JP6953817B2 - Device that discharges liquid - Google Patents

Description

The present invention relates to a device that discharges a liquid.

An inkjet type image forming apparatus is known in which a droplet of a recording liquid such as ink is ejected from a recording head to form an image. Since this image forming apparatus has a structure in which droplets are ejected from the recording head, some of the droplets are separated during flight, or the droplets do not land on the recording medium due to rebound when the ink lands on the recording medium. Becomes an ink mist. This ink mist scatters inside the machine, and as a result, adheres to the inside of the image forming apparatus or is discharged to the outside of the machine through a gap in the exterior. The ink mist adhering to the inside / outside of the image forming apparatus becomes dirty, which causes a problem that the fingers and clothes are soiled when the user touches the image forming apparatus, and the surrounding area where the image forming apparatus is installed is soiled.
Further, there is a problem that the ink mist adheres to the reflective or transmissive optical sensor inside the image forming apparatus, the encoder, or the like, and the detection accuracy is lowered.

According to Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-103857), a transfer belt arranged to face the injection side of a recording head is charged with a high voltage to form an electric field, so that a recording medium is attracted to the transfer belt and conveyed. An inkjet recording device including an electric suction belt type transfer device is disclosed.
However, there is a problem that the ink mist is adsorbed on the charged transport belt and stains the transport belt.

An object of the present invention is to significantly reduce the amount of suspended liquid adhering to a member other than the suspended liquid recovery member, particularly to a charged member to which the suspended liquid does not want to adhere.

In order to achieve the above object, the device for discharging the liquid according to the present invention is arranged with a carriage that reciprocates with a liquid discharge head for discharging the liquid and a moving area of the carriage, and collects the suspended liquid. A charged recovery member, a transport belt having a recessed portion, and a charging member arranged in the recessed portion and charging the facing region of the transport belt facing the carriage with a constant polarity. It is characterized by that.

According to the present invention, it is possible to significantly reduce the amount of suspended liquid adhering to a member other than the suspended liquid recovery member, particularly to a charged member to which the suspended liquid does not want to adhere.

It is a figure which shows the schematic structure of the inkjet recording apparatus as an example of the image forming apparatus provided with the apparatus which ejects the liquid which concerns on one Embodiment of this invention. It is a block diagram which shows the electrical structure of an inkjet recording apparatus. It is a figure explaining the generation principle of ink mist. (A) is a block diagram of an electrostatic adsorption transfer belt, and (b) is a diagram for explaining alternating charging in the electrostatic adsorption transfer belt. It is explanatory drawing about the scanning area of a carriage, that is, the printing area. It is explanatory drawing about the generation state of ink mist by charge of an electrostatic adsorption transport belt. It is explanatory drawing about the arrangement of the airflow generated by the scanning of a carriage and the ink mist recovery member. It is a schematic block diagram which shows the 1st Embodiment of the inkjet recording apparatus provided with the measures for preventing the generation of neutral ink mist. It is a schematic block diagram which shows the 2nd Embodiment of the inkjet recording apparatus provided with the measures for preventing the generation of neutral ink mist. It is a schematic block diagram which shows the 3rd Embodiment of the inkjet recording apparatus provided with the measures for preventing the generation of neutral ink mist.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.
<Basic configuration of image forming device>
FIG. 1 is a diagram showing a schematic configuration of an inkjet recording device as an example of an image forming device including a device for discharging a liquid according to an embodiment of the present invention.
In the present invention, when collecting ink mist as floating fine droplets in a device that discharges liquid, power is input according to the air flow generated in the machine by the reciprocating movement of the carriage that supports the recording head as the liquid discharge head. Arrange an appropriate number of ink mist collecting members that operate when the ink mist is suspended and collect the ink mist floating in the air flow at an appropriate position, and move the ink mist collecting member to the ink mist collecting member according to the operation of the carriage and the recording head. The on / off switching of the applied voltage, the voltage value, the on / off timing, etc. are controlled.
In this embodiment and all the following embodiments, the device for discharging the liquid will be described as an inkjet recording device. However, it can be applied to any liquid such as UV ink, edible ink, and pretreatment liquid.

Specifically, the liquid may have a viscosity and surface tension that can be discharged from the recording head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, normal pressure, or by heating or cooling. Is preferable.
The liquid discharge head will be described using a recording head as an example thereof.
The ink mist recovery member is expressed as a recovery member which is an abbreviation.
The device for discharging the liquid according to the present invention is not limited to the inkjet recording device, but can be applied to an image forming device using a fluid such as any kind of liquid, powder, or granular material.

The inkjet recording apparatus 100 includes an image forming unit 101 that forms an image on the paper P that is a recording medium, a paper feeding unit 120 that supplies the paper P to the image forming unit, and an image forming unit 101 that forms the paper from the paper feeding unit. A paper transport unit 130 for transporting the paper to the paper transport unit 130, and a paper discharge unit 140 such as a paper discharge tray for stocking the paper P on which the image is recorded and formed in the image forming unit 101 are roughly provided.

The paper feeding unit 120 is arranged to face the paper tray 121 for loading the paper P, the half-moon roller 123 as a paper-feeding roller for separately feeding the paper one by one from the paper loading unit, and the friction coefficient. A separation pad 124 made of a large material is provided, and the separation pad is urged on the paper feed roller side.
The transport unit 130 for transporting the paper fed from the paper feed unit 120 on the lower side of the recording head 165 includes a transport belt 131 as an electrostatic suction type transport belt for electrostatically sucking and transporting the paper. A transport guide 135 for turning the paper fed substantially vertically upward by approximately 90 ° and imitating it on the transport belt, and a tip pressurizing roller 136 urged on the transport belt side by a pressing member are provided. There is. Further, it is provided with a charging roller 138 which is a charging means for charging the surface of the transport belt.
The transport belt 131 is an endless belt, which is hung between the transport roller 132 and the tension roller 133 and circulates in the belt transport direction. The charging roller 138 is arranged so as to come into contact with the surface layer of the transport belt and rotate in accordance with the rotation of the transport belt.
The amount of movement of the transport belt is controlled by monitoring the rotation of the rotary encoder 132a coaxial with the transport roller.

In addition, an ink mist recovery member (not shown) that is charged to electrostatically adsorb floating ink mist is arranged in the machine.
Further, the paper ejection unit 140 for ejecting the paper recorded by the recording head 165 is provided with a separation claw 141 for separating the paper from the transport belt and a paper ejection roller 142, and is provided below the paper ejection roller. A paper ejection tray 143 is provided.

Next, FIG. 2 is a block diagram showing an electrical configuration of the inkjet recording device.
The inside of the dotted line in FIG. 2 shows the components of the control board, and the outside of the dotted line shows the unit connected to the control board, specifically, the power supply, various control objects, sensors, and the like.

The control board 222 includes a power supply circuit that receives power from the power supply. The control board 222 is connected to an operation panel for inputting and displaying information necessary for the inkjet recording device 100. The control board receives print data from the host side such as an information processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera by HOST I / F via a cable or a net. Then, the CPU as a control means reads out the print data in the reception buffer included in the HOST I / F, analyzes the print data, performs image processing and data rearrangement processing necessary for the CPU, and outputs an image to the head control unit. Transfer data. Note that the dot pattern data for image output may be generated by storing the font data in the ROM, for example, or the printer driver on the host side expands the image data into bitmap data and transfers it to this device. You may do so.

When the head control unit receives the image data corresponding to one line of the recording head, that is, the dot pattern data, the head control unit transmits the dot pattern data for one line to the carriage as serial data in synchronization with the clock signal. In addition, a latch signal is sent to the carriage at a predetermined timing.
The head drive unit includes a drive waveform stored in the ROM, that is, a D / A converter that reads pattern data of the head drive signal and D / A converts the drive waveform data, that is, a waveform generation circuit including a DAC, an amplifier, and the like. Includes a drive waveform generator.

The head mounting unit called the carriage 160 has a shift register for inputting a clock signal from the head control unit and serial data which is image data, and a latch circuit for latching the registration value of the shift register with a latch signal from the head control unit. , A level shifter as a level conversion circuit for changing the output value of a latch circuit, an analog switch array as a switch means for controlling on / off by this level shifter, and the like are included. Then, by controlling the on / off of the analog switch array, the required drive waveform included in the drive waveform is selectively applied to the actuator means of the recording head mounted in the carriage to drive the recording head.
Further, the CPU receives the detection signal of the sensor via an A / D converter that performs A / D conversion, that is, an ADC.

The main scanning, sub-scanning motor, and supply motor drive unit drives the motor by sending a drive signal to the main scanning motor and sub-scanning motor in response to a command signal from the CPU to excite the motor, and the movement of the motor is read by the encoder sensor. The rotation speed of the motor is controlled by feeding back the read result to the CPU.
The transfer amount of the transfer belt is managed by the number of pulses output from the sub-scanning encoder 132a in response to the drive of the sub-scanning motor, and the control signal is output to the high-voltage circuit for each constant transfer amount to generate the high-voltage circuit. Invert the high pressure polarity.

<Explanation of matters that are the premise of the embodiment>
Next, the principle of generating ink mist will be described with reference to FIG.
The main causes of the generation of ink mist include the rear end of the droplet at the time of ejection from the nozzle 166 of the recording head 165 and the rebound after landing on the paper surface. If a uniform electric field is present when the ink mist is generated, the charge distribution of the ink mist will be biased in one direction due to the action of electrostatic induction even if the original droplet is electrically neutral. That is, when the transport belt 131 side is positively charged, a negative charge is induced in the portion of the droplet on the transport belt side, and a positive charge is induced in the portion opposite to the transport belt of the droplet. NS.
Since the droplet, that is, the ink mist separated from the main droplet is a part of the droplet charged on the positive side, the ink mist is positively charged. That is, the ink mist is no longer electrically neutral. Therefore, the repulsive force acts on the positively charged transport belt, and the ink mist soars and floats in the upward direction of FIG. 3, that is, toward the recording head.

Next, FIG. 4A is a configuration diagram of the electrostatic adsorption transfer belt, and FIG. 4B is a diagram for explaining alternating charging in the electrostatic adsorption transfer belt.
The transport belt 131 rotates clockwise as the transport roller 132 rotates, and at the same time, positive and negative charges are alternately applied to the insulating layer on the transport belt by alternately applying a high-pressure square wave to the charging roller 138. An alternating electric field is formed on the transport belt (FIG. 4 (b)). When the paper P reaches the transport belt 131 in which the alternating electric field is formed, the electric charge in the paper is attracted to the electric field on the transport belt to generate an attractive force.

FIG. 5 is an explanatory diagram of a scanning area of the carriage, that is, a printing area.
The carriage 160 moves in the paper transport direction, that is, in the direction orthogonal to the paper surface of FIG. 5, that is, in the left-right direction of the paper surface of FIG. 5, and scans back and forth.
FIG. 5 shows a state in which the carriage 160 is in the intermediate position, and the carriage can move in either the left or right direction within the range of the left and right side plates 167 and 168 of the exterior as the recovery member support member. Generally, the carriage is equipped with a reflective optical sensor 160a for detecting paper and an encoder sensor 160b. The reflective optical sensor 160a detects the reflected light from the paper to identify the paper edge, and the encoder sensor 160b counts to identify the distance from the paper edge, that is, the position in the main scanning direction. In order for the reflective optical sensor to correctly detect the edge of the paper, it is necessary that there is a sufficient reflectance difference between the surface of the transport belt adsorbing the paper and the paper to be detected.
In this example, the recovery member support member that supports the ink mist recovery member has been described as the left and right side plates 167 and 168 constituting the exterior, but it may be another member that is equipped regardless of the exterior.
The scanning area is the same range as the print area.

FIG. 6 is an explanatory diagram of a state in which ink mist is generated due to charging of the electrostatic adsorption transport belt.
Due to the electric field between the transport belt 131 and the recording head 165, which are positively (+) charged during electrostatic adsorption transport, the ejected ink as the main droplet has a polarity (-) opposite to the charge polarity of the belt. It becomes charged. Therefore, as described with reference to FIG. 3, positively charged ink mist is generated.
Since the electrostatic adsorption type transport belt 131 changes its polarity periodically by alternating charging, a positively charged state and a negatively charged state alternately occur. Therefore, a situation in which positively charged ink mist is generated and a situation in which negatively charged ink mist is generated alternately appear according to the change in the polarity of the electrostatic adsorption type transport belt.

Next, FIG. 7 is an explanatory diagram of the air flow generated by scanning the carriage and the arrangement of the ink mist collecting member.
Ink mist collecting members 200 and 210 are arranged on the side plates 167 and 168 located on the left and right sides of the carriage in the main scanning direction, respectively. Each of the ink mist recovery members 200 and 210 includes paired recovery electrodes 200a and 200b and recovery electrodes 210a and 210b, respectively, and forms an electric field between the recovery electrodes 200a and 200b and between the recovery electrodes 210a and 210b, respectively.
In the process in which the carriage 160 moves in the air in the outward direction, the air that was ahead of the carriage in the moving direction, that is, in front of the carriage moves in the original position of the carriage, that is, in the rear of the moving direction, according to the principle of slipstream. Therefore, the airflow generated by the movement of the carriage is the airflow that flows from the front of the carriage, that is, the front direction of the movement direction to the rear of the carriage, that is, the opposite side of the movement direction.

In this way, the ink mist flies in the machine by riding on the air flow generated by the movement of the carriage in the scanning direction. In order to efficiently collect the ink mist flying in this way, the mist collecting member is arranged in the air flow path.
The positively charged ink mist and the negatively charged ink mist generated by the alternating charging of the transport belt 131 are attracted to each other by an electrostatic force and are combined to generate an electrically neutral ink mist. The neutral ink mist cannot be recovered even if the recovery member is charged, and the neutral ink mist is adsorbed on an unintended place, causing a malfunction of the device.
The above-mentioned items described with reference to FIGS. 3 to 7 are for contributing to the understanding of problems and the like when the conveyor belt is alternately charged, and are comparative examples which are premised on each embodiment of the present invention described below. Is.

<First embodiment: Measures to prevent the generation of neutral ink mist>
FIG. 8 is a schematic configuration explanatory view showing a first embodiment of an inkjet recording apparatus provided with measures for preventing the generation of neutral ink mist.
Further, FIG. 8 is a diagram illustrating a method of unifying the polarity of the generated ink mist by making the charging polarity of the conveying belt the same by the charging rollers arranged in front of the printing area and below the conveying belt.

The inkjet recording apparatus 100 according to the present embodiment is arranged at a position corresponding to a carriage 160 that reciprocates with a recording head 165 and an air flow generated by the movement of the carriage, and collects suspended liquid when a voltage is applied. It is characterized by including an ink mist collecting member 200, a transport belt 131, and a charging member 300 that charges at least the facing region L, which is a region on the transport belt side facing the print region of the carriage, to a constant polarity. Is.
The charging member 300 has a function of unifying the polarity of the floating ink mist by charging the facing region L on the transport belt side to a constant polarity.
As a result, it is possible to reduce the amount of neutral ink mist generated due to the floating of the ink mist charged in a different electrode, and prevent malfunction of the device due to the adhesion of the neutral ink mist.

In this example, the charging member for unifying the polarity of the ink mist is the charging roller 300, and the charging roller 300 is charged by applying a voltage from the high-voltage circuit 1, and the contact belt surface is charged at the same potential as the charging roller. It is a means to make it. The charging roller 300 is separate from the charging roller 138 for alternating charging, and a voltage is applied to the charging roller 138 from the high voltage circuit 2.
In this example, the charging roller 300 for unifying the polarity of the ink mist is arranged on the upstream side in the transport direction of the facing region L facing the printing region, that is, on the front side, and on the side opposite to the carriage of the transport belt 131, that is, on the lower surface side. ing. By making the charging polarity of the facing region L and the transport belt portion on the downstream side of the facing region L the same by the charging roller 300, the polarity of the ink mist determined by the polarity of the transport belt can be unified. As shown in the figure, the charging roller 300 in this example charges the charging layer 131a on the lower surface side, that is, the lower layer side of the transport belt 131.
The recovery member 200 as the recovery electrode is provided on both side surfaces in a direction orthogonal to the transport direction of the transport belt 131, for example. The recovery member 200 may be arranged on both sides of the carriage in the transport direction or at any other location.

In the present embodiment, the CPU, which is a control means, controls the high-voltage circuit 1 to charge the appropriate position of the transport belt to the same potential by the electric field from the charging roller 300 arranged on the upstream side in the transport direction of the print region, thereby charging the opposite region. The charging polarity of the transport belt portion on the downstream side of L is unified to either positive or negative. Since the polarity of the ink mist generated in the print area is determined by the polarity of the transport belt directly under the ink nozzle 166, the polarity of the ink mist generated in the machine is unified by unifying the charging polarity of the transport belt with the charging roller 300. can do.
As a result, the generation of neutral ink mist can be suppressed, so that the ink mist recovery efficiency of the recovery member 200 can be improved, and as a result, the neutral ink mist can be prevented from adhering to unintended locations in the machine. can.

At this time, the ink mist (FIG. 3) can be efficiently recovered by the recovery member.
The position corresponding to the airflow generated by the movement of the carriage includes all the spaces and regions where the airflow moves. For example, the position corresponding to the air flow includes the inside of the housing facing the moving area of the carriage, the four sides of the carriage facing the moving area of the carriage, and the like. The recovery member that recovers the suspended liquid when a voltage is applied is a means that is charged by the application of a voltage and sucks, adsorbs, and recovers the suspended liquid.

<Second embodiment: Measures to prevent the generation of neutral ink mist>
FIG. 9 is a schematic configuration explanatory view showing a second embodiment of an inkjet recording apparatus provided with measures for preventing the generation of neutral ink mist.
FIG. 9 is a diagram illustrating a method of making the charging polarities of the conveying belts the same by means of charging rollers arranged in front of the printing area and above the conveying belts, and unifying the polarities of the generated ink mist.

The difference between this embodiment and the first embodiment is the location of the charging roller 300 in relation to the transport belt 131. Specifically, it differs from the first embodiment in that the charging roller 300 is arranged on the upper surface of the transport belt, that is, on the surface side facing the printing area and in contact with the recording medium. In this example, the charging roller 300 positions a part of the upper surface of the transport belt, that is, the upstream side position of the region L facing the printing region so that the charging roller 300 does not interfere with the transport of the recording medium P on the transport belt surface. It is placed in a depressed state. Therefore, the surface of the transport belt other than the recessed portion is flat, and there is no problem in transporting the recording medium.
In the charging method using the charging roller 300 arranged on the lower surface side of the transport belt 131 as in the first embodiment, the charging layer 131a on the lower surface side of the transport belt is the main charging range. Therefore, when the thickness of the transport belt 131 is large to some extent, the distance between the charging layer 131a on the lower surface side, the charging layer 131b on the upper side of the transport belt, and the recording medium P becomes large, and the floating ink mist is sufficiently generated. There is a possibility that the amount of charge is insufficient to charge the ink.
Therefore, as in the present embodiment, the charging roller 300 is arranged on the upper surface side of the transport belt 131, and the charging layer 131b on the upper side of the transport belt is charged at the same potential as the charging roller 300. The electric field from the upper charging layer 131b, which is closer to the distance between the two, makes it possible to increase the amount of charge of the floating ink mist.

In the present embodiment, the CPU, which is a control means, controls the high-voltage circuit 1 to charge the transport belt to the same potential by an electric field from a charging roller 300 arranged on the upstream side of the facing region L in the transport direction and on the upper surface side of the transport belt. By doing so, the charging polarity of the transport belt portion 131b on the downstream side including the facing region L is unified to either positive or negative. By unifying the charging polarity of the transport belt with the charging roller 300, the polarity of the ink mist generated in the machine can be unified.
As a result, the generation of neutral ink mist can be suppressed, so that the ink mist recovery efficiency of the recovery member 200 can be improved, and as a result, the neutral ink mist can be prevented from adhering to unintended locations in the machine. can.

<Third embodiment: Measures to prevent the generation of neutral ink mist>
FIG. 10 is a schematic configuration explanatory view showing a third embodiment of an inkjet recording apparatus provided with measures for preventing the generation of neutral ink mist.
In FIG. 10, a boosted voltage is applied to a charging roller arranged in front of the printing area and below the transport belt, the charging polarity of the transport belt is made the same by the charging roller, and the polarity of the generated ink mist is unified. It is a figure explaining the method.

The difference from the embodiment of FIG. 8 is that the booster circuit 310 is inserted between the charging roller 300 and the high voltage circuit.
In this example, the voltage generated by the high-voltage circuit 1 is increased by the booster circuit 310 and then applied to the charging roller 300 arranged in front of the printing area and on the lower surface side of the conveyor belt.
In other words, the present embodiment includes a high-voltage circuit that supplies electric power to the charging roller 300, and has a booster circuit 310 between the high-voltage circuit and the charging roller.
According to this configuration, since the ink droplets ejected from the nozzle 166 are strongly polarized as compared with the first embodiment, the amount of charge of the ink mist generated accordingly is also larger than that of the first embodiment.
As in the first embodiment, the voltage of only the charging member that requires boosting, that is, the charging roller 300 that requires boosting, is increased by the boosting circuit 310 as in the method of the third embodiment. It is possible to increase the amount of mist charge more efficiently as compared with the configuration in which the voltage of the charging roller 300 is increased only by the high voltage circuit.
If necessary, a boosted voltage may be applied to the charging roller 300 of the second embodiment.

In the present embodiment, the polarity of the ink mist generated in the machine can be unified by unifying the charging polarity of the transport belt by the charging roller 300.
As a result, the generation of neutral ink mist can be suppressed, so that the ink mist recovery efficiency of the recovery member 200 can be improved, and as a result, the neutral ink mist can be prevented from adhering to unintended locations in the machine. can.

<Summary of Actions and Effects of the Present Invention>
In the present invention, the polarity of the facing region and the transport belt portion on the downstream side thereof are unified by the electric field from the charging roller arranged on the upstream side of the facing region where the transport belt faces the printing region. As a result, the charging polarities of the ink mists generated in the machine can be made the same, and as a result, the generation of neutral mist can be suppressed. As a result, the efficiency of collecting ink mist by the collecting member can be improved, and the amount of ink mist adhering to the charged member that the ink mist does not want to adhere to can be significantly reduced, and malfunction and failure of the device can be prevented.

100 ... Inkjet recording device (image forming device), 101 ... Image forming unit, 120 ... Feeding unit, 124 ... Separation pad, 130 ... Conveying unit, 130 ... Paper transporting unit, 131 ... Conveying belt, 132 ... Conveying roller, 132a ... Rotary encoder, 133 ... Tension roller, 135 ... Transport guide, 136 ... Tip pressurizing roller, 138 ... Charging roller, 140 ... Paper ejection part, 141 ... Separation claw, 142 ... Paper ejection roller, 143 ... Paper ejection tray, 160 ... Carriage, 165 ... Recording head (liquid discharge head), 167 ... Side plate, 168 ... Side plate, 200 ... Ink mist recovery member (recovery member), 200a, 200b ... Recovery electrode, 210 ... Ink mist recovery member (recovery member), 210a, 210b ... Recovery electrode, 222 ... Control board (control means)

Japanese Patent Application Laid-Open No. 2003-103857

Claims (6)

A carriage that reciprocates with a liquid discharge head that discharges liquid,
A charged recovery member that is arranged facing the moving region of the carriage and recovers the suspended liquid, and
A transport belt with a depressed part and
A charging member arranged in the recessed portion and charging the opposite region of the transport belt facing the carriage to a constant polarity.
A device that discharges a liquid, which is characterized by being equipped with. The device for discharging a liquid according to claim 1, wherein the recovery member is charged with a polarity opposite to that of the opposite region of the transport belt. The device for discharging a liquid according to claim 1 or 2, wherein the recovery member is provided on the side in a direction orthogonal to the transport direction of the transport belt. The liquid according to any one of claims 1 to 3, wherein the charging member is arranged on the upstream side of the facing region of the transport belt in the transport direction of the transport belt. Device. A high-voltage circuit that supplies electric power to the charging member is provided.
The device for discharging a liquid according to any one of claims 1 to 4 , wherein a booster circuit is provided between the high voltage circuit and the charging member. The device for discharging a liquid according to any one of claims 1 to 5 , wherein the charging member is a charging roller.

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