JPS62163595A - Stepping motor driving device - Google Patents

Abstract

PURPOSE:To contrive not to apply unnecessary torque and prevent power from being wastefully consumed, by setting the phase current of a stepping motor to an adequate degree according to load torque. CONSTITUTION:According to the timing of changing load torque, by load torque signal b, a transistor Q3 is turned ON/OFF. Then, a detection value for detecting motor current is changed, and by an IC comparator, the value is compared with reference voltage V1, and a transistor Q1 is ON/OFF-controlled. Accordingly, by turning the transistor ON or OFF, motor current is changed, and the generating torque of a motor can be set to an adequate degree according to the desired torque of a load.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a stepping motor drive device.

[Conventional technology]

FIG. 3 shows a diagram of a conventional stepping motor drive device 3 using a constant current drive method using chopper control.

However, since each phase of the stepping motor drive device 3 has the same configuration, only one phase is shown as shown within the broken line.

The motor excitation signal a generated by the signal circuit l is input to the base of the transistor Q2 and turns on the transistor Q2, so that the current supplied from the DC power supply 2 is applied to the stepping motor (stator) 4 via the transistor Ql. It flows into the motor winding 6. The motor is driven by supplying this current to each phase in accordance with the excitation signal a output from the signal circuit 1. The comparator IC has a reference voltage V set in advance by the reference voltage generator 7.

and the voltage v2 generated by the phase current flowing through the resistor R2 inserted in series with the motor winding a6, and if the voltage v2 is lower than the reference voltage v1, the transistor Q,
is turned on, and when the voltage v2 is higher than the reference voltage V, the transistor Q1 is turned off to perform chopper control of the phase power supply. Therefore, the magnitude of the phase current is determined by the value of resistor R2, and this current naturally determines the torque generated by the motor.

The coil energy absorption circuit 5 is a circuit for absorbing the electromagnetic energy of the coil when the motor phase current is interrupted.

FIG. 4 shows the main parts of the laser beam printer driven by the above-mentioned stepping motor, from the paper feed roller 8 to the paper discharge roller 12. The paper fed to the printer by the paper feed roller 8 is placed on the photosensitive drum 9. A latent image of the formed print pattern is transferred to the sheet, and the sheet is discharged via a conveyance roller 10, a fixing roller 11, and a discharge roller 12. In this process, it is known that the load torque on the stepping motor is greatest when the paper is caught between the paper feed rollers 8 and fed to the photosensitive drum 9.

[Problem that the invention seeks to solve]

The conventional stepping motor drive device described above determines the phase current according to this maximum torque.

Since the resistor R2 is set, the same amount of current is supplied to each phase even when the maximum torque is not required at low load torque, which means that unnecessary torque is given, which is wasted. The disadvantage is that it consumes electricity.

An object of the present invention is to provide a stepping motor drive device that reduces power consumption by supplying a necessary phase current according to the load torque in a device in which the process is repeated at a constant cycle and the load torque on the motor can be predicted. The goal is to provide the following.

[Means for solving problems]

The stepping motor drive device of the present invention changes the magnitude of the phase current of the motor to the required magnitude according to the fluctuation of the known load torque, according to the input information that conveys the magnitude of the known load torque and the timing of the fluctuation. It has a control means that performs control in accordance with the timing of fluctuations in load torque.

Therefore, when applied to a device where the process is repeated at a certain period, depending on the fluctuations in the torque required by the load, the phase current of the appropriate magnitude is supplied to the motor in accordance with the timing of the fluctuations. This reduces power consumption.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit configuration diagram showing an embodiment of a stepping motor drive device of the present invention, and FIG. 2 shows an example of a phase current chart when this embodiment is applied to the above-described printer.

In the transistor Q2, the transistor Ql and the motor coil 6 are connected in series between the collector and the DC power supply 2.
A resistor R2 and a resistor R3 are connected in series between the emitter and ground, and an excitation signal a is input from the signal circuit 1 to the base. The transistor Q3 has its collector connected to the connection point between the resistors R2 and R3, and its emitter connected to ground, and a load torque signal is inputted to its base from a microcomputer (not shown) that controls the process.

Coil energy absorption circuit 5 is connected in parallel with transistor Ql and motor coil 6 between transistor Q2 and DC power supply 2. The reference voltage generator 7 has one end connected to the DC power supply 2 and the other end connected to the ground via a resistor R, and the comparator IC has the inverting terminal connected to the reference voltage generator 7.
The reference voltage v1 outputted by the transistor Q1 is inputted to the non-inverting terminal, and the voltage v2 between the emitter of the transistor Q2 and the ground is inputted to the non-inverting terminal, and the output thereof is inputted to the base of the transistor QI.

Next, the operation will be described when this embodiment is applied to the printer.

The load torque signal inputted to the transistor Q3 remains at "H"°° level when the paper passes the paper feed roller 8, that is, when the load torque applied to the motor is at its maximum, and at times other than the paper feed timing. It is set to "L" level. This can be easily set by controlling the process with a microcomputer or the like. Therefore, transistor Q3 is turned on at the paper feeding timing and short-circuits the resistor R3, and is turned off at other times than the paper feeding timing and the resistor R3 is inserted into the motor circuit. Therefore, the resistance value of the motor circuit is determined by the motor winding resistance. In addition, in the former case, it is determined by the resistance R2, and in the latter case, it is determined by the total value of the series resistance consisting of the resistance R2 and the resistance R3.

On the other hand, the time constant when the resistance drop voltage v2 due to the motor current reaches the reference voltage v1 set for constant current driving by chopper control is determined by the inductance of the motor winding yj6 and its resistance value, and the resistor R2, or the resistor R2 and the resistor R3. It is determined by the resistance value of the series resistor.

Therefore, as shown in FIG. 2, when transistor Q3 is off, the rising time constant of voltage v2 is
is shorter than when it is on, and the phase current value is naturally smaller (
Current waveform 14). The opposite is true when transistor Q3 is on (current waveform 13).

Therefore, if the phase current value is set by selecting resistor R3 so that the motor can sufficiently drive the device at times other than the paper feeding timing (maximum load torque), it will be possible to adjust the phase current value according to the timing when the load torque changes. By turning on/off the transistor Q3 in response to the load torque signal, the phase current of the stepping motor can be adjusted to an appropriate magnitude according to the load torque.

Note that in the above example, the current supplied to the motor was changed in two ways depending on the magnitude of the load torque, but it is also possible to add and combine a circuit similar to the combination of resistor R3 and transistor Q3 to the motor circuit. As a result, the phase current of the motor can be controlled to an appropriate magnitude based on the information on the magnitude of the load torque divided into several stages.

〔Effect of the invention〕

As explained above, the present invention has a control means that controls the magnitude of the phase current of the motor to a required magnitude in accordance with known fluctuations in load torque in accordance with the timing of the fluctuation, thereby controlling the generated torque of the motor. can be set to an appropriate size according to the required torque of the load, which has the effect of reducing power consumption of the motor drive device.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram showing an embodiment of the stepping motor drive device of the present invention, Fig. 2 is an example of a phase current chart when the unembodied embodiment is applied to the above-mentioned printer, and Fig. 3 is a diagram of a conventional stepping motor drive device. A circuit configuration diagram showing an example of a driving device, and FIG. 4 is an explanatory diagram showing main parts of a printer driven by a stepping motor. 1...Signal circuit, 2...DC power supply, 3...
- Stepping motor drive device, 4... Stepping motor (stator), 5... Coil energy absorption circuit, 6... Motor winding, 7... Reference voltage generator, 8... Paper feed roller, 9... Photosensitive roller, 10... Conveyance roller, 11... Fixing roller, 12... Paper ejection roller, 13... Phase current waveform at paper feeding timing, 14...
Phase current waveforms, Ql, Q2 at times other than paper feeding timing
．． Q:4...Transistor, R,, R2, R3...
- Resistor, IC... Comparator, a... Excitation signal, b... Load torque signal, V,... Reference voltage, v2... Voltage between the emitter of transistor Q2 and ground. Figure 1 Figure 2

Claims (1)

[Claims] In a stepping motor drive device that drives a device in which a process is repeated at a certain period, the magnitude of the motor phase current is adjusted to the required magnitude and load torque according to known variations in load torque. 1. A stepping motor drive device comprising a control means that performs control in accordance with the timing of fluctuations in the stepping motor drive device.