JPH0217895A - Driving of stepping motor - Google Patents

Abstract

PURPOSE:To make it a high speed to start a stepping motor for rotation and to minimize the damping in stopping the motor rotation by changing exciting current, exciting time, etc., corresponding to the rotating speed and exciting phase of the motor. CONSTITUTION:A control section 100 is equipped with a built-in CPU 103. It is also furnished with a ROM 104 loaded with control programmes and various kinds of data for CPU 103, a RAM 105 used as a work area for the CPU 103, etc. The outputs 110, 121 to 124 of the control section 100 are inputted into a D/A converter 107 and drivers A and B, with which a stepping motor 125 is driven. Here, in the control section 100 the present number of steps and the exciting phases of the stepping motor 125 are detected when the motor is driven for rotation, and then the phase-exciting current value or the exciting time is changed corresponding to each exciting phase and number of steps.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a stepping motor drive method, and in particular, the present invention relates to a stepping motor drive method, and in particular, a stepping motor with an irregular cycle, such as a motor used as a motor for conveying recording paper or original documents in a facsimile machine, etc. The present invention relates to a stepping motor driving method that is effective when rotationally driven by a predetermined amount.

[Prior Art] In general, a stepping motor is used in a facsimile machine or the like as a drive source for conveying recording paper, a document, or the like in a sub-scanning direction perpendicular to a main-scanning direction in which the document is read, recorded, etc. Excitation methods for this stepping motor include 1-phase excitation, 2-phase excitation, and 1-2 phase excitation. The l-2 excitation method is used for the stepping motor for feeding. When driving such a motor, the step drive rate and phase excitation energy are usually fixed to simplify control and hardware configuration.
When rotating the motor at 0 pps, each phase should be 2.5
The motor was driven by applying the same current every ms.

[Problems to be Solved by the Invention] During the operation of conveying recording paper, originals, etc. in such a facsimile machine, the time required for reading and recording in each main scanning direction is reduced due to the image pattern of the original image, encoding, decoding, etc. Since the distances are different, the feeding in the sub-scanning direction is intermittent and the intervals are not constant. - When driving a stepping motor intermittently for boat fishing, when the motor starts driving,
For example, to rotate at 800pps, 400pps-
There was acceleration/deceleration control that increased the pulse rate to 600pps-800pps to perform acceleration control, or conversely, performed deceleration control to stop the motor. However, while this kind of control is meaningful as a drive control for rotating a motor at a relatively long and high speed at fixed time intervals, such as when conveying recording paper or conveying a carriage in a normal printer, it is useful for facsimile machines. When a device is driven intermittently and at irregular intervals, such as when driving paper in a device, and when the drive is performed in small steps, such as 4 or 8 steps, sufficient acceleration and deceleration cannot be achieved. Moreover, there was no stalling effect because extra time was required for acceleration and deceleration.

In order to solve this problem, it is possible to use a somewhat larger motor that can obtain sufficient torque at high speeds, or to increase the excitation current of the motor.
When a large motor is used, there are problems such as high cost and slow start-up of rotation. Therefore, it is possible to drive the motor by applying a sufficient current when the motor starts up, but if the current is applied at the start up, the damping will increase when the motor stops and the motor will start rotating. After that, the current required during startup is no longer needed, so there is a problem that power is wasted.

The present invention has been made in view of the above-mentioned conventional example, and by changing the excitation current, excitation time, etc. of the stepping motor in accordance with the rotation speed and excitation phase, the motor starts rotating at high speed, and the motor rotates. An object of the present invention is to provide a stepping motor drive method that can minimize damping when stopped.

[Means for Solving the Problems] In order to achieve the above object, the stepping motor drive system of the present invention has the following configuration.

That is, the stepping motor drive method rotates the stepping motor by the number of steps specified by one drive start instruction, and includes a detection means that detects the current number of steps and the excitation phase of the stepping motor during rotational driving. and,
and excitation control means for changing the phase excitation current value or excitation time in accordance with each of the excitation phases and the number of steps.

According to another claim, the excitation control means lengthens the excitation time at the start of driving, or shortens the excitation time at the time of l-phase excitation than at the time of two-phase excitation, and at the time of final l-phase excitation, The excitation current is reduced.

[Function] In the above configuration, during rotational driving, the current number of steps and the excitation phase of the stepping motor are detected, and the phase excitation current value or excitation time is changed in accordance with each excitation phase and the number of steps. ing.

Further, according to the structure of another claim, the excitation time is made longer at the start of driving based on the current number of steps and the excitation phase of the stepping motor, or the excitation time is made longer during l-phase excitation than during two-phase excitation. It operates so that the excitation current per phase is made smaller during the final l-phase excitation.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Description of Motor Control Circuit (FIGS. 1 and 2)] FIG. 1 is a block diagram showing a schematic configuration of a paper feed motor control circuit employed in the recording section of the facsimile machine of the embodiment.

In the figure, reference numeral 100 denotes a control unit with a built-in CPU 103 such as a microprocessor. Interface unit 1 that returns information such as motor drive completion and error information to the control unit
01, CPU 10 shown in the flowchart of FIG.
RO stores the control programs and various data of 3.
It is equipped with a RAM, etc., which is used as a work area for the M104 and the CPU 103. This RAM 105 includes a CNT that stores the number of rotations (number of steps) of the motor 125 instructed by the main control section, a PH that stores the current excitation phase of the motor 125, and the like.

106 is a power source for driving the stepping motor 125, which outputs +24V DC. 107 is a D/A converter, which receives a multi-bit digital control signal 1 from the control unit 100;
10 is input, converted into an analog voltage signal, and outputted to the VR terminals of driver circuits 108 and 109. Both 108 and 109 are motor drive driver circuits whose details are shown in FIG.
) is used.

121 is a phase signal output from the control unit 100 to control the phase current direction of the A phase, and is used for excitation of the A phase or negative phase excitation of the A phase (
AX) is controlled. Reference numeral 122 is a 2-bit winding current control signal that changes the A-phase winding current to adjust the excitation energy. Similarly, 123 is a phase signal that controls the B-phase current direction to control B-phase excitation and its opposite phase excitation (BX), and 124 is a winding current control signal that adjusts the B-phase excitation energy. .

FIG. 2 is a block diagram showing the configuration of the driver circuit of the embodiment, and as mentioned above, this circuit consists of the Thomson 3718 (
S).

This circuit is a bipolar chopper driver circuit.
The reference voltage terminal vR is a reference voltage that determines the chopper current value, and the output voltage 127 of the D/A converter 107 is input thereto. Therefore, the control unit 100 controls the output voltage value of the D/A converter 107 using this control signal 110, and
The winding current (excitation energy) of the motor 125 can be changed. Further, this circuit is configured so that the excitation energy of the stepping motor 125 can be adjusted by adjusting the driving current of the motor 125 in four stages using each of the 2-bit winding current control signals 122 or 124. has been done.

Examples of current control using the winding current control signal 122 or signal 124 are shown in the table below.

In this way, the value of the winding current flowing through the stepping motor 125 can be controlled by the winding current control signals 122 and 124 input to the terminal IoIl, and furthermore, the reference voltage VR can be controlled by the control signal 110. Can be changed to adjust excitation energy.

The phase signals 121, 123 input to the terminal P are signals that determine the direction in which the phase current flows, as described above, and when this phase signal becomes high level, the current flows from MA to the Ma side through the winding of the motor 125. flows.

Conversely, when the phase signal 121 or 123 becomes low level, the current flows from M to MA through the winding of the motor 125.
flows to the side. In this way, the phase excitation direction of the motor 125 can be changed by the phase signals 121, 123. V am is a power input terminal that inputs +24V from the power supply 106 .

FIG. 3 is a diagram showing a torque model of 1-2 phase excitation of a two-pole stepping motor, and the A phase and B phase and their opposite phase excitation are indicated by AX and BX.

[Explanation of damping of a stepping motor (Figure 4)] Figure 4 shows the damping characteristics when a stepping motor that is stopped (held) with the A phase excited is driven in 4 steps with 1-2 phase excitation. It is a diagram. In the figure, a dotted line 45 indicates the ideal conveyance amount S of recording paper, original documents, etc. conveyed by phase excitation of the motor.

Reference numeral 41 shows a conventional case in which the excitation current and the like and the excitation time are not controlled, and in this case, the amount of movement of the recording paper etc. conveyed by the rotational drive of the motor is as shown by the solid line 43. .

The torque during two-phase excitation in 1-2 phase drive varies depending on the characteristics of the motor, but unless the excitation current is controlled, about twice as much torque as during one-phase excitation will be generated. Therefore,
When performing control as shown in 41, first, the motor held in the A phase is excited to the AB phase, which is the next excitation phase. Due to this excitation, the next l-phase excitation (B) occurs before the motor hardly rotates due to frictional load or the like.

For this reason, as shown in 43, the start-up of the motor's rotation becomes slow, and even if the AX phase of the final step is excited, the ability to follow the actual motor rotation is poor, so the motor's rotation speed becomes slower than the ideal rotation amount. Not only will the amount of rotation decrease, but the subsequent damping will also increase.

On the other hand, 42 shows an example of the control timing of excitation energy and phase excitation time when the stepping motor 125 is rotationally driven in four steps according to the method of this embodiment. 25 is stationary, or has not reached the predetermined position due to damping after the previous rotation, or a rotational force is generated in the opposite direction to the normal rotation direction, etc. The two phases (AB) with larger torque (or the powered-up phase) are excited by increasing the excitation time.

44 shows the conveyance amount based on the rotation amount of the motor at this time. In this way, the start-up of the motor 125 is faster than that of 43, and even if damping in the forward rotation direction occurs due to the previous motor rotation drive, it can be handled by controlling the phase excitation energy and phase excitation time of this first time. can. The second step, phase excitation 1ifl (B), is l-phase excitation with small torque, so the excitation time is shortened and the next BA
By lengthening the excitation time of the X phase, the movement distance (rotation amount) is gained as much as possible before the final phase is excited.

Note that although excitation is performed using 1-2 phase drive here, it is also possible to skip the B-phase excitation in the second step and use 2-phase excitation drive only here.Also, except for the final step, the load of the drive system is Appropriate excitation energy and excitation time may be selected depending on the drive speed and drive speed. However, it is necessary to ensure that the moving position at the time of phase excitation in the final step is as close to the final excitation phase as possible, and that the moving torque is small.

42, the damping of the motor is reduced by powering down the AX phase excitation, which is the final phase.
The damping amount can be reduced as the position at the time of exciting this phase is as close as possible to the A phase and the slope of the curve indicated by 44 is small. In addition, in Fig. 4,
The shaded area indicates the time during which the windings of the motor are energized according to this embodiment.

[Description of motor drive processing (FIGS. 1 to 5)] FIGS. 5 and 5B are flowcharts showing motor drive processing by the control unit 100. A control program for executing this processing is stored in the ROM 104. There is.

In step Sl, wait for the input of a motor drive trigger from the main control section, and when the motor drive trigger is input, the process proceeds to step S2, where the motor 12 that is sent together with the drive trigger is
Read the number of steps n for rotationally driving the RAM 105.
Set it to CNT. In step S3, the interface unit 101 turns on the G signal to the main control unit, and prohibits input of the next rotational drive trigger until the rotational drive of the motor 125 is completed.

In step S4, it is determined whether or not it is the first step drive for that trigger. If it is the first step drive, the process proceeds to step S5, and the next phase to be excited is determined based on the phase signal 121 and the phase signal 121 based on the excitation phase stored in the PH. 123. At the same time, the PH is also updated to the latest excitation phase. Then, in step S6, the winding current control signals 122 and 124 or the control signal 110, or all of these signals,
Increase the excitation energy of the motor 125. Further, in step S7, excitation is performed for a phase excitation time (Tn) that is longer than the normal excitation time, which corresponds to the first step. When this excitation is completed, the process proceeds to step S8, where CNT is -1 and step S4 Return to

This phase excitation is shown at 51 in FIG.

If it is not the first phase excitation in step S4, step S9
It is checked whether CNT is "1", that is, during the final step of driving. If it is not the final step, the process proceeds to step SIO, where the next phase stored in the PH is excited and the PH is updated. In step Sll, it is determined whether the excitation phase is one phase or two phases based on the PH value. If it is one-phase excitation, the process proceeds to step S12, where a predetermined excitation energy is set, and excitation is performed for one-phase excitation time TH in step S13. This TN time is different from the above-mentioned Tn as T n > T
It is in the relationship of s. When the one-phase excitation time ends in this manner, the process proceeds to step S8. As a result, 52 in Figure 4
As shown, the second step B-phase excitation is completed in a short time.

On the other hand, when two-phase excitation is performed in step Sll, step S1
4, the excitation energy is set using the winding current control signals 122, 124 or the control signal 110, and an arbitrary excitation time (T i ) is measured in step S15. This time is T n > T i compared to the excitation time described above.
> T s. This corresponds to the phase excitation indicated by 53 in FIG.

If the CNT is "l" in step S9, that is, the last phase is excited, the process proceeds to step S16, where the last phase is excited, and in step S17, the excitation energy is set to normal using the winding current control signals 122 and 124 or the control signal 100, etc. The power is lowered than during one-phase excitation, and a shorter phase excitation time TJ is measured in step S18. Then, in step S19, the G signal is turned off and the next motor trigger from the main control section is waited for. This time Tj is approximately equal to the first phase excitation time TN of the second step.

The increase/decrease in excitation energy and the excitation time of each phase, such as Tn, TN, T i , T j , etc., can be arbitrarily selected so that the rise is fastest and the damping is small in each system.

In this embodiment, the case of four steps has been described, but the invention is not limited to this, and the same can be done as long as the driving is performed in a plurality of steps. Further, the stepping motor can be driven in the same way even in the case of bipolar, unipolar, or step drive other than l-2 phase.

Moreover, as shown in FIG. 6, the final step of excitation is n
It is also possible to shorten the driving time of the motor by sending the signal after the time required for each step has elapsed. In other words, if the next drive trigger is input immediately after the time required to excite n thrusters at timing T1 in FIG. Therefore, it rotates smoothly without exciting the final phase (AX).

On the other hand, at timing T2, after the time required for excitation for the next n thrusts has elapsed, since the next drive trigger has not been input, the A phase is excited by the excitation signal of the final step. In this way, if the interval until timing T3 when the next trigger is input is long, the phase (A) of the n-th step remains excited and is held at one phase.

As explained above, according to this embodiment, the motor can be smoothly driven at high speed by determining the excitation energy and phase excitation time of each phase during n steps depending on the phase to be excited and the number of steps. At the same time, the motor can be driven with less power consumption. Furthermore, it has the effect of reducing vibration and noise of the motor.

In addition, even if the trigger interval changes, the first phase excitation can be made longer,
In addition, by increasing the excitation power, the influence of damping can be absorbed. Furthermore, the phase excitation in the final step can be controlled to minimize damping.

[Effects of the Invention] As explained above, according to the present invention, by changing the excitation current, excitation time, etc. of the stepping motor in accordance with the rotational speed and excitation phase, the motor can be started to rotate at high speed. −, it has the effect of minimizing damping when the rotation stops in the evening.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the schematic configuration of the motor drive circuit of the embodiment, Fig. 2 is a diagram showing the schematic configuration of the driver circuit of the embodiment, and Fig. 3 is a diagram showing the 1-2 phase excitation model of the stepping motor. , FIG. 4 is a diagram showing the relationship between the excitation of the stepping motor and the amount of movement S of recording paper etc. conveyed by the motor, FIG. 5 is a flowchart showing the motor control operation by the motor control circuit of the embodiment, FIG. 6 is a diagram showing the excitation timing of the motor in another embodiment. In the figure, 100...control unit, 101...interface unit, 103...020% 104...ROM,
105...RAM% 106...Power supply, 107...
・D/A converter, 108.109...driver,
110... Control signal, 121, 123... Phase signal,
122, 124...Winding current control signal, 125...
Stepping motor, 127...Reference voltage. ~-( Figure 3 Figure 4

Claims (2)

[Claims] (1) A stepping motor driving method that rotates the stepping motor by the number of steps specified by one drive start instruction, and when driving the stepping motor, the current number of steps and the excitation phase of the stepping motor are A driving method for a stepping motor, comprising: a detection means for detecting the step; and an excitation control means for changing a phase excitation current value or excitation time in accordance with each of the excitation phases and the number of steps. (2) The excitation control means increases the excitation time at the start of driving, or makes the excitation time shorter during one-phase excitation than during two-phase excitation, and reduces the excitation current per phase during final one-phase excitation. 2. The stepping motor driving method according to claim 1, wherein: