JPS61270163A - Printing-controlling circuit for dot matrix type printer - Google Patents

Abstract

PURPOSE:To obtain a stable printing operation, by a method wherein when a power source voltage is lowered below a preset level, driving timings of a dot-generating mechanism and a carriage-driving motor are lowered to preset values. CONSTITUTION:When a printing signal requiring a high dot density is outputted, electric power to be supplied to a printing head 3 is increased, and an output voltage of a power source circuit 1 is lowered. A driving circuit 5 for a dot- generating mechanism supplies the dot-generating mechanism 3 with a driving signal with a pulse width inversely proportional to the power source voltage, thereby preventing the printed density from being lowered. When the output voltage of the circuit 1 is further lowered to become lower than the preset level, a power source voltage detecting circuit 7 outputs a signal to a printing speed controlling circuit 8. On receiving the signal, the circuit 8 divides the frequency of the timing pulse from a timing pulse generating circuit 9 to 1/2 of the original value, and outputs the resultant timing pulse to the circuit 5 and a pulse motor driving circuit 10, whereby the dot-generating mechanism of a printing head 3 and the carriage-driving motor 2 are driven at a fixed speed corresponding to 1/2 of the printing timing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to print control for a dot matrix printer.

(Prior art) A dot matrix printer has a print head in which dot generating mechanisms such as print bins and heating elements are arranged vertically, and while moving in the width direction of the paper, the dot generating mechanisms corresponding to the print pattern are arranged at the printing timing. This is a device that generates dots and prints by supplying power to the dots, and the driving power to be supplied to the print head is proportional to the dot density of the print pattern.

By the way, 2. In normal character printing, only about 1/3 to 1/2 of the number of dot generating mechanisms need to be driven at the same time, so a power supply device with a capacity of about 1/2 of the power required to drive all of them is installed. This is aimed at reducing costs.

For this reason, when printing patterns that require high dot density, such as solid black patterns, the power supply from the power supply cannot keep up, causing trouble in the print head's operation or breakdown of the power supply. be.

In order to solve this problem, Japanese Unexamined Patent Publication No. 57-180
As shown in Japanese Patent No. 657, a printing method has been proposed in which the drive timing of the dot generation mechanism is changed depending on the power supply voltage, but since the printing timing always changes depending on the power supply voltage, There is a problem in that the operation of the dot generation mechanism is unstable and there is a risk of deterioration in print quality.

(Objective) In view of these problems, the present invention aims to provide a printing control device that can obtain stable printing operation by printing at a predetermined constant speed regardless of fluctuations in power supply voltage. purpose.

(Example) The details of the present invention will be described below based on illustrated examples.

Fig. 1 shows an embodiment of the present invention, and group number 1 in Fig. 1 receives power from a commercial power supply and supplies DC power to a carriage drive motor 2 and a print head 3, which will be described later. The power supply circuit consists of a power transformer 1a, a rectifier 1b, and a smoothing capacitor IC, and is configured to be able to supply 1/2 of the power required to drive all the dot generation mechanisms.
Reference numeral 2 denotes the aforementioned carriage drive motor, which moves the carriage on which the print head 3 is mounted in the axial direction of the platen in synchronization with a signal from the pulse motor drive circuit 10. Reference numeral 3 denotes a print head mounted on a carriage (not shown), which is constructed by vertically arranging a plurality of dot generating mechanisms such as print pins and heating elements. 4 is an A/D converter that converts the output voltage of the power supply circuit 1 into a digital signal, and 5 is a dot generation mechanism drive circuit, into which the signal from the line buffer memory 6 and the signal from the A/D converter 4 are input. However, a current is supplied to the dot generation R mechanism 3 of the printing head 3 for a time width inversely proportional to the power supply voltage, so that dots of a constant density are generated regardless of the power supply voltage.

Reference numeral 7 denotes a power supply voltage detection circuit, which has a set level as a lower rated voltage capable of driving the device, and is configured to output a signal when the power supply voltage falls below this set level. 8 is a printing speed adjustment circuit which divides the frequency of the timing pulse generation circuit 9 into 1/2 when the signal from the power supply voltage detection circuit 7 is input, and controls the dot generation mechanism drive circuit 5 and the pulse motor drive circuit 10. is configured to output to .

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

When a character code signal is input from a host device (not shown), this character code signal is converted into a dot pattern by a character generator and is sent to the line buffer memory 6.
is stored in When data for one line is thus stored, a print command is output, and a dot signal is output from the line buffer memory 6 to the dot generation mechanism drive circuit 5.

At this point, the power supply circuit 1 is outputting a voltage higher than the lower limit voltage, so the printing speed adjustment circuit 8 directly transmits the signal from the timing pulse generation circuit 9 to the dot generation mechanism drive circuit 5 and the pulse motor drive circuit. The print pattern is changed during the printing process, and a print signal that requires high dot density is output. When this occurs, the power to be supplied to the print head 3 increases and the output voltage of the power supply circuit 1 decreases. The dot generation mechanism drive circuit 5 supplies a drive signal having a pulse width inversely proportional to the power supply voltage to the dot generation mechanism 3 to prevent a decrease in print density. When the output voltage of the power supply circuit 1 further progresses and falls below the set level (FIG. ffi2), the power supply voltage detection circuit 7 outputs a signal to the printing speed adjustment circuit 8. In response to this signal, the printing speed adjustment circuit 8 divides the frequency of the timing pulse from the timing pulse generation circuit 9 into 172 and outputs it to the dot generation mechanism drive circuit 5 and the pulse motor drive circuit 10. The dot generating mechanism and carriage drive motor 2 are driven at a constant speed of 1/2 of the printing timing. As a result, the printing mechanism has 1/2 of the printing timing.
It operates at a constant speed and continues printing character patterns one after another while consuming power within a range commensurate with the output power of the power supply circuit l.

FIG. 3 shows a second embodiment of the present invention,
Reference numeral 11 in the figure is a power supply voltage detection circuit, which outputs a first signal when the voltage falls below a first set level whose set value is the lower limit voltage that can drive the device, and which outputs a first signal slightly higher than this first set level. The second signal is output when the voltage exceeds a second set level. 1
Reference numeral 2 denotes a printing speed adjustment circuit, which is configured to frequency-divide a timing pulse signal in response to a signal from the power supply voltage detection circuit 11 and output the divided signal.

In this embodiment, the output voltage from power supply circuit l is the first
When the frequency falls below the set level, the printing speed adjustment circuit 12 reduces the printing timing to 1/2 the frequency and continues printing at a constant speed. While this state continues, when the dot density of the pattern to be printed becomes smaller and the output voltage of the power supply circuit l starts to rise and exceeds the second set level (Fig. 4), the power supply voltage decreases. The detection circuit 11 outputs a second signal to the printing speed adjustment circuit 12. In response to this second signal, the printing speed adjustment circuit 12 outputs a pulse to the dot generating mechanism drive circuit 5 and the pulse motor drive circuit 10 at the normal printing timing, and switches to printing at the normal printing timing. According to this embodiment, it is possible to detect a decrease in print dot density and automatically switch the printing speed to normal printing timing.

In this embodiment, the printing speed when the power supply voltage decreases is set to 1/2 of the rated speed, but it goes without saying that it is sufficient to reduce the speed to a level that is in balance with the output of the power supply circuit. Nor.

(Effects) As explained above, according to the present invention, when the power supply voltage falls below a set level, the drive timing of the dot generation mechanism and carriage drive motor is reduced to a preset constant value. ,゛Printing speed is not always influenced by power supply voltage, stabilizing printing operation,
Breakdown of the power supply circuit can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention;
2 is a timing diagram showing the operation of the device shown in the above, FIG. 3 is a block diagram of the device showing another embodiment of the present invention, and FIG. 4 is a timing diagram showing the operation of the device shown in FIG. 3. be. l... Power supply circuit 2... Carriage drive motor 3... Print head

Claims (1)

[Claims] A power supply means for supplying driving power to a print head and a carriage drive motor comprising a plurality of dot generation mechanisms, a timing pulse generation means for regulating the operation timing of the print head and the carriage drive motor, and an output voltage of the power supply means. A print control circuit for a dot matrix type printer, comprising voltage detection means for outputting a signal when the voltage drops below a rated voltage, and means for reducing the frequency of the timing pulse to a preset value based on the signal from the voltage detection means. .