JP2009061541A - Overload detecting mechanism and industrial robot equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overload detecting mechanism which directly detects an overload imposed on a rotating shaft of a movable portion. <P>SOLUTION: The overload detecting mechanism is formed of: first and second gears (1), (2), each having a tapered shape and engageable in each other; the rotating shaft (3) having the first gear (1) fitted to the periphery thereof, holding the first gear (1) in an axially slidable manner, and rotatable together with the first gear (1); an energizing means (5) for energizing the first gear (1) toward the second gear (2) along an axial direction in a manner eliminating backlash between the first and second gears; a bearing (7) held on the periphery of the first gear (1); a movable plate (8) held on the periphery of the bearing (7); and a sensor (9) for detecting movement of the movable plate (8) along the axial direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an overload detection mechanism that is used in an industrial robot, and particularly detects an overload of a rotary shaft that drives an end effector and the like.

  In a conventional industrial robot, an overload detector may be built in the end effector when detecting an overload when a load force (external force) is applied to the end effector. In this case, it is effective as protection for the end effector, but overload detection cannot be correctly performed on the rotating shaft that drives the end effector. In addition, as a general method, overload detection is performed in a control manner by monitoring a voltage value detected from a motor that drives each axis of the robot by a controller of the robot. In this case, since the motor itself that drives each axis is used for voltage value overload detection, the accuracy of the load force of each axis that is inherently necessary for protecting the rotating shaft that is the drive unit includes an uncertain element. It depends on the control equation. Therefore, there is a need for a load detection method that can detect the overload of the rotation axis itself of each axis of the robot and that does not include calculation of the above-described arithmetic expressions as much as possible.

However, in conventional industrial robot overload detection, each axis of the robot is not equipped with an overload detector, so overload detection for each axis of the robot cannot be performed correctly, or from the drive motor of each axis. Therefore, there is a problem that detection of load force on the output side of each axis depends on a control arithmetic expression including an uncertain element and detection accuracy is not good.
Then, this invention makes it a subject to solve said problem.

In order to solve the above problems, the present invention is configured as follows.
According to a first aspect of the present invention, in the overload detection mechanism for detecting an overload applied to the rotating shaft of the movable portion, the first and second gears meshed with each other by the tapered gear, and the first gear is arranged around the periphery. The first gear is fitted and slidably held in the axial direction so as to remove the backlash between the rotating shaft rotating with the first gear and the first and second gears. Biasing means for urging the first gear toward the second gear, a bearing held on the outer circumference of the first gear, a moving plate held on the outer circumference of the bearing, and the movement An overload detection mechanism comprising: a sensor capable of detecting movement of the plate along the axial direction.
The invention according to claim 2 is the overload detection mechanism according to claim 1, wherein the biasing means is a coil spring.
The invention according to claim 3 is the overload detection mechanism according to claim 1, wherein the biasing means is a disc spring.
The invention according to claim 4 is the overload detection mechanism according to claim 1, wherein the sensor is a switch type sensor that outputs a signal by contacting the moving plate.
The invention according to claim 5 is the overload detection according to claim 1, wherein the sensor is a non-contact type sensor capable of detecting movement of the moving plate along the axial direction without contacting the moving plate. It is a mechanism.
The invention according to claim 6 is the overload detection mechanism according to claim 1, wherein the sensor is a sensor capable of steplessly detecting the movement of the movable plate along the axial direction.
The invention according to claim 7 is an industrial robot provided with the overload detection mechanism according to any one of claims 1 to 5.
The invention according to claim 8 is an industrial robot provided with the overload detection mechanism according to claim 6.
In the invention according to claim 9, the controller of the industrial robot calculates the axial force acting on the first gear and the rotational torque of the rotary shaft from the output of the sensor. 9. The industrial robot according to claim 8, wherein feedback control of the rotating shaft is performed.
In the invention according to claim 10, the controller of the industrial robot stores the initial detection value of the sensor, and compares the initial detection value with the current detection value of the sensor, thereby 9. The industrial robot according to claim 8, wherein the secular change of the means is judged.

According to the present invention, in the overload detection mechanism for detecting an overload applied to the rotating shaft of the movable part, the first and second gears that transmit the rotational force of the motor or the like to the rotating shaft are configured in a tapered shape. Since the first gear is slidably held along the rotating shaft and the first gear is slidably held along the rotating shaft so as to remove the backlash of these two gears, the first gear is rotated in the rotating shaft direction when the rotating shaft is overloaded. Since the force is generated and the sensor is operated by the first gear that moves by the axial force, the relationship between the axial force generated in the gear, the rotational torque, the spring constant of the spring, and the amount of spring displacement Therefore, it is possible to detect the load torque on the output side and operate the switch, and there is an effect that the mechanism part can be protected by detecting overload.
In addition, since it is possible to detect a change in load torque on the output side by using a sensor that can detect a change in spring displacement, that is, a change in movement of the switch plate in a stepless manner, this change can be detected. Torque control of the output shaft can be performed using the detected value.
In addition, by pre-determining the initial value of the sensor detection value when a static load is applied to the output shaft, it is possible to check the secular change of the spring characteristics after long-term use. Etc. can be easily known.
Further, the biasing means uses not only a coil spring but also a characteristic of an elastic deformable body, for example, a disc spring, etc., as long as it can quantitatively determine the relationship between the amount of deformation or the amount of displacement and the generated force. It is applicable and can be selected in consideration of the size of the apparatus, the range of detection values, and the sensitivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a side view of an industrial robot 50 having the overload detection mechanism of the present invention.
In FIG. 2, (51) is a fixed base, (52) is a revolving barrel that is rotatable with respect to the fixed base (51), and (53) is rotatably supported by the revolving barrel (52) by the first arm. Yes. Reference numeral (54) denotes a second arm, the end of which is rotatably supported by the first arm (53), and (55) has a pivotable axis. The wrist (56) is rotatably supported at the other end of the second arm (54), and the wrist (56) has a pivot having a freely pivotable shaft at the lower part of the wrist (56). A shaft (57) is provided. Further, (58) is a welding torch which is an end effector connected to the tip of the wrist 56, and an overload detector (59) is provided on the base end side of the welding torch (58). This overload detector (59) directly monitors the load on the welding torch (58) when an external force is applied to the welding torch (58), and has been conventionally provided.

Hereinafter, the overload detection mechanism of the present invention will be described with reference to FIG. In this embodiment, the overload detection mechanism 10 is provided on the rotating shaft (57). The rotating shaft 57 in FIG. 1 drives the rotating shaft 57. FIG. 1 is a sectional view of a mechanism for driving the rotating shaft 57.
In FIG. 1, power generated by a motor and a speed reducer (not shown) is transmitted to the gear (2). (2) is a gear having a tapered gear shape, (1) is a gear meshing with the gear of (2), (3) is a rotating shaft for transmitting the power of the gear (1), (4) is A guide portion fixed to the rotation shaft of (3) and held by the gear of (1) so as to be movable in the axial direction of the rotation shaft (3), and (5) having the gear of (1) in the axial direction. Urging means for urging the gear (2) toward the gear (2) for removing backlash of the gears (1) and (2). In this embodiment, the coil spring (5a) is used. (6) is a spring holding member that is removably fixed to the tip of the rotating shaft of (4) to transmit the spring force of the coil spring of (5a) to the gear of (1), and (7) (1) A bearing provided on the gear, (8) is a moving plate fitted to the outer ring of the bearing of (7), and (9) is a switch operated by the moving plate of (8). It is.

  The operation of the overload detection mechanism configured as described above will be described. It is assumed that the industrial robot (50) operates and some overload external force is applied to the welding torch (58). At this time, the power generated by the motor and the speed reducer (not shown) is transmitted to the gear (2), and the rotating shaft (3), that is, the rotating shaft 57 tries to execute a desired operation, but an external force is applied to this. Therefore, the gear (1) acts along the guide portion (4) so as to move away from the gear (2) while resisting the pressing force of the coil spring (5a) on the left side in FIG. With this operation, the moving plate (8) also moves away from the gear (2), and the switch of the sensor (9) is pressed. The signal of the switch (9) is transmitted to the controller of the industrial robot (50) (not shown), and the controller detects the overload of the rotating shaft (57). For example, the controller takes action such as stopping the operation if the signal is continuously detected for a predetermined time or more.

FIG. 3 is a view when a sensor (9a) capable of detecting a change in the amount of movement of the movable plate (8) steplessly is used instead of the switch type sensor (9) in FIG. In this case, it becomes possible to detect the load torque change of the output shaft from the rotational torque of the gear (1), and the torque control of the output shaft can be performed using the detected value of the torque change. The sensor (9) can be either a contact type or a non-contact type, and can be selectively used depending on the size of the device and the detection sensitivity.
In the embodiment shown in FIG. 5, the initial value of the detection value of the sensor (9a) when a constant static load is applied to the rotating shaft (3) in the initial state when the apparatus is not used is obtained in advance. By comparing the detected value under the same condition after the long-term use with the initial value, it is possible to confirm the secular change of the characteristics of the coil spring (5) and easily know the replacement time due to the deterioration of the performance of the coil spring (5). be able to.

  FIG. 4 shows a case in which the coil spring (5a) of the biasing means (5) in FIG. 1 is a disc spring (5b). Since the spring is smaller than the coil spring, the apparatus can be miniaturized. Note that, by applying a sensor (9a) capable of detecting a change in the amount of movement of the movable plate (8) steplessly instead of the sensor (9) in FIG. 4, a spring that can perform torque control as described above. As described above, it is possible to easily know the replacement time due to the deterioration of the performance.

Sectional drawing of the rotating shaft provided with the overload detection mechanism of this invention. 1 is an external side view of an industrial robot provided with an overload detection mechanism of the present invention. Sectional drawing of the rotating shaft provided with the overload detection mechanism of the other Example of this invention Sectional drawing of the rotating shaft provided with the further another overload detection mechanism of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gear 2 Gear 3 Rotating shaft 4 Guide part 5 Energizing means 6 Spring holding member 7 Bearing 8 Moving plate 9 Sensor

DESCRIPTION OF SYMBOLS 50 Industrial robot 51 Fixed base 52 Turning trunk 53 1st arm 54 2nd arm 55 Axis 56 Wrist part 57 Rotating axis 58 Welding torch 59 Overload detector

Claims (10)

In the overload detection mechanism that detects overload on the rotating shaft of the movable part,
A first gear and a second gear meshing with each other with a tapered gear, and the first gear are fitted around the first gear, and the first gear is slidably held in the axial direction. The rotating shaft that rotates together with the first gear, a biasing means that biases the first gear toward the second gear so as to remove backlash of the first and second gears, and the first gear An overload detection comprising: a bearing held on the outer periphery of the gear; a moving plate held on the outer periphery of the bearing; and a sensor capable of detecting movement of the moving plate along the axial direction. mechanism.   The overload detection mechanism according to claim 1, wherein the biasing means is a coil spring.   The overload detection mechanism according to claim 1, wherein the biasing means is a disc spring.   The overload detection mechanism according to claim 1, wherein the sensor is a switch type sensor that outputs a signal by contacting the moving plate.   The overload detection mechanism according to claim 1, wherein the sensor is a non-contact type sensor capable of detecting movement of the moving plate along the axial direction without contacting the moving plate.   The overload detection mechanism according to claim 1, wherein the sensor is a sensor capable of steplessly detecting movement of the moving plate along the axial direction.   An industrial robot comprising the overload detection mechanism according to claim 1.   An industrial robot comprising the overload detection mechanism according to claim 6.   The industrial robot controller calculates the axial force acting on the first gear and the rotational torque of the rotary shaft from the output of the sensor, thereby performing feedback control of the rotary shaft. The industrial robot according to claim 8.   The controller of the industrial robot stores the initial detection value of the sensor and determines the secular change of the biasing means by comparing the initial detection value with the current detection value of the sensor. The industrial robot according to claim 8.

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