JPH047710B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dot printer that drives a plurality of pins to form and print characters using dots, and in particular copes with fluctuations in the power supply voltage of the coil that drives the pins. The present invention relates to a voltage detection level switching method that improves the stability of printing performance and prevents a rise in temperature of the coil by changing the division printing start level.

A dot printer has a print head consisting of a plurality of pins and a plurality of coils that drive the pins, and while moving the print head in the digit direction, the desired coil is activated based on a print signal given from a control circuit. When energized, the pin strikes the paper through the ink ribbon, forming characters by dots. This excited coil is operated by being energized for a time equal to the pulse width by a driver that is turned on by a pulse. A direct current obtained by rectifying a commercial power source is usually used as a power source for supplying energy to operate the coil. Few power sources that supply this direct current are equipped with a constant voltage device due to cost considerations, and are generally of the type that supplies the rectified current to the commercial power source. Therefore, voltage fluctuations in the commercial power supply directly appear as voltage fluctuations in the DC power supply.

The energy supplied to the coil is determined by voltage and current. Therefore, when the power supply voltage decreases, countermeasures are taken to prevent the printing performance from decreasing by increasing the duration of the current supplied to the coil. In other words, a voltage fluctuation detection circuit for the power supply is provided, so that when the voltage is high, pulses with a short width are supplied to the driver that supplies excitation current to the coil, and as the voltage decreases, pulses with a longer width are supplied. controlled. However, if the voltage drops below a certain limit, the current supply time becomes too long, and the total power supplied to the coil becomes larger than when the voltage is above the limit, causing an overload of the power supply. Since the coil generates heat, which increases the temperature of the print head, split printing is used to divide the amount of energy required at one time. That is, when printing a certain character, for example, if 8 dots are to be printed at the same timing, the dots are divided into 4 dots each and the same character is printed twice.

By controlling as described above, it is possible to reduce the influence of voltage fluctuations of the commercial power supply, but depending on the width of voltage fluctuations, depending on the setting conditions of the voltage level to start split printing, the setting conditions may be frequently exceeded. This may lead to a large temperature rise in the print head and an increase in the frequency of divided printing, which may lead to a decrease in printing performance, so countermeasures are required.

[Conventional technology]

FIG. 2 is a diagram of a conventional voltage fluctuation detection circuit.

Let Vd be the DC voltage obtained by rectifying the commercial power supply, and Vs be the standard voltage. Standard voltage Vs is divided by resistor R1 and resistor R2, and operational amplifiers 1, 2, 3, 4,
5 respectively. DC voltage Vd is resistor R3 ~
The voltage is divided by R8 and applied to operational amplifiers 1 to 5, respectively. When the DC voltage Vd is high and the voltage between the terminals of resistor R8 is greater than the voltage between the terminals of resistor R2, all operational amplifiers 1, 2, 3, 4, and 5 have their respective outputs.
Send "1" to VL0, VL1, VL2, VL3, and VL4. As the DC voltage Vd decreases, the operational amplifier 5 sets the output VL4 to "0", then the operational amplifier 4 sets the output VL3 to "0", and in turn VL2,
VL1 and VL0 become “0”. Conventionally, time-division printing was started when the operational amplifier 1 set the output VL0 to "0", that is, when all the operational amplifiers 1 to 5 were turned off.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional division printing start voltage detection method, the DC voltage level at which division printing starts is fixed, so the number of dots that make up a character is large.
When a large amount of power is supplied to the coil, if the commercial power supply is relatively low, the voltage fluctuations will be large, resulting in quick split printing, which will reduce printing efficiency and cause the printing head to be energized for a long time, resulting in a temperature rise. growing. There is also the problem that the power supply becomes overloaded.

The present invention aims to solve these conventional problems.

[Means for solving problems]

The above problem is that when printing by driving a plurality of pins, when the voltage fluctuation of the DC power supply applied to the coil that drives the plurality of pins is detected and the voltage drops below a certain limit, In a dot printer that performs divisional printing, a divisional printing start voltage determination means is provided, and a divisional printing start voltage detection level detected by the divisional printing start voltage determination means is made variable based on the voltage of the DC power supply. teeth,
Voltage detection level switching according to the present invention, wherein when the voltage of the DC power supply is high, the division printing start voltage detection level is set high, and when the voltage of the DC power supply is low, the division printing start voltage detection level is set low. Solved by method.

[Effect]

That is, unlike conventional methods, the detection level of the division printing start voltage is not kept constant, but the detection level of the division printing start voltage is varied based on the voltage of the power supply, and if the input voltage is high, the voltage at which division printing is started is also increased. If the input voltage is low, the division printing start voltage is also controlled to be low.

〔Example〕

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention.

The voltage fluctuation detection circuit 6 is similar to that shown in FIG. For example, the overload output circuit 7 checks the DC power supply voltage when the printing device starts printing (for example, when the space operation starts), and outputs an output when only the operational amplifier 5 is off.
When VL4 is "0", that is, when the voltage of the DC power supply is relatively high, the operational amplifier 3 is turned off, and when the output VL2 is "0", that is, at a high voltage level, division printing starts. It is determined that the point has been reached, and the control circuit 8 is notified. Also, when the operational amplifiers 4 and 5 are off and the outputs VL3 and VL4 are "0", that is, when the voltage of the DC power supply is relatively low, when the output VL1 of the operational amplifier 2 becomes "0", That is, it is determined that the division printing start point has been reached at a low voltage level, and the control circuit 8 is notified. Further, when the outputs VL2-4 of the operational amplifiers 3-5 are "0", when the output VL0 of the operational amplifier 1 becomes "0", it is determined that the division printing start point has been reached, and the control device 8 is notified. As described above, the overload point output circuit 7 varies the division printing start voltage level according to the voltage level of the power supply detected by the voltage fluctuation detection circuit 6.

The overload point output circuit 7 operates as described above, and also outputs the outputs VL0 to VL0 of the operational amplifiers 1 to 5 to the timer 9.
The AND circuits 12 and 13 are caused to send out pulses with different pulse widths depending on the situation in step 4. That is, VL
When 4 is “0”, VL When 4 and 3 are “0”, VL
When VL2 to VL4 are "0", a pulse with a wider width is sent out in sequence when VL1 to VL4 are "0".

The control circuit 8 sends data to the data latch circuit 10 to drive a coil determined by the character to be printed. Output of data latch circuit 10 of AND circuits 12 to 13 and output of timer 9 are superimposed
The AND circuit is turned on, and the transistors TR1 to TR2 in the driver 11 are turned on.
The transistor corresponding to the circuit is driven. Therefore, among the coils connected to terminals A to B, the coil corresponding to the transistor is excited.

When the control circuit 8 receives a signal indicating that the division printing start point has been reached from the overload point output circuit 7, the control circuit 8 thins out the print data sent to the data latch circuit 10 to perform division printing.

〔Effect of the invention〕

As described above, the present invention can improve the stability of printing performance even when the power supply voltage fluctuates, prevent temperature rise of the coil, and prevent overload of the power supply.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention, and FIG. 2 is a diagram of a conventional voltage fluctuation detection circuit. In the figure, 1 to 5 are operational amplifiers, 6 is a voltage fluctuation detection circuit, 7 is an overload point output circuit, 8 is a control circuit, 9 is a timer, 10 is a data latch circuit, and 11
is the driver.

Claims (1)

[Claims] 1. When printing by driving a plurality of pins, voltage fluctuations of a DC power supply applied to a coil that drives the plurality of pins are detected, and the voltage drops below a certain limit. In a dot printer that performs divisional printing, a divisional printing start voltage determination means 7 is provided, and the detection level of the divisional printing start voltage detected by the divisional printing start voltage determination means 7 is made variable based on the voltage of the DC power supply. A voltage detection level switching method characterized by: 2. The voltage detection level switching method according to claim 1, wherein the detection level of the divided printing start voltage is set high when the DC voltage is high and set low when the DC voltage is low.