JPS6027563A - Recorder - Google Patents

Abstract

PURPOSE:To equalize the densities of recording without the power source of recording being complicated by a method in which the supply of the electric power of recording to a recording element is ended at a time when the amount of power actually supplied to the recording element coincides with a reference power amount. CONSTITUTION:A recording power source 7 uses a constant-voltage power source in general. The voltage of the power source, however, is varied transiently when the recording power is supplied. If the variation is not occurred, the amount of recording power could be linearly raised, as shown by broken line from the startup time t0 of recording to coincide with reference recording power amount at the time t1, but the recording power amount raises along the curve of full line with the transient variation of the voltage of power source. When the supply of recording power is interrupted at the time t1, the recording power amount runs short and sufficient recording density is not obtained. The amount of recording power amount actually supplied is measured by a measuring circuit 8, and a coincidence signal (a) is sent out at the time t2 when the measured amount coincides with the reference recording power amount to interrupt the supply of recording power. The unevenness of recording density can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording apparatus that records an image by supplying recording power to a recording element.

Conventional configuration and problems A thermal recording device supplies recording power from a power supply to a heating element (recording element) corresponding to a black pixel in an image signal, and performs thermal recording using the Joule heat generated by the heating element. Image signals are recorded by coloring the paper or by transferring ink or dye from thermal transfer paper to plain paper. Therefore, when the amount of recording power applied to the heating element changes, the recording density changes.

Now, in such a conventional thermal recording device, by using a constant voltage power source as a power source (hereinafter referred to as a recording power source) for supplying recording power to a heating element, recording can be performed while suppressing fluctuations in recording power amount. Efforts are being made to make the concentration uniform. However, even though it is a constant voltage power supply, transient fluctuations in the power supply voltage occur when the load current changes, and the width of the fluctuation in the power supply voltage and the time during which the power supply voltage fluctuates (hereinafter referred to as transient time) occur.
is the number of black pixels recorded simultaneously due to the magnitude of the load current,
(proportional to the black rate of the image signal). Since such fluctuations in the power supply voltage range and transient time result in fluctuations in the amount of recording power applied to the heating element, there has conventionally been a problem in that the recording density changes depending on the black ratio of the image signal.

In particular, in recent high-speed thermal recording devices, since the recording time approaches the transient time, it is no longer possible to ignore recording density unevenness due to transient fluctuations in the power supply voltage.

It is conceivable to deal with such problems by further increasing the voltage stability of the recording power source, further suppressing the fluctuation width of the power source voltage, and further shortening the transition time. However, this causes the recording power source to become more complex, larger, and more expensive, resulting in another problem in that the recording apparatus becomes larger and more expensive.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and aims to provide a recording device that achieves uniform recording density without complicating the recording power source, increasing its size, or increasing cost. shall be.

Structure of the Invention The present invention measures the amount of recording power supplied from the recording power source to the recording element by the driving means or an amount related thereto using a measuring means based on the output voltage (power supply voltage) of the recording power source, and calculates the measured amount. The above-mentioned object is achieved by comparing the comparison means with the reference amount and causing the drive means to terminate the supply of recording power to the recording element when a matching signal is output from the comparison means.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a thermal recording device according to an embodiment of the present invention. 1 is the input terminal for the image signal P1X, 2 is the input terminal for the start pulse ST, and 3 is the reference recording power amount R.
This is the input terminal of F.

Reference numeral 4 denotes a thermal recording head, which comprises a heating element play 6 in which a plurality of heating elements as recording elements are arranged, and a drive circuit 6 for driving each heating element.

7 is a recording power source for supplying recording power to the heating element. Reference numeral 8 denotes a measuring circuit for measuring the amount of recording power supplied to the heating element; It is comprised of a ROM 10 to which an output signal is input as an address signal, and an accumulator 11 that accumulates the output value of the ROMtO. 12 is a digital comparator, which compares the value of the output signal of the accumulator 11, that is, the recording power amount measured by the measuring circuit 8, and the reference recording power amount input from the input terminal 3, and when they match, outputs a match signal. Output.

Next, the operation will be explained. The image signal PIX to be recorded is transferred to the input terminal 1 from the outside. This image signal is sequentially taken and stored in a shift register provided inside the drive circuit 6 in an appropriate amount. Inside the drive circuit 6, there is a heating element play 6.
A plurality of switching elements are provided for opening and closing current paths between each heating element and the recording power source 7.

When the transfer of the image signal to be recorded in one recording operation is completed, a start pulse ST is input. The drive circuit 6 uses the start pulse 2 as an opportunity to turn on the switching element of the heating element corresponding to the black pixel of the image signal. This results in
The recording power source 7 starts supplying recording power to the heating element corresponding to the black pixel. On the other hand, the analog/digital converter 9 samples the power supply voltage at a sufficiently short constant period, and the sampled value is converted into a digital signal and read out, which is accumulated by the accumulator 11. In addition,
The accumulator 11 is cleared by a start pulse ST. Further, R is the resistance value of the heating element. Therefore, the value of the accumulator 11 corresponds to the amount of recording power supplied to the heating element array from the time when the start pulse 2 was input.

If the recording power amount measured by the measuring circuit 8 is smaller than the reference recording power amount, the digital comparator 12 does not send out the coincidence signal a (makes the coincidence signal a L level), but if the former is greater than the latter, Output the coincidence signal a (set the coincidence signal a to H level). When the coincidence signal a is generated (when it becomes H level), the drive circuit 6 turns off the switching element,
Cut off the supply of recording power to the heating element.

The above operation will be further explained with reference to the waveform diagram in FIG. 2 and the characteristic diagram in FIG. 3.

The recording power supply 7 generally uses a constant voltage power supply, but the power supply voltage fluctuates transiently as shown in FIG. 2 when recording power is supplied. If there were no such fluctuations, the recording power amount would rise linearly from the recording start time to as shown by the broken line in Figure 3, and would match the reference recording power amount at time t1, but due to the transient Due to the fluctuation, the recording power amount increases along the solid curve in FIG. Therefore, if the supply of recording power is cut off at time t1, the amount of recording power will be insufficient and sufficient recording density will not be obtained. Furthermore, since the rising curve of the recording power amount changes depending on the magnitude of the load current of the recording power source 7 and the number of black pixels in the -1 pixel signal, the recording density changes depending on the number of black pixels.

However, in this embodiment, the measuring circuit 8 measures the amount of recording power actually supplied, and at time t2 when the measured amount matches the reference recording power amount, a coincidence signal a is generated to stop the supply of recording power. Therefore, such recording density unevenness no longer occurs.

Furthermore, since it is no longer necessary to suppress fluctuations in the power supply voltage so strictly, a relatively simple and inexpensive power supply can be used as the recording power source.

In this embodiment, the measurement circuit 8 is configured as a digital circuit, but it can also be configured as an analog circuit. However, in that case, the digital comparator 12 must be replaced with an all-analog comparator, or the digital comparator 12 must be replaced with an analog comparator.
It is necessary to provide an analog/digital converter between the measurement circuit 8 and the measurement circuit 8.

Furthermore, although this embodiment has a configuration in which the recording power amount is measured by the measurement circuit 8, it is also possible to use a configuration in which the cumulative value (time integral value) of the power supply voltage is measured as an approximate value. In this case, the error in the recording power amount increases, but the R of the measuring circuit 8
The advantage is that the OM10 can be omitted or a simple analog integration circuit can be used as the measurement circuit.

Further, although the above embodiment is a thermal recording apparatus, the present invention can be applied to recording apparatuses using other recording methods as appropriate.

Effect of the invention As mentioned above, the present invention was actually applied to a recording element.

A comparator is used to compare the measured amount with a reference amount, such as the cumulative value of recording power or power supply voltage.When the comparison results in a match, the supply of recording power to the recording element is terminated. Because it is possible to obtain a uniform recording density without having to suppress the fluctuations so strictly, the effect is that the recording power source can be simplified, downsized, and cost reduced, and the recording device can be downsized and cost reduced. You can get

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recording apparatus according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram of the same apparatus, and FIG. 3 is a characteristic diagram showing temporal changes in recording power amount. 4...Thermal recording head, 6...Heating element array, 6...Drive circuit, 7...Recording power supply, 8...Measurement circuit, 12...Digital comparator. Name of agent Patent attorney Toshio Nakao I'i or 1 name 〒 −-＋／＋7、＋／＋

Claims (1)

[Claims] a recording power source, a recording element, a driving means for supplying recording power to the recording element from the recording power source, and an amount of recording power supplied to the recording element or an amount having a specific relation thereto;
Measuring means for measuring based on the output voltage of the recording power source;
Comparing means compares the measured amount of the measuring means with a reference amount and outputs a matching signal when a match is found, and the driving means drives the recording element when receiving the matching signal from the comparison signal. A recording device characterized by stopping the supply of recording power.