JP4667475B2 - Thermal printer - Google Patents

Description

  The present invention relates to a thermal printer, and more particularly to a thermal printer capable of improving print quality.

  Thermal printers can be reduced in size and weight, so they are widely applied as printing devices for portable terminal devices. However, for thermal paper feeding, which is printing paper, a stepping motor is used, and for dot printing, It is common to use thermal heads arranged in a line in the width direction of the thermal paper.

  The thermal head has a predetermined number (for example, 384) of heating elements. However, when a battery is used as a power source, it is difficult to supply current to all the heating elements at a time in terms of power supply capacity. One heating element is used as one block, and the thermal head is divided into a plurality of blocks (6 blocks in the case of 384), and the power consumption is suppressed by energizing each block.

  Further, in order to improve the printing speed, the stepping motor is excited during the switching of the energization block, and the thermal paper is fed by a predetermined length (for example, see Patent Document 1).

  FIG. 1 is an explanatory diagram of a conventional thermal printer control method, in which a thermal head has 384 heating elements, 64 heating elements are divided into 6 blocks, and one dot line is being printed. In the figure, the stepping motor advances 4 steps (distance L, for example, 0.125 mm).

  That is, after the # 1 block is energized, the stepping motor advances one step, after the # 2 block is energized, the stepping motor advances one step, after the # 3 and 4 blocks are energized, the stepping motor advances one step, and after the # 5 and 6 blocks are energized The stepping motor advances one step.

  For this reason, when all the 384 heating elements are energized and the ruled lines are printed, the lines are not straight but are hatched.

  In addition, because the rubber roller vibrates due to the start / stop of the stepping motor, the dots printed when the amplitude is large are large and light in density, but printed when the amplitude is small. The dots are small in size and dark.

  FIG. 2 is an explanatory diagram of the relationship between the vibration of the rubber roller, the dot size, and the print density, and shows step # 3 of the stepping motor.

  That is, when the stepping motor is started, the rubber roller is greatly vibrated, and thereafter the amplitude gradually decreases. When the stepping motor is stopped, the rubber roller is vibrated again, and thereafter the amplitude is gradually attenuated.

  When the stepping motor stops, energization of the # 3 block of the heating element is started. However, since the rubber rotor vibrates with a large amplitude, the size of the dots increases and the heating amount per unit area of the thermal paper is small. The print density becomes thin.

  Next, energization of the # 4 block of the heating element is started, but since the amplitude of the rubber roller is small, the size of the dots is small, the heating amount per unit area of the thermal paper is large, and the printing density is It becomes darker.

JP 2001-63124 A

  That is, during one dot line printing, the stepping motor rotates, not only causing a step in printing, but also the printing quality deteriorates due to changes in dot size and density due to vibration of the rubber roller. I can't avoid that.

  The present invention has been made in view of the above problems, and provides a thermal printer that can reduce printing steps and can suppress the occurrence of uneven printing due to vibration of a rubber roller, thereby improving printing quality. Objective.

  A thermal printer according to the present invention is conveyed by a stepping motor, a rotational force transmission mechanism that transmits the rotational force of the stepping motor, a roller that is driven by the rotational force of the stepping motor that is transmitted by the rotational force transmission mechanism, and the roller. A thermal head having a plurality of heating elements arranged in a line in the width direction of the printing paper, a control unit for controlling the rotation of the stepping motor and energization of the thermal head, and the thermal head before printing ruled lines in the width direction of the printing paper. A pre-processing unit that reverses the stepping motor by the number of steps of the stepping motor that rotates during printing of one dot line is provided.

  In the present invention, when a ruled line is printed in the width direction of the printing paper, the stepping motor is reversed in advance by the rotation angle of the stepping motor during one-dot line printing.

  According to the thermal printer of the present invention, when a ruled line is printed in the width direction of the printing paper, the stepping motor is reversely rotated in advance, and a step is generated in the ruled line even if the stepping motor rotates during one-dot line printing. Or, it is possible to maintain the print quality by energizing all the blocks while changing the order while the stepping motor rotates one step.

  FIG. 3 is a functional diagram of the thermal printer according to the first invention. The thermal printer 3 includes a printing unit 31 and a control unit 32.

  The printing unit 31 includes a thermal head 311, a rubber roller 312, a stepping motor 313, and the like, and performs printing with the thermal head 311 on thermal paper transported by the rubber roller 312.

  The control unit 32 includes an MPU (microprocessor unit) 321, a stepping motor drive unit 322, an energization pulse control unit 323, an energization order control unit 324, and a print data transfer unit 325, and rotation control of the stepping motor 313 of the printing unit 31. And the energization control of the thermal head 311 is executed.

  FIG. 4 is a perspective view of the printing unit. In the gear box 314 of the printing unit 31, a speed reduction mechanism 315 including four sets of spur gears is stored. That is, the rotation of the stepping motor 313 is decelerated by the reduction mechanism 315 and drives the rubber roller 312.

  A thermal head 311 is in contact with the rubber roller 312, and thermal paper passes between the rubber roller 312 and the thermal head 311.

  FIG. 5 is a cross-sectional view of the thermal head, in which a heating element 112 is mounted on a protrusion 111 on the upper surface of the substrate 110. Both ends of the heating element 112 are connected to conductors 113 and 114 printed on the substrate 110. When the conductors 113 and 114 are energized, the heating element 112 generates heat, and the thermal agent applied to the thermal paper 115 develops color. Note that the heating element 112 and the conductors 113 and 114 are coated with a protective coating layer 116 in order to protect them from mechanical abrasion with the thermal paper.

  A first aspect of the present invention aims to eliminate a level difference that has occurred when a ruled line is printed in the width direction of a conventional thermal paper.

  That is, the speed reduction mechanism 315 is provided with a backlash as shown in the enlarged view of FIG. 4, and its width is set to about 0.75 mm (corresponding to 6 dot lines).

  When the stepping motor is continuously transporting the thermal paper in the forward direction, the gear of the speed reduction mechanism 315 maintains the contact state, so that backlash does not affect the thermal paper. 116 is successfully transferred.

  On the other hand, when the thermal paper 116 is transferred in the reverse direction, the gear of the speed reduction mechanism 315 comes into contact after the stepping motor 315 rotates reversely by the amount of backlash, and the transfer of the thermal paper 116 is started.

  In the first invention, in order to draw a straight line using backlash, when drawing a ruled line, the stepping motor 315 is equivalent to one dot line (0.75 / 6 = 0.125 mm), that is, It is possible to print a ruled line in a straight line by controlling the energization to the thermal head 311 and the rotation of the stepping motor 315 in accordance with a normal operation after reversing by 4 steps.

  FIG. 6 is a flowchart of a ruled line printing routine executed in the MPU 321 in the first invention, and is executed when a ruled line print command is received from a host computer (not shown).

  When a ruled line print command is received from the host computer in step 60, in step 61, the stepping motor 315 is reversely rotated by 4 steps (corresponding to 0.125 mm).

  Next, in step 62, an energization command is output to the # 1 block of the thermal head 311 to print ruled lines for 64 dots. In step 63, the stepping motor 315 is rotated by one step (equivalent to 0.03 mm) in the forward direction. However, since the stepping motor 315 has been reversely rotated by four steps in advance, the rubber roller 312 does not rotate, and thus the thermal paper 115 is not transferred. , Keep the original position.

  In step 64, power is supplied to the # 2 block of the thermal head 311 and a ruled line for 64 dots is printed in line with the ruled line printed in the # 1 block. In step 65, the stepping motor 315 is rotated in the forward direction by one step, but the thermal paper 115 maintains the original position.

  In step 66, the # 3 and # 4 blocks of the thermal head 311 are energized, and a 128-dot ruled line is printed in line with the already printed ruled line. In step 67, the stepping motor 315 is rotated in the positive direction by one step, but the thermal paper 115 maintains the original position.

  In step 68, the # 5 and # 6 blocks of the thermal head 311 are energized, and a 128-dot ruled line is printed in line with the already printed ruled line. In step 67, the stepping motor 315 is rotated in the positive direction by one step to return to the state before the reverse rotation.

  FIG. 7 is a diagram for explaining the operation of the first invention. The upper part of FIG. 7 shows an energization sequence to the blocks # 1 to # 6 of the thermal head 311 and the lower part of FIG. 7 shows the printing result.

  As described above, according to the first invention, although it is possible to print a straight ruled line strictly, the thermal paper 115 is not transferred while the ruled line for one dot line is being printed. When the thermal agent applied to the thermal paper 115 melts and then solidifies, it adheres to the protective coating layer 116 of the thermal head 311 and then the thermal paper 115 when the thermal paper 115 is transferred in the forward direction. Not only does it not be possible to avoid the generation of abnormal noise and the deterioration of printing quality due to the peeling of the protective coating layer 116, but printing of normal characters / graphics may cause crushing of the print head. It cannot be avoided.

  In the second invention, the stepping motor 313 is controlled in the same manner as in the prior art. A standby time is provided from when the stepping motor 313 is stopped until the thermal head 311 is energized. As a result, the print quality is improved.

  FIG. 8 is a diagram for explaining the operation of the second invention. A standby time is set from when the stepping motor 313 is stopped until the thermal head 311 is energized.

  In the third aspect of the invention, the thermal head is converted into logical blocks having a number smaller than the number of physical blocks, and all the logical blocks are energized during one step of the stepping motor.

  FIG. 9 is a configuration diagram of the thermal printer according to the third aspect of the invention, and a logic block generation unit 326 is installed between the MPU 321 and the energization order control unit 324 with respect to FIG.

  FIG. 10 is a flowchart of a print control routine executed by the MPU 321. In step 100, print data is read from a host computer (not shown). In step 101, an index i indicating a dot line is set to an initial value “1”.

  In step 102, the data of the i-th dot line is read from the print data (for example, 128 dots / dot line × I dot line), and in step 103, the logic block generation routine is executed. To do.

  In step 104, an index j indicating the number of steps of the stepping motor 313 during one-dot line printing is set to an initial value “1”. In step 105, an index k is set to an initial value “1”. Next, in step 106, the logic block LBK (k) is energized.

  In step 107, it is determined whether or not the index k has reached the maximum value K. If a negative determination is made, the index k is incremented in step 108, and the execution of the logic block energization routine is repeated in step 106.

  When an affirmative determination is made in step 107, that is, when the index k reaches the maximum value K, in step 109, the stepping motor is moved one step and the process proceeds to step 110.

  In step 110, it is determined whether or not the index j has reached the maximum value J (for example, “4”). If the determination is negative, in step 111, the index j is incremented and the processing from steps 105 to 109 is repeated.

  When an affirmative determination is made in step 110, that is, when the index j has reached the maximum value J, it is determined in step 112 whether the index i has reached the maximum value I.

  When a negative determination is made at step 112, that is, when the index i has not reached the maximum value I, at step 112, the index i is incremented and the processing of steps 102 to 110 is repeated.

  When the determination at step 112 is affirmative, that is, when the index i reaches the maximum value I, this routine is terminated.

  FIG. 11 is a flowchart of a logical block generation routine executed in step 103, in which physical blocks are grouped to form logical blocks and printed in units of logical blocks, thereby reducing the number of print blocks.

  In step 11a, the logical block LBK (k) is cleared, and in step 11b, an index k indicating the number of logical blocks and an index m indicating the number of physical blocks are respectively set to initial values “1”.

  In step 11c, the kth logical block LBK (k) is updated as the sum of the kth logical block LBK (k) and the mth physical block PLB (m).

  In step 11d, it is determined whether the total number of print dots of the kth logical block LBK (k) and the (m + 1) th physical block PLB (m + 1) is equal to or greater than the maximum number N of dots that can be printed at one time.

  When a negative determination is made in step 11d, that is, when the m + 1th physical block PLB (m + 1) is added to the kth logical block LBK (k), the number of print dots is less than the maximum number of dots N In step 11e, the index m is incremented and the process returns to step 11c.

  When an affirmative determination is made in step 11d, that is, when the (m + 1) th physical block PLB (m + 1) is added to the kth logical block LBK (k), the number of printed dots is equal to or greater than the maximum number of dots N. In step 11f, the index m + 1 is compared with the maximum physical block number M.

  When the calculation result in step 11f is positive, that is, when the index m + 1 is less than M, in step 11g, the index k is incremented and the process proceeds to step 1f.

  When the calculation result of step 11f is zero, that is, when the index m + 1 is equal to M, in step 11h, the (k + 1) th logical block LBK (k + 1) is replaced with the (m + 1) th physical block PLB (m + 1). Proceed to step 1i.

  When the calculation result of step 11f is zero, that is, when the index m + 1 is larger than Mmax, the process proceeds directly to step 11i. However, in step 11i, the index k + 1 is set as the parameter K and this routine is terminated.

  In the first logical block generation routine, continuous physical blocks are grouped to form a logical block, but the number of logical blocks is further reduced by generating non-continuous physical blocks and generating a logical block. It is also possible.

  FIG. 12 is a printing timing chart when the logical block is 2, wherein the first to third physical blocks form the first logical block, and the fourth to sixth physical blocks form the second logical block.

  That is, the first logic block is energized in the first half of the first step and the third step, and the second logic block is energized in the second half. The first logic block is energized in the first half of the second step and the fourth step, and the first logic block is energized in the second half.

  As described above, the print density and size between the first logic block and the second logic block are made uniform by alternately energizing the first logic block and the second logic block in the first half and the second half of each step. Is possible.

  FIG. 13 is a printing timing chart when the logical block is 4, where the first physical block is the first logical block, the second and third physical blocks are the second logical block, and the fourth and fifth physical blocks are the first. Three logical blocks form a sixth logical block and a fourth logical block forms a fourth logical block.

  In the first step, energization is performed in the order of the first, second, third, and fourth logic blocks. In the second step, energization is performed in the order of the second, third, fourth, and first logic blocks. In the step, power is supplied in the order of the third, fourth, first, and second logical blocks, and in the fourth step, power is supplied in the order of the fourth, first, second, and third logical blocks.

  Note that the second invention may be applied to the third invention to provide a waiting time before the logic block is energized.

  FIG. 14 is a timing chart in the case where a standby time is provided in the case of the logic block 2, and printing is performed after the vibration of the rubber roller 312 is reduced by providing the standby time before energization in the first to fourth steps. This makes it possible to further reduce the size of the printing dots.

  In the above embodiment, the energization order of the physical block or logical block is fixed, but the energization state of the stepping motor to be excited, the vibration characteristics unique to the stepping motor, the frequency condition, the stepping motor drive circuit Depending on the characteristics, the energization order may be set so that the variation in the shape of the colored dots is minimized. It is also effective to finely adjust the color dot shape by controlling the energization time of the thermal head heating element.

  The specific method of the energization order and the color dot shape fine adjustment method is shown below.

  FIG. 15 is an explanatory diagram of the energization order and dot shape adjustment method. (B) is an example of the energization order and dot shape adjustment data stored in the non-volatile memory, as shown in [Table 1]. 256 pieces of bit data are stored.

  (C) is a block diagram of one data, and the energization order of 6 blocks is stored as 3 bits of data in 18 bits of bits 00-17. In 6 bits of bits 18 to 23, data indicating the necessity of energization correction for each block is stored.

  Data in the non-volatile memory is indexed by an offset, which is set according to (a). The offset is composed of 8 bits, and a total of 256 data can be set for the four types of values for each of the four types of parameters (motor drive current, motor drive frequency, motor drive voltage, and environmental temperature).

  That is, when print data is generated, motor drive current, frequency and voltage, and environmental temperature are measured, and an offset is set according to the measured values. Then, the address of the nonvolatile memory is specified based on this offset, and the data stored at the address is read out.

  FIG. 16 is a flowchart of the energization sequence and dot shape adjustment routine. In step 16a, it is determined whether or not it is the first energization of one dot line. If the determination is affirmative, the process proceeds to step 16b.

  In step 16b, four types of 2-bit values (00, 01, 10, 11) are set in the 0th and 1st bits of the offset in accordance with the motor drive current. In step 16c, four types of 2-bit values are set in the second and third bits of the offset in accordance with the motor driving frequency. In step 16d, four types of 2-bit values are set in the fourth and fifth bits of the offset in accordance with the motor drive voltage. Further, in step 16e, four types of 2-bit values are set in the sixth and seventh bits of the offset in accordance with the environmental temperature.

  Next, in step 16f, three times the offset data is stored in the accumulator register. In step 16g, the start address of the nonvolatile memory is added to the value of the accumulator register, and in step 16h, it is stored in that address. The energization sequence data and the energization correction data are read out to the accumulator register.

  In step 16i, the contents of the accumulator register are transferred to a predetermined memory work.

  In step 16j, the value stored in the memory work is read, and in step 16k, head energization block control is executed based on this value.

  When a negative determination is made in step 16a, that is, when the first energization of one dot line is not performed, the process proceeds directly to step 16j.

  In the above embodiment, it is assumed that printing of one dot line is fixed to 4 steps. For example, when the number of printing blocks is 3, the fourth step is to actually perform printing. There is no substantial increase in printing time.

  Therefore, if the number of steps of the step motor can be controlled according to the number of printing blocks, the printing time can be shortened.

  FIG. 17 is a structural diagram of a step motor. In the step motor 17, a rotor 172 in which N-pole and S-pole protrusions of a permanent magnet are alternately arranged is installed in a stator 171 having a coil.

  A, B, and C phase coils are wound around the protrusions of the stator 171. In the case of 4-step drive, the stator 171 is driven in the sequence shown in [Table 2].

  That is, when stopping at a certain position, only the A-phase coil is excited with the current i, and in the first step, the A-phase coil and the B-phase coil are excited with the current i / 2.

  Then, at the time of a stop, the protrusion which was under the A phase coil rotates to between the A phase coil and the B phase coil. In the second step, only the B-phase coil is excited with the current i, and the protrusion moves below the B-phase coil. In the third step, the B phase coil and the C phase coil are excited with the current i / 2, and in the fourth step, only the C phase coil is excited with the current i.

  Since the excitation current and sequence of the step motor can be controlled by the MPU 321, the number of steps of one dot line can be changed by changing the control program.

  [Table 3] shows current values and sequences when one dot line is controlled in three steps.

  That is, when stopping at a certain position, only the A-phase coil is excited by the current i. In the first step, when the A-phase coil is excited with an i / 3 current and the B-phase coil is excited with an i (2/3) current, the rotor 172 is 1/3 of the angle formed by the A-phase coil and the C-phase coil. Stop at the position. In the second step, when the B phase coil is excited with the current of i / 3 and the C phase coil is excited with the current of i (2/3), the rotor 172 has a 2/3 angle between the A phase coil and the C phase coil. Stop at the position. In the third step, only phase C is excited with current i.

  [Table 4] shows a current value and a sequence when one dot line is controlled in 6 steps, and is a combination of a case where control is performed in 4 steps and a case where control is performed in 3 steps.

It is explanatory drawing of the control method of the conventional thermal printer. It is explanatory drawing of the relationship between the vibration of a rubber roller, the size of a dot, and printing density. It is a functional diagram of the thermal printer which concerns on 1st invention. It is a see-through | perspective perspective view of a printing part. It is sectional drawing of a thermal head. It is a flowchart of a ruled line printing routine. It is operation | movement explanatory drawing of 1st invention. It is operation | movement explanatory drawing of 2nd invention. It is a block diagram of the thermal printer which concerns on 2nd invention. 4 is a flowchart of a print control routine. It is a flowchart of a logic block generation routine. 10 is a printing timing chart when the logical block is 2. 10 is a printing timing chart when the logical block is 4. 6 is a printing timing chart when a standby time is provided. It is explanatory drawing of an electricity supply order and a dot shape adjustment method. It is a flowchart of an electricity supply sequence and a dot shape adjustment routine. It is a structural diagram of a step motor.

Explanation of symbols

3 Thermal Printer 31 Printing Unit 311 Thermal Head 312 Rubber Roller 313 Stepping Motor 32 Control Unit 321 MPU
322 Stepping motor drive unit 323 Energization pulse generation unit 324 Energization sequence control unit 325 Print data transfer unit 326 Logic block generation unit

Claims (1)

A stepping motor,
A rotational force transmission mechanism for transmitting the rotational force of the stepping motor;
A roller driven by the rotational force of the stepping motor transmitted by the rotational force transmission mechanism;
A thermal head having a plurality of heating elements arranged in a line in the width direction of the printing paper on the printing paper conveyed by the roller;
A controller for controlling rotation of the stepping motor and energization of the thermal head;
Just before starting the received and Borders printing of the print paper width direction borders print instruction, the processing unit prior to reversing the number of steps only the stepping motor of the stepping motor to rotate during printing of one dot line by the thermal head Thermal printer provided.

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