JPS63173667A - Recorder capable of maintaining constant recorded density - Google Patents

Abstract

PURPOSE:To perform inexpensive high-accuracy control, by measuring the recording pause period from the preceding recording to the present recording, and obtaining the duration of a thermal head-driving pulse for the present recording on the basis of the sum of the duration of a head driving pulse for the preceding recording and the recording pause period. CONSTITUTION:Upon the arrival of a pulse from an encoder 6, an interruption is made, and a CPU 9 starts executing a printing process routine. Then, a recording (printing) pause period T (the period from the end of the preceding recording to the start of the present recording) is calculated. Then, the value P of the duration of a head-driving pulse for the preceding recording is read from a memory 12, and is added to the pause period T to obtain a value Q, which represents the period of a driving signal. Next, a pulse duration data according to the value Q is read from a pulse duration table 10, the pulse duration data P' is set on a timer 11, and simultaneously, a new value P is stored into the memory 12. After printing data is outputted to a thermal head 4, the driving pulse is outputted from the timer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording device that achieves uniformity of recording density, and particularly to a recording device that is characterized in determining the driving pulse width of a thermal helad.

[Background of the invention]

As an image recording device using a thermal head, there is a handy type device as shown in FIG.

This is achieved by providing a running roller 2 inside the box 1 and a thermal head 4 with a thermal transfer ribbon 3 suspended on the surface of the heating element at the tip of the thermal transfer ribbon 3 to transfer the thermal transfer ribbon 3 to the heating element selected by the recorded data of the thermal head. It is configured to apply a driving pulse to generate heat, transfer the ribbon 3 to the recording paper 5 on the lower surface, and record data. Reference numeral 6 denotes an encoder for detecting the running speed (scanning speed, ie, recording speed) of the running roller 1, and the pulses detected here serve as a signal that determines the timing of recording. For example, if the running speed is fast, recording is performed at a fast speed, and if the running speed is slow, recording is performed at a slow speed. Note that although the recording device has been described here, in the case of a handy copier, a document reading section is added thereto.

Furthermore, if the recording paper 5 is thermal paper, the thermal transfer ribbon 3 is not necessary.

By the way, in a handheld recording device, the speed varies because it is moved and scanned by hand, so the pulse width (applied energy) of the head drive pulse must be adjusted to a value that corresponds to the scanning speed as well as the temperature of the head. It is necessary to control the

Therefore, conventionally, a counter 7 as shown in FIG. 5 has been used. That is, when the first pulse arrives from the encoder 6, the counter 7 starts counting the clock from the clock source 8, and when the next pulse arrives from the encoder 6, the CPU 9 reads the count value of the counter 7, and the counter 7 starts counting. is cleared to prompt the start of the next count, read pulse width data from the pulse width value table 10 according to the above count value, send it to the timer 11, and send a drive pulse with a pulse width determined by the timer 11 to the thermal head 4. was. Incidentally, since a heat generating element is selected in accordance with the print data signal before the drive pulse arrives at the thermal head 4, the selected heat generating element is driven to generate heat by the drive pulse.

Therefore, this device requires a special counter for measuring the encoder pulse period, which increases the cost and also reduces the measurement accuracy of the encoder pulse period (driving speed measurement accuracy).
In order to increase the frequency, it is necessary to increase the frequency of the clock input to Calantuff, but this requires a counter with a large number of digits to ensure the measurement range.
More expensive. Furthermore, the counter 7 described above requires an element such as a flip-flop for detecting overflow, which complicates the circuit.

[Purpose of the invention]

An object of the present invention is to eliminate the need for a counter for measuring encoder pulses, aim at lower costs, and enable highly accurate control to achieve higher quality printing.

[Structure of the invention]

To this end, the present invention, in a recording apparatus that records using a thermal head, measures the recording pause period from the previous recording to the current recording, and calculates the pulse width of the previous thermal head drive pulse and the above recording. The configuration is such that the current head drive pulse width is obtained from the value obtained by adding it to the rest period.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing the hardware configuration of one embodiment. In this embodiment, the counter 7 and clock source 8 used in FIG. 3 are unnecessary, and the head drive pulse width is determined by software. FIG. 2 is a flowchart for this purpose, and FIG. 3 is a timing chart of head drive signals.

(2) The CPU 9 executes a main routine that monitors whether the device is currently capable of printing, whether the power is turned on, etc. This includes processing to increment variable A, and the entire process is a loop. If the processing time of one loop of the main routine is t, the variable A increases by one every time. When the value of this variable A is incremented, it is checked for overflow, and if it overflows, its state is stored in the memory 12. The value of this variable A is read from the memory 12 during a print processing routine to be described later, and then cleared in preparation for the next print processing routine.

(2) When a pulse from the encoder 6 arrives, an interrupt occurs, and the CPU 9 starts executing the print processing routine.

■First, read the value of variable A from memory 12, and if it does not overflow, record it from T=A×t (
Printing) Calculate the pause period T (period from the end of the previous recording to the start of the current recording).

If variable A has overflowed, the period T is set to a preset max value.

08 Next, the value P of the drive pulse width during the previous head drive is read from the memory 12 and added to the above-mentioned period T to obtain the value Q. This value Q indicates the period of the drive signal.

(2) Read the pulse width data corresponding to the above value Q from the pulse width value table 10, and read out the pulse width data P'
is set in the timer 11, and at the same time, P(
new value).

(2) After sending the printing data to the thermal head 4, a driving pulse is sent from the timer 1 to apply printing energy. Then, when the time P' set in the timer 11 has elapsed, the drive signal is turned off.

■ Return to the main routine.

By configuring as described above, a counter for measuring the encoder pulse period is not required, the number of hardware elements is reduced, cost can be reduced, and reliability is improved. Also, since a software counter is used,
It is possible to count numerical values with any large number of digits, making it possible to measure time with high precision and a wide range. Furthermore, since the overflow of the count value is checked by software, no hardware is required, and costs can be reduced in this respect as well. Note that devices such as those described above usually use a CPU for system control, so this CPU
It is also possible to perform the above functions using a PU.

〔Effect of the invention〕

As described above, according to the present invention, a counter for measuring the encoder pulse period is not required, cost reduction is realized, highly accurate thermal head control is possible, and recording quality can be further improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the hardware configuration of an image recording apparatus according to an embodiment of the present invention, Fig. 2 is a flowchart of the recording operation, Fig. 3 is a timing chart of head drive, and Fig. 4 is a conventional image recording apparatus. FIG. 5 is a block diagram of the hardware configuration of a conventional image recording apparatus.

Claims (1)

[Claims] (1) In a recording device that records using a thermal head, measure the recording pause period from the previous recording to the current recording, and compare the pulse width of the previous thermal head drive pulse with the recording pause period described above. 1. A recording apparatus characterized in that the current head drive pulse width data is obtained from the value obtained by the sum of .