JP2009125964A - Inkjet image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a capping mechanism which hinders adhesion of marks of an ink to a nozzle surface for a long time. <P>SOLUTION: An inclined surface 40d is formed to an edge part 40b of a cap 40 which caps a recording head 30. The edge part 40b is larger than an outline of the recording head 30, and an outer edge part 31a of the recording head 30 comes in contact with the inclined surface 40d at the time of capping. The edge part 40b is accordingly prevented from coming into contact with the nozzle surface 31, so that adhesion of stains by the ink can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet image forming apparatus that forms an image by ejecting fine ink droplets onto a recording medium, and more particularly to a capping mechanism of a recording head at rest.

As a prior art related to this type of capping mechanism, there is known a technique in which capping is performed by pressing a seal surface of a cap against a nozzle surface. (For example, refer to Patent Document 1). In this prior art, while the cap housed in the cap holder is urged upward by a spring, the cap holder is moved upward by the moving mechanism, and the edge portion of the cap (“seal surface” in Patent Document 1) is moved. It adheres to the nozzle surface. According to such a prior art, the cap surface is strongly pressed against the recording head by the elastic force of the spring at the time of capping, so it is considered that the nozzle surface can be reliably sealed.
JP 2000-2111148 A (FIGS. 2 and 11)

  However, since the above-described prior art has a structure in which the edge portion of the cap is pressed against the nozzle surface, there is a possibility that the following problems may occur while continuing to be used to some extent.

  First, since the prior art has a structure in which the edge portion of the cap is in close contact with the nozzle surface, if ink remains on the nozzle surface even after cleaning, the residual ink adheres to the edge portion, and the ink stains on the cap itself. Easy to stick. Even if a small amount of ink remains after cleaning, the cap accumulates as it continues to be used, causing a seal failure.

  The cap also has a function of receiving and collecting ink discharged from the head when the recording head discharge is recovered. At this time, if the edge of the cap is in close contact with the nozzle surface as in the prior art, the cap is discharged. Ink may scatter and adhere to the edge of the cap. After the ejection recovery, the nozzle surface is wiped with the waste ink adhering to the nozzle surface by the blade while the cap is lowered, and the nozzle surface is once clean.

  However, when capping is performed thereafter, the edge portion of the cap that remains dirty as described above comes into contact with the nozzle surface, so if the capping state continues for a long time, ink traces along the edge portion of the cap on the nozzle surface. Will remain. The ink trace remains until the next nozzle surface is wiped, causing a seal failure.

  Also, if the ink trace remaining on the nozzle surface dries and adheres, the ink trace adhered when the nozzle surface is wiped with a blade after recovery of discharge becomes a resistance (hook), and the blade is deformed. May cause wiping failure.

  In view of this, an object of the present invention is to realize a capping mechanism that makes it difficult for ink marks to adhere to the nozzle surface over a long period of time.

  The present invention is an ink jet image forming apparatus that forms an image by ejecting fine ink droplets onto a recording medium. In particular, an ink jet image forming apparatus according to the present invention includes a recording head having a nozzle surface substantially parallel to the recording medium and having an angular outer edge formed around the nozzle surface, and the recording head. An inclined surface that is inclined at a predetermined angle is formed on the facing edge portion, and a cap that tightly contacts the inclined surface with the outer edge portion is provided.

  According to the present invention, when the recording head is capped by the cap, the edge portion does not contact the nozzle surface, and the inclined surface only contacts the outer edge portion of the recording head. For this reason, even when ink is discharged from the recording head during ejection recovery, the ink does not adhere to the edge portion of the cap, so that the edge portion is not stained with ink. Further, since the edge portion does not come into contact with the nozzle surface at the time of capping, the edge portion does not contaminate the nozzle surface, and contamination can be prevented from each other.

  Note that the inclined surface of the cap preferably has a tapered shape constricted in the center direction of the nozzle surface. In this case, even if ink adheres to the inclined surface, the ink is collected in the central direction along the inclination, so that the ink can be collected in the cap.

  The inclined surface of the cap preferably has an inclination of 45 degrees or less with respect to the direction perpendicular to the nozzle surface. As a result, the ink adhering to the inclined surface easily slides down, so that no ink remains on the inclined surface.

  In addition, the cap has an edge portion on which the inclined surface is formed of an elastic body. In this case, since the edge portion is slightly elastically deformed along the outer shape of the nozzle surface (the shape of the outer edge portion) at the time of capping, the sealing performance can be further improved.

  As described above, according to the present invention, it is possible to prevent dirt from adhering to the nozzle surface of the recording head over a long period of time.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
FIG. 1 is a schematic vertical sectional view showing a schematic structure of an ink jet printer which is an example of an ink jet image forming apparatus.

[Outline of inkjet printer]
First, an outline of the ink jet printer 1 (hereinafter simply referred to as “printer”) will be described. A paper feed cassette 6 that is a paper storage unit is disposed below the inside of the main body of the printer 1. Inside the paper feed cassette 6, a single sheet P is stored in a state of being stacked vertically. A paper feed mechanism 7 is disposed downstream (upper right in FIG. 1) in the paper transport direction of the paper feed cassette 6. The paper feed mechanism 7 feeds the paper P toward the upper right of the paper feed cassette 6 in FIG.

  In addition, a paper feed roller 5, a paper transport path 8, a registration roller 9, an image forming unit 3, and a transport unit 2 are disposed downstream of the paper feed cassette 6 in the paper transport direction. First, the paper P sent out from the paper feed cassette 6 is sent to the paper feed roller 5, passes through the paper transport path 8, and reaches the downstream (upward in FIG. 1) registration roller 9. The registration roller 9 corrects the oblique feeding of the paper P, measures the timing of the ink ejection operation performed by the image forming unit 3, and sends the paper P to the transport unit 2.

  The transport unit 2 includes an endless transport belt 22 wound around a plurality of rollers (a driving roller 20, a driven roller 21, and a tension roller 23). The transport belt 22 travels counterclockwise in FIG. 1 by a drive mechanism (motor) (not shown). The paper P sent out by the registration rollers 9 is placed on the upper surface of the transport belt 22 and is transported from right to left in FIG.

  A suction unit 24 is provided below the upper surface portion of the conveyor belt 22, and the suction unit 24 generates a suction force by a suction source (not shown). The conveying belt 22 is provided with a number of through holes for suction (not shown). During recording, the suction force of the suction unit 24 is applied to the paper P through the through holes. As a result, the transport unit 2 can transport the paper P while adsorbing the paper P on the upper surface of the transport belt 22.

  On the other hand, the printer 1 receives image data signals such as characters, graphics, and patterns from an external computer (not shown), for example. This image data signal is processed by an image processing unit (not shown) and converted into a drive signal for the recording head 30 of the image forming unit 3. Note that the image forming unit 3 is disposed above the transport unit 2, and a minute interval is secured between the bottom surface of the image forming unit 3 and the sheet transport surface that is the top surface of the transport belt 22.

  The image forming unit 3 includes four sets of line-type ink jet recording heads 30 (hereinafter simply referred to as “recording heads”). Each of the recording heads 30 extends in the paper width direction perpendicular to the paper conveyance direction, and three recording heads are arranged in two rows in the front and rear in the paper width direction. As shown in FIG. 1, the four sets of recording heads 30 are arranged in tandem along the rotation direction of the conveyor belt 22 from the upstream side to the downstream side in the rotation direction. The four sets of recording heads 30 are for black color, cyan color, magenta color, and yellow color one by one in order from the upstream side.

  For example, four ink tanks (not shown) are provided below the transport unit 2 in correspondence with the four colors and four sets of recording heads 30. Each color ink is supplied from the ink tank to each set of recording heads 30 through a supply tube (not shown).

  Each recording head 30 of the image forming unit 3 discharges ink toward the recording surface of the paper P adsorbed on the surface of the conveyance belt 22 in accordance with the image data information received from the external computer. As the transport belt 22 travels, ink of each color is sequentially ejected from each recording head 30 at a predetermined timing, so that the paper P on the surface of the transport belt 22 has four colors of black, cyan, magenta, and yellow. A color ink image in which the ink is superimposed is formed and printed.

  A drying unit 11 is disposed downstream of the transport unit 2 in the paper transport direction. The ink ejected from the recording head 30 onto the paper P is dried by the drying unit 11.

  A discharge roller 13 and a discharge tray 15 are provided at a downstream position of the drying unit 11. The paper P after the ink has been dried by the drying unit 11 is sent to the left by the discharge roller 13 and discharged onto a discharge tray 15 provided outside the left side surface of the main body.

  Further, the transport unit 2 can be moved up and down in the main body as shown by an arrow in FIG. For example, the elevating mechanism holds the transport unit 2 at the raised position during recording, and appropriately holds the distance from the image forming unit 3. In this state, ink droplets are ejected from each recording head 30, and printing and image formation are performed as described above. The elevating mechanism can lower the transport unit 2 when the image forming unit 3 is stopped, for example, and can secure a space for capping with the image forming unit 3.

[Details of capping mechanism]
Next, the capping mechanism in this embodiment will be described.
FIG. 2 is a plan view schematically showing the internal structure of the printer 1. In FIG. 2, the lower side corresponds to the front side facing the user of the printer 1, and the upper side corresponds to the rear side of the printer 1.

  A cap unit 4 is provided in the main body of the printer 1 behind the image forming unit 3 and the transport unit 2. However, the cap unit 4 horizontally moves between a cap position A on the lower side of the image forming unit 3 and a standby position B on the rear side thereof. The cap unit 4 moves up and down at the cap position A. Such horizontal movement and raising / lowering operations of the cap unit 4 are realized by, for example, a horizontal movement mechanism and a raising / lowering mechanism (not shown). As the horizontal movement mechanism, for example, a belt transmission mechanism can be applied. Moreover, as a raising / lowering mechanism, the mechanism which drives the cam etc. which were distribute | arranged to four corners synchronously, for example can be applied.

  As described above, the image forming section 3 has a total of twelve recording heads 30 for each color group, three for each group and four groups. The three recording heads 30 forming one set are arranged in a staggered manner in the paper transport direction and the width direction. Specifically, the recording head 30b positioned in the center in the sheet width direction is positioned upstream in the transport direction, and the two recording heads 30a and 30c positioned on both sides in the width direction are positioned downstream of the recording head 30b. ing.

  The cap unit 4 has twelve caps 40 corresponding to the twelve recording heads 30 respectively. These caps 40 are arranged in accordance with the staggered arrangement of the recording heads 30 described above. The details of the cap 40 will be described later with reference to another drawing.

  The cap unit 4 has a wiping mechanism 41. The wiping mechanism 41 is positioned on one side edge portion in the horizontal movement direction of the cap unit 4 and extends in the sheet conveyance direction (the direction in which the four sets of recording heads 30 are arranged) at this position. The wiping mechanism 41 has a total of eight wiper members 47 corresponding to the recording heads 30 in each set of two rows. These wiper members 47 wipe the recording heads 30 as the cap unit 4 moves horizontally. The wiper member 47 will be described later with reference to still another drawing.

  FIG. 3 is a vertical sectional view showing the configuration of the cap unit 4 in more detail. The cross section of FIG. 3 corresponds to a vertical cross section along the horizontal movement direction of the cap unit 4.

  As described above, each cap 40 is formed upward corresponding to each recording head 30. The cap unit 4 moves horizontally from the cap position A to the standby position B during recording. On the other hand, when the cap 40 is put on each of the recording heads 30 (during capping), the cap unit 4 moves up after moving horizontally from the standby position B to the cap position A, and the cap 40 is put on the recording head 30 along with this rise. It is done. Each cap 40 is supported in a state of being biased upward by, for example, a coil spring, and is pressed against the recording head 30 by the elastic force of the coil spring at the time of capping.

  Further, when moving from capping to recording, the cap unit 4 is lowered and the cap 40 is detached from the recording head 30, and then moves horizontally to the standby position B. As described above, the wiping mechanism 41 cleans the lower surface of the image forming unit 3, that is, the nozzle surface. The wiping mechanism 41 is also provided on the upper surface of the cap unit 4.

  FIG. 4 is a diagram showing the configuration of the wiping mechanism 41 in more detail. 4A is an enlarged view of the wiping mechanism 41 shown in FIG. 4B is a cross-sectional view showing the internal structure of the wiping mechanism 41 in detail.

  The wiper member 47 includes, for example, a rubber blade 47a and a support portion 47b that supports the blade 47a, and each support portion 47b is supported by a horizontal shaft 48. A gear 48 a is attached to the horizontal shaft 48, and a gear 49 a attached to the rotation shaft of the drive motor 49 is meshed with the gear 48 a and the rotation angle of the wiper member 47 is adjusted by the rotation of the drive motor 49. It is a configuration. Note that the rotation angle of the wiper member 47 is regulated by, for example, the stopper 50.

[Operation of wiping mechanism]
FIG. 5 is a diagram illustrating the operation of the wiping mechanism 41. In the following, description will be given in order.

  5A: An ink discharge port (not shown) is formed on the lower surface of the recording head 30 (hereinafter referred to as “nozzle surface 31”), and from the ink discharge port during recording by the image forming unit 3. Fine ink droplets are ejected. For this reason, the ink K may scatter and adhere to the nozzle surface 31 after the recording in the image forming unit 3 is completed. The nozzle surface 31 has a long and thin rectangular shape, and an outer edge portion 31a having an angular shape of approximately 90 degrees is formed around the nozzle surface 31.

  FIG. 5B: When capping is performed after the recording is finished, the drive motor 49 (see FIG. 4) is driven to rotate the wiper member 47, and the blade 47a is inclined to the opposite side of the traveling direction. Fix in position. When the cap unit 4 is moved to the cap position A in this state, the tip of the blade 47a moves while being in contact with the nozzle surface 31 as shown in the figure. At this time, the ink K adhering to the nozzle surface 31 is scraped off by the blade 47a, and the nozzle surface 31 is wiped.

  (C) in FIG. 5: It is the figure which looked at this from the moving direction of the wiper member 47 about said wiping operation | movement. At this time, it can be seen that the blade 47a is in good contact with the nozzle surface 31 over its entire width.

  Thereafter, as the cap unit 4 moves horizontally, the wiping mechanism 41 passes below the recording head 30 and when the cap unit 4 stops at the cap position A, all the caps 40 face each recording head 30 from below. Stop where you want to go. As described above, the cap unit 4 is lifted by the lifting mechanism (not shown), and each cap 40 is capped to the recording head 30.

  Although the above is the outline | summary about the cap unit 4, in addition, in this embodiment, it has the following characteristics about the shape of each cap 40. FIG.

[Cap shape]
FIG. 6 is a detailed view showing the shape of the cap 40. 6A corresponds to a plan view of the cap 40, and FIG. 6B corresponds to a vertical sectional view.

  6A: The cap 40 has an upper surface that is elongated and has a rectangular shape in accordance with the outer shape of the recording head 30. FIG. The inside of the cap 40 has a square funnel shape for receiving the discharged ink. A drain hole 40e for collecting the discharged ink is formed in the center of the cap 40, and the cap 40 is inclined downward toward the drain hole 40e.

  In FIG. 6, (B): The cap 40 is composed of two parts, a main body portion 40a and an edge portion 40b. Of these, the main body 40a is a rigid member such as SUS (stainless steel) or resin. On the other hand, the edge portion 40b is an elastic member such as EPDM or fluororubber. A tube joint 40c is formed around the drain hole 40e at the lower end of the main body 40a, and a collection tube (not shown) is connected to the tube joint 40c. The discharged ink is guided to a waste liquid tank (not shown) through this collection tube.

  The edge portion 40b is bonded and fixed above the main body portion 40a. Further, an inclined surface 40d is formed on the edge portion 40b along the opening edges (four sides) on the upper surface. The inclined surface 40d is inclined by an angle α of 45 degrees or less (preferably 30 degrees) with respect to the vertical direction (direction perpendicular to the nozzle surface 31). Such an inclined surface 40 d has a tapered shape constricted in the center direction of the nozzle surface 31.

[When capping]
FIG. 7 is a continuous diagram showing the capping operation by the cap 40. In the following, description will be given in order.

  7A: When the cap unit 4 stops at the cap position A, the cap 40 is positioned directly opposite the recording head 30 as illustrated. At this time, the tip portion of the edge portion 40b of the cap 40 is formed so that the distance between the opposite tip portions is larger than the length of the outer edge portion 31a of the corresponding recording head 30. A certain outer edge portion 31 a is located inside the opening of the cap 40 in the vertical direction.

  7B: When the cap unit 4 is raised, the edge portion 40b of the cap 40 is pressed against the recording head 30, and the capping operation is performed. Although the edge portion 40b is an elastic body, it has a thickness of 3 to 5 mm, for example, so that it does not deform excessively even when pressed against the recording head 30.

  As described above, the outer shape of the edge portion 40 b is formed larger than the outer shape of the recording head 30. For this reason, at the time of capping, the outer edge portion 31a on the outer periphery of the recording head 30 contacts the inclined surface 40d, whereby the nozzle surface 31 is sealed. Therefore, since the edge portion 40b never contacts the area of the nozzle surface 31, no ink adheres to the nozzle surface 31 even if the edge portion 40b is contaminated with the discharged ink.

  Furthermore, since the edge portion 40b is larger than the outer shape of the recording head 30 at the time of ejection recovery, the possibility that the discharged ink adheres to the edge portion 40b is extremely low. Even if ink adheres to the edge portion 40b, the place where the ink adheres is limited to the inclined surface 40d of the edge portion 40b. Since the inclined surface 40d is inclined at 45 degrees or less with respect to the vertical direction, the adhered ink easily slides down the inclined surface 40d. As a result, the edge portion 40b is not stained with ink.

[Comparison with conventional example]
Next, this embodiment will be verified by comparing with a conventional example.
FIG. 8 is a detailed view showing the shape of a conventional cap 400 and its capping operation. As shown in FIG. 8A, the conventional cap 400 is smaller than the outer periphery of the recording head 30. Therefore, as shown in FIG. 8B, the tip (upper end) of the edge portion 400b contacts the nozzle surface 31 during capping. The edge portion 400b is an elastic member, and such an edge portion 400b is bonded and fixed above the main body portion 400a of the rigid member.

  FIG. 9 is a diagram showing a wiping operation when the conventional cap 400 is used. In the following, description will be given in order.

  In FIG. 9, (A): In the conventional example, since the edge portion 400b is in contact with the nozzle surface 31 while being soiled with ink, if the capping state continues for a long time, the ink surface of the edge portion 400b along the tip shape of the edge portion 400b Trace K will remain. In particular, when the recording head 30 is enlarged or made porous, the amount of ink that is discharged increases, and the edge portion 400b tends to become dirty. In addition, when pigment-based ink is used, the ink contains a resin component, so that it is easy to solidify when dried and ink marks are easily formed on the nozzle surface 31.

  9B and 9C: When ink marks are formed on the nozzle surface 31, the blade 47a is distorted by the ink marks K on the nozzle surface 31 when the nozzle surface 31 is wiped by the blade 47a after recovery of ejection. The edge of the blade 47a cannot be completely brought into contact with the nozzle surface 31. For this reason, a gap is formed between the blade 47a and the nozzle surface 31 during wiping, and the ink adhering to the nozzle surface 31 is left unwiped.

  On the other hand, in the present embodiment, since the edge portion 40 b does not contact the nozzle surface 31, the edge portion 40 b is not stained with ink, and as a result, ink is not attached to the nozzle surface 31. For this reason, as shown in FIG. 5C, the edge of the blade 47a can always be brought into close contact with the nozzle surface 31, thereby wiping ink reliably.

  The present invention can be implemented with various modifications without being limited to the above-described embodiments. In one embodiment, an example in which three recording heads 30 are provided in one group is given, but four or more recording heads 30 may be arranged in one group. Further, the size of the recording head 30 and the cap 40 can be appropriately modified, and is not particularly limited to the illustrated example.

It is a model vertical sectional view showing a schematic structure of an ink jet printer. FIG. 2 is a plan view schematically showing an internal structure of the printer. It is a vertical sectional view showing the configuration of the cap unit in more detail. It is a figure which shows the structure of a wiping mechanism in detail. It is a figure which shows operation | movement of a wiping mechanism. It is detail drawing which shows the shape of a cap. It is a continuation figure showing capping operation by a cap. It is detail drawing which shows the shape of the cap of a prior art example, and its capping operation | movement. It is a figure which shows the wiping operation | movement at the time of using the cap of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 3 Recording head 4 Cap unit 30 Recording head 31 Nozzle surface 31a Outer edge part 40 Cap 40b Edge part 40d Inclined surface 41 Wiping mechanism

Claims (4)

In an inkjet image forming apparatus that forms an image by ejecting fine ink droplets onto a recording medium.
A recording head having a nozzle surface substantially parallel to the recording medium and having an angular outer edge formed around the nozzle surface;
An ink jet image forming apparatus, comprising: an inclined surface inclined at a predetermined angle at an edge portion facing the recording head; and a cap for closely attaching the inclined surface to the outer edge portion. The inkjet image forming apparatus according to claim 1,
The inclined surface of the cap is
An ink jet image forming apparatus having a tapered shape constricted in a central direction of the nozzle surface. The inkjet image forming apparatus according to claim 1 or 2,
The inclined surface of the cap is
An inkjet image forming apparatus having an inclination of 45 degrees or less with respect to a vertical direction of the nozzle surface. The inkjet image forming apparatus according to any one of claims 1 to 3,
The cap is
An ink jet image forming apparatus, wherein an edge portion on which the inclined surface is formed is made of an elastic body.

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