JPS63162254A - Serial dot printer - Google Patents

Abstract

PURPOSE:To enable a serial doe printer to be driven at a suitable drive timing even in the case of multiple pin printing by preventing the decrease of a supply voltage, by specifying motor constants such as the winding resistance of a space motor, a torque constant, and an induced voltage constant. CONSTITUTION:The winding resistance RM of a space motor, a torque constant Kt, and an induced voltage constant Ke are so set as to conform to the formula. VCL is a lower limit voltage to which a print head can be driven when a supply voltage is decreased. Vd is the collector emitter saturation voltage, R is a resistance, F is the friction of a mechanism, Kv is the viscosity coefficient of the mechanism, I is a current flowing in a space motor, and f is the revolutional number of the space motor. The speed of the space motor M does not decrease until the supply voltage VCC decrease to the lower limit voltage VCL. When the supply voltage VCC decreases lower than the lower limit voltage VCL, the revolutional number of the motor decreases, the drive timing period of the head is prolonged, the average power consumption of the print head decreases and the voltage decreases of the supply voltage VCC is prevented. Therefore, a suitable print head in which missing dot or the like does not occur can be driven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a serial dot printer that prevents a voltage drop in the power supply voltage and properly drives a print head.

[Conventional technology]

Conventionally, various serial dot printers of this type have been implemented, including one shown in FIG. 2, for example.

In the figure, 1 is an inverter υ, and this inverter 1 has a function of inverting the polarity of an input signal and an output signal by energizing the drive coil 3 of the print head 2.

The output terminal of the inverter 1 is connected between a resistor R1 and a capacitor C connected in series between a power supply Vcc and ground, and further connected to a "-" input terminal of a comparator 4.

A reference signal of voltage 5V is input to the 10'' input terminal of the comparator 4.

TRI and TR2 are switching transistors,
The switching transistors TRI and TR2 have a switching function to cut and paste the application of the power supply voltage Vcc to the drive coil 3 of the print head 2.

Next, the operation of the printer configured as described above will be explained.

When the HEAD-ON signal, that is, the TRI signal of the print head 2, is input, the output of the inverter 1 becomes L'', the output of the comparator 4 becomes no impedance, and the switching transistors TRI and TR2 are turned ON. .

When the HEAD-ON signal becomes uL'' in a short time of 10 μs, for example, the output of the inverter 1 becomes high impedance, and the ``-'' input of the comparator 4 becomes the power supply Vc.
c, capacitor C1 becomes high level with time depending on the condition of resistor R1.

The output of the comparator 4 is in a high impedance state until the potential of the "-" input of the comparator 4 exceeds the voltage.

As a result, the switching transistor TRI.

When TR2 is in the ON state, the print head 2 is driven.

The drive time T is obtained from the following formula.

That is, the drive time T changes depending on the power supply voltage Vec, and the print head 2 is driven with an appropriate drive time T.

[Problem that the invention seeks to solve]

However, in a printer with the above configuration, when a multi-pin head is used, more power is required and the voltage drop is large, so the drive time T of the print head is too long and the timing cycle of the head drive is also shortened. There was a problem in that it became long, and as a result, it interfered with control.

To explain this in detail using FIG. 3, the power supply voltage VC
C varies from the normal voltage v1 to ν2→υ) depending on the load, and the drive time accordingly changes from T1→T2→T.
5 (see Figure 2).

As is clear from the relationship between υ5 and T5 at this time, if the voltage drop is too large, the dry 1 hour T5 will also become larger than the head drive timing period To, and will overlap with the next head drive timing.
This means that T5 cannot be increased in actual purchase compared to To.

As a result, appropriate control becomes impossible.

Therefore, the present invention has been devised by paying attention to the above-mentioned problems, and its purpose is to prevent the voltage drop in the power supply voltage so that even in the case of multi-bin printing, it can be driven with an appropriate drive time. The purpose of the present invention is to provide a serial dot printer.

[Means for solving problems]

The gist of the configuration of the present invention in accordance with the above object is that motor constants such as a winding resistance RM, a torque constant Kt, and an induced voltage constant Ke of the space motor are set to satisfy the following formula.

However, VCL is the lower limit voltage that can drive the print head when the power supply voltage applied to the space motor and head is lowered, Vd is the collector-emitter saturation voltage of the switching transistor, R is the resistance, F is the friction of the mechanism, and K1
7 is the viscosity coefficient of the mechanism, ■ is the KL flowing to the space motor
f is the rotation speed of the space motor.

[Effect]

In the above configuration, when the multi-pin printing stain original voltage Vec drops below the lower limit voltage VCL, the space speed decreases and the drive timing period of the print head is extended.

As a result, the power consumption of the print head is reduced and a voltage drop in the power supply voltage can be prevented.

Therefore, the drive timing cycle can be suppressed within an appropriate range, and therefore, the drive control of the print head can be performed appropriately, and the above-mentioned problems can be eliminated.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit diagram showing the space system of a serial dot printer.

In the figure, M is a space motor, and this space motor M is connected between a power supply Vcc and ground via four Darlington transistors TRI, TR2, TR3°TR4.

6 is an optical encoder, and this encoder 6
is composed of a slit disk and a 7-on sensor, and has a function of optically detecting the rotational position of the space motor M.

7 is a speed recognition circuit, and this speed recognition circuit T is a circuit that differentiates the rotational position of the space motor M detected by the encoder 6 and converts it into a rotational speed.

Reference numeral 8 denotes a μCPU, which not only controls the entire printer, but also sends a signal via the Ilo boat 9 to switch the transistor TRI or TR3 at a duty according to the circuit speed of the space motor M converted by the speed recognition circuit 7. The signal can be output to the input terminal AI or B1 of the transistor TRI or TR3.

Next, the operation of the drive circuit having the above configuration will be explained.

The rotational position of the space motor M is optically detected by an optical encoder 6, and the detected rotational position is converted into a speed by a speed recognition circuit 7 and sent to the μCPU 8.

The μCPU 8 switches the switching transistor TRI or TR3 with a duty according to its speed.

Here, in order to drive the space motor M at full duty, switching transistors T R1, T
Fix R4 ON and switch transistor TR2
, TR3 are fixed to OFF, the space speed and the number of revolutions of the space motor will not exceed a certain value depending on conditions such as the power supply voltage Vcc, so the following can be said.

Switching transistor TRI and TR4 are turned on and L is turned on.
When TR2 and TR3 are turned off and current flows through the space motor M in the direction of the arrow X, if multi-pin printing is performed continuously with the print head, the power supply voltage Vcc will drop, so the motor rotation speed will decrease. Optical encoder 6
output decreases.

Even if the output from optical encoder 6 decreases, μ
Although the CPU 8 instructs the switching transistor TRI to perform full-duty switching, the motor rotation speed remains reduced by the amount that the power supply voltage Vcc has decreased, and as a result, the space speed decreases.

For example, the base (carriage) unit is 1 //
In printers where the sensor output is one pulse when moving, the dot timing control method when printing 120DPI (dots per inch) characters is to count three "-" encoder outputs and output the head drive. do.

Therefore, when the space velocity decreases as mentioned above,
The head drive timing cycle is extended.

As a result, the average power consumption of the head is reduced and the power supply voltage V
cc voltage drop can be prevented.

Therefore, focusing on the self-preventing effect of the voltage drop in the power supply voltage Vcc, a method for selecting a space motor that automatically provides feedback will be explained using the following equation.

Regarding the symbols used in the formula: Vcc: power supply voltage vd switching transistors TRI and T
Collector-emitter saturation voltage RM of R4 Winding resistance R of Ni-space motor: Resistance F Ni-space motor? Friction of the mechanism including υ Viscosity coefficient of the mechanism including the Nice Space motor Ke Induced voltage constant of the Nice Space motor Kt Torque constant of the Nice Space motor =Vd+I (Ry+R)+Ke −f ・
・・・・・・・・・・・・■ Regarding torque, ■・Kt=F+ and υ・f ・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・■［F］
■ If VCL is the minimum lower limit voltage that can drive the printing head, that is, the lower limit voltage that allows normal printing without causing dots, etc., then substitute VCL in place of Vcc in formula (■), and formula (2) is established. What is necessary is to determine the motor constant, the armature winding resistance RM, the torque constant Ktv, and the induced voltage constant Ke such that.

As a result, the speed of the space motor M does not decrease until the power supply voltage Vcc drops to the lower limit voltage VCL, and the power supply voltage V
When cc falls below the lower limit voltage VCL, the motor rotation speed decreases, the disk space speed decreases, the head drive timing period increases, the average power consumption of the print head decreases, and the voltage drop of the power supply voltage Vcc is prevented. is,
Therefore, it is possible to drive the print head appropriately without causing dot removal or the like.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the space motor has a configuration in which the motor constants, such as the winding resistance RM, the torque constant Kt, and the induced voltage constant Ke, are set to satisfy the following formula.

Therefore, when the power supply voltage Vcc falls below the lower limit voltage VcL, the motor rotation speed and space speed decrease, the head drive timing period increases, and the average power consumption of the print head decreases accordingly. , a voltage drop in the power supply voltage Vcc is prevented.

As a result, it is possible to drive the print head appropriately without causing dots, etc., and the printing quality is improved.

[Brief explanation of the drawing]

Figure 1 shows the serial dot printer according to the embodiment.
2 is a circuit diagram showing a conventional print head drive circuit, and FIG. 3 is a time chart showing output waveforms of various parts of the drive circuit. 2...Print head, 3...Drive coil, 6...
・Optical encoder, 7...Speed recognition circuit 8
...μCPU 9...I/Q boat.

Claims (1)

[Claims] 1. In a serial dot printer that prints on paper set on a platen by driving a print head that moves along the platen by driving a space motor in accordance with print data. A serial dot printer characterized in that motor constants such as a space motor winding resistance R_M, a torque constant Kt, and an induced voltage constant Ke are set to satisfy the following formula. V_c_L=V_d+[R+R_M/K_t]・F+(
K_v+K_e)・f However, V_c_L is the lower limit voltage at which the power supply voltage applied to the space motor and print head can drop and drive the print head, V_d is the collector-emitter saturation voltage of the switching transistor, R is the resistance, and F is the friction of the mechanism. , K_v is the viscosity coefficient of the mechanism, I is the current flowing to the space motor, and f is the rotation speed of the space motor.