JP2004276472A - Ink supply device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that leakage of ink, defective ejection, or entrainment of a bubble occurs due to natural supplying or reverse flowing by virtue of a positional relationship of a hydraulic head difference between a face of a head connected to a sub-tank and a liquid level of a main tank. <P>SOLUTION: This ink supply device comprises a piston pump 101 for conveying the ink. A pump seal 111 closes a communication passage 110a of a piston shaft 103A when the piston pump 101 conveys the ink or stops the conveyance, and then the flow of the ink is blocked at a portion between a liquid chamber 130 in a cylinder 102 at the side of an ink supply hole 121 and a liquid chamber 131 into which a supply needle 90 is inserted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to an ink supply device and an image forming device.
[0002]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-246920
[Prior art]
As an image forming apparatus (or also referred to as an image recording apparatus) such as a printer, a facsimile, and a copying apparatus, for example, an ink jet recording apparatus is known. The ink jet recording apparatus applies ink from a recording head to paper (meaning that an image including OHP is formed, not limited to paper, and is also referred to as a recording medium or recording medium, recording paper, or the like). It prints high-definition images at high speed, running costs are low, noise is low, and color images are recorded using multicolor inks. It has advantages such as being easy.
[0004]
In such an ink jet recording apparatus, the main tank (ink cartridge) and the sub-tank arranged on the head side are connected by a flexible tube (including a pipe), and when the ink capacity of the sub-tank decreases, ink is discharged from the main tank. Some are supplied (supplied).
[0005]
[Problems to be solved by the invention]
By the way, when the ink supply mechanism as described above is used, it is necessary to prevent the movement of the ink between the sub tank and the main tank after supplying a predetermined amount of ink to the sub tank.
[0006]
That is, unless the replenishment of the head surface pressure due to the natural replenishment or the backflow due to the positional relationship of the head difference between the head surface connected to the sub tank and the main tank liquid surface and the backflow, the head surface pressure becomes positive pressure and the nozzle meniscus And the ink may flow out from the sub-tank on the reverse flow side, resulting in an excessive negative pressure on the head surface, which may result in poor ink ejection or entrainment of air bubbles from the nozzles. .
[0007]
In this case, it is generally considered that a backflow can be prevented by using a check valve in the ink flow path (for example,
[Patent Document 1]).
[0008]
However, for example, when a check valve such as a commonly known umbrella valve is used, it is desirable to set the valve opening pressure as small as possible because of fluid resistance when ink is supplied. Side will be disadvantaged.
[0009]
In addition, the umbrella valve leaks and flows backward due to the accuracy (surface roughness) of the mounting surface thereof. In particular, when the umbrella mounting shape is injection molding, a weld line easily enters and the surface roughness deteriorates. is there.
[0010]
Further, the structure of the umbrella valve is relatively strong when the flow is relatively fast, and the check effect is obtained. However, when the flow of the ink which is a problem here is stopped, the check effect is small. For this reason, there is a problem that a leak easily occurs with respect to a minute flow of ink generated due to a head difference.
[0011]
The present invention has been made in view of the above points, and includes an ink supply device that can obtain required liquid supply performance when ink is supplied and has high sealing properties against natural replenishment and backflow when stopped, and the ink supply device. It is an object of the present invention to provide an image forming apparatus.
[0012]
[Means for Solving the Problems]
In order to solve the above problems and achieve the object, an ink supply device according to the present invention includes a piston pump for sending ink, and the piston pump is provided with a pump seal for sending liquid provided on a piston shaft. The configuration is such that the flow of ink is always blocked during the liquid supply and during the stop.
[0013]
An image forming apparatus according to the present invention supplies ink from an ink cartridge to a sub-tank, and includes an ink supply device according to the present invention for sending ink between the ink cartridge and the sub-tank. .
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory perspective view of an ink jet recording apparatus as an image forming apparatus according to the present invention provided with the ink supply device according to the present invention, as viewed from the front side.
[0015]
This ink jet recording apparatus includes an apparatus main body 1, a paper feed tray 2 for loading sheets mounted on the apparatus main body 1, and a discharge tray for stocking sheets on which an image is recorded (formed) mounted on the apparatus main body 1. A paper tray 3; and a cartridge loading section 6 protruding forward from the front face 4 and lower than the upper face 5 at one end of the front face 4 of the apparatus main body 1. An operation unit 7 such as an operation key or a display is arranged on the upper surface of the device. The cartridge loading section 6 has an openable and closable front cover 8 for attaching and detaching the ink cartridge 11.
[0016]
Next, the mechanism of the inkjet recording apparatus will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram for explaining the overall configuration of the mechanical unit, and FIG. 3 is a plan view of a main part of the mechanical unit.
[0017]
A carriage 33 is slidably held in the main scanning direction by a guide rod 31 and a stay 32, which are guide members that are laterally mounted on left and right side plates (not shown), and is moved by a main scanning motor (not shown) in the direction indicated by the arrow in FIG. I do.
[0018]
The carriage 33 is provided with a plurality of ink ejection orifices through a recording head 34 composed of four inkjet heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.
[0019]
The ink-jet head constituting the recording head 34 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator using a phase change due to film boiling of a liquid using an electrothermal conversion element such as a heating resistor, and a metal phase change due to a temperature change. An actuator having a shape memory alloy actuator to be used, an electrostatic actuator using electrostatic force, or the like as an energy generating means for discharging ink can be used.
[0020]
The carriage 33 has a sub-tank 35 for each color for supplying each color ink to the recording head 34. The sub tank 35 is supplied with ink from the main tank (ink cartridge) 11 via an ink supply tube 36.
[0021]
On the other hand, as a paper feeding unit for feeding the paper 42 loaded on the paper loading unit (pressing plate) 41 of the paper feed tray 3, a half-month roller (feeding) that separates and feeds the papers 42 one by one from the paper loading unit 41. A separation pad 44 made of a material having a large friction coefficient is provided facing the paper roller 43 and the paper feed roller 43, and the separation pad 44 is urged toward the paper feed roller 43.
[0022]
As a transport unit for transporting the paper 42 fed from the paper feed unit below the recording head 34, a transport belt 51 for electrostatically attracting and transporting the paper 42 and a feed belt 51 A counter roller 52 for sandwiching and transporting the sheet 42 sent via the guide 45 between the transport belt 51 and a counter roller 52 for turning the sheet 42 sent substantially vertically upward by approximately 90 ° to copy the sheet 42 onto the transfer belt 51. The transport guide 53 includes a pressing guide roller 55 and a tip pressing roller 55 urged toward the transport belt 51 by a pressing member 54. Further, a charging roller 56 as charging means for charging the surface of the transport belt 51 is provided.
[0023]
Here, the transport belt 51 is an endless belt, is stretched between the transport roller 57 and the tension roller 58, and is configured to orbit in the direction of arrow A (belt transport direction). The charging roller 56 is arranged so as to be in contact with the surface layer of the transport belt 51 and rotate following the rotation of the transport belt 51, and apply 2.5 N to both ends of the shaft as a pressing force.
[0024]
A guide member 61 is disposed on the back side of the transport belt 51 so as to correspond to the printing area of the recording head 34. The guide member 61 has an upper surface protruding toward the recording head 34 beyond a tangent line of two rollers (the transport roller 57 and the tension roller 58) supporting the transport belt 51. As a result, the transport belt 51 is pushed up and guided by the upper surface of the guide member 61 in the printing area, so that highly accurate flatness is maintained.
[0025]
Furthermore, a plurality of grooves are formed in the main scanning direction, that is, a direction orthogonal to the conveyance direction, on the surface of the guide member 61 that contacts the back surface of the conveyance belt 51, so that the contact area with the conveyance belt 51 is reduced. Thus, the transport belt 51 can be smoothly moved along the surface of the guide member 61.
[0026]
Further, as a paper discharge unit for discharging the paper 42 recorded by the recording head 34, a separation claw 71 for separating the paper 42 from the transport belt 51, a paper discharge roller 72, and a paper discharge roller 73 are provided. The discharge tray 3 is provided below the discharge roller 72. Here, the height from the space between the paper discharge roller 72 and the paper discharge roller 73 to the paper discharge tray 3 is set to be somewhat high in order to increase the amount that can be stocked in the paper discharge tray 3.
[0027]
A double-sided paper feeding unit 81 is detachably mounted on the back of the apparatus main body 1. The double-sided paper feeding unit 81 takes in the paper 42 returned by the reverse rotation of the transport belt 51, reverses the paper 42, and feeds the paper 42 again between the counter roller 52 and the transport belt 51. A manual paper feed unit 82 is provided on the upper surface of the duplex paper feed unit 81.
[0028]
In the ink jet recording apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feeding tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and the conveyance belt 51 and the counter roller The sheet is conveyed by being sandwiched between the transfer roller 52 and the conveyance guide 53, and the tip is pressed against the conveyance belt 51 by the pressure roller 55, thereby changing the conveyance direction by approximately 90 °.
[0029]
At this time, a positive voltage and a negative output are alternately repeated from the high voltage power supply to the charging roller 56 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the transport belt 21 alternates, that is, In the sub-scanning direction, which is the circling direction, plus and minus are alternately charged in a belt shape with a predetermined width. When the paper 42 is fed onto the positively and negatively charged conveyor belt 51, the paper 42 is polarized in the paper 42 to a charge opposite to the charge pattern, so that a parallel-connected capacitor is formed. The sheet 42 is attracted to the transport belt 51, and the paper 42 is transported in the sub-scanning direction by the orbital movement of the transport belt 51.
[0030]
Therefore, by driving the recording head 34 in accordance with the image signal while moving the carriage 33, ink droplets are ejected onto the stopped paper 42 to record one line, and after the paper 42 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal indicating that the rear end of the sheet 42 has reached the recording area, the recording operation ends, and the sheet 42 is discharged to the discharge tray 3.
[0031]
Next, the ink cartridge (main tank) 11 used in the image forming apparatus will be briefly described with reference to FIGS. FIG. 4 is an external perspective view of the ink cartridge 11, and FIG. 5 is a side view.
The ink cartridge 11 has a substantially square ink bag 81 housed in a housing 83. The housing 83 includes a first housing 85 for holding a holding member 82 provided in the ink bag 81, The second housing 86 having an outer shape similar to that of the first housing 85 and the ink supply of the first housing 85 and the second housing 86 in a state where the first housing 85 and the second housing 86 are combined. A third housing 87 fitted into the front side.
[0032]
The holding member 82 of the ink bag 81 is provided with an ink discharge port (supplied as a supply port) 88. When the ink cartridge 11 is loaded in the image forming apparatus main body 1, as shown in FIG. The hollow needle 90 on the side is pierced into the ink discharge port 88 to supply ink.
[0033]
Therefore, an ink supply device according to the present invention will be described with reference to FIGS. FIG. 6 is a schematic configuration diagram of an ink supply device, and FIG. 7 is a sectional explanatory view of a piston pump of the ink supply device.
This ink supply device includes a piston pump 101 for sending ink from the ink cartridge 11 to the sub tank 35. The piston pump 101 includes a cylinder 102 and a piston 103, and the cylinder 102 is connected to the other end of a hollow needle 90 inserted into the ink discharge port 88 of the ink cartridge (main tank) 11 described above. 36 is provided.
[0034]
The piston 103 of the piston pump 101 is driven by a cam 109 provided integrally with the worm wheel 108 by rotating a worm wheel 108 through a worm gear 107 to rotate a drive motor 106 (reciprocating motion). ) Is done.
[0035]
In the supply device thus configured, the ink in the ink cartridge 11 is guided into the cylinder 102 through the hollow needle 90 inserted by the negative pressure generated when the piston pump 101 operates, and The entered ink is sent from the connecting portion 104 to the sub-tank 35 via the ink supply tube 36 by the reciprocating operation of the piston 103.
[0036]
Here, as shown in FIG. 7, an ink flow passage 110a and a communication passage 110b communicating with the ink flow passage 110a are formed at the tip of a shaft (piston shaft) 103A of the piston 103 of the piston pump 101. A pump seal 111 that opens and closes the communication passage 110b is slidably mounted on the tip of the shaft 103A.
[0037]
One end surface of the pump seal 111 is regulated by a flange portion 103a formed on the piston shaft 103A. A pump seal pressing spring 114 interposed between a stopper 112 fixed to the tip of the piston shaft 103A and a collar 113 slidably mounted on the piston shaft 103A is disposed on the other end surface side of the pump seal 111. The pump seal 111 is urged toward the flange 103a of the piston shaft 103A via the collar 113 by the pump seal pressing spring 114.
[0038]
Further, an ink supply port 121 is formed on the tip end side of the cylinder 102, and an umbrella valve 122, which is a check valve for opening and closing the ink supply port 121, is provided.
[0039]
With this configuration, the pump seal 111 seals the communication passage 110a of the piston shaft 103A when the ink is supplied and stopped, so that the liquid chamber 130 on the ink supply port 121 side in the cylinder 102 and the supply needle 90 The flow of ink is blocked between the liquid chamber 131 and the liquid chamber 131.
[0040]
Here, assuming that the ink is fed during the reciprocating operation of the piston 103 during the forward movement (moving in the direction of arrow D in FIG. 7), the returning movement (moving in the direction of arrow E in FIG. 7) is as follows. Operating conditions.
[0041]
That is, when the backward movement of the piston 103 starts, the umbrella valve 122 attached to the ink supply port 121 of the cylinder 102 closes instantly. After that, when the piston 103 continues the backward movement, the liquid chamber 130 sealed by the umbrella valve 122 and the pump seal 111 has a negative pressure, and when the pump seal pressing spring 114 loses its pressure and contracts, the pump seal 111 is compressed. In FIG. 7, the communication passage 110b opened to the side of the piston shaft 103A by moving to the left opens, and ink flows from the liquid chamber 131 through which the supply needle 90 communicates through the communication passage 110b and the ink passage 110a. It flows into 130.
[0042]
As a result, the negative pressure in the liquid chamber 130 between the umbrella valve 122 and the pump seal 111 is reduced, and the pump seal 111 is pressed against the flange 103a of the piston shaft 103A again, closing the communication passage 110b.
[0043]
By this series of operations, the feeding of liquid and the prevention of ink flow are performed.
[0044]
Here, in order to satisfy the condition that the ink flow path (communication path 110a) is always sealed when the piston 103 is stopped, the pressing force of the pump seal pressing spring 114 is set as follows. I have.
[0045]
That is, when the frictional force between the cylinder 102 and the pump seal 111 is F1 and the pressing force of the pump seal pressing spring 114 is F2, the relationship of F1 <F2 is established. Further, it is necessary to communicate the ink flow path at the time of returning. Here, assuming that the difference between the main tank (ink cartridge 11) side pressure and the umbrella valve 122 side pressure generated during the return path operation is P1, the force F3 applied to the pump seal 111 is S assuming that the sectional area in the cylinder 102 is S. , F3 = PS. Therefore, it is necessary that F2 <F1 + F3.
[0046]
Therefore, the pressing force F2 of the pump seal pressing spring 114 is set to a pressing force in a range of F1 <F2 <F1 + F3.
[0047]
As described above, the piston pump for feeding ink is provided. In this piston pump, the pump seal for feeding provided on the piston shaft always blocks the flow of ink at the time of feeding and at the time of stopping. In some cases, the required liquid sending performance can be obtained, and when stopped, natural replenishment and high sealing performance against backflow can be obtained.
[0048]
In the above embodiment, the present invention has been described as an example in which the present invention is applied to a serial type (shuttle type) ink jet recording apparatus in which a carriage scans. However, the present invention is similarly applied to a line type ink jet recording apparatus having a line type head. be able to. Further, the image forming apparatus according to the present invention can be applied to a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction peripheral, etc. in addition to the ink jet printer.
[0049]
【The invention's effect】
As described above, according to the ink supply device of the present invention, the piston pump for supplying ink is provided, and the pump seal for the liquid supply provided on the piston shaft is stopped when the liquid is supplied. At times, the flow of ink is always blocked, so that a required liquid sending performance can be obtained at the time of ink feeding, and a high sealing property against natural replenishment and backflow can be obtained at the time of stopping.
[0050]
According to the image forming apparatus of the present invention, the ink is supplied from the ink cartridge to the sub-tank, and the ink supply apparatus of the present invention for supplying ink between the ink cartridge and the sub-tank is provided. In addition, natural replenishment and backflow from the sub tank can be prevented, and ink leakage, ink ejection failure, and air bubbles from the nozzles can be prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory perspective view of an ink jet recording apparatus as an image forming apparatus according to the present invention including an ink supply apparatus according to the present invention, as viewed from the front side. FIG. 2 is a configuration diagram schematically showing a mechanism of the recording apparatus. FIG. 3 is an explanatory plan view of a main part of the mechanism part. FIG. 4 is a perspective explanatory view of an ink cartridge of the recording apparatus. FIG. 5 is a lateral explanatory view of the ink cartridge. FIG. 6 is an ink supply apparatus according to the present invention. FIG. 7 is a schematic sectional view of a piston pump of the ink supply device.
DESCRIPTION OF SYMBOLS 1 ... Device main body, 11 ... Ink cartridge, 33 ... Carriage, 34 ... Recording head, 35 ... Sub tank, 36 ... Ink supply tube, 101 ... Piston pump, 102 ... Cylinder, 103 ... Piston, 103A ... Piston shaft, 110a ... Ink Flow path, 110b: communication path, 111: pump seal, 114: pump seal pressing spring.

Claims (2)

In an ink supply device for supplying ink, a piston pump for supplying the ink is provided, and the piston pump always blocks the flow of ink when a liquid supply pump seal provided on a piston shaft is supplied and stopped. An ink supply device, comprising: An image forming apparatus configured to supply ink from an ink cartridge to a sub-tank, comprising the ink supply device according to claim 1 for feeding ink between the ink cartridge and the sub-tank. Image forming apparatus.

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