Thermal printer and method for controlling thermal printer

Abstract

To improve a user's convenience.SOLUTION: A thermal printer 1 comprises: a battery 18 which functions as a power source; a voltage sensor 17 which detects voltage VB of the battery 18; a print head 161 which prints images on recording paper; and a control part 11 which controls the print head 161, wherein the control part 11 changes a printing condition CP of the print head 161 on the basis of the voltage VB detected by the voltage sensor 17.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal printer and a method for controlling a thermal printer. [Background technology]

[0002] Patent Document 1 discloses a portable printer that is equipped with a rechargeable battery and operates by supplying power to a printing unit (thermal head, drive motor, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-56742 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the printer described in Patent Document 1 and the like cannot be used when the remaining battery power is low, so there is a need to improve user convenience. [Means for solving the problem]

[0005] One aspect of a thermal printer that solves the above problem includes a battery that functions as a power source, a detector that detects the voltage of the battery, a thermal head that prints an image on recording paper, and a control unit that controls the thermal head, and the control unit changes the printing conditions of the thermal head based on the voltage detected by the detector.

[0006] Another aspect of the method for controlling a thermal printer that solves the above problem is a method for controlling a thermal printer that uses a battery as a power source, which detects the voltage of the battery and changes the printing conditions of the thermal head based on the detected voltage. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a thermal printer according to an embodiment of the present invention. [Figure 2] 10 is a chart showing an example of the relationship between the remaining battery charge and print density. [Figure 3] 10 is a flowchart illustrating an example of processing by a control unit of a thermal printer. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment will be described with reference to the drawings.

[0009] FIG. 1 is a diagram showing an example of the configuration of a thermal printer 1. As shown in Figure 1, the thermal printer 1 stores thermal roll paper (not shown) as "recording paper" and prints images such as characters and figures by applying heat to the recording surface of the thermal roll paper using a print head 161 equipped with a heating element. The thermal printer 1 is equipped with a battery 18 and operates by receiving power from the battery 18. The thermal printer 1 is configured to be portable by the user. The thermal printer 1 includes a control unit 11, a communication interface 12, a display unit 14, an operation panel 15, a printing unit 16, a voltage sensor 17, and a battery 18.

[0010] The control unit 11 includes a processor 11A such as a CPU (Central Processing Unit), a memory device 11B such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and other peripheral circuits, and controls each part of the thermal printer 1. The memory device 11B stores a control program.

[0011] The processor 11A may be configured as a single processor, or may be configured such that multiple processors function as the processor 11A.

[0012] The communication interface 12 communicates with the smartphone 2 in accordance with, for example, the Bluetooth (registered trademark) standard in accordance with instructions from the control unit 11. The communication interface 12 includes an antenna for transmitting and receiving Bluetooth signals and an interface circuit for processing the Bluetooth signals. The communication interface 12 is an interface board having an interface circuit, and is connected to a main board on which the processor 11A and the like of the control unit 11 are mounted. Alternatively, the interface circuit that constitutes the communication interface 12 is mounted on the main board of the control unit 11.

[0013] The operation panel 15 is disposed on the thermal printer 1. The operation panel 15 has unillustrated keys and buttons, and detects user operations on the keys and buttons. When the operation panel 15 detects a user operation on a key or button, it outputs an operation signal for the key or button to the control unit 11.

[0014] The operation panel 15 includes, for example, a button switch 151 that switches between enabling and disabling control for changing the printing conditions CP based on the voltage VB of the battery 18. The user switches between enabling and disabling control for changing the printing conditions CP based on the voltage VB of the battery 18 by, for example, operating the button switch 151. The button switch 151 corresponds to an example of an "operation receiving mechanism."

[0015] The printing conditions CP include the print density PD, the power supply conditions CE for the print head 161, and the transport speed VP of the thermal roll paper. The print density PD is controlled by a density control unit 113. The energization conditions CE are controlled by an energization control unit 114. The conveying speed VP is controlled by a speed control unit 115.

[0016] The printing unit 16 executes printing based on the print data DP in accordance with instructions from the control unit 11. The printing unit 16 includes a print head 161, a transport roller 162, and a cutter drive motor 163. The print head 161 has a large number of heating elements (not shown) arranged in a direction perpendicular to the transport direction of the thermal roll paper, and prints images such as letters and figures by passing electricity through the heating elements and applying heat to the printing surface of the thermal roll paper in accordance with instructions from the control unit 11. The print head 161 corresponds to an example of a "thermal head."

[0017] The transport roller 162 is driven to rotate by a transport motor (not shown) in accordance with instructions from the control unit 11, and transports the thermal roll paper. The transport roller 162 and the transport motor correspond to an example of a "transport mechanism." The cutter drive motor 163 drives the movable blade (not shown) to slide toward the fixed blade (not shown) in accordance with instructions from the control unit 11, thereby cutting the thermal roll paper.

[0018] The voltage sensor 17 detects the voltage VB of the battery 18. The voltage sensor 17 also outputs a signal indicating the voltage VB of the battery 18 to the control unit 11. The voltage sensor 17 corresponds to an example of a "detector." The battery 18 is a rechargeable secondary battery, and may be, for example, a lithium-ion battery.

[0019] The control unit 11 includes an operation reception unit 111 , a voltage detection unit 112 , a concentration control unit 113 , a current control unit 114 , and a speed control unit 115 . Specifically, the processor 11A of the control unit 11 executes a control program stored in the memory device 11B, thereby functioning as an operation reception unit 111, a voltage detection unit 112, a concentration control unit 113, a current control unit 114, and a speed control unit 115.

[0020] The operation receiving unit 111 switches between valid and invalid control for changing the printing conditions CP based on the voltage VB of the battery 18, based on an operation signal from the button switch 151. The control for changing the printing conditions CP based on the voltage VB of the battery 18 is executed by the voltage detection unit 112, the density control unit 113, the power supply control unit 114, and the speed control unit 115.

[0021] When the control for changing the printing condition CP based on the voltage VB of the battery 18 is disabled, the voltage detection unit 112, the density control unit 113, the energization control unit 114, and the speed control unit 115 do not execute the processes described below. When the control for changing the printing condition CP based on the voltage VB of the battery 18 is enabled, the voltage detection unit 112, the density control unit 113, the energization control unit 114, and the speed control unit 115 execute the processes described below.

[0022] The voltage detection unit 112 receives a signal indicating the voltage VB of the battery 18 from the voltage sensor 17 and acquires the voltage VB of the battery 18.

[0023] The density control unit 113 reduces the print density PD when the voltage VB of the battery 18 is equal to or lower than a first threshold TH1. The first threshold TH1 corresponds to the voltage VB when the remaining charge RQ of the battery 18 is 20% of the amount of power when the battery 18 is fully charged, for example. The concentration control unit 113 calculates the remaining capacity RQ of the battery 18 from the voltage VB of the battery 18. For example, a table that associates the voltage VB of the battery 18 with the remaining capacity RQ of the battery 18 is stored in advance in the memory device 11B, and the concentration control unit 113 calculates the remaining capacity RQ of the battery 18 from the voltage VB of the battery 18 by referring to the table.

[0024] When the voltage VB of the battery 18 is equal to or lower than the first threshold value TH1, the density control unit 113 reduces the print density PD in stages based on the voltage VB. The density control unit 113 reduces the print density PD in stages based on, for example, the remaining capacity RQ of the battery 18 corresponding to the voltage VB. The processing of the concentration control unit 113 will be further described with reference to FIG.

[0025] When the voltage VB of the battery 18 is equal to or lower than the second threshold TH2, the energization control unit 114 changes the energization condition CE of the print head 161 from full energization CE1 to thinned energization CE2. The second threshold TH2 is, for example, the same value as the first threshold TH1. The energization condition CE is included in the printing condition CP.

[0026] Full energization CE1 is an energization condition CE that allows current to be applied to all the heat generating elements. Thinning-out energization CE2 is an energization condition CE that cuts off power to heating elements every specified number N. The specified number N is, for example, nine. In other words, thinning-out energization CE2 is an energization condition CE that cuts off power to heating elements every nine. Heating elements that have been de-energized cannot apply heat to the printing surface of the thermal roll paper. In other words, heating elements that have been de-energized cannot form an image on the printing surface of the thermal roll paper.

[0027] The second threshold value TH2 corresponds to, for example, the voltage VB when the remaining capacity RQ of the battery 18 is 20% of the amount of power when the battery 18 is fully charged. The energization control unit 114 may, for example, reduce the designated number N in stages based on the remaining capacity RQ of the battery 18 corresponding to the voltage VB. For example, when the remaining capacity RQ of the battery 18 is 20% or less, the energization control unit 114 sets the designated number N to 9. Also, for example, when the remaining capacity RQ of the battery 18 is 15% or less, the energization control unit 114 sets the designated number N to 8. Also, for example, when the remaining capacity RQ of the battery 18 is 15% or less, the energization control unit 114 sets the designated number N to 7.

[0028] When voltage VB is equal to or lower than a third threshold value TH3, speed control unit 115 gradually reduces thermal roll paper transport speed VP based on voltage VB. Third threshold value TH3 is, for example, the same value as first threshold value TH1. Thermal roll paper transport speed VP is included in printing conditions CP. When the voltage VB is equal to or lower than the third threshold value TH3, the speed control unit 115 reduces the transport speed VP in stages based on the voltage VB.

[0029] The third threshold TH3 corresponds to, for example, the voltage VB when the remaining capacity RQ of the battery 18 is 20% of the amount of power when the battery 18 is fully charged. The speed control unit 115 may reduce the transport speed VP in stages based on, for example, the remaining capacity RQ of the battery 18 corresponding to the voltage VB. For example, the speed control unit 115 sets the conveying speed VP to 90% when the remaining capacity RQ of the battery 18 is 20% or less. Also, for example, the speed control unit 115 sets the conveying speed VP to 80% when the remaining capacity RQ of the battery 18 is 15% or less. Also, for example, the speed control unit 115 sets the conveying speed VP to 70% when the remaining capacity RQ of the battery 18 is 10% or less.

[0030] Next, the relationship between the remaining capacity RQ of the battery 18 and the print density PD will be described with reference to Fig. 2. Fig. 2 is a chart showing an example of the relationship between the remaining capacity RQ of the battery 18 and the print density PD. In FIG. 2, the remaining charge RQ of the battery 18 is shown in the left column, the print density PD is shown in the center column, and the print density PDA when the density setting value is 100% is shown in the right column.

[0031] As shown in FIG. 2, for example, when the remaining amount RQ is greater than 20%, the density control unit 113 makes the print density PD equal to the density setting value. For example, if the density setting value is 100%, the density control unit 113 sets the print density PD to "100%" as shown in the print density PDA. Also, if the density setting value is 95%, the density control unit 113 sets the print density PD to "95%". Also, if the density setting value is 90%, the density control unit 113 sets the print density PD to "90%".

[0032] Also, for example, if the remaining amount RQ is greater than 10% and less than or equal to 20%, the density control unit 113 reduces the print density PD by one step from the density setting value. "Reducing by one step" means, for example, a reduction of 5%. For example, if the density setting value is 100%, the density control unit 113 sets the print density PD to "95%" as shown in the print density PDA. Also, for example, if the density setting value is 95%, the density control unit 113 sets the print density PD to "90%". Also, for example, if the density setting value is 90%, the density control unit 113 sets the print density PD to "85%".

[0033] Also, for example, if the remaining amount RQ is 10% or less, the density control unit 113 reduces the print density PD by two steps from the density setting value. "Two steps reduction" means, for example, a 10% reduction. For example, if the density setting value is 100%, the density control unit 113 sets the print density PD to "90%" as shown in the print density PDA. Also, if the density setting value is 95%, the density control unit 113 sets the print density PD to "85%". Also, if the density setting value is 90%, the density control unit 113 sets the print density PD to "80%". Also, for example, if the remaining amount RQ is 0%, the density control unit 113 does not allow printing.

[0034] Next, the processing of the control unit 11 of the thermal printer 1 will be described with reference to Fig. 3. Fig. 3 is a flowchart showing an example of the processing of the control unit 11 of the thermal printer 1. First, in step S101, the operation acceptance unit 111 determines whether or not the control for changing the printing conditions CP based on the voltage VB of the battery 18 is valid. If the operation acceptance unit 111 determines that the control for changing the printing condition CP based on the voltage VB of the battery 18 is not valid (step S101; NO), the process enters a standby state. If the operation acceptance unit 111 determines that the control for changing the printing condition CP based on the voltage VB of the battery 18 is valid (step S101; YES), the process proceeds to step S103.

[0035] Next, in step S103, the voltage detection unit 112 receives a signal indicating the voltage VB of the battery 18 from the voltage sensor 17 and acquires the voltage VB of the battery 18. Next, in step S105, the concentration control unit 113 determines whether the voltage VB of the battery 18 is equal to or lower than the first threshold value TH1. If the concentration control unit 113 determines that the voltage VB of the battery 18 is not equal to or less than the first threshold value TH1 (step S105; NO), the process proceeds to step S111. If the concentration control unit 113 determines that the voltage VB of the battery 18 is equal to or less than the first threshold value TH1 (step S105; YES), the process proceeds to step S107.

[0036] Then, in step S107, the concentration control unit 113 calculates the remaining capacity RQ of the battery 18 from the voltage VB of the battery 18. Next, in step S109, the density control unit 113 reduces the print density PD in stages based on the remaining capacity RQ of the battery 18.

[0037] Next, in step S111, the energization control unit 114 determines whether the voltage VB of the battery 18 is equal to or lower than the second threshold value TH2. If the energization control unit 114 determines that the voltage VB of the battery 18 is not equal to or less than the second threshold value TH2 (step S111; NO), the process proceeds to step S115. If the energization control unit 114 determines that the voltage VB of the battery 18 is equal to or less than the second threshold value TH2 (step S111; YES), the process proceeds to step S113. Then, in step S113, the energization control unit 114 changes the energization condition CE of the print head 161 from full energization CE1 to thinned energization CE2.

[0038] Next, in step S115, the speed control unit 115 determines whether the voltage VB of the battery 18 is equal to or lower than the third threshold value TH3. If the speed control unit 115 determines that the voltage VB of the battery 18 is not equal to or less than the third threshold value TH3 (step S115; NO), the process then returns to step S101. If the speed control unit 115 determines that the voltage VB of the battery 18 is equal to or less than the third threshold value TH3 (step S115; YES), the process proceeds to step S117. Then, in step S117, the speed control unit 115 gradually reduces the conveying speed VP based on the voltage VB, after which the process returns to step S101.

[0039] As described above with reference to the drawings, the thermal printer 1 according to this embodiment comprises a battery 18 that functions as a power source, a voltage sensor 17 that detects the voltage VB of the battery 18, a print head 161 that prints an image on recording paper, and a control unit 11 that controls the print head 161, and the control unit 11 changes the printing conditions CP of the print head 161 based on the voltage VB detected by the voltage sensor 17.

[0040] According to this configuration, the printing conditions CP of the print head 161 are changed based on the voltage VB, and by changing the printing conditions CP to conditions that consume less power, it is possible to suppress a decrease in the remaining charge RQ of the battery 18. This improves user convenience.

[0041] Furthermore, in the thermal printer 1 according to this embodiment, the printing conditions CP include the print density PD, and the control unit 11 reduces the print density PD when the voltage VB is equal to or lower than the first threshold value TH1.

[0042] According to this configuration, when voltage VB is equal to or lower than first threshold TH1, print density PD is reduced. Therefore, by appropriately setting first threshold TH1, the timing for reducing print density PD can be appropriately set. Furthermore, by reducing print density PD, power consumption can be reduced. Therefore, the decrease in remaining capacity RQ of battery 18 can be suppressed.

[0043] Furthermore, in the thermal printer 1 according to this embodiment, when the voltage VB is equal to or less than the first threshold value TH1, the control unit 11 reduces the print density PD in stages based on the voltage VB.

[0044] With this configuration, when voltage VB is equal to or less than first threshold TH1, print density PD is gradually reduced based on voltage VB, thereby appropriately reducing power consumption and appropriately suppressing reduction in remaining capacity RQ of battery 18.

[0045] Furthermore, in the thermal printer 1 according to this embodiment, the printing conditions CP include the power supply conditions CE for the print head 161, and when the voltage VB is equal to or less than the second threshold TH2, the control unit 11 changes the power supply conditions CE from full power supply CE1 to thinned power supply CE2.

[0046] According to this configuration, when the voltage VB is equal to or lower than the second threshold TH2, the current supply condition CE is changed from full current supply CE1 to thinning-out current supply CE2. Therefore, by appropriately setting the second threshold TH2, the timing for changing from full current supply CE1 to thinning-out current supply CE2 can be appropriately set. Furthermore, because the current supply condition CE is changed from full current supply CE1 to thinning-out current supply CE2, power consumption can be reduced. Therefore, a decrease in the remaining capacity RQ of the battery 18 can be suppressed.

[0047] Furthermore, the thermal printer 1 according to this embodiment is provided with a transport roller 162 that transports the recording paper, the printing conditions CP include a transport speed VP of the recording paper, and the control unit 11 reduces the transport speed VP when the voltage VB is equal to or less than a third threshold TH3.

[0048] With this configuration, when the voltage VB is equal to or less than the third threshold TH3, the conveying speed VP is reduced, and by appropriately setting the third threshold TH3, the timing for reducing the conveying speed VP can be appropriately set. In addition, by reducing the conveying speed VP, it is possible to suppress momentary voltage drops caused by paper feeding operations.

[0049] Furthermore, in the thermal printer 1 according to this embodiment, when the voltage VB is equal to or lower than the third threshold value TH3, the control unit 11 reduces the transport speed VP in stages based on the voltage VB.

[0050] According to this configuration, when the voltage VB is equal to or lower than the third threshold TH3, the conveying speed VP is gradually reduced based on the voltage VB, thereby appropriately reducing the amount of power consumed and appropriately suppressing the decrease in the remaining capacity RQ of the battery 18.

[0051] The thermal printer 1 according to this embodiment also includes a button switch 151 that accepts operations from the user, and the control unit 11 switches between enabling and disabling control for changing the printing conditions CP based on the operation.

[0052] This configuration improves user convenience by switching between enabling and disabling the control for changing the printing conditions CP based on user operation. For example, if the user does not want to allow a decrease in the density of the printed image, the user can simply disable the control for changing the printing conditions CP.

[0053] The control method for the thermal printer 1 according to this embodiment is a control method for the thermal printer 1 that uses a battery 18 as a power source, and detects the voltage VB of the battery 18 and changes the printing conditions CP of the print head 161 based on the detected voltage VB.

[0054] With this configuration, the method for controlling the thermal printer 1 according to this embodiment achieves the same effects as the thermal printer 1 according to this embodiment.

[0055] It should be noted that the above-described embodiment merely shows one aspect of the present invention, and any modifications and applications are possible within the scope of the present invention.

[0056] For example, in this embodiment, a case is described in which the user operates the button switch 151 to switch between enabling and disabling control for changing the printing conditions CP based on the voltage VB of the battery 18, but the embodiment is not limited to this. For example, when the thermal printer 1 is connected to a commercial power source, the control for changing the printing conditions CP based on the voltage VB of the battery 18 may be disabled. Also, for example, when the battery 18 is being charged, the control for changing the printing conditions CP based on the voltage VB of the battery 18 may be disabled.

[0057] For example, in this embodiment, a case will be described in which the user operates the button switch 151 to switch between enabling and disabling the control that changes the printing conditions CP based on the voltage VB of the battery 18, but the embodiment is not limited to this. The user may also operate the smartphone 2, for example, to switch between enabling and disabling the control that changes the printing conditions CP based on the voltage VB of the battery 18.

[0058] In addition, in the present embodiment, a case will be described in which the communication interface 12 communicates with the smartphone 2 in accordance with the Bluetooth (registered trademark) standard, but the embodiment is not limited to this. The communication interface 12 may also communicate with the smartphone 2 in accordance with, for example, the Wi-Fi (registered trademark) standard.

[0059] Furthermore, in this embodiment, a control method is described in which the processor 11A provided in the thermal printer 1 executes a control program, but the control program executed by the processor 11A to realize this control method can also be configured in the form of a recording medium on which the control program is recorded so as to be readable by a computer, or a transmission medium for transmitting this control program. The recording medium may be a magnetic or optical recording medium or a semiconductor memory device, including portable or fixed recording media such as flexible disks, HDDs, CD-ROMs (Compact Disk Read Only Memory), DVDs (Digital Versatile Disks), Blu-ray (registered trademark) Discs, magneto-optical disks, flash memories, and card-type recording media. The recording medium may be a non-volatile storage device such as RAM, ROM, or HDD, which is an internal storage device provided in the thermal printer 1.

[0060] In this embodiment, the processor 11A executes a control program to control each part of the thermal printer 1, but this is not limiting. The control unit 11 may include, for example, an application specific integrated circuit (ASIC), and the ASIC may execute processing using implemented functions. The control unit 11 may also include, for example, a signal processing circuit, and the signal processing circuit may execute processing by performing signal processing.

[0061] The functions of the control unit 11 may be realized by one or more processors or semiconductor chips. The control unit 11 may further include a co-processor such as an SoC (System-on-a-Chip), an MCU (Micro Control Unit), or an FPGA (Field-Programmable Gate Array). The control unit 11 may perform various controls by using both the CPU and the co-processor in cooperation with each other, or by selectively using one of the two.

[0062] 3 are divided according to the main processing content to facilitate understanding of the processing of control unit 11, and the present invention is not limited by the way in which the processing units are divided or the names of the processing units. The processing of control unit 11 may be divided into more processing units according to the processing content. Furthermore, one processing unit may be divided so as to include more processes.

[0063] In addition, in this embodiment, the processing of the control unit 11 has been described using the flowchart shown in Fig. 3, but the embodiment is not limited to this. For example, the order in which the reduction of the print density PD (step S109 in Fig. 3), the change to the thinning-out energization CE2 (step S113 in Fig. 3), and the reduction of the conveying speed VP (step S117 in Fig. 3) are performed may be reversed. In this embodiment, the printing conditions CP include print density PD, power supply conditions CE for the print head 161, and the transport speed VP for the thermal roll paper. In other words, the printing conditions CP include three printing conditions: print density PD, power supply conditions CE, and transport speed VP. However, the embodiment is not limited to this. For example, the printing conditions CP may include only one or two of the three printing conditions.

[0064] Furthermore, the functional units shown in FIG. 1 represent functional configurations, and specific implementation forms are not particularly limited. In other words, it is not necessary to implement hardware that corresponds to each functional unit individually; it is of course possible to implement a configuration in which a single processor executes a program to realize the functions of multiple functional units. Furthermore, in each of the above-described embodiments, some of the functions realized by software may be implemented by hardware, or some of the functions realized by hardware may be implemented by software. The specific detailed configurations of the other units of the thermal printer 1 may also be changed as desired without departing from the spirit of the present invention. [Explanation of symbols]

[0065] 1...thermal printer, 11...control unit, 11A...first processor, 11B...first memory device, 111...operation reception unit, 112...voltage detection unit, 113...density control unit, 114...power control unit, 115...speed control unit, 12...communication interface, 15...operation panel, 151...button switch (operation reception mechanism), 16...printing unit, 161...print head (thermal head), 162...transport roller (transport mechanism), 17...voltage sensor (detector), 18...battery, 2...smartphone, CE...power supply conditions, CE1...full power supply, CE2...thinning power supply, CP...printing conditions, PD, PDA...print density, RQ...remaining amount, TH1...first threshold, TH2...second threshold, TH3...third threshold, VB...voltage, VP...transport speed.

Claims

1. A battery that acts as a power source; a detector for detecting the voltage of the battery; a thermal head that prints images on recording paper; a control unit for controlling the thermal head; Equipped with the control unit changes the printing conditions of the thermal head based on the voltage detected by the detector. Thermal printer.

2. the printing conditions include print density; the control unit reduces the print density when the voltage is equal to or less than a first threshold value; The thermal printer according to claim 1 .

3. the control unit, when the voltage is equal to or less than a first threshold, reduces the print density in stages based on the voltage; The thermal printer according to claim 2 .

4. the printing conditions include energization conditions for the thermal head, the control unit changes the energization condition from full energization to thinned energization when the voltage is equal to or lower than a second threshold value. The thermal printer according to claim 1 .

5. a conveying mechanism for conveying the recording paper; the printing conditions include a conveyance speed of the recording paper; The control unit reduces the conveying speed when the voltage is equal to or less than a third threshold. The thermal printer according to any one of claims 1 to 4.

6. When the voltage is equal to or less than a third threshold, the control unit gradually reduces the conveying speed based on the voltage. The thermal printer according to claim 5 .

7. Equipped with an operation reception mechanism that accepts operations from users, the control unit switches between enabling and disabling control for changing the printing conditions based on the operation. The thermal printer according to any one of claims 1 to 4.

8. A method for controlling a thermal printer that uses a battery as a power source, comprising: Detecting the voltage of the battery; changing the printing conditions of the thermal head based on the detected voltage; How to control a thermal printer.

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