JPH0965692A - Dot printer shuttle control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption of a printer without deteriorating a printing speed and print quality by a method wherein a current applied to a motor coil is changed in accordance with the operation state of a stepping motor. SOLUTION: A resistor 80 is connected to a '0' level with a changeover switch 100 which is switched by the S-output of a controller 10. The D-output of the controller 10 is '0' and the output of an AND circuit 50 is '0'. If the operation of a stepping motor is transferred from an acceleration state to a constant speed state, the controller 10 switches the changeover switch 100 to connect a resistor 90 which has a lower resistance than the resistor 80 to the '0' level. In this state, the voltage of the B-input of a voltage comparator 40 is lower than the voltage in the previous acceleration state, so that a current applied to a motor coil 20 is also smaller than the current in the acceleration state. As a result, always an optimum current can be applied, so that the power consumption can be reduced without deteriorating a printing speed and print quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current control system in a shuttle mechanism section of a dot printer using a stepping motor.

[0002]

2. Description of the Related Art FIG. 4 shows the printing principle of a dot printer.

In FIG. 4, a printing hammer (not shown)
The hammer bank 200 equipped with is a timing belt 2
It is attached to the two pulleys 260 via 70, and the pulley 260 is attached by the stepping motor 210.
When one of them is driven, it reciprocates in the horizontal direction with a predetermined stroke width. In the process of reciprocating the hammer bank 200, the printing hammer is driven by the printing control device (not shown), and the ink ribbon 220
Printing is performed at a predetermined position on the printing paper 230. When printing of one stroke of the hammer bank 200 is completed, the stepping motor 210 rotates in the opposite direction, so that the hammer bank 200 is reversed and is used for transporting the paper before moving to the next printing position. The paper transporting tractor 250 driven by the motor 240 transports the print paper 230 by a predetermined amount and starts printing of the next stroke.

FIG. 5 shows a hammer bank 2 for one stroke.
9 shows a speed waveform of 00.

In order to perform high quality printing, it is ideal to perform printing only in the constant speed state shown in FIG. But,
The maximum speed Vmax of the hammer bank 200 is determined by the time (hereinafter referred to as the hammer response time) during which the next dot can be printed after a certain dot is printed by the hammer. This is, for example, 180 dots per inch (hereinafter 180
When printing (referred to as “dpi”), the hammer bank 20
This is because if 0 moves 1/180 inch in a time faster than the response time of the hammer, the hammer cannot follow and printing cannot be performed. Therefore, when the response time of the hammer is constant, it is necessary to shorten the time of the acceleration state and the deceleration state of FIG. 5 in order to increase the printing speed of the printer.

6 and 7 show a conventional stepping motor driving method.

FIG. 6 is generally called a constant voltage drive system, which is a system in which a constant voltage is applied to the motor coil 30, and the current value flowing in the motor coil is determined by the value of the resistor 300.

FIG. 7 shows a circuit generally called a current detection type constant current drive system, and shows a circuit for one phase of a stepping motor. In FIG. 7, when the transistor 30 is turned on, the current flowing through the motor coil 30 is converted into a voltage by the resistor 60 and input to the A input of the voltage comparison circuit 40. A voltage obtained by dividing the power supply voltage by the resistors 70 and 80 is input to the B input of the voltage comparison circuit 40. The voltage comparison circuit 40 compares the voltages of the A input and the B input, and turns off the transistor 30 if the voltage of the A input is higher, and turns on the transistor 30 if the voltage of the A input is lower.
As a result, the value of the current flowing through the motor coil 20 becomes constant.

In either method, the resistor 8 is conventionally used.
Since the values of 0, 90, and 300 are one type depending on the device, it was not possible to switch the current value flowing through the motor coil 20 in the operating state of the stepping motor. Since the driving torque of the stepping motor is proportional to the current flowing through the motor coil 20, conventionally, the resistor 80 is used so that the current required for the accelerating state where the stepping motor requires the most torque flows through the motor coil 20. , 9
Values of 0 and 300 were determined.

[0010]

When the hammer bank is moving at a constant speed, the driving torque required is smaller than when the hammer bank is performing an accelerating motion or a decelerating motion, and the extra current is consumed as heat. To be done.

Therefore, the stepping motor main body and the drive circuit for the stepping motor generate heat, and there is a problem that the cost of the equipment increases due to the cooling of these. At the same time, since the hammer bank continues to move while the printer is printing, the maximum current required by the stepping motor continues to flow to the stepping motor while the printer is printing, which reduces the current consumption of the device. There was a problem of causing an increase.

On the contrary, in order to reduce the current consumption of the device,
When the current flowing through the motor coil is reduced, the driving torque of the stepping motor decreases, so the acceleration / deceleration time becomes longer, the printing speed decreases, and the printing quality is reduced due to printing in the acceleration / deceleration state. There was a problem of lowering.

An object of the present invention is to reduce the power consumption of the printer without lowering the printing speed and the printing quality by always supplying the optimum current to the stepping motor.

[0014]

The above object can be achieved by arbitrarily changing the value of the current flowing through the motor coil in accordance with the operating state of the stepping motor.

[0015]

According to the present invention, the optimum current can be always supplied according to the operating state of the stepping motor, so that the current consumption of the printer can be reduced without lowering the printing speed and the printing quality. .

[0016]

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention.

FIG. 1 is a current detection type constant current drive system and shows a circuit for one phase of a stepping motor. In FIG. 1, the resistor 80 is now connected to the 0V level by the changeover switch 100 that is switched by the S output of the control circuit 10, and the B input of the voltage comparison circuit 40 is
A voltage obtained by dividing the power supply voltage Vcc by the resistors 70 and 80 is input. The D output of the control circuit 10 is "0", and the output of the AND circuit 50 which outputs "1" only when the two inputs are "1" is "0". In this state,
Since the NPN transistor 30 is off and no current flows through the motor coil 20 and the resistor 60, the A input of the voltage comparison circuit 40 becomes 0V. Voltage comparison circuit 40
Outputs "0" when the A input is higher of the two input voltages, and outputs "1" when the A input is lower.
Therefore, "1" is output in this case. In this state, when the control circuit 10 sets the D output to "1" in order to drive the stepping motor, the output of the AND circuit 50 becomes "1" and the transistor 30 is turned on. And a current flows through the resistor 60. The current flowing through the motor coil 20 rises and the voltage comparison circuit 4
When the A input of 0 becomes higher, the voltage comparison circuit 40 becomes "0".
Is output, and the transistor 30 is turned off. This allows
The current value flowing in the motor coil 20 is kept constant.

When the stepping motor shifts from the acceleration state to the constant velocity state, the control circuit 10 switches the changeover switch 10
The resistor 9 that switches 0 and has a lower resistance value than the resistor 80
Connect 0 to 0V level. In this state, the voltage of the B input of the voltage comparison circuit 40 is lower than that in the previous acceleration state, so that the current value flowing through the motor coil 20 is smaller than that in the acceleration state.

FIG. 2 generally shows pulse width control (PWM control)
A second embodiment of the present invention using a control method called as follows is shown.

In FIG. 2, the transistor 30 is turned on and off only by the D output of the control circuit 10, and at that time, the transistor 30 is turned on.
The relationship between the waveform of the current flowing through the coil 20 and the on / off state of the transistor 30 is shown in FIG. In the acceleration state of the stepping motor in FIG. 3, the control circuit 10 keeps the transistor 30 turned on. At this time, the current I of FIG. 3 is determined by the resistance value of the resistor 60 in the motor coil 20.
a flows. When the stepping motor shifts to the constant speed state, the control circuit 10 turns on and off the transistor 30 at a certain ratio. At this time, the current flowing through the motor coil 20 rises or falls while drawing a curve determined by the time constant of the circuit of FIG. 2, so that the average value becomes Ib of FIG.

The control circuit 10 can arbitrarily change the current flowing through the motor coil by changing the on / off ratio of the transistor 30.

[0023]

As described in detail above, according to the present invention, an optimum current can be always supplied to the stepping motor according to the operating state of the stepping motor. As a result, the current consumption can be reduced without lowering the printing speed and print quality of the printer.

[Brief description of drawings]

FIG. 1 is a stepping motor showing a first embodiment of the present invention.
Drive circuit diagram

FIG. 2 is a stepping motor showing a second embodiment of the present invention.
Drive circuit diagram

FIG. 3 is a diagram showing a current waveform according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a printing principle of a dot printer.

FIG. 5 is a diagram showing a velocity waveform of a hammer bank.

FIG. 6 is a drive circuit diagram of a conventional stepping motor.

FIG. 7 is a drive circuit diagram of another stepping motor according to the related art.

[Explanation of symbols]

10 is a control circuit, 20 is a motor coil, 30 is a transistor, 40 is a voltage comparison circuit, 50 is an AND circuit, 60,
70, 80, 90 and 300 are resistors, 100 is a switching switch, 200 is a hammer bank, 210 is a stepping motor, 220 is an ink ribbon, 230 is a printing paper, 240 is a paper transportation motor, and 250 is a paper transportation. Tractor 260, pulley 270 and timing belt 270.

Claims (3)

[Claims] 1. The hammers are formed by connecting two pulleys by an endless carrier having a hammer bank having a printing hammer attached thereto and driving one of the pulleys by a stepping motor. A shuttle control system for a dot printer, characterized in that, in a shuttle mechanism section of a dot printer that reciprocates a bank, a current value flowing through the stepping motor is arbitrarily changed according to an operating state of the stepping motor. 2. The shuttle control system for a dot printer according to claim 1, wherein the current value changing means is performed by switching a reference voltage of a voltage comparison circuit. 3. The shuttle control system for a dot printer according to claim 1, wherein the current value changing means is performed by switching a ratio of an on time and an off time of a transistor.