Stirring shaft drive unit

Abstract

To provide a stirring shaft drive unit which can secure desired performance suitable for the stirring drive unit and is more inexpensive.SOLUTION: A stirring shaft drive unit 10 comprises: a stirring shaft 11; a motor 20 which drives the stirring shaft 11; and a control unit 30 which controls the motor 20, wherein the motor 20 is an induction motor, and the control unit 30 specifies torque information regarding torque of the stirring shaft 11 on the basis of motor state information regarding a state of the motor 20 and controls the motor 20 on the basis of the torque information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an agitation shaft drive device.

Background Art

[0002] Patent Document 1 describes an agitation device that drives an agitation shaft equipped with agitation blades with a servo motor and controls the agitation and mixing of a fluid to be processed by utilizing the characteristics of the servo motor. When rotationally driving an agitation shaft equipped with agitation blades with a servo motor, this device electrically detects the torque acting on the agitation shaft, compares and calculates it with agitation data pre-input and set by control means, and controls the rotational speed of the agitation shaft by the servo motor according to the calculation result.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The agitation device described in Patent Document 1 is composed of a servo motor that rotationally drives an agitation shaft equipped with agitation blades and control means for controlling this motor. In this control means, a drive current value of a servo motor directly connected to the agitation shaft is detected by a current sensor, the inverter section is controlled based on the result of comparing the drive current value with a reference value, and it is output to the servo motor so as to achieve an appropriate rotational speed. In this control, the correlation between the rotational torque of the agitation shaft and the power of the motor is stored in advance, and the rotational speed of the motor is controlled using the measured value of the drive current value of the motor and this correlation.

[0005] However, the above control by the servo motor is over-spec for the required performance of the agitation device, and the use of an expensive servo motor has been an obstacle to cost reduction.

[0006] The present invention has been made in view of such problems, and one of its objects is to provide a stirring shaft drive device that can ensure desired performance suitable for a stirring drive device and is less expensive.

Means for Solving the Problems

[0007] In order to solve the above problems, a stirring shaft drive device according to an aspect of the present invention is a stirring shaft drive device including a stirring shaft, a motor that drives the stirring shaft, and a control unit that controls the motor, wherein the motor is an induction motor, and the control unit specifies torque information regarding the torque of the stirring shaft based on motor state information regarding the state of the motor, and controls the motor based on the torque information.

[0008] Another aspect of the present invention is also a stirring shaft drive device. This device is a stirring shaft drive device including a stirring shaft, a motor that drives the stirring shaft, and a control unit that controls the motor, wherein the motor is a motor that does not have an encoder or has an encoder with a resolution of 10,000 pulses or less per rotation, and the control unit specifies torque information regarding the torque of the stirring shaft based on motor state information regarding the state of the motor, and controls the motor based on the torque information.

[0009] Yet another aspect of the present invention is also a stirring shaft drive device. This device is a stirring shaft drive device including a stirring shaft, a motor that drives the stirring shaft, and a control unit that controls the motor, wherein the motor is a gear motor including a motor body and a speed reducer, and the control unit controls the motor based on detection information of a sensor that detects information regarding the torque acting on the motor and incorporated in the motor.

[0010] Note that any combination of the above components, or those obtained by mutually replacing the components and expressions of the present invention among methods, systems, etc., are also effective as aspects of the present invention.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a stirring shaft drive device that can ensure desired performance and is less expensive.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described with reference to each drawing based on preferred embodiments. In the embodiments and modifications, the same or equivalent components and members are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. In addition, some of the members that are not important for explaining the embodiments in each drawing are omitted.

[0014] In addition, terms including ordinals such as first and second are used to describe various components, but this term is used only for the purpose of distinguishing one component from another component, and the components are not limited by this term.

[0015] [First Embodiment] With reference to FIGS. 1 and 2, the configuration of the stirring system 100 provided with the stirring shaft drive device 10 according to the first embodiment of the present invention will be described. FIG. 1 is a diagram schematically showing the stirring system 100. FIG. 2 is a block diagram of the stirring shaft drive device 10.

[0016] The stirring system 100 is a system that stirs the material 96 to be stirred in the container 92 of the stirring tank 90 by rotating the stirring blade 94. The stirring system 100 can be suitably used, for example, in processes such as the chemical industry and the food industry. The stirring system 100 can be used, for example, for various purposes such as mixing, dispersing, dissolving, and reacting the material to be stirred.

[0017] The stirring system 100 includes a stirring shaft driving device 10 and a stirring tank 90. The stirring tank 90 stirs the material 96 to be stirred accommodated in the container 92 by rotating the stirring blade 94 in the container 92. The stirring shaft driving device 10 has a stirring shaft 11, a motor 20 that drives the stirring shaft 11, a vector inverter 41 that drives the motor 20, and a control unit 30 that controls the motor 20 via the vector inverter 41. One side of the stirring shaft 11 is connected to the output shaft of the motor 20 and rotates integrally with the output shaft of the motor 20. The other side of the stirring shaft 11 protrudes into the container 92, and the stirring blade 94 is connected to the tip. When the stirring shaft 11 rotates due to the drive of the motor 20, the stirring blade 94 rotates simultaneously to stir the material 96 to be stirred.

[0018] As the motor 20, a motor other than a servo motor can be used. In this specification, a servo motor refers to a motor system that includes a rotor equipped with a permanent magnet, a stator equipped with armature windings, a servo amplifier that supplies drive power to the armature windings according to a signal from the outside, and a high-resolution encoder capable of detecting the rotational position of the rotor, and feeds back the detection signal of this encoder to the servo amplifier to control the position (angle) and speed of the rotor. A servo motor is equipped with, for example, a high-resolution encoder with a resolution of 20 bit to 26 bit, and exhibits a high response speed, but is correspondingly expensive.

[0019] The motor 20 of the first embodiment is an induction motor as an example of a motor other than a servo motor. Compared with a servo motor, an induction motor has characteristics such as being inexpensive, robust, excellent in durability, and having a low maintenance frequency. Also, although a high-output motor is suitable for driving the stirring shaft, the servo motors available on the market have insufficient output and poor availability of high-output motors. For example, servo motors with an output exceeding 5 kW are poorly available. In contrast, induction motors have been manufactured with high output for many years, and the availability of high-output motors is particularly good. For example, the availability of induction motors with an output of 55 kW or more is good. Note that the motor 20 may be one in which a speed reducer is incorporated into the motor body as a prime mover. In this case, the output shaft of the speed reducer is the output shaft of the motor 20.

[0020] In order for the stirring system 100 to process various materials to be stirred 96, it is important to meet the explosion-proof standards for preventing fires and explosions. The explosion-proof standards are standard specifications for confirming that the manufactured explosion-proof equipment has sufficient explosion-proof performance, and only products recognized as conforming to the standards by a predetermined test can be used for explosion-proof applications. In order for the stirring system 100 to meet the explosion-proof standards, it is important that the stirring shaft drive device 10 constituting the system meets the explosion-proof standards. Also, in order for the stirring shaft drive device 10 to meet the explosion-proof standards, it is important that the motor 20 and the control unit 30 constituting the stirring shaft drive device 10 meet the explosion-proof standards. For example, as the motor 20, a model that has passed the type inspection for explosion-proof structural electrical and mechanical appliances can be adopted.

[0021] On the other hand, few servo motors meet the explosion-proof standards, and the availability of those meeting the explosion-proof standards with a desired output is poor. In contrast, induction motors have a track record of being manufactured for many years, and the availability of high-output motors meeting the explosion-proof standards is good.

[0022] As shown in FIGS. 1 and 2, the stirring shaft drive device 10 includes a vector inverter 41 that drives the motor 20 of the first embodiment. The vector inverter 41 may or may not be sensorless. The vector inverter 41 is an inverter that supplies three-phase drive power to an induction motor or a synchronous motor, and performs current vector control to correct the output waveform with reference to the voltage and current output from the inverter to the motor. Vector control controls the d-axis current, which is the current component that generates torque, and the q-axis current, which is the current component that generates magnetic flux in the rotor, respectively. Vector control is a control system that estimates and controls the rotational speed and output torque of the motor from the voltage and current output, and can realize the characteristic that the actual speed follows the command frequency even in an induction motor that has more unstable characteristics than a servo motor alone.

[0023] As shown in FIGS. 1 and 2, the motor 20 is open-loop controlled with respect to speed. That is, the stirring shaft drive device 10 does not have feedback control that negatively feeds back the speed of the motor 20 for speed control. When alternating current power of a constant frequency is supplied to an induction motor, it has a loose constant speed characteristic within the range where slip is allowed.

[0024] In the process of stirring the material to be stirred 96, the distribution of the material to be stirred 96 is quite uneven, and due to this uneven distribution, a large load fluctuation is applied to the stirring shaft 11 as the rotational position changes. Since the servo motor is equipped with a high-resolution encoder and has a high response speed, it sensitively detects the speed change due to the load fluctuation and generates a large torque change at a high speed to cancel it. This torque change may give a torque shock to the material to be stirred 96 and the stirring shaft 11, and may have an adverse effect on the material to be stirred 96. On the other hand, the motor 20 that is open-loop controlled by the vector inverter 41 has low responsiveness, so it is difficult to give a torque shock to the material to be stirred 96 due to the unevenness of the material to be stirred 96.

[0025] The control unit 30 will be described. The control unit 30 includes a motor state information acquisition unit 24 that acquires motor state information regarding the state of the motor 20, such as the electrical state of the motor 20, and a torque information acquisition unit 23 that specifies torque information T1 regarding the torque of the stirring shaft 11 based on the motor state information acquired by the motor state information acquisition unit 24. The control unit 30 controls the motor 20 based on the torque information T1 specified by the torque information acquisition unit 23. The torque of the stirring shaft 11 (hereinafter sometimes simply referred to as "torque") is equal to the output torque of the motor 20 when no torque is applied to the stirring shaft 11 from other sources.

[0026] The motor state information is not particularly limited as long as it is information regarding the motor that is correlated with the torque acting on the stirring shaft 11. For example, the motor state information may be electrical state information regarding the electrical state of the motor 20, such as the drive current or drive voltage of the motor 20, or the temperature of the motor 20. Note that, as will be described later, since the temperature of the motor 20 changes according to the motor current, it can also be regarded as electrical state information.

[0027] As an example, the motor state information may be data of a motor-related current such as the drive current of the motor 20 (hereinafter sometimes referred to as "motor current"), or data of a motor-related voltage such as the drive voltage supplied to the motor 20 (hereinafter sometimes referred to as "motor voltage"). The motor state information may be the drive current data of the motor 20 as it is, or filtered data.

[0028] The torque information T1 is not limited as long as it is information regarding the torque of the stirring shaft 11, and may be information converted from the motor state information, or may be the motor state information as it is. In the first embodiment, the torque information T1 is the current value of the current of the motor 20 detected by the current sensor 25. The current sensor 25 is a sensor that provides current as data, and as an example, may be a shunt resistor (not shown) disposed on the bus of the vector inverter 41, or a magnetic field detection type current sensor (not shown) that detects the magnetic field generated by the drive current supplied to each of the three phases.

[0029] Next, the control unit 30 of the first embodiment will be described with reference to FIG. 2. In the example of FIG. 2, the control unit 30 includes a first control unit 32 and a second control unit 36. The first control unit 32 outputs a current command C1 to the vector inverter 41 based on the speed command S1 from the second control unit 36. As an example, the first control unit 32 holds in advance the correlation between the desired current command C1 for the speed command S1 as a data table, and specifies and outputs the current command C1 by referring to the data table. To the vector inverter 41, the combined value of the current command from the first control unit 32 and the torque command P1 from the second control unit 36 is provided as a target value, and the current of the motor 20 detected by the current sensor 25 is feedback as a measured value for current.

[0030] The second control unit 36 outputs a speed command S1 to the first control unit 32 and outputs a torque command P1 to the vector inverter 41 based on the torque information T1. The second control unit 36 functions as a higher-level control unit of the first control unit 32. As an example, the second control unit 36 holds in advance the correlation between the desired speed command S1 and torque command P1 for the torque information T1 as a data table, and specifies and outputs the speed command S1 and the torque command P1 by referring to the data table. In the first embodiment, the torque information T1 is the current value of the current of the motor 20 detected by the current sensor 25.

[0031] Regarding the control of the motor 20 based on the torque information T1, there is no limitation as long as it is control based on the torque information T1. As an example, the following controls (1) to (5) can be mentioned. (1) Torque limit control for stopping the motor 20 and stopping the operation of the stirring system 100 when the torque information T1 reaches a predetermined torque. (2) Constant speed control for continuing the operation of the stirring system 100 while maintaining the speed of the motor 20 when the torque information T1 reaches a predetermined torque.

[0032] (3) When the torque information T1 reaches a predetermined torque, constant torque control is performed to operate the stirring system 100 while automatically adjusting the rotational speed of the motor 20 capable of maintaining that torque. In this case, since the rotational speed increases when the torque becomes lighter, control may be performed so that when a certain upper limit rotational speed is reached, the operation is changed to constant speed operation. (4) Upper limit torque management control for reducing the rotational speed of the motor 20 and lowering the torque when approaching the upper limit so that the torque information T1 does not reach the predetermined torque. (5) Constant acceleration control for operating the stirring system 100 while maintaining the torque increase rate of the torque information T1 at a constant ratio.

[0033] The features of the stirring shaft drive device 10 of the first embodiment will be described. The stirring shaft drive device 10 is a stirring shaft drive device including a stirring shaft 11, a motor 20 that drives the stirring shaft 11, and a control unit 30 that controls the motor 20. The motor 20 is an induction motor, and the control unit 30 identifies torque information T1 regarding the torque of the stirring shaft 11 based on motor state information regarding the state of the motor 20, and controls the motor 20 based on the torque information T1.

[0034] According to this configuration, since an induction motor is used, it is more cost - advantageous than the case of using a servo motor. Also, since the stirring shaft drive device 10 has low responsiveness, it is difficult to apply a torque shock caused by the non - uniformity of the material to be stirred to the material to be stirred. Further, various controls can be realized for the stirring system 100 including the stirring shaft drive device 10 based on the torque information T1.

[0035] [Second Embodiment] Referring to FIG. 3, the stirring shaft drive device 10 according to the second embodiment of the present invention will be described. FIG. 3 is a block diagram of the stirring shaft drive device 10 according to the second embodiment. In the description of the second embodiment, the descriptions overlapping with those of the first embodiment will be omitted as appropriate, and the points different from those of the first embodiment will be mainly described. In the first embodiment, an example in which the motor 20 does not include an encoder and is open-loop controlled with respect to speed is shown, but the present invention is not limited thereto. The motor 20 is different from the first embodiment in that it includes a low-resolution encoder 26 and the detection result of the encoder 26 is speed-feedback, and other configurations are the same.

[0036] The stirring shaft drive device 10 according to the second embodiment is a stirring shaft drive device having a stirring shaft 11, a motor 20 for driving the stirring shaft 11, and a control unit 30 for controlling the motor 20. The motor 20 is a motor having an encoder 26 with a resolution per revolution (hereinafter simply referred to as "resolution") of 10,000 pulses or less. The control unit 30 specifies torque information T1 regarding the torque of the stirring shaft 11 based on the motor state information regarding the state of the motor 20, and controls the motor 20 based on the torque information T1. Since the resolution of the encoder 26 is 10,000 pulses or less, the response speed of the speed control is limited by the waste time element determined by the period of the pulses of the encoder 26, and the response speed can be lowered to such an extent that it is difficult to apply the torque impact due to the non-uniformity of the material to be stirred 96 to the material to be stirred 96. From the same point of view, the resolution of the encoder 26 is more preferably 3,000 pulses or less, and in the embodiment, it is 2,024 pulses.

[0037] According to the second embodiment, the same operations and effects as those of the first embodiment are achieved. In addition, the accuracy of the rotational speed of the stirring shaft 11 is improved compared to the first embodiment.

[0038] [Third Embodiment] Referring to FIG. 4, the stirring shaft driving device 10 according to the third embodiment of the present invention will be described. FIG. 4 is a block diagram of the stirring shaft driving device 10 according to the third embodiment. In the description of the third embodiment, the description overlapping with that of the first embodiment will be omitted as appropriate, and the points different from the first embodiment will be mainly described. The third embodiment is different from the first embodiment in that the configurations of the motor 20 and the control unit 30 are different, and other configurations are the same.

[0039] In the third embodiment, the motor 20 is a gear motor including a motor body 22, a speed reducer 27 for reducing the output rotation of the motor body 22, and a torque sensor 28. In this example, the speed reducer 27 and the torque sensor 28 are integrally incorporated. The torque sensor 28 is incorporated in the motor 20 and detects information regarding the torque acting on the motor 20. The control unit 30 controls the motor 20 based on the detection information of the torque sensor 28. That is, in the third embodiment, the second control unit 36 uses the detection information of the torque sensor 28 as torque information T2, and based on the torque information T2, outputs a speed command S1 to the first control unit 32 and outputs a torque command P1 to the vector inverter 41.

[0040] The motor 20 of the third embodiment has a motor body 22 and a speed reducer 27 for reducing the rotation of the output shaft of the motor body 22 housed in a single housing 21. The stirring shaft 11 is connected to the output shaft of the speed reducer 27 and rotates integrally with the output shaft. As the speed reducer 27, for example, an eccentric swing type speed reducer, a flexure engagement type speed reducer, etc. can be adopted. A torque sensor 28 for detecting the torque applied to the output shaft of the speed reducer 27 is incorporated in the speed reducer 27. For example, the torque sensor 28 is a torque sensor that detects a torque value and provides the detected torque value as information T2 regarding torque. As an example, the torque sensor 28 is a strain sensor that detects the strain generated in the output shaft in response to the torque applied to the output shaft of the speed reducer 27. For example, when the speed reducer is a planetary gear speed reducer such as an eccentric swing type, the torque sensor 28 is a sensor provided on the internal gear. When torque is applied to the output shaft, the load torque is applied to the internal gear, and the strain of the strain sensor generated by the load torque is measured.

[0041] The motor 20 of the third embodiment has a torque limiter function that limits the torque of the motor body 22 when the detected torque reaches a predetermined upper limit value, and the torque sensor 28 also serves as a torque sensor for detecting the detected torque. The motor 20 of the third embodiment configured in this way functions as a gear motor that controls the motor body 22 according to the torque value detected by the torque sensor 28.

[0042] According to the third embodiment, the same operations and effects as those of the first embodiment are achieved.

[0043] [Fourth Embodiment] Referring to FIG. 5, the stirring shaft drive device 10 according to the fourth embodiment will be described. FIG. 5 is a block diagram of the stirring shaft drive device 10 according to the fourth embodiment. When the motor 20 is rotating at a low speed, the current and voltage of the motor 20 are unstable, so the torque information specified from these may be inaccurate. Therefore, in the fourth embodiment, it is different from the third embodiment in that the control unit 30 controls the motor 20 by using both the torque information T1 acquired by the current sensor 25 and the torque information T2 acquired by the torque sensor 28, and other configurations are the same. For example, the control unit 30 can selectively use the torque information T1 and the torque information T2 according to the rotation speed of the motor 20.

[0044] In the fourth embodiment, the torque information T1 acquired by the current sensor 25 and the torque information T2 acquired by the torque sensor 28 are provided to the control unit 30. When the speed of the motor 20 is lower than a preset reference speed, the control unit 30 controls the motor 20 by using the torque information T2 acquired by the torque sensor 28 in combination. This reference speed can be set experimentally so that a desired accuracy can be obtained for the torque information. When the speed of the motor 20 exceeds the reference speed, the control unit 30 controls the motor 20 based on one of the torque information T1 and the torque information T2.

[0045] According to the fourth embodiment, the same operations and effects as those of the third embodiment are achieved. In addition, since the fourth embodiment uses the torque information T2 from the relatively accurate torque sensor 28 during low-speed rotation, the control accuracy can be improved.

[0046] [Fifth Embodiment] Referring to FIG. 6, the stirring shaft drive device 10 according to the fifth embodiment will be described. FIG. 6 is a block diagram of the stirring shaft drive device 10 according to the fifth embodiment. The fifth embodiment is different from the first embodiment in that it includes a temperature sensor 29 for acquiring the temperature of the motor 20, and the other configurations are the same.

[0047] The temperature of the motor 20 changes as the current of the motor 20 changes. Therefore, the temperature of the motor 20 is information related to the current of the motor 20, and by extension, information related to the torque of the motor 20. Therefore, the detection result of the temperature sensor 29 that acquires the temperature of the motor 20 can be used as torque information T3 regarding the torque of the stirring shaft 11. In particular, the torque information T3 can be considered as the average value of the torque of the stirring shaft 11. The control unit 30 may be configured to control the motor 20 based on the torque information T3 specified by the temperature sensor 29. The torque information T3 may be used in combination with at least one of the torque information T1 and the torque information T2. The control unit 30 may be configured to control the motor 20 based on at least one or more of the torque information T1, the torque information T2, and the torque information T3.

[0048] When the temperature of the motor 20 changes, the relationship (torque constant) between the torque of the motor 20 and the current of the motor 20 changes, which may be a factor in reducing the control accuracy. Therefore, in the fifth embodiment, the control unit 30 controls the motor 20 based on the torque information T1 and the torque information T3. The control unit 30 corrects the torque constant of the motor 20 according to the temperature of the motor 20.

[0049] According to the fifth embodiment, the same operations and effects as those of the first embodiment are achieved. In addition, since the fifth embodiment can correct the torque constant of the motor 20 according to the temperature of the motor 20, it is possible to suppress a decrease in control accuracy due to temperature rise.

[0050] The present invention has been described based on several embodiments. These embodiments are illustrative, and it is understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and such modifications and changes are also within the scope of the claims of the present invention. Therefore, the descriptions and drawings in this specification should be treated as illustrative rather than restrictive.

[0051] (Modification example) Hereinafter, a modification example will be described. In the drawings and descriptions of the modification example, the same or equivalent components and members as those in the first embodiment are denoted by the same reference numerals. Descriptions overlapping with those of the first embodiment are omitted as appropriate, and the configurations different from those of the first embodiment will be mainly described.

[0052] In the description of the first embodiment, an example in which the control unit 30 specifies the torque information T1 from a single motor state information (the current of the motor 20) has been shown, but the present invention is not limited thereto. For example, the control unit may specify the torque information by using a plurality of motor state information. For example, the control unit may specify the torque information by using the current of the motor and the voltage of the motor.

[0053] In the above description, an example in which the control unit specifies the torque information from any one or more of the current of the motor, the voltage of the motor, and the temperature of the motor has been shown, but the present invention is not limited thereto. For example, the motor is a gear motor incorporating a speed reducer, and the control unit may control the motor by using the detection information of a sensor that detects information regarding the torque acting on the motor incorporated in the motor. As the speed reducer and the sensor in this case, the speed reducer 27 and the torque sensor 28 described in the third embodiment can be adopted.

[0054] In the description of the embodiment, an example in which the motor 20 is an induction motor has been shown, but the motor may be, for example, a synchronous motor other than an induction motor within a range not conflicting with the description of the claims.

[0055] In the description of the embodiment, an example was shown in which the second control unit 36 outputs a torque command P1 to the vector inverter 41 based on the torque information T1. However, the present invention is not limited to this. For example, the torque command P1 may not be provided to the vector inverter 41.

[0056] Each of these modifications has the same operations and effects as each embodiment.

[0057] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. Applying some components of an embodiment and a modification to another embodiment or modification is also useful as an embodiment of the present invention. A new embodiment generated by the combination has the effects of the embodiments and modifications combined.

Description of Reference Numerals

[0058] 10 Stirring shaft drive device, 11 Stirring shaft, 20 Motor, 22 Motor body, 26 Encoder, 27 Reducer, 28 Torque sensor, 30 Control unit, 90 Stirring tank.

Claims

1. A stirring shaft drive device having a stirring shaft, a motor for driving the stirring shaft, and a control unit for controlling the motor, wherein the motor is an induction motor, and the control unit identifies torque information regarding the torque of the stirring shaft based on motor state information regarding the state of the motor, and controls the motor based on the torque information.

2. A stirring shaft drive device having a stirring shaft, a motor for driving the stirring shaft, and a control unit for controlling the motor, wherein the motor is a motor that does not have an encoder or has an encoder with a resolution of 10,000 pulses or less per revolution, and the control unit identifies torque information regarding the torque of the stirring shaft based on motor state information regarding the state of the motor, and controls the motor based on the torque information.

3. The stirring shaft drive device according to claim 1 or 2, wherein the motor is open-loop controlled with respect to speed.

4. The stirring shaft drive device according to claim 1 or 2, wherein the control unit identifies the torque information by using a plurality of pieces of the motor state information.

5. The stirring shaft drive device according to claim 4, wherein the plurality of pieces of motor state information includes the temperature of the motor.

6. The motor is a geared motor including a motor body and a speed reducer, and includes a sensor incorporated in the motor for detecting information regarding the torque acting on the motor, and the control unit controls the motor based on the motor state information and the detection information of the sensor.

7. The stirring shaft driving device according to claim 6, wherein the control unit controls the motor based on detection information of the sensor when the speed of the motor is lower than a preset speed.

8. A stirring shaft driving device comprising a stirring shaft, a motor for driving the stirring shaft, and a control unit for controlling the motor, wherein the motor is a gear motor including a motor body and a speed reducer, The stirring shaft driving device, wherein the control unit controls the motor based on detection information of a sensor incorporated in the motor and detecting information regarding torque acting on the motor.

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