JP2008126641A - Ink-jet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording apparatus capable of maintaining an appropriate ink feeding amount to a head by a simple structure. <P>SOLUTION: A compression spring 40 which has elasticity and supports a sub tank 22 is provided. As a result, a water head difference D is constantly maintained in the ink-jet recording apparatus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that records an image (including characters, drawings, symbols, and the like) on a recording medium by ejecting ink droplets toward a recording medium such as paper.

  The ink jet recording apparatus is an apparatus that ejects ink from a head in accordance with an ejection signal from a control device and records an image on a recording medium using the ink. The ink jet recording apparatus has a configuration in which ink is stored in a main tank, ink is temporarily held by a sub tank in the middle of supply from the main tank to the head, and ink is supplied from the sub tank to the head by negative pressure. There is something to prepare.

In order to keep an appropriate amount of ink supplied to the head, it is necessary to keep this negative pressure at a predetermined level. Therefore, conventionally, a configuration has been proposed for keeping the water head difference between the ink level in the sub-tank and the head constant in order to make the negative pressure constant. For example, in the ink jet recording apparatus of Patent Document 1, a sensor for detecting the height of the liquid level in the sub-tank is provided, and based on the detection result of the sensor so that the height of the liquid level is within a certain range. It describes that the ink supply from the main tank to the sub tank is controlled.
JP 2002-120374 A (published on April 23, 2002)

  However, in recent years, due to an increasing demand for downsizing of the device, a device having a simple configuration is desired. However, the conventional device cannot sufficiently meet such a request.

  Accordingly, an object of the present invention is to provide an ink jet recording apparatus capable of keeping the above-described negative pressure constant with a simple configuration.

  In order to solve the above problems, an ink jet recording apparatus according to claim 1 is an ink jet recording apparatus that records an image on a recording medium with ink ejected from a head, and a main tank in which ink is stored; The ink from the main tank to the head is stored inside, and the sub tank that supplies a predetermined amount of ink to the head due to the water head difference between the ink inside and the ink in the head, and the magnitude of the applied force A support member that supports the sub-tank in the direction of gravity, and the support member is configured to support the sub tank by the elasticity of the elastic material according to a change in the amount of ink in the sub tank. By changing the position in the direction of gravity, the water head difference is kept constant.

  The ink jet recording apparatus uses the elasticity of the support member to move the sub tank in the gravitational direction and keep the water head difference between the ink in the sub tank and the head constant. That is, the water head difference can be kept constant by a simple configuration called a support member.

  According to a second aspect of the present invention, the ink jet recording apparatus according to the first aspect includes a position detection unit that detects a position of the sub tank in the direction of gravity, and a liquid feeding unit that moves the ink from the main tank to the sub tank. The liquid feeding unit moves ink from the main tank to the sub tank when the position detecting unit detects that the sub tank is positioned at a predetermined first height. May be.

  When the ink in the sub tank decreases, the combined weight of the sub tank and the ink, that is, the force applied to the support member in the direction of gravity decreases. Therefore, the lower the ink in the sub tank, the higher the height of the sub tank in the direction of gravity. Therefore, as in the ink jet recording apparatus according to claim 2, by including a liquid feeding unit that moves ink from the main tank to the sub tank when the position of the sub tank reaches a predetermined height (first height), The amount of ink in the sub tank can be kept above a certain value.

  According to a third aspect of the present invention, in the ink jet recording apparatus according to the second aspect, the liquid feeding unit is configured so that the position detection unit detects that the sub tank is positioned at the first height. In addition, the same amount of ink may be moved to the sub tank.

  In addition, as described in claim 4, in the ink jet recording apparatus according to claim 2, the liquid feeding unit is configured so that the sub tank is positioned at a second height lower than the first height. When the position detection unit detects, the movement of the ink to the sub tank may be stopped.

  According to the ink jet recording apparatus of the present invention, since the hydraulic head difference between the sub tank and the head is maintained using the elasticity of the support member, the negative pressure can be kept constant without complicating the configuration.

  The ink jet recording apparatus of the present invention will be specifically described by showing its embodiment. However, the present invention is not limited to the following description.

<First embodiment>
[1] Inkjet Printer As an inkjet recording apparatus, a line type inkjet printer provided with a head having a number of nozzles will be described below as an example, but the present invention is not limited to this.

  As the line-type ink jet printer, the technique described in JP-A-2006-12397 (published on May 18, 2006) can be suitably used. An example of the structure of a line type ink jet printer is shown in FIGS. FIG. 1 is a front view showing the main configuration of the ink jet printer, and FIG. 2 is a plan view showing the structure around the head as viewed from the ink ejection surface side. In FIG. 2, for convenience of explanation, the conveyor belt 111 is indicated by a dotted line.

  A printer 100 shown in FIG. 1 is a line head type color ink jet printer having four heads 12 arranged in the transport direction of the printing paper P. Each head 12 has a rectangular outer shape that is elongated in a direction orthogonal to the conveyance direction of the paper P (a direction perpendicular to the paper surface in the drawing). The printer 100 is provided with a paper feeding device 114 on the lower side, a paper receiving unit 116 on the upper side, and a transport unit 120 on the middle in the installation posture. Further, the printer 100 includes a control device 200 that controls these operations.

  The paper feeding device 114 is a paper storage unit 115 that can store a plurality of stacked rectangular papers P, and a paper supply unit that feeds the uppermost paper P in the paper storage unit 115 to the transport unit 120 one by one. And a roller 145. In the paper storage unit 115, the paper P is stored so as to be fed in a direction parallel to the long side. A plurality of feed rollers 118 are appropriately disposed along the transport path between the paper storage unit 115 and the transport unit 120. The printing paper P discharged from the paper feeding device 114 is sent to the transport unit 120 by the feed roller 118 with one short side as the leading edge.

  The transport unit 120 includes an endless transport belt 111 and a plurality of belt rollers 106 around which the transport belt 111 is wound. A predetermined tension is generated on the conveyor belt 111 wound between the individual belt rollers 106. Also, one surface (conveying surface 127) of the conveying belt 111 is treated with adhesive silicon rubber, and the printing paper P is securely adhered to the conveying surface 127. Alternatively, a large number of small-diameter holes are formed in the transport belt 111, and suction means such as a fan for sucking air from the opposite side of the surface of the transport belt 111 on which the printing paper P is held is provided. It is good also as a structure hold | maintained at the conveyance belt 111 by the suction force of. Further, the transport surface 127 is arranged so as to face the head 12. The printing paper P sent out from the paper feeding device 114 is transported by the transport belt 111 while being printed by the head 12 on the upper surface (printing surface), and reaches the paper receiving section 116. In the paper receiving unit 116, a plurality of printed printing papers P are placed so as to overlap each other.

  The four heads 12 are arranged close to each other along the paper transport direction. A large number of nozzles 8 having a minute diameter are provided on the bottom surfaces (ejection surfaces 13) of the four heads 12 (see FIG. 2). The ink color ejected from the nozzle 8 is one of magenta (M), yellow (Y), cyan (C), and black (K), and is ejected from a number of nozzles 8 belonging to the same head 12. The color is the same. In addition, inks of different colors selected from the four colors magenta, yellow, cyan, and black are ejected from a large number of ink ejection ports belonging to the four heads 12.

  A slight gap is formed between the discharge surface 13 and the transport surface 127 of the transport belt 111. The printing paper P is transported along the transport direction indicated by the arrows with this gap. When the printing paper P sequentially passes below the ejection surface 13, a desired color image is formed on the printing paper P by ejecting ink from the nozzles 8 according to the image data toward the upper surface of the printing paper P. Is done.

  A peeling plate 140 is provided downstream of the transport unit 120 in the paper transport direction. The peeling plate 140 peels the printing paper P adhered to the conveyance surface 127 of the conveyance belt 111 from the conveyance surface 127 when the end of the conveyance unit 120 enters between the printing paper P and the conveyance belt 111. To do.

  A plurality of feed rollers 121 are arranged between the transport unit 120 and the paper receiver 116. The printing paper P discharged from the transport unit 120 is sent to the paper receiving unit 116 by the feed roller 121.

  A paper surface sensor 133, which is an optical sensor composed of a light emitting element and a light receiving element, is detected upstream of the head 12, which is the most upstream in the conveying direction, in order to detect the leading end position of the printing paper P on the conveying belt 111. Has been placed. Since it can be seen from the output signal from the paper surface sensor 133 that the leading edge of the printing paper P has reached the detection position, an ejection signal is supplied from the control device 200 to the head 12 accordingly. Thus, an image is formed on the printing paper P with ink. This image includes characters, symbols, figures, and the like.

  The control device 200 transmits / receives data signals and control signals to / from each unit of the printer 100 in accordance with instructions received from the user via an operation panel (not shown) and detection results of various sensors, thereby performing image forming operations, It controls the ink temperature adjustment operation and the like which will be described later. Specifically, the control device 200 can be configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU can perform various calculations and execute programs. The ROM stores a program related to control performed by the CPU, a program related to the operation of each unit in the printer 100, and the like. In addition to functioning as a work area for the CPU, the RAM has an area for holding user input contents and the like.

  The ink ejected by the inkjet printer 100 is not particularly limited in terms of its properties and configuration, such as aqueous, oily, a solution in which a dye is dissolved, a dispersion in which particles such as pigment are dispersed, and the like.

[2] Ink supply system In this embodiment, the head 12, the main tank 21 for storing ink, the sub tank 22 provided between the main tank 21 and the head 12, and the ink from the main tank 21 to the sub tank are supplied. A first supply path 23 for supplying, a second supply path 24 for supplying ink from the sub tank 22 to the head 12, and a pump 25 provided in the supply path 23 for sending ink from the main tank 21 to the sub tank 22. The ink supply system 20 is formed.

  The main tank 21 is provided with a vent hole 31 through which air flows from the outside as the ink inside the main tank 21 decreases. The printer 100 is detachably provided. When the ink remaining amount sensor (not shown) detects that the ink in the main tank 21 is low, the control unit 200 prompts the user to replace the tank with a display unit (not shown).

  Similar to the main tank 21, the sub tank 22 includes a vent hole 32 through which air flows from the outside as the ink inside decreases. The sub tank 22 has a smaller ink capacity than the main tank 21. The sub tank 22 can store ink from the main tank 21.

  The sub tank 22 is supported by a compression spring 40. One end of the compression spring 40 is fixed to the bottom of the sub tank 22, and the other end is fixed to the main body of the printer 100. The compression spring 40 appropriately supplies a difference between the water head of the ink in the sub tank 22 and the liquid level of the ink in the ejection hole that discharges ink in the head 12, that is, the water head difference D, so The amount can be adjusted.

  In order to maintain the water head difference D, more specifically, the compression spring 40 is configured such that the amount of ink liquid level in the sub tank 22 due to ink consumption and the amount of ink in the sub tank 22 due to ink consumption are reduced. The spring constant of the compression spring is set so that the push-up amounts are substantially the same. For example, the compression spring 40 is used to push up the sub tank 22 by about 2 cm in response to the ink level in the sub tank 22 being lowered by 2 cm.

  In addition, the printer 100 includes a first light receiving unit 41 and a second light receiving unit 42 that are two optical sensors fixed to the main body of the printer 100 similarly to the other end of the compression spring 40. A light emitting unit 43 is provided on the outer wall of the sub tank 22, the surface facing the first light receiving unit 41 and the second light receiving unit 42. The second light receiving unit 42 is provided at a position lower than the first light receiving unit 42. When the first light receiving unit 41 and the second light receiving unit 42 detect light from the light emitting unit 43, the second light receiving unit 42 detects the light from the control device 200. Send a signal.

[3] Ink Supply to Subtank As shown in FIG. 4, the control unit 200 includes an ink supply control unit 201. When the ink in the sub tank 22 is consumed, the position of the sub tank 22 in the direction of gravity gradually increases. When the first light receiving unit 41 detects the light from the light emitting unit 43, the ink supply control unit 201 drives the motor 25 to move the ink from the main tank 21 to the sub tank 22 (FIG. 5).

  When ink is supplied to the sub tank 22 in this way, the weight of the sub tank 22 including the ink increases, so that the position of the sub tank 22 gradually decreases. And if the 2nd light-receiving part 42 detects the light from the light emission part 43, the ink supply control part 201 will stop the motor 25 and will stop the movement of an ink (FIG. 6).

<Second embodiment>
The printer 101 of the present embodiment includes only the first light receiving unit 41 as the light receiving unit for the light emitting unit 43, does not include the second light receiving unit 42, and includes the timer 202. The printer 100 of the first embodiment. (FIG. 7).

  Also in the printer 101, as described in the section [3] above, when the first light receiving unit 41 detects light from the light emitting unit 43, the ink supply control unit 201 drives the motor 25 to supply ink to the sub tank 22. Executed. The timer 202 counts the time from the start of ink supply. When the count by the cannabis 202 reaches a predetermined time, the ink supply control unit 201 stops the motor 25 and ends the ink supply.

<Third embodiment>
The printer 102 of this embodiment has the same configuration as that of the first embodiment except that the printer 100 of the first embodiment includes a tension spring 45 instead of the compression spring 40. Unlike the compression spring 40, the tension spring 45 has one end fixed to the upper side of the sub tank 22 and the other end fixed to the printer main body, so that the sub tank 22 is suspended from above.

<Fourth embodiment>
The printer 103 according to the present embodiment includes a light receiving unit 46 positioned between the first light receiving unit 41 and the second light receiving unit 42 as a light receiving unit for the light emitting unit 43, as the first light receiving unit 41 and the second light receiving unit 42. The configuration is substantially the same as that of the printer 100 of the first embodiment except that it is provided instead (FIG. 9).

  In the present embodiment, the ink supply control unit 201 controls the movement of ink from the main tank 21 to the sub tank 22 depending on whether or not the light receiving unit 46 receives light. Details are as follows. When the amount of ink in the sub tank 22 decreases due to ink ejection, the sub tank 22, that is, the light emitting portion 43 fixed to the sub tank 22, moves upward. When the light receiving unit 46 cannot receive the light from the light emitting unit 43 due to this movement, the ink supply control unit 201 drives the motor 25 to start the movement of ink from the main tank 21 to the sub tank 22. The position of the light emitting unit 43 at this time is indicated by a dotted line in FIG.

  Then, when the light emitting unit 43 moves again to a position where the light receiving unit 46 can receive the light from the light emitting unit 43 due to the movement of the ink, the ink supply control is received by receiving a signal indicating that the light receiving unit 46 has received light. The unit 201 controls the motor 25 to stop the movement of ink from the main tank 21 to the sub tank 22.

  According to this embodiment, ink replenishment can be controlled more finely than in the first embodiment. Therefore, the water head difference D can always be kept substantially constant.

  Further, as in the second embodiment, the supply amount in one supply from the main tank 21 to the sub tank 22 may be determined to be a constant amount. Further, it is possible to determine how much the ink amount is reduced by the experiment so that the first light receiving unit 41 cannot receive the light from the light emitting unit 43, and this amount can be set as the above-described supply amount. For example, if the driving time of the motor 25 is set to a certain time, a certain amount can be supplied every time.

  In the above embodiment, the spring is used as the support member for supporting the sub tank 22, but, of course, the present invention is not limited to this, and elasticity that can keep the water head difference D constant is provided. If it is a member provided, the supporting member which consists of various raw materials, such as rubber and resin, can be used.

  As described above, the items described in the different columns can be appropriately combined with each other, and known techniques can also be combined. It goes without saying that the technique thus obtained is also included in the present invention.

1 is a front view showing a main configuration of a printer 100 according to an embodiment of the present invention. FIG. 6 is a plan view showing a structure around the head viewed from the ink ejection surface 13 side. FIG. 2 is a front view showing the configuration of an ink supply system 20 and its surroundings. 3 is a block diagram illustrating a signal flow when ink is supplied to a sub tank 22 in the printer 100. FIG. FIG. 3 is a front view showing a configuration of an ink supply system 20 and its surroundings when the amount of ink in a sub tank 22 is decreasing (when a lower limit value is reached). FIG. 3 is a front view showing a configuration of an ink supply system 20 and its surroundings when the amount of ink in a sub tank 22 reaches an upper limit value. FIG. 10 is a block diagram illustrating a printer 101 according to another embodiment of the present invention. It is a front view which shows the printer 102 which is further another form of implementation of this invention. It is a front view which shows the printer 103 which is further another form of implementation of this invention.

Claims (4)

An inkjet recording apparatus that records an image on a recording medium with ink ejected from a head,
A main tank in which ink is stored;
A sub-tank that stores ink from the main tank toward the head inside, and supplies a predetermined amount of ink to the head due to a water head difference between the ink inside the head and the head;
It is made of an elastic material that changes its magnitude according to the magnitude of the applied force, and includes a support member that supports the sub-tank in the direction of gravity.
The support member is configured to change the position of the sub tank in the direction of gravity by the elasticity of the elastic material according to the change in the ink amount in the sub tank, thereby maintaining the water head difference constant. apparatus. A position detector for detecting the position of the sub tank in the direction of gravity;
A liquid feeding section for moving ink from the main tank to the sub tank, and
2. The liquid feeding unit according to claim 1, wherein when the position detecting unit detects that the sub tank is positioned at a predetermined first height, the liquid feeding unit moves ink from the main tank to the sub tank. The ink jet recording apparatus described.   The liquid feeding unit moves the same amount of ink to the sub tank every time the position detection unit detects that the sub tank is positioned at the first height. Inkjet recording apparatus.   When the position detection unit detects that the sub tank is positioned at a second height lower than the first height, the liquid feeding unit stops the movement of ink to the sub tank. The ink jet recording apparatus according to claim 2.

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