This application is based on and claims the benefit of priority from Japanese patent application No. 2022-208895 filed on Dec. 26, 2022, which is incorporated by reference in its entirety.
The present disclosure relates to a cap unit.
In an inkjet recording apparatus that uses water-based ink, there is a problem that moisture evaporates from the ink in a nozzle while printing is not performed, resulting in an increase in viscosity. This causes ejection failure and clogging. Therefore, a technique to suppress the evaporation of moisture from the ink in the nozzle has been conventionally discussed. For example, a head holder holding a head is provided with an annular cap covering an ejection surface, and when humidifying maintenance is performed, in a state where a projection of the cap comes into contact with a support surface of a conveyance belt, humidified air is supplied into an ejection space formed between the ejection surface and the support surface until concentration or viscosity of ink in an ejection port becomes less than an appropriate value.
However, in the above configuration, since the space inside the cap is sealed, if a temperature inside the cap changes, condensation may occur on the nozzle surface, which may reduce the viscosity of the ink. In addition, air pressure changes according to the temperature change in the cap, which may cause meniscus in the nozzle to collapse and make it impossible to eject the ink.
A cap unit according to the present disclosure includes a cap, a tank, a first pipe, a second pipe, a pump, and a vent port. The cap is attached to and detached from a nozzle surface of an inkjet head. The tank stores humidifying liquid. The first pipe and the second pipe connect the cap and the tank. The pump is provided in the first pipe and pumping air in the tank into the cap. The vent port is provided in the cap.
The above and other objects, features, and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present disclosure is shown by way of illustrative example.
Hereinafter, with reference to the drawings, an inkjet recording apparatus 1 and a cap unit 70 according to one embodiment of the present disclosure will be described.
First, an entire structure of the inkjet recording apparatus 1 will be described.
The inkjet recording apparatus 1 (see
Inside the body housing 3, a conveyance path 10 is provided from the sheet feeding roller 5 through a gap between the conveyance unit 7 and the image forming unit 6 to the discharge roller 8. The conveyance path 10 is formed mainly by plate-like members facing each other with a gap for passing the sheet S. On the conveyance path 10, conveyance rollers 17 which hold the sheet S and convey it are provided. A registration roller 18 is provided on the upstream side of the image forming unit 6 in the conveyance direction Y.
The conveyance unit 7 includes an endless conveyance belt 21, a support plate 23, and a suction part 24. The conveyance belt 21 has a number of vent holes (not shown) and is wound around a drive roller 25 and a driven roller 22. The support plate 23 has a number of vent holes, and the upper surface is in contact with the inner surface of the conveyance belt 21. The suction part 24 attracts the sheet S to the conveyance belt 21 by sucking air through the vent holes of the support plate 23 and the vent holes of the conveyance belt 21. When the drive roller 25 is driven in the counterclockwise direction by a drive unit (not shown) including a motor and a reduction gear, the conveyance belt 21 travels in the counterclockwise direction, and the sheet S attracted to the conveyance belt 21 is conveyed in the Y direction.
The inkjet recording apparatus 1 includes an ink supply path 60 (see
The image forming unit 6 includes head units 11Y, 11Bk, 11C and 11M (collectively referred to as a head unit 11). The head unit 11 contains one or more inkjet heads 12, for example, three inkjet heads 12 arranged in a staggered manner (see
The inkjet head 12 (see
A control part 2 (see
A display operating part 19 is provided on the upper portion of the body housing 3 (see
The basic image forming operation of the inkjet recording apparatus 1 is as follows. When an image forming job is input to the inkjet recording apparatus 1 from the display operating part 19 or an external computer, the sheet feeding roller 5 feeds the sheet S from the sheet feeding cassette 4 to the conveyance path 10, and the registration roller 18, whose rotation has been stopped, corrects the skew of the sheet S. When the registration roller 18 feeds the sheet S to the conveyance unit 7 at a prescribed timing, the conveyance unit 7 attracts the sheet S to the conveyance belt 21 and conveys it in the Y direction. When the control part 2 supplies a raster-type image data to the drive circuit in synchronization with the conveyance of the sheet S, the drive circuit supplies an ejection signal corresponding to the gradation of the image data to the pressurizing element 12Z, and the ink is ejected from the nozzle 12N to form an image on the sheet S. The discharge roller 8 discharges the sheet S on which the image is formed to the discharge tray 9.
[Maintenance Device] Next, a configuration of a maintenance device 30 will be described.
The maintenance device 30 is provided for each head unit 11 on the left side of the head unit 11 (on the downstream side in the conveyance direction Y) (see
The maintenance device 30 includes the cap unit 70 with the cap 72 attached to the nozzle surface 12F, the wipe unit 80 with a wipe blade 82 which removes the ink remaining on the nozzle surface 12F, and a housing 31 in which the cap unit 70 and the wipe unit 80 are housed. The housing 31 is formed in a rectangular box-like shape whose longitudinal direction is along the front-and-rear direction, and an opening is provided on the right side surface. The maintenance device 30 includes a cap moving mechanism (not shown) for moving the cap unit 70 in the left-and-right direction and a wipe moving mechanism (not shown) for moving the wipe unit 80 in the left-and-right direction.
[Cap Unit] The cap unit 70 (see
[Wipe Unit] The wipe unit 80 (see
[Lifting Mechanism] The inkjet recording apparatus 1 includes a lifting mechanism (not shown) for lifting and lowering the head unit 11. The lifting mechanism lifts and lowers the head unit 11 between an image forming position when the image forming operation is performed and a retreating position above the image forming position. At the image forming position, the head unit 11 is positioned so that a distance between the conveyance belt 21 and the nozzle surface 12F is a predetermined distance. At the retreating position, a space is formed between the conveyance belt 21 and the nozzle surface 12F in which the cap unit 70 and the wipe unit 80 can be moved.
Next, the operation of the maintenance device 30 will be described.
First, the control part 2 operates the lifting mechanism to lift the head unit 11 to the retreating position (see
Next, the control part 2 operates the lifting mechanism to lift the head unit 11 to the retreating position (see
Then, the control part 2 operates the cleaning liquid supply part 13 to supply the cleaning liquid to the nozzle surface 12F, and operates the carriage moving mechanism to move the wipe blade 82. The wipe blade 82 is moved while scraping the cleaning liquid and the ink from the nozzle surface 12F. The ink is diluted with the cleaning liquid and falls off. The waste liquid, which is a mixture of the ink and the cleaning liquid, is received by the cap 72.
Next, the control part 2 operates the lifting mechanism to lift the head unit 11 to the retreating position (see
When the image forming operation is performed, the control part 2 operates the lifting mechanism to lift the head unit 11 to the retreating position (see
Next, the cap unit 70 will be described in detail. The cap unit 70 according to the present embodiment includes the cap 72 attached to and detached from the nozzle surface 12F of the inkjet head 12, a tank 73 storing humidifying liquid W, a first pipe 73A and a second pipe 73B connecting the cap 72 and the tank 73, a pump 74 provided in the first pipe 73A and pumping air in the tank 73 into the cap 72, and a vent port 72D provided in the cap 72.
[Tank] The tank 73 (see
[First Pipe, Second Pipe] The tank 73 and the cap 72 are connected by the first pipe 73A and the second pipe 73B. The first pipe 73A and the second pipe 73B are connected to the upper portion of the tank 73 and the bottom portion 72B of the cap 72. The lower ends of the first pipe 73A and the second pipe 73B are positioned above the liquid level of the humidifying liquid W. The upper ends of the first pipe 73A and the second pipe 73B protrude above the bottom portion 72B of the cap 72 to prevent the waste liquid from flowing in, and are positioned below the upper edge of the cap 72 to prevent contact with the nozzle surface 12F. When the cap 72 is viewed from above (see
[Pump] The pump 74 is provided in the first pipe 73A. The pump 74 is capable of normal rotation for pumping the air in the tank 73 into the cap 72 and reverse rotation for pumping the air in the cap 72 into the tank 73. The pump 74 is preferably one that can supply air, but it is preferable to use a diaphragm pump.
[Vent Port] The vent port 72D penetrating in the front-and-rear direction is provided on the rear wall of the recess 720 of the cap 72. The vent port 72D forms an air passage connecting the space in the cap 72 with a space (atmosphere) outside the cap 72. The vent port 72D is formed using a tube whose longitudinal direction is along the front-and-rear direction. In order not to block the air circulation through the second pipe 73B, it is desirable that a fluid resistance of the vent port 72D is larger than that of the second pipe 73B. A cross section of the vent port 72D is preferably a circle with an inner diameter of 0.05 mm or more and 10 mm or less, or a shape other than a circle with the same cross-sectional area (ellipse, rectangle, or the others). A length of the vent port 72D should be 0.1 mm or more and 1000 mm or less.
In order not to block the supply of water vapor from the first pipe 73A, it is desirable that the vent port 72D be provided on the side wall of the recess 72U of the cap 72 on the side closer to of the second pipe 73B. In order not to block the air circulation through the second pipe 73B, it is desirable that the vent port 72D be separated from the line L connecting the first pipe 73A and the second pipe 73B at the bottom portion 72B in a plan view. To prevent drying of the ink in the nozzle 12N, it is desirable that the vent port 72D be separated from the nozzle surface 12F. For example, the vent port 72D is preferably provided closer to the bottom portion 72B than the center portion of the side wall in the upper-and-lower direction.
Next, the operation of the cap unit 70 will be described.
Here, since the vent port 72D is provided on the side of the second pipe 73B, due to the influence of the airflow flowing from the first pipe 73A side to the second pipe 73B side, an airflow from the inside to the outside of the cap 72 tends to occur near the vent port 72D. On the other hand,
It may be configured such that switching the rotation of the pump 74 between the normal direction and the reverse direction is performed according to the temperature and the humidity in the cap 72. For example, a sensor (not shown) for measuring the temperature and humidity is provided in the cap 72. In the storage part of the control part 2, a table (not shown) relating the temperature and humidity to the presence or absence of condensation is stored. When a combination of the temperature and humidity measured by the sensor corresponds to the condensation, the control part 2 switches the rotation of the pump 74 from the normal direction to the reverse direction. It may be configured such that switching the rotation of the pump 74 between the normal direction and the reverse direction is performed according to the air pressure in the cap 72.
The cap unit 70 according to the present embodiment described above includes the cap 72 to be attached to and detached from the nozzle surface 12F of the inkjet head 12, the tank 73 in which the humidifying liquid W is stored, the first pipe 73A and the second pipe 73B connecting the cap 72 and the tank 73, the pump 74 provided in the first pipe 73A for pumping the air in the tank 73 into the cap 72, and the vent port 72D provided in the cap 72. The air in the tank 73 is humidified with the humidifying liquid W and circulates in the order of the first pipe 73A, the cap 72, the second pipe 73B and the tank 73. In the cap 72, the humidified air suppresses the evaporation of moisture from the ink in the nozzle 12N. When the temperature in the cap 72 decreases, since the air pressure also decreases, the outside air is introduced into the cap 72 from the vent port 72D to moderate the decrease of the air temperature and pressure, air thereby suppressing the condensation. On the other hand, when the temperature in the cap 72 increases, since the air pressure also increases, the air is discharged out of the cap 72 through the vent port 72D to moderate the increase of the temperature and air pressure, thereby preventing the collapse of the meniscus. Therefore, according to the present embodiment, the humidified air can be supplied into the cap 72, and the condensation and pressure change in the cap 72 can be suppressed.
According to the cap unit 70 according to the present embodiment, the fluid resistance of the vent port 72D is larger than that of the second pipe 73B. According to this configuration, the circulation of the humidified air cannot be inhibited.
According to the cap unit 70 according to the present embodiment, the first pipe 73A and the second pipe 73B are connected to the bottom portion 72B of the cap 72, and the vent port 72D is provided in the side wall closer to the second pipe 73B, and in a plan view, is separated from the line L connecting the first pipe 73A and the second pipe 73B at the bottom portion 72B. According to this configuration, the circulation of the humidified air cannot be inhibited.
In addition, according to the cap unit 70 according to the present embodiment, the vent port 72D is separated from the nozzle surface 12F. According to this configuration, it is possible to suppress the influence of the airflow through the vent port 72D on the meniscus in the nozzle 12N.
In addition, according to the cap unit 70 according to the present embodiment, the vent port 72D is provided closer to the bottom portion 72B than the center portion of the side wall in the upper-and-lower direction. According to this configuration, the influence of the airflow through the vent port 72D on the meniscus in the nozzle 12N can be further suppressed.
In addition, according to the cap unit 70 of the present embodiment, the pump 74 can be normally rotated for feeding the air in the tank 73 into the cap 72 and reversely rotated for feeding the air in the cap 72 into the tank 73. According to this configuration, the humidity can be reduced when the humidity in the cap 72 is excessive.
The above embodiment may be modified as follows.
Number | Date | Country | Kind |
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2022-208895 | Dec 2022 | JP | national |