JPS6242861A - Apparatus for detecting trouble of thermal printer - Google Patents

Abstract

PURPOSE:To simply and exactly detect the trouble of each heat generator, by allowing a transistor for inspecting trouble to take switching operation and successively subjecting control transistors to switching operation to detect the level state of voltage generated in each heat generator. CONSTITUTION:A trouble inspecting transistor 16 is subjected to switching operation only at the time of the inspection of trouble by a power source control part 18. When the voltage level (reference voltage level) at the connection point of the resistors 19, 20 of a reference voltage generation circuit is set to VR and the voltage level at the connection point of a limit resistor 15 and each of heat generators 131-13n is set to VI, if the resistance values of resistors 15, 19, 20 are set so that the voltage level VI shifts up and down with respect to the reference voltage level VR when a certain heat generator came to an open state by trouble and, when each heat generator is normal, VR<VI is formed when the heat generator came to an open state by trouble and a high level signal is outputted from a comparator 21 and, because a microprocessor controls a data control part 17, the heat generator developing trouble can be easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a failure detection device for detecting failure of each heating element of a thermal printer.

[Prior Art] Conventionally, in order to detect a failure in each heating element in a thermal printer, a test pattern such as diagonal printing is printed, and the printed result is visually inspected.

[Problems to be Solved by the Invention] However, when the inspection is performed visually as described above, there is a problem that the inspection is time-consuming and may be overlooked.

If such an oversight occurs, when printing a barcode with this printer, the bar in that area will be poorly printed, but it is difficult to detect this at the time of printing, making it difficult for a barcode reader to read it. There was a problem in that a large number of unusable defective prints were produced.

The present invention has been made to solve these problems, and provides a failure detection device for a thermal printer that can easily and reliably detect failures in each heating element.

[Means for Solving the Problems] The present invention includes a thermal head provided with a plurality of heating elements, and a plurality of control transistors that are connected in series with each heating element of the thermal head and perform switching operations according to data. A power supply transistor connected to a DC power supply through a parallel circuit formed by connecting a plurality of series circuits of a heating element and a control transistor in parallel, and a power supply transistor connected in parallel to this power supply transistor through a limiting resistor. Consisting of a connected failure testing transistor and a level state detection means that performs a switching operation on the failure testing transistor and sequentially switches each control transistor to detect the level state of the voltage generated in each heating element. It is something that will be done.

[Function] In the present invention having such a configuration, the failure test transistor is switched during inspection, and each control transistor is sequentially switched to sequentially energize each heating element via the limiting resistor. By detecting the level of voltage generated in each heating element at the time, it is detected whether or not the heating element is malfunctioning.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the present invention will be described as applied to a measuring device.

Figure 1 is a block diagram, where 1 indicates a load cell, an amplifier, an A/
This is a weighing section consisting of a D converter.

The weighing data from the weighing section 1 is sent to 110 of the weighing device main body 2.
It is supplied to port 3. The weighing device main body 2 includes a microprocessor 4 that controls each part based on program data, a RAM (random access memory) 5 formed with a memory that stores various processing data, a printer controller 6, a display controller 7, etc. is provided. A thermal printer 8 constituting a main part of the present invention is connected to the printer controller 6, and a display 9 is connected to the display controller 7.

From the power supply circuit 10 to the microprocessor 4 and RAM
5. DC voltage is applied to each controller 6.7, thermal printer 8, display 9, etc.

The microprocessor 4 loads the weighing data inputted from the weighing section 1 into the RAM 5, edits it into print data and display data, controls the printer controller 6 to print out the print data by the thermal printer 8, and also prints out the print data using the thermal printer 8. Display data is displayed on a display 9 by controlling a display controller 7.

The thermal printer 8 has a thermal head 12 in which a plurality of heating elements 111, 112, . . . 11rL are arranged side by side as shown in FIG.
NPN type control transistors 131 and 13, respectively.
2,...13n are connected in series.

An NPN type power supply is applied to the DC voltage VPI applied from the power supply circuit 10 through a parallel circuit of a series circuit formed by connecting each of the heating elements 111 to 11rL and each of the control transistors 131 to 13n in series. A supply transistor 14 is connected thereto. An NPN type failure testing transistor 16 is connected in parallel to the power supply transistor 14 via a limiting resistor 15.

The control transistors 131 to 13n are switched based on data by a data control section 17 that latches serial or ATA signals input from the printer controller 6 controlled by the microprocessor 4. That is, during normal operation, the control signal C8 from the printer controller 6
The control transistors 131 to 13n are simultaneously switched based on the data latched by +, and the control transistors 131 to 13n are sequentially switched based on the data latched by the control signal C82 from the printer controller 6 during failure inspection. Operate switching.

The power supply transistor 14 is a power supply control section 18 to which a control signal C83 from the printer controller 6 controlled by the microprocessor 4 is input.
The switching operation is performed during normal data printing, and the failure testing transistor 16 is operated by the power supply control section 1.
8, the switching operation is performed only when inspecting for a failure.

Further, the DC voltage VP2 applied from the power supply circuit 10
A reference voltage generation circuit formed by connecting resistors 19 and 20 in series is connected to the reference voltage generating circuit. A comparator 21 compares the voltage level (reference voltage level) VR at the connection point between the resistors 19 and 20 of the reference voltage generating circuit with the voltage level Vr at the connection point between the limiting resistor 15 and each heating element 131 to 13n. ing. That is, the reference voltage level vR is input to the inverting input terminal (-) of the comparator 21, and the level Vr is input to the non-inverting input terminal (-) of the comparator 21.
+) has already been entered. The reference voltage level vR is the DC voltage vP1 when each of the heating elements 111 to lln is normal.
is set to a higher level than the voltage level divided by the limiting resistor 15 and one of the heating elements 111 to 11n.

The comparator 21 supplies its comparison output to the microprocessor 4 via the blink controller 6.

In the embodiment of the present invention having such a configuration, the reference voltage level vR generated from the reference voltage generation circuit is VR-VF6 XR2o/(Rla +R20).
...■ becomes. Note that Rla is the resistance value of the resistor 19, and R2[1 is the resistance value of the resistor 20.

Further, the voltage level v■ at the connection point between the limiting resistor 15 and each heating element 111 to lln is V■= ((Vp+ -VT2-VTII)XRa/(
RrL+Rs ) ) +VT a −■. Note that VT2 is the voltage between the collector and emitter of the failure testing transistor 16, ■TrL is the voltage between the collector and emitter of the control transistor during switching operation, and R
a is the resistance value of the heating element, and R6 is the resistance value of the limiting resistor 15.

The above equation 0 can be simplified as VI -kl XI/ (1+R6/R11)+ and 2.
・・■ Tonaru. However, kl 4; tVp I -V72-V7
2 in n% is vTn.

Here, the range of resistance values Rn of the heating elements 111 to 11n is Rr
If Lmin≦Rn≦Rn1Ilax, the heating element is broken [
7. If the difference between the voltage level vrop when the circuit is open and the voltage level Vr when it is normal is ΔvI, then VIop- + XI/ (1+Rs/Rnop) Rs (Rn
o p), ΔvI is ΔVI = kl XR
6/ (R5+Rn) -■, and at least ΔVI = + in the open state and normal state of the heating element.
A potential difference of XRs/(Rs +Rn max ) will occur.

Therefore, if the resistance values of each resistor 15, 19, and 20 are set so that the voltage level v■ increases or decreases with respect to the reference level vR due to this potential difference, then when the heating element malfunctions and becomes an oven, VR<VI. A high level signal is output from the comparator 21 and supplied to the microprocessor 4.

Therefore, the microprocessor 4 can easily and reliably know from the signal from the comparator 21 whether or not the heating elements 111 to 11n are out of order. Furthermore, since the data control unit 17 is controlled by the microprocessor 4, it is possible to know which heating element is currently being checked, and a malfunctioning heating element can be easily detected.

In addition, in the embodiment, the control transistors 131 to 13
Failure detection was carried out by sequentially switching the control transistors to energize the heating elements one by one, but the invention is not necessarily limited to this. Failure detection may be performed in groups by operating and energizing a plurality of heating elements at the same time, or failure detection may be performed for all of them at once. Of course, in this case, the level of reference voltage vR is changed accordingly.

Next, another embodiment of the invention will be described with reference to the drawings.

Note that the same parts as in the above embodiment are given the same reference numerals and detailed explanations will be omitted.

As shown in FIG. 3, a two-contact changeover switch 31 and an A/D converter 32 are provided in place of the reference voltage generation circuit and comparator 21, and one fixed contact 311 of the changeover switch 31 is connected to the VPI terminal. , the other fixed contact 312
is connected to the connection point between the limiting resistor 15 and each heating element 111 to 11n, and the common contact 31c is connected to the A/D converter 32.
is connected to the input terminal of The A/D converter 32 converts the input voltage level into a digital signal and supplies it to the microprocessor 4 via the printer controller 6.

In such a configuration, the selector switch 31 is first switched to one of the fixed contacts 311, and the microprocessor 4 reads a digital signal corresponding to the DC voltage vP1. Next, the changeover switch 31 is switched to the other fixed contact 312 side, and each control transistor 131 to 13n is sequentially switched by the data control unit 17 to obtain the voltage level v.
I is converted into a digital signal by the A/D converter 32 and read by the microprocessor 4.

By calculating the ratio of the digital signal corresponding to the voltage level vP and the digital signal corresponding to the voltage level vl in the microprocessor 4, it is possible to determine whether the heating element under test is normal or in an oven state. A short circuit can be easily detected. Also,
When compared using digital signals in this way, considerable accuracy can be obtained, so even if the heating element to be inspected is in contact with an adjacent heating element, it can be detected.

Also, first connect the changeover switch 31 to one of the fixed contacts 311
Since the digital value corresponding to the DC voltage VPI is obtained by switching to It is possible to detect faults with high accuracy.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a thermal link failure detection device that can easily and reliably detect failures of each heating element.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show an embodiment of this invention.
FIG. 1 is a block diagram showing the circuit configuration of a measuring device, FIG. 2 is a diagram showing the circuit configuration of a main part, and FIG. 3 is a diagram showing a circuit diagram of a main part showing another embodiment of the present invention. 4... Microprocessor, 8... Thermal printer, 111-lln... Heating element, 12... Thermal head, 131-13n... Control transistor, 1
4... Transistor for power supply, 15... Limiting resistor, 16... Transistor for failure inspection, 19.20...
- Resistor, 21... Comparator, 31... Selector switch, 32... A/D converter.

Claims (1)

[Claims] A thermal head provided with a plurality of heating elements, a plurality of control transistors each connected in series with each heating element of the thermal head and switched in accordance with data, and a DC power source connected to the heating elements and the control transistor. A power supply transistor connected through a parallel circuit formed by connecting multiple series circuits in parallel, a failure testing transistor connected in parallel to this power supply transistor via a limiting resistor, and a failure testing transistor connected in parallel to the power supply transistor through a limiting resistor. failure of a thermal printer, characterized in that the thermal printer is equipped with level state detection means for switching the control transistors, and sequentially switching the respective control transistors to detect the level state of the voltage generated in each of the heating elements; Detection device.