JP4124809B2 - Ink supply apparatus and image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an ink supply device and an image forming apparatus.
[0002]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-246920
[Prior art]
As an image forming apparatus (or image recording apparatus) such as a printer, a facsimile machine, and a copying apparatus, for example, an ink jet recording apparatus is known. The ink jet recording apparatus uses ink from a recording head to paper (not limited to paper, meaning that an image including OHP is formed and is also called a recording medium, a recording medium, or recording paper). It is possible to record high-definition images at high speed, with low running costs, low noise, and to record color images using multi-colored inks. It has the advantage of being easy.
[0004]
In such an ink jet recording apparatus, a main tank (ink cartridge) and a sub tank arranged on the head side are connected by a flexible tube (including a pipe), and ink is discharged from the main tank when the ink capacity of the sub tank decreases. There is something to be supplied (supplemented).
[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 ink from moving between the sub tank and the main tank after supplying a predetermined amount of ink to the sub tank.
[0006]
In other words, if natural replenishment due to the positional relationship of the head difference between the head surface connected to the sub tank and the liquid level of the main tank or the influence of the back flow on the head surface pressure is not prevented, the head surface pressure becomes positive in natural replenishment and the meniscus of the nozzle. May break and ink leakage may occur. On the reverse flow side, ink flows out from the sub-tank, so that the head surface pressure becomes excessively negative, and ink ejection failure or bubble entrapment from the nozzles may occur. .
[0007]
In this case, it is generally considered that backflow can be prevented by using a check valve in the ink flow path (for example, Patent Document 1).
[0008]
However, for example, when using a generally known check valve such as an umbrella valve, it is necessary to set the valve opening pressure as small as possible because it causes fluid resistance when ink is fed. It will be disadvantageous to the side.
[0009]
In addition, the umbrella valve leaks due to the accuracy (surface roughness) of its mounting surface and flows backward, especially when the umbrella mounting shape is injection molding, a weld line is likely to enter, and the surface roughness becomes poor. is there.
[0010]
In addition, the umbrella valve is structurally strong and provides a non-return effect when the flow is relatively fast, but the non-return effect is small when the ink flow, which is a problem here, stops. For this reason, there is a problem that leakage is liable to occur in a minute ink flow that occurs due to a water head difference.
[0011]
The present invention has been made in view of the above points, and includes an ink supply device that provides a required liquid supply performance when ink is supplied and has a high sealing property against natural replenishment and backflow when stopped, and the ink supply device. Another object of the present invention is to provide an image forming apparatus.
[0012]
[Means for Solving the Problems]
To solve the above problems, an ink supply device according to the present invention comprises a pump for feeding the ink, the pump includes a cylinder, a piston shaft which is movably disposed within the cylinder, A pump seal that is slidably mounted on the piston shaft between the inner peripheral surface of the cylinder and two fluid chambers that are partitioned by the pump seal communicate with each other and are connected to the piston shaft that is opened and closed by the pump seal. A pressure spring that urges the passage and the pump seal in a direction to close the communication passage, and the pressure of the pressure spring is communicated with the pump seal when the piston shaft is stopped and moved in the liquid feeding direction. The force is set to close the passage.
[0013]
An image forming apparatus according to the present invention includes an ink supply device according to the present invention for supplying ink from an ink cartridge to a sub tank and feeding ink between the ink cartridge and the sub tank. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective explanatory view seen from the front side of an ink jet recording apparatus as an image forming apparatus according to the present invention provided with an ink supply apparatus according to the present invention.
[0015]
This ink jet recording apparatus includes an apparatus main body 1, a paper feed tray 2 for loading paper loaded in the apparatus main body 1, and a waste paper for stocking paper on which an image is recorded (formed) mounted on the apparatus main body 1. The apparatus main body 1 further includes a cartridge loading portion 6 that protrudes forward from the front surface 4 and is lower than the upper surface 5 on one end side of the front surface 4 of the apparatus main body 1. An operation unit 7 such as operation keys and a display is arranged on the upper surface of the display. The cartridge loading section 6 has a front cover 8 that can be opened and closed for attaching and detaching the ink cartridge 11.
[0016]
Next, the mechanism part of the ink jet recording apparatus will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram for explaining the overall configuration of the mechanism unit, and FIG. 3 is a plan view for explaining a main part of the mechanism unit.
[0017]
A carriage 33 is slidably held in the main scanning direction by guide rods 31 and stays 32 that are horizontally mounted on left and right side plates (not shown), and is moved and scanned in the direction of the arrow in FIG. 3 by a main scanning motor (not shown). To do.
[0018]
The carriage 33 is provided with a recording head 34 including four ink jet 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]
As an inkjet head constituting the recording head 34, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like as an energy generating means for discharging ink can be used.
[0020]
In addition, the carriage 33 is equipped with a sub tank 35 for each color for supplying ink of each color to the recording head 34. Ink is supplied to the sub tank 35 from the main tank (ink cartridge) 11 through the ink supply tube 36.
[0021]
On the other hand, as a paper feeding unit for feeding the papers 42 stacked on the paper stacking unit (pressure plate) 41 of the paper feed tray 3, a half-moon roller (feeding) that separates and feeds the papers 42 from the paper stacking unit 41 one by one. 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 side.
[0022]
As a transport unit for transporting the paper 42 fed from the paper feed unit on the lower side of the recording head 34, a transport belt 51 for transporting the paper 42 by electrostatic adsorption, and a paper feed unit The counter roller 52 for transporting the paper 42 fed through the guide 45 while sandwiching it between the transport belt 51 and the paper 42 fed substantially vertically upward are changed by approximately 90 ° and copied onto the transport belt 51. A conveyance guide 53 for adjusting the pressure and a tip pressure roller 55 urged toward the conveyance belt 51 by a pressing member 54. In addition, a charging roller 56 that is a charging unit for charging the surface of the conveyance belt 51 is provided.
[0023]
Here, the conveyance belt 51 is an endless belt, and is configured to be looped around the conveyance roller 57 and the tension roller 58 and to circulate in an arrow A direction (belt conveyance direction). The charging roller 56 is disposed so as to come into contact with the surface layer of the conveyor belt 51 and to be rotated by the rotation of the conveyor belt 51, and 2.5N is applied to both ends of the shaft as a pressing force.
[0024]
In addition, a guide member 61 is disposed on the back side of the conveyance belt 51 so as to correspond to a printing area by the recording head 34. The upper surface of the guide member 61 protrudes closer to the recording head 34 than the tangent line of the two rollers (the conveyance roller 57 and the tension roller 58) that support the conveyance belt 51. As a result, the conveyance belt 51 is pushed up and guided by the upper surface of the guide member 61 in the printing region, so that highly accurate flatness is maintained.
[0025]
Further, a plurality of grooves are formed in the main scanning direction, that is, in a direction orthogonal to the transport direction, on the surface side of the guide member 61 that contacts the back surface of the transport belt 51 to reduce the contact area with the transport belt 51. The transport belt 51 can smoothly move 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. A paper discharge tray 3 is provided below the paper discharge roller 72. Here, the height from between the paper discharge roller 72 and the paper discharge roller 73 to the paper discharge tray 3 is increased to some extent in order to increase the amount that can be stored in the paper discharge tray 3.
[0027]
A double-sided paper feeding unit 81 is detachably attached to the back surface of the apparatus body 1. The double-sided paper feed unit 81 takes in the paper 42 returned by the reverse rotation of the transport belt 51, reverses it, and feeds it 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 transport belt 51 and the counter roller 52, the leading end is guided by the conveying guide 53 and pressed against the conveying belt 51 by the leading end pressing roller 55, and the conveying direction is changed by about 90 °.
[0029]
At this time, a positive voltage and a negative output are alternately repeated from the high voltage power source 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 conveying belt 21 is alternating, that is, In the sub-scanning direction, which is the circumferential direction, plus and minus are alternately charged in a band shape with a predetermined width. When the paper 42 is fed onto the conveying belt 51 that is alternately charged with plus and minus, it polarizes to the opposite charge to the charging pattern in the paper 42, so that a capacitor connected in parallel is formed. 42 is attracted to the transport belt 51, and the paper 42 is transported in the sub-scanning direction by the circular movement of the transport belt 51.
[0030]
Therefore, by driving the recording head 34 according to 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 that the trailing edge of the paper 42 has reached the recording area, the recording operation is finished and the paper 42 is discharged onto the paper 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. 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 rectangular ink bag 81 stored in a housing 83, and the housing 83 has a first housing 85 for holding a holding member 82 provided in the ink bag 81, Ink supply to the first casing 85 and the second casing 86 in a state where the second casing 86 having a similar outer shape to the first casing 85 and the first casing 85 and the second casing 86 are combined. And a third housing 87 fitted to the front side.
[0032]
The holding member 82 of the ink bag 81 is provided with an ink discharge port portion (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 can be inserted into the ink discharge port 88 to supply ink.
[0033]
An ink supply apparatus according to the present invention will be described with reference to FIGS. 6 is a schematic configuration diagram of the ink supply device, and FIG. 7 is a cross-sectional explanatory view of a piston pump of the supply device.
The ink supply device includes a piston pump 101 for feeding ink from the ink cartridge 11 to the sub tank 35. The piston pump 101 includes a cylinder 102 and a piston 103. The cylinder 102 is connected to the other end of a hollow needle 90 that is inserted into the ink discharge port 88 of the ink cartridge (main tank) 11 described above, and an ink supply tube. 36 is provided.
[0034]
The piston 103 of the piston pump 101 is driven (reciprocating) by a cam 109 provided integrally with the worm wheel 108 by rotating the drive motor 106 via the worm gear 107. )
[0035]
In this supply device configured as described above, 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, The ink that has entered is sent from the connecting portion 104 to the sub tank 35 via the ink supply tube 36 by the reciprocating motion of the piston 103.
[0036]
Here, as shown in FIG. 7, an ink flow path 110a and a communication path 110b communicating with the ink flow path 110a are formed at the tip of the 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 attached to the tip of the shaft 103A.
[0037]
One end surface side of the pump seal 111 is regulated by a flange portion 103a formed on the piston shaft 103A. On the other end surface side of the pump seal 111, 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. The pump seal 111 is urged by the pump seal pressing spring 114 through the collar 113 toward the flange portion 103a of the piston shaft 103A.
[0038]
Further, an ink supply port 121 is formed on the tip end side of the cylinder 102, and an umbrella valve 122 that 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 ink is fed and stopped, so that the liquid chamber 130 and the supply needle 90 on the ink supply port 121 side in the cylinder 102 are sealed. Is prevented from flowing between the liquid chamber 131 side facing the ink.
[0040]
Here, when the ink is fed during the reciprocating operation of the piston 103 as the forward path (movement moving in the liquid feeding direction in FIG. 7), the following path is the next movement (movement moving in the direction opposite to the liquid feeding direction in FIG. 7). The operating situation is as follows.
[0041]
That is, when the return path operation of the piston 103 starts, the umbrella valve 122 attached to the ink supply port 121 of the cylinder 102 is instantaneously closed. After that, when the piston 103 continues the return path operation, the liquid chamber 130 sealed by the umbrella valve 122 and the pump seal 111 becomes negative pressure. When the pump seal pressing spring 114 is contracted by the pressure, the pump seal 111 is released. In FIG. 7, the communication passage 110b opened to the left by moving to the left in the piston shaft 103A is opened, and ink is supplied from the liquid chamber 131 side through which the supply needle 90 communicates to the liquid chamber through the communication passage 110b and the ink passage 110a. Flows into 130.
[0042]
Thereby, the negative pressure in the liquid chamber 130 between the umbrella valve 122 and the pump seal 111 is reduced, the pump seal 111 is again pressed against the flange portion 103a of the piston shaft 103A, and the communication passage 110b is closed.
[0043]
By this series of operations, liquid feeding and ink flow prevention 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. Yes.
[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. Furthermore, it is necessary to communicate the ink flow path during the return path. Here, if the difference between the pressure on the main tank (ink cartridge 11) side and the pressure on the umbrella valve 122 generated during the return path operation is P1, the force F3 applied to the pump seal 111 is S in the cross-sectional area in the cylinder 102. 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 the pressing force in the region of F1 <F2 <F1 + F3.
[0047]
Thus, with the pump for feeding the ink, the pump cylinder and a piston shaft which is movably disposed in the cylinder, sliding the piston axis between the inner peripheral surface of the cylinder The movably mounted pump seal communicates with the two liquid chambers partitioned by the pump seal, and is opened and closed by the pump seal. The communication path provided in the piston shaft, and the pump seal in the direction to close the communication path Since the pressing force of the pressing spring is set to a force that causes the pump seal to close the communication path when the piston shaft stops and moves in the liquid feeding direction. Since the pump seal always blocks the flow of ink at the time of liquid feeding and at the time of stopping, the required liquid feeding performance can be obtained at the time of ink feeding, and high sealing performance against natural replenishment and backflow can be obtained at the time of stopping.
[0048]
In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to a serial (shuttle type) ink jet recording apparatus that is scanned by a carriage. However, the present invention is similarly applied to a line type ink jet recording apparatus having a line type head. be able to. The image forming apparatus according to the present invention can be applied to a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, etc., in addition to an ink jet printer.
[0049]
【The invention's effect】
As described above, according to the ink supply device according to the present invention, includes a pump for feeding the ink, pump this both when the pump seal liquid transfer for feeding provided on the piston shaft Since the ink flow is always blocked when the ink is stopped, the required liquid supply performance can be obtained when the ink is supplied, and high sealing performance against natural replenishment and backflow can be obtained when the ink is stopped.
[0050]
The image forming apparatus according to the present invention includes the ink supply device according to the present invention for supplying ink from the ink cartridge to the sub-tank and feeding ink between the ink cartridge and the sub-tank. Thus, natural replenishment and backflow from the sub tank can be prevented, and ink leakage, ink ejection failure, and bubble entrainment from the nozzle can be prevented.
[Brief description of the drawings]
FIG. 1 is a perspective explanatory view seen from the front side 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. FIG. 2 is a configuration diagram schematically showing a mechanism part of the recording apparatus. FIG. 3 is an explanatory plan view of a main part of the mechanism unit. FIG. 4 is a perspective view of an ink cartridge of the recording apparatus. FIG. 5 is a side view of the ink cartridge. Schematic configuration diagram [FIG. 7] Cross-sectional explanatory diagram of the piston pump of the same ink supply device
DESCRIPTION OF SYMBOLS 1 ... Apparatus 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,
Comprising a pump for feeding the ink,
The pump includes a cylinder, a piston shaft movably disposed in the cylinder, a pump seal mounted on the piston shaft so as to be slidable between an inner peripheral surface of the cylinder, and the pump seal. A communication passage provided in the piston shaft that communicates between two partitioned liquid chambers and is opened and closed by the pump seal; and a pressing spring that biases the pump seal in a direction to close the communication passage;
The pressing force of the pressing spring is set to a force that causes the pump seal to close the communication path when the piston shaft is stopped and moved in the liquid feeding direction. An ink supply device.   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. An image forming apparatus.

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