JPH079691A - Apparatus for detection of abnormality of thermal head - Google Patents

Abstract

PURPOSE:To prevent preliminarily abnormality from being generated by detecting whether the abnormality of a thermal head is generated or not by providing a comparison means wherein a drop in voltage of a heating element to which electric power is supplied is compared with a threshold voltage and when both values being in a specific voltage relation is detected, an abnormality-generated signal is emitted. CONSTITUTION:When electric power is supplied, and if a heating element (r1) is damaged, in the case of a wire-broken state, a drop in voltage of the element (r1) is not generated. Then, a voltage VEC to a contact EC comes to be almost equal to that of a power source VDD. Further, since a comparator OP of an abnormality detection circuit compares the voltage VEC with a threshold voltage VTH, and emits an output at a high voltage level, a detection data DEC of a theoretical value H indicating occurrence of the abnormality is transferred to a central control circuit MPU. Besides, when the element (r1) is normal, a drop in voltage of the element (r1) is generated. Therefore, the voltage VEC at the contact EC comes to be lower than the threshold voltage VTH, an output of the comparator OP comes to be at a low voltage level, and the detection value DEC of a theoretical value L indicating the normal state is transferred to the central control circuit MPU.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting device for detecting the presence / absence of an abnormality in a thermal head, and more particularly to independently detecting the occurrence of an abnormality in a heating resistor provided for dot printing. The present invention relates to an abnormality detection device for detecting.

[0002]

2. Description of the Related Art A thermal head has a large number of heating resistors of several tens μm to hundreds of tens μm installed on an insulating substrate.
The Joule heat generated by selectively energizing these heating resistors is transferred to thermal paper or transfer film to print characters and pictures as a mosaic of dots. Is applied to a wide range of recording devices such as measuring instruments, printers for various terminals, and automatic ticket vending machines at stations.

By the way, in such a thermal head, since each heating resistor generates a high-temperature heat pulse, it has excellent temperature resistance and has high reliability such as low abrasion due to sliding and high mechanical strength. Sex is required. Furthermore, high-speed printability is required such that a short thermal time constant can be set and a heat pulse that can be printed on a thermal paper in a short time can be generated. Further, good print quality is required.

In order to satisfy such requirements, conventionally, the manufacturer of the thermal head supplier has improved the material of the heating resistor, structural improvement including the insulating substrate, and method of arranging the heating resistor. And driving methods have been improved.

[0005]

However, even in the thermal head which has been improved in this way,
Under continuous circumstances, it is inevitable that abnormalities such as characteristic deterioration and failures cannot be avoided under continuous driving conditions.

Therefore, manufacturers, etc., who implement various recording devices by incorporating such a thermal head, have an automatic monitoring system that can prevent the occurrence of abnormality of the incorporated thermal head, and once In the event of an occurrence, there is a demand for a device configuration that can promptly deal with it. In particular, in a device applied to various kinds of work for a customer, it is extremely important for quick processing of work and execution of reliable work.

[0007] As an example, a thermal head installed in an automatic ticket vending machine installed on the premises of a station or the like needs to perform prompt ticket sales processing to an extremely large number of users due to the nature of ticket sales. High-speed and high-quality printing is performed while maintaining the state of maximum operating capacity for a long time, and the frequency of occurrence of abnormality increases. This is clear from the fact that there have been many users who have experienced blurring due to print crushing or blurring when purchasing a ticket. In many cases, the cause of such unclear printing is thermal or mechanical damage to the heating resistor of the thermal head. Therefore, in a field such as an automatic ticket vending machine, which has a time limit such as targeting a large number of customers, abnormality detecting means for preventing such a situation of occurrence of abnormality is extremely important. Particularly in recent years, the high-speed rail network represented by the Shinkansen has been developed and high-priced express tickets are being issued under unmanned management. If a blank ticket is released or a ticket with an unknown date is issued, the passengers and the transportation will be in a great deal of confusion. It is an object of the present invention to provide an abnormality detection device capable of reliably detecting whether or not an abnormality has occurred in a thermal head and preventing the abnormality from occurring.

[0008]

In order to achieve such an object, the present invention provides a plurality of heat generating resistors by supplying power from a power source according to dot information to be dot-recorded. Targeting a thermal head abnormality detection device applied to a thermal head for dot recording by Joule heat generated in the above, dot information specifying one or more heating resistors to detect an abnormality among the plurality of heating resistors Generating means, driving means for supplying power only to the heating resistor to be abnormally detected from the power source according to the dot information, and a voltage drop of the powered heating resistor as a threshold voltage. In comparison, when it is detected that the voltage drop has a predetermined voltage relationship with the threshold voltage,
It is configured to include a comparison unit that generates a detection signal indicating that an abnormality has occurred.

[0009]

With such a configuration, the specific heating resistor is energized based on the dot information corresponding to each heating resistor,
If the voltage drop of the specific heating resistor due to the energization is different from the voltage drop during normal operation by comparison with a predetermined threshold voltage, a detection signal of abnormality occurrence is output.
Therefore, it is possible to independently detect the characteristic deterioration and damage of the heating resistor. In addition, depending on the dot resolution such as printing, the plurality of heating resistors are simultaneously energized to detect abnormalities from changes in the voltage drop at that time, or one or more heating resistors that are frequently used. It is a technology with extremely excellent versatility that can be applied to various detection methods such as detecting abnormalities.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a thermal head abnormality detecting device according to the present invention will be described below with reference to the drawings. First, the structure will be described with reference to FIG. 1. This thermal head is formed on an insulating substrate in a row along the longitudinal direction thereof.
It has zero minute heating resistors r _{1 to} r ₃₂₀ , and further driver circuits DR _{1 to} DR ₄ for independently energizing these heating resistors r _{1 to} r ₃₂₀ , and these driver circuits DR. Multiplexer circuits M _{1 to} M ₄ that select and transfer 320-bit dot data D _{1 to} D ₃₂₀ for instructing energization to _{1 to} DR ₄ and 320-bit data to these multiplexer circuits M _{1 to} M ₄ . Dot data D _{1 to} D
A 320-bit shift register (serial input parallel output shift register) SR for transferring ₃₂₀ in parallel, and a line-type thermal head unitized by forming a control circuit and an abnormality detection circuit described later on the same insulating substrate. Has become. Then, it is driven by a central control unit MPU such as a microprocessor connected through a connection terminal group provided in this unitized thermal head.

The configuration will be further described in detail. The above control circuit
A monostable multivibrator MB, two-input AND gates AN _{1 to} AN ₄ , a thermistor TM provided on the insulating substrate in the vicinity of the heating resistors r _{1 to} r ₃₂₀ , and a P-type MOS.
The FET Tr ₀ is provided.

Here, the monostable multivibrator MB
Is supplied with the trigger data T _G , the capacitive element C _τ
Strobe data STB that becomes a logic "H" in a time width determined by the resistance R _τ and the resistance value R _TM of the thermistor TM, that is, τ = 1 / C _τ (R _τ + R _TM ).
To occur. Since the resistance value R _TM changes according to the temperature of the insulating substrate, the time constant τ also changes, and at the same time, the time width of the strobe data STB also changes. AND gate AN
_{1 to} AN ₄ are active data E _{1 to} E ₄ and strobe data STB input from the central control unit MPU.
AND data (hereinafter referred to as select data) S ₁
~ S ₄ are generated and the corresponding multiplexer circuits M are generated.
Supply to select terminals _{1 to} M ₄ . As it is apparent from the figure, strobe data STB and active data E ₁ to E ₄ is at the logical "H", the select data S ₁ to S ₄ is logic "H". P-type MOSFET T
r ₀ is turned on when the power control data P applied to the gate terminal is logic “L”, so that the power supply V _DD
Drive power is supplied to the driver circuits DR ₁ to DR ₄ from
When it is a logic "H", it is turned off to cut off the supply of drive power.

Next, the shift register SR sequentially serially inputs and parallel outputs dot data D _S transferred bit by bit in synchronization with the clock data CK, and at the same time, synchronizes with the input latch data LH. Then, the parallel outputs are latched in parallel to generate 320-bit dot data D _{1 to} D ₃₂₀ . Although not shown, 320 built in the shift register SR
A group of D-type flip-flops for bits performs the above-mentioned latch.

Of the four multiplexer circuits M _{1 to} M ₄ , the first multiplexer circuit M ₁ is the first to the eighth multiplexer circuits.
During the period in which the dot data D _{1 to} D _{80 of} up to 0 bits are input in parallel and the select data S ₁ of logic “H” is supplied, these dot data D _{1 to} D ₈₀ are parallel to the first driver circuit DR ₁ . Forward. The second multiplexer circuit M ₂ receives the dot data D _{81 to} D _{160 of the 81st} to 160th bits in parallel and supplies the dot data D _{81 of} the logic “H” during the period in which the select data S ₂ is supplied.
_{81 to} D ₁₆₀ are transferred in parallel to the second driver circuit DR ₂ . The third multiplexer circuit M ₃ receives the dot data D _{161 to} D _{240 of the 161st} to 240th bits in parallel and supplies the dot data D _{161 of the} logic “H” during the period in which the select data S ₃ is supplied. ~ D ₂₄₀ third
In parallel to the driver circuit DR ₃ . The fourth multiplexer circuit M ₄ receives the dot data D _{241 to} D _{320 of the 241st} to 320th bits in parallel and supplies the dot data D _{241 of the} logic “H” during the period in which the select data S ₄ is supplied. ~ D ₃₂₀ is the fourth driver circuit D
Transfer to R ₄ in parallel.

Therefore, if each logical value of the 4-bit active data E _{1 to} E ₄ is arbitrarily set, all the multiplexer circuits M _{1 to} M ₄ can be designated at the same time, or individually designated. You can also do it. That is, it is possible to select the dot data D _{1 to} D ₃₂₀ by dividing the dot data into 4 by 80 bits and transfer the selected dot data to the corresponding driver circuits DR ₁ to DR ₄ .

The four driver circuits DR _{1 to} DR ₄ also have a division structure corresponding to the multiplexer circuits M _{1 to} M ₄ , and inside of each of them is controlled to be turned on / off by dot data D _{1 to} D ₃₂₀ . For example, 320 N-type MO
SFET is built-in, multiplexer circuit M ₁ ~
The drive power is supplied only to the corresponding heating resistor via the N-type MOSFET which is designated and turned on by each dot data D _{1 to} D ₃₂₀ transferred from M ₄ .

FIG. 2 shows a more detailed configuration example of the multiplexer circuits M _{1 to} M ₄ and the driver circuits DR _{1 to} DR ₄ .
First multiplexer M ₁ and first driver circuit DR ₁
The configuration is shown as a representative.

In FIG. 2, the multiplexer M ₁ is supplied with the _first select data S ₁ at one input terminal and the dot data D _{1 to} D ₈₀ are correspondingly input at the other input terminal. 80 2-input AND gates m ₁ ~
It is composed of m ₈₀ . The driver circuit DR ₁ is composed of 80 N-type MOSFETs Tr _{1 to} Tr _80. These MOSFETs Tr _{1 to} Tr ₈₀ are supplied with the outputs of the corresponding AND gates m _{1 to} m ₈₀ to their gates, and have their drains. It is connected to the drain of a P-type MOSFET Tr ₀ for power supply, and each source has heating resistors r _{1 to} r _80.
Is connected to. The remaining multiplexers M _{2 to} M ₄ and the driver circuits DR _{2 to} DR ₄ also have the same circuit configuration.

Referring again to FIG. 1, in the above-mentioned abnormality detection circuit, the non-inverting input terminal is a P-type MOSFET for power supply.
A comparator OP which is connected to the drain of Tr ₀ (hereinafter, referred to as a detection contact EC) and whose inverting input terminal is applied with a divided voltage (hereinafter, referred to as a threshold voltage) V _TH by the resistors R ₁ and R _2. , A D-type flip-flop DFF for waveform shaping the output of the comparator OP into binary logic detection data D _EC . Then, the detection data D _EC, the voltage V _EC detection contact EC is a logical value indicating the abnormality when the V _EC ≧ V _TH "H", and the logical value indicating normal when the V _EC <V _TH " L ". In addition, D-type flip-flop D
FF is reset data RST from the central control circuit MPU.
Is supplied to reset the internal state.

Next, the operation of the embodiment having such a configuration will be described. First, the most basic operation of dot printing will be described with reference to FIG. For example, such a thermal head is applied to a thermal printer built into a ticket vending machine at a station, and after recording information such as the fare amount and the date of use on the original thermal paper coated with a thermal layer, the passengers get a ticket. In the case of issuing a ticket as described above, the arrangement direction of the heating resistors r _{1 to} r ₃₂₀ is the main scanning direction, and the direction orthogonal to the heating resistors r _{1 to} r ₃₂₀ (the direction in which the thermal paper is relatively moved) is It is in the sub-scanning direction. FIG. 3 shows the recording operation in the one main scanning period T _H.

First data input period T_INAt Schiff
Register SR from the central control circuit MPU bit by bit
Data D transferred to the_SClock data C
Serial input in synchronization with K and dot for 320 bits
Data D₁~ D₃₂₀Enter to continue. here,
Dot data corresponding to the dot recording area is a logical value
"H", the dot data corresponding to the part not recorded is logical
It is set to the value "L". Further, one main scanning period T_HThen
The power control data P becomes the logical value "L", and the P-type MOSF
ET Tr₀Set to ON state. Next, shift register
Star SR is 320 bits of dot data D₁~ D
₃₂₀Is input, the latch data LH of logical value "H"
When supplied, these are latched and
Comb circuit M ₁~ M₃₂₀Transfer in parallel to.

In the next recording period T _WT , first, the single pulse-shaped trigger data T _G having the logical value “H” and the active data E ₁ having the logical value “H” almost in the recording period T _WT .
~ E ₄ is output from the central control circuit MPU. And
The monostable multivibrator MB synchronizes with the trigger data T _G and has a logical value "H" in a time width corresponding to the time constant τ.
And outputs strobe data STB
The D gates AN _{1 to} AN ₄ obtain the logical product of the strobe data STB and the active data E _{1 to} E _4, and output select data S _{1 to} S ₄ .

Although the timing chart of FIG. 3 shows the case where all the multiplexer circuits M _{1 to} M ₄ are designated by setting all the active data E _{1 to} E ₄ to the logical value “H”, Only a part of the active data E _{1 to} E ₄ is set to the logical value “H”, and the multiplexer circuit M ₁
It is also possible to specify a part of ~ M ₄ .

In this way, when the select data S _{1 to} S ₄ are supplied to the multiplexer circuits M _{1 to} M ₄ , the multiplexer circuit M selected by the select data S _{1 to} S ₄ is selected.
_{1 to} M ₄ drive dot data D _{1 to} D ₃₂₀ to drive circuit D
The heating resistors corresponding to the dot data transferred to R _{1 to} DR _{4 and} having the logical value “H” in the dot data D _{1 to} D ₃₂₀ (that is, corresponding to the heating resistors r _{1 to} r ₃₂₀ ). Object) to generate Joule heat and dots are recorded.

After the dot recording in one main scanning period T _H is completed, the thermal paper is moved in the sub scanning direction by a predetermined distance and the same process as in FIG. 3 is performed again. By repeating the scanning process, two-dimensional dot recording becomes possible.

[0026] Incidentally, as the resistance value R _TM of the thermistor TM is changed according to the temperature change of the thermal head, since the time width of the strobe data STB outputted from the monostable multivibrator MB is changed, the heating resistor r ₁ ~
The driving power supplied to r ₃₂₀ is automatically controlled according to the temperature change of the thermal head, and the heating resistor r ₁ to
The destruction of r ₃₂₀ is prevented and the dot recording in the optimum temperature state is maintained. Incidentally, when the temperature of the thermal head rises, the time width of the strobe data STB becomes shorter and the driving power decreases. On the contrary, when the temperature of the thermal head drops, the time width of the strobe data STB becomes longer and the driving power increases. To do.

Next, the operation of abnormality detection, which is the main part of the present invention, will be described with reference to FIG. The operation of detecting the abnormality is performed in an arbitrary free time or the like that does not hinder the dot recording (see FIG. 3). In this example,
The abnormality inspection period T _{CHK in} FIG. 4 is _{equal to} one main scanning period T in FIG.
It is set to the same time as _H.

First, in the data input period T _IN of FIG. 4, 320 bits of dot data D _S are input to the shift register SR as in the case of dot recording. However, at this time, only the dot data corresponding to the heating resistor for which the presence or absence of the abnormality occurrence should be detected has the logical value “H”,
The dot data D _{1 to} D ₃₂₀ that makes the remaining dot data a logical value “L” are input to the shift register SR. Further, during the abnormality inspection period T _CHK , the power control data P becomes the logical value “L”, and the P-type MOSFET Tr ₀ is held in the ON state.

As a typical example, the case of detecting the abnormality of the heating resistor r ₁ will be described. In the period from the beginning to the 319th cycle of the clock data CK, the dot data D _S are all logical values “L” and last. Becomes the logical value "H" in the 320th cycle of, and these are latched in the shift register SR in synchronization with the latch data LH becoming the logical value "H".

Next, in the period T _WT , first, the trigger data T _G is supplied to the monostable multivibrator MB, and at the same time, a multiplexer circuit (that is, M _{1 to} M ₄₎ corresponding to the heating resistor to be detected as an abnormality. AND) of active data E _{1 to} E ₄ of logical value for selecting
It is supplied to the gates AN _{1 to} AN ₄ .

According to the above-mentioned representative example for detecting the abnormality of the heating resistor r ₁ , only the active data E ₁ has the logical value "H".
Becomes Then, as shown in FIG. 4, the monostable multivibrator MB generates the strobe data STB, and the AND gates AN _{1 to} AN ₄ obtain the logical product of the active data E _{1 to} E ₄ and the strobe data STB. Then, the select data S ₁ having the logical value “H” and the select data S _{2 to} S ₄ having the logical value “L” are output. Therefore, according to the representative example, power is supplied only to the heating resistor r ₁ .

When power is supplied in this way,
If the heating resistor r ₁ is broken and has a broken wire, the voltage drop of the heating resistor r ₁ will not occur.
As shown in the case (1) in FIG. 4, the voltage V _{EC of the} contact EC is
Becomes almost equal to the power supply V _DD (24V), and further, the comparator OP of the abnormality detection circuit detects the voltage V _EC and the threshold voltage V
_{Since a} high voltage level output is generated by comparing with _TH , the detection data D of the logical value "H" indicating the occurrence of an abnormality
_{The EC} is transferred to the central control circuit MPU. On the other hand, if the heating resistor r ₁ is normal, a voltage drop occurs in the heating resistor r ₁ , so as shown in case (2) in FIG.
The voltage V _{EC of} C becomes lower than the threshold voltage V _TH , the output of the comparator OP becomes a low voltage level (ground level), and the detection data D of the logical value “L” indicating the normal state is sent to the central control circuit MPU. _EC is transferred.

[0033] Then, the central control unit MPU is, by depending on the reception of the detection data D _EC logical value "H", for controlling the alarm device provided in advance (e.g., such as an alarm buzzer or a display), abnormal By instructing the monitoring personnel or the like of the occurrence of the above, the sale can be stopped, and the issuance of blank tickets and tickets with unclear printed contents can be prevented and early repair can be performed.

In this embodiment, only one kind of threshold value V _TH set in the comparator OP is provided, but a plurality of kinds of threshold values having different levels are set and these threshold values are set. The degree of characteristic deterioration of the heating resistor may be detected by sequentially comparing the threshold value and the voltage V _{EC of the} contact EC.

Further, for the sake of explanation, the abnormality detection of the heating resistor r ₁ has been described as a representative, but the abnormality detection of other heating resistors can be realized by the same processing.

Further, it is possible not only to detect the abnormality of the heating resistors one by one, but also to detect the abnormality of the heating resistors collectively. That is, by arbitrarily changing and setting the respective logical values of the dot data D ₁ to D ₃₂₀ to be set in the shift register SR during anomaly detection, it is possible to set the various aspects of the abnormality detection, the abnormality detection processing It is an extremely versatile technology that can deal with both the shortening of the time and the detailed detection of abnormalities.

Furthermore, in this embodiment, a so-called positive logic circuit structure is applied, but a negative logic circuit structure may be used. Further, the thermal head provided with 320 heating resistors per line has been described, but the present invention is not limited to this, and the present invention can be applied to a thermal head provided with an arbitrary number of heating resistors.

[0038]

As described above, according to the present invention,
Selection means for generating dot information designating one or more heating resistors to detect anomaly among the plurality of heating resistors, and power from the power source to the heating resistor to be anomaly detected according to the dot information. Comparing the voltage drop of the heating means supplied with the driving means and the power supply with the threshold voltage, and detecting that the voltage drop has a predetermined voltage relationship with respect to the threshold voltage, Since the constitution is provided with the comparison means for generating the detection signal indicating the occurrence of the abnormality, it is possible to individually and finely detect the characteristic deterioration and damage of the heating resistor. Further, it is also possible to detect an abnormality for each of the plurality of heat generating resistors according to the dot resolution such as printing. As described above, since various inspection modes can be obtained depending on how to set the dot information generated by the selection unit, it is possible to reliably detect the presence or absence of an abnormality in the thermal head and prevent the abnormality from occurring. It is possible to provide a highly versatile technique suitable for various applications.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an example.

FIG. 2 is a circuit diagram showing in more detail the main part configuration of FIG.

FIG. 3 is a timing chart for explaining the operation of the circuit shown in FIG. 1 during dot recording.

FIG. 4 is a timing chart for explaining an operation of the circuit shown in FIG. 1 at the time of abnormality inspection.

[Explanation of symbols]

r _{1 to} r ₃₂₀ ... Heating resistor, DR _{1 to} DR ₄ ... Drive circuit, M _{1 to} M ₄ ... Multiplexer circuit, SR ... Shift register, AN _{1 to} AN ₄ ... AND gate, Tr ₀ , T
r _{1 to} Tr ₈₀ ... MOSFET, MB ... Monostable multivibrator, TM ... Thermistor, OP ... Comparator, R
₁ , R ₂ ... Dividing resistance, DFF ... D-type flip-flop,
MPU ... Central control circuit.

Claims (1)

[Claims] 1. A thermal head abnormality detection device for a thermal head, which supplies electric power from a power source to a plurality of heating resistors in accordance with dot information to be dot-recorded and performs dot recording by Joule heat generated in each heating resistor. A selection means for generating dot information designating one or more heating resistors to detect an abnormality among the plurality of heating resistors, and the heating resistor to be detected abnormally from the power source according to the dot information. The voltage drop of the driving means for supplying power only to the body and the heating resistor to which the power is supplied is compared with a threshold voltage, and the voltage drop has a predetermined voltage relationship with the threshold voltage. A thermal head abnormality detection device, comprising: a comparison unit that generates a signal indicating that an abnormality has occurred.