Linear motion device, conversion mechanism, construction machine, and railway brake

Abstract

The purpose of the present invention is to mitigate shock transmitted to a linear motion mechanism that converts rotational motion into linear motion. This linear motion device is provided with: a drive unit that outputs rotation; a linear motion mechanism that converts the rotational motion input from the drive unit into linear motion; a cylinder that accommodates a fluid to which linear motion is input from the linear motion mechanism; and an output member to which the linear motion input from the linear motion mechanism is transmitted via the fluid.

Description

Technical Field

[0001] The present invention relates to a linear motion device, a conversion mechanism, a construction machine, and a railway brake. Background Art

[0002] Conventionally, a device that converts a rotational motion output from an electric mechanism into a linear motion has been known. For example, Patent Document 1 describes an electric linear actuator used to obtain a propulsive force for a linear drive portion in a construction device such as a power shovel. In particular, Patent Document 1 describes that the electric linear actuator drives a boom, an arm, a bucket, etc. of a power shovel.

[0003] The electric linear actuator described in Patent Document 1 includes: an electric mechanism having a rotating shaft; and a feed screw device having a feed screw shaft and a linear motion nut. The feed screw device is configured such that when the feed screw is rotated by the electric mechanism, the linear motion nut engaged with the feed screw performs a linear motion. The electric linear actuator described in Patent Document 1 converts a rotational motion into a linear motion through this feed screw device.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2013 / 114451 Summary of the Invention

[0007] For example, a mechanism that converts a rotational motion into a linear motion such as the feed screw device described in Patent Document 1 may transmit an impact from the side that outputs the linear motion. In particular, when this mechanism is used for driving a construction device, such as driving a boom, an arm, a bucket, etc. of a power shovel, a relatively large impact may be transmitted to the mechanism. It is conceivable that the mechanism may be damaged due to the transmission of a large impact to the mechanism that converts a rotational motion into a linear motion. Therefore, a technique for mitigating the impact transmitted to the mechanism that converts a rotational motion into a linear motion is sought.

[0008] The present invention has been made in view of such circumstances, and an object thereof is to mitigate the impact transmitted to a linear motion mechanism that converts a rotational motion into a linear motion.

[0009] A first aspect of the present invention is a linear motion device, wherein:

[0010] It has:

[0011] A drive portion that outputs rotation;

[0012] A linear motion mechanism that converts the rotational motion input from the drive portion into a linear motion;

[0013] A cylinder that houses a fluid into which linear motion is input from the linear motion mechanism; and

[0014] An output member, to which the linear motion input from the linear motion mechanism is transmitted via the fluid.

[0015] In a second aspect of the present invention, in the linear motion device of the first aspect, the drive unit may include: an electric mechanism; and a reduction unit that decelerates the rotation of the electric mechanism and transmits it to the linear motion mechanism.

[0016] In a third aspect of the present invention, in the linear motion device of the first aspect or the second aspect, the area of the surface of the linear motion mechanism that presses the fluid may be different from the area of the surface of the output member that is pressed by the fluid.

[0017] In a fourth aspect of the present invention, in the linear motion device of the third aspect, the area of the surface of the linear motion mechanism that presses the fluid may be larger than the area of the surface of the output member that is pressed by the fluid.

[0018] In a fifth aspect of the present invention, in each of the linear motion devices of the first aspect to the fourth aspect,

[0019] the cylinder may have a cylindrical shape,

[0020] the linear motion mechanism may have a surface that presses the fluid,

[0021] the output member may have a surface that is pressed by the fluid,

[0022] the fluid may be sealed in a space surrounded by the inner surface of the cylinder, the surface of the linear motion mechanism that presses the fluid, and the surface of the output member that is pressed by the fluid.

[0023] In a sixth aspect of the present invention, in the linear motion device of the fifth aspect, the linear motion device may further include a reservoir having: a first chamber that opens to the inner surface of the cylinder to communicate with the space; and a second chamber whose volume changes according to the pressure in the first chamber, thereby changing the volume of the first chamber.

[0024] In a seventh aspect of the present invention, in each of the linear motion devices of the first aspect to the sixth aspect, the linear motion device may further include:

[0025] a housing member that houses at least a rotating portion of the linear motion mechanism that rotates when receiving rotational motion from the drive unit; and

[0026] a bearing that contacts the rotating portion and the housing member to enable the rotating portion to rotate relative to the housing member.

[0027] In the eighth aspect of the present invention, in the linear motion device of the second aspect described above,

[0028] the deceleration section may include:

[0029] a first member having internal teeth;

[0030] a second member capable of rotating relative to the first member;

[0031] a crankshaft supported by the second member so as to be rotatable; and

[0032] an external gear provided with a through-hole through which the crankshaft passes and having external teeth meshing with the internal teeth of the first member;

[0033] the rotation of the second member may be input to the linear motion mechanism.

[0034] In the ninth aspect of the present invention, in each of the linear motion devices of the first aspect to the eighth aspect described above, the linear motion mechanism may include a ball screw having a screw shaft and a nut.

[0035] In the tenth aspect of the present invention, a conversion mechanism for converting a rotational motion into a linear motion, wherein

[0036] the conversion mechanism includes:

[0037] a linear motion mechanism for converting an input rotational motion into a linear motion;

[0038] a cylinder for accommodating a fluid into which a linear motion is input from the linear motion mechanism; and

[0039] an output member to which the linear motion input from the linear motion mechanism is transmitted via the fluid.

[0040] In the eleventh aspect of the present invention, a construction machine, wherein

[0041] it includes:

[0042] each of the linear motion devices of the first aspect to the ninth aspect described above; and

[0043] an acting portion directly driven by the linear motion device.

[0044] In the twelfth aspect of the present invention, a railway brake, which includes each of the linear motion devices of the first aspect to the ninth aspect described above.

[0045] According to the present invention, it is possible to mitigate the impact transmitted to the linear motion mechanism for converting a rotational motion into a linear motion. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a cross-sectional view showing a structural example of a linear motion device in one embodiment.

[0047] Figure 2 This is a cross-sectional view of a speed reduction unit in one embodiment.

[0048] Figure 3 This is a cross-sectional view of a speed reduction unit in one embodiment.

[0049] Figure 4 This is a cross-sectional view showing a structural example of the linear motion device in Modification 1.

[0050] Figure 5 This is a cross-sectional view showing a structural example of the linear motion device in Modification 2.

[0051] Figure 6 This is a cross-sectional view showing a structural example of the linear motion device in Modification 3.

[0052] Figure 7 This is a cross-sectional view showing a structural example of the linear motion device in Modification 4.

[0053] Figure 8 This is a cross-sectional view showing a structural example of the linear motion device in Modification 4. Detailed Description of the Embodiment

[0054] This embodiment will be described in detail with reference to the accompanying drawings. First, the linear motion device 1 of this embodiment will be described. Figure 1 This is a cross-sectional view showing a structural example of the linear motion device 1. In particular, Figure 1 This is a cross-sectional view of the linear motion device 1 cut along a plane passing through the axis of rotation LA of the rotation output by the drive unit 2 described later.

[0055] The linear motion device 1 includes a drive unit 2 that outputs rotation, a linear motion mechanism 5, a cylinder 6, and an output member 7. The linear motion mechanism 5 converts the rotational motion input from the drive unit 2 into linear motion. The cylinder 6 houses a fluid L that is input with linear motion from the linear motion mechanism 5. The linear motion input from the linear motion mechanism 5 is transmitted to the output member 7 via the fluid L. The direction in which the axis LA extends is referred to as the axis direction DA. The side on which the output member 7 is located with respect to the linear motion mechanism 5 in the axis direction DA is referred to as the first side SA1. In addition, the side on which the linear motion mechanism 5 is located with respect to the output member 7 in the axis direction DA is referred to as the second side SA2. In addition, the direction around the axis LA is referred to as the circumferential direction DB, and the direction perpendicular to the axis LA is referred to as the radial direction DC.

[0056] The drive unit 2 will be described in more detail. The drive unit 2 includes an electric mechanism 3 and a speed reduction unit 4 that decelerates the rotation of the electric mechanism 3 and transmits it to the linear motion mechanism 5.

[0057] In the present embodiment, the electric mechanism 3 is a general electric motor. In Figure 1 , the electric mechanism 3 is fixed to the mounting member 47 of the speed reduction unit 4 described later. Although not shown, the electric mechanism 3 is fixedly connected to the mounting member 47 by bolts, and thus is fixed to the surface of the second side SA2 of the mounting member 47. As Figure 1 shown, a through-hole 471 penetrating the mounting member 47 in the axial direction DA is provided in the mounting member 47. The rotating shaft 31 of the electric mechanism 3 is inserted into the through-hole 471. The rotating shaft 31 protrudes toward the first side SA1 and extends in the axial direction DA. In Figure 1 , the rotation axis of the rotating shaft 31 coincides with the rotation axis LA of the rotation output from the drive unit 2.

[0058] The speed reduction unit 4 will be described. The speed reduction unit 4 is disposed on the first side SA1 in the axial direction DA of the electric mechanism 3.

[0059] Figure 2 FIG. Figure 2 is a cross-sectional view of the speed reduction unit 4 taken along a plane passing through the axis LA. In addition, in Figure 3 , the illustration of the mounting member 47 is omitted. Figure 2 FIG.

[0060] is a cross-sectional view of the speed reduction unit 4 taken along the line III-III of

[0061] In the present embodiment, a through hole 44d through which the crankshaft 43 passes is provided in the external gear 44. That is, the reduction unit 4 of the present embodiment includes: a first member 41 having an internal tooth 412; a second member 42 that is relatively rotatable with respect to the first member 41; a crankshaft 43 that is supported by the second member 42 so as to be rotatable; and an external gear 44 having a through hole 44d through which the crankshaft 43 passes and having external teeth 441a, 442a that mesh with the internal tooth 412 of the first member 41. And, the rotation of the second member 42 is input to the linear motion mechanism 5. In this case, it can be said that the reduction unit 4 has the crankshaft 43 and the external gear 44 as the reduction mechanism 45.

[0062] In the present embodiment, the reduction mechanism 45 includes a plurality of crankshafts 43. The plurality of crankshafts 43 extend through the through holes 44d of the external gear 44. A plurality of through holes 44d are provided in the external gear 44, and each of the plurality of crankshafts 43 extends through each of the plurality of through holes 44d.

[0063] In the present embodiment, the reduction unit 4 has a cylindrical housing 41a as the first member 41. Further, the reduction unit 4 has a gear carrier 42a disposed inside the radial direction DC of the housing 41a (on the side closer to the axis LA in the radial direction DC) as the second member 42. Further, the reduction unit 4 has an input shaft 46 that imparts a driving force for rotating the gear carrier 42a. Further, the reduction unit 4 has a mounting member 47 provided with a through hole 471 and fixing the electric mechanism 3. The mounting member 47 has a cylindrical shape. Further, the reduction unit 4 has a third member 48 fixed to the first member 41 (housing 41a). The third member 48 has a cylindrical shape. The third member 48 is located on the first side SA1 in the axial direction DA of the housing 41a. In the axial direction DA, a part near the end on the outer side of the radial direction DC of the housing 41a (on the side away from the axis LA in the radial direction DC) is sandwiched between the third member 48 and the mounting member 47.

[0064] Near the end on the outer side of the radial DC of the housing 41a (the side away from the axis LA on the radial DC), a threaded hole 41b is provided which extends in the axial direction DA and opens on the second side SA2. By using the threaded hole 41b, the mounting member 47 is fastened to the housing 41a by a bolt, thereby fixing the mounting member 47 to the housing 41a. By fixing the mounting member 47 to the housing 41a and fixing the electric mechanism 3 to the mounting member 47, the electric mechanism 3 is fixed to the housing 41a via the mounting member 47. Further, near the end on the outer side of the radial DC of the housing 41a, a through hole 41c is provided which extends in the axial direction DA and penetrates the housing 41a. And a threaded hole 48a which extends in the axial direction DA and opens on the second side SA2 is provided in the third member 48. By using the threaded hole 48a and the through hole 41c, the mounting member 47 and the third member 48 can be fastened to the housing 41a by a bolt. Specifically, by fastening the bolt inserted into the through hole of the mounting member 47 (not shown) and the through hole 41c of the housing 41a to the threaded hole 48a of the third member 48, the mounting member 47 and the third member 48 can be fastened to the housing 41a. Figure 3 The mounting member 47 and the third member 48 can be fastened to the housing 41a by fastening the bolt inserted into the through hole of the mounting member 47 (not shown) and the through hole 41c of the housing 41a to the threaded hole 48a of the third member 48.

[0065] Internal teeth 412 are provided on the inner peripheral surface of the housing 41a. The internal teeth 412 are pin-shaped (cylindrical) teeth provided on the inner peripheral surface of the housing 41a. In particular, the first member 41 has an internal tooth pin 412a which is inserted into the pin slot 412b as the internal teeth 412. A plurality of internal teeth 412 are arranged at equal intervals in the radial DC.

[0066] The gear carrier 42a is supported by the housing 41a by a pair of main bearings 42j arranged at intervals in the axial direction DA so as to be rotatable freely. The main bearings 42j are, for example, angular contact ball bearings. The gear carrier 42a is arranged coaxially with the housing 41a and the axis LA.

[0067] The gear carrier 42a has: a disk-shaped end plate portion 421, arranged on the second side SA2 in the axial direction DA; a disk-shaped base plate portion 422, arranged on the first side SA1 in the axial direction DA; and three column portions 423, integrally formed with the base plate portion 422 and protruding from the base plate portion 422 toward the end plate portion 421. Figure 3 The shown column portion 423 has a columnar shape like a substantially triangle with rounded corners at the corners in a cross section perpendicular to the axial direction DA. The column portions 423 are arranged at equal intervals in the circumferential direction DB. In a state where the top surface of the column portion 423 coincides with the end plate portion 421, the column portion 423 and the end plate portion 421 are fastened and connected to each other by a bolt 42b and thus fixed. In this state, a space having a predetermined width in the axial direction is formed between the base plate portion 422 and the end plate portion 421.

[0068] The bolt fastening hole 42c of the fastening bolt 42b is formed in the column portion 423. In addition, a bolt insertion hole 42d for inserting the bolt 42b is formed in the end plate portion 421. The bolt 42b inserted into the bolt insertion hole 42d from the opposite side of the column portion 423 across the end plate portion 421 is fastened to the bolt fastening hole 42c of the column portion 423. At a position radially inward of the bolt 42b, a pin 42e for positioning the end plate portion 421 on the base plate portion 422 is provided. The pin 42e is arranged so as to straddle the column portion 423 and the end plate portion 421. In addition, the column portion 423 may not be integrally formed with the base plate portion 422. In this case, the column portion 423 is fastened and connected to the base plate portion 422. In addition, the column portion 423 is not limited to a columnar shape such as a substantially triangular shape with a rounded corner at the corner in a cross section perpendicular to the axis direction DA. As long as a space having a predetermined width in the axis direction DA can be formed between the base plate portion 422 and the end plate portion 421 by using the column portion 423, the column portion 423 may also be cylindrical.

[0069] A plurality of (for example, three in the present embodiment) hole portions 42f, 42g for inserting the crankshaft 43 of the reduction mechanism 45 are respectively formed in the end plate portion 421 and the base plate portion 422. The hole portions 42f, 42g are arranged at equal intervals in the circumferential direction. And, through holes 42h, 42i penetrating in the axis direction DA are formed at the centers of the end plate portion 421 and the base plate portion 422 in the radial direction DC. The input shaft 46 is arranged coaxially with the housing 41a and the axis LA.

[0070] The base end portion of the input shaft 46 on the side of the electric mechanism 3 (the second side SA2 in the axis direction DA) is coupled to the rotating shaft 31 of the electric mechanism 3. Thus, the input shaft 46 rotates integrally with the rotating shaft 31. The tip portion 46a of the input shaft 46 on the side opposite to the electric mechanism 3 (the first side SA1 in the axis direction DA) is disposed inside the mounting member 47. A drive gear 461 having external teeth is integrally provided at the tip portion 46a of the input shaft 46. In Figure 2 the example shown, the lead screw shaft 54 of the linear motion mechanism 5 described later is inserted into the through hole 42i of the base plate portion 422, the first through hole 44a of the first external gear 441 and the second external gear 442, and the through hole 42h of the end plate portion 421. And, in Figure 1 the example shown, the end portion of the lead screw shaft 54 on the second side SA2 in the axis direction DA is disposed inside the mounting member 47. Thus, in the present embodiment, the lead screw shaft 54 of the linear motion mechanism 5 can enter the through hole 42i of the base plate portion 422, the first through hole 44a of the first external gear 441 and the second external gear 442, the through hole 42h of the end plate portion 421, and the inside of the mounting member 47. Thereby, the width of the space in which the lead screw shaft 54 can linearly move can be ensured.

[0071] The speed reduction mechanism 45 rotates the gear holder 42a at a speed reduced from the rotational speed of the input shaft 46 at a prescribed ratio. The speed reduction mechanism 45 has a plurality (for example, three in the present embodiment) of transmission gears 431 that mesh with the drive gear 461 and a plurality (for example, three in the present embodiment) of crankshafts 43 with one end fixed to the transmission gear 431. Further, in the present embodiment, the speed reduction mechanism 45 has a first external gear 441 and a second external gear 442 that swing and rotate as the crankshaft 43 rotates, as the external gears 44.

[0072] Since the transmission gear 431 is fixed to one end of the crankshaft 43, the rotation of the rotary shaft 31 is transmitted to the crankshaft 43 via the transmission gear 431. The crankshaft 43 is arranged parallel to the input shaft 46. That is, the crankshaft 43 rotates about a rotation axis parallel to the rotation axis LA of the rotation output from the drive unit 2. The crankshaft 43 is supported by the end plate portion 421 via the first crankshaft bearing 43a so as to be rotatable freely. Further, the crankshaft 43 is supported by the substrate portion 422 via the second crankshaft bearing 43b so as to be rotatable freely. The first crankshaft bearing 43a and the second crankshaft bearing 43b are, for example, tapered roller bearings.

[0073] A first eccentric portion 43c and a second eccentric portion 43d that are eccentric from the axis of the crankshaft 43 are formed at the axial center of the crankshaft 43. The first eccentric portion 43c and the second eccentric portion 43d are arranged adjacent to each other in the axial direction DA between the first crankshaft bearing 43a and the second crankshaft bearing 43b. The first eccentric portion 43c is adjacent to the first crankshaft bearing 43a. The second eccentric portion 43d is adjacent to the second crankshaft bearing 43b. Further, the phase angles of the first eccentric portion 43c and the second eccentric portion 43d are offset from each other.

[0074] Such a crankshaft 43 is inserted into the respective hole portions 42f, 42g of the end plate portion 421 and the substrate portion 422. That is, the crankshaft 43 is also arranged at equal intervals in the circumferential direction DB like the respective hole portions 42f, 42g.

[0075] Further, a first roller bearing 43e is mounted on the first eccentric portion 43c of the crankshaft 43. A second roller bearing 43f is mounted on the second eccentric portion 43d. The first roller bearing 43e is, for example, a cylindrical roller bearing. Via the respective roller bearings 43e, 43f, the first external gear 441 and the second external gear 442 swing and rotate as the crankshaft 43 rotates.

[0076] The first external gear 441 and the second external gear 442 are arranged in the space between the base plate portion 422 and the end plate portion 421 of the gear carrier 42a. The first external gear 441 and the second external gear 442 have external teeth 441a, 442a that mesh with the internal teeth 412 of the housing 41a. A first through hole 44a centered on the axis LA, a second through hole 44b for inserting the column portion 423, and a through hole 44d for inserting the crankshaft 43 are formed in the first external gear 441 and the second external gear 442. The eccentric portions 43c, 43d of the crankshaft 43 are inserted into the through hole 44d.

[0077] The first eccentric portion 43c of the crankshaft 43 and the first roller bearing 43e are inserted into the through hole 44d of the first external gear 441. The second eccentric portion 43d of the crankshaft 43 and the second roller bearing 43f are inserted into the through hole 44d of the second external gear 442. Thus, the first eccentric portion 43c and the second eccentric portion 43d swing and rotate due to the rotation of the crankshaft 43. Consequently, the first external gear 441 and the second external gear 442 swing and rotate while meshing with the internal teeth 412 of the housing 41a.

[0078] The operation of the reduction unit 4 will be described. If the electric motor 3 is driven, the input shaft 46 is driven integrally with the rotating shaft 31. Then, due to the rotation of the input shaft 46, the transmission gear 431 rotates via the drive gear 461. Thus, the crankshaft 43 rotates integrally with the transmission gear 431.

[0079] If the crankshaft 43 rotates, the first external gear 441 rotates while meshing with the internal teeth 412 as the first eccentric portion 43c swings. In addition, the second external gear 442 rotates while meshing with the internal teeth 412 as the second eccentric portion 43d swings. That is, the crankshaft 43 rotates about a rotation axis parallel to the rotation axis LA of the rotation output from the drive unit 2, and revolves around the rotation axis LA. Thus, by the rotation of the crankshaft 43, the first external gear 441 and the second external gear 442 are driven.

[0080] If the first external gear 441 and the second external gear 442 are driven, the second member 42 (gear carrier 42a) into which the column portion 423 is inserted in the first external gear 441 and the second external gear 442 is driven by the first external gear 441 and the second external gear 442. Thus, relative to the housing 41a fixed to the electric motor 3 via the mounting member 47, the gear carrier 42a rotates at a speed reduced compared to the input shaft 46. Thus, the rotation of the electric motor 3 can be reduced by the reduction unit 4.

[0081] In addition, as the speed reduction unit 4, the speed reduction unit 4 in which the speed reduction mechanism 45 includes a crankshaft 43 and an external gear 44 is especially described, but the form of the speed reduction unit 4 is not limited thereto. The speed reduction mechanism 45 of the speed reduction unit 4 may also include a planetary gear rotatably supported by the second member 42. By meshing the planetary gear, which is input with rotation, with the internal teeth 412 of the first member 41, the first member 41 and the second member 42 rotate relative to each other. That is, the speed reduction unit 4 may also be a planetary gear speed reducer.

[0082] The linear motion mechanism 5 will be described. The linear motion mechanism 5 converts the rotational motion input from the drive unit 2 into a linear motion. The linear motion mechanism 5 is disposed on the first side SA1 in the axial direction DA of the speed reduction unit 4. The linear motion mechanism 5 includes: a rotation unit 51 that rotates by receiving the rotational motion input from the drive unit 2; and a linear motion unit 52 that is driven to linearly move by the rotational motion of the rotation unit 51. The rotation unit 51 is fixed to the rotating part of the drive unit 2 and rotates as the rotating part rotates. The linear motion unit 52 is restricted from rotating in the circumferential direction DB with respect to the cylinder 6. In the present embodiment, the rotation unit 51 is fixed to the second member 42 (the gear carrier 42a) of the speed reduction unit 4. In particular, the rotation unit 51 is fixed to the second member 42 via a third member 48. Thus, the rotation of the second member 42 (the gear carrier 42a) that rotates at a speed reduced compared to the input shaft 46 is input to the rotation unit 51.

[0083] In the present embodiment, the linear motion mechanism 5 includes a ball screw 53 having a screw shaft 54 and a nut 55. Further, the nut 55 of the ball screw 53 is fixed to the second member 42. The nut 55 is fixed to the end portion on the first side SA1 in the axial direction DA of the second member 42. In the present embodiment, the nut 55 forms the rotation unit 51 that rotates by receiving the rotational motion input from the drive unit 2. Additionally, in the present embodiment, the screw shaft 54 forms the linear motion unit 52 that is driven to linearly move by the rotational motion of the rotation unit 51.

[0084] The nut 55 is a member provided with a through hole 55b formed with an internal thread 55a. The internal thread 55a is provided on the inner wall of the through hole 55b. In the present embodiment, the through hole 55b extends in the axial direction DA. The through hole 55b is arranged such that the axis LA is located at the center of the through hole 55b.

[0085] The screw shaft 54 is a rod-shaped member formed with an external thread 54a. In the present embodiment, the external thread 54a extends in the axial direction DA. The screw shaft 54 and the axis LA are arranged coaxially.

[0086] The external thread 54a of the lead screw shaft 54 meshes with the internal thread 55a of the nut 55. Therefore, if one of the lead screw shaft 54 and the nut 55 is rotated circumferentially in the DB direction relative to the other, the positional relationship in the DA direction of the axes of the lead screw shaft 54 and the nut 55 changes.

[0087] In the present embodiment, if the nut 55 is rotated by inputting a rotational motion from the drive unit 2, the lead screw shaft 54 is driven by the rotational motion of the nut 55 to perform a linear motion. Thus, as the linear motion mechanism 5, by using the ball screw 53 having the lead screw shaft 54 and the nut 55, a rotational motion can be converted into a linear motion. When the linear motion mechanism 5 has the ball screw 53, the linear motion unit 52 linearly moves in the direction in which the through hole 55b and the lead screw shaft 54 extend. In the present embodiment, the linear motion unit 52 linearly moves in the DA direction of the axis.

[0088] The linear motion mechanism 5 has a surface 56 that presses the fluid L accommodated in the cylinder 6 described later. The surface 56 that presses the fluid L of the linear motion mechanism 5 is also referred to as the pressing surface 56. The pressing surface 56 is the surface that presses the fluid L when a linear motion is input to the fluid L. In the present embodiment, the linear motion unit 52 of the linear motion mechanism 5 has the pressing surface 56. In the present embodiment, the pressing surface 56 is a surface perpendicular to the direction (DA direction of the axis) in which the linear motion unit 52 linearly moves. In the present embodiment, the lead screw shaft 54 of the linear motion unit 52 has a lead screw shaft main body 54b formed with an external thread 54a and a pressing portion 54c provided at the end on the first side SA1 in the DA direction of the axis of the lead screw shaft main body 54b. In the radial direction DC, the pressing portion 54c has a larger size than the lead screw shaft main body 54b. In the present embodiment, the surface on the first side SA1 in the DA direction of the pressing portion 54c forms the pressing surface 56.

[0089] The cylinder 6 will be described. The cylinder 6 is a member that accommodates the fluid L to which a linear motion is input from the linear motion mechanism 5. In the present embodiment, the cylinder 6 has a cylindrical shape. The cylinder 6 is disposed on the first side SA1 in the DA direction of the axis of the linear motion mechanism 5.

[0090] The cylinder 6 houses the portion of the linear motion mechanism 5 that has the pressing surface 56. In the present embodiment, the cylinder 6 houses the pressing portion 54c of the lead screw shaft 54. In the present embodiment, a part of the linear motion portion 52 enters the interior of the cylinder 6 through the opening on the first side SA1 in the axial direction DA of the cylindrical cylinder 6. Thus, the cylinder 6 houses the portion of the linear motion mechanism 5 that has the pressing surface 56. Further, the cylinder 6 extends in the direction of the linear motion output by the linear motion mechanism 5 in the portion where it houses the portion of the linear motion mechanism 5 that has the pressing surface 56. In the present embodiment, in a cross-section perpendicular to the direction of linear motion (axial direction DA) of the linear motion portion 52, the cylinder 6 has a portion in which a hollow portion having the same shape as the pressing surface 56 is formed. Such a portion is referred to as the first portion 61 of the cylinder 6. The first portion 61 is continuous in the direction of linear motion of the linear motion portion 52. Thus, the linear motion portion 52 of the linear motion mechanism 5 can perform linear motion within a range where the portion having the pressing surface 56 does not protrude outside the first portion 61. In the present embodiment, the entire cylinder 6 extends in the axial direction DA. The cylinder 6 and the axis LA are arranged coaxially.

[0091] The cylinder 6 houses the fluid L. The fluid L is housed in the cylinder 6 so as to span the first portion 61 of the cylinder 6 and a second portion 62 of the cylinder 6 described later.

[0092] There are no particular limitations on the material of the fluid L as long as it can transmit the linear motion input from the linear motion mechanism 5 to the output member 7 described later. The fluid L can be a liquid or a gas. From the viewpoint of effectively transmitting the linear motion input from the linear motion mechanism 5 to the output member 7, and from the viewpoint of mitigating the impact transmitted to the linear motion mechanism 5 through the fluid L as described later, it is preferable that the fluid L is a material with high viscosity. For example, since oil generally has higher viscosity than water, oil is preferably used as the material of the fluid L compared to water. In the case where a gas is used as the fluid L, as the fluid L, for example, a gas compressed under high pressure can be used.

[0093] The output member 7 will be described. The output member 7 is a member to which the linear motion input from the linear motion mechanism 5 is transmitted via the fluid L. In the present embodiment, the output member 7 is arranged on the first side SA1 in the axial direction DA of the cylinder 6. In the present embodiment, the output member 7 is a rod-shaped member. The output member 7 extends in the axial direction DA. The output member 7 and the axis LA are arranged coaxially.

[0094] The output member 7 has a surface 71 that is pushed by the fluid L. The surface 71 of the output member 7 that is pushed by the fluid L is also referred to as the pushed surface 71. The pushed surface 71 is the surface that is pushed by the fluid L when the linear motion is transmitted to the output member 7 via the fluid L. In the present embodiment, the surface on the second side SA2 in the axial direction DA of the output member 7 forms the pushed surface 71.

[0095] Here, the cylinder 6 houses the portion of the output member 7 having the pressed surface 71. In the present embodiment, a part of the output member 7 enters the inside of the cylinder 6 through the opening on the second side SA2 in the axial direction DA of the cylindrical cylinder 6. Thus, the cylinder 6 houses the portion of the output member 7 having the pressed surface 71.

[0096] In the present embodiment, in a cross-section perpendicular to the extending direction (axial direction DA) of the portion of the output member 7 housed in the cylinder 6, the cylinder 6 has a portion where a hollow portion having the same shape as the pressed surface 71 is formed. Such a portion is referred to as the second portion 62 of the cylinder 6. The second portion 62 is continuous in the extending direction of the portion of the output member 7 housed in the cylinder 6. Thus, the output member 7 can linearly move in the extending direction of the portion of the output member 7 housed in the cylinder 6 within the range where the portion of the output member 7 having the pressed surface 71 does not protrude outside the second portion 62. In the present embodiment, the linear motion portion 52 of the linear motion mechanism 5 and the output member 7 linearly move on the same line. In particular, the linear motion portion 52 of the linear motion mechanism 5 and the output member 7 linearly move on the axis LA.

[0097] The output member 7 of the present embodiment further has a mounting portion 72 to which an acting portion driven by the linear motion device 1 is mounted. The mounting portion 72 is provided at the end of the output member 7 on the side opposite to the side having the pressed surface 71 (the first side SA1 in the axial direction DA). The shape of the mounting portion 72 is not particularly limited as long as it can mount the acting portion driven by the linear motion device 1. In the present embodiment, the mounting portion 72 is a rod end that can be coupled to other members. In this case, the mounting portion 72 as the rod end may also have an annular shape.

[0098] In the present embodiment, as described above, the cylinder 6 has a cylindrical shape. In addition, the linear motion mechanism 5 has a surface 56 (pushing surface 56) that pushes the fluid L when a linear motion is input to the fluid L. In addition, the output member 7 has a surface 71 (pressed surface 71) that is pushed by the fluid L when the linear motion is transmitted through the fluid L. And, the fluid L is sealed in the space 65 surrounded by the inner surface of the cylinder 6, the surface 56 of the linear motion mechanism 5 that pushes the fluid L, and the surface 71 of the output member 7 that is pushed by the fluid L.

[0099] Here, the cylinder 6 having a cylindrical shape may have a cylindrical shape or a square cylindrical shape. When the cylinder 6 has a square cylindrical shape, the shape of the hollow portion in the cross section perpendicular to the extending direction of the cylinder 6 may be triangular, quadrilateral, or other polygons. When the cylinder 6 has a square cylindrical shape at least in the first portion 61, the following effects can be obtained. By setting the shape of the pressing surface 56 to be the same as the shape of the hollow portion of the first portion 61 in the cross section perpendicular to the extending direction of the cylinder 6, the linear motion portion 52 having the pressing surface 56 can be inhibited from rotating in the circumferential direction DB with respect to the cylinder 6. In addition, when the cylinder 6 has a square cylindrical shape at least in the second portion 62, the following effects can be obtained. By setting the shape of the pressed surface 71 to be the same as the shape of the hollow portion of the second portion 62 in the cross section perpendicular to the extending direction of the cylinder 6, the output member 7 having the pressed surface 71 can be inhibited from rotating in the circumferential direction DB with respect to the cylinder 6.

[0100] In the present embodiment, the area of the pressing surface 56 is different from the area of the pressed surface 71. In particular, the area of the pressing surface 56 is larger than the area of the pressed surface 71. In addition, in the present embodiment, the cross-sectional area of the hollow portion of the cylinder 6 in the first portion 61 in the cross section perpendicular to the direction (axial direction DA) in which the linear motion portion 52 moves linearly is different from the cross-sectional area of the hollow portion of the cylinder 6 in the second portion 62 in the direction (axial direction DA) in which the output member 7 moves linearly. The cross-sectional area of the hollow portion of the cylinder 6 in the first portion 61 is larger than the cross-sectional area of the hollow portion of the cylinder 6 in the second portion 62.

[0101] The linear motion device 1 of the present embodiment further includes a housing member 81 that at least houses the rotating portion 51 of the linear motion mechanism 5 that rotates by receiving a rotational motion from the driving portion 2. In addition, the linear motion device 1 of the present embodiment further includes a bearing 82 that contacts the rotating portion 51 and the housing member 81 so that the rotating portion 51 can rotate with respect to the housing member 81.

[0102] In the present embodiment, the housing member 81 houses at least a part of the rotating portion 51. The housing member 81 covers the rotating portion 51 of the linear motion mechanism 5 from the radial direction DC. In the present embodiment, a third member 48 is fixed to the first member 41 (housing 41a) of the reduction portion 4. The third member 48 extends toward the first side SA1 in the axial direction DA. And, a nut 55 that is the rotating portion 51 of the linear motion mechanism 5 is housed in the extended portion of the third member 48. In this case, it can be said that a part of the third member 48 forms the housing member 81.

[0103] In addition, the cylinder 6 extends toward the second side SA2 in the axial direction DA, so that the cylinder 6 can also accommodate the rotating portion 51. In this case, it can be said that a part of the cylinder 6 forms the accommodating member 81. Additionally, the accommodating member 81 can be a member different from both the members included in the speed reduction unit 4 and the cylinder 6.

[0104] In the present embodiment, the bearing 82 contacts the rotating portion 51 and the portion of the third member 48 that forms the accommodating member 81, so that the rotating portion 51 can rotate relative to the portion of the third member 48 that forms the accommodating member 81. As long as it can contact the rotating portion 51 and the accommodating member 81 so that the rotating portion 51 can rotate relative to the accommodating member 81, the type of the bearing 82 is not particularly limited.

[0105] In addition, in the case where a part of the cylinder 6 forms the accommodating member 81, the bearing 82 contacts the rotating portion 51 and the portion of the cylinder 6 that forms the accommodating member 81, so that the rotating portion 51 can rotate relative to the portion of the cylinder 6 that forms the accommodating member 81.

[0106] In the present embodiment, the end portion of the second side SA2 in the axial direction DA of the cylinder 6 is connected to the end portion of the first side SA1 in the axial direction DA of the third member 48 of the speed reduction unit 4. Additionally, the end portion of the second side SA2 in the axial direction DA of the first member 41 of the speed reduction unit 4 is connected to the end portion of the first side SA1 in the axial direction DA of the mounting member 47 of the speed reduction unit 4. Thus, the portion of the output member 7 having the pressed surface 71, the linear motion mechanism 5, the second member 42 (gear rack 42a) of the speed reduction unit 4, and the speed reduction mechanism 45 are accommodated in the space defined by the cylinder 6, the first member 41 of the speed reduction unit 4, the mounting member 47, and the third member 48. Thereby, it is possible to protect the portion of the output member 7 having the pressed surface 71, the linear motion mechanism 5, the second member 42 (gear rack 42a) of the speed reduction unit 4, and the speed reduction mechanism 45 from the influence of external dust and the like.

[0107] In addition, the linear motion device 1 of the present embodiment further includes a first sealing member 85 that seals between the portion of the output member 7 on the side closer to the mounting portion 72 than the pressed surface 71 and the cylinder 6. Thereby, it is possible to more stably protect the pressed surface 71 and the like of the output member 7. In addition, the linear motion device 1 of the present embodiment further includes a second sealing member 86 that seals between the portion of the linear motion portion 52 on the side closer to the driving portion 2 than the pressing surface 56 and the cylinder 6. Thereby, it is possible to suppress the mixing of the fluid L with the lubricating oil and the like used in the linear motion mechanism 5 or the speed reduction unit 4.

[0108] The linear motion device 1 of the present embodiment further includes a reservoir 83. The reservoir 83 has: a first chamber 831 that opens on the inner surface of the cylinder 6 to communicate with the space 65; a second chamber 832 whose volume changes according to the pressure in the first chamber 831, thereby changing the volume of the first chamber 831. In the present embodiment, the reservoir 83 has the shape of a container that opens on the inner surface of the cylinder 6 to communicate with the space 65. The first chamber 831 and the second chamber 832 are formed inside the reservoir 83. The first chamber 831 communicates with the space 65 via an opening. Thus, the fluid L enters the first chamber 831. The second chamber 832 is separated from the first chamber 831 by a diaphragm 833. The diaphragm 833 deforms according to the pressure difference between the first chamber 831 and the second chamber 832. A gas such as nitrogen is filled in the second chamber 832.

[0109] In a state where the pressures in the space 65 and the first chamber 831 are higher than the pressure in the second chamber 832, the diaphragm 833 deforms due to the pressure difference between the first chamber 831 and the second chamber 832, and the volume of the second chamber 832 becomes smaller. The volume of the first chamber 831 becomes larger because the volume of the second chamber 832 becomes smaller. In addition, in a state where the pressures in the space 65 and the first chamber 831 are lower than the pressure in the second chamber 832, the diaphragm 833 deforms due to the pressure difference between the first chamber 831 and the second chamber 832, and the volume of the second chamber 832 becomes larger. The volume of the first chamber 831 becomes smaller because the volume of the second chamber 832 becomes larger. In this way, the volume of the second chamber 832 changes according to the pressure in the first chamber 831, thereby changing the volume of the first chamber 831. As described above, when the pressure in the space 65 is high, the reservoir 83 expands the volume of the first chamber 831 into which the fluid L can enter, and when the pressure in the space 65 is low, the reservoir 83 reduces the volume of the first chamber 831 into which the fluid L can enter.

[0110] Next, the operation of the linear motion device 1 of the present embodiment will be described. First, the operation of the linear motion device 1 when driving the acting portion will be described. The acting portion is, for example, a construction machine such as a power shovel, a railway brake, or the like. When using the linear motion device 1 to drive the acting portion, the acting portion is attached to the attachment portion 72 of the output member 7. Then, rotation is output from the drive portion 2. When the drive portion 2 includes the electric mechanism 3 and the reduction portion 4, the drive portion 2 outputs the rotation output from the electric mechanism 3 and reduced by the reduction portion 4. Thus, the rotational motion is input from the drive portion 2 to the linear motion mechanism 5. Next, the linear motion mechanism 5 converts the rotational motion input from the drive portion 2 into a linear motion. In the present embodiment, due to the rotational motion of the rotating portion 51 that rotates by inputting the rotational motion from the drive portion 2, the linear motion portion 52 is driven to perform a linear motion, and thus, the rotational motion is converted into a linear motion. As a result, inside the cylinder 6, particularly inside the first portion 61 of the cylinder 6, the portion of the linear motion portion 52 having the pressing surface 56 performs a linear motion. Therefore, the fluid L accommodated inside the cylinder 6 is pressed by the pressing surface 56. In the present embodiment, the fluid L is pressed by the pressing surface 56 toward the first side SA1 in the axial direction DA. The fluid L pressed by the pressing surface 56 presses the portion of the output member 7 having the pressed surface 71. In the present embodiment, the fluid L presses the portion of the output member 7 having the pressed surface 71 toward the first side SA1 in the axial direction DA. As a result, the output member 7 is pressed by the fluid L and linearly moves along the extending direction of the portion of the output member 7 accommodated in the cylinder 6. Thus, the acting portion attached to the attachment portion 72 of the output member 7 can linearly move together with the output member 7.

[0111] Next, the operation of cushioning the impact transmitted to the linear motion mechanism 5 when the linear motion device 1 receives an impact from the side that outputs the linear motion will be described. In particular, the operation of cushioning the impact transmitted to the linear motion mechanism 5 when the linear motion device 1 receives an impact from the acting portion attached to the attachment portion 72 of the output member 7 will be described. When the linear motion device 1 receives an impact from the acting portion attached to the attachment portion 72 of the output member 7, the output member 7 can be pressed into the side where the linear motion mechanism 5 is located (the second side SA2 in the axial direction DA). In this case, it is considered that the output member 7 moves toward the second side SA2 in the axial direction DA and presses the fluid L.

[0112] Here, the linear motion device 1 of the present embodiment includes: a linear motion mechanism 5 that converts the rotational motion input from the drive unit 2 into linear motion; a cylinder 6 that houses the fluid L to which the linear motion is input from the linear motion mechanism 5; and an output member 7 to which the linear motion input from the linear motion mechanism 5 is transmitted via the fluid L. Thus, the fluid L is located between the output member 7 and the linear motion mechanism 5. By having the fluid L located between the output member 7 and the linear motion mechanism 5, it is possible to use the fluid L to mitigate the impact transmitted from the output member 7 to the linear motion mechanism 5. In particular, when a temporary strong impact is applied to the acting portion mounted on the output member 7, it is possible to use the fluid L to mitigate the impact transmitted from the output member 7 to the linear motion mechanism 5. In this way, according to the linear motion device 1 of the present embodiment, it is possible to mitigate the impact transmitted to the linear motion mechanism 5.

[0113] In addition, in the present embodiment, the drive unit 2 is located on the side opposite to the side where the output member 7 and the cylinder 6 are located with respect to the linear motion mechanism 5. Here, according to the linear motion device 1 of the present embodiment, by using the fluid L to mitigate the impact transmitted from the output member 7 to the linear motion mechanism 5, it is possible to suppress the transmission of a strong impact from the output member 7 to the drive unit 2.

[0114] In the present embodiment, the drive unit 2 includes: an electric mechanism 3; and a reduction unit 4 that decelerates the rotation of the electric mechanism 3 and transmits it to the linear motion mechanism 5. Since the drive unit 2 has both the electric mechanism 3 and the reduction unit 4, the following effects can be obtained. Assuming that the drive unit 2 does not have the reduction unit 4, in order to make the drive unit 2 output a large torque, it is necessary to increase the size of the electric mechanism 3. In contrast, by having the reduction unit 4 in the drive unit 2, it is possible to reduce the size of the electric mechanism 3 used and make the drive unit 2 output a large torque. In addition, according to the linear motion device 1 of the present embodiment, when the drive unit 2 has the electric mechanism 3 and the reduction unit 4, the fluid L is used to mitigate the impact transmitted from the output member 7 to the linear motion mechanism 5, so that it is possible to suppress the transmission of a strong impact from the output member 7 to the electric mechanism 3 and the reduction unit 4. Thus, it is possible to stably protect the reduction unit 4 from impact.

[0115] In addition, in the present embodiment, as described above, the reduction unit 4 includes: a first member 41 having internal teeth 412; a second member 42 that can rotate relative to the first member 41; a crankshaft 43 that is supported by the second member 42 so as to be rotatable; and an external gear 44 that is provided with a through hole 44d through which the crankshaft 43 passes and has external teeth 441a, 442a that mesh with the internal teeth 412 of the first member 41. According to the linear motion device 1 of the present embodiment, even when such a reduction unit 4 is used as the reduction unit 4, it is possible to stably protect the reduction unit 4 from impact.

[0116] In addition, in the present embodiment, the fluid L is sealed in a space 65 surrounded by the inner surface of the cylinder 6, the surface 56 of the linear motion mechanism 5 that presses the fluid L, and the surface 71 of the output member 7 that is pressed by the fluid L. Thus, when the linear motion device 1 is used to drive the acting portion, the force with which the pressing surface 56 presses the fluid L can be effectively transmitted to the output member 7 via the fluid L.

[0117] In addition, in the present embodiment, the area of the surface 56 (pressing surface 56) of the linear motion mechanism 5 that presses the fluid L is different from the area of the surface 71 (pressed surface 71) of the output member 7 that is pressed by the fluid L. Further, in the present embodiment, the cross-sectional area of the hollow portion of the cylinder 6 in the first portion 61 in a cross-section perpendicular to the direction (axial direction DA) in which the linear motion portion 52 performs linear motion is different from the cross-sectional area of the hollow portion of the cylinder 6 in the second portion 62 in the direction (axial direction DA) in which the output member 7 performs linear motion. Thus, according to Pascal's principle, the ratio of the distance by which the pressed surface 71 moves to the distance by which the pressing surface 56 moves can be adjusted. For example, when the area of the pressing surface 56 is larger than the area of the pressed surface 71, the ratio of the distance by which the pressed surface 71 moves to the distance by which the pressing surface 56 moves can be made greater than 1. In addition, the area of the surface 56 (pressing surface 56) of the linear motion mechanism 5 that presses the fluid L may be smaller than the area of the surface 71 (pressed surface 71) of the output member 7 that is pressed by the fluid L. When the area of the pressing surface 56 is smaller than the area of the pressed surface 71, the ratio of the distance by which the pressed surface 71 moves to the distance by which the pressing surface 56 moves can be made less than 1. Similarly, the ratio of the speed by which the pressed surface 71 moves to the speed by which the pressing surface 56 moves can be adjusted.

[0118] The effects brought about by the difference between the area of the pressing surface 56 and the area of the pressed surface 71 in the present embodiment will be further described. As a comparison object, a linear motion device 1 in which the area of the pressing surface 56 is equal to the area of the pressed surface 71 is considered. In this case, it is necessary to move the linear motion portion 52 at a speed equal to the desired linear motion output by the linear motion device 1 over a moving distance equal to the desired linear motion output by the linear motion device 1. For example, when the linear motion mechanism 5 has a ball screw 53, it is necessary to adjust the pitch interval of the thread teeth of the external thread 54a of the screw shaft 54 and the internal thread 55a of the nut 55, and the length of the screw shaft 54 in the direction in which the linear motion portion 52 performs linear motion so that the linear motion portion 52 can move at a desired speed over a desired moving distance. In contrast, in the linear motion device 1 according to the present embodiment, since the area of the pressing surface 56 is different from the area of the pressed surface 71, the speed and the moving distance of the linear motion output from the linear motion mechanism 5 can be converted by the action of the fluid L accommodated in the cylinder 6 and transmitted to the output member 7. Thus, the degree of freedom in selecting the linear motion mechanism 5 used in the linear motion device 1 can be increased.

[0119] In the present embodiment, the area of the surface 56 (pushing surface 56) of the linear motion mechanism 5 that pushes the fluid L is larger than the area of the surface 71 (pushed surface 71) of the output member 7 that is pushed by the fluid L. Further, in the present embodiment, the sectional area of the hollow portion of the cylinder 6 in the first portion 61 in a cross-section perpendicular to the direction (axial direction DA) in which the linear motion portion 52 performs linear motion is larger than the sectional area of the hollow portion of the cylinder 6 in the second portion 62 in the direction (axial direction DA) in which the output member 7 performs linear motion. Thus, according to Pascal's principle, the ratio of the distance by which the pushed surface 71 moves with respect to the distance by which the pushing surface 56 moves can be made greater than 1. Therefore, by causing the linear motion portion 52 of the linear motion mechanism 5 to perform linear motion at a speed lower than the speed of the linear motion required by the output member 7 and by a distance smaller than the distance of the linear motion required by the output member 7, the output member 7 can be caused to perform the desired linear motion. Thus, for example, even when the speed and the moving distance of the linear motion required by the output member 7 are relatively large, the speed and the moving distance of the linear motion required by the linear motion portion 52 can be reduced. In summary, the output member 7 can be caused to perform the desired linear motion, and the linear motion mechanism 5 can be miniaturized.

[0120] In the present embodiment, the drive unit 2 has a reduction unit 4. Further, the area of the pushing surface 56 is larger than the area of the pushed surface 71. Therefore, the rotational motion output from the electric mechanism 3 of the drive unit 2 is first decelerated in the reduction unit 4, then converted into linear motion in the linear motion mechanism 5, and then accelerated by the action of the fluid L accommodated in the cylinder 6 and transmitted to the output member 7. According to such a linear motion device 1, as described above, the electric mechanism 3 and the linear motion mechanism 5 can be miniaturized, and the output member 7 can be caused to perform linear motion of moving a large distance at a high speed. Further, when causing the output member 7 to perform linear motion of a desired specific speed for a desired specific moving distance, the electric power input to the electric mechanism 3 for this linear motion can be suppressed to be small.

[0121] The linear motion device 1 of the present embodiment further includes: a housing member 81 that houses at least the rotating portion 51 of the linear motion mechanism 5; and a bearing 82 that contacts the rotating portion 51 and the housing member 81 so that the rotating portion 51 can rotate relative to the housing member 81. Thus, the rotating portion 51 can be rotated, and the rotating portion 51 can be supported by the housing member 81 via the bearing 82. Further, when an impact is transmitted from the output member 7 to the linear motion mechanism 5, the impact can be released to the housing member 81 via the bearing 82. Thus, the tolerance of the linear motion mechanism 5 to impacts can be improved. For example, deformation of members such as the rotating portion 51 and the linear motion portion 52 included in the linear motion mechanism 5 due to impacts can be suppressed.

[0122] The linear motion device 1 of the present embodiment further includes a reservoir 83 having: a first chamber 831 that opens to the inner surface of the cylinder 6 to communicate with the space 65; and a second chamber 832 whose volume changes according to the pressure in the first chamber 831, thereby changing the volume of the first chamber 831. When the pressure in the space 65 is high, the reservoir 83 expands the volume of the first chamber 831 into which the fluid L can enter. When the pressure in the space 65 is low, the reservoir 83 reduces the volume of the first chamber 831 into which the fluid L can enter. Therefore, the reservoir 83 can suppress a sharp rise or fall in the pressure in the space 65. In particular, in a situation where an impact is applied to the output member 7 and the output member 7 is pressed into the interior of the cylinder 6, etc., a sharp rise in the pressure in the space 65 can be suppressed.

[0123] In addition, the linear motion device 1 of the present embodiment may further include: a force sensor that measures the force applied to the linear motion portion 52 of the linear motion mechanism 5 and the output member 7; and a position sensor that measures the displacement of the linear motion portion 52 of the linear motion mechanism 5 and the output member 7. Since the linear motion device 1 is provided with a force sensor and a position sensor, it can detect an impact applied from the outside to the linear motion portion 52 and the output member 7. Therefore, at the moment when it is detected that an impact has been applied from the outside to the linear motion portion 52 and the output member 7, by outputting a rotational motion from the drive unit 2 to the linear motion mechanism 5, a force that repels the impact can be generated to protect the linear motion mechanism 5 and the drive unit 2.

[0124] In addition, the portion of the linear motion device 1 of the present embodiment having the linear motion mechanism 5, the cylinder 6, and the output member 7 is also referred to as a conversion mechanism 10. The conversion mechanism 10 is a conversion mechanism 10 that converts a rotational motion into a linear motion, and includes: a linear motion mechanism 5 that converts the input rotational motion into a linear motion; a cylinder 6 that houses the fluid L that has been input with the linear motion from the linear motion mechanism 5; and an output member 7 to which the linear motion input from the linear motion mechanism 5 is transmitted via the fluid L. According to the conversion mechanism 10, the impact transmitted from the output member 7 to the linear motion mechanism 5 can be mitigated by the fluid L.

[0125] The above-described linear motion device 1 of the present embodiment can also be used in construction machinery. In this case, it can be said that the construction machinery has a linear motion device 1 and an acting portion directly driven by the linear motion device 1. The acting portion is, for example, mounted on the mounting portion 72 of the output member 7. The construction machinery is, for example, a power shovel. When the construction machinery is a power shovel, the acting portion is, for example, the boom, arm, bucket, etc. of the power shovel. According to the construction machinery having the linear motion device 1 of the present embodiment, the acting portion can be directly driven by the linear motion device 1, and the impact transmitted from the acting portion to the linear motion mechanism 5 can be mitigated by the fluid L.

[0126] The linear motion device 1 of the above-described embodiment can also be used for a railway brake. In this case, it can be said that the railway brake has the linear motion device 1. According to the railway brake with the linear drive of this embodiment, the acting portion of the railway brake can be linearly driven by the linear motion device 1, and the impact transmitted from the acting portion of the railway brake to the linear motion mechanism 5 can be mitigated by the fluid L.

[0127] The present embodiment has been described by specific examples, but these specific examples do not limit the present embodiment. The above-described embodiment can be implemented by various other specific examples, and various omissions, substitutions, changes, and additions can be made without departing from its gist.

[0128] Next, an example of a modification will be described with reference to the drawings. In the drawings used in the following description and the following description, for the parts that can be configured in the same manner as the above specific examples, the same reference numerals as those of the corresponding parts used in the above specific examples are used, and the repeated description is omitted.

[0129] (Modification Example 1)

[0130] In the above-described embodiment, the case where the nut 55 forms the rotating portion 51 and the screw shaft 54 forms the linear motion portion 52 in the linear motion mechanism 5 having the ball screw 53 has been described. However, the mode of the linear motion mechanism 5 is not limited to this. Figure 4 It is a cross-sectional view of the linear motion device 1 of Modification Example 1. In particular, Figure 4 It is a cross-sectional view obtained by cutting the linear motion device 1 along the plane of the rotation axis LA of the rotation output from the drive portion 2.

[0131] In Modification Example 1, the screw shaft 54 of the ball screw 53 forms the rotating portion 51, and the nut 55 forms the linear motion portion 52. In Modification Example 1, the screw shaft 54 is fixed to the second member 42 (gear rack 42a) of the reduction portion 4. Thus, the screw shaft 54 forms the rotating portion 51, and the rotating portion 51 is rotated by the rotation input to the second member 42. Further, in Modification Example 1, the nut 55 is not fixed to the second member 42 (gear rack 42a). Therefore, the nut 55 forms the linear motion portion 52 that is linearly moved by the rotational motion of the screw shaft 54 serving as the rotating portion 51.

[0132] In Modification Example 1, the surface on the first side SA1 in the axial direction DA of the nut 55 forms the pressing surface 56 for pressing the fluid L accommodated in the cylinder 6. In the linear motion mechanism 5 of Modification Example 1, the nut 55 is linearly moved by the rotational motion of the screw shaft 54, and thus the fluid L is pressed by the pressing surface 56 formed on the nut 55.

[0133] In addition, in variant example 1, the containing member 81 contains the screw shaft 54 ​​as the rotating portion 51. In addition, in variant example 1, the bearing 82 is in contact with the screw shaft 54 ​​and the containing member 81 so that the screw shaft 54 ​​as the rotating portion 51 can rotate relative to the containing member 81. The bearing 82 is in contact with the portion of the screw shaft 54 ​​where the external thread 54a is not formed. In addition, in variant example 1, the containing member 81 is a member that is different from the members included in the reduction portion 4 and the cylinder 6. The containing member 81 is connected to the cylinder 6 on the first side SA1 in the axial direction DA, and is connected to the second member 42 (gear frame 42a) on the second side SA2 in the axial direction DA. Thus, the internal space of the direct-acting device 1 is divided by the containing member 81, the cylinder 6, the second member 42 of the reduction portion 4, and the mounting member 47.

[0134] In addition, the direct-acting device 1 of modification 1 further includes a rotation suppressing member 84 that suppresses the rotation of the linear motion portion 52 relative to the cylinder 6. The rotation suppressing member 84 is a rod-shaped member extending in the direction of the linear motion of the linear motion portion 52 inside the first portion 61 of the cylinder 6. The direct-acting device 1 of modification 1 includes two rotation suppressing members 84. In modification 1, the linear motion portion 52 is provided with a through hole 52a extending in the direction of the linear motion of the linear motion portion 52. The rotation suppressing member 84 passes through the through hole 52a. In addition, the rotation suppressing member 84 is fixed to the accommodating member 81. According to such a rotation suppressing member 84, it is possible to suppress the linear motion portion 52 from performing movements other than linear motion.

[0135] Although not shown, the direct-acting mechanism 5 may have a sealing portion that prevents the fluid L from entering the interior of the through hole 55b of the nut 55. As an example, the sealing portion prevents the fluid L from entering between the nut 55 and the screw shaft 54. The sealing portion is mounted on the nut 55 forming the linear motion portion 52, and performs linear motion together with the nut 55.

[0136] (Variant 2)

[0137] In the above-described embodiment and modified example, the case where the linear motion portion 52 of the linear motion mechanism 5 and the output member 7 perform linear motion on the same line is described. However, the form of the linear motion device 1 is not limited to this. Figure 5 2 is a cross-sectional view of the linear motion device 1 according to the modification 1. In particular, Figure 5 This is a cross-sectional view of the linear motion device 1 cut along a plane passing through the rotation axis LA of the rotation output by the drive unit 2 and the axis LB of the output member 7 .

[0138] In Modification 2, the first part 61 of the cylinder 6 is arranged coaxially with the axis LA. Therefore, the linear motion part 52 moves linearly on the axis LA. On the other hand, the second part 62 of the cylinder 6 is not arranged coaxially with the axis LA. Therefore, the axis LB of the output member 7 does not coincide with the axis of rotation LA of the rotation output by the drive part 2 and the axis of the linear motion part 52.

[0139] In Modification 2, the linear motion part 52 moves linearly on the axis LA. In addition, the output member 7 moves linearly on an axis LB that does not coincide with the axis LA. Thus, in Modification 2, the linear motion part 52 and the output member 7 perform linear motion on different lines.

[0140] In Modification 2, the first part 61 and the second part 62 may extend in directions parallel to each other or may extend in directions not parallel to each other. In addition, the linear motion part 52 and the output member 7 may perform linear motion on lines parallel to each other or may perform linear motion on lines not parallel to each other.

[0141] In Modification 2, the cylinder 6 has: a first part 61, inside which the part of the linear motion part 52 having the pressing surface 56 can move; a second part 62, inside which the part of the output member 7 having the pressed surface 71 can move; and a third part 63, which extends in a direction not parallel to the extending directions of the first part 61 and the second part 62 and connects the first part 61 and the second part 62. The fluid L is accommodated in the cylinder 6 so as to fill the third part 63 and span the first part 61 and the second part 62. Therefore, similarly to the above-described embodiment and modification, in Modification 2, the fluid L is pressed by the pressing surface 56 of the linear motion part 52, and the pressed surface 71 of the output member 7 is pressed by the fluid L, whereby the output member 7 performs linear motion.

[0142] (Modification 3)

[0143] The third part 63 that connects the first part 61 and the second part 62 of the cylinder 6 may include a part formed of a flexible material. Figure 6 is a cross-sectional view of the linear motion device 1 of Modification 3. In particular, Figure 6 is a cross-sectional view obtained by cutting the linear motion device 1 along a plane passing through the axis of rotation LA of the rotation output by the drive part 2 and the axis LB of the output member 7.

[0144] In modification 3, the third portion 63 of the cylinder 6 includes a deformable portion 64 formed of a flexible material. The material of the deformable portion 64 is not particularly limited as long as it is flexible and can transmit the linear motion input from the direct-acting mechanism 5 to the output member 7. The deformable portion 64 is, for example, a rubber hose. In modification 3, the fluid L is also contained in the cylinder 6 in a manner that fills the third portion 63 and spans the first portion 61 and the second portion 62. Therefore, similarly to the above-mentioned embodiment and each modification, in modification 3, the fluid L is pushed by the pushing surface 56 of the linear motion portion 52, and the pushed surface 71 of the output member 7 is pushed by the fluid L, so that the output member 7 performs linear motion.

[0145] According to the linear motion device 1 of the third modification, the positional relationship among the output member 7 , the linear motion mechanism 5 , and the drive unit 2 can be freely changed by deforming the deformable portion 64 .

[0146] (Variant 4)

[0147] In the above-described embodiment and modified example, the case where the linear motion mechanism 5 includes the ball screw 53 has been described. However, the form of the linear motion mechanism 5 is not limited to this. Figure 7 and Figure 8 2 is a cross-sectional view of the linear motion device 1 according to the modification 4. In particular, Figure 7 This is a cross-sectional view of the linear motion device 1 cut along a plane passing through the axis LB of the output member 7 and perpendicular to the axis LA. Figure 8 The dashed line with reference numeral L1 is closer to the output member 7. Figure 7 The cross section formed by cutting the direct-acting device 1 along the line VIIIa-VIIIa in FIG. 1 shows the position closer to the driving unit 2 than the dotted line marked with the reference numeral L1. Figure 7 A cross section formed by cutting the linear motion device 1 along the line VIIIb-VIIIb in FIG.

[0148] In modification 4, the direct-acting mechanism 5 has a rack 58 and a pinion 59. The rack 58 is a rod-shaped member having teeth 58a. The teeth 58a are located on the side of the rack 58 and are arranged along the direction in which the rack extends. In modification 4, the rack 58 extends along the extension direction of the axis LB of the output member 7. The pinion 59 has a general circular gear shape. The teeth 58a of the rack 58 mesh with the teeth 59a of the pinion 59. Therefore, when the pinion 59 is rotated, the rack 58 is driven by the pinion 59, and the positional relationship between the rack 58 and the pinion 59 changes. In other words, the direct-acting mechanism 5 has a so-called rack and pinion.

[0149] In Modification 4, the pinion gear 59 forms a rotating portion 51 that is input with a rotational motion from the drive unit 2 and rotates. The pinion gear 59 is fixed to an end portion on the first side SA1 in the axial direction DA of the second member 42. Further, in Modification 4, the rack 58 forms a linear motion portion 52 that is driven to perform a linear motion by the rotational motion of the rotating portion 51. In Modification 4, when a rotational motion is output from the drive unit 2, this rotational motion is input to the pinion gear 59, so that the pinion gear 59 rotates in the circumferential direction DB. When the pinion gear 59 rotates, the rack 58 is driven by the rotational motion of the pinion gear 59. At this time, the rack 58 linearly moves in the direction in which the rack 58 extends. Thus, by using the linear motion mechanism 5 of Modification 4, it is also possible to convert the rotational motion input from the drive unit 2 into a linear motion.

[0150] In Modification 4, the rack 58 as the linear motion portion 52 linearly moves on a line that does not coincide with the rotational axis LA of the rotation output from the drive unit 2. In Modification 4, the rack 58 linearly moves in a direction orthogonal to the axial direction DA in which the axis LA extends. Further, in Modification 4, the rack 58 and the axis LB of the output member 7 are arranged coaxially, and the linear motion is performed on the axis LB.

[0151] In the embodiments disclosed in this specification, a member composed of a plurality of objects can integrate the plurality of objects. Conversely, a member composed of one object can also be divided into a plurality of objects. Whether integrated or not, as long as it is configured to be able to achieve the object of the present invention.

[0152] The embodiments of the present invention are not limited to the above-described respective embodiments, and also include various modifications that can be conceived by those skilled in the art. The effects of the present invention are not limited to the above content. That is, various additions, changes, and partial deletions can be made without departing from the content defined in the claims and the conceptual ideas and gists of the present invention derived from their equivalents.

[0153] Explanation of reference numerals:

[0154] 1 Linear motion device

[0155] 2 Drive unit

[0156] 3 Electric mechanism

[0157] 31 Rotating shaft

[0158] 4 Reduction unit

[0159] 41 First member

[0160] 42 Second member

[0161] 43 Crankshaft

[0162] 44 External gear

[0163] 5 Linear motion mechanism

[0164] 53 Ball screw

[0165] 54 Screw shaft

[0166] 55 Nut

[0167] 56 Pushing surface

[0168] 6 Cylinder

[0169] 65 Space

[0170] 7 Output member

[0171] 81 Receiving member

[0172] 82 Bearing

[0173] 83 Reservoir

[0174] 10 Conversion mechanism

Claims

1. A linear motion device, wherein: It has: A driving part that outputs rotation; A linear motion mechanism that converts the rotational motion input from the driving part into a linear motion; A cylinder that houses the fluid into which the linear motion is input from the linear motion mechanism; And An output member, and the linear motion input from the linear motion mechanism is transmitted to the output member via the fluid.

2. The linear motion device according to claim 1, wherein: The driving part has: An electric mechanism; and A reduction part that decelerates the rotation of the electric mechanism and transmits it to the linear motion mechanism.

3. The linear motion device according to claim 1, wherein: The area of the surface of the linear motion mechanism that presses the fluid is different from the area of the surface of the output member that is pressed by the fluid.

4. The linear motion device according to claim 3, wherein: The area of the surface of the linear motion mechanism that presses the fluid is larger than the area of the surface of the output member that is pressed by the fluid.

5. The linear motion device according to claim 1, wherein: The cylinder has a cylindrical shape, The linear motion mechanism has a surface that presses the fluid, The output member has a surface that is pressed by the fluid, The fluid is sealed in a space surrounded by the inner surface of the cylinder, the surface of the linear motion mechanism that presses the fluid, and the surface of the output member that is pressed by the fluid.

6. The linear motion device according to claim 5, wherein: The linear motion device further has a reservoir, The reservoir has: A first chamber that opens on the inner surface of the cylinder to communicate with the space; and A second chamber, the volume of which changes according to the pressure in the first chamber, so as to change the volume of the first chamber.

7. The linear motion device according to claim 1, wherein: The linear motion device further has: A housing member that houses at least the rotating part of the linear motion mechanism that rotates when the rotational motion is input from the driving part; And A bearing that contacts the rotating part and the housing member so that the rotating part can rotate relative to the housing member.

8. The linear motion device according to claim 2, wherein: The reduction part has: A first member having internal teeth; A second member that can rotate relative to the first member; A crankshaft that is supported by the second member so as to be able to rotate; And An external gear having a through hole through which the crankshaft passes and having external teeth that mesh with the internal teeth of the first member; The rotation of the second member is input to the linear motion mechanism.

9. The linear motion device according to claim 1, wherein: The linear motion mechanism has a ball screw, and the ball screw has a screw shaft and a nut.

10. A conversion mechanism that converts a rotational motion into a linear motion, wherein: The conversion mechanism has: A linear motion mechanism that converts the input rotational motion into a linear motion; A cylinder that houses the fluid into which the linear motion is input from the linear motion mechanism; And An output member, and the linear motion input from the linear motion mechanism is transmitted to the output member via the fluid.

11. A construction machine, wherein: It has: The linear motion device according to any one of claims 1 to 9; and An acting part that is linearly driven by the linear motion device.

12. A railway brake, wherein, it has a direct-acting device according to any one of claims 1 to 9.

Images