Printing device

Abstract

To start printing without performing many arithmetic processing before starting the printing.SOLUTION: A printer comprises: a printing part 5 which prints on printing paper; conveyance means 4 which conveys the printing paper at intervals of one dot line; an interface part 3 which receives a printing command; application time determination means which calculates an application time based upon the number of divisions calculated from the number of dots for which electricity can be supplied at a time and the number of dots of each dot line of the printing command that the interface part 3 receives; speed calculation means which calculates a conveying speed of the conveyance part based upon the application time that the application time determination means determines; storage means 7 which stores the conveyance speed that the speed calculation means calculates corresponding to the dot line; and speed correction means which corrects the conveyance speed that the storage means 7 stores. The speed correction means makes correction so that a speed difference in conveyance speed stored in the storage means 7 and corresponding to precedent and following dot lines is at a certain ratio or less.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a printing apparatus having a thermal head.

Background Art

[0002] Generally, a thermal printer is known as a printing apparatus that presses a thermal head including a heating element against a conveyed sheet (thermal paper), selectively applies a voltage to the heating element to generate heat, and forms an image by heating an arbitrary portion of the sheet. As a sheet conveying means, a stepping motor (pulse motor) is often used.

[0003] In a printing apparatus using a thermal head, it is necessary to supply sufficient current to the heating element during the conveyance of one dot line. However, if the conveyance speed is too fast compared to the printing amount (number of dots), it is impossible to secure sufficient energization time for the heating element, and the print quality deteriorates. Therefore, the target speed of sheet conveyance is set corresponding to the energization time of the thermal head.

[0004] Normally, since the number of dots that can be energized at one time in a thermal head is limited, for print data of ruled lines or solid black with a large number of dots, printing is enabled by dividing the blocks that generate heat during the conveyance of one dot line into a plurality of blocks and sequentially energizing them. The number of divisions during this printing changes dynamically according to the number of dots in the print data. Conventionally, there is a control method that pre-reads the dots in the subsequent dot line for printing and decelerates the conveyance speed in advance so as to ensure sufficient energization time according to the number of divisions.

[0005] For example, in Patent Document 1, for the stepping motor used for paper conveyance, the speed at which conveyance is possible is calculated based on the application time for each dot line, and printing control is performed characterized by accelerating and decelerating to a target speed based on a predetermined acceleration / deceleration table. In this case, in order to change based on the acceleration / deceleration table, in order to conform to the preset acceleration / deceleration table, even in a situation where conveyance is possible at a speed between the preset speeds, it is necessary to convey at a speed set lower than that, and the printing speed may decrease.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] On the other hand, in order to ensure the energization time to the heating element of the thermal head, it is conceivable to perform look-ahead to obtain the necessary conveyance speed. However, in order to ensure sufficient energization time even in the worst case, if a large number of dot lines are read and look-ahead processing is performed, a large amount of arithmetic processing is required before printing, and it may take time until the paper is actually conveyed and printing starts.

Means for Solving the Problems

[0008] In view of the above, in the printing apparatus according to the present invention, a printing unit having a thermal head that performs printing on printing paper; a conveyance unit that conveys the printing paper one dot line at a time; an interface unit that receives a printing instruction; Applying time determination means for calculating an applying time required for printing of one dot line including an energization time of the current based on a division number calculated from a number of dots that can be energized to the thermal head at one time and a number of dots for each dot line of the printing command received by the interface unit; Speed calculation means for calculating a conveyance speed of the conveyance unit based on the applying time calculated by the applying time determination means; Storage means for sequentially storing by switching conveyance speeds of a plurality of dot lines of a preset number read out in the printing order from the printing command each time printing of each dot line by the printing unit is completed; Speed correction means for correcting the conveyance speed stored in the storage means; Comprising; When a speed ratio of the conveyance speed of the first dot line read out from the printing command to the conveyance speed of the second dot line stored immediately before the first dot line in the storage means is a constant ratio, for each of the plurality of dot lines sequentially stored in the storage means, the conveyance speeds of the plurality of dot lines are sequentially corrected so that the speed ratio of the conveyance speeds of the front and rear dot lines becomes the constant ratio. Next When it is, for each of the plurality of dot lines sequentially stored in the storage means, the conveyance speeds of the front and rear dot lines become the constant ratio Above So as to, the conveyance speeds of the plurality of dot lines are From the second dotted line Sequentially corrected, which is characterized in that.

Effect of the Invention

[0009] According to the present invention, printing can be started without performing a lot of arithmetic processing before starting printing.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] (First Embodiment) Hereinafter, a printing apparatus according to an embodiment of the present invention will be described. FIG. 1 is a perspective view of the configuration of a printing apparatus 100 according to an embodiment of the present invention as viewed from the front side.

[0012] The printing apparatus 100 includes a main body 101 formed of a substantially rectangular parallelepiped housing, and the main body 101 is formed of metal, for example, aluminum or synthetic resin. On the front surface of the main body 101 when viewed in the direction of arrow A in the figure, a discharge port for printing paper (hereinafter referred to as "printer exit") 103 is provided.

[0013] Furthermore, a recessed portion 104 is formed on the upper surface of the main body 101 when viewed in the direction of arrow A in the figure. A printer entrance, which is an insertion port for printing paper, is provided in the recessed portion 104.

[0014] The printer exit 103 and the printer entrance are open along the longitudinal direction of the main body 101.

[0015] An operation display unit 221 is provided on the upper left side of the main body 101 when viewed in the direction of arrow A in the figure. The operation display unit 221 is composed of a switch, a touch panel, etc., and the user can operate the printer. Also, information is displayed to the user by an LED, a liquid crystal panel, etc.

[0016] In the printing device 100, printing paper, which is thermal paper inserted from the printer entrance, is conveyed in a predetermined direction (the conveyance direction orthogonal to the longitudinal direction) while being sandwiched between a thermal head and a platen roller disposed in the housing, and is conveyed to the printer exit 103. With respect to the printing paper conveyed while being sandwiched between the thermal head and the platen roller, printing is performed by driving the thermal head according to a control instruction from the control CPU1 described later to cause the heating element to generate heat.

[0017] The control of the printing device is performed by the control block shown in FIG. 2. The control CPU1 controls the entire device by, for example, expanding and executing the control program stored in the ROM8 in the RAM7. The temperature sensor 2 is composed of a thermistor or the like, and includes a head thermistor that measures the temperature of the thermal head and an ambient temperature thermistor that measures the temperature of the ambient environment of the thermal head. The temperatures acquired by these are used for the purpose of determining the amount of heat applied to the paper and for the purpose of monitoring so as not to burn out the thermal head. Note that, as the ambient temperature thermistor, a thermistor provided on the control board where the control CPU1 is disposed and a thermistor provided in the battery unit for measuring the temperature of the battery are provided, and either one or both of the thermistors may be used in combination.

[0018] The interface unit 3 is composed of a USB, a BLUETOOTH (registered trademark) module, a wireless LAN module, etc., and receives a printing command for the control CPU1 by wire or wirelessly, or transmits a reply from the control CPU1 to a status inquiry. The control of the printing device 100 is performed according to a command (printing command) transmitted from this interface unit 3.

[0019] The conveyance unit 4 is composed of a platen roller that conveys the paper inserted from the printer entrance, a stepping motor that rotates the platen roller, etc., and conveys the paper in the printing direction. It also includes a paper detection sensor that detects the inserted paper.

[0020] The printing unit 5 is composed of a thermal head or the like in which heating elements are arranged orthogonally to the paper conveyance direction, and performs printing by applying the heat generated by energizing the heating elements block by block to the thermal paper.

[0021] The battery voltage detection unit 6 measures the voltage state of the battery. The measured voltage is used for determining the energization time for determining the amount of heat applied to the paper and for monitoring the voltage drop state.

[0022] The RAM 7 is used as a working area for the control CPU 1, stores measurement data of various sensors, stores received commands and received printing data, and stores the energization time for each dot line of the pre-read printing data and the corresponding conveyance speed.

[0023] The ROM 8 stores a control program for controlling the entire device and font information used for printing. The EEPROM 9 stores device parameters related to the control of the device.

[0024] FIG. 3 shows the control in the control CPU 1 from the start to the end of printing in this control in a flowchart. First, for each dot line of the printing data received from the interface unit 3, the application time of the thermal head and the conveyance speed of the motor are calculated.

[0025] Next, in step S1, the battery voltage is acquired using the battery voltage detection unit 6, and in step S2, the temperature of the thermal head and the ambient temperature are acquired using the temperature sensor 2.

[0026] Next, in step S3, first, the number of divisions for each dot line is calculated from the number of dots in the current dot line and the dot number limit that can be energized at once for the thermal head. Also, the energization time is calculated from the battery voltage acquired in step S1, and the calculated energization time is corrected using the head temperature and ambient temperature acquired in step S2. The application time of the thermal head is calculated including the corrected energization time using temperature, the number of divisions, the latch time for data switching of the thermal head, and the protection time for preventing continuous energization, and is added to the end of the application time buffer in RAM7. At this time, the control CPU1 functions as an application time determination means.

[0027] In step S4, the control CPU1 functioning as a speed calculation means calculates the conveyance speed at which the calculated application time can be secured between dot lines, and in step S5, the calculated conveyance speed is added to the end of the conveyance speed buffer in RAM7 as a storage means.

[0028] In step S6, it is determined whether the application time and conveyance speed for each dot line for a pre-specified number of specified lines are stored in the buffer in RAM7 by repeating the above steps S1 to S5.

[0029] If the answer in step S6 is No, the process returns to step S1 again, replaces the next dot line with the current dot line, and executes the process. If the answer in step S6 is Yes, the process proceeds to step S7, reads the application time from the buffer head, and then reads the conveyance time from the buffer head in step S8, emptying each buffer by one.

[0030] In step S9, the thermal head is energized according to the read application time, and the motor is operated at the read conveyance speed to perform print control.

[0031] After that, one dot line is read from the print data, and the one-line look-ahead process described below is executed to add the application time and the conveyance speed to the end of the buffer. The processes of steps S7 to S10 above are repeated until the end of the print data to complete the print control. Near the end of the print data, there are no more lines to look ahead, but in this case, step S10 may be omitted and the process may proceed.

[0032] Figure 4 shows a flowchart of the one-line look-ahead process for calculating the application time of the thermal head and the conveyance speed of the motor for each dot line from the print data. Since steps S1 to S4 are the same processes as in FIG. 3, the same step numbers are used and the description is omitted.

[0033] In step S12, the speed difference between the conveyance speed of the previous dot line and the current dot line is calculated. Since the already calculated conveyance speed stored at the end of the conveyance speed buffer corresponds to the conveyance speed of the dot line immediately before the current dot line, the speed difference from that conveyance speed is calculated.

[0034] Proceed to step S13. If the conveyance speed of the current dot line is faster, it is determined that there is acceleration with respect to the previous conveyance speed, and the process proceeds to step S16. Otherwise, it is determined that there is deceleration or the speed is the same as the current speed, and the process proceeds to step S14.

[0035] If the answer in step S13 is No (in the case of deceleration), the process proceeds to step S14. If the speed with respect to the previous conveyance speed is lower than a preset speed ratio (for example, 0.8), it is determined that the previous conveyance speed is too fast with respect to the current conveyance speed, and it is determined that the previous conveyance speed needs to be corrected (Yes in step S14). As a result, in step S15, the previous conveyance speed is decelerated and corrected to a conveyance speed that matches the preset speed ratio (for example, 1.25) with respect to the current conveyance speed, and the speed is slowed down. Then, it is replaced with the conveyance speed (the previous conveyance speed) stored at the end of the conveyance speed buffer. After that, the process proceeds to step S5, the current conveyance speed is stored at the end of the conveyance speed buffer, and the process proceeds to step S18.

[0036] If the answer in step S13 is Yes (in the case of acceleration), proceed to step S16. If the speed relative to the previous conveyance speed exceeds a preset speed ratio (for example, 1.25), it is determined that the current conveyance speed is too fast relative to the previous conveyance speed, and it is determined that the current conveyance speed needs to be corrected (Yes in step S16). As a result, in step S17, the current conveyance speed is decelerated and corrected to a conveyance speed that changes to match the preset speed ratio with respect to the previous speed, thereby slowing down the speed. Thereafter, proceed to step S5, store the corrected current conveyance speed at the end of the conveyance speed buffer, and proceed to step S18.

[0037] As described above, since the conveyance speed in the conveyance speed buffer changes by being corrected in step S15, the speed difference from the previous conveyance speed is further calculated, and the processes of steps S12 to S17 and S5 are repeated up to the conveyance speed in the conveyance speed buffer corresponding to a specified number of dot lines, thereby correcting the conveyance speed at the location where deceleration is required. In step S18, it is determined whether the confirmation up to the buffer position corresponding to this preset number of dot lines has been completed. If the specified number of confirmations has not been completed, return to step S12, and if the confirmation has been completed, end the process.

[0038] These speed corrections give priority to the deceleration process of the dot line with the higher speed in accordance with the conveyance speeds in the previous and subsequent dot lines, taking into account the time required for printing. However, if the application time can be ensured even with the speed correction by the acceleration process, the correction by the acceleration process may be performed.

[0039] Figure 5 shows the change in the dot line position of the conveyance speed calculated in step S4 of Figure 4. At this point, since the conveyance speed of the paper is calculated only according to the application time required for the print data, the speed becomes slow where the print amount of the dot line is large, and the speed becomes fast where the amount is small. Therefore, the speed becomes slower or faster according to the printing status of the dot line, and the speed change between dot lines with many dot number changes becomes steep. If the paper is conveyed according to this conveyance speed, the stepping motor is likely to get out of sync and unable to operate.

[0040] On the other hand, Figure 6 shows the change in the dot line position of the conveyance speed stored in the conveyance speed buffer after correction using the speed difference and speed ratio of the conveyance speed for each of the front and rear dot lines in the processes of steps S12 to S18 described with reference to Figure 4. By correcting the speed toward the line that requires deceleration so that the speed change becomes a smooth change, and similarly, the acceleration is also corrected smoothly.

[0041] Also, in the case where the print amount of the dot line instantaneously decreases and acceleration is possible considering only the print data, the conveyance speed is corrected within the range that the motor can follow so that the speed ratio of the front and rear dot lines becomes equal to or less than a certain ratio, thereby enabling conveyance control at the fastest possible conveyance speed while maintaining the required speed within the range without getting out of sync.

[0042] (Second Embodiment) Hereinafter, a printing apparatus according to a second embodiment of the present invention will be described. In the printing apparatus according to this embodiment, it is characterized in that, with respect to the printing apparatus according to the first embodiment, when correcting the conveyance speed, the conveyance speed is corrected using a table of conveyance speeds that are not used. Therefore, in the following description, only the parts different from the first embodiment will be described.

[0043] In the stepping motor used as the drive source for paper conveyance in the printing apparatus 100, a resonance phenomenon may occur in a specific speed band where the amplitude during operation increases due to the natural frequency and rotational vibration of the motor and the peripheral mechanism, resulting in noise.

[0044] In the present embodiment, in order to avoid the specific speed band and operate without resonance, a prohibited speed band is provided and the conveyance speed is readjusted to reduce noise.

[0045] When the conveyance speed calculated in step S4 in FIG. 4 or the conveyance speed added to the conveyance speed buffer by step S5 is a speed included in the prohibited speed band, it will be changed to the upper limit or lower limit value of the prohibited speed band. However, in a thermal printer, since there is an application time required to color the thermal paper, if the speed is increased with respect to the prohibited speed band, the application time will be shortened and the coloring will become lighter. Therefore, in the present embodiment, in order to guarantee (ensure) the application time, the speed included in the prohibited speed band is corrected to the lower limit value of the prohibited speed band.

[0046] FIG. 7 shows a state in which the speed included in the prohibited speed band is corrected to the lower limit value of the prohibited speed band with respect to the conveyance speed shown in FIG. 6 described in the first embodiment. Each conveyance speed included in the prohibited speed band is corrected to the lower limit value of the prohibited speed band. In FIG. 7, only the conveyance speed included in the prohibited speed band is corrected to the lower limit value of the prohibited speed band. However, considering the speed ratio between the conveyance speeds before and after that by correcting the conveyance speed included in the prohibited speed band to the lower limit value, the conveyance speeds before and after may be corrected again. At that time, the conveyance speed after correction is calculated so that the conveyance speeds before and after correction are also conveyance speeds not included in the prohibited speed band.

[0047] FIG. 8 is a flowchart showing a process of correcting the transport speed to the lower limit value of the prohibited speed band when there are a plurality of such prohibited speed bands and the calculated transport speed is included in the prohibited speed band. Note that the process of this flowchart may be executed every time a transport speed is stored in the transport speed buffer in FIG. 4, or may be separately executed after all the processes in FIG. 4 are completed. When the process of this flowchart corrects the transport speed after all the processes in FIG. 4 are completed, it is preferable to execute the processes after step S12 in FIG. 4 again for the corrected transport speed.

[0048] In step S21, one transport speed is acquired from the head of the transport speed buffer. Next, in step S22, the upper limit speed and the lower limit speed of one prohibited speed band of the fastest speed band are acquired.

[0049] In order to check whether the transport speed acquired from the transport speed buffer is included in the range of the acquired prohibited speed band, in step S23, it is determined whether the transport speed is less than the lower limit value of the prohibited speed band.

[0050] If the transport speed is greater than or equal to the lower limit value of the prohibited speed band, in step S24, it is determined whether the transport speed is greater than the upper limit value of the prohibited speed band. If the transport speed is less than or equal to the upper limit value of the prohibited speed band, in step S25, the transport speed is corrected to the speed of the lower limit value of the prohibited speed band, and in step S26, it is overwritten and added to the transport speed buffer.

[0051] As a result of the determination in step S23, if it is less than the lower limit value of the prohibited speed band, in S27, it is checked whether there is a next prohibited speed band. If there is, the process returns to step S22, and the upper limit speed and the lower limit speed of the prohibited speed band of the slower speed band are acquired.

[0052] Note that as a result of the determination in step S24, if the transport speed is greater than the upper limit value of the prohibited speed band, the process ends, and when the next transport speed is calculated or exists, this series of processes is executed again.

[0053] By the process described above, it is possible to avoid speeds that are included in the prohibited speed band, which is a speed band with large vibrations during operation, and to reduce noise during driving.

Explanation of Signs

[0054] 1 Control CPU 2 Temperature sensor 3 Interface section 4 Conveyor section 5 Printing section 6 Battery voltage detection section 7 RAM (Storage means) 8 ROM 9 EEPROM

Claims

1. A printing unit having a thermal head for printing on printing paper, A conveying unit for conveying the printing paper one dot line at a time, An interface unit for receiving a printing command, Application time determination means for calculating the application time required for printing of the one dot line including the energization time of the current based on the number of dots that can be energized to the thermal head at one time and the number of dots per dot line of the printing command received by the interface unit, Speed calculation means for calculating the conveyance speed of the conveying unit based on the application time calculated by the application time determination means, Storage means for sequentially storing, for each of a plurality of dot lines of a predetermined number read in order from the printing command, the conveyance speed of each dot line after switching each time the printing of each dot line by the printing unit is completed, Speed correction means for correcting the conveyance speed stored in the storage means and comprising, The speed correction means, when the speed ratio of the conveyance speed of the first dot line read from the printing command to the conveyance speed of the second dot line stored one before the first dot line in the storage means is less than a certain ratio, for each of the plurality of dot lines sequentially stored in the storage means, corrects the conveyance speed of the plurality of dot lines sequentially from the second dot line so that the speed ratio of the conveyance speeds of the front and rear dot lines is equal to or greater than the certain ratio. A printing apparatus characterized by this.

2. The speed correction means, when the speed ratio of the conveyance speed of the first dot line to the conveyance speed of the second dot line is less than the certain ratio, corrects the conveyance speed of the second dot line so that the speed ratio becomes equal to or greater than the certain ratio, and then, so that the speed ratio of the conveyance speed of the second dot line to the conveyance speed of the third dot line stored one before the second dot line in the storage means is equal to or greater than the certain ratio, corrects the conveyance speed of the third dot line. The printing apparatus according to Claim 1, characterized by this.

3. The speed correction means, when the corrected conveyance speed is included in a preset first speed band, corrects the conveyance speed to the lower limit value of the first speed band. The printing apparatus according to Claim 1 or 2, characterized by this.

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