JP2003237153A - Thermal printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper setting process function of a thermal printer which can surely set papers while saving wasteful feeding of papers. <P>SOLUTION: The thermal printer for printing in a state with the paper held between a platen and a printing head is provided with a paper setting process control means 41 for controlling a paper feed motor 15A which rotates to drive the platen at a paper setting process time when a leading end of the paper fed along a paper introduction path is inserted between the platen and the printing head, and a load detecting circuit 44 for detecting a change of a quantity of electricity which reflects a rotational load of the paper feed motor 15A. When the paper feed motor 15A is rotated to drive and the load detecting circuit detects the paper presence at the paper setting process time, the driving of the paper feed motor 15A is stopped on the basis of the detection. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer which presses a sheet between a platen and a print head to perform printing, and more particularly to a technique useful when applied to a thermal printer mounted on a cash register.

[0002]

2. Description of the Related Art For example, a direct line thermal printer has been widely used in recent years as a printer installed in a cash register of a store. A direct line thermal printer is a printer that performs printing by bringing a heating element into contact with a thermal paper, and a plurality of heating elements that print at least one line are arranged on the print head. Printing is performed by driving the print head while intermittently moving the paper in the vertical direction without moving it in the (line direction).

In such a direct line thermal printer, it is general that a platen is pressed against the print head so that printing is performed while the paper is pressed by the print head. Roll paper is used as the paper, and the paper is fed in the vertical direction by rotating the platen.

[0004]

There are roughly two types of methods for setting paper in the above-mentioned direct line thermal printer. One is a system in which a head release mechanism that releases the pressing force between the print head and the platen is provided, and when setting the paper, the print head is separated from the platen and the paper is inserted between them. The other is to rotate the platen with no paper and insert the leading edge of the paper between the rotating platen and the print head so that the platen automatically feeds the paper between the print heads. It is an automatic insertion method.

The former method requires the operation of moving the print head or the platen to release the pressing force. Therefore, when the thermal printer is mounted on the main body device such as a cash register, the above releasing operation can be performed easily. Since it is necessary to mount a thermal printer at a location where it can be installed, there is a problem that the degree of freedom in designing the main body device is reduced.

When only a small gap is opened between the print head and the platen, the friction resistance of the platen is so great that it is difficult to easily pass through the paper. For example, the leading edge of the paper is cut or bent. Then, there is a problem that the work of replacing the paper becomes complicated because it is necessary to process the paper so that the paper can be easily passed through.

In the latter automatic insertion method, when the platen is rotated for a long period of time when the paper is set, the platen continues to rotate even after the leading edge of the paper is inserted between the platen and the print head. As a result, a large amount of paper is fed and waste of paper is increased, and there is a drawback that the setting process takes a long time due to wasteful paper feeding.
On the other hand, if the rotation period of the platen is short when the paper is set, the rotation of the platen may stop before the leading edge of the paper is inserted between the platen and the print head, and the paper may not be set. .

Further, in the case of adopting the above-mentioned automatic insertion system, a paper introducing path for guiding the paper between the platen and the print head is provided, and when setting the paper, the operator manually inserts the paper into the paper introducing path. In general, the leading edge of the paper was fed between the platen and the print head. In the case of such a configuration, the time from when the paper is fed to when the leading edge of the paper reaches the platen / print head does not vary depending on the time or the skill of the operator.
Therefore, when the above-described automatic insertion method is adopted, it is usual that the rotation time of the platen is set to be sufficiently long with a margin for the paper insertion time. Therefore, waste of paper and waste of processing time are long.

Further, an optical sensor or the like for detecting the presence or absence of the paper is provided at the place where the paper passes between the platen and the print head, and the platen is controlled to stop the rotation when the paper comes out. It was possible to avoid feeding, but in thermal printers that are installed in cash registers, etc., the platen and print head are often located adjacent to the paper ejection port, so when paper comes out. It was difficult to install the sensor because there was no space in the room. Further, even if there is a space, scattered light enters from the outside, so that it is difficult to perform accurate detection with an optical sensor or the like.

Further, even when the thermal printer is mounted at a position away from the sheet discharge port of the main body apparatus, the thermal printer itself is required to be unitized and downsized. It was not preferable to attach the sensor.

An object of the present invention is to make it possible to detect whether or not there is a sheet between the platen and the print head without providing a sensor or the like around the platen or the print head.
It is an object of the present invention to provide a thermal printer having a paper setting processing function that can reliably set paper while eliminating wasteful feeding of the paper even when the automatic insertion method is used for the paper setting process.

[0012]

In order to achieve the above object, the present invention provides a thermal printer in which printing is performed with a sheet sandwiched between a platen and a print head.
A load detecting means for detecting a predetermined amount of electricity that reflects the rotation load of the drive motor for rotating the platen;
The presence / absence of paper between the platen and the print head is determined based on the detection result of the load detection means.

According to such a means, even if the load detecting means does not provide a detecting means such as an optical sensor around the platen or the print head, is there a sheet between the platen and the print head? It is possible to detect if there is no.

Further, according to the present invention, a sheet introduction path for guiding the sheet between the platen and the print head, and a sheet fed along the sheet introduction path so that the front end of the sheet is between the platen and the print head. A sheet setting process control unit that controls the drive motor during a sheet setting process that is inserted into the sheet setting process, wherein the sheet setting process control unit drives the drive motor during the sheet setting process, and When the presence of paper is detected by the load detection means,
The drive of the drive motor is stopped based on the detection.

According to such means, when the paper is set, the paper is inserted between the platen and the print head even if the time until the paper is sent between the platen and the print head along the paper introduction path varies. After that, the platen is stopped at an appropriate timing, so that the paper can be set with reliability and unnecessary feeding of the paper can be omitted.

Specifically, a paper detection sensor for detecting the presence / absence of paper is provided on the way of the paper introduction path, and the paper setting process control means detects the presence of paper from the detection condition of the paper detection sensor. The driving of the drive motor may be started based on the change in the state, and the drive motor may be driven by a predetermined amount after the presence of paper is detected by the load detection means, and then the drive motor may be stopped. . As a result, it is possible to eliminate the waste of the operation of the platen for setting the paper and to optimize the discharge length of the paper after setting the paper.

The means as described above is particularly useful for a thermal printer in which the contact portion between the print head and the platen is arranged so as to be adjacent to the paper discharge port for discharging the printed paper to the outside. Is.

Specifically, the print head has a structure in which a plurality of heating elements for performing dot printing for at least one line on a thermal paper are arranged along the axial direction of the rotation axis of the platen. .

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing the structure of a thermal printer according to an embodiment of the present invention.

The thermal printer 1 of this embodiment is
For example, it is a unit device mounted in a cash register for printing a receipt, and is provided with a print head 10, a platen 15, a paper introduction path 20 and the like in a substantially rectangular parallelepiped casing. Although the front view and the plan view are omitted, the housing of the thermal printer 1 and the paper introduction path 2
0 is formed to be slightly wider than the paper width of the roll paper R, and the print head 10 and the platen 1
5 has a width of about the width of the roll paper R.

The print head 10 is provided with a plurality of heating elements for dot printing arranged side by side in the line direction (width direction). These heating elements act on roll paper, which is a thermal paper, to perform line printing. To do. The print head 10 has a spindle 12
It is rotatably supported around the platen and is pressed against the platen 15 by the spring 11, and the heating element is arranged in the part pressed by the platen 15.

The platen 15 is rotatably supported together with a rotary shaft 16, and the rotary shaft 16 is connected via a gear to a paper feed motor 15A (FIG. 2) which is a drive motor.

The sheet introduction path 20 is formed so as to reach between the print head 10 and the platen 15 from the introduction port on the upper surface side of the housing, through the lower side of the platen 15. Further, when passing between the print head 10 and the platen 15,
A discharge port 2 for discharging the roll paper R to the outside of the housing in the immediate vicinity thereof
Two are provided.

A paper sensor (optical sensor or the like) 25 for detecting the presence or absence of paper is provided in the middle of the paper introduction path 20.

Although not shown in FIG. 1, the thermal printer 1 includes a print head 10 and a head release mechanism that slides the position of the print head 10 to release the pressure between the print head 10 and the platen 15. A head release detection switch 13 (FIG. 2) for detecting that the slide is released and the pressure is released is provided.

FIG. 2 is a block diagram showing the electrical construction of the thermal printer and the controller for controlling it.

The thermal printer 1 is wire-connected to a control board 40 which is constructed separately, and
It is configured to be controlled by a control circuit on the control board 40.

In the control circuit, an MPU (Micro Processing Unit) 41 that performs overall control of the thermal printer 1 and that also functions as a paper setting process control unit, and an MPU
A memory 42 for providing a working memory space to 41 for storing print data, a motor driver 43 for supplying power to drive the paper feed motor 15A based on a command from the MPU 41, and a predetermined amount of electricity of the motor driver 43. A detection circuit 44 as a load detection means for monitoring the change of the load applied to the paper feed motor 15A and an interface 45 for inputting / outputting data to / from the host computer 50 of the main body device in which the thermal printer 1 is mounted. Is provided. Power is supplied from an external power supply device 52.

FIG. 3 is a circuit diagram showing a first embodiment of the motor driver 43 and the detection circuit 44 of FIG.

The motor driver 43 carries out unipolar drive for the paper feed motor 15A consisting of a two-phase stepping motor, and has input terminals IN1, IN2 and I.
When the pulse signals are sequentially input to N3 and IN4, the corresponding transistors Tr1 to Tr4 are turned on, and a current is caused to flow from the terminals of the motor drive voltage VL to the corresponding windings L1 to L4 of the paper feed motor 15A. The paper feed motor 15A is adapted to rotate by a predetermined angle.

Since the amount of change in the current flowing through the windings L1 to L4 is almost proportional to the torque of the paper feed motor 15A, the magnitude of the rotational load applied to the paper feed motor 15A can be recognized from this current value. Then, this current value is voltage-converted by the resistors R1 and R2 at the upper end nodes n1 and n2, and is output to the detection circuit 44. These potentials are, for example, the normal level potential V when the paper feed motor 15A is rotating with the roll paper R being pressed between the platen 15 and the print head 10.
n, and the potential Vu is at a low level when the platen 15 is rotating without the roll paper R in direct contact with the print head 10. That is, the paper feed motor 15A
The amount of electricity reflects the rotational load of.

The detection circuit 44 includes resistors R5, R6, R7 and R8 for generating the comparison potential Vref and the motor driver 4
It is composed of comparators CMP1 and CMP2 for comparing the potential input from 3 with the comparison potential Vref, and a logic gate OR1 for taking the OR logic of both outputs of these comparators CMP1 and CMP2 in the negative logic form. The comparison potential Vref is set to an intermediate potential between the normal level potential Vn and the low level potential Vu. The resistors R3 and R4 are connected to the comparators CMP1 and CMP.
When the output of 2 becomes unstable, the potential of this output node is compensated to a high level.

With this configuration, when the paper feed motor 15A is driven to rotate without the roll paper R,
The outputs of both comparators CMP1 and CMP2 are both at high level, and the output of the logic gate OR1 is at high level. On the other hand, with the roll paper R present, the paper feed motor 15
When A rotates, both comparators CMP1, CM
One of the outputs of P2 becomes low level, which causes the output of the logic gate OR1 to become low level. And
Based on these outputs, the platen 15 and the print head 10
The MPU 41 determines whether or not there is the roll paper R between the sheets.

FIG. 4 is a circuit diagram showing a second embodiment of the motor driver 43 and the detection circuit 44 of FIG. In the second embodiment, the motor driver is 43A and the detection circuit is 44A.
Write A.

The motor driver 43A is a drive circuit for unipolarly driving a two-phase stepping motor, and further has a PWM (Pulse Width Modulation) drive to reduce power consumption. In this motor driver 43A, the input terminals IN1, IN2 and IN3, I
When the pulse signals are sequentially input to N4, the corresponding transistors Tr5 to Tr8 are turned on, and the corresponding winding L of the paper feed motor 15A is fed from the terminal of the motor drive voltage VL.
A current is applied to 1 to L4, whereby the paper feed motor 15A
Is rotated by a predetermined angle. At that time, the currents flowing through the windings L1 to L4 are converted into voltages by the resistors R9 and R10, and this potential is compared with the sawtooth wave by the comparators CMP3 and CMP4 to generate the PWM signals S1 and S2,
With the PWM signals S1 and S2, the transistor Tr9,
The on period of Tr12 is controlled to make the current flowing through the windings L1 to L4 constant.

In the case of such a drive circuit, a change in the load applied to the paper feed motor 15A appears as a change in the on-pulse period of the PWM signals S1 and S2.
When the paper feed motor 15A is rotating with the roll paper R between the sheet No. 5 and the print head 10, the normal on-pulse period T0 is reached, while the roll paper R is not present and the platen 15 is not present.
Is rotating while being in direct contact with the print head 10, the on-pulse period T1 is short.

The detection circuit 44A uses the PWM signals S1 and S for the above two phases as a predetermined amount of electricity that reflects the rotational load.
Upon reception of 2, these signals are collectively output as one signal by the logic gate OR2. Logic gates G1 to G
Reference numeral 3 is for outputting a signal only when receiving a select signal SEL from the outside.

The MPU 41 counts the on-pulse width of the signal supplied from the detection circuit 44A using an internal timer function, so that the platen 15 and the paper feed motor 15
It is possible to determine whether or not there is a sheet between A and A. In the case of the second embodiment, the detection circuit 44A and the MPU
A load detecting unit is configured by 41.

Next, a paper setting process executed when setting a new roll paper R in the thermal printer 1 having the above-mentioned configuration will be described.

FIG. 5 shows a flowchart of the paper setting process executed by the MPU 41 of FIG.

The paper setting process is started, for example, when there is no paper in the paper introducing path 20 due to the detection signal of the paper sensor 25 or when a start command is input from the host PC 50. When the paper setting process starts,
First, in step S1, it is determined based on the detection output of the paper sensor 25 whether or not the paper is present and the paper is present, that is, whether or not a paper is inserted in the paper introduction path 20 and the paper is inserted. If there is paper, the process proceeds to the next step S2, but if there is no paper, step S1 is repeated.

In step S2, whether or not the print head 10 has been released is detected based on the output of the head release detection switch 13 (FIG. 2). If the print head 10 has been released, the automatic insertion type paper setting process is not performed. Although this set process ends, if it has not been released, the process proceeds to the next step S3 assuming that the automatic insert type set process is performed.

In step S3, the paper feed motor 15A is fed one step, and the process proceeds to the next step S4.

In step S4, it is confirmed based on the detection output of the paper sensor 25 whether the paper is pulled out from the paper introducing path 20, and if the paper is still inserted, the process directly proceeds to the next step S5. If the paper has been pulled out and has run out, the processing from step S1 is repeated again assuming that the paper insertion has failed and the paper has been pulled out.

In step S5, the detection circuit 44 when the paper feed motor 15A is rotationally driven in step S3 described above.
If there is a low level output indicating that a sheet is inserted between the platen 15 and the print head 10 based on the output of step S6, the process proceeds to step S6, but if there is a high level output indicating that there is no sheet. To return to step S3, the process of steps S3 to S5 is repeated.

Incidentally, the motor driver 43A of the second embodiment.
And the detection circuit 44A is used, in step S5, the period of the ON pulse width of the output signal of the detection circuit 44A is counted inside the MPU 41, and if the period is close to the normal ON pulse period T0, the process proceeds to step S6. If the period is close to the short on-pulse period T1, step S3
Returned to.

As a result, the platen 15 and the print head 10
If it is determined that a sheet has been inserted between the sheet feeding path and the step S6, the sheet feeding motor 1
5A is rotated by a predetermined amount to feed the paper a little, and then, in step S7, the paper feed motor 15A is stopped to end the paper setting process.

As described above, according to the thermal printer 1 of this embodiment, the detection circuit 44 (or the detection circuit 44A) can be provided without providing the detection means such as the optical sensor around the platen 15 or the print head 10. And MPU 41) detect the change in the amount of electricity representing the load of the paper feed motor 15A, it is possible to detect whether or not there is paper between the platen 15 and the print head 10.

As a result, it is possible to detect that the paper is inserted between the platen 15 and the print head 10 during the paper setting process, and whether the roll paper R is inserted slowly or quickly is always used. The paper setting process can be completed with the discharge amount of the roll paper R being constant. Further, by such a processing, there is an advantage that the paper can be reliably set while omitting the wasteful paper feeding.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the embodiment, the current value flowing in the paper feed motor 15A and the on-pulse width of the PWM signal are exemplified as the electric quantity that reflects the rotational load of the platen 15, but the electric quantity that similarly reflects the load is also used. Any kind may be used.

Further, in the above embodiment, the platen 15
When there is paper between the print head 10 and the print head 10, the current value flowing in the paper feed motor 15A becomes larger (in the case of FIG. 3), or the on-pulse width of the PWM signal becomes wider (FIG. 3). 4), but the direction of change in the electric quantity may be reversed due to the relationship between the platen 15, the paper, and the friction resistance between the print head 10 and the like.

Further, in the embodiment, the detection circuits 44, 44
Although A has been described as a configuration different from the motor driver 43 and the MPU 41, these detection circuits 44 and 44A may be provided on the same chip as the motor drivers 43 and 43A or may be incorporated in the MPU. Further, the detection circuit 44 of FIG. 3 is not provided, and the MPU 41 with a built-in A / D converter is used to directly input the potentials of the nodes n1 and n2 of the motor driver 43 to this A / D converter, and the potential is MP
It can be configured so that it is converted into a digital value inside the U41 and used for determining whether or not a sheet is inserted.

[0054]

As described above, according to the present invention,
It is possible to detect whether or not a sheet is inserted between the platen and the print head without providing a detection means such as an optical sensor around the platen and the print head.

Further, by applying the detection of the paper insertion to the paper setting process, there is an effect that the paper can be surely set while eliminating wasteful paper discharge and wasted processing time. .

[Brief description of drawings]

FIG. 1 is a side view showing a structure of a direct line thermal printer according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a thermal printer and a controller that controls the thermal printer.

FIG. 3 is a circuit diagram showing a first example of a motor driver and a detection circuit of FIG.

FIG. 4 is a circuit diagram showing a second example of the motor driver and the detection circuit of FIG.

5 is a flowchart showing a procedure of a paper setting process executed by the MPU of FIG.

[Explanation of symbols]

1 Thermal Printer 10 Print Head 15 Platen 20 Paper Introductory Path 22 Ejection Port 25 Paper Sensor 40 Control Board 41 MPU 43 Motor Driver 44 Detection Circuit R Roll Paper n1, n2 Output Node S1 of Potential Reflecting Load of Paper Feed Motor S2 PWM signal

Claims (5)

[Claims] 1. A sheet is fed by rotating the platen while the sheet is sandwiched between the platen and the print head, and the print head is driven to print to print on the sheet. In the thermal printer configured as described above, a load detection unit that detects a change in a predetermined amount of electricity that reflects the rotational load of the drive motor that rotationally drives the platen is provided, and the platen is detected based on the detection result of the load detection unit. A thermal printer characterized in that the presence or absence of paper between print heads is determined. 2. A paper introducing path for guiding the paper between the platen and the print head, and a paper is fed along the paper introducing path so that the front end of the paper is inserted between the platen and the print head. A paper setting process control means for controlling the drive motor during the paper setting process, wherein the paper setting process control means drives the drive motor during the paper setting process and 2. The thermal printer according to claim 1, wherein when the presence of paper is detected, the drive of the drive motor is stopped based on the detection. 3. A paper detection sensor for detecting the presence / absence of paper in the middle of the paper introduction path is provided, and the paper setting processing control means changes the detection status of the paper detection sensor from the absence of paper to the presence of paper. Based on this, the drive motor is started, and after the load detection unit detects the presence of paper, the drive motor is driven by a predetermined amount and then the drive motor is stopped. The thermal printer according to claim 2, which is characterized in that. 4. The contact portion between the platen and the print head is arranged so as to be adjacent to a paper discharge port for discharging the printed paper to the outside.
The thermal printer according to any one of 1. 5. The print head has a structure in which a plurality of heating elements for performing dot printing for at least one line on a thermal paper are arranged along an axial direction of a platen rotation shaft. The thermal printer according to any one of 1 to 4.