JP2006161648A - Pump unit and recovering mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump unit of simple structure for sucking (or discharging) a fluid and capable of changing quantity of the fluid to be sucked (or discharged). <P>SOLUTION: A cylindrical cam 240 is turned around a cam shaft (turning center shaft) 242. The peripheral surface of the cam 240 is formed with three flat parts of a first flat surface 244, a second flat surface 246 and a third flat surface 248. The first flat part 244 is formed in the closest part to the cam shaft 242, and the third flat surface 248 is formed in the farthest part from the cam shaft 242. The second flat surface 246 is formed in a part farther from the cam shaft 242 than the first flat surface 244 and closer to the cam shaft 242 than the third flat surface 248. The cam shaft 242 is connected to a stepping motor, and turned at an angle corresponding to an angle of rotation of the stepping motor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pump unit that sucks or discharges fluid by changing a volume of a cylinder chamber by rotating a cam, and a recovery mechanism that restores an ink discharge state from a print head to an initial ink discharge state.

  2. Description of the Related Art Inkjet image forming apparatuses that form images by ejecting ink onto recording media such as recording paper are widely used. The image forming apparatus includes a print head (recording head) in which a plurality of nozzles that eject ink are formed. The nozzles of the print head may be clogged with dust such as paper dust or bubbles, causing problems such as ink ejection failure or image distortion. As one technique for solving such a problem, a technique is known in which ink is ejected from a print head and dust and bubbles in the nozzle are discharged together with the ink. A technique is also known in which the inside of a print head is pressurized to discharge ink from nozzles. A recovery mechanism is incorporated in the image forming apparatus in order to discharge (or pour out) ink from the print head and discharge dust and bubbles in the nozzle.

  The recovery mechanism includes a cap that closes the face surface, a pump unit that sucks ink from the nozzle, and the like. The pump unit can be a reciprocating pump unit that changes the volume of the cylinder chamber by rotating a cam (pump cam) and reciprocating the piston in a predetermined reciprocating direction, or flexing the diaphragm by rotating the cam. Thus, a diaphragm type pump unit or the like that changes the volume of the cylinder chamber is used.

When the pump unit as described above is used for recovery, a certain amount of ink is sucked from the nozzles of the print head by rotating the cam once (see Patent Document 1).
JP 2002-180968 A

  However, even when there is no need to suck a large amount of ink at the time of recovery, the above-described conventional technique sucks a certain amount of ink from the nozzles of the print head, and thus the ink may be wasted. . In addition, if it is attempted to control the ink suction amount according to the need for recovery, the apparatus configuration becomes complicated, resulting in an increase in size and cost.

  An object of this invention is to provide the pump unit which can change the fluid quantity which attracts | sucks (or discharge | releases) a fluid with a simple structure in view of the said situation, and the recovery mechanism incorporating this pump unit.

To achieve the above object, the pump unit of the present invention is a pump unit that sucks or discharges fluid by changing the volume of a cylinder chamber by rotating a cam.
(1) The amount of fluid sucked or discharged is changed according to the stop position of the cam.

here,
(2) A reciprocating pump unit that changes the volume of the cylinder chamber by changing the volume of the cylinder chamber by rotating the cam and reciprocating the piston in a predetermined reciprocating direction.

Also,
(3) A diaphragm-type pump unit that changes the volume of the cylinder chamber by changing the volume of the cylinder chamber by rotating the cam to bend the diaphragm.

further,
(4) The cam may have a stop position corresponding to a rotation angle from a predetermined initial position.

Furthermore,
(5) The cam may be rotated by a force greater than a predetermined value.

Furthermore,
(6) The cam may rotate at a predetermined timing.

Furthermore,
(7) The timing may be determined based on the passage of a predetermined time.

In addition, the recovery mechanism of the present invention for achieving the above object provides an ink discharge state from the print head in an inkjet image forming apparatus that forms an image by discharging ink from a print head that discharges ink onto a recording medium In the recovery mechanism that recovers the initial ink ejection state,
(8) including any of the pump units described above,
(9) The pump unit sucks ink from the print head or pressurizes the print head.

here,
(10) The fluid amount may be changed based on the elapsed time from the previous recovery.

further,
(11) The fluid amount may be changed based on a predetermined printing duty.

  According to the present invention, since the amount of fluid is changed according to the stop position of the cam, the amount of fluid can be changed by changing the stop position of the cam. For this reason, the fluid amount can be changed with a simple configuration.

  The present invention has been realized in an ink jet printer that forms an image by ejecting ink onto a recording medium such as recording paper.

  An example of a printer incorporating the recovery mechanism of the present invention will be described with reference to FIG.

  FIG. 1 is a front view schematically showing an example of a printer in which a recovery mechanism of the present invention is incorporated.

  The printer 10 is connected to a host PC (personal computer) 12 that sends image information to the printer 10. In the printer 10, four (four) print heads 22 </ b> K, 22 </ b> C, 22 </ b> M, and 22 </ b> Y are arranged side by side in the conveyance direction (arrow A direction) of the recording medium (roll paper in this case). The four print heads 22K, 22C, 22M, and 22Y respectively eject black, cyan, magenta, and yellow inks. These four print heads 22K, 22C, 22M, and 22Y are so-called line heads, and extend in a direction orthogonal to the paper surface of FIG. 1 (a direction orthogonal to the arrow A direction). The lengths of these four print heads 22K, 22C, 22M, and 22Y are slightly longer than the maximum width (the length in the direction perpendicular to the paper surface of FIG. 1) of the recording medium that can be printed by the printer 10. These four print heads 22K, 22C, 22M, and 22Y are fixed and do not move during image formation.

  A recovery mechanism 40 is incorporated in the printer 10 so that ink can be stably ejected from the four print heads 22K, 22C, 22M, and 22Y. By the recovery mechanism 40, the ink discharge state from the print heads 22K, 22C, 22M, and 22Y is restored to the initial ink discharge state. The recovery mechanism 40 includes a capping mechanism 50 that removes ink from the ink discharge port formation surfaces 22Ks, 22Cs, 22Ms, and 22Ys of the four print heads 22K, 22C, 22M, and 22Y during the recovery operation. The capping mechanism 50 is provided independently for each print head 22K, 22C, 22M, 22Y. In the example of FIG. 1, six colors (that is, six capping mechanisms 50) are shown. The color component is a preliminary mechanism when the print head is added. The capping mechanism 50 includes a known blade, an ink removing member, a blade holding member, a cap, and the like.

  The roll paper P is supplied from the roll paper supply unit 24 and is conveyed in the direction of arrow A by the conveyance mechanism 26 incorporated in the printer 10. The transport mechanism 26 includes a transport belt 26a for loading and transporting the roll paper P, a transport motor 26b for rotating the transport belt 26a, and a roller 26c for applying tension to the transport belt 26a.

  When forming an image on the roll paper P, after the recording start position of the roll paper P being conveyed reaches below the black print head 22K, the print head is based on the recording data (image information). Black ink is selectively ejected from 22K. Similarly, ink of each color is ejected in the order of the print head 22C, the print head 22M, and the print head 22Y to form a color image on the roll paper P. The printer 10 includes main tanks 28K, 28C, 28M, and 28Y for storing ink supplied to the print heads 22K, 22C, 22M, and 22Y, and the print heads 22K, 22C, and 22M, in addition to the components and members described above. , 22Y are provided with various pumps (see FIG. 3 and the like) for supplying ink and performing a recovery operation.

  The electrical system of the printer 10 will be described with reference to FIG.

  FIG. 2 is a block diagram showing an electrical system of the printer of FIG.

  Recording data and commands transmitted from the host PC 12 are received by the CPU 100 via the interface controller 102. The CPU 100 is an arithmetic processing unit that performs overall control such as reception of recording data of the printer 10, recording operation, handling of the roll paper P, and the like. After analyzing the received command, the CPU 100 renders the image data of each color component of the recording data by developing a bitmap on the image memory 106. As an operation process before recording, the capping motor 122 and the head up / down motor 118 are driven via the output port 114 and the motor driving unit 116, and the print heads 22K, 22C, 22M, and 22Y are separated from the capping mechanism 50 for recording. Move to position (image forming position).

  Subsequently, the roll motor (not shown) that feeds the roll paper P through the output port 114 and the motor drive unit 116, the transport motor 120 that transports the roll paper P at a low speed, and the like are driven to drive the roll paper P. -The paper P is conveyed to the recording position. The leading end position of the roll paper P is detected by a leading edge detection sensor (not shown) for determining the timing (recording timing) at which ink starts to be discharged onto the roll paper P conveyed at a constant speed. Thereafter, in synchronization with the conveyance of the roll paper P, the CPU 100 sequentially reads out the corresponding color recording data from the image memory 106, and the read data is passed through the print head control circuit 112 (via). Transfer to each print head 22K, 22C, 22M, 22Y.

  The operation of the CPU 100 is executed based on a processing program stored in the program ROM 104. The program ROM 104 stores processing programs and tables corresponding to the control flow. A work RAM 108 is used as a working memory. During the cleaning and recovery operations of the print heads 22K, 22C, 22M, and 22Y, the CPU 100 drives the pump motor 124 via the output port 114 and the motor driving unit 116, and controls ink pressurization and suction.

  A recovery mechanism and an ink supply mechanism incorporated in the printer 10 will be described with reference to FIGS.

  FIG. 3 is a schematic diagram showing a recovery mechanism and an ink supply mechanism incorporated in the inkjet image forming apparatus. FIG. 4 is a flowchart showing a procedure for cleaning the print head. FIG. 5 is a schematic diagram showing a procedure for wiping ink from the ink ejection surface, where (a) shows the state before the start of wiping, (b) shows the state immediately after the end of wiping, and (c) shows the standby after the end of wiping. Indicates the state. Although FIG. 3 shows a mechanism for supplying ink to the print head 22K and for recovering the print head 22K, the other print heads 22C, 22M, and 22Y also have an ink supply mechanism having the same configuration. ing. 3 and 5, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

  The printer 10 (see FIG. 1) incorporates an ink supply mechanism 60 and a recovery mechanism 40 that recover the ink discharge state from the print head 22K to the initial ink discharge state. The ink supply mechanism 60 includes an ink tank 70 detachably attached to the main body of the printer 10 and a sub tank 80 disposed in the middle of an ink supply path 62 that connects the ink tank 70 and the print head 22K. A print head 22K is disposed under the sub tank 80. The liquid level of the ink stored in the sub tank 80 is located above the ink discharge port of the nozzle 22Kn of the print head 22K.

  The sub tank 80 and the print head 22K are connected (connected) by two ink flow paths 64 and 66. The sub tank 80 and the print head 22K are fixed to the same frame (not shown), and the sub tank 80 and the ink flow paths 64 and 66 move together with the print head 22K.

  The ink flow path 64 connects the bottom of the sub tank 80 and the upper part of the liquid chamber (the chamber in which ink is stored) 22Kr of the print head 22K. On the other hand, the ink channel 66 connects the bottom of the sub tank 80 and the upper part of the liquid chamber 22Kr of the print head 22K at a portion different from the portion to which the ink channel 64 is connected.

  A pressure pump 68 that sends ink from the sub tank 80 to the liquid chamber 22Kr to pressurize the inside of the print head 22K is attached to the ink flow path 64. By driving the pressurizing pump 68, the ink in the sub tank 80 flows into the liquid chamber 22Kr through the ink flow path 64 and pressurizes the inside of the print head 22K. As a result, the ink flows out from the nozzles 22Kn together with bubbles and dust, and the print head 22K is cleaned (a kind of recovery operation).

  A standby valve 69 that opens and closes the ink flow path 64 at a predetermined timing is attached to the ink flow path 64. On the other hand, a pressure valve 67 that opens and closes the ink channel 66 at a predetermined timing is attached to the ink channel 66. A pressure detection sensor 81 for detecting the ink pressure in the ink channel 66 is attached to a portion of the ink channel 66 between the pressurizing valve 67 and the sub tank 80.

  On the upper wall of the sub tank 80, an air release valve 84 for fixing the internal pressure of the sub tank 80 to atmospheric pressure is fixed. By opening the atmosphere release valve 84, the internal pressure of the sub tank 80 becomes equal to the atmospheric pressure. The sub tank 80 is provided with a well-known liquid level detection sensor 86 for detecting the liquid level of the ink (stored ink) stored in the sub tank 80. When the liquid level detection sensor 86 detects that the ink level in the sub tank 80 is below a certain level, the supply pump 72 starts to operate and ink is sucked from the ink tank 70 and supplied to the sub tank 80. On the other hand, when the liquid level detection sensor 86 detects that the ink liquid level in the sub tank 80 has reached a predetermined upper limit level, the supply pump 72 is stopped and the ink supply is stopped.

  A detection sensor (not shown) that detects the presence or absence of ink in the ink tank 70 is attached to the ink tank 70. An air release valve 74 for bringing the internal pressure of the ink tank 70 to atmospheric pressure is attached to an air flow path connected when the ink tank 70 is attached to the main body of the printer 10.

  The recovery operation of the print head 22K will be described.

  The recovery operation herein refers to an operation performed to continuously maintain the ink discharge quality of the print head 22K, and when the conditions such as the elapsed time and the discharge status are satisfied, the image quality is abnormal. In some cases, this is done automatically or arbitrarily.

  As shown in the flow of FIG. 4, the recovery operation is started by receiving a cleaning command (S401). After receiving the cleaning command, the atmosphere release valve 84, the pressurization valve 67, and the standby valve 69 are sequentially opened (S402 to S404). Subsequently, the pressurizing pump 68 is operated (S405), and the ink is pressure-fed from the sub tank 80 to the print head 22K via the ink flow path 64. By this ink pumping, bubbles accumulated on the side of the sub tank 80 of the filter 90 during the recording operation or the like are pushed again into the sub tank 80.

  After operating the pressurizing pump 68 for a predetermined time, the pressurizing valve 67 is closed (S406), and the ink flow path 66 is shut off (closed). As a result, a large positive pressure is applied (acts) to the liquid chamber 22Kr of the print head 22K. With this large positive pressure, ink is discharged (flowed out) from each nozzle 22Kn of the print head 22K, and foreign matters such as bubbles and dust existing in the nozzle 22Kn and its peripheral part are removed.

  Further, after a predetermined time has elapsed, the pressurization pump 68 is stopped (S407), and the standby valve 69 and the atmosphere release valve 84 are closed in order (S408, S409). In this state, ink adheres to the face surface 22Ks including the opening of each nozzle 22Kn of the print head 22K and is dirty. In order to remove this dirt, the face surface 22Ks is wiped with a wiper 52 fixed to the capping mechanism 50 as shown in FIG. In this operation, first, as shown in FIG. 5A, the print head 22K moves above the recovery cap 54 (S410). Subsequently, when the recovery cap 54 moves in the direction of arrow B, as shown in FIG. 5B, dirt such as ink adhering to the face surface 22Ks is wiped off by the wiper 52 (S411). This operation is called a wiping operation. After completion of the wiping operation, as shown in FIG. 5C, the print head 22K is capped again and enters a standby state (S412). Since the print head 22K in this standby state has its face surface 22Ks capped (closed) by the recovery cap 54, thickening of the ink in the nozzle 22Kn is prevented. The ink (waste ink) discharged from the print head 22K is received by the recovery cap 54 and sucked by the suction pump 92 (see FIG. 3). The waste ink is filtered by a filter 94 (see FIG. 3) to remove foreign matter (screened), and then returned to the ink tank 70 again. In addition, only the wiping operation described above may be performed at an appropriate timing.

  As the recovery operation, in addition to the above, there is also an operation in which the pressure valve 67 and the standby valve 69 are closed with the face surface 22Ks capped by the recovery cap 54, and the suction pump 92 is driven to suck ink from the nozzles 22Kn. is there.

  In the recovery operation as described above, the pressure pump 68 and the suction pump 92 are driven. The pressurizing pump 68 and the suction pump 92 will be described. Since the two pumps 68 and 92 have the same structure, the suction pump 92 will be described here with reference to FIGS. 6 to 8. The suction pump 92 is an example of a pump unit according to the present invention.

  FIG. 6 is a partial longitudinal sectional view showing the suction pump when the cam is located at the home position. FIG. 7 is a partial longitudinal sectional view showing the suction pump when the cam is located at the first suction position. FIG. 8 is a partial longitudinal sectional view showing the suction pump when the cam is located at the second suction position.

  The suction pump 92 is roughly composed of a cylindrical cylinder 200, a columnar piston 220 that reciprocates inside the cylinder 200, and a cam 240 that reciprocates the piston 220. The cylinder 200 includes a flow path 202 connected to the inside of the cap 54, a flow path 204 connected to the ink tank 70 (see FIG. 3), and a cylinder chamber 206 that selectively communicates with the two flow paths 202 and 204. Is formed. A suction one-way valve 208 that opens only when a fluid such as ink is sucked from the flow path 202 into the cylinder chamber 206 is disposed at the boundary between the flow path 202 and the cylinder chamber 206. A discharge one-way valve 210 that opens only when a fluid such as ink is discharged from the cylinder chamber 206 to the flow path 204 is disposed at the boundary between the flow path 204 and the cylinder chamber 206. Moreover, the longitudinal direction one end part of the cylinder 200 is a little thin, and this thin part is the cylindrical part 212 to which the piston 220 reciprocates.

  As will be described later, when the piston 240 is reciprocated by rotationally driving the cam 240, when the volume of the cylinder chamber 206 decreases, the suction one-way valve 208 is caused by the pressure increase (pressurizing force) generated during the decrease. Since the discharge one-way valve 210 is opened at the same time as closing, the fluid (ink or air) in the cylinder chamber 206 is discharged to the flow path 204 through the discharge one-way valve 210. On the contrary, when the volume of the cylinder chamber 206 increases, the suction one-way valve 208 is opened and the discharge one-way valve 210 is closed by the negative pressure (suction force) generated at the time of the increase. Fluid is sucked (introduced) from the flow path 202 into the cylinder chamber 206 through the valve 208.

  A disc-shaped and rubber-like elastic member 222 is engaged (attached) to one end portion in the longitudinal direction of the piston 220 (a tip portion located inside the cylinder chamber 206). The elastic member 222 is for sealing the cylinder chamber 206, and shuts off between the cylinder chamber 206 and the outside in a sealed state. The peripheral portion (outer peripheral portion) of the elastic member 222 is engaged (fixed) with the peripheral wall surface portion of the cylinder chamber 206.

  A portion of the piston 220 adjacent to the elastic member 222 is a fixing portion 224 that is slightly narrowed, so that the elastic member 222 can be easily fixed. A portion of the piston 220 that is slightly separated from the elastic member 222 is formed with a columnar body portion 226 that slides on the inner wall surface of the cylindrical portion 212. A cam contact portion 228 having a U-shaped longitudinal section is formed adjacent to the main body portion 226. A cam 240 is arranged inside the cam contact portion 228. When the cam 240 rotates, the cam contact portion 228 moves in the direction of arrow C or arrow D, and the piston 220 also moves in the direction of arrow C or arrow. Move in the D direction.

  The cam 240 is cylindrical and rotates about a cam shaft (rotation center axis) 242. Three flat portions (first flat surface 244, second flat surface 246, and third flat surface 248) are formed on the outer peripheral surface of the cam 240. Therefore, the vertical section of the cam 240 is not a perfect circle, but has a shape in which three straight portions 244, 246, and 248 are formed on the circumference of the perfect circle. The first flat surface 244 is formed at a portion closest to the cam shaft 242, and the third flat surface 248 is formed at a portion farthest from the cam shaft 242. The second flat surface 246 is formed at a portion farther from the cam shaft 242 than the first flat surface 244 and closer to the cam shaft 242 than the third flat surface 248. The cam shaft 242 is connected to a stepping motor (not shown) and rotates by an angle corresponding to the rotation angle of the stepping motor.

  Any one of the first flat surface 244, the second flat surface 246, and the third flat surface 248 of the cam 240 selectively contacts (contacts) the cam contact portion 228 described above. Is formed. The contact surface 228 a is formed in a portion of the cam contact portion 228 that intersects the widthwise center line L of the longitudinal section of the main body portion 226 of the piston 220. Further, the center point 242a of the longitudinal section (circle) of the cam shaft 242 is located at a position where the width direction center line L is extended. That is, a straight line connecting the center of the contact surface 228a and the center point 242a coincides with the width direction center line L described above.

  Assuming two straight lines L1 (corresponding to the width direction center line L) and L2 orthogonal to each other through the center point 242a of the cam shaft 242, in the state shown in FIG. 6, the first flat surface 244 and The third flat surface 248 intersects the straight line L1, the second flat surface 246 does not intersect the straight line L2, and is closer to the first flat surface 244 than the point where the straight line L2 intersects the circumference of the cam 240. Is formed. When the first flat surface 244 is used as a reference, the second flat surface 246 is located about 80 ° away from the center angle with respect to the center point 242a of the cam shaft 242, and the third flat surface 248 is a cam The central point 242a of the shaft 242 is located 180 degrees away from the center angle.

  As shown in FIG. 6, when the first flat surface 244 is in contact with the contact surface 228 a, the third flat surface 248 is a portion (surface) on the opposite side to the contact surface 228 a of the cam contact portion 228. Abut. Since the third flat surface 248 is farthest from the center point 242a of the cam shaft 242, the piston 220 is pushed up most and the cylinder chamber 206 is narrowest. Thus, the position of the cam 240 when the cylinder chamber 206 is the narrowest is the home position (an example of a predetermined initial position in the present invention). When the cam 240 is located at the home position, the third flat surface 248 is in contact with the surface of the cam contact portion 228 opposite to the contact surface 228a, so that the first flat surface is in contact with the contact surface 228a. When the 244 is in contact with each other, the flat surfaces are in contact with the cam contact portion 228, and the center point 242a of the cam shaft 242 is on the center line L in the width direction. Even if the connected stepping motor is not excited, both sides are in contact with each other. That is, the cam shaft 242 does not rotate or rotate only by increasing or decreasing the internal pressure of the cylinder chamber 206. The cam shaft 242 is rotated or rotated only by the driving force of the stepping motor (an example of a force greater than a predetermined value in the present invention).

  The stepping motor is driven from the state where the cam 240 is located at the home position, and as shown in FIG. 7, the cam shaft 242 is rotated about 70 ° around the center point 242a of the cam shaft 242 (see FIG. 7). 7 is rotated counterclockwise), the second flat surface 246 comes into contact with the contact surface 228a. This state is a state where the cam 240 is located at the first suction position. When the cam 240 rotates from the home position to the first suction position, the piston 220 moves in the direction of the arrow C (for example, about 2 mm), and the volume of the cylinder chamber 206 increases, resulting from this increase. A negative pressure (suction force) is generated, whereby the suction one-way valve 208 is opened and the discharge one-way valve 210 is closed. The ink in the nozzle 22Kn (see FIG. 3) is sucked into the cap 54 (see FIG. 3). It is sucked into the cylinder chamber 206 through the directional valve 208. After this suction, the cam shaft 242 is rotated clockwise on the paper surface of FIG. 7 by about 70 ° centering on the center point 242a of the cam shaft 242 (until the third flat surface 248 comes into contact with the contact surface 228a). By moving the piston 220, the piston 220 moves in the direction of the arrow D to reduce the volume of the cylinder chamber 206. Due to this decrease, the pressure in the cylinder chamber 206 rises, whereby the suction one-way valve 208 is closed and discharged. The one-way valve 210 is opened, and the ink in the cylinder chamber 206 is discharged through the discharge one-way valve 210 to the ink tank 70 (see FIG. 3).

  As described above, when the cam 240 is rotated from the state where the first flat surface 244 contacts the contact surface 228a until the second flat surface 246 contacts, the volume of the cylinder chamber 206 increases. The increase amount is smaller than the maximum increase amount of the cylinder chamber 206. That is, the amount of ink in the nozzle 22Kn (see FIG. 3) is sucked into the cylinder chamber 206 is smaller than the maximum suction amount of the suction pump 92. In this way, by controlling the rotation of the cam 240, the suction pump 92 can suck ink with a suction amount smaller than the maximum suction amount, and can perform a recovery operation.

  In order to perform the recovery operation by sucking the maximum amount of ink from the nozzle 22Kn by the suction pump 92, the cam 240 is maintained from the state where the first flat surface 244 contacts the contact surface 228a until the third flat surface 248 contacts. Is rotated 180 °. This state is a state where the cam 240 is located at the second suction position. When the cam 240 rotates from the home position to the second suction position, the piston 220 moves in the direction of arrow C (for example, about 5 mm), and the volume of the cylinder chamber 206 increases to the maximum. As a result, the maximum negative pressure (suction force) is generated, whereby the suction one-way valve 208 is opened and the discharge one-way valve 210 is closed, and the ink in the nozzle 22Kn (see FIG. 3) is placed in the cap 54 (FIG. 3). And the suction one-way valve 208 is sucked into the cylinder chamber 206. After this suction, the cam shaft 242 is rotated counterclockwise on the paper surface of FIG. 8 by 180 ° about the center point 242a of the cam shaft 242 (until the first flat surface 244 contacts the contact surface 228a). By moving the piston 220, the piston 220 moves in the direction of the arrow D to reduce the volume of the cylinder chamber 206. Due to this decrease, the pressure in the cylinder chamber 206 rises, whereby the suction one-way valve 208 is closed and discharged. The one-way valve 210 is opened, and the ink in the cylinder chamber 206 is discharged through the discharge one-way valve 210 to the ink tank 70 (see FIG. 3).

  As described above, when the cam 240 is rotated from the state in which the first flat surface 244 contacts the contact surface 228a until the third flat surface 248 contacts, the volume of the cylinder chamber 206 increases to the maximum. . That is, the amount by which the ink in the nozzle 22Kn (see FIG. 3) is sucked into the cylinder chamber 206 is the maximum amount of the suction pump 92. Thus, by controlling the rotation of the cam 240, the suction pump 92 can suck the maximum amount of ink and perform a recovery operation.

  The timing of rotation of the cam 240 is a timing based on the printing duty (an example of a predetermined timing according to the present invention) or a timing based on the elapsed time since the last recovery operation ended (this It is an example of a predetermined time passage in the invention).

  As described above, since the suction pump 92 can change the amount of ink to be sucked according to the stop position of the cam 240, the amount of ink to be sucked can be easily changed by changing the stop position of the cam 240. For this reason, the ink amount at the time of the recovery operation can be changed with a simple configuration.

  In the above example, three flat surfaces 244, 246, and 248 are formed on the cam 240 and the ink suction amount is changed in two stages. However, by forming four or more flat surfaces on the cam 240, 3 The ink suction amount may be changed in stages or more. Further, the pressurization amount can be changed in a plurality of stages by making the pressurization pump 68 the same as the suction pump 92. Moreover, although the vertical cross section of the cam 240 was made into the shape which formed the several linear part in the perfect circle, you may make it the shape which formed the several linear part in the ellipse.

  In the above example, the reciprocating pump unit that changes the volume of the ink to be sucked by changing the volume of the cylinder chamber 206 by rotating the cam 240 and reciprocating the piston 220 has been described. The present invention can also be applied to a diaphragm-type pump unit that changes the ink volume (fluid volume) by changing the volume of the cylinder chamber by rotating the nozzle to bend the diaphragm.

It is a front view showing typically an example of a printer incorporating a recovery mechanism of the present invention. FIG. 2 is a block diagram illustrating an electrical system of the printer of FIG. 1. It is a schematic diagram showing a recovery mechanism and an ink supply mechanism incorporated in the ink jet type image forming apparatus. It is a flowchart which shows the procedure at the time of cleaning a print head. It is a schematic diagram which shows the procedure of wiping off an ink from an ink discharge surface, (a) shows before wiping start, (b) shows immediately after completion | finish of wiping, (c) shows the standby state after completion | finish of wiping. It is a fragmentary longitudinal cross-section which shows a suction pump when a cam is located in a home position. It is a fragmentary longitudinal cross-section which shows a suction pump when a cam is located in a 1st suction position. It is a fragmentary longitudinal cross-section which shows a suction pump when a cam is located in a 2nd suction position.

Explanation of symbols

10 Printer 40 Recovery mechanism 92 Suction pump 200 Cylinder 206 Cylinder chamber 220 Piston 240 Cam 244 First flat surface 246 Second flat surface 248 Third flat surface

Claims (10)

In a pump unit that sucks or discharges fluid by changing the volume of a cylinder chamber by rotating a cam,
A pump unit characterized in that the amount of fluid sucked or discharged is changed according to the stop position of the cam. 2. The reciprocating pump unit according to claim 1, wherein the reciprocating pump unit changes the volume of the cylinder chamber by changing the volume of the cylinder chamber by rotating the cam and reciprocating the piston in a predetermined reciprocating direction. The pump unit described. 2. The pump unit according to claim 1, wherein the pump unit is a diaphragm type pump unit that changes the volume of the cylinder chamber by changing the volume of a cylinder chamber by rotating the cam to bend the diaphragm. 3. The pump unit according to claim 1, 2, or 3, wherein the cam has a stop position corresponding to a rotation angle from a predetermined initial position. The pump unit according to any one of claims 1 to 4, wherein the cam rotates when a force greater than a predetermined value is applied. The pump unit according to any one of claims 1 to 5, wherein the cam rotates at a predetermined timing. The pump unit according to claim 6, wherein the timing is determined based on the passage of a predetermined time. In a recovery mechanism for recovering an ink discharge state from the print head to an initial ink discharge state in an inkjet image forming apparatus that forms an image by discharging ink from a print head that discharges ink to a recording medium.
A pump unit according to any one of claims 1 to 7,
A recovery mechanism, wherein the pump unit sucks ink from the print head or pressurizes the print head. The recovery mechanism according to claim 8, wherein the fluid amount is changed based on an elapsed time since the previous recovery. The recovery mechanism according to claim 8, wherein the fluid amount is changed based on a predetermined printing duty.

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