JP6314864B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an ink jet image forming apparatus including a recording head that discharges ink onto a recording medium such as paper.

  2. Description of the Related Art Conventionally, an ink jet image forming apparatus includes a recording head that ejects ink onto a recording medium such as paper, and an ink container that accommodates the ink. Some have a sub ink tank at a low position and temporarily store ink supplied from an ink container to a recording head in the sub ink tank.

  In an inkjet image forming apparatus, a purge that forcibly ejects ink from a nozzle when the viscosity of the ink in the nozzle of the recording head is estimated to be high and ejection failure is estimated to have occurred. There is a known method for recovering from a discharge failure that discharges foreign matter, bubbles, or the like in the head. In order to perform this purge, an ink supply unit such as a syringe pump is provided between the sub ink tank and the recording head, and the ink supply unit can reciprocate within the cylinder and a cylinder filled with ink. The piston consists of a piston, and the piston pushes the ink in the cylinder to supply the ink in the cylinder to the recording head.

  For example, in the ink jet recording apparatus of Patent Document 1, a sub tank (sub ink tank) and a syringe pump are arranged between a main tank (ink container) and a recording head, and the sub tank and the syringe pump are connected by a first ink flow path. Has been. The syringe pump includes a cylinder and a piston, and the piston moves up and down by a drive device (drive mechanism). The drive device has a ball screw, a nut portion, and a drive motor. The ball screw rotates with the rotation of the drive motor, and the nut portion is screwed to the ball screw. Accordingly, the nut portion moves in the vertical direction. The nut portion is connected to the piston, and when the drive motor rotates, the piston moves in the vertical direction together with the nut portion. Then, using such a syringe pump, a recovery operation (purge operation) of the recording head that forcibly discharges thickened ink, foreign matter, bubbles, and the like in the nozzle is performed.

JP 2013-154666 A

  When the drive mechanism for driving the ink supply unit such as the syringe pump is configured by the ball screw method as described above, the back when the ink filling and supply is switched, that is, when the piston movement direction is switched. Although the rush is reduced, it is necessary to use expensive parts, which increases the manufacturing cost.

  In order to reduce costs, the drive mechanism may be configured by a rack and pinion system. However, in the rack-and-pinion type drive mechanism, the pinion gear meshed between the motor and the rack has a backlash, so the motor and gear are rotated immediately after switching the piston movement direction. Nevertheless, there is a time during which the rack cannot be moved, and the discharge amount varies, for example, the discharge amount corresponding to this time decreases. The decrease in the discharge amount also affects the purge performance, and it may be impossible to recover from a discharge failure (clogging or the like) of the nozzles of the recording head. Further, if the ink discharge amount is increased in order to improve the purge performance, the ink consumption amount increases, and the cost for printing and maintenance increases.

  In view of the above circumstances, an object of the present invention is to supply ink while suppressing the cost and stabilizing the ejection amount.

  An image forming apparatus according to the present invention includes a recording head that ejects ink onto a sheet, an ink container that stores the ink, and a recording head that is disposed below the recording head and supplies the recording head from the ink container A sub-ink tank for temporarily storing the ink to be stored, a housing provided at an end portion with a discharge port connected to the recording head and a filling port connected to the sub-ink tank, and the end portion within the housing An ink supply part having a pressing part movable in one direction approaching the first part and in another direction away from the end part, and a drive mechanism for driving the pressing part of the ink supply part. When supplying the ink to the recording head, the mechanism moves the pressing portion in the one direction, and also fills the casing of the ink supply portion with the ink. The pressing portion is moved in the other direction to a predetermined position, the pressing portion is further moved in the other direction by a first adjustment amount, and then the pressing portion is moved in the one direction by a second adjustment amount. It is characterized by that.

  According to the present invention, it is possible to supply ink while reducing the cost and stabilizing the ejection amount.

1 is a diagram illustrating a configuration of a printer according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a recording head, an ink container, and an ink flow path of a printer according to an embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating an ink supply unit and a drive mechanism during purging in the printer according to the embodiment of the present invention. FIG. 4 is a partially enlarged view of the drive mechanism shown in FIG. 3. FIG. 4 is a cross-sectional view illustrating an ink supply unit and a drive mechanism when ink is filled in a printer according to an embodiment of the present invention. FIG. 6 is a partially enlarged view of the drive mechanism shown in FIG. 5. FIG. 5 is a cross-sectional view illustrating an ink supply unit and a drive mechanism during a first adjustment operation after ink filling in a printer according to an embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating an ink supply unit and a drive mechanism during a second adjustment operation after ink filling in a printer according to an embodiment of the present invention.

  First, an overall configuration of a color printer 1 (hereinafter, simply referred to as “printer 1”) as an ink jet image forming apparatus will be described with reference to FIG. Hereinafter, the front side in FIG. 1 is the front side (front side) of the printer 1.

  As shown in FIG. 1, the printer 1 includes a box-shaped printer main body 2. A paper feed cassette 3 for storing paper P is accommodated in a lower portion of the printer main body 2 so as to be drawn out.

  A conveyance path 4 for the paper P is formed on the right side of the printer body 2. A paper feed roller 5 is provided near the paper feed cassette 3 at the lower end of the transport path 4, and a pair of transport rollers 6 is provided to the right of the paper feed roller 5. A registration roller pair 7 is provided at the upper end of the conveyance path 4.

  At the center of the printer main body 2, a paper transport unit 8 that can be raised and lowered is provided. The paper transport unit 8 includes a transport frame 10, a driving roller 11, a driven roller 12, a tension roller 13, an endless transport belt 14, and an air intake unit 15.

  The driving roller 11 is rotatably supported at the upper left corner of the transport frame 10, the driven roller 12 is rotatably supported at the upper right corner of the transport frame 10, and the tension roller 13 is disposed at the center lower portion of the transport frame 10. It is rotatably supported.

  The conveyor belt 14 is wound around the driving roller 11, the driven roller 12 and the tension roller 13. The conveyance belt 14 is provided with a number of intake holes (not shown).

  The intake portion 15 is disposed so as to be surrounded by the conveyance belt 14, and has an intake port (not shown) on the upper side, and is configured to intake air from above the conveyance belt 14 to the inside.

  In addition, a pair of left and right lifting units 16 are provided below the transport unit 8 at the lower center of the printer body 2. Each elevating unit 16 includes a rotating shaft 17 and a cam 18 supported by the rotating shaft 17. Each rotary shaft 17 is connected to a drive unit (not shown) such as a drive motor. By operating this drive unit, the rotary shaft 17 rotates about the rotary shaft 17, and the posture of each cam 18 stands up (see FIG. 1) (see the solid line 1) and the lying posture (see the two-dot chain line in FIG. 1). Each cam 18 is configured to lift the transport frame 10 and raise the transport unit 8 by taking a standing posture, and to release the lift of the transport frame 10 and lower the transport unit 8 by taking a lying posture. ing.

  Further, four sets of recording heads 20 (20K, 20C, 20M, and 20Y) are arranged in parallel at the center of the printer main body 2 above the paper transport unit 8. Each recording head 20 corresponds to each color of black (K), cyan (C), magenta (M), and yellow (Y) in order from the upstream side (right side in the present embodiment) in the conveyance direction of the paper P. . Hereinafter, the symbols “K”, “C”, “M”, and “Y” are omitted for the recording head 20 except for the case of specifying the color. Each recording head 20 is provided with a nozzle (not shown) so as to face the upper surface of the conveyance belt 14.

  Four ink containers 21 (21K, 21C, 21M, and 21Y) are arranged in parallel on the top of the printer main body 2 so as to be detachable in the front-rear direction. The four ink containers 21 are provided for each ink color, and in order from the upstream side (right side in the present embodiment) in the transport direction of the paper P, black (K), cyan (C), magenta (M), The ink of each color of yellow (Y) is accommodated. Hereinafter, the symbols “K”, “C”, “M”, and “Y” are omitted for the ink container 21 except when a color is specifically described.

  Each ink container 21 is connected to each recording head 20 via a sub ink tank 22 and a syringe pump 23 (ink supply unit), and the ink stored in each ink container 21 is temporarily stored in the sub ink tank 22. After that, each recording head 20 is supplied by a syringe pump 23. The sub ink tank 22 and the syringe pump 23 are provided corresponding to each color of black (K), cyan (C), magenta (M), and yellow (Y), similarly to the recording head 20 and the ink container 21. However, in FIG. 1, only the sub ink tank 22 and syringe pump 23 corresponding to black (K) are illustrated, and the sub ink tank 22 and syringe pump corresponding to cyan (C), magenta (M), and yellow (Y). Illustration of 23 is omitted. The ink supply mechanism from the ink container 21 to the recording head 20 will be described later.

  A discharge mechanism 24 is provided on the left side of the printer body 2. The discharge mechanism 24 is provided with a drying device 25 provided on the upper left side of the paper transport unit 8, a discharge roller pair 26 provided on the left side of the drying device 25, and a discharge roller 27 provided below the discharge roller pair 26 via the discharge port 27. And a paper discharge tray 28 protruding outside the printer main body 2.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 receives image data from an external computer or the like, the paper P stored in the paper feed cassette 3 is sent out to the transport path 4 by the paper feed roller 5. The paper P sent to the transport path 4 is transported to the downstream side of the transport path 4 by the transport roller pair 6, and is transported from the transport path 4 to the upper surface of the transport belt 14 by the registration roller pair 7.

  At this time, the intake unit 15 is operated, and air is sucked from the upper surface side of the conveyance belt 14 to the intake unit 15 through the intake holes of the conveyance belt 14 and the intake port of the intake unit 15. Then, the sheet P sent out to the upper surface of the transport belt 14 is adsorbed on the upper surface of the transport belt 14 by the suction force of the intake portion 15.

  On the other hand, each recording head 20 is supplied with ink from each ink container 21. Each recording head 20 ejects ink to the paper P adsorbed on the conveyance belt 14 based on information of image data received from an external computer or the like. Thereby, a color ink image is formed on the surface of the paper P. The paper P on which the color ink image is formed is discharged on the discharge tray 28 from the discharge port 27 by the discharge roller 26 after the ink on the surface is dried by the drying device 25.

  Next, an ink supply mechanism from the ink container 21 to the recording head 20 will be described with reference to FIG.

  As shown in FIG. 2, the ink container 21 and the sub ink tank 22 are connected via a first ink flow path 30, and a control unit 36 composed of a CPU or the like is disposed in the middle portion of the first ink flow path 30. A first electromagnetic valve 31 that is opened and closed by (see FIG. 1) is provided so as to open or close the first ink flow path 30.

  The sub ink tank 22 is disposed below the ink container 21 and slightly below the recording head 20 so as to store ink at a position lower than the ink container 21 and slightly lower than the recording head 20. Has been. Further, the sub ink tank 22 and the syringe pump 23 are connected via the second ink flow path 32, and the middle portion of the second ink flow path 32 is opened and closed by the control unit 36 (see FIG. 1). A second electromagnetic valve 33 is provided so as to open or close the second ink flow path 32. Note that the end of the second ink flow path 32 on the sub ink tank 22 side extends to the vicinity of the bottom of the sub ink tank 22.

  The syringe pump 23 and the recording head 20 are connected via a third ink flow path 34, and a third electromagnetic wave that is opened and closed by a control unit 36 (see FIG. 1) in the middle portion of the third ink flow path 34. A valve 35 is provided so as to open or close the third ink flow path 34.

  Next, the syringe pump 23 and the drive mechanism 40 that drives the syringe pump 23 will be described with reference to FIGS.

  As shown in FIG. 3 and the like, the syringe pump 23 includes a cylinder 41 (housing) formed in a cylindrical shape and a piston 42 (pressing portion) formed in a disk shape.

  At one end of the cylinder 41, a filling port 43 (filling port) connected to the second ink flow path 32 (sub ink tank 22) and a discharge port 44 connected to the third ink flow path 34 (recording head 20). (Discharge port) is provided. The other end of the cylinder 41 opens so that the piston 42 can be inserted.

  The piston 42 is fitted inside the cylinder 41 so as to be able to reciprocate. An O-ring 45 is attached between the outer peripheral surface of the piston 42 and the inner peripheral surface of the cylinder 41 so that the piston 42 can slide while sealing the inside of the cylinder 41. Hereinafter, the direction in which the piston 42 moves toward the filling port 43 side and the discharge port 44 side (one end side) of the cylinder 41 is defined as the forward direction, and the direction in which the piston 42 moves toward the opening side (the other end side) of the cylinder 41 is retracted. The direction. The origin O (predetermined position) in the direction of movement of the piston 42 is set near the other end of the cylinder 1 (see FIG. 3 and the like).

  The drive mechanism 40 includes a rack unit 46, a drive gear 47, a roller 48, an idle gear 50, a motor 51, an origin detection unit 52, and a detected unit 53, that is, a rack and pinion system. It consists of

  The rack part 46 has a long shape in the moving direction of the piston 42. One end (end portion on the forward direction side) of the rack portion 46 is attached to the piston 42 from the cylinder 41 side, and is configured to reciprocate the piston 42 as the rack portion 46 moves in the forward direction and the backward direction. Has been. A rack gear 54 having a plurality of teeth is provided below the rack portion 46 at intervals in the longitudinal direction (movement direction of the piston 42).

  The drive gear 47 is provided below the rack portion 45 and meshed with the rack gear 54 of the rack portion 45. The roller 48 is provided above the drive gear 47 with the rack portion 46 interposed therebetween. That is, the drive gear 47 and the roller 48 sandwich the rack portion 46 from above and below.

  The idle gear 50 is provided below the drive gear 47 and has a small diameter gear 55 and a large diameter gear 56 coaxially. The small-diameter gear 55 of the idle gear 50 is engaged with the drive gear 47.

  The motor 51 is controlled by the control unit 36 (see FIG. 1) to generate a driving force, and is provided below the idle gear 50 and has a gear portion 57 that transmits the driving force. The gear portion 57 of the motor 51 is meshed with the large diameter gear 56 of the idle gear 50.

  The origin detection unit 52 detects whether or not the piston 42 is located at the origin O, and is configured by, for example, a photo interrupter. The origin detection unit 52 is provided on the backward direction side of the rack unit 46. The detected portion 53 is provided at the other end (end portion on the backward direction side) of the rack portion 46 so as to be detected by the origin detecting portion 52 when the piston 42 is located at the origin O.

  Next, the ink supply operation from the ink container 21 to the recording head 20 will be described with reference to FIGS.

  First, as shown in FIG. 2, since the ink container 21 is provided at a position higher than the sub ink tank 22, when the first electromagnetic valve 31 is in the open state, the ink container 21 is pressurized by the water head difference. Then, ink is supplied to the sub ink tank 22 through the first ink flow path 30. The amount of ink in the sub ink tank 22 is detected by an ink amount detection unit (not shown). When a predetermined amount of ink is stored in the sub ink tank 22, the first electromagnetic valve 31 is switched to the closed state, and ink supply from the ink container 21 to the sub ink tank 22 is stopped. Thereby, the ink in the sub ink tank 22 is maintained at a predetermined amount.

  When performing normal printing, the second electromagnetic valve 33 and the third electromagnetic valve 35 are opened, and the sub ink tank 22 is provided at a position slightly lower than the recording head 20. The water head difference between the sub ink tank 22 and the recording head 20 is maintained within a certain range. For this reason, the inside of the recording head 20 can be maintained in a slightly negative pressure state.

  When purging the recording head 20, the second electromagnetic valve 33 is switched to the closed state while the third electromagnetic valve 35 is kept open, and the motor 51 is driven to rotate forward (arrow shown in FIG. 3). X1). The driving force of the motor 51 at this time moves the rack portion 46 via the gear portion 57, the idle gear 50 and the driving gear 47 of the motor 51 in order to move the rack portion 46 in the forward direction (see arrow Y1 shown in FIG. 3). 46.

  It should be noted that there is a slight gap between the gear portion 57 of the motor 51 and the idle gear 50, between the idle gear 50 and the drive gear 47, and between the drive gear 47 and the rack gear 54 of the rack portion 46, respectively. Backlash) has occurred. For example, as shown in FIG. 4, in order for the drive gear 47 to press the rack gear 54 in the forward direction (see arrow Y1), the teeth 58 of the drive gear 47 are in contact with the teeth 60 of the rack gear 54 on the forward direction side. Between the teeth 58 of the drive gear 47 and the teeth 60 of the rack gear 54, a slight backlash B1 occurs on the backward direction side.

  As the rack portion 46 moves in the forward direction Y1 by the driving force from the motor 51, the piston 42 of the syringe pump 23 slides in the forward direction Y1 in the cylinder 41, and the ink in the cylinder 41 is moved by the piston 42. Pressed. The second ink flow path 32 connected to the filling port 43 of the cylinder 41 is closed by the closed second electromagnetic valve 33, but the third ink flow path 34 connected to the discharge port 44 of the cylinder 41 is opened. Since the ink is opened by the third electromagnetic valve 35 in the state, the ink pressed in the cylinder 41 is supplied to the recording head 20 via the discharge port 44 and the third ink flow path 34 (shown in FIG. 3). (See arrow Z1). In the recording head 20, foreign matter, bubbles, or the like in the recording head 20 (nozzles) are discharged by the ink to which the pressing force is applied.

  When refilling the ink in the syringe pump 23 that has decreased due to the purge of the recording head 20, the second electromagnetic valve 33 is switched to the open state, the third electromagnetic valve 35 is switched to the closed state, and the motor 51 is turned on. Drive in reverse (see arrow X2 shown in FIG. 5). The driving force of the motor 51 at this time is transmitted to the gear portion 57, the idle gear 50, and the driving gear 47 in order to move the rack portion 46 in the backward direction (see arrow Y2 shown in FIG. 5).

  During the purge, backlash occurs between each of the gear portion 57, the idle gear 50, the drive gear 57, and the rack gear 54. Therefore, immediately after the reverse rotation of the motor 51, the gear portion 57, After the gear 50 and the drive gear 57 are rotated by the amount of backlash, the gear portion 57, the idle gear 50, the drive gear 57, and the rack gear 54 are brought into contact with each other. For example, before the motor 51 is driven in reverse, the backlash B1 is generated between the teeth 58 of the drive gear 47 and the teeth 60 of the rack gear 54 of the rack portion 46 on the backward direction side (see FIG. 4). Immediately after the reverse drive of the motor 51, as shown in FIG. 6, the teeth 58 of the drive gear 47 abut against the teeth 60 of the rack gear 54 after the drive gear 47 rotates in the backward direction by the amount of backlash. At this time, backlash occurs between the gear portion 57, the idle gear 50, the drive gear 47, and the rack gear 54 on the opposite side to the purge. For example, as shown in FIG. The backlash B2 is generated on the forward direction side between the teeth 58 and the teeth 60 of the rack gear 54.

  Thereafter, the motor 51 is further driven, and the driving force from the motor 51 is transmitted to the rack portion 46. As the rack portion 46 moves in the backward direction Y2 by the driving force from the motor 51, the piston 42 of the syringe pump 23 slides in the backward direction Y2 in the cylinder 41, and the inside of the cylinder 41 is decompressed. At this time, the third ink flow path 34 connected to the discharge port 44 of the cylinder 41 is closed by the closed third electromagnetic valve 35, but the second ink flow path connected to the filling port 43 of the cylinder 41. 32 is opened by the opened second electromagnetic valve 33, so that the ink in the sub ink tank 22 flows into the cylinder 41 via the second ink flow path 32 and the filling port 34 as the pressure in the cylinder 41 is reduced. Sucked up (see arrow Z2 shown in FIG. 5). When the rack portion 46 moves in the backward direction Y2, the detected portion 53 attached to the rack portion 46 is detected by the origin detection portion 52, and it is detected that the piston 42 has moved to the origin O. The reverse drive of the motor 51 is stopped.

  Further, as described above, the ink stored in the sub ink tank 22 is reduced by refilling the ink from the sub ink tank 22 to the syringe pump 23, so that an ink amount detection unit (not shown). However, the ink in the sub ink tank 22 cannot be detected. Therefore, the first electromagnetic valve 31 is switched to the open state until a predetermined amount of ink is stored in the sub ink tank 22, and ink is supplied from the ink container 21 to the sub ink tank 22.

  Subsequently, an adjustment process for backlash (see FIG. 6) generated by refilling the ink of the syringe pump 23 is performed.

  In this adjustment process, the motor is operated so that the rack portion 46 and the piston 42 move in the backward direction Y2 by a predetermined first adjustment amount while maintaining the open / closed state of the second electromagnetic valve 33 and the third electromagnetic valve 35. 51 is further reversely driven (see arrow X2 shown in FIG. 7). The first adjustment amount is obtained when the gear portion 57 of the motor 51, the idle gear 50, the drive gear 47, and the rack gear 54 of the rack portion 46 are engaged with each other, and the gear portion 57, the idle gear 50, the drive gear 47, and the rack gear 54, respectively. For example, it is set to 1 mm. As described above, the driving force of the motor 51 is transmitted to the gear portion 57, the idle gear 50, the driving gear 47, and the rack gear 54 of the rack portion 46, and the rack portion 46 and the piston 42 are moved backward by a predetermined first adjustment amount. Move in direction Y2.

  Thereafter, the motor 51 is driven to rotate forward so that the rack portion 46 and the piston 42 move in the forward direction Y1 by a predetermined second adjustment amount (see arrow X1 shown in FIG. 8). As for the second adjustment amount, each of the gear portion 57, the idle gear 50, the drive gear 47, and the rack gear 54 is in a state where the gear portion 57 of the motor 51, the idle gear 50, the drive gear 47, and the rack gear 54 of the rack portion 46 are engaged. For example, it is set to 1 mm. Similarly to the above, the driving force of the motor 51 is transmitted to the gear portion 57, the idle gear 50, the driving gear 47, and the rack gear 54 of the rack portion 46, and the rack portion 46 and the piston 42 are advanced by a predetermined second adjustment amount. The piston 42 is positioned at the origin O by moving in the direction Y1.

  It should be noted that backlash has occurred between the gear portion 57 of the motor 51, the idle gear 50, the drive gear 47, and the rack gear 54 of the rack portion 46 when refilling the ink into the syringe pump 23 described above. Immediately after the forward rotation of the motor 51, after the gear portion 57, the idle gear 50 and the drive gear 47 have been rotated by the amount of backlash, the gear portion 57, the idle gear 50, the drive gear 47 and the rack gear 54 are respectively applied. Touch. For example, before the motor 51 is driven to rotate forward, the backlash B2 is generated between the teeth 58 of the drive gear 47 and the teeth 60 of the rack gear 57 of the rack portion 46 on the forward direction side (see FIG. 6). Immediately after the forward rotation of the motor 51, after the drive gear 47 rotates in the forward direction by the amount of backlash, the teeth 58 of the drive gear 47 abut on the teeth 60 of the rack gear 57 (see FIG. 4).

  Thereby, the gear part 57, the idle gear 50, the drive gear 47, and the rack gear 54 are in the state which can transmit the driving force by the normal rotation drive of the motor 51 immediately. Therefore, at the time of the next purge, the motor 51 is not affected by backlash among the gear portion 57, the idle gear 50, the drive gear 47, and the rack gear 54 even immediately after the forward rotation of the motor 51. Can be transmitted to the rack portion 46 and the piston 42.

  Even if the piston 42 is moved in the forward direction by a predetermined second adjustment amount in the backlash adjustment process as described above, the third ink flow path 34 connected to the discharge port 44 of the cylinder 41 is in the closed state. Since the ink is blocked by the third electromagnetic valve 35, the ink is not supplied to the recording head 20, and the second electromagnetic valve 32 connected to the filling port 43 of the cylinder 41 is open. Therefore, the ink is returned to the sub ink tank 22 (see arrow Z3 shown in FIG. 8).

  In the present embodiment, as described above, the printer 1 includes the recording head 20 that ejects ink onto the paper, the ink container 21 that stores the ink, and the ink container 21 that is disposed below the recording head 20. A sub ink tank 22 that temporarily stores ink to be supplied to the recording head 20, a syringe pump 23 (ink supply unit) having a cylinder 41 (housing) and a piston 42 (pressing unit), and a piston 42 of the syringe pump 23. And a drive mechanism 40 for driving the motor. The cylinder 41 has a discharge port 44 (discharge port) connected to the recording head 20 and a filling port 43 (filling port) connected to the sub ink tank 22 at the end. The piston 42 is movable in a forward direction (one direction) approaching the end portion in the cylinder 41 and a backward direction (other direction) separated from the end portion. The drive mechanism 40 moves the piston 42 in the forward direction when supplying ink to the recording head 20, and moves the piston 42 to the origin O (predetermined position) when filling the cylinder 41 of the syringe pump 23 with ink. After moving in the backward direction and further moving the piston 42 in the backward direction by the first adjustment amount, the piston 42 is moved in the forward direction by the second adjustment amount.

  As a result, the drive mechanism 40 can immediately move the piston 42 of the syringe pump 23 without being affected by backlash when purging by the syringe pump 23, and always records ink at a desired discharge amount. It is possible to supply the head 20 for purging. As described above, in the printer 1 of the present invention, it is possible to supply ink while reducing the cost and stabilizing the ejection amount.

  In the present embodiment, the drive mechanism 40 includes a rack portion 46 that is attached to the piston 42 and has a plurality of teeth 60 spaced in the movement direction of the piston 42, an idle gear 50 that meshes with the rack portion 46, and The drive gear 47 (pinion part) and the motor 51 which rotationally drives the idle gear 50 and the drive gear 47 are comprised. Thereby, the drive mechanism 40 is realized simply and at low cost by the rack and pinion method, and is not affected by the backlash as described above.

  Further, in the present embodiment, the drive mechanism 40 is configured to move forward or backward between the rack portion 46, the idle gear 50, and the drive gear 47 in a state where the rack portion 46, the idle gear 50, and the drive gear 47 are engaged with each other. The piston 42 is moved using the first adjustment amount and the second adjustment amount set to be larger than the direction backlash (gap). Accordingly, the drive mechanism 40 can reliably avoid the influence of backlash generated between the rack portion 46, the idle gear 50, and the drive gear 47 when purging by the syringe pump 23.

  In the present embodiment, the configuration of the rack-and-pinion type drive mechanism 40 has been described, but the drive mechanism 40 is not limited to this configuration, and may be another configuration such as a ball screw type.

  In this embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other different image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine. It is also possible to do.

1 Printer (image forming device)
20 Recording Head 21 Ink Container 22 Sub Ink Tank 23 Syringe Pump (Ink Supply Unit)
40 Drive mechanism 41 Cylinder (housing)
42 Piston (Pressing part)
43 Filling port (filling port)
44 discharge port (discharge port)
46 Rack 47 Drive gear 50 Idle gear 51 Motor

Claims (2)

A recording head for ejecting ink onto paper;
An ink container for containing the ink;
A sub ink tank that is disposed below the recording head and temporarily stores the ink supplied from the ink container to the recording head;
A housing provided at its end with a discharge port connected to the recording head and a filling port connected to the sub-ink tank, one direction approaching the end within the housing, and spaced from the end An ink supply unit having a pressing unit movable in the other direction;
A drive mechanism for driving the pressing portion of the ink supply unit;
A first solenoid valve provided in a first ink flow path connecting the ink container and the sub ink tank;
A second solenoid valve provided in a second ink flow path connecting the sub ink tank and the ink supply unit;
A third electromagnetic valve provided in a third ink flow path for connecting the ink supply unit and the recording head,
The drive mechanism is attached to the pressing portion and has a rack portion having a plurality of teeth spaced in the movement direction of the pressing portion, a pinion portion meshing with the rack portion, and the pinion portion being driven to rotate. And a motor,
When performing normal printing using the recording head, the second electromagnetic valve and the third electromagnetic valve are opened,
When supplying the ink to the recording head when purging the recording head, the second electromagnetic valve is switched to a closed state while the third electromagnetic valve is open, and the drive mechanism is Moving the pressing portion in the one direction;
When filling the casing of the ink supply unit with the ink reduced by the purge of the recording head, the second electromagnetic valve is switched to an open state, the third electromagnetic valve is switched to a closed state, and the drive mechanism Move the pressing part in the other direction to a predetermined position,
When adjusting the backlash generated by refilling the ink in the ink supply unit, the drive mechanism is configured to keep the second electromagnetic valve open and the third electromagnetic valve closed. An image forming apparatus comprising: moving the pressing portion in the other direction by a first adjustment amount; and then moving the pressing portion in the one direction by a second adjustment amount. The drive mechanism has the first adjustment amount set larger than the gap in the one direction or the other direction generated between the rack portion and the pinion portion in a state where the rack portion and the pinion portion are engaged with each other. The image forming apparatus according to claim 1 , wherein the pressing portion is moved using the second adjustment amount.

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