JP7371438B2 - printing device - Google Patents

Description

The present invention relates to a printing device.

Research and development on printing devices is underway.

In this regard, a printing apparatus is known that includes a line head and is supplied with two voltages: a printing voltage used during printing and an inspection voltage used to inspect the line head (see Patent Document 1).

Japanese Patent Application Publication No. 2000-141730

However, such conventional printing apparatuses switch the voltage used between a printing voltage and an inspection voltage depending on the application. For this reason, in the printing apparatus, a current corresponding to the printing voltage flows into the power supply that supplies the testing voltage, which may cause a problem. Note that the current flowing into the power source is an event that may occur due to, for example, firmware runaway, noise, or the like.

In order to solve such problems, conventional printing apparatuses are sometimes equipped with a current flow suppression circuit that suppresses a current corresponding to the printing voltage from flowing into a power supply that supplies the test voltage. In the printing apparatus, the more complicated the current flow suppression circuit is, the more reliably the current can be prevented from flowing into the power supply. However, complication of the current flow suppression circuit is not desirable for the printing apparatus because it increases the manufacturing cost of the printing apparatus.

As a method to suppress the flow of current corresponding to the printing voltage into the power supply that supplies the test voltage while suppressing an increase in manufacturing costs, a diode is installed in conventional printing equipment instead of a current flow suppression circuit. There are also known methods for providing. However, diodes have large variations in the magnitude of forward voltage drop from individual to individual. As a result, even if the printing apparatus is able to suppress the current from flowing into the power supply, it may not be possible to accurately inspect the line head. That is, the printing apparatus may not be able to simultaneously suppress the current from flowing into the power supply and ensure high accuracy in line head inspection.

In order to solve the above problems, one aspect of the present invention includes a line head having a plurality of heating elements, a first power source, and a first switch that supplies a first voltage from the first power source to the plurality of heating elements. , a second power source, a second switch that supplies a second voltage from the second power source to the plurality of heating elements, a diode that prevents current from flowing from the first power source to the second power source, and a diode that prevents current from flowing from the first power source to the second power source. a first resistance element that drops the second voltage between the second switch and the diode, a second resistance element provided between a transmission line connecting the diode and the plurality of heating elements, and ground; The printing apparatus includes a resistive element and a third switch provided between the second resistive element and the ground.

Further, in one aspect of the present invention, in the printing apparatus, when measuring the forward voltage drop of the diode, the first switch is turned off, and the second switch and the third switch are turned off. is turned on, the second voltage is applied to the first resistance element and the second resistance element, and the order of the diodes is determined based on the divided voltage between the first resistance element and the second resistance element. A configuration including a control unit that calculates the directional voltage drop may be used.

Further, in one aspect of the present invention, in the printing apparatus, when the control unit causes a first heating element included in the plurality of heating elements to form dots on the recording paper when printing is performed by the line head, the control unit controls the A configuration may be used in which one switch is turned on and the first voltage is applied to the first heating element.

Further, in one aspect of the present invention, in the printing apparatus, when inspecting a second heating element included in the plurality of heating elements, the control unit turns off the state of the first switch and the third switch. state, the second switch is turned on, the second voltage is applied to the second heating element and the first resistance element, and the second voltage is applied to the second heating element and the first resistance element. A configuration may be used in which the resistance value of the second heating element is calculated based on the divided voltage and the forward voltage drop.

Further, in one aspect of the present invention, in the printing apparatus, the control unit determines that the second heating element is malfunctioning when the calculated resistance value is equal to or higher than a predetermined threshold value. Good too.

Moreover, in one aspect of the present invention, in the printing apparatus, a configuration may be used in which the second voltage is a voltage lower than the first voltage.

Further, one aspect of the present invention is a printing apparatus that performs printing using a line head having a plurality of heating elements, the A/D (Analog/Digital Digital The printing apparatus is equipped with a digital converter, and performs an inspection of each heating element included in the plurality of heating elements as an inspection of the line head based on the inspection voltage.

FIG. 1 is a diagram showing an example of the appearance of a printing device 1 according to an embodiment. 1 is a diagram showing an example of an internal structure of a printing device 1. FIG. 3 is a diagram showing an example of the configuration of a drive circuit 7 and a line head 35. FIG. 3 is a diagram illustrating an example of the flow of processing in which the printing apparatus 1 inspects the line head 35. FIG. 7 is a diagram illustrating an example of a circuit equivalent to the drive circuit 7 at a stage where the process of step S140 is performed. FIG. 7 is a diagram showing an example of a circuit equivalent to the drive circuit 7 at a stage where the process of step S170 is performed. FIG.

<Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. Note that, for convenience of explanation, hereinafter, a state in which the source terminal and drain terminal of a certain field effect transistor are electrically connected will be referred to as the state of the field effect transistor being in an on state. Further, for convenience of explanation, hereinafter, a state in which the source terminal and drain terminal of a certain field effect transistor are not electrically connected will be referred to as an OFF state of the field effect transistor. Furthermore, for convenience of explanation, a state in which the collector terminal and emitter terminal of a certain transistor are electrically connected will be referred to as an on state in the following description. Further, in the following description, for convenience of explanation, a state where the collector terminal and emitter terminal of a certain transistor are not electrically connected will be referred to as an OFF state of the transistor. Further, in the following description, a potential difference from a predetermined ground potential will be referred to as a voltage.

<Overview of printing device>
First, an overview of a printing apparatus according to an embodiment will be explained.

The printing apparatus according to the embodiment includes a line head having a plurality of heat generating elements, a first power source, a first switch that supplies a first voltage from the first power source to the plurality of heat generating elements, a second power source, and a second power source. a second switch that supplies a second voltage from the power source to the plurality of heating elements; a diode that prevents current from flowing from the first power source to the second power source; and a second voltage drop between the second switch and the diode. a first resistance element provided between the transmission line connecting the diode and the plurality of heating elements, and a second resistance element provided between the second resistance element and the ground; and a second resistance element provided between the second resistance element and the ground. and a third switch.

Thereby, the printing apparatus according to the embodiment can accurately inspect the line head while suppressing current from flowing from the first power source to the second power source. In addition, in order to suppress the current from flowing from the first power source to the second power source by the diode, the printing device may suppress the current from flowing from the first power source to the second power source by another circuit. Compared to the above, it is possible to suppress an increase in the manufacturing cost of the printing apparatus, and it is also possible to reduce the size of the printing apparatus. Below, the configuration of such a printing device will be explained in detail.

<Printing device configuration>
Hereinafter, the configuration of the printing apparatus according to the embodiment will be described using the printing apparatus 1 as an example of the printing apparatus according to the embodiment.

FIG. 1 is a diagram showing an example of the appearance of a printing apparatus 1 according to an embodiment. FIG. 2 is a diagram showing an example of the internal structure of the printing device 1. As shown in FIG.

The printing device 1 is, for example, a thermal printer. More specifically, the printing device 1 is a direct thermal printer that thermally records an image using the line head 35 shown in FIG. Note that the printing device 1 may be another thermal printer instead of the direct thermal printer.

Roll paper 20 is loaded inside the printing device 1 as a medium on which the printing device 1 prints images. The roll paper 20 is a long recording paper wound into a roll.

In the example shown in FIG. 1, the printing apparatus 1 includes an upper case 2, a lower case 3, and a front cover 4, which constitute an exterior cover. Further, in the printing apparatus 1, the upper case 2, the lower case 3, and the front cover 4 cover the printing apparatus main body 11 shown in FIG. Further, the upper case 2 includes a discharge port 5 extending in the width direction of the upper case 2, and an upper cover 6 that can be opened and closed in the direction indicated by the arrow shown in FIG. In the printing apparatus 1, by opening the upper cover 6, the roll paper 20 shown in FIG. 2 can be loaded or removed. Further, an open button B is provided at the upper end of the upper case 2 to release a locking mechanism (not shown) that holds the upper cover 6 in a closed state and to open the upper cover 6.

Further, as shown in FIG. 2, the printing apparatus main body 11 includes a main body frame 12, a cover frame 13, a roll loading section 31, a platen roller 34, a line head 35, and a cutting section 36. The main body frame 12 is a generally box-shaped frame that is open at the top. The cover frame 13 is a frame provided on the main body frame 12 via a support shaft 14 so as to be openable and closable. Further, the cover frame 13 is attached to the back side of the upper cover 6 and opens and closes integrally with the upper cover 6. The roll loading section 31 is formed between the main body frame 12 and the cover frame 13. The roll paper 20 is loaded into the roll loading section 31 . The platen roller 34 is a roller that conveys the leading end 25 of the roll paper 20 from the outlet 32 to the discharge outlet 33. The line head 35 is provided at a position facing the platen roller 34 so as to sandwich the tip 25 therebetween. The cutting unit 36 cuts off the leading end 25 that is discharged from the discharge port 33 after printing the image.

Here, the roll loading section 31 is provided with a concave bottom wall 15 recessed in a substantially arc shape along the outer shape of the roll paper 20 formed on the main body frame 12, and a cover frame 13 at a position above the concave bottom wall 15. It also has a convex cover 16 that protrudes in a substantially arc shape. In the printing device 1 , a concave bottom wall 15 and a convex cover 16 define a storage space for the roll paper 20 .

Further, the platen roller 34 extends in the width direction of the printing apparatus main body 11 and is supported by the cover frame 13. Therefore, when the cover frame 13 is opened, the platen roller 34 moves upward together with the cover frame 13, and the platen roller 34 does not get in the way when loading or unloading the roll paper 20, making loading or unloading work easier. can be done.

Furthermore, a gear (not shown) is provided at one end of the shaft of the platen roller 34. The main body frame 12 is provided with a gear transmission mechanism (not shown) that meshes with the gear when the cover frame 13 is closed, and a motor (not shown). The motor is, for example, a DC (Direct Current) motor. Note that the motor may be another motor such as a stepping motor instead of the DC motor. The driving force of the motor is transmitted to the platen roller 34 via a gear transmission mechanism, and the tip 25 is conveyed by rotation of the platen roller 34.

Further, the line head 35 is a line thermal head having a plurality of heating elements RH not shown in FIGS. 1 and 2. More specifically, the line head 35 is a line thermal head in which a plurality of heating elements RH are arranged in a straight line and extend in the width direction. Further, the line head 35 is rotatably supported by the main body frame 12 via a support shaft 35A. A pressing plate 39 fixed to the main body frame 12 is located on the back side of the line head 35. A biasing member 40 is inserted between the pressing plate 39 and the line head 35. As a result, the line head 35 is urged toward the platen roller 34 by the urging member 40 and is configured to come into contact with the leading end 25 of the roll paper 20 . Here, the biasing member 40 is, for example, a coil spring, but is not limited to this. The head surface of the line head 35 is made of a glass-based member in order to protect the heating element RH, have heat conductivity for transmitting the heat of the heating element RH, and have wear resistance.

Further, the cutting section 36 includes a fixed blade 37 and a movable blade 38. The fixed blade 37 is attached to the cover frame 13. The movable blade 38 is attached to the main body frame 12 so as to be movable back and forth in a direction perpendicular to the leading end 25 of the roll paper 20. When the cover frame 13 is closed, the fixed blade 37 and the movable blade 38 are arranged opposite to each other across the transport path of the roll paper 20, and when the movable blade 38 is driven by a movable blade drive unit (not shown), the movable blade 38 is moved. It crosses the fixed blade 37 and cuts the tip 25 of the roll paper 20.

The printing device 1 also includes an operation receiving section (not shown). The operation reception unit is configured with various buttons, various switches, a touch panel, etc., and is an input device that accepts operations from the user.

Further, as shown in FIG. 3, the printing apparatus 1 includes a drive circuit 7 that drives the line head 35 described above, a first power source 8A that supplies a predetermined first voltage to the drive circuit 7, and a predetermined first voltage. The second power supply 8B supplies the second voltage to the drive circuit 7 from a system different from that of the first power supply 8A, and the control unit 9 controls the line head 35 via the drive circuit 7. FIG. 3 is a diagram showing an example of the configuration of the drive circuit 7 and the line head 35. In addition, in FIG. 3, in order to simplify the diagram, the transmission path connecting the line head 35 and the control section 9 is omitted. In embodiments, the transmission path may be, for example, a conductor printed on a substrate, a conductor formed in a linear shape, or another conductor.

The control unit 9 is, for example, a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Note that some or all of the functions of the control unit 9 may be realized by another processor such as an FPGA (Field Programmable Gate Array).

The first power supply 8A is a power supply that supplies a first voltage to the line head 35 via the drive circuit 7 when the printing apparatus 1 executes printing by the line head 35. That is, the first voltage is a printing voltage. The first voltage is, for example, 24 volts. Note that the first voltage may be a voltage lower than 24 volts or may be a voltage higher than 24 volts.

The second power supply 8B supplies a second voltage to the line head 35 via the drive circuit 7 when the printing apparatus 1 inspects each of the plurality of heat generating elements RH included in the line head 35. It is a power source. That is, the second voltage is a test voltage. The second voltage is lower than the first voltage, for example 3.3 volts. Note that the second voltage may be lower than 3.3 volts or higher than 3.3 volts as long as it is lower than the first voltage.

The drive circuit 7 is a circuit that drives the line head 35 based on control by the control section 9. The drive circuit 7 includes, for example, seven resistance elements R1 to R7, four field effect transistors Q1 to Q4, and a diode D.

The field effect transistor Q1 is, for example, a p-channel field effect transistor. Note that the drive circuit 7 may be configured to include another switching element instead of the field effect transistor Q1. Field effect transistor Q1 is an example of a first switch.

A parasitic diode is connected between the source terminal and drain terminal of the field effect transistor Q1. A source terminal of the field effect transistor Q1 is connected to a power supply terminal 8AE of a first power supply 8A via a transmission line. Further, a power terminal 35E of the line head 35 is connected to the drain terminal of the field effect transistor Q1 via a transmission path. Therefore, when the field effect transistor Q1 is in the on state, the line head 35 is supplied with the first voltage from the first power supply 8A. On the other hand, when the field effect transistor Q1 is in the off state, the line head 35 is not supplied with the first voltage from the first power supply 8A.

One of the two terminals of the resistive element R1 is connected to a transmission line connecting the source terminal of the field effect transistor Q1 and the power supply terminal 8AE of the first power supply 8A. The other of the two terminals of the resistance element R1 is connected to the gate terminal of the field effect transistor Q1 via a transmission path.

One of the two terminals of the resistance element R2 is connected to the transmission line connecting the gate terminal of the field effect transistor Q1 and the resistance element R1 via the transmission line. The other of the two terminals of the resistance element R2 is connected to the drain terminal of the field effect transistor Q2 via a transmission path.

Field effect transistor Q2 is, for example, an n-channel field effect transistor. Note that the drive circuit 7 may be configured to include another switching element instead of the field effect transistor Q2.

A parasitic diode is connected between the source terminal and drain terminal of the field effect transistor Q2. A source terminal of the field effect transistor Q2 is grounded via a transmission line. Therefore, when the field effect transistor Q2 is in the on state, the field effect transistor Q2 is in the on state. On the other hand, when the field effect transistor Q2 is in the off state, the field effect transistor Q2 is in the off state.

One of the two terminals of the resistive element R3 is connected to the transmission line connecting the source terminal of the field effect transistor Q2 and the ground via the transmission line. The other of the two terminals of the resistance element R3 is connected to the gate terminal of the field effect transistor Q2 via a transmission path.

A first signal output terminal 9O1 of the control unit 9 is connected to a transmission line connecting the gate terminal of the field effect transistor Q2 and the resistance element R3 via a transmission line. Thereby, the control unit 9 can switch the state of the field effect transistor Q2 between an on state and an off state. As a result, the control unit 9 can switch the state of the field effect transistor Q1 between the on state and the off state.

Field effect transistor Q3 is, for example, a p-channel field effect transistor. Note that the drive circuit 7 may be configured to include another switching element instead of the field effect transistor Q3. Field effect transistor Q3 is an example of a second switch.

A parasitic diode is connected between the source terminal and drain terminal of the field effect transistor Q3. A source terminal of the field effect transistor Q3 is connected to a power supply terminal 8BE of a second power supply 8B via a transmission path. Furthermore, one of the two terminals of the resistance element R5 is connected to the drain terminal of the field effect transistor Q3 via a transmission path. An anode of a diode D is connected to the other of the two terminals of the resistance element R5 via a transmission path. The cathode of the diode D is connected to a transmission line that connects the drain terminal of the field effect transistor Q1 and the power supply terminal 35E of the line head 35 via a transmission line. Therefore, when the field effect transistor Q3 is in the on state, the second voltage is supplied to the line head 35 from the second power supply 8B. On the other hand, when the field effect transistor Q3 is in the off state, the second voltage is not supplied to the line head 35 from the second power supply 8B.

Here, since the drive circuit 7 includes the diode D, the printing apparatus 1 is configured such that both the state of the field effect transistor Q1 and the state of the field effect transistor Q3 are in the on state due to the influence of firmware runaway, noise, etc. Even if this occurs, it is possible to prevent current from flowing from the first power source 8A to the second power source 8B.

One of the two terminals of the resistance element R4 is connected to the gate terminal of the field effect transistor Q3 via a transmission path. A transmission line that connects the source terminal of the field effect transistor Q3 and the power supply terminal 8BE of the second power supply 8B is connected to the other of the two terminals of the resistance element R4 via a transmission line. . A second signal output terminal 9O2 of the control section 9 is connected to a transmission line connecting the gate terminal of the field effect transistor Q3 and the resistive element R4. Thereby, the control unit 9 can switch the state of the field effect transistor Q3 between an on state and an off state.

Further, an A/D (Analog/Digital) converter 9I of the control section 9 is connected to the transmission line connecting between the resistive element R5 and the diode D via the transmission line. The power supply voltage of the A/D converter 9I is the second voltage. That is, the A/D converter 9I is supplied with the second voltage as the power supply voltage from the second power supply 8B. The voltage on the transmission path is input to the A/D converter 9I as an input voltage.

Furthermore, one of the two terminals of the resistive element R6 is connected to the transmission line connecting the diode D and the power supply terminal 35E of the line head 35 via the transmission line. A drain terminal of a field effect transistor Q4 is connected to the other of the two terminals of the resistance element R6 via a transmission path.

Field effect transistor Q4 is, for example, an n-channel field effect transistor. Note that the drive circuit 7 may be configured to include another switching element instead of the field effect transistor Q4. Field effect transistor Q4 is an example of a third switch.

A parasitic diode is connected between the source terminal and drain terminal of the field effect transistor Q4. A source terminal of the field effect transistor Q4 is grounded via a transmission path. Therefore, even if the field effect transistor Q3 is in the on state, the second voltage is not supplied to the line head 35 from the second power supply 8B in this case. That is, in the printing apparatus 1, when either the first voltage or the second voltage is supplied to the line head 35, the field effect transistor Q4 is in the off state.

One of the two terminals of the resistive element R7 is connected to the transmission line connecting the source terminal of the field effect transistor Q4 and the ground via the transmission line. The other of the two terminals of the resistance element R7 is connected to the gate terminal of the field effect transistor Q4 via a transmission path. Further, the third signal output terminal 9O3 of the control section 9 is connected to the transmission line connecting between the gate terminal of the field effect transistor Q4 and the resistance element R7 via the transmission line. Thereby, the control unit 9 can switch the state of the field effect transistor Q4 between an on state and an off state.

The line head 35 includes n heating elements RH, n transistors QH, a latch driver 35L, and a shift register 35S. n may be any number as long as it is an integer of 1 or more. In FIG. 3, the n heating elements RH are shown as heating elements RH1 to RHn. Further, in FIG. 3, n transistors QH are shown as transistors QH1 to QHn.

Each of the heating elements RH1 to RHn is a resistance element. Each of the heating elements RH1 to RHn is connected in parallel to the power terminal 35E of the line head 35.

Each of transistors QH1 to QHn is an NPN type transistor. Note that some or all of the transistors QH1 to QHn may be other switching elements.

The i-th transistor QHi among the transistors QH1 to QHn is connected to the i-th heating element RHi among the heating elements RH1 to RHn. Here, i may be any number as long as it is an integer greater than or equal to 1 and less than or equal to n. Specifically, the collector terminal of the transistor QHi is connected to the terminal of the two terminals of the heating element RHi that is not connected to the power supply terminal 35E of the line head 35. Further, the emitter terminal of the transistor QHi is grounded. Furthermore, the i-th signal output terminal among the n signal output terminals of the latch driver 35L is connected to the base terminal of the transistor QHi.

The latch driver 35L has a signal input terminal STB to which a strobe signal is input from the control section 9, and a signal input terminal LAT to which a latch signal is input from the control section 9. The latch driver 35L temporarily latches the data signal input from the shift register 35S using a latch signal input to the signal input terminal LAT. The latch driver 35L switches the state of each of the n transistors QH between an on state and an off state based on the strobe signal input to the signal input terminal STB. Thereby, the latch driver 35L controls the heat generation of each of the n heating elements RH.

Shift register 35S has n flip-flops. Each of the n flip-flops included in the shift register 35S has a signal input terminal DI to which a data signal, which is serial data, is input from the control unit 9, and a clock signal synchronized with the data signal is input from the control unit 9. It includes a signal input terminal CLK and a signal output terminal (not shown) through which an overflow data signal is output to the latch driver 35L. In the shift register 35S, n flip-flops are sequentially connected such that the signal output terminal of the first flip-flop is connected to the signal input terminal DI of the second flip-flop.

In the line head 35 having such a configuration, when the field effect transistor Q1 is on, and the field effect transistors Q3 and Q4 are off, the data input from the control unit 9 Based on the signal and the clock signal, the state of each of the n transistors QH is switched between an on state and an off state. For example, the i-th transistor QHi among the n transistors QH is turned on, the (n-1) transistors QH other than the transistor QHi among the n transistors QH are turned off, and the field effect transistor Q1 When the state of the field effect transistor Q3 and the state of the field effect transistor Q4 are turned on and off, the heating element RHi of the n heating elements RH generates heat. In this case, among the n heating elements RH, (n-1) heating elements RH other than the heating element RHi do not generate heat. That is, the control unit 9 can selectively cause one or more heating elements RH to generate heat among the n heating elements RH to generate heat based on the data signal.

Therefore, the control unit 9 can cause one or more of the n heating elements RH to generate heat in accordance with the data signal, and the line head 35 can perform printing on the recording paper. In the following, for convenience of explanation, each of the one or more heating elements RH selected as the heating element RH to be heated by the data signal from among the n heating elements RH will be referred to as a first heating element. .

In other words, the control unit 9 controls the state of the field effect transistor Q1 when forming dots on the recording paper by one or more first heating elements included in the n heating elements RH during printing by the line head 35. The device is turned on, and a first voltage is applied to each of the one or more first heating elements. Thereby, the control unit 9 can cause each of the one or more first heating elements to generate heat, and cause each of the one or more first heating elements to form dots on the recording paper. That is, the control unit 9 can perform printing on recording paper using the line head 35.

Here, the printing apparatus 1 that prints on recording paper using the line head 35 in this manner inspects the line head 35 when a predetermined inspection start condition is satisfied. In other words, the inspection of the line head 35 is an inspection of the resistance value of each of the n heating elements RH included in the line head 35. For example, when a malfunction occurs in the i-th heating element RHi among the n heating elements RH, the resistance value of the heating element RHi increases to a value equal to or higher than a predetermined threshold value. By testing each of the n heating elements RH to see if such an increase in resistance value has occurred, it is possible to test whether or not the line head 35 is malfunctioning. Note that the predetermined test start conditions are, for example, that the printing device 1 accepts an operation to start the test, that the continuous usage time of the printing device 1 exceeds a predetermined threshold, but are limited to these. Do not mean. Further, the predetermined threshold value may be a value determined in advance through an endurance test for the heating element RH, or may be a catalog value given by the manufacturer.

<Processing in which the printing device inspects the line head>
The process by which the printing apparatus 1 inspects the line head 35 will be described below. FIG. 4 is a diagram illustrating an example of a process flow in which the printing apparatus 1 inspects the line head 35. Note that, as an example, a case will be described below in which the above-mentioned test start condition is satisfied at a timing before the process of step S110 shown in FIG. 4 is performed.

The control unit 9 turns off the field effect transistor Q1 (step S110). More specifically, when the current state of the field effect transistor Q1 is in the off state, the control unit 9 maintains the state of the field effect transistor Q1 in the off state. On the other hand, when the current state of the field effect transistor Q1 is the on state, the control unit 9 switches the state of the field effect transistor Q1 to the off state. In FIG. 4, such processing in step S110 is indicated by "turn off the first switch". As described above, when the control section 9 turns off the field effect transistor Q1, the control section 9 turns off the field effect transistor Q2. Further, when the control section 9 turns on the field effect transistor Q1, the control section 9 turns on the field effect transistor Q2.

Next, the control unit 9 turns on the field effect transistor Q3 (step S120). More specifically, when the current state of the field effect transistor Q3 is in the on state, the control unit 9 maintains the state of the field effect transistor Q3 in the on state. On the other hand, when the current state of the field effect transistor Q3 is the off state, the control unit 9 switches the state of the field effect transistor Q3 to the on state. In FIG. 4, such processing in step S120 is indicated by "turning on the second switch".

Next, the control unit 9 turns on the field effect transistor Q4 (step S130). More specifically, when the current state of the field effect transistor Q4 is in the on state, the control unit 9 maintains the state of the field effect transistor Q4 in the on state. On the other hand, when the current state of the field effect transistor Q4 is the off state, the control unit 9 switches the state of the field effect transistor Q4 to the on state. In FIG. 4, such processing in step S130 is indicated by "turning on the third switch".

Note that the control unit 9 may be configured to perform the processing in step S110 and the processing in step S120 in parallel. Further, the control unit 9 may be configured to perform the processing in step S120 and the processing in step S130 in the reverse order, or may be configured to perform the processing in step S120 and the processing in step S130 in parallel. Further, the control unit 9 may be configured to perform the processing in step S110 and the processing in step S130 in parallel. Furthermore, the control unit 9 may be configured to perform the processes of steps S110 to S130 in parallel.

Next, the control unit 9 detects the input voltage to the A/D converter 9I described above (step S140). Here, the process of step S140 will be explained.

Through the processing from step S110 to step S130, the drive circuit 7 has become a circuit equivalent to the circuit shown in FIG. 5. FIG. 5 is a diagram showing an example of a circuit equivalent to the drive circuit 7 at the stage where the process of step S140 is performed. As shown in FIG. 5, the drive circuit 7 at the stage where the process of step S140 is performed applies the second voltage supplied from the second power supply 8B to the resistance element R5 and the resistance element R6. Thereby, the second voltage is divided by resistance element R5 and resistance element R6. In this case, the divided voltage obtained by dividing the second voltage by the resistive element R5 and the resistive element R6 is input to the A/D converter 9I as an input voltage. That is, in step S140, the control unit 9 detects the input voltage input to the A/D converter 9I as a voltage divided by the resistance element R5 and the resistance element R6. However, this divided voltage includes the influence of a voltage drop due to the forward voltage drop of the diode D. The control unit 9 stores first divided voltage information indicating the detected divided voltage in a storage unit (not shown). The storage unit is a storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), but is not limited to these. Furthermore, the storage unit may be a storage device built into the printing device 1 or a storage device externally attached to the printing device 1.

After the process of step S140 is performed, the control unit 9 switches the state of the field effect transistor Q4 to the off state (step S150). In FIG. 4, such processing in step S150 is indicated by "turn off the third switch".

Next, the control unit 9 selects the heating elements RH to be inspected one by one from among the n heating elements RH included in the line head 35, and performs a step for each selected heating element. The processes from S170 to S180 are repeated (step S160). Note that the target heating element is an example of the second heating element.

The control unit 9 energizes the target heating element selected in step S160 (step S170). More specifically, in step S170, the control unit 9 turns on the transistor QH connected to the target heating element to energize the target heating element. Note that, in step S170, the control unit 9 does not energize the heating elements RH other than the target heating element among the n heating elements RH included in the line head 35. In this case, the drive circuit 7 is a circuit equivalent to the circuit shown in FIG. FIG. 6 is a diagram showing an example of a circuit equivalent to the drive circuit 7 at the stage where the process of step S170 is performed. As shown in FIG. 6, the drive circuit 7 at the stage where the process of step S170 is performed applies the second voltage supplied from the second power supply 8B to the resistance element R5 and the target heating element. Thereby, the second voltage is divided by the resistance element R5 and the target heating element. In FIG. 6, the target heating element is indicated by the target heating element RHS.

Next, the control unit 9 detects the input voltage to the A/D converter of the control unit 9 (step S180). Here, in step S180, the divided voltage after the second voltage is divided by the resistance element R5 and the target heating element is input to the A/D converter 9I as an input voltage by the process of step S170. Ru. That is, in step S140, the control unit 9 detects the input voltage input to the A/D converter 9I as a divided voltage between the resistance element R5 and the target heating element. However, this divided voltage also includes the influence of a voltage drop due to the forward voltage drop of the diode D. The control unit 9 stores second divided voltage information indicating the detected divided voltage in a storage unit (not shown) in association with heating element information indicating the target heating element.

After the process of step S180 is performed, the control unit 9 moves to step S160 and selects the next target heating element from among the unselected heating elements RH. Note that if there is no unselected heating element RH in step S160, the control unit 9 ends the repeating process of steps S160 to S180 and proceeds to step S190.

After completing the repeated processing of steps S160 to S180, the control unit 9 calculates the resistance value of each of the n heating elements RH (step S190). Here, the process of step S190 will be explained.

Here, in the circuit shown in FIG. 5, the resistance value of resistance element R5 is RD, the resistance value of resistance element R6 is RVF, the divided voltage between resistance element R5 and resistance element R6 is VAD1, and the forward drop of diode D is When the voltage is expressed by VF, the resistance value RD, the resistance value RVF, the divided voltage VAD1, and the forward drop voltage VF are related by the following equation (1).

((Second voltage)-VF):(RD+RH)=((Second voltage)-VAD1):RD...(1)

The above equation (1) can be easily derived from Ohm's law. Therefore, a description of the process of deriving equation (1) will be omitted below. The fact that the forward drop voltage VF is included in the above equation (1) means that the divided voltage detected in step S140 includes the influence of the voltage drop due to the forward drop voltage of the diode D, as described above. This is a manifestation of this. The above formula (1) can be rearranged and expressed as the following formula (2).

VF=(VAD1×(RD+RVF)-(second voltage)×RVF)/RD...(2)

In addition, in the circuit shown in FIG. 6, the resistance value of the resistive element R5 is RD, the resistance value of the target heating element RHS is RHD, the divided voltage between the resistive element R5 and the target heating element RHS is VAD2, and the forward direction of the diode D is When the voltage drop is expressed by VF, the resistance value RD, the resistance value RHD, the divided voltage VAD2, and the forward voltage drop VF are related by the following equation (3).

RHD=RD×(VAD2-VF)/((second voltage)-VAD2)...(3)

The above equation (3) can be easily derived from Ohm's law. Therefore, a description of the process of deriving equation (3) will be omitted below. The fact that the forward drop voltage VF is included in the above equation (3) means that the voltage drop due to the forward drop voltage of the diode D is included in the divided voltage detected in step S180, as described above. This is a manifestation of this. By substituting equation (2) into equation (3) above, we can calculate the effect of the voltage drop due to the forward drop voltage of diode D included in equation (1), and the effect of voltage drop due to the forward voltage drop of diode D included in equation (3). The influence of the voltage drop due to the forward voltage drop of D can be canceled out. The following equation (4) is obtained as a result of substituting equation (2) into equation (3).

RHD=(RD×(VAD2-VAD1)+RVF×((second voltage)-VAD1))/((second voltage)-VAD2)...(4)

That is, in the process of step S190, the control unit 9 uses the above equation (4), the divided voltage indicated by the first divided voltage information stored in advance in the storage unit, and the heating element information stored in advance in the storage unit. The divided voltage indicated by the second divided voltage information associated with The resistance value of each heating element RH is calculated based on the voltage. Thereby, the control unit 9 can accurately calculate the resistance value of each heating element RH without being affected by the voltage drop due to the forward voltage drop of the diode D.

In other words, the process of step S190 corresponds to calculating the forward voltage drop of the diode D and calculating the resistance value of each heating element RH based on the calculated forward voltage drop. Here, the forward voltage drop of the diode D has large individual differences. Therefore, if the forward voltage drop of the diode D cannot be determined, that is, if the influence of the voltage drop due to the forward voltage drop cannot be canceled, the measurement error of the resistance value of each heating element RH of the line head 35 will be It gets bigger. That is, in this case, the printing apparatus 1 cannot accurately inspect the line head 35. In order to solve such a problem, the printing apparatus 1 calculates the resistance value of each heating element RH using the above equation (4) in step S190. Thereby, the printing apparatus 1 can accurately inspect the line head 35 without being affected by the voltage drop due to the forward voltage drop of the diode D.

Furthermore, since the printing device 1 uses the diode D to suppress the flow of current from the first power source 8A to the second power source 8B, the manufacturing cost increases due to the circuit for suppressing the current. In addition, it is possible to suppress an increase in the mounting area due to the circuit.

In addition, in step S190, the control unit 9 calculates the forward drop voltage of the diode D based on the divided voltage indicated by the first divided voltage information and the above equation (2), and calculates the forward drop voltage of the diode D. The resistance value of each heating element RH is calculated based on the voltage, the divided voltage indicated by the second divided voltage information associated with each heating element information, and the above equation (3). Good too.

Further, the control unit 9 may be configured to calculate the resistance value of the target heating element based on the above equation (4) in the process of step S180. In this case, the control section 9 may or may not store the second divided voltage information in the storage section.

After the process of step S190 is performed, the control unit 9 determines for each heating element RH whether or not the heating element RH is out of order (step S200). Specifically, the control unit 9 determines for each heating element RH whether the resistance value calculated in step S190 is greater than or equal to a predetermined threshold value. The control unit 9 determines that the heating element RH whose resistance value calculated in step S190 is equal to or higher than a predetermined threshold value is malfunctioning. On the other hand, the control unit 9 determines that the heating element RH whose resistance value calculated in step S190 is less than the predetermined threshold is not in failure. Here, since the control unit 9 performs the failure determination in step S200 based on the resistance value calculated by equation (4) in step S190, it is possible to accurately determine the failure of the heating element RH. That is, the control unit 9 can inspect the line head 35 with high accuracy.

Here, in the process of the flowchart shown in FIG. 4, the ambient temperature of the diode D hardly changes. Therefore, through the process, the control unit 9 can suppress variations in the forward voltage drop of the diode D due to changes in the ambient temperature, and as a result, the line head 35 can be inspected more reliably and accurately. I can do it.

Next, the control unit 9 switches the state of the field effect transistor Q3 to the off state (step S210), and ends the process. In FIG. 4, such processing in step S210 is indicated by "turn off the second switch".

Note that in the printing apparatus 1 described above, the second voltage was 3.3 volts. Therefore, in the printing apparatus 1, the power supply voltage of the A/D converter 9I, to which the second voltage is supplied from the second power supply 8B, was also 3.3 volts. However, in printing device 1, the second voltage may be less than 3.3 volts. For example, in printing device 1, the second voltage may be 1.8 volts. In this case, the power supply voltage is also 1.8 volts. In this way, by setting the second voltage and the power supply voltage to the same voltage, the printing device 1 can also inspect the line head 35 using a voltage of less than 3.3 volts as the inspection voltage. .

Further, the printing apparatus 1 may be configured to calculate the forward voltage drop of the diode D described above independently and separately from the inspection of the line head 35. In this case, the control unit 9 calculates the forward voltage drop based on the above equation (2) after performing the processing in steps S110 to S140, for example.

As described above, the printing apparatus according to the embodiment includes a line head having a plurality of heating elements, a first power source, a first switch that supplies a first voltage from the first power source to the plurality of heating elements, and a first switch that supplies a first voltage from the first power source to the plurality of heating elements. a second power source, a second switch that supplies a second voltage from the second power source to the plurality of heating elements, a diode that prevents current from flowing from the first power source to the second power source, and between the second switch and the diode. a first resistance element that lowers a second voltage at the second resistance element, a second resistance element provided between the transmission path connecting the diode and the plurality of heating elements, and ground; and a second resistance element provided between the second resistance element and the ground. and a third switch provided between the two. Thereby, the printing apparatus can accurately calculate the resistance value of each of the plurality of heating elements while suppressing current from flowing from the first power source to the second power source. Note that in the example described above, the printing device 1 is an example of a printing device. Furthermore, in the example described above, the line head 35 is an example of a line head. Further, in the example described above, the first power source 8A is an example of the first power source. Furthermore, in the example described above, the n heating elements RH are an example of a plurality of heating elements. Furthermore, in the example described above, the field effect transistor Q1 is an example of the first switch. Furthermore, in the example described above, the second power supply 8B is an example of the second power supply. Furthermore, in the example described above, the field effect transistor Q3 is an example of the second switch. Furthermore, in the example described above, the diode D is an example of a diode. Furthermore, in the example described above, the resistance element R5 is an example of the first resistance element. Furthermore, in the example described above, the resistance element R6 is an example of the second resistance element. Furthermore, in the example described above, the field effect transistor Q4 is an example of the third switch.

Further, when measuring the forward voltage drop of the diode, the printing device turns the first switch off, turns the second switch and the third switch on, and connects the first resistance element to the off-state. Even if a configuration is used that includes a control unit that applies a second voltage to the second resistance element and calculates the forward voltage drop of the diode based on the voltage divided by the first resistance element and the second resistance element. good. Thereby, the printing apparatus can accurately calculate the resistance value of each of the plurality of heating elements based on the calculated forward voltage drop. Note that in the example described above, the control unit 9 is an example of a control unit.

Further, in the printing device, when the line head is printing and causes a first heating element included in the plurality of heating elements to form dots on the recording paper, the control unit turns the first switch on and the first switch is turned on. A configuration may be used in which a first voltage is applied to one heating element.

Further, in the printing apparatus, when inspecting a second heating element included in the plurality of heating elements, the control unit turns off the first switch and the third switch, and changes the state of the second switch. A second voltage is applied to the second heating element and the first resistance element in the on state, and a second voltage is applied to the second heating element and the first resistance element based on the divided voltage between the second heating element and the first resistance element and the forward voltage drop of the diode. A configuration may be used in which the resistance values of two heating elements are calculated. Note that in the example described above, the target heating element is an example of the second heating element.

Further, in the printing apparatus, a configuration may be used in which the control unit determines that the second heating element is malfunctioning when the calculated resistance value is equal to or greater than a predetermined threshold value.

Further, in the printing apparatus, a configuration may be used in which the second voltage is lower than the first voltage.

Further, the printing device according to the embodiment is a printing device that performs printing using a line head having a plurality of heating elements, and includes an A/D converter that is supplied with the same voltage as the inspection voltage of the line head as a power supply voltage; , and performs an inspection of each heating element included in the plurality of heating elements as a line head inspection based on the inspection voltage. Thereby, the printing apparatus can accurately calculate the resistance value of each of the plurality of heating elements while suppressing current from flowing from the first power source to the second power source.

Although the embodiments of this invention have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications, substitutions, deletions, etc. may be made without departing from the gist of this invention. may be done.

DESCRIPTION OF SYMBOLS 1...Printing device, 2...Upper case, 3...Lower case, 4...Front cover, 5...Ejection port, 6...Upper cover, 7...Drive circuit, 8A...First power supply, 8AE, 8BE...Power terminal, 8B... 2nd power supply, 9...control unit, 9I...A/D converter, 9O1...first signal output terminal, 9O2...second signal output terminal, 9O3...third signal output terminal, 11...printing device main body, 12...main body frame , 13... cover frame, 14... spindle, 15... concave bottom wall, 16... convex cover, 20... roll paper, 25... tip, 31... roll loading section, 32... outlet, 33... discharge port, 34... Platen roller, 35... Line head, 35A... Support shaft, 35E... Power terminal, 35L... Latch driver, 35S... Shift register, 36... Cutting section, 37... Fixed blade, 38... Movable blade, 39... Pressing plate, 40... Biasing member, B...Open button, CLK...signal input terminal, D...diode, DI...signal input terminal, LAT...signal input terminal, Q1, Q2, Q3, Q4...field effect transistor, QH, QH1, QHi, QHn ...Transistor, R1, R2, R3, R4, R5, R6, R7...Resistance element, RH, RH1, RHi, RHn...Heating element, RHS...Target heating element, STB...Signal input terminal

Claims (5)

a line head having multiple heating elements;
a first power source;
a first switch that supplies a first voltage from the first power source to the plurality of heating elements;
a second power supply;
a second switch that supplies a second voltage from the second power source to the plurality of heating elements;
a diode that prevents current from flowing from the first power source to the second power source;
a first resistance element that drops the second voltage between the second switch and the diode;
a second resistance element provided between a transmission line connecting the diode and the plurality of heating elements and ground;
a third switch provided between the second resistance element and the ground;
The first switch is turned off, the second switch and the third switch are turned on, and the second voltage is applied to the first resistance element and the second resistance element. , a control unit into which a divided voltage generated by the first resistance element and the second resistance element is input;
A printing device comprising: When causing a first heating element included in the plurality of heating elements to form dots on the recording paper when printing is performed by the line head, the control unit turns on the first switch to turn on the first heating element. applying the first voltage to the body;
The printing device according to claim 1 . When inspecting a second heating element included in the plurality of heating elements, the control unit turns off the first switch and the third switch, and turns on the second switch. the second voltage is applied to the second heating element and the first resistance element, and the divided voltage between the second heating element and the first resistance element and the first resistance element and the calculating the resistance value of the second heating element based on the divided voltage by the second resistance element;
The printing device according to claim 2. The control unit determines that the second heating element is out of order when the calculated resistance value is equal to or higher than a predetermined threshold.
The printing device according to claim 3 . the second voltage is lower than the first voltage;
The printing device according to any one of claims 1 to 4 .

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