JPH05193178A - Line thermal printer - Google Patents

Abstract

PURPOSE:To accurately detect a medium to be printed regardless of the kind thereof, upgrade the printing quality and reduce erroneous operation. CONSTITUTION:A paper feed sensor 55 detecting the presence of a medium to be printed and a paper top detecting sensor 56 are provided and the sensor outputs of both sensors 55, 56 are compared with a slice level by a comparator to output a comparison result. An operation panel 66 is provided in order to indicate the kind of the medium to be printed and the slice level is altered corresponding to the kind of the medium to be printed. Even when the medium to be printed is replaced, the printing position on the medium to be printed becomes accurate and the superposition of colors can be also accurately performed. Further, the energy applied to a thermal head 1 can be altered according to the kind of the medium to be printed. In this case, the pulse width of a strobe signal is altered according to the kind of the medium to be printed and the energy applied to the thermal head 1 becomes proper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line thermal printer provided with a sensor control device for accurately performing a printing operation.

[0002]

2. Description of the Related Art Conventionally, in a line thermal printer, a thermal head constructed by arranging a large number of heating resistance elements in a line is made to face a print medium on a platen via an ink ribbon, and Is selectively driven to perform printing.

FIG. 2 is a schematic diagram of a conventional line thermal printer. In the figure, 1 is a thermal head for printing, 42 is a platen for sandwiching the print medium 43 and the ink ribbon 44 to apply pressure to the thermal head 1 at the time of printing, and 45 is a supply side core of the ink ribbon 44. Four
Reference numeral 6 is a winding side winding core of the ink ribbon 44. Also, 4
Reference numerals 8 and 49 denote pressure rollers for winding the print medium 43 around the platen 42. Reference numerals 50 and 51 denote the print medium 43 supplied from the paper cassette 52 by the hopping roller 54 to the platen 42 and the pressure roller 48.
A registration roller for feeding between 49, a paper feed sensor 55 for detecting the beginning of the print medium 43, and a paper feed sensor 56.
In the case of color printing, is a paper top detection sensor for detecting the head of the printing medium 43 when back feeding and superimposing each color.

Each of the paper feed sensor 55 and the paper top detection sensor 56 is composed of a light emitting element and a light receiving element. The light receiving element detects the light emitted by the light emitting element and reflected by the print medium 43. The print medium 43 is detected. In the line thermal printer having the above-described configuration, the print medium 43 and the ink ribbon 44 are supplied between the platen 42 and the thermal head 1, and the thermal head 1 is operated in accordance with print data to heat the ink ribbon 44. The ink of the ink ribbon 44 is melted and transferred to the print medium 43.

Then, three or four color inks are transferred in the order of Y (yellow), M (magenta), C (cyan) or Y, M, C, Bk (black) in the order of frame, and the color of Printing is possible. FIG. 3 is a circuit block diagram for operating a conventional line thermal printer.

In the figure, 1 is a thermal head, 21 is a microprocessor, read only memory (ROM),
A control unit including a random access memory (RAM), a timer, etc., 22 is an interface line for inputting print data from an external device, 23 is an I / O port for controlling the thermal head 1, the motor 24, etc. And is connected to the control unit 21 by a common bus 25.
The motor 24 is driven by a motor driver circuit 26 connected to the I / O port 23.

FIG. 4 is a block diagram showing the structure of a conventional thermal head. In the figure, reference numeral 10 denotes a shift register circuit (SR), which receives a data (DATA) signal for one line serially input and stored in synchronization with a clock (CLOCK) signal. 11 is a latch circuit (LT)
That is, the DATA signal stored in the shift register circuit 10 is fetched by inputting a pulse by the latch (LATCH) signal.

Further, r ₁ , r ₂ , ..., R _m are m heating resistance elements arranged in the line direction, which are divided into n blocks to form m dots. Output data of the latch circuit 11 and strobe (STB) signals (STB1, STB2, ..., STBn) for each block
Is input to the NAND circuit 12 to take a logical product, and as a result, the heating resistance elements r ₁ , r ₂ , ..., R _m are selectively energized to generate heat.

Next, the operation of the line thermal printer having the above structure will be described. FIG. 5 is an operation time chart of the conventional line thermal printer. In the figure, when the motor 24 (FIG. 3) is driven, the i-1 line to the i
The print-receiving medium 43 (FIG. 2) is sent to the line and printing of the i-line is started. At this time, the DATA signal is transferred to the shift register circuit 10 (FIG. 4) in synchronization with the CLOCK signal.

Then, the shift register circuit 10 has 1
When the DATA signals for the lines are stored, a short pulse is input to the LATCH signal, and the DATA signal stored in the shift register circuit 10 is taken into the latch circuit 11. Next, the STB signal with a constant pulse width is sequentially transmitted in time division for each block, and the corresponding NAND
The output of the circuit 12 is set to low level and the heating resistance elements r ₁ , r
₂ , ..., R _m are made to generate heat. In this case, only the latch circuit 11 outputting a high level signal generates heat.

By the above operation, the printing operation for one line is completed, and thereafter the same operation is continuously performed for the characters,
Graphics etc. are printed.

[0012]

However, in the above-described conventional line thermal printer, the paper feed sensor 55 and the paper top detection sensor 56 regardless of the type of the print medium 43, whether it is plain paper or OHP. However, the sensor detection level varies depending on the surface state of the print-receiving medium 43, and the line thermal printer malfunctions or an incorrect printing operation is performed.

Further, under the condition that the print duty is high, O
In the case of printing on the HP, in the latter half of the printing, printing may be performed on the non-printed portion due to the excess heat storage energy, so-called printing dripping may occur, or wrinkles may occur on the ink ribbon 44. When printing on plain paper, the print density may decrease. The present invention solves the above problems of the conventional line thermal printer,
An object of the present invention is to provide a line thermal printer capable of accurately detecting a print medium regardless of the type of the print medium and performing printing with high printing quality and less malfunction.

[0014]

Therefore, in the line thermal printer of the present invention, the ink of the ink ribbon is transferred to the print medium by sandwiching the ink ribbon and the print medium between the thermal head and the platen. Is becoming A sensor for detecting the presence / absence of the print medium is provided, and the comparator compares the sensor output from the sensor with the slice level and outputs the comparison result.

Designating means is provided for designating the type of the printing medium, and the slice level is changed according to the type of the printing medium. Further, the energy applied to the thermal head is changed depending on the type of print medium. Therefore, a shift register circuit that stores a data signal for one line, a latch circuit that takes in the data signal in the shift register circuit, a plurality of heating resistance elements arranged in the line direction, and each block of the heating resistance element Strobe signal generating means for generating a strobe signal,
Means are provided for selectively energizing the heat generating resistance element in response to the output data of the latch circuit and the strobe signal.

When the type of the printing medium is designated by the designating means, the pulse width of the strobe signal is changed according to the type of the printing medium.

[0017]

According to the present invention, as described above, the ink ribbon and the print medium are sandwiched between the thermal head and the platen,
When the ink ribbon is heated, the ink is transferred to the print medium. A sensor for detecting the presence / absence of the print medium is provided, and the comparator compares the sensor output from the sensor with the slice level and outputs the comparison result.

Designating means is provided for designating the type of the printing medium, and the slice level is changed according to the type of the printing medium. Therefore, even if the print medium changes and the sensor output from the sensor changes, the presence or absence of the print medium can be accurately detected. Further, the energy applied to the thermal head can be changed depending on the type of print medium.

A data signal for one line is stored in the shift register circuit, and the data signal in the shift register circuit is taken in by the latch circuit. on the other hand,
A plurality of heating resistance elements are arranged in the line direction, and a strobe signal is generated for each block of the heating resistance elements. Upon receiving the output data and the strobe signal of the latch circuit, the heating resistance element is selectively energized to heat the ink ribbon.

When the type of the print medium is designated by the designating means, the pulse width of the strobe signal is changed according to the type of the print medium. Therefore, more energy than necessary is not applied to the thermal head, and the energy does not run short.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of a line thermal printer showing an embodiment of the present invention. In the figure, 23 is an I / O port for controlling the thermal head 1, the motor 24, and the like. The motor 24 is
It is driven by a motor driver circuit 26 connected to the / O port 23. Further, 66 is an operation panel for designating different print target media such as plain paper and OHP depending on the operator, 67 is a microprocessor for performing a printing operation based on the input from the operation panel 66, and 68 is plain paper and Data of the applied energy of the thermal head 1 set for each of the OHPs, and the sensor detection circuit 6
ROM storing data for switching 9
70 is a port for receiving the output of the sensor detection circuit 69 and transmitting it to the microprocessor 67. Further, 55 is a paper feed sensor, and 56 is a paper top detection sensor.

FIG. 6 is a detailed diagram of the sensor detection circuit, and FIG. 7 is a detection state diagram of the sensor detection circuit. In the figure, a, b
Is a signal for changing the slice level of the paper feed sensor 55 (FIG. 1) and the paper top detection sensor 56 depending on the type of the print medium 43 (see FIG. 2), and selectively turns on the switching transistors Tr1 and Tr2. Turn off. In this case, when plain paper is designated, the signal a goes high and the signal b goes low, turning on the switching transistor Tr1 and turning on the switching transistor Tr1.
2 is off. When OHP is designated, the signal a goes low and the signal b goes high, turning off the switching transistor Tr1 and turning on the switching transistor Tr2. c is a sensor output signal of the paper feed sensor 55 and the paper top detection sensor 56.
It is read from M68. Further, d is a comparator CMP for the slice level corresponding to the signal c and the printing medium 43.
It is a signal showing the result of comparison in 1. The signal d is input to the microprocessor 67 via the port 70.

Reference numerals 73 to 75 are resistors having resistance values R1, R2 and R3, and have a relationship of R1 / R3> R2 / R3. R1 / R3 is a resistance ratio for setting a slice level when plain paper is designated as the print medium 43 and the switching transistor Tr1 is turned on, and R2 / R3 is a switching transistor Tr2 when OHP is designated. This is the resistance ratio for setting the slice level when is turned on.

When plain paper is designated in the line thermal printer having the above-mentioned structure, when the light emitting elements of the paper feed sensor 55 and the paper top detecting sensor 56 emit light, the reflectance of the plain paper is high, so that the light receiving element receives a large amount. As a result, the voltage of the signal c, that is, the sensor output V becomes high as shown in FIG. On the other hand, when OHP is designated, a part of the light emitted from the light emitting element passes through the OHP, and the sensor output V becomes low. Therefore, the switching transistor Tr1 is turned on and the high slice level v
_If it is set to a, the area where OHP cannot be detected will occur. Therefore, it sets the slice level v _b for OHP lower than the slice level v _a for plain paper by turning on the switching transistor Tr2.

On the contrary, the slice level v for OHP
_If you try to detect plain paper with _b still, the light may be detected excessively and malfunction. Therefore, when specifying plain paper, the switching transistor Tr1 is turned on to set the high slice level v _a for plain paper.
As described above, since the slice levels v _a and v _b are switched according to the type of the print-receiving medium 43, not only the print-receiving medium 43 before printing can be set accurately, but also the color overlapping is achieved. Printing with high alignment accuracy and high printing quality can be performed.

By the way, when the printing medium 43 is accurately set at the printing position of the thermal head 1, the heating resistance elements r ₁ , r ₂ , ..., R _{m of} the thermal head 1 are selectively energized for printing. However, the applied energy is different when the print-receiving medium 43 is plain paper and when it is OHP. That is, when the print-receiving medium 43 is set, the microprocessor 67 reads the applied energy of the thermal head 1 stored in the ROM 68 as data for each set print-receiving medium 43.
Here, the energy applied to the thermal head 1 is determined by the pulse width of the STB signal. When printing on OHP having a smoothness higher than that of plain paper, the required applied energy may be smaller than the applied energy when printing on plain paper. Therefore, when the OHP is designated as the print medium 43 by the operation panel 66, the OH in the ROM 68 is
The data for P is read out and the pulse width of the STB signal is set short to reduce the applied energy. When plain paper is designated, the data for plain paper in the ROM 68 is read, the pulse width of the STB signal is set long, and the applied energy is increased.

FIG. 8 is a time chart of the line thermal printer of the present invention. The STB signals when printing on OHP and when printing on plain paper are shown. As shown in the figure, the heating resistor element r ₁ of the thermal head 1 (FIG. 1),
STB1 to be divided and output for r ₂ , ..., R _m
The pulse width of the STBn signal is set to be long or short within the range of one step of the motor 24. In this way, the applied energies that match the smoothness of plain paper and OHP are set.

Therefore, when printing on the OHP, the applied energy does not become excessive, and it is possible to prevent the occurrence of print dripping and wrinkling of the ink ribbon 44 (see FIG. 2). Further, when printing on plain paper, the applied energy does not become insufficient, and it is possible to prevent the print density from decreasing. It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0029]

As described in detail above, according to the present invention, a sensor for detecting the presence or absence of a print medium is provided,
A comparator compares the sensor output from the sensor with the slice level and outputs the comparison result. Designating means is provided for designating the type of the printing medium, and the slice level is changed corresponding to the type of the printing medium. Even if the print medium changes and the sensor output of the sensor changes, the presence or absence of the print medium can be accurately detected.
Therefore, not only the printing position on the printing medium becomes accurate, but also in the case of color printing, it is possible to accurately perform color registration.

Further, the energy applied to the thermal head can be changed depending on the type of print medium. That is, when the type of the printing medium is designated by the designating unit, the pulse width of the strobe signal is changed according to the type of the printing medium, and the energy applied to the thermal head becomes appropriate. Therefore, more energy than necessary is not applied to the thermal head, and it is possible to prevent the occurrence of print dripping and wrinkling of the ink ribbon. Further, the applied energy is not insufficient, and the print density is appropriate.

[Brief description of drawings]

FIG. 1 is a block diagram of a line thermal printer showing an embodiment of the present invention.

FIG. 2 is a schematic view of a conventional line thermal printer.

FIG. 3 is a circuit block diagram for operating a conventional line thermal printer.

FIG. 4 is a block diagram showing a configuration of a conventional thermal head.

FIG. 5 is an operation time chart of a conventional line thermal printer.

FIG. 6 is a detailed diagram of a sensor detection circuit.

FIG. 7 is a detection state diagram of a sensor detection circuit.

FIG. 8 is a time chart of the line thermal printer of the present invention.

[Explanation of symbols]

1 Thermal Head 10 Shift Register Circuit 11 Latch Circuit 12 NAND Circuit 23 I / O Port 42 Platen 43 Printed Medium 44 Ink Ribbon 55 Paper Feed Sensor 56 Paper Top Detection Sensor 66 Operation Panel (Designating Means) 67 Microprocessor 68 ROM 69 Sensor detection circuit CPM1 comparator _{r 1, r 2, ...,} r m heating resistance element

Claims (2)

[Claims] 1. A line thermal printer for transferring ink of an ink ribbon to a print medium by sandwiching the ink ribbon and the print medium between a thermal head and a platen, and (a) a sensor for detecting the presence or absence of the print medium. When,
Corresponding to (b) a comparator for comparing the sensor output of the sensor with a slice level and outputting a comparison result, (c) a designating unit for designating the type of the print medium, and (d) designation by the designating unit. A line thermal printer having means for changing the slice level. 2. A line thermal printer for transferring ink of an ink ribbon to a print medium by sandwiching the ink ribbon and the print medium between a thermal head and a platen, and (a) a shift for storing a data signal for one line. A register circuit, (b) a latch circuit for taking in the data signal in the shift register circuit, (c) a plurality of heating resistor elements arranged in the line direction, and (d) a strobe signal for each block of the heating resistor element. A strobe signal generating means for generating the above, (e) means for selectively energizing the heating resistance element by receiving the output data and strobe signal of the latch circuit, and (f) a specifying means for specifying the type of the print medium. And (g) means for changing the pulse width of the strobe signal in response to the designation by the designating means. Maru printer.