JP2010012710A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder using a pressure reducing valve which is easy to work and manufacture and enables pressure control of a minute flow-rate ink. <P>SOLUTION: In the pressure reducing valve which controls a pressure of the ink by opening and closing an ink channel by bringing a valve body and a valve seat used in the inkjet recorder in and out of contact each other to adjust a flow rate of the ink, a seal member bonded to at least one of the valve body and valve seat and formed of rubber or the like with a compression restorability is arranged at a contact part between the valve body and the valve seat. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that adjusts an ink ejection pressure from a nozzle by a pressure reducing valve.

  In an ink circulation system of an ink jet recording apparatus, ink in an ink container is sucked and pressurized by a supply pump, and the pressurized ink is supplied to a print head through a filter or a pressure adjusting valve (pressure reducing valve) to perform printing. A configuration is disclosed in which ink that has not been used for printing in the head is sucked with a recovery pump and recovered again into an ink container (see, for example, Patent Document 1).

JP 2003-220713 A

  In an ink jet recording apparatus, it is necessary to adjust the ink pressure supplied to the print head in order to perform stable printing, and a pressure reducing valve is used. Here, for example, when the nozzle hole diameter is 65 [μm], the amount of ink supplied to the print head through the pressure reducing valve is about 3.5 [cc / min], and the pressure reducing valve needs to control ink with a minute flow rate. There is. As a pressure reducing valve used here, there is one that controls ink pressure by opening and closing an ink flow path by contacting and separating a valve body (valve) and a valve seat (valve seat). In such a conventional pressure reducing valve, the contact portion between the valve body and the valve seat is made of metal or resin, and particularly when controlling a fluid with a small flow rate, the metal of the valve body and the valve seat, or If the surface of the resin contact portion is rough, the ink flow rate cannot be reduced even if the contact portion is brought into close contact, and the supplied ink pressure cannot be reduced. Therefore, precise processing such as polishing finish is required for the contact portion.

  However, in order to perform the above-described precision processing, skilled techniques are required together with a plurality of processes, which requires a large number of processing steps. As a result, the cost of manufacturing the pressure reducing valve is increased, and the cost of the ink jet recording apparatus is increased. Has led to up.

  Further, if the contact portion is scratched or a foreign object is inserted, a gap is formed on the contact surface between the valve body and the valve seat, and the accuracy of ink pressure control is deteriorated due to ink leakage.

  An object of the present invention is to provide an ink jet recording apparatus using a pressure reducing valve that can be easily processed and manufactured at low cost and can control the pressure of a minute flow rate ink.

  In order to achieve the above object, the present invention provides a pressure reducing valve that controls the pressure of ink by opening and closing an ink flow path by adjusting a flow rate of ink by bringing a valve body and a valve seat into contact with each other. And a seal member having a compression restoring property bonded to at least one of the valve body and the valve seat.

  According to the present invention, by using a seal member having a compression restoring property at the contact portion between the valve body and the valve seat, the contact portion fills a gap due to the surface roughness of the contact portion by elastic deformation of the seal member. The surface accuracy can be roughened. Therefore, it is possible to provide a pressure reducing valve that can be easily processed and can control the pressure of a minute ink without precisely processing the surface of the contact portion.

  In addition, when a seal member with compression recovery that is vulcanized and bonded to either the valve body or the valve seat is provided, mass production processing is easier, reducing the cost of manufacturing the pressure reducing valve, and reducing the cost of the inkjet recording apparatus. Connected.

  In addition, for example, even when some foreign matter is caught in the contact portion between the valve body and the valve seat, the gap between the contact surfaces can be filled with the elastic deformation of the seal member having compression recovery characteristics. The influence on the control of the ink pressure can be further reduced.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the illustrated example.

  FIG. 1 is a perspective view showing an ink jet recording apparatus 100 according to a first embodiment of the present invention. The ink jet recording apparatus 100 includes a main body 1 provided with an operation display unit 3 and a print head 2 outside. The main body 1 and the print head 2 are connected by a conduit 4.

  Here, the operation principle of the inkjet recording apparatus 100 will be described. As shown in FIG. 2, the ink in the ink container 18 is sucked and pressurized by the pump 25 to become the ink column 7 and is ejected from the nozzle 8. The nozzle 8 is provided with an electrostrictive element 9, and the ink column 7 ejected from the nozzle 8 is made into particles by applying vibration to the ink at a predetermined frequency. The number of ink particles 10 thus generated is determined by the frequency of the excitation voltage applied to the electrostrictive element 9, and is the same as the frequency. The ink particles 10 are given a charge by applying a voltage having a magnitude corresponding to the print information at the charging electrode 11. The ink particles 10 charged by the charging electrode 11 are deflected by receiving a force proportional to the amount of charge while flying in the electric field between the deflection electrodes 12, flying toward the print target 13, and landing. To do. At that time, the landing position of the ink particle 10 in the deflection direction changes according to the charge amount, and the production line moves the print target 13 in the direction orthogonal to the deflection direction, so that the ink particle 10 also moves in the direction orthogonal to the deflection direction. Particles can be landed, and a character is composed of a plurality of landed particles for printing.

  Ink particles 10 that have not been used for printing fly linearly between the deflection electrodes 12 and are collected by the main ink container 18 via a path after being captured by the gutter 14.

  FIG. 3 shows an example of an actual use state of the ink jet recording apparatus 100. The ink jet recording apparatus 100 is installed on a production line in a factory where food, beverages, and the like are produced, for example, the main body 1 is installed at a position where the user can operate, and the print head 2 is on a production line such as a belt conveyor 15. Is placed at a position where it can come close to the printing object 13 to be fed.

  In order to print on the production line such as the belt conveyor 15 with the same width regardless of the feeding speed, the encoder 16 that outputs a signal corresponding to the feeding speed to the inkjet recording apparatus 100 and the printing object 13 are detected. A print sensor 17 that outputs a signal for instructing printing to the inkjet recording apparatus 100 is installed, and each is connected to a control unit (not shown) in the main body 1.

  In accordance with signals from the encoder 16 and the print sensor 17, the control unit controls the charge amount and charging timing of the ink particles 10 ejected from the nozzle 8, and charges while the print target 13 passes near the print head 2. The deflected ink particles 10 are attached to the print object 13 for printing.

  FIG. 4 is an explanatory diagram showing an overall path configuration of the inkjet recording apparatus 100. The main body 1 is provided with a main ink container 18 for holding circulating ink, and the main ink container 18 has a reference liquid having an appropriate amount for holding the liquid in the main ink container 18 therein. A liquid level sensor 38 for detecting whether or not the level has been reached is provided. The main ink container 18 is connected to a viscosity measuring device 21 which is a drop type viscometer for measuring the viscosity of the ink via a path 101 for circulating the ink.

  The viscosity measuring instrument 21 is connected to an electromagnetic valve 22 that opens and closes a path via a path 102, and the electromagnetic valve 22 is connected to a pump 25 that is used for suction and pressure feeding of ink and solvent via a path 103. Yes. The pump 25 is connected via a path 104 to a filter 28 that removes foreign matters mixed in the ink.

  The filter 28 is connected to a pressure reducing valve 30 that adjusts to an appropriate pressure for printing the ink pumped from the pump 25 via the path 105, and the pressure reducing valve 30 controls the pressure of the ink via the path 106. It is connected to a pressure gauge 31 for detection.

  The pressure gauge 31 is connected to a nozzle 8 provided with a discharge port for discharging ink provided in the print head 2 via a path 107 passing through the conduit 4.

  In the ink discharge direction of the nozzle 8, a charging electrode 11 that charges the particle with a charge amount corresponding to character information printed on the ink particle 10 discharged from the nozzle 8 is disposed. In the flying direction of the ink particles 10 charged by the charging electrode 11, a deflection electrode 12 that generates an electric field that deflects the charged ink particles 10 is disposed.

  On the ink flying direction side of the deflection electrode 12, a gutter 14 for capturing the ink particles 10 that fly linearly without being charged and deflected because they are not used for printing is disposed.

  The gutter 14 is connected to a filter 29 that removes foreign matters mixed in the ink disposed in the main body 1 via a path 108 passing through the conduit 4, and the filter 29 is connected via the path 109. A pump 26 that sucks the ink particles 10 captured by the gutter 14 is connected. Then, the pump 26 collects the ink particles 10 sucked through the path 110 in the main ink container 18.

  The main body 1 is provided with an exhaust port 32, and the exhaust port 32 is connected to the main ink container 18 via a path 150. Volatile solvent components in the ink are connected to the main body 1 via the path 150. Exhausted outside.

  Further, the main body 1 is provided with a solvent container 20 that adjusts the ink contamination and ink concentration in the nozzle 8, and the solvent container 20 is connected to a pump 27 that sucks and pumps the solvent through a path 111. Has been. The pump 27 is connected to the electromagnetic valve 24 that opens and closes the path via the path 112, and the electromagnetic valve 24 is connected to the main ink container 18 via the path 113.

  Further, the main body 1 is provided with an auxiliary ink container 19 that holds replenishing ink. The auxiliary ink container 19 is connected to an electromagnetic valve 23 that opens and closes a path via a path 120. The electromagnetic valve 23 is connected to the path 103 via the path 121.

  Next, FIG. 5 shows a functional block diagram of the inkjet recording apparatus 100. The ink jet recording apparatus 100 includes a control unit 200 including, for example, an MPU. The control unit 200 includes an operation display unit 3, a nozzle 8, a charging electrode 11, a deflection electrode 12, an encoder 16, and the like via a bus line 201. The print sensor 17, viscosity measuring device 21, electromagnetic valves 22, 23, 24, pumps 25, 26, 27, pressure reducing valve 30, liquid level sensor 38, and recording unit 202 are controlled.

  The recording unit 202 stores a program for controlling the ink jet recording apparatus 100, and the control unit 200 controls each part of the ink jet recording apparatus 100 based on this program.

  The recording unit 202 records an appropriate ink pressure of ink for printing, that is, an upper limit (P max) and a lower limit (P min) for printing.

  In an ink jet recording apparatus, it is necessary to control the pressure of ink ejected from the nozzle within a range where printing can be performed properly. When ink pressure deviates from the proper range, the ink ejected from the nozzle becomes particulate. As a result, a phenomenon such as a change in the position of the ink particles or a phenomenon that the ink particles are not formed into a uniform shape occurs, a desired charge amount cannot be given to the ink particles, and an appropriate printing result cannot be obtained.

  Therefore, in order to avoid the occurrence of the above phenomenon, the ink jet recording apparatus requires means for adjusting the ink pressure and maintaining it at a constant pressure.

  FIG. 6 shows an operation principle diagram of a pressure reducing valve in a known technique. In such a pressure reducing valve, a pilot valve 41 that is a valve body, and a valve seat 42 that is a valve seat having a metal contact portion 42A at a contact portion with the pilot valve 41 are provided. The ink flow rate is adjusted and the ink pressure is controlled by contacting and separating the contact portion 42A. 6A shows a closed state of the pressure reducing valve, and FIG. 6B shows an opened state of the pressure reducing valve. The valve seat 42 is made of stainless steel, the contact surface with the pilot valve 41 is provided with a step to obtain a sufficient surface pressure for sealing, the contact area is reduced, and the contact surface roughness is Ra = 0.2. Precision polishing was performed with a flatness of 0.005. The pilot valve 41 uses an expensive but highly rigid PCTFE (polychlorotrifluoroethylene) resin in order to prevent permanent distortion, and requires machining for molding.

  FIG. 7 shows a longitudinal sectional view of a pressure reducing valve according to one embodiment of the present invention, and FIG. 8 shows an enlarged longitudinal sectional view of part A of FIG. The pressure reducing valve 30 according to the present embodiment includes a body 51 having a primary flow path 51A and a secondary flow path 51B to which a fluid pressurized by the pump 25 is supplied, and an air release hole 52A. And a case 52 provided on the upper side.

  The body 51 is a connection part with other equipment or a part of a manifold attached together with other equipment, and a primary side flow path 51A and a secondary side flow path 51B are provided at a connection part with the outside, and each flow The path leads to the bottom of the pressure chamber 51C.

  A configuration for realizing the pressure adjusting means will be described. A body 51 that forms a pressure chamber 51C that is a flow path that communicates with the secondary flow path 51B, an inflow hole 51D that communicates with the pressure chamber 51C and communicates with the primary flow path 51A, and a fluid that flows through the pressure chamber 51C. And a diaphragm 53 that is in direct contact with the pipe and receives a pressure in the pipeline to deform. The diaphragm 53 in the pressure chamber 51C is for receiving a pressure in the pipe line in direct contact with the fluid, and is made of a thin film, and a groove for fixing the diaphragm 53 is formed around the diaphragm. A pilot pin 54 that moves in the central axis direction according to the mechanical deformation amount of the diaphragm 53 and a pilot valve 55 that moves in the axial direction in conjunction with the pilot pin 54 are provided. A valve seat 56 provided with a rubber 56A at the contact portion with the pilot valve 55 and fixed to the body 51, a second spring 57 for pressing the pilot valve 55 against the valve seat 56, and a primary side inside the body 51 A piece 58 for creating the flow path 51A and fixing the second spring 57, a pressure adjustment chamber 51E surrounded by the piece 58 and the valve seat 56 and communicating with the primary side flow path, a pressure adjustment chamber 51E, and a pressure chamber In order to block the flow of ink from other than the valve portion of 51C, the valve seat 56, the piece 58, and an O-ring 66 in contact with the body 51 are formed. A rubber 56 </ b> A, which is a seal member having a compression restoring property, is bonded to a contact surface of the valve seat 56 with the pilot valve 55.

  The rubber 56 </ b> A can be formed from rubber, synthetic resin, or other materials having compression / restoration properties. When the ink solvent is an organic solvent, EPDM (ethylene propylene diene) rubber having high solvent resistance can be used. When the seal member made of EPDM is fixed to the valve seat by vulcanization adhesion, since the vulcanization temperature is about 200 ° C., a material having heat resistance equal to or higher than the vulcanization temperature is used for the valve seat. In order to further improve the adhesion, glass fiber reinforced PBT (polybutylene terephthalate) or PPS (polyphenylene sulfide) can be used.

  When other metals or synthetic resins are used for the valve seat material, it is effective to improve the adhesion by applying a surface treatment to give an appropriate surface roughness.

  Similarly, PBT, PPS, POM (polyacetal) or stainless steel, which is a synthetic resin having high solvent resistance, can be used for the pilot valve 55. When the seal member is vulcanized and bonded to the pilot valve instead of the valve seat, the above-described material conditions of the valve seat are applied to the pilot valve as they are.

  The load by which the first spring 59 installed in the case 52 presses the diaphragm 53 is a first spring seat 60 that contacts the diaphragm 53 on the central axis of the first spring 59 and the first spring across the diaphragm 53. A plunger 65 on the opposite side of the seat 60 and fixing the diaphragm 53; and a second spring seat 61 installed on the central axis opposite to the first spring seat 60 across the first spring 59 A case 52 fixed to the body 51 by surrounding assembly screws 62, and a first spring 59 which is fixed to the body 51 and coaxial with the first spring 59, and is desired for the first spring 62 via the second spring seat 61. And an adjustment screw 63 for applying the load.

  Next, the operation of the pressure reducing valve 30 of this embodiment will be described with reference to FIG. First, in the ink jet recording apparatus 100, the ink in the main ink container 18 is sucked by the pump 25, the ink is reduced to a predetermined value by the pressure reducing valve 30 through the filter 28, and the ink is ejected from the nozzle 8 for printing. . Ink not used for printing is captured by the gutter 14 and returned to the main ink container 18 by the pump 26.

  7 and 8 again, the ink pressurized in the pressure reducing valve 30 flows into the pressure adjusting chamber 51E through the primary side flow path 51A, and in a process of flowing into the pressure chamber 51C from the pressure adjusting chamber 51E. The ink is adjusted to the ink pressure, and the ink is supplied to the nozzle 8 through the secondary channel 51B. The primary side flow path 51A and the secondary side flow path 51B are always filled with ink, and the ink is supplied from the secondary side flow path 51B to the nozzle 8 while ink is ejected from the nozzle 8.

  FIG. 9 is a schematic diagram for explaining the operation of the pressure reducing valve. The total value of the secondary side pressure received by the diaphragm 53 and the force by which the second spring 57 pushes up the pilot valve 55 is opposite across the diaphragm 53. On the side center shaft, the load applied to the diaphragm 53 by the first spring 59 installed inside the case 52 is substantially balanced.

  As shown in FIG. 9A, when the ink pressure on the secondary side in the pressure chamber 51C is higher than the pressing pressure of the first spring 59, the diaphragm 53 is displaced in the opposite direction to the pressure chamber 51C. There is no gap between the valve seat 56 and the pilot valve 55, and no ink flows. However, since the ink in the pressure chamber 51C is gradually supplied to the nozzle 8 through the secondary side flow path 51B, the ink pressure on the secondary side in the pressure chamber 51C decreases, and the diaphragm 53 narrows the pressure chamber 51C. Transition so as to displace in the direction.

  Next, as shown in FIG. 9B, when the ink pressure on the secondary side in the pressure chamber 51C is lower than the pressing force of the first spring 59, the diaphragm 53 narrows the pressure chamber 51C. Therefore, the pilot valve 55 is displaced in the direction of being pushed down via the pilot pin 54 in conjunction with the plunger 65, and a gap is formed between the valve seat 56 and the pilot valve 55, so that the ink is in the pressure adjustment chamber 51E. Into the pressure chamber 51C. However, the amount of ink flowing into the pressure chamber 51C increases, the ink pressure on the secondary side increases, and the diaphragm 53 shifts in the direction opposite to the pressure chamber 51C. The pressure reducing valve 30 repeats the states shown in FIGS. 9A and 9B and controls the ink pressure on the secondary side by controlling the ink flow in accordance with the ink pressure fluctuation on the secondary side.

  Note that the load applied by the first spring 59 to the diaphragm 53 can be changed by turning the adjusting screw 63 attached to the case 52, and the secondary ink pressure is adjusted to a predetermined value.

  According to this embodiment, the following effects can be obtained. In the pressure reducing valve 30, the rubber 56 </ b> A is used for either of the contact portions between the valve seat 56 and the pilot valve 55, so that the rubber 56 </ b> A is elastically deformed and closes the contact surface even when a foreign object is caught in the contact surface. Therefore, a desired ink pressure can be obtained. Further, since the rubber 56A is elastically deformed by using the rubber 56A and a gap due to the surface roughness of the contact portion between the valve seat 56 and the pilot valve 55 is filled, the contact between the valve seat 56 and the pilot valve 55 is increased. Since the surface accuracy of the contact portion can be made rough, mass production processing becomes easy. As a result, the cost for manufacturing the pressure reducing valve 30 is reduced, and the cost for manufacturing the inkjet recording apparatus 100 is reduced.

  Further, in the present embodiment, the valve seat 56 with the rubber 56A attached to the contact portion with the pilot valve 55 is used. In addition, FIG. 10 shows a second embodiment of the present invention. As shown in the enlarged sectional view of the valve seat and the valve body portion, a pilot valve 71 in which rubber 71A is attached to the contact portion with the valve seat 72 may be used.

1 is an overall view of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is an operation principle diagram of the ink jet recording apparatus of FIG. 1. It is a perspective view which shows the actual use state of the inkjet recording device of this invention. It is explanatory drawing which shows the path | route structure of the inkjet recording device in one Embodiment of this invention. 1 is a functional block diagram of an inkjet recording apparatus 100 of the present invention. It is a schematic diagram explaining operation | movement of the pressure reducing valve in a well-known technique. It is a longitudinal cross-sectional view of the pressure-reduction valve in one Embodiment of this invention. FIG. 8 is an enlarged longitudinal sectional view of a part A in FIG. 7. It is a schematic diagram explaining operation | movement of the pressure-reduction valve used for this invention. It is an expansion longitudinal cross-sectional view of a valve seat and a valve body part which shows another embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main-body part, 2 ... Print head part, 8 ... Nozzle, 10 ... Ink particle, 18 ... Main ink container, 19 ... Ink container, 25 ... Pump (for ink supply), 26 ... Pump (for ink collection), 30 DESCRIPTION OF SYMBOLS ... Pressure-reducing valve, 41 ... Pilot valve, 42 ... Valve seat, 42A ... Metal contact part, 51A ... Primary side flow path, 51B ... Secondary side flow path, 55 ... Pilot valve, 56 ... Valve seat, 56A ... Rubber 71 ... Pilot valve, 71A ... Rubber, 72 ... Valve seat, 100 ... Inkjet recording apparatus

Claims (12)

An ink container for holding printing ink, a supply pump that sucks ink from the ink container via a piping path and supplies the ink to the ink discharge nozzle under pressure, and a pipe disposed between the supply pump and the ink discharge nozzle In an ink jet recording apparatus provided with a pressure reducing valve for adjusting ink pressure in a path,
The pressure reducing valve has a valve body and a valve seat, and adjusts the pressure in the piping path by adjusting the flow rate of ink in the piping path by bringing the valve body and the valve seat into contact with each other. An ink jet recording apparatus, comprising: a seal member having a compression restoring property at a contact portion between the valve body and the valve seat.   2. The ink jet recording apparatus according to claim 1, wherein the sealing member is made of a synthetic resin having a solvent resistance against an ink solvent.   3. The ink jet recording apparatus according to claim 1, wherein the sealing member is made of a synthetic rubber having a solvent resistance against the ink solvent.   4. The ink jet recording apparatus according to claim 3, wherein the seal member is made of ethylene propylene diene rubber.   5. The ink jet recording apparatus according to claim 3, further comprising a seal member vulcanized and bonded to a contact surface of the pressure reducing valve on the valve seat side.   5. The ink jet recording apparatus according to claim 3, further comprising a seal member vulcanized and bonded to a contact surface of the pressure reducing valve on the valve body side.   5. The ink jet recording apparatus according to claim 3, further comprising a seal member vulcanized and bonded to the contact surface on the valve seat side of the pressure reducing valve, and added to the valve seat contact surface to which the seal member is bonded. An ink jet recording apparatus using a material having heat resistance equal to or higher than a sulfur temperature.   8. An ink jet recording apparatus according to claim 7, wherein the valve seat side contact surface member for adhering the seal member is made of either polybutylene terephthalate or polyphenylene terephthalate containing glass fiber on the surface. Recording device.   8. The ink jet recording apparatus according to claim 7, wherein a member surface of a valve seat side contact surface to which the seal member is bonded has a surface roughness which gives an adhesive strength to the vulcanized and bonded seal member. apparatus   5. The ink jet recording apparatus according to claim 3, further comprising a seal member that is vulcanized and bonded to a contact surface on the valve body side of the pressure reducing valve, and vulcanized to a valve body contact surface that bonds the seal member. An ink jet recording apparatus using a material having heat resistance equal to or higher than a temperature.   11. The ink jet recording apparatus according to claim 10, wherein the member on the valve-body-side contact surface to which the seal member is bonded uses either polybutylene terephthalate or polyphenylene terephthalate containing glass fiber on the surface. apparatus.   11. The ink jet recording apparatus according to claim 10, wherein a member surface of the valve element side contact surface to which the seal member is bonded has a surface roughness that gives adhesion strength to the vulcanized seal member.

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