JPS62280053A - Thermal recorder - Google Patents

Abstract

PURPOSE:To obtain a stable high quality recording without an unevenness of density by a simple processing, by a method wherein when an uneveness of density is detected to be generated, a width value of a pulse applied to a heating element is corrected only for said particular record. CONSTITUTION:A temperature detection part 3 of a thermal head monitors the temperature of a heating part and transmits the temperature information of the ambience of an heating element during heating by application of current to a recorded control part 1. When an uneveness of density is detected to be generated in the next recording, said purport is transmitted to the record control part 1 by a density unevenness generation detecting part 21. The record control part 1 transmits temperature information and recording pulse width value alteration information to a width value correction means 22. The width value correction means 22 calculates correction data of a density unevenness corresponding to the temperature information and transmits said correction data to a record pulse control part 5. When an application pulse of a suitable pulse width value is outputted from a gate circuit 7 via a protection circuit 6 by the record pulse control part 5, it is inputted to gate circuits 8-11 selectively controlled by a drive control part 2, and outputted to a heating element at a selected printing position. Thus, the unevenness of recording density caused by the shortage of the heating amount of the heating element is corrected.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Application Field The present invention is directed to heating a plurality of heating elements constituting a thermal head by applying electricity to heat-sensitive recording paper that is brought into contact with the heating elements. The present invention relates to a thermal recording device that performs recording.

Conventional technology 2, -7 This kind of conventional thermal recording device, as shown in FIG.
A recording control section 1 that controls the heating of a plurality of heat generating elements constituting a thermal head, a thermal head drive control section 2 that controls the order of energization and heating of the heat generating elements (order of application of printing pulses), and the heat generating elements. a thermal throat temperature detection unit 3 that detects the temperature of the surrounding area (hereinafter referred to as the temperature of the heat generating part);
A recording pulse width value memory 4 stores a recording pulse width value corresponding to the heat generating part temperature, and a recording pulse width value memory 4 stores a recording pulse width value corresponding to the heat generating part temperature information from the recording control section 1.
A recording pulse control unit 5 that outputs a recording pulse having a pulse width value extracted from the recording pulse in a hardware manner, a thermal head protection circuit 6 that prevents destruction of the heating element caused by abnormal application of the recording pulse, and the circuit thereof. A gate circuit 7 outputs a recording pulse from the recording pulse control section 5 based on the output information of the thermal head drive control section 2, and a gate circuit 7 outputs a recording pulse from the recording pulse control section 5 based on the output information of the thermal head drive control section 2. The recording control section 1 is provided with gate circuits 8 to 11 for outputting pulses, and the recording control section 1 is connected to a thermal circuit 31,-.

By taking out the recording pulse width value corresponding to the heat generating part temperature information from the Rad temperature detection section 3 from the recording pulse width value memory 4 and supplying the recording pulse having the pulse width value to the recording pulse control section 5, a constant The configuration is such that a print pulse (recording pulse with a constant width value) is applied to the heating element.

Problems to be Solved by the Invention However, with this configuration, apart from the case where recording is performed at a uniform speed from the leading edge to the trailing edge, recording may be stopped frequently, such as in a thermal recording device of a facsimile communication machine. When recording is repeatedly performed at non-uniform speeds, especially when the stop period is long, the temperature of the heat generating part decreases, making it impossible to restart recording under the same temperature conditions as the previous recording. That is, when recording is restarted, the amount of heat generated by the heating element is insufficient in order to perform recording in the same state as the previous recording, and the recording density is lower than during the previous recording. Due to this decrease in density, unevenness in recording density and so-called white spots a and b occur as shown in FIG. 5, which causes a decrease in both values. in short,
The conventional apparatus described above does not have a function of detecting and correcting unevenness in recording density caused by the decrease in density.

Therefore, in order to prevent the concentration from decreasing, there is a method of always preheating the heat generating element to prevent the temperature of the heat generating part from decreasing, but this method has various problems listed below. , cannot be a fundamental solution.

(1) Constant heating is required, which places a burden on the power supply section.

(2) The control process becomes complicated unless the previous recording state is memorized and the preheating is controlled accordingly.

(3) The configuration of the peripheral circuit for the processing becomes complicated;
This increases the board area and costs.

The present invention has been made in view of the above-mentioned problems, and it is possible to detect and correct recording density unevenness (including so-called white spots) with simple processing, thereby making it possible to perform high-quality recording. The purpose of the present invention is to provide a heat-sensitive recording device with the following features.

Means 5A for Solving the Problem: In order to achieve the above-mentioned object, the present invention includes a density unevenness occurrence detection section, and when density unevenness occurrence is detected by this detection section,
A recording pulse width value correction means is provided for correcting the width value of the recording pulse in accordance with heat generating part temperature information, and the recording pulse having the corrected width value corresponding to the density unevenness correction is outputted from this means. The main points are as follows.

In the present invention, when the density unevenness occurrence detecting section detects that density unevenness occurs during the next recording (resuming recording), the correction means adjusts the normal recording pulse width to the density according to the heat generating part temperature information. Calculations are performed to correct (change) by the amount of unevenness correction, and density unevenness correction data (recording pulse width value for density unevenness correction) resulting from the calculation is supplied to the recording pulse control section.

As a result, a recording pulse having a pulse width value necessary for correcting density unevenness is outputted to the output gate circuit, and the insufficient amount of heat generated by the heating element is compensated for. Therefore, even when recording and stopping are frequently repeated and recording is performed at uneven speeds,
It becomes possible to record at a uniform density from the incisal to the posterior trench at a uniform speed of 611.7 degrees.

Embodiment FIG. 1 is a schematic configuration diagram showing an embodiment of a thermal recording apparatus according to the present invention. This apparatus includes a recording control section 1 and a thermal head drive control section similar to those shown in FIG. 2. Thermal head temperature detection section 3, Recording pulse control section (input information is different from conventional devices) 5. Thermal head protection circuit 6
, and gate circuits 7 to 11, a density unevenness occurrence detection section 21 is newly connected to the recording control section 1, and the density unevenness detection section 21 is connected between the recording control section 1 and the recording panel control section 5. A configuration in which recording pulse width value correction means 22 is connected in series to correct the width value of the recording pulse in correspondence with heat generating part temperature information when the occurrence of density unevenness is detected by the unevenness occurrence detection section 21. It consists of

The density unevenness occurrence detection section 2] includes a recording line number counter 211, a recording data buffer monitoring section 212, and a recording pulse width switching control section 213, and includes 17.
- Before recording a line, there may be density unevenness or so-called white spots (see a and b in Figure 5) in the recording, which is a cause of deterioration in image quality on the recording surface (referred to as density unevenness in this specification). The counter 211 and the buffer monitoring unit 212 detect whether density unevenness occurs, and when the occurrence of density unevenness is detected, the switching control unit 21 instructs that the recording pulse width should be switched to the optimum value.
It has a function of transmitting the information to the recording control section through the recording control section 3.

The recording pulse width value correction means 22 includes a recording pulse width value memory 221 in which recording pulse width values corresponding to the linear density during recording and the temperature of the thermal head (heating part temperature) are stored in a table, and A recording correction pulse width value memory 222 in which pulse width values for correction corresponding to the temperature are stored in a table; an arithmetic unit 223 for calculating a pulse width value (density unevenness correction data) necessary for correcting density unevenness based on the value, in correspondence with heat generating part temperature information when density unevenness occurs, which is given from the recording control unit 1; It consists of

FIG. 2 is a timing chart of signals in each part of the thermal recording device having the above-described configuration.
The print pulse output waveform is shown when a pulse width value necessary to correct density unevenness is added.

Next, the operation of the apparatus shown in FIG. 1 will be explained.

The thermal head temperature detection unit 3 monitors the temperature of the heat generating part,
Information on the temperature of the surrounding heating element (thermal head) being heated by electricity is transmitted to the recording control unit 1.

On the other hand, when the density unevenness occurrence detection section 21 detects that density unevenness occurs during the next recording, it notifies the recording control section 1 to that effect (change in the width value of the recording pulse). The information and the recording pulse width value change information are transmitted to the recording pulse width value correction means 22.

The width value correction unit 22 calculates density unevenness correction data corresponding to the temperature information, and transmits the correction data (width value of the recording pulse) to the recording pulse control unit 5.

The recording pulse control unit 5 generates the width of the pulse to be applied to the heating element based on the correction data, and gates the applied pulse (recording pulse having a pulse width value outside the density unevenness correction). Output to circuit 7.

At this time, if the pulse width of the applied pulse outputted from the recording pulse control section 5 is larger than the specified value, there is a risk of destroying the heating element, so an appropriate pulse is applied via the thermal head protection circuit 6. The width value is applied to the gate circuit 7.
It is designed to output more.

The applied pulses having the appropriate pulse width value outputted from the gate circuit 7 are inputted to the gate circuits 8 to 11 which are selectively controlled by the thermal hendo drive control section 2 which operates based on the commands from the recording control section 1. It is output to the heating element at the selected printing location.

In this way, an application pulse with a pulse width value that compensates for the lack of heat generation of the heat generation element due to a decrease in the temperature of the heat generation part is appropriately applied to the heat generation element at the printing location, thereby eliminating uneven recording density due to the lack of heat generation of the heat generation element. Corrections are made. As a result, as shown in FIG. 3, stable high-quality recording without density unevenness can be obtained.

However, when the density unevenness occurrence detection section 21 does not detect the occurrence of density unevenness (normal case), the recording pulse width value correction means 22 adjusts the recording pulse width value according to the temperature information from the recording control section 1. Select a pulse width value corresponding to the temperature information (temperature of the heat generating part) from the table in the memory 221, and output it to the recording pulse control unit 5 as is (without performing calculation with the pulse width value in the other memory 222). do. In short, in the so-called normal state where no density unevenness occurs, the values on the table in the recording pulse width value memory 221 are used, and those in the other recording correction pulse width value memory 222 are not used.

Effects of the Invention As is clear from the above explanation, the present invention is limited to recording when density unevenness is detected.
7. By correcting the width value of the applied pulse (recording pulse) applied to the heating element (thermal head), it is possible to correct the recording that occurs due to insufficient heat generation of the heating element due to a decrease in the temperature of the heating element. Since it is designed to correct density unevenness, it has the effect that stable, high-quality recording without density unevenness can be obtained with simple processing.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of a thermal recording device according to the present invention, FIG. 2 is a timing chart of signals of each part in the device shown in FIG. 1, and FIG. 3 is a thermal head according to the present invention. 4 is a block diagram showing the schematic configuration of a conventional thermal recording device. FIG. 5 is a characteristic diagram showing the relationship between temperature and recording density of a thermal head based on the conventional device. It is a characteristic diagram. DESCRIPTION OF SYMBOLS 1... Recording control part, 3... Thermal head temperature detection part, 2... Recording pulse control part, 21... Density unevenness occurrence detection part, 211... Recording line number counter, 212...
...Record data buffer monitoring unit, 213...Record pulse width switching control unit, 22...Record pulse width value correction means, 221...Record pulse width value memory, 222...Record correction pulse width value Memory, 223... calculation unit. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] Before recording one line, there is a density unevenness detection section that detects whether or not density unevenness occurs in the recording, and when this detection section detects that density unevenness occurs, it detects the density. recording pulse width value correction means for determining a pulse width value for correction of unevenness in correspondence with heat generating part temperature information;
A thermal recording apparatus characterized in that an application pulse having the pulse width value determined by the correction means is applied to a heating element of a thermal head.