JP2003080758A - Thermal printer and method for detecting residual capacity of battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer in which the residual capacity of a battery can be managed regardless of the discharging characteristics of the battery and print processing can be carried out efficiently. SOLUTION: The thermal printer performing printing by supplying power to a plurality of heating elements in a head from a drive power supply of battery comprises means for measuring the output voltage of the battery, means for calculating current consumption at the time of printing one line based on print data, and means for calculating residual capacity of the battery after printing based on the battery capacity before printing and a current consumption required for printing calculated by the current consumption calculating means wherein print processing is controlled based on the residual capacity of the battery thus calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer that prints with a thermal head, and more particularly to a method for detecting the remaining battery charge in a thermal printer that uses a battery as a driving power source.

[0002]

2. Description of the Related Art A thermal printer includes a thermal head in which a plurality of heating elements are arranged, and supplies an energizing pulse signal according to print data to the heating element to perform printing by thermal color development or thermal transfer. Is. In recent years, thermal printers have been widely used in small electronic devices having a print function, and in such small electronic devices, a battery is often used as a driving power source so as not to impair portability and convenience. .

As described above, in the case of a thermal printer using a battery as a driving power source, the battery capacity is exhausted as the printer is operated, the print density is reduced, the print quality is deteriorated, and finally the print becomes impossible. . Also, when the battery capacity becomes 0, not only printing becomes impossible but also RAM (Rand
Information recorded in volatile memory such as om access memory) may be lost.

By the way, conventionally, a secondary battery such as a Ni-Cd (nickel-cadmium) battery has been generally used as a driving power source for a thermal printer. Since this Ni-Cd battery has a discharge characteristic that the output voltage gradually decreases as the battery capacity runs out, the remaining capacity of the battery can be easily grasped by measuring the output voltage. That is, it is possible to detect that the battery capacity is low in association with the decrease in the output voltage, and it is possible to predict the end point of the battery capacity (battery capacity = 0) to some extent.

Specifically, the threshold of the output voltage is set, and when the measured voltage of the Ni-Cd battery becomes less than or equal to the preset threshold, the remaining capacity of the battery becomes small. The user is informed of the fact and prompted to replace or charge the battery.

As described above, according to the prior art, it is possible to predict in advance that the battery capacity will become 0 and to charge the battery before it becomes 0, so that the printing process is stopped during printing. It is possible to prevent the information stored in the volatile memory from being lost.

[0007]

On the other hand, recently, Ni-
Lithium-ion batteries, which can supply electric power more stably for a longer period of time than Cd batteries, have begun to be adopted as driving power sources for thermal printers. This lithium-ion battery has a flat discharge characteristic capable of outputting a constant voltage for a long time, and the output voltage sharply decreases immediately before the battery capacity runs out.

Therefore, even if a threshold value is set for the output voltage and it is detected that the battery capacity is small when the output voltage of the battery drops below the threshold value as in the prior art, the output voltage can be reduced. The battery capacity may become 0 during printing due to a sharp decrease in In other words, it is difficult to replace or charge the battery after detecting that the battery capacity is low based on the output voltage drop, and the battery capacity is exhausted before the user takes action. Probability is high.

As described above, the conventional method of grasping the remaining capacity of the battery by measuring the output voltage of the battery may not be applicable depending on the discharge characteristics of the battery.

Therefore, an object of the present invention is to provide a thermal printer and a battery capacity detecting method capable of grasping the remaining capacity of the battery regardless of the discharge characteristics of the battery and efficiently performing the printing process.

[0011]

DISCLOSURE OF THE INVENTION The present invention has a line dot type head having a plurality of heating elements for printing on printing paper by energizing the heating elements corresponding to print data. A battery as a driving power source for applying a predetermined voltage, a voltage measuring unit for measuring an output voltage of the battery, and a consumption amount calculating unit for calculating a current consumption amount when printing one line based on the print data. A battery remaining capacity calculation means for calculating the remaining battery capacity after printing based on the battery capacity before printing and the current consumption required for printing one line calculated by the consumption calculation means; and the remaining battery capacity calculation. The thermal printer includes at least a print processing control unit that controls the print processing based on the remaining battery charge calculated by the unit.

This thermal printer calculates the amount of current consumption associated with the printing process of one line before printing, calculates the remaining battery capacity after printing from this amount of current consumption and the battery capacity before printing, and prints. Since it is controlled whether or not the battery capacity required for the processing is sufficient, it is possible to solve the problem that the battery capacity is exhausted during the printing processing of one line and the printing processing is disabled. Further, since the remaining capacity of the battery is calculated from the current consumption amount associated with the printing process, it can be applied to all batteries regardless of the discharge characteristics of the battery, and the remaining capacity of the battery can be accurately detected.

Further, the remaining battery capacity is corrected by detecting a change in the resistance value of the heating element or the internal resistance value of the battery which changes according to the ambient environmental temperature. As a result, the remaining battery charge can be accurately calculated even when the ambient environment temperature changes and the resistance value inside the printer changes.

Further, the battery remaining capacity calculated by the battery remaining capacity calculating means may be notified to the user.
As a result, the user can grasp the current battery capacity, so that the effective use period of the battery can be predicted to some extent.

Further, when the remaining battery capacity calculated by the remaining battery capacity calculation means becomes smaller than the preset first capacity value, the printing process is stopped.
That is, the printing process is not started when the battery capacity sufficient to execute the printing process for one line does not remain. This eliminates the problem of interrupting the printing process for one line. Further, since the data stored in the storage means such as the RAM is retained for a while due to the small battery capacity, the data will not be lost if the user charges the battery during that time.

Further, when the battery remaining capacity calculated by the battery remaining capacity calculation means becomes smaller than a second capacity value which is larger than the preset first capacity value,
The user is notified that the power capacity has decreased. As a result, the user can perform the charging process of the battery and the like with a margin, so that the problem due to the exhaustion of the battery capacity does not occur.

[0017]

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

FIG. 1 is a block diagram showing the schematic arrangement of a thermal printer according to this embodiment. The thermal printer according to the present embodiment operates a printer engine unit PE that executes printing based on print data transmitted from a personal computer, a control circuit board PC that controls the printer engine unit PE, and an operation panel. And a input unit 40 for inputting a key operation signal input by a user and a print data signal from an external device or the like, and is driven by the lithium ion battery 21.

The printer engine PE is driven by an energizing pulse supplied from the lithium-ion battery 21 to print a line dot type thermal head 1, and the thermal head 1 is moved and the printing paper is fed. A motor unit 2 including a motor for performing the above and a motor drive circuit for controlling the operation of the motor, and a temperature sensor 3 such as a thermistor for measuring the environmental temperature of the thermal head 1.

On the other hand, the control circuit board PC has an input section 40.
C that controls the entire printer according to control commands from C
PU (Central Processing Unit) 30 and CPU 30
ROM that stores programs and parameters executed by
(Read Only Memory) 32 and RAM (Random Access Memo) for temporarily storing print data, control constants, etc.
ry) 31, a voltage measuring circuit 34 for measuring the output voltage of the lithium-ion battery 21, a print control circuit 35 for controlling the thermal head 1 as a printing unit, and a temperature near the thermal head 1 and the battery 21. Environmental temperature measurement circuit 3
6, an I / O port 37 for transmitting and receiving data to and from a personal computer, and a battery charging circuit 33 for charging the lithium ion battery 21 as a driving power source using a power source 20 such as an AC adapter. I have it.

The battery 21 used in this embodiment is a lithium ion battery capable of applying a voltage of 4.2 to 8.5 V to the thermal head 1. This lithium-ion battery 2
1 has an initial capacity (battery capacity immediately after charging) of about 1350 m
Ah, and its battery capacity is charged by the AC power source 20 connected to the battery charging circuit 33.

FIG. 2 is a flow chart showing an example of a procedure for calculating the remaining battery capacity of the lithium ion battery 21 used in this embodiment and controlling the printing process based on the remaining battery capacity. The values (initial value of battery capacity, current coefficient, print pulse width, current consumption, remaining battery capacity, etc.) set or calculated in each step are stored in the RAM 31 and can be read or rewritten as necessary. Be seen.

First, the battery charging circuit 33 connected to the AC power source 20 is activated to completely charge the lithium ion battery 21 (step S1). Here, the battery charging circuit 3
3 is provided with a charging status informing means so that it can detect that the battery 21 is completely charged. Then, after confirming that the battery 21 is completely charged by the detection signal from the charging status notifying means, the printing process is started (step S2). In other words, since the present invention calculates the remaining battery capacity after printing based on the battery capacity before printing and the current consumption amount associated with the printing process, it is necessary to accurately set the initial capacity of the battery, for which Must be charged to.

Next, in step S3, the capacity value of the lithium ion battery 21 is initialized. Since the capacity of the lithium-ion battery 21 used in this embodiment is 1350 mAh, the battery capacity value immediately after being fully charged is 1350 mA.
h, which is set as the initial battery capacity. For example, the user may manually set using an external input means such as an operation panel, or the battery capacity may be automatically set to 1350 mAh when the charging of the battery 21 is completed.

Next, the print data transmitted from an external personal computer or the like is received, and the process waits until it is determined that a print request is made (step S4). When it is determined in step S4 that a print request has been issued, the process proceeds to step S5, and print processing is performed based on the results calculated in the subsequent steps.

In step S5, the value of the current flowing through the thermal head 1 when printing one line is calculated based on the print data. Specifically, the number of print dots in one line is counted based on the print data, and the total resistance of the heating elements is determined by using this count value as the number of heating elements that are energized during the printing process. Next, the voltage measuring circuit 34 measures the output voltage of the battery 21, and the current value flowing through the thermal head 1 can be calculated based on the resistance value of the heating element and the output voltage. Hereinafter, this current value is referred to as a current coefficient. Here, since the number of dots to be printed differs for each line, the flowing current, that is, the current coefficient is 1 even if the output voltage of the battery 21 is the same.
The current coefficient is calculated every time the printing process of one line is performed because it differs for each printing process of the line.

Next, the energization pulse width that is optimum for printing is calculated based on the output voltage of the battery 21 measured in step S5 (step S6). Generally, energizing pulse width (m
s) is calculated by multiplying the value calculated based on the standard applied energy (mJ), the resistance value (Ω) of the head, and the energization voltage (V) by the correction coefficient.

Next, the current consumption amount consumed when printing one line is calculated by multiplying the current coefficient calculated in step S5 and the energization pulse width calculated in step S6 (step S7).

Next, in step S8, the remaining capacity of the battery is calculated. Specifically, it can be calculated by subtracting the current consumption amount due to the printing process of one line calculated in step S7 from the battery capacity before printing. For example, when the remaining battery capacity after printing n lines is C _n and the current consumption amount due to the printing processing of the nth line is C ′ _n , it can be expressed as C _n = C _n-1 −C ′ _n .

Next, the current capacity value is corrected based on the environmental temperature of the printer measured by the environmental temperature measuring circuit (step S9). For example, the heating element of the thermal head and the internal resistance of the battery are affected by the temperature in the vicinity of the position where they are arranged, and the resistance value changes. Therefore, the current consumption also increases or decreases depending on the environmental temperature, and the current consumption is calculated in consideration of this. Specifically, the environmental temperature of the thermal head 1 can be measured by a signal from the temperature sensor 3 such as a thermistor. The environmental temperature of the part where the battery 21 is arranged can be similarly measured by providing a temperature sensor.

Next, it is judged from the calculated remaining battery capacity whether or not the remaining battery capacity remains after printing (step S10). If the remaining battery capacity remains, the process proceeds to step S11 to execute printing of one dot line, After that, the process proceeds to step S4 and the printing process is continued. On the other hand, when it is determined in step S10 that the battery capacity does not remain, the printing process ends.

In the present embodiment, the current consumption amount for printing one dot line is calculated in advance and it is determined whether or not the battery capacity is sufficient for the printing process. It is possible to solve the problem that the battery runs out on the way and the printing process is interrupted or stopped. As described above, in the present embodiment, the battery remaining capacity is calculated based on the current consumption amount that is actually consumed. Therefore, the battery capacity can be managed regardless of the discharge characteristics of the battery, and the charging timing of the battery can be determined. You can know exactly.

When it is determined in step S10 that there is no remaining battery charge and the printing process ends, it is preferable to notify the user that the remaining battery charge is low and to prompt the user to charge the battery.
This allows the user to charge the battery while holding the data recorded in the RAM 31 with the remaining small battery capacity, so that the battery capacity is completely lost.
It is less likely that the data stored in will be lost.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-mentioned embodiments.

For example, in step S10 of the present embodiment, execution / stop of the printing process is determined depending on whether or not the remaining battery capacity becomes 0. However, the remaining battery capacity for determination in step S10 is It can also be set to a few percent of the initial capacity of the battery. As a result, even when the actual remaining battery capacity is smaller than the calculated remaining battery capacity due to the measurement error, charging can be promoted before the remaining battery capacity runs out.

The battery remaining capacity calculated in step S8 may be displayed on the display unit (not shown) of the printer so that the user can grasp the current battery remaining capacity. For example, the battery remaining capacity calculated in step S8 is compared with the battery initial capacity set in step S3, and the remaining capacity is displayed as a percentage. As a result, the user can specify the remaining battery capacity specifically, and can predict the effective usage period of the battery to some extent.

In this embodiment, the remaining battery capacity is 0.
If the battery is charged before the above condition, the process always returns to step S1 in FIG.

[0038]

According to the present invention, the current consumption amount associated with the printing process is calculated before printing, and the remaining battery capacity after printing is calculated from this current consumption amount and the battery capacity before printing. Therefore, it can be applied to all batteries regardless of the discharge characteristics of the batteries, and the remaining capacity can be accurately detected. As a result, it is possible to judge from the calculated remaining battery capacity after printing whether there is sufficient battery capacity necessary for the printing process, and by controlling the printing process according to the judgment result, the process is interrupted during printing. The effect of not causing the problem

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a thermal printer P according to the present embodiment.

FIG. 2 is a flowchart showing an example of a procedure for calculating a battery remaining capacity of a lithium ion battery 21 used in the present embodiment and controlling a printing process based on the calculated remaining battery capacity.

[Explanation of symbols]

1 thermal head 2 Motor part 3 Temperature sensor 20 power supplies 21 Lithium-ion battery 30 CPU 31 RAM 32 ROM 33 Battery charging circuit 34 Voltage measurement circuit 35 Print control circuit 36 Environmental temperature measurement circuit 37 I / O ports 40 Input section PE printer engine PC control circuit board

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C055 CC00 CC03                 2C061 AQ04 HJ10 HK10 HK11 HK18                       HV01 HV32                 2C066 AA18 AC01 CB01 CB07 CB09                 5G003 BA01 DA02 EA05 GC05                 5H030 AS11 FF42

Claims (7)

[Claims] 1. A line-dot type head having a plurality of heating elements, which prints on a print sheet when the heating elements are energized corresponding to print data, and a drive for applying a predetermined voltage to the head. A battery as a power source, a voltage measuring unit that measures the output voltage of the battery, a consumption amount calculating unit that calculates a current consumption amount when printing one line based on the print data, and a battery capacity before printing. And a remaining battery capacity calculating means for calculating the remaining battery capacity after printing based on the current consumption calculated by the remaining capacity calculating means, and a printing process based on the remaining battery capacity calculated by the remaining battery capacity calculating means. A thermal printer comprising at least a print processing control means for controlling the. 2. The remaining battery capacity calculation means detects a change in the resistance value of the heating element or the internal resistance value of the battery, which changes in accordance with the ambient environmental temperature, and corrects the remaining battery capacity. The thermal printer according to claim 1, further comprising a correction unit. 3. The thermal printer according to claim 1, further comprising a battery remaining capacity notifying unit for notifying a user of the battery remaining capacity calculated by the battery remaining capacity calculating unit. 4. The print processing control means may stop the print processing when the remaining battery charge calculated by the remaining battery charge calculating means becomes smaller than a preset first capacity value. The thermal printer according to any one of claims 1 to 3, which is characterized. 5. The print processing control means, when the remaining battery capacity calculated by the remaining battery capacity calculation means becomes smaller than a second capacity value which is larger than the preset first capacity value. The thermal printer according to any one of claims 1 to 4, wherein the thermal printer notifies the user that the power supply capacity has decreased. 6. A method for detecting a remaining battery level of a thermal printer, wherein a line dot type thermal head including a plurality of heating elements is used as a driving power source for a battery, and a method for detecting the remaining battery level is one line of print dots based on print data. The battery capacity consumed by the printing process of one line is calculated from the number, and the remaining battery capacity after printing is calculated based on the capacity of the battery before printing and the battery capacity consumed by the printing process of one line. A method for detecting the remaining battery capacity, which comprises calculating. 7. The battery remaining capacity is corrected by detecting a change in the resistance value of the heating element or the internal resistance value of the battery, which changes according to the ambient environmental temperature.
The method for detecting the remaining battery capacity described in.