JPS60207499A - Drive device for stepping motor - Google Patents

Abstract

PURPOSE:To increase a drive torque when a speed is varied by exciting via high power a stepping motor at speed varying time. CONSTITUTION:A controller 10 generates a phase excitation signal and a high power generation signal on the basis of a speed signal from a speed signal generator 11. A drive unit 12 generates phase excitation signals phiA, phiB, phiC and phiD in the phases A, B, C and D, respectively of a stepping motor on the basis of a signal from the controller 10, and generates a high power signal. An exciting current is flowed during one phase exciting period for the prescribed time in a constant speed area to obtain a large torque, but high power generation signals are generated twice during one phase exciting period in an acceleration area to double the time when large exciting current is flowed during one phase exciting period, thereby obtaining a large torque.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a stepping motor drive device for driving a stepping motor.

[Technical background of the invention and its problems]

Stepping motors are often used as drive motors in information devices such as printers.

As a method for driving this stepping motor, there is a method in which a high power current having a high current value is passed through the excitation winding for a certain period within the phase excitation period, and a current having a current value lower than the high power signal is caused to flow during the remaining period.

However, when driving a printer carriage using this driving method, the load on the carriage increases at low temperatures, which may result in step-out due to insufficient torque. That is, in this driving method, as shown in FIG. 1, A, B', C,
D The initial fixed period T of the phase excitation period TATBTcTD of each phase. It is designed to output a high power signal,
This is true both in the acceleration area where the carriage is moved by the acceleration section and in the constant speed area where the carriage is driven at a constant speed. Therefore, in the acceleration area at low temperatures where more drive torque is required, torque is insufficient and the motor loses synchronism.To prevent this kind of adjustment, conventionally the high power current is increased during acceleration to increase the drive torque. Ta. However, in order to increase the high-power current, a special power source is required, which increases costs. Furthermore, there is a problem in that increasing the excitation current accelerates the deterioration of the stepping motor.

Another method is to vary the time width of the high power signal in accordance with the phase excitation period of each phase during acceleration. However, there is a problem in that changing the high power signal increases the amount of hardware and costs.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a stepping motor drive device that can increase drive torque when speed changes.

[Summary of the invention]

To achieve this object, the stepping motor drive device according to the present invention includes a control unit that generates a phase excitation signal and a high power signal for the stepping motor, and excite each phase of the stepping motor using the phase excitation signal generated by the control unit. and a drive unit that increases the excitation current for a certain period of time using the high power signal to perform high power excitation,
The control unit emits a high power signal multiple times during the phase excitation period of υ and toto when the speed changes, and performs high power excitation multiple times at a fixed time width during one phase excitation period using these high power signals. , which is characterized by greatly increasing the driving torque when the speed changes.

[Embodiments of the invention]

A stepping motor driving device according to an embodiment of the present invention is shown in FIG. 2. A control section 10 receives a speed signal from a speed signal generating section //. This speed signal generating section /l generates a speed signal under the control of the control section IO. This speed signal is, for example, a pulse proportional to the speed, and the faster the speed, the higher the frequency, and the lower the speed, the lower the frequency. This matches the phase switching frequency of the stepping motor SM.

The control unit IO generates a phase excitation signal and a no-power generation signal based on the speed signal. The phase excitation signal is a signal that controls the excitation of each phase A, B, C, and D of the stepping motor SM. The no power generation signal is a signal that generates a high power signal that increases the phase excitation current. This embodiment is characterized by the way this high power generation signal is generated. The drive section // receives a high power generation signal and a phase excitation signal from the control section 10 . The drive unit /l is based on the phase excitation signal,
Each phase A, B, C, DK excitation signal φA, φB, φC1φD of the stepping motor SM is generated. In this embodiment, as shown in FIGS. 2 and 3, an excitation signal is output by a unipolar drive type/phase excitation method.

Further, the drive section // operates for a certain period T based on the high power generation signal. , generates a high power signal.

The stepping motor SM of this embodiment has G-phase windings A, B, C, and D arranged around the rotor R, and each phase winding A, B, C, and D receives a phase excitation signal φA. ,φB
, a drive transistor QA whose base input is φC9φD
The collector of Q8QcQD is connected. The emitters of the drive transistors QAQBQ (, QD are commonly connected and grounded via a resistor R1. Each phase winding A, B,
The other ends of C and D are commonly connected to drive transistor Q.

is connected to the collector of diode D and the cathode of diode D. Drive transistor Q. is a transistor whose base input is an inverted signal of the ipower signal, and whose emitter is connected to a high voltage power supply of +/coV via a resistor R.

The anode of diode D is connected to a +tV normal voltage power supply via resistor R2.

In the constant speed area, as shown in Figure 3, the phase excitation signal φ
A, φB, φC2φD are generated. Phase excitation M-F+φA
When the voltage becomes H level, the drive transistor QA is turned on, and an excitation current flows through the phase winding A. This high power signal is also applied to the drive transistor Q at the same time.

is turned on, +ll burns and a large excitation current is applied to the phase winding A.
, and a large driving torque can be obtained. T for a certain period of time. After , the power signal changes from L level to H level, and the drive transistor Q changes. turns on. Therefore, during the remaining excitation period, phase winding A is connected to resistor R1 and diode D.
Since +S■ is applied through the terminal, only a relatively small excitation current flows. Similarly, the excitation current sequentially flows through the phase windings B, C, and D, causing the stepping motor SM to rotate.

In this way, in the constant speed area, the constant period T during each phase excitation period. However, since a large torque is required in the acceleration area, in this example, as shown in Figure 3, a high power signal is generated λ times, that is, in the acceleration area. A high power generation signal is generated twice during one phase excitation period, and the time during which a large excitation current flows during one phase excitation period is doubled, thereby obtaining a large torque. Assuming that the phase excitation period of the phase winding A is TA, the control unit IO generates a high power generation signal at the same time as the phase excitation signal φA becomes H level, and once the half of the phase excitation period has passed, the control unit IO generates a high power generation signal again. occurs. Similarly, for the phase windings B, C, and D, high power generation signals are generated during the phase excitation period TBToTD.

Therefore, in the acceleration area, each phase excitation period TA,
The period during which a large excitation current flows during TB, Tc, and TD is 2
To, the driving torque increases.

As described above, according to this embodiment, a larger torque can be obtained in the acceleration area, and the stepping motor will not step out. Furthermore, according to this embodiment, it is only necessary to generate the no-power generation signal in the middle of the phase excitation period.
Torque can be increased without providing a special power source, and manufacturing costs do not increase.

In the previous embodiment, the high power generation signal was generated once in the acceleration area, but the high power generation signal may also be generated λ times in the deceleration area. This is because high torque may be required during deceleration as well as during acceleration. Further, even in a constant speed area, if the speed changes and particularly high torque is required, an extra high power generation signal may be generated.

Further, the high power generation signal may be generated two or more times during one phase excitation period. Further, the timing of its occurrence may be any time as long as it is during the phase excitation period.

Further, in the previous embodiment, the stepping motor was driven by a unipolar drive method/phase excitation method, but the present invention can be similarly applied to a bipolar drive method. The present invention can also be applied to the U-phase excitation method and the /-C phase excitation method.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve the torque of a stepping motor without making any major changes to the hardware. Further, according to the present invention, since the stepping motor can be driven to improve torque without exceeding its rating, the stepping motor does not deteriorate. In particular, the present invention is effective as a driving device for a stepping motor that moves the carriage of a kanji printer that frequently oscillates and stops.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing a conventional driving method, FIG. 2 is a diagram showing a step motor driving device according to an embodiment of the present invention, and FIG. 3 is a time chart showing the operation of the same driving device. IQ...Control unit, l/...Speed signal generation unit, /Y
... Drive unit, QoQAQBQcQD... Drive transistor, RI+R2, R,... Resistor, SM... Stepping motor, R... Rotor, A, B, C, D...
... Phase winding, φA, φB. φC1φD...phase excitation signal. Applicant's agent Kiyoshi Inomata

Claims (1)

[Scope of Claims] A control unit that generates a phase excitation signal and a high power signal for a stepping motor; and a control unit that excites each phase of the stepping motor using the phase excitation signal generated by the control unit, and that the high power signal excites each phase of the stepping motor for a certain period of time. and a drive section that increases the excitation current to perform high-power excitation, and the control section emits a high-power signal multiple times during one phase excitation period when the speed changes, and uses these high-power signals to perform high-power excitation during one phase excitation period. A stepping motor drive device that performs high-power excitation multiple times over a certain period of time to increase drive torque when speed changes.