JP2013116615A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that supply failure occurs due to simultaneous driving of a solution sending pump when supply control to a head tank is performed with a sensor on a carriage.SOLUTION: Ink supply to the head tank 5 is started after an ink consumption from the time when a displacement member 205 which displaces in a reduction direction is detected by a first sensor 251 on the carriage 3 reaches a predetermined amount. During a difference supply time t corresponding to a difference supply amount after the first sensor 251 detects the displacement member 205 which displaces in an increase direction, the solution sending pump 241 is driven to continue filling. If the filling continues, when supply operations from one main tank 10 to two head tanks 5a and 5b conflict with each other, a supply flow rate supplied by the solution sending pumps 241a and 241b is increased more than a supply flow rate supplied by the one solution pump 241a or 241b.

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus including a recording head that discharges droplets and a head tank that supplies liquid to the recording head.

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a complex machine of these, for example, a liquid discharge recording type image forming using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. As an apparatus, an ink jet recording apparatus or the like is known.

  In such an image forming apparatus, a head tank (also referred to as a sub-tank) provided on the recording head side can be replenished with liquid from the main tank even during a printing operation. A first sensor that detects that the displacement member has reached a predetermined first position on the carriage, and detects that the displacement member has reached a predetermined second position on the apparatus body side. A second sensor is provided to detect and hold a difference amount corresponding to the displacement amount of the displacement member between the position detected by the first sensor and the position detected by the second sensor. When the liquid is supplied from the main tank to the head tank without using the second sensor, the first sensor detects the displacement member and then controls to supply the differential supply amount of liquid to the head tank. That (Patent Document 1).

JP 2011-297206 A

  In the configuration disclosed in Patent Document 1 described above, when it is necessary to simultaneously supply liquid from one main tank to a plurality of head tanks, the supply flow rate to each head tank varies, resulting in insufficient supply. May occur, resulting in nozzle down (undischargeable).

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent discharge failure due to insufficient supply and improve image quality.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head for discharging droplets;
A head tank for storing liquid to be supplied to the recording head;
A carriage on which the recording head and the head tank are mounted;
A main tank for storing liquid to be supplied to the head tank;
At least two liquid feeding means for respectively supplying liquid from the main tank to the at least two head tanks;
Supply control means for controlling the liquid supply from the main tank to the head tank by driving the liquid feeding means,
A plurality of head tanks connected to one main tank, and a plurality of liquid feeding means for supplying liquid to each head tank;
The head tank has a displacement member that is displaced according to the remaining amount of liquid,
The carriage is provided with first detection means for detecting the displacement member,
The apparatus main body side is provided with second detection means for detecting the displacement member,
The first position of the displacement member detected by the first detection means is a position where the remaining amount of liquid in the head tank is less than the second position of the displacement member detected by the second detection means,
The supply control means includes
Detecting and holding a difference amount corresponding to a displacement amount of the displacement member between a position detected by the first detection means and a position detected by the second detection means;
When supplying the liquid from the main tank to the head tank without using the second detection means,
When the liquid consumption amount of the head tank becomes a predetermined liquid consumption amount in which the remaining amount of liquid in the head tank is smaller than the position where the displacement member is detected by the first detection means, the main tank releases the liquid consumption amount. Start liquid feeding to the head tank,
After the first detecting means detects the displacement member, it performs control to supply the difference amount,
A configuration in which when supplying liquid from the main tank to the plurality of head tanks simultaneously, control is performed to increase the supply flow rate of the liquid supply means, compared to when supplying liquid to the plurality of head tanks individually. did.

  According to the image forming apparatus of the present invention, it is possible to prevent ejection failure due to insufficient supply to the head tank and improve image quality.

FIG. 3 is a plan view of relevant parts for explaining a mechanical part of an example of an image forming apparatus according to the present invention. It is a principal part side surface explanatory drawing similarly. It is a typical plane explanatory view showing an example of a head tank. FIG. 4 is a schematic front sectional view of FIG. 3. FIG. 3 is a schematic explanatory diagram for explaining an ink supply / discharge system. It is a principal front schematic explanatory drawing similarly. It is explanatory drawing explaining the 1st example of the example of arrangement | positioning of a 1st sensor and a 2nd sensor. It is explanatory drawing explaining the 2nd example of the example of arrangement | positioning of a 1st sensor and a 2nd sensor. It is block explanatory drawing explaining the outline | summary of a control part. FIG. 6 is a schematic plan view for explaining the position detection of the head tank displacement member. It is explanatory drawing explaining the relationship between the negative pressure in a head tank, and the amount of liquids. It is explanatory drawing with which it uses for description of the ink supply upper limit setting position of a head tank. It is explanatory drawing with which it uses for description of the method of setting the ink amount in a head tank to a filling full tank position at the time of air release. It is explanatory drawing with which it uses for description of the detection method of difference supply amount. It is a flowchart with which it uses for description of calculation control (process) of the difference supply amount by a control part. It is a flowchart with which it uses for description of an example of the ink filling control (supply control) which does not use the 2nd sensor by a control part. It is a flowchart with which it uses for description of the supply flow volume setting process by the drive control of the liquid feeding pump in 1st Embodiment of this invention. It is explanatory drawing with which it uses for description of the 1st example of drive control of the liquid feeding pump in 2nd Embodiment of this invention. It is explanatory drawing similarly provided to description of the 2nd example of drive control of a liquid feeding pump. It is explanatory drawing with which it uses for description of the 3rd example of drive control of a liquid feeding pump similarly.

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

  This image forming apparatus is a serial type image forming apparatus, and a carriage 3 is movably held by a main guide member 1 and a sub guide member (not shown) spanned between left and right side plates (not shown), and is moved by a main scanning motor (not shown). The carriage 3 is moved and scanned in the main scanning direction via a timing belt spanned between the driving pulley and the driven pulley.

  In the carriage 3, a recording head 4a, 4b, 4c, 4d (which is referred to as “recording head 4” when not distinguished) is composed of a plurality of nozzles. They are arranged in the sub-scanning direction orthogonal to the scanning direction, and are mounted with the droplet discharge direction facing downward.

  Here, the recording head 4a and the recording heads 4b to 4d are arranged by shifting the position of one head (one nozzle row) in the sub-scanning direction which is a direction orthogonal to the main scanning direction. Each of the recording heads 4a to 4d has two nozzle rows. The recording heads 4a and 4b eject black droplets having the same color, and magenta (M), cyan (C), and yellow (Y) droplets are ejected from the nozzle arrays of the recording heads 4c and 4d. To do.

  As a result, monochrome images can be formed with a width of two heads in one scan (main scanning) using the recording heads 4a and 4b, and color images are formed using, for example, the recording heads 4b to 4d. be able to.

  The recording heads 4a to 4d are each provided with a head tank 5 for supplying a liquid to each head 4. The head tank 5 is supplied with ink of each color via a supply tube 6 from ink cartridges 10k, 10c, 10m, and 10y, which are main tanks that are replaceably attached to the apparatus main body. At this time, ink is supplied from one ink cartridge 10k to the two recording heads 4a and 4b that discharge droplets of the same color.

  An encoder scale 91 is provided along the main scanning direction of the carriage 3, and an encoder sensor 92 for reading the encoder scale 91 is provided on the carriage 3. The linear encoder 90 is configured by the encoder scale 91 and the encoder sensor 92. The main scanning position (carriage position) and the movement amount of the carriage 3 are detected by the detection signal of the linear encoder 90.

  On the other hand, in order to transport the paper, a transport belt 12 is provided as a transport means for electrostatically attracting the paper and transporting the paper at a position facing the recording head 4. The transport belt 12 is an endless belt, is configured to wrap around the transport roller 13 and the tension roller 14 and circulate in the belt transport direction (sub-scanning direction). 15 is charged (charged).

  In addition, the conveyance belt 12 rotates in the sub-scanning direction when the conveyance roller 13 is rotationally driven by a sub-scanning motor (not shown) via a timing belt and a timing pulley.

  Further, a maintenance / recovery mechanism 20 that performs maintenance / recovery of the recording head 4 on the side of the conveyance belt 12 is arranged on one side of the carriage 3 in the main scanning direction, and the recording head 4 is arranged on the side of the conveyance belt 12 on the other side. The empty discharge receivers 24 for discharging the droplets that do not contribute to image formation are disposed.

  The maintenance / recovery mechanism 20 includes a first maintenance / recovery unit 21 held in the apparatus main body and a second maintenance / recovery part 22 held in the apparatus main body so as to be able to reciprocate in the sub-scanning direction (arrow direction). . The second maintenance / recovery unit 22 is at the position shown in FIG. 1 when performing the maintenance / recovery of the recording head 4a, and moves to the same position in the sub-scanning direction as the first maintenance / recovery unit 21 when performing the maintenance / recovery of the recording heads 4b to 4d.

  The maintenance / recovery mechanism 20 includes, for example, a suction cap 31 and a moisture retaining cap 32 that also serve as a moisture retaining cap for capping the nozzle surface (the surface on which the nozzle is formed) of the recording head 4, a wiper member 33 for wiping the nozzle surface, and image formation. A blank discharge receptacle 34 for receiving droplets (empty discharge droplets) that do not contribute to the above.

  In this image forming apparatus configured as described above, the sheet P is fed from the sheet feeding tray (not shown) onto the charged conveying belt 12 and sucked, and the sheet P is moved in the sub-scanning direction by the circular movement of the conveying belt 12. Be transported. Therefore, by driving the recording head 4 in accordance with the image signal while moving the carriage 3 in the main scanning direction, droplets are ejected onto the stopped paper P to record one line, and the paper P is placed in place. After the quantitative transport, record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper P reaches the recording area, the recording operation is finished, and the paper P is discharged onto a paper discharge tray (not shown).

  Next, an example of the head tank 5 will be described with reference to FIGS. 3 is a schematic top explanatory view of the head tank 5, and FIG. 4 is a schematic front explanatory view of the same.

  The head tank 5 has a tank case 201 that forms an ink containing portion that is open at one side for holding ink, and the opening of the tank case 201 is a film member 203 that can be bent. The ink container 202 is formed in a sealed state, and the film member 203 is constantly urged outward by the restoring force of the spring 204 as an elastic member disposed in the tank case 201. As described above, the restoring force of the spring 204 acts on the film member 203 of the tank case 201, so that a negative pressure is generated by reducing the ink remaining amount in the ink storage portion 202 of the tank case 201.

  In addition, a displacement member (hereinafter referred to as a filler) that is supported on the outer side of the tank case 201 so that the one end side can be swung by the support shaft 206 and is urged toward the tank case 201 by a spring 210 (hereinafter referred to as a “displacement member”). , 205 may be simply referred to as “filler.”) 205 is fixed to the film member 203 by adhesion or the like, and the displacement member 205 is displaced in conjunction with the movement of the film member 203. The head tank 5 is detected by detecting the displacement member 205 by a first detection means (first sensor) 251 described later provided on the carriage 3 or a second detection means (second sensor) 301 described later disposed on the apparatus main body side. It is possible to detect the remaining amount of ink, negative pressure, and the like.

  In addition, a supply port 209 for supplying ink from the ink cartridge 10 is connected to the ink supply tube 6 at the upper part of the tank case 201. An air release mechanism 207 that opens the inside of the head tank 5 to the atmosphere is provided on the side of the tank case 201. The atmosphere release mechanism 207 includes a valve body 207b that opens and closes an atmosphere release path 207a communicating with the inside of the head tank 5, a spring 207c that biases the valve body 207b to a closed state, and the like. When the valve body 207b is pushed by 302, the valve body 207b is opened, and the head tank 5 is opened to the atmosphere (connected to the atmosphere).

  Further, electrode pins 208a and 208b for detecting the ink liquid level in the head tank 5 are attached. Since the ink has electrical conductivity, when the ink reaches the electrode pins 208a and 208b, a current flows between the electrode pins 208a and 208b, and the resistance value of the two changes. That is, it can be detected that the air amount in the head tank 5 has exceeded a predetermined amount.

  Next, an ink supply / discharge system in the image forming apparatus will be described with reference to FIGS. FIG. 5 is a schematic explanatory diagram of the supply / discharge system, and FIG. 6 is a schematic explanatory diagram of the supply system for two recording heads that discharge droplets of the same color.

  First, ink is supplied from an ink cartridge (hereinafter referred to as “main tank”) 10 to the head tank 5 through a supply tube 6 by a liquid supply pump 241 which is a liquid supply means. The liquid feed pump 241 is a reversible pump constituted by a tube pump or the like, and can perform an operation of supplying ink from the ink cartridge 10 to the head tank 5 and an operation of returning ink from the head tank 5 to the ink cartridge 10. I try to do it.

  In this embodiment, as shown in FIG. 6, the same color ink is supplied from one main tank 10k to the two head tanks 5a and 5b for the recording heads 4a and 4b. Ink is supplied from pumps 241a and 241b through supply tubes (supply paths) 6a and 6b.

  The maintenance / recovery mechanism 20 has the suction cap 31 for capping the nozzle surface of the recording head 4 and the suction pump 812 connected to the suction cap 31 as described above. By driving 812, ink in the head tank 5 can be sucked by sucking ink from the nozzles via the suction tube 811. The sucked waste ink is discharged to the waste liquid tank 100.

  Further, an air release solenoid 302 which is a member for opening and closing the air release mechanism 207 of the head tank 5 is disposed on the apparatus main body side, and the air release mechanism 207 can be opened by operating the air release solenoid 302. .

  Further, the carriage 3 is provided with a first sensor 251 that is an optical sensor that is a first detection means for detecting the displacement member 205, and a second detection means that is an optical sensor for detecting the displacement member 205 on the apparatus body side. A second sensor 301 is provided. As will be described later, the ink supply operation to the head tank 5 is controlled using the detection results of the first sensor 251 and the second sensor 301.

  The controller 500 performs the drive control of the liquid feed pump 241, the air release solenoid 302, and the suction pump 812, and the ink supply control operation according to the present invention.

  Next, different examples of arrangement of the first sensor and the second sensor will be described with reference to FIGS. 7 and 8 are side explanatory views for explaining the arrangement example.

  In the first example shown in FIG. 7, detection units 205 </ b> A and 205 </ b> B having different lengths from the support shaft 206 (support point) are provided below the displacement member 205 of the head tank 5, and the first sensor 251 provided on the carriage 3. Thus, the detection unit 205A is configured to detect the detection unit 205B by the second sensor 301 provided on the member (base member) 101 on the apparatus main body side.

  In the second example shown in FIG. 8, detection units 205 </ b> A and 205 </ b> B having the same length from the support shaft 206 (support point) are provided on the displacement member 205 of the head tank 5, and the detection unit 205 </ b> A is detected by the first sensor 251 of the carriage 3. The detection unit 205B is detected by the second sensor 301 on the apparatus main body side.

  Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. FIG. 9 is an explanatory block diagram of the entire control unit.

  The control unit 500 controls the entire apparatus. The CPU 501 also serves as various control means such as a supply control means in the present invention, a ROM 502 that stores programs executed by the CPU 501 and other fixed data, and image data. RAM 503 for temporary storage, rewritable non-volatile 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 control.

  In addition, a print control unit 508 including a data transfer unit for driving and controlling the recording head 4 and a driving signal generating unit, a head driver (driver IC) 509 for driving the recording head 4 provided on the carriage 3 side, An AC bias is applied to the charging roller 15, a main scanning motor 554 that moves and scans the carriage 3, a sub-scanning motor 555 that moves the conveyor belt 12 around, a motor drive unit 510 that drives the maintenance / recovery motor 556 of the maintenance / recovery mechanism 20. An AC bias supply unit 511 to supply, an air release solenoid 302 provided on the apparatus main body side that opens and closes the air release mechanism 207 of the head tank 5, a supply system drive unit 512 that drives the liquid feed pump 241, and the like are provided.

  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, an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, and the like. From the host 600 side via the cable or network via the I / F 506.

  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. Including a D / A converter for D / A converting D / A conversion of drive pulse pattern data stored in the ROM, a voltage signal amplifier, a current amplifier, and the like, and a drive signal or a plurality of drive pulses Is output to the head driver 509.

  The head driver 509 selectively selects droplets of the recording head 4 based on image data corresponding to one line of the recording head 4 input serially, and a driving pulse constituting a driving signal provided from the print control unit 508. The recording head 4 is driven by applying it to a drive element (for example, a piezoelectric element) that generates energy to be discharged. At this time, by selecting a driving pulse constituting the driving signal, for example, dots having different sizes such as a large droplet, a medium droplet, and a small droplet can be sorted.

  The I / O unit 513 acquires information from various sensor groups 515 mounted on the apparatus, extracts information necessary for controlling the printer, a print control unit 508, a motor drive unit 510, and an AC bias supply unit. It is used to control 511, control ink supply to the head tank 5, and the like.

  In addition to the first sensor 251, the second sensor 301, and the detection electrode pins 208a and 208b, the sensor group 515 includes an optical sensor for detecting the position of the paper and a thermistor for monitoring the temperature and humidity in the machine ( Environmental temperature sensor, environmental humidity sensor), a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like, and the I / O unit 513 can process various sensor information.

  Next, position detection of the displacement member 205 of the head tank 5 will be described with reference to FIG. FIG. 10 is a schematic explanatory diagram for explaining the displacement of the displacement member of the head tank. In the following drawings, the head tank is illustrated in a simplified manner.

  The displacement member 205 of the head tank 5 is displaced, for example, between a position indicated by a solid line in FIG. 10A and a position indicated by a broken line in FIG.

  Therefore, the position of the carriage 3 when the displacement member 205 of the head tank 5 is detected by the second sensor 301 on the apparatus main body side is stored in the encoder 90, and when the displacement member 205 of the head tank 5 is displaced. The carriage 3 is moved until the displacement sensor 205 of the head tank 5 is detected again by the second sensor 301, and the position of the displacement member 205 is read by the encoder 90 by reading the position of the carriage 3 at that time. It can be detected as a position difference.

  At this time, by knowing in advance the remaining amount of liquid in the head tank 5 corresponding to the initial position of the displacement member 205 and the amount of liquid corresponding to the displacement amount of the displacement member 205, the detected displacement amount of the displacement member 205 can be determined. The remaining amount of liquid in the head tank 5 can be grasped.

  Therefore, for example, when the liquid supply to the head tank 5 is controlled by detecting the displacement member 205 of the head tank 5 using the second sensor 301, the printing operation is stopped and the displacement member 205 is stopped by the second sensor 301. The liquid supply operation is performed by moving the carriage 3 to a position where the liquid is detected.

  On the other hand, when liquid is supplied to the head tank 5 during the printing operation, the first sensor 251 is used without moving the carriage 3 to a position where the displacement member 205 is detected by the second sensor 301, as will be described later. Liquid supply operation.

  Next, the relationship between the negative pressure in the head tank 5 and the amount of liquid will be described with reference to FIG. FIG. 11 is an explanatory diagram for explaining the relationship between the negative pressure in the head tank and the amount of liquid (hereinafter also referred to as “ink amount”).

  As described above, with the ink supplied to the head tank 5, the ink in the head tank 5 is sucked and discharged from the nozzles, or is sent back to the main tank 10 by the liquid feed pump 241. The member 203 is pulled inward against the restoring force of the spring 204, and the spring 204 is compressed to increase the negative pressure. When ink is supplied into the head tank 5 from this state, the film member 203 is pushed outward, so that the spring 204 extends and the negative pressure decreases.

  Here, if the negative pressure in the head tank 5 is too weak (the negative pressure is too low), ink leakage from the nozzles of the recording head 4 occurs. Conversely, if the negative pressure is too strong (too high), the nozzles Air or dust is drawn into the inside of the product, causing discharge failure. Further, in order to maintain the meniscus shape optimized for good droplet discharge, it is necessary to control the negative pressure (pressure) in the head tank 5 to be within a certain range.

  That is, as shown in FIG. 11, the negative pressure in the head tank 5 has a correlation with the ink amount in the head tank 5, and when the ink amount in the head tank 5 is large, the negative pressure in the head tank 5 is small. When the ink is weak and the amount of ink is small, the negative pressure in the head tank 5 becomes large and strong.

  Therefore, the amount of ink discharged from the head tank 5 is set so that the negative pressure in the head tank 5 falls within the range of the discharged ink amount B that falls within the predetermined negative pressure management range A. The supply is controlled.

  The ink discharge amount of the head tank 5 corresponding to the lower limit value of the negative pressure management range A (a value with a small negative pressure and a value with a small amount of ink discharge) is expressed as an “ink supply upper limit position” (ink amount) at the displacement position of the displacement member 205. Ink supply upper limit value)), and the ink discharge amount of the head tank 5 corresponding to the upper limit value (a value with a large negative pressure and a large amount of ink discharge) is set to the “ink consumption lower limit position” at the displacement position of the displacement member 205. (Ink amount “ink consumption lower limit value”). FIG. 11 additionally shows the state of the head tank 5 at each position.

  Next, the ink supply upper limit setting position of the head tank 5 will be described with reference to FIG. FIG. 12 is an explanatory diagram for explaining the set position.

  In the present embodiment, the head tank 5 has an atmosphere release mechanism (atmosphere release valve) 207. When the atmosphere release mechanism 207 is opened, air flows into the head tank 5 and is displaced until the film member 203 is fully extended, and the position at which the displacement member 205 is also displaced becomes the atmosphere release position. This is the reference of the displacement member 205. Position. In the present embodiment, the ink supply upper limit value is set at a position where the displacement member 205 is displaced from the atmospheric release position by a predetermined displacement amount r1 in the direction in which the remaining liquid amount decreases.

  As described above, the position where the displacement member 205 is detected by the second sensor 301 is detected by the encoder 90 as the position of the carriage 3 and stored in the atmosphere release position and the ink supply upper limit position.

  Next, a method of setting the ink amount in the head tank 5 to the full filling position when the atmosphere is released will be described with reference to FIG. FIG. 13 is an explanatory diagram for explaining the method.

  As described above, the head tank 5 has the electrode pins 208 capable of detecting the liquid level, the atmosphere opening path 207a for communicating the inside of the head tank 5 with the atmosphere, and the atmosphere that opens and closes the atmosphere opening path 207a. An opening mechanism 207 is provided. The atmosphere release mechanism 207 is schematically illustrated.

  As an example of setting the inside of the head tank 5 to the full filling position, first, from the state shown in FIG. 13A, the atmospheric pressure release mechanism 207 is opened to release the negative pressure in the head tank 5, thereby FIG. As shown in b), the liquid level in the head tank 5 is lowered.

  At this time, the supply port 209a of the supply port unit 209 is preferably below the liquid level. That is, when the supply port 209a is on the liquid level, air is mixed into the supply tube 6 via the supply port 209a or the supply port portion 209, and when ink is supplied next, bubbles are discharged from the supply port 209a together with the ink. If the supply is continued as it is, bubbles may adhere to the atmosphere opening mechanism 207, causing the valve to stick or leak.

  Then, after the negative pressure in the head tank 5 is released and the liquid level is lowered, the ink 300 is supplied as shown in FIG. By supplying the ink 300, the liquid level rises, and the ink 300 is supplied to a predetermined position until the electrode pins 208a and 208b detect the liquid level at a predetermined height.

  Thereafter, the atmosphere release mechanism 207 is closed, and for example, a predetermined amount of ink is discharged from the nozzle or is sent back to the main tank 10 to obtain a predetermined negative pressure value, and the ink amount in the head tank 5 is set to a predetermined negative pressure value. Can be obtained.

  Next, an outline of ink supply control will be described.

  In the present embodiment, the position of the displacement member 205 detected by the carriage-side first sensor 251 installed on the carriage 3 (this is referred to as “first position”) and the body-side first installed on the body base 101 side. The amount of filler displacement that is the difference between the atmospheric release detection position detected by the two sensors 301 (this is referred to as “second position”) is detected, and the ink supply set based on the detection position by the first sensor 251 during printing. Ink supply management during printing is performed by managing the upper limit position (upper limit value) and the ink consumption lower limit position (lower limit value).

  As described above, when ink supply control is performed during printing, the reference is moved from the atmospheric release position, which is the original reference position, to the detection position by the carriage-side first sensor 251, and the detection position by the carriage-side first sensor 251 is used as a reference. The ink consumption and the ink supply are repeatedly performed within the set ink supply upper limit position and the ink consumption lower limit position, and the remaining amount of ink in the head tank 5 is controlled to be always an appropriate amount.

  Here, since there are various variations for each device, such as the installation position of the carriage-side first sensor 251 on the carriage 3, the component dimensions of the head tank 5, and the expansion and contraction displacement of the film member 203 due to the influence of the humidity environment, individual variations exist. It is necessary to manage ink supply control suitable for this apparatus.

  Next, detection of the difference supply amount will be described with reference to FIG.

  In the ink supply control during printing, the detection position (first position) of the displacement member 205 by the carriage-side first sensor 251 is used as a reference, and therefore the carriage is moved from the atmospheric reference position (or full filling position) as the original reference. The displacement distance L [mm] of the displacement member 205 to the detection position by the side first sensor 251 is measured.

  That is, as shown in FIG. 14A, the main body side second sensor 301 moves the carriage 3 to a position where the displacement member 205 can be detected. Then, as shown in FIG. 14B, the liquid feed pump 241 is reversely driven from the state in which the displacement member 205 is in the atmospheric release position, and is fed backward from the head tank 5 to the main tank 10, and the carriage-side first sensor. After the ink is discharged from the head tank 5 until 251 detects the displacement member 205, the reverse feeding operation is stopped.

  Thereafter, as shown in FIG. 14C, the carriage 3 is moved until the main body side second sensor 301 detects the displacement member 205 while the carriage side first sensor 251 detects the displacement member 205. . By measuring the moving distance at this time with the encoder 90, the displacement distance (difference displacement amount) L [mm] of the displacement member 205 from the atmospheric release position until the carriage-side first sensor 251 detects the displacement member 205 is measured. To do.

  Then, based on the measured displacement distance L [mm], a difference supply amount after the first sensor 251 detects the displacement member 205 at the time of ink supply is calculated, and the driving time of the liquid feeding pump 241 corresponding to this supply amount is calculated. (Differential supply time) t [sec] is calculated and stored.

  Next, difference supply amount calculation control (difference supply time setting processing) by the control unit will be described with reference to the flowchart of FIG.

  First, the head tank 5 is opened to the atmosphere, and the carriage 3 is moved to a position where the second sensor 301 detects the displacement member 205 (this is referred to as a “second position”).

  Then, in the reverse rotation operation of the liquid feed pump 241, the reverse rotation operation is stopped after the ink is sucked until the first sensor 251 detects the displacement member 205.

  Next, the carriage 3 starts moving to a position where the second sensor 301 detects the displacement member 205, starts counting by the linear encoder 90, and stops counting when the second sensor 301 detects the displacement member 205. .

  As a result, a displacement amount (displacement distance) L of the displacement member 205 between the atmospheric release position (second position) and the first position where the first sensor 251 detects the displacement member 205 is calculated.

  Thereafter, as described above, the driving time (difference supply time) t of the liquid feed pump 241 corresponding to the difference supply amount when ink is supplied without using the second sensor 301 is set from the displacement amount L.

  Here, the atmospheric release position is the second position. However, as described above, the supply full tank position itself is the second position, and the supply amount corresponding to the displacement amount between the second position and the first position. Can be stored as a differential supply. This is due to how the filling full tank position is determined.

  Next, an example of ink filling control (supply control) that does not use the second sensor by the control unit will be described with reference to the flowchart of FIG.

  During the printing operation, when the ink is consumed from the full filling state, the displacement member 205 is displaced in a direction in which the ink remaining amount (liquid remaining amount) in the head tank 5 is decreased, so that the first sensor 251 is displaced. It is determined whether or not 205 is detected.

  When the displacement member 205 is displaced in the direction in which the remaining amount of ink in the head tank 5 decreases and the first sensor 251 detects the displacement member 205, the subsequent ink consumption is calculated, and the ink consumption is determined in advance. It is determined whether or not a predetermined liquid consumption amount (predetermined amount) has been reached.

  Here, the ink consumption is calculated by, for example, counting the number of droplets ejected for image formation or the number of droplets ejected in the idle ejection operation during the printing operation, and multiplying the count value by the droplet amount of the droplet. (This is called a soft count, and the liquid consumption measuring means is configured by the soft count.) Further, when a cleaning operation for sucking ink from the recording head 4 is performed, the amount of consumption (suction amount) by the suction is determined in advance, and the suction amount may be added.

  Then, when the ink consumption amount becomes equal to or higher than a predetermined liquid consumption amount (predetermined amount: threshold) W, the supply start position is set, and the liquid feed pump 241 is driven to rotate forward to move from the main tank 10 to the head tank 5. Ink filling (supply) is started.

  At this time, it is determined whether or not the first sensor 251 has detected the displacement member 205 of the head tank 5. When the first sensor 251 has detected the displacement member 205 of the head tank 5, the difference supply time t is further increased from that time. The head tank 5 is filled with ink by continuing driving only.

  Thereafter, the liquid feed pump 241 is stopped, and the calculated value of the ink consumption is reset.

  In this manner, the head tank 5 can be filled with ink without returning the carriage 3 to the home position even during the printing operation.

  Next, the supply flow rate setting process in the drive control of the liquid feed pump in the first embodiment of the present invention will be described with reference to the flowchart of FIG.

  First, before starting ink supply, it is determined whether the liquid feed pump 241 to be driven is one of a plurality of liquid feed pumps 241 connected to one main tank 10 (common main tank).

  Here, when the liquid feed pump 241 to be driven is one of a plurality of liquid feed pumps 241 connected to one main tank 10 (common main tank), the plurality of liquid feed pumps 241 are simultaneously driven. It is determined whether or not to do so.

  When a plurality of liquid feed pumps 241 are driven simultaneously, the supply flow rate (liquid feed amount per unit time) of the liquid feed pump 241 is set to the supply flow rate when driving one liquid feed pump 241 (this is referred to as “basic”). "Supply flow rate").

  Thereafter, it is determined whether or not the filling is performed during the printing operation. In the filling operation during printing, the supply flow rate is increased compared to the filling (supply) other than during the printing operation.

  Then, the operation proceeds to the ink supply operation.

  Here, in order to increase the supply flow rate by the liquid feed pump 241, the drive voltage or drive current applied to the drive source of the liquid feed pump 241 is increased to increase the rotation speed of the liquid feed pump 241. Alternatively, the drive duty ratio of the drive source of the liquid feed pump 241 is increased to increase the rotational speed of the liquid feed pump 241.

  Moreover, when using a tubing pump as the liquid feeding pump 241, it can prevent falling below minimum flow volume by changing the rotation speed of a liquid feeding pump with temperature. In other words, the tubing pump has a lower restoring force in a low temperature environment than in a high temperature environment, and the flow rate decreases even at the same rotation speed. Therefore, by increasing the pump rotation speed in a low temperature environment, the flow rate can be reduced. Supply shortage due to decline can be prevented.

  In this way, when a plurality of liquid feed pumps connected to one main tank are simultaneously driven, it is possible to prevent supply shortage by performing control to increase the supply flow rate.

  That is, as described with reference to FIG. 6 described above, in the configuration in which the liquid pumps 241a and 241b supply the two head tanks 5a and 5b from one main tank 10k, the two head tanks 5a and 5b are supplied with two head tanks 5a and 5b. There may be cases where they must be supplied simultaneously.

  In this case, since the plurality of liquid feed pumps 241a and 241b pull the ink from the main tank 10k to each other, the supply flow rates of the supply paths 6a and 6b vary, and the supply path 6 that does not satisfy the specified minimum flow rate is generated. there is a possibility. If the minimum flow rate is not satisfied, nozzle down (discharge failure) may occur due to insufficient supply.

  Therefore, when it is necessary to drive a plurality of liquid feed pumps 241 at the same time, the supply flow rate (liquid feed flow rate) is increased to prevent nozzle down (discharge failure) due to insufficient supply.

  Further, during the printing operation, the ink is supplied while consuming the ink in the head tank 5, so the difference between the supply amount and the consumption amount becomes the actual increase amount. By increasing the (liquid feed flow rate), nozzle down (discharge failure) due to insufficient supply is prevented.

  In the above-described embodiment, the case where the liquid is simultaneously supplied to the plurality of head tanks 5 has been described. However, the plurality of liquid supply pumps 241 are simultaneously driven in reverse to reversely send ink from the head tank 5 to the main tank 10. Sometimes, the pressure between the supply path and the main tank 10 increases due to insufficient suction amount, and the supply tube may be ruptured or the connection portion (joint) with the main tank 10 may be disconnected.

  Therefore, even when such a reverse operation is performed, the above-described inconvenience can be avoided by applying this embodiment.

  Next, drive control of the liquid feed pump in the second embodiment of the present invention will be described with reference to FIGS.

  As described above, when the plurality of liquid feed pumps 241 are simultaneously driven, if the drive start timings of the plurality of liquid feed pumps 241 overlap, the currents flowing through the liquid feed pumps 241 are instantaneously accumulated and a large current flows. This requires a power source with a large current capacity, which increases the size and cost of the device.

  Therefore, in this embodiment, by shifting the driving start timing of each liquid feeding means, the current that flows instantaneously at the start of driving can be reduced, and the current capacity of the power supply can be reduced.

  For example, in the first example shown in FIG. 18, when the ink supply to the head tanks 5a and 5b competes (when the supply operation is performed at the same time), a predetermined time a has elapsed after the liquid feed pump 241a starts to be driven. Sometimes, driving of the liquid feed pump 241b is started.

  As described above, by shifting the drive start timings of the two liquid feed pumps 241a and 241b, it is possible to minimize the accumulation of current flowing when the liquid feed pump is driven.

  In this case, the predetermined time a for shifting the drive start timing is set shorter than the time for the ink consumption of the head tank corresponding to the liquid feed pump whose drive start timing is delayed to reach the lower limit value of the ink consumption that can be normally ejected. As a result, the remaining amount of ink in the head tank whose drive start timing is delayed becomes too small, and it is possible to prevent the recording head from being nozzle-down due to insufficient ink supply to the recording head.

  Further, the predetermined time a for shifting the drive start timing is set shorter than the time for the negative pressure of the head tank corresponding to the liquid feed pump whose drive start timing is delayed to reach the negative pressure lower limit value that allows normal discharge. As a result, the negative pressure of the head tank, which is delayed in the drive start timing, becomes excessive, and insufficient ink supply to the recording head can be prevented, so that the recording head can be prevented from being nozzle-down, and the meniscus formation failure of the recording head can be prevented. Can do.

  Further, the predetermined time a can be changed according to the change in the ink discharge amount so as to be shortened when the discharge amount from the recording head is large and to be long when the discharge amount is small. Thereby, the useless stop time of the liquid feeding pump which has not started driving can be omitted.

  Further, when the sum of the drive currents of the plurality of liquid feeding pumps exceeds a predetermined threshold (predetermined value), the driving start timing is shifted by a predetermined time a, and when the sum does not exceed the threshold, the driving timing is not shifted. You can also control it.

  For example, when three liquid pumps (liquid pumps Pa, Pb, and Pc) are used, the sum of the current values of the liquid pump Pa that started driving and the liquid pump Pb exceeded the threshold value. In this case, the liquid feed pump Pc does not start driving until after a predetermined time has elapsed. In addition, when the sum of the current values of the liquid feeding pump Pa and the liquid feeding pump Pb that have started driving does not exceed the threshold value, the liquid feeding pump Pc starts driving without waiting for the elapse of a predetermined time. By doing in this way, the electric current which flows instantaneously at the time of a drive start can be reduced, without stopping a liquid feeding pump uselessly.

  Next, in the second example shown in FIG. 19, when the ink supply to the head tanks 5a and 5b competes (when the supply operation is performed simultaneously), the driving of the liquid feeding pump 241a is started and then the driving of the liquid feeding pump 241a is performed. When the number of times reaches a predetermined driving number b, driving of the liquid feeding pump 241b is started.

  By using the pump driving frequency, the driving start timing can be shifted without requiring a new means such as a timer.

  Next, in the third example shown in FIG. 20, when the ink supply to the head tanks 5a and 5b competes (when the supply operation is performed simultaneously), the liquid feed pump 241a starts to be driven and then supplied by the liquid feed pump 241a. When the supply amount to the head tank 5a to be reached reaches a predetermined supply amount c, driving of the liquid feed pump 241b is started.

  In this case, when the displacement member 205 of the head tank 5a is detected by the first sensor 251, driving of the liquid feeding pump 241b can be started.

  In the above-described embodiment, the case where the liquid is simultaneously supplied to the plurality of head tanks 5 has been described. However, the plurality of liquid supply pumps 241 are simultaneously driven in reverse to reversely send ink from the head tank 5 to the main tank 10. Even when driving is started at the same time, the current flowing through each liquid feed pump 241 is instantaneously accumulated and a large current flows.

  Therefore, even when such a reverse operation is performed, the above-described inconvenience can be avoided by applying this embodiment.

  The reverse feeding operation from the head tank 5 to the main tank 10 is performed, for example, when a negative pressure is formed in the head tank 5 or for the purpose of releasing the sticking of the supply tube.

  This reverse feed operation for releasing tube sticking is performed at the same time as the cap decapping operation to keep the recording head moisturized before printing and before the maintenance operation. I can't take it. Further, by performing a reverse feeding operation before printing, it is possible to prevent liquid from being supplied to the head tank due to tube fixation during printing, and to reliably supply liquid to the head tank. In addition, by performing the reverse operation when a certain stop time is exceeded, unnecessary operations can be omitted and wasteful power consumption can be reduced.

  In addition, before the liquid feed pump that has started driving finishes driving, the liquid feed pump that has not started driving starts to shorten the time for driving a plurality of pumps at the same time. Efficiency can be increased.

  In the present application, the “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, etc., and means a material to which ink droplets or other liquids can be attached. , 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)
3 Carriage 4, 4a to 4d Recording head (liquid ejection head)
5 Head tank 201 Tank case (liquid container)
203 Film member 205 Displacement member (Filler)
241 Liquid feed pump 251 1st sensor (1st detection means)
301 ... 2nd sensor (2nd detection means)
500 ... control unit

Claims (4)

A recording head for discharging droplets;
A head tank for storing liquid to be supplied to the recording head;
A carriage on which the recording head and the head tank are mounted;
A main tank for storing liquid to be supplied to the head tank;
At least two liquid feeding means for respectively supplying liquid from the main tank to the at least two head tanks;
Supply control means for controlling the liquid supply from the main tank to the head tank by driving the liquid feeding means,
A plurality of head tanks connected to one main tank, and a plurality of liquid feeding means for supplying liquid to each head tank;
The head tank has a displacement member that is displaced according to the remaining amount of liquid,
The carriage is provided with first detection means for detecting the displacement member,
The apparatus main body side is provided with second detection means for detecting the displacement member,
The first position of the displacement member detected by the first detection means is a position where the remaining amount of liquid in the head tank is less than the second position of the displacement member detected by the second detection means,
The supply control means includes
Detecting and holding a difference amount corresponding to a displacement amount of the displacement member between a position detected by the first detection means and a position detected by the second detection means;
When supplying the liquid from the main tank to the head tank without using the second detection means,
When the liquid consumption amount of the head tank becomes a predetermined liquid consumption amount in which the remaining amount of liquid in the head tank is smaller than the position where the displacement member is detected by the first detection means, the main tank releases the liquid consumption amount. Start liquid feeding to the head tank,
After the first detecting means detects the displacement member, it performs control to supply the difference amount,
When liquid is simultaneously supplied from the main tank to the plurality of head tanks, control is performed to increase the supply flow rate of the liquid supply means, compared to when liquid is individually supplied to the plurality of head tanks. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein when liquid feeding is simultaneously performed from the main tank to the plurality of head tanks, driving start timings of the respective liquid feeding units are shifted.   The liquid feeding means whose driving start timing is relatively delayed starts driving before the liquid consumption amount of the head tank fed by the liquid feeding means reaches a predetermined threshold at the latest. The image forming apparatus according to claim 2.   4. The image forming apparatus according to claim 1, wherein at least one of a driving current, a driving voltage, and a driving duty for the liquid feeding unit is changed to increase a supply flow rate of the liquid feeding unit. .

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