JP2011041424A - Method and device for predicting temperature of servomotor-driven reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively perform prediction without directly detecting a temperature rise at a reducer part in a servomotor-driven reducer by a temperature detector, and without increasing the number of components. <P>SOLUTION: A current value Ii fed back to a servo amplifier for driving a servomotor 5 of the servomotor-driven reducer 20 and to a control device, and a rotational angle θm are read, and a calorific value of the reducer part 7 is calculated from the current value and the rotational angle, thus predicting a temperature rise. An arithmetic expression for uniquely obtaining a temperature rise value from an input torque Ti and an input rotational speed N at the reducer part, or a data table is predetermined, and the temperature rise is predicted with an output torque conversion value of the current value as the input torque and with a rotational speed obtained by converting the rotational angle as the input rotational speed. Further, the temperature rise at the reducer part is predicted with the input torque as an average input torque per cycle, and with a rotational speed as an average rotational speed per cycle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a temperature prediction method and apparatus for a reduction gear driven by a servo motor.

  The speed reducer has moving parts such as a gear train and a bearing, and generates heat due to mechanical loss such as friction. Depending on the use conditions, this heat generation becomes excessive, and the surface pressure of the gears and bearings may increase due to the play of the gear train, the clearance between the bearings and the lubrication performance. When used in such a high temperature environment, gears and bearings wear and wear, and the life of the reduction gear is greatly affected. Therefore, it is important to recognize the temperature state of the reduction gear.

  Therefore, in order to operate the speed reducer safely, it is desired to predict the amount of heat generated by the speed reducer according to the driving situation and to predict the temperature rise. For example, in Patent Document 1, when the movement of the robot is completed, if the detected temperature from the temperature detecting device provided in the drive unit is within the allowable range, the drive speed is set to the normal speed, and the detected temperature is a predetermined value before the allowable range is exceeded. When the temperature is high, the driving speed is lowered so that the temperature of the driving unit does not rise, and the robot is stopped due to the temperature rise.

  However, in the thing of patent document 1, since it is necessary to provide a temperature detection apparatus in a drive part in order to detect temperature, it is necessary to provide a wiring part which transmits a signal from a temperature detection apparatus and a temperature detection apparatus, Since the structure becomes complicated and the number of parts increases, there is a cost problem. Also, in machines equipped with multiple reduction gears that use servo motors as the drive source, such as industrial robots, the number of temperature detection devices and wiring increases by the number of axes, which is not only a cost issue but also maintenance and inspection points. There is also a problem that increases.

  Therefore, in Patent Document 2, in the numerical control machine device, the current data or torque command data from the servo control unit is used without using the temperature detection device, and the temperature curve of the driving means is calculated from the current data or torque command data. By creating data and controlling the acceleration / deceleration time constant of the feed shaft that is driven and controlled based on the data, overheating of the drive means is suppressed. Further, in Patent Document 3, a square average of a motor current value is obtained, a temperature rise value is predicted based on a comparison with a predetermined allowable value, and a time constant and an operation duty of an acceleration / deceleration operation are changed. To keep driving.

Japanese Patent Laid-Open No. 5-111891 Japanese Patent No. 2885003 JP-A-9-91025

  In Patent Documents 2 and 3, temperature curve data of the driving means is created from current data or torque command data from the servo control unit to suppress overheating (excessive temperature rise) of the servo motor. However, in a servo motor drive reduction device, the temperature at which the lubricant contained in the reduction device is generally lower than the allowable temperature of the servo motor described above, and the temperature increase of the servo motor is predicted. However, preventing overheating of the servo motor did not prevent overheating and thermal degradation on the reduction gear side. Also, in an industrial robot having a servo motor drive speed reducer drive means, it is relatively easy to replace the servo motor due to maintenance or failure, but the speed reducer may also connect the robot arm to the arm. It is not easy to replace the reducer, and it takes a lot of time to replace the reducer if it is damaged. Predicting the temperature rise of the reducer for planned maintenance and inspection prevents the reducer from overheating. It was hoped to do.

  Further, the heat generation amount of the servo motor is calculated by the mean square of the current value. However, the reduction gears including gears and bearing rows include heat generation due to friction resistance and viscous resistance between each mechanical element included in the mechanism and lubricant, and heat generation considering heat dissipation from the reduction gear to the external environment. Calculation is required. Therefore, even if the conventional motor can prevent overheating of the servo motor, it cannot prevent overheating on the reduction gear side, and there is a problem that a temperature detector must be provided in the reduction gear unit that is the drive unit.

  In view of the above-mentioned problems, the problem of the present invention is that the temperature increase of the speed reducer using a servo motor as a drive source can be predicted at low cost without directly detecting the temperature increase with a temperature detector, and without increasing the number of parts. Is to do.

  In the present invention, a servo amplifier for driving a servomotor of a servomotor drive reduction device and a current value fed back to a control device and a rotation angle are read, and the servomotor drive reduction device is read from the current value and the rotation angle. The above-described problem has been solved by providing a method for predicting the temperature rise of the servo motor driven speed reducer that calculates the amount of heat generated by the speed reducer and predicts the temperature rise of the speed reducer.

That is, the reduction gear generates heat due to mechanical loss. This mechanical loss is due to viscous resistance and friction resistance other than the inertial term that actually performs the work. Viscous resistance is a function of angular velocity ω, and friction is a function of torque T. Therefore, the amount of heat Q1 generated by the reduction gear due to mechanical loss is
Q1 = Q1 (ω, T)
And a function of angular velocity and torque.

Further, the temperature rise X of the speed reducer is obtained by dividing the amount of generated heat Q1 by the amount of heat released Q2 of the speed reducer by the specific heat C of the speed reducer. Therefore, the temperature rise X is
X = (Q1-Q2) / C = (Q1 (ω, T) −Q2) / C
Thus, the temperature rise can also be expressed as a function of angular velocity and torque. Here, the heat radiation amount Q2 is a specific value determined by the structure and installation state of the reduction gear.

  On the other hand, the angular velocity of the reduction gear can be grasped as the rotation speed by differentiating the angle, which is the encoder output of the servo motor that drives the reduction gear, with respect to time. Further, the torque of the reduction gear coincides with the output torque of the servo motor, and the output torque is converted into the current value of the servo motor. For example, the input torque Ti of the reduction gear can be calculated by multiplying the drive current Ii by the torque constant ki of the servo motor.

Accordingly, the temperature rise X is obtained by using the output torque T (I) obtained by converting the current value I fed back from the servo motor and the rotational speed ω (N) obtained by differentiating the rotational angle θ.
X = (Q1 (ω (N), T (I)) − Q2) / C
Or
X = (Q1 (ω (N), ki × Ii) −Q2) / C
It becomes. Thus, according to the present invention, the temperature rise X can be obtained as a function of the current value I and the rotation speed N. Thereby, the calorific value of the reduction gear unit can be calculated, and the temperature rise of the reduction gear unit can be predicted.

  Such a function can be obtained on the assumption of the passage of time and various conditions, but in the simplest case, it is created based on experimental data by rotating an actual speed reducer with various torques and rotational speeds. Convenient. Therefore, in the invention according to claim 2, there is provided an arithmetic expression or a data table in which the temperature rise value is uniquely determined from the input torque and the input rotation speed of the predetermined reduction gear unit to which the servo motor is attached. Predetermined, the output torque converted value of the servo motor of the current value is set as the input torque, and the rotation speed obtained by converting the rotation angle is input as the input rotation speed into the arithmetic expression or the data table. And a temperature rise prediction method for a servo motor driven speed reducer that performs temperature rise prediction of the speed reducer.

  Moreover, it can obtain | require from the average in 1 cycle more simply. Therefore, in the invention according to claim 3, the input torque is set as an average input torque per cycle, and the rotation speed is input as an average rotation speed per cycle to the arithmetic expression or the data table to reduce the deceleration. Provided is a temperature rise prediction method for a servo motor drive speed reducer that performs temperature rise prediction of an apparatus unit.

  In order to realize such a temperature rise prediction method, in the invention according to claim 4, a servo motor, a predetermined reduction gear unit to which the servo motor is attached, an input torque and an input rotation speed of the reduction gear unit, An arithmetic expression or a data table in which the temperature rise value is uniquely obtained from the servo motor, a servo amplifier and a control device for driving the servo motor, and an output torque conversion of the current value fed back from the servo motor to the servo motor The value is input torque and read for one cycle, the rotation number obtained by differentiating the rotation angle from the servo motor encoder is read for one cycle, the input torque is averaged input torque per cycle, and the rotation number is one cycle. A calorific value calculation unit with an average rotation speed per unit, and the average input torque calculated by the calorific value calculation unit. To provide a temperature rise predicting apparatus of a servo motor drive reduction device including an output display unit which outputs the temperature rise value click and the said average rotational speed is input to the arithmetic expression or a data table, a.

  As described above, according to the present invention, the temperature rise of the speed reduction device portion of the servo motor drive speed reduction device is predicted based on the output of the current and the rotation speed of the servo motor. Therefore, it can be provided at low cost without complicating the structure of the reduction gear and increasing the number of parts. By predicting the temperature rise, it is possible to prevent the overheating of the reduction gear unit. Further, as in the prior art, the temperature increase of the servo motor itself can be predicted from the current value of the servo motor, and various controls are possible.

  Further, since the current value and the rotational speed of the servo motor can be input to a previously created arithmetic expression or data table to predict the temperature increase of the reduction gear unit, the control is also simple. Further, if the prediction is as simple as an abnormality detection, the data can be obtained relatively easily from the empirical formula (claim 2). More simply, since the temperature rise can be predicted from the average current value and the average rotation speed during one cycle, the control is simpler (Claim 3). Note that if the average current value is obtained by the root mean square, the empirical formula or the data table becomes more linear.

  In the apparatus of the present invention, a signal is taken out from a feedback line basically used for a servo motor, and a calorific value calculation unit and an output display unit may be provided as software. It became applicable.

It is a flowchart which shows the calculation processing procedure of the temperature rise of the reduction gear part of the servomotor drive reduction device which shows embodiment of this invention. It is a block diagram of the servo control system which drives the servomotor of the servomotor drive reduction device which shows the embodiment of the present invention. It is the graph which showed the relationship between the temperature rise value of the reduction gear part of the servo motor drive reduction gear apparatus which shows embodiment of this invention, input torque, and input rotation speed.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram of a servo control system that drives the servo motor of the servo motor drive speed reducer of the present invention, in which 1 is a position command calculation unit, 2 is a position loop, 3 is a speed loop, 4 is a current loop, 5 is a servo motor, 6 is an encoder, 7 is a speed reduction device that predicts a temperature increase (monitoring target), 8 is a calorific value calculation unit that calculates the temperature increase of the speed reduction device, and 10 is a temperature that detects the ambient temperature A sensor 9 is an output display unit for the result 8. Further, S in the figure is a Laplace operator as a differentiator.

  In FIG. 2, the actual angle θm of the motor shaft, which is position data detected by the encoder 6, is converted into an actual angular velocity ωi by the differentiator S. The actual angle θm is transferred to the position loop 2 and the actual angular velocity (rotation speed) ωi is While being fed back to the speed loop 3, the actual angular speed ωi is also transmitted to the calculation unit 8 as data necessary for calculating the temperature rise as the rotation speed N. The drive current output from the current loop 4 is detected by a current detector 22 provided on the transmission path 21 between the current loop 4 and the motor 5, and the detected drive current Ii is fed back to the current loop 4. At the same time, it is transmitted to the calculation unit 8 as data necessary for calculating the temperature rise. When calculating the saturation temperature of the reduction gear unit 7 more accurately from the temperature rise value of the reduction gear unit 7, a temperature sensor 10 that can output to the calculation unit 8 is installed, and the detected ambient temperature ti is calculated by the calculation unit 8. Transmit to.

  FIG. 1 is a flowchart showing a process for calculating a temperature rise of the reduction gear, which is performed by the calculation unit 8 shown in FIG. In step 11, the actual angular velocity ωi obtained by differentiating the actual angle θm of the drive shaft, which is position data detected by the encoder 6, with the differentiator S is fetched and stored as the rotational speed N. In step 12, the servo motor drive current I i detected by the current detector 22 provided on the transmission path 21 between the current loop 4 and the motor 5 is taken in and multiplied by the torque constant ki of the motor 5. The torque input to the reduction gear, that is, the input torque Ti is calculated.

  FIG. 3 is an example of actual measurement data showing the relationship between the temperature rise value, input torque Ti, and input rotation speed N of the reduction gear section of the servo motor drive reduction gear. From the input rotation speed N and the input torque Ti, the reduction gear section is shown. Can be obtained. In step 13, the input engine speed N taken in step 11 and the input torque Ti calculated in step 12 are input to the data table shown in FIG. A warning is issued if the temperature rise value is higher than a predetermined value. Alternatively, the overheating is prevented or monitored by automatically decreasing the time constant or decreasing the speed.

  As described above, according to the embodiment of the present invention, the abnormal heating (overheating) of the reduction gear unit can be monitored based on the output of the current of the servo motor and the angular velocity (number of rotations). It is not necessary to newly provide a temperature detector for wiring and a wiring means for transmitting a signal from the temperature detector, and can be provided at low cost without complicating the structure of the reduction gear unit and increasing the number of parts. It became.

5 Servo motor 6 Encoder 7 Deceleration unit 8 Heat generation amount calculation unit 9 Output display unit 20 Servo motor drive reduction unit θm Rotation angle Ii Current value N Input rotation speed Q1 Heat generation amount Ti Input torque X Temperature rise value

Claims (4)

  Read the current value fed back to the servo amplifier and control device that drives the servo motor of the servo motor drive reduction device and the rotation angle, and read the current value and rotation angle of the reduction device portion of the servo motor drive reduction device. A method for predicting a temperature rise in a servo motor driven speed reducer, wherein a calorific value is calculated and a temperature rise prediction of the speed reducer unit is performed.   The current according to claim 1, wherein an arithmetic expression or a data table in which a temperature rise value is uniquely determined from an input torque and an input rotation speed of a predetermined reduction gear unit to which the servo motor is attached is determined in advance. The servo motor output torque converted value of the value is the input torque, and the rotation speed obtained by converting the rotation angle is the input rotation speed, which is input to the arithmetic expression or the data table and the temperature of the reduction gear unit 2. The method for predicting a temperature rise in a servo motor driven speed reducer according to claim 1, wherein the temperature rise is predicted.   The input torque is set as an average input torque per cycle, and the rotation speed is input as an average rotation speed per cycle to the arithmetic expression or the data table to predict the temperature rise of the reduction gear unit. A method for predicting a temperature increase in a servo motor drive reduction device according to claim 2.   A servo motor, a predetermined reduction gear unit to which the servo motor is attached, an arithmetic expression or a data table in which a temperature rise value is uniquely determined from an input torque and an input rotation speed of the reduction gear unit, The servo amplifier and control device that drives the servo motor, and the servo motor output torque converted value of the current value fed back from the servo motor as input torque are read for one cycle, and the rotation angle from the encoder of the servo motor is differentiated And the calorific value calculation unit which calculates the input torque as the average input torque per cycle and the rotation number as the average revolution per cycle, and the calorific value calculation unit. The average input torque and the average rotational speed are input to the calculation formula or data table to increase the temperature. Temperature rise predicting apparatus of a servo motor drive reduction apparatus characterized by comprising an output display unit for outputting a value, the.

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