JP2013216072A - Liquid ejection apparatus and liquid circulation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve control of a flow rate of liquid and temperature by a simple configuration at low cost.SOLUTION: A liquid ejection apparatus includes: a head to eject liquid; a circulation pump to make the liquid circulate by a circulation path that passes the head; a pulse motor to drive the circulation pump; a temperature sensor that outputs a detection signal corresponding to a temperature of the liquid; and a control part that independently controls the amount of the current and the pulse signal supplied to the pulse motor based on the detection signal of the temperature sensor, respectively.

Description

  The present invention relates to a liquid ejection apparatus and a liquid circulation method.

  As a liquid ejecting apparatus, an ink jet printer that ejects ink (a kind of liquid) from a head to form an image is known. In addition, such a printer includes a circulation pump (and a motor that drives the circulation pump) for circulating ink in a circulation path, and a heater disposed immediately in front of the head, so that the ink flow rate and temperature (in other words, An apparatus has been proposed that adjusts (ink viscosity) to prevent deterioration in image quality (see, for example, Patent Document 1).

JP 2011-207064 A

However, the above-described printer has a problem that it is necessary to separately provide a circulation pump (and a motor) and a heater, which is expensive.
Accordingly, an object of the present invention is to realize control of the flow rate and temperature of a liquid with a simple configuration and low cost.

The main invention for achieving the above object is:
A head for discharging liquid;
A circulation pump for circulating the liquid in a circulation path passing through the head;
A pulse motor for driving the circulation pump;
A temperature sensor that outputs a detection signal corresponding to the temperature of the liquid;
Based on the detection signal of the temperature sensor, a control unit that independently controls the amount of current supplied to the pulse motor and the pulse signal;
A liquid ejecting apparatus comprising:

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a schematic sectional view of a printer 1. 2 is a block diagram illustrating a configuration example of a printer 1. FIG. It is a figure which shows the structure of the ink supply unit 35 of a comparative example. It is a figure which shows the structure of the ink supply unit 35 of this embodiment. It is the figure which showed the structure of the circulation pump 353 vicinity of FIG. 4 in detail. 6A is a diagram illustrating an example of the configuration of the stepping motor 354, and FIG. 6B is a connection diagram of FIG. 6A. It is a figure for demonstrating the excitation system (two phase excitation) of the stepping motor 354

At least the following matters will become clear from the description of the present specification and the accompanying drawings.
A head for discharging liquid;
A circulation pump for circulating the liquid in a circulation path passing through the head;
A pulse motor for driving the circulation pump;
A temperature sensor that outputs a detection signal corresponding to the temperature of the liquid;
Based on the detection signal of the temperature sensor, a control unit that independently controls the amount of current supplied to the pulse motor and the pulse signal;
A liquid ejection apparatus characterized by comprising:
According to such a liquid ejection device, the temperature of the liquid can be controlled without using a heater (independent of the control of the flow rate of the liquid). Therefore, the flow rate and temperature of the liquid can be controlled with a simple configuration and at a low cost.

In this liquid ejection apparatus, the controller, when heating the liquid, changes the amount of current without increasing the number of rotations of the pulse motor based on the detection signal, thereby changing the current of the pulse motor. It is desirable to increase the calorific value.
According to such a liquid ejection device, the liquid can be heated without changing the flow rate of the liquid.

In this liquid ejection apparatus, the control unit changes the pulse signal without increasing the heat generation amount of the pulse motor when the temperature of the liquid is lowered based on the detection signal, and rotates the pulse motor. It is desirable to increase the number.
According to such a liquid ejecting apparatus, the temperature of the liquid can be lowered by increasing the flow rate of the liquid.

In this liquid ejection apparatus, it is preferable that the circulation path is disposed so as to wind around the pulse motor.
According to such a liquid ejecting apparatus, heat generated by the pulse motor can be efficiently transmitted to the liquid.

In this liquid ejection apparatus, it is desirable to have a cover member that covers the pulse motor and the circulation path disposed in the vicinity of the pulse motor.
According to such a liquid ejecting apparatus, it is possible to prevent the heat generated by the pulse motor from escaping, so that the heat can be transmitted more efficiently.

In this liquid discharge apparatus, it is preferable that the liquid is a light curable liquid that is cured by light irradiation, and includes a light source that irradiates the liquid discharged from the head and landed on the medium. .
According to such a liquid ejecting apparatus, it is more effective to control the flow rate and the temperature because the thickening of the photocurable liquid that tends to increase the viscosity can be prevented.

  Further, it is a liquid circulation method by a liquid ejection device having a head for ejecting liquid, a circulation pump provided in a circulation path passing through the head, and a pulse motor for driving the circulation pump, the temperature of the liquid being adjusted. A step of generating a corresponding detection signal, a step of independently controlling a pulse signal and an amount of current based on the detection signal, and supplying the pulse motor to the pulse motor, and driving the circulation pump by the pulse motor, And a step of circulating the liquid in the circulation path.

=== Embodiment ===
≪About printer configuration examples≫
A configuration example of a printer 1 as an example of a liquid ejecting apparatus (in the present embodiment, an ink jet printer, in particular, a lateral scan type label printing machine) will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic sectional view of the printer 1. FIG. 2 is a block diagram illustrating a configuration example of the printer 1.
In the following description, when referring to “up and down direction” and “left and right direction”, the direction indicated by the arrow in FIG. 1 is used as a reference. In addition, the “front-rear direction” refers to a direction orthogonal to the paper surface in FIG.
Further, in the present embodiment, as an example of a medium on which the printer 1 records an image, a paper wound in a roll shape (hereinafter referred to as roll paper (continuous paper)) will be described.

  As shown in FIGS. 1 and 2, the printer 1 according to this embodiment includes a transport unit 20 and a transport path through which the transport unit 20 transports the roll paper 2 (in FIG. 1, the transport path is a roll paper winding). A feed unit 10, a platen 29, a take-up unit 90, along the axis 18 to the roll take-up drive shaft 92 (represented by the portion where the roll paper 2 is located), and A head unit 30 that performs image printing by ejecting a plurality of types of ink in a printing region R on the transport path, an ink supply unit 35, a carriage unit 40, a heater unit 70 as an example of a heating unit, and a platen 29 A blower unit 80 for sending wind to the roll paper 2, a controller 60 for controlling these units and controlling the operation as the printer 1, It has a left instrument group 50, a.

  The feeding unit 10 feeds the roll paper 2 to the transport unit 20. The feeding unit 10 includes a roll paper winding shaft 18 around which the roll paper 2 is wound and rotatably supported, and a relay roller 19 for winding the roll paper 2 fed from the roll paper winding shaft 18 and guiding the roll paper 2 to the transport unit 20. And have.

  The transport unit 20 transports the roll paper 2 sent by the feeding unit 10 along a preset transport path. As shown in FIG. 1, the transport unit 20 includes a relay roller 21 that is positioned horizontally to the right of the relay roller 19, a relay roller 22 that is positioned obliquely downward to the right when viewed from the relay roller 21, and the relay roller 22. A first conveyance roller 23 located obliquely right above (as viewed from the platen 29 in the conveyance direction), and a steering unit (steering unit) 20a positioned between the relay roller 22 and the first conveyance roller 23, A second transport roller 24 positioned on the right side (downstream in the transport direction as viewed from the platen 29) as viewed from the first transport roller 23, a reversing roller 25 positioned vertically downward as viewed from the second transport roller 24, A relay roller 26 located on the right side when viewed from the reversing roller 25, a delivery roller 27 positioned above when viewed from the relay roller 26, It has.

The relay roller 21 is a roller that winds the roll paper 2 sent from the relay roller 19 from the left side and loosens it downward.
The relay roller 22 is a roller that winds the roll paper 2 sent from the relay roller 21 from the left side and conveys it obliquely upward to the right.
The first transport roller 23 includes a first drive roller 23a driven by a motor (not shown), and a first driven roller 23b arranged to face the first drive roller 23a with the roll paper 2 interposed therebetween. have. The first transport roller 23 is a roller that pulls up the roll paper 2 slacked downward and transports it to the printing region R facing the platen 29. The first transport roller 23 is configured to temporarily stop transport during a period in which image printing is performed on a portion of the roll paper 2 on the print region R. In addition, the conveyance amount of the roll paper 2 positioned on the platen 29 is adjusted by rotating the first driven roller 23b in accordance with the rotational drive of the first drive roller 23a by the drive control of the controller 60.

  As described above, the transport unit 20 has a mechanism for transporting the portion of the roll paper 2 wound between the relay rollers 21 and 22 and the first transport roller 23 by slacking it downward. The slackness of the roll paper 2 is monitored by the controller 60 based on a detection signal from a slack detection sensor (not shown). Specifically, when a portion of the roll paper 2 slackened between the relay rollers 21 and 22 and the first transport roller 23 is detected by the slack detection sensor, a tension of an appropriate magnitude is applied to the portion. Therefore, the transport unit 20 can transport the roll paper 2 in a relaxed state. On the other hand, when the portion of the roll paper 2 that has been loosened is not detected by the slack detection sensor, an excessive amount of tension is applied to the portion, so that the roll paper 2 is transported by the transport unit 20. It is temporarily stopped and the tension is adjusted to an appropriate magnitude.

  As shown in FIG. 1, the steering unit 20a is positioned on the conveyance path in an inclined state, and rotates to roll paper 2 in the width direction position (width direction (front-back direction shown in FIG. 1)) of the roll paper 2. This is for changing the position at which is located. That is, when the roll paper 2 is conveyed along the conveyance path, the tension applied to the roll paper 2 fluctuates due to an axial deviation or an assembly error of a relay roller or the like. The position may be displaced. The steering unit 20 a is for adjusting the position in the width direction of the roll paper 2.

  The second transport roller 24 includes a second drive roller 24a driven by a motor (not shown), and a second driven roller 24b disposed so as to face the second drive roller 24a with the roll paper 2 interposed therebetween. have. The second transport roller 24 is a roller that transports the portion of the roll paper 2 on which the image is recorded by the head unit 30 in the horizontal right direction along the support surface of the platen 29 and then transports it vertically downward. Thereby, the conveyance direction of the roll paper 2 is changed. The second driven roller 24b rotates as the second drive roller 24a is driven to rotate by the drive control of the controller 60, whereby a predetermined amount given to the portion of the roll paper 2 located on the platen 29 is obtained. Tension is adjusted.

The reversing roller 25 is a roller that wraps the roll paper 2 sent from the second conveying roller 24 from the upper left side and conveys it diagonally upward to the right.
The relay roller 26 is a roller that winds the roll paper 2 sent from the reversing roller 25 from the lower left side and conveys it upward.
The delivery roller 27 winds the roll paper 2 sent from the relay roller 26 from the lower left side and sends it to the take-up unit 90.

  As described above, the roll paper 2 moves sequentially through the rollers, whereby a transport path for transporting the roll paper 2 is formed. The roll paper 2 is intermittently conveyed along the conveyance path by the conveyance unit 20 in units of areas corresponding to the printing areas R.

  The head unit 30 is for recording an image on a portion of the roll paper 2 located in the printing region R on the transport path. That is, the head unit 30 forms an image by ejecting ink from the ink ejection nozzles onto the portion of the roll paper 2 that has been fed into the printing region R (on the platen 29) on the transport path by the transport unit 20. In the present embodiment, the head unit 30 has M heads 31.

  Each head 31 has an ink discharge nozzle row in which ink discharge nozzles are arranged in the row direction (front-rear direction) on the lower surface (that is, the nozzle surface). In the present embodiment, an ink discharge nozzle row having a plurality of ink discharge nozzles # 1 to #N is provided for each color such as yellow (Y), magenta (M), cyan (C), and black (K). ing. The ink discharge nozzles # 1 to #N in each ink discharge nozzle row are linear in the crossing direction (that is, the crossing direction is the above-described row direction) crossing the roll paper 2 conveyance direction (left-right direction). It is arranged. The respective ink discharge nozzle rows are arranged in parallel with a space therebetween along the transport direction.

  Each of the ink discharge nozzles # 1 to #N is provided with a piezo element (not shown) as a drive element for discharging ink droplets. When a voltage having a predetermined time width is applied between the electrodes provided at both ends of the piezoelectric element, the piezoelectric element expands according to the voltage application time and deforms the side wall of the ink flow path. As a result, the volume of the ink flow path contracts according to the expansion and contraction of the piezo element, and the ink corresponding to the contraction is ejected from the ink ejection nozzles # 1 to #N of the respective colors as ink droplets.

  Then, M such heads 31 are arranged in the intersecting direction (the row direction), thereby forming the head unit 30. Therefore, the head unit 30 has M × N ink ejection nozzles for each color.

  The ink supply unit 35 is for supplying ink to the head unit 30 when the amount of ink in the head unit 30 decreases due to ink ejection by the head 31.

  The ink supply unit 35 is provided for each ink color. That is, a yellow ink supply unit for supplying yellow ink, a magenta ink supply unit for supplying magenta ink, a cyan ink supply unit for supplying cyan ink, and a black ink supply For this purpose, a black ink supply unit or the like is provided.

  The ink supply unit 35 includes an ink cartridge, a large number of tubes serving as ink flow paths (passages), a large number of valves (valves) for opening and closing the tubes, and the like. In the present embodiment, a circulation path passing through the head 31 is formed in the ink flow path, and the ink supply unit 35 has a circulation pump (described later) for circulating the ink along the circulation flow path. doing. The ink flow path and the configuration of the flow path (circulation pump, etc.) will be described later.

  The carriage unit 40 is for moving the head unit 30 (head 31). The carriage unit 40 is supported by a carriage guide rail 41 (indicated by a two-dot chain line in FIG. 1) extending in the transport direction (left-right direction) and reciprocally movable along the carriage guide rail 41 in the transport direction (left-right direction). A carriage 42 and a motor (not shown).

  The carriage 42 is provided with a head unit 30 (head 31). The carriage 42 is configured to move in the transport direction (left-right direction) together with the head unit 30 (head 31) by driving a motor (not shown). When the head unit 30 (head 31) is cleaned after image printing, the carriage 42 is integrated with the head unit 30 (head 31) along the carriage guide rail 41 on the upstream side (from the platen 29). It moves to the upstream side in the transport direction as viewed, and stops at a home position (hereinafter referred to as HP) for cleaning (see FIG. 1).

  In addition, a flushing unit (not shown) is provided between the HP and the platen 29 in the transport direction (left and right direction), and the head 31 (carriage 42) moves in the transport direction (left and right direction) to flush the unit. The head 31 executes a flushing operation for performing flushing by discharging ink from each ink discharge nozzle belonging to the ink discharge nozzle row.

  The platen 29 supports the part of the roll paper 2 located in the printing region R on the conveyance path and heats the part. As shown in FIG. 1, the platen 29 is provided in correspondence with the printing region R on the conveyance path, and in a region along the conveyance path between the first conveyance roller 23 and the second conveyance roller 24. Has been placed. Further, the platen 29 can heat the portion of the roll paper 2 by receiving the supply of heat generated by the heater unit 70.

  The heater unit 70 is for heating the roll paper 2 and has a heater (not shown). This heater has a nichrome wire, and the nichrome wire is arranged inside the platen 29 so as to be at a fixed distance from the support surface of the platen 29. For this reason, when the heater is energized, the nichrome wire itself generates heat, and heat can be conducted to the portion of the roll paper 2 located on the support surface of the platen 29. This heater is configured, for example, by incorporating a nichrome wire in the entire area of the platen 29 and can conduct heat uniformly to the portion of the roll paper 2 on the platen 29. In this embodiment, the part of the roll paper 2 is uniformly heated so that the temperature of the part of the roll paper 2 on the platen is 45 ° C. Thereby, drying of the ink landed on the roll paper 2 can be promoted.

  The blower unit 80 is for sending wind to the roll paper 2 on the platen 29 and the like. The blower unit 80 includes a fan 81 and a motor (not shown) that rotates the fan 81. The fan 81 rotates to send air to the roll paper 2 on the platen 29 and promote drying of the ink landed on the roll paper 2. As shown in FIG. 1, a plurality of fans 81 are provided on an openable / closable cover (not shown) provided in the main body above the carriage 42. Each fan 81 is positioned above the platen 29 when the cover is closed, and faces the support surface of the platen 29 (the roll paper 2 on the platen 29).

  The winding unit 90 is for winding the roll paper 2 (image-printed roll paper) sent by the transport unit 20. This take-up unit 90 is fed from the relay roller 91 that is rotatably supported by the relay roller 91 for winding the roll paper 2 sent from the feed roller 27 from the upper left side and conveying it to the lower right side. A roll paper take-up drive shaft 92 for taking up the roll paper 2.

  The controller 60 is a control unit for controlling the printer 1. As shown in FIG. 2, the controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 is for transmitting and receiving data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like. The CPU 62 controls each unit by a unit control circuit 64 according to a program stored in the memory 63.

  The detector group 50 is for monitoring the situation in the printer 1. For example, the above-described slack detection sensor, a rotary encoder attached to the conveyance roller and used for controlling the conveyance of the roll paper 2, and the like A paper detection sensor for detecting the presence or absence of the roll paper 2 to be detected, a linear encoder for detecting the position of the carriage 42 (or head 31) in the transport direction (left-right direction), and a paper edge (edge) in the width direction of the roll paper 2 ) A paper edge position detection sensor for detecting the position is included.

  Further, the printer 1 of the present embodiment includes a temperature sensor 52 (described later) that outputs a detection signal corresponding to the ink temperature of the head 31 as the detector group 50.

≪About ink circulation≫
<Comparative example>
FIG. 3 is a diagram illustrating a configuration of an ink supply unit 35 ′ of the comparative example. As shown in FIG. 3, the ink supply unit 35 ′ of this comparative example has an ink circulation type structure that circulates ink (from a circulation path R described later) supplied from a removable ink cartridge 351. In the figure, a portion corresponding to one color (one nozzle row) of the plurality of nozzle rows of the head 31 is schematically shown.

  The comparative ink supply unit 35 ′ has an ink cartridge 351, an ink supply valve 352, a circulation pump 353, and a heater 72.

  As described above, the head 31 is a head that ejects ink using a piezo element, and is provided with a number of nozzles that eject ink, and ejects ink from each nozzle onto the roll paper 2. Further, as shown in FIG. 3, the head 31 includes a temperature sensor 52 for directly or indirectly measuring the temperature of the ink. The temperature sensor 52 generates a detection signal corresponding to the ink temperature and outputs it to the controller 60. Note that the temperature sensor 52 may be installed not in the head 31 but in the vicinity of the outside of the head 31, for example, as long as a certain degree of accuracy can be expected.

  In the ink supply unit 35 of the comparative example, as indicated by an arrow in FIG. 3, a circulation path R of the head 31 → the circulation pump 353 → the heater 72 → the head 31 is formed. Further, ink is supplied from the ink cartridge 351 to the circulation path R through the ink supply path Q. An ink supply valve 352 for opening and closing the flow path is formed in the ink supply path Q. Ink supply from the ink cartridge 351 to the circulation path R is controlled by opening and closing the ink supply valve 352. The ink flow paths in the ink supply path Q and the circulation path R are formed by pipes made of resin or metal, or tubes made of resin or the like.

  The heater 72 is provided on the upstream side of the ink flow path from the head 31 in the ink circulation path R, and heats the ink supplied to the head 31. In order to quickly and accurately control the temperature of the ink supplied to the head 31, the heater 72 is disposed near (immediately before) the head 31 and heats the ink at a position close to the head 31. It is like that.

  The circulation pump 353 is provided on the downstream side of the ink flow path with respect to the head 31 in the circulation path R, and circulates the ink in the circulation path R. In this comparative example, the circulation pump 353 is driven by a DC motor (not shown). The rotational speed of the DC motor is determined according to the input current. That is, the operation of the circulation pump 353 can be controlled by the amount of current supplied to the DC motor, and the ink flow rate can be controlled thereby. However, in the DC motor, heat is generated (heat generation) according to the amount of current supplied.

  With the above configuration, the controller 60 adjusts the temperature setting of the heater 72 based on the detection signal output from the temperature sensor 52. This controls the temperature of the ink. Furthermore, the controller 60 adjusts the rotational speed of the DC motor of the circulation pump 353 and controls the flow rate of ink flowing in the circulation path R.

  In this comparative example, a circulation pump 353 and a heater 72 are provided in order to control the ink flow rate and the ink temperature. Thus, in the comparative example, since the circulation pump 353 that circulates the ink and the heater 72 that heats the ink are separately provided, there is a problem that costs (for example, manufacturing cost and power consumption) are increased. Therefore, in this embodiment, a stepping motor (corresponding to a pulse motor) that is driven according to a pulse signal is used as a motor that drives the circulation pump 353, thereby simplifying the configuration and reducing the cost.

<This embodiment>
FIG. 4 is a diagram showing the configuration of the ink supply unit 35 of the present embodiment. In FIG. 4, the same components as those in the comparative example (FIG. 3) are denoted by the same reference numerals, and description thereof is omitted. FIG. 5 is a diagram showing the configuration in the vicinity of the circulation pump 353 in FIG. 4 in more detail.

  In the comparative example (FIG. 3), the heater 72 is provided on the circulation path R, but in this embodiment, no heater is provided as shown in FIG. Further, in the printer 1 of this embodiment, as shown in FIG. 5, a stepping motor 354 (corresponding to a pulse motor) that drives the circulation pump 353 as the ink supply unit 35, and the periphery of the stepping motor 354 and the circulation pump 353. The cover member 355 is covered. In the present embodiment, the ink is circulated in the circulation path S of the head 31 → the circulation pump 353 → the circulation pump 353 (stepping motor 354) → the head 31.

  The stepping motor 354 is a motor for driving the circulation pump 353. Further, as shown in FIG. 5, an ink flow path (resin tube or the like) from the output side of the circulation pump 353 is wound around the stepping motor 354. Then, the ink is supplied to the head 31 at the subsequent stage through the flow path wound around the stepping motor 354.

  The cover member 355 is a heat insulating material having a heat insulating property formed by, for example, resin, and is formed so as to cover the stepping motor 354, the circulation pump 353, and the circulation path S in the vicinity thereof. In the present embodiment, the cover member 355 covers the periphery of the stepping motor 354 (including the surrounding ink flow path) and the circulation pump 353, but the cover member 355 is at least the periphery of the stepping motor 354 (in the drawing). It is only necessary to cover the portion on the left side of the dotted line. In this way, the heat generated by the stepping motor 354 can be efficiently used for controlling the ink temperature.

<Stepping motor>
The stepping motor 354 is a kind of brushless motor, and is a motor that rotates by a step unit determined by giving a pulse signal. The rotation angle and rotation speed of the stepping motor 354 are determined by the number and period of pulse signals.
6A is a diagram illustrating an example of the configuration of the stepping motor 354, and FIG. 6B is a connection diagram of FIG. 6A. The stepping motor 354 of this embodiment is a unipolar drive type two-phase excitation motor. The stepping motor 354 includes a rotor (rotor) 361, coils 362 and 363, and a stator (stator) 364.

The rotor 361 is a rotating part of the stepping motor 354 and is made of, for example, a permanent magnet.
The stator 364 is formed in a circular shape so as to surround the rotor 361, and four protrusions are formed on the inside thereof.

  Current supply terminals DC are formed at intermediate points of the coils 362 and 363, respectively, an X coil and an X ′ coil are formed on the coil 362, and a Y coil and a Y ′ coil are formed on the coil 363, respectively. In the stator 364, the four protrusions are in positions facing each other vertically and horizontally, and the X coil and the X ′ coil, and the Y coil and the Y ′ coil are formed on the facing protrusions, respectively. Then, the coils (X coil, X ′ coil, Y coil, Y ′ coil) that flow current from the terminal DC are switched according to the pulse signal. In this way, current is sequentially supplied to each coil to rotate the rotor 361.

  FIG. 7 is a diagram for explaining an example of an excitation method (two-phase excitation) of the stepping motor 354. In the figure, the horizontal axis represents time, and the vertical axis represents a pulse (current flowing through each coil). In two-phase excitation, excitation is performed while shifting from the next phase by one pulse at a time.

  For example, when the rotor 361 is rotated in the forward rotation direction, current is passed in the order of X → Y → X ′ → Y ′ as shown in the left diagram of FIG. Specifically, X becomes high level at time t1, and Y becomes high level at time t2. At time t3, X becomes low level and X ′ becomes high level. At time t4, Y becomes low level and Y ′ becomes high level. Hereinafter, similarly, control is performed so that a current flows through each coil. Thereby, the rotor 361 rotates in the forward rotation direction (for example, the clockwise direction in FIG. 6A).

  On the other hand, when the rotor 361 is rotated in the reverse direction, a current is supplied in the order of Y ′ → X ′ → Y → X as shown in the right side of FIG. Specifically, Y ′ becomes high level at time t1, and X ′ becomes high level at time t2. At time t3, Y ′ becomes low level and Y becomes high level. At time t4, X becomes low level and X becomes high level. Hereinafter, similarly, control is performed so that a current flows through each coil. Thereby, the rotor 361 rotates in the reverse rotation direction (for example, the counterclockwise direction in FIG. 6A).

  Thus, the direction of rotation changes according to the pulse signal. The rotation speed (rotation speed) of the stepping motor 354 is determined according to the pulse switching timing in the pulse signal. For example, even if the amount of current supplied to the stepping motor 354 is increased, only the magnitude of the pulse changes and the rotation speed does not change. However, the amount of heat generated by the stepping motor increases as the amount of current increases. On the other hand, when the pulse signal waveform (pulse switching timing) is changed, the rotation speed of the stepping motor 354 changes, but the amount of heat generated by the stepping motor 354 does not change.

  In the present embodiment, since the ink is circulated through the circulation path S, the rotation direction is the same (one direction), and only the rotation speed is controlled.

  Thus, by independently controlling the pulse signal to the stepping motor 354 and the amount of current, it is possible to control the rotation speed (rotation speed) and the heat generation amount of the stepping motor 354, respectively.

  In the case of the present embodiment, as shown in FIG. 5, the circulation path S (ink flow path) is wound around the stepping motor 354, so that the amount of current to the stepping motor 354 is controlled. Ink temperature can be adjusted efficiently. Therefore, the temperature of the ink can be adjusted without using the heater 72 as in the comparative example.

  Further, the rotation speed of the stepping motor 354 can be adjusted by changing the pulse signal (pulse switching timing). That is, the flow rate of ink flowing in the circulation path S can be adjusted.

≪Ink temperature adjustment≫
The ink temperature adjustment process in the circulation path S will be described below.

<When heated>
When the controller 60 determines that the detection signal received from the temperature sensor 52 is lower than the set temperature, the controller 60 performs a process of heating the ink temperature. In this case, the amount of current is increased while the switching timing of the pulse signal to the stepping motor 354 (the timing of waveform change in FIG. 7) remains unchanged. That is, the magnitude (height) of the pulse is changed. As a result, the number of rotations of the stepping motor 354 does not increase, and the amount of heat generated by the stepping motor 354 increases. In other words, the ink flow rate in the circulation path S by the circulation pump 353 does not change, and the temperature of the ink supplied to the head 31 rises.

<When the temperature drops>
On the other hand, when the controller 60 determines that the detection signal received from the temperature sensor 52 is higher than the set temperature, the controller 60 performs a process of lowering the temperature of the ink. In this case, the amount of current to the stepping motor 354 is kept as it is, and the pulse signal switching timing is changed earlier. As a result, the amount of heat generated by the stepping motor 354 does not increase, and the rotational speed of the stepping motor 354 increases. In other words, the ink flow rate in the circulation path S by the circulation pump 353 increases. By increasing the flow rate of the ink flowing in the circulation path S in this way, the ink can be easily cooled, and the temperature of the ink can be lowered. At this time, the amount of heat generated by the stepping motor 354 may be reduced by reducing the amount of current. In this case, the temperature can be lowered more quickly.

  As described above, the printer 1 according to this embodiment includes the head 31 that ejects ink, the circulation pump 353 that circulates ink in the circulation path S that passes through the head 31, and the stepping motor 354 that drives the circulation pump 353. And a temperature sensor 52 that outputs a detection signal corresponding to the temperature of the ink. The controller 60 of the printer 1 independently controls the amount of current supplied to the stepping motor 354 and the pulse signal based on the detection signal of the temperature sensor 52. As a result, the rotation speed and the heat generation amount of the stepping motor 354 can be controlled. Therefore, it is not necessary to provide the heater 72 as in the comparative example, so that the configuration can be simplified and the cost can be reduced.

=== Other Embodiments ===
The above-described embodiment is mainly described with respect to the liquid ejection device, but also includes disclosure of a liquid circulation method and the like. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, the printer has been described as an example of the liquid ejection apparatus, but the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied.
In the above-described embodiment, the printer is a lateral scan type printer, but is not limited thereto. For example, while moving the head unit in the moving direction intersecting the nozzle row direction, a dot forming operation for forming a dot row along the moving direction and a transport operation (moving operation) for transporting the medium in the transport direction that is the nozzle row direction ) May be alternately repeated to form an image (so-called serial printer). Also, for example, a plurality of heads are arranged so as to face the peripheral surface of a cylindrical transport drum, and an image is formed by ejecting ink from each head to the medium while transporting the medium along the peripheral surface of the transport drum. It may be a printer.

<About media>
In the above-described embodiment, the roll paper 2 has been described as an example of the medium. However, the present invention is not limited to this, and may be cut paper, film, or cloth, for example.

<Discharge method>
In the above-described embodiment, ink is ejected using a piezoelectric element (piezo element). However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<About the head>
In the embodiment described above, the head unit 30 has a plurality (M) of heads 31, but the present invention is not limited to this. For example, the head unit 30 may be composed of one head 31.

<About ink>
In the above-described embodiment, since the embodiment is a printer, ink is used as the liquid. However, the liquid ejected from the nozzle is not limited to such ink. For example, liquids (including water) including metal materials, organic materials (especially polymer materials), magnetic materials, conductive materials, wiring materials, film-forming materials, electronic inks, processing liquids, gene solutions, etc. are ejected from nozzles. May be.
Further, an ultraviolet curable ink (hereinafter also referred to as UV ink) that is cured by irradiation with ultraviolet rays (UV: a type of light) may be used as the ink. The UV ink corresponds to a photocurable liquid. A printer that uses UV ink is provided with a light source that irradiates UV, and after ejecting UV ink from the head onto the medium, UV ink (dots) that landed on the medium is irradiated with UV from the light source to form dots. Harden. Thus, printing can be suitably performed even on a medium that hardly absorbs ink.
The UV ink has a characteristic that the viscosity is likely to be higher than the normal ink (it tends to increase the viscosity), but in this embodiment, the temperature is controlled without using a heater (the ink is heated). In addition, the ink flow rate can be controlled independently of the temperature. Therefore, this embodiment is more effective when UV ink is used.

<Stepping motor>
In the above-described embodiment, the unipolar stepping motor 354 is used as the pulse motor, but the present invention is not limited to this. For example, a bipolar stepping motor may be used. The stepping motor 354 of the present embodiment is a two-phase excitation type, but is not limited to this. For example, a one-phase excitation type or a 1-2 phase excitation type may be used.

<About ink flow path>
In the above-described embodiment, the circulation path S is arranged so as to wind around the stepping motor 354, but is not limited thereto. For example, the circulation path S may be in contact with only one point on the outer peripheral surface of the stepping motor 354. However, if the circulation path S is wound around the stepping motor 354 as in the present embodiment, the heat generated by the stepping motor 354 can be easily transferred to the ink (the temperature control of the ink is efficient). Can be done).

DESCRIPTION OF SYMBOLS 1 Printer 2 Roll paper 10 Feeding unit 18 Roll paper winding shaft 19 Relay roller 20 Transport unit 20a Steering unit 21 Relay roller 22 Relay roller 23 First transport roller 23a First drive roller 23b First driven roller 24 Second transport roller 24a First Two-drive roller 24b Second driven roller 25 Reverse roller 26 Relay roller 27 Delivery roller 29 Platen 30 Head unit 31 Head 35 Ink supply unit 40 Carriage unit 41 Guide rail 42 Carriage 50 Detector group 52 Temperature sensor 60 Controller 61 Interface unit 62 CPU
63 Memory 64 Unit control circuit 70 Heater unit 72 Heater 80 Blower unit 81 Fan 90 Winding unit 91 Relay roller 92 Roll paper winding drive shaft 110 Computer 351 Ink cartridge 352 Ink supply valve 353 Circulating pump 354 Stepping motor 355 Cover member 361 Rotor 362 Coil 363 Coil 364 Stator

Claims (7)

A head for discharging liquid;
A circulation pump for circulating the liquid in a circulation path passing through the head;
A pulse motor for driving the circulation pump;
A temperature sensor that outputs a detection signal corresponding to the temperature of the liquid;
Based on the detection signal of the temperature sensor, a control unit that independently controls the amount of current supplied to the pulse motor and the pulse signal;
A liquid ejection apparatus comprising: The liquid ejection device according to claim 1,
The controller, based on the detection signal, increases the heat generation amount of the pulse motor by changing the amount of current without increasing the number of rotations of the pulse motor when heating the liquid. Liquid ejecting device. The liquid ejection device according to claim 1 or 2, wherein
The controller may change the pulse signal to increase the rotation speed of the pulse motor without increasing the heat generation amount of the pulse motor when the temperature of the liquid is lowered based on the detection signal. Liquid ejection device. The liquid ejection device according to any one of claims 1 to 3,
The liquid discharge apparatus according to claim 1, wherein the circulation path is arranged so as to wind around the pulse motor. A liquid ejection apparatus according to any one of claims 1 to 4,
A liquid ejecting apparatus comprising: a cover member that covers the circulation path disposed in the vicinity of the pulse motor and the pulse motor. A liquid ejection apparatus according to any one of claims 1 to 5,
The liquid is a photocurable liquid that is cured by light irradiation,
A liquid ejecting apparatus comprising: a light source that irradiates the liquid ejected from the head and landed on a medium. A liquid circulation method by a liquid ejection device having a head for ejecting liquid, a circulation pump provided in a circulation path passing through the head, and a pulse motor for driving the circulation pump,
Generating a detection signal corresponding to the temperature of the liquid;
A step of independently controlling a pulse signal and an amount of current based on the detection signal and supplying the pulse signal to the pulse motor;
Driving the circulation pump by the pulse motor to circulate the liquid in the circulation path;
A liquid circulation method characterized by comprising:

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