Electric cylinders and work machines

Abstract

To effectively release heat from a motor and heat on a sun gear tooth surface to an outside.SOLUTION: An electric cylinder comprises: a motor which is a drive source; an output shaft rotating as the motor is driven; a sun gear coupled to the output shaft and rotating as the output shaft rotates; a cylindrical holder disposed adjacently to an axial end surface of the motor and having a fluid storage portion in which a magnetic fluid can be stored between itself and the outer circumference of the sun gear; a pair of pole pieces provided on an inner circumferential surface of the holder; and a magnet disposed between the pair of pole pieces and retaining the magnetic fluid in the fluid storage portion by an action of a magnetic field.SELECTED DRAWING: Figure 17

Description

Technical Field

[0001] The present invention relates to an electric cylinder and a working machine.

Background Art

[0002] Patent Document 1 discloses an electric excavator as an example of a working machine. The electric excavator includes a vehicle body, a boom rotatably provided with respect to the vehicle body, and an electric cylinder. The boom is driven by the electric cylinder. On the other hand, the electric cylinder may include a planetary gear mechanism that transmits the driving force of a motor, which is a driving source, to a piston. The planetary gear mechanism includes a sun gear connected to the output shaft of the motor and a plurality of planetary gears adjacent to the sun gear. The sun gear rotates by the rotation of the output shaft. The plurality of planetary gears rotate by the rotation of the sun gear. The tooth surface of the sun gear contacts the tooth surface of the planetary gear.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of Patent Document 1, the boom rotates by the drive of the electric cylinder. In Patent Document 1, in order to prevent problems caused by the heat generation of the motor, which is the drive source of the electric cylinder, it is required to efficiently release the heat from the motor to the outside. For example, when the motor used as power is miniaturized, the ratio used in the acceleration region increases, so heat dissipation from the motor surface alone is not sufficient, and the temperature is likely to rise. If the motor overheats, the performance of the motor may deteriorate or malfunction may occur. Therefore, it is necessary to efficiently transfer the heat of the motor and release it to the outside. On the other hand, when an electric cylinder is equipped with a planetary gear mechanism, the area around the sun gear becomes hot due to the heat transmitted from the motor's output shaft and the heat generated on the sun gear's tooth surface. This high temperature can cause lubricants such as grease to melt, making it highly likely that lubrication will fail. When lubrication fails, frictional heat can cause localized deterioration or wear of the gear surface, leading to problems such as seizure of the sun gear's sliding parts. Therefore, to prevent problems caused by high temperatures around the sun gear, it is necessary to efficiently dissipate the heat from the sun gear's tooth surface, in addition to the heat from the motor, to the outside.

[0005] Therefore, the present invention aims to provide an electric cylinder and a work machine that can efficiently dissipate heat from the motor and heat from the sun gear tooth surface to the outside. [Means for solving the problem]

[0006] An electric cylinder according to one aspect of the present invention comprises a motor which is a drive source; an output shaft which rotates by the drive of the motor; a sun gear which is connected to the output shaft and rotates by the rotation of the output shaft; a cylindrical holder which is arranged adjacent to the axial end face of the motor and has a fluid reservoir capable of accommodating magnetic fluid between itself and the outer circumference of the sun gear; a pair of magnetic pole pieces provided on the inner circumferential surface of the holder; and a magnet which is arranged between the pair of magnetic pole pieces and holds the magnetic fluid in the fluid reservoir by the action of a magnetic field. [Effects of the Invention]

[0007] According to the above embodiment, heat from the motor and heat from the sun gear tooth surface can be efficiently dissipated to the outside. [Brief explanation of the drawing]

[0008] [Figure 1] A side view of an excavator according to an embodiment. [Figure 2] A side view of a work machine according to an embodiment, showing the inside of the boom and arm through a transparent view. [Figure 3] A perspective view of a boom according to an embodiment, showing the inside of the boom through a transparent view. [Figure 4] Perspective view of the arm according to the embodiment, showing through the inside of the arm. [Figure 5] Perspective view of the electric cylinder according to the embodiment. [Figure 6] View of the electric cylinder according to the embodiment as seen from one side in the axial direction. [Figure 7] View of the electric cylinder according to the embodiment as seen from the other side in the axial direction. [Figure 8] Figure including the VIII-VIII cross section of FIG. 7. [Figure 9] Enlarged view of part IX of FIG. 8. [Figure 10] Figure including the X-X cross section of FIG. 9. [Figure 11] Perspective view of the first carrier according to the embodiment. [Figure 12] Perspective view of the second carrier according to the embodiment. [Figure 13] Exploded perspective view of the peripheral structure including the fluid holding structure according to the embodiment. [Figure 14] Cross-sectional perspective view of the peripheral structure including the fluid holding structure according to the embodiment. [Figure 15] View of the peripheral structure including the fluid holding structure according to the embodiment as seen from one side in the axial direction. [Figure 16] View of the peripheral structure including the fluid holding structure according to the embodiment as seen from the other side in the axial direction. [Figure 17] Figure including the XVII-XVII cross section of FIG. 16. [Figure 18] Figure for explaining an example of the flow of the lubricant according to the embodiment. [Figure 19] Figure for explaining an example in which heat from the motor and heat from the sun gear tooth surface move according to the embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, an excavator will be described as an example of a working machine (working vehicle).

[0010] <Excavator (Work Machine)> As shown in FIG. 1, the excavator 1 as a work machine includes a vehicle body 2 and a work implement 3 connected to the vehicle body 2. Hereinafter, the forward direction, backward direction, and vehicle width direction of the excavator 1 are referred to as "vehicle front (one side of the vehicle longitudinal direction)", "vehicle rear (the other side of the vehicle longitudinal direction)", and "vehicle width direction", respectively. The vehicle width direction may also be referred to as "left side (one side of the vehicle width direction)" or "right side (the other side of the vehicle width direction)". The right hand is referred to as the right side with respect to the direction in which the excavator 1 moves forward, and the left hand is referred to as the left side with respect to the direction in which the excavator 1 moves forward. The vertical direction, upward, and downward in the state where the excavator 1 is arranged on a horizontal plane are simply referred to as "vertical direction", "upward", and "downward", respectively.

[0011] <Vehicle Body> The vehicle body 2 includes a self-propelled lower traveling body 5 and an upper revolving body 6 provided rotatably on the lower traveling body 5.

[0012] The lower traveling body 5 has a pair of left and right crawler belts 7. The lower traveling body 5 includes an electric motor (not shown) for driving the crawler belts 7. The lower traveling body 5 travels by driving the crawler belts 7 with the electric motor. Note that the lower traveling body 5 may include a hydraulic motor instead of the electric motor.

[0013] At the front of the lower traveling body 5, a blade 8 as an earth discharge plate extending in the vehicle width direction of the lower traveling body 5 is provided. The lower traveling body 5 includes an electric actuator (not shown) for driving the blade 8. The height position of the blade 8 can be adjusted by driving the electric actuator.

[0014] The upper revolving body 6 is provided on the upper part of the lower traveling body 5. The upper revolving body 6 is provided with a traveling electric motor that is a drive source of the lower traveling body 5, a motor of an electric cylinder that is a drive source of the work implement 3, a battery that is a power source of each motor, an inverter, etc. (not shown). The upper revolving body 6 is rotatable around an axis extending in the vertical direction with respect to the lower traveling body 5.

[0015] The upper rotating body 6 is provided with a canopy 10. The canopy 10 has a driver's space 11 capable of accommodating a driver. The canopy 10 comprises a hood 12 that forms the ceiling of the driver's space 11, rear support columns 13 provided on both sides in the vehicle width direction at the rear of the hood 12 and extending downward from the hood 12, and front support columns 14 provided on both sides in the vehicle width direction at the front of the hood 12 and extending downward from the hood 12.

[0016] A bracket 15 supporting the boom 20 is provided at the front of the upper slewing body 6. As shown in Figure 2, the bracket 15 has a first hole 15a and a second hole 15b that open in the vehicle width direction of the upper slewing body 6. The first hole 15a is located near the upper end of the bracket 15. The second hole 15b is located below and in front of the first hole 15a.

[0017] <Working equipment> As shown in Figure 1, the work machine 3 is mounted so as to bend and raise relative to the upper slewing body 6. The work machine 3 comprises a boom 20, an arm 30, a bucket 40 (working tool), and a plurality of (for example, three in this embodiment) electric cylinders 100A to 100C. The three electric cylinders 100A to 100C are the first electric cylinder 100A which operates the boom 20, the second electric cylinder 100B which operates the arm 30, and the third electric cylinder 100C which operates the bucket 40. The base end of the boom 20 is rotatably connected to the upper slewing body 6. The tip of the boom 20 is rotatably connected to the base end of the arm 30. The tip of the arm 30 is rotatably connected to the bucket 40.

[0018] <boom> In the posture shown in Figure 1, the boom 20 extends upward from the bracket 15 when viewed from the vehicle width direction of the upper slewing body 6, then bends and extends forward and upward. Hereinafter, the direction in which the boom 20 extends when viewed from the vehicle width direction of the upper slewing body 6 will be referred to as the "boom extension direction," and the direction perpendicular to the boom extension direction will be referred to as the "boom plate width direction." In the boom extension direction, one end of the boom 20 (the end on the bracket 15 side) will be referred to as the "boom base end." In the boom extension direction, the other end of the boom 20 (the end opposite to the boom base end) will be referred to as the "boom tip." The dimensions in the boom plate width direction gradually increase from the boom base end towards the vicinity of the center in the boom extension direction, and then gradually decrease towards the boom tip.

[0019] As shown in Figure 3, the boom 20 comprises a pair of boom side plates 21 spaced apart in the vehicle width direction of the upper slewing body 6, a boom base plate 22 extending in the vehicle width direction of the upper slewing body 6 and connecting the pair of boom side plates 21, a boom base end connecting plate 23 connected to the boom base end side of the boom base plate 22, a boom tip connecting plate 24 connected to the boom tip side of the boom base plate 22, a boom partition member 25 that partitions the space sandwiched between the pair of boom side plates 21 near the center in the boom extending direction, a boom base end support member 26 that allows the boom base end to be supported by the upper slewing body 6, and an arm support plate 27 that supports the arm 30.

[0020] The boom side plate 21 has a first cylinder base end side hole 21a and a second cylinder base end side hole 21b that open in the vehicle width direction of the upper slewing body 6. As shown in Figure 2, the first cylinder base end side hole 21a is located near the center of the boom extension direction when viewed from the vehicle width direction of the upper slewing body 6, and overlaps with a part of the first electric cylinder 100A (near the upper end in Figure 2). The second cylinder base end side hole 21b is located near the center of the boom extension direction when viewed from the vehicle width direction of the upper slewing body 6, and overlaps with a part of the second electric cylinder 100B (near the lower end in Figure 2).

[0021] As shown in Figure 3, the boom base plate 22 is provided on the edge of the boom side plate 21 opposite to the upper slewing body 6 in the boom plate width direction. The boom base plate 22 extends along the boom extension direction. The boom base plate 22 curves near the center in the boom extension direction toward the space between the first cylinder base end side hole 21a and the second cylinder base end side hole 21b.

[0022] The boom base end connecting plate 23 extends in the vehicle width direction of the upper slewing body 6 at the boom base end and connects the pair of boom side plates 21 together. The boom base end connecting plate 23 extends from the connection point with the boom bottom plate 22 away from the boom plate width direction, approaching the boom base end, then bends and extends toward the boom base end.

[0023] The boom tip connecting plate 24 extends in the vehicle width direction of the upper slewing body 6 at the boom tip end and connects a pair of boom side plates 21 together. The boom tip connecting plate 24 extends from the connection point with the boom bottom plate 22, moving away in the boom plate width direction, and then bends to extend toward the boom tip. The boom tip connecting plate 24 has an opening 24a that opens in the boom extension direction at a position adjacent to one of the boom side plates 21.

[0024] The boom partition member 25 extends in the vehicle width direction of the upper slewing body 6 near the center in the boom extension direction and connects the pair of boom side plates 21 together. The boom partition member 25 extends along the boom plate width direction. The boom partition member 25 is positioned between the first cylinder base end side hole 21a and the second cylinder base end side hole 21b. The boom partition member 25 is spaced apart from the boom bottom plate 22 in the boom plate width direction.

[0025] The boom base support member 26 is provided on the boom base end side. The boom base support member 26 has a first through hole 26a that opens in the vehicle width direction of the upper slewing body 6. A first pin 28 (see Figure 2) extending in the vehicle width direction of the upper slewing body 6 is inserted through the first through hole 26a. The boom 20 is supported so as to be rotatable around the central axis O1 of the first pin 28 by inserting the first pin 28 through the first through hole 26a of the boom base support member 26 and the second hole 15b of the bracket 15.

[0026] The arm support plate 27 is provided on the boom tip side. The arm support portion 16 is provided on the outer surface of the boom side plates 21 so as to sandwich the pair of boom side plates 21 from the outside in the vehicle width direction of the upper slewing body 6. The arm support plate 27 protrudes outward in the boom extension direction from the boom side plates 21. The arm support plate 27 has a second through hole 27a that opens in the vehicle width direction of the upper slewing body 6. The second through hole 27a is provided in the portion of the arm support plate 27 that protrudes outward in the boom extension direction from the boom side plates 21. A second pin 29 (see Figure 2) extending in the vehicle width direction of the upper slewing body 6 is inserted through the second through hole 27a.

[0027] <arm> In the posture shown in Figure 1, the arm 30 extends downward and forward from a portion that overlaps with a part of the second electric cylinder 100B (near the upper end in Figure 1) when viewed from the vehicle width direction of the upper slewing body 6. Hereinafter, the direction in which the arm 30 extends when viewed from the vehicle width direction of the upper slewing body 6 will be referred to as the "arm extension direction," and the direction perpendicular to the arm extension direction will be referred to as the "arm plate width direction." In the arm extension direction, one end of the arm 30 (the end on the second electric cylinder 100B side) will be referred to as the "arm base end." In the arm extension direction, the other end of the arm 30 (the end opposite to the arm base end) will be referred to as the "arm tip." The dimensions in the arm plate width direction gradually increase from the arm base end towards the vicinity of the boom connection in the arm extension direction, and then gradually decrease towards the arm tip.

[0028] As shown in Figure 4, the arm 30 comprises a pair of arm side plates 31 spaced apart in the vehicle width direction of the upper slewing body 6, an arm bottom plate 32 extending in the vehicle width direction of the upper slewing body 6 and connecting the pair of arm side plates 31, an arm side connecting plate 33 connected to the arm bottom plate 32, an arm partition member 34 that partitions the space sandwiched between the pair of arm side plates 31 near the base end of the arm, a boom tip connecting member 35 connected to the boom tip, a bucket support member 36 that supports the bucket 40 (see Figure 2), and a link support member 37 that supports one end of the first link member 41 (see Figure 2).

[0029] The arm side plate 31 has a second cylinder tip side hole 31a and a third cylinder base end side hole 31b that open in the vehicle width direction of the upper slewing body 6. As shown in Figure 2, the second cylinder tip side hole 31a is located near the arm base end when viewed from the vehicle width direction of the upper slewing body 6, and overlaps with a part of the second electric cylinder 100B (near the upper end in Figure 2). The third cylinder base end side hole 31b is located on the opposite side of the arm plate width direction from the part that overlaps with the boom tip when viewed from the vehicle width direction of the upper slewing body 6, and overlaps with a part of the third electric cylinder 100C (near the upper end in Figure 2).

[0030] In the posture shown in Figure 2, the arm base plate 32 is provided on the edge of the arm side plate 31 on the upper slewing body 6 side (boom 20 side) in the arm plate width direction. The arm base plate 32 extends along the arm extension direction. As shown in Figure 4, the arm base plate 32 extends between the boom tip connecting member 35 and the bucket support member 36 in the arm extension direction.

[0031] The arm-side connecting plate 33 extends in the vehicle width direction of the upper slewing body 6 at the arm tip end and connects the pair of arm-side plates 31 together. The arm-side connecting plate 33 extends from the connection point with the arm base plate 32 away from the arm plate width direction, approaching the arm tip, then bends and extends toward the arm tip.

[0032] The arm partition member 34 extends in the vehicle width direction of the upper slewing body 6 near the base end of the arm and connects the pair of arm side plates 31 together. The arm partition member 34 is positioned between the second cylinder tip side hole 31a and the third cylinder base end side hole 31b. The arm partition member 34 is positioned spaced apart from the boom tip connecting member 35. When viewed from the vehicle width direction of the upper slewing body 6, the arm partition member 34 extends from near the boom tip connecting member 35 toward the arm tip, then bends and extends across the space between the second cylinder tip side hole 31a and the third cylinder base end side hole 31b.

[0033] The boom tip connecting member 35 is formed in a cylindrical shape that extends in the vehicle width direction of the upper slewing body 6. The boom tip connecting member 35 has a boom connecting hole 35a that opens in the vehicle width direction of the upper slewing body 6. As shown in Figure 2, the boom connecting hole 35a overlaps with the second through hole 27a of the arm support plate 27 when viewed from the vehicle width direction of the upper slewing body 6. The arm 30 is supported so as to be rotatable around the central axis O2 (see Figure 4) of the second pin 29 by inserting the second pin 29 through the second through hole 27a of the arm support plate 27 and the boom connecting hole 35a of the boom tip connecting member 35.

[0034] As shown in Figure 4, the bucket support member 36 is provided at the tip of the arm. The bucket support member 36 is formed in a cylindrical shape that extends in the vehicle width direction of the upper slewing body 6. The bucket support member 36 has a third through hole 36a that opens in the vehicle width direction of the upper slewing body 6. A third pin 38 (see Figure 2) that extends in the vehicle width direction of the upper slewing body 6 is inserted through the third through hole 36a.

[0035] As shown in Figure 4, the link support member 37 is positioned between the arm base plate 32 and the arm-side connecting plate 33. The link support member 37 is positioned near the bucket support member 36. The link support member 37 is formed in a cylindrical shape that extends in the vehicle width direction of the upper slewing body 6. The link support member 37 protrudes outward in the vehicle width direction of the upper slewing body 6 beyond the pair of arm side plates 31. The link support member 37 has a first link connecting hole 37a that opens in the vehicle width direction of the upper slewing body 6.

[0036] <bucket> In the posture shown in Figure 2, the bucket 40 is tilted from the tip of the arm toward the vicinity of the center in the boom extension direction. The bucket 40 has a bucket connection hole 40a and a second link connection hole 40b that open in the vehicle width direction of the upper slewing body 6.

[0037] The bucket connection hole 40a, when viewed from the vehicle width direction of the upper rotating body 6, coincides with the third through hole 36a of the bucket support member 36. The bucket 40 is supported so as to be rotatable around the central axis O3 (see Figure 4) of the third pin 38 by inserting the third pin 38 through the third through hole 36a of the bucket support member 36 and the bucket connection hole 40a of the bucket 40. In the orientation shown in Figure 2, the second link connection hole 40b is located below and further back than the bucket connection hole 40a.

[0038] <First Electric Cylinder> As shown in Figure 2, the first electric cylinder 100A is positioned closer to the boom base end than the boom partition member 25. The first electric cylinder 100A comprises a first cylinder body 103A configured to extend and retract along the boom extension direction, a first motor 101A which is a drive source, and a first power transmission unit 102A which transmits the driving force of the first motor 101A to the first cylinder body 103A.

[0039] The first cylinder body 103A and the first motor 101A extend parallel to each other. The first end of the first cylinder body 103A is connected to a pin 51 inserted through the first hole 15a of the bracket 15. The first electric cylinder 100A is supported on the upper slewing body 6 via the bracket 15 so as to be rotatable about the central axis of the pin 51 which extends in the width direction of the upper slewing body 6.

[0040] The second end of the first cylinder body 103A is connected to a pin 52 inserted through the first cylinder base end side hole 21a of the boom 20. The first electric cylinder 100A is supported on the boom 20 so as to be rotatable around the central axis of the pin 52 which extends in the width direction of the upper slewing body 6.

[0041] The first motor 101A is located on the second end side of the first cylinder body 103A. The first motor 101A is located inward in the boom plate width direction compared to the first cylinder body 103A. The first motor 101A operates the first cylinder body 103A using a battery (not shown) located in the upper slewing body 6 as its power source. The boom 20 rotates around the central axis O1 of the first pin 28 (see Figure 3) relative to the upper slewing body 6 as the first cylinder body 103A extends and retracts due to the drive of the first motor 101A.

[0042] A first wiring harness 61 extends from the first motor 101A. The first wiring harness 61 extends along the boom base end connecting plate 23 and passes through the bracket 15. The first wiring harness 61 is connected to a battery (not shown) through the bracket 15.

[0043] <Second Electric Cylinder> The second electric cylinder 100B is positioned closer to the boom tip than the boom partition member 25. The second electric cylinder 100B comprises a second cylinder body 103B configured to extend and retract along the boom extension direction, a second motor 101B which is a drive source, and a second power transmission unit 102B which transmits the driving force of the second motor 101B to the second cylinder body 103B.

[0044] The second cylinder body 103B and the second motor 101B extend parallel to each other. The first end of the second cylinder body 103B is connected to a pin 53 inserted through the second cylinder base end side hole 21b of the boom 20. The second electric cylinder 100B is supported on the boom 20 so as to be rotatable around the central axis of the pin 53 that extends in the width direction of the upper slewing body 6 relative to the boom 20.

[0045] The second end of the second cylinder body 103B is connected to a pin 54 inserted through the second cylinder tip side hole 31a of the arm 30. The second electric cylinder 100B is supported on the arm 30 so as to be rotatable around the central axis of the pin 54, which extends in the width direction of the upper slewing body 6 relative to the arm 30.

[0046] The second motor 101B is located on the first end side of the second cylinder body 103B. The second motor 101B is located inward in the boom plate width direction compared to the second cylinder body 103B. The second motor 101B operates the second cylinder body 103B using a battery (not shown) located in the upper slewing body 6 as its power source. The arm 30 rotates around the central axis O2 of the second pin 29 (see Figure 3) relative to the boom 20 as the second cylinder body 103B extends and retracts due to the drive of the second motor 101B.

[0047] A second wiring harness 62 extends from the second motor 101B. The second wiring harness 62 extends toward the first motor 101A, then, together with the first wiring harness 61, extends along the boom base end connecting plate 23 and leads into the bracket 15. The second wiring harness 62 is connected to a battery (not shown) through the bracket 15.

[0048] <Third Electric Cylinder> The third electric cylinder 100C is positioned closer to the arm tip than the arm partition member 34. The third electric cylinder 100C comprises a third cylinder body 103C configured to extend and retract along the arm extension direction, a third motor 101C which is a drive source, and a third power transmission unit 102C which transmits the driving force of the third motor 101C to the third cylinder body 103C.

[0049] The third cylinder body 103C and the third motor 101C extend parallel to each other. The first end of the third cylinder body 103C is connected to a pin 55 inserted through the third cylinder base end side hole 31b of the arm 30. The third electric cylinder 100C is supported on the arm 30 so as to be rotatable around the central axis of the pin 55 that extends in the width direction of the upper slewing body 6 relative to the arm 30.

[0050] The second end of the third cylinder body 103C is connected to the first end of the first link member 41. The first end of the first link member 41 has a first link hole 41a that opens in the width direction of the upper slewing body 6. The second end of the third cylinder body 103C is connected to a pin 56 inserted through the first link hole 41a. The third electric cylinder 100C supports the first link member 41 so as to be rotatable around the central axis of the pin 56 that extends in the width direction of the upper slewing body 6 relative to the first link member 41.

[0051] The second end of the first link member 41 has a second link hole 41b that opens in the width direction of the upper slewing body 6. A pin 57 is inserted through the second link hole 41b together with the first link connection hole 37a of the arm 30. The first link member 41 is supported by the arm 30 so as to be rotatable around the central axis of the pin 57 that extends in the width direction of the upper slewing body 6 relative to the arm 30.

[0052] The second end of the third cylinder body 103C is connected to the first end of the second link member 42. The first end of the second link member 42 has a third link hole 42a that opens in the width direction of the upper slewing body 6. The second end of the third cylinder body 103C is connected to a pin 56 that is inserted through the third link hole 42a together with the first link hole 41a. The second link member 42 is rotatably mounted around the central axis of the pin 56 that extends in the width direction of the upper slewing body 6 relative to the second end of the third cylinder body 103C and the first end of the first link member 41.

[0053] The second end of the second link member 42 has a fourth link hole 42b that penetrates the upper slewing body 6 in the width direction. A pin 58 is inserted through the fourth link hole 42b together with the second link connection hole 40b of the bucket 40. The second link member 42 is rotatably mounted relative to the bucket 40 around the central axis of the pin 58 that extends in the width direction of the upper slewing body 6.

[0054] The third motor 101C is located on the first end side of the third cylinder body 103C. The third motor 101C is located inward in the arm plate width direction compared to the third cylinder body 103C. The third motor 101C operates the third cylinder body 103C using a battery (not shown) provided in the upper slewing body 6 as a power source. The bucket 40 rotates around the central axis O3 of the third pin 38 (see Figure 4) relative to the arm 30 as the third cylinder body 103C extends and retracts due to the drive of the third motor 101C.

[0055] A third wire 63 extends from the third motor 101C. The third wire 63 extends toward the boom 20 and then passes through the opening 24a (see Figure 3) of the boom tip connecting plate 24. Subsequently, the third wire 63 extends toward the first motor 101A and then, together with the first wire 61 and the second wire 62, extends along the boom base connecting plate 23 and leads into the bracket 15. The third wire 63 is connected to a battery (not shown) through the bracket 15.

[0056] <Electric Cylinder> As shown in Figure 1, the first electric cylinder 100A, the second electric cylinder 100B, and the third electric cylinder 100C are all electric cylinders 100 that are common to each other. As shown in Figure 5, the electric cylinder 100 comprises a motor 101, a power transmission unit 102, and a cylinder body 103.

[0057] Motor 101 is the drive source for the electric cylinder 100. For example, motor 101 is a servo motor. As shown in Figure 8, motor 101 and cylinder body 103 extend parallel to each other. Motor 101 and cylinder body 103 are spaced apart from each other.

[0058] The electric cylinder 100 has an output shaft 105 that rotates when driven by the motor 101. The output shaft 105 is mounted coaxially with the central axis of the motor 101. The output shaft 105 protrudes axially outward from the axial end face 101f of the motor 101. In the figure, the symbol C1 indicates the motor axis line along the central axis of the motor 101.

[0059] The power transmission unit 102 transmits the driving force of the motor 101 to the piston 182. The power transmission unit 102 includes a planetary gear mechanism 110 that changes the speed (for example, reduces) of the driving force of the output shaft 105, and a transmission gear mechanism 120 that transmits the speed-changed driving force from the planetary gear mechanism 110 to the piston 182.

[0060] <Planetary gear mechanism> As shown in Figure 9, the planetary gear mechanism 110 comprises a sun gear 111 (an example of a rotating body) connected to the output shaft 105, a plurality of planetary gears 112 arranged adjacent to the sun gear 111, carriers 114 and 115 that rotatably support the central axes 113 of the plurality of planetary gears 112 (hereinafter also referred to as "planetary shafts 113"), and a ring gear 116 surrounding the plurality of planetary gears 112. The planetary gear mechanism 110 is covered by a cylindrical case 106 arranged adjacent to the axial end face 101f of the motor 101.

[0061] <Sangia> The sun gear 111 rotates due to the rotation of the output shaft 105. The sun gear 111 is formed in a cylindrical shape coaxial with the output shaft 105. The axial length of the sun gear 111 is longer than the length by which the output shaft 105 protrudes from the axial end face 101f of the motor 101. The axial base end of the sun gear 111 (the end on the motor 101 side) is spaced apart from the axial end face 101f of the motor 101. The axial base end of the sun gear 111 has a larger diameter than the axial tip end of the sun gear 111 (the end opposite to the motor 101).

[0062] The sun gear 111 has a hollow portion 111a that opens to accommodate lubricant. The hollow portion 111a opens axially outward. The hollow portion 111a is a space enclosed by the axial end of the output shaft 105 and the inner circumferential surface of the sun gear 111. The hollow portion 111a is provided between the axial end of the output shaft 105 and the axial end of the sun gear 111.

[0063] As shown in Figure 14, the sun gear 111 comprises a connecting cylindrical portion 111b connected to the output shaft 105, and a gear-side cylindrical portion 111c connected to the axial end of the connecting cylindrical portion 111b. The connecting cylindrical portion 111b is the axial base end portion of the sun gear 111. The connecting cylindrical portion 111b is formed in a cylindrical shape coaxial with the output shaft 105.

[0064] A keyway 111d is formed on the inner circumferential surface of the connecting cylinder portion 111b, into which a protrusion provided on the outer circumferential surface of the output shaft 105 can be fitted. The keyway 111d extends linearly in the axial direction of the output shaft 105. In Figure 14, the output shaft 105 is shown by a dashed line. As shown in Figure 15, the keyway 111d is formed in a rectangular concave shape when viewed from the axial direction.

[0065] As shown in Figure 14, the connecting cylinder portion 111b has a tapered portion 111e that slopes from the outer peripheral edge of the connecting cylinder portion 111b toward the axial base end of the gear-side cylinder portion 111c. The outer peripheral surface of the tapered portion 111e is sloped so as it moves from the outer peripheral edge of the connecting cylinder portion 111b toward the axial end of the gear-side cylinder portion 111c, it is positioned radially inward.

[0066] The gear-side cylindrical portion 111c is the part of the sun gear 111 that has external teeth. The gear-side cylindrical portion 111c is the part of the sun gear 111 that is on the axial end side. The gear-side cylindrical portion 111c extends axially outward from the axial end of the tapered portion 111e. The gear-side cylindrical portion 111c is formed in a cylindrical shape coaxial with the connecting cylindrical portion 111b. The gear-side cylindrical portion 111c and the connecting cylindrical portion 111b are integrally formed from the same material. As shown in Figure 10, the tooth surface of the sun gear 111 (the surface of the external teeth of the sun gear 111) is in contact with the tooth surface of the planetary gear 112 (the surface of the external teeth of the planetary gear 112).

[0067] <Planetary Gear> The planetary gear 112 rotates due to the rotation of the sun gear 111. As shown in Figure 10, multiple planetary gears 112 (for example, three in this embodiment) are arranged at equal intervals from each other along the circumferential direction of the sun gear 111. The external teeth on the outer circumference of the planetary gear 112 mesh with the external teeth on the outer circumference of the sun gear 111. By meshing with the sun gear 111, the planetary gear 112 rotates on its axis and revolves around the sun gear 111. The planetary gear 112 is rotatable around the planetary shaft 113, which extends parallel to the output shaft 105.

[0068] <Career> As shown in Figure 9, the carriers 114 and 115 are mounted coaxially with the output shaft 105. The carriers 114 and 115 support both axial ends of the planetary shaft 113. The carriers 114 and 115 extend toward the planetary shaft 113 from a position facing the outer circumference of the sun gear 111 and have guide grooves 143a and 151a that are recessed to allow lubricant to flow through.

[0069] The carriers 114 and 115 are a first carrier 114 positioned on the axial end side of the output shaft 105 and a second carrier 115 positioned on the axial center side of the output shaft 105. As shown in Figure 10, the first carrier 114 and the second carrier 115 are connected to each other by a plurality of bolts 145 (for example, six in this embodiment).

[0070] <First Career> As shown in Figure 11, the first carrier 114 has a first shaft hole 114a that opens to allow the insertion of a planetary shaft 113, and a first bolt hole 114b that opens to allow the insertion of a bolt 145 (see Figure 10). The first carrier 114 comprises an annular first carrier base 140, a cylindrical carrier tip cylinder 141 (see Figure 9) that protrudes axially outward from the first carrier base 140, a plurality of carrier wall portions 142 that extend axially inward from the first carrier base 140 (in the opposite direction to the direction in which the carrier tip cylinder 141 protrudes), and a first groove forming portion 143 provided between two adjacent carrier wall portions 142 in the circumferential direction. The first carrier base 140, the carrier tip cylinder 141, the carrier wall portions 142, and the first groove forming portion 143 are integrally formed from the same member.

[0071] As shown in Figure 9, the outer diameter of the first carrier base 140 is larger than the outer diameter of the carrier tip cylinder 141. The outer peripheral edge of the first carrier base 140 is spaced radially inward from the inner peripheral surface of the case 106.

[0072] As shown in Figure 11, the first carrier base 140 has an annular groove 140a positioned opposite the axial end of the output shaft 105, and a plurality of intermediate grooves 140b connected to the annular groove 140a. The annular groove 140a is formed in an annular shape along the inner circumference of the first carrier base 140. The intermediate grooves 140b are curved radially outward from the outer edge of the annular groove 140a.

[0073] Multiple carrier wall portions 142 (for example, three in this embodiment) are arranged at equal intervals from one another along the circumferential direction of the first carrier base 140. The carrier wall portions 142 are provided between the outer peripheral edge of the annular groove 140a and the outer peripheral edge of the first carrier base 140. When viewed from the axial direction, the carrier wall portions 142 have an outer shape that bulges outward in the circumferential direction of the first carrier base 140 as it extends radially outward from the first carrier base 140. The side surface of the carrier wall portion 142 in the circumferential direction of the first carrier base 140 is curved in an arc shape along the outer shape of the first groove forming portion 143. Two first bolt holes 114b are provided in each carrier wall portion 142.

[0074] Multiple (for example, three in this embodiment) first groove-forming portions 143 are arranged at equal intervals from each other along the circumferential direction of the first carrier base portion 140. The first groove-forming portions 143 are spaced equally apart from each other with respect to the sides of two circumferentially adjacent carrier wall portions 142. The first groove-forming portions 143 are provided in a position that overlaps with the planetary gear 112 when viewed from the axial direction.

[0075] The first groove forming section 143 has a first guide groove 143a that is recessed to allow lubricant to flow through. The first guide groove 143a is formed on a virtual line connecting the axis of the carrier tip cylinder 141 and the axis of the first shaft hole 114a when viewed from the axial direction. As shown in Figure 9, the first guide groove 143a extends from a position facing the axial tip of the sun gear 111 toward the first shaft hole 114a. As shown in Figure 11, the first guide groove 143a is located between the first shaft hole 114a and the intermediate groove 140b. The depth of the first guide groove 143a gradually increases from the first shaft hole 114a side toward the intermediate groove 140b.

[0076] The first groove forming portion 143 has a first receiving surface 143b that receives the axial outer end surface of the planetary gear 112. The first receiving surface 143b is formed in a C-shape that opens at the portion of the first guide groove 143a when viewed from the axial direction. The first receiving surface 143b is configured to be able to contact the axial outer end surface of the planetary gear 112 in portions other than the first guide groove 143a. The inner periphery of the first receiving surface 143b is spaced radially outward from the outer periphery of the first shaft hole 114a.

[0077] <Second Career> As shown in Figure 12, the second carrier 115 has a second shaft hole 115a that opens to allow the planetary shaft 113 to be inserted, and a second bolt hole 115b that opens to allow the bolt 145 (see Figure 10) to be inserted. The second carrier 115 comprises an annular second carrier base 150 and a second groove forming portion 151 provided at a position axially opposite to the first groove forming portion 143 (see Figure 11). The second carrier base 150 and the second groove forming portion 151 are integrally formed from the same member.

[0078] As shown in Figure 9, the outer diameter of the second carrier base 150 is approximately the same as the outer diameter of the first carrier base 140. The outer peripheral edge of the second carrier base 150 is spaced radially inward from the inner circumferential surface of the case 106.

[0079] The second carrier base 150 has an opening 150a that allows the output shaft 105 to be inserted. The second carrier base 150 has a wall support portion 150b that receives the carrier wall portion 142 of the first carrier 114.

[0080] The wall support portion 150b is provided in a position that overlaps with the carrier wall portion 142 when viewed from the axial direction. As shown in Figure 12, there are multiple wall support portions 150b (for example, three in this embodiment) corresponding to the carrier wall portion 142. Two second bolt holes 115b are provided in each wall support portion 150b.

[0081] Multiple (for example, three in this embodiment) second groove-forming portions 151 are arranged at equal intervals from one another along the circumferential direction of the second carrier base portion 150. The second groove-forming portions 151 are provided in positions that overlap with the planetary gear 112 when viewed from the axial direction.

[0082] The second groove forming section 151 has a second guide groove 151a that is recessed to allow lubricant to flow through. The second guide groove 151a is formed on a virtual line connecting the center of the opening 150a and the axis of the second shaft hole 115a when viewed from the axial direction. As shown in Figure 9, the second guide groove 151a extends from a position facing the outer circumference of the sun gear 111 toward the second shaft hole 115a. As shown in Figure 12, the second guide groove 151a is positioned between the second shaft hole 115a and the opening 150a. The depth of the second guide groove 151a gradually increases from the second shaft hole 115a side toward the opening 150a.

[0083] The second groove forming portion 151 has a second receiving surface 151b that receives the axial inner end face of the planetary gear 112. The second receiving surface 151b is formed in a C-shape that opens at the portion of the second guide groove 151a when viewed from the axial direction. The second receiving surface 151b is configured to be able to contact the axial inner end face of the planetary gear 112 in portions other than the second guide groove 151a. The inner peripheral edge of the second receiving surface 151b is spaced radially outward from the outer peripheral edge of the second shaft hole 115a.

[0084] <Ring Gear> As shown in Figure 10, the internal teeth on the inner circumference of the ring gear 116 mesh with the external teeth on the outer circumference of each planetary gear 112. The outer circumferential surface of the ring gear 116 is provided with multiple gear-side recesses 116a into which the anti-rotation pin 117 fits. The multiple (for example, four in this embodiment) gear-side recesses 116a are spaced equally apart from each other in the circumferential direction.

[0085] The inner circumferential surface of the case 106 is provided with a plurality of case-side recesses 106a into which the anti-rotation pin 117 fits. The plurality (for example, four in this embodiment) of case-side recesses 106a are spaced equally apart from each other in the circumferential direction. For example, by inserting the anti-rotation pin 117 into each recess 106a, 116a with the circumferential positions of the gear-side recess 116a and the case-side recess 106a aligned, the rotation of the ring gear 116 can be prevented (the movement of the ring gear 116 in the circumferential direction relative to the case 106 is restricted).

[0086] <Holder> As shown in Figure 9, the electric cylinder 100 includes a holder 118 positioned adjacent to the axial end face 101f of the motor 101. The holder 118 is positioned between the axial end face 101f of the motor 101 and the carriers 114 and 115. The holder 118 is formed to surround the space between the axial end face 101f of the motor 101 and the second carrier 115 from the radially outer side.

[0087] As shown in Figure 17, the holder 118 has a fluid reservoir 201 between it and the outer circumference of the sun gear 111 that can accommodate the magnetic fluid 200. For example, the magnetic fluid 200 is a liquid in which magnetic fine particles such as magnetite are dispersed in a base liquid with a surfactant. The thermal conductivity of the magnetic fluid 200 is higher than that of air. The form of the magnetic fluid 200 can be changed according to the required specifications.

[0088] The holder 118 is formed in a cylindrical shape. The holder 118 has a through hole 118a that opens in the axial direction of the motor 101, with a gap between it and the outer peripheral edge (radial outer edge) of the connecting cylindrical portion 111b of the sun gear 111. The gap in the through hole 118a is formed to a size that allows lubricant to flow through. The holder 118 has an inner recess 118b that opens axially inward at a position facing the axial end face 101f of the motor 101, an outer recess 118c that opens axially outward to accommodate the second carrier 115, and a accommodating recess 119 that opens axially outward at a position facing the fluid accommodating portion 201. In Figure 17, the motor 101 and the output shaft 105 are shown by dashed lines.

[0089] The through-hole 118a connects the radial centers (the portion on the sun gear 111 side) of the inner recess 118b and the housing recess 119 in the axial direction. The axial inner end of the through-hole 118a is connected to the radial center of the inner recess 118b. The axial outer end of the through-hole 118a is connected to the radial center of the housing recess 119. The inner diameter of the inner recess 118b is larger than the inner diameter of the outer recess 118c. The inner diameter of the housing recess 119 is smaller than the inner diameter of the outer recess 118c. The inner circumferential edge of the outer recess 118c is spaced radially outward from the outer circumferential edge of the second carrier 115. The inner circumferential surface of the outer recess 118c is located axially outward from the motor 101 than from the fluid housing 201. The inner circumferential surface of the outer recess 118c is located radially outward from the sun gear 111 than from the fluid housing 201. The inner circumferential surface of the receiving recess 119 is positioned radially inward of the sun gear 111 than the inner circumferential surface of the outer recess 118c.

[0090] As shown in Figure 13, the receiving recess 119 has a support surface 119a that is formed in an annular shape coaxial with the sun gear 111. As shown in Figure 17, the support surface 119a extends radially with respect to the sun gear 111. The support surface 119a is formed parallel to the axial inner surface of the inner recess 118b.

[0091] The holder 118 has a holder groove 118d that extends from the inner circumferential edge of the outer recess 118c toward the axial inner end of the ring gear 116 and is recessed to allow lubricant to flow through. The depth of the holder groove 118d gradually increases from the inner circumferential edge side of the outer recess 118c toward the axial inner end of the ring gear 116.

[0092] <Magnetic pole piece> The electric cylinder 100 includes a pair of magnetic pole pieces 211, 212 provided on the inner circumferential surface of the holder 118. The pair of magnetic pole pieces 211, 212 are provided on the inner circumferential surface of the housing recess 119. As shown in Figure 13, the pair of magnetic pole pieces 211, 212 are formed in an annular shape coaxial with the sun gear 111. The pair of magnetic pole pieces 211, 212 consists of a first magnetic pole piece 211 positioned between the support surface 119a of the holder 118 and the magnet 210, and a second magnetic pole piece 212 positioned adjacent to the side of the magnet 210 opposite to the first magnetic pole piece 211. The first magnetic pole piece 211 and the second magnetic pole piece 212 are formed in an annular shape of the same size.

[0093] As shown in Figure 17, for example, it is preferable that the outer circumferential surfaces of the magnetic pole pieces 211 and 212 are in contact with the inner circumferential surface of the housing recess 119. This makes it possible to suppress radial displacement of the magnetic pole pieces 211 and 212 with respect to the inner circumferential surface of the housing recess 119.

[0094] <Magnet> The electric cylinder 100 includes a magnet 210 positioned between a pair of pole pieces 211 and 212. The magnet 210 holds the magnetic fluid 200 in the fluid reservoir 201 through the action of a magnetic field. As shown in Figure 13, the magnet 210 is formed in an annular shape coaxial with the sun gear 111. The magnet 210 is a ring-shaped magnetized in the axial direction. The magnet 210 is formed in an annular shape with an inner diameter larger than that of the pole pieces 211 and 212. The magnet 210 has the same outer diameter as the pole pieces 211 and 212. As shown in Figure 17, the inner circumferential surface of the magnet 210 is positioned radially outward from the sun gear 111 than the inner circumferential surfaces of the pole pieces 211 and 212.

[0095] For example, it is preferable that the magnet 210 is in contact with the inner circumferential surface of the housing recess 119. This makes it possible to suppress radial displacement of the magnet 210 relative to the inner circumferential surface of the housing recess 119.

[0096] The magnet 210, together with the first pole piece 211 and the second pole piece 212, holds the magnetic fluid 200 in the fluid reservoir 201. The magnet 210, the first pole piece 211, and the second pole piece 212 constitute a fluid holding structure 209 that holds the magnetic fluid 200 in the fluid reservoir 201. In this embodiment, one fluid holding structure 209 is provided on the inner circumferential surface of the receiving recess 119 of the holder 118.

[0097] <Retaining ring> The electric cylinder 100 is equipped with a retaining ring 215 that prevents the second pole piece 212 from coming out axially outward from the motor 101. For example, the retaining ring 215 is a snap ring. The retaining ring 215 is positioned adjacent to the side of the second pole piece 212 opposite to the magnet 210. As shown in Figure 16, the retaining ring 215 is formed in a C shape when viewed from the axial direction. The retaining ring 215 is formed in an arc shape that overlaps with the outer circumference of the second pole piece 212 when viewed from the axial direction.

[0098] As shown in Figure 17, the holder 118 has a fitting groove 119b into which the retaining ring 215 can be fitted. The fitting groove 119b is located near the axial outer end on the inner circumferential surface of the receiving recess 119. The fitting groove 119b is recessed radially outward along the entire circumference of the inner circumferential surface of the receiving recess 119. The fitting groove 119b is formed in an annular shape along the inner circumference of the receiving recess 119. The fitting groove 119b is formed in an annular shape along the outer circumference of the retaining ring 215. Between the support surface 119a of the holder 118 and the retaining ring 215, the first pole piece 211, the magnet 210, and the second pole piece 212 are arranged in this order in the axial direction.

[0099] For example, when the retaining ring 215 is fitted into the fitting groove 119b, it is preferable that the support surface 119a of the housing recess 119, the first pole piece 211, the magnet 210, the second pole piece 212, and the retaining ring 215 are in contact with each other on axially adjacent surfaces. This makes it possible to suppress axial misalignment of the first pole piece 211, the magnet 210, and the second pole piece 212 with respect to the support surface 119a of the housing recess 119.

[0100] <Fluid containment section> The fluid containment section 201 is provided so as to surround the outer circumference of the axial base end side of the sun gear 111 (the outer circumference of the connecting cylinder portion 111b) in the circumferential direction. The fluid containment section 201 is partitioned by the outer circumferential surface of the axial base end side of the sun gear 111 (the outer circumferential surface of the connecting cylinder portion 111b), the inner circumferential surfaces of the pair of magnetic pole pieces 211, 212, and the inner circumferential surface of the magnet 210. The fluid containment section 201 includes gaps 201a, 201b between the outer circumferential surface of the sun gear 111 and the inner circumferential surfaces of the magnetic pole pieces 211, 212 that can contain the magnetic fluid 200, and a space 201c between the outer circumferential surface of the sun gear 111 and the inner circumferential surface of the magnet 210 that can contain the magnetic fluid 200.

[0101] Hereinafter, the gap 201a between the outer surface of the sun gear 111 and the inner surface of the first pole piece 211 will also be referred to as the "first gap 201a," and the gap 201b between the outer surface of the sun gear 111 and the inner surface of the second pole piece 212 will also be referred to as the "second gap 201b." The first gap 201a and the second gap 201b are connected to each other via space 201c. Magnetic fluid 200 is contained in the first gap 201a, the second gap 201b, and space 201c.

[0102] For example, the sun gear 111 may be made of a magnetic material. For example, at least the portion of the sun gear 111 facing the fluid reservoir 201 (connecting cylinder portion 111b) may be made of a magnetic material. With this configuration, the magnetic fluid 200 can be held in the fluid reservoir 201 by the action of the magnetic field generated by the magnet 210, the magnetic pole pieces 211, 212 and the sun gear 111.

[0103] <Supplementary section> The electric cylinder 100 includes a capture portion 216 capable of capturing lubricant flowing from the axial tip side of the sun gear 111 toward the fluid reservoir 201. The capture portion 216 protrudes from the outer circumferential surface of the sun gear 111 toward the inner circumferential surface of the outer recess 118c. As shown in Figure 16, the capture portion 216 is formed in an annular shape coaxial with the sun gear 111. For example, the capture portion 216 is an annular member that can be attached to the outer circumferential surface of the sun gear 111 by press-fitting.

[0104] As shown in Figure 14, the capture portion 216 comprises a first annular portion 216a that runs along the outer circumference of the connecting cylindrical portion 111b of the sun gear 111, and a second annular portion 216b that is connected to the first annular portion 216a and runs along the outer circumference of the tapered portion 111e. The first annular portion 216a and the second annular portion 216b are integrally formed from the same material.

[0105] The inner circumferential surface of the first annular portion 216a is in contact with the outer circumferential surface of the connecting cylindrical portion 111b. The inner circumferential surface of the second annular portion 216b is in contact with the outer circumferential surface of the tapered portion 111e. The inner circumferential surface of the second annular portion 216b is inclined along the outer circumferential surface of the tapered portion 111e from the inner circumferential edge of the first annular portion 216a. As shown in Figure 17, the axial end surface of the second annular portion 216b extends in the radial direction of the sun gear 111.

[0106] In the cross-sectional view shown in Figure 17, the cross-sectional shape of the radial tip of the capturing part 216 is rectangular convex. However, the cross-sectional shape of the radial tip of the capturing part 216 may be other shapes, such as an arc shape, trapezoidal shape, or triangular shape. For example, the cross-sectional shape of the radial tip of the capturing part 216 can be changed according to the required specifications.

[0107] <Transmission Gear Mechanism> As shown in Figure 8, the transmission gear mechanism 120 includes a transfer gear 121 that transmits the rotational force of the carriers 114 and 115 to the piston 182, a transfer shaft 122 that extends axially outward from a position facing the axial outer end of the sun gear 111, an idler gear 123 positioned adjacent to the transfer gear 121, and a driven gear 124 positioned on the opposite side of the idler gear 123 from the transfer gear 121. The transmission gear mechanism 120 is covered by a cover unit 160 positioned adjacent to the case 106.

[0108] As shown in Figure 9, the transfer gear 121 is mounted coaxially with the output shaft 105. The transfer gear 121 is formed in a cylindrical shape with an opening through which the transfer shaft 122 can be inserted. The transfer gear 121 comprises a cylindrical gear body 121a having external teeth that mesh with the idler gear 123, an inner cylinder 121b protruding axially inward from the gear body 121a, and an outer cylinder 121c protruding axially outward from the gear body 121a. The gear body 121a, the inner cylinder 121b, and the outer cylinder 121c are integrally formed from the same material. The transfer gear 121 is supported by the cover unit 160 so as to be rotatable around the motor axis C1 by an inner bearing 130 provided on the outer circumference of the inner cylinder 121b and an outer bearing 131 provided on the outer circumference of the outer cylinder 121c.

[0109] The transfer shaft 122 is mounted coaxially with the output shaft 105. The carrier tip cylinder 141 is connected to the axial end of the transfer shaft 122 by a spline. The inner circumference of the carrier tip cylinder 141 is provided with internal teeth having tooth surfaces parallel to the axial direction of the carrier tip cylinder 141. The outer circumference of the axial end of the transfer shaft 122 is provided with external teeth having tooth surfaces parallel to the axial direction of the transfer shaft 122 and meshing with the internal teeth of the carrier tip cylinder 141. A gap is formed between the external teeth on the axial end of the transfer shaft 122 and the internal teeth of the carrier tip cylinder 141, allowing lubricant to flow through.

[0110] The gear body 121a of the transfer gear 121 is connected to the other axial end of the transfer shaft 122 by a spline. The inner circumference of the gear body 121a is provided with internal teeth having tooth surfaces parallel to the axial direction of the transfer gear 121. The outer circumference of the other axial end of the transfer shaft 122 is provided with external teeth having tooth surfaces parallel to the axial direction of the transfer shaft 122 and meshing with the internal teeth of the gear body 121a. A gap is formed between the external teeth on the other axial end of the transfer shaft 122 and the internal teeth of the gear body 121a, allowing lubricant to flow through.

[0111] The axial inner end of the inner cylinder 121b is connected to the tip of the carrier tip cylinder 141 via an O-ring 132. A bearing 133 is provided between the inner circumference of the inner cylinder 121b and the outer circumference of the axial center of the transfer shaft 122. For example, the bearing 133 is composed of a pair of semi-circular rings (so-called split rings). A gap is formed between the axial center of the transfer shaft 122 and the bearing 133, allowing lubricant to flow through.

[0112] A cover member 135 is detachably attached to the outer cylindrical body 121c. The cover member 135 has a supply hole 135a that opens to allow lubricant to be supplied from the outside to the other axial end of the transfer shaft 122. The supply hole 135a is formed on the motor axis C1. A gap is formed between the axial outer end of the transfer shaft 122 and the cover member 135, allowing lubricant to flow through.

[0113] The cover member 135 is provided with a grease nipple 136 that can be opened and closed to allow lubricant to be supplied to the supply hole 135a from the outside. The grease nipple 136 is located on the motor axis C1. The grease nipple 136 extends axially outward from the cover member 135. The grease nipple 136 has a lubricant injection port (not shown) that leads to the supply hole 135a. The grease nipple 136 has a check valve in which a ball is pressed against the injection port from the inside by a spring. For example, by connecting a grease gun or the like to the grease nipple 136 and applying pressure, the grease nipple 136 can be opened and lubricant can be supplied to the supply hole 135a through the injection port.

[0114] The idler gear 123 rotates due to the rotation of the transfer gear 121. The idler gear is rotatable around an idler shaft 123a that extends parallel to the transfer shaft 122. The idler gear 123 is formed in a cylindrical shape with an opening that allows the idler shaft 123a to be inserted. A bearing 123b is provided between the inner circumference of the idler gear 123 and the outer circumference of the idler shaft 123a.

[0115] As shown in Figure 8, the driven gear 124 is positioned adjacent to the idler gear 123. The driven gear 124 rotates with the rotation of the idler gear 123. The driven gear 124 is coaxial with the cylinder shaft 180, which is housed inside the cylinder body 103. In the figure, reference numeral C2 indicates the cylinder axis along the cylinder shaft 180.

[0116] The driven gear 124 is formed in a cylindrical shape with an opening that allows the first end of the cylinder shaft 180 to be inserted. The driven gear 124 comprises a cylindrical gear body 124a having external teeth that mesh with the idler gear 123, an inner cylindrical body 124b protruding axially inward from the gear body 124a, and an outer cylindrical body 124c protruding axially outward from the gear body 124a. The gear body 124a, the inner cylindrical body 124b, and the outer cylindrical body 124c are integrally formed from the same material.

[0117] The driven gear 124 is supported by an inner bearing 155 located on the outer circumference of the inner cylinder 124b and an outer bearing 156 located on the outer circumference of the outer cylinder 124c, so as to be rotatable around the cylinder axis C2 relative to the cover unit 160. In the figure, reference numeral 137 denotes a cover member that is detachably attached to the outer cylindrical body 124c, and reference numeral 138 denotes a grease nipple provided on the cover member 137 and which can be opened and closed to allow lubricant to be supplied from the outside to the supply hole of the cover member 137.

[0118] <Cover Unit> The cover unit 160 includes a first cover 161 that covers the transfer gear 121 from the axial outward direction, a second cover 162 that covers the driven gear 124 from the axial outward direction, and a third cover 163 that covers the transfer gear 121, idler gear 123, and driven gear 124 from the radial outward direction of each gear.

[0119] As shown in Figure 7, the first cover 161 has a rectangular shape when viewed from the axial direction. As shown in Figure 9, the first cover 161 has a first supply opening 161a that opens to allow lubricant to be supplied from the outside to the other axial end of the transfer shaft 122. The first supply opening 161a is formed on the motor axis C1. A gap is formed between the axial outer end of the transfer gear 121 and the first cover 161, allowing lubricant to flow through. A first lid member 165 is detachably attached to the first cover 161 so as to be able to open and close the first supply opening 161a.

[0120] As shown in Figure 8, the second cover 162 has a second supply opening 162a that opens to allow lubricant to be supplied from the outside to the first end side of the cylinder shaft 180. The second supply opening 162a is formed on the cylinder axis C2. A gap is formed between the axial outer end of the tribun gear 124 and the second cover 162, allowing lubricant to flow through. A second lid member 166 is detachably attached to the second cover 162 so as to be able to open and close the second supply opening 162a.

[0121] As shown in Figure 7, the second cover 162 comprises an idler cover portion 162b positioned to overlap with the idler gear 123 when viewed from the axial direction, and a driven cover portion 162c positioned to overlap with the driven gear 124. The idler cover portion 162b and the driven cover portion 162c are integrally formed from the same material. As shown in Figure 9, the idler cover portion 162b fixes the idler shaft 123a with a bolt 170.

[0122] As shown in Figure 5, the third cover 163 comprises a case-side cover portion 163a provided between the case 106 and the first cover 161, and a screw-side cover portion 163b provided between the cylinder body 103 and the second cover 162.

[0123] As shown in Figure 9, the case-side cover portion 163a has an opening coaxial with the motor axis C1. In the figure, reference numeral 167 denotes an inner spacer provided between the inner circumferential surface of the axially inner portion of the case-side cover portion 163a and the inner bearing 130, and reference numeral 168 denotes an outer spacer provided between the inner circumferential surface of the axially outer portion of the case-side cover portion 163a and the outer bearing 131.

[0124] As shown in Figure 5, the first cover 161 is fastened to the case 106 via the case-side cover portion 163a by a plurality of bolts 171 (for example, four in this embodiment). The axial inner end of the case-side cover portion 163a is connected to the axial outer end of the case 106 by fastening the bolts 171 together.

[0125] The driven cover portion 162c is fixed to the threaded cover portion 163b by a number of bolts 172 (for example, eight in this embodiment). The threaded cover portion 163b is fixed to the cylinder body 103 by a number of bolts 173 (for example, four in this embodiment).

[0126] <Cylinder body> As shown in Figure 8, the cylinder body 103 comprises a cylinder shaft 180, a nut 181 screwed onto the threaded shaft 180a of the cylinder shaft 180, a piston 182 provided on the outer circumference of the nut 181, a cylindrical piston rod 183 connected to the piston 182, a joint member 184 provided at the tip of the piston rod 183, a cylindrical cylinder tube 185 housing the piston rod 183, a retaining member 186 provided between the first end of the cylinder tube 185 and the threaded side cover portion 163b, and a rod cover 187 provided at the second end of the cylinder tube 185.

[0127] A ball (not shown) is interposed between the screw shaft 180a and the nut 181. The screw shaft 180a and the nut 181 constitute a ball screw that converts the rotational motion of the motor 101 into linear motion. The nut 181 is connected to the piston 182 by multiple bolts. The piston 182 is configured to move along the screw shaft 180a integrally with the nut 181. The piston rod 183 is configured to move along the cylinder axis C2 integrally with the piston 182.

[0128] As shown in Figure 6, the joint member 184 protrudes outward from the outer edge of the rod cover 187. As shown in Figure 8, the joint member 184 has a connecting hole 184a that opens in a direction perpendicular to the cylinder axis C2. A bearing 188 is provided between the inner surface of the cylinder tube 185 and the outer surface of the piston 182.

[0129] As shown in Figure 5, the retaining member 186 comprises a cylindrical retaining body 190 and a trunnion portion 191 that protrudes radially outward from the retaining body 190. As shown in Figure 8, the retaining body 190 opens coaxially with the cylinder axis C2. Multiple bearings 189 are provided between the inner circumferential surface of the retaining body 190 and the screw shaft 180a. As shown in Figure 5, the trunnion portion 191 has a connection hole 191a that opens in a direction perpendicular to the cylinder axis C2. The connection hole 191a of the trunnion portion 191 opens parallel to the connection hole 184a of the joint member 184.

[0130] <Operation of the electric cylinder> The following describes an example of the operation of the electric cylinder 100. As shown in Figure 8, the driving force from the motor 101 is reduced through the power transmission unit 102 and transmitted to the cylinder shaft 180. Specifically, the driving force from the motor 101 is a rotational force around the motor axis C1, and is reduced by the output shaft 105, sun gear 111, multiple planetary gears 112, and carriers 114 and 115. The rotational force reduced by the carriers 114 and 115 is transmitted to the transfer gear 121 through the transfer shaft 122. The rotational force transmitted to the transfer gear 121 is transmitted to the cylinder shaft 180 through the idler gear 123 and driven gear 124.

[0131] For example, when the motor 101 rotates in the forward direction, the cylinder shaft 180 rotates in one direction around the cylinder axis C2. Due to the rotation of the cylinder shaft 180 in one direction, the nut 181, which is screwed onto the threaded shaft 180a of the cylinder shaft 180, moves along the cylinder axis C2 in the direction of arrow M1. Due to the movement of the nut 181 in the direction of arrow M1, the piston 182, piston rod 183, and joint member 184 move together in the direction of arrow M1. As a result, the cylinder body 103 extends.

[0132] On the other hand, when the motor 101 is rotated in the reverse direction from the extended state of the cylinder body 103, the cylinder shaft 180 rotates in the opposite direction around the cylinder axis C2. Due to the rotation of the cylinder shaft 180 in the opposite direction, the nut 181, which is screwed onto the threaded shaft 180a of the cylinder shaft 180, moves along the cylinder axis C2 in the opposite direction to the direction of arrow M1. Due to the movement of the nut 181 in the opposite direction to the direction of arrow M1, the piston 182, piston rod 183, and joint member 184 move together in the opposite direction to the direction of arrow M1. As a result, the cylinder body 103 retracts. Thus, the electric cylinder 100 is configured such that the cylinder body 103 extends and retracts due to the forward and reverse rotation of the motor 101.

[0133] <Lubricant flow> The following describes an example of lubricant flow. As shown in Figure 18, first, the first lid member 165 is removed from the cover unit 160 to open the first supply opening 161a. This exposes the grease nipple 136 through the first supply opening 161a. Next, by connecting a grease gun or the like to the grease nipple 136 and applying pressure, the grease nipple 136 is opened, and lubricant is supplied to the inner circumference (gap) of the transfer gear 121 through the supply hole 135a (in the direction of arrow L1 in the figure). The lubricant then travels along the outer circumference (spline gap) of the transfer shaft 122 to the inner circumference (gap) of the carriers 114 and 115 (in the direction of arrow L2 in the figure). Subsequently, the lubricant enters the hollow portion 111a of the sun gear 111 (in the direction of arrow L3 in the figure). This allows the lubricant to accumulate in the hollow portion 111a.

[0134] When the output shaft 105 is rotated by the motor 101, the sun gear 111 rotates. As a result, the lubricant in the hollow portion 111a of the sun gear 111 flows radially outward from the axial end of the sun gear 111 due to centrifugal force. Then, a portion of the lubricant that has come out from the axial end of the sun gear 111 flows along the first guide groove 143a of the first carrier 114 in the direction of arrow L4 and enters the inner circumference (gap) and the side (gap) of the planetary gear 112. Subsequently, the lubricant enters the inner circumference (gap) of the ring gear 116. In this way, the sun gear 111, planetary gear 112, and ring gear 116 can be lubricated.

[0135] Meanwhile, some of the lubricant released from the axial end of the sun gear 111 flows along the outer circumference of the sun gear 111 in the direction of arrow L5 and towards the capture portion 216. Some of the lubricant flowing towards the capture portion 216 flows along the axial end surface of the capture portion 216 in the direction of arrow L6 and towards the inner surface of the outer recess 118c. Subsequently, the lubricant flows along the inner surface of the outer recess 118c and enters the inner side (gap) of the ring gear 116. This allows the sun gear 111, planetary gear 112, and ring gear 116 to be lubricated.

[0136] A portion of the lubricant flowing along the outer circumference of the sun gear 111 flows through the second guide groove 151a of the second carrier 115 in the direction of arrow L7, and enters the inner circumference (gap) and the side (gap) of the planetary gear 112. Subsequently, the lubricant enters the inner circumference (gap) of the ring gear 116. This allows the sun gear 111, planetary gear 112, and ring gear 116 to be lubricated. Furthermore, some of the lubricant flowing along the outer circumference of the sun gear 111 may enter the inner recess 118b of the holder 118. This allows the lubricant to accumulate in the inner recess 118b of the holder 118.

[0137] As described above, by opening the grease nipple 136 with a grease gun or the like, supplying lubricant through the supply hole 135a, and driving the motor 101, the lubricant is interposed in the hollow portion 111a of the sun gear 111, the meshing parts of each gear, and the gap between the motor 101 and the holder 118. This allows the heat generated by the motor 101 and the heat generated by friction in each part to be released to the outside through the parts where the lubricant is interposed. Therefore, the cooling of the motor 101 and the planetary gear mechanism 110 can be promoted.

[0138] <Effects and Effects> As described above, the electric cylinder 100 of this embodiment comprises a motor 101 which is a drive source, an output shaft 105 which rotates when driven by the motor 101, a sun gear 111 which is connected to the output shaft 105 and rotates when the output shaft 105 rotates, a cylindrical holder 118 which is positioned adjacent to the axial end face 101f of the motor 101 and has a fluid storage portion 201 which can accommodate magnetic fluid 200 between itself and the outer circumference of the sun gear 111, a pair of magnetic pole pieces 211, 212 provided on the inner circumferential surface of the holder 118, and a magnet 210 which is positioned between the pair of magnetic pole pieces 211, 212 and holds the magnetic fluid 200 in the fluid storage portion 201 by the action of a magnetic field. With this configuration, the magnetic fluid 200 can be held in the fluid reservoir 201 by the action of the magnetic field. As a result, the gap between the outer surface of the sun gear 111 and the inner surface of the holder 118 is filled with the magnetic fluid 200. Therefore, the heat transfer path from the output shaft 105 to the holder 118 and the heat transfer path from the tooth surface of the sun gear 111 to the holder 118 can be maintained via the magnetic fluid 200. Thus, when heat generated by the motor 101 is transferred from the output shaft 105 to the sun gear 111, it can be dissipated to the outside via the portion where the magnetic fluid 200 is interposed. In addition, heat generated on the tooth surface of the sun gear 111 can be dissipated to the outside via the portion where the magnetic fluid 200 is interposed. Therefore, heat from the motor 101 and heat from the tooth surface of the sun gear 111 can be efficiently dissipated to the outside. For example, if a lubricant such as grease were to be interposed in the gap, the lubricant would be scattered by the rotation of the sun gear 111, making it difficult to maintain the heat transfer path from the output shaft 105 to the holder 118. In contrast, in this embodiment, even when the sun gear 111 rotates, the magnetic fluid 200 can be held in the fluid reservoir 201 by the action of the magnetic field. Furthermore, even when the magnetic fluid 200 becomes hot, it is held in the fluid reservoir 201 by the action of the magnetic field, thus maintaining the heat transfer path.

[0139] In this embodiment, the output shaft 105 protrudes axially outward from the axial end face 101f of the motor 101. The sun gear 111 is formed in a cylindrical shape coaxial with the output shaft 105. The magnetic pole pieces 211 and 212 are formed in an annular shape coaxial with the sun gear 111. The fluid containment section 201 includes gaps 201a and 201b between the outer circumferential surface of the sun gear 111 and the inner circumferential surfaces of the magnetic pole pieces 211 and 212 that can accommodate magnetic fluid 200. In this configuration, the gaps 201a and 201b are formed in an annular shape along the outer surface of the sun gear 111 and the inner surfaces of the magnetic pole pieces 211 and 212. Due to the action of the magnetic field, the magnetic fluid 200 is held in the annular gaps 201a and 201b. Therefore, the heat transfer path from the output shaft 105 to the holder 118 and the heat transfer path from the tooth surface of the sun gear 111 to the holder 118 can be maintained through the magnetic fluid 200 held in the annular gaps 201a and 201b. As a result, when heat generated by the motor 101 is transferred from the output shaft 105 to the sun gear 111, the heat can be dissipated to the outside through the portion where the magnetic fluid 200 is interposed in the annular gaps 201a and 201b and through the inner surfaces of the magnetic pole pieces 211 and 212. In addition, the heat generated on the tooth surface of the sun gear 111 can be dissipated to the outside through the portion where the magnetic fluid 200 is interposed in the annular gaps 201a and 201b, and through the inner circumferential surfaces of the magnetic pole pieces 211 and 212. Therefore, the heat from the motor 101 and the heat from the tooth surface of the sun gear 111 can be dissipated to the outside even more efficiently.

[0140] In this embodiment, the magnet 210 is formed in an annular shape coaxial with the sun gear 111. The fluid containment section 201 includes a space 201c between the outer circumferential surface of the sun gear 111 and the inner circumferential surface of the magnet 210 that can contain magnetic fluid 200. In this configuration, space 201c is formed in an annular shape along the outer surface of the sun gear 111 and the inner surface of the magnet 210. Due to the action of the magnetic field, the magnetic fluid 200 is held in the annular space 201c. Therefore, the heat transfer path from the output shaft 105 to the holder 118 and the heat transfer path from the tooth surface of the sun gear 111 to the holder 118 can be maintained through the magnetic fluid 200 held in the annular space 201c. As a result, when heat generated by the motor 101 is transferred from the output shaft 105 to the sun gear 111, the heat can be dissipated to the outside via the portion of the annular space 201c where the magnetic fluid 200 is interposed and the inner surface of the magnet 210. In addition, the heat generated on the tooth surface of the sun gear 111 can be dissipated to the outside via the portion of the annular space 201c where the magnetic fluid 200 is interposed and the inner surface of the magnet 210. Therefore, the heat from the motor 101 and the heat from the tooth surface of the sun gear 111 can be dissipated to the outside more efficiently.

[0141] In this embodiment, the holder 118 is formed in an annular shape coaxial with the sun gear 111 and has a support surface 119a extending radially from the sun gear 111. The pair of pole pieces 211, 212 consist of a first pole piece 211 positioned between the support surface 119a and the magnet 210, and a second pole piece 212 positioned adjacent to the side of the magnet 210 opposite to the first pole piece 211. In this configuration, the first gap 201a is formed in an annular shape along the outer surface of the sun gear 111 and the inner surface of the first pole piece 211. The second gap 201b is formed in an annular shape along the outer surface of the sun gear 111 and the inner surface of the second pole piece 212. Due to the action of the magnetic field, the magnetic fluid 200 is held in the annular first gap 201a and second gap 201b. Therefore, the heat transfer path from the output shaft 105 to the holder 118 and the heat transfer path from the tooth surface of the sun gear 111 to the holder 118 can be maintained via the magnetic fluid 200 held in the annular first gap 201a and second gap 201b. Therefore, when heat generated by the motor 101 is transferred from the output shaft 105 to the sun gear 111, it can be dissipated to the outside via the portion where the magnetic fluid 200 is interposed in the annular first gap 201a and second gap 201b, and via the inner circumferential surfaces of the first and second pole pieces 211 and 212. In addition, heat generated on the tooth surface of the sun gear 111 can be dissipated to the outside via the portion where the magnetic fluid 200 is interposed in the annular first gap 201a and second gap 201b, and via the inner circumferential surfaces of the first and second pole pieces 211 and 212. Thus, the heat from the motor 101 and the heat from the tooth surface of the sun gear 111 can be dissipated to the outside even more efficiently. For example, as shown in Figure 19, heat from the motor 101 may travel along the output shaft 105 in the direction of arrow H1 and then along the connecting cylindrical portion 111b of the sun gear 111 in the direction of arrow H2. In this case, the heat from the connecting cylindrical portion 111b of the sun gear 111 travels in the direction of arrow H3 via the portion where the magnetic fluid 200 is interposed in the annular first gap 201a and the inner circumferential surface of the first magnetic pole piece 211. The heat that has traveled in the direction of arrow H3 is directed to the outside via the holder 118 and the case 106. Therefore, heat from the motor 101 can be efficiently dissipated to the outside. For example, as shown in Figure 19, heat generated on the tooth surface of the sun gear 111 may travel along the connecting cylindrical portion 111b of the sun gear 111 in the direction of arrow H4. In this case, the heat from the connecting cylinder portion 111b of the sun gear 111 moves in the direction of arrow H5, through the portion where the magnetic fluid 200 is interposed in the annular second gap 201b and through the inner circumferential surface of the second magnetic pole piece 212. The heat that moves in the direction of arrow H5 is directed to the outside via the holder 118 and case 106. Therefore, the heat from the tooth surface of the sun gear 111 can be efficiently dissipated to the outside.

[0142] In this embodiment, the electric cylinder 100 is provided with a retaining ring 215 positioned adjacent to the side of the second pole piece 212 opposite to the magnet 210, and which prevents the second pole piece 212 from coming out axially outward from the motor 101. The holder 118 has a fitting groove 119b into which the retaining ring 215 can be fitted. With this configuration, the retaining ring 215 can be fitted into the fitting groove 119b of the holder 118, preventing the second magnetic pole piece 212 from coming out axially outward from the motor 101. In addition, compared to the case where the fitting groove 119b is provided on a separate component from the holder 118, the number of parts can be reduced and costs can be lowered.

[0143] In this embodiment, the holder 118 has an outer recess 118c that opens axially outward from the motor 101. The inner circumferential surface of the outer recess 118c is positioned axially outward from the motor 101 than the fluid reservoir 201, and radially outward from the sun gear 111 than the fluid reservoir 201. The electric cylinder 100 includes a capturing portion 216 that protrudes from the outer circumferential surface of the sun gear 111 toward the inner circumferential surface of the outer recess 118c. The capturing portion 216 is capable of capturing lubricant that is about to flow from the axial tip side of the sun gear 111 toward the fluid reservoir 201. With this configuration, the capture unit 216 can capture the lubricant that is trying to flow from the axial tip side of the sun gear 111 toward the fluid reservoir 201, thereby preventing the lubricant from entering the fluid reservoir 201. Therefore, mixing of the lubricant with the magnetic fluid 200 held in the fluid reservoir 201 can be prevented. In addition, when the sun gear 111 rotates, the lubricant flowing toward the capture unit 201 is carried by centrifugal force toward the inner surface of the outer recess 118c. Therefore, lubricant can be supplied to the inner surface of the outer recess 118c. For example, as shown in Figure 18, another portion of the lubricant that has come out from the axial tip of the sun gear 111 flows along the outer circumference of the sun gear 111 in the direction of arrow L5 and toward the capture unit 216. A portion of the lubricant flowing toward the capture unit 216 is carried by centrifugal force along the axial tip surface of the capture unit 216 in the direction of arrow L6 and toward the inner surface of the outer recess 118c. Subsequently, the lubricant flows along the inner surface of the outer recess 118c and enters the inner side (gap) of the ring gear 116. This allows the sun gear 111, planetary gear 112, and ring gear 116 to be lubricated.

[0144] In this embodiment, the shovel 1 comprises a vehicle body 2 and a work implement 3 connected to the vehicle body 2. The work implement 3 is equipped with the electric cylinder 100 described above. Therefore, it is possible to provide a shovel 1 that can efficiently dissipate heat from the motor 101 and the heat from the sun gear tooth surface to the outside.

[0145] In this embodiment, the work machine 3 is equipped with a common electric cylinder 100, which is designated as the first electric cylinder 100A, the second electric cylinder 100B, and the third electric cylinder 100C. Therefore, compared to a system with three different electric cylinders, designated as the first electric cylinder 100A, the second electric cylinder 100B, and the third electric cylinder 100C, the number of parts can be reduced and costs can be lowered.

[0146] <Other Embodiments> In the embodiments described above, the electric cylinder was explained using an example that includes a planetary gear mechanism for transmitting the driving force of the motor to the piston, but it is not limited to this. For example, the electric cylinder does not have to include a planetary gear mechanism. For example, the electric cylinder may include a power transmission mechanism other than a planetary gear mechanism, such as a belt pulley mechanism or a rack and pinion mechanism. For example, the configuration of the power transmission mechanism can be changed according to the required specifications.

[0147] In the embodiments described above, the electric cylinder was described as comprising a sun gear that rotates by the rotation of the output shaft, a planetary gear that rotates by the rotation of the sun gear, and a cylindrical holder having a fluid reservoir capable of accommodating magnetic fluid between it and the outer circumference of the sun gear, but it is not limited to this. For example, the electric cylinder may comprise a pulley that rotates by the rotation of the output shaft, a belt that rotates by the rotation of the pulley, and a cylindrical holder having a fluid reservoir capable of accommodating magnetic fluid between it and the outer circumference of the pulley. For example, the electric cylinder may comprise a pinion that rotates by the rotation of the output shaft, a belt that moves by the rotation of the pinion, a gear that rotates by the movement of the belt, and a cylindrical holder having a fluid reservoir capable of accommodating magnetic fluid between it and the outer circumference of the pinion. For example, an electric cylinder may include a motor as a drive source, an output shaft that rotates by the drive of the motor, a rotating body connected to the output shaft and rotating by the rotation of the output shaft, a cylindrical holder positioned adjacent to the axial end face of the motor and having a fluid reservoir capable of accommodating magnetic fluid between itself and the outer circumference of the rotating body, a pair of magnetic pole pieces provided on the inner circumferential surface of the holder, and a magnet positioned between the pair of magnetic pole pieces and holding the magnetic fluid in the fluid reservoir by the action of a magnetic field. For example, the configuration of the rotating body that rotates by the rotation of the output shaft can be changed according to the required specifications.

[0148] In the embodiments described above, the pole pieces were explained as being formed in an annular shape coaxial with the sun gear, but this is not limited to this. For example, the pole pieces do not have to be formed in an annular shape coaxial with the sun gear. For example, the pole pieces may be formed by arranging a plurality of small pole pieces in an annular shape. For example, the configuration of the pole pieces can be changed according to the required specifications.

[0149] In the embodiments described above, the magnet was explained as being formed in an annular shape coaxial with the sun gear, but this is not limited to this. For example, the magnet does not have to be formed in an annular shape coaxial with the sun gear. For example, the magnet may be formed by arranging a plurality of small magnets in an annular shape. For example, the configuration of the magnet can be changed according to the required specifications.

[0150] In the embodiments described above, the fluid reservoir was described as including a space capable of accommodating magnetic fluid between the outer surface of the sun gear and the inner surface of the magnet, but it is not limited to this. For example, the fluid reservoir does not need to include a space capable of accommodating magnetic fluid between the outer surface of the sun gear and the inner surface of the magnet. For example, the fluid reservoir only needs to include a gap capable of accommodating magnetic fluid between the outer surface of the sun gear and the inner surface of the magnetic pole piece. For example, the configuration of the fluid reservoir can be changed according to the required specifications.

[0151] In the embodiments described above, the inner surface of the magnet was described as being positioned radially outward from the inner surface of the pole piece relative to the sun gear, but this is not limited to this example. For example, the inner surface of the magnet does not have to be positioned radially outward from the inner surface of the pole piece relative to the sun gear. For example, the inner surface of the magnet may be positioned radially inward from the inner surface of the pole piece relative to the sun gear. For example, the inner surface of the magnet may be positioned at the same location as the inner surface of the pole piece relative to the sun gear in the radial direction. For example, the arrangement of the inner surface of the magnet can be changed according to the required specifications.

[0152] In the embodiments described above, the holder was described as being formed in an annular shape coaxial with the sun gear and having a support surface extending in the radial direction of the sun gear, but it is not limited to this. For example, the holder does not have to have a support surface. For example, the support surface may be provided on a member other than the holder. For example, the configuration of the holder can be changed according to the required specifications.

[0153] In the embodiment described above, the pair of pole pieces consist of a first pole piece positioned between the support surface and the magnet, and a second pole piece positioned adjacent to the side of the magnet opposite to the first pole piece. The magnet, the first pole piece, and the second pole piece constitute a fluid holding structure that holds magnetic fluid in the fluid holding section. The fluid holding structure was described in an example where only one is provided on the inner circumferential surface of the holding recess, but it is not limited to this. For example, multiple fluid holding structures may be provided on the inner circumferential surface of the holding recess of the holder. For example, two or more magnets and three or more pole pieces may be arranged alternately adjacent to each other. For example, the arrangement of the magnet, the first pole piece, and the second pole piece (the arrangement of the fluid holding structure) can be changed according to the required specifications.

[0154] In the embodiments described above, the electric cylinder was described as having a retaining ring positioned adjacent to the side of the second pole piece opposite to the magnet, and which prevents the second pole piece from coming out axially outward of the motor. However, it is not limited to this example. For example, the electric cylinder may not have a retaining ring. For example, the mounting method of the retaining ring can be changed according to the required specifications. For example, the outer circumference of the pole piece may be fixed to the inner circumferential surface of the housing recess of the holder by screwing it in. For example, the pole piece may be fixed by a plate and bolts. For example, the holding method of the pole piece and magnet can be changed according to the required specifications.

[0155] In the embodiments described above, the holder was described as having a fitting groove into which a retaining ring can be fitted, but it is not limited to this. For example, the holder does not have to have a fitting groove. For example, the fitting groove may be provided on a member other than the holder. For example, the manner in which the fitting groove is installed can be changed according to the required specifications.

[0156] In the embodiments described above, the electric cylinder was described as having a capture portion that protrudes from the outer circumferential surface of the sun gear toward the inner circumferential surface of the outer recess of the holder, in order to capture the lubricant that is flowing from the axial tip side of the sun gear toward the fluid reservoir, but it is not limited to this. For example, the electric cylinder does not have to have a capture portion. For example, the installation method of the capture portion can be changed according to the required specifications.

[0157] In the embodiments described above, the work machine was described using an example in which a common electric cylinder is provided as the first electric cylinder, second electric cylinder, and third electric cylinder, but it is not limited to this. For example, the work machine may be equipped with different electric cylinders as the first electric cylinder, second electric cylinder, and third electric cylinder. For example, the installation configuration of the electric cylinders can be changed according to the required specifications.

[0158] In the embodiments described above, a shovel was used as an example of a work machine (work vehicle), but the present invention is not limited to this. For example, the present invention may be applied to other work vehicles such as dump trucks, bulldozers, and wheel loaders.

[0159] Although embodiments of the present invention have been described above, the present invention is not limited thereto, and additions, omissions, substitutions, and other modifications to the configuration are possible without departing from the spirit of the invention, and the above embodiments can be combined as appropriate. [Explanation of symbols]

[0160] 1...Shovel (working machine), 2...Vehicle body, 3...Working equipment, 100...Electric cylinder, 100A...First electric cylinder (electric cylinder), 100B...Second electric cylinder (electric cylinder), 100C...Third electric cylinder (electric cylinder), 101...Motor, 101f...Axial end face of motor, 101A...First motor (motor), 101B...Second motor (motor), 101C...Third motor 105…Output shaft, 111…Sun gear, 118…Holder, 118c…Outer recess, 119a…Support surface, 119b…Matching groove, 200…Magnetic fluid, 201…Fluid containment section, 201a…First gap, 201b…Second gap, 201c…Space, 210…Magnet, 211…First magnetic pole piece, 212…Second magnetic pole piece, 215…Retaining ring, 216…Capture section

Claims

1. The motor is the driving source, The output shaft rotates by the drive of the aforementioned motor, A sun gear connected to the output shaft and rotating by the rotation of the output shaft, A cylindrical holder is positioned adjacent to the axial end face of the motor and has a fluid reservoir capable of accommodating magnetic fluid between itself and the outer circumference of the sun gear, A pair of magnetic pole pieces provided on the inner circumferential surface of the holder, The system includes a magnet positioned between the pair of magnetic pole pieces, which holds the magnetic fluid in the fluid reservoir through the action of a magnetic field. Electric cylinder.

2. The output shaft protrudes axially outward from the axial end face of the motor. The sun gear is formed in a cylindrical shape coaxial with the output shaft, The aforementioned pole piece is formed in an annular shape coaxial with the sun gear, The fluid containment portion includes a gap between the outer circumferential surface of the sun gear and the inner circumferential surface of the magnetic pole piece that can contain the magnetic fluid. The electric cylinder according to claim 1.

3. The magnet is formed in an annular shape coaxial with the sun gear, The fluid containment section further includes a space capable of containing the magnetic fluid between the outer circumferential surface of the sun gear and the inner circumferential surface of the magnet. The electric cylinder according to claim 2.

4. The inner circumferential surface of the magnet is positioned radially outward from the sun gear than the inner circumferential surface of the magnetic pole piece. The electric cylinder according to claim 3.

5. The holder is formed in an annular shape coaxial with the sun gear and has a support surface extending radially with respect to the sun gear. The pair of magnetic pole pieces are A first pole piece is disposed between the support surface and the magnet, The magnet has a second pole piece positioned adjacent to the side opposite to the first pole piece. An electric cylinder according to any one of claims 2 to 4.

6. The second pole piece is further provided with a retaining ring positioned adjacent to the side opposite to the magnet, and which prevents the second pole piece from coming out in the axial direction outward of the motor. The holder has a fitting groove into which the retaining ring can be fitted. The electric cylinder according to claim 5.

7. The holder has an outer recess that opens outward in the axial direction of the motor, The inner circumferential surface of the outer recess is positioned axially outward from the motor than the fluid storage portion, and radially outward from the sun gear than the fluid storage portion. The sun gear is further provided with a capturing portion that protrudes from the outer circumferential surface of the sun gear toward the inner circumferential surface of the outer recess, enabling it to capture lubricant attempting to flow from the axial tip of the sun gear toward the fluid reservoir. An electric cylinder according to any one of claims 1 to 6.

8. The vehicle body and The vehicle body is equipped with a work machine connected to it, The aforementioned work machine comprises an electric cylinder as described in any one of claims 1 to 7. A type of machinery used for industrial work.

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