Printing device and control method of printing device

Abstract

To improve a printing quality of a printing object to be printed such as a label paper that has to be positioned.SOLUTION: A printing device is provided with: an optical detection part that comprises a light emitting part and a light receiving part and detects a position to which a printing object is fed, on the basis of reflection of light emitted from the light emitting part to the printing object or a result of transmitted light received by the light receiving part; a current adjustment part that adjusts magnitude of driving currents supplied from a power source to the light emitting part; a detection part that detects magnitude of driving currents supplied from the current adjustment part to the light emitting part; and a control part that controls the driving current adjustment part so that magnitude of the driving currents adjusted by the current adjustment part gets close to a reference current value, on the basis of detected magnitude of the driving currents and a predetermined reference current value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, line printers equipped with thermal heads have been known. Such line printers may be used to print on objects that require positioning of the print position, such as label paper. For example, Patent Document 1 discloses a known technique for positioning the print position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-132087 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the print quality when printing on label paper or the like, it is necessary to improve the accuracy of the print position.

[0005] The present invention has been made in view of the above circumstances, and has as its object to improve the print quality of printing objects that require print positioning, such as label paper. [Means for solving the problem]

[0006] A printing device according to one aspect of the present invention comprises an optical detection unit that detects the feed position of the printing object based on the result of the light receiving unit receiving the reflection or transmission of light irradiated onto the printing object from the light emitting unit, a current adjustment unit that adjusts the magnitude of the drive current supplied from a power source to the light emitting unit, a detection unit that detects the magnitude of the drive current supplied from the current adjustment unit to the light emitting unit, and a control unit that controls the magnitude of the drive current adjusted by the current adjustment unit to approach a predetermined reference current value based on the magnitude of the detected drive current and the reference current value.

[0007] A control method for a printing device according to one aspect of the present invention includes detecting a feed position of a printing object based on the result of a light receiving unit receiving the reflection or transmission of light irradiated onto the printing object from a light emitting unit, adjusting the magnitude of a drive current supplied from a power source to the light emitting unit by a current adjusting unit, detecting the magnitude of the drive current supplied from the current adjusting unit to the light emitting unit, and controlling the magnitude of the drive current adjusted by the current adjusting unit to approach the reference current value based on the detected magnitude of the drive current and a predetermined reference current value. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the print quality of a printing object that requires print positioning, such as label paper. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of a printer device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of thermal paper according to the present embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of a functional configuration of a control unit according to the present embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a current control unit and a control circuit according to the present embodiment. [Figure 5] FIG. 10 is a diagram illustrating another example of the configuration of the current control unit and the control circuit of the present embodiment. [Figure 6] FIG. 4 is a diagram illustrating an example of the flow of operations of a control unit according to the present embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of a threshold value for gap determination according to the present embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of the accuracy of position detection in a conventional printer device. [Figure 9] 10A and 10B are diagrams illustrating an example of the accuracy of position detection in the printer device of the present embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a correspondence relationship between position detection accuracy and print quality. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplicate descriptions of those components may be omitted.

[0011] 1 is a schematic cross-sectional view of a printer device 1 according to this embodiment. The printer device 1 includes a thermal printer mechanism 10, a control unit 20, a paper storage unit 30, and a paper discharge unit 40. The paper storage unit 30 stores thermal paper 310. In this embodiment, the thermal paper 310 is, for example, roll paper. When heat equal to or greater than the coloring threshold is applied to the thermal paper 310, the portion to which heat is applied develops color. The paper discharge unit 40 discharges the paper printed by the thermal printer mechanism 10 (that is, the printed thermal paper 310) to the outside of the printer device 1.

[0012] [Example of thermal paper composition] 2 is a diagram showing an example of the configuration of the thermal paper 310 of this embodiment. The thermal paper 310 of this embodiment is a so-called thermal label roll paper, and has a label portion 311 and a gap portion 312. The label portion 311 has a heat-sensitive agent applied to the printing surface and an adhesive applied to the backside, and is removable from the backing of the thermal label roll paper. The thermal paper 310 has multiple label portions 311 arranged along the paper feed direction D1 (also called the forward feed direction) of the roll paper during printing. In the example shown in the figure, the thermal paper 310 has multiple label portions 311 in printing order: first label 310-1, second label 310-2, etc. The gap portion 312 is an area where the backing of the thermal label roll paper is exposed and sandwiched between adjacent labels 311. In the example shown in the figure, the first gap portion 312-1 is sandwiched between the label portion 311-1 of the first label 310-1 and the label portion 311-2 of the second label 310-2.

[0013] As an example, the label portion 311 of the thermal paper 310 is white, and the gap portion 312 (that is, the backing portion) is blue. The thermal paper 310 has a different light reflectance R1 for the portion corresponding to the label portion 311 and a light reflectance R2 for the portion corresponding to the gap portion 312. For example, the reflectance R1 of the label portion 311 is greater than the reflectance R2 of the gap portion 312.

[0014] The above-described configurations and arrangements of the label portion 311 and the gap portion 312 are merely examples. The thermal paper 310 only needs to have a light reflectance R1 of the portion corresponding to the label portion 311 and a light reflectance R2 of the portion corresponding to the gap portion 312 that are different from each other, and the configurations and arrangements of the label portion 311 and the gap portion 312 can be selected arbitrarily.

[0015] [Example of thermal printer mechanism configuration] Returning to FIG. 1, the thermal printer mechanism 10 includes a motor 110, a thermal head 120, a platen roller 130, and an optical detection unit 140.

[0016] The motor 110 drives and rotates the platen roller 130 under the control of the control unit 20. The platen roller 130 rotates in conjunction with the rotation of the motor 110 while pressing the color-developing surface of the thermal paper 310 against the thermal head 120, thereby moving the thermal paper 310. As a result, the thermal paper 310 moves relative to the thermal head 120. That is, the motor 110 moves the thermal paper 310 relative to the thermal head 120 via the platen roller 130. In the following description, the movement of the thermal paper 310 by the motor 110 relative to the thermal head 120 is also referred to as paper feeding.

[0017] Here, relative movement refers to the relative movement between the thermal paper 310 and the thermal head 120. That is, relative movement includes a case where the thermal head 120 is fixed and the thermal paper 310 moves, a case where the thermal paper 310 is fixed and the thermal head 120 moves, and a case where both the thermal paper 310 and the thermal head 120 move. In this embodiment, the thermal head 120 is fixed, and the thermal paper 310 moves relative to the thermal head 120.

[0018] The thermal head 120 is a so-called line-type thermal head in which multiple heating elements H are arranged in a line. Based on the control of the control unit 20, the thermal head 120 applies heat to the thermal paper 310 pressed against the platen roller 130, causing the thermal paper 310 to develop color at desired positions.

[0019] The optical detection unit 140 includes a light-emitting unit 141 and a light-receiving unit 142. The optical detection unit 140 detects the feed position of the printing object (i.e., the thermal paper 310) based on the result of the light-receiving unit 142 receiving the reflection or transmission of light irradiated from the light-emitting unit 141 onto the printing object (i.e., the thermal paper 310). As described above, the optical detection unit 140 can be a reflective photointerrupter that uses light reflected by the printing object, or a transmissive photointerrupter that uses light that passes through the printing object. In this embodiment, a case where the optical detection unit 140 is a reflective photointerrupter will be described as an example.

[0020] The configuration of the optical detection unit 140 will be described in more detail. The light-emitting unit 141 includes, for example, a light-emitting diode. The light-emitting diode emits light when a driving current Id is supplied between the anode terminal and the cathode terminal. The light-emitting unit 141 irradiates the light emitted by the light-emitting diode toward the thermal paper 310.

[0021] The thermal paper 310 reflects the light emitted by the light-emitting unit 141 at a predetermined reflectance. As described above, the thermal paper 310 has a portion corresponding to the label portion 311 with a different reflectance R1 and a portion corresponding to the gap portion 312 with a different reflectance R2. For example, the reflectance R1 of the label portion 311 is greater than the reflectance R2 of the gap portion 312.

[0022] The light receiving unit 142 receives light reflected by the thermal paper 310. The light receiving unit 142 includes, for example, a photodiode. The photodiode changes the amount of current flowing from the anode terminal to the cathode terminal according to the intensity of the incident light. In the following description, a state in which strong light is incident on a photodiode and a large current flows from the anode terminal to the cathode terminal is also referred to as a low resistance value of the photodiode.Furthermore, a state in which the intensity of light incident on the photodiode is weak (or no light is incident on the photodiode) and a small current flows from the anode terminal to the cathode terminal is also referred to as a high resistance value of the photodiode. That is, the resistance value of the photodiode decreases as the intensity of incident light increases, and increases as the intensity of incident light decreases.

[0023] As described above, the light receiving unit 142 changes the resistance between the anode terminal and the cathode terminal of the photodiode according to the intensity of the incident light (that is, the reflectance of the thermal paper 310). That is, the light receiving unit 142 can indicate whether the thermal paper 310 passing the position of the optical detection unit 140 is the label portion 311 or the gap portion 312 by the change in the resistance value of the photodiode.

[0024] The control unit 20 includes a computer device. The control unit 20 controls the motor 110 and the thermal head 120 based on a program stored in a storage unit (not shown), print data stored in the storage unit (not shown), or print data provided from an external device (not shown). The thermal head 120 of this embodiment is a so-called line-type thermal head, and performs printing line by line LN.

[0025] [Controller function configuration] 3 is a diagram showing an example of the functional configuration of the control unit 20 of this embodiment. The control unit 20 includes a print data acquisition unit 210, a drive plan generation unit 220, a motor drive unit 230, a head drive unit 240, a current control unit 250, and a control circuit 260.

[0026] The print data acquisition unit 210 acquires print data from a storage unit (not shown) or an external device (not shown). As described above, print data is data that is composed of multiple lines LN and indicates the coloring state of each pixel PX included in the lines LN. The print data represents the print object using black pixels PX-BK and white pixels PX-WH.

[0027] The drive plan generating unit 220 generates information on a plan for driving the motor 110 and a plan for driving the thermal head 120 (that is, a motor drive plan and a head drive plan) based on the print data acquired by the print data acquiring unit 210.

[0028] The drive plan generator 220 generates a motor drive plan and a head drive plan to control the relative movement speed of the thermal paper 310 moved by the motor 110 and the drive state of the thermal head 120 for each pixel PX. The motor driving unit 230 supplies the motor 110 with a driving current for step driving for each line LN based on the motor driving plan generated by the driving plan generating unit 220. The head driving section 240 supplies the thermal head 120 with a current (that is, a head driving current) that heats the thermal head 120 for each pixel PX, based on the head driving plan generated by the driving plan generating section 220.

[0029] As described above, the printer 1 of this embodiment is a so-called line printer. For each line LN of print data, the printer 1 moves the thermal paper 310 by one line, stops the movement of the thermal paper 310, and drives the thermal head 120 to color the thermal paper 310. This operation is repeated to sequentially print multiple lines LN. Next, the configurations of the current control section 250 and the control circuit 260 will be described.

[0030] [Configuration example of current control section and control circuit (part 1)] FIG. 4 is a diagram showing an example of the configuration of the current control section 250 and the control circuit 260 of this embodiment. The current control unit 250 includes a first terminal 251, a second terminal 252, a third terminal 253, and a fourth terminal 254.

[0031] The first terminal 251 can output a control signal with an arbitrary duty ratio, for example, by pulse width modulation (PWM). In the following description, the first terminal 251 is also referred to as a control signal output terminal.

[0032] The second terminal 252 and the third terminal 253 are voltage detection terminals. The second terminal 252 detects a voltage with the third terminal 253 as a reference potential. That is, the current control unit 250 can detect a differential voltage between the second terminal 252 and the third terminal 253. In the following description, the second terminal 252 is also referred to as a voltage detection terminal. The third terminal 253 is also referred to as a reference potential terminal.

[0033] The fourth terminal 254 is a voltage detection terminal that is connected to the connection point 153 of the received light intensity detection unit 150 and detects a voltage with the ground potential GND as a reference potential.

[0034] The received light intensity detection unit 150 will now be described. The received light intensity detection unit 150 includes a pull-up resistor 151 and a capacitor 152. The pull-up resistor 151 is connected between a power supply Vdd and a connection point 153. The capacitor 152 is connected between the connection point 153 and the ground potential GND. The output terminal of the light receiving unit 142 is connected to the connection point 153. A potential corresponding to the intensity of light received by the light receiving unit 142 appears at the connection point 153. The fourth terminal 254 detects the potential difference across the capacitor 152, i.e., the potential corresponding to the intensity of light received by the light receiving unit 142.

[0035] Here, the light receiving intensity of the light receiving unit 142 represents the difference in reflectance of the thermal paper 310 passing through the optical detection unit 140. As described above, the light receiving unit 142 is composed of, for example, a photodiode, and the resistance value decreases as the intensity of the incident light increases, and increases as the intensity of the incident light decreases. For example, if the reflectance of the thermal paper 310 is relatively high, more light is incident on the light receiving unit 142, increasing the intensity of the light received by the light receiving unit 142. In this case, the resistance value of the light receiving unit 142 becomes relatively small, and the potential difference across the capacitor 152 becomes relatively small. Furthermore, for example, if the reflectance of the thermal paper 310 is relatively low, less light is incident on the light receiving unit 142, and the intensity of the light received by the light receiving unit 142 weakens. In this case, the resistance value of the light receiving unit 142 becomes relatively large, and the potential difference across the capacitor 152 becomes relatively large. In other words, the potential of the fourth terminal 254 indicates the reflectance of the thermal paper 310.

[0036] The control unit 20 detects the position of the label portion 311 or the gap portion 312 when the motor 110 moves the thermal paper 310 based on the potential applied to the fourth terminal 254 of the current control unit 250 (i.e., the reflectivity of the thermal paper 310).

[0037] Next, a description will be given of the control circuit 260. The control circuit 260 is a circuit that controls the current flowing to the light emitting unit 141 of the optical detection unit 140. The control circuit 260 includes a current adjusting unit 261 and a current detecting unit 262.

[0038] The current adjusting unit 261 includes, for example, a P-channel field effect transistor (PchFET) 2611, a pull-up resistor 2612, and a connection point 2613. The field effect transistor 2611 has a source terminal connected to a power supply Vdd, a drain terminal connected to the current detection unit 262 , and a gate terminal connected to a connection point 2613 . The pull-up resistor 2612 is connected between the source terminal of the field effect transistor 2611 and the node 2613 . The connection point 2613 is connected to a first terminal 251 (ie, a control signal output terminal) of the current control section 250.

[0039] The field effect transistor 2611 performs an on / off operation based on a control signal output from the first terminal 251. When the field effect transistor 2611 performs an on / off operation, the magnitude of the drive current Id supplied from the power supply Vdd to the light emitting unit 141 (i.e., the current value of the drive current Id) changes.

[0040] That is, the current adjusting section 261 adjusts the magnitude of the drive current Id supplied to the light emitting section 141 from the power supply.

[0041] As described above, the field effect transistor 2611 has a gate terminal connected to a control signal from the control unit 20, a source terminal connected to the power supply Vdd, and a drain terminal connected to the supply line to the light emitting unit 141. Here, the supply line refers to a wiring that supplies a drive current Id from a power supply Vdd to the light-emitting unit 141 via a field-effect transistor 2611 .

[0042] That is, the current adjusting section 261 includes a field effect transistor 2611 having a gate terminal connected to a control signal from the control section 20, a source terminal connected to a power source, and a drain terminal connected to a supply line to the light emitting section 141.

[0043] The current detection unit 262 (detection unit) detects the magnitude of the drive current Id supplied from the current adjustment unit 261 to the light emitting unit 141. Specifically, the current detection unit 262 includes a current limiting resistor 2621 , a current detection resistor 2622 , and a smoothing capacitor 2623 .

[0044] A current limiting resistor 2621 is connected between the drain terminal of the field effect transistor 2611 and a node 2624 . The current sensing resistor 2622 is connected between the node 2624 and the node 2625 . That is, the current limiting resistor 2621 and the current detecting resistor 2622 are connected in series to the supply line to the light emitting unit 141 . The smoothing capacitor 2623 is connected between the connection point 2624 and the ground potential GND.

[0045] That is, the current detection unit 262 (detection unit) includes a current limiting resistor 2621 connected in series to a supply line to the light emitting unit 141, a current detection resistor 2622 connected in series to the supply line, and a smoothing capacitor 2623 having one terminal connected to a position between the current limiting resistor 2621 and the current detection resistor 2622. The current detection unit 262 (detection unit) detects the magnitude of the drive current Id based on the potential difference between both ends of the current detection resistor 2622.

[0046] As described above, second terminal 252 and third terminal 253 are both voltage detection terminals. Second terminal 252 detects the potential of connection point 2624 relative to ground potential GND. Third terminal 253 detects the potential of connection point 2625 relative to ground potential GND. That is, the second terminal 252 and the third terminal 253 detect the potential difference across the current detection resistor 2622 .

[0047] The current control unit 250 may also include a reference current value setting unit 256. In one example of this embodiment, the reference current value setting unit 256 is connected to the reference current value setting switch 270 via a fifth terminal 255. The reference current value setting switch 270 is a so-called DIP switch, and multiple reference current values ​​can be set by switching the switch. The reference current value setting unit 256 variably sets the reference current value by reading the switch setting of the reference current value setting switch 270 via the fifth terminal 255.

[0048] In the above description, the reference current value setting switch 270 is described as a physical switch, but is not limited to this. The reference current value setting switch 270 may be a logical (i.e., non-physical) switch configured by software or the like as long as it is capable of setting a plurality of reference current values.

[0049] Furthermore, the reference current value setting switch 270 may be configured as an external device of the printer device 1 and connected to the printer device 1 via wired or wireless communication. For example, the reference current value setting switch 270 may be a calibration device that is connected to the printer device 1 in a shipping inspection process at a manufacturing factory of the printer device 1.

[0050] Moreover, the current control unit 250 may include a storage unit 257. In this case, the reference current value setting unit 256 stores the set reference current value in the storage unit 257. The storage unit 257 stores the reference current value set by the reference current value setting unit 256. For example, the reference current value setting switch 270 may be a calibration device connected to the printer device 1. In this case, the reference current value setting unit 256 acquires reference current value setting information output by the calibration device. The reference current value setting unit 256 stores the acquired reference current value setting information in the storage unit 257. That is, the storage unit 257 stores the reference current value set for each individual printer device 1 at the time of shipment from the factory.

[0051] [Configuration example of current control section and control circuit (part 2)] Fig. 5 is a diagram showing another example of the configuration of the current control unit 250 and the control circuit 260 of this embodiment. Fig. 5 shows an example of a control circuit 260A instead of the above-mentioned control circuit 260. Note that the same components as those shown in Fig. 4 are given the same reference numerals, and their description will be omitted.

[0052] In the above-described control circuit 260, the current detection resistor 2622 is arranged on the anode side of the light-emitting unit 141 (i.e., closer to the power supply Vdd). The control circuit 260A differs from the above-described control circuit 260 in that the current detection resistor 2622 is arranged on the cathode side of the light-emitting unit 141 (i.e., closer to the ground battery GND).

[0053] In the example shown in the figure, second terminal 252 is connected to connection point 2626 on the cathode side of light-emitting unit 141. Current detection resistor 2622 is connected between connection point 2626 and ground battery GND. Second terminal 252 detects the potential difference between connection point 2626 and ground battery GND, that is, the potential difference across current detection resistor 2622. According to the control circuit 260A configured in this manner, the third terminal 253 becomes unnecessary, and the circuit configuration can be further simplified. Next, the flow of operations of the control unit 20 will be described with reference to FIG.

[0054] [Controller operation flow] 6 is a diagram showing an example of the flow of operations of the control unit 20 of this embodiment. The diagram shows an example of the flow of operations by the control circuit 260 out of the control circuit 260 and the control circuit 260A described above.

[0055] Note that in the flow of operation shown in the figure, the print data acquisition unit 210 acquires print data, the drive plan generation unit 220 generates a drive plan for the motor 110 and thermal head 120, the motor drive unit 230 moves the thermal paper 310, and the head drive unit 240 drives the thermal head 120 to print. This description does not include details.

[0056] (Step S10) The current control unit 250 outputs a control signal with a predetermined duty ratio from the first terminal 251 (control signal output terminal). As a result, the field effect transistor 2611 is turned on and off according to the duty ratio of the control signal, and a drive current Id having a magnitude according to the duty ratio of the control signal flows.

[0057] That is, the control unit 20 controls the magnitude of the drive current Id by driving the field effect transistor 2611 in a time-division manner.

[0058] The driving current Id flows from the power supply Vdd through the field effect transistor 2611, the current limiting resistor 2621, the current detection resistor 2622, and the light emitting unit 141, before finally flowing into the ground potential GND. As a result, the light emitting unit 141 emits light with an intensity according to the magnitude of the driving current Id.

[0059] When the field-effect transistor 2611 turns on and off according to the duty ratio of the control signal, the drive current Id is time-divided and takes on a waveform that includes ripples. If the drive current Id includes ripples, the light-emitting intensity of the light-emitting unit 141 changes over time (i.e., flickering of light). Therefore, it is desirable that the drive current Id be a DC waveform with smoothed ripples. Smoothing capacitor 2623 smoothes the ripple of drive current Id that occurs due to the on / off of field effect transistor 2611. In other words, smoothing capacitor 2623 reduces the change over time in the light emission intensity of light emitting unit 141 that is caused by the ripple of drive current Id.

[0060] When the drive current Id flows through the current detection resistor 2622, a potential difference according to the magnitude of the drive current Id occurs across the current detection resistor 2622. That is, a potential difference according to the magnitude of the drive current Id occurs between the connection points 2624 and 2625.

[0061] The second terminal 252 (voltage detection terminal) generates the potential of the connection point 2624. The third terminal 253 (reference potential terminal) generates the potential of the connection point 2625. That is, a potential difference according to the magnitude of the drive current Id occurs between the second terminal 252 and the third terminal 253.

[0062] As described above, the smoothing capacitor 2623 smoothes the ripples in the drive current Id. Therefore, it can be said that the smoothing capacitor 2623 reduces the change over time in the potential difference generated between the second terminal 252 and the third terminal 253. That is, smoothing capacitor 2623 contributes to reducing the change over time in the light emission intensity of light-emitting section 141, and also contributes to reducing the change over time in the potential difference generated between second terminal 252 and third terminal 253.

[0063] The current control unit 250 calculates the differential voltage between the second terminal 252 (voltage detection terminal) and the third terminal 253 (reference potential terminal).

[0064] (Step S20) Current control unit 250 determines whether the differential voltage calculated in step S10 matches a predetermined constant current setting voltage. Here, the constant current setting voltage is a voltage based on a reference current value preset in current control unit 250 (for example, storage unit 257). As an example, the constant current setting voltage is calculated by multiplying a reference current value preset in storage unit 257 by the resistance value of current detection resistor 2622. In this case, storage unit 257 may store a pair of the reference current value and the resistance value of current detection resistor 2622 as information for calculating the constant current setting voltage. Alternatively, storage unit 257 may store the constant current setting voltage instead of the pair of the reference current value and the resistance value of current detection resistor 2622.

[0065] As described above, the current control unit 250 may include the reference current value setting unit 256. In this case, the current control unit 250 uses the reference current value set by the reference current value setting unit 256 as information for calculating the constant current setting voltage. That is, it can be said that the control unit 20 controls the magnitude of the drive current Id based on the set reference current value (for example, the reference current value stored in the storage unit 257).

[0066] If the current control unit 250 determines that the differential voltage calculated in step S10 matches the predetermined constant current setting voltage (step S20; YES), it ends the series of processes for changing the duty ratio of the control signal. If the current control unit 250 determines that the differential voltage calculated in step S10 does not match the predetermined constant current setting voltage (step S20; NO), the process proceeds to step S30.

[0067] (Step S30) The current control unit 250 determines whether the differential voltage calculated in step S10 is smaller than a predetermined constant current setting voltage. Here, the differential voltage calculated in step S10 represents the magnitude of the drive current Id. That is, the current control unit 250 determines whether the magnitude of the drive current Id is smaller than a predetermined reference current value.

[0068] If the current control unit 250 determines that the differential voltage calculated in step S10 is smaller than the predetermined constant current setting voltage (step S30; YES), the process proceeds to step S40. If the current control unit 250 determines that the differential voltage calculated in step S10 is equal to or greater than the predetermined constant current setting voltage (step S30; NO), the process proceeds to step S50.

[0069] (Step S40) Current control unit 250 increases the duty ratio of the control signal output from first terminal 251. As a result, in the on / off control of field effect transistor 2611, the proportion of the on state per unit time increases compared to before the duty ratio was increased, and drive current Id increases. As drive current Id increases, the light emission intensity of light-emitting unit 141 increases compared to before the duty ratio was increased.

[0070] (Step S50) Current control unit 250 reduces the duty ratio of the control signal output from first terminal 251. As a result, in the on / off control of field effect transistor 2611, the proportion of on states per unit time decreases compared to before the duty ratio was reduced, and drive current Id decreases. As drive current Id decreases, the light emission intensity of light-emitting unit 141 decreases compared to before the duty ratio was reduced.

[0071] That is, the control unit 20 controls the magnitude of the drive current Id adjusted by the current adjusting unit 261 based on the magnitude of the detected drive current Id and a predetermined reference current value so that the magnitude approaches the reference current value.

[0072] That is, the control unit 20 performs feedback control on the magnitude of the drive current Id based on the reference current value. In the configuration of the control circuit 260 of this embodiment, the magnitude of the drive current Id varies depending on the voltage of the power supply Vdd, the on-resistance value of the field effect transistor 2611, the resistance value of the current limiting resistor 2621, the resistance value of the current detection resistor 2622, and the forward voltage of the diode of the light-emitting unit 141. In particular, the forward voltage of the diode of the light-emitting unit 141 generally varies greatly from one printer device to another, and therefore may have a different value for each printer device 1. Furthermore, the forward voltage of the diode of the light emitting section 141 may change due to changes in the environmental temperature or aging.

[0073] According to the printer device 1 of this embodiment, even if there is individual variation in the forward voltage of the diode of the light-emitting unit 141, the magnitude of the drive current Id can be made to approach the reference current value by feedback controlling the magnitude of the drive current Id. Therefore, according to the printer device 1 of this embodiment, it is possible to reduce (or omit) the need for, for example, individually adjusting the magnitude of the drive current Id for each printer device 1.

[0074] In addition, in order to reduce the influence of changes in the forward voltage due to changes in the environmental temperature, the current control unit 250 may be configured to feedback control the magnitude of the drive current Id when the environmental temperature of the printer device 1 changes. In addition, in order to reduce the influence of changes in the forward voltage due to aging, the current control unit 250 may be configured to feedback control the magnitude of the drive current Id every time a predetermined amount of time has elapsed since the printer device 1 started operating.

[0075] An example of the effect of feedback controlling the magnitude of the drive current Id as in the printer device 1 of this embodiment will be described.

[0076] FIG. 7 is a diagram showing an example of the gap determination threshold value in this embodiment. The vertical axis in this diagram represents the detected voltage of the fourth terminal 254 (voltage detection terminal). As described above, in this example of this embodiment, the reflectance R1 of the label portion 311 is greater than the reflectance R2 of the gap portion 312. In the circuit configurations of the control circuit 260 shown in FIG. 4 and the control circuit 260A shown in FIG. 5, when the optical detection unit 140 detects the label portion 311, the detected potential by the fourth terminal 254 is relatively low. On the other hand, when the optical detection unit 140 detects the gap portion 312, the detected potential of the fourth terminal 254 is relatively high.

[0077] When the detected potential of the fourth terminal 254 is lower than a predetermined threshold (for example, label determination threshold Th1), the control unit 20 determines that the label portion 311 is passing through the optical detection unit 140. When the detected potential of the fourth terminal 254 is higher than a predetermined threshold (for example, gap determination threshold Th2), the control unit 20 determines that the gap portion 312 is passing through the optical detection unit 140.

[0078] Here, the control unit 20 needs to avoid erroneously determining that the label portion 311 is the gap portion 312, or that the gap portion 312 is the label portion 311. For this reason, a sufficient potential difference is provided between the label determination threshold value Th1 and the gap determination threshold value Th2 to avoid such erroneous determination. In the following description, the potential difference between the label determination threshold value Th1 and the gap determination threshold value Th2 is also referred to as the determination margin. To simplify the manufacturing process of the printer device 1, it is preferable to avoid setting different values ​​for the determination margin for each individual printer device 1 and to set a common value for printer devices 1 of the same product.

[0079] FIG. 1A shows an example of threshold setting for a conventional printer. This conventional printer does not perform feedback control of the drive current Id. As a result, there may be significant individual differences in the magnitude of the drive current Id between conventional printers. In this case, to avoid erroneous determination, a sufficiently large determination margin VR1 is set for the magnitude of the drive current Id, taking into account the individual variations between printers.

[0080] FIG. 1B shows an example of threshold setting for the printer 1 of this embodiment. As described above, the printer 1 of this embodiment uses feedback control of the drive current Id. This reduces the individual differences in the magnitude of the drive current Id between printers. In this case, erroneous determination can be avoided even if the determination margin VR2 is set sufficiently small. In this example, the threshold for determining the gap portion 312 is set to a gap determination threshold Th3, which is lower in potential than the conventional gap determination threshold Th2 described above. A sufficiently small determination margin VR2 contributes to improving the accuracy of the position detection of the thermal paper 310 by the optical detection unit 140.

[0081] 8 is a diagram showing an example of the accuracy of position detection in a conventional printer device, specifically, the diagram shows an example of the accuracy of position detection of the gap portion 312 when a relatively large determination margin VR1 is set. The horizontal axis of the figure indicates the position where the thermal paper 310 is fed by the motor 110 and changes from the label portion 311 to the gap portion 312 for each individual printer device.

[0082] In conventional printer devices, the drive current Id is not feedback-controlled, so the detected voltage varies between units, and the slope of the change in detected voltage when changing from the label portion 311 to the gap portion 312 also varies between units. For this reason, as described above, conventional printers are set with a relatively large determination margin VR1 to reduce erroneous determinations between the label portion 311 and the gap portion 312. A relatively large determination margin VR1 means that the potential difference between the label determination threshold value Th1 and the gap determination threshold value Th2 is relatively large. In other words, the determination margin VR1 represents the width of the so-called gray zone where it is impossible to determine whether the label portion 311 or the gap portion 312 is present. Therefore, if the determination margin VR1 is relatively large, the gray zone expands, reducing the accuracy of detecting the position where the thermal paper 310 changes from the label portion 311 to the gap portion 312 as the paper is fed, resulting in greater individual differences between printers.

[0083] 9 is a diagram showing an example of the accuracy of position detection in the printer device 1 of this embodiment. That is, this figure shows an example of the accuracy of position detection of the gap portion 312 when a relatively small determination margin VR2 is set.

[0084] In the printer device 1 of this embodiment, the drive current Id is feedback controlled. As a result, the variation in the detected voltage between individual devices is relatively small, and the slope of the change in the detected voltage when changing from the label portion 311 to the gap portion 312 also varies relatively small between individual devices. For this reason, in the printer 1 of this embodiment, as described above, a relatively small determination margin VR2 is set to reduce the likelihood of erroneous determination of the label portion 311 and the gap portion 312. A relatively small determination margin VR2 means that the potential difference between the label determination threshold value Th1 and the gap determination threshold value Th3 is relatively small. Therefore, when the determination margin VR2 is relatively small, the gray zone described above is reduced, improving the accuracy of detecting the position where the thermal paper 310 changes from the label portion 311 to the gap portion 312 as the paper is fed.

[0085] 10 is a diagram showing an example of the correspondence between position detection accuracy and print quality. [A] in the figure shows an example of a print result from a conventional printer (i.e., a printer that does not perform feedback control of the drive current Id). [B] in the figure shows an example of a print result from the printer 1 of this embodiment (i.e., a printer that performs feedback control of the drive current Id). As shown in FIG. 1A, in the case of conventional printers, the accuracy of detecting the position of the gap 312 is low and there is a large variation between individual printers, resulting in variations in the print position between printers. On the other hand, as shown in the same figure [B], in the case of the printer device 1 of this embodiment, the position detection accuracy of the gap portion 312 is high and there is little individual variation between printers, so the variation in printing position between printer devices is reduced. That is, according to the printer device 1 of this embodiment, print positioning can be performed with high precision, particularly when the printing object is label paper, thereby improving print quality.

[0086] All or part of the functions of the control unit 20 of the printer device 1 described above may be recorded as a program on a computer-readable recording medium, and this program may be executed by a computer system. The computer system includes hardware such as an OS and peripheral devices. Examples of computer-readable recording media include portable media such as flexible disks, optical magnetic disks, read-only memory (ROM), and CD-ROMs, storage devices such as hard disks built into computer systems, and volatile memory (Random Access Memory: RAM) provided in servers on networks such as the Internet. Volatile memory is an example of a recording medium that retains a program for a certain period of time.

[0087] Furthermore, the above-described program may be transmitted to another computer system via a transmission medium, for example, a network such as the Internet, or a communication line such as a telephone line.

[0088] The program may be a program that realizes all or part of the above-described functions. Note that the program that realizes part of the above-described functions may be a so-called differential program, which is a program that can realize the above-described functions in combination with a program pre-recorded in the computer system.

[0089] The above describes an embodiment of the present invention with reference to the drawings, but the specific configuration is not limited to the above-described embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0090] 1...printer device, 10...thermal printer mechanism, 20...control unit, 30...paper storage unit, 40...paper discharge unit, 110...motor, 120...thermal head, 140...optical detection unit, 210...print data acquisition unit, 220...drive plan generation unit, 230...motor drive unit, 240...head drive unit, 250...current control unit, 260...control circuit

Claims

1. an optical detection unit including a light emitting unit and a light receiving unit, which detects the feed position of the printing object based on the result of the light receiving unit receiving the reflection or transmission of light irradiated onto the printing object from the light emitting unit; a current adjusting unit that adjusts the magnitude of a drive current supplied from a power source to the light emitting unit; a detection unit that detects the magnitude of the drive current supplied from the current adjustment unit to the light emitting unit; a control unit that controls the magnitude of the drive current adjusted by the current adjustment unit based on the magnitude of the detected drive current and a predetermined reference current value so that the magnitude of the drive current approaches the reference current value; A printing device comprising:

2. the current adjusting unit includes a field effect transistor having a gate terminal connected to a control signal from the control unit, a source terminal connected to the power supply, and a drain terminal connected to a supply line to the light emitting unit, The control unit controls the magnitude of the drive current by driving the field effect transistor in a time-division manner. The printing device of claim 1 .

3. The detection unit includes a current limiting resistor connected in series to a supply line to the light emitting unit, a current detection resistor connected in series to the supply line, and a smoothing capacitor having one terminal connected to a position between the current limiting resistor and the current detection resistor, and detects the magnitude of the drive current based on a potential difference across the current detection resistor. The printing device according to claim 2 .

4. a reference current value setting unit that variably sets the reference current value; Furthermore, The control unit controls the magnitude of the drive current based on the set reference current value. The printing device of claim 1 .

5. a storage unit for storing the set reference current value; Furthermore, the reference current value setting unit stores the set reference current value in the storage unit; The control unit controls the magnitude of the drive current based on the stored reference current value. The printing device according to claim 4 .

6. Detecting a feed position of the printing object based on a result of reception by a light receiving unit of reflection or transmission of light irradiated onto the printing object from a light emitting unit; adjusting the magnitude of a drive current supplied from a power supply to the light-emitting unit by a current adjusting unit; Detecting the magnitude of the drive current supplied from the current adjustment unit to the light emitting unit; Based on the magnitude of the detected drive current and a predetermined reference current value, the magnitude of the drive current adjusted by the current adjusting unit is controlled so as to approach the reference current value; A method for controlling a printing device having the above construction.

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