portion, the second large diameter portion, and the first large diameter portion so that the outer diameter gradually decreases from one side along the axial direction toward the other side . 2. The shaft member according to claim 3, wherein the crank portion and the second small diameter portion are arranged in this order.

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