MOTOR DRIVE CONTROL DEVICE, MOTOR UNIT, AND MOTOR DRIVE CONTROL METHOD

Abstract

To enhance stability of a driving control of a two-phase stepping motor against a load fluctuation.SOLUTION: A motor driving control device 10 comprises a control part 11 and a driving part 12, in which the control part monitors a rotational state of a rotor 22 of a two-phase stepping motor 20 and sets an energization angle θ that indicates the magnitude of an electric angle continuously energizing a coil in one phase of coils 21A and 21B in two phases in the two-phase stepping motor 20 on the basis of a rotational state of the rotor 22, and generates a control signal Sd for controlling drive of the two-phase stepping motor 20 on the basis of the set energization angle θ, and the driving part drives the coils 21A and 21B in two phases on the basis of the control signal Sd.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor drive control device, a motor unit, and a motor drive control method, and relates to a motor drive control device for driving a stepping motor, for example. [Background technology]

[0002] As a stepping motor, a two-phase stepping motor having two phases is known. Known drive methods for a two-phase stepping motor include a one-phase excitation method, a two-phase excitation method, and a one-two phase excitation method.

[0003] The one-phase excitation method switches the excited phase one by one. In the one-phase excitation method, the conduction angle, which represents the size of the electrical angle when the coil of one phase is continuously energized in one direction, is 90 degrees, and the two-phase stepping motor commutates every 90 degrees.

[0004] The two-phase excitation method switches between two excited phases. In the two-phase excitation method, the conduction angle is 180 degrees, and the two-phase stepping motor is commutated every 90 degrees.

[0005] The 1-2 phase excitation method switches between one-phase excitation and two-phase excitation to switch the excited phase. In the 1-2 phase excitation method, the conduction angle is generally 135 degrees, and the two-phase stepping motor is commutated every 45 degrees.

[0006] For example, Patent Document 1 discloses a motor drive control technology in which, in order to suppress variations in the rotation speed of a two-phase stepping motor when driven by a 1-2 phase excitation method, a period of two-phase excitation is provided during a one-phase excitation period in the same phase as the next two-phase excitation period. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-93914 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present inventors have studied a control method for varying the rotation speed of a two-phase stepping motor according to the load using a 1-2 phase excitation method that generates a larger torque than one-phase excitation, as a method for controlling the drive of a two-phase stepping motor to be used in a specific application. Specifically, this control method is a closed-loop control method that generates an appropriate torque for the load by detecting the point (zero cross point) where the back electromotive force of a non-excited coil becomes zero during the one-phase excitation period and determining the commutation timing based on the identified rotor position.

[0009] According to the above-mentioned control method studied by the inventors, when the load on the two-phase stepping motor is heavy, the rotor rotation speed decreases, and when the load is light, the rotor rotation speed increases, thereby making it possible to adjust the torque by changing the rotation speed according to the load.

[0010] However, the inventors' investigations have revealed that if the load is suddenly reduced, for example by the application of a load in the opposite direction, the rotor's rotational speed will increase too much, and the data processing by the microcontroller that constitutes the motor drive control device will not be able to keep up with the rotor's rotational speed, causing the drive control of the two-phase stepping motor to become unstable, and there is a risk that the object driven by the two-phase stepping motor will vibrate or produce abnormal noise.

[0011] The present invention has been made in consideration of the above-mentioned problems, and has an object to improve the stability of drive control of a two-phase stepping motor against load fluctuations. [Means for solving the problem]

[0012] A motor drive control device according to a representative embodiment of the present invention is characterized in that it includes a control unit that monitors the rotational state of a rotor of a two-phase stepping motor, and sets a conduction angle indicating the magnitude of the electrical angle at which current is continuously passed in one direction through one of the two-phase coils in the two-phase stepping motor based on the rotational state of the rotor, and generates a control signal for controlling the drive of the two-phase stepping motor based on the set conduction angle, and a drive unit that drives the two-phase coils based on the control signal. Effect of the Invention

[0013] According to the motor drive control device of the present invention, it is possible to improve the stability of drive control of a two-phase stepping motor against load fluctuations. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a configuration of a motor unit according to a first embodiment. [Diagram 2] 1 is a diagram illustrating a schematic configuration of a two-phase stepping motor 20 according to a first embodiment. [Diagram 3] 1 is a diagram showing the relationship between the conduction angle and the one-phase excitation period and the two-phase excitation period in the conduction switching control of a two-phase stepping motor. FIG. [Figure 4] FIG. 4 is a diagram showing an example of a method for setting a conduction angle θ according to the first embodiment. [Diagram 5] 5 is a diagram for explaining energization switching control of a two-phase stepping motor in a 1-2 phase excitation mode according to the first embodiment. FIG. [Figure 6] 10 is a diagram for explaining a method of determining a target current application time for two-phase excitation in a 1-2 phase excitation mode. FIG. [Figure 7] 3 is a diagram showing a functional block configuration of a control unit according to the first embodiment; FIG. [Figure 8] 5 is a flowchart showing the flow of a method for setting a conduction angle θ according to the first embodiment. [Figure 9A]10 is a flowchart showing the flow of a method for setting a conduction angle θ according to the second embodiment. [Figure 9B] 10 is a flowchart showing the flow of a method for setting a conduction angle θ according to the second embodiment. [Figure 10] FIG. 11 is a diagram showing an example of a method for setting a conduction angle θ according to the third embodiment. [Figure 11] FIG. 13 is a diagram showing another example of the method for setting the conduction angle θ according to the third embodiment. [Figure 12] 11 is a flowchart showing the flow of a method for setting a conduction angle θ according to the third embodiment. [Figure 13] 4 is a diagram showing a functional block configuration of a control unit that sets a conduction angle θ in accordance with a load on a rotor. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1. Overview of the embodiment First, a typical embodiment of the invention disclosed in this application will be outlined. In the following description, as an example, reference numerals in the drawings corresponding to components of the invention are given in parentheses.

[0016] [1] A motor drive control device (10) according to a representative embodiment of the present invention is characterized in that it includes a control unit (11, 11A) that monitors the rotational state of a rotor (22) of a two-phase stepping motor (20) and sets, based on the rotational state of the rotor, a conduction angle (θ) indicating the magnitude of the electrical angle at which current is continuously passed in one direction through one of the two-phase coils (21, 21A, 21B) of the two-phase stepping motor, and generates a control signal (Sd) for controlling the drive of the two-phase stepping motor based on the set conduction angle, and a drive unit (12) that drives the two-phase coils based on the control signal.

[0017] [2] In the motor drive control device described in [1] above, the control unit may monitor the rotational speed of the rotor as the rotational state of the rotor, and set the conduction angle so that the conduction angle becomes smaller as the rotational speed of the rotor becomes higher.

[0018] [3] In the motor drive control device described in [1] above, the control unit (11A) may monitor the load on the rotor as the rotation state of the rotor, and set the conduction angle so that the conduction angle becomes smaller as the load on the rotor becomes smaller.

[0019] [4] In the motor drive control device described in [2] above, the control unit has as operating modes a 1-2 phase excitation mode in which a 1-phase excitation mode in which one of the two-phase coils is excited and a 2-phase excitation mode in which two of the two-phase coils are excited are alternately repeated, and a 1-phase excitation mode in which one of the two-phase coils is excited. When the rotation speed of the rotor becomes equal to or greater than an upper threshold value (Rtu), the control unit may set the conduction angle to 90° and select the 1-phase excitation mode, and when the rotation speed of the rotor becomes equal to or less than a lower threshold value (Rtd) that is smaller than the upper threshold value, the control unit may set the conduction angle to a value greater than 90° and select the 1-2 phase excitation mode.

[0020] [5] In the motor drive control device described in [4] above, when the conduction angle is set to 90° and the rotational speed of the rotor becomes lower than the lower threshold value, the control unit may change the conduction angle over time from 90° to a value greater than 90°.

[0021] [6] In the motor drive control device described in [5] above, when the conduction angle is set to a value greater than 90° and the rotational speed of the rotor becomes equal to or greater than the upper threshold value, the control unit may change the conduction angle over time from a value greater than 90° to 90°.

[0022] [7] In the motor drive control device described in [4] above, the control unit may, when the conduction angle is set to 90°, gradually change the conduction angle from 90° to a value greater than 90° in response to a decrease in the rotational speed of the rotor.

[0023] [8] In the motor drive control device described in [7] above, when the conduction angle is set to a value greater than 90° and the rotational speed of the rotor becomes equal to or greater than the upper threshold value, the control unit may change the conduction angle in stages from a value greater than 90° to 90° in response to an increase in the rotational speed of the rotor.

[0024] [9] A motor unit (1) according to a representative embodiment of the present invention is characterized in that it comprises a motor drive control device (10) described in any one of [1] to [8] above, and the two-phase stepping motor (20).

[0025]

[10] A method according to a representative embodiment of the present invention is a motor drive control method for controlling the drive of a two-phase stepping motor (20) by a motor drive control device (10). This method includes a first step (S4, S9) in which the motor drive control device monitors a rotation state of a rotor of the two-phase stepping motor, a second step (S8, S13) in which the motor drive control device sets an energization angle (θ) indicating the magnitude of an electrical angle at which current is continuously applied in one direction to one of two phase coils in the two-phase stepping motor based on the rotation state of the rotor, a third step (S8, S13) in which the motor drive control device generates a control signal for controlling the drive of the two-phase stepping motor based on the energization angle set in the second step, and a fourth step (S8, S13) in which the motor drive control device drives the two-phase coils based on the control signal.

[0026] 2. Specific examples of embodiments DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples of embodiments of the present invention will be described with reference to the drawings. In the following description, components common to the respective embodiments are designated by the same reference numerals, and repeated description will be omitted.

[0027] First Embodiment FIG. 1 is a block diagram showing a configuration of a motor unit according to the first embodiment. 1, the motor unit 1 includes a two-phase stepping motor 20 and a motor drive control device 10 that drives the two-phase stepping motor 20. The motor unit 1 is applicable to various devices that use a motor as a power source, such as an actuator that can be used in an HVAC (Heating Ventilation and Air-Conditioning) system as an in-vehicle air conditioning unit.

[0028] FIG. 2 is a diagram illustrating a schematic configuration of a two-phase stepping motor 20 according to the first embodiment.

[0029] The two-phase stepping motor 20 is, for example, a stepping motor having two-phase coils. As shown in Fig. 2, the two-phase stepping motor 20 has an A-phase coil 21A, a B-phase coil 21B, a rotor 22, and a two-phase stator yoke (not shown).

[0030] The coils 21A and 21B are coils that excite a stator yoke (not shown). The coils 21A and 21B are each connected to a driving unit 12, which will be described later. Currents (coil currents) of different phases flow through the coils 21A and 21B.

[0031] In this embodiment, when there is no need to distinguish between coils 21A and 21B, they may be simply referred to as "coil 21."

[0032] The rotor 22 includes a multi-pole magnetized permanent magnet such that S poles 22S and N poles 22N are alternately inverted along the circumferential direction. Note that Fig. 2 shows an example in which the rotor 22 has two poles.

[0033] The stator yoke is disposed around the rotor 22 and close to the outer periphery of the rotor 22. The rotor 22 rotates by periodically switching the phase of the coil current flowing through the coils 21A and 21B. An output shaft (not shown) is connected to the rotor 22, and the output shaft is driven by the rotational force of the rotor 22.

[0034] The motor drive control device 10 is a device for driving the two-phase stepping motor 20. The motor drive control device 10 controls the rotation and stopping of the two-phase stepping motor 20 by controlling the energization state of the coils 21A, 21B of each phase of the two-phase stepping motor 20 based on a drive command from, for example, a higher-level device (not shown).

[0035] As shown in FIG. 1, the motor drive control device 10 includes a control unit 11 and a drive unit 12. The driving unit 12 is a functional unit that energizes the coils 21A, 21B of the two-phase stepping motor 20 to drive the two-phase stepping motor 20. The driving unit 12 has a motor driving unit 13.

[0036] The motor driving unit 13 supplies driving power to the two-phase stepping motor 20 based on a control signal Sd generated by the control unit 11. As shown in Fig. 2, the motor driving unit 13 is connected to a positive terminal AP of the coil 21A, a negative terminal AN of the coil 21A, a positive terminal BP of the coil 21B, and a negative terminal BN of the coil 21B, and energizes the coils 21A and 21B by applying a voltage to each of the terminals AP, AN, BP, and BN.

[0037] The motor drive unit 13 is configured, for example, by an H-bridge circuit constituted by four switching elements (for example, transistors). The motor drive unit 13 switches the energization of the coils 21A and 21B, for example, by selectively turning on and off each of the switching elements constituting the H-bridge circuit.

[0038] 2, when a current +Ia flows through the A-phase coil 21A, the motor drive unit 13 applies a voltage of "+Va" to the terminal AP of the coil 21A with respect to the terminal AN of the coil 21A, for example. On the other hand, when a current -Ia flows through the A-phase coil 21A, the motor drive unit 13 applies a voltage of "-Va" to the terminal AP of the coil 21A with respect to the terminal AN of the coil 21A. Similarly, when a current +Ib flows through the B-phase coil 21B, the motor drive unit 13 applies a voltage of "+Vb" to the terminal BP of the terminal BN of the coil 21B, for example, and when a current -Ib flows through the B-phase coil 21B, the motor drive unit 13 applies a voltage of "-Vb" to the terminal BP of the terminal BN of the coil 21B.

[0039] The motor driving unit 13 switches the energized state of each of the coils 21A, 21B by switching the voltage applied between the terminals of each of the coils 21A, 21B as described above based on a control signal Sd given from the control unit 11 for controlling the driving of the two-phase stepping motor 20.

[0040] The control unit 11 is a functional unit that performs overall control of the motor drive control device 10. The control unit 11 is, for example, a program processing device (for example, a microcontroller) having a configuration in which a processor such as a CPU, various storage devices such as a RAM and a ROM, and peripheral circuits such as a timer (counter), an A / D conversion circuit, a D / A conversion circuit, and an input / output I / F circuit are connected to each other via a bus. In this embodiment, the control unit 11 is packaged as an IC (integrated circuit), but is not limited to this.

[0041] The control unit 11 has two operating modes for controlling the current switching of the two-phase stepping motor 20: a 1-2 phase excitation mode in which the two-phase stepping motor 20 is driven by a 1-2 phase excitation method, and a 1-phase excitation mode in which the two-phase stepping motor 20 is driven by a 1-phase excitation method.

[0042] The 1-2 phase excitation mode is an operation mode in which one-phase excitation, which excites one of the two-phase coils 21 in the two-phase stepping motor 20, and two-phase excitation, which excites two of the two-phase coils 21, are alternately repeated. The one-phase excitation mode is an operation mode in which one of the two-phase coils 21 is excited.

[0043] The control unit 11 generates a control signal Sd for controlling the driving of the two-phase stepping motor 20 in accordance with the set operation mode, and drives the two-phase stepping motor 20 via the drive unit 12.

[0044] As described above, if the load becomes lighter or a load in the opposite direction is applied when driving two-phase stepping motor 20 in 1-2 phase excitation mode, the rotation speed of rotor 22 becomes too fast, and the data processing of the microcontroller acting as control unit 11, which performs overall control of motor drive control device 10, cannot keep up, which may result in unstable motor drive control. Therefore, when controlling the current supply switching of the two-phase stepping motor 20, the control unit 11 performs the following process in order to limit the change in the rotation speed of the rotor 22 caused by the load fluctuation.

[0045] First, the relationship between the conduction angle and each of the one-phase excitation and two-phase excitation periods in the conduction switching control of the two-phase stepping motor 20 will be described.

[0046] FIG. 3 is a diagram showing the relationship between the conduction angle and the one-phase excitation period and the two-phase excitation period in the conduction switching control of a two-phase stepping motor.

[0047] In Fig. 3, the horizontal axis represents the electrical angle. The upper part of the figure shows the excitation states of the A-phase and B-phase coils when the conduction angle θ = 120°, the middle part shows the excitation states of the A-phase and B-phase coils when the conduction angle θ = 100°, and the lower part shows the excitation states of the A-phase and B-phase coils when the conduction angle θ = 90°.

[0048] In general, in energization switching control in the 1-2 phase excitation mode of a two-phase stepping motor, as the energization angle θ decreases, the 1-phase excitation period becomes longer, while the 2-phase excitation period becomes shorter. For example, as shown in the upper part of Fig. 3, when the energization angle θ is set to 120° in the 1-2 phase excitation mode, the electrical angle of the 1-phase excitation period is 60°, and the electrical angle of the 2-phase excitation period is 30°. However, as shown in the middle part of Fig. 3, when the energization angle θ is set to 100° in the 1-2 phase excitation mode, the electrical angle of the 1-phase excitation period is 80°, and the electrical angle of the 2-phase excitation period is 10°. Then, as shown in the lower part of Fig. 3, when the energization angle θ is reduced to 90°, the 2-phase excitation period disappears, and the mode is switched from the 1-2 phase excitation mode to the 1-phase excitation mode.

[0049] In this way, in the energization switching control of a two-phase stepping motor, the one-phase excitation period and the two-phase excitation period can be changed by changing the energization angle θ.

[0050] In general, in the energization switching control of a two-phase stepping motor, the shorter the period of two-phase excitation, the smaller the torque of the two-phase stepping motor. Therefore, when the load of the two-phase stepping motor 20 is constant, the smaller the energization angle θ, the shorter the period of two-phase excitation and the smaller the torque, and as a result, the rotation speed of the rotor 22 decreases. For example, when the two-phase stepping motor is driven in the 1-2 phase excitation mode, the rotation speed of the rotor 22 when the energization angle θ is set to 100° is lower than the rotation speed of the rotor 22 when the energization angle θ is set to 120°. When the energization angle is further reduced to 90°, that is, when the two-phase stepping motor 20 is driven in the 1-phase excitation mode, the rotation speed of the rotor 22 further decreases.

[0051] Therefore, the control unit 11 changes the conduction angle θ according to the rotation state of the rotor 22 of the two-phase stepping motor 20, thereby limiting the change in the rotation speed of the rotor 22 that accompanies the load fluctuation of the two-phase stepping motor 20.

[0052] Specifically, the control unit 11 monitors the rotation state of the rotor 22 of the two-phase stepping motor 20, and sets the conduction angle θ based on the rotation state of the rotor 22. More specifically, the control unit 11 monitors the rotation speed of the rotor 22 as the rotation state of the rotor 22, and switches the operation mode by setting the conduction angle θ to be smaller as the rotation speed of the rotor 22 is higher.

[0053] FIG. 4 is a diagram showing an example of a method for setting the conduction angle θ according to the first embodiment. 4, the horizontal axis represents the conduction angle θ (°), and the vertical axis represents the rotation speed (rpm) (one example) of the rotor 22 of the two-phase stepping motor 20. Reference numeral 301 represents the change in the conduction angle θ when the rotation speed increases, and reference numeral 302 represents the change in the conduction angle θ when the rotation speed decreases.

[0054] For example, as shown in FIG. 4, an upper threshold value Rtu and a lower threshold value Rtd smaller than the upper threshold value Rtu are set as rotation speed determination values ​​for switching the operation mode (conduction angle θ).

[0055] The upper limit threshold Rtu is a threshold of the rotation speed for switching the operation mode from the 1-2 phase excitation mode to the 1 phase excitation mode. When the rotation speed of the rotor 22 becomes equal to or higher than the upper limit threshold Rtu, the control unit 11 sets the conduction angle θ to 90° and selects the 1 phase excitation mode.

[0056] The lower limit threshold Rtd is a threshold of the rotation speed for switching the operation mode from the one-phase excitation mode to the one-two phase excitation mode. When the rotation speed of the rotor 22 becomes equal to or lower than the lower limit threshold Rtd, the control unit 11 sets the conduction angle θ to a value greater than 90° (for example, 90°<θ≦135°) and selects the one-two phase excitation mode. In this embodiment, the conduction angle θ is set to 120° in the 1-2 phase excitation mode as an example; however, the value of the conduction angle θ is not limited to this and can be set to any value within the range of 90°<θ≦135°.

[0057] For example, as shown in FIG. 4, when the control unit 11 is driving the two-phase stepping motor 20 in the 1-2 phase excitation mode with the conduction angle θ=120° and the rotation speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or higher than the upper limit threshold value Rtu, the control unit 11 sets the conduction angle θ to 90° and switches to the one-phase excitation mode.

[0058] Also, as shown in FIG. 4, when the two-phase stepping motor 20 is driven in the one-phase excitation mode, if the rotational speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or lower than the lower threshold value Rtd, the conduction angle θ is set to 120° and the mode is switched to the 1-2 phase excitation mode.

[0059] Although there may be only one rotation speed determination value for switching the conduction angle θ, it is preferable to provide two thresholds, an upper threshold Rtu and a lower threshold Rtd, as described above, in order to improve the stability of the drive control of the motor. For example, it is preferable that the difference between the upper threshold Rtu and the lower threshold Rtd is at least 100 rpm. This makes it possible to prevent, for example, repeated switching of the operation mode due to fluctuations in the drive speed of the rotor 22 immediately after switching the operation mode.

[0060] Next, a method of switching between 1-phase excitation and 2-phase excitation in the 1-2 phase excitation mode will be described. In each operation mode, the control unit 11 switches the energization of the coil 21 based on the set energization angle θ and the detection result of the zero crossing of the back electromotive voltage generated in the non-excited coil 21 during one-phase excitation.

[0061] First, the energization switching control of the coil 21 in the 1-2 phase excitation mode will be described. FIG. 5 is a diagram for explaining energization switching control of a two-phase stepping motor in a 1-2 phase excitation mode according to the first embodiment.

[0062] In the figure, reference numeral 401 denotes the voltage of terminal AP relative to terminal AN of A-phase coil 21A (hereinafter also referred to as "A-phase voltage"), and reference numeral 402 denotes the back electromotive force of A-phase coil 21A. As an example, the figure shows a voltage waveform of the A-phase coil when the current switching control of the two-phase stepping motor 20 is performed in 1-2 phase excitation mode with the current angle θ set to 120°. Note that the periods indicated by the symbols AP, AN, BP, and BN in the figure indicate a state in which voltage is applied to each terminal corresponding to those symbols (for example, terminal AP on the positive pole side of A-phase coil 21A).

[0063] As shown in Fig. 4, when the control unit 11 drives the two-phase stepping motor 20 in the 1-2 phase excitation mode, the control unit 11 switches the energization state of the two-phase stepping motor 20 so as to alternately repeat one-phase excitation and two-phase excitation. For example, in Fig. 4, during a period of two-phase excitation from 180° to 210° (electrical angle 30°), the A-phase voltage is set to "-Va" to negatively excite the coil 21A, and the B-phase voltage is set to "-Vb" to negatively excite the coil 21B. During the next period of two-phase excitation from 210° to 270° (electrical angle 60°), the A-phase voltage is set to "0" to not excite the coil 21A, while the B-phase voltage is continued to be set to "-Vb" to negatively excite the coil 21B. During the next two-phase excitation period from 270° to 300° (electrical angle 30°), the A-phase voltage is set to “+Va” to excite coil 21A positively (+), and subsequently, the B-phase voltage is set to “-Vb” to excite coil 21B negatively.

[0064] Here, the period during which one-phase excitation and the period during which two-phase excitation of two-phase stepping motor 20 is performed are determined based on the back electromotive voltage generated in coils 21A and 21B and the set value of conduction angle θ.

[0065] First, the period of one-phase excitation of the two-phase stepping motor 20 is determined as follows. The period of one phase excitation of the two-phase stepping motor 20 is determined based on the back electromotive voltage generated in one coil 21 that is not excited while the other coil 21 is excited.

[0066] Specifically, after switching from two-phase excitation to one-phase excitation, the control unit 11 generates a control signal Sd to switch the excitation state of the two-phase stepping motor 20 from one-phase excitation to two-phase excitation in accordance with the detection result of the zero-cross point of the back electromotive force generated in the non-excited coil 21.

[0067] 5, during the period from electrical angle 210° to 270° of one-phase excitation, a positive spike-like voltage is generated in the non-excited A-phase coil 21A, and then a back electromotive voltage synchronized with the rotation of the rotor 22 of the two-phase stepping motor 20 is generated. After that, when the control unit 11 detects a point (zero cross point) at which the back electromotive voltage of the A-phase coil 21A becomes 0V at time ta, it generates a control signal Sd to switch from one-phase excitation to two-phase excitation.

[0068] The period of two-phase excitation of the two-phase stepping motor 20 is determined as follows. As described above, during a period in which one-phase excitation of the two-phase stepping motor 20 is performed, a back electromotive voltage is generated in the non-excited coil 21. On the other hand, during a period in which two-phase excitation of the two-phase stepping motor 20 is performed (for example, periods from electrical angle 180° to 210° and from electrical angle 270° to 300° in FIG. 3), the A-phase coil 21A and the B-phase coil 21B are both excited, so that it is not possible to measure the back electromotive voltage of either of the coils 21A and 21B. Therefore, the timing of switching from two-phase excitation to one-phase excitation cannot be determined based on the back electromotive voltage of the coil 21, as is the case when switching from one-phase excitation to two-phase excitation.

[0069] Therefore, the control unit 11 determines a period during which two-phase excitation is performed based on the elapsed time per unit angle when the two-phase stepping motor 20 is excited and a preset conduction angle θ.

[0070] Specifically, the control unit 11 determines the period during which the two-phase excitation is performed, that is, the target energization time T2n of the two-phase excitation, based on the elapsed time per unit angle when the two-phase stepping motor 20 is excited and the energization angle θ. The target energization time T2n of the two-phase excitation can be determined, for example, by the following method.

[0071] FIG. 6 is a diagram for explaining a method of determining a target current application time for two-phase excitation in the one-two phase excitation mode.

[0072] In Fig. 6, the horizontal axis represents time and electrical angle. The upper part of the figure shows the energization state of phase A, and the lower part of the figure shows the energization state of phase B. In Fig. 6, T1n represents the nth (n is an integer equal to or greater than 1) one-phase excitation period, T1n-1 represents the (n-1)th one-phase excitation period, T2n represents the nth two-phase excitation period, and T2n-1 represents the (n-1)th two-phase excitation period.

[0073] 6, when the conduction angle is θ, the magnitude of the electrical angle corresponding to the one-phase excitation periods T1n-1 and T1n can be expressed as (180°-θ), and the magnitude of the electrical angle corresponding to the two-phase excitation periods T2n-1 and T2n can be expressed as (θ-90°).

[0074] 6, the control unit 11 first measures a period T1n of one-phase excitation. Next, the control unit 11 calculates an elapsed time per unit angle based on the measured value of the period T1n of one-phase excitation and the magnitude of the electrical angle (180°-θ) corresponding to the period T1n of one-phase excitation, and calculates a target energization time T2n of the next two-phase excitation based on the calculated elapsed time and the set energization angle θ.

[0075] For example, the control unit 11 calculates the target current application time T2n based on the following formula (1).

[0076]

number

[0077] In the above formula (1), "T1n / (180-θ)" represents the elapsed time per unit angle when the two-phase stepping motor 20 is in one-phase excitation, i.e., the time required for the electrical angle to advance by a unit angle (1°) during the one-phase excitation period T1n. Also, (θ-90) is the electrical angle corresponding to the two-phase excitation period.

[0078] For example, when the conduction angle θ is 120°, equation (1) can be expressed as the following equation (2).

[0079]

number

[0080] As can be seen from equation (2), the target energization time (period of two-phase excitation) T2n is the time required for energizing an electrical angle of 30°.

[0081] When calculating the target energization time T2n of the two-phase excitation based on the above formula (1), the control unit 11 may measure the period of the one-phase excitation performed immediately before the two-phase excitation and use the period as the measured value of the one-phase excitation period T1n. Alternatively, the control unit 11 may measure each of the periods of the one-phase excitation performed before the two-phase excitation and use the average value of the measured periods as the measured value of the one-phase excitation period T1n.

[0082] Here, the average value of the multiple one-phase excitation periods may be a simple average value, or the multiple one-phase excitation periods performed before the two-phase excitation may be weighted to calculate an average value, and the target energization time T2n may be set based on the average value. For example, the average value may be calculated by weighting each one-phase excitation period so that the weight is greater for periods closer in time to the two-phase excitation for which the target energization time T2n is calculated.

[0083] The control unit 11 determines the target energization time T2n of the two-phase excitation based on the above-mentioned method. Then, when the target energization time T2n has elapsed after the start of the two-phase excitation, the control unit 11 generates a control signal Sd to switch the excitation state of the two-phase stepping motor 20 from two-phase excitation to one-phase excitation.

[0084] 5, during the period from electrical angle 270° to 300° when two-phase excitation is performed, A-phase coil 21A and B-phase coil 21B are both excited, so that the back electromotive voltage cannot be measured. Therefore, control unit 11 generates a control signal Sd to switch from two-phase excitation to one-phase excitation at time tb (electrical angle 300°) when target current application time T2n of 30 electrical degrees has elapsed after starting two-phase excitation at time ta (electrical angle 270°).

[0085] As described above, when driving two-phase stepping motor 20 in 1-2 phase excitation mode, control unit 11 switches from one-phase excitation to two-phase excitation in response to detection of the zero-cross point of the back electromotive force generated in non-excited coil 21 during one-phase excitation, and switches from two-phase excitation to one-phase excitation after the start of two-phase excitation has elapsed a target energization time T2n that is set based on the elapsed time per unit angle when two-phase stepping motor 20 is excited and the energization angle θ.

[0086] Next, the current switching control of the coil 21 in the one-phase excitation mode will be described. When the conduction angle θ is set to 90°, the target conduction time T2n of the two-phase excitation becomes 0 (zero) according to the above formula (1). That is, the operation mode switches from the 1-2 phase excitation mode to the one-phase excitation mode. In the one-phase excitation mode, the control unit 11 detects the zero-cross point of the back electromotive voltage generated in the non-excited coils 21 during the one-phase excitation, similar to the 1-2 phase excitation mode. Every time the control unit 11 detects the zero-cross point of the back electromotive voltage, it switches one of the coils 21 to be excited and the excitation direction (see the lower part of FIG. 3).

[0087] FIG. 7 is a diagram showing a functional block configuration of the control unit 11 according to the first embodiment.

[0088] As shown in FIG. 7, the control unit 11 has, as functional units for realizing the energization switching control of the coils 21A, 21B of the two-phase stepping motor 20 described above, a back electromotive force monitoring unit 111, a zero-cross point detection unit 112, a one-phase excitation period timing unit 113, a two-phase excitation period calculation unit 114, a two-phase excitation period timing unit 115, a memory unit 116, a control signal generation unit 117, a rotational speed measurement unit 118, a rotational speed determination unit 119, and an energization angle switching unit 120.

[0089] These functional units are realized, for example, in a program processing device (microcontroller) serving as the control unit 11 described above, by a processor executing various calculations in accordance with programs stored in a storage device and controlling peripheral circuits such as an A / D conversion circuit and a timer.

[0090] The back electromotive voltage monitoring unit 111 is a functional unit that monitors the back electromotive voltage generated in the coils 21A, 21B of each phase.

[0091] The zero-cross point detection unit 112 is a functional unit for detecting the zero-cross point of the back electromotive voltage generated in the coils 21A, 21B of the two-phase stepping motor 20 based on the monitoring result of the back electromotive voltage monitoring unit 111. When the zero-cross point detection unit 112 detects the zero-cross point of the back electromotive voltage of the non-excited coil 21, it outputs a detection signal Sz indicating that the zero-cross point has been detected.

[0092] The one-phase excitation period counting unit 113 is a functional unit for measuring the one-phase excitation period T1n of the two-phase stepping motor 20. The one-phase excitation period counting unit 113 can be realized by, for example, a timer (counter) constituting the above-mentioned microcontroller.

[0093] The one-phase excitation period counter 113 starts measuring time in response to the excitation state of the two-phase stepping motor 20 being switched from two-phase excitation to one-phase excitation. For example, the one-phase excitation period counter 113 starts measuring the one-phase excitation period T1n in response to a signal notifying the end of the two-phase excitation period output from a two-phase excitation period counter 115 described later.

[0094] The one-phase excitation period counter 113 stops timing when a zero-cross point of the back electromotive voltage is detected. For example, the one-phase excitation period counter 113 stops measuring the one-phase excitation period T1n in response to a detection signal Sz output from the zero-cross point detector 112 indicating that a zero-cross point has been detected, stores the measurement value of the one-phase excitation period T1n in the memory 116, and outputs a notification signal indicating the end of the one-phase excitation period T1n to the two-phase excitation period calculator 114.

[0095] Here, the memory unit 116 may store information on a plurality of one-phase excitation periods measured by the one-phase excitation period counter unit 113, or may store only information on the most recent one-phase excitation period.

[0096] The storage unit 116 is a functional unit for storing various data necessary for performing energization switching control. For example, the storage unit 116 stores the measurement value of the one-phase excitation period T1n measured by the one-phase excitation period timing unit 113 described above, the value of the energization angle θ, the information of the above formula (1), and the value of the target energization time T2n of the two-phase excitation period described later.

[0097] The two-phase excitation period calculation unit 114 is a functional unit for calculating a target current application time T2n of two-phase excitation of the two-phase stepping motor 20. The two-phase excitation period calculation unit 114 calculates the target current application time T2n of two-phase excitation in response to the excitation state of the two-phase stepping motor 20 being switched from one-phase excitation to two-phase excitation.

[0098] The two-phase excitation period calculation unit 114 reads data required to calculate a target current conduction time T2n of two-phase excitation from the storage unit 116 in response to a signal indicating the end of the one-phase excitation period T1n output from the one-phase excitation period counter unit 113, and calculates the target current conduction time T2n. The two-phase excitation period calculation unit 114 reads the value of the current conduction angle θ, the measured value (T1n) of the one-phase excitation period, and the information of the above formula (1) from the storage unit 116, calculates the target current conduction time T2n by performing calculation based on the above formula (1), and stores it in the storage unit 116.

[0099] When calculating target current conduction time T2n, two-phase excitation period calculation unit 114 reads out from storage unit 116 the value of the conduction angle corresponding to the operation mode specified by conduction angle switching unit 120, which will be described later. For example, when an operation mode signal instructing the 1-2 phase excitation mode is output from conduction angle switching unit 120, two-phase excitation period calculation unit 114 reads out "120°" from storage unit 116 as the value of conduction angle θ and calculates target current conduction time T2n. On the other hand, when an operation mode signal instructing the 1-phase excitation mode is output from conduction angle switching unit 120, two-phase excitation period calculation unit 114 reads out "90°" from storage unit 116 as the value of conduction angle θ and calculates target current conduction time T2n.

[0100] After calculating the target current application time T2n, the two-phase excitation period calculation section 114 instructs the two-phase excitation period counter 115 to start measuring the two-phase excitation period.

[0101] The two-phase excitation period counting unit 115 is a functional unit for measuring the period of two-phase excitation of the two-phase stepping motor 20. The two-phase excitation period counting unit 115 can be realized by, for example, a timer (counter) constituting the above-mentioned microcontroller.

[0102] The two-phase excitation period counter 115 starts measuring the two-phase excitation period in response to a measurement start instruction from the two-phase excitation period calculation unit 114. For example, in response to a measurement start instruction from the two-phase excitation period calculation unit 114, the two-phase excitation period counter 115 reads the target current application time T2n from the storage unit 116, sets it in its own timer, and starts measurement. When the measured time reaches the target current application time T2n, the two-phase excitation period counter 115 stops measurement and outputs a signal indicating the end of two-phase excitation.

[0103] When the above-mentioned first method is used as the method for determining the target energization time T2n of two-phase excitation, the timer included in the one-phase excitation period timing unit 113 and the timer included in the two-phase excitation period timing unit 115 are not used simultaneously. Therefore, in this case, only one timer may be provided, and the one-phase excitation period timing unit 113 and the two-phase excitation period timing unit 115 may share the one timer.

[0104] On the other hand, when the above-mentioned second method is used as the method for determining the target energization time T2n of two-phase excitation, the timer included in the one-phase excitation period timing unit 113 measures the time between zero-crossing points of the back electromotive voltage, and the timer included in the two-phase excitation period timing unit 115 measures the two-phase excitation period. Therefore, a period occurs in which the timers of the one-phase excitation period timing unit 113 and the two-phase excitation period timing unit 115 are used simultaneously. Therefore, in this case, the one-phase excitation period timing unit 113 and the two-phase excitation period timing unit 115 cannot share a single timer, and therefore each of the one-phase excitation period timing unit 113 and the two-phase excitation period timing unit 115 needs to have a timer.

[0105] The control signal generating unit 117 is a functional unit that generates a control signal Sd for controlling the driving of the two-phase stepping motor 20. The control signal generating unit 117 can be realized, for example, by program processing by a processor constituting the above-mentioned microcontroller and peripheral circuits such as an input / output I / F circuit.

[0106] The control signal generating unit 117 uses the control signal Sd to instruct switching between one-phase excitation and two-phase excitation of the two-phase stepping motor 20. The control signal generating unit 117 generates and outputs the control signal Sd according to the operation mode designated by the operation mode signal output from the conduction angle switching unit 120, which will be described later.

[0107] For example, when the operation mode signal specifies the one-phase excitation mode, the control signal generating unit 117 generates a control signal Sd to switch the excitation state of the two-phase stepping motor 20 every time the zero-cross point of the back electromotive voltage is detected by the zero-cross point detecting unit 112. On the other hand, when the operation mode signal specifies the one-two-phase excitation mode, the control signal generating unit 117 generates a control signal Sd to switch the excitation state of the two-phase stepping motor 20 from one-phase excitation to two-phase excitation in accordance with the detection signal Sz of the zero-cross point detecting unit 112 during the one-phase excitation period T1n. In addition, when the time measured by the two-phase excitation period timing unit 115 reaches the target energization time T2n during the two-phase excitation, the control signal generating unit 117 generates a control signal Sd to switch the excitation state of the two-phase stepping motor 20 from two-phase excitation to one-phase excitation. Furthermore, the control signal generating unit 117 generates a control signal Sd to switch the excitation state of the two-phase stepping motor 20 from two-phase excitation to one-phase excitation in response to a signal indicating the end of two-phase excitation output from the two-phase excitation period timing unit 115.

[0108] In addition, the control signal generating unit 117 may generate the control signal Sd so as to switch the excitation state of the two-phase stepping motor 20 from one-phase excitation to two-phase excitation in response to a signal indicating the end of one-phase excitation output from the one-phase excitation period timing unit 113, rather than the detection signal Sz of the zero-cross point detecting unit 112.

[0109] The rotation speed measurement unit 118 is a functional unit that measures the rotation speed of the rotor 22 of the two-phase stepping motor 20. For example, similar to the two-phase excitation period calculation unit 114, the rotation speed measurement unit 118 calculates the number of rotations per unit time of the rotor 22 based on the one-phase excitation period T1n measured by the one-phase excitation period timing unit 113, and sets it as a measurement value of the rotation speed of the rotor 22.

[0110] In addition, if the motor unit 1 is provided with a rotational speed detection device such as an encoder for measuring the rotational speed of the rotor 22 of the two-phase stepping motor 20, the rotational speed measurement unit 118 may measure the rotational speed of the rotor 22 based on a detection signal from the rotational speed detection device.

[0111] The rotation speed determination unit 119 is a functional unit that compares the rotation speed of the rotor 22 of the two-phase stepping motor 20 with a rotation speed determination value for switching the conduction angle θ. As described above, in the motor drive control device 100, an upper threshold Rtu and a lower threshold Rtd smaller than the upper threshold Rtu are set as rotational speed determination values ​​for switching the conduction angle θ. Information on the upper threshold Rtu and the lower threshold Rtd is stored in, for example, the storage unit 116.

[0112] Rotation speed determination unit 119 is a functional unit that compares the measurement value of the rotation speed by rotation speed measurement unit 118 with an upper threshold value Rtu and a lower threshold value Rtd. For example, when the measurement value of the rotation speed becomes equal to or greater than the upper threshold value Rtu, rotation speed determination unit 119 provides a signal indicating this to conduction angle switching unit 120. Also, when the measurement value of the rotation speed becomes equal to or less than the lower threshold value Rtd, rotation speed determination unit 119 provides a signal indicating this to conduction angle switching unit 120.

[0113] Conduction angle switching unit 120 is a functional unit that instructs switching of conduction angle θ. Conduction angle switching unit 120 outputs an operation mode signal that instructs the conduction angle θ, i.e., the operation mode, in response to a signal from rotation speed determination unit 119.

[0114] For example, when the rotation speed determination unit 119 outputs a signal indicating that the measured value of the rotation speed is equal to or greater than the upper limit threshold value Rtu in a state where the energization switching control is being performed in the 1-2 phase excitation mode (energization angle θ=120°), the energization angle switching unit 120 outputs an operation mode signal instructing the 1-phase excitation mode (energization angle θ=90°). When the 2-phase excitation period calculation unit 114 receives an operation mode signal instructing the 1-phase excitation mode, it sets the energization angle θ to 90° and sets the target energization time T2n of the 2-phase excitation to "0". When the control signal generation unit 117 receives an operation mode signal instructing the 1-phase excitation mode, it generates a control signal Sd to drive the 2-phase stepping motor 20 in the 1-phase excitation mode and provides the control signal Sd to the drive unit 12.

[0115] When the rotation speed determination unit 119 outputs an operation mode signal indicating that the measured value of the rotation speed has become equal to or lower than the lower limit threshold value Rtd while the energization switching control is being performed in the one-phase excitation mode (energization angle θ=90°), the energization angle switching unit 120 outputs an operation mode signal instructing the one-two phase excitation mode (energization angle θ=120°). When the two-phase excitation period calculation unit 114 receives an operation mode signal instructing the one-two phase excitation mode, it sets the energization angle θ to 120° and calculates the target energization time T2n of the two-phase excitation. When the control signal generation unit 117 receives a signal instructing the one-two phase excitation mode, it generates a control signal Sd to drive the two-phase stepping motor 20 in the one-two phase excitation mode, and provides the control signal Sd to the drive unit 12.

[0116] The switching of the operation mode is preferably executed when the rotation speed is detected to have risen or fallen multiple times relative to the upper threshold value Rtu and the lower threshold value Rtd, respectively. For example, conduction angle switching unit 120 may have a rotation speed rise determination counter 121 and a rotation speed fall determination counter 122, and may count the number of times the rotation speed has become equal to or greater than the upper threshold value Rtu using rotation speed rise determination counter 121 and count the number of times the rotation speed has become equal to or less than the lower threshold value Rtd using rotation speed fall determination counter 122, and switch the operation mode based on the count values ​​of these counters.

[0117] Specifically, when a signal indicating that the measured value of the rotation speed has become equal to or greater than the upper limit threshold value Rtu is output from rotation speed determination unit 119, conduction angle switching unit 120 increments (+1) rotation speed increase determination counter 121, and when the measured value of the rotation speed has become less than the upper limit threshold value Rtu, conduction angle switching unit 120 resets rotation speed increase determination counter 121.

[0118] Furthermore, when a signal indicating that the measured value of the rotation speed has become equal to or lower than the lower threshold value Rtd is output from rotation speed determination unit 119, conduction angle switching unit 120 increments (+1) rotation speed increase determination counter 121, and when the measured value of the rotation speed has become greater than the lower threshold value Rtd, conduction angle switching unit 120 resets rotation speed increase determination counter 121.

[0119] Conduction angle switching unit 120 outputs an operation mode signal instructing a one-phase excitation mode (conduction angle θ=90°) when the count value of rotation speed increase determination counter 121 becomes equal to or greater than a first threshold value (e.g., an integer equal to or greater than 2). Conduction angle switching unit 120 also outputs an operation mode signal instructing a one-two phase excitation mode (conduction angle θ=120°) when the count value of rotation speed decrease determination counter 122 becomes equal to or greater than a second threshold value (e.g., an integer equal to or greater than 2). The first threshold value and the second threshold value may be the same value or different values. Information on the first threshold value and the second threshold value is stored in advance in the storage unit 116, for example.

[0120] In this manner, by using the rotation speed increase determination counter 121 and the rotation speed decrease determination counter 122, it is possible to prevent switching of the operation mode in response to an instantaneous change in the rotation speed of the rotor 22. In the present embodiment, as an example, the conduction angle switching unit 120 will be described as having a rotation speed increase determination counter 121 and a rotation speed decrease determination counter 122.

[0121] FIG. 8 is a flowchart showing the flow of a method for setting the conduction angle θ according to the first embodiment.

[0122] For example, after power is turned on, when a drive command for the two-phase stepping motor 20 is input from an external higher-level device, the motor drive control device 10 starts drive control (excitation mode transition control) for the two-phase stepping motor 20 (step S1).

[0123] First, the motor drive control device 10 sets a rotation speed judgment value corresponding to the conduction angle θ set at that time (step S2). Here, as an example, it is assumed that the one-phase excitation mode is set first after power-on, and the conduction angle θ is set to 90°. In this case, in step S2, the motor drive control device 10 sets a lower threshold value Rtd as a rotation speed judgment value for switching the conduction angle θ from 90° to 120° (switching the operation mode from the one-phase excitation mode to the one-two phase excitation mode).

[0124] Next, the motor drive control device 10 determines whether the operation mode set at that time is the one-phase excitation mode (step S3). Here, as described above, since the next excitation state to be transitioned to is the one-phase excitation of the A phase (step S3: YES), the conduction angle switching unit 120 determines whether the rotation speed of the rotor 22 of the two-phase stepping motor 20 is equal to or lower than the lower threshold value Rtd (step S4). If the rotation speed is not equal to or lower than the lower threshold value Rtd (step S4: NO), the conduction angle switching unit 120 resets the count value q of the rotation speed reduction determination counter 122 (step S5).

[0125] On the other hand, if the rotation speed is equal to or less than the lower limit threshold Rtd (step S4: YES), conduction angle switching unit 120 increments count value q of rotation speed reduction determination counter 122 (step S6). Next, conduction angle switching unit 120 determines whether count value q of rotation speed reduction determination counter 122 is equal to or more than a second threshold (step S7).

[0126] If the count value q of the rotation speed decrease determination counter 122 is not equal to or greater than the second threshold value (step S7: NO), the motor drive control device 10 returns to step S2.

[0127] If the count value q of the rotation speed reduction determination counter 122 is equal to or greater than the second threshold value (step S7: YES), the motor drive control device 10 switches the operation mode from the one-phase excitation mode to the one-two phase excitation mode (step S8). Specifically, as described above, the conduction angle switching unit 120 outputs an operation mode signal instructing the one-two phase excitation mode, and the two-phase excitation period calculation unit 114 that receives the operation mode signal sets the conduction angle θ to 120° and calculates the target conduction time T2n of two-phase excitation, and the control signal generation unit 117 generates and provides the control signal Sd to the drive unit 12 so as to drive the two-phase stepping motor 20 in the one-two phase excitation mode.

[0128] After that, motor drive control device 10 returns to step S2 and sets a rotation speed judgment value corresponding to the conduction angle θ set at that time. Here, since the operation mode was set to 1-2 phase excitation mode (conduction angle θ=120°) in the previous step S8, motor drive control device 10 sets upper limit threshold Rtu as the rotation speed judgment value for switching conduction angle θ from 120° to 90° (switching the operation mode from 1-2 phase excitation mode to 1 phase excitation mode).

[0129] Next, the motor drive control device 10 determines the operation mode that is set at that time (step S3). Here, since the operation mode was set to the 1-2 phase excitation mode in the previous step S8 (step S3: NO), the conduction angle switching unit 120 determines whether the rotation speed of the rotor 22 of the two-phase stepping motor 20 is equal to or higher than the upper limit threshold value Rtu (step S9).

[0130] If the rotation speed is not equal to or higher than the upper limit threshold value Rtu (step S9: NO), the conduction angle change unit 120 resets the count value p of the rotation speed increase determination counter 121 (step S10).

[0131] On the other hand, if the rotation speed is equal to or greater than the upper limit threshold value Rtu (step S9: YES), conduction angle change unit 120 increments count value p of rotation speed increase determination counter 121 (step S11).

[0132] Next, conduction angle switching unit 120 determines whether or not count value p of rotation speed increase determination counter 121 is equal to or greater than a first threshold value (step S12). If count value p of rotation speed increase determination counter 121 is not equal to or greater than the first threshold value (step S12: NO), motor drive control device 10 returns to step S2 and executes the above-mentioned processes of steps S2 to S10 again.

[0133] If the count value p of the rotation speed increase determination counter 121 is equal to or greater than the first threshold value (step S12: YES), the motor drive control device 10 switches the operation mode from the 1-2 phase excitation mode to the 1 phase excitation mode (step S13). Specifically, as described above, the conduction angle switching unit 120 outputs an operation mode signal instructing the 1 phase excitation mode, and the 2 phase excitation period calculation unit 114 that receives the operation mode signal sets the conduction angle θ to 90° and sets the target conduction time T2n of the 2 phase excitation to 0 (zero), and the control signal generation unit 117 generates and provides the control signal Sd to the drive unit 12 so as to drive the 2 phase stepping motor 20 in the 1 phase excitation mode. Thereafter, the motor drive control device 10 returns to step S2 and repeats the processes from steps S2 to S13 described above.

[0134] As described above, the motor drive control device 10 according to the first embodiment monitors the rotational speed of the rotor 22 of the two-phase stepping motor 20, and sets the conduction angle θ so that the conduction angle θ becomes smaller as the rotational speed of the rotor 22 increases, thereby performing current switching control of the coil 21 of the two-phase stepping motor 20.

[0135] According to this, when the load of the two-phase stepping motor 20 is reduced and the rotational speed of the rotor 22 increases, the energization angle θ can be decreased to reduce the torque of the two-phase stepping motor 20, so that it is possible to suppress the increase in the rotational speed of the rotor 22. As a result, it is possible to prevent the data processing by the microcontroller constituting the motor drive control device 10 (control unit 11) from falling behind the rotational speed of the rotor 22 and the drive control of the two-phase stepping motor 20 from becoming unstable. That is, according to the motor drive control device 10 according to the first embodiment, it is possible to enhance the stability of the drive control of the two-phase stepping motor 20 against load fluctuations.

[0136] Further, in the motor drive control device 10 according to the first embodiment, the control unit 11 has a single-phase excitation mode and a 1-2 phase excitation mode as operation modes, and when the rotational speed of the rotor 22 becomes equal to or higher than the upper limit threshold value Rtu, the energization angle is set to 90° and the single-phase excitation mode is selected, and when the rotational speed of the rotor 22 becomes equal to or lower than the lower limit threshold value Rtd (<Rtu), the energization angle θ is set to a value larger than 90° (for example, 120°) and the 1-2 phase excitation mode is selected.

[0137] According to this, it can be easily realized as the switching of the energization angle θ corresponding to the rotational speed of the rotor 22 and the switching of the excitation method. Further, since two threshold values, an upper limit threshold value Rtu and a lower limit threshold value Rtd, are provided as determination values of the rotational speed for switching the energization angle θ, as described above, it is possible to prevent the switching of the operation mode from being repeatedly performed many times due to the change in the drive speed of the rotor 22 immediately after the operation mode is switched.

[0138] <<Second Embodiment>> In the first embodiment, as a method for switching the energization angle, the case where the single-phase excitation mode (θ = 90°) and the 1-2 phase excitation mode (θ = 120°) are quickly switched is exemplified. However, the method for switching the energization angle according to the second embodiment is to gradually change the energization angle θ over time.

[0139] Specifically, when the conduction angle is set to 90° (i.e., in one-phase excitation mode), if the rotational speed of the rotor 22 falls below the lower threshold value Rtd, the control unit 11 changes the conduction angle θ from 90° to a value greater than 90° over time.

[0140] 4, in the one-phase excitation mode in which the conduction angle is set to 90°, when the rotation speed of rotor 22 falls below lower limit threshold Rtd, conduction angle switching unit 120 increases conduction angle θ from 90° to 120° by unit angle φ at regular time intervals. As a result, after the operation mode is switched from the one-phase excitation mode to the 1-2 phase excitation mode, the conduction angle θ changes continuously in the 1-2 phase excitation mode, so that the increase in the rotation speed of rotor 22 can be made gradual.

[0141] In addition, when the conduction angle θ is set to a value greater than 90° (e.g., 120°) (i.e., in a 1-2 phase excitation mode), if the rotational speed of the rotor 22 becomes equal to or greater than the upper threshold value Rtu, the control unit 11 changes the conduction angle θ from a value greater than 90° to 90° over time.

[0142] 4, in the 1-2 phase excitation mode in which the conduction angle is set to 120°, when the rotation speed of rotor 22 becomes equal to or higher than upper limit threshold value Rtu, conduction angle switching unit 120 reduces conduction angle θ from 120° to 90° by unit angle φ at regular time intervals. As a result, after the conduction angle θ changes continuously from 120° to 90° in the 1-2 phase excitation mode, the operation mode is switched to the 1 excitation mode when the conduction angle θ reaches 90°, so that the decrease in the rotation speed of rotor 22 can be made gradual.

[0143] FIG. 9 is a flowchart showing the flow of a method for setting the conduction angle θ according to the second embodiment.

[0144] In FIG. 9, for example, after power-on, when a drive command for the two-phase stepping motor 20 is input from an external higher-level device, the motor drive control device 10 starts drive control (excitation mode transition control) for the two-phase stepping motor 20 (step S21).

[0145] Next, the motor drive control device 10 sets a determination value for the rotation speed (step S22). For example, the motor drive control device 10 sets an upper threshold value Rtu as a judgment value for the rotational speed for switching the conduction angle θ from 120° to 90° (switching the operating mode from 1-2 phase excitation mode to 1-phase excitation mode), and sets a lower threshold value Rtd as a judgment value for the rotational speed for switching the conduction angle θ from 90° to 120° (switching the operating mode from 1-phase excitation mode to 1-2 phase excitation mode).

[0146] Next, the motor drive control device 10 determines whether or not a process is being executed to increase or decrease the conduction angle θ at regular intervals (step S23). For example, immediately after the motor drive control device 10 is started, the conduction angle θ is fixed (step S23: NO). In this case, the conduction angle switching unit 120 determines whether or not the rotation speed of the rotor 22 of the two-phase stepping motor 20 is equal to or greater than the upper limit threshold value Rtu (step S24).

[0147] If the rotation speed is not equal to or higher than the upper threshold value Rtu (step S24: NO), the conduction angle switching unit 120 resets the count value p of the rotation speed increase determination counter 121 (step S5). Next, the conduction angle switching unit 120 determines whether the rotation speed of the rotor 22 of the two-phase stepping motor 20 is equal to or lower than the lower threshold value Rtd (step S26).

[0148] If the rotation speed is not equal to or lower than the lower limit threshold Rtd (step S26: NO), conduction angle switching unit 120 resets count value q of rotation speed reduction determination counter 122 (step S27). After that, motor drive control device 10 returns to step S22.

[0149] On the other hand, if the rotation speed is equal to or less than the lower threshold Rtd (step S26: YES), conduction angle switching unit 120 increments count value q of rotation speed reduction determination counter 122 (step S28). Next, conduction angle switching unit 120 determines whether count value q of rotation speed reduction determination counter 122 is equal to or more than a second threshold (step S29).

[0150] If the count value q of the rotation speed decrease determination counter 122 is not equal to or greater than the second threshold value (step S29: NO), the motor drive control device 10 returns to step S22.

[0151] If the count value q of the rotation speed reduction determination counter 122 is equal to or greater than the second threshold value (step S29: YES), the motor drive control device 10 determines to increase the conduction angle θ in order to switch the operation mode from the one-phase excitation mode to the one-two phase excitation mode (step S30). Then, the conduction angle switching unit 120 increases the conduction angle θ by the unit angle φ (step S31). Then, the process returns to step S22.

[0152] In step S24, if the rotation speed is equal to or greater than the upper limit threshold value Rtu (step S24: YES), conduction angle switching unit 120 increments count value p of rotation speed increase determination counter 121 (step S32).

[0153] Next, conduction angle switching unit 120 determines whether or not the count value p of rotation speed increase determination counter 121 is equal to or greater than the first threshold value (step S33). If the count value p of rotation speed increase determination counter 121 is not equal to or greater than the first threshold value (step S33: NO), motor drive control device 10 returns to step S22. If the count value p of rotation speed increase determination counter 121 is equal to or greater than the first threshold value (step S33: YES), motor drive control device 10 determines to reduce conduction angle θ in order to switch the operation mode from the 1-2 phase excitation mode to the 1 phase excitation mode (step S34). Then, conduction angle switching unit 120 reduces conduction angle θ by a unit angle φ (step S35). Thereafter, the process returns to step S22.

[0154] In step S23, if the process of increasing the conduction angle θ at regular time intervals is being executed (step S23: YES1), conduction angle switching unit 120 further increases the conduction angle θ by the unit angle φ (step S36).

[0155] Next, conduction angle switching unit 120 determines whether conduction angle θ has reached an upper limit (e.g., 120°) (step S37). If conduction angle θ has not reached the upper limit (step S37: NO), the process returns to step S22 and repeats the above process until conduction angle θ reaches the upper limit. If conduction angle θ has reached the upper limit (step S37: YES), the process of increasing conduction angle θ at regular time intervals is stopped (step S38). Then, the process returns to step S22.

[0156] In step S23, if the process of decreasing the conduction angle θ at regular time intervals is being executed (step S23: YES2), conduction angle switching unit 120 further decreases the conduction angle θ by the unit angle φ (step S39).

[0157] Next, conduction angle switching unit 120 determines whether conduction angle θ has reached a lower limit (90°) (step S40). If conduction angle θ has not reached the lower limit (step S40: NO), the process returns to step S22 and repeats the above process until conduction angle θ reaches the lower limit. If conduction angle θ has reached the lower limit (90°) (step S40: YES), the process of decreasing conduction angle θ at regular intervals is stopped (step S41). Then, the process returns to step S22.

[0158] By the above processing procedure, the conduction angle θ can be changed continuously at regular time intervals.

[0159] As described above, according to the method of switching the conduction angle θ of embodiment 2, the conduction angle θ is changed continuously, so that the rotational speed of the rotor 22 can be changed gradually, thereby enabling more stable driving of the two-phase stepping motor 20.

[0160] Third Embodiment In the second embodiment, a method of switching the conduction angle is described in which the conduction angle θ is continuously changed at regular time intervals. However, in the method of switching the conduction angle in the third embodiment, the conduction angle is changed in a stepwise manner.

[0161] FIG. 10 is a diagram showing an example of a method for setting the conduction angle θ according to the third embodiment. 10, the horizontal axis represents the conduction angle θ [°], and the vertical axis represents the rotation speed [rpm] of the rotor 22 of the two-phase stepping motor 20. Reference numeral 501 represents the change in the upper threshold Rtu when the rotation speed increases, and reference numeral 502 represents the change in the lower threshold Rtd when the rotation speed decreases. In this example, the lower threshold Rtd is set for each conduction angle θ that has been set until the rotation speed decreases and the conduction angle θ changes to 120°.

[0162] In the third embodiment, when the conduction angle is set to 90°, control unit 11 changes the conduction angle in stages from 90° to a value greater than 90° in response to a decrease in the rotation speed of rotor 22.

[0163] For example, as shown in FIG. 10, an upper threshold value Rtu and a plurality of lower threshold values ​​Rtd1 to Rtd3 are set as rotation speed determination values ​​for switching the operation mode (conduction angle θ).

[0164] The lower limit threshold Rtd1 is a rotation speed threshold for switching the operation mode from the 1-phase excitation mode to the 1-2 phase excitation mode, and the lower limit thresholds Rtd2 and Rtd3 are rotation speed thresholds for stepwise switching (increasing) the conduction angle θ in the 1-2 phase excitation mode. For example, as shown in Fig. 10, in a state in which the 2-phase stepping motor 20 is driven in the 1-phase excitation mode with the conduction angle θ = 90°, if the rotation speed of the rotor 22 of the 2-phase stepping motor 20 becomes equal to or lower than the lower limit threshold Rtd1, the control unit 11 (conduction angle switching unit 120) sets the conduction angle θ from 90° to 100° and drives the 2-phase stepping motor 20 in the 1-2 phase excitation mode.

[0165] Next, as shown in FIG. 10, in a state where the two-phase stepping motor 20 is being driven in a 1-2 phase excitation mode with an energization angle θ = 100°, when the rotational speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or lower than a lower threshold value Rtd2 (<Rtd1), the control unit 11 (energization angle switching unit 120) sets the energization angle θ from 100° to 110° and drives the two-phase stepping motor 20 in the 1-2 phase excitation mode.

[0166] Furthermore, as shown in FIG. 10, in a state where the two-phase stepping motor 20 is being driven in a 1-2 phase excitation mode with an energization angle θ = 110°, when the rotational speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or lower than a lower threshold value Rtd3 (<Rtd2), the control unit 11 (energization angle switching unit 120) sets the energization angle θ from 110° to 120° and drives the two-phase stepping motor 20 in the 1-2 phase excitation mode.

[0167] Note that in the 1-2 phase excitation mode, when the rotational speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or higher than an upper threshold value Rtu regardless of whether the energization angle θ is 100°, 110°, or 120°, the control unit 11 (energization angle switching unit 120) promptly sets the energization angle θ to 90°.

[0168] According to this, after the operation mode switches from the 1-phase excitation mode to the 1-2 excitation mode, since the energization angle θ changes stepwise in the 1-2 phase excitation mode, the rate at which the rotational speed of the rotor 22 decreases can be moderated.

[0169] FIG. 11 is a diagram showing another example of a method for setting the energization angle θ according to Embodiment 3. 11, the horizontal axis represents the conduction angle θ [°], and the vertical axis represents the rotation speed [rpm] of the rotor 22 of the two-phase stepping motor 20. Reference numeral 601 represents the change in the upper threshold Rtu when the rotation speed increases, and reference numeral 602 represents the change in the lower threshold Rtd when the rotation speed decreases. In this example, the lower threshold Rtd is set for each conduction angle θ until the conduction angle θ changes from 90° to 120° as the rotation speed decreases, and the upper threshold Rtu is set until the conduction angle θ changes from 120° to 90° as the rotation angle increases.

[0170] As shown in FIG. 11, when the conduction angle is set to 90°, control unit 11 may not only gradually change the conduction angle from 90° to a value greater than 90° (e.g., 120°) in response to a decrease in the rotational speed of rotor 22, but may also gradually change the conduction angle from a value greater than 90° to 90° in response to a decrease in the rotational speed of rotor 22 when the conduction angle is set to a value greater than 90°.

[0171] In the third embodiment, for example, as shown in FIG. 11, a plurality of upper threshold values ​​Rtu1 to Rtu3 and a plurality of lower threshold values ​​Rtd1 to Rtd3 are set as rotation speed determination values ​​for switching the conduction angle θ.

[0172] The upper limit thresholds Rtu1 and Rtu2 are rotation speed thresholds for gradually switching (reducing) the conduction angle θ in the 1-2 phase excitation mode, and the upper limit threshold Rtu3 is a rotation speed threshold for switching the operating mode from the 1-2 phase excitation mode to the 1 phase excitation mode. For example, as shown in FIG. 11, when two-phase stepping motor 20 is driven in 1-2 phase excitation mode with conduction angle θ=120°, if the rotational speed of rotor 22 of two-phase stepping motor 20 becomes equal to or greater than upper limit threshold value Rtu1, control unit 11 (conduction angle switching unit 120) sets conduction angle θ from 120° to 110°, and drives two-phase stepping motor 20 in 1-2 phase excitation mode.

[0173] Next, as shown in FIG. 11, when the two-phase stepping motor 20 is driven in 1-2 phase excitation mode with conduction angle θ=110°, if the rotational speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or higher than the upper limit threshold value Rtu2 (>Rtu1), the control unit 11 (conduction angle switching unit 120) sets the conduction angle θ from 110° to 100°, and drives the two-phase stepping motor 20 in the 1-2 phase excitation mode.

[0174] Furthermore, as shown in FIG. 11, when the two-phase stepping motor 20 is driven in the 1-2 phase excitation mode with the conduction angle θ=100°, if the rotational speed of the rotor 22 of the two-phase stepping motor 20 becomes equal to or higher than the upper limit threshold value Rtu3 (>Rtu2), the control unit 11 (conduction angle switching unit 120) sets the conduction angle θ from 100° to 90°, and drives the two-phase stepping motor 20 in the 1-phase excitation mode.

[0175] When switching from the 1-phase excitation mode to the 1-2 excitation mode, as in FIG. 10 described above, the conduction angle θ switches in the order of 90°, 100°, 110°, and 120° in response to a decrease in the rotational speed of the rotor 22 of the two-phase stepping motor 20.

[0176] The upper thresholds Rtu1 to Rtu3 and the lower thresholds Rtd1 to Rtd3 are set to appropriate values ​​according to the set value of the conduction angle θ.

[0177] For example, when the conduction angle θ is set to 90°, a lower limit threshold Rtd3 is set, when the conduction angle θ is set to 100°, an upper limit threshold Rtu3 and a lower limit threshold Rtd2 are set, when the conduction angle θ is set to 110°, an upper limit threshold Rtu2 and a lower limit threshold Rtd3 are set, and when the conduction angle θ is set to 120°, an upper limit threshold Rtu1 is set.

[0178] According to this, after the operating mode is switched from the 1-phase excitation mode to the 1-2 excitation mode, the conduction angle θ changes stepwise in the 1-2 phase excitation mode, so that the rate at which the rotational speed of the rotor 22 decreases can be made gentler, and since the conduction angle θ changes stepwise when the operating mode is switched from the 1-2 phase excitation mode to the 1 excitation mode, the rate at which the rotational speed of the rotor 22 increases can be made gentler.

[0179] FIG. 12 is a flowchart showing the flow of a method for setting the conduction angle θ according to the third embodiment. This figure shows a specific process flow for implementing the method for setting the conduction angle θ shown in FIG.

[0180] In FIG. 12, first, when a drive command for the two-phase stepping motor 20 is input from an external higher-level device after power-on, the motor drive control device 10 starts drive control (excitation mode transition control) for the two-phase stepping motor 20 (step S51).

[0181] Next, the motor drive control device 10 sets an upper threshold Rtu and a lower threshold Rtd as the rotation speed judgment values ​​corresponding to the conduction angle θ at that time (step S52). For example, when the conduction angle θ is set to 110°, the motor drive control device 10 sets an upper threshold Rtu2 and a lower threshold Rtd3 as the rotation speed judgment values.

[0182] Next, conduction angle switching unit 120 determines whether the rotation speed of rotor 22 of two-phase stepping motor 20 is equal to or greater than upper limit threshold value Rtu set in the immediately preceding step S52 (step S53). If the rotation speed is not equal to or greater than upper limit threshold value Rtu (step S53: NO), conduction angle switching unit 120 resets count value p of rotation speed increase determination counter 121 (step S54).

[0183] Next, the conduction angle switching unit 120 determines whether the rotation speed of the rotor 22 of the two-phase stepping motor 20 is equal to or lower than the lower threshold Rtd set in the immediately preceding step S52 (step S55). If the rotation speed is not equal to or lower than the lower threshold Rtd (step S55: NO), the conduction angle switching unit 120 resets the count value q of the rotation speed reduction determination counter 122 (step S56). Thereafter, the motor drive control device 10 returns to step S52.

[0184] On the other hand, if the rotation speed is equal to or less than the lower threshold Rtd (step S55: YES), conduction angle switching unit 120 increments count value q of rotation speed reduction determination counter 122 (step S57). Next, conduction angle switching unit 120 determines whether count value q of rotation speed reduction determination counter 122 is equal to or more than the second threshold and conduction angle θ is less than an upper limit value (e.g., 120°) (step S58).

[0185] If the count value q of the rotation speed reduction determination counter 122 is equal to or greater than the second threshold value and the conduction angle θ is not less than the upper limit value (step S58: NO), the motor drive control device 10 returns to step S52.

[0186] On the other hand, if the count value q of the rotation speed reduction determination counter 122 is equal to or greater than the second threshold value and the conduction angle θ is less than the upper limit value (step S58: YES), the conduction angle switching unit 120 increases the conduction angle θ by one step toward the upper limit value (120°) (step S59). For example, when the conduction angle θ is 100°, the conduction angle switching unit 120 sets the conduction angle θ to 110°. The motor drive control device 10 then returns to step S52, sets an upper limit threshold Rtu and a lower limit threshold Rtd corresponding to the newly set conduction angle θ, and executes the processes from step S53 onward.

[0187] In step S53, if the rotation speed is equal to or greater than the upper threshold value Rtu (step S53: YES), conduction angle switching unit 120 increments count value p of rotation speed increase determination counter 121 (step S60). Next, conduction angle switching unit 120 determines whether count value p of rotation speed increase determination counter 121 is equal to or greater than the first threshold value and conduction angle θ is greater than the lower limit value (90°) (step S61).

[0188] If the count value p of the rotation speed increase determination counter 121 is equal to or greater than the first threshold value and the conduction angle θ does not exceed the lower limit, ie, θ=90° (step S61: NO), the motor drive control device 10 returns to step S52.

[0189] On the other hand, if the count value p of the rotation speed increase determination counter 121 is equal to or greater than the first threshold value and the conduction angle θ is greater than the lower limit value (step S61: YES), the conduction angle switching unit 120 decreases the conduction angle θ by one step toward the lower limit value (90°) (step S62). For example, if the conduction angle θ is 100°, the conduction angle switching unit 120 sets the conduction angle θ to 90°.

[0190] Thereafter, motor drive control device 10 returns to step S52, sets upper threshold value Rtu and lower threshold value Rtd corresponding to the newly set conduction angle θ, and repeats the processes from step S53 onwards.

[0191] As described above, according to the method of switching the conduction angle according to the third embodiment, the conduction angle θ is changed in a stepwise manner, so that the rotational speed of the rotor 22 can be changed gradually, thereby enabling more stable driving of the two-phase stepping motor 20 to be achieved.

[0192] <<Extension of the embodiment>> The invention made by the present inventors has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0193] For example, in the above embodiment, the two-phase stepping motor 20 has the rotor 22 with two poles, but the number of poles of the rotor 22 is not particularly limited.

[0194] The motor unit 1 according to the above embodiment is not limited to the configuration disclosed in Fig. 1. For example, the drive unit 12 may have other circuits, such as a current detection circuit for detecting coil currents in the coils 21A and 21B, in addition to the motor drive unit 13 described above.

[0195] In addition, the above-mentioned flowchart shows an example for explaining the operation, and is not limited to this. That is, the steps shown in each figure of the flowchart are specific examples, and are not limited to this flow. For example, the order of some processes may be changed, other processes may be inserted between each process, and some processes may be performed in parallel.

[0196] In the above embodiment, the controller 11 monitors the rotation speed of the rotor 22 as the rotation state of the rotor 22, and sets the conduction angle θ so that the conduction angle θ decreases as the rotation speed of the rotor 22 increases. However, the rotation state of the rotor 22 is not limited to the rotation speed. For example, the controller 11 may monitor the load of the rotor 22 as the rotation state of the rotor 22, and set the conduction angle θ so that the conduction angle θ decreases as the load of the rotor 22 decreases. A specific example of monitoring the load of the rotor 22 and setting the conduction angle θ in accordance with the load will be described below.

[0197] FIG. 13 is a diagram showing a functional block configuration of the control unit 11A that sets the conduction angle θ in accordance with the load on the rotor 22.

[0198] As shown in FIG. 13, the control unit 11A has a load measurement unit 118A, a load judgment unit 119A, a load increase judgment counter 121A, and a load decrease judgment counter 122A instead of (or in addition to) the rotation speed measurement unit 118, the rotation speed judgment unit 119, the rotation speed increase judgment counter 121, and the rotation speed decrease judgment counter 122 in the control unit 11 shown in FIG. 7.

[0199] The load measurement unit 118A is a functional unit that measures the load of the rotor 22 of the two-phase stepping motor 20. The load measurement unit 118A measures, for example, the magnitude of the current flowing through the A-phase coil 21A and the B-phase coil 21B of the two-phase stepping motor 20, and regards the current value as a measurement value of the load of the rotor 22.

[0200] Load determination unit 119A is a functional unit that compares the load measurement value of rotor 22 of two-phase stepping motor 20 with a load determination value for switching conduction angle θ. Load determination unit 119A is a functional unit that compares the load measurement value obtained by load measurement unit 118A with an upper limit threshold Ltu and a lower limit threshold Ltd of the load. For example, when the load measurement value becomes equal to or greater than the upper limit threshold Ltu, load determination unit 119A provides a signal indicating this to conduction angle switching unit 120A. Also, when the load measurement value becomes equal to or less than the lower limit threshold Ltd, load determination unit 119A provides a signal indicating this to conduction angle switching unit 120A.

[0201] Conduction angle switching unit 120A outputs a conduction angle θ, that is, an operation mode signal that indicates an operation mode, in response to a signal from load determining unit 119A.

[0202] For example, when energization switching control is being performed in a 1-2 phase excitation mode (e.g., energization angle θ=120°), if a signal indicating that the load measurement value has become equal to or lower than a lower threshold value Ltu is output from load determination unit 119A, energization angle switching unit 120 outputs an operation mode signal instructing the 1 phase excitation mode (energization angle θ=90°) to two phase excitation period calculation unit 114.

[0203] Furthermore, when energization switching control is being performed in the 1-phase excitation mode (energization angle θ=90°), if the load determination unit 119A outputs an operation mode signal indicating that the load measurement value has reached or exceeded the upper limit threshold value Ltd, the energization angle switching unit 120A outputs an operation mode signal instructing the 1-2 phase excitation mode (for example, energization angle θ=120°) to the 2-phase excitation period calculation unit 114.

[0204] According to control unit 11A, it is possible to improve the stability of drive control of a two-phase stepping motor against load fluctuations, in the same way as in the case where conduction angle θ is set according to the rotation speed.

[0205] As in the case of monitoring the rotation speed, it is preferable that control unit 11A switches the operation mode when an increase and decrease in the load relative to the upper limit threshold Ltu and the lower limit threshold Ltd are detected multiple times. For example, as shown in Fig. 13, conduction angle switching unit 120A may have a load increase determination counter 121A and a load decrease determination counter 122A, and may count the number of times the load of rotor 22 becomes equal to or greater than the upper limit threshold Ltu using load increase determination counter 121A and count the number of times the load of rotor 22 becomes equal to or less than the lower limit threshold Ltd using load decrease determination counter 122A, and switch the operation mode based on the count values ​​of these counters.

[0206] Specifically, when a signal indicating that the load measurement value has become equal to or greater than the upper limit threshold value Ltu is output from load determination unit 119A, current angle switching unit 120A increments load increase determination counter 121A (+1), and when the load measurement value becomes less than the upper limit threshold value Ltu, current angle switching unit 120A resets load increase determination counter 121A.

[0207] In addition, when a signal indicating that the load measurement value has become equal to or lower than the lower limit threshold value Ltd is output from the load determination unit 119A, the conduction angle switching unit 120A increments (+1) the load reduction determination counter 122A, and when the load measurement value becomes greater than the lower limit threshold value Ltd, the conduction angle switching unit 120A resets the load reduction determination counter 122A.

[0208] Conduction angle switching unit 120A outputs an operation mode signal instructing a 1-2 phase excitation mode (conduction angle θ=120°, for example) when the count value of load increase determination counter 121A is equal to or greater than a first threshold value (for example, an integer equal to or greater than 2). Conduction angle switching unit 120A also outputs an operation mode signal instructing a 1 phase excitation mode (conduction angle θ=90°) when the count value of load decrease determination counter 122A is equal to or greater than a second threshold value (for example, an integer equal to or greater than 2). The first threshold value and the second threshold value may be the same value or different values. Information on the first threshold value and the second threshold value is stored in advance in the storage unit 116, for example.

[0209] In this manner, by using the load increase determination counter 121A and the load decrease determination counter 122A, switching of the operation mode in response to an instantaneous change in the load on the rotor 22 can be prevented. [Explanation of symbols]

[0210] 1...motor unit, 10...motor drive control device, 11, 11A...control unit, 12...drive unit, 13...motor drive unit, 20...two-phase stepping motor, 21...coil, 21A...A-phase coil, 21B...B-phase coil, 22...rotor, 22N...N-pole, 22S...S-pole, 111...back electromotive force monitoring unit, 112...zero-cross point detection unit, 113...one-phase excitation period timing unit, 114...two-phase excitation period calculation unit, 115...two-phase excitation period timing unit, 116...storage unit, 117...control signal generation unit, 118...rotational speed measurement unit, 118A...load measurement unit, 119...rotational speed determination unit, 119A...load determination unit determination unit, 120, 120A...conduction angle switching unit, 121...rotation speed increase determination counter, 121A...load increase determination counter, 122...rotation speed decrease determination counter, 122A...load decrease determination counter, Sd...control signal, Sz...detection signal, T1n...1-phase excitation period, T2n...target current supply time (2-phase excitation period), AP...positive terminal of A-phase coil, AN...negative terminal of A-phase coil, BP...positive terminal of B-phase coil, BN...negative terminal of B-phase coil, Rtu, Rtu1 to Rtu3, Ltu...upper threshold, Rtd, Rtd1 to Rtd3, Ltd...lower threshold.

Claims

1. a control unit that monitors a rotation state of a rotor of the two-phase stepping motor, and sets a conduction angle indicating a magnitude of an electrical angle at which current is continuously supplied in one direction to one of two phase coils in the two-phase stepping motor based on the rotation state of the rotor, and generates a control signal for controlling driving of the two-phase stepping motor based on the set conduction angle; a drive unit that drives the two-phase coils based on the control signal, The control unit monitors a rotation speed of the rotor as a rotation state of the rotor, and sets the conduction angle so that the conduction angle becomes smaller as the rotation speed of the rotor becomes higher. Motor drive control device.

2. A control unit that monitors the rotational state of a rotor of a two-phase stepping motor, and sets an energization angle indicating the magnitude of the electrical angle at which current is continuously applied in one direction to one of the two-phase coils in the two-phase stepping motor based on the rotational state of the rotor, and generates a control signal for controlling the drive of the two-phase stepping motor based on the set energization angle; a drive unit that drives the two-phase coils based on the control signal, The control unit monitors a load on the rotor as a rotation state of the rotor, and sets the conduction angle so that the conduction angle becomes smaller as the load on the rotor becomes smaller. Motor drive control device.

3. 2. The motor drive control device according to claim 1, the control unit has, as operation modes, a 1-2 phase excitation mode in which a 1-phase excitation in which one of the two-phase coils is excited and a 2-phase excitation in which two of the two-phase coils are excited are alternately repeated, and a 1-phase excitation mode in which one of the two-phase coils is excited; The control unit sets the conduction angle to 90° and selects the one-phase excitation mode when the rotation speed of the rotor becomes equal to or higher than an upper threshold, and sets the conduction angle to a value greater than 90° and selects the one-two phase excitation mode when the rotation speed of the rotor becomes equal to or lower than a lower threshold that is smaller than the upper threshold. A motor drive control device comprising:

4. 4. The motor drive control device according to claim 3, When the rotation speed of the rotor becomes equal to or lower than the lower threshold value in a state in which the conduction angle is set to 90°, the control unit changes the conduction angle from 90° to a value greater than 90° over time. A motor drive control device comprising:

5. 5. The motor drive control device according to claim 4, When the rotation speed of the rotor becomes equal to or higher than the upper limit threshold in a state in which the conduction angle is set to a value greater than 90°, the control unit changes the conduction angle over time from a value greater than 90° to 90°. A motor drive control device comprising:

6. 4. The motor drive control device according to claim 3, The control unit changes the conduction angle in a stepwise manner from 90° to a value greater than 90° in response to a decrease in the rotation speed of the rotor in a state in which the conduction angle is set to 90°. A motor drive control device comprising:

7. 7. The motor drive control device according to claim 6, When the rotation speed of the rotor becomes equal to or higher than the upper limit threshold in a state in which the conduction angle is set to a value greater than 90°, the control unit changes the conduction angle in stages from the value greater than 90° to 90° in response to an increase in the rotation speed of the rotor. A motor drive control device comprising:

8. A motor drive control device according to any one of claims 1 to 7, The two-phase stepping motor. A motor unit characterized by:

9. A motor drive control method for controlling the drive of a two-phase stepping motor by a motor drive control device, comprising: a first step in which the motor drive control device monitors a rotation state of a rotor of the two-phase stepping motor; a second step in which the motor drive control device sets a conduction angle indicating a magnitude of an electrical angle at which current is continuously conducted in one direction through one of two-phase coils in the two-phase stepping motor based on a rotation state of the rotor; a third step in which the motor drive control device generates a control signal for controlling the drive of the two-phase stepping motor based on the conduction angle set in the second step; a fourth step of the motor drive control device driving the two-phase coils based on the control signal; The second step includes a step of the motor drive control device monitoring a rotation speed of the rotor as a rotation state of the rotor, and setting the conduction angle so that the conduction angle becomes smaller as the rotation speed of the rotor becomes higher. A motor drive control method.

10. A motor drive control method for controlling the drive of a two-phase stepping motor by a motor drive control device, comprising: a first step in which the motor drive control device monitors a rotation state of a rotor of the two-phase stepping motor; a second step in which the motor drive control device sets a conduction angle indicating a magnitude of an electrical angle at which current is continuously conducted in one direction through one of two-phase coils in the two-phase stepping motor based on a rotation state of the rotor; a third step in which the motor drive control device generates a control signal for controlling the drive of the two-phase stepping motor based on the conduction angle set in the second step; a fourth step of the motor drive control device driving the two-phase coils based on the control signal; The second step includes a step of the motor drive control device monitoring a load on the rotor as a rotation state of the rotor, and setting the conduction angle so that the conduction angle becomes smaller as the load on the rotor becomes smaller. A motor drive control method.

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