JP2010000647A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device which controls discharging by a method except by actuators. <P>SOLUTION: This inkjet recording device, for producing an image by discharging ink from a recording head 40 having a recording element board 27 provided with electrothermal converters 29 for discharging the ink from discharging ports 25, has a sub-tank 203 for generating negative pressure in the recording head 40 and a controlling part 701 for controlling the magnitude of the negative pressure generating by a negative pressure generating means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that forms an image by ejecting ink, and more particularly, to an ink jet recording apparatus in which a discharge amount is controlled.

  Conventionally, as a recording method of an ink jet recording apparatus, a method using a piezoelectric element or a method using thermal energy has been proposed. The method using a piezoelectric element is a method of recording by causing a change in pressure in the liquid flow path by changing the volume of the liquid flow path by mechanical deformation of the piezoelectric element and discharging a droplet from the discharge port. is there. In the method using thermal energy, bubbles are instantaneously generated by abruptly generating heat from the electrothermal converter disposed in the liquid flow path, and droplets are discharged from the discharge port by the discharge force generated by the generation of the bubbles. This is a method of recording by discharging.

  Among them, an inkjet recording system head that uses thermal energy to eject ink droplets can arrange discharge ports at high density, and therefore can perform high-resolution recording. A recording head using a piezoelectric element as an energy generating element is superior in terms of ejecting ink with high viscosity and head life. In addition, a recording head using an electrothermal transducer as an energy generating element can easily be miniaturized, and can sufficiently overcome the advantages of IC technology and micromachining technology that have made remarkable progress in technology and improved reliability in the recent semiconductor field. Can be used in two minutes. For this reason, a recording head using an electrothermal transducer is advantageous in that it can be easily mounted at high density and the manufacturing cost is low.

  Next, an example of an ink supply configuration and supply sequence of a conventional serial printer or full line printer will be described with reference to FIG.

  As shown in FIG. 13A, an ink supply system having a conventional configuration includes a sub tank 2203 and a main tank 2205, and the sub tank 2203 and the main tank 2205 are connected to each other through tubes. The sub tank 2203 is an ink tank for supplying ink to the recording head 2040 and the recording head 2040 to make the negative pressure of the head constant. The main tank 2205 is an ink tank for supplying ink to the sub tank 2203. The liquid level of the sub tank 2203 is lower than that of the main tank 2205, and ink flows from the main tank 2205 to the sub tank 2203 only by opening the valve 2301.

  A time-series flow of ink supply in the ink supply system having such a configuration will be described with reference to FIG.

  First, in order to forcibly fill the sub tank 2203 with ink, when the power is turned off, the closed valve 2301 is opened, and the pump 2501 is driven in the direction of the arrow in FIG. Since the sub tank 2203 is provided with electrodes 2401 to 2404 at four levels, the ink level in the sub tank 2203 can be detected. By having such a configuration, the liquid level can be controlled at the time of forced filling of the sub tank.

  Next, the initial ink filling from the sub tank 2203 to the recording head 2040 will be described. First, the valve 2301 disposed between the tube connecting the sub tank 2203 and the main tank 2205 and the valve 2304 communicating the inside of the sub tank 2203 with the atmosphere are closed. On the other hand, when the power is turned off, the closed valves 2302 and 2303 are opened. Thereafter, the ink in the sub tank 1203 is supplied to the recording head 2040 by driving the pump 2501 in the direction of the arrow (forward rotation) in FIG. In this way, the pump 2501 is normally rotated so that the recording head 2040 is basically filled with ink.

After the recording head 2040 is filled with ink, a recording operation is performed. During the recording operation, the valves 2302 and 2303 are opened so that the ink is refilled from the sub tank 2203. Further, by opening the valve 2304, the inside of the sub tank 2203 is set to the same pressure as the atmosphere. Although the valve 2301 is basically closed, when continuous recording is performed and the amount of ink in the sub tank 2203 decreases, the valve 2301 is opened so that the sub tank 2203 is filled with ink from the main tank 2205. To.
JP 11-348300 A

  An ink jet recording apparatus using an electrothermal transducer as an actuator discharges ink by generating boiling of ink as the electrothermal transducer generates heat. For this reason, when the ejection is continued, the recording element substrate becomes in a high temperature state due to the heat generated by the electrothermal transducer. Further, it is necessary to continuously perform the recording operation without pausing to achieve high-speed recording. As a result, the recording element substrate is in a higher temperature state.

  In general, when a temperature distribution is generated in a recording element substrate, the ejection amount of ink droplets ejected from each nozzle increases in proportion to the temperature. The amount of change in a recent print head tends to vary by about 1 to several percent as the ink temperature increases by 1 ° C. Therefore, for example, assuming that the variation in the ejection amount when the ink temperature rises by 1 ° C. is 1%, the ejection amount changes by 30% when the temperature of the recording element substrate is, for example, 30 ° C. due to continuous recording. For this reason, there is a need for a technique capable of reducing fluctuations in the ejection amount even when the temperature of the recording element substrate rises due to continuous recording.

  Further, when the actuator disposed on the recording element substrate is a piezoelectric element, the ejection amount can be varied by positively controlling the displacement of the diaphragm. In order to perform further discharge amount control, it is necessary to review the configuration of the apparatus, but this increases the cost of the apparatus.

  In view of the above problems, an object of the present invention is to provide an ink jet recording apparatus capable of controlling ejection by means other than an actuator.

  To achieve the above object, an ink jet recording apparatus according to the present invention forms an image by ejecting ink by a recording head having a recording element substrate provided with an actuator for ejecting ink from an ejection port. The recording head includes a negative pressure generating means for generating a negative pressure in the recording head, and a control means for controlling the magnitude of the negative pressure generated by the negative pressure generating means.

  According to the present invention, in an ink jet recording apparatus, it is possible to perform discharge control by means other than an actuator.

Next, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
[Configuration of ink supply system]
FIG. 1 shows a configuration diagram of an ink supply system and an ink supply sequence diagram of the ink jet recording apparatus according to the present embodiment.

  First, the configuration of the ink supply system of the ink jet recording apparatus according to the present embodiment will be described with reference to FIG.

  The ink supply system of the ink jet recording apparatus includes a recording head 40, a sub tank 203, a main tank 205, valves 301 to 304, pumps 501, 502, a waste ink tank 206, a cap 601, a control unit 701, A height adjustment stage 702.

  A sub tank 203 serving as an ink storage unit is a tank for supplying ink to the recording head 40 and controlling the negative pressure of the head, and is placed on a height adjustment stage 702 that adjusts the height of the sub tank 203. Yes. The sub tank 203 functions as a negative pressure generating means as will be described later. The height adjusting stage 702 adjusts the position height of the sub tank 203 with respect to the recording head 40.

  The main tank 205 stores ink for supplying ink to the sub tank 203. The recording head 40, the sub tank 203, and the main tank 205 are connected by tubes. A valve 302 is arranged on a tube connecting the recording head 40 and the sub tank 203. A valve 301 and a pump 501 are arranged on a tube connecting the sub tank 203 and the main tank 205. A tube from the recording head 40 is connected to a tube connecting the valve 301 and the pump 501, and a valve 303 is disposed on the tube from the recording head 40. A valve 304 is disposed at a communication portion that communicates the inside of the sub tank 203 with the atmosphere. A pump 502 is disposed in a tube connected to a cap 601 for capping the recording head 40, and the waste ink is discharged to the waste ink tank 206 by the pump 502.

  Also, the sub tank 203 is provided with electrodes 401 to 404 at four levels, and the ink liquid level in the sub tank 203 is detected by the electrodes 401 to 404. The liquid level of the sub tank 203 is lower than that of the main tank 205, and ink can flow by simply opening the valve 301.

  A recording element substrate 27 (described later) on which the recording head 40 is mounted is provided with a temperature sensor (not shown) for measuring the temperature.

A control unit 701 serving as a control unit monitors the temperature of the recording element substrate 27 and adjusts the height of the height adjustment stage 702 during continuous recording based on a chip temperature-negative pressure control line calibrated in advance. . The control unit 701 also performs opening / closing of the valves 301 to 304 and driving control of the pumps 501 and 502.
[Negative pressure control of ink supply system]
Next, negative pressure control in the ink supply system of the present embodiment will be described with reference to FIGS. 1 (a) and 1 (b).

  First, FIG. 2 shows an example of the temperature of the recording element substrate 27 when 200 sheets are continuously recorded with 100% solid using the recording head 40 whose actuator is a heat generating element and the ejection amount is 2 pl. When solid images are continuously recorded on the recording medium, a difference occurs in the chip temperature of the recording head 40 between the initial recording time and the continuous recording time (for example, continuous recording of 200 sheets) as shown in FIG. In FIG. 2, a temperature difference of about 30 ° C. occurs between the start of recording and the continuous recording of 200 sheets. Assuming that the variation in the ejection amount when the ink temperature rises by 1 ° C. is an increase of about 1%, if the recording is continued as it is, the difference in the ejection amount of about 30% between the start of recording and the continuous recording of 200 sheets. Will occur. Therefore, if a temperature difference of 30 ° C. occurs between the start of recording and the continuous recording of 200 sheets, 2 × 1.3 = 2.6 pl, and the ejection amount during continuous recording of 200 sheets with respect to the start of recording greatly increases. It becomes.

  On the other hand, when the negative pressure applied to the recording head is changed, as shown in FIG. 3, at a high recording duty, the negative pressure increases, that is, the image density decreases as the negative pressure increases. This indicates that the discharge amount decreases as the negative pressure increases at a high recording duty. That is, in order to increase the negative pressure in the recording head 40, the discharge amount can be reduced as a whole by increasing the negative pressure in the sub tank 203 communicating with the recording head 40.

  In this embodiment, this physical phenomenon is used to control the discharge amount when the head is heated when the actuator disposed on the recording element substrate 27 is a heating element. As shown in FIG. 4, by performing continuous recording, the discharge amount increases as the chip temperature rises (in FIG. 4, the line indicated by “at a constant negative pressure”). The negative pressure 203 is also increased (broken line in FIG. 4). By performing such control, it is possible to suppress an increase in discharge amount during continuous recording (a line indicated by “during active negative pressure control” in FIG. 4).

  Hereinafter, the negative pressure control of this embodiment will be described in more detail.

  First, in order to forcibly fill the sub tank 203 with ink, when the power is turned off, the closed valve 301 is opened, and the pump 501 is driven in the direction of the arrow in FIG.

  Next, the initial ink filling from the sub tank 203 to the recording head 40 will be described.

  First, the valves 301 and 304 are closed. When the power is turned off, the closed valves 302 and 303 are opened. After that, the ink in the sub tank 203 is supplied to the recording head 40 by driving the pump 501 in the direction of the arrow in FIG. In this way, the ink is filled into the recording head 40 basically by rotating the pump 501 forward.

  After the recording head is filled with ink, a recording operation is performed. Also during the recording operation, the valve 302 and the valve 303 are opened so that the ink is refilled from the sub tank 203, and further, the valve 304 is opened to set the inside of the sub tank 203 to the same pressure as the atmosphere. Although the valve 301 is basically closed during recording, continuous recording is performed, and when the amount of ink in the sub tank decreases, the valve 301 is opened and the main tank 205 fills the sub tank 203 with ink. (The state of recording 1 in FIG. 1B).

  Next, an active negative pressure control method in this embodiment will be described.

  When the temperature of the recording element substrate 27 increases as a result of continuous recording, the ink discharge amount increases as compared with the temperature of the recording element substrate 27 during initial recording. For this reason, in order to perform continuous recording at a uniform image density, it is necessary to perform ejection amount control.

  Therefore, when the control unit 701 determines that the temperature of the recording element substrate 27 has increased based on the measurement result of the temperature sensor, the following control is performed. The control unit 701 drives the height adjustment stage 702 to lower the height of the sub tank 203 with respect to the recording head 40 and increase the negative pressure applied to the recording head 40. That is, the water level difference is increased by lowering the liquid level in the sub tank 203 with respect to the ink level in the recording head 40. Thereby, it is possible to suppress an increase in the discharge amount accompanying the temperature rise of the recording element substrate 27.

  On the other hand, when the control unit 701 determines that the temperature of the recording element substrate 27 has decreased based on the measurement result of the temperature sensor, the following control is performed. The controller 701 drives the height adjustment stage 702 to increase the height of the sub tank 203 with respect to the recording head 40, thereby reducing the negative pressure applied to the recording head 40 and controlling the discharge amount.

  At this time, in order to maintain the liquid level in the sub tank 203, the valve 301 is opened and closed as necessary to maintain the ink height in the sub tank 203 (in FIG. Status). That is, although a certain amount of ink is always filled in the sub tank 203, active negative pressure control can be achieved by controlling the height of the adjustment stage 702. Further, the pressure in the sub tank 203 is maintained at atmospheric pressure.

As described above, it is possible to prevent an increase in the discharge amount accompanying the temperature rise of the recording element substrate 27 during continuous recording.
[Configuration of recording head]
Next, a configuration example of the recording element substrate 27 having the electrothermal transducer provided in the recording head 40 will be described. FIG. 5 shows a broken structure of the recording element substrate 27, and FIG. 6 shows the AA ′ cross-sectional structure thereof. The recording element substrate 27 according to the present embodiment includes a discharge energy generation unit, a common ink chamber 31, an ink flow path 33, a discharge port 25, and the like on a silicon substrate having a thickness of 0.5 mm to 1 mm using a film forming technique. Formed. That is, the recording element substrate 27 is formed with an elongated ink supply port 28 penetrating therethrough.

  On both sides of the ink supply port 28, a plurality of electrothermal transducers 29 arranged in two rows at predetermined intervals along the conveyance direction of the recording medium, that is, the longitudinal direction of the ink supply port 28 are shifted from each other by a half pitch. Each of them forms a discharge energy generating part. On the recording element substrate 27, in addition to the electrothermal transducer 29, an electrode terminal 30 for electrical connection between the electrothermal transducer 29 and the recording apparatus main body, and an electrical wiring (not shown) formed of aluminum or the like. Etc. are formed by a film forming technique.

  An electric wiring board (not shown) connected to the electrode terminal 30 formed on the recording element substrate 27 is for applying an electric signal for ejecting ink to the recording element substrate 27. This electrical wiring board has electrical wiring corresponding to the recording element substrate 27 and a contact part that is located at the end of the electrical wiring and receives an electrical signal from the recording apparatus main body. A drive signal for the electrothermal transducer 29 is given from a drive IC (not shown) via the electrical wiring board, and at the same time, drive power is supplied to the electrothermal transducer 29.

  On the recording element substrate 27, an upper plate member 32 having a plurality of ejection ports 25 respectively facing the electrothermal transducer 29 via a common ink chamber 31 communicating with the ink supply port 28 is formed. That is, between the upper plate member 32 and the recording element substrate 27, ink flow paths 33 communicating with the individual ejection ports 25 and the common ink chamber 31 are formed, and between the adjacent ink flow paths 33. A partition wall 34 is formed. The common ink chamber 31, the ink flow path 33, the partition wall 34, and the like are formed together with the upper plate member 32 by the photolithography technique in the same manner as the ejection port 25.

  The liquid supplied from the ink supply port 28 into each ink flow path 33 is supplied with a drive signal to the electrothermal converter 29 facing the corresponding ink flow path 33, so that the heat generated by the electrothermal converter 29 is generated. It boiles and is discharged from the discharge port 25 by the pressure of bubbles generated thereby.

  In the present invention, in addition to the electrothermal transducer described above, a piezoelectric element can also be used for the recording element substrate. A recording element substrate when such an actuator is a piezoelectric element will be described.

As shown in FIG. 7, in the recording element substrate using the piezoelectric element, a diaphragm 1014 having an individual electrode 1033 on the lower surface is disposed on a substrate 1012 having a common electrode 1032 on the upper surface. Further, a top plate 1013 constituting a common ink chamber 1034, an ink flow path 1016, and an ejection port 1017 is arranged on the vibration plate 1014. There is an appropriate gap between the common electrode 1032 and the individual electrode 1033, and this gap is filled with the ferroelectric liquid crystal 1031. By applying a pulse voltage between the individual electrode 1033 and the common electrode 1032, the vibration plate 1014 is vibrated by the electrostatic force, thereby changing the volume of the ink flow path 1016, and ink is ejected from the ejection port 1017. Discharged.
[Configuration example of recording device]
Both the serial type method and the full line type method can be applied to the recording apparatus of the present invention. The serial type method is a method in which an image is formed on a recording medium by a reciprocating operation of a carriage on which a recording head is mounted. On the other hand, in the full line type system, a long inkjet head having a width equal to or larger than the width of the recording medium is fixed to the printer housing, and the recording medium is ejected from the long inkjet head. In this method, an image is formed.

  First, the serial type configuration will be described. FIG. 8 shows the external appearance of the mechanism portion of the serial inkjet recording apparatus according to this embodiment. In the serial printer, a carriage 231 on which the recording head 40 is mounted is attached to the timing belt 233. The timing belt 231 is rotated by driving the carriage motor 234, and recording is performed on the recording medium S by the carriage 231 reciprocating left and right on the guide shaft 232. For paper feeding, a paper feeding motor (not shown) is provided in the recording apparatus main body.

  The serial type recording head 40 is provided with a recording element substrate 27 for ejecting inks corresponding to black, cyan, magenta and yellow. Further, ink is supplied from the main tank 205 (not shown) to the sub tanks 203a to 203d via the ink supply tubes 204a to 204d.

  Next, the configuration of a full-line type ink jet recording apparatus will be described with reference to FIG. Compared with the serial type, the full line type capable of recording on the recording medium with a single transport operation enables overwhelming high-speed recording.

  In the block 42, recording heads 40Bk, 40Y, 40M, 40C and a reading head 41 are provided. The recording heads 40Bk, 40Y, 40M, and 40C are recording heads corresponding to black, yellow, magenta, and cyan ink colors, respectively. The read head 41 is for detecting the number of ejection and non-ejection outlets in the block 42.

  The capping unit 43 seals the capping unit 43 against the recording heads 40C to 40Bk by pulling up the block 42 at the time of non-recording such as standby. Further, the capping unit 43 serves as a tray for waste ink that is fed from a recovery pump (not shown) and an ink supply system during circulation recovery and pushed out from the ejection port. Waste ink collected in the capping unit 43 is guided to a waste ink tank 206.

  The electrification adsorption belt 44 is an endless belt for transporting a recording medium disposed to face each of the recording heads 40Bk, 40Y, 40M, and 40C at a predetermined interval. The back platen 45 is disposed to face each recording head via the charging adsorption belt 44. The paper feed cassette 46 stores a recording sheet 47 such as plain paper and is detachably attached to the apparatus main body. The pickup roller 48 feeds and feeds only one uppermost recording sheet 47.

  The conveyance roller 49 is a roller for conveying the recording sheet 47 sent out from the pickup roller 48 to the conveyance path 50. The transport roller 51 is disposed on the exit side of the transport path 50. Ink droplets attached to the recording sheet 47 by recording are dried and fixed by hot air from the heater 53 and the fan 54. The discharge roller 55 is a roller for discharging the recording sheet 47 after fixing to the outside of the apparatus, and the discharged recording sheet 47 is sequentially stocked on the tray 56.

  Next, the operation of the full line type recording apparatus having the above configuration will be described.

  First, the recording operation will be described. When a recording start operation is performed, a recording sheet 47 of a designated size is sent out from the paper feed cassette 46 by a pickup roller 48. The fed recording sheet 47 is rotated in a precharged state by the conveying rollers 49 and 51 and is placed on the charging adsorption belt 44 having a planar shape by the back platen 45. In conjunction with the leading end of the recording sheet 47 arriving at the lower part of each of the heads 40C, 40M, 40Y, and 40Bk, the electrothermal conversion element of each recording head is driven in accordance with the image data. By this driving, ink droplets corresponding to the image information fly from the ejection port toward the surface of the recording sheet 47, and recording is performed by the landing.

  When the recording sheet 47 has poor hygroscopicity, the droplets adhering to the surface are not dried and are rubbed to cause recording stains. Therefore, forced drying is performed by the heater 53 and the fan 54 to fix them. The recording sheet 47 that has been fixed is discharged to a tray 56 by a discharge roller 55.

  As described above, a recording image corresponding to each of the cyan, magenta, yellow, and black inks is given to each recording head, whereby a color image is formed at a higher speed than a normal serial printer.

Next, a cross-sectional view of the full-line type recording head 40 is shown in FIG. The recording head 40 includes a tank unit 107 that stores predetermined ink, a recording element substrate 27, a support substrate 102 that supports the recording element substrate 27, and an individual filter 105 and a filter plate 104. The recording element substrate 27 has a plurality of ink ejection openings for ejecting ink from the tank 106 and ink from the tank unit 107. The full-line type supply 40 can record the width of the recording medium by one paper conveyance by arranging a plurality of recording element substrates 27 on the support substrate 102 along the longitudinal direction of the head. Configures the head width.
(Second Embodiment)
FIG. 11 shows a configuration diagram of an ink supply system and an ink supply sequence diagram of the ink jet recording apparatus according to the present embodiment. In addition, about the part which overlaps with 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In this embodiment, the waste ink tank 206 is used as a negative pressure control tank in order to perform active negative pressure control of the sub tank 203 during continuous recording.

  In this embodiment, the waste ink tank 206, the sub tank 203 and the main tank 205 are connected via a tube 603. That is, the tube 603 is connected to a tube connecting the sub tank 203 and the main tank 205. The tube 603 is provided with a valve 306 and a filtration filter 307. In this embodiment, a tube that directly connects the waste ink tank 206 and the sub tank 203 is also provided. A valve 305 and a pump 502 are arranged in this tube.

  Further, a waste ink tank 206 for storing waste ink generated at the time of pressure recovery and a cap 601 communicate with each other through a tube 602. The tube 602 is provided with a pump 502.

  The ink stored in the waste ink tank 206 is basically recycled and reused. That is, the ink stored in the waste ink tank 206 is filtered by the filtration filter 307 and then filled again into the sub tank 203 or the main tank 205 by the pump 501.

  In addition, when the ink stored in the cap 601 is removed to the waste ink tank 206 when the pressure is recovered, the control unit 701 drives the pump 502.

  Next, operation control of the ink supply system in the ink jet recording apparatus of the present embodiment having the above-described configuration will be described with reference to FIG.

  When recording is performed with the sub-tank liquid level being kept constant without performing active negative pressure control (the state of recording 1 in FIG. 11B), the control unit 701 outputs to the outputs of the electrodes 401 to 404. In response, the valve 301 is opened. As a result, the main tank 205 fills the sub tank 203 with ink.

  When the temperature of the recording element substrate 27 rises due to continuous recording, the control unit 701 performs active negative pressure control. That is, the ink discharge amount is suppressed by increasing the negative pressure applied to the recording head 40. In order to increase the negative pressure applied to the recording head 40, it is necessary to lower the ink level in the sub tank 203 with respect to the ink level in the recording head 40. Therefore, the control unit 701 opens the valve 305 in the tube between the sub tank 203 and the waste ink tank 206 and drives the pump 502. As a result, the ink in the sub tank 203 is moved to the waste ink tank 206. Since the ink level in the sub tank 203 is lowered by the amount of ink moved to the waste ink tank 206, the ink level in the sub tank 203 is equal to the ink level in the recording head 40. On the other hand, it becomes lower (the state of recording 2 in FIG. 11B). Thereby, the negative pressure applied to the recording head 40 can be increased.

Even when the temperature of the recording element substrate 27 decreases, the control unit 701 performs active negative pressure control. In this case, it is necessary to increase the ink discharge amount by reducing the negative pressure applied to the recording head 40. Therefore, the control unit 701 opens the valve 306, closes the valve 301, and causes the pump 501 to rotate forward. As a result, the ink in the waste ink tank 206 is moved into the sub tank 203. Since the ink level in the sub tank 203 is increased by the amount of ink moved from the waste ink tank 206, the ink level in the sub tank 203 is equal to the ink level in the recording head 40. (State of record 3 in FIG. 11B). Thereby, the negative pressure applied to the recording head 40 can be kept low. This operation is also performed when the amount of ink in the sub tank 203 becomes smaller during recording.
(Third embodiment)
FIG. 12 is a configuration diagram of an ink supply system of the ink jet recording apparatus according to the present embodiment. In addition, about the part which overlaps with 1st and 2nd embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the first and second embodiments, the head level difference is adjusted by moving the ink level in the sub tank 203 up and down with respect to the ink level in the recording head 40, so that the recording head 40 can be adjusted. The example which controls this negative pressure was shown. On the other hand, in this embodiment, the negative pressure applied to the recording head 40 is controlled by adjusting the internal pressure of the sub tank 203.

  The outline of the internal pressure adjusting mechanism of the sub tank 203 of this embodiment will be described below.

  In the present embodiment, the ink in the sub tank 203 is stored in a flexible bag 801 made of a flexible material. An elastic member 803 is attached to the flexible bag 801. Further, the elastic member 803 is connected to a drive source 802 that is driven based on a signal from the control unit 701. That is, in the present embodiment, the internal pressure of the flexible bag 801 is controlled by driving the drive source 802 based on the signal from the control unit 701 and inflating and contracting the flexible bag 801 via the elastic member 803. Do. Specifically, when the drive source 802 pulls the elastic member 803 (in the direction of arrow A in FIG. 12), the flexible bag 801 expands, and the pressure inside the flexible bag 801 decreases. On the other hand, when the drive source 802 pushes the elastic member 803 (in the direction of arrow B in FIG. 12), the flexible bag 801 contracts, and the pressure inside the flexible bag 801 increases.

  Next, a negative pressure control method in the ink supply system of the present embodiment having the above configuration will be described.

  When the temperature of the recording element substrate 27 rises due to continuous recording, the control unit 701 suppresses the ink ejection amount by increasing the negative pressure applied to the recording head 40. In order to increase the negative pressure applied to the recording head 40, it is necessary to decrease the pressure inside the flexible bag 801. Therefore, the control unit 701 drives the drive source 802 to pull the elastic member 803. As a result, the flexible bag 801 is inflated, the pressure inside the flexible bag 801 is reduced, and the negative pressure applied to the recording head 40 is increased, so that the ink discharge amount can be suppressed.

  On the other hand, when the temperature of the recording element substrate 27 decreases, the control unit 701 increases the ink discharge amount by reducing the negative pressure applied to the recording head 40. In order to reduce the negative pressure applied to the recording head 40, it is necessary to increase the pressure inside the flexible bag 801. Therefore, the control unit 701 drives the drive source 802 so as to push in the elastic member 803. As a result, the flexible bag 801 contracts, the pressure inside the flexible bag 801 increases, and the negative pressure applied to the recording head 40 decreases, so that the ink discharge amount can be suppressed.

The basic ink supply sequence is the same as the sequence shown in FIG.
(Fourth embodiment)
In the present embodiment, a description will be given of the point that the discharge amount control can be performed using the active negative pressure control in each of the above-described embodiments.

  For example, when the actuator is a piezoelectric element, the discharge amount is basically controlled by controlling the diaphragm 1014. By adding the active negative pressure control of the present invention to this basic control, various discharge amount control becomes possible.

  For example, in a serial type recording apparatus that performs recording by moving the carriage 231 left and right, it is assumed that there is a solid black image in a part of one printed image. In this case, when recording the portion of the solid black image, if the total discharge amount is increased by the active negative pressure control of the present invention, the number of left and right reciprocations of the carriage can be reduced, leading to an increase in recording speed. . That is, when recording a portion where a fine image such as a solid image portion is not required, the discharge amount can be made larger than usual by lowering the negative pressure applied to the recording head 40 in order to prioritize the recording speed. it can.

  As described above, the control unit 701 of the present invention controls the ejection amount according to the image density data not only when the actuator is a piezoelectric element but also when the actuator is a heating element.

  In each of the above embodiments, the configuration having the sub tank and the main tank has been described as an example. However, the configuration can be applied to a configuration having only the main tank. In this case, it is possible to adjust the position height of the main tank that is the ink storage unit, increase or decrease the amount of ink in the main tank, or the main tank may have a flexible bag.

1 is a configuration diagram of an ink supply system and an ink supply sequence diagram of an ink jet recording apparatus according to a first embodiment of the present invention. It is a graph which shows the relationship between the temperature of a recording element board | substrate at the time of continuous recording, and discharge amount. It is a graph showing the relationship between the negative pressure of a sub tank and image density. It is a graph which shows the change of the discharge amount at the time of the active negative pressure control of this invention. 1 is a perspective view of a recording element substrate to which the present invention is applicable. FIG. 6 is a cross-sectional view of the recording element substrate shown in FIG. 5. It is sectional drawing of one example of the recording element board | substrate using the piezoelectric element applicable to this invention. 1 is a partial schematic diagram of a serial type ink jet recording apparatus applicable to the present invention. 1 is a side sectional view of a full line type ink jet recording apparatus applicable to the present invention. FIG. 3 is a cross-sectional view of a full line type recording head applicable to the present invention. FIG. 5 is a configuration diagram of an ink supply system and an ink supply sequence diagram of an ink jet recording apparatus according to a second embodiment of the present invention. It is a block diagram of the ink supply system of the inkjet recording device of the 3rd Embodiment of this invention. It is a block diagram and an ink supply sequence diagram of an ink supply system in an example of a conventional ink jet recording apparatus.

Explanation of symbols

25 discharge port 29 electrothermal transducer 40 recording head 203 sub tank 701 control unit

Claims (13)

In an inkjet recording apparatus that forms an image by ejecting ink by a recording head having a recording element substrate provided with an actuator for ejecting ink from an ejection port.
Negative pressure generating means for generating a negative pressure in the recording head;
An ink jet recording apparatus comprising: control means for controlling the magnitude of the negative pressure generated by the negative pressure generating means.   The control means increases the negative pressure generated by the negative pressure generating means when the ink discharge amount from the recording head increases, and the negative pressure when the ink discharge amount from the recording head decreases. The inkjet recording apparatus according to claim 1, wherein the negative pressure generating unit is controlled so as to reduce a negative pressure generated by the generating unit.   The inkjet recording apparatus according to claim 2, further comprising a temperature sensor that measures a temperature of the recording element substrate, wherein the control unit controls the negative pressure generating unit based on a measurement result of the temperature sensor.   When it is determined from the measurement result of the temperature sensor that the temperature of the recording element substrate has increased, the control unit increases the negative pressure generated by the negative pressure generating means, and the temperature of the recording element substrate decreases. The inkjet recording apparatus according to claim 3, wherein when it is determined that the negative pressure generated by the negative pressure generating means is reduced.   The inkjet recording apparatus according to claim 2, wherein the control unit controls the negative pressure generation unit based on image density data.   6. The ink jet recording apparatus according to claim 1, wherein the negative pressure generating unit includes an ink storage unit that supplies ink stored therein to the recording head.   The ink jet recording apparatus according to claim 6, wherein the control unit adjusts a liquid level height of ink in the ink storage unit with respect to the recording head.   A height adjusting unit that adjusts a position height of the ink storing unit with respect to the recording head is provided, and the control unit controls the height adjusting unit to control the liquid level height of the ink in the ink storing unit. The inkjet recording apparatus according to claim 7, wherein the adjustment is performed.   The ink jet recording apparatus according to claim 7, wherein the control unit adjusts the liquid level height of the ink in the ink storage unit with respect to the recording head by increasing or decreasing the amount of ink in the ink storage unit.   The inkjet recording apparatus according to claim 6, wherein the control unit adjusts a pressure in the ink storage unit.   The ink jet recording apparatus according to claim 10, further comprising means for inflating or contracting a flexible bag that stores ink in an inside provided in the ink storing section.   The ink jet recording apparatus according to claim 1, wherein the actuator is an electrothermal transducer.   The ink jet recording apparatus according to claim 1, wherein the actuator is a piezoelectric element.

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