JP2018094643A - Power transmission mechanism and robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a rotation angle error of an output shaft.SOLUTION: A power transmission device includes: a pinion gear (26a) connected to a rotation shaft of a drive motor (26); a gear (27c) connected to an output shaft (29), having the number of teeth larger than that of the pinion gear (26a) and rotating in conjunction with the pinion gear (26a) directly or via an intermediate gear; and a rotation angle sensor (28) for detecting a rotation angle of the pinion gear (26a).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power transmission mechanism that controls rotation of an output shaft by transmission of power from a drive motor, and a robot in which the power transmission mechanism is provided at a predetermined joint.

  Conventionally, when a humanoid or animal type robot toy (hereinafter simply referred to as “robot”) performs various movements, each structure such as two arms (arms) or two legs (legs) via joints. The rotation angle between them is changed. In other words, the robot is controlled to be freely rotatable by a plurality of rotation shafts having a plurality of rigid structures such as a head (head), a neck (neck), a torso (body), an arm, and a leg as joints. To have a desired posture. And a drive mechanism is built in structures, such as an arm or a leg. Patent Document 1 discloses a robot toy in which a deceleration drive mechanism is incorporated in the structure as described above.

  FIG. 7A shows a close-up of the arms 121 and 123 and the joints 122 of the conventional robot toy. As shown in the figure, a reduction driving mechanism 120 including a driving motor 126 for generating power is provided on the arm 123 which is one of two arms 121 and 123 connected by an output shaft 129 serving as a rotating shaft. Yes.

  The reduction drive mechanism 120 monitors the state of the reduction gear train 127 and the arms 121 and 123 that generate torque force by reducing the rotational force of the drive motor 126 to a desired number of rotations, and obtains angle information that changes with the operation. Rotation angle sensor 128 and the like. Then, while monitoring the angle information, the angle between the two arms is changed at a predetermined speed based on the next operation instruction to perform a desired operation.

  FIG. 7B shows the internal structure of the arm 123 shown in FIG. The rotation angle sensor 128 described above is provided on the same axis as the output shaft 129 of the gear 127c, and detects the rotation angle of the gear 127c. The rotation angle sensor 128 includes a magnetic body and a magnetic sensor.

JP 2006-337206 A (released on December 14, 2006)

  However, the above-described prior art has a problem that the detection accuracy of the angle information of the gear 127c depends on the detection accuracy of the rotation angle sensor 128 itself on the same axis and the individual variation, resulting in a certain error. This error affects the rotation angle adjustment of the gear 127c, and an error also occurs in the rotation angles of the arms 121 and 123. More specifically, when the detection error of the rotation angle sensor 128 is assumed to be 1 °, the angle error (shift amount) between the gear 127c and the arms 121 and 123 on the same axis is also 1 °. Therefore, a measure for reducing the rotation angle error of the gear 127c is required.

  The present invention has been made in view of the above problems, and an object thereof is to realize a power transmission mechanism and the like that can reduce a rotation angle error of an output shaft.

  In order to solve the above problem, a power transmission mechanism according to an aspect of the present invention is a power transmission mechanism that controls rotation of an output shaft by transmission of power from a drive motor, and is coupled to the rotation shaft of the drive motor. The first gear and the second gear connected to the output shaft and having a larger number of teeth than the first gear and rotating in conjunction with the first gear directly or via an intermediate gear And a rotation angle detector for detecting the rotation angle of the first gear.

  According to the power transmission mechanism of one aspect of the present invention, there is an effect that the rotation angle error of the output shaft can be reduced.

(A) is a figure which shows the structure of the joint of the front leg concerning Embodiment 1 of this invention, (b) is a figure which shows the internal structure (power transmission mechanism) of the 2nd arm 23 shown to (a). is there. It is a figure which shows schematic structure of the robot which concerns on one Embodiment of this invention. It is a flowchart which shows the flow of operation | movement in the power transmission mechanism which concerns on the said Embodiment 1. FIG. (A) is a figure which shows the structure of the joint of the front leg concerning Embodiment 2 of this invention, (b) is a figure which shows the internal structure (power transmission mechanism) of the 2nd arm 23 shown to (a). is there. (A) is a figure which shows the structure of the joint of the front leg concerning Embodiment 3 of this invention, (b) is a figure which shows the internal structure (power transmission mechanism) of the 2nd arm 23 shown to (a). is there. It is a flowchart which shows the flow of operation | movement in the power transmission mechanism which concerns on the said Embodiment 3. FIG. (A) is a figure which shows the structure of the joint of the front leg in the conventional robot, (b) is a figure which shows the internal structure of the arm 123 shown to (a).

  The embodiment of the present invention will be described with reference to FIGS. Hereinafter, for convenience of explanation, components having the same functions as those described in the specific items may be denoted by the same reference numerals and description thereof may be omitted.

[Robot outline configuration]
First, a schematic configuration of a robot according to an embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of the robot. As shown in the figure, the robot is a four-legged walking robot that imitates an animal walking on four legs, such as a dog or a cat. In this embodiment, a case where a quadruped walking robot is adopted as an example of a robot to which the present invention can be applied will be described. However, the type of robot is not limited to this, and biped walking imitating a person. The present invention can also be applied to a robot of the type. Further, the present invention can be widely applied to robots having rotating joints, such as robots that imitate only the upper body of humans, and industrial robots that are configured by only arms and perform work. However, the application range of the present invention is not particularly limited to the joint portion of the robot, but can be applied to other portions that transmit the power of the robot, and also to the power transmission mechanism of equipment other than the robot.

  As shown in the figure, the robot of the present embodiment includes a head 10, a neck 11, a body 12, a neck joint 13, a front leg first joint 14, a rear leg first joint 15, a first arm 21, and a front leg second joint. (Joint portion) 22, second arm 23, first leg 31, rear leg second joint 32, and second leg 33. The robot of this embodiment calculates the joint state (rotation angle) in a desired posture with respect to the current joint state (rotation angle), and rotates a plurality of joints at a predetermined speed to the desired state. This is done by driving.

Embodiment 1
Next, the structure of the power transmission mechanism according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1A is a view showing the structure of the joint of the front leg according to Embodiment 1 of the present invention. FIG. 1B is a diagram showing the internal structure (power transmission mechanism) of the second arm 23 shown in FIG.

  In order to change the angle formed by the first arm 21 and the second arm 23, the front leg second joint 22 of the present embodiment shown in FIG. A power transmission mechanism including a gear (second gear) 27c, a rotation angle sensor (rotation angle detector) 28, and the like is incorporated. And it is comprised so that the 2nd arm 23 may rotate relatively with respect to the 1st arm 21 with which the output shaft 29 of the gear 27c is engaged. The power transmission mechanism of the present embodiment is a power transmission mechanism related to the joint portion of the robot that controls the rotation of the output shaft 29 by transmitting the power of the drive motor 26.

  In the robot according to the embodiment of the present invention, the above-described neck joint 13, the first front leg joint 14, the second front leg joint 22, the first rear leg joint 15, and the second rear leg joint 32 are illustrated in FIG. The power transmission mechanism as shown in (a) is incorporated and driven to rotate, whereby the posture of the robot can be changed to a desired state.

  In the present embodiment, a description will be given assuming that a front leg second joint 22 that is rotatable about one axis is provided between the first arm 21 and the second arm 23. Another power transmission mechanism may be provided so as to have a rotation axis orthogonal to the axis of the joint 22 so as to increase the degree of freedom of the posture between the first arm 21 and the second arm 23.

  Next, the power transmission mechanism of the present embodiment is connected to a pinion gear (first gear) 26 a connected to the rotation shaft of the drive motor 26 and an output shaft 29 as shown in FIG. The pinion gear 26a includes a gear 27c that has more teeth than the pinion gear 26a and rotates in conjunction with the pinion gear 26a that directly meshes with the gear, and further includes a rotation angle sensor 28 that detects the rotation angle of the pinion gear 26a. ing. The pinion gear 26a is composed of a small-diameter circular gear, and the gear 27c is composed of a large-diameter spur gear.

  A drive motor 26 for generating power is coaxially provided in the second arm 23, which is one of the two first arms 21 and the second arm 23 connected by an output shaft 29 serving as a rotation shaft in the front leg second joint 22. A pinion gear 26a disposed on the top is provided. In order to reduce the rotational force of the pinion gear 26a (drive motor 26) to a desired rotational speed and generate a torque force, the power transmission mechanism of this embodiment is configured by directly meshing the gears of the pinion gear 26a and the gear 27c. Has been. The rotation angle sensor 28 is coaxially connected to the D-shaped engagement shaft portion 27d arranged coaxially with the pinion gear 26a, and monitors rotation angle information of the pinion gear 26a.

  The rotation angle sensor 28 includes a magnetized magnetic body and a magnetic sensor that detects a change in magnetic flux associated with the rotation of the magnetic body as a change in voltage. Moreover, the magnetic sensor is comprised from magnetic detection elements, such as a Hall element which outputs the change of magnetic flux as a change of voltage, for example. Further, the processing unit 50 is connected to each of the rotation angle sensor 28 and the drive motor 26. The processing unit 50 has a function of processing the detection result of the rotation angle sensor 28, a function of controlling driving of the drive motor 26, and the like.

  The structure of the power transmission mechanism of this embodiment is provided with a rotation angle sensor 28 for detecting the rotation angle of the pinion gear 26a connected to the rotation shaft of the drive motor 26, not the gear 27c connected to the output shaft 29. This is different from the structure of the conventional power transmission mechanism shown in FIG. In other words, the power transmission mechanism of the present embodiment does not monitor the rotation angle of the gear 27c related to the rotation of the output shaft 29 that directly contributes to the rotation angles of the first arm 21 and the second arm 23, but the gear 27c. This is different from the prior art in that the rotation angle of the pinion gear 26a associated with the rotation of the drive motor 26, which has a smaller number of teeth, is monitored.

  In the power transmission mechanism shown in FIG. 2B, when the pinion gear 26a is rotated at an arbitrary angle, the gear 27c rotates by an angle obtained by multiplying the rotation angle by the gear ratio. Expressed by the equation, “the number of teeth of the pinion gear 26a: the number of teeth of the gear 27c = the rotation angle of the gear 27c: the rotation angle of the pinion gear 26a” is expressed by equation (1).

  The processing unit 50 adjusts the rotation angle of the pinion gear 26a (the rotation angle of the drive motor 26) using the rotation angle of the pinion gear 26a detected by the rotation angle sensor 28 connected coaxially with the pinion gear 26a. For this reason, for example, when it is assumed that the detection error of the rotation angle sensor 28 is 1 °, for example, the adjustment angle of the pinion gear 26a is shifted (rotates) by 1 ° with respect to the original target angle, but the gear 27c The angle error (shift amount) is “angle error of gear 27c = (number of teeth of pinion gear 26a ÷ number of teeth of gear 27c) × 1 °” according to the above equation (1).

  As a premise, since the number of teeth of the pinion gear 26a <the number of teeth of the gear 27c, the angle error of the gear 27c is reduced from 1 ° (the angle error of the pinion gear 26a), and the accuracy of the rotation angle adjustment of the gear 27c is the gear ratio. It will be higher by As a result, it is possible to reduce the error of the rotation angle of the first arm 21 and the second arm 23 shown in FIG.

(Effect of power transmission mechanism)
According to the power transmission mechanism described above, the pinion gear 26 a is connected to the rotation shaft of the drive motor 26, and the gear 27 c is connected to the output shaft 29. Further, the gear 27c has more teeth than the pinion gear 26a. Further, the rotation angle sensor 28 detects the rotation angle of the pinion gear 26a. Thereby, the rotation angle error of the output shaft 29 becomes smaller by the gear ratio related to the pinion gear 26a and the gear 27c than the rotation angle error of the pinion gear 26a detected by the rotation angle sensor 28. For this reason, the rotation angle error of the output shaft 29 can be reduced.

(Operation of power transmission mechanism)
Next, based on FIG. 3, the flow of operation | movement of the power transmission mechanism of this embodiment is demonstrated. FIG. 3 is a flowchart showing an operation flow in the power transmission mechanism. In step S (hereinafter, “step” is omitted) 11, the processing unit 50 detects the current angular position of the pinion gear 26a from the rotation angle sensor 28 and proceeds to S12. In S12, the current angular position of the gear 27c is calculated from the result in S11 as follows, and the process proceeds to S13. Since the above formula (1) is satisfied as a premise, the angular position of the gear 27c is “angular position of the gear 27c = (number of teeth of the pinion gear 26a ÷ number of teeth of the gear 27c) × angular position of the pinion gear 26a”. -It can calculate with Formula (2).

  In S13, the processing unit 50 determines how to move the front leg second joint 22 shown in FIG. 2A, determines to which angular position the gear 27c is rotated, and proceeds to S14. In S14, the processor 50 calculates the target angular position of the pinion gear 26a by substituting the angular position determined in S13 into the expression (2) of S12, and proceeds to S15.

  In S15, the processing unit 50 inputs the result of S11 (the current angular position of the pinion gear 26a) and the result of S14 (the target angular position of the pinion gear 26a) to the drive motor 26, and the process proceeds to S16. In S16, the drive motor 26 sets a control parameter based on the input data in S15, and proceeds to S17. Here, the control parameter is a parameter for driving the drive motor 26 based on the result calculated by the processing unit 50. Although the types of control parameters differ depending on the motor driving method, specifically, examples of the control parameters include a drive voltage, a drive current, and a pulse signal. Further, the time and timing for driving with the control parameters can be included as control parameters.

  In S17, the rotation of the drive motor 26 is started and the process proceeds to S18. In S18, the angular position of the pinion gear 26a is detected by the rotation angle sensor 28, and the process proceeds to S19. In S19, the processing unit 50 confirms whether the pinion gear 26a has reached the target angular position. As a result, when the pinion gear 26a has not reached the target angular position (No), the process returns to S18.

  On the other hand, if the pinion gear 26a has reached the target angular position (YES), the process proceeds to S20. Here, the routines of S18 and S19 are repeated until the pinion gear 26a reaches the target angular position. In S20, the processing unit 50 stops the rotation of the drive motor 26 and becomes END.

  When the pinion gear 26a is rotated at an arbitrary angle, the gear 27c rotates by an angle obtained by multiplying the rotation angle by the gear ratio. This is expressed by the above equation (1). Using the rotation angle of the pinion gear 26a detected by the rotation angle sensor 28, the processing unit 50 adjusts the angular position of the pinion gear 26a (the angular position of the drive motor 26).

  Here, since the rotation angle sensor 28 has a certain detection error, a certain detection error (deviation amount) occurs in the angular position of the pinion gear 26a in S11 and S18 of FIG. When this amount of displacement is replaced with the “rotation angle” of the above equation (2), the equation is as follows: “deviation amount of gear 27c = (number of teeth of pinion gear 26a ÷ number of teeth of gear 27c) × deviation of pinion gear 26a” “Amount”: Equation (3).

  For example, assuming that the detection error of the rotation angle sensor 28 (deviation amount of the pinion gear 26a) is 2 °, the number of teeth of the pinion gear 26a is 30, and the number of teeth of the gear 27c is 60, the deviation of the gear 27c is obtained from the above equation (3). The amount is 1 °. Thereby, in the conventional technique, the detection error of the rotation angle sensor 28 is directly reflected in the shift amount of the gear 27c. However, in the power transmission mechanism of the present embodiment, the shift amount of the gear 27c is reduced (in the above example, 2). From 1 ° to 1 °).

(Supplementary information)
The power transmission mechanism of the present embodiment can be realized by any of the above-described gear types of parallel axes, intersecting axes, and staggered axes. However, the shape of each gear must be circular, and cannot be realized with a non-circular gear such as an ellipse or a rack (changes rotational motion to linear motion). In the power transmission mechanism composed of three or more gears, there is no problem even if the middle stage gears except the first stage and the last stage have a rack shape (linear gear). In addition, the power transmission mechanism according to one embodiment of the present invention cannot be realized by the speed increasing drive mechanism (a method of obtaining a speed by reducing torque).

  Next, the type of the rotation angle sensor 28 must be able to know the absolute angle even when the gear to be detected is stationary. For example, an incremental rotary encoder is a counting measurement method that outputs pulses corresponding to the rotation angle only during rotation and integrates pulses from the measurement start point, but it cannot be used, but an absolute rotary encoder rotates regardless of whether or not it rotates. Since the signal of the position according to an angle is output with a code | cord, it can employ | adopt. It can also be realized with a magnetic sensor or a rotary potentiometer.

[Embodiment 2]
Next, the structure of the power transmission mechanism according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4A is a view showing the structure of the joint of the front leg according to Embodiment 2 of the present invention. On the other hand, FIG. 4B is a diagram showing an internal structure (power transmission mechanism) of the second arm 23 shown in FIG.

  In the first embodiment described above, the gear 27c and the pinion gear 26a are directly meshed with each other. However, the present embodiment is different in that a gear (intermediate gear) 27a and a gear (intermediate gear) 27b are incorporated therebetween. . In the present embodiment, the number of intermediate gears interposed between the pinion gear 26a and the gear 27c is two, but the number of intermediate gears is not limited to this. The number of intermediate gears may be set to an appropriate number in consideration of an improvement in the deceleration rate within a range where the size of the power transmission mechanism does not become too large.

  According to the above configuration, the driving force by the drive motor 26 is transmitted one after another from the pinion gear 26a to the gear 27a, the gear 27b, and the gear 27c and decelerated, and the rotation shaft of the final gear 27c is used as the power transmission mechanism. Output shaft 29.

  The gear 27a includes an input-side gear 271a that receives transmission of power from the preceding gear, and an output-side gear 272a that has fewer teeth than the input-side gear 271a and sends the power received by the input-side gear 271a to the subsequent-stage gear. Is an integrated gear. The front gear is a gear on the power generation source side, and the rear gear is a gear on the power output side.

  The gear 27b includes an input side gear 271b that receives transmission of power from the preceding gear, and an output side gear that has fewer teeth than the input side gear 271b and sends the power received by the input side gear 271b to the subsequent gear. 272b is an integrated gear. Since these gears are used as intermediate gears, the power transmission mechanism of this embodiment is a mechanism with a very good reduction rate.

  In general, when a motor is used for a joint of a robot, the rotation angle range is narrow within 360 degrees, and it is often necessary to increase the driving torque. However, there may be cases where sufficient deceleration cannot be secured due to problems such as cost and space. In that sense, in this embodiment, the gear 27a and the gear 27b are added to improve the deceleration rate.

  In the power transmission mechanism of the present embodiment, as shown in FIG. 4B, the large and small spur gears provided on the gear 27a and the gear 27b are alternately arranged, and the gear 27a and the gear 27b are arranged. And the space | interval of the rotation bearing of the gear 27c is made small, and it can be made thin.

  The equation (2) described in the first embodiment is obtained as follows in the present embodiment. First, the number of teeth of the input gear (input side gear) of each gear and the number of teeth of the output gear (output side gear) are symbolized as shown in Table 1 below. For example, the number of teeth of the pinion gear 26a is symbolized as “26ao”. Here, the symbol “o” at the end indicates an output, and the symbol “i” indicates an input.

  Then, the angular position of the gear 27c is calculated by “the angular position of the gear 27c = (26ao ÷ 27ai) × (27ao ÷ 27bi) × (27bo ÷ 27ci) × the angular position of the pinion gear 26a” ”(4). It is done.

(Operation of power transmission mechanism)
The operation of the power transmission mechanism of the present embodiment is generally the same as the operation described in FIG. 3 of the first embodiment, but the equation (2) used in S12 and S14 of the first embodiment is the above equation (4). You can replace it with.

(Effect of power transmission mechanism)
In the present embodiment, the above-described formula (3) of the first embodiment is replaced by the following formula (5). Refer to Table 1 for the meaning of the following symbols. The shift amount of the gear 27c is “shift amount of the gear 27c = (26ao ÷ 27ai) × (27ao ÷ 27bi) × (27bo ÷ 27ci) × shift amount of the pinion gear 26a” (5).

  According to the power transmission mechanism of the present embodiment described above, since the intermediate gears (the gear 27a and the gear 27b) are interposed between the pinion gear 26a and the gear 27c, the pinion gear 26a and the gear 27c in the first embodiment The speed reduction rate can be improved as compared with the case where these are directly meshed.

[Embodiment 3]
Next, the structure of the power transmission mechanism according to the third embodiment of the present invention will be described with reference to FIG. FIG. 5A is a view showing the structure of the joint of the front leg according to Embodiment 3 of the present invention. On the other hand, FIG. 5B is a diagram showing the internal structure (power transmission mechanism) of the second arm 23 shown in FIG.

  In the first and second embodiments described above, there are practical problems described below depending on circumstances. In this embodiment, a new configuration (see a rotation angle sensor 30 described later) is added to the power transmission mechanism of the second embodiment. doing. The above problem will be described based on the power transmission mechanism of the second embodiment.

  In the power transmission mechanism of the second embodiment, as shown in FIG. 4B, each of the pinion gear 26a, the gear 27a, the gear 27b, and the gear 27c constitutes a power transmission mechanism in which the number of gear teeth is different from each other. doing. Therefore, if the total gear ratio from the pinion gear 26a to the gear 27c is four times, the pinion gear 26a needs to be rotated four times in order to rotate the gear 27c once. The problem here is that the rotation angle sensor 28 can detect the angular position of the pinion gear 26a within a rotation angle range of 360 °. However, the rotation angle sensor itself is in what rotation number, that is, 0 °, 360 °. , 720 °, 1080 °, and 1440 ° cannot be grasped. With this, the gear 27c cannot be rotated to the target angle.

  In the present embodiment, a rotation angle sensor (rotational speed detection unit) 30 is provided on the gear 27c side in order to solve the above problem. Specifically, as shown in FIG. 5B, a D-shaped engagement shaft portion 27e is arranged coaxially with the gear 27c, and the rotation angle sensor 30 is also connected coaxially. In the present embodiment, the processing unit 50 is connected to each of the rotation angle sensor 28, the rotation angle sensor 30, and the drive motor 26.

  The processing unit 50 specifies how many positions the pinion gear 26a has rotated based on the rotation angle of the gear 27c detected by the rotation angle sensor 30 and the total gear ratio from the pinion gear 26a to the gear 27a. As a result, the rotation position of the pinion gear 26a can be grasped by directly detecting the angular position of the gear 27c. In other words, according to the power transmission mechanism of this embodiment, the rotation angle sensor 30 is installed to detect how many times the pinion gear 26a has rotated (the number of rotations of the pinion gear 26a).

(Operation of power transmission mechanism)
The operation of the power transmission mechanism of the present embodiment is substantially the same as the operation described with reference to FIG. 3 of the first embodiment, but the rotational speed of the pinion gear 26a is detected by the rotation angle sensor 30 in S118 (pinion gear 26a And the angle position of the pinion gear 26a is detected by the rotation angle sensor 28 in S119. The operations from S111 to S117 are the same as the operations from S11 to S17 described in FIG. The operations in S120 and S121 are the same as the operations in S19 and S20 described with reference to FIG. The formula (2) used in the first embodiment may be replaced with the formula (4) described in the second embodiment.

(Effect of power transmission mechanism)
The equation (3) of the first embodiment described above may be replaced with the equation (5) described in the second embodiment. That is, the shift amount of the gear 27c can be obtained by “the shift amount of the gear 27c = (26ao ÷ 27ai) × (27ao ÷ 27bi) × (27bo ÷ 27ci) × the shift amount of the pinion gear 26a”. Refer to Table 1 for the meaning of the above symbols.

  According to the power transmission mechanism of the present embodiment, the rotation angle sensor 30 can detect how many times the pinion gear 26a has rotated (the number of rotations of the pinion gear 26a).

(Supplementary information)
A problem in the angle control of the joint portion of the robot as in the present embodiment is the origin movement at the time of power activation. When the power supply of the robot is activated, the joint portion needs to move to a predetermined origin angle. If the robot is activated, the rotation speed of the pinion gear 26a can be stored in a predetermined storage unit (not shown). However, once the power is turned off, the joint portion can be freely rotated manually. no longer know what is rotated to any angle position for. For this reason, when the power is turned on, it is necessary to detect the current absolute angle of the gear 27c in a stationary state before rotating the joint portion.

  Therefore, in the present embodiment, the rotation angle sensor 30 that can detect the rotation angle of the gear 27c is arranged coaxially with the gear 27c. Since the rotation angle sensor 30 only needs to detect how many times the pinion gear 26a has rotated (the number of rotations of the pinion gear 26a), the rotation angle sensor 30 is more accurate than the rotation angle sensor 28 arranged coaxially with the pinion gear 26a. Even if it is low, it does not affect the overall detection accuracy.

  For example, if the total gear ratio from the pinion gear 26a to the gear 27c is four times as in the power transmission mechanism of the present embodiment, the rotation angle sensor 30 is in any range of 360 ° divided into four ranges. If there is an accuracy capable of detecting only the position, the final rotational position of the output shaft 29 can be detected, and the accuracy is not shown by the accuracy of the rotation angle sensor 30, but the calculation represented by the above equation (5). According to the formula.

[Summary]
The power transmission mechanism according to aspect 1 of the present invention is a power transmission mechanism that controls the rotation of the output shaft (29) by transmission of power from the drive motor (26), and is a first power transmission mechanism coupled to the rotation shaft of the drive motor. The first gear (pinion gear 26a) and the second gear connected to the output shaft have a larger number of teeth than the first gear and rotate in conjunction with the first gear directly or via an intermediate gear. And a rotation angle detector (rotation angle sensor 28) for detecting the rotation angle of the first gear.

  According to the above configuration, the first gear is connected to the rotation shaft of the drive motor, and the second gear is connected to the output shaft. The number of teeth of the second gear is larger than that of the first gear. Furthermore, the rotation angle detector detects the rotation angle of the first gear. Thereby, the rotation angle error of the output shaft is compared with the error of the rotation angle of the first gear detected by the rotation angle detection unit, or the gear ratio related to the first gear and the second gear, or the first And the total gear ratio of the intermediate gear and the second gear are reduced. For this reason, the rotation angle error of the output shaft can be reduced.

  The power transmission mechanism according to aspect 2 of the present invention is the power transmission mechanism according to aspect 1, in which the intermediate gear (gear 27a, gear 27b) is more than the input side gear that receives power transmission from the preceding gear and the input side gear. The gear preferably has a small number of teeth and is integrated with an output gear that sends power received by the input gear to a subsequent gear. According to the above configuration, the intermediate gear has an input side gear that receives transmission of power from the preceding gear, and has fewer teeth than the input side gear, and transmits the power received by the input side gear to the subsequent gear. The output side gear is an integrated gear. For this reason, when the intermediate gear is interposed between the first gear and the second gear, the reduction rate can be improved.

  The power transmission mechanism according to aspect 3 of the present invention may further include a rotational speed detection unit (rotational angle sensor 30) that detects the rotational speed of the first gear in the above aspect 1 or 2. According to the said structure, the rotation speed detection part can detect the rotation speed of a 1st gear.

  In the robot according to the aspect 4 of the present invention, it is preferable that the power transmission mechanism according to any one of the aspects 1 to 3 is provided at a predetermined joint. According to the above configuration, a robot capable of reducing the rotation angle error of the output shaft can be realized.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

13 Neck joint 14 First leg first joint 15 Rear leg first joint 22 Front leg second joint (joint part)
26 drive motor 26a pinion gear (first gear)
27a Gear (intermediate gear)
27b Gear (intermediate gear)
27c Gear (second gear)
28 Rotation angle sensor (Rotation angle detector)
29 Output shaft 30 Rotation angle sensor (Rotation speed detector)
32 Rear leg second joint 271a Input side gear 272a Output side gear 271b Input side gear 272b Output side gear

Claims (4)

A power transmission mechanism for controlling the rotation of the output shaft by transmission of power from the drive motor,
A first gear coupled to the rotating shaft of the drive motor;
A second gear connected to the output shaft and having a larger number of teeth than the first gear and rotating in conjunction with the first gear directly or via an intermediate gear;
A power transmission mechanism, further comprising a rotation angle detector that detects a rotation angle of the first gear.   The intermediate gear includes an input-side gear that receives power transmitted from the preceding gear, and an output-side gear that has fewer teeth than the input-side gear and sends the power received by the input-side gear to the subsequent gear. The power transmission mechanism according to claim 1, wherein the power transmission mechanism is an integrated gear.   The power transmission mechanism according to claim 1, further comprising a rotation speed detection unit that detects the rotation speed of the first gear.   A robot characterized in that the power transmission mechanism according to any one of claims 1 to 3 is provided at a predetermined joint.

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