Stepping motor control apparatus

Abstract

To suppress a temperature rise without reducing the driving performance of a stepping motor.SOLUTION: A stepping motor control apparatus 200 comprises: a stepping motor 2; and an excitation control unit 112 that performs current period control processing for controlling a current period at which the stepping motor is energized in accordance with a constant current control period such that the current period is two or more periods of the constant current control period.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a stepping motor control device. [Background technology]

[0002] Conventionally, when a supplier of a unipolar stepping motor drive control IC (Integrated Circuit), i.e., a stepping motor control device, discontinues production, a huge amount of development costs are incurred in developing a replacement IC for the discontinued drive control IC. For this reason, it is common to build a stepping motor control device with equivalent functions using discrete components and a control device. In addition, examples of control devices include general-purpose CPUs (Central Processing Units), DSPs (digital signal processors), and FPGAs (Field Programmable Gate Arrays). However, from a cost perspective, there is no choice but to select a CPU that is cheaper than DSPs and FPGAs. In addition, it is required to use a low-end inexpensive CPU rather than a high-performance CPU to control a single function that drives a stepping motor.

[0003] Generally, in a stepping motor control device, a process is performed to suppress a temperature rise of the stepping motor so that the temperature of the stepping motor does not exceed an upper limit. For example, Patent Document 1 discloses a technique for suppressing a temperature rise of a stepping motor.

[0004] The stepping motor control device described in Patent Document 1 performs control so as to reduce the constant current by the constant current switching means and also reduce the maximum rotation speed when the temperature detected by the temperature measuring means reaches or exceeds a predetermined temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 11-313500 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, conventionally, in a stepping motor control device, control is performed to suppress a temperature rise of a stepping motor. In the case of PWM (Pulse Width Modulation) constant current control of a stepping motor, constant current control is performed to turn on (ON) the power supply to the stepping motor in a fixed period (constant current control period), and control is performed to turn off (OFF) the power supply to the stepping motor when it is detected that the detected current value has reached a set constant current control threshold. However, while the timing to turn on the power supply is constant in the constant current control period, the timing to turn off the power supply changes depending on the arbitrary timing at which the detected current value reaches the constant current control threshold, and therefore cannot be controlled. For this reason, depending on the timing of turning off the power supply, the current value may not reach the constant current control threshold by the time of the next constant current control period, and a transition may occur to two-period control in which the power supply is turned off in the constant current period after the next.

[0007] In addition, the cycle of the current flowing through a stepping motor is usually controlled at one constant current control cycle, and the number of switching times in this case is greater than the number of switching times when it is controlled at two constant current control cycles. In addition, the greater the number of switching times, the greater the switching loss and the greater the temperature rise of the stepping motor. If the temperature of the stepping motor rises excessively, it can lead to deterioration and failure of the stepping motor. In addition, the technology described in Patent Document 1 can suppress the temperature rise of the motor, but it also reduces the rotation speed, which causes a problem of reduced productivity.

[0008] Furthermore, when a low-end CPU is applied to a stepping motor control device, a problem occurs in that the driving performance of the stepping motor deteriorates due to insufficient performance aspects such as the operating CLK of the low-end CPU.

[0009] The present invention has been made to solve the above problems, and an object of the present invention is to suppress an increase in temperature without degrading the driving performance of a stepping motor. [Means for solving the problem]

[0010] The stepping motor control device of the present invention includes a stepping motor and a current period control unit that performs current period control processing to control the current period supplied to the stepping motor in accordance with a constant current control period so that the current period is at least two constant current control periods. Effect of the Invention

[0011] According to the present invention having the above configuration, it is possible to suppress an increase in temperature without deteriorating the driving performance of the stepping motor. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a stepping motor control device. [Diagram 2] FIG. 2 is a diagram for explaining phase currents of a stepping motor. [Diagram 3] FIG. 4 is a diagram for explaining a driving phase current of a stepping motor. [Figure 4] 1 is a diagram illustrating an example of the configuration of a stepping motor control device according to an embodiment of the present invention. [Diagram 5] 4 is a diagram for explaining the relationship between an external clock and a current conduction pattern of a stepping motor in a stepping motor control device according to an embodiment of the present invention. FIG. [Figure 6] FIG. 2 is a diagram for explaining one-cycle control in a stepping motor control device. [Figure 7] FIG. 2 is a diagram for explaining two-period control in a stepping motor control device. [Figure 8]FIG. 11 is a diagram showing the temperature change time characteristics of an FET under one-cycle control and two-cycle control in a stepping motor control device. [Figure 9] FIG. 2 is a diagram for explaining Example 1 of two-cycle control in the stepping motor control device according to one embodiment of the present invention. [Figure 10] FIG. 11 is a diagram for explaining Example 2 of two-cycle control in the stepping motor control device according to one embodiment of the present invention. [Figure 11] FIG. 11 is a diagram for explaining Example 3 of two-cycle control in the stepping motor control device according to one embodiment of the present invention. [Figure 12] FIG. 11 is a diagram for explaining Example 4 of two-cycle control in the stepping motor control device according to one embodiment of the present invention. [Figure 13] FIG. 4 is a diagram for explaining the start timing of the current period control process after switching of the external clock in the stepping motor control device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] <One embodiment> [Stepping motor control device configuration] First, the configuration of a stepping motor control device will be described. Fig. 1 is a diagram showing an example of the configuration of a stepping motor control device 100. As shown in Fig. 1, the stepping motor control device 100 includes a control device 1, a stepping motor 2, and a fuse 3. The control device 1 is connected to the stepping motor 2, and controls the energization of the stepping motor 2.

[0015] The stepping motor 2 is a unipolar two-phase stepping motor that drives, for example, a conveying roller, a registration roller, etc. of an image forming apparatus, and has coils 21 to 24. One end of the coils 21 to 24 is connected to a power supply unit (24 [V]) of a driving power source via a fuse 3. This power supply unit is not limited to 24 [V], and may be 36 [V] or the like. The coils 21 and 22 form a pair, and the coils 23 and 24 form a pair. The pairs are coupled so that when a current flows in the same direction (power supply → each coil terminal), the current flows in the opposite magnetic directions. For convenience, each pair is called an A-phase and a B-phase, and the terminals on the power supply side and the opposite side of the coils of the A-phase pair are called the A-phase terminal and the AB-phase terminal, respectively, and the terminals on the power supply side and the opposite side of the coils of the B-phase pair are called the B-phase terminal and the BB-phase terminal, respectively. In addition, coil 21 is a coil corresponding to phase A, coil 22 paired with coil 21 is a coil corresponding to phase AB, coil 23 is a coil corresponding to phase B, and coil 24 paired with coil 23 is a coil corresponding to phase BB.

[0016] The excitation methods for the stepping motor 2 include "2-phase full step", "1-2 phase", "W1-2 phase", "2W1-2 phase", and "4W1-2 phase". "2-phase full step" is a method in which two phases are excited at a time (2-phase excitation). "1-2 phase" is a method in which the resolution is doubled by alternating between a method in which one phase is excited at a time (1-phase excitation) and 2-phase excitation. "W1-2 phase" is a method in which one rotation takes four times the basic step number (the number of full steps per rotation). "2W1-2 phase" is a method in which one rotation takes eight times the basic step number. "4W1-2 phase" is a method in which one rotation takes 16 times the basic step number.

[0017] 1, the control device 1 includes a control unit 10, a pre-driver 11, FETs (Field Effect Transistors) 121 to 124, AMPs (Amplifiers) 13 and 14, and shunt resistors 15 and 16. In FIG. 1, the "shunt resistor" is abbreviated to "shunt."

[0018] The pre-driver 11 is a driver circuit, with four terminals on one side connected to an excitation control section 112 (to be described later) of the control section 10, and four terminals on the other side connected to the gates of the FETs 121 to 124, respectively.

[0019] The FET 121 is a switching element having a drain connected to the terminal A of the coil 21, a source connected to the shunt resistor 15, and a diode that rectifies from the source to the drain. The FET 122 is a switching element having a drain connected to the terminal AB of the coil 22, a source connected to the shunt resistor 15, and a diode that rectifies from the source to the drain. The FET 123 is a switching element having a drain connected to the terminal B of the coil 23, a source connected to the shunt resistor 16, and a diode that rectifies from the source to the drain. The FET 124 is a switching element having a drain connected to the terminal BB of the coil 24, a source connected to the shunt resistor 16, and a diode that rectifies from the source to the drain.

[0020] One end of the shunt resistor 15 is connected to the FET 121 and the FET 122, and the other end is connected to the ground portion 17, and is a resistor for detecting a current between the terminals. One end of the shunt resistor 16 is connected to the FET 123 and the FET 124, and the other end is connected to the ground portion 17, and is a resistor for detecting a current between the terminals.

[0021] An input terminal of AMP13 is connected to the sources of FET121 and FET122, and amplifies the voltages of the sources. An output terminal of AMP13 is connected to an input terminal of a comparator 108 (described later) of the control unit 10, and outputs an amplified voltage value to the comparator 108. An input terminal of AMP14 is connected to the sources of FET123 and FET124, and amplifies the voltages of the sources. An output terminal of AMP14 is connected to an input terminal of a comparator 109 (described later) of the control unit 10, and outputs an amplified voltage value to the comparator 109.

[0022] The control unit 10 is configured with, for example, a low-end CPU, a RAM (Random Access Memory), a ROM (Read Only Memory), and a storage device (not shown). As shown in Fig. 1, the control unit 10 includes an excitation mode setting unit 101, an edge detection unit 102, a phase advance counter 103, a current table 104, and a current value calculation unit 105. The control unit 10 also includes a D / A (Digital to Analog) converter 106, a D / A converter 107, a comparator (COMP) 108, a comparator (COMP) 109, an oscillator 110, a clock generation unit 111, and an excitation control unit 112.

[0023] The excitation mode setting unit 101 outputs a setting signal for the excitation method of the stepping motor 2 in response to a MODE signal input from the outside.

[0024] The edge detection unit 102 detects an edge for each period of an external clock (CLOCK signal) input from the outside, and outputs an edge detection signal to the phase lead counter 103 .

[0025] The phase lead counter 103 generates a phase lead amount signal indicating a phase lead count value corresponding to the excitation method and the rotation direction in response to a DIRECTION signal input from an external device, an excitation method setting signal input from an excitation mode setting unit 101, and an edge detection signal input from an edge detection unit 102. The phase lead counter 103 also outputs the generated phase lead amount signal to a current table 104.

[0026] The current table 104 stores a preset current table. The current table is a table showing a current control pattern for the electrical angle of the stepping motor 2 according to the excitation method and the direction of rotation. For example, which of the A-phase FET 121 and the AB-phase FET 122 is turned on is determined by the electrical angle of the current control pattern (leading by an external CLOCK signal with a different lead angle for each excitation method). The same applies to the B-phase and the BB-phase.

[0027] The current value calculation unit 105 reads out a current table from the current table 104, calculates the current values ​​to be passed through the coils 21 to 24 of the stepping motor 2 based on the read out current table, the VREF voltage input from the outside, and the phase lead signal according to the excitation method and rotation direction input from the phase lead counter 103, and outputs the calculated current values ​​to the excitation control unit 112, and also to the D / A converter 106 and the D / A converter 107.

[0028] D / A converter 106 and D / A converter 107 input the current value from current value calculation unit 105, generate a current setting reference voltage corresponding to the input current value, and output the current setting reference voltage to comparator 108 and comparator 109, respectively.

[0029] Comparator 108 compares the voltage input from AMP 13 with the current setting reference voltage input from D / A converter 106, generates a comparator output signal indicating the comparison result, and outputs it to excitation control unit 112. Comparator 109 compares the voltage input from AMP 14 with the current setting reference voltage input from D / A converter 107, generates a comparator output signal indicating the comparison result, and outputs it to excitation control unit 112.

[0030] The oscillator 110 generates an oscillation signal that is sufficiently faster than the CLOCK signal input from the outside, and outputs the oscillation signal to the clock generation unit 111. The clock generation unit 111 receives the oscillation signal from the oscillator 110, generates an internal clock signal in response to the input oscillation signal, and outputs the internal clock signal to the excitation control unit 112.

[0031] The excitation control unit 112 generates control signals for the FETs 121 to 124 in response to an internal clock signal input from the clock generation unit 111, an ENABLE signal input from the outside, a current value signal input from the current value calculation unit 105, and a comparator output signal input from the comparator 108 and the comparator 109, and outputs the control signals to the pre-driver 11 to turn on / off the FETs 121 to 124. The excitation control unit 112 is an example of a current cycle control unit, and controls the energization of the stepping motor 2 by controlling the ON / OFF of the FETs 121 to 124. In the following, the energization control of the A-phase coil 21 and the AB-phase coil 22 by controlling the ON / OFF of the A-phase FET 121 and the AB-phase FET 122 will be described as an example, and a description of the B-phase will be omitted.

[0032] Next, an explanation will be given of the phase currents of the stepping motor 2. Fig. 2 is a diagram for explaining the phase currents of the stepping motor 2. Fig. 2 shows the time change characteristics of the gate voltage of the A-phase FET 121 ("A-phase FET voltage" shown in the figure), the gate voltage of the AB-phase FET 122 ("AB-phase FET voltage" shown in the figure), the A-phase current (driving phase current), and the AB-phase current (inverted phase current).

[0033] At time t1 shown in Fig. 2, the excitation control unit 112 turns on the A-phase FET 121 and turns off the AB-phase FET 122. Therefore, at time t1, the AB-phase FET voltage is 0V. Furthermore, when the FET 121 is turned on, an A-phase current (driving phase current) flows from the power supply unit of the driving power supply through the A-phase coil 21, the drain-source of the FET 121, and the shunt resistor 15 to the ground unit 17 (see Fig. 3A described later). Furthermore, the current value of the A-phase current increases over time. At this time, the AB-phase FET 122 is OFF, so the AB-phase current flowing through the AB-phase coil 22 is 0A.

[0034] At time t2 shown in FIG. 2, the A-phase current reaches a constant current control threshold determined by the current setting reference voltage of the comparator 108, and the comparator 108 outputs a comparator output signal for turning off the A-phase to the excitation control unit 112. The excitation control unit 112 turns off the A-phase FET 121 in response to the comparator output signal for turning off the A-phase input from the comparator 108. As the A-phase FET 121 is turned off, the A-phase current (driving phase current) becomes 0 A. Also, at time t2, an AB-phase current (inverted phase current) is generated, which is a reverse current having the same magnitude as the A-phase current and flows from the ground unit 17 through the shunt resistor 15, the diode (asynchronous rectification) of the FET 122, and the coil 22 to the power supply unit (see FIG. 3B described later), and the absolute value of the current value of the AB-phase current decreases over time.

[0035] 2, the excitation control unit 112 turns on the A-phase FET 121 and turns off the AB-phase FET 122. Therefore, at time t3, the AB-phase FET voltage is 0V. Furthermore, when the FET 121 is turned on, an A-phase current (driving phase current) flows from the power supply unit of the driving power supply through the A-phase coil 21, the drain-source of the FET 121, and the shunt resistor 15 to the ground unit 17. Furthermore, the current value of the A-phase current increases over time. At this time, the AB-phase FET 122 is OFF, so the AB-phase current flowing through the AB-phase coil 22 is 0A.

[0036] The time from time t1 to time t3 is a constant current control period. As described above, the excitation control unit 112 repeatedly performs constant current control to control the driving phase current (for example, the A phase current shown in FIG. 2) to be constant. The current control for currents supplied to the AB phase, B phase, and BB phase is the same as the current control for current supplied to the A phase described above.

[0037] Fig. 3 is a diagram for explaining the driving phase current of a stepping motor. Fig. 3A shows the A-phase current (see the dashed line in the figure) from time t1 to time t2 shown in Fig. 2, that is, the driving phase current flowing from the power supply unit of the driving power supply to the ground unit 17 via the A-phase coil 21, the drain-source of the FET 121, and the shunt resistor 15. Fig. 3B shows the AB-phase current (see the dashed line in the figure) from time t2 to time t3 shown in Fig. 2, that is, the inverted phase current flowing from the ground unit 17 to the power supply unit via the shunt resistor 15, the diode (asynchronous rectification) of the FET 122, and the coil 22.

[0038] Next, the configuration of the stepping motor control device 200 according to this embodiment will be described. FIG. 4 is a diagram showing an example of the configuration of the stepping motor control device 200 according to this embodiment. The configuration of the stepping motor control device 200 shown in FIG. 4 is the same as that of the stepping motor control device 100 shown in FIG. 1, so a duplicated description will be omitted. In the stepping motor control device 200, the process of advancing the excitation pattern by the external clock (CLOCK signal) (see (a) in the figure) is called an "external clock interrupt". Also, the internal clock signal generated by the clock generation unit 111, that is, the ON / OFF control process of each FET by the constant current control period (see (b) in the figure) is called a "constant current control period interrupt". Also, when the drive phase current reaches the constant current control threshold, the ON / OFF control process of each FET according to the comparator output signal generated by the comparator 108 or the comparator 109 (see (c) in the figure) is called a "comparator interrupt".

[0039] In the stepping motor control device 200, the excitation control unit 112 (current cycle control unit) of the control unit 10 performs a current cycle control process to control the cycle of the current supplied to the stepping motor 2 in accordance with the constant current control cycle so that the cycle is equal to or longer than two constant current control cycles. The cycle of the current supplied to the stepping motor 2 is, in other words, the chopping cycle of the drive phase current.

[0040] Before describing the current cycle control process in the excitation control section 112 (current cycle control section), the relationship between the external clock (CLOCK signal) and the excitation pattern of the stepping motor 2 will be described first. Fig. 5 is a diagram for explaining the relationship between the external clock of the stepping motor control device 200 according to this embodiment and the current conduction pattern of the stepping motor. Fig. 5 shows the time correspondence relationship between the external clock signal and the phase current signals of each phase (A, AB, B, BB) when the stepping motor 2 is excited in two-phase full steps. Ta in Fig. 5 is the period of the external clock.

[0041] Next, a process (one-period control) for controlling the period of the current supplied to the stepping motor 2 within one period (Ta) of the external clock shown in Fig. 5 to be one period of the constant current control period will be described. Fig. 6 is a diagram for explaining the one-period control in the stepping motor control device.

[0042] Tb shown in FIG. 6 is a constant current control period, that is, a period of the internal clock signal (see (b) in FIG. 4) generated by the clock generating unit 111. When the stepping motor 2 is energized and the current value of the drive phase current (portion drawn by a broken line) increases and reaches a constant current control threshold within the current control period Tb as shown in FIG. 6, the FET connected to the drive phase is turned OFF by a comparator interrupt, and a reverse current (portion drawn by a broken line) having the same magnitude as the drive phase current is generated in the inverted phase of the drive phase. Tc shown in FIG. 6 is a current period for energizing the stepping motor 2 after the first chopping, that is, a chopping period of the drive phase current. As shown in FIG. 6, in one-period control of the current period for energizing the stepping motor 2, the drive phase current is turned OFF within each constant current control period and turned ON at the start of the next constant current control period. Note that, although chopping usually occurs 10 times or more within one period of the external clock, only five choppings are shown in FIG. 6 for convenience of explanation.

[0043] Next, a process (two-period control) for controlling the current period for energizing the stepping motor 2 within one period (Ta) of the external clock shown in Fig. 5 to be two periods of the constant current control period will be described. Fig. 7 is a diagram for explaining the two-period control in a stepping motor control device. In the two-period control shown in Fig. 7, after the driving phase current (FET connected to the driving phase) is turned OFF for the first time (initial chopping), it is not turned OFF in the next constant current control period (see the second Tb), but is turned OFF in the next constant current control period (see the third Tb). Therefore, the chopping period Tc of the driving phase current is two periods of the constant current control period Tb.

[0044] As can be seen by comparing Figure 7 with Figure 6, the number of times the drive phase current is chopped in one-cycle control, i.e., the number of times the FET connected to the drive phase is switched, is about twice as many as the number of times the drive phase current is chopped (the number of times the FET is switched) in two-cycle control. Note that the number of times the FET is switched leads to an increase in the temperature of the FET, and the doubled number of times the FET is switched greatly affects the switching loss of the FET.

[0045] Next, the temperature change of the FET due to one-cycle control and two-cycle control of the current cycle passing through the stepping motor 2 will be described. FIG. 8 is a diagram showing the temperature change time characteristics of the FET due to one-cycle control and two-cycle control in a stepping motor control device. The horizontal axis in FIG. 8 represents time in seconds (s). The vertical axis in FIG. 8 represents thermistor temperature (°C). In FIG. 8, the curve drawn with a solid line represents the temperature change time characteristics of the FET due to one-cycle control, the curve drawn with a dashed line represents the temperature change time characteristics of the FET due to two-cycle control, and the straight line drawn with a dashed dotted line represents the upper temperature limit value of the FET.

[0046] As shown in Figure 8, at time tp, the temperature of the FET under single-cycle control is the same as the temperature of the FET under double-cycle control. After time 100 s, the temperature of the FET under single-cycle control and the temperature of the FET under double-cycle control become almost constant. At this time, the temperature of the FET under single-cycle control (about 85°C) is about 42% higher (worsened) than the temperature of the FET under double-cycle control (about 60°C).

[0047] Next, the two-cycle control in the stepping motor control device 200 will be described. In the following description, an example of a current cycle control process will be described in which the cycle of the current supplied to the stepping motor 2 is controlled to be two cycles of the constant current control cycle, but the present invention is not limited to this. The excitation control unit 112 (current cycle control unit) may control the cycle of the current supplied to the stepping motor 2 to be any cycle equal to or greater than two cycles of the constant current control cycle.

[0048] Fig. 9 is a diagram for explaining Example 1 of two-cycle control in the stepping motor control device 200 according to this embodiment. In Example 1 of two-cycle control shown in Fig. 9, the excitation control unit 112 (current cycle control unit) performs a current cycle control process in which, when the period during which current is supplied to the stepping motor 2 reaches or exceeds a predetermined time, the excitation control unit 112 turns off the power supply to the stepping motor 2, thereby controlling the cycle of the current supplied to the stepping motor 2 to be two cycles of the constant current control cycle.

[0049] As a result of the above-described current period control process, as shown in Fig. 9, after the first chopping (time T1), the FET connected to the drive phase is turned ON at the start of the next current control period (time T2), so the current value of the drive phase current increases. When a predetermined time Ts has elapsed since time T2, the FET connected to the drive phase is turned OFF, so that at time T3, an inverted phase current of the same magnitude as the drive phase current is generated. Then, the chopping period of the drive phase current after time T3, i.e., the current period (Tc) for supplying current to the stepping motor 2, becomes two constant current control periods (2Tb), as shown in Fig. 9.

[0050] The above-mentioned predetermined time Ts is registered in advance in the stepping motor control device 200 and is a time shorter than the ON period of the constant current control cycle. The predetermined time Ts may be set to, for example, 1 / n of the ON period of the constant current control cycle, or may be set to any time interval shorter than the ON period of the constant current control cycle. Here, n is any positive number.

[0051] Fig. 10 is a diagram for explaining Example 2 of the two-cycle control in the stepping motor control device 200 according to this embodiment. In Example 2 of the two-cycle control shown in Fig. 10, the excitation control unit 112 (current cycle control unit) performs a current cycle control process in which, when the current value of the current supplied to the stepping motor 2 becomes equal to or greater than a predetermined judgment value, the excitation control unit 112 turns off the current supply to the stepping motor 2, thereby controlling the current cycle of the current supplied to the stepping motor 2 to be two cycles of the constant current control cycle.

[0052] As a result of the above-described current period control process, as shown in Fig. 10, after the first chopping (time T1), the FET connected to the drive phase is turned ON at the start of the next current control period (time T2), so that the current value of the current flow increases. When the current value of the drive phase current reaches or exceeds a predetermined determination value (for example, time T3), the FET connected to the drive phase is turned OFF, so that at time T3, an inverted phase current of the same magnitude as the drive phase current is generated. Then, the chopping period of the drive phase current after time T3, i.e., the current period (Tc) flowing through the stepping motor 2, becomes two constant current control periods (2Tb) as shown in Fig. 10.

[0053] The above-mentioned specified judgment value is registered in advance in the stepping motor control device 200 and is a current value smaller than the constant current control threshold determined by the current setting reference voltage of the comparator, i.e., the constant current control threshold at which power supply to the stepping motor 2 is turned off.

[0054] Fig. 11 is a diagram for explaining Example 3 of two-cycle control in the stepping motor control device 200 according to this embodiment. In Example 3 of two-cycle control shown in Fig. 11, the excitation control unit 112 (current cycle control unit) lowers the constant current control threshold for turning off the power supply to the stepping motor 2, and after turning off the power supply to the stepping motor 2 when the current value of the power supply to the stepping motor 2 exceeds the lowered constant current control threshold, returns the lowered constant current control threshold to its original state. The excitation control unit 112 (current cycle control unit) performs a current cycle control process for controlling the current cycle for powering the stepping motor 2 to be two cycles of the constant current control cycle by the above-mentioned process.

[0055] As a result of the above control, as shown in FIG. 11, after the first chopping (time T1), the FET connected to the drive phase is turned ON at the start of the next constant current control period (time T2), so the current value of the drive phase current increases. At time T3, the constant current control threshold is lowered, so the current value of the drive phase current exceeds the lowered constant current control threshold, the FET connected to the drive phase is turned OFF, and an inverted phase current of the same magnitude as the drive phase current is generated. Thereafter, the lowered constant current control threshold is returned to its original state. Then, the chopping period of the drive phase current after time T3, i.e., the current period (Tc) for supplying current to the stepping motor 2, becomes two periods (2Tb) of the current control period, as shown in FIG. 11.

[0056] The timing (time T3) for temporarily lowering the constant current control threshold may be set to any time within the next constant current control period after the initial chopping of the drive phase current, and the timing (time T4) for returning the temporarily lowered constant current control threshold to its original state may be set to any time after time T3 within the next current control period after the initial chopping of the drive phase current.

[0057] Fig. 12 is a diagram for explaining Example 4 of two-cycle control in the stepping motor control device 200 according to this embodiment. In Example 4 of two-cycle control shown in Fig. 12, the excitation control unit 112 (current cycle control unit) increases the constant current control threshold for turning off the power supply to the stepping motor 2, turns off the power supply to the stepping motor 2 when the current value of the power supply to the stepping motor 2 exceeds the increased constant current control threshold, and then returns the increased constant current control threshold to its original state. The excitation control unit 112 (current cycle control unit) performs a current cycle control process for controlling the current cycle for powering the stepping motor 2 to be two cycles of the constant current control cycle by the above-mentioned process.

[0058] As a result of the above control, as shown in FIG. 12, after the first chopping (time T1), the FET connected to the driving phase is turned ON at the start of the next constant current control period (time T2), so the current value of the driving phase current increases. At time T3, the current value of the driving phase current exceeds the increased constant current control threshold, the FET connected to the driving phase is turned OFF, and an inverted phase current of the same magnitude as the driving phase current is generated. Thereafter, the increased constant current control threshold is restored. Then, at the start of the next current control period (time T4), the FET connected to the driving phase is turned ON, so the current value increases. At time T5, the current value of the driving phase current exceeds the restored constant current control threshold, the FET connected to the driving phase is turned OFF, and an inverted phase current of the same magnitude as the driving phase current is generated. Then, the chopping period of the driving phase current after time T5, i.e., the current period (Tc) for energizing the stepping motor 2, is two periods (2Tb) of the current control period, as shown in FIG. 12.

[0059] The timing for temporarily increasing the constant current control threshold may be set to any time within the next constant current control period after the first chopping of the drive phase current, and the timing for returning the temporarily increased constant current control threshold to its original state may be set to any time within the current control period in which the first chopping of the drive phase current occurs, after the constant current control threshold was increased.

[0060] Next, the start timing of the current cycle control process after switching of the external clock (CLOCK signal) will be described. Fig. 13 is a diagram for explaining the start timing of the current cycle control process after switching of the external clock in the stepping motor control device 200 according to this embodiment.

[0061] Time T1 shown in Fig. 13 is the timing for switching the external clock from outside. The excitation control section 112 (current cycle control section) of the stepping motor control device 200 performs a current cycle control process after switching the external clock from outside (after time T1) and turning off the power supply to the stepping motor 2 for the first time, i.e., after the first chopping. Here, the current cycle control process may be any of Examples 1 to 4 of the two-cycle control described with reference to Figs. 9 to 12.

[0062] Also, the excitation pattern of the stepping motor 2 may be switched at the timing of switching the external clock. Also, for example, as shown in FIG. 13, the driving phase and the inverted phase may be switched at the timing of switching the external clock.

[0063] [effect] As described above, the excitation control unit 112 (current cycle control unit) of the stepping motor control device 200 according to this embodiment performs a current cycle control process that controls the current cycle passed through the stepping motor 2 to be two or more constant current control cycles after the initial chopping of the drive phase current. Control of two or more constant current control cycles reduces the number of chopping times of the FET by half or more compared to one cycle control, so the stepping motor control device 200 according to this embodiment can suppress temperature rise without degrading the driving performance of the stepping motor.

[0064] The present invention is not limited to the above-described embodiment, and it goes without saying that various other applications and modifications are possible without departing from the gist of the present invention as set forth in the claims. For example, the above-described embodiment describes the configuration of a stepping motor control device in detail and specifically in order to easily explain the present invention, and is not necessarily limited to having all of the configurations described. In addition, it is possible to replace part of the configuration of the embodiment described here with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is also possible to add, delete, or replace part of the configuration of an embodiment with another configuration. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0065] 1...control device, 2...stepping motor, 3...fuse, 10...control unit, 11...pre-driver, 13,14...AMP, 15,16...shunt resistor, 17...ground unit, 21,22,23,24...coil, 100,200...stepping motor control device, 101...excitation mode setting unit, 102...edge detection unit, 103...phase advance counter, 104...current table, 105...current value calculation unit, 106,107...D / A converter, 108,109...comparator, 110...oscillator, 111...clock generation unit, 112...excitation control unit, 121,122,123,124...FET

Claims

1. A stepping motor, a current cycle control unit that performs a current cycle control process to control the current cycle applied to the stepping motor in accordance with a constant current control cycle so that the current cycle is equal to or greater than two of the constant current control cycles. Stepper motor control device.

2. The current cycle control unit performs the current cycle control process by turning off the power supply to the stepping motor when the current value of the power supply to the stepping motor becomes equal to or greater than a predetermined judgment value.

2. The stepping motor control device according to claim 1.

3. The predetermined judgment value is a current value smaller than a constant current control threshold value at which power supply to the stepping motor is turned off. The stepping motor control device according to claim 2 .

4. The current cycle control unit performs the current cycle control process by turning off the power supply to the stepping motor when the power supply period to the stepping motor reaches or exceeds a predetermined time.

2. The stepping motor control device according to claim 1.

5. The predetermined time is shorter than the ON period of the constant current control cycle. The stepping motor control device according to claim 4.

6. The current cycle control unit performs the current cycle control process by lowering a constant current control threshold for turning off current supply to the stepping motor, turning off current supply to the stepping motor when a current value of current supply to the stepping motor exceeds the lowered constant current control threshold, and then returning the lowered constant current control threshold to an original value.

2. The stepping motor control device according to claim 1.

7. The current cycle control unit performs the current cycle control process by increasing a constant current control threshold for turning off power supply to the stepping motor, turning off power supply to the stepping motor when a current value of power supply to the stepping motor exceeds the increased constant current control threshold, and then returning the increased constant current control threshold to an original value.

2. The stepping motor control device according to claim 1.

8. The current cycle control unit performs the current cycle control process after switching an external clock from the outside and turning off the power supply to the stepping motor for the first time. The stepping motor control device according to any one of claims 1 to 7.

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