Overload protection device, motor, and geared motor

Abstract

To provide an overload protection device that makes it possible to protect an overload on a motor, etc., without being affected from external environments.SOLUTION: An overload protection device comprises: a revolving shaft connected so as to synchronously rotate with the motor shaft of a motor; a rotary disk that rotates around the revolving shaft as an axis and has one or more slits; a photosensor for detecting passage of one or more slits when the rotary disk rotates; and a control unit having monitoring means for monitoring the revolution speed of the rotary disk on the basis of the output signals of the photosensor when the motor is running and controlling the motion of the motor on the basis of information from the monitoring means. The control unit detects that the motor is overloaded when the revolution speed of the rotary disk while the motor is running decreases to reach a predetermined threshold, and stops power delivery to the motor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an overload protection device that monitors the load state of a motor driving a driven device, and prevents damage to the driven device, the motor, and / or the geared motor by cutting off or limiting the power supply to the motor when an excessive load is detected, and also relates to a motor and a geared motor provided with the overload protection device.

Background Art

[0002] Conventionally, when driving a driven device such as a conveyor device with a motor (or a geared motor), if the load suddenly increases due to foreign matter being caught or the like, and the motor continues to drive in this overload state, one or both of the motor and the driven device may be physically damaged. In response to this, an overload protection device has been developed that detects the overload of the motor and prevents damage to the motor and the driven device by cutting off or limiting the power supply to the motor.

[0003] For example, Patent Document 1 discloses an overload protection device that prevents the destruction of a geared motor and an industrial machine. Hereinafter, in this paragraph, the reference numerals of Patent Document 1 are shown in parentheses. The overload cut-off device (4) selects a predetermined current value less than the rated current value of the motor (2) as the current specified value (6), and selects the predetermined time during which a current flows at an overload current value (5) exceeding the current specified value (6) as the specified value of the overload current time (7) by a specified value setting means (14). An overcurrent detection means (15) detects an overload current value (5) and an overload current time exceeding the current specified value (6) selected by the specified value setting means (14), and a power supply cut-off means (19) that cuts off the power supply to the motor (2) when it is detected by the overcurrent detection means (15) that the overload current time has exceeded the specified value of the overload current time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional overload protection devices such as Patent Document 1 read an increase in the value of the current flowing through a motor, and when the measured current value exceeds the specified value of the current, detect an overload and cut off the power supply to the motor. However, in conventional overload protection devices, when the device is used in an installation environment where the power supply is unstable, there are current fluctuations in the equipment (for example, the occurrence of power supply voltage imbalance due to the use of a specific single-phase power supply, etc.) or noise from mechanical devices (for example, voltage fluctuations and noise generation due to the acceleration and deceleration of a large-capacity servo motor), the problem is that the overload protection device is easily electrically affected by the external environment, reads an incorrect current value, and is prone to malfunction. Therefore, there is a risk that the overload protection device may stop the motor unnecessarily or be unable to appropriately stop the motor despite an overload, resulting in damage to the motor or the like.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide an overload protection device, a motor, and a geared motor that can protect a motor or the like from an overload without being affected by the external environment.

Means for Solving the Problems

[0007] The overload protection device according to one aspect of the present invention is an overload protection device that is connected to a motor that drives a driven device and operates to protect the motor from an overload, a rotating shaft connected to rotate in synchronization with the motor shaft of the motor, a rotating disk that rotates about the rotating shaft and has one or more slits, a photosensor that detects the passage of the one or more slits when the rotating disk is rotating, When the motor operates, it has monitoring means for monitoring the rotational speed of the rotating disk based on the output signal of the photosensor, and a control unit for controlling the operation of the motor based on the information of the monitoring means. When the rotational speed of the rotating disk decreases until it reaches a predetermined threshold value during the operation of the motor, the control unit detects that the motor is in an overload state and stops the power supply to the motor.

[0008] In the overload protection device of the present invention, the photosensor detects the passage of the slit of the rotating disk during rotation, so that the monitoring means constantly monitors the rotational speed of the motor shaft. Then, when the monitoring means monitors a decrease in the physical rotational speed of the motor shaft due to the occurrence of an overload and the rotational speed decreases until it reaches a predetermined threshold value, the control unit detects the overload state of the motor and stops the power supply to the motor. That is, the overload protection device of the present invention uses the physical value of the rotational speed of the motor shaft as the criterion for the overload of the motor, so that it can detect the overload state without being affected by the electrical influence from the external environment and appropriately stop the motor.

[0009] In a further form of the overload protection device of the present invention, the motor is an induction motor. That is, since an induction motor has the property that its rotational speed decreases as the load increases, the motor can be appropriately protected from overload by setting a threshold value based on the rotational speed-torque characteristic of the motor.

[0010] In a further form of the overload protection device of the present invention, the rotating shaft is connected to the end of the output end of the motor shaft via a bearing on the opposite side. That is, the overprotection load device is easy to retrofit to an existing motor.

[0011] In a further form of the overload protection device of the present invention, the threshold value is the rated rotational speed at which the motor can operate at the rated torque. That is, by setting the threshold value to the rated rotational speed of the motor, it is possible to prevent the heat generation of the motor from increasing due to an overload.

[0012] In a further form of the overload protection device of the present invention, when the detection time for the control unit to detect that the rotational speed of the rotating disk is equal to or lower than the threshold value exceeds a predetermined time, the control unit stops the power supply to the motor. That is, when the detection time of the overload state exceeds a predetermined time, by cutting off the power supply to the motor, it is possible to allow a short-time or instantaneous load increase with relatively little impact on the motor and appropriately reduce the frequency of the motor stopping.

[0013] A further form of the overload protection device of the present invention further includes a user interface that receives an input from a user, notifies the user of an overload state, and requests confirmation of the removal of the load cause. After the control unit stops the power supply to the motor, when the user inputs confirmation of the removal of the load cause via the user interface, the power supply to the motor can be turned on. That is, by notifying the user of the overload state via the user interface and requesting confirmation of the removal of the load cause, it is possible to prevent the user from turning on the power while the load cause remains, thereby further improving the safety of the device.

[0014] A further form of the overload protection device of the present invention further includes a relay configured to receive a stop signal for stopping the power supply from the control unit to the motor and to switch the relay contacts upon receiving the stop signal to cut off the power supply to the motor. That is, the relay that has received the power supply stop signal mechanically switches the relay contacts to cut off the power supply to the motor on the mechanical device side, so that overload protection can be more reliably executed without being affected by the electrical environment of the external environment.

[0015] A motor according to an embodiment of the present invention is characterized by including the overload protection device described above. That is, the motor of the present invention can exhibit the effect of the overload protection device as a motor.

[0016] A geared motor according to an embodiment of the present invention includes the motor described above and a speed reducer connected to an output end of a motor shaft of the motor to output power to a driven device. That is, the geared motor of the present invention can exhibit the effect of the overload protection device as a geared motor.

Advantages of the Invention

[0017] The overload protection device of the present invention can protect a motor or the like from overload without being affected by electrical influences from the external environment.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the shapes of the respective drawings referred to in the following description are conceptual diagrams or schematic diagrams for explaining suitable shapes, and the dimensional ratios and the like do not necessarily match the actual dimensional ratios. That is, the present invention is not limited to the dimensional ratios in the drawings.

[0020] FIG. 1 is a schematic diagram exemplarily showing a motor 11 according to an embodiment of the present invention. FIG. 2 is a view taken along the line A-A of the motor 11 in FIG. 1. FIG. 3 is a block diagram showing the configuration of an overload protection device 100 according to an embodiment of the present invention.

[0021] As shown in FIG. 1, the motor 11 of the present embodiment includes a motor main body 12, a motor shaft 13 provided on the motor main body 12, a terminal box 14 electrically connected to the motor main body 12, and an overload protection device 100 introduced into the motor main body 12. The motor main body 12 is composed of a general motor, and a detailed description thereof is omitted.

[0022] In the present embodiment, the motor 11 is an induction motor. The induction motor has a characteristic that the rotational speed decreases as the load increases. The motor 11 has a rotational speed-torque characteristic according to each specification. FIG. 4 exemplifies the rotational speed-torque characteristic of a typical motor. In particular, the motor 11 has a no-load rotational speed at which the rotational speed is maximum when the load is 0, and has a characteristic that the rotational speed decreases as the load on the motor shaft 13 increases. Further, as a general specification, a rated rotational speed and a rated torque (indicating the torque generated at the rated rotational speed) are set for the motor 11. Since heat generation rapidly increases when the motor 11 operates at a torque exceeding the rated torque, continuous operation below the rated torque is preferably performed. Further, up to a certain load, the load and the torque are balanced, but when the load exceeds the stall torque (the maximum torque that the motor can generate), the motor 11 is forcibly stopped, and the risk of damage to the motor 11 and the driven device increases.

[0023] The terminal box 14 further includes power terminals (U, V, W) connected to the three-phase power supply 18, motor terminals electrically connected to the motor 11, and external terminals for connecting to external devices. The power terminals are electrically connected to the motor terminals via a circuit board. This terminal box 14 includes a circuit board incorporated with a processor, a communication circuit, a relay circuit, etc., and the circuit board constitutes some components (control unit 110 and monitoring means) of the overload protection device (or overload protection system) 100. Note that the terminal box 14 may be configured such that an independent control power supply 19 (for example, a battery) that is not affected by the external power environment is supplied to the control unit 110 separately from the three-phase power supply 18. This control power supply 19 may be provided inside the terminal box 14 of the motor 11.

[0024] Then, by connecting the output end of the motor shaft 13 to the driven device (optionally via a speed reducer), the driven device can be driven. The driven device is, for example, a chip conveyor (not shown), and the motor shaft 13 of the motor 11 is directly or indirectly connected to the sprocket of the chip conveyor. On the other hand, the opposite side of the output end of the motor shaft 13 is connected to the physical components of the overload protection device 100.

[0025] As shown in FIGS. 1 to 3, the overload protection device 100 includes a rotating shaft 101 connected to rotate synchronously with the motor shaft 13 of the motor 11, a rotating disk 102 that rotates about the rotating shaft 101 and has a plurality of slits 103, a photosensor 104 that detects the passage of the plurality of slits 103 when the rotating disk 102 rotates, and a control unit (MCU) 110 that monitors the rotation speed of the rotating disk 102 based on the output signal of the photosensor 104 during the operation of the motor 11 and controls the operation of the motor 11 based on the information of the monitoring means. The mechanical part of the overload protection device 100 is provided on the rear end side of the motor body 12 and is housed in a housing extended from the motor body 12 to the rear end side.

[0026] Specifically, one end of the rotating shaft 101 is connected to the end of the motor shaft 13 on the opposite side of the output end thereof via a bearing 15 so as to rotate synchronously with the motor shaft 13. And a rotating disk 102 is provided on the other end of the rotating shaft 101. Four slits 103 are formed at equal intervals in the circumferential direction on this rotating disk 102. Note that the number of slits 103 may be one, but a plurality of slits enables more precise measurement of the rotation speed. The photosensor 104 is fixed to the housing of the motor 11 and is electrically connected to the terminal box 14 via a cable. The photosensor 104 is arranged so as to sandwich the front and back surfaces of the rotating disk 102 and detects the passage of the rotating slit 103. The output signal from the photosensor 104 is sent to the control unit 110, and the rotation speed (rpm) of the rotating disk 102 is calculated based on the number of passages of the slit 103 per unit time. The rotation speed of this rotating disk 102 is the same as the rotation speed of the motor shaft 13. Alternatively, the rotation speed of the rotating disk 102 is proportional to the rotation speed of the motor shaft 13.

[0027] As shown in FIG. 3, the overload protection device 100 is provided with a relay 111 as power cut-off means. The relay 111 is directly or indirectly connected to the control unit 110 and the three-phase power supply 18. The relay 111 is configured to receive an instruction from the control unit 110, control the three-phase power supply 18, and cut off the power supply from the three-phase power supply 18 to the motor 11. In the present embodiment, the relay 111 operates by mechanical switching of relay contacts. In the overload protection device 100 of the present embodiment, the control unit 110 monitors the rotation speed of the rotating disk 102 (motor shaft 13) over time, and when the rotation speed falls below (or reaches) a predetermined threshold value, it detects that the motor 11 is in an overload state, controls the relay 111 to cut off the power supply, and stops the power supply to the motor 11. Alternatively, the control unit 110 may be set to detect an overload state when the detection time during which the rotation speed of the motor 11 falls below a predetermined threshold value exceeds a predetermined time (or when it continues for a predetermined time) and stop the power supply to the motor 11.

[0028] In this embodiment, the threshold value can be arbitrarily selected by the user as the reduction rate with respect to the no-load rotation speed. For example, the user can set the rotation speed reduced by 30% with respect to the no-load rotation speed as the threshold value. Also, the user can set the threshold value based on the rotation speed-torque characteristics specific to the motor shown in FIG. 4. In the form illustrated in FIG. 4, the rated rotation speed is set as the first threshold value N1, and the rotation speed between the rated rotation speed and the rotation speed at the stall torque on the characteristic graph (the rotation speed immediately before exceeding the stall torque) is set as the second threshold value N2. Then, when the detection time during which the rotation speed is lower than the first threshold value N1 continues for a predetermined time (seconds), the control unit 110 may control to stop the power supply to the motor 11. The detection time can be set, for example, to 0.5 to 1.0 seconds. Also, when the rotation speed reaches the second threshold value N2, the control unit 110 may control to immediately stop the power supply to the motor 11. That is, the user can perform finer control by setting the detection time for each of the plurality of threshold values.

[0029] In addition, as shown in FIG. 3, the overload protection device 100 is provided with a user interface 113 that enables interaction between the user and the system. The user interface 113 can be selected from any means such as a display, a touch panel, and audio input / output means, which are connected to the control unit 110. The user interface 113 can receive input from the user and enable operations and settings of the motor 11. The settings include a threshold value that defines the overload state of the motor 11 and the detection time required to cut off the power supply. Further, the user interface 113 may notify the user that the overload state has been detected when the overload state of the motor 11 is detected. Furthermore, after stopping the power supply to the motor 11 based on the detection of the overload state, the user interface 113 may operate to request confirmation of the removal of the load cause (safety confirmation). In this case, the user can input via the user interface 113 that the load cause has been removed, thereby releasing the power supply stop state to the motor 11 and enabling the restart of the motor 11. In other words, without the input confirming the removal of the load cause, the power supply to the motor 11 is restricted.

[0030] Furthermore, the overload protection device 100 may include a communication circuit as a means for communicating with the outside. The communication circuit connects the control unit 110 and an external server and enables data transmission and reception therebetween. By using the external server, the user can obtain a lot of data regarding the motor characteristics for each type of motor, and moreover, the setting and update / correction of the device are facilitated. Also, the external server may store the logs of various data output via the communication circuit by the control unit 110 during motor driving. Alternatively, a storage unit for storing various data may be incorporated as a recording medium such as a memory or a hard disk on the substrate inside the terminal box 14.

[0031] In addition, the communication circuit may optionally connect the control unit 110 and the user terminal. The user terminal is a terminal operable by the user, such as a control panel, a smartphone, a personal computer, etc. By using this user terminal, the operation of the motor 11 can be monitored and displayed on the monitor, or device settings can be remotely input to the control unit 110. The connection between the communication circuit and the above external device may be either wired or wireless. Examples of wireless connection means include WiFi (registered trademark), Bluetooth (registered trademark), etc.

[0032] Subsequently, with reference to the flowchart of FIG. 5, the operation of the motor 11 with the overload protection device 100 will be described. First, the user turns on the power of the motor 11. Thereby, a power supply is supplied from the three-phase power supply 18 to the motor 11. Next, when the user turns on the control power supply 19 and inputs an instruction to start operation via the user interface 113. Thereby, the operation of the motor 11 starts. During operation, in the case of a normal load where the overload protection device 100 does not detect an overload state, the motor 11 operates normally, and the operation ends by stopping the motor 11 by the user's operation. On the other hand, when an overload occurs during operation, the rotational speed of the motor 11 decreases. When the rotational speed of the rotating disk 102 reaches a threshold value, or when the detection time during which the rotational speed becomes equal to or lower than the threshold value exceeds a predetermined time, the overload protection device 100 detects or determines that the motor 11 is in an overload state. Then, the control unit 110 transmits a stop signal to the relay 111. The relay 111 mechanically switches its relay contacts upon receiving the stop signal. By this switching of the relay contacts, the power supply from the three-phase power supply 18 to the motor 11 is cut off. The user receives a notification of motor power cut-off via the user interface 113. After the user removes the cause of the load, by inputting "confirmation of removal of load cause" (safety confirmation) via the user interface 113, the motor power cut-off is released and the motor power-on becomes possible.

[0033] FIG. 6 is a block diagram of an entire system including a motor 11 with an overload protection device 100. As shown in FIG. 6, the system includes a geared motor in which the output side of the motor 11 including the overload protection device 100 is connected to a speed reducer 16. A three-phase power supply 18 supplies power to the motor 11. A control power supply 19 supplies control power to the overload protection device 100 (control unit 110). Further, the output shaft of the speed reducer 16 is connected to a chip conveyor 17 as a driven device. The system obtains an output of low rotation speed and high torque at the output shaft of the speed reducer 16 and drives the chip conveyor 17. During the driving of the chip conveyor 17, when an object being transported becomes overloaded or a foreign object jams into the chip conveyor 17, resulting in an overload state and the rotational speed of the motor shaft 13 decreases, the overload protection device 100 detects the overload state, and the relay contact of the relay 111 switches, thereby cutting off the power supply from the three-phase power supply 18 to the motor 11.

[0034] That is, in the overload protection device 100 of the present embodiment, when the photosensor 104 detects the passage of the slit 103 of the rotating disk 102, the monitoring means constantly monitors the physical rotational speed of the motor shaft 13. Then, when the monitoring means monitors a decrease in the physical rotational speed of the motor shaft 13 due to the occurrence of an overload and the rotational speed decreases until it reaches a predetermined threshold value (N1, N2), the control unit 110 detects the overload state of the motor 11 and stops the power supply to the motor 11. That is, by using the physical value of the rotational speed of the motor shaft 13 as a criterion for the overload of the motor 11, the overload protection device 100 can detect the overload state without being affected by the external environment and appropriately stop the motor.

[0035] [Alternative Embodiment / Modification Example] The present invention is not limited to the above-described embodiment and can take various embodiments and modification examples. Hereinafter, alternative embodiments and modification examples of the present invention will be described.

[0036] (1) In the above embodiment, the control unit of the overload protection device is integrated on a control board built in the terminal box of the motor, but as long as each component can be controlled, it may be provided separately from the motor.

[0037] (2) In the above embodiment, in the overload protection device, the rotating shaft is connected coaxially with the motor shaft, but the present invention is not limited thereto. For example, a hypoid gear or the like may be used so that the rotating shaft is orthogonal to the motor shaft and is connected to be rotatable synchronously with the motor shaft.

[0038] (3) In the overload protection device of the above embodiment, the relay as the power cut-off means is configured to send a power cut-off signal to the power supply, but the power cut-off means is arranged between the motor and the power supply, and the power supply may be cut off by opening and closing a switch. That is, the configuration of the above embodiment is only an example, and those skilled in the art can make various modifications under the technical idea of the present invention.

[0039] The present invention is not limited to the above-described embodiments and modifications, and can be implemented in various forms as long as it belongs to the technical scope of the present invention.

Explanation of Reference Numerals

[0040] 11 Motor 12 Motor Body 13 Motor Shaft 14 Terminal Box 15 Bearing 16 Reducer 17 Chip Conveyor (Driven Device) 18 Three-Phase Power Supply 19 Control Power Supply 100 Overload Protection Device 101 Rotating Shaft 102 Rotating Disk 103 Slit 104 Photo Sensor 110 Control Unit (MCU) 111 Relay (Power Cut-Off Means) 113 User Interface

Claims

1. An overload protection device connected to a motor that drives a driven device and operates to protect the motor from overload, comprising: a rotating shaft connected to rotate in synchronization with the motor shaft of the motor; a rotating disk that rotates about the rotating shaft and has one or more slits; a photosensor that detects the passage of the one or more slits when the rotating disk is rotating; monitoring means for monitoring the rotational speed of the rotating disk based on the output signal of the photosensor during operation of the motor, and a control unit for controlling the operation of the motor based on the information of the monitoring means; The control unit detects that the motor is in an overload state when the rotational speed of the rotating disk decreases until it reaches a predetermined threshold value during operation of the motor, and stops the power supply to the motor. An overload protection device characterized by that.

2. The overload protection device according to claim 1, wherein the motor is an induction motor.

3. The overload protection device according to claim 2, wherein the rotating shaft is connected to an end portion on the opposite side of the output end of the motor shaft via a bearing.

4. The overload protection device according to claim 1, wherein the threshold value is a rated rotational speed at which the motor can operate at a rated torque.

5. The overload protection device according to claim 1, wherein the control unit stops the power supply to the motor when a detection time for detecting that the rotational speed of the rotating disk is equal to or lower than the threshold value exceeds a predetermined time.

6. Further comprising a user interface that receives an input from a user, notifies the user that there is an overload, and requests confirmation of removal of the load cause, After the control unit detects that the motor is in an overload state and stops the power supply to the motor, when the user inputs confirmation of removal of the load cause via the user interface, power can be supplied to the motor. The overload protection device according to claim 1, characterized in that.

7. The overload protection device according to claim 1, further comprising a relay configured to receive a stop signal for stopping the power supply from the control unit to the motor, and to switch a relay contact by receiving the stop signal to cut off the power supply to the motor.

8. A motor characterized by comprising the overload protection device according to any one of claims 1 to 7.

9. A geared motor characterized by comprising the motor according to claim 8 and a speed reducer connected to an output end of a motor shaft of the motor to output power to a driven device.

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