JP7270923B2 - Overload protection device, geared motor, and method for outputting torque conversion value of motor - Google Patents

Description

The present invention monitors the load state of a geared motor that drives a driven device, and cuts off or limits the supply of power to the geared motor when an excessive load is detected. and a geared motor equipped with the overload protection device. Furthermore, the present invention relates to a method of outputting a torque conversion value at the output shaft of a motor from the current measurement value and the voltage measurement value of the motor.

Conventionally, when a driven device such as a conveyor device is driven by a geared motor, the load suddenly increases due to foreign objects being caught in the geared motor. may be physically damaged. In response to this, an overload protection device has been developed that detects an overload of the geared motor and cuts off or limits the power supply to the geared motor to prevent damage to the geared motor and the driven device.

For example, Patent Literature 1 discloses a geared motor provided with an overload protection device for preventing destruction of an industrial machine using the geared motor. In the following paragraphs, the reference numerals of Patent Document 1 are shown in parentheses. An overload breaker (4) selects a specified current value less than the rated current value of the motor (2) as a specified current value (6), and an overload current value exceeding the specified current value (6) Designated value setting means (14) for selecting a predetermined time of current flow in (5) as a designated value (7) of overload current time; ) and overcurrent detection means (15) for detecting the overload current value (5) and the overload current time exceeding the overload current time, and the overcurrent detection means ( 15), a power cutoff means (19) for cutting off the power supply to the motor (2) when detected by the motor (2).

Japanese Patent No. 6216110

A conventional overload protection device such as that disclosed in Patent Document 1 detects an overload and shuts off the motor from the power supply when the measured current value exceeds a specified current value by reading an increase in the value of the current flowing through the motor. do. However, the measured values of current and voltage do not accurately reflect the actual torque value of the motor, so the motor could not be reliably stopped at the desired torque value. For example, if the torque value of the specified current value is larger than the assumed torque value, the motor may operate even if the desired torque value is exceeded, damaging the driven device or the geared motor. On the other hand, if a margin is provided in anticipation of the deviation of the torque value and the specified value of the current is lowered, it is conceivable that the motor will stop frequently. In other words, the problem with the conventional overload protection device is that the motor overload cannot be controlled with an accurate torque value.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an overload protection device and a geared motor that can control motor overload with a more accurate torque value.

An overload protection device according to one aspect of the present invention is electrically connected to a motor that drives a driven device, and operates to protect the motor when an overload of the motor is detected. a device,
current measuring means for measuring the current flowing through the motor over time and obtaining a current measurement value;
Voltage measuring means for measuring the voltage of the motor over time and acquiring a voltage measurement value;
power cutoff means for cutting off or reducing the supply of power from a power source to the motor;
a storage unit that stores a lookup table of motor characteristics consisting of a data group of current values, voltage values, and torque values of the motor collected in advance;
a control unit that controls operations of the current measuring means, the voltage measuring means, and the power cutoff means;
The control unit refers to the lookup table from the storage unit, outputs the torque conversion value of the motor over time based on the time-dependent data of the current measurement value and the voltage measurement value,
The controller cuts off the power supply by the power cutoff means when detecting that the torque conversion value exceeds a preset cutoff threshold value or reaches the predetermined cutoff threshold value. or reduced.

The overload protection device of the present invention refers to a lookup table showing the current-voltage-torque characteristics of the motor, and acquires the torque conversion value over time from the current measurement value and voltage measurement value acquired over time. , overload is prevented by utilizing temporal data of the torque conversion value. Since this torque conversion value uses a torque curve corresponding to the characteristics of the motor, it reflects the actual torque fluctuation of the motor more accurately than the conventional monitoring based on the current value. Therefore, the overload protection device of the present invention enables motor overload control with a more accurate torque value.

According to a further aspect of the overload protection device of the present invention, the current values and torque values in the lookup table are obtained from approximate curves of measurement plots of current values and torque values measured multiple times at a constant voltage, and the lookup table The table is characterized by having the approximate curve for each of a plurality of voltage values. That is, by interpolating the data between the measurement plots with the approximation curve, it is possible to output a torque conversion value with higher accuracy that corresponds to fine fluctuations in the current value.

A further form of the overload protection device of the present invention comprises a first approximation curve of current and torque values measured at a first constant voltage value, and current and torque values measured at a second constant voltage value. A torque conversion value in a voltage measurement value between the first constant voltage value and the second constant voltage value is interpolated based on the second approximation curve of . That is, even for voltage measurement values for which actual measurement plots are not obtained, the torque conversion value can be output by referring to the lookup table by complementing the data in the lookup table with the estimated torque value. is possible.

A further embodiment of the overload protection device of the present invention is characterized in that it further comprises communication means for transmitting and receiving data, and the storage section is provided in an external server capable of communicating via the communication means. . In other words, by providing the storage unit in the external server, it is possible to handle a large amount of data without hardware limitations, and also facilitate operations such as addition, deletion, and update of data.

A geared motor according to one embodiment of the present invention is characterized by comprising a motor, a speed reducer connected to an output shaft of the motor and outputting power to a driven device, and an overload protection device. That is, the geared motor of the present invention can exhibit the effects of the overload protection device as a geared motor.

A method according to an embodiment of the present invention is a method for outputting a torque conversion value of a motor,
a step of collecting data groups of current values, voltage values and torque values of the motor and generating a lookup table of motor characteristics;
a step of measuring the current flowing through the motor over time with a current measuring means to obtain a current measurement value;
measuring the voltage of the motor over time with a voltage measuring means to acquire a voltage measurement value;
a step of referring to the lookup table and temporally outputting the torque conversion value of the motor based on the temporal data of the current measurement value and the voltage measurement value.

A method of outputting a torque conversion value of a motor of the present invention generates a lookup table indicating the current-voltage-torque characteristics of the motor, refers to the lookup table, and measures current values acquired over time and It is characterized in that a torque conversion value is acquired over time from a voltage measurement value, and time-lapse data of the torque conversion value is output. Since this torque conversion value uses a torque curve corresponding to the characteristics of the motor, it reflects the actual torque fluctuation of the motor more accurately than the conventional monitoring based on the current value. Therefore, the method of the present invention outputs a more accurate torque conversion value without measuring the actual torque value, enabling accurate control of the motor.

An overload protection device according to one aspect of the present invention enables motor overload control with a more accurate torque value.

1 is a schematic side view of a geared motor according to one embodiment of the present invention; FIG. FIG. 2 is a schematic diagram showing the inside of the terminal box of the geared motor in FIG. 1; 1 is a block diagram of an overload protection device according to one embodiment of the present invention; FIG. 5 is a graph showing a lookup table of motor characteristics of the overload protection device of one embodiment of the present invention; 5 is a graph showing measurement plots of current values and torque values for each constant voltage of the motor in the overload protection device of one embodiment of the present invention. 5 is a graph illustrating approximate curves of current value and torque at a constant voltage of 180 V in the overload protection device of one embodiment of the present invention; 5 is a graph illustrating approximate curves of current value and torque at a constant voltage of 200 V in the overload protection device of one embodiment of the present invention; 5 is a graph showing temporal changes in motor current measurement values, voltage measurement values, and torque conversion values in the overload protection device of one embodiment of the present invention.

An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the shape of each figure referred to in the following description is a conceptual diagram or a schematic diagram for explaining a suitable shape, and the dimensional ratio and the like do not necessarily match the actual dimensional ratio. That is, the present invention is not limited to the dimensional ratios in the drawings.

FIG. 1 is a schematic diagram exemplifying a geared motor according to one embodiment of the present invention. A geared motor 10 of this embodiment includes a motor 11 , a speed reducer 12 and a terminal box 13 . By connecting the output shaft of the motor 11 to the speed reducer 12, the output shaft of the speed reducer 12 can obtain an output of low rotation speed and high torque to drive the driven device. The driven device is, for example, a chip conveyor device (not shown), and the output shaft of the geared motor is connected to the sprocket of the chip conveyor device.

As shown in FIG. 2, the terminal box 13 includes power terminals (U, V, W) 13a connected to the three-phase power supply 14, motor terminals 13b electrically connected to the motor 11, and external equipment. and an external terminal 13c for connecting to. The power terminal 13a is electrically connected to the motor terminal 13b through the board. The terminal box 13 includes a board in which a control unit (MCU), a current measurement circuit, a voltage measurement circuit, a communication circuit, and a relay circuit are incorporated, and the board constitutes an overload protection device (or overload protection system) 100. do.

FIG. 3 is a block diagram of the overload protection device 100 of this embodiment. The overload protection device 100 has a control unit (MCU) 101 for monitoring and controlling the operation of the motor 11 . Power is supplied to the control unit 101 from the three-phase power supply 14 through the power supply terminal 13a. A three-phase power supply 14 is connected to the U, V, and W phases of the motor 11 , and drive power is supplied to the motor 11 from the three-phase power supply 14 .

The overload protection device 100 includes a current measuring circuit (current measuring means) 102 that measures the current flowing through the motor 11 over time and obtains a current measurement value, and a voltage measurement circuit that measures the voltage of the motor 11 over time and measures voltage. A voltage measuring circuit (voltage measuring means) 103 for obtaining a value is provided. The current measurement circuit 102 and the voltage measurement circuit 103 are connected to the control unit 101 and are configured to output the measured current value and the measured voltage value of the motor 11 to the control unit 101 over time. Here, the measured current value is the value of the input current of the motor 11 and the measured voltage value is the value of the voltage applied to the motor 11 . The current measuring means and voltage circuit means of the present invention may be external equipment such as an oscilloscope.

The overload protection device 100 is provided with a relay 104 as power cutoff means. The relay 104 is directly or indirectly connected to the controller 101 and the three-phase power supply 14 . The relay 104 is configured to receive an instruction from the control unit 101 and control the three-phase power supply 14 to cut off or reduce the power supply from the three-phase power supply 14 to the motor 11 . In the overload protection device 100 of the present embodiment, the control unit 101 monitors the torque conversion value over time, and controls the relay 104 when the torque conversion value exceeds or reaches a predetermined cutoff threshold. Cut off or reduce power. Alternatively, the control unit 101 may be set to cut off or reduce power after a predetermined set time has elapsed without falling below the cutoff threshold.

The overload protection device 100 also includes a setting input section 105 for the user to input settings. The settings include the motor model, motor rotation direction, cutoff threshold, monitoring time, and the like. Furthermore, the overload protection device 100 includes a communication circuit 106 as communication means with the outside. The communication circuit 106 connects the control unit 101 and the external server 107 to enable mutual data transmission/reception. In this embodiment, the external server 107 is set as the storage unit of the overload protection device 100 . The overload protection device 100 of the present embodiment can hold a large amount of data related to the lookup table of the motor characteristics by providing the storage unit in the external server 107, and furthermore, the data can be easily updated and corrected. . The external server 107 may also store a log of various data output by the control unit 101 through the communication circuit 106 when the geared motor 10 is driven. However, the present invention is not limited to the above embodiment, and the storage unit may be incorporated as a recording medium such as a memory or hard disk in the substrate inside the terminal box 13 .

Also, the communication circuit 106 may optionally connect the control unit 101 and the user terminal 108 . A user terminal 108 is a user-operable terminal such as a control panel, a smart phone, or a personal computer. By using this user terminal 108, the operation of the geared motor 10 (e.g., current measurement value, voltage measurement value, torque conversion value) can be displayed on the monitor for monitoring, and device settings can be remotely input to the control unit 101. can do.

The connection between the communication circuit 106 and the external device may be wired or wireless. Examples of wireless connection means include WiFi (registered trademark) and Bluetooth (registered trademark).

The storage unit of the overload protection device 100 is configured to store a lookup table of motor characteristics, which is a data group of the current value, voltage value, and torque value of the motor 11 collected in advance. The lookup table is an array of numerical values consisting of current values, voltage values and torque values. In the overload protection device 100 of the present embodiment, the control unit 101 accesses the storage unit and refers to a lookup table consisting of data groups of motor current values, voltage values and torque values. The current measurement value and voltage measurement value measured over time by the measurement circuit 103 are applied to the current value and voltage value of the lookup table, and the torque value of the lookup table is output as the torque conversion value. Output of the torque conversion value is performed over time along with current and voltage measurements. In other words, the control unit 101 continuously inputs the voltage measurement value and the current measurement value to the lookup table, and continuously outputs the torque conversion value from the lookup table.

FIG. 4 is a graph of one example of the lookup table used in the present invention. Such a lookup table is prepared according to at least conditions such as motor model, rotation direction, and power supply frequency. This is because the motor characteristics differ for each of these conditions. It is preferable that the user inputs the above conditions via the setting input unit 105 and switches the lookup table according to the conditions. Note that the lookup table in FIG. 4 shows the torque characteristic specific to the motor under the conditions of clockwise rotation and power supply frequency of 60 Hz. Preferably, multiple lookup tables are created for different conditions.

Each motor characteristic (current/torque) curve in FIG. 4 is a set of data groups (arrangements) of current values and torque values at each constant voltage (180V, 190V, 200V, 210V, 220V, 230V, 240V). In this embodiment, each motor characteristic curve is an approximation curve of current/voltage plots collected in advance for the motor 11, and is represented by a predetermined polynomial curve (a fifth-order polynomial in this embodiment) as described later. ing. A torque conversion value is derived from the lookup table based on the current measurement value and the voltage measurement value. More specifically, a motor characteristic curve is selected from the voltage measurement value of the motor 11, and the torque conversion value is read from the current measurement value of the selected motor characteristic curve. The torque conversion value is obtained by inputting the current measurement value into a polynomial that approximately represents the selected motor characteristic curve and calculating. For example, when the voltage measurement value of the motor 11 is 200 V and the current measurement value is 0.5 A, a motor characteristic curve of 200 V is selected, and a torque conversion value of 142 N·m is output from the motor characteristic curve. This torque conversion value is a value according to the current-voltage-torque characteristics unique to the motor, and reproduces the actual torque value at the output shaft of the motor 11 almost faithfully.

In this embodiment, even if the voltage measurement does not correspond to any voltage on the motor characteristic curve collected in advance and deviates from the constant voltage value of the motor characteristic curve, the voltage measurement is interleaved. Two motor characteristic curves can complement the lookup table torque conversion values. That is, the first approximate curve measured at the first constant voltage value V1 that is lower than the voltage measurement value Vm and is closest to the voltage measurement value Vm, and is higher than the voltage measurement value Vm and is the voltage measurement value A torque conversion value at a voltage measurement value Vm between the first constant voltage value V1 and the second constant voltage value V2 based on the second approximation curve measured at the second constant voltage value V2 closest to Vm. is complemented. In this embodiment, the torque conversion values T1 and T2 are calculated by inputting the current measurement values into the polynomials of the approximate curves of the first and second constant voltage values V1 and V2, and using the following equations, the torque conversion values Calculate T.
T=T1+(T2-T1)×(Vm-V1)/(V2-V1)

That is, the method of outputting the torque conversion value of the motor 11 includes the steps of collecting data groups of the current value, voltage value and torque value of the motor 11 in advance and generating a lookup table of motor characteristics; A step of measuring the current flowing to the motor 11 over time to acquire a current measurement value, a step of measuring the voltage of the motor 11 over time by the voltage measurement circuit 103 to acquire the voltage measurement value, and a lookup table and temporally outputting the torque conversion value of the motor 11 based on the temporal data of the current measurement value and the voltage measurement value. The task of generating the lookup table of motor characteristics and the task of updating or expanding the lookup table is primarily performed by the manufacturer or the user. Also, the step of generating the look-up table of the method may be performed by comparing the current and torque values measured multiple times at a constant voltage so that the multiple plots of the current and torque values in the look-up table are represented as a motor characteristic curve. It includes the step of creating a fitted curve for the measurement plot. The lookup table has approximate curves for each of the plurality of voltage values. Furthermore, the method includes a first approximation curve of the current value I1 and the torque value T1 measured at the first constant voltage value V1 and the current value measured at the second constant voltage value V2 by the control unit 101. A step of interpolating and outputting the torque conversion value at the voltage measurement value Vm between the first constant voltage value V1 and the second constant voltage value V2 based on the second approximation curve of I2 and the torque value T2. .

Next, a method for creating the lookup table of the motor characteristics of FIG. 4 will be described. FIG. 5 is a graph showing measurement plots of current values and torque values for each constant voltage of the motor 11 . Each measurement plot is a data group of current values, voltage values, and torque values previously measured and collected for the motor 11 in order to determine the motor characteristics. For the motor 11 incorporated in the geared motor 10, the torque value was measured by increasing the input current to the motor 11 under a plurality of constant voltage conditions. The current and voltage values of the input current were recorded by common measuring instruments such as an oscilloscope. The torque value was obtained by attaching a torque meter to the output shaft of the motor 11 and recording the value of the torque meter. In the present embodiment, data was collected under seven constant voltage conditions at intervals of 10 V as an example. However, if more precise data is required, more data may be collected under more detailed conditions. In this way, the data group of measurement plots shown in FIG. 5 was obtained.

According to FIG. 5, the current-torque characteristics of the motor are different at each voltage, and the current and torque are not directly proportional. Therefore, if only the fluctuation of the current value is used as an index of the fluctuation of the torque value, as in the conventional art, the error from the actual torque value becomes large, and it can be seen that the overload protection device cannot accurately control the motor.

Although the data group of the measurement plots in FIG. 5 can sufficiently exhibit the function of the lookup table, the overload protection device 100 of the present embodiment can output a precise torque conversion value. In order to interpolate the data between the measurement plots, an approximation curve was created for each plot.

6 and 7 exemplify approximated curves obtained from plots of current value-torque value at constant voltages of 180V and 200V. In this embodiment, each plot is calculated so as to be approximated by a fifth-order polynomial approximation curve. The approximate curve is derived by a known statistical technique such as regression analysis using the least squares method. It should be noted that although the fifth-order polynomial is optimally selected in this embodiment, the order of the polynomial can be arbitrarily selected. A motor characteristic curve at a constant voltage of 180 V was represented by a fifth-order polynomial (see FIG. 6) of x (current value) and y (torque value). Similarly, the motor characteristic curve at a constant voltage of 200 V was represented by a fifth-order polynomial (see FIG. 7) of x (current value) and y (torque value). By inputting the current measurement value to x of the fifth-order polynomial by the control unit 101, the torque conversion value is output as y. A lookup table of motor characteristics was created by creating an approximation curve for all constant-voltage current value-torque value plots collected in advance.

FIG. 8 shows temporal changes in the current measurement value, voltage measurement value, and torque conversion value of the motor 11 in the overload protection device 100 for the geared motor 10 until the load from the driven device increases and the power is cut off. graph. The motor 11 was driven at a constant voltage of 200V, and the voltage measurement value Vm was also measured over time as about 200V. Current measurements Im were measured over time as about 0.38 A under a constant load from time t=0 to about 8 seconds. Then, the torque conversion value T is calculated over time as about 42 N m from the voltage measurement value Vm ~ 200 V and the current measurement value Im ~ 0.38 A with reference to the lookup table of the motor characteristics in FIG. . Then, the load from the driven device rises from the time when the time t is about 8 seconds, and the current measurement value Im rises as the load rises while Vm remains substantially constant. The torque conversion value T at the time of load increase was also output with reference to the motor characteristic lookup table. In this embodiment, the cut-off threshold Tt is preset as 140 N·m. When the time t is 51 seconds, the torque conversion value T reaches and exceeds the cutoff threshold Tt. The control unit 101 detected that the torque conversion value T exceeded the cutoff threshold Tt, and immediately cut off the power supply by driving the relay 104, and the operation of the motor 11 stopped.

That is, in the overload protection device 100 of the present embodiment, since the torque conversion value reproduces the torque value at the output shaft of the motor 11, it is geared so that the output of the motor 11 does not exceed the desired torque value. Motor 10 can be controlled. As a result, the user can determine the cut-off threshold value Tt according to the specification of the driven device (limitation of the input torque value) and the standard of the geared motor 10 to more reliably prevent damage to the driven device and geared motor 10 due to an increase in load. It is possible to prevent

[Another embodiment/modification]
The present invention is not limited to the above embodiments, and can take various embodiments and modifications. Another embodiment and modifications of the present invention will be described below.

(1) In the above embodiment, the overload protection device is integrated into the control board built into the terminal box, but as long as each member can be controlled, it may be provided separately from the geared motor or the motor. .

(2) In the present embodiment, the overload protection device is incorporated in the geared motor and used, but it may be used without the speed reducer.

(3) The look-up table of the overload protection device of the present invention should consist of at least a data group of the motor current value, voltage value and torque value, and the approximate curve and voltage value interpolation function are omitted. may be

(4) In the overload protection device of the present invention, the relay as the power cut-off means is configured to send a power cut-off signal to the power supply. Power may be cut off by opening and closing. That is, the configuration of the above embodiment is merely an example, and a person skilled in the art can make various modifications under the technical idea of the present invention.

The present invention is not limited to the above-described embodiments and modifications, and can be implemented in various forms within the technical scope of the present invention.

10 Geared motor 11 Motor 12 Reduction gear 13 Terminal box 14 Three-phase power supply 100 Overload protection device 101 Control unit (MCU)
102 current measurement circuit (current measurement means)
103 voltage measurement circuit (voltage measurement means)
104 relay (power cutoff means)
105 setting input unit 106 communication circuit (communication means)
107 External server 108 User terminal

Claims (6)

An overload protection device electrically connected to a motor that drives a driven device and operating to protect the motor when an overload of the motor is detected,
current measuring means for measuring the current flowing through the motor over time and obtaining a current measurement value;
Voltage measuring means for measuring the voltage of the motor over time and acquiring a voltage measurement value;
power cutoff means for cutting off or reducing the supply of power from a power source to the motor;
a storage unit that stores a lookup table of motor characteristics consisting of a data group of current values, voltage values, and torque values of the motor collected in advance;
a control unit that controls operations of the current measuring means, the voltage measuring means, and the power cutoff means;
The control unit refers to the lookup table from the storage unit, outputs the torque conversion value of the motor over time based on the time-lapse data of the current measurement value and the voltage measurement value,
The controller cuts off the power supply by the power cutoff means when detecting that the torque conversion value exceeds a preset cutoff threshold value or reaches the predetermined cutoff threshold value. or reduce the overload protection device. The current values and torque values in the lookup table are obtained from approximate curves of measurement plots of current values and torque values measured multiple times at a constant voltage, and the lookup table is obtained from the approximate curve for each of a plurality of voltage values. 2. The overload protection device according to claim 1, wherein each of the overload protection devices comprises: Based on the first approximate curve of the current value and torque value measured at the first constant voltage value and the second approximate curve of the current value and torque value measured at the second constant voltage value, the first 3. The overload protection device according to claim 2, wherein torque conversion values are interpolated at voltage measurements between the constant voltage value of and the second constant voltage value. 4. The apparatus according to any one of claims 1 to 3, further comprising communication means for transmitting and receiving data, wherein said storage unit is provided in an external server capable of communicating via said communication means. overload protection device. A geared motor comprising: a motor, a speed reducer connected to an output shaft of the motor and outputting power to a driven device, and the overload protection device according to any one of claims 1 to 4. . A method for outputting a torque conversion value of a motor, comprising:
a step of collecting data groups of current values, voltage values and torque values of the motor and generating a lookup table of motor characteristics;
a step of measuring the current flowing through the motor over time with a current measuring means to obtain a current measurement value;
measuring the voltage of the motor over time with a voltage measuring means to acquire a voltage measurement value;
and referencing the lookup table and outputting the torque conversion value of the motor over time based on the time-varying data of the current measurement value and the voltage measurement value.

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