Printing apparatus and method for controlling the printing apparatus

Abstract

To solve such a problem that there is such a risk that deformation of a roller affects printing.SOLUTION: A printer comprises: a printing unit which performs printing on a recording sheet; a conveyance unit which holds the recording sheet with the printing unit and itself, has a roller that rotates in the first direction and the second direction opposite to the first direction around a shaft and a motor that rotates the shaft; a detection unit which detects the rotation of the shaft; a storage unit which stores a first rotation amount based on detection of the shaft by the detection unit in a period from the time when the shaft is rotated in the first direction by the motor of the conveyance unit and stopped to the time when the prescribed time or more elapses after the stop; and a control unit which controls the printing unit and the conveyance unit. The control unit stops after being rotated in the first direction with respect to the shaft by the motor of the conveyance unit, is rotated in the second direction by a second rotation amount calculated by using a first rotation amount stored in the storage unit when the printing unit performs printing in a period less than the prescribed time from the stop, and is rotated in the first direction before printing by the printing unit by a third rotation amount calculated by using the first rotation amount stored in the storage unit.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a printing apparatus and a method for controlling the printing apparatus.

Background Art

[0002] Conventionally, as shown in Patent Document 1, there is known a printing apparatus that sandwiches a printing medium between a platen roller and a thermal head and performs forward conveyance and reverse conveyance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the printing apparatus described in Patent Document 1 does not consider deformation of the platen roller during conveyance, which may affect printing.

Means for Solving the Problems

[0005] The printing apparatus comprises a printing unit for printing on recording paper, a transport unit having rollers that, together with the printing unit, sandwich the recording paper and rotate around an axis in a first direction and a second direction opposite to the first direction to transport the recording paper, and a motor for rotating the axis, a detection unit for detecting the rotation of the axis, a storage unit for storing a first amount of rotation based on the detection of the axis by the detection unit for a predetermined time or longer after the axis is rotated in the first direction by the motor of the transport unit and then stopped, and before printing by the printing unit, the control unit rotates the axis in the second direction by a second amount of rotation calculated using the first amount of rotation stored in the storage unit, and rotates the axis in the first direction before printing by the printing unit by a third amount of rotation calculated using the first amount of rotation stored in the storage unit.

[0006] A control method for a printing apparatus comprising: a printing unit for printing on recording paper; a transport unit having rollers that sandwich the recording paper together with the printing unit and rotate around an axis in a first direction and a second direction opposite to the first direction to transport the recording paper, and a motor for rotating the axis; a detection unit for detecting the rotation of the axis; and a storage unit that stores a first amount of rotation based on the detection of the axis by the detection unit for a predetermined time or longer after the motor of the transport unit rotates the axis in the first direction and stops, wherein when the motor of the transport unit rotates the axis in the first direction and stops, and printing is performed by the printing unit before the predetermined time after stopping, the unit rotates in the second direction by a second amount of rotation calculated using the first amount of rotation stored in the storage unit, and rotates in the first direction before printing by the printing unit by a third amount of rotation calculated using the first amount of rotation stored in the storage unit. [Brief explanation of the drawing]

[0007] [Figure 1] A block diagram showing the configuration of a printing device. [Figure 2]A schematic cross-sectional view showing the main components of a printing device. [Figure 3] A cross-sectional view showing the deformation of the platen roller at the start of paper feeding. [Figure 4] A cross-sectional view showing the deformation of the platen roller when the paper feed stops. [Figure 5] A flowchart illustrating paper feed control. [Figure 6] A time chart showing paper feed control. [Figure 7] A schematic diagram showing the printing result due to paper feed control. [Modes for carrying out the invention]

[0008] 1. Embodiment 1-1. Configuration of the printing device The printing device 1 shown in Figures 1 and 2 is a line thermal printer that prints, for example, receipts. As shown in Figure 1, the printing device 1 comprises a control unit 10, a storage unit 20, a printing unit 30, a transport unit 40, a detection unit 50, and a cutting unit 60.

[0009] The storage unit 20 is a rewritable non-volatile memory, such as flash ROM (Read Only Memory), and can store predetermined information including firmware (a program) and information related to the control of each part. The storage unit 20 also includes RAM (Random Access Memory), which is a volatile memory used as a work area by the control unit 10. The control unit 10 is equipped with a CPU (Central Processing Unit) that performs various controls on each part of the printing device 1. The CPU is also called a processor. The CPU of the control unit 10 reads and executes firmware and predetermined information stored in the storage unit 20.

[0010] The printing unit 30 includes a head 31 and a heat sink 32, as shown in Figure 2. The head 31 is, for example, a line thermal head. The head 31 is supported by a heat sink 32 made of aluminum or the like. The printing unit 30 also includes a pressing mechanism (not shown) that presses the head 31 toward the roller 43. The recording paper 90 is thermal paper, and while in contact with the head 31 by the pressing mechanism, it is colored and printed by the heat generated by the head 31. The control unit 10 controls the head 31 to print on the recording paper 90 based on print data received from an external device. The recording paper 90 printed by the head 31 is cut by a cutting unit 60 having a moving cutter blade and discharged from an outlet (not shown).

[0011] As shown in Figure 2, the transport unit 40 is composed of a motor 41, a gear 42, and rollers 43. The rollers 43 have an axle 44. The transport unit 40 is configured such that, under the control of the control unit 10, the motor 41 rotates, and the rotation is transmitted to the axle 44 via the gear 42 while being reduced in speed, causing the rollers 43 to rotate around the axle 44 and transport the recording paper 90. The roller 43 is formed in a cylindrical shape from a flexible resin such as silicone rubber and is fixed to the shaft 44. The roller 43 is located opposite the head 31 via the recording paper 90 and is also called the platen roller.

[0012] The motor 41 is, for example, a DC motor. The control unit 10 receives the detection signal from the detection unit 50 (described later) to detect the speed of the motor 41 and controls the motor 41 using PWM (Pulse Width Modulation) to rotate it at a predetermined speed.

[0013] The recording paper 90 is in a long, rectangular shape and is stored in the printing device 1 as roll paper 91, which is wound into a roll. The rollers 43 of the transport unit 40, together with the head 31 of the opposing printing unit 30, hold the recording paper 90. When printing on the recording paper 90, the rollers 43 rotate, pulling the recording paper 90 from the roll paper 91 and transporting it.

[0014] When the recording paper 90 is printed by the head 31, the directions in which the roller 43 and the shaft 44 rotate are the first direction, which is the clockwise direction, the CW direction. At this time, the roller 43 conveys the recording paper 90 in the forward direction, the F direction. The control unit 10 performs printing by the head 31 while conveying the recording paper 90 in the F direction by the roller 43.

[0015] The roller 43 and the shaft 44 can also rotate in a second direction opposite to the first direction. The second direction is the counterclockwise direction, the CCW direction. At this time, the roller 43 conveys the recording paper 90 in the reverse direction, the R direction, which is opposite to the F direction. Note that when the control unit 10 conveys the recording paper 90 in the R direction by the roller 43, it does not perform printing by the head 31.

[0016] The detection unit 50 is a so-called rotary encoder that can detect the rotation of the shaft 44. Specifically, the detection unit 50 is configured to detect the position of the shaft 44. As shown in FIG. 2, the detection unit 50 is an optical rotary encoder including a disk 52, which is a scale with slits opened at predetermined intervals on the circumference, and a transmissive photosensor 51 that detects the slits of the disk 52.

[0017] The photosensor 51 includes a light-emitting element and a light-receiving element. The light-emitting element and the light-receiving element are arranged so as to sandwich the disk 52. The disk 52 is fixed to the shaft 44 and is attached so as to rotate about the shaft 44. When the shaft 44 rotates by the motor 41, the disk 52 also rotates, and the positions of the slits provided on the disk 52 also rotate. When the position of the slit becomes the position on the optical path of the light-emitting element, light passes through the slit and reaches the light-receiving element, and the light-receiving element detects the light. At this time, since the light-receiving element generates a predetermined current, it can be taken out as a detection signal of a high-level voltage. On the other hand, when the position of the slit is out of the optical path of the light-emitting element, the light is blocked by the disk 52, and the light-receiving element does not detect the light. At this time, since the light-receiving element does not generate a predetermined current, it can be taken out as a detection signal of a low-level voltage.

[0018] 1-2. Deformation of the roller As described above, the roller 43 of the conveyance unit 40 is pressed against the head 31 by the pressing of the pressing mechanism of the printing unit 30. Further, the roller 43 is formed of a material such as a flexible resin such as silicone rubber. Therefore, as the shaft 44 rotates and stops, the portion including the portion in contact with the head 31 of the roller 43 is deformed or tries to return from the deformation.

[0019] Referring to FIG. 3, the deformation of the roller 43 when the control unit 10 rotates the shaft 44 by the motor 41 and starts to convey the recording paper 90 in the F direction will be described. The states X1, X2, and X3 indicate the deformation states of the roller 43 and the transition of the deformation.

[0020] In the roller 43, with the portion in contact with the head 31 as the center, the upstream portion in the F direction is defined as the A portion, and the downstream portion in the F direction is defined as the B portion. The state X1 indicates the stopped state before the roller 43 and the shaft 44 rotate. The roller 43 sandwiches the recording paper 90 together with the head 31. The roller 43 is in the state before deformation and is substantially circular. [[ID=…]] [[ID=…]]

[0021] [[ID=…]] The state X2 indicates the state when the motor 41 starts to rotate and the shaft 44 starts to rotate in the CW direction under the control of the control unit 10. At this time, due to the flexibility of the roller 43, torsional deflection occurs in the roller 43 with respect to the shaft 44, and it is deformed. In the state X2, the portion including the portion in contact with the head 31 in the roller 43 is deformed so as to move closer to the upstream in the F direction. Specifically, the A portion of the roller 43 is deformed so as to bulge, and the B portion is deformed so as to shrink. In other words, the A portion of the roller 43 is deformed so as to protrude, and the B portion is deformed so as to retract. Although the shaft 44 is rotating in the CW direction, the torque of the shaft 44 is used to deform the roller 43, so the roller 43 only deforms and does not rotate. Therefore, the roller 43 does not transport the recording paper 90 in the F direction.

[0022] State X3 further describes the state when the motor 41 rotates and the shaft 44 rotates in the CW direction. Once the deformation of the roller 43 is complete, the torque of the shaft 44 is used to rotate the roller 43, so the roller 43 also begins to rotate in the CW direction. Consequently, the roller 43 begins to transport the recording paper 90 in the F direction. The roller 43 remains in its deformed state.

[0023] In Figure 3, the control unit 10 shows the case where the roller 43 starts transporting the recording paper 90 in the F direction, but the same applies when transport is started in the R direction, which is the opposite direction to the F direction. In this case, the portion of the roller 43 that is in contact with the head 31 deforms in the opposite direction to the above case, moving towards the direction of the cut portion 60. Specifically, portion B of the roller 43 deforms to bulge out, and portion A deforms to shrink. In other words, portion B of the roller 43 deforms to protrude, and portion A deforms to recede.

[0024] Referring to Figure 4, the return of the deformation of the roller 43 when the roller 43 stops transporting the recording paper 90 will be explained. States X4, X5, and X6 show the state of the roller 43's deformation return and the progression of the deformation return. State X4 is the same as state X3 shown in Figure 3. The shaft 44 and roller 43 are rotating in the CW direction, and the roller 43 is transporting the recording paper 90 in the F direction. The roller 43 remains in its deformed state. As will be described later, the time at this time is denoted as time t0, as shown in Figure 6.

[0025] State X5 indicates the state of the roller 43 when the control unit 10 stops the rotation of the motor 41. The shaft 44 and roller 43 also stop rotating. The roller 43 stops transporting the recording paper 90 in the F direction. The roller 43 is still in its deformed state. As described later, the time at this time is denoted as time t1, as shown in Figure 6. At this time, the control unit 10 detects the position P1 of the axis 44 using the detection unit 50.

[0026] State X6 further describes the state after time has passed. Due to the flexibility of the roller 43, a force acts on the shaft 44 to restore the deformation to its original state. Specifically, the roller 43 attempts to restore the torsional deflection of the shaft 44. As described above, shaft 44 is connected to motor 41 via gear 42. The head 31 is pressed against roller 43 by the pressing force of the pressing mechanism of the printing unit 30. The detent torque that works to maintain the rotor position within motor 41 is less than the pressing force of the pressing mechanism of the printing unit 30. Therefore, the force attempting to restore the deformation of the roller 43 acts to rotate the shaft 44 in the opposite direction. Specifically, the shaft 44 rotates in the CCW direction, which is the direction of the reaction force to the torsional deflection force in the CW direction that was generated in the roller 43.

[0027] As a result, the deformation of the roller 43 returns to its original state. As described later, time t4 is defined as the time after a predetermined time T or more has elapsed from time t1, when the control unit 10 stops the rotation of the motor 41, as shown in Figure 6. At time t4, the deformation of the roller 43 has fully returned to its original state. The roller 43 has returned to its pre-deformation state and is almost circular. Furthermore, as will be described later, the time when the predetermined time T is less than is defined as time t3, as shown in Figure 6. At time t3, the deformation of the roller 43 has not fully returned to its original state. Furthermore, when state X6 is reached, the control unit 10 detects the position P2 of the shaft 44 using the detection unit 50. The control unit 10 calculates the amount of reverse rotation ΔP when the shaft 44 rotates in the reverse direction using the formula ΔP = |P1 - P2|.

[0028] In Figure 4, the control unit 10 is shown transporting the recording paper 90 in the F direction using the roller 43 and then stopping. However, the same applies when the paper is transported in the R direction, which is the opposite direction to the F direction, and then stops. In this case, the force attempting to restore the deformation of the roller 43 acts to rotate the shaft 44 in the opposite direction. Specifically, the shaft 44 rotates in the CW direction, which is the direction of the reaction force to the torsional deflection force in the CCW direction that was generated in the roller 43.

[0029] 1-3. Control Method for Printing Devices The control method for the printing device 1 will be explained with reference to Figures 5 and 6, and also with corresponding information in Figure 4. First, the detection signal of the detection unit 50 shown in Figure 6 will be explained.

[0030] As shown in Figure 6, when the voltage of the detection signal output by the detection unit 50 is high, it means that the photosensor 51 of the detection unit 50 has detected the position of a slit provided on the disc 52 which is coaxial with the axis 44. When the voltage of the detection signal is low, it means that the photosensor 51 has detected the position of a part of the disc 52 that is not a slit.

[0031] The disc 52 has two sets of slits arranged with different phases, and each set is configured to be detected by the photosensor 51. Therefore, as shown in Figure 6, the detection unit 50 outputs detection signals for phases A and B that are shifted by 90 degrees in phase, i.e., shifted by 1 / 4 period, and inputs them to the control unit 10. The control unit 10 can determine from the order of phase displacements of phase A and phase B whether the direction of rotation of the shaft 44 is the CW direction or the CCW direction, which is the opposite direction to the CW direction. The CW direction is the first direction, and the CCW direction is the second direction.

[0032] Figure 6 shows the detection signals output from the detection unit 50 in a time series from t0 to t8, indicating the time. The detection signal from the detection unit 50 is output as a pulse with a predetermined period. One pulse in one period of the detection signal from the detection unit 50 is defined as 1 pulse. The occurrence of this pulse indicates that the shaft 44 is rotating, and the number of pulses indicates the amount of rotation of the shaft 44. As described above, the control unit 10 can determine the rotation direction, amount of rotation, and position of the shaft 44 based on the detection signal from the detection unit 50.

[0033] Now, let's assume that the control unit 10 of the printing device 1 starts rotating the motor 41, and the shaft 44 starts rotating in the CW direction. As shown in Figure 3, as the shaft 44 rotates, the roller 43 deforms from state X1 through state X2 to state X3. Then, the roller 43, together with the head 31, grips the recording paper 90 and transports it in the F direction. As shown in Figure 5, the control unit 10 uses the roller 43 to transport the recording paper 90 in the F direction, which is the printing direction, in what is called forward feeding (S100). This state corresponds to state X4 in Figure 4 and corresponds to time t0 in Figure 6. At this time, the control unit 10 can perform printing with the head 31 while transporting the recording paper 90 in the F direction by the roller 43, based on the print data received from the external device.

[0034] Next, as shown in Figure 5, the control unit 10 stops the motor 41, and also stops the rotation of the shaft 44 and roller 43 (S101). This state corresponds to state X5 in Figure 4 and corresponds to time t1 in Figure 6. The control unit 10 detects the position P1 of the axis 44 when it stops based on the detection signal from the detection unit 50 (S102).

[0035] The control unit 10 determines whether it has received print data from the external device (S103). If the control unit 10 has not received print data from the external device, it waits until it receives it (S103: NO). During this time, including the time it takes for the control unit 10 to determine whether it has received print data, the shaft 44 rotates in the reverse direction in the CCW direction due to the force of the roller 43 trying to return to its original shape. This state corresponds to state X6 in Figure 4, and to time t3 or time t4 in Figure 6. Time t2 in Figure 6 is the timing when the shaft 44 begins to rotate in the reverse direction due to the force of the roller 43 trying to return to its original shape. The control unit 10 may also perform hold control of the motor 41 between time t1 and time t2 by short-circuiting the motor 41 through a resistor. Hold control is also called brake control.

[0036] When the control unit 10 determines that it has received print data from an external device (S103: YES), it detects the position P2 of the axis 44 based on the detection signal from the detection unit 50 (S104). The control unit 10 calculates ΔP = |P1 - P2|, which is the amount of reverse rotation when the shaft 44 rotates in the opposite direction due to the force of the roller 43 trying to return to its original shape (S105). The amount of reverse rotation ΔP is the absolute value of the difference between the positions P1 and P2 of the shaft 44.

[0037] Thus, the reverse rotation amount ΔP is the first rotation amount based on the detection of the shaft by the detection unit 50 during the period from when the motor 41 of the transport unit 40 rotates the shaft 44 in the first direction, the CW direction, and then stops, until a predetermined time T or more has elapsed since stopping. Specifically, the detection of the shaft by the detection unit 50 refers to the detection of positions P1 and P2 of the shaft 44 by the detection unit 50.

[0038] The control unit 10 determines whether the time from when the motor 41 is stopped until the position P2 of the shaft 44 is detected is equal to or greater than a predetermined time T (S106). As shown in Figure 6, if it is time t4, which is a predetermined time T or more after time t1 when the control unit 10 stopped the motor 41, the deformation of the roller 43 has fully returned to its original state. If the control unit 10 determines that the time from stopping the motor 41 until detecting the position P2 of the shaft 44 is greater than or equal to a predetermined time T, as shown in the time t4 in Figure 6 (S106: YES), it sets ΔPX = ΔP (S107) and stores it in the storage unit 20.

[0039] The reverse rotation amount ΔP and the reverse rotation amount ΔPX stored in the memory unit 20 are used to calculate the second rotation amount, which is the reverse feed amount R1, and the third rotation amount, which is the forward feed amount F1, as described later. The reverse rotation amount ΔPX is the first rotation amount of the shaft 44 detected by the detection unit 50 during the period from when the motor 41 is stopped until a predetermined time T or more has elapsed, and is the first rotation amount previously stored in the memory unit 20. Furthermore, if the control unit 10 determines that the time from stopping the motor 41 until detecting the position P2 of the shaft 44 is greater than or equal to a predetermined time T, it sets ΔPX = ΔP, and therefore does not use the reverse rotation amount ΔPX previously stored in the memory unit 20. The control unit 10 uses the reverse rotation amount ΔP, which is the first rotation amount based on the detection of the shaft 44 by the detection unit 50, as the reverse rotation amount ΔPX to calculate the reverse feed amount R1 and the forward feed amount F1.

[0040] On the other hand, if the control unit 10 determines that the time from stopping the motor 41 until detecting the position P2 of the shaft 44 is less than a predetermined time T, as shown in the time t3 in Figure 6, and not greater than or equal to the predetermined time T (S106: NO), it does not store the reverse rotation amount ΔP as the reverse rotation amount ΔPX in the storage unit 20 and does not update the reverse rotation amount ΔPX. This is because, at time t3, which is less than the predetermined time T shown in Figure 6, the deformation of the roller 43 has not fully returned to its original state.

[0041] Now, referring to Figure 7, we will explain the margin at the leading edge of the recording paper 90 caused by the difference in position between the print head 31 and the cutting section 60 of the printing section 30. The control unit 10 transports the recording paper 90 in the F direction using the rollers 43, prints with the head 31, and cuts with the cutting unit 60.

[0042] The recording paper 90 shown on the left of Figure 7 represents the state after the previous receipt has been printed, cut by the cutting unit 60, and discharged from the output port. The characters shown on the recording paper 90 represent an image of what the next receipt might look like if printed by the head 31. Thus, the length from the leading edge of the recording paper 90 cut by the cutting section 60 to the next printing position by the head 31 is generated as a margin G. For a printed receipt, a margin G of a length exceeding what is necessary becomes a waste of recording paper 90.

[0043] Therefore, the control unit 10 uses the roller 43 to transport the recording paper 90 in the R direction, which is the opposite direction to the F direction, and returns it, in what is known as reverse feeding. The margin reduction amount c, which is a set value for reducing the margin G, is stored in the storage unit 20. The control unit 10 may store the margin reduction amount c in the storage unit 20 based on a command from an external device. Based on the margin reduction amount c stored in the storage unit 20, the control unit 10 uses the roller 43 to transport and return the recording paper 90 in the R direction. As shown in the recording paper 90 on the right of Figure 7, the control unit 10 uses the roller 43 to return the recording paper 90 by the amount of margin reduction c, thereby reducing at least a portion of the margin G.

[0044] Now, let's assume that, as described above, the control unit 10 rotates the shaft 44 in the CCW direction using the motor 41 to reduce the margin G, and the roller 43 transports the recording paper 90 in the R direction by the amount of margin reduction c and returns it. After that, let's assume that the control unit 10 rotates the shaft 44 in the CW direction using the motor 41, and while the roller 43 transports the recording paper 90 in the F direction, the head 31 attempts to start printing the print data. At this time, the roller 43 is in the state X2 shown in Figure 3. In other words, even though the control unit 10 starts the rotation of the motor 41 and the shaft 44 rotates in the CW direction, the torque of the shaft 44 is used to deform the roller 43, so the roller 43 does not rotate. Consequently, the roller 43 does not transport the recording paper 90 in the F direction.

[0045] However, as soon as the motor 41 starts rotating, the control unit 10 has already started printing the print data with the head 31. Therefore, even when the rollers 43 are not transporting the recording paper 90, the control unit 10 is printing on the recording paper 90 with the head 31. As a result, the print output of the print data printed on the recording paper 90 may become jammed or smudged, and may deteriorate. The print output at the start of printing is particularly susceptible to deterioration.

[0046] Therefore, as shown in Figures 6 and 7, the control unit 10 corrects the rotation amount, which is the amount of rotation of the shaft 44 in the CCW and CW directions by the motor 41, using the reverse feed amount R1 and the forward feed amount F1. The forward feed amount F1 is the amount of rotation of the shaft 44 in the CW direction by the motor 41 before printing on the recording paper 90 by the head 31. As will be described later, the amount of rotation of the shaft 44 can be converted into the amount of recording paper 90 transported.

[0047] Returning to Figure 5, let's continue the explanation. As described above, the control unit 10 rotates the shaft 44 in the CCW direction using the motor 41 and transports the recording paper 90 in the R direction using the roller 43, performing a reverse feed with a reverse feed amount R1 (S108). This corresponds to the time t5 to t6 in Figure 6.

[0048] At this time, the control unit 10 calculates the reverse feed amount R1, which is the second amount of rotation that reverses the shaft 44, using the formula R1 = L + c - ΔP, where c is the margin reduction amount stored in the memory unit 20. The reverse rotation amount ΔP used to calculate the reverse feed amount R1 is the first amount of rotation based on the detection of the shaft 44 by the detection unit 50, and is the amount of reverse rotation of the shaft 44 after the motor 41 has stopped. In this way, the control unit 10 calculates the reverse feed amount R1, which is the second amount of rotation, using the reverse rotation amount ΔP, which is the first amount of rotation, and the margin reduction amount c, which is the amount that reduces the margin G of the recording paper 90.

[0049] The control unit 10 calculates L at this time using the formula L = a × ΔPX + b. The reverse rotation amount ΔPX is the amount of reverse rotation of the shaft 44 when a predetermined time T or more has elapsed after the motor 41 has stopped and the deformation of the roller 43 has sufficiently returned to its original state. As described above, the reverse rotation amount ΔPX is stored in the memory unit 20 in the past. As described above, if the control unit 10 determines that the time from stopping the motor 41 until detecting the position P2 of the shaft 44 is greater than or equal to a predetermined time T, it sets ΔPX = ΔP and therefore does not use the reverse rotation amount ΔPX previously stored in the memory unit 20. The control unit 10 uses the reverse rotation amount ΔP, which is the first rotation amount based on the detection of the shaft 44 by the detection unit 50, as the reverse rotation amount ΔPX, and calculates the reverse feed amount R1 and the forward feed amount F1 as described later.

[0050] a is a coefficient related to the deformation of the roller 43 when the shaft 44 moves from reverse to forward or from forward to reverse. In other words, a is a coefficient used to calculate the amount of rotation of the shaft 44 required for the deformation of the roller 43 that occurs when the shaft 44 changes its conveying direction, from the amount of reverse rotation ΔPX. b is the amount of positional misalignment caused by the transport section 40, such as backlash in the gear 42 and play in the torque transmission mechanism from the motor 41 to the shaft 44 via the gear 42. The control unit 10 will compensate for these as well.

[0051] Next, as described above, before printing by the head 31, the control unit 10 rotates the shaft 44 in the CW direction with the motor 41 and feeds the recording paper 90 in the F direction with the roller 43, so that the feed amount F1 is correct (S109). This corresponds to time t7 to time t8 in Figure 6. At this time, the control unit 10 calculates the forward feed amount F1, which is the third amount of rotation that feeds the shaft 44 in the forward direction, using the formula F1 = L. As mentioned above, L = a × ΔPX + b.

[0052] The reverse rotation amount ΔPX used to calculate the forward feed amount F1 is the first rotation amount based on the detection of the shaft 44 by the detection unit 50, and is the reverse rotation amount of the shaft 44 after the motor 41 has stopped. As described above, the reverse rotation amount ΔPX is stored in the memory unit 20 in the past. Furthermore, similar to the calculation of the reverse feed amount R1 described above, if the control unit 10 determines that the time from stopping the motor 41 until detecting the position P2 of the shaft 44 is less than a predetermined time T, it calculates the forward feed amount F1 using the reverse rotation amount ΔPX previously stored in the storage unit 20. If the control unit 10 determines that the time from stopping the motor 41 until detecting the position P2 of the shaft 44 is greater than or equal to the predetermined time T, it calculates the forward feed amount F1 without using the reverse rotation amount ΔPX previously stored in the storage unit 20, and instead uses the reverse rotation amount ΔP, which is the first rotation amount based on the detection of the shaft 44 by the detection unit 50, as the reverse rotation amount ΔPX.

[0053] When the control unit 10 moves the shaft 44 forward to a forward feed amount F1 (S109), the deformation of the roller 43 due to the rotation of the shaft 44 is completed, and the roller 43 finally begins to rotate in the CW direction, transporting the recording paper 90 in the F direction. Subsequently, the control unit 10 continues to rotate the shaft 44 in the CW direction using the motor 41 to perform forward feeding, and while the roller 43 transports the recording paper 90 in the F direction, the head 31 starts printing the print data (S110). This corresponds to time t8 onwards in Figure 6. In this way, printing is started by the head 31 only after the deformation of the roller 43 is complete and the recording paper 90 can be transported. As a result, the print data printed on the recording paper 90 is printed normally without jamming or distortion.

[0054] As described above, the control unit 10 stops the rotation of the motor 41 and shaft 44 (S101), reverses the shaft 44 to a reverse feed amount R1 (S108) so that the recording paper 90 is fed in the reverse direction by the roller 43, and then, before printing with the head 31 (S110), it forwards the shaft 44 to a forward feed amount F1 (S109). Finally, the amount by which the control unit 10 reverses the movement of the shaft 44 after stopping the motor 41 can be calculated as R1-F1. Since R1=L+c-ΔP and F1=L, R1-F1=(L+c-ΔP)-(L), which equals c-ΔP.

[0055] On the other hand, referring to Figure 6, the amount by which the shaft 44 itself ultimately rotated in the reverse direction from time t1 when the control unit 10 stopped the motor 41 until time t8 when printing started can be calculated as ΔP + R1 - F1. Since R1 = L + c - ΔP and F1 = L, ΔP + R1 - F1 = ΔP + (L + c - ΔP) - (L) = c, which is the margin reduction amount c. This is because the amount by which the shaft 44 rotates in the reverse direction includes the amount of reverse rotation ΔP caused by the roller 43 returning from deformation, regardless of the motor 41.

[0056] As a result, the control unit 10 can transport and return the recording paper 90 by the roller 43 by the desired margin reduction amount c, as shown on the right in Figure 7. Then, the control unit 10 can print the print data on the recording paper 90 with the head 31 after reducing the margin reduction amount c.

[0057] Incidentally, as mentioned above, when the control unit 10 calculates the reverse feed amount R1 and the forward feed amount F1, it uses the reverse rotation amount ΔPX of the shaft 44 stored in the memory unit 20. This control will be explained in detail with reference to Figure 5. The reverse rotation amount ΔPX is the amount of reverse rotation of the shaft 44 detected by the detection unit 50 after a predetermined time T or more has elapsed since the motor 41 stopped and the deformation of the roller 43 has sufficiently returned to its original state.

[0058] The control unit 10, as shown at time t4 in Figure 6, determines that if a predetermined time T or more has elapsed since the motor 41 stopped (S106: YES), then ΔPX = ΔP. Therefore, both the reverse rotation amount ΔP and ΔPX will be the reverse rotation amount of the shaft 44 most recently detected by the detection unit 50. The control unit 10 then stores the reverse rotation amount ΔP as the reverse rotation amount ΔPX in the storage unit 20. On the other hand, if the motor 41 has stopped for less than a predetermined time T (S106:NO), as shown in Figure 6 at time t3, the control unit 10 uses the reverse rotation amount ΔP of the shaft 44 most recently detected by the detection unit 50, and the reverse rotation amount ΔPX is the reverse rotation amount previously stored in the storage unit 20.

[0059] If the control unit 10 has already received print data from an external device before stopping the motor 41 (S101) and detecting the position P1 of the shaft 44 with the detection unit 50 (S102), it can immediately determine that print data has been received (S103: YES), read out the reverse rotation amount ΔPX previously stored in the storage unit 20, and immediately calculate the reverse feed amount R1 and the forward feed amount F1. Thus, if the control unit 10 has already received print data from an external device, it can use the reverse rotation amount ΔPX previously stored in the storage unit 20, thus avoiding the need to wait for a predetermined time T or longer, which is the time it takes for the deformation of the roller 43 to fully return to its original state.

[0060] As a result, if the control unit 10 has received print data from an external device (S103:YES), it can reverse the movement of the axis 44 to a reverse feed amount R1 (S108), then forward the movement to a forward feed amount F1 (S109), and immediately print with the head 31 (S110). In this way, the control unit 10 can improve the throughput of printing print data received from an external device.

[0061] The amount of reverse rotation ΔPX required for the roller 43 to fully return to its original state varies depending on environmental conditions such as temperature and humidity, as well as the number of times the printing device 1, including the printing unit 30 and the transport unit 40, is operated and its operating time. Therefore, while the printing device 1 is in use, the reverse rotation amount ΔPX does not fluctuate suddenly in a short period of time. Also, there are times when the printing device 1 does not print receipts, such as when there is no line of customers making payments in the store or when the operator is handling money. In these cases, the control unit 10 can ensure a predetermined time T or longer, so it can store the reverse rotation amount ΔPX in the storage unit 20. Thus, the reverse rotation amount ΔPX stored in the storage unit 20 is a relatively recent value, having been stored some time ago. Therefore, the control unit 10 can appropriately perform the above-mentioned control even if it uses the reverse rotation amount ΔPX previously stored in the memory unit 20.

[0062] Here, we will explain an example of how the control unit 10 calculates the reverse feed amount R1 and the forward feed amount F1. First, we will explain the relationship between the detection signal from the detection unit 50 and the resolution of the head 31, as shown in Figure 6. The detection unit 50 is set, for example, to have a detection signal resolution of 8 pulses / 0.125 mm. In other words, it is set so that an 8-pulse detection signal is output from the detection unit 50 every time the transport unit 40 transports the recording paper 90 for a length of 0.125 mm. In this way, the amount of rotation of the shaft 44, indicated by the number of pulses of the detection signal from the detection unit 50, can be converted into the amount of transported recording paper 90. On the other hand, for example, the resolution of the head 31 is 0.125 mm, with 1 dot per 0.125 mm. When the recording paper 90 is transported by the transport unit 40 for a length of 0.125 mm, the same as the resolution of the head 31, the detection unit 50 outputs a detection signal of 8 pulses.

[0063] Therefore, the control unit 10 controls the head 31 at a timing such that it drives one dot during the period when the detection signal input from the detection unit 50 is 8 pulses, and prints one dot on the recording paper 90. In the following, the length over which the recording paper 90 is transported by the transport unit 40 during the detection signal of the detection unit 50 is expressed as 1 EP (Encoder Pulse). Note that 1 EP is approximately 0.0156 mm.

[0064] The coefficients used to calculate the reverse feed amount R1 and the forward feed amount F1 described above will now be explained. a and b are experimentally determined for the printing device 1, for example, a = 2.0 and b = 50 EP. The margin reduction amount c is set, for example, c = 7.5 mm = 480 EP. The control unit 10 uses these values ​​to calculate the reverse feed amount R1 and the forward feed amount F1 as follows.

[0065] If the control unit 10 detects a reverse rotation amount ΔP by the detection unit 50 within a predetermined time T or longer after the motor 41 has stopped, for example, ΔPX = ΔP = 10EP. At this time, L = a × ΔPX + b, so L = 2.0 × 10 + 50 = 70 EP. The reverse feed amount R1 is R1 = L + c - ΔP, so R1 = 70 + 480 - 10 = 540 EP. The forward feed amount F1 is F1 = L, so F1 = 70 EP.

[0066] On the other hand, if the control unit 10 detects a reverse rotation amount ΔP by the detection unit 50 within a predetermined time T after the motor 41 has stopped, for example, ΔP = 6EP. Assuming that ΔPX = 10EP is stored in the storage unit 20, ΔPX = 10EP will be used. At this time, L = a × ΔPX + b, so L = 2.0 × 10 + 50 = 70 EP. The reverse feed amount R1 is R1 = L + c - ΔP, so R1 = 70 + 480 - 6 = 544 EP. The forward feed amount F1 is F1 = L, so F1 = 70 EP.

[0067] As described above, the control unit 10 can calculate the reverse feed amount R1 and the forward feed amount F1. Using these calculated values, the control unit 10 reverses the axis 44 to the reverse feed amount R1, then forwards it to the forward feed amount F1, and then starts printing the print data with the head 31. As a result, the print data printed on the recording paper 90 is printed normally without jamming or distortion, and the margins are reduced by the desired margin reduction amount c = 7.5 mm.

[0068] According to the embodiment described above, the control unit 10 detects the amount of reverse rotation ΔP of the shaft 44 based on the deformation of the roller 43 using the detection unit 50, and based on this amount of reverse rotation ΔP, the transport unit 40 can transport the reverse feed amount R1 and the forward feed amount F1. The forward feed amount F1 is the forward feed amount before the print data is printed by the head 31. As a result, the printout on the recording paper 90 is normal, without jamming or distortion. Furthermore, the margins on the recording paper 90 are reduced by the desired margin reduction amount c. Furthermore, if less than a predetermined time T has passed since the motor 41 stopped, the control unit 10 can use the reverse rotation amount ΔPX stored in the storage unit 20 to print the print data with the head 31 without waiting for a predetermined time T or longer.

[0069] Although these embodiments have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and modifications, substitutions, deletions, etc., may be made as long as they do not depart from the spirit of this invention.

[0070] For example, although the printing device 1 was described using a line thermal head as an example for the head 31, the type of head 31 is not limited. For example, an inkjet head may also be used. Furthermore, although motor 41 was explained using the example of a DC motor, other types such as a stepper motor may also be used. Furthermore, although the detection unit 50 was described using a rotary encoder as an example, other detection methods such as a tachogenerator may also be used. Furthermore, although the recording paper 90 was described as roll paper 91 wound into a roll, it may also be single sheets of paper such as A4.

[0071] Furthermore, the shaft 44 may be the same as the shaft of the gear 42 or the shaft of the motor 41. In this case, the disc 52 of the detection unit 50 will be directly attached to the shaft of the gear 42 or the shaft of the motor 41. The detection unit 50 will then be able to directly detect the rotation of the shaft of the gear 42 or the shaft of the motor 41.

[0072] Furthermore, in Figure 5, when the control unit 10 stopped the motor 41 (S101), it detected the position P1 of the shaft 44 (S102). In cases where the control unit 10 has been controlling the motor 41 in a way that causes it to overrun, the shaft 44 may continue to rotate for a while after the motor 41 has been stopped. For this reason, the control unit 10 may wait after stopping the motor 41 until the rotation of the shaft 44 due to overrun or other reasons has stopped, and then detect the position P1 of the shaft 44 using the detection unit 50. The cessation of the rotation of the shaft 44 can be detected by the detection unit 50. [Explanation of symbols]

[0073] 1...Printing device, 10...Control unit, 20...Storage unit, 30...Printing unit, 31...Head, 40...Transport unit, 41...Motor, 42...Gear, 43...Roller, 44...Shaft, 50...Detection unit, 90...Recording paper, c...Margin reduction amount, F1...Forward feed amount, P1, P2...Position, R1...Reverse feed amount, ΔP, ΔPX...Reverse rotation amount.

Claims

1. The printing unit prints onto the recording paper, A transport unit having rollers that, together with the printing unit, sandwich the recording paper and rotate around an axis in a first direction and a second direction opposite to the first direction to transport the recording paper, and a motor that rotates the axis, A detection unit for detecting the rotation of the shaft, The motor of the transport unit rotates the shaft in the first direction and then stops, and the storage unit stores the first amount of rotation based on the detection of the shaft by the detection unit after a predetermined time has elapsed since stopping. The system comprises a control unit that controls the printing unit and the transport unit, The control unit controls the shaft by the motor of the transport unit. It rotates in the first direction and then stops. If printing is performed by the printing unit within the predetermined time after stopping, the unit rotates in the second direction by a second rotation amount calculated using the first rotation amount stored in the memory unit and the reverse rotation amount detected by the detection unit. A printing apparatus that rotates in the first direction before printing by the printing unit, based on a third rotation amount calculated using the first rotation amount stored in the memory unit.

2. The control unit controls the shaft by the motor of the transport unit. It rotates in the first direction and then stops. The printing apparatus according to claim 1, wherein when printing is performed by the printing unit after a predetermined time has elapsed since stopping, the machine rotates in the second direction by a second rotation amount calculated using the first rotation amount based on the detection of the axis by the detection unit, rather than the first rotation amount stored in the storage unit, and rotates in the first direction before printing by the printing unit by a third rotation amount calculated using the first rotation amount based on the detection of the axis by the detection unit, rather than the first rotation amount stored in the storage unit.

3. The aforementioned printing unit is a line thermal head. The motor is a DC motor, The printing apparatus according to claim 1 or claim 2, wherein the detection unit includes a rotary encoder for detecting the rotation of the shaft.

4. A control method for a printing apparatus comprising: a printing unit for printing on recording paper; a transport unit having rollers that, together with the printing unit, sandwich the recording paper and rotate around an axis in a first direction and a second direction opposite to the first direction to transport the recording paper, and a motor for rotating the axis; a detection unit for detecting the rotation of the axis; and a storage unit that rotates the axis in the first direction by the motor of the transport unit and then stops, and stores a first amount of rotation based on the detection of the axis by the detection unit after a predetermined time has elapsed since stopping; The motor of the transport unit controls the shaft, It rotates in the first direction and then stops. If printing is performed by the printing unit within the predetermined time after stopping, the unit rotates in the second direction by a second rotation amount calculated using the first rotation amount stored in the memory unit and the reverse rotation amount detected by the detection unit. A control method for a printing apparatus, wherein the apparatus rotates in the first direction before printing by the printing unit, based on a third rotation amount calculated using the first rotation amount stored in the memory unit.

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