JPH0837799A - Method and circuit for driving stepping motor - Google Patents

Abstract

PURPOSE:To suppress phase jump or the like by continuing the drive in a first phase excitation mode without switching the phase excitation mode until the next step even when the instruction to switch the phase excitation mode is given while being transferred to the next step. CONSTITUTION:When 2W1-2 phase is switched to W1-2 phase, this signal switching is judged to be invalid at this point inside a driver 12, and the driving with 2W1-2 phase before switching is continued without switching the excitation mode inside. Then, the rise of the number of revolutions designating clock CLK is inputted from the time point when the excitation mode signals M1, M2 are switched. The noise is removed from this clock CLK by a rise detecting circuit 14, and then, this clock is received by an up-sown counter 15. The driver 12 judges the switching of the excitation mode signals M1, M2 to be effective at the time point when this internal clock rises, the internally set clock of the up-down counter 12 is switched, and then, the phase switch instructing clock is outputted to a phase signal generating part 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method and a driving circuit for a stepping motor, more specifically, a stepping motor used for driving a carriage section, an image reading section, a rotating drum section of a printer or a copying machine. The objective is to improve the circuit that performs the micro-step driving.

[0002]

2. Description of the Related Art Before describing a conventional stepping motor drive circuit, microstep driving of a stepping motor will be described with reference to the drawings. FIG. 4 is a phase transition state diagram for explaining each excitation mode of micro-step driving when driving a two-phase stepping motor.

In the two-phase excitation mode, which is the mode shown on the innermost side of the concentric circles in FIG. 4, the motor operates in three steps in four steps.
In the 1-2 phase excitation mode, which is a mode in which the motor rotates by 60 °, the motor rotates by 360 ° in eight steps, which is twice that. Further, the W1-2 phase excitation mode on the outer side is a mode in which the motor rotates 360 ° in 16 steps that is double that. In the 2W1-2 phase excitation mode, the motor rotates 360 ° in 32 steps that is double that. Mode.

That is, as described above, the number of steps in rotation increases as the outer excitation mode in the concentric circles in FIG. 4 increases, and it is possible to drive at a low speed but with smooth and small vibration. As it goes to the inner excitation mode, the number of steps during rotation decreases, and although there is some vibration, high-speed drive can be performed, so the excitation mode is switched as necessary and the excitation mode suitable for the purpose is selected. Was.

Particularly, the operation of the carriage portion of the printer, the image reading portion of the copying machine, the rotating drum portion, etc., which requires high resolution by using the stepping motor, uses the microstep drive, and the vibration from the motor is small. It was driven by the method. For example, in the operation of the carriage unit, the image reading unit, the rotating drum unit, etc., microstep drive such as 2W1-2 phase excitation is used during acceleration,
Full-step driving such as two-phase excitation was used during constant speed driving, and micro-step driving was used during deceleration.

A stepping motor drive circuit for performing microstep driving of a stepping motor according to a conventional example will be described below with reference to FIG. The drive circuit of the stepping motor according to the conventional example is a CPU
It is a circuit that includes (1) and a driver circuit (2) and drives a stepping motor (3). According to the circuit, the driver (2) drives the stepping motor (3) in microsteps on the basis of the control pulse (SS) from the CPU (1) and the excitation mode signals (M1, M2). CPU when switching modes
When the switching instruction of the excitation mode signals (M1, M2) was issued from (1), the driver (2) immediately changed the driving state of the stepping motor (3) internally in response to the switching of the excitation mode. .

[0007]

However, the conventional circuit described above has the following problems. That is, the excitation mode signal is switched to the W1-2 phase while the motor that is performing the micro-step drive as shown in FIG. 6 is transitioning from step A3 to A4 in the 2W1-2 phase of FIG. In that case, originally, the process should proceed to step B2 of the W1-2 phase in FIG. 6 and proceed to the next B3, but in reality the position of the motor in the middle of going from A3 to A4 cannot be determined. , It is not possible to determine where the motor will go afterwards, and when it is terrible, there is a phenomenon in which the phase shifts to a completely different phase (hereinafter this phenomenon is referred to as "phase jump"). In such a case, there has been a problem that characters are distorted or omitted.

[0008]

The present invention has been made in view of the above-mentioned drawbacks of the prior art. The stepping motor driven in the first phase excitation mode is switched to the drive in the second phase excitation mode. At this time, in the first phase excitation mode, even if an instruction to switch the phase excitation mode is issued during the transition from the first step to the second step, the phase excitation mode is switched until the second step. Without continuing the driving in the first phase excitation mode, and switching the excitation mode at the time when the second step is reached and switching to the drive in the second phase excitation mode, "phase jump" It is intended to provide a drive circuit for a stepping motor that can drive a highly accurate and highly reliable stepping motor by suppressing such problems as much as possible.

[0009]

[Operation] According to the stepping motor driving method of the present invention, the first phase excitation is performed when the stepping motor driven in the first phase excitation mode is switched to the second phase excitation mode. In the mode, even if an instruction to switch the phase excitation mode is issued during the transition from the first step to the second step, the phase excitation mode is not switched until the second step and the phase excitation mode is not changed in the first phase excitation mode. The drive is continued, and when the second step is reached, the excitation mode is switched to drive in the second phase excitation mode.

Therefore, during microstep driving,
Even if the phase excitation mode signal is switched during the transition from one step to the next step, the phase excitation mode does not switch from the moving position to the next step, and the motor position is changed in the next step. Since the phase excitation mode is switched after it is confirmed, it is possible to suppress the occurrence of "phase jump" which has conventionally been caused by the indefinite position of the stepping motor before switching the mode.

As a result, the reliability of the operation of the stepping motor is improved. Further, according to the drive circuit of the stepping motor of the present invention, it is provided with the central processing unit and the drive control unit. That is, a state designating clock for instructing the drive state of the stepping motor and an excitation mode signal for setting the phase excitation mode are output from the central processing unit, and the drive control unit outputs the stepping motor based on the state designating clock and the excitation mode signal. When the excitation mode is switched and the excitation mode signal is input, the internal excitation mode is switched in synchronization with rising / falling of the state designation clock.

Therefore, during microstep driving,
Even if the excitation mode signal is switched during the transition from one step to the next step, the drive control unit keeps the motor in the excitation mode before switching until the rising / falling of the state designation clock that regulates the rotation state of the motor. Since the phase excitation mode is switched and driven at the time of driving and rising / falling of the state designation clock, that is, when the motor position is determined in the next step, the position of the stepping motor has conventionally been changed before switching the phase excitation mode. It is possible to suppress as much as possible the occurrence of "phase jump" or the like, which has been caused by the uncertainties.

As a result, the reliability of driving the stepping motor is improved, and when the stepping motor is used in the carriage portion of a printer,
It is possible to suppress as much as possible the disturbance of characters and omissions of characters that have been caused by "phase jump".

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of driving a stepping motor and a driving circuit according to embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a stepping motor drive circuit according to an exemplary embodiment of the present invention includes a CPU (1
1) and a driver (12), which is a circuit that includes coils (L1 to L4) and performs micro-step driving of a two-phase stepping motor (SM) used in a carriage section of a printer, a copier, or the like. Is.

The CPU (11) is an example of a central processing unit, and is an excitation mode signal (M1, M) which is an example of a control command signal (SS) of the stepping motor (SM).
2), a rotation number designating clock (CLK), a rotation direction setting signal (CWB), an IC internal reset signal (RESET), and an origin restart signal (RETURN) are generated and output to the driver (12).

The driver (12) is an example of a drive control section, and is a first part of a stepping motor (SM).
Is a circuit for supplying / non-supplying current to the fourth coil (L1 to L4) to drive the stepping motor (SM). As shown in FIG. 2, the configuration is such that the start-up detection circuit (14), the signal generation section (12B) and the drive section (12C).
Consists of

The start-up detection circuit (14) is an example of the noise removal section (12A), and is composed of four-stage flip-flop circuits, and has a start point restart signal (RETURN) and a motor rotation number designation (CLK) rising edge. It is a circuit that cancels the noise of the original signal by delaying and outputting the signal up to "0011" at the time of raising. Signal generator (12
B) is composed of an up / down counter (15) and a phase signal generator (17), and has a rotation speed designation clock (CLK).
The drive control signals (A, B, AB, BB) are generated based on

The up / down counter (15) is a circuit for outputting a count signal (KS) obtained by counting the number of pulses of a rotation speed designation clock (CLK) to a reference signal generation circuit (18) and a phase signal generation unit (17). is there. The phase signal generator (17) is configured to divide the reference clock (CK), PWM
Based on the signal (PS) and the count signal (KS), the drive control signals (A,
B, AB, BB) is generated and output.

The drive section (12C) has a drive control signal (A,
B, AB, BB), the stepping motor (SM) is supplied or not supplied to the coils (L1 to L4) forming the stepping motor (SM).
Of the PWM circuit (16), the reference signal generation circuit (18), the D / A converters (19A, 19B), and the comparators (20A, 20).
B), power MOSFETs (F1 to F4), a clock generating circuit (21), a frequency dividing circuit (22), and a mode setting circuit (13).

The PWM circuit (16) includes a comparator (2
0A, 20B) PWM signal (P
S) is output to the phase signal generator (17). The reference signal generation circuit (18) is a circuit that outputs a 10-bit reference signal (ST) to each of the D / A converters (19A, 19B) based on the count signal (KS).

The D / A converter (19A, 19B) is
Digital / analog conversion of reference signal (ST) (hereinafter D
/ A conversion) to generate stepwise pseudo sine waves (DAOUT, DBOUT) corresponding to the A phase and the B phase, respectively, and generate the comparator (20) via the operational amplifiers (OP1, OP2).
A, 20B). Comparator (2
0A, 20B) is a step-like pseudo sine wave (DAOUT, DBOUT) input through the operational amplifier (OP1, OP2).
And a voltage obtained by converting the drain current of the driving power MOSFETs (F3, F4) into a voltage, and outputting the comparison result to the PWM circuit (16).

The power MOSFETs (F1 to F4) are coils (L1 to L1) which form a stepping motor (SM).
L4) is a switching element for driving which supplies / non-supplies current to each. The clock generation circuit (21) generates a reference clock (CK) for the entire driver (12),
This is a circuit for outputting to the frequency dividing circuit (22).

The frequency dividing circuit (22) is a reference clock (CK).
Is a circuit that divides the frequency and outputs it to the D / A converters (19A, 19B) and the phase signal generation unit (17). The mode setting circuit (13) is a circuit that selects the excitation mode of the stepping motor (SM) based on the excitation mode signals (M1, M2) and outputs it to the up / down counter (15).

The operation of the drive circuit for the stepping motor according to this embodiment will be described below. First,
Initial settings for the entire system are made. At this time, a reset signal (RESET) inside the IC resets all the circuits in the circuit to the initial state. Next, the excitation mode is set to 2 by the 2-bit excitation mode signal (M1, M2).
Phase, 1-2 phase, W1-2 phase, or 2W1-2 phase is set, and the rotation direction setting input (CW
B) is input from the CPU (11) to the driver (12) to determine the rotation direction.

Next, the rotation speed designation clock (CLK) is input and input to the start-up detection circuit (14), where the noise on the rotation speed designation clock (CLK) is removed and the up / down counter (15). ) Is entered. At the same time, the rotation direction setting signal (CWB) and the excitation mode signal (M1,
And M2) are input to the up / down counter (15).

Next, the rise detection circuit (14) removes noise when the rotation number designation clock (CLK) rises. That is, the rotation speed designation clock (CLK)
Is delayed by the four-stage flip-flops forming the rise detection circuit (14) and is not output from the rise detection circuit (14) until the number of clocks exceeds "0011" from the beginning.

Actually, the noise generated at the time of startup is generated in the range where the clock number is less than "0011" from the beginning,
Since it is unlikely that noise will be generated over a larger time zone than this, this delay removes noise of the rotation speed designation clock (CLK). Next, the rotation speed designation clock (CL) from which noise has been removed by the start-up detection circuit (14) as described above.
K) is counted by the up / down counter (15) in synchronization with the reference clock (CK) from the clock generation circuit (21), and the count result is stored in the reference signal generation circuit (18) and the phase signal generation unit (17). Is output.

Next, the output signal of the up / down counter (15) is counted by the reference signal generation circuit (18) composed of a counter, and the 10-bit reference signal from which the stepwise pseudo sine wave is generated later is generated. (ST) is D /
It is input to the A converter (19A, 19B). Next, the reference signal (ST) of the reference signal generation circuit (18) is D / A.
D / A conversion is performed by the converters (19A, 19B), and a stepped pseudo sine wave (DAOUT, DBOUT) is generated.

This pseudo sine wave (DAOUT, DBOUT) is D / A
Impedance matching is performed by operational amplifiers (OP1, OP2) connected to the converters (19A, 19B),
It is output to the inverting input unit (-) of the comparator (20A, 20B). The non-inverting input section (+) of the comparators (20A, 20B) is connected to the drains of the power MOSFETs (F3, F4) that drive the stepping motor (SM), and these drain currents and the operational amplifier (O
The output signal from P1, OP2) is compared with the comparator (20
A, 20B) and the comparator (2
0A, 20B) output pulse rising edge is PW
It is input to the M circuit (16), and the PWM circuit (16) outputs P
The WM-modulated output signals of the comparators (20A, 20B) are output to the phase signal generator (17).

Then, based on the count signal (KS) output from the up / down counter (15) by the phase signal generator (17), in synchronization with the reference clock (CK) from the clock generator (21), Power MOSFET (F for driving stepping motor (SM)
The signals (A, B, AB, BB) for driving (1 to F4) are output to the power MOSFETs (F1 to F4), so that the motor starts driving in accordance with the instruction of the CPU (11).

The operation when the excitation mode is switched in the above circuit will be described below with reference to the timing chart of FIG. Here, as an example, 2W
A case where the 1-2 phase is switched to the W1-2 phase will be described. First, as shown in the timing chart of FIG. 2, the excitation mode signal (M
1, M2) is switched (initially "H",
"L" (M1, M2) is "L",
It has been switched to "H").

At this point in time, the signal switching is still judged to be invalid inside the driver (12), the excitation mode is not switched inside, and the 2W1-2 phase drive before switching is continued. After that, the first rising edge of the rotation speed designation clock (CLK) is input from the time when the excitation mode signals (M1, M2) are switched.

The rotation speed designation clock (CLK) is noise-removed by the rise detection circuit (14) as described above, and then input to the up / down counter (15) as an internal clock (IK). This internal clock (IK)
The driver (12) determines that the switching of the excitation mode signals (M1, M2) is valid at the time of rising, and the internal setting clock (UK) of the up / down counter (12) is switched, and then the phase signal generation unit (17). The phase switching instruction clock (KK) is output to.

Based on the phase switching instruction clock (KK) generated in this way, the phase signal generator (17) causes the phase signals (A, B, AB,
BB) is output and the stepping motor (SM) is driven accordingly. At this time, the actual driving state of the motor will be described with reference to FIG. FIG. 3 is a phase state transition diagram when transitioning from the 2W1-2 phase to the W1-2 phase.

In FIG. 3, step A of 2W1-2 phase
During the transition from 3 to A4, the excitation mode signal (M
Consider the case where (1, M2) is switched. In this case, even if the excitation mode signals (M1, M2) are switched, the 2W1-2 phase driving is continued until the rising of the rotation speed designation clock (CLK) is detected as described above, and the rotation speed designation clock When the rising edge of (CLK) is detected, it is switched to the W1-2 phase.

Since the time point at which the rising of the rotation speed designation clock (CLK) is detected corresponds to each step of the 2W1-2 phase before the switching, it seems that the process shifts from step A3 to A4. In this case, the rising of the rotation speed designation clock (CLK) is detected when the next step A4 is reached. Therefore, the phase excitation mode becomes 2W1 when the motor reaches A4.
-2 phase is switched to W1-2 phase. Thus, as shown in FIG. 3, the motor reaches 2W1 after reaching A3 to A4.
The process shifts to step B2 of the W1-2 phase corresponding to the A4 of the −2 phase, the restart is started, and thereafter, the driving by the W1-2 phase is performed.

As described above, according to the method of driving the stepping motor according to the present embodiment, the phase excitation mode is switched to the W1-2 phase after the position of the motor is determined in step A4 of the 2W1-2 phase. Therefore, it is possible to suppress as much as possible the occurrence of “phase jump” or the like, which has conventionally been caused by the indeterminate position of the stepping motor before switching the phase excitation mode. This improves the reliability of operation of the stepping motor.

Further, according to the drive circuit of the stepping motor according to the embodiment of the present invention, as shown in FIG.
(11) and a driver (12) are provided. Therefore, in the micro step drive, even if the excitation mode signal is switched during the transition from one step to the next step, the driver is not operated until the rise of the rotation number designation clock (CLK) that defines the rotation state of the motor. (1
In 2), the motor is driven in the excitation mode before switching, and the phase excitation mode is set at the time of rising of the rotation speed designation clock (CLK), that is, when the position of the stepping motor (15) is determined in step A4 following A3. Since it is driven by switching to the W1-2 phase, it is possible to suppress as much as possible the "phase jump" that has conventionally occurred due to the indefinite position of the stepping motor before switching the phase excitation mode. Become.

As a result, the reliability of the driving of the stepping motor is improved, and especially when the stepping motor is used for the carriage portion of a printer or the like, the characters are distorted or missing due to "phase jump". Can be suppressed as much as possible. It should be noted that although the present embodiment describes the switching of the phase excitation mode from the 2W1-2 phase to the W1-2 phase, the present invention is not limited to this, and for example, from 2W1-2 phase to 1-2 phase, or Similar effects can be obtained for switching of almost any phase such as 1-2 phase to W1-2 phase.

[0040]

As described above, according to the driving method of the stepping motor according to the present invention, when the stepping motor driven in the first phase excitation mode is switched to the drive in the second phase excitation mode. In the first phase excitation mode, even if the phase excitation mode switching instruction is issued during the transition from the first step to the second step, the second phase
The driving in the first phase excitation mode is continued without switching the phase excitation mode until the step, and the excitation mode is switched and switched to the drive in the second phase excitation mode when the second step is reached. Therefore, it is possible to suppress the occurrence of “phase jump” or the like, which has occurred due to the indefinite position of the stepping motor before switching the conventional mode, and improve the reliability of the operation of the stepping motor.

Further, the stepping motor drive circuit according to the present invention includes the central processing unit and the drive control unit. Therefore, the excitation mode signal of the excitation mode signal is changed during the transition from one step to the next step. Even if it is switched
The drive control unit drives the motor in the excitation mode before switching until the rising / falling of the state designation clock that defines the rotation state of the motor, and at the time of rising / falling of the state designation clock, that is, the motor position is Since the phase excitation mode is switched and driven when the step is confirmed, it is necessary to suppress the occurrence of "phase jump" that has been caused by the indefinite position of the stepping motor before switching the phase excitation mode. Will be possible.

As a result, the reliability of driving the stepping motor is improved, and when the stepping motor is used in the carriage portion of a printer,
It is possible to suppress as much as possible the disturbance of characters and omissions of characters that have been caused by "phase jump".

[Brief description of drawings]

FIG. 1 is a circuit diagram of a drive circuit for a stepping motor according to an embodiment of the present invention.

FIG. 2 is a timing chart illustrating a phase excitation switching state of a stepping motor drive circuit according to an embodiment of the present invention.

FIG. 3 is a phase state transition diagram illustrating an operation of a drive circuit of a stepping motor according to an exemplary embodiment of the present invention.

FIG. 4 is a phase state transition diagram illustrating microstep driving of a stepping motor.

FIG. 5 is a configuration diagram of a drive circuit of a stepping motor according to a conventional example.

FIG. 6 is a phase state transition diagram for explaining the problems of the conventional example.

[Description of Reference Signs] (11) CPU (Central Processing Unit) (12) Driver (Drive Control Unit) (12A) Noise Removal Unit (12B) Signal Generation Unit (12C) Drive Unit (13) Mode Setting Unit (14) Start-up detection circuit (15) Up-down counter (16) PWM circuit (17) Phase signal generation section (18) Reference signal generation circuit (19A) D / A converter (19B) D / A converter (20A) Comparator (20B) Comparator (21) Clock generation circuit (22) Frequency divider circuit (SM) Stepping motor (F1 to F4) Power MOSFET (L1 to L4) Coil (A, B, AB, BB) Drive control signal (DS) Drive signal (CK ) Reference clock (KS) Count signal (PS) PWM signal (ST) Reference signal (DAOUT, DBOUT) Pseudo sine wave (M 1, M2) Excitation mode signal (CLK) Rotation speed designation clock (CWB) Rotation direction setting signal (RESET) Reset signal (RETURN) Origin restart signal

Claims (2)

[Claims] 1. When switching a stepping motor, which is driven in a first phase excitation mode, to a drive in a second phase excitation mode, in the first phase excitation mode, a first step to a second step is performed. Even if an instruction to switch the phase excitation mode is issued during the transition to the step, the drive in the first phase excitation mode is continued without switching the phase excitation mode until the second step, and the second A method of driving a stepping motor, characterized in that when the step is reached, the excitation mode is switched to switch to driving in the second phase excitation mode. 2. A central processing unit for outputting a state designation clock for instructing a driving state of a stepping motor and an excitation mode signal for setting a phase excitation mode, and stepping based on the state designation clock and the excitation mode signal. A drive control unit for driving a motor, wherein the drive control unit switches the internal excitation mode in synchronization with a state designation clock after the excitation mode signal is input, when switching the excitation mode. A stepping motor drive circuit characterized by driving a stepping motor.