JPH05278293A - Method for driving stepping motor - Google Patents

Abstract

PURPOSE:To efficiently conduct driving at a low noise level with the use of inexpensive CPU. CONSTITUTION:At least in the acceleration region of a stepping motor equipped with an acceleration region and a deceleration region, the driving mode of the motor is switched between 1-2 phase driving and 2-2 phase driving. Since the motor has enough torque at its start-up, the 1-2 phase driving, which is effective to depress vibration, is used to actuate the motor, and the driving mode is switched to 2-2 phase driving when the speed has increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor used for running a carriage equipped with a print head in a printer, and more particularly to an improvement of a driving method thereof.

[0002]

2. Description of the Related Art Generally, the driving of the above stepping motor includes 1-2 phase driving and 2-2 phase driving.

FIG. 3 is a simplified model of the stepping motor. The numbers 1 to 8 are numbers indicating the position of the rotor, which is formed by dividing the entire circumference into eight parts by 45 degrees.
B, A ′ and B ′ are reference numerals indicating the positions of the electromagnets which are formed by dividing the entire circumference into four by 90 degrees.

As shown in FIG. 4 (A), the 1-2 phase drive of the stepping motor is performed immediately after the rotor passes through the electromagnets on the front side so that the rotor rotates clockwise in FIG. The driving method is to sequentially excite A, B, A ', and B'.

In the 2-2 phase driving of the stepping motor, as shown in FIG. 4 (B), only one of the paired electromagnets A and A'is rotated so that the rotor rotates clockwise in FIG. The magnetic field is alternately excited by 180 degrees, and only one of the other electromagnets B and B'combined is alternately excited by 180 degrees and the excitation timings of the electromagnets A and A'are shifted from each other by 90 degrees. It is a driving method. The excitation timing of each electromagnet A, B, A ', B'in this 2-2 phase drive is when the rotor faces the front electromagnet.

[0006]

Among the two types of driving methods described above, the 1-2 phase driving has the advantage that it can drive the stepping motor with less noise than the 2-2 phase driving, but The 1-2 phase drive has a problem that the torque for driving the motor decreases.

Further, the 1-2 phase drive requires twice the number of motor drive steps in the same time as the 2-2 phase drive, and therefore it is inexpensive to perform the 1-2 phase drive at a high speed. CPU
When using, there is a possibility that the processing speed in the CPU may not catch up.

SUMMARY OF THE INVENTION An object of the present invention is to provide a driving method of a stepping motor which overcomes the above-mentioned problems in the prior art and can efficiently drive a low noise by using an inexpensive CPU.

[0009]

In order to achieve the above-mentioned object, a method of driving a stepping motor according to a first aspect of the present invention is to drive a motor in at least an acceleration region of an acceleration region and a deceleration region of a stepping motor. The feature is that switching is performed between two-phase driving and two-two-phase driving.

A stepping motor driving method according to a second aspect of the present invention is the method of driving the stepping motor according to the first aspect, in which the 1-2 phase driving is performed.
It is characterized in that the switching to the -2 phase drive is performed in the 2-phase excitation state.

[0011]

When the carriage of the printer is driven by the method of driving the stepping motor of the present invention having the above-mentioned structure, the motor has a sufficient torque when the motor is started. Then
When the speed becomes high, switch to 2-2 phase drive.
At the constant speed after the end of acceleration, the 2-2 phase drive is continued to drive the motor.

Further, even during deceleration, if necessary, the mode is switched to the 1-2 phase drive and the motor drive is terminated.

By the way, when the 1-2 phase drive is switched to the 2-2 phase drive, the switching is smoothly performed by switching to the 2-2 phase drive in the 2-phase excitation state in the 1-2 phase drive. There is no unevenness in the feed amount.

[0014]

The present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 shows the driving speed of a stepping motor,
It shows changes over time in the required torque of the stepping motor and the output torque of the stepping motor.

In FIG. 1, a trapezoidal line A indicates the driving speed of the stepping motor, A1 indicates an acceleration region, A2 indicates a constant velocity region, and A3 indicates a deceleration region.

Further, in FIG. 1, a stepped line B shows the torque required for the stepping motor,
The required torque is the highest when the motor is accelerated, and the required torque is smaller at constant speed than during acceleration. Note that little torque is required during deceleration.

Further, represents the output torque of the stepping motor, of which the line C1 represents the output torque of the stepping motor in the 1-2 phase drive, and
Line C2 shows the output torque of the stepping motor in the 2-2 phase drive. As is clear by comparing the lines C1 and C2, the output torque of 2-2 phase drive is always larger than that of 1-2 phase drive. It should be noted that any output torque gradually decreases during acceleration, maintains a constant value during constant speed, and gradually increases during deceleration. Further, the output torque of the stepping motor in the 1-2 phase drive indicated by the line C1 is below the motor required torque at the final stage of acceleration.

By the way, at the beginning and the end of the driving of the stepping motor, the driving of the motor is not stable, so that vibration and noise are likely to occur. Further, when the stepping motor is driven by 1-2 phase using an inexpensive CPU, the processing of the CPU may not be able to catch up at the time of high speed rotation.

Therefore, in the present embodiment, when the output torque of the stepping motor is low in the acceleration region where there is a margin, the stepping motor is driven in the 1-2 phase to prevent the generation of vibration and noise, and also in the acceleration region, it is high speed. When it is in the driving state, it is switched to the 2-2 phase driving.

By the way, as shown in FIG. 2, the switching from the 1-2 phase drive to the 2-2 phase drive is a two-phase excitation state (in this embodiment, the electromagnets A'and B'are in the excitation state). It is desirable to end the 1-2 phase drive and switch to the 2-2 phase drive at the time of (1). This is because if the 1-2 phase drive is switched to the 2-2 phase drive in the 1-phase excitation state, there is a risk of uneven rotation or step out at the time of switching.

Then, the stepping motor continues to be driven even in the constant velocity region as it is in the 2-2 phase drive, and when the motor becomes low in the deceleration region, the 2-2 phase drive is terminated and switched to the 1-2 phase drive. Then, the driving of the motor is finished.

A thick line C3 in FIG. 1 indicates 1-2 phase drive and 2-2.
The output torque of the motor when the phase drive is switched to drive the stepping motor is shown.

In this way, the driving of the stepping motor is reduced to 1
By switching between the -2 phase drive and the 2-2 phase drive, vibration and noise do not occur at low speed, and even if an inexpensive CPU is used, the number of motor drive steps is small at high speed. Since it is a 2-2 phase drive, the processing of the CPU does not catch up.

Therefore, low-noise driving can be efficiently performed by using an inexpensive CPU. When the noise was compared by the printer manufactured by the applicant, the noise level was reduced by 2 dB according to the driving method of the stepping motor of the present invention as compared with the conventional driving method of the stepping motor.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made if necessary. For example, the driving method of the present invention is not limited to only the stepping motor used in the printer. Further, in the deceleration area, the rotation of the motor is not as unstable as in the acceleration area.
The 2-phase drive is never switched to the 1-2-phase drive.

[0027]

As described above, according to the present invention, an inexpensive CPU can be used to efficiently perform low noise driving. Further, if the switching from the 1-2 phase drive to the 2-2 phase drive is performed in the two-phase excitation state, it is possible to perform stable switching without uneven rotation or step out at the time of switching.

[Brief description of drawings]

FIG. 1 is a graph showing changes over time in driving speed of a stepping motor, required torque of the stepping motor, and output torque of the stepping motor showing an embodiment of the present invention.

FIG. 2 is a graph showing an excited state of an electromagnet when switching between 1-2 phase driving and 2-2 phase driving.

FIG. 3 is an explanatory diagram showing a simple model of a stepping motor.

FIG. 4 (A) is a graph showing an excited state of an electromagnet in 1-2 phase driving. FIG. 4 (B) is a graph showing an excited state of an electromagnet in 2-2 phase driving.

Claims (2)

[Claims] 1. The motor driving is performed in at least an acceleration region of an acceleration region and a deceleration region of a stepping motor.
A method of driving a stepping motor, characterized in that switching is performed between -2 phase driving and 2-2 phase driving. 2. The method of driving a stepping motor according to claim 1, wherein the switching from the 1-2 phase drive to the 2-2 phase drive is performed in a two-phase excitation state.