JP2010058412A - Ink-jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet printer capable of measuring the internal pressure of a back pressure holding device without making a pressure detection means contact an ink. <P>SOLUTION: The ink-jet printer includes recording heads 11A to 11C for discharging the ink from an outlet port to a recording medium, and the back-pressure holding device 12 which makes the ink feed to the recording head while storing it on an ink supply course leading to the recording head and maintains the internal pressure of the outlet port to be negative. In the back-pressure holding device 12, a communication opening to outside air 123a formed in the upper part is provided with a channel 17 branched in the two directions. One side of the channel 17 is used as a pressure detection channel 17a connected to a pressure detection means SP1 for detecting the internal pressure of the back-pressure holding device 12, and other side is used as a channel opening to outside air 17b connected to an opening port to outside air 17c through a valve opening to outside air V3, and at the same time the pressure detection means SP1 is arranged in the position higher than the channel opening to outside air 17b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet printer, and more specifically, is provided above the recording head on an ink supply path to the recording head, supplies ink to the recording head while storing ink, and discharges the inside of the ejection port to a predetermined negative pressure. The present invention relates to an ink jet printer including a back pressure maintaining device that maintains pressure.

  In an inkjet printer that performs recording by ejecting ink from a discharge port to a recording medium, it is known that ink discharge can be maintained well by maintaining the pressure (back pressure) inside the discharge port at a predetermined negative pressure. It has been.

  For this reason, conventionally, a back pressure maintaining device that supplies ink to the recording head while storing ink is interposed on an ink supply path for supplying ink to the recording head, and the pressure of the back pressure maintaining device is controlled. The control is performed so that a predetermined back pressure is applied to the inside of the ejection port of the recording head.

In this case, in order to properly maintain the back pressure inside the discharge port of the recording head, it is necessary to manage the pressure of the back pressure maintenance device. For this purpose, the back pressure maintenance device is provided with a pressure sensor to maintain the back pressure. It is necessary to measure the pressure of the device.
JP 2006-150745 A JP 2005-34999 A

  Inkjet printers are now used in various fields, and a wide variety of inks are used. Here, when considering applying the back pressure maintaining device to various types of ink, there are the following problems.

  Some inks have corrosive properties. When such corrosive inks are used and stored in the back pressure maintenance device, they are non-contact so that the pressure sensor does not come into contact with the ink. It is necessary to be able to measure the pressure in the back pressure maintenance device. In general, the back pressure maintenance device has an air release valve in order to return the inside to the atmospheric pressure, and if a pressure sensor is provided in parallel with a passage communicating with the air release valve, the back pressure maintaining device is in the vicinity of the pressure sensor by long-term use. In addition, the air in the back pressure maintaining device dissolves in the ink, so that the liquid level rises and comes into contact with the pressure sensor, which may cause destruction of the pressure sensor.

  In addition, in order to maintain the discharge performance of the recording head, there is a case where a maintenance operation for sucking ink is performed by bringing the cap into close contact with the discharge port and making the inside of the cap have a negative pressure. By repeating this suction, the pressure in the back pressure maintaining device is repeatedly reduced, and there is a possibility that the liquid level rises and comes into contact with the pressure sensor as described above. The same applies to the case where ink is sucked by increasing the suction pressure in order to further improve the cleaning performance of the recording head.

  Therefore, an object of the present invention is to provide an ink jet printer capable of measuring the pressure in the back pressure maintaining device without the pressure detecting means contacting the ink.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

  According to a first aspect of the present invention, a recording head that discharges ink from a discharge port to a recording medium, and supplies the recording head while storing ink on an ink supply path to the recording head. An ink jet printer provided with a back pressure maintaining device for maintaining the inside at a predetermined negative pressure, wherein the back pressure maintaining device is provided with a flow path branched in two directions at an air communication port formed at an upper portion. One of the flow paths is a pressure detection flow path connected to a pressure detection means for detecting the pressure in the back pressure maintenance device, and the other is open to the atmosphere via an air release valve. The ink jet printer is characterized in that it is a flow path and the pressure detecting means is disposed at a position higher than the atmosphere open flow path.

  According to a second aspect of the present invention, the back pressure maintaining device includes a flexible membrane and a spring that urges the membrane in a direction to inflate the membrane, and the membrane is inflated by the urging force of the spring. The inkjet printer according to claim 1, wherein the inside of the discharge port is maintained at a predetermined negative pressure.

  According to a third aspect of the present invention, there are provided a plurality of the recording heads, and the back pressure maintaining device supplies ink to the plurality of recording heads in common. It is a printer.

  According to a fourth aspect of the present invention, there is provided control means for calibrating the back pressure maintaining device by opening the atmosphere release valve and opening the atmosphere release flow path to the atmosphere when the printer power is turned on. Item 4. The inkjet printer according to Item 1, 2 or 3.

  According to a fifth aspect of the present invention, there is provided control means for calibrating the back pressure maintaining device by opening the atmosphere release valve at regular intervals after the printer power is turned on to release the atmosphere release flow path to the atmosphere. It is an inkjet printer in any one of Claims 1-4 characterized by the above-mentioned.

  According to a sixth aspect of the present invention, there is provided maintenance means for sucking ink by bringing a cap into close contact with the discharge port of the recording head and making the inside of the cap have a negative pressure, and after the maintenance by the maintenance means, The inkjet printer according to claim 1, further comprising a control unit that opens a release valve to open the atmosphere release flow path to the atmosphere and calibrates the back pressure maintenance device.

  ADVANTAGE OF THE INVENTION According to this invention, the ink jet printer which can measure the pressure in a back pressure maintenance apparatus, without a pressure detection means contacting with ink can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram showing an outline of a main part of an ink jet printer according to the present invention. This ink jet printer mainly includes a head that ejects ink, and includes a printer main body 100 that performs printing on a recording medium such as paper, fabric, and plastic sheet, and an ink rack 200 that mainly includes ink supplied to the head. It is configured.

  The printer main body 100 is supplied with ink from the ink rack 200 and is driven and controlled by a print control unit (not shown). The carriage 1 is mounted with a number of heads 11A to 11C, and the heads 11A to 11C on the carriage 1 are mounted. And a maintenance unit 2 for performing maintenance.

  On the carriage 1, a plurality of heads 11 </ b> A to 11 </ b> C that are arranged such that discharge port surfaces 11 a that discharge ink from a large number of discharge ports respectively face the lower surface according to print data, and ink supplied from the ink rack 200. Is stored, and a predetermined back pressure is applied to each of the heads 11A to 11C, thereby having a damper 12 that functions to maintain a predetermined negative pressure in the discharge ports of the heads 11A to 11C. The damper 12 can communicate with the atmosphere via an atmosphere release valve V3 and a filter 13 which are electromagnetic valves, and communicates with the back pressure air pressure sensor SP1. The back pressure air pressure sensor SP1 allows the pressure in the damper 12 to be communicated. Is supposed to be detected. 15A to 15C are ink supply pipes connecting the damper 12 and the heads 11A to 11C, V4 to V6 are on-off valves made up of electromagnetic valves provided in the ink supply pipes 15A to 15C, and SH4 is a liquid level in the damper 12. It is a liquid level sensor to detect.

  The air release valve V3 and the open / close valves V4 to V6 on the carriage 1 are controlled by control means (not shown) including a CPU in the printer main body 100, and the detection signals of the back pressure air pressure sensor SP1 and the liquid level sensor SH4 are: It is input to the control means.

  The maintenance unit 2 is a maintenance means in the present invention for performing maintenance of the heads 11A to 11C. The maintenance unit 2 covers caps 21A to 21C and covers the discharge port surfaces corresponding to the heads 11A to 11C, and suction paths. It has a suction pump P2 for sucking ink from the discharge ports of the heads 11A to 11C under a negative pressure inside the caps 21A to 21C via 22A to 22C, and a waste liquid tank 23 for storing the sucked waste ink. . V7 to V9 are open / close valves including solenoid valves that open and close the suction paths 22A to 22C to the caps 21A to 21C. The maintenance unit 2 performs a maintenance operation by moving the carriage 1 to above the maintenance unit 2 when maintenance of the heads 11A to 11C is necessary.

  The suction pump P2 and the on-off valves V7 to V8 in the maintenance unit 2 are controlled by the control means.

  The maintenance unit 2 is not limited to the ink suction unit, and in addition to this, although not shown, the discharge port surface 11a of the heads 11A to 11C is rubbed with an elastic blade, a wiping roller, or the like. In addition, a wiping means for removing residual ink adhering to the discharge port surface 11a can be provided.

  The in-crack 200 includes an ink tank 3, a deaeration device 5 for removing dissolved gas in the ink from the ink tank 3 toward the carriage 1 of the printer main body 100, and a deaeration device 5. And an intermediate tank 6 for temporarily storing the ink deaerated by. 41 is an ink path connecting the ink tank 3 and the deaeration device 5 so that ink can be supplied; 42 is an ink path connecting the deaeration device 5 and the intermediate tank 6 so that ink can be supplied; The ink path connects the damper 12 on the carriage 1 so that ink can be supplied.

  The ink path 41 is provided with an on-off valve V0 composed of an electromagnetic valve and a liquid feed pump P0 that sends ink in the ink tank 3 to the intermediate tank 6 via the deaeration device 5. The on-off valve V0 and the liquid feed pump P0 are controlled by the control means in the printer main body 100.

  The ink tank 3 is provided with an ink replacement detection sensor SH5 and an empty detection sensor SH6, for example, including a float sensor. The ink replacement detection sensor SH5 transmits a detection signal to the control means in the printer main body 100 when it detects that the ink in the ink tank 3 has become small and informs the ink replacement timing. The empty detection sensor SH6 transmits a detection signal to the control means in the printer main body 100 when it is detected that the ink in the ink tank 3 has run out. The printer main body 100 has a warning means (not shown) that issues a warning in response to these detection signals. The control means controls the warning means to change the ink replacement time or ink by means of a monitor screen or a warning lamp. Empty information is displayed.

  In addition, the ink path 43 includes an on-off valve V1 formed of an electromagnetic valve and a liquid feed pump P1 that sends ink in the intermediate tank 6 to the damper 12 on the carriage 1 of the printer main body 100. The on-off valve V1 and the liquid feed pump P1 are controlled by the control means in the printer main body 100.

  The deaeration device 5 connects the deaeration module 51 constituted by a gas permeable membrane, the vacuum pump P3 for depressurizing the inside of the deaeration module 51, and the vacuum pump P3 and the deaeration module 51. The vacuum path 52 includes a degassing module 51 and a vacuum pressure sensor SP <b> 2 that detects the degree of vacuum in the vacuum path 52, provided in the branch path 53 branched from the vacuum path 52. V10 is a leak valve comprising an electromagnetic valve provided in the vacuum path 52, which is closed when the vacuum pump P3 is operated, but opens the inside of the vacuum path 52 to the atmosphere when opened. The vacuum pump P3 and the leak valve V10 are controlled by the control means in the printer main body 100, and the detection signal of the vacuum pressure sensor SP2 is input to the control means.

  The deaeration module 51 can remove dissolved oxygen in ink by bringing one side of a gas permeable membrane into contact with ink and reducing the pressure on the other side through a vacuum path 52 by a vacuum pump P3. Any membrane module in which a number of hollow fiber membranes are bundled is preferably used as the membrane.

  The intermediate tank 6 is formed of a flexible film, and expands when ink is sent through the deaeration device 5 by the liquid feeding pump P0, and contracts when the ink inside is sent to the damper 12 by the liquid feeding pump P1. To do. The intermediate tank 6 is provided with a no-ink detection sensor SH3 composed of, for example, an optical actuator. The intermediate tank 6 detects whether or not the ink has run out by detecting the swelling of the intermediate tank 6, and It transmits to the said control means.

  FIG. 2 is a schematic diagram of the carriage 1. On the carriage 1, here, three heads 11 </ b> A to 11 </ b> C per damper 12 are connected by ink supply pipes 15 </ b> A to 15 </ b> C so that ink can be supplied. In this embodiment, eight dampers 12 (for eight colors) are mounted on the carriage 1, and accordingly, 24 heads 11 </ b> A to 11 </ b> C are mounted on the carriage 1, and main scanning is performed by a moving mechanism (not shown). A desired print is performed by reciprocating along the direction, and discharging ink to the recording medium facing downward from the discharge ports of the heads 11A to 11C according to the print data in the process of the reciprocation.

  FIG. 3 is a front view showing a set of dampers 12 and heads 11A to 11C on the carriage 1, and FIG. 4 is a cross-sectional view of the damper 12 portion.

  The damper 12 is a back pressure maintaining device according to the present invention, and is disposed on the carriage 1 above the heads 11A to 11C. The damper 12 is connected to the carriage 1 from the liquid feed pump V1 of the ink rack 200 via the ink path 43. The ink to be fed is temporarily stored in the internal ink chamber 121 while being supplied to the heads 11A to 11C by a fixed amount, and a large number of inks are ejected along the direction perpendicular to the main scanning direction on the ejection port surfaces 11a of the heads 11A to 11C. The inside of each of the arranged discharge ports is maintained at a predetermined negative pressure (about -3 cmAq in this embodiment). That is, if the height difference between the liquid level determined by the liquid level sensor SH4 and the discharge port surface 11a is h1 cm, the damper 12 maintains the inside of the ink chamber 121 at about − (h1 + 3) cmAq.

  The damper 12 includes a casing member 123 in which a concave portion 122 is formed, a flexible film 125 that covers the opening 124 of the concave portion 122, and the flexible film 125 is urged to the outside of the concave portion 122 so that each of the heads 11 </ b> A to 11 </ b> C. The spring member 126 has a negative internal pressure (back pressure) at the discharge port.

  The casing member 123 is formed of a material having corrosion resistance, such as polypropylene or polyethylene, and is disposed on the carriage 1 so that the concave portion 122 faces a direction perpendicular to the main scanning direction. The ink in the recess 122 is supplied to the heads 11A to 11C through the ink supply pipes 16A to 16C through the formed through-holes.

  The flexible film 125 is a flexible film-like member, and an ink chamber 121 is formed between the flexible film 125 and the casing member 123. As the flexible film 125, it is preferable to use a film made of a polymer material such as polyethylene terephthalate, for example. From the viewpoint of preventing the gas from dissolving in the ink as much as possible, a plurality of materials are laminated so as to make the gas difficult to pass. It is preferable to use a film that has been made to adhere.

  The flexible film 125 is arranged so that the film surface is parallel to the main scanning direction, and therefore pressure fluctuation due to acceleration / deceleration when the carriage 1 moves along the main scanning direction does not occur. I am doing so.

  The spring member 126 is interposed between the casing member 123 and the flexible film 125, and is in perpendicular contact with the flexible film 125 at one end (the left end with respect to FIG. 4). The spring member 126 is not limited to the illustrated coil spring, and may be a spring having another shape such as a leaf spring.

  The liquid feed pump P1 that feeds ink from the in-crack 200 to the damper 12 generates a negative pressure due to the displacement of the flexible film 125 of the damper 12, so that the sent ink is directly subjected to pressure on the heads 11A to 11C. Therefore, it is desirable that the resolution of the liquid supply amount per time of the liquid supply pump P1 is finer, and a pump having a larger flow rate than the ink flow rate (the maximum discharge flow rate when all the heads 11A to 11C are driven) is used. Is preferred. In the present embodiment, a flow rate of the ink is 52 ml / min, and a diaphragm pump having a liquid feed amount of 100 ml / min is used as the liquid feed pump P1.

  In the present embodiment, the flexible film 125 of the damper 12 has a circular shape of φ65 mm, and the spring pressure of the spring member 126 in the damper 12 is 39 gf / mm. Accordingly, when 1 cc of ink is put into the ink chamber 121 of the damper 12, the pressure fluctuation is 38 mmAq. That is, by controlling the liquid feeding pump P1 for 100 msec to feed the liquid, 6.3 mmAq can be controlled.

  One end of a T-tube (flow path in the present invention) 17 is connected to the through-hole 123a (atmospheric communication port) on the upper side wall of the casing member 123 of the damper 12 via a liquid level sensor SH4, and the other two end portions One end of which is a pressure detection flow path 17a extending linearly upward, and connected to the back pressure air pressure sensor SP1, and the other end extends linearly toward the side, with the air release valve V3 and The air release channel 17b is opened to the atmosphere via the filter 13. Reference numeral 17c denotes an atmosphere opening opening formed at the end of the atmosphere opening channel 17b. Thereby, the back pressure air pressure sensor SP1 connected to the pressure detection flow path 17a is disposed at a position higher than the air release flow path 17b.

  In this case, the reference of the height of the back pressure air pressure sensor SP1 and the atmospheric open flow path 17b will be described in detail. The lower end of the pressure receiving portion of the back pressure air pressure sensor SP1 and the top of the inner surface of the air open flow path 17b (maximum height position) ) 17d. When the air release channel 17b extends sideways in a straight line as shown in the figure, the apex 17d becomes the upper end of the inner surface of the atmosphere release port 17c.

  The lower end of the pressure receiving portion of the back pressure air pressure sensor SP1 is positioned higher than the vertex 17d of the inner surface of the atmosphere release channel 17b, so that the atmosphere release channel 17b is not in the straight shape shown in the figure, for example, an inverted U shape. Even when it is bent in a uniform manner, the position can always be higher than the atmosphere open flow path 17b.

  For example, when the back pressure air pressure sensor SP1 is constituted by a piezoresistive semiconductor pressure sensor, as shown in FIG. 5, it has a diaphragm 18 in which a silicon substrate is thinned as a pressure receiving portion, and this diaphragm 18 is a pressure detection channel 17a. By receiving the pressure via the pressure, an electric signal corresponding to the amount of the bending is generated, and the pressure in the ink chamber 121 of the damper 12 is detected. Therefore, if the lower end of the pressure receiving portion (diaphragm 18) is at a position higher than the apex 17d of the inner surface of the air release flow path 17b, the ink liquid level in the ink chamber 121 should be the casing member 123 of the damper 12. Even if it rises higher than the through-hole 123a on the upper side wall of the gas, it can escape from the atmospheric open flow path 17b lower than the back pressure air pressure sensor SP1, and flows into the pressure detection flow path 17a side. The pressure in the ink chamber 121 of the damper 12 can be normally detected by the back pressure air pressure sensor SP1 without contacting the pressure receiving portion (diaphragm 18) of the back pressure air pressure sensor SP1.

  In addition, since the ink in the ink chamber 121 of the damper 12 does not come into contact with the back pressure air pressure sensor SP1, the present invention can be used regardless of the type of ink, and even highly corrosive ink can be used. Moreover, since the back pressure air pressure sensor SP1 can detect the pressure inside the damper 12 without contact with ink, an inexpensive sensor can be used, and the cost of the ink jet printer can be reduced.

  The height h2 of the back pressure air pressure sensor SP1 with respect to the apex 17d on the inner surface of the open air channel 17b is preferably 30 mm in order to obtain the effect of the present invention more preferably.

  In this embodiment, the T-shaped tube 17 is configured so that the pressure detection flow path 17a and the air release flow path 17b are substantially orthogonal to each other. According to this, when the atmosphere release valve V3 is opened and the atmosphere is released, the ink flowing out from the atmosphere release port 17c falls in the vertical direction, so that the ink in the tube is better cut out and the response is excellent. preferable.

  However, the present invention is not limited to such a mode as long as the back pressure air pressure sensor SP1 is at a position higher than the atmosphere open flow path 17b. Therefore, for example, the flow path connected to the through-hole 123a on the upper side wall of the casing member 123 of the damper 12 is branched in a Y shape at the tip, and both the pressure detection flow path 17a and the air release flow path 17b are directed upward. You may be comprised so that it may extend toward. In this case, back pressure air pressure sensor SP1 should just be in the position where the lower end of the pressure receiving part is higher than atmosphere open mouth 17c of atmosphere open channel 17b opened upwards.

  An example of the overall operation flow of the ink jet printer will be described with reference to the flowchart shown in FIG. This overall operation is executed in accordance with a program stored in advance in the control means in the printer main body 100.

  When the printer power is turned on, first, the operation of the vacuum pump P3 of the ink rack 200 is started (S1), and then it is determined whether an error recovery is necessary when the operation stops during the maintenance operation by the maintenance unit 2 (S2). ). If necessary, after performing an error recovery process (S3), preparation of the deaeration module 51 is started, and whether or not the inside of the deaeration module 51 has a predetermined degree of vacuum (for example, −70 kPa or less) by the vacuum pressure sensor SP2. Whether or not it is detected (S4) and when a predetermined degree of vacuum is reached, control of the ink rack 200 is started (S5). That is, the ink feeding control to the intermediate tank 6 through the deaeration device 5 by driving the liquid feeding pump P0, and the ink feeding from the intermediate tank 6 to the damper 12 on the carriage 1 by driving the liquid feeding pump P1. Start control etc.

  Thereafter, the process proceeds to an initialization sequence. In the initialization sequence, the carriage 1 moves to above the maintenance unit 2 and then descends to bring the respective chaps 21A to 21C into close contact with the discharge port surfaces 11a of the corresponding heads 11A to 11C (S6). The back pressure air pressure sensor SP1 is calibrated (S7).

  FIG. 7 shows a control flow of calibration of the back pressure air pressure sensor SP1.

  First, the air release valve V3 is opened, and all the on-off valves V4 to V6 of the corresponding heads 11A to 11C are closed (S70), and then waiting for a predetermined time (1 sec) (S71). After waiting for a predetermined time, the damper 12 is filled with ink (S72).

  A control flow of ink filling into the damper 12 is shown in FIG.

  First, after opening the air release valve V3 and closing all the on-off valves V4 to V6 of the heads 11A to 11C (S720), the ink level of the ink chamber 121 in the damper 12 is detected by the liquid level sensor SH4 of the damper 12. (S721). When the ink level can be detected (Yes in S721), the on-off valves V4 to V6 of the heads 11A to 11C are sequentially opened in order to discharge the ink in the T-shaped tube 17 and make the level constant. After the suction pump P2 of the maintenance unit 2 is driven for a predetermined time and ink is sequentially sucked into the heads 11A to 11C one by one (S723), the on-off valves V4 to V6 are closed and the predetermined time (for example, 4 sec) ) Wait and return to the process from step S721 (S724).

  When the liquid level is not detected in step S721 (No), the on-off valve V1 of the ink rack 200 is opened (S725), the liquid feed pump P1 is driven, and the damper is passed from the intermediate tank 6 through the ink path 43. Ink is sent to 12 (S726). The liquid feed pump P1 is driven until the liquid level sensor SH4 detects ink (S727).

  If the liquid level sensor SH4 detects the liquid level in step S727 (Yes), the liquid feed pump P1 is stopped (S728), and the atmosphere release valve V3 is closed (S729). As a result, a predetermined amount of ink is filled in the ink chamber 121 of the damper 12.

  Next, returning to the flowchart of FIG. 7, the print head pressure value is set (S73). The setting of the print head pressure value is to perform dynamic back pressure setting during printer standby or printing.

  FIG. 9 shows a control flow for setting the print head pressure value.

  First, after closing the air release valve V3 (S730), the opening / closing valves V4 to V6 of the heads 11A to 11C are sequentially opened, and the suction pump P2 of the maintenance unit 2 is driven for a predetermined time, so that the heads 11A to 11C are driven. In contrast, ink suction is sequentially performed for each head (S731). Here, the suction pump P2 is driven intermittently, such as 3 seconds suction and 4 seconds standby, and suction is alternately performed by the heads 11A to 11C. When the ink suction is completed, all the on-off valves V4 to V6 of the heads 11A to 11C are closed.

  Next, the detection value of the back pressure air pressure sensor SP1 of the damper 12 is compared with Dp (the height of the nozzle surface 11a + 3 cmAq from the position of the liquid level stopped by the liquid level sensor SH4) (S732).

  Here, only when the detection value of the back pressure air pressure sensor SP1 is smaller than Dp-1 cmAq (SP1 <Dp-1), the on-off valve V1 is opened and the feed pump P1 feeds for a predetermined time (0.1 sec). The liquid is started, and ink is fed into the damper 12 until the detected value becomes Dp (S733).

  Thus, chattering can be prevented by providing a hysteresis of Dp-1 cmAq, and it can be kept within 1 cmAq from the value of Dp.

  After the above processing is performed on all the heads 11A to 11C (S734), the on-off valve V1 of the ink rack 200 is closed (S736), and the print head value setting operation is completed.

  Through the above processing, the back pressure air pressure sensor SP1 is calibrated by opening the atmosphere release valve V3 and releasing the atmosphere when the printer power is turned on. As a result, the damper 12 can stably produce a constant pressure, and has the effect of enabling high-quality printing.

  Returning to the flow of FIG. 6, after the calibration of the back pressure air pressure sensor SP1 (S7), it is determined whether or not to start cleaning when the printer power is turned on (S8). Here, when the user designates, the cleaning operation of each of the heads 11A to 11C is executed according to a predetermined sequence (S9), and when it is unnecessary, the next normal back pressure is set as it is (S10).

  A control flow for normal back pressure setting is shown in FIG.

  First, the pressure value of the back pressure air pressure sensor SP1 of the damper 12 is detected, and it is determined whether or not the value is smaller than a predetermined back pressure value (Dp-1 cmAq) (S100).

  If it is smaller in this step S100 (Yes), the on-off valve V0 is opened (S101), and the liquid feed pump P1 is driven for a predetermined time to feed ink from the intermediate tank 6 to the damper 12 (S102). This process continues until the pressure value of the back pressure air pressure sensor SP1 becomes larger than a predetermined back pressure value (DpcmAq) (S103), and when it becomes larger (Yes in S103), the on-off valve V0 is closed (S104), Thereafter, the driving of the liquid feed pump P1 is stopped (S105), and the normal back pressure setting is ended.

  Returning to the flow of FIG. 6, after the normal back pressure setting (S10), the ejection port surfaces 11a of the heads 11A to 11C are wiped to remove residual ink (S11), and the initial sequence is completed.

  After such an initial sequence, the printer operation enters a standby state, and a normal back pressure setting operation is executed during the standby state (S12), and thereafter a maintenance execution command from the user is accepted (S13). If there is an instruction here (Yes), for example, various cleaning processes of each head, ink introduction process, head replacement process, etc. are performed (S14). If there is no instruction (No), the power is prepared and the instruction is waited ( S15).

  If there is a power-off command in step S15 (Yes), flushing is performed to forcibly eject ink from the heads 11A to 11C to the caps 21A to 21C (S16). Wiping to remove residual ink is performed (S17). Thereafter, the back pressure control by the damper 12 is stopped by stopping the ink supply operation (S18), the vacuum pump P3 of the deaeration device 5 is further stopped (S19), and the leak valve V10 of the deaeration device 5 is stopped. Is opened for 30 seconds, for example, and the inside of the deaerator 5 is returned to atmospheric pressure (S20), and then the power is turned off.

  In the overall operation flow described above, the calibration of the back pressure air pressure sensor SP1 is performed when the printer power is turned on. However, after the printer power is turned on, the air in the ink in the damper 12 is in the middle of continuing the printer operation. There is also a possibility that the liquid level in the damper 12 rises due to dissolution or the like. For this reason, it is also preferable to perform calibration of the back pressure air pressure sensor SP1 at regular time intervals after the printer power is turned on. It is also preferable that the fixed time interval can be changed according to the operating environment.

  Further, as in the present embodiment, in order to maintain the ejection performance of the heads 11A to 11C, the caps 21A to 21C are brought into close contact with the ejection ports, and the interior of the caps 21A to 21C is made negative pressure to suck ink. When the maintenance unit 2 for performing the maintenance operation is provided, the back pressure air pressure sensor SP1 is calibrated after the maintenance every time the maintenance operation is executed during the printing operation, not only when the printer power is turned on. It is also preferable.

1 is a configuration diagram showing an outline of a main part of an ink jet printer according to the present invention. Schematic view of the carriage from a plane Front view showing a pair of damper and head on the carriage Cross section of damper part The figure explaining the height relationship between the back pressure air pressure sensor and the atmosphere opening Flowchart for explaining the overall operation flow of the ink jet printer according to the present invention. Flow chart for explaining the calibration flow of the back pressure air pressure sensor Flow chart for explaining the flow of ink filling in the damper Flowchart explaining the flow of printing water head pressure value setting Flow chart explaining the flow of normal back pressure setting

Explanation of symbols

1: Carriage 11A to 11C: Head 11a: Ejection port surface 12: Damper 13: Filter 15A to 15C: Ink supply path 17: T-shaped tube (flow path)
17a: Pressure detection channel 17b: Atmospheric release channel 17c: Atmospheric release port 17d: Apex of inner surface of atmospheric release channel 18: Diaphragm (pressure receiving portion)
2: Maintenance section 21A-21C: Cap 22A-22C: Suction path 23: Waste liquid tank 3: Ink tank 4, 41-43: Ink path
5: Deaeration device 51: Deaeration module 52: Vacuum path 53: Branch path 6: Intermediate tank V0 to V2, V4 to V9: Open / close valve V3: Atmospheric release valve V10: Leak valve P0, P1: Liquid feed pump P2: Suction pump SP1: Back pressure air pressure sensor SP2: Vacuum pressure sensor SH3: No ink detection sensor SH4: Liquid level sensor SH5: Ink replacement detection sensor SH6: Ink empty detection sensor

Claims (6)

A recording head that discharges ink from a discharge port to a recording medium, and supplies the recording head while storing ink on an ink supply path to the recording head, and maintains the inside of the discharge port at a predetermined negative pressure. An ink jet printer comprising a back pressure maintaining device
The back pressure maintaining device is provided with a flow path branched in two directions at an air communication port formed in the upper part,
One of the flow paths is a pressure detection flow path connected to a pressure detection means for detecting the pressure in the back pressure maintaining device, and the other is an atmospheric open flow path that is connected to an atmospheric open port via an atmospheric release valve The inkjet printer is characterized in that the pressure detection means is disposed at a position higher than the air release channel.   The back pressure maintaining device includes a flexible membrane and a spring that urges the membrane in a direction to inflate the membrane, and the inside of the discharge port is predetermined by inflating the membrane with the urging force of the spring. 2. The ink jet printer according to claim 1, wherein the negative pressure is maintained.   3. The ink jet printer according to claim 1, wherein a plurality of the recording heads are provided, and the back pressure maintaining device supplies ink to the plurality of recording heads in common.   4. The control device according to claim 1, further comprising a control unit that calibrates the back pressure maintaining device by opening the atmosphere release valve and opening the atmosphere release flow path to the atmosphere when the printer power is turned on. Inkjet printer.   5. A control means for calibrating the back pressure maintaining device by opening the atmosphere release valve at regular intervals after turning on the printer to release the atmosphere release flow path to the atmosphere. An inkjet printer according to any one of the above. A maintenance means for sucking ink by bringing a cap into close contact with the ejection port of the recording head and making the inside of the cap negative pressure;
6. The apparatus according to claim 1, further comprising a control unit configured to calibrate the back pressure maintaining device by opening the atmosphere release valve and opening the atmosphere release channel to the atmosphere after maintenance by the maintenance unit. An ink jet printer according to claim 1.

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