JPH05169707A - Recording apparatus - Google Patents

Abstract

PURPOSE:To detect defect or deterioration of a heat evolutional resistor which influences on the quality of an image without being influenced by fluctuation of the value of the initial resistance of the heat evolutional resistor and with better accuracy than a conventional case and to attempt to improve reliability. CONSTITUTION:A printer control CPU 22 obtains the value of an output of an A/D converter 21 on each heat evolutional resistor 11 by switching a relay 16 for switching a driving electric source e.g. when an electric source is on and printing is not performed e.g. during feeding papers. In addition, the printer control CPU 22 calculates the absolute value of the difference in the values of resistance between the heat evolutional resistor 11 of the adjoining image element from the value of A/D conversion on each heat evolutional resistor 11 and compares successively it with the standard value and when it is larger than the standard value, it is judged that defect etc., occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device used for various printing.

[0002]

2. Description of the Related Art In recent years, in a recording apparatus, a heating resistor of a thermal head has been made smaller to achieve higher resolution, a resistance value of the heating resistor varies, heat accumulated in the heating resistor, environmental temperature, etc. By compensating for the uneven density due to the influence, it is possible to improve the image quality.

In the heat generating resistor of the thermal head, the resistance value gradually increases from the initial value during the life period,
Eventually, the wire breaks, but as the resistance value increases, the heat generation energy decreases, so the recording density also decreases, and uneven density occurs in the recorded image. Further, even when a minute foreign substance having a high hardness is caught between the thermal head and the recording medium and a defect occurs in the heating resistor, the resistance value of the heating resistor also increases and the degree of the defect increases. In severe cases, the wire will be disconnected.

If printing is performed in the state where such a defect of the heating resistor has occurred, a printed matter having streak-like defects will be generated. For this reason, for example, a switch such as a relay is provided between the thermal head drive power supply terminal and the drive power supply, and during normal printing, the thermal head drive power supply terminal and the drive power supply terminal are directly connected to each other, and the At the time of diagnosis, a circuit in which a resistor is inserted between both terminals is connected, N heat generating resistors are sequentially energized and driven, and the voltage between the resistor and the thermal head at this time, that is, the thermal head drive power supply. There has been proposed a recording apparatus including a detection unit that compares a voltage between terminals with a reference voltage by a comparator and detects a defect of a heating resistor.

[0005]

By the way, in the case of a sublimation type thermal transfer printer, the recording density is controlled by the heat energy of the heat generating resistors, and when there is a difference in the resistance value of each heat generating resistor, energization drive is performed. A difference occurs in heat generation energy at the time, and uneven recording density occurs. For example, if a defect occurs in one heating resistor and the difference in the resistance value between the heating resistor of the adjacent pixel becomes large, the density of the defective pixel becomes thin, resulting in streaky density unevenness. It becomes remarkable as the resistance value increases.

On the other hand, the heating resistor of the thermal head is
Generally, there is a resistance value variation of about ± 20%, but the one having a large resistance value difference between adjacent pixels is excluded at the time of manufacturing because the recording density difference is remarkable. However, as a whole, there is a variation in the resistance value of about ± 20%, so when detecting a defect of the heating resistor with the above-described conventional recording device, the threshold value of the comparator, that is, the reference voltage is
It is necessary to set the value in consideration of the initial resistance value variation. For this reason, it is possible to detect only a defect in which the increase in resistance value is extremely remarkable. For example, when a defect in which the resistance value does not increase significantly occurs in the heating resistor, this defect cannot be found, and the streak pattern cannot be detected. There was a problem that printing with uneven density was performed.

The present invention has been made in consideration of such a conventional situation, and defects such as a defect or deterioration of the heating resistor which affects the recording image quality are influenced by the variation in the initial resistance value of the heating resistor. It is therefore an object of the present invention to provide a recording apparatus that can detect with higher accuracy than before and can improve reliability.

[0008]

That is, according to the recording apparatus of the present invention as set forth in claim 1, a plurality of regularly arranged heating resistors and by selectively energizing and driving the heating resistors, Energization control means for generating thermal energy for recording, diagnostic drive means for sequentially energizing the heating resistors for self-diagnosis, and resistance value of each heating resistor when energized by the diagnostic driving means And a means for determining the quality of the heating resistor by comparing the difference between the resistance values of the adjacent heating resistors measured by the resistance value measuring means. Characterize.

According to a second aspect of the present invention, there is provided a plurality of heating resistors arranged regularly, and the heating resistors are selectively energized and driven to generate thermal energy for recording. Generating means, a diagnostic driving means for sequentially energizing the heating resistors for self-diagnosis, and a resistance value measurement for measuring the resistance value of each heating resistor during energization driving by the diagnostic driving means. Means and storage means for storing an initial resistance value of each of the heating resistors,
It is characterized by further comprising means for comparing the result measured by the resistance value measuring means with the initial resistance value stored in the storage means to judge the quality of the heating resistor.

[0010]

In the recording apparatus of the present invention having the above-described structure, the heating resistors are sequentially energized and driven by the diagnostic driving means, and the resistance value of each heating resistor is measured from the drive current value of the heating resistor by the resistance value measuring means. .. Then, the quality of the heating resistors is determined by comparing the differences in the resistance values of the adjacent heating resistors, or by measuring the initial resistance value and the measured resistance value stored in the storage means. ..

Therefore, a defect or deterioration of the heating resistor that affects the recording image quality can be detected more accurately than before without being affected by the variation in the initial resistance value of the heating resistor, and the reliability can be improved. It is possible to improve the sex.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a main structure of a recording apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 10 shows a thermal head. In the thermal head 10, N heat generating resistors 11 are linearly arranged on an insulating substrate. Then, the same number of N 1's as those of the heating resistors 11
The pixel signals of the lines are serially input to the pixel signal input terminal 12 and read into the N shift registers 13 in the same number as the heating resistors 11.

The pixel signals read into the shift register 13 are the data signals connected to the respective heating resistors 11.
It is supplied to the drive circuit 14 including a latch circuit and a switching element such as an FET, and the drive circuit 14 is selectively driven according to a pixel signal. As a result, a current is supplied from the thermal head drive power supply 15 to the heating resistor 11, causing the heating resistor 11 to generate heat in accordance with the pixel signal and performing predetermined printing.

The heat generation energy of the heat generating resistor 11 is determined by the resistance value of the heat generating resistor 11, the supplied current and the energization time. When a sublimable ink ribbon or the like is used and the transfer density difference is used for gradation expression. The heat energy is controlled by adjusting the energization drive time. Therefore, when a defect occurs in one pixel of the heating resistor 11 and the resistance value increases, the heating energy becomes smaller than that in the peripheral pixels, and the defective pixel becomes thinner than the desired transfer density. For example, in uniform density, it appears as streaky density unevenness.

Therefore, the recording apparatus of the present embodiment is provided with the following self-diagnosis mechanism, and is constructed so that defects or deterioration of the heating resistor 11 can be found out. ..

That is, the drive power source switching relay 1 is provided between the thermal head drive power source 15 and the heating resistor 11.
6 is provided to supply electric power to the heating resistor 11 and the thermal head drive power source 15 and the self-diagnosis constant voltage circuit 17
It is configured so that it can be switched to and. Further, the self-diagnosis constant voltage circuit 17 is provided with a drive current detection resistor 18 for detecting a current supplied from the self-diagnosis constant voltage circuit 17 to the heating resistor 11.
Further, a control signal generation circuit 19 is connected to the shift register 13 and the drive circuit 14 as a means for sequentially energizing the heating resistor 11 dot by dot.
Then, the voltage drop of the drive current detection resistor 18 that occurs when the heating resistor 11 is driven dot by dot is determined by the amplifier circuit 2
It is configured to be detected by 0, converted into a digital signal by the A / D converter 21, input to the printer control CPU 22, and stored in the memory.

The printer control CPU 22 performs the self-diagnosis by switching the drive power source switching relay 16 to obtain the output value of the A / D converter 21 when the power source is turned on or when printing is not performed, such as during paper feeding. .. Since this value is almost equivalent to the resistance value of the heating resistor 11, in the recording apparatus of this embodiment, the difference in the output value of the A / D converter 21 is considered to be the difference in the resistance value of the heating resistor 11. And the printer control CP
U22 uses each A / D converted value to generate each heating resistor 11
The absolute value of the difference between the resistance value of the adjacent pixel and the heating resistor 11 is calculated, and compared sequentially with the reference value. If the difference is larger than the reference value, it is determined that a defect or the like has occurred, and a display not shown is shown. Display on the display and interrupt the operation.

As described above, in the recording apparatus of this embodiment, the resistance value of each heating resistor 11 is measured, the absolute value of the difference between the resistances of the adjacent pixels and the heating resistor 11 is calculated, and the absolute value of the difference is used as the reference value. Since the occurrence of defects and the like is diagnosed by comparison, even if there is a variation in the initial resistance value of about 20% for the entire heating resistor 11, the resistance value of the heating resistor 11 can be increased regardless of this. It is possible to detect the defect, and it is possible to detect the defect or deterioration of the heating resistor 11 that affects the recording image quality more accurately than in the conventional case. In the above embodiment, the absolute value of the difference between the resistance values of the adjacent heating resistors 11 was obtained. However, in a recording device that requires high image quality,
In order to compensate for the difference in resistance value due to variations in initial resistance value,
For example, the energization time is controlled for each heating resistor 11 to reduce the difference in recording density. In such a case, the difference in resistance value between the heating resistors 11 of adjacent pixels in the initial stage is large. Since the object is also accepted, there arises a problem that the reference value of the difference in resistance value has to be large.

In such a case, for example, as shown in FIG. 2, the initial resistance values of all the heating resistors 11 are stored in a memory such as the ROM 30 and the A / D conversion is taken into the printer control CPU 22. The absolute value of the difference between the resistance value obtained from the value and the initial resistance value is sequentially compared with the reference value in the same manner as in the previous embodiment, and if it is larger than the reference value, it is determined that a defect has occurred. Configure as follows. As a result, defects or deterioration of the heating resistor 11 can be detected more accurately than before without being affected by variations in the initial resistance value of the heating resistor 11.

[0021]

As described above, according to the recording apparatus of the present invention, the defect or deterioration of the heating resistor that affects the recording image quality is affected by the variation in the initial resistance value of the heating resistor. Instead, the detection can be performed more accurately than in the conventional case, and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of a recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a main configuration of a recording apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 10 Thermal Head 11 Heating Resistor 12 Pixel Signal Input Terminal 13 Shift Register 14 Drive Circuit 15 Thermal Head Drive Power Supply 16 Drive Power Supply Switching Relay 17 Self-Diagnosis Constant Voltage Circuit 18 Drive Current Detection Resistor 19 Control Signal Generation Circuit 20 Amplifier Circuit 21 A / D converter 22 Printer control CPU

Claims (2)

[Claims] 1. A plurality of heating resistors arranged regularly, an energization control unit for generating thermal energy for recording by selectively energizing and driving the heating resistors, and the heating resistor. Is sequentially driven for self-diagnosis by a driving means for diagnosis, a resistance value measuring means for measuring a resistance value of each heating resistor at the time of energization driving by the driving means for diagnosis, and a resistance value measuring means. A recording apparatus, comprising means for comparing the resistance values of the heating resistors adjacent to each other to determine the quality of the heating resistors. 2. A plurality of heating resistors arranged regularly, an energization control unit for generating thermal energy for recording by selectively energizing and driving the heating resistors, and the heating resistor. Diagnostic drive means for sequentially energizing for self-diagnosis, resistance value measuring means for measuring the resistance value of each heating resistor during energization driving by the diagnosing driving means, and the initial resistance of each heating resistor A storage unit for storing a value; and a unit for comparing the result measured by the resistance value measuring unit with the initial resistance value stored in the storage unit to determine the quality of the heating resistor. A recording device characterized by the above.