Drive systems and work machines

Abstract

This technology allows for a simplified structure and enables accurate detection of torque acting on an elastic body. [Solution] The drive device comprises a drive source that generates rotational driving force and an elastic body that connects the drive source and the load. The elastic body is composed of a torsion bar.

Description

Technical Field

[0001] The present invention relates to a drive device and a working machine.

Background Art

[0002] A series elastic actuator incorporating a motor is known as the prior art (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a drive device composed of a series elastic actuator, for example, when a coil spring constitutes an elastic body, members for connecting a motor as a drive source and the coil spring, a support member for the coil spring, a member for connecting the coil spring and an external load, etc. are required. Therefore, the structure of the drive device tends to become complicated. Further, in a drive device composed of a series elastic actuator, in order to improve controllability, it is desirable to accurately detect the torque acting on the elastic body.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a technology capable of simplifying the structure and accurately detecting the torque acting on the elastic body.

Means for Solving the Problems

[0006] A drive device according to an aspect of the present invention includes a drive source that generates a rotational driving force, and an elastic body that connects the drive source and a load, and the elastic body is configured to include a torsion bar.

[0007] A working machine according to another aspect of the present invention comprises the above-described drive device and the load driven by the drive device. [Effects of the Invention]

[0008] The above configuration allows for a simplified structure and accurate detection of torque acting on an elastic body. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view showing the schematic configuration of an electric excavator, which is an example of a work machine according to one embodiment of the present invention. [Figure 2] This is a perspective view from the left rear showing the general configuration of the drive system installed in the above-mentioned electric excavator. [Figure 3] This is a perspective view from the front right showing the general configuration of the above-mentioned drive unit. [Figure 4] This is a horizontal cross-sectional view showing the configuration of the above-mentioned drive unit. [Figure 5] This is a perspective view from the left rear showing the general configuration of a modified example of the drive device described above. [Figure 6] This is a horizontal cross-sectional view showing the configuration of a modified example of the drive device described above. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] [1. Outline configuration of the work machine] Figure 1 is a side view showing a schematic configuration of an electric excavator 1, which is an example of a work machine according to one embodiment of the present invention. The electric excavator 1 comprises a body 2 and a work machine section 3. The body 2 is configured to be mobile. However, the body 2 may be configured to be non-mobile. That is, for example, the body 2 may be fixed to the ground.

[0012] Herein, directions are defined as follows: The direction in which the machine body 2 moves in a straight line is the front-rear direction, with one side being referred to as "front" and the other as "rear." In this specification, the side on which the work machine unit 3 is located relative to the machine body 2 is referred to as "front." The lateral direction perpendicular to the front-rear direction is referred to as the left-right direction, with one side being referred to as "left" and the other as "right." In this specification, the side that is to the left when looking from rear to front is referred to as "left," and the side that is to the right is referred to as "right." Furthermore, the direction of gravity perpendicular to the front-rear and left-right directions is referred to as the up-down direction, with the upstream side of the direction of gravity being referred to as "up" and the downstream side as "down." In the drawings, the front is indicated by the symbol "F," the rear by "B," the left by "L," the right by "R," the upper by "U," and the lower by "D," as needed. Note that these directions are merely descriptive names and are not intended to limit the actual positional relationships and directions.

[0013] The machine body 2 has a battery unit 21. The battery unit 21 is composed of, for example, a lithium-ion battery and stores the power supplied to each of the drive devices 100, which will be described later. The machine body 2 also rotatably supports the work machine section 3.

[0014] The working machine section 3 comprises a boom 31, an arm 32, and an attachment 33. Each of the boom 31, arm 32, and attachment 33 is an example of a load 4. In other words, the electric excavator 1 is equipped with a load 4. Note that the load 4 is not limited to the boom 31, arm 32, and attachment 33. For example, the load 4 may be a blade 22 rotatably supported on the machine body 2. The blade 22 is used for leveling, soil removal, etc.

[0015] Various operations can be performed by independently driving the boom 31, arm 32, and attachment 33. More specifically, the boom 31 is composed of a metal member that curves and extends in one direction (the front-to-back direction in Figure 1). The boom 31 is not limited to the above configuration and may extend along the above-mentioned one direction, for example. The base end of the boom 31 is rotatably supported at the front of the machine body 2. More specifically, the base end of the boom 31 is connected to the front of the machine body 2 via a boom drive unit 31A. When the boom drive unit 31A is driven, the boom 31 rotates in the vertical and front-to-back directions relative to the machine body 2. In addition to rotating in the vertical and front-to-back directions relative to the machine body 2, the boom 31 may also swing (rotate) in the left-to-right direction.

[0016] The arm 32 is composed of a metal member extending in one direction. However, the arm 32 is not limited to the above configuration and may, for example, extend while curving in one direction. The base end of the arm 32 is rotatably supported at the tip of the boom 31. In detail, the base end of the arm 32 is connected to the tip of the boom 31 via the arm drive unit 32A. When the arm drive unit 32A is driven, the arm 32 rotates relative to the boom 31 in the vertical and longitudinal directions.

[0017] The attachment 33 comprises a coupling member 331 and an attachment body 332. The coupling member 331 is rotatably supported at the tip of the arm 32. More specifically, the coupling member 331 is connected to the tip of the arm 32 via an attachment drive unit 33A.

[0018] An attachment body 332 is detachably attached to a joint member 331. That is, the attachment body 332 can be replaced with various types. In FIG. 1, the attachment body 332 is a bucket used for excavation work such as earth and sand. The attachment body 332 may be, for example, a breaker, a grapple, etc. instead of the bucket. Note that the attachment body 332 may be non-detachably attached to the joint member 331 (may be provided integrally). When the attachment drive unit 33A is driven, the attachment 33 rotates with respect to the arm 32 in the vertical and front-rear directions. The configuration of the joint member 331 will be described later.

[0019] Each of the boom drive unit 31A, the arm drive unit 32A, and the attachment drive unit 33A includes a drive device 100. When the drive device 100 included in the boom drive unit 31A is driven, the boom 31 rotates. When the drive device 100 included in the arm drive unit 32A is driven, the arm 32 rotates. When the drive device 100 included in the attachment drive unit 33A is driven, the attachment 33 rotates. That is, the electric excavator 1 includes the drive device 100. Hereinafter, as an example, based on the drive device 100 included in the attachment drive unit 33A, the configuration of the drive device 100 will be described.

[0020] 〔2. Configuration of Drive Device〕 FIG. 2 and FIG. 3 are perspective views from the left rear and the right front showing the schematic configuration of the drive device 100. In the drawings after FIG. 2, for convenience, the illustration of the attachment body 332 is omitted. The drive device 100 includes a drive source 101, an elastic body 102, and a detection unit 103. The drive source 101 includes an electric motor 101a.

[0021] The electric motor 101a is driven by power supplied from the battery unit 21 (see Figure 1). In other words, the electric motor 101a is driven by electricity. Power is supplied from the battery unit 21 to the electric motor 101a via an inverter (not shown) or the like, which is located inside the machine body 2 (see Figure 1). When the electric motor 101a is driven, it outputs a rotational driving force. In other words, the drive source 101 (electric motor 101a in this embodiment) generates a rotational driving force. The electric motor 101a is composed of a synchronous motor or an induction motor, etc. However, the configuration of the electric motor 101a is not limited to the above types of motors.

[0022] From the viewpoint of easily realizing a configuration suitable for an electric excavator 1 (electric work machine), it is desirable that the drive source 101 be configured to include an electric motor 101a driven by electricity, as in this embodiment.

[0023] However, the configuration of the drive source 101 is not limited to the above. For example, the drive source 101 may include a hydraulic motor driven by hydraulic fluid, or it may include a pneumatic motor driven by compressed air.

[0024] The elastic body 102 is configured to be elastically deformable. Specifically, when an external force is applied to the elastic body 102, it deforms, and when the external force is removed, the elastic body 102 returns to its original shape. The displacement (amount of deformation) of the elastic body 102 is detected by the detection unit 103. More details are as follows. Figure 4 is a horizontal cross-sectional view of the drive device 100 cut horizontally at the position through which the line A-A' in Figure 1 passes.

[0025] The elastic body 102 is composed of a metal member integrally comprising a shaft portion 102a and a flange portion 102b. The shaft portion 102a is formed in the shape of a rod extending in the left-right direction. Furthermore, the shaft portion 102a is configured to be elastically deformable in the torsional direction.

[0026] The flange portion 102b is composed of a first flange portion 102b1 and a second flange portion 102b2. Each of the first flange portion 102b1 and the second flange portion 102b2 is formed in a flat plate shape extending in the vertical and horizontal directions. Each of the first flange portion 102b1 and the second flange portion 102b2 is formed in a circular shape when viewed from the left or right of the drive device 100, but is not limited to this, and may be, for example, elliptical, rectangular, square, or a polygonal shape other than rectangular and square. A projection 102b3 is formed in the center of the second flange portion 102b2, projecting to the right.

[0027] The first flange portion 102b1 is integrally formed with the shaft portion 102a, with the central part of its right side intersecting with the left end of the shaft portion 102a. The second flange portion 102b2 is integrally formed with the shaft portion 102a, with the central part of its left side intersecting with the right end of the shaft portion 102a. Therefore, the shaft portion 102a, the first flange portion 102b1, and the second flange portion 102b2 are positioned in the order of first flange portion 102b1, shaft portion 102a, and second flange portion 102b2 from left to right.

[0028] The first flange portion 102b1 is rotatably supported on the coupling member 331 via the first bearing BR1. The first flange portion 102b1 is also connected to the electric motor 101a via the transmission 104. In other words, the elastic body 102 is connected to the drive source 101 (via the transmission 104). The electric motor 101a is fixed to the arm 32.

[0029] The transmission 104 reduces or increases the rotational driving force of the electric motor 101a and transmits it to the first flange portion 102b1. The transmission 104 in this embodiment is a reduction gear that reduces the rotational driving force of the electric motor 101a. However, the configuration of the transmission 104 is not limited to the above, and for example, it may be a speed increaser that increases the rotational driving force of the electric motor 101a. The transmission 104 is composed of various gears and the like. The transmission 104 may also be composed of a power-transmitting belt. In other words, the electric shovel 1 is equipped with a transmission 104, and this transmission 104 changes the rotational driving force of the drive source 101 and outputs it to the elastic body 102 (torsion bar 102c, described later).

[0030] The second flange portion 102b2 is connected to the joint member 331 of the attachment 33. In other words, the elastic body 102 is connected to the load 4 (attachment 33 in Figure 4). Therefore, the elastic body 102 connects the drive source 101 (electric motor 101a in this embodiment) and the load 4 (attachment 33, etc. in this embodiment).

[0031] The joint member 331 is composed of a metal member that integrally includes a cover portion 331a and a mounting portion 331b. The cover portion 331a is formed in a cylindrical shape that extends in the left-right direction and has a closed right end. A fitting hole 331a1 that penetrates in the left-right direction is provided in the closed right end (right side portion).

[0032] When connecting the second flange portion 102b2 and the joint member 331, for example, first the joint member 331 is moved from the right to the left of the elastic body 102. At this time, the fitting hole 331a1 of the joint member 331 is moved while corresponding to (aligning) the protruding portion 102b3 of the second flange portion 102b2. As a result, the protruding portion 102b3 fits into the fitting hole 331a1, and the joint member 331 is positioned so as to cover at least a part of the elastic body 102. Next, the joint member 331 and the second flange portion 102b2 are fastened together with fastening members such as bolts (not shown). This connects the second flange portion 102b2 and the joint member 331. Note that the connection between the second flange portion 102b2 and the joint member 331 may be performed by welding or other means instead of fastening with the above-mentioned fastening members.

[0033] The mounting portion 331b is formed extending in a direction perpendicular to the axial direction (left-right direction in this embodiment) of the cover portion 331a (front-rear direction in Figure 4). The base end (right rear end in Figure 4) of the mounting portion 331b intersects with the left end of the cover portion 331a and is formed integrally. The tip of the mounting portion 331b (front end in Figure 4) is configured to allow attachment of the attachment body 332 (see Figure 1).

[0034] In this embodiment, the shaft portion 102a and the flange portion 102b constitute the torsion bar 102c. Therefore, the torsion bar 102c is configured to be elastically deformable in the torsional direction. However, the configuration of the torsion bar 102c is not limited to the above. For example, the torsion bar 102c may be configured without the flange portion 102b, or it may be configured with components other than the flange portion 102b.

[0035] As described above, the shaft portion 102a constituting the torsion bar 102c is located between the first flange portion 102b1 and the second flange portion 102b2 constituting the torsion bar 102c in the left-right direction and extends in the left-right direction. Therefore, the torsion bar 102c is located extending in the left-right direction. For this reason, in this embodiment, the axial direction of the torsion bar 102c means the left-right direction.

[0036] The torsion bar 102c is provided with a through portion 102c1 that penetrates in the left-right direction. More specifically, the through portion 102c1 penetrates the first flange portion 102b1, the shaft portion 102a, and the second flange portion 102b2 from left to right. In other words, the torsion bar 102c has a through portion 102c1 that penetrates in the axial direction (left-right direction in this embodiment) of the torsion bar 102c.

[0037] The torsion bar 102c constitutes a transmission shaft that transmits the rotational driving force of the electric motor 101a to the attachment 33, and also constitutes an output shaft 105 that drives the load 4 (attachment 33 in this embodiment). More specifically, when the electric motor 101a is driven, the rotational driving force of the electric motor 101a is transmitted to the torsion bar 102c via the transmission 104. As a result, the torsion bar 102c rotates, for example, to one side in the circumferential direction of the torsion bar 102c. The circumferential direction of the torsion bar 102c means the direction along the arc drawn with respect to the central axis of the torsion bar 102c.

[0038] Since the second flange portion 102b2 constituting the torsion bar 102c is connected to the joint member 331 of the attachment 33, the torsion bar 102c rotates and transmits the rotational driving force transmitted from the electric motor 101a to the attachment 33. As a result, the attachment 33 rotates to one side in the circumferential direction of the torsion bar 102c. Therefore, it can be said that the attachment 33 rotates due to the rotation of the torsion bar 102c. In other words, the load 4 (attachment 33, etc., in this embodiment) is driven by the drive device 100 (in this embodiment, in particular the output shaft 105 constituting the torsion bar 102c). That is, the torsion bar 102c functions as both a transmission shaft and an output shaft 105.

[0039] Here, let us assume, for example, that the rotating attachment 33 becomes lodged in the ground and its movement stops. In this assumption, if the electric motor 101a continues to drive, the first flange portion 102b1 of the torsion bar 102c is rotated by the electric motor 101a, while the rotation of the second flange portion 102b2 stops due to the cessation of the attachment 33's movement. As a result, torque (also called torsional moment) acts on the torsion bar 102c, causing it to twist. At this time, torsional stress is generated in the torsion bar 102c. In other words, the drive device 100 of this embodiment is a series elastic actuator in which the drive source 101 (electric motor 101a in this embodiment) is connected to the load 4 (attachment 33, etc., in this embodiment) via an elastic body 102. This elastic body 102 is composed of a torsion bar 102c.

[0040] With the above configuration, for example, the drive unit 100 can be devoid of the members that connect the drive source 101 and the coil spring, the support members for the coil spring, the members that connect the coil spring and the load 4, etc., which are necessary in a series elastic actuator where a coil spring constitutes the elastic body 102. In other words, if the torsion bar 102c constitutes the elastic body 102, the above-mentioned members that are necessary when a coil spring constitutes the elastic body 102 become unnecessary. This reduces the number of parts in the drive unit 100 (especially on the output side of the drive unit 100). Therefore, the structure of the drive unit 100 can be simplified. Furthermore, when detecting the torque acting on the elastic body 102, it is possible to avoid a decrease in detection accuracy due to resistance occurring within or between the above-mentioned members. Therefore, when the torsion bar 102c constitutes the elastic body 102, the torque acting on the elastic body 102 can be detected with greater accuracy than when a coil spring constitutes the elastic body 102. As a result, the structure of the drive unit 100 can be simplified, and the torque acting on the elastic body 102 can be detected with high accuracy.

[0041] In the drive unit 100, particularly from the viewpoint of simplifying the structure for driving the load 4 (attachment 33, etc., in this embodiment), it is desirable that the torsion bar 102c constitutes the output shaft 105 that drives the load 4, as in this embodiment.

[0042] Furthermore, when torque is no longer applied to the torsion bar 102c, the torsion bar 102c returns to its original shape. In other words, the torsion bar 102c functions as a rod-shaped torsion spring.

[0043] The detection unit 103 includes a detection shaft 103a and a detector 103b. The detection shaft 103a (also called the input shaft) is constructed by welding or the like to the left end of a rod-shaped member extending in the left-right direction to a plate-shaped member extending in the up-down and left-right directions. That is, the detection shaft 103a is located extending in the axial direction (left-right direction in this embodiment) of the torsion bar 102c. The rod-shaped member is configured to be elastically deformable in the torsional direction. The plate-shaped member is formed in a circular shape when viewed from the left of the detection shaft 103a, but is not limited to this, and may be, for example, elliptical, rectangular, square, or a polygonal shape other than rectangular and square.

[0044] The detector 103b is constructed by housing electronic components and the like within a cylindrical housing that extends in the left-right direction. In this embodiment, the detector 103b is composed of an encoder 103b1. The encoder 103b1 is fixed to a protrusion 102b3 of the second flange portion 102b2. That is, the encoder 103b1 is fixed to the central part of the second flange portion 102b2. The protrusion 102b3 constitutes one end portion 102c2 located on the right side of the torsion bar 102c. That is, the detector 103b is fixed to one end portion 102c2 on one side (the right side in this embodiment) of the torsion bar 102c in the axial direction. However, the fixing position of the detector 103b on the torsion bar 102c is not limited to one end portion 102c2. For example, the fixing position of the detector 103b on the torsion bar 102c may be to the left of one end 102c2 and to the right of the center in the left-right direction (of the torsion bar 102c). In other words, the detector 103b may be fixed to one side of the torsion bar 102c in the axial direction (the right side in this embodiment).

[0045] Furthermore, a configuration may be provided between the detector 103b and the end portion 102c2, for example, a flat plate-shaped conversion member. That is, the detector 103b may be fixed to the end portion 102c2 via the above-mentioned conversion member.

[0046] The detector 103b is rotatably connected to the detection shaft 103a. More specifically, the right end of the detection shaft 103a is connected to the left side (bottom) of the detector 103b (encoder 103b1). When connecting the detection shaft 103a to the detector 103b, for example, before making the above connection, the detector 103b is fixed to one end 102c2 of the torsion bar 102c. Then, the detection shaft 103a is moved from the left to the right of the torsion bar 102c. At this time, the detection shaft 103a is moved while corresponding to (aligning with) the through-hole 102c1 of the torsion bar 102c. As a result, the detection shaft 103a can be inserted into the through-hole 102c1 and connected to the detector 103b. Therefore, the detection unit 103 (especially the detection shaft 103a) is provided in the through-hole 102c1.

[0047] In a configuration where the torsion bar 102c has a through-hole 102c1 that penetrates the torsion bar 102c in the axial direction (left-right direction in this embodiment), the following configuration is desirable from the viewpoint of compactly (efficiently) installing the detection unit 103 and facilitating miniaturization of the drive device 100. That is, it is desirable that the detection unit 103 be provided in the through-hole 102c1.

[0048] The detection shaft 103a, inserted into the through-hole 102c1, is rotatably supported by the through-hole 102c1 via the second bearing BR2, and the plate-shaped member is connected to the central part of the first flange portion 102b1. The first flange portion 102b1 constitutes the other end 102c3 located on the left side of the torsion bar 102c. That is, the detection shaft 103a is connected to the other end 102c3 on the other axial side (the left side in this embodiment) of the torsion bar 102c. However, the connection position of the detection shaft 103a on the torsion bar 102c is not limited to the other end 102c3. For example, the connection position of the detection shaft 103a on the torsion bar 102c may be to the right of the other end 102c3 and to the left of the central part (in the left-right direction of the torsion bar 102c). In other words, the detection axis 103a may be connected to the other axial side (the left side in this embodiment) of the torsion bar 102c.

[0049] When the torsion bar 102c is twisted, for example, the first flange portion 102b1 rotates to one side in the circumferential direction of the torsion bar 102c relative to the second flange portion 102b2. That is, a relative angle is created between the first flange portion 102b1 and the second flange portion 102b2. Also, as described above, the central part of the first flange portion 102b1 is connected to the detection shaft 103a, and a detector 103b is fixed to the central part of the second flange portion 102b2, to which the detection shaft 103a is rotatably connected. Therefore, when the torsion bar 102c is twisted and the first flange portion 102b1 rotates to one side in the circumferential direction of the torsion bar 102c relative to the second flange portion 102b2, the detection shaft 103a rotates to the aforementioned one side in the circumferential direction relative to the detector 103b. That is, a relative angle (rotational displacement) is created between the detection shaft 103a and the detector 103b. The relative angle of the detection axis 103a is an example of the displacement of the detection axis 103a and is detected by the detector 103b. Therefore, the detector 103b detects the displacement of the detection axis 103a (in this embodiment, the relative angle with respect to the detector 103b).

[0050] The relative angle of the detection axis 103a with respect to the detector 103b corresponds to the twist angle of the torsion bar 102c. Therefore, the detection of the displacement of the detection axis 103a by the detector 103b makes it possible to detect the displacement of the torsion bar 102c. In other words, the detection unit 103 detects the displacement (twist angle in this embodiment) of the torsion bar 102c using the detector 103b.

[0051] From the perspective of detecting torque by estimating the torque acting on the torsion bar 102c based on the displacement of the torsion bar 102c (twist angle in this embodiment) using a known conversion formula, the following configuration is desirable. That is, as in this embodiment, it is desirable that the drive device 100 includes a detection unit 103 that detects the displacement of the torsion bar 102c.

[0052] Furthermore, once the torque acting on the torsion bar 102c is estimated (detected), the external force applied to the workpiece is estimated based on the above torque and the distance from the central axis of the torsion bar 102c to the contact point (point of application) with the workpiece on the attachment 33.

[0053] For example, if the detection unit 103 directly detects the displacement of the torsion bar 102c, the detection unit 103 may become larger, making it difficult to miniaturize the drive unit 100. Therefore, in this case, it is desirable to indirectly detect the displacement of the torsion bar 102c using the detection unit 103 in order to facilitate miniaturization of the drive unit 100. From this viewpoint, it is desirable that the detection unit 103, as in this embodiment, has a detection shaft 103a and a detector 103b connected to the detection shaft 103a that detects the displacement of the detection shaft 103a.

[0054] Furthermore, in a configuration where the detection shaft 103a connected to the detector 103b extends in the axial direction of the torsion bar 102c, the following configuration is desirable from the viewpoint of making it easier to rotate the detection shaft 103a so that the detector 103b can reliably detect the displacement of the detection shaft 103a. That is, as in this embodiment, it is desirable that the detector 103b is fixed to one side of the torsion bar 102c in the axial direction (the right side in this embodiment), and the detection shaft 103a is connected to the other side of the torsion bar 102c in the axial direction (the left side in this embodiment).

[0055] From the viewpoint of reliably realizing a configuration in which the detection shaft 103a can be easily rotated (for example, a configuration in which the detection shaft 103a can be rotated even if the torque acting on the detection shaft 103a is small), the following configuration is desirable. That is, as in this embodiment, it is desirable that the detector 103b be fixed to one end 102c2 of the torsion bar 102c on one side in the axial direction of the torsion bar 102c (the right side in this embodiment). In addition, it is desirable that the detection shaft 103a be connected to the other end 102c3 of the torsion bar 102c on the other side in the axial direction of the torsion bar 102c (the left side in this embodiment).

[0056] In order to accurately detect the displacement of the detection axis 103a (the relative angle with respect to the detector 103b in this embodiment) and to miniaturize the detector 103b itself, thereby facilitating miniaturization of the drive unit 100, the following configuration is desirable. That is, as in this embodiment, it is desirable that the detector 103b be composed of an encoder 103b1.

[0057] However, the configuration of the detector 103b is not limited to the encoder 103b1, and other detectors may be used as long as they can detect the displacement of the torsion bar 102c or the displacement of the detection shaft 103a. For example, the detector 103b may be composed of a strain gauge capable of detecting the strain occurring on the circumferential surface of the torsion bar 102c as the displacement of the torsion bar 102c. In this configuration, the through portion 102c1 may be removed from the torsion bar 102c. That is, for example, the torsion bar 102c may be solid. Alternatively, the detector 103b may be composed of a laser-type displacement meter capable of detecting the amount of movement of the torsion bar 102c in the circumferential direction of the other end 102c3 relative to one end 102c2 as the displacement of the torsion bar 102c.

[0058] As described above, the first flange portion 102b1 located on the left side of the torsion bar 102c is connected to the electric motor 101a. That is, the drive source 101 (electric motor 101a in this embodiment) is connected to the other axial side (left side in this embodiment) of the torsion bar 102c. Also, as described above, the second flange portion 102b2 located on the right side of the torsion bar 102c is connected to the attachment 33. That is, the load 4 (attachment 33, etc. in this embodiment) is connected to one axial side (right side in this embodiment) of the torsion bar 102c.

[0059] The torsion bar 102c is rotated by the drive source 101. That is, the torsion bar 102c is rotatable relative to the drive source 101. For this reason, in order to protect the connection between the torsion bar 102c and the drive source 101 from soil and other debris flying in from outside the drive device 100, the drive source 101 side of the torsion bar 102c is often positioned in a location that is difficult to access from outside the drive device 100. On the other hand, the torsion bar 102c and the load 4 are connected in a way that prevents rotation. For this reason, the load 4 side of the torsion bar 102c is often positioned in a location that is easier to access from outside the drive device 100 compared to the drive source 101 side. Therefore, when the detector 103b is fixed to the torsion bar 102c, if the detector 103b is positioned closer to the load 4 than to the drive source 101, it becomes easier to access the detector 103b from outside the drive device 100 compared to when it is positioned closer to the drive source 101 than to the load 4. This makes it easier to fix the detector 103b in place. If fixing the detector 103b is easy, the work efficiency of tasks such as replacing the detector 103b will improve. Also, if the detector 103b is located in a place that is easily accessible from outside the drive unit 100, it becomes easier to secure space for the detector 103b, making it easier to install even a relatively large detector 103b.

[0060] As described above, the detector 103b is fixed to one side of the torsion bar 102c in the axial direction (the right side in this embodiment). Therefore, from the viewpoint of easily realizing a configuration in which the detector 103b is fixed to the torsion bar 102c closer to the load 4 than to the drive source 101, the following configuration is desirable. That is, as in this embodiment, it is desirable that the drive source 101 (electric motor 101a in this embodiment) be connected to the other side of the torsion bar 102c in the axial direction (the left side in this embodiment). In addition, it is desirable that the load 4 (attachment 33, etc. in this embodiment) be connected to one side of the torsion bar 102c in the axial direction (the right side in this embodiment).

[0061] In this embodiment, the electric motor 101a and the torsion bar 102c are connected via a transmission 104, as described above. The transmission 104 is located to the left of the first flange portion 102b1. That is, the transmission 104 is positioned on the other axial side of the torsion bar 102c (to the left in this embodiment) relative to the torsion bar 102c. More specifically, the transmission 104, torsion bar 102c, and detector 103b are arranged in that order, from the other axial side of the torsion bar 102c toward one axial side of the torsion bar 102c (to the right in this embodiment). Therefore, the transmission 104 is positioned on the opposite side of the torsion bar 102c from the detector 103b in the axial direction of the torsion bar 102c (left-right direction in this embodiment).

[0062] However, the position of the transmission 104 is not limited to the above. For example, the transmission 104 may be positioned on one side of the torsion bar 102c in the axial direction. Alternatively, the transmission 104 may be positioned on both the one side of the torsion bar 102c in the axial direction and the other side of the torsion bar 102c. In other words, the transmission 104 may be positioned on at least one of the two sides of the torsion bar 102c in the axial direction.

[0063] Even if the drive unit 100 is configured to include a transmission 104 that changes the rotational driving force of the drive source 101 (electric motor 101a in this embodiment) and outputs it to the torsion bar 102c, it is desirable to avoid increasing the size of the drive unit 100 in the radial direction of the torsion bar 102c. From this viewpoint, as in this embodiment, it is desirable that the transmission 104 be positioned on at least one side of the torsion bar 102c in the axial direction and the other side of the torsion bar 102c with respect to the torsion bar 102c. Note that the radial direction of the torsion bar 102c means the direction perpendicular to the central axis of the torsion bar 102c.

[0064] Even if the drive unit 100 is configured to include a transmission 104, it is desirable to improve the workability of replacing the detector 103b by ensuring access to the detector 103b and facilitating the fixing work of the detector 103b. From this viewpoint, as in this embodiment, it is desirable that the transmission 104 be positioned on the opposite side of the torsion bar 102c from the detector 103b in the axial direction of the torsion bar 102c (left-right direction in this embodiment).

[0065] [3. Modified examples of drive devices] A modified configuration of the drive unit 100 will be described based on Figures 5 and 6. Figure 5 is a perspective view from the left rear showing the modified configuration of the drive unit 100. Figure 6 is a horizontal cross-sectional view obtained by cutting the drive unit 100 horizontally at the position through which the central axis of the torsion bar 102c passes. For convenience, the arms 32 and other components are omitted from the illustration in Figures 5 and 6. The drive unit 100 shown in Figures 5 and 6 has the same configuration as the drive unit 100 shown in Figure 1, etc., except that the shape of the torsion bar 102c is different. Also, the joint member 331 shown in Figures 5 and 6 has a different shape from the joint member 331 shown in Figure 1, etc., because it corresponds to the shape of the torsion bar 102c. Therefore, the following explanation will focus on these differences, and the same points will be omitted from the explanation. In addition, the same reference numerals will be used to describe the same components as in the drive unit 100 shown in Figure 1, etc.

[0066] In the modified torsion bar 102c, a protrusion 102b4 is formed at the tip (right end) of the projection 102b3 of the second flange portion 102b2, projecting to the right. The outer circumference of the protrusion 102b4 is smaller than the outer circumference of the projection 102b3. An encoder 103b1 (detector 103b) is fixed to the right end of the protrusion 102b4. In other words, in the modified example, the protrusion 102b4 specifically constitutes one end portion 102c2 of the torsion bar 102c. However, the entire second flange portion 102b2, including the protrusion 102b4 and the projection 102b3, may also constitute one end portion 102c2.

[0067] The joint member 331 is composed of a plate-shaped metal member extending in one direction (the front-to-back direction in Figures 5 and 6). The joint member 331 is provided with a through hole 331c that penetrates in the left-to-right direction. With the projection 102b3 fitted into the through hole 331c, the torsion bar 102c and the attachment 33 are connected by joining the second flange portion 102b2 and the joint member 331 by welding or the like.

[0068] [4. Supplement] In this embodiment, the left-right direction is defined as the "axial direction of the torsion bar 102c," the right side as "one side in the axial direction of the torsion bar 102c," and the left side as "the other side in the axial direction of the torsion bar 102c," but the embodiment is not limited to this. For example, the axial direction of the torsion bar 102c may be the front-back direction, the up-down direction, or an oblique direction inclined with respect to at least one of the left-right direction, the front-back direction, or the up-down direction. Alternatively, the left side may be defined as "one side in the axial direction of the torsion bar 102c," and the right side as "the other side in the axial direction of the torsion bar 102c." In other words, the left and right sides may be reversed.

[0069] In this embodiment, a configuration in which there is one detector 103b has been described, but the number of detectors 103b is not limited to one. For example, there may be two detectors 103b, or three or more. In particular, when there are two, the two detectors 103b may be fixed separately on one side (the right side in this embodiment) and the other side (the left side in this embodiment) of the torsion bar 102c in the axial direction of the torsion bar 102c.

[0070] In this embodiment, a configuration has been described in which the detector 103b is fixed to one axial side of the torsion bar 102c and the detection shaft 103a is connected to the other axial side of the torsion bar 102c, but the embodiment is not limited to this configuration. For example, the detector 103b may be fixed to the other axial side of the torsion bar 102c and the detection shaft 103a may be connected to one axial side of the torsion bar 102c.

[0071] [5. Addendum] The drive unit 100 and electric excavator 1 described in this embodiment can also be expressed as the drive unit and work machine shown in the following appendix.

[0072] The drive device in Appendix (1) is A drive source that generates rotational driving force, The system includes an elastic body that connects the drive source and the load, The elastic body is comprised of a torsion bar.

[0073] The drive device in Appendix (2) is the drive device described in Appendix (1), The torsion bar constitutes the output shaft that drives the load.

[0074] The drive device in Appendix (3) is the drive device described in Appendix (1) or (2), The system includes a detection unit for detecting the displacement of the torsion bar.

[0075] The drive device in Appendix (4) is the drive device described in Appendix (3), The torsion bar has a through portion that penetrates in the axial direction of the torsion bar, The detection unit is provided in the penetration portion.

[0076] The drive device in Appendix (5) is the drive device described in Appendix (4), The detection unit, The detection axis extending in the axial direction, It includes a detector that detects the displacement of the aforementioned detection axis, The detector is fixed to one side of the torsion bar in the axial direction, The detection shaft is connected to the other side of the torsion bar in the axial direction.

[0077] The drive device in Appendix (6) is the drive device described in Appendix (5), The detector is fixed to one end of the torsion bar on one side in the axial direction, The detection shaft is connected to the other end of the torsion bar on the other side in the axial direction.

[0078] The drive device in Appendix (7) is the drive device described in Appendix (5) or (6), The drive source is connected to the other axial side of the torsion bar, The load is connected to one side of the torsion bar in the axial direction.

[0079] The drive device in Appendix (8) is the drive device described in any of Appendix (5) to (7), The detector is composed of an encoder.

[0080] The drive device in Appendix (9) is the drive device described in any of Appendix (5) to (8), The system includes a transmission that changes the rotational driving force of the aforementioned drive source and outputs it to the torsion bar, The transmission is positioned on at least one of the axial sides and the other axial side with respect to the torsion bar.

[0081] The drive device in Appendix (10) is the drive device described in Appendix (9), The transmission is positioned in the axial direction on the opposite side of the torsion bar from the detector.

[0082] The drive device in Appendix (11) is the drive device described in any of Appendix (1) to (10), The aforementioned drive source is configured to include an electric motor driven by electricity.

[0083] The work machines mentioned in Appendix (12) are: A drive device as described in any of the appendices (1) to (11), The system comprises the load driven by the aforementioned drive device.

[0084] Although embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and it can be expanded or modified without departing from the spirit of the invention. [Industrial applicability]

[0085] This invention can be used, for example, in work machinery such as construction machinery and agricultural machinery. [Explanation of Symbols]

[0086] 1. Electric excavator (working machine) 4 load 100 Drive unit 101 Power source 101a Electric motor 102 Elastic body 102c Torsion Bar 102c1 Penetration 102c2 One end 102c3 Other end 103 Detection unit 103a Detection axis 103b Detector 103b1 encoder 104 transmission 105 Output shaft

Claims

1. A drive source that generates rotational driving force, The system includes an elastic body that connects the drive source and the load, The aforementioned elastic body is a drive device comprising a torsion bar.

2. The drive device according to claim 1, wherein the torsion bar constitutes an output shaft for driving the load.

3. The drive device according to claim 1, further comprising a detection unit for detecting the displacement of the torsion bar.

4. The torsion bar has a through portion that penetrates in the axial direction of the torsion bar, The drive device according to claim 3, wherein the detection unit is provided in the through-hole.

5. The detection unit, The detection axis extending in the axial direction, It includes a detector that detects the displacement of the aforementioned detection axis, The detector is fixed to one side of the torsion bar in the axial direction, The drive device according to claim 4, wherein the detection shaft is connected to the other side in the axial direction of the torsion bar.

6. The detector is fixed to one end of the torsion bar on one side in the axial direction, The drive device according to claim 5, wherein the detection shaft is connected to the other end of the torsion bar on the other side in the axial direction.

7. The drive source is connected to the other axial side of the torsion bar, The drive device according to claim 5, wherein the load is connected to one side of the torsion bar in the axial direction.

8. The drive device according to claim 5, wherein the detector is composed of an encoder.

9. The system includes a transmission that changes the rotational driving force of the aforementioned drive source and outputs it to the torsion bar, The drive device according to claim 5, wherein the transmission is positioned on at least one of the axial sides and the other axial side with respect to the torsion bar.

10. The drive device according to claim 9, wherein the transmission is positioned in the axial direction on the opposite side of the torsion bar from the detector.

11. The drive device according to claim 1, wherein the drive source includes an electric motor driven by electricity.

12. A drive device according to any one of claims 1 to 11, A working machine comprising the load driven by the drive device.

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