Drive mechanism

Abstract

A drive mechanism (1) comprises: a first link mechanism for tilting an eyeball member (30) with a yaw axis as a rotation center; and a second link mechanism for tilting the eyeball member (30) with a pitch axis intersecting the yaw axis as a rotation center. The first link mechanism has: a joint part (J1) that allows the eyeball member (30) to tilt with each of the yaw axis and the pitch axis as a rotation center; and a first elastic spring (50) that biases one of a holding part and a held part included in the first joint part (J1) toward the other.

Description

Drive mechanism

[0001] The present disclosure relates to a drive mechanism.

[0002] Patent Literature 1 discloses a so-called four-bar parallel link mechanism for moving a robot. Also, a mechanism that enables movement in two axes by arranging two four-bar parallel link mechanisms perpendicular to each other is known. By using such a mechanism, it becomes possible to change the posture of a moving object by rotating in two axes.

[0003] Japanese Patent Application Publication No. 6-320449

[0004] In a link mechanism that changes the posture of a moving object by rotating in two axial directions as described above, it is necessary to provide a joint that can prevent interference between the links due to rotation in two axial directions. However, in a link mechanism that uses such a joint, the high degree of freedom of movement makes it easy for rattle to occur, and it may not be possible to move the moving object with precision.

[0005] An object of the present disclosure is to provide a drive mechanism that suppresses rattles and thereby moves an object to be moved with high precision.

[0006] The drive mechanism according to the present disclosure is a drive mechanism including a first link mechanism for tilting an object to be moved around a first axis as a center of rotation, and a second link mechanism for tilting the object to be moved around a second axis intersecting the first axis as a center of rotation, wherein the first link mechanism includes a first joint portion that connects two links to each other and allows the object to be moved around each of the first axis and the second axis as a center of rotation, and a first biasing member that biases one of a holding portion held by the holding portion of one of the two links against the other.

[0007] 1 is a perspective view of the drive mechanism according to this embodiment, viewed from diagonally above the rear right; FIG. 2 is a perspective view of the drive mechanism according to this embodiment, viewed from diagonally above the front left; FIG. 3 is a top view of the drive mechanism according to this embodiment, viewed from above; FIG. 4 is a perspective view of the drive mechanism according to this embodiment, viewed from above; FIG. 5 is a right side view of the drive mechanism according to this embodiment, viewed from the right; FIG. 6 is a perspective view of the drive mechanism according to this embodiment, viewed from below; FIG. 7 is a schematic diagram for explaining the operation of the link when tilting the eyeball member in the yaw direction and pitch direction; FIG. 8 is a schematic diagram for explaining the operation of the link when tilting the eyeball member in the yaw direction and pitch direction; FIG. 9 is a schematic diagram for explaining the operation of the link when tilting the eyeball member in the yaw direction and pitch direction; FIG. 10 is a schematic diagram for explaining a mechanism for suppressing rattle in the drive mechanism.

[0008] [Summary] An example of an embodiment of a drive mechanism according to the present disclosure will be described below with reference to the drawings.

[0009] Fig. 1 is a perspective view of the drive mechanism according to this embodiment, seen from diagonally above the rear right. Fig. 2 is a perspective view of the drive mechanism according to this embodiment, seen from diagonally above the front left. Fig. 3 is a top view of the drive mechanism according to this embodiment, seen from above. Fig. 4 is a perspective view of the drive mechanism according to this embodiment, seen from above. Fig. 5 is a right side view of the drive mechanism according to this embodiment, seen from the right. Fig. 6 is a perspective view of the drive mechanism according to this embodiment, seen from below.

[0010] In this embodiment, the up-down direction, the front-back direction, and the left-right direction refer to directions based on the direction of the line of sight of the eyeball member 30, which is the object of movement. The eyeball member 30 is a member having an appearance that imitates a part of a human eyeball. In this embodiment, the posture of the eyeball member 30 facing forward (X1 direction in the figure) is called the "basic posture."

[0011] The drive mechanism 1 is a mechanism for tilting the eyeball member 30 in the yaw and pitch directions from a basic attitude. The yaw direction is the direction of rotation around the yaw axis in the figure. The yaw axis is an axis extending in the up-down direction (the Z1 and Z2 directions in the figure). The pitch direction is the direction of rotation around the pitch axis in the figure. The pitch axis is an axis extending in the left-right direction (the Y1 and Y2 directions in the figure). Note that the yaw axis and pitch axis referred to here do not refer to physical components, but to axes that are the centers of rotation. The eyeball member 30 is supported by the drive mechanism 1 so as to be able to rotate around the yaw axis and pitch axis.

[0012] The drive mechanism 1 includes a first link mechanism, a second link mechanism, an eyeball member 30, an actuator 80 serving as a first power source, and an actuator 90 serving as a second power source. The first link mechanism and the second link mechanism each include a plurality of links (also called arms), and are mechanisms configured such that each link is rotatably connected via a joint (also called a pair).

[0013] [First Link Mechanism] The first link mechanism will be described mainly with reference to Figures 3 and 4. The first link mechanism is a mechanism that tilts the eyeball member 30 in the yaw direction by operating using power from the actuator 80.

[0014] The first link mechanism includes a first operating link 11 and a first driving link 12 .

[0015] The first driving link 12 is driven by power from the actuator 80. Specifically, the first driving link 12 rotates around an axis O1 extending in the vertical direction as a rotation center by power from the actuator 80. For example, the axis O1 may coincide with the rotation center of the actuator 80. The rotation center of the first driving link 12 is stationary.

[0016] The first operating link 11 is a member extending in the front-to-rear direction and controls the yaw movement of the eyeball member 30. The front part of the first operating link 11 is connected to the right part of the eyeball member 30, and the rear part is connected to the right part of the first drive link 12 via a joint J1 described below. The front part of the first operating link 11 is preferably connected to the eyeball member 30 so as to allow rotation in the yaw and pitch directions.

[0017] The first operating link 11 can move in the forward and backward directions by following the rotation of the first driving link 12. For example, when the first driving link 12 rotates counterclockwise in FIG. 3 around the axis O1 as the center of rotation, the first operating link 11 moves forward as the joint J1 moves forward. As a result, the eyeball member 30 is pushed forward by the first operating link 11, and its posture is tilted around the yaw axis so that its line of sight faces leftward.

[0018] [Second Link Mechanism] The second link mechanism will be described mainly with reference to Figures 1, 3, and 5. The second link mechanism is a mechanism that tilts the eyeball member 30 in the pitch direction by operating with power from the actuator 90.

[0019] The second link mechanism includes a second operating link 21 and a second driving link 22 .

[0020] The second driving link 22 is driven by power from the actuator 90. Specifically, the second driving link 22 rotates around an axis O2 extending in the left-right direction as a rotation center by power from the actuator 90. For example, the axis O2 may coincide with the rotation center of the actuator 90. The rotation center of the second driving link 22 is stationary.

[0021] The second operating link 21 is a member extending in the front-to-rear direction and controls the pitch movement of the eyeball member 30. The front part of the second operating link 21 is connected to the upper part of the eyeball member 30, and the rear part is connected to the upper part of the second drive link 22 via joint J2. The front part of the second operating link 21 is preferably connected to the eyeball member 30 so as to allow rotation in the yaw and pitch directions.

[0022] The second operating link 21 can move in the forward and backward directions by following the rotation of the second driving link 22. For example, when the second driving link 22 rotates clockwise in Fig. 5 around the axis O2 as the rotation center, the second operating link 21 moves forward as the joint J2 moves forward. As a result, the eyeball member 30 is pushed forward by the second operating link 21, and its posture is tilted around the pitch axis so that its line of sight faces downward.

[0023] 7A to 7C, the reason for using a ball joint in the link mechanism that tilts the eyeball member 30 in the yaw and pitch directions will be explained. A ball joint is a spherical part that constitutes a joint that connects links and is held rotatably.

[0024] 7A to 7C are schematic diagrams illustrating the operation of the link when tilting the eyeball member 30 in the yaw and pitch directions. Note that Figures 7A to 7C are simplified schematic diagrams to explain why ball joints are used in the mechanism for tilting the eyeball member 30 in the yaw and pitch directions, and the specific mechanism differs from that of the present embodiment shown in Figures 1 to 6.

[0025] Fig. 7A shows the eyeball member in the basic position as viewed from above, and the eyeball member tilted in the yaw direction as viewed from above. Fig. 7B shows the eyeball member in the basic position as viewed from the right, and the eyeball member tilted in the yaw direction as viewed from the right. Fig. 7C shows the eyeball member tilted in the yaw and pitch directions as viewed from the right.

[0026] As shown in Fig. 7A, in order to allow the eyeball member 30 to rotate in the yaw direction, at least a portion of each joint of the link mechanism must be rotatable in the yaw direction. Also, as shown in Fig. 7B, in order to allow the eyeball member 30 to rotate in the pitch direction, at least a portion of each joint of the link mechanism must be rotatable in the pitch direction. Therefore, in order to allow the eyeball member 30 to rotate in two directions, the yaw direction and the pitch direction, it is necessary to include a joint J1 that allows rotation in both the yaw direction and the pitch direction, as shown in Fig. 7C.

[0027] Therefore, the drive mechanism 1 of this embodiment employs a configuration in which the first operating link 11 and the first driving link 12 are connected via a joint J1 including a ball joint. Specifically, a ball joint is provided on the right side of the first driving link 12, and a holder for holding the ball joint is provided on the rear side of the first operating link 11. This makes it possible to tilt the eyeball member 30 in two directions, the yaw direction and the pitch direction, while avoiding interference between the links.

[0028] [Wobble Suppression: First Additional Link and First Elastic Spring] Next, a mechanism for suppressing wobble in the drive mechanism 1 will be described with reference mainly to Fig. 3 and Fig. 8. Fig. 8 is a schematic diagram for explaining the mechanism for suppressing wobble in the drive mechanism. Note that Fig. 8 is a schematic diagram corresponding to the top view shown in Fig. 3, and shows a state in which the eyeball member 30 is tilted in the yaw direction.

[0029] As described above, this embodiment employs a configuration in which the first operating link 11 and the first drive link 12 are connected via a joint J1 including a ball joint. In a configuration employing a ball joint, rattle may occur due to a gap between the ball joint and a holder that holds the ball joint. In particular, for small mechanisms, a resin ball joint may be used due to ease of molding. Resin ball joints are more susceptible to rattle problems than highly rigid metal ball joints.

[0030] Therefore, in this embodiment, a configuration is adopted to suppress rattle in the joint part J1 including a resin ball joint. Specifically, in addition to the above-mentioned configuration, the first link mechanism is configured to include a first additional link 13 and a first elastic spring 40 as a first biasing member.

[0031] The first additional link 13 is supported rotatably around an axis O3 extending in the vertical direction. The first additional link 13 may be rotatably supported via a joint J3 on a support base included in the drive mechanism 1. The joint J3 may be composed of, for example, a round hole formed in the first additional link and a support shaft formed on the fixed base that is inserted into the round hole.

[0032] The first additional link 13 has a lower portion rotatably supported via a joint J4 relative to the first operating link 11. The joint J4 is disposed between the joint J1 and the eyeball member 30. For example, the joint J4 may be configured with a long hole formed in the right portion of the first additional link 13, and a support shaft formed in the first operating link 11 that is inserted into the long hole.

[0033] The first elastic spring 40 is connected to the left portion of the first driving link 12 and the left portion of the first additional link 13. For example, the rear portion of the first elastic spring 40 may be hooked onto a protrusion P1 provided on the left portion of the first driving link 12, thereby connecting the first driving link 12. Furthermore, for example, the front portion of the first elastic spring 40 may be hooked onto a protrusion P2 provided on the left portion of the first additional link 13, thereby connecting the first elastic spring 40 to the first additional link 13.

[0034] The first elastic spring 40 elastically urges the left portion of the first additional link 13 rearward with its elastic force. Therefore, the first additional link 13 is urged in the counterclockwise direction in FIG. 8 around the axis O3 as the center of rotation. As a result, the lower portion of the first additional link 13 is urged forward. As a result, a forward urging force F1 acts on the joint part J1 including the ball joint. Therefore, the occurrence of rattle in the joint part J1 caused by a gap between the ball joint and the holding part that holds it is suppressed.

[0035] The first operating link 11, the first elastic spring 40, the first driving link 12, and the first additional link 13 form a so-called four-bar parallel link. Therefore, the length between the protrusions P1 and P2 is the same as the length between the joints J1 and J4, and is invariable. In other words, the first elastic spring 40 is designed to maintain the same length, always generating a constant elastic force. Therefore, the first elastic spring 40 applies a constant biasing force F1 to the joint J1, including the ball joint, regardless of the position of the eyeball member 30, i.e., regardless of the rotation angle of the actuator 80.

[0036] [Suppression of rattle: second additional link and second elastic spring] Furthermore, as shown in Figures 3, 8, etc., the first link mechanism employs a configuration including, in addition to the above-mentioned configuration, a second additional link 14 and a second elastic spring 50 which is a second biasing member.

[0037] The second additional link 14 is supported rotatably relative to the fixed link 210, with an axis O4 extending in the up-down direction as the center of rotation. The fixed link 210 is a stationary link that extends in the front-to-rear direction. The second additional link 14 and the fixed link 210 are connected via a joint J6 that includes a ball joint. Specifically, it is preferable that a ball joint is provided in the fixed link 210, and that a holding part that holds the ball joint is provided in the second additional link 14.

[0038] The right part of the second additional link 14 is rotatably supported via a joint part J5 relative to the first operating link 11. For example, the joint part J5 may be configured with an elongated hole formed in the right part of the second additional link 14, and a support shaft formed in the first operating link 11 that is inserted into the elongated hole.

[0039] The second elastic spring 50 is connected to the left part of the eyeball member 30 and the left part of the second additional link 14. For example, the rear part of the second elastic spring 50 may be hooked onto a protrusion P3 provided on the left part of the second additional link 14, thereby connecting the second elastic spring 50 to the second additional link 14. The front part of the second elastic spring 50 may be attached to an attachment part P4 provided on the left part of the eyeball member 30, thereby connecting the second elastic spring 50 to the eyeball member 30.

[0040] 8, the second elastic spring 50 elastically biases the left portion of the eyeball member 30 rearward with its elastic force. As a result, a rearward biasing force F2 acts on the eyeball member 30. Therefore, rattle of the eyeball member 30 around the yaw axis is suppressed.

[0041] Furthermore, the second elastic spring 50 elastically biases the left portion of the second additional link 14 forward with its elastic force. As a result, a biasing force F3 acts forward on the joint J6. Therefore, rattles at the joint J6 caused by a gap between the ball joint and the holding portion that holds it are suppressed.

[0042] The first operating link 11, the second elastic spring 50, the second additional link 14, and the eyeball member 30 form a so-called four-bar parallel link. Therefore, the length between the protrusion P3 and the attachment point P4 is constant. That is, the second elastic spring 50 is provided to maintain the same length, always generating a constant elastic force. Therefore, regardless of the posture of the eyeball member 30, i.e., regardless of the rotation angle of the actuator 80, the second elastic spring 50 applies a constant biasing force F2 to the eyeball member 30 and a constant biasing force F3 to the joint J6, which includes a ball joint.

[0043] [Suppression of rattle: third additional link and third elastic spring] Furthermore, as shown in Figure 5 etc., in the second link mechanism, in addition to the above-mentioned configuration, a configuration including a third additional link 23 and a third elastic spring 60 which is a third biasing member is adopted.

[0044] The third additional link 23 is supported to be rotatable relative to the fixed link 210 (see FIG. 6; in FIG. 5, it is disposed behind the first operating link 11) around an axis O5 extending in the left-right direction as the center of rotation. Furthermore, the third additional link 23 has an upper portion rotatably supported relative to the second operating link 21 via a joint J7. For example, the joint J7 may be composed of an elongated hole formed in the upper portion of the third additional link 23 and a support shaft formed in the second operating link 21 that is inserted into the elongated hole.

[0045] The third elastic spring 60 is connected to the lower part of the eyeball member 30 and the lower part of the third additional link 23. For example, the third elastic spring 60 may be connected to the third additional link 23 by having its rear part hooked onto a protrusion P5 provided on the lower part of the third additional link 23. The third elastic spring 60 may also be connected to the eyeball member 30 by having its front part attached to an attachment part (not shown) provided on the lower part of the eyeball member 30.

[0046] The third elastic spring 60 biases the lower part of the eyeball member 30 rearward with its elastic force, thereby suppressing rattle of the eyeball member 30 around the pitch axis. Furthermore, by using the third spring 60 and the second elastic spring 50, which suppresses rattle of the eyeball member 30 around the yaw axis, it is possible to suppress rattle of the eyeball member 30 in both directions around the yaw axis and the pitch axis.

[0047] [Summary] In the drive mechanism 1 according to the present embodiment described above, by suppressing rattle, it is possible to improve the accuracy of angle control of each link. As a result, it is possible to move the eyeball member 30, which is the object of movement, with high accuracy. In particular, the mechanism according to the present embodiment is effective in cases where rattle is likely to occur in the joints when the power from the power source is increased.

[0048] In the present embodiment, the eyeball member 30 has been described as an example of the object to be moved, but the present invention is not limited to this. The object to be moved may be any other part of a robot that imitates a human or another animal. For example, the object to be moved may be a member that imitates a human ankle or wrist, and the drive mechanism 1 may control the movement of the joint.

[0049] In addition, in this embodiment, an example has been described in which the link mechanism has a joint portion including a ball joint, but this is not limited to this, and the joint portion may have another configuration as long as it has a structure that allows rotation in two axial directions. Furthermore, the material that makes up the ball joint is not limited to resin.

[0050] In addition, in this embodiment, an example is shown in which the first link mechanism and the second link mechanism are arranged so as to be perpendicular to each other, but this is not limited to this, and it is sufficient if these mechanisms are arranged so as to intersect with each other.

[0051] In addition, in this embodiment, an elastic spring that is a coil spring has been used as an example of a biasing member, but this is not limited to this, and other members or mechanisms may be used as long as they bias the joint portion or the eyeball member 30.

[0052] The yaw axis and pitch axis shown in this embodiment are merely examples, and the drive mechanism 1 may be a mechanism that controls movement in two axes around the roll axis as the center of rotation.

[0053] [Note] For example, the drive mechanism may have the following configuration: (1) A drive mechanism including a first link mechanism for tilting an object to be moved about a first axis as a rotation center, and a second link mechanism for tilting the object to be moved about a second axis intersecting the first axis as a rotation center, wherein the first link mechanism includes: a first joint portion that connects two links to each other and allows the object to be moved about each of the first axis and the second axis as a rotation center, and a first biasing member that biases either a holding portion included in one of the two links or a held portion held by the holding portion included in the other link, toward the other. (2) The drive mechanism described in (1), wherein the held portion is a ball joint, and the first biasing member is provided to bias either the ball joint or the holding portion toward the other. (3) The drive mechanism according to (1) or (2), wherein the first link mechanism includes: a first operating link connected to the object to be moved and operating the object to be moved, a first drive link connected to the first operating link via the first joint portion and driven by power from a first power source, and a first additional link connected to the operating link between the first joint portion and the object to be moved, and the first biasing member is an elastic spring having one end connected to the first drive link and the other end connected to the first additional link. (4) The drive mechanism according to (3), wherein the first link mechanism includes: a second additional link connected to the first operating link between the first additional link and the object to be moved, and an elastic spring as a second biasing member having one end connected to the second additional link and the other end connected to the object to be moved.(5) The drive mechanism according to (4), wherein the second link mechanism includes: a second operating link connected to the object to be moved and operating the object to be moved, a second drive link connected to the second operating link and driven by power from a second power source, a third additional link connected to the second operating link between the second drive link and the object to be moved, and an elastic spring as a third biasing member having one end connected to the third additional link and the other end connected to the object to be moved. (6) The drive mechanism according to (5), wherein the second biasing member is connected to the object to bias the object to rotate either around the first axis or the second axis, and the third biasing member is connected to the object to bias the object to rotate either around the first axis or the second axis.

Claims

1. A drive mechanism including a first link mechanism for tilting an object to be moved around a first axis as a center of rotation, and a second link mechanism for tilting the object to be moved around a second axis intersecting the first axis as a center of rotation, wherein the first link mechanism includes: a first joint portion that connects two links to each other and allows the object to be moved around each of the first axis and the second axis as a center of rotation, and a first biasing member that biases either a holding portion held by one of the two links or a held portion held by the holding portion held by the other link, against the other.

2. The drive mechanism according to claim 1, wherein the held portion is a ball joint, and the first biasing member is arranged to bias either the ball joint or the holding portion against the other.

3. The drive mechanism according to claim 1 or 2, wherein the first link mechanism includes: a first operating link connected to the object to be moved and operating the object to be moved; a first driving link connected to the first operating link via the first joint portion and driven by power from a first power source; and a first additional link connected to the operating link between the first joint portion and the object to be moved; and the first biasing member is an elastic spring having one end connected to the first driving link and the other end connected to the first additional link.

4. A drive mechanism as described in claim 3, wherein the first link mechanism includes: a second additional link connected to the first operating link between the first additional link and the object to be moved; and a second biasing member, an elastic spring, having one end connected to the second additional link and the other end connected to the object to be moved.

5. The drive mechanism according to claim 4, wherein the second link mechanism includes: a second operating link connected to the object to be moved and operating the object to be moved; a second drive link connected to the second operating link and driven by power from a second power source; a third additional link connected to the second operating link between the second drive link and the object to be moved; and an elastic spring which is a third biasing member having one end connected to the third additional link and the other end connected to the object to be moved.

6. A drive mechanism as described in claim 5, wherein the second biasing member is connected to the object to be moved so as to bias the object to move in one of the directions around the first axis or the second axis, and the third biasing member is connected to the object to be moved so as to bias the object to the other direction of the direction around the first axis or the second axis.

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