JP3219601B2 - Driving method and driving circuit for stepping motor - Google Patents

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, and more particularly, to a stepping motor used for driving a carriage section, an image reading section, a rotary drum section, etc. of a printer or a copying machine. The purpose of the present invention is to improve a circuit for microstep driving.

[0002]

2. Description of the Related Art Before describing a conventional driving circuit for a stepping motor, a micro-step driving of the 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.

The two-phase excitation mode, which is the mode shown on the innermost side of the concentric circle in FIG.
The 1-2-phase excitation mode is a mode in which the motor rotates 360 ° in eight steps, which is twice the mode. In addition, the W1-2 phase excitation mode on the outer side is a mode in which the motor rotates 360 ° in 16 steps of the double, and the 2W1-2 phase excitation mode rotates the motor 360 ° in 32 steps of the double. Mode.

That is, as described above, the number of steps during rotation increases as the outer excitation mode of the concentric circle in FIG. 4 is set, and the drive can be performed at low speed but with smooth vibration with little vibration. As the inner excitation mode is set, the number of steps during rotation is reduced, and high-speed driving can be performed with some vibration, so switch the excitation mode as necessary and select the excitation mode suitable for the purpose Was.

[0005] In particular, the operation of a carriage unit of a printer, an image reading unit of a copying machine, a rotating drum unit, etc., which requires a high resolution using a stepping motor, uses a micro-step drive and generates little vibration from the motor. Driving was done in a way. For example, in operations of a carriage unit, an image reading unit, a rotating drum unit, and the like, micro-step driving such as 2W1-2-phase excitation is used during acceleration,
At the time of traveling at a constant speed, full step drive such as two-phase excitation is used, and at the time of deceleration, micro step drive is used.

Hereinafter, a conventional stepping motor driving circuit for performing microstep driving of a stepping motor will be described with reference to FIG. The driving circuit of the stepping motor according to the conventional example is a CPU
This circuit is composed of (1) and a driver circuit (2) and drives a stepping motor (3). According to the circuit, the driver (2) drives the stepping motor (3) based on the control pulse (SS) from the CPU (1) and the excitation mode signals (M1 and M2) to perform microstep driving. When switching modes, the CPU
When the switching instruction of the excitation mode signals (M1, M2) is issued from (1), the driver (2) immediately changes the drive state of the stepping motor (3) in response to the switching of the excitation mode internally. .

[0007]

However, according to the above-mentioned conventional circuit, the following problems occur. In other words, it is assumed that the motor performing the micro-step drive as shown in FIG. 6 switches the excitation mode signal to the W1-2 phase during the transition from step A3 to A4 in the 2W1-2 phase in FIG. In this case, the process should originally proceed to step B2 of the W1-2 phase in FIG. 6 and proceed to the next B3. However, since the position of the motor in the course of A3 to A4 cannot be determined in practice, However, it is not possible to determine where the motor will go afterwards, and in severe cases, a phase shifts to a completely different phase (hereinafter, this phenomenon is referred to as “phase skip”). This stepping motor is used in printers and the like. In such a case, there is a problem that characters are disturbed or spelled out.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and switches a stepping motor driven in a first phase excitation mode to a drive in a 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. By continuing the drive in the first phase excitation mode without changing the excitation mode and switching to the drive in the second phase excitation mode when the second step is reached, "phase jump" is achieved. It is an object of the present invention to provide a stepping motor drive circuit capable of driving a stepping motor with higher accuracy and higher reliability while minimizing such problems.

[0009]

According to the stepping motor driving method of the present invention, when the stepping motor being driven in the first phase excitation mode is switched to the driving in the second phase excitation mode, the first phase excitation is performed. 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 first phase excitation mode is not used. The driving is continued, and when the second step is reached, the excitation mode is switched to the driving in the second phase excitation mode.

For this reason, in the case of micro-step 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 until the transition 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 the determination is made, it is possible to suppress as much as possible the occurrence of “phase jump” or the like which has conventionally occurred due to the indeterminate position of the stepping motor before the mode switching.

Thus, the reliability of the operation of the stepping motor is improved. Further, according to the drive circuit for a stepping motor according to the present invention, the drive circuit includes a central processing unit and a drive control unit. That is, a state designation clock indicating 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 stepping motor is controlled by the drive control unit based on the state designation clock and the excitation mode signal. When the excitation mode is switched and the excitation mode is switched, the internal excitation mode is switched in synchronization with the rise / fall of the state designation clock after the excitation mode signal is input.

For this reason, at the time of micro-step driving,
Even if the excitation mode signal is switched during the transition from a certain step to the next step, the drive control unit operates in the excitation mode before switching the motor until the rise / fall of the state designation clock that defines the rotation state of the motor. When the motor is driven, the phase excitation mode is switched and driven at the time of rising / falling of the state designation clock, that is, at the time when the position of the motor is determined in the next step. Therefore, conventionally, the position of the stepping motor is switched before switching the phase excitation mode. It is possible to suppress as much as possible the occurrence of “out-of-phase” or the like, which has occurred due to the indeterminateness of.

As a result, the driving reliability of the stepping motor is improved, and when this stepping motor is used in a carriage section of a printer, etc.
It is possible to suppress as much as possible the disorder of characters and the omission of characters caused by the “skip”.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a driving method and a driving circuit of a stepping motor according to an embodiment of the present invention will be described with reference to the drawings. A driving circuit for a stepping motor according to an embodiment of the present invention includes a CPU (1) as shown in FIG.
A circuit comprising a coil (L1 to L4) and a micro-step drive of a two-phase stepping motor (SM) used for a carriage unit of a printer, a copying machine or the like. It is.

The CPU (11) is an example of a central processing unit and is an example of a control command signal (SS) for the stepping motor (SM).
2) A circuit for generating a rotation number designation clock (CLK), a rotation direction setting signal (CWB), a reset signal (RESET) inside the IC, and an origin restart signal (RETURN) and outputting them to the driver (12).

The driver (12) is an example of a drive control unit, and is a first controller constituting a stepping motor (SM).
To the fourth coil (L1 to L4) to supply / non-supply current to drive the stepping motor (SM). As shown in FIG. 2, the configuration includes a start-up detection circuit (14), a signal generation unit (12B), and a drive unit (12C).
Consists of

The start-up detection circuit (14) is an example of a noise elimination unit (12A), and is composed of a four-stage flip-flop circuit. The start-up restart signal (RETURN) and the motor rotation number designation (CLK) are specified. This circuit cancels the noise of the original signal by delaying the signal until "0011" and not outputting it. Signal generator (12
B) is composed of an up / down counter (15) and a phase signal generator (17).
, And generates drive control signals (A, B, AB, BB).

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

The drive section (12C) receives a drive control signal (A,
B, AB, BB) to supply / non-supply current to the coils (L1 to L4) constituting the stepping motor (SM), thereby providing the stepping motor (SM).
, A PWM circuit (16), a reference signal generating circuit (18), D / A converters (19A, 19B), and comparators (20A, 20A).
B), a power MOSFET (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), the PWM signal (P
S) is a circuit that outputs S) to the phase signal generation unit (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)
Digital / analog conversion of reference signal (ST) (hereinafter D
/ A conversion) to generate stair-like pseudo sine waves (DAOUT, DBOUT) corresponding to the A-phase and B-phase, respectively, and to output the comparator (20) via operational amplifiers (OP1, OP2).
A, 20B). Comparator (2
0A, 20B) are step-like pseudo sine waves (DAOUT, DBOUT) input via the operational amplifiers (OP1, OP2).
And a voltage obtained by voltage-converting the drain currents of the driving power MOSFETs (F3, F4) and outputting the comparison result to the PWM circuit (16).

The power MOSFETs (F1 to F4) include coils (L1 to L4) constituting a stepping motor (SM).
L4) are driving switching elements for supplying / non-supplying current to the respective elements. 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) has a reference clock (CK).
Is a circuit that divides the frequency and outputs it to the D / A converters (19A, 19B), the phase signal generator (17), and the like. 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 the selected mode to the up / down counter (15).

The operation of the driving 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, all the circuits in the above circuit are reset to the initial state by the reset signal (RESET) in the IC. 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 number designation clock (CLK) is input and input to the rise detection circuit (14), where noise on the rotation number designation clock (CLK) is removed, and the up / down counter (15) is removed. ). At the same time, the rotation direction setting signal (CWB) and the excitation mode signal (M1,
M2) is input to the up / down counter (15).

Next, the rise detection circuit (14) removes noise at the rise of the rotation number designation clock (CLK). That is, the rotation number designation clock (CLK)
Is delayed by the four-stage flip-flop constituting 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 from the beginning when the number of clocks is less than “0011”.
Since it is unlikely that noise over a longer time period will occur, this delay will remove the noise of the rotation number designation clock (CLK). Next, the rotation number designation clock (CL) from which noise has been removed by the rise 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 sent to 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 a reference signal generation circuit (18) composed of a counter, and a 10-bit reference signal from which a step-like pseudo sine wave is generated later. (ST) is D /
The signals are input to A converters (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 step-like pseudo sine wave (DAOUT, DBOUT) is generated.

This pseudo sine wave (DAOUT, DBOUT) is D / A
The impedance is matched by the operational amplifiers (OP1, OP2) connected to the converters (19A, 19B),
It is output to the inverting input section (-) of the comparator (20A, 20B). The non-inverting input portions (+) of the comparators (20A, 20B) are connected to the drains of power MOSFETs (F3, F4) for driving the stepping motor (SM).
P1, OP2) and the output signal from the comparator (20
A, 20B) and the comparator (2
0A, 20B), the rising edge of the output pulse is PW
The signal is input to the M circuit (16), and the P
The WM-modulated output signals of the comparators (20A, 20B) are output to the phase signal generator (17).

Thereafter, 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), A power MOSFET (F) for driving a stepping motor (SM)
When the signals (A, B, AB, BB) for driving the motors (1 to F4) are output to the power MOSFETs (F1 to F4), the motor starts driving according to 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
The case where the phase is switched from the 1-2 phase 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) (Initially “H”,
(M1, M2) which were “L” are “L”,
It has been switched to "H").

At this point, the driver (12) still determines that this signal switching is invalid inside the driver (12), does not switch the excitation mode internally, and continues driving in the 2W1-2 phase before switching. After that, the first rise of the rotation number designation clock (CLK) is input from the time when the excitation mode signals (M1, M2) are switched.

The rotation number designation clock (CLK) is input to the up / down counter (15) as an internal clock (IK) after the noise is removed by the rise detection circuit (14) as described above. This internal clock (IK)
The driver (12) determines that the switching of the excitation mode signals (M1 and M2) is valid at the time when the clock rises, and the internal setting clock (UK) of the up / down counter (12) is switched. Outputs a phase switching instruction clock (KK).

Based on the phase switching instruction clock (KK) generated in this way, the phase signal generation section (17) performs the phase signals (A, B, AB, and AB) corresponding to the driving in the W1-2 phase after the switching.
BB) 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 shifting from the 2W1-2 phase to the W1-2 phase.

In FIG. 3, step A of 2W1-2 phase
During the transition from A3 to A4, the excitation mode signal (M
(1, M2) is switched. In this case, even if the excitation mode signals (M1 and M2) are switched, the 2W1-2 phase driving is continued until the rising edge of the rotation speed designation clock (CLK) is detected as described above, and the rotation speed designation clock is output. When the rise of (CLK) is detected, the phase is switched to the W1-2 phase.

Since the time point at which the rise of the rotation number designation clock (CLK) is detected corresponds to each step of the 2W1-2 phase before the switching, it is apparent that the process has shifted from step A3 to A4. In such a case, the rise of the rotation number designation clock (CLK) is detected when the next step, A4, is reached. Therefore, when the motor reaches A4, the phase excitation mode becomes 2W1.
-2 phase is switched to W1-2 phase. Thus, as shown in FIG. 3, after the motor reaches A4 from A3, 2W1
The process proceeds to the step B2 of the W1-2 phase corresponding to the A4 of the -2 phase to start the restart, and thereafter, the drive by the W1-2 phase is performed.

As described above, according to the stepping motor driving method 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 occurred because the position of the stepping motor is uncertain before switching the phase excitation mode. Thereby, the reliability of the operation of the stepping motor is improved.

According to the stepping motor drive circuit according to the embodiment of the present invention, as shown in FIG.
(11) and a driver (12). For this reason, even if the excitation mode signal is switched during the transition from one step to the next step during micro-step driving, the driver is not driven until the rise of the rotation number designation clock (CLK) that defines the rotation state of the motor. (1
2) The motor is driven in the excitation mode before switching, and the phase excitation mode is set at the time of the rise of the rotation number designation clock (CLK), that is, at the time when the position of the stepping motor (15) is determined in step A4 following A3. Since the drive is performed by switching to the W1-2 phase, it is possible to minimize the occurrence of “phase jump” which has conventionally occurred due to the indeterminate 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. In particular, when this stepping motor is used in a carriage section of a printer, etc., character distortion or missing characters caused by "skip" may occur. Can be suppressed as much as possible. In this embodiment, the switching of the phase excitation mode from the 2W1-2 phase to the W1-2 phase is described. However, the present invention is not limited to this. For example, the 2W1-2 phase is switched to the 1-2 phase, or A similar effect can be obtained for almost any phase switching, such as from the 1-2 phase to the W1-2 phase.

[0040]

As described above, according to the method of driving a 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 an instruction to switch the phase excitation mode is issued during the transition from the first step to the second step, the second
Until the step, the drive in the first phase excitation mode is continued without switching the phase excitation mode, and when the second step is reached, the excitation mode is switched to the drive in the second phase excitation mode. Therefore, it is possible to minimize the occurrence of “phase jump” or the like, which has occurred because the position of the stepping motor is indeterminate before the switching of the conventional mode, and the reliability of the operation of the stepping motor is improved.

Further, according to the stepping motor drive circuit of the present invention, since the central processing unit and the drive control unit are provided, the excitation mode signal is generated during the transition from one step to the next step. Even if the switch is made,
The drive control unit drives the motor in the excitation mode before switching until the rising / falling of the state designating clock that defines the rotation state of the motor. Since the drive is performed by switching the phase excitation mode at the time determined in the step, it is necessary to minimize the occurrence of "phase jump" that occurred because the position of the stepping motor was indefinite before switching the phase excitation mode. Becomes possible.

Thus, the driving reliability of the stepping motor is improved, and when this stepping motor is used in a carriage section of a printer, etc.
It is possible to suppress as much as possible the disorder of characters and the omission of characters caused by the “skip”.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a driving circuit of 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 transition diagram for explaining the operation of the stepping motor driving circuit according to the embodiment of the present invention.

FIG. 4 is a phase state transition diagram illustrating a micro step drive of a stepping motor.

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

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

[Explanation of symbols]

 (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 generator (18) Reference signal generator (19A) D / A converter (19B) D / A converter (20A) Comparator (20B) Comparator (21) Clock Generation circuit (22) Divider circuit (SM) Stepping motor (F1-F4) Power MOSFET (L1-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 (M1, M2) Excitation Mode signal (CLK) Rotation speed designation clock (CWB) Rotation direction setting signal (RESET) Reset signal (RETURN) Origin restart signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-325898 (JP, A) JP-A-62-114497 (JP, A) JP-A-5-81763 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02P 8/00

Claims (2)

(57) [Claims] 1. When a stepping motor driven in a first phase excitation mode is switched to a drive in a second phase excitation mode, a transition is made from the first step to the second step of the first phase excitation mode. During the first excitation mode from the central processing unit.
The signal from the mode setting unit based on the mode signal is the second excitation
Switch to signal from mode setting unit based on mode signal
Even if the first excitation mode signal is detected, the rising or falling of the rotation number designation clock is detected.
The motor is driven in the original phase excitation mode by the signal from the mode setting section.
It is determined that the switching of the phase excitation mode signal is valid at the time when the rotation speed designation clock reaches the rising or falling second step, which is the time determined at the last step, and the internal setting clock of the up / down counter is determined. A stepping motor driving method, comprising outputting a phase switching instruction clock from a switching and up / down counter, and switching to driving in the second phase excitation mode. 2. A central processing unit for outputting a rotation number designation clock for defining a rotation state of a stepping motor, and first and second phase excitation mode signals for setting first and second phase excitation modes. Said rotation constituted by a flip-flop and inputted
A start-up detection circuit that delays and outputs a number-designated clock;
It is counted in synchronization with the clock and the first and
A drive control unit having an up / down counter to which a second phase excitation mode signal is added , wherein the drive control unit includes a motor added to a rise detection circuit.
It is determined that the switching of the phase excitation mode signal is valid at the time when the rotation position of the motor has reached the second step at which the rotation speed designation clock rises or falls at the time when it is determined in the next step. A stepping motor drive circuit, which outputs a phase switching instruction clock from an up / down counter and switches to driving in the second phase excitation mode to drive the stepping motor.