JP2014226915A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of efficiently discharging air bubbles naturally generated by a temperature change of liquid in a head while reducing liquid consumption.SOLUTION: A piezoelectric actuator of an individual liquid chamber 106 communicated with the downstream side of a common liquid chamber is not driven, a piezoelectric actuator of the individual liquid chamber 106 communicated with the upstream side of the common liquid chamber is subjected to extension driving and, thereby, recovery movement is performed while fluid resistance of the individual liquid chamber 106 communicated with the downstream side of the common liquid chamber is made relatively smaller than a fluid resistance of the individual liquid chamber 106 communicated with the upstream side of the common liquid chamber.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a recording head for discharging droplets.

  As an image forming apparatus such as a printer, a facsimile, a copying apparatus, a plotter, and a complex machine of these, for example, a liquid discharge recording type image forming apparatus using a recording head composed of a liquid discharge head (droplet discharge head) for discharging droplets Inkjet recording apparatuses are known.

  In such an image forming apparatus, when bubbles are mixed in the recording head, ejection defects occur due to the bubbles.

  2. Description of the Related Art Conventionally, a device that performs a preliminary ejection operation for ejecting droplets that do not contribute to image formation at intervals determined by the temperature inside the apparatus detected by a temperature detection unit is known (Patent Document 1).

JP 2002-178533 A

  By the way, if the environment of the apparatus main body is an environment in which the temperature change is relatively large and the frequency thereof is high, the amount of gas exceeding the amount of saturated gas that can be dissolved in the liquid of the recording head is generated. This gas clogs the flow path in the recording head and causes nozzle missing (cannot be ejected), or becomes a resistance in the liquid chamber and causes insufficient supply (decrease in droplet characteristics).

  Therefore, it is required to efficiently discharge bubbles that are naturally generated in the recording head due to a temperature change.

  The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to efficiently discharge bubbles naturally generated in the head while reducing wasteful liquid consumption.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A plurality of first flow paths that communicate with a plurality of nozzles that discharge droplets; a second flow path that communicates with the plurality of first flow paths; and a fluid resistance variable means that changes the fluid resistance of the first flow path; A recording head having
Temperature detecting means for detecting the temperature in the apparatus body;
Recovery control means for controlling the recovery operation of the recording head based on the detection result of the temperature detection means,
The recovery control means includes
Stores the detected temperature when the previous recovery operation was performed, and performs the recovery operation based on the temperature change with respect to the stored detection temperature,
When performing the recovery operation, the fluid resistance variable means is driven to set the fluid resistance of the first flow path leading to the upstream side of the second flow path in the liquid flow direction of the second flow path, The fluid resistance of the first flow path leading to the downstream side of the second flow path is set to be larger.

  According to the present invention, bubbles that are naturally generated in the head can be efficiently discharged while reducing wasteful liquid consumption.

FIG. 3 is a side explanatory view illustrating a mechanism unit of an example of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. FIG. 2 is a schematic explanatory diagram for explaining an outline of an ink supply / discharge system in the apparatus. FIG. 5 is a cross-sectional explanatory diagram along a direction orthogonal to a nozzle arrangement direction of an example of a liquid discharge head constituting the recording head. FIG. 5 is an explanatory cross-sectional view of a main part in the nozzle arrangement direction along the line XX in FIG. 4. It is block explanatory drawing with which the outline | summary of the control part of the apparatus is provided. It is explanatory drawing which shows an example of the relationship between the temperature of a liquid, and the amount of saturated dissolved gas. FIG. 5 is a schematic explanatory diagram for explaining a state where bubbles are generated in the recording head. It is a typical perspective explanatory view of a channel from a supply port to a nozzle in the same liquid chamber. FIG. 5 is a schematic perspective explanatory view for explaining a discharge process of bubbles generated in a common liquid chamber. It is an equivalent circuit diagram with which it uses for description of control of fluid resistance. It is explanatory drawing with which it demonstrates to the case where the piezoelectric actuator which is a fluid resistance control means is driven, and fluid resistance is enlarged. It is explanatory drawing with which it uses for description similarly when making fluid resistance small. It is explanatory drawing which shows an example of time passage and temperature change with which it uses for description of the start of the bubble discharge | emission recovery operation | movement in 1st Embodiment of this invention. It is explanatory drawing which shows an example of time passage and temperature change with which it uses for description of the start of recovery operation | movement of bubble discharge | emission in 2nd Embodiment of this invention. It is explanatory drawing which shows an example of time passage and temperature change with which it uses for description of the start of the bubble discharge | emission recovery operation | movement in 3rd Embodiment of this invention. It is sectional explanatory drawing with which it uses for description of recovery operation | movement in 4th Embodiment of this invention. It is sectional explanatory drawing with which it uses for description of recovery operation | movement in 5th Embodiment of this invention. It is sectional explanatory drawing with which it uses for description of recovery operation | movement in 6th Embodiment of this invention. It is explanatory drawing explaining the example from which the relationship between the common liquid chamber shape and the fluid resistance at the time of recovery operation differs. It is explanatory drawing explaining the example from which the relationship between the common liquid chamber shape and the fluid resistance at the time of recovery operation differs.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining a mechanism part of the image forming apparatus, and FIG. 2 is a plan view for explaining a main part of the mechanism part.

  This image forming apparatus is a serial type ink jet recording apparatus. The carriage 33 is slidably held in the main scanning direction by main and sub guide rods 31 and 32 which are guide members laid over the left and right side plates 21A and 21B of the apparatus main body 1. The main scanning motor moves and scans in the carriage main scanning direction via the timing belt.

  The carriage 33 is provided with recording heads 34a and 34b composed of liquid ejection heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (K). "Recording head 34"). The recording head 34 is mounted with a nozzle row composed of a plurality of nozzles arranged in the sub-scanning direction orthogonal to the main scanning direction and the droplet discharge direction facing downward.

  Each recording head 34 has two nozzle rows. One nozzle row of the recording head 34a discharges black (K) droplets, and the other nozzle row discharges cyan (C) droplets. One nozzle row of the recording head 34b discharges magenta (M) droplets, and the other nozzle row discharges yellow (Y) droplets.

  The carriage 33 is mounted with head tanks 35a and 35b (referred to as “head tank 35” when not distinguished) that temporarily store ink to be supplied corresponding to the nozzle rows of the recording head 34. The head tank 35 is supplementarily supplied with ink of each color from the ink cartridges 10y, 10m, 10c, and 10k via the supply tube 36 of each color by the supply pump unit 24. The ink cartridge 10 is detachably attached to the cartridge loading unit 4.

  On the other hand, as a paper feeding unit for feeding the papers 42 stacked on the paper stacking unit (pressure plate) 41 of the paper feeding tray 2, a half-moon roller (feeding) that separates and feeds the papers 42 one by one from the paper stacking unit 41. And a separation pad 44 facing the paper feed roller 43. The separation pad 44 is urged toward the paper feed roller 43 side.

  In order to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34, a guide member 45 for guiding the paper 42, a counter roller 46, a transport guide member 47, and a tip pressure roller. And a pressing member 48 having 49. A transport belt 51 is provided as a transport unit for electrostatically attracting the fed paper 42 and transporting the paper 42 at a position facing the recording head 34.

  The transport belt 51 is an endless belt, and is configured to wrap around the transport roller 52 and the tension roller 53 and circulate in the belt transport direction (sub-scanning direction).

  Further, a charging roller 56 that is a charging unit for charging the surface of the transport belt 51 is provided. The charging roller 56 is disposed so as to come into contact with the surface layer of the transport belt 51 and to rotate following the rotation of the transport belt 51. The transport belt 51 rotates in the belt transport direction when the transport roller 52 is rotationally driven through timing by a sub-scanning motor described later.

  Further, as a paper discharge unit for discharging the paper 42 recorded by the recording head 34, a separation claw 61 for separating the paper 42 from the conveying belt 51, a paper discharge roller 62, and a spur 63 that is a paper discharge roller. And a paper discharge tray 3 below the paper discharge roller 62.

  A duplex unit 71 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 71 takes in the paper 42 returned by the reverse rotation of the conveyance belt 51, reverses it, and feeds it again between the counter roller 46 and the conveyance belt 51. The upper surface of the duplex unit 71 is a manual feed tray 72.

  Further, a maintenance / recovery mechanism 81 for maintaining and recovering the nozzle state of the recording head 34 is disposed in the non-printing area on one side of the carriage 33 in the scanning direction.

  The maintenance and recovery mechanism 81 includes caps 82a and 82b for capping each nozzle surface of the recording head 34 (referred to as “cap 82” when not distinguished), and a wiper member (wiper blade) for wiping the nozzle surface. 83). The maintenance / recovery mechanism 81 includes an idle discharge receiver 84 that receives droplets when performing idle discharge for discharging droplets that do not contribute to recording in order to discharge the thickened recording liquid, and a carriage that locks the carriage 33. A lock 87 and the like.

  A waste liquid tank 100 for storing waste liquid generated by the maintenance recovery operation is mounted on the lower side of the head recovery mechanism 81 in a replaceable manner with respect to the apparatus main body.

  Further, in the non-printing area on the other side of the carriage 33 in the scanning direction, there is an empty space for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. A discharge receiver 88 is disposed. The idle discharge receiver 88 includes an opening 89 along the nozzle row direction of the recording head 34.

  In the image forming apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feed tray 2, and the sheets 42 fed substantially vertically upward are guided by the guide member 45, It is sandwiched between the counter roller 46 and conveyed. Then, the leading edge of the paper 42 is guided by the conveying guide 37 and pressed against the conveying belt 51 by the leading pressure roller 49, and the conveying direction is changed by approximately 90 °.

  When the paper 42 is fed onto the charged transport belt 51, the paper 42 is attracted to the transport belt 51, and the paper 42 is transported in the sub-scanning direction by the circular movement of the transport belt 51.

  Therefore, by driving the recording head 34 according to the image signal while moving the carriage 33, ink droplets are ejected onto the stopped paper 42 to record one line, and after the paper 42 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 42 has reached the recording area, the recording operation is finished and the paper 42 is discharged onto the paper discharge tray 3.

  Further, when performing the maintenance recovery of the nozzles of the recording head 34, the carriage 33 is moved to a position facing the maintenance recovery mechanism 81 which is the home position. Then, by performing a maintenance recovery operation such as nozzle suction for performing capping by the cap 82 to perform suction from the nozzles, and idle discharge for discharging liquid droplets that do not contribute to image formation, image formation by stable liquid droplet ejection is performed. be able to.

  Next, an outline of an ink supply / discharge system in the image forming apparatus will be described with reference to FIG.

  First, ink is supplied from the ink cartridge 10, which is a liquid cartridge, to the head tank 35 by the liquid feed pump 241 through the supply tube 36, and the ink is supplied from the head tank 35 to the recording head 34.

  When the recovery operation of the recording head 34 is performed, the nozzle surface of the recording head 34 is capped by the suction cap 82a of the maintenance recovery mechanism 81. Thereafter, the suction pump 812 of the maintenance and recovery mechanism 81 is driven to forcibly suck and discharge ink from the nozzles via the suction tube 811 (recovery operation by nozzle suction). The sucked waste ink is discharged to the waste liquid tank 100.

  Next, an example of the liquid discharge head constituting the recording head 34 will be described with reference to FIGS. 4 is a cross-sectional explanatory view taken along a direction orthogonal to the nozzle arrangement direction of the head, and FIG. 5 is a principal cross-sectional explanatory view along the XX line of FIG.

  The liquid discharge head includes a flow path plate 101, a vibration plate member 102 bonded to the lower surface of the flow path plate 101, and a nozzle plate 103 bonded to the upper surface of the flow path plate 101.

  As a result, the individual liquid chamber 106 through which the nozzle 104 that discharges droplets (ink droplets) communicates through the passage 105, the fluid resistance portion (liquid supply passage) 107 that communicates with the individual liquid chamber 106, and the liquid introduction portion 108 are formed. Yes. Then, ink is supplied from the common liquid chamber 110 serving as the second flow path to the individual liquid chamber 106 through the supply port 109.

  For example, the flow path plate 101 is formed by anisotropically etching a single crystal silicon substrate having a crystal plane orientation (110) using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the passage 105, the individual liquid chamber 106, The recessed part and hole part which become are formed. Note that the present invention is not limited to a single crystal silicon substrate, and other stainless steel substrates or photosensitive resins can also be used. For example, it can be formed by etching a SUS substrate with an acidic etchant or machining such as punching (press). A space between the individual liquid chambers 106 of the flow path plate 101 is a liquid chamber interval wall 106a.

  The diaphragm member 102 is formed of the first layer 102A and the second layer 102B, the first layer 102A forms a thin portion, and the first layer 102A and the second layer 102B form a thick portion. . The diaphragm member 102 has each vibration region (diaphragm portion) 102a formed by the first layer 102A that forms the wall surface corresponding to each individual liquid chamber 106. Further, in this vibration region 102a, an island-shaped convex portion 102b formed by the thick portions of the first layer 102A and the second layer 102B is provided on the outer surface (the surface opposite to the individual liquid chamber 106). .

  A piezoelectric actuator 111 including an electromechanical conversion element is disposed as a driving unit (actuator unit, pressure generating unit) which is joined to the island-shaped convex portion 102b of the diaphragm member 102 and deforms (displaces) the vibration region 102a. doing.

  This piezoelectric actuator 111 has two laminated piezoelectric members 112 bonded on a base member 113 with an adhesive. In the piezoelectric member 112, grooves are processed by half-cut dicing, and a required number of columnar piezoelectric elements (piezoelectric columns) 112A and 112B are formed in a comb shape at a predetermined interval with respect to one piezoelectric member 112.

  The piezoelectric columns 112A and 112B of the piezoelectric member 112 are the same, but the driving piezoelectric column to be driven by applying a driving waveform is a piezoelectric column (driving column) 112A, and is used as a simple column without applying a driving waveform. The driving piezoelectric column is distinguished as a piezoelectric column (non-driving column) 112B.

  Then, the upper end surface (joint surface) of the drive column 112 </ b> A is joined to the island-shaped convex portion 102 b of the diaphragm member 102.

  Here, the piezoelectric member 112 is formed by alternately laminating the piezoelectric material layers 121 and the internal electrodes 122A and 122B. The internal electrodes 122A and 122B are drawn out to the end surfaces, respectively, and end electrodes (external electrodes) formed on the end surfaces are formed. ) 123 and 124. A displacement in the stacking direction is generated by applying a voltage between the end face electrodes (external electrodes) 123 and 124. Here, the external electrode 123 is used as an individual external electrode (individual electrode), and the external electrode 124 is used as a common external electrode (common electrode).

  Further, the piezoelectric member 112 is connected to an FPC 115 as a wiring member that can bend to give a driving signal to the driving column 112A. The FPC 115 is mounted with a driver IC (drive circuit) that gives a drive waveform to the drive column 112A (not shown).

  The nozzle plate 103 is formed from a nickel (Ni) metal plate, and is formed by an electroforming method (electroforming). In addition, for example, a metal such as stainless steel, a resin such as a polyimide resin film, silicon, or a combination thereof can be used. In this nozzle plate 103, nozzles 104 having a diameter of 10 to 35 μm are formed corresponding to the individual liquid chambers 106 and bonded to the flow path plate 101 with an adhesive. A liquid repellent layer is provided on the droplet discharge side surface (surface in the discharge direction: discharge surface or the surface opposite to the individual liquid chamber 106 side) of the nozzle plate 103.

  Further, a frame member 117 formed by injection molding with epoxy resin or polyphenylene sulfite is joined to the outer peripheral side of the piezoelectric actuator 111 composed of the piezoelectric member 112, the base member 113 as a base member, and the FPC 115. ing. In the frame member 117, the common liquid chamber 110 described above is formed, and a supply port 119 for supplying ink from the outside to the common liquid chamber 110 is further formed.

  In the liquid discharge head configured as described above, for example, the drive column 112A contracts by lowering the voltage applied to the drive column 112A from the reference potential Ve, the diaphragm member 102 is displaced, and the volume of the individual liquid chamber 106 expands. . As a result, ink flows into the individual liquid chamber 106.

  Thereafter, the voltage applied to the drive column 112A is increased to extend the drive column 112A in the stacking direction, and the diaphragm member 102 is deformed in the nozzle 104 direction to contract the volume of the individual liquid chamber 106. As a result, the ink in the individual liquid chamber 106 is pressurized, and ink droplets are ejected (ejected) from the nozzle 104.

  Then, by returning the voltage applied to the driving column 112A to the reference potential Ve, the diaphragm member 102 is restored to the initial position, and the individual liquid chamber 106 expands to generate a negative pressure. The individual liquid chamber 106 is filled with ink. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on the direction of the drive waveform.

  In such a recording head 34 (liquid ejection head), the vibration region 102a is pushed into the individual liquid chamber 106 side by extending and displacing the driving column 112A of the piezoelectric member 112, so that the individual liquid chamber 110 is separated from the common liquid chamber 110. The fluid resistance between 106 can be increased.

  In addition, since the vibration region 102a is pulled to the side opposite to the individual liquid chamber 106 side by contracting and displacing the drive column 112A, the fluid resistance between the common liquid chamber 110 and the individual liquid chamber 106 can be reduced.

  Further, by changing the displacement amount of the drive column 112A, the magnitude of the fluid resistance between the common liquid chamber 110 and the individual liquid chamber 106 can be changed according to the displacement amount of the drive column 112A.

  In other words, in this embodiment, the individual liquid chamber 106 is used as the first flow path, and the fluid is generated by the piezoelectric actuator 111 including the vibration region (vibration plate) 102 a of the vibration plate member 102 and the piezoelectric member 112 that form the wall surface of the individual liquid chamber 106. The resistance variable means is also used.

  However, a means for changing the fluid resistance of the flow path from the common liquid chamber 110 to the individual liquid chamber 106 may be provided separately. Further, the flow resistance between the common liquid chamber 110 and the nozzle 104 can be used as a first flow path so that the fluid resistance can be changed outside the individual liquid chamber 106.

  Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. FIG. 6 is a block diagram of the control unit.

  The control unit 500 controls the entire apparatus, and temporarily stores a CPU 501 that also serves as a recovery control unit according to the present invention, a ROM 502 that stores a program executed by the CPU 501 and other fixed data, and image data. And a RAM 503.

  The control unit 500 also includes a rewritable nonvolatile memory 504 for holding data while the apparatus is powered off, image processing for performing various signal processing and rearrangement on image data, and other entire apparatus. And an ASIC 505 for processing input / output signals for controlling.

  The control unit 500 also includes a print control unit 508 including a data transfer unit for driving and controlling the recording head 34 and a driving signal generation unit, and a head driver (driver) for driving the recording head 34 provided on the carriage 33 side. IC) 509.

  The control unit 500 also includes a main scanning motor 554 that moves and scans the carriage 33, a sub-scanning motor 555 that rotates the conveyor belt 51, and a motor driving unit 510 that drives a maintenance and recovery motor 556. The maintenance / recovery motor 556 operates a cap lifting / lowering mechanism 820 that moves the suction pump 812 and the cap 82 of the maintenance / recovery mechanism 81 forward and backward. The control unit 500 includes an AC bias supply unit 511 that supplies an AC bias to the charging roller 56.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 has an I / F 506 for transmitting and receiving data and signals to and from the host side. From the host 600 side such as an information processing apparatus such as a personal computer, the I / F 506 is connected via a cable or a network. Receive at.

  The CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the ASIC 505, and prints the image data. The data is transferred from the unit 508 to the head driver 509. Note that generation of dot pattern data for image output is performed by the printer driver 601 on the host 600 side.

  The print control unit 508 transfers the above-described image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509.

  The print control unit 508 also includes a drive signal generation unit including a D / A converter that converts D / A conversion of drive waveform pattern data stored in the ROM 502, a voltage amplifier, a current amplifier, and the like. Then, the print control unit 508 outputs a drive signal composed of one drive pulse or a plurality of drive pulses to the head driver 509.

  The head driver 509 selectively applies a driving pulse constituting a driving waveform supplied from the print control unit 508 to each piezoelectric actuator 111 of the recording head 34 based on the image data. Thereby, the recording head 34 is driven. At this time, by selecting a driving pulse constituting the driving waveform, for example, dots having different sizes such as large droplets, medium droplets, and small droplets can be sorted.

  The I / O unit 513 acquires information from various sensor groups 515 mounted on the apparatus and a temperature sensor 516 that is a temperature detecting means for detecting the temperature in the apparatus body, and provides information necessary for controlling the apparatus. The data is extracted and used to control the print control unit 508, the motor drive unit 510, and the AC bias supply unit 511.

  The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the humidity in the machine, a sensor for monitoring the voltage of the charging belt, and an interlock switch for detecting opening and closing of the cover. The I / O unit 513 can process various sensor information.

  The control unit 500 controls the recovery operation based on the temperature detected by the temperature sensor 516. The recovery operation is performed by driving the suction pump 812 with the suction cap 82a capping (sealing) the nozzle surface of the recording head 34, and forcibly sucking and discharging the ink from the nozzle. At this time, the fluid resistance variable means of the recording head 34 is driven and controlled to change the fluid resistance of the flow path from the common liquid chamber 110 to the individual liquid chamber 106 according to the position where the individual liquid chamber 106 communicates with the common liquid chamber 110. Let

  Next, generation of bubbles due to temperature change in the head will be described with reference to FIG. FIG. 7 is an explanatory diagram showing an example of the relationship between the temperature of the liquid and the amount of saturated dissolved gas.

  As shown in FIG. 7, the amount of saturated dissolved gas varies depending on the temperature of the liquid, and the amount of saturated dissolved gas is relatively higher at a lower temperature than when it is at a higher temperature.

  Therefore, when the temperature of the liquid changes from a low temperature to a high temperature, the amount of saturated dissolved gas decreases, so that the gas dissolved in the liquid appears as bubbles.

  Bubbles that naturally occur from the liquid (ink) in the recording head 34 due to such a temperature change are particularly likely to occur in the common liquid chamber 110 having a large ink capacity.

  Next, generation of bubbles in the recording head in the present embodiment will be described with reference to FIGS. FIG. 8 is a schematic explanatory view for explaining the state in which bubbles are generated in the recording head, and FIG. 9 is a schematic perspective explanatory view of the flow path from the supply port to the nozzle in the common liquid chamber.

  In this image forming apparatus, the recording head 34 is arranged with the nozzle surface facing downward. Then, ink is supplied from the storage portion 202 of the head tank 35 to the common liquid chamber 110 via the filter member 220 and the supply port 119 of the recording head 34.

  Here, the common liquid chamber 110 of the recording head 34 is configured to supply liquid from a supply port 119 disposed at one end in the nozzle arrangement direction.

  Moreover, the cross-sectional shape along the nozzle arrangement direction of the common liquid chamber 110 is such that the opening cross-sectional area of the flow path is formed by forming the inclined portion 110a at the other end opposite to the one end where the supply port 119 is disposed. The shape is narrowed down. Here, since the liquid supplied from the supply port 119 flows toward the inclined portion 110a, the opening cross-sectional area is a cross-sectional area of a cross section in a direction orthogonal to the liquid flow direction.

  In this case, the bubble 300 naturally generated in the common liquid chamber 110 is likely to accumulate on the inner top surface side of the common liquid chamber 110 due to buoyancy. As described above, when bubbles are generated in the common liquid chamber 110, if the bubbles 300 flow into the individual liquid chamber 106, ejection failure occurs. In addition, since the bubble 300 becomes a resistance in the common liquid chamber 110, the ink supply to the individual liquid chamber 106 side is obstructed, resulting in insufficient supply (insufficient refill) and defective ejection.

  Therefore, for example, the recovery operation by nozzle suction as described above is performed to discharge the bubble 300 together with the ink from the nozzle 104. For this bubble discharge, it is sufficient to discharge and replace at least the amount of ink that exceeds the capacity of the individual liquid chamber 106 and the common liquid chamber 110.

  However, since the recovery operation for discharging the ink exceeding the capacity of the individual liquid chamber 106 and the common liquid chamber 110 is performed in order to discharge the bubbles, a large amount of ink is wasted.

  Therefore, it is required to efficiently perform a recovery operation for discharging bubbles to suppress wasteful liquid consumption.

  Next, a process of discharging bubbles generated in the common liquid chamber will be described with reference to FIG. FIG. 10 is a schematic perspective view for explaining the same.

  The bubble 300 naturally generated in the common liquid chamber 110 due to the temperature change moves to the top surface side of the common liquid chamber 110 by buoyancy as shown in FIG. Here, when the recovery operation by the nozzle suction is performed, the bubble 300 moves along the flow of the liquid from the supply port 119 to the inclined portion 110a as shown in FIG. This is because in the common liquid chamber 110, the flow velocity Sb along the inclined portion 110a is larger than the flow velocity Sa in the vertical direction.

  Then, as shown in FIG. 10C, the bubbles 300 move along the top surface of the inclined portion 110a, and as shown in FIG. 10D, the individual liquid on the end side away from the supply port 119 is obtained. It is discharged from the chamber 106 through the nozzle 104.

  As described above, the bubbles 300 accumulated on the top surface side (vertical upper side) of the common liquid chamber 110 are guided to the individual liquid chamber 106 communicating with the downstream side of the common liquid chamber 110 far from the supply port 119. .

  Therefore, in the present invention, when performing the recovery operation, the fluid resistance variable means (piezoelectric actuator 111) is driven, and the upstream side of the common liquid chamber 110 in the liquid flow direction in the common liquid chamber 110 that is the second flow path. The fluid resistance of the individual liquid chamber 106, which is the first flow path leading to, is made larger than the fluid resistance of the individual liquid chamber 106 leading to the downstream side of the common liquid chamber 110.

  The downstream side of the second flow path (common liquid chamber 110) and the upstream side of the second flow path (common liquid chamber 110) are both downstream and upstream in the second flow path (in the common liquid chamber 110). Means the side. Hereinafter, the individual liquid chamber 106 communicating with the downstream side of the common liquid chamber 110 is also referred to as “downstream individual liquid chamber 106”, and the individual liquid chamber 106 communicating with the upstream side of the common liquid chamber 110 is also referred to as “upstream individual liquid chamber 106”. .

  The individual liquid chamber 106 that communicates with the downstream side of the common liquid chamber 110 may be one or a plurality of individual liquid chambers, and the individual liquid chambers 106 other than the individual liquid chamber 106 that communicate with the downstream side of the common liquid chamber 110 may be used. The individual liquid chamber 106 is located upstream of the common liquid chamber 110.

  Thereby, the bubbles in the common liquid chamber 110 are positively guided to the downstream individual liquid chamber 106 having a relatively small fluid resistance and discharged from the nozzle 104. On the other hand, it is difficult for the liquid to be discharged from the upstream individual liquid chamber 106 having a relatively large fluid resistance, and the liquid consumption is reduced.

  In this way, when performing the recovery operation, a relatively large amount of liquid is discharged from the individual liquid chamber and the nozzle that are low in fluid resistance and easy to flow to the downstream side of the common liquid chamber, and on the other hand, to the upstream side of the common liquid chamber. The amount of liquid discharged from the individual liquid chamber and the nozzle is reduced. Therefore, it is possible to efficiently discharge bubbles while reducing wasteful liquid consumption accompanying the recovery operation.

  Next, the control of the fluid resistance will be described with reference to the equivalent circuit of FIG.

  In the liquid supply / discharge system when performing the recovery operation, the n first flow paths 120A that communicate with the downstream side of the common liquid chamber 110 and the m first flow paths 120B that communicate with the upstream side of the common liquid chamber 110 are arranged in parallel. And a circuit diagram in which ink is discharged by suction from the recovery means (suction pump 812).

  Here, when each fluid resistance of the first flow path 120A leading to the common liquid chamber downstream side is R1, and each fluid resistance of the first flow path 120B leading to the common liquid chamber upstream side is R2, Since the same suction pressure is applied to the nozzles 104, ink flows through the first flow paths 120A and 120B with the ink amounts I1 and I2 corresponding to the respective fluid resistances R1 and R2. The total ink amount I is expressed as I1 × n + I2 × m.

  At this time, the first flow path 120A that communicates with the downstream side of the common liquid chamber has a smaller fluid resistance (R1 <R2) than the first flow path 120B that communicates with the upstream side of the common liquid chamber. It flows (I1> I2).

  Thereby, since a large amount of ink flows from the downstream side of the common liquid chamber, bubbles are easily removed. Further, since the amount of ink flowing downstream of the common liquid chamber is large, it is possible to stop the suction in a shorter time than usual, and it is possible to suppress ink consumption in the entire maintenance.

  In this way, it is possible to improve the bubble discharge performance while reducing the liquid consumption associated with the recovery operation for discharging the bubbles as a whole.

  Next, driving of a piezoelectric actuator that is a fluid resistance control means and a change in fluid resistance will be described with reference to FIGS. FIG. 12 is an explanatory diagram for explaining the case of increasing the fluid resistance, and FIG. 13 is an explanatory diagram for explaining the case of reducing the fluid resistance.

  As shown in FIG. 12A, by applying a voltage higher than the intermediate potential Ve to the drive column 112A of the piezoelectric member 112, the state 1 shown in FIG. 12A to the state 2 shown in FIG. 12C. As shown, the drive column 112A extends. As a result, the vibration region 102 a is pushed into the individual liquid chamber 106, so that the fluid resistance of the individual liquid chamber 106 is larger in the state 2 than in the state 1.

  As shown in FIG. 13A, by applying a voltage lower than the intermediate potential Ve to the drive column 112A of the piezoelectric member 112, the state 1 shown in FIG. 13A to the state 2 shown in FIG. 12C. As shown, the driving column 112A contracts. As a result, the vibration region 102 a is pulled out from the individual liquid chamber 106 side, and therefore the fluid resistance of the individual liquid chamber 106 is smaller in the state 2 than in the state 1.

  Therefore, by combining these state 1 with state 2 in FIG. 12C and state 2 in FIG. 13C, the fluid resistance of the individual liquid chamber 106 leading to the downstream side of the common liquid chamber is increased to the upstream side of the common liquid chamber. The fluid resistance of the individual liquid chamber 106 to be communicated is reduced.

  Next, the start of the bubble discharge recovery operation in the first embodiment of the present invention will be described with reference to FIG. FIG. 14 is an explanatory diagram showing an example of the passage of time and temperature change provided for the explanation.

  As described above, since the saturated dissolved gas amount changes depending on the temperature, it can be converted into the gas amount by detecting the temperature.

  In this embodiment, the detected temperature when the previous recovery means is performed (time A) is stored, the current detected temperature (time B) is obtained, and the stored detected temperature and the current detected temperature are stored. When the difference is equal to or higher than a predetermined temperature, the bubble discharge recovery operation is performed.

  In this manner, the detected temperature (detection result) when the previous recovery operation is performed is stored, and the recovery operation for discharging the bubbles is started based on the temperature change with respect to the stored detection temperature. According to this embodiment, the recovery operation (maintenance) for reliably discharging bubbles even in a situation where the temperature change cannot be continuously detected because the power of the apparatus main body is turned off. Can be implemented.

  However, since it is not known what temperature change has occurred between the previous time and the present time, there is a possibility that it is far from the actual gas amount.

  Next, the start of the bubble discharge recovery operation in the second embodiment of the present invention will be described with reference to FIG. FIG. 15 is an explanatory diagram showing an example of the passage of time and temperature change for the same explanation.

  In the present embodiment, the detected temperature when the previous recovery means is performed (time A) is stored, temperature detection is continued thereafter, and only the amount of gas generated that cannot be dissolved in the liquid is accumulated. When the amount of gas exceeds a specific threshold (time B), the recovery operation for discharging the bubbles is performed.

  Also in this case, the detected temperature when the previous recovery operation is performed is stored, and the recovery operation for discharging bubbles is started based on the temperature change with respect to the stored detection temperature. In the present embodiment, the amount of gas generated due to temperature changes is grasped as needed, so that recovery operation (maintenance) can be started at an optimal timing, and image defects are less likely to occur. However, since only the amount of gas generated due to the temperature rise is accumulated, the frequency of the recovery operation may be increased.

  Next, the start of the bubble discharge recovery operation in the third embodiment of the present invention will be described with reference to FIG. FIG. 16 is an explanatory diagram showing an example of the passage of time and temperature change for the same explanation.

  In the present embodiment, the detected temperature when the previous recovery means is performed (time A) is stored, the temperature detection is continued thereafter, and the amount of gas generated by being unable to dissolve in the liquid due to the temperature rise and the temperature drop To accumulate the difference in the amount of gas dissolved in the liquid. Then, when the accumulated gas amount exceeds a predetermined threshold (time point B), a recovery operation for discharging bubbles is started.

  Also in this case, the detected temperature when the previous recovery operation is performed is stored, and the recovery operation for discharging bubbles is started based on the temperature change with respect to the stored detection temperature. In the present embodiment, both the amount of gas generated by the temperature change and the amount of gas to be dissolved are grasped as needed, so that the amount of gas can be estimated accurately. The bubble discharge recovery operation (maintenance) can be carried out at a more optimal timing than in the second embodiment.

  Next, the recovery operation according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 17A is a cross-sectional explanatory view of a downstream individual liquid chamber provided for the description, and FIG. 17B is a cross-sectional explanatory view of an upstream individual liquid chamber.

  In this embodiment, as shown in FIG. 17A, the piezoelectric actuator 111 in the downstream individual liquid chamber 106 is not driven, and as shown in FIG. The recovery operation is performed while the piezoelectric actuator 111 is driven in the extending direction.

  As a result, the fluid resistance of the downstream individual liquid chamber 106 becomes smaller than the fluid resistance of the other upstream individual liquid chamber 106.

  Therefore, when performing the recovery operation, a relatively large amount of ink is discharged from the nozzle 104 communicating with the downstream individual liquid chamber 106 with a small fluid resistance and easy to flow, and bubbles are also discharged along the flow. On the other hand, since the amount of ink discharged from the nozzles communicating with the other upstream individual liquid chambers 106 is reduced, the wasteful ink consumption associated with the recovery process is reduced.

  Next, the recovery operation according to the fifth embodiment of the present invention will be described with reference to FIG. FIG. 18A is a cross-sectional explanatory view of the downstream-side individual liquid chamber provided for the description, and FIG. 18B is a cross-sectional explanatory view of the upstream-side individual liquid chamber.

  In this embodiment, as shown in FIG. 18 (a), the piezoelectric actuator 111 of the downstream individual liquid chamber 106 is driven in the contraction direction, and as shown in FIG. 18 (b), the other upstream individual liquid chambers are driven. The piezoelectric actuator 111 of 106 performs a recovery operation in a non-driven state.

  As a result, the fluid resistance of the downstream individual liquid chamber 106 becomes smaller than the fluid resistance of the other upstream individual liquid chamber 106.

  Therefore, when performing the recovery operation, a relatively large amount of ink is discharged from the nozzle 104 communicating with the downstream individual liquid chamber 106 with a small fluid resistance and easy to flow, and bubbles are also discharged along the flow. On the other hand, since the amount of ink discharged from the nozzles communicating with the other upstream individual liquid chambers 106 is reduced, the wasteful ink consumption associated with the recovery process is reduced.

  Next, the recovery operation according to the sixth embodiment of the present invention will be described with reference to FIG. FIG. 19A is a cross-sectional explanatory view of a downstream individual liquid chamber provided for the description, and FIG. 19B is a cross-sectional explanatory view of an upstream individual liquid chamber.

  In this embodiment, as shown in FIG. 19A, the piezoelectric actuator 111 of the downstream individual liquid chamber 106 is driven in the contraction direction, and as shown in FIG. 18B, other upstream individual liquid chambers are driven. The recovery operation is performed with the piezoelectric actuator 111 of 106 being driven in the extension direction.

  That is, in this embodiment, the piezoelectric actuators 111 in both the downstream individual liquid chamber 106 and the upstream individual liquid chamber 106 are driven, but the fluid resistance is varied by varying the driving amount (including the driving direction). Yes. Therefore, the fluid resistances of the downstream individual liquid chamber 106 and the upstream individual liquid chamber 106 can be made different by making the expansion / contraction direction of the drive column 112A the same and by varying the extension amount or the contraction amount. Can be made.

  As a result, the fluid resistance of the downstream individual liquid chamber 106 becomes smaller than the fluid resistance of the other upstream individual liquid chamber 106.

  Therefore, when performing the recovery operation, a relatively large amount of ink is discharged from the nozzle 104 communicating with the downstream individual liquid chamber 106 with a small fluid resistance and easy to flow, and bubbles are also discharged along the flow. On the other hand, since the amount of ink discharged from the nozzles communicating with the other upstream individual liquid chambers 106 is reduced, the wasteful ink consumption associated with the recovery process is reduced.

  The first to third embodiments relating to the start of the recovery operation and the fourth to sixth embodiments relating to driving of the fluid resistance control means during the recovery operation can be combined with each other.

  Moreover, although the said embodiment demonstrated in the example which controls the fluid resistance to change in two steps, it is not restricted to this.

  This point will be described with reference to FIGS. 20 and 21 are explanatory diagrams for explaining different examples of the relationship between different common liquid chamber shapes and fluid resistance during the recovery operation.

  FIG. 20 shows an example in which the fluid resistance is different at each position in the nozzle arrangement direction when the supply port 119 is provided on the one end side with respect to the common liquid chamber 110.

  FIG. 20B shows an example in which the fluid resistance is made different in two stages, the downstream side and the upstream side, as described in the above embodiment. 20C to 20F are examples in which the fluid resistance gradually changes from the most downstream side to the most upstream side. The value of the fluid resistance can be controlled by the value of the driving voltage applied to the piezoelectric actuator 111.

  FIG. 21 shows an example in which the fluid resistance is different at each position in the nozzle arrangement direction when the supply port 119 is provided in the central portion with respect to the common liquid chamber 110. In this case, the position corresponding to the supply port 119 in the central portion is the upstream side, and both end portions are the downstream side.

  FIG. 21B shows an example in which the fluid resistance is varied in two stages, that is, the downstream side and the upstream side as described in the above embodiment. FIGS. 21C to 21F are examples in which the fluid resistance gradually changes from the most downstream side to the most upstream side.

  In the above-described embodiment, an example in which nozzle suction is performed as the recovery operation has been described. However, the present invention is similarly applied to a recovery operation in which a pressurized liquid is supplied to the head, and also in a case where pressure and suction are combined. Can be applied to.

  The processing according to the present invention such as the above-described recovery control is executed by a computer by a program stored in the ROM 502. This program can be downloaded to the information processing apparatus (host 600) and installed in the image forming apparatus. Further, the above processing may be performed by a printer driver on the information processing apparatus (host 600) side. Furthermore, the image forming apparatus according to the present invention and an information processing apparatus or an image forming apparatus and an information processing apparatus having a program for performing processing according to the present invention can be combined to form an image forming system.

  Further, in the present application, the “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, and the like, and means a material to which ink droplets, other liquids, and the like can adhere. , Recording media, recording paper, recording paper, and the like. In addition, image formation, recording, printing, printing, and printing are all synonymous.

  The “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. “Formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply causing a droplet to land on the medium). ) Also means.

  The “ink” is not limited to an ink unless otherwise specified, but includes any liquid that can form an image, such as a recording liquid, a fixing processing liquid, or a liquid. Used generically, for example, includes DNA samples, resists, pattern materials, resins, and the like.

  In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  Further, the image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

10 Ink cartridge (main tank)
33 Carriage 34, 34a, 34b Recording head (liquid ejection head)
81 Maintenance and recovery mechanism 82 Cap 102 Diaphragm member 104 Nozzle 106 Individual liquid chamber (first flow path)
110 Common liquid chamber (second flow path)
111 Piezoelectric actuator (fluid resistance variable means)
112 Piezoelectric member (pressure generating means)
500 Control unit (recovery control means)

Claims (5)

A plurality of first flow paths that communicate with a plurality of nozzles that discharge droplets; a second flow path that communicates with the plurality of first flow paths; and a fluid resistance variable means that changes the fluid resistance of the first flow path; A recording head having
Temperature detecting means for detecting the temperature in the apparatus body;
Recovery control means for controlling the recovery operation of the recording head based on the detection result of the temperature detection means,
The recovery control means includes
Stores the detected temperature when the previous recovery operation was performed, and performs the recovery operation based on the temperature change with respect to the stored detection temperature,
When performing the recovery operation, the fluid resistance variable means is driven to set the fluid resistance of the first flow path leading to the upstream side of the second flow path in the liquid flow direction of the second flow path, An image forming apparatus, wherein the fluid resistance of the first flow path leading to the downstream side of the second flow path is larger. The recording head is
A diaphragm member forming at least one deformable wall surface of the first flow path;
Driving means for displacing the diaphragm member;
The image forming apparatus according to claim 1, wherein the driving unit and the diaphragm member also serve as the fluid resistance variable unit. The recovery control means includes
The drive means of the fluid resistance variable means of the first flow path leading to the downstream side of the second flow path is non-driven;
Driving the drive means of the fluid resistance variable means of the first flow path leading to the upstream side of the second flow path to make the fluid resistance larger than the fluid resistance when the drive means is not driven;
The image forming apparatus according to claim 2, wherein control is performed. The recovery control means includes
Driving the drive means of the fluid resistance variable means of the first flow path leading to the downstream side of the second flow path, making the fluid resistance smaller than the fluid resistance when the drive means is not driven,
The drive means of the fluid resistance variable means of the first flow path leading to the upstream side of the second flow path is non-driven;
The image forming apparatus according to claim 2, wherein control is performed. The recovery control means includes
The driving means of the fluid resistance variable means of the first flow path communicating with the downstream side of the second flow path, and the fluid resistance variable means of the first flow path communicating with the upstream side of the second flow path. Drive all the driving means,
2. The image forming apparatus according to claim 1, wherein control is performed to vary the fluid resistance by varying the driving amount.

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