JP2008030333A - Liquid ejection head unit and image forming apparatus - Google Patents

Abstract

In a configuration in which a top surface of a portion where bubbles tend to remain is formed with an inclined surface and moved using a bubble buoyancy to a bubble discharge port provided at the top, bubbles cannot be discharged unless a large gradient is provided. In addition, when ink enters the dummy channel, the bubble discharge is hindered.
A top surface of a flat first space 31A along a filter longitudinal direction which is an upstream space of a filter 32 in a filter chamber 31 is directed from one end side to the other end side in the nozzle arrangement direction. In other words, the inclined surface 35 is inclined downward from the supply port 33 side toward the side corresponding to the discharge port 34, and the bubble discharge port 36 that faces the first space 31A and serves as a bubble discharge path for discharging bubbles, The filter 32 is provided at a corresponding location on the upper side opposite to the discharge port 34.
[Selection] Figure 2

Description

  The present invention relates to a liquid discharge head unit and an image forming apparatus, and more particularly to a liquid discharge head unit including a filter unit that filters liquid supplied to the liquid discharge head, and an image forming apparatus including the liquid discharge head unit.

  In general, a printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a recording head composed of a liquid ejection head that ejects liquid droplets of recording liquid (liquid). Using a liquid ejection apparatus, while conveying a medium (hereinafter also referred to as “paper”, the material is not limited, and a recording medium, a recording medium, a transfer material, recording paper, and the like are also used synonymously). In some cases, a recording liquid (hereinafter also referred to as ink) as a liquid is attached to a sheet to form an image (recording, printing, printing, and printing are also used synonymously).

  The “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. “Formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium. The “liquid” is not limited to recording liquid and ink, and is not particularly limited as long as it becomes a fluid when ejected, and includes, for example, a DNA sample, a resist, a pattern material, and the like. It is. Further, the “liquid ejecting apparatus” is an apparatus that ejects liquid from a liquid ejecting head and is not limited to an apparatus that forms an image.

  By the way, in order to respond to the demand for higher speed in the image forming apparatus, the drive frequency of the liquid discharge head active element for droplet discharge, the increase in the number of nozzles or the number of heads, etc. have been performed. In order to realize high-speed recording, since the appropriate amount of liquid discharged from the liquid discharge head increases, it is necessary to supply liquid to the head without delaying the discharge of droplets. On the other hand, an increase in the flow rate of liquid that can be supplied is unavoidable.

  As the flow rate increases, it is necessary to reduce the resistance value of the flow path from the liquid container that supplies the liquid to the liquid ejection head. The flow path of the liquid discharge head is set in consideration of this resistance value, but there is a problem of bubbles as another major factor that must be taken into consideration. If there are bubbles in the flow path and the bubbles flow into the head during recording, droplets are not ejected and an abnormal image is generated.

  In addition to the mixing of bubbles in the liquid discharge head, there is a filter unit that filters the liquid supplied to the liquid discharge head as a part where bubbles are a problem. The filter is provided in the flow path for the purpose of preventing poor printing due to fine dust from the upstream side flowing into the head. In the liquid discharge head, a filter having a filtration ability that takes in almost 100% of particles of several microns is usually used, and thus the filter has a large fluid resistance.

  As described above, in order to supply a large flow rate of liquid, it is necessary to increase the filter size. However, the larger the filter, the worse the ink filling property, and more bubbles tend to remain in the filter portion. When the bubbles come into contact with the filter to form a liquid film, the liquid does not flow through that portion, so that the fluid resistance increases and the liquid supply amount becomes insufficient. In addition, even if air bubbles pass through the filter during printing and flow into the head, the printing quality is adversely affected.

  Generally, a liquid storage unit such as a cartridge or a sub tank (head tank) that supplies liquid to the liquid discharge head is disposed above the liquid discharge head, and a filter is disposed between the liquid storage unit and the liquid discharge head. In many cases, however, the liquid flows from the upper side to the lower side of the filter.

Therefore, Patent Document 1 describes a configuration in which a top surface of a portion where bubbles tend to remain is formed as an inclined surface, and the bubbles are discharged to a bubble discharge port provided at the uppermost portion by using the buoyancy of the bubbles. .
JP 2002-144576 A

Further, in Patent Document 2, an approximately rhombus-shaped intermediate member is provided on the upstream side of the filter in the filter chamber in order to improve the ink filling property without impairing the bubble discharge property, and the intermediate member is supplied to the filter chamber. It is described that the ink is divided into two to substantially halve the space for filling, making the filter chamber a small size that is relatively easy to fill, and simultaneously making the filter easy to wet with ink.
Japanese Patent Laid-Open No. 2002-079694

  However, in the configuration in which the top surface of the portion where bubbles are likely to remain is formed as an inclined surface as in the invention described in Patent Document 1 and moved using the buoyancy of the bubbles to the bubble outlet provided at the top, a large gradient is used. There are problems such as that bubbles cannot be discharged unless they are provided, and that bubbles are hindered when ink enters the dummy channel. The invention described in Patent Document 2 is not intended to directly discharge bubbles.

  The present invention has been made in view of the above problems, and a liquid discharge head unit capable of improving the liquid filling property of the filter part without being affected by bubbles even when a large filter is disposed at a position close to the head. An object of the present invention is to provide an image forming apparatus including a liquid discharge head unit.

  In order to solve the above-described problems, a liquid discharge head unit according to the present invention includes a liquid discharge head that discharges droplets and a filter section that includes a filter chamber in which a filter that filters the liquid supplied to the liquid discharge head is incorporated. In the liquid discharge head unit, the filter chamber has a configuration in which a space for generating a liquid flow is formed on the upstream side of the filter in the longitudinal direction of the filter, and a bubble discharge path facing the space is provided. The “liquid discharge head unit” in the present invention does not mean that all are integrated, but means a member constituted by each part.

  A liquid discharge head unit according to the present invention includes a liquid discharge head that discharges liquid droplets, a filter unit that includes a filter chamber that includes a filter that filters the liquid supplied to the liquid discharge head, and a connection to the filter unit. In the liquid discharge head unit including the liquid storage portion for storing the liquid, the filter chamber is formed with a space for generating a liquid flow in the longitudinal direction of the filter on the upstream side of the filter, and discharging the bubbles facing the space. A path is provided, and the discharge side opening of the bubble discharge path faces the liquid container.

  In the liquid discharge head unit, the liquid storage portion may be provided with an air release means that opens and closes communication between the interior and the atmosphere, and air bubbles are discharged from the liquid storage portion of the bubble discharge path. The side opening can be configured to be provided at a position higher than the liquid supply port from the liquid storage part to the filter part.

  In these liquid discharge head units according to the present invention, the upstream space of the filter in the filter chamber has a flat structure, and a bubble discharge path is provided at one end of the space. A liquid supply port to the liquid discharge head may be formed on the substantially opposite side across the discharge path and the filter.

  The image forming apparatus according to the present invention includes the liquid discharge head unit according to the present invention.

  According to the liquid discharge head unit of the present invention, the filter chamber has a structure in which a space for generating a liquid flow is formed on the upstream side of the filter in the longitudinal direction of the filter, and a bubble discharge path facing this space is provided. Therefore, even if the filter is enlarged, the bubble discharge performance is improved, and a good liquid filling property in which bubbles do not remain in the filter chamber can be obtained.

  According to the liquid discharge head unit of the present invention, the filter chamber is formed with a space for generating a liquid flow in the longitudinal direction of the filter on the upstream side of the filter, and a bubble discharge path facing this space is provided. Since the discharge opening is provided in the liquid storage portion, the bubble discharge performance is improved even when the filter is enlarged, and a good liquid filling property in which no bubbles remain in the filter chamber is obtained.

  According to the image forming apparatus of the present invention, since the liquid discharge head unit according to the present invention is provided, the liquid discharge property to the liquid discharge head is good and a high-quality image can be formed at high speed.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. A liquid discharge head unit according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram of the configuration of the liquid discharge head unit, and FIG. 2 is an explanatory sectional view taken along line AA in FIG.

  The liquid discharge head unit 1 includes a liquid discharge head 2 that discharges droplets, and a filter unit 3 that is a filter unit having a filter chamber in which a filter for filtering the liquid supplied to the liquid discharge head 2 is built. ing.

  The liquid discharge head 2 is composed of a plurality of pressurized liquids that connect a flow path plate 11, a nozzle plate 12, and a vibration plate 13 and communicate with a plurality of nozzles 14 that discharge droplets formed on the nozzle plate 12. A fluid resistance portion 17 and a communication portion 18 on the upstream side of the fluid resistance portion 17 are formed on the upstream side corresponding to the chamber 16 and each pressurized liquid chamber 16. A laminated piezoelectric element 21 that pressurizes ink in the liquid chamber 16 is bonded to the surface of the diaphragm 13 opposite to each liquid chamber 16, and the rear end side of each laminated piezoelectric element 21 is a base member. 22 is joined. The piezoelectric element 21 is connected to an FPC cable 27 that gives a drive waveform.

  Further, a frame member 23 is joined to the surface of the diaphragm 13 opposite to the liquid chamber 16, and a common liquid chamber 24 is formed in the frame member 23, and the diaphragm 13 is formed from the common liquid chamber 24. Ink is supplied to each liquid chamber 16 via the liquid chamber supply port 25 corresponding to each liquid chamber 16, the communication portion 18, and the fluid resistance portion 17. Ink is supplied from the filter unit 3 to the common liquid chamber 24 through the supply port 26.

  In the liquid discharge head 2, for example, the voltage applied to the piezoelectric element 21 is lowered from the reference potential, the piezoelectric element 21 contracts, and the diaphragm 13 is lowered (pulled upward in the drawing). Is expanded, the ink flows into the liquid chamber 16, and then the voltage applied to the piezoelectric element 21 is increased to extend the piezoelectric element 21 in the stacking direction (arrow direction), and the diaphragm 13 is moved in the direction of the nozzle 14. By deforming and shrinking the volume / volume of the liquid chamber 16, the ink in the liquid chamber 16 is pressurized, and ink droplets are ejected (jetted) from the nozzle 14.

  Then, by returning the voltage applied to the piezoelectric element 21 to the reference potential, the diaphragm 13 is restored to the initial position, and the liquid chamber 16 expands to generate a negative pressure. 16 is filled with ink. Therefore, after the vibration of the meniscus surface of the nozzle 14 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  In the filter unit 3, a filter chamber 31 is formed in the filter case 30, and a filter 32 that filters ink supplied to the liquid ejection head 2 is provided in the filter chamber 31. Here, a space upstream of the filter 32 in the filter chamber 31 is a first space 31A, and a downstream space is a second space 31B.

  The first space 31 </ b> A of the filter chamber 31 of the filter case 30 is formed in a long and flat shape along the arrangement direction of the nozzles 14 of the liquid ejection head 2, and one end of the filter chamber 31 in the nozzle arrangement direction. A supply port (supply port) 33 through which ink is supplied from a liquid storage portion (not shown) facing the first space 31A is formed on the side. Further, on the other end side of the filter chamber 31 in the nozzle arrangement direction, a discharge port serving as a supply port for supplying ink to the liquid discharge head 2 from the second space 31 </ b> B to the liquid supply port 26 of the liquid discharge head 2. An outlet (discharge port) 34 is formed.

  Further, the top surface of the flat first space 31A along the filter longitudinal direction, which is the upstream space of the filter 32 in the filter chamber 31, is directed from one end side to the other end side in the nozzle arrangement direction, that is, The inclined surface 35 is inclined downward from the supply port 33 side toward the side corresponding to the discharge port 34. Since the first space 31A of the filter chamber 31 has a long shape along the filter longitudinal direction, a liquid flow occurs along the filter longitudinal direction. Furthermore, a bubble discharge port 36 that faces the first space 31A along the filter longitudinal direction, which is a space upstream of the filter 32, and serves as a bubble discharge path for discharging bubbles is provided on the opposite side of the discharge port 34 via the filter 32. It is provided at a corresponding location above.

  The filter unit 3 and the frame member 23 of the liquid discharge head 2 are connected (coupled) via a seal member 41. The frame member 23 is formed of resin, and if the thermoplastic resin is used, the filter 32 can be easily fixed directly to the frame member. Here, the frame member 23 is made of thermosetting resin, metal, ceramics, glass, or the like. For example, when it is difficult to fix the filter directly or when the filter area is increased, the filter unit 3 and the liquid discharge head 2 are separated from each other. The filter unit 3 is connected to a liquid storage unit (not shown) via seal members 42 and 43.

  With such a configuration, when the liquid discharge head 2 is filled with ink in the liquid discharge head unit 1, the nozzles of the nozzle plate 12 of the liquid discharge head 2 are used as shown in FIG. By operating the suction pump 52 in a state where the surface 12a is capped by the cap member 51, suction is performed from the nozzle 14 of the liquid ejection head 2, so that ink is supplied from a liquid storage portion (not shown) from the supply port 33 of the filter unit 3. Ink is supplied from the discharge port 34 to the common liquid chamber 24 of the liquid ejection head 2 through the first space 31A, the filter 32, and the second space 31B of the filter chamber 31.

  In this case, if ink is supplied from the liquid container only to the supply port 33 of the filter unit 3, ink flows in the longitudinal direction of the filter, and the ink is opposite from the supply port 33 across the filter 32. To the discharge port 34 on the side. At this time, the air previously stored in the first space 31A above the filter 32 in the filter chamber 31 is discharged from the bubble discharge port 36, and the filter unit 3 is filled with ink.

  Here, the liquid discharge head unit of the comparative example will be described with reference to FIGS. The liquid discharge head unit of this comparative example is an example of a filter unit that does not have the bubble discharge port 36, and other configurations are the same as those of the first embodiment. In this liquid discharge head unit, when the ink is filled by performing suction from the nozzle 14 as described above, the filter unit 3 is satisfactorily filled with ink under the condition that the filter 32 is completely dry. Although it can be satisfied, under conditions where the filter 32 is wet, the air previously in the first space 31A above the filter 32 cannot pass through the filter 32 due to the liquid film formed on the filter 32. As shown in FIG. 5, a large amount of air 39 remains in the first space 31A above the filter 32, the filling property is poor, and in some cases, air is bubbled and sent to the liquid ejection head 2. Will be.

  On the other hand, since the bubble discharge port 36 is formed above the first space 31A in the filter unit 3 of the present embodiment, air (bubbles) is discharged from the bubble discharge port by the ink flow and buoyancy generated by the cap suction. Thus, good ink filling can be performed.

  In this way, the filter chamber is formed with a space for generating a liquid flow in the longitudinal direction of the filter on the upstream side of the filter, and the bubble discharge path facing this space is provided. As a result, a good liquid filling property without bubbles remaining in the filter chamber can be obtained.

Next, a second embodiment of the liquid discharge head unit according to the present invention will be described with reference to FIGS. 6 is an explanatory diagram for explaining the configuration of the embodiment, and FIG. 7 is an explanatory plan view of FIG.
The liquid discharge head unit 1 includes a liquid discharge head 2 according to the first embodiment, a filter unit 3 that is a filter unit, and a head tank (ink reservoir) 4 that is a liquid storage unit that supplies ink to the liquid discharge head 2. Are connected.

  The head tank 4 is a flexible film-like member that seals an opening (one surface of the head tank 4) of the ink containing portion 61 to a container main body (case main body) 62 that forms an ink containing portion 61 that contains ink. (Flexible film-like member) 63 is attached by adhesion or welding, and further, the film-like member 63 is biased outwardly between the case main body 62 and the film-like member 63 inside the ink containing portion 61. A spring 64 for generating negative pressure, which is an elastic member, is provided. The negative pressure generating spring 64 presses the film-like member 63 outward in the direction in which the volume of the ink containing portion 61 is expanded, so that a negative pressure is formed.

  A displacement member 66 that is displaced according to the displacement of the film-like member 63 is swingably attached to a support portion 67 provided on the side portion of the case main body 62. A full tank detection sensor 68 made of a transmission type photosensor for detecting the detection piece 66a of the displacement member 66 is provided.

  An air communication hole 69 that communicates the ink containing portion 62 with the atmosphere is formed in the upper side surface of the case body 62, and an air release mechanism 70 that is an air release means that opens and closes the air communication hole 69 is provided. The air release mechanism 70 is a normally closed valve that is configured by housing a valve seat 72, a ball 73 that is a valve body, and a spring 74 that biases the ball 73 toward the valve seat 72 in a cylindrical holder 71. . This atmospheric release mechanism 70 is driven into the atmospheric state by driving the atmospheric release solenoid 80 and pressing the ball 73 against the spring 74 with the plunger pin 80a, and the plunger is released by deactivating the atmospheric release solenoid 80. The pin 80a is retracted and the ball 73 is returned to the closed state.

  Further, an ink introduction path 75 for replenishing ink is provided in the ink storage section 61, and ink is supplied from the ink cartridge 81 to the ink storage section 61 through the supply tube 83 and the ink introduction path section 75 by the supply pump 82. Is replenished.

  Further, two detection electrodes 76 and 77 for detecting that the remaining amount of ink has become a predetermined amount or less are mounted on the upper portion of the case main body 62. The amount of ink can be detected by changing the conduction state between the detection electrodes 76 and 77 in a state where both the detection electrodes 76 and 77 are immersed in ink and in a state where at least one of the detection electrodes 76 and 77 is not immersed in ink. it can.

  The filter unit 3 is connected to the bottom of the head tank 4. A supply port 33A that forms the supply port 33 of the filter unit 2 and a bubble discharge passage portion 36A that forms the bubble discharge port 36 are attached to the ink storage portion 61 of the head tank 4 in an open state, respectively. The outer periphery of the portion 33A and the bubble discharge port portion 36A and the case body 62 are sealed with seal members 42 and 43. As the sealing members 42 and 43, an O-ring or a plate-like rubber sheet can be used with a rubber material such as fluorine rubber, silicone rubber, epichlorohydrin rubber or the like.

  Here, the bubble discharge side opening in the head tank (liquid storage unit) 4 of the bubble discharge port 36 of the filter unit 3 is a liquid supply for supplying liquid from the head tank (liquid storage unit) 4 to the filter unit 3. It is configured to be arranged at a position higher than the mouth 33. Thereby, it is possible to prevent the bubbles discharged from the bubble discharge port 36 of the filter unit 3 into the head tank 4 from entering the liquid supply port 33 of the filter unit 3 again.

The ink filling operation of the liquid discharge head unit configured as described above in the air release state with respect to the liquid discharge head 2 will be described with reference to FIG.
<Step 1-1>
First, as shown in FIG. 8A, the atmosphere release mechanism 70 of the head tank 4 is opened, and the ink containing portion 61 is opened to the atmosphere. In this state, the supply pump 82 is operated to supply ink from the liquid cartridge 81 into the ink containing portion 61. At this time, since the supply port 33 is lower than the opening position of the bubble discharge port 36, the ink supplied to the ink containing portion 61 is a first space which is an upper space of the filter 32 of the filter unit 3 from the supply port 33. The air in the first space 31 </ b> A is discharged from the bubble discharge port 36 into the ink containing portion 61, and further discharged from the atmosphere opening hole 69 through the standby release mechanism 70 to the first space above the filter 32. 31A is filled.

  At this time, since a liquid film of ink is formed on the filter 32, the ink hardly flows into the second space 31B below the filter 32. After the filter chamber 31 is filled with ink, the liquid level of the ink rises in the ink container 61, and when the liquid level reaches the detection electrodes 76 and 77, the impedance between the electrodes 76 and 77 changes. When the change is detected, the supply pump 82 is stopped, so that ink can be filled in the ink containing portion 61.

<Step 1-2>
Next, the nozzle surface 12 a of the nozzle plate 12 is capped by the cap member 51 similar to that described in the first embodiment, and the suction pump 52 is operated to perform suction from the nozzle 14. By this suction, the ink remaining on the upper side of the filter 32 flows out into the second space 31 </ b> B on the lower side of the filter 32, and the ink is filled into each liquid chamber 16 from the supply port 26 via the common liquid chamber 24. Thereafter, the supply pump 82 is operated again to fill the ink container 61 with ink. Then, as shown in FIG. 8B, the atmosphere release mechanism 70 is closed to make the inside of the ink container 61 sealed. In this state, the inside of the ink containing portion 61 is at a positive pressure corresponding to the interval of the air release mechanism 70 from the nozzle surface, and the ink oozes from the nozzle 14.

<Step 1-3>
Therefore, in order to form a negative pressure in the ink storage portion 61 of the head tank 4, an appropriate amount of ink is sucked and discharged from the nozzle 14 by capping the cap member 51 and driving the suction pump 52 as described above. The nozzle surface 12a is wiped by wiping means (not shown). As a result of this suction and wiping, a meniscus is formed in the nozzle 14 and, as shown in FIG. 8C, the volume acts by the spring force of the negative pressure generating spring 64 inside the ink containing portion 61. Therefore, an appropriate negative pressure can be obtained. If the position of the displacement member 66 in this state is detected by the detection sensor 68 and stored, the ink replenishment amount after the ink is consumed by printing or the like can be controlled based on the position of the displacement member 66.

  In this ink filling operation, if the initial state in the filter chamber 31 is completely dry, the inside of the filter chamber 31 can be easily filled with ink. In the wet state, air 39 may remain in the first space 31A on the upper side of the filter 32 as shown in FIG. 9 after step 1-1 described above. It may happen that the filling quality is not improved even by suction after 1-2.

  To prevent the air layer from remaining in close contact with the upper surface of the filter 32 after step 1-1, for example, the height of the first space 31A on the filter 32 is increased to stabilize the horizontal liquid level in the space 31A. However, there is a problem that the head size becomes large, and if the filter chamber is bubbled in advance or large bubbles are mixed in the ink, it cannot be discharged. There is a problem that.

  Therefore, the first space 31A on the filter 32 has a flat structure, and the air flow is discharged by increasing the flow velocity in the direction parallel to the filter 32 surface. According to this configuration, even when the air 39 remains in step 1-1 as shown in FIG. 9, the ink flows vigorously from the supply port 33 toward the bubble discharge port 36 when the cap is sucked after step 1-2. Therefore, air can be discharged from the bubble discharge port 36.

  In the case of this configuration, in order to remove the air in the entire filter chamber 31, it is preferable to provide the supply port 33 and the bubble discharge port 36 at different ends of the filter chamber 31 so as to be separated as much as possible.

  In the present embodiment, the head tank 4 as the liquid storage unit includes an atmosphere release mechanism 70 that opens the inside to the atmosphere. For this reason, when the internal pressure changes due to a temperature change or the like, it is easy to open the atmosphere once and recreate the negative pressure, and it is possible to stably supply ink to the liquid ejection head 2 over a long period of time. .

  Further, in the present embodiment, the air in the filter unit 3 is returned to the head tank 4 and the air is discharged to the outside by the air release function of the air release mechanism 70 of the head tank 4. Can be obtained.

  Thus, the filter chamber is formed with a space for generating a liquid flow in the longitudinal direction of the filter on the upstream side of the filter, and a bubble discharge path facing this space is provided. The discharge-side opening of the bubble discharge path is a liquid container. Therefore, even if the filter is enlarged, the bubble discharge performance is improved, and a good liquid filling property without bubbles remaining in the filter chamber can be obtained.

Next, a third embodiment of the liquid discharge head unit according to the present invention will be described with reference to FIGS. 10 is an explanatory diagram for explaining the configuration of the embodiment, and FIG. 11 is an explanatory plan view of FIG.
The liquid discharge head unit 101 includes a liquid discharge head 2 according to the first embodiment, a filter unit 103 that is a filter unit, and a liquid storage unit that supplies ink to the liquid discharge head 2 via the filter unit 103. A head tank (ink reservoir) 104 is provided.

  First, the head tank 104 is a flexible film that seals an opening (one surface of the head tank 104) of the ink storage portion 161 to a container main body (case main body) 162 that forms an ink storage portion 161 that stores ink. A film-like member (flexible film-like member) 163 is attached by adhesion or welding, and the film-like member 163 is urged outwardly between the case main body 162 and the film-like member 163 inside the ink containing portion 161. A spring (spring) 164 for generating negative pressure, which is an elastic member, is provided. The negative pressure generating spring 164 presses the film-like member 163 outward in a direction in which the volume of the ink containing portion 161 is expanded, thereby forming a negative pressure.

  A displacement member 166 that is displaced according to the displacement of the film-like member 163 is swingably attached to a support portion 167 provided on a side portion of the case main body 162. It has a full tank detection sensor 168 made up of a transmission type photosensor that detects the detection piece 166a of the displacement member 166.

  Further, an ink introduction path 175 for replenishing ink is provided in the ink storage section 161, and ink is supplied from the ink cartridge 81 to the ink storage section 161 through the supply tube 83 by the supply pump 82 through the ink introduction path section 175. Is replenished.

  Further, a partition wall 178 is formed between a part of the case body 162 and the ink storage unit 161 to form an ink supply path 179 to the filter unit 103, and the ink supply path 179 is near the upper portion of the ink storage unit 161. Open.

  In the filter unit 103, a first space 131A, which is an upper space of the filter 132 of the filter chamber 131 of the filter case 130, is formed in a long and flat shape along the direction in which the nozzles 14 of the liquid discharge head 2 are arranged. A supply port (supply port) 133 through which ink is supplied from the ink supply path 179 of the head tank 104 facing the first space 131A is formed on one end side in the nozzle arrangement direction of 131. Further, on the other end side in the nozzle arrangement direction of the filter chamber 131, a discharge port serving as a supply port for supplying ink to the liquid discharge head 2 from the second space 131 </ b> B to the liquid supply port 26 of the liquid discharge head 2. An outlet (discharge port) 134 is formed.

  Further, the top surface of the first space 131A along the filter longitudinal direction, which is the upstream space of the filter 132 in the filter chamber 131, is directed from one end side to the other end side in the nozzle arrangement direction, that is, supplied. The inclined surface 135 is inclined downward from the mouth 133 side toward the side corresponding to the discharge port 134. Since the first space 131A of the filter chamber 131 has an elongated flat shape along the filter longitudinal direction, a liquid flow occurs along the filter longitudinal direction. Furthermore, a bubble discharge port 136 that faces the first space 131A along the filter longitudinal direction, which is a space upstream of the filter 132, and serves as a bubble discharge path for discharging bubbles is provided on the opposite side of the discharge port 134 via the filter 132. It is provided at a corresponding location above.

  Here, the bubble discharge port 136 is extended to the top surface of the head tank 104 through the extending portion 141, and an air release valve 180 that opens and closes the upper end opening of the bubble discharge port 136 is provided. The air release valve 180 is provided at the upper end of the bubble discharge port 136 by a seal member 183 provided at the tip of a lever member 182 pivotally supported by a support shaft 181 at the upper portion of the case main body 162 of the head tank 104. Open and close parts. A spring 184 is interposed between the rear end portion of the lever member 182 and the upper surface of the case main body 162, and the seal member 183 is urged so that the bubble discharge port 136 is always closed. Actuator means 185 such as a solenoid that presses the rear end portion of the lever member 182 against the spring 184 is disposed. By driving the actuator 185, the plunger 185a is protruded, the lever member 182 is swung, and the seal The member 183 opens the upper end opening of the bubble discharge port 136.

  In addition, electrode pairs 186 and 187 are provided at the tip of the bubble discharge port 136.

An ink filling operation in the liquid discharge head unit configured as described above will be described.
<Step 2-1>
First, the bubble discharge port 136 of the filter unit 103 is opened to the atmosphere by operating the actuator 185 to swing the lever member 182 to bring the seal member 183 into the open position. Next, the supply pump 82 is operated to supply ink from the liquid cartridge 81 into the ink storage portion 161 of the head tank 104. After the ink level in the ink containing portion 161 reaches the upper opening position of the ink supply path 179, it flows into the first space 131 </ b> A of the filter unit 103 from the supply port 133 through the ink supply path 179.

  At this time, the ink hardly passes through the filter 132 having a high fluid resistance, flows through the upper surface of the filter 132 and flows to the bubble outlet 136. Since the first space 131A on the upper side of the filter 132 has a flat shape, the air filled before ink filling is filled with ink while being efficiently pushed out to the bubble discharge port 136. The ink flows toward the tip outlet of the bubble discharge port 136, and when the liquid level reaches the electrode pair 186, 187, the drop of the interelectrode impedance is detected and the operation of the supply pump 82 is stopped. Next, after the actuator 185 is deactivated and the air opening of the bubble outlet 136 is closed by the seal member 183, the position of the displacement member 166 is detected by the detection sensor 168 and stored in the internal memory.

<Step 2-2>
Next, as described above, in a state where the nozzle surface 12a of the nozzle plate 12 is sealed with a cap member (not shown), a suction pump (not shown) is operated to perform nozzle suction. As a result of this suction, the ink remaining on the upper side of the filter 132 flows out to the lower side of the filter 132 and is supplied into the common liquid chamber 24 via the supply path 26 of the liquid discharge head 2, and the ink is supplied to each liquid chamber 16. Filled. Thereafter, the supply pump 82 is operated again, and ink is filled in the head tank 104 until the displacement member 166 moves to the state stored in step 2-1.

<Step 2-3>
In order to form a negative pressure in the head tank 104, as described above, an appropriate amount of ink is sucked using a cap member (not shown) and a suction pump, and the nozzle surface 12a is wiped by a wiping means (not shown). By this suction and wiping, a meniscus is formed in the nozzle 14, and the head tank 104 can obtain an appropriate negative pressure by the spring force of the negative pressure forming spring 164. The position of the displacement member 166 in a state where the initial negative pressure is formed is stored, and the initial filling is completed.

  In the above embodiment, a piezoelectric liquid discharge head using piezoelectric elements as actuator means is described as the liquid discharge head, but a thermal liquid discharge head using film boiling, an electrostatic liquid using electrostatic force It can also be composed of a discharge head or the like. The thermal type and electrostatic type are particularly effective when the number of nozzles is large or the filter size is increased in a liquid discharge head that performs high-speed printing. Moreover, in the said embodiment, although the liquid discharge head, the filter part, and the liquid storage part were provided independently and each demonstrated via the seal member etc., any two parts are demonstrated. It is also possible to adopt a configuration in which the seal connection is not performed integrally or all together.

Next, specific examples will be described.
<Example 1>
As the liquid discharge head 2, a piezoelectric element member was bonded and fixed to the stainless base member 22 with an anaerobic adhesive. The piezoelectric element member has a laminated structure in which internal electrodes on the GND side and the Hot side are alternately arranged, and each internal electrode is connected to an external electrode formed on two different insulated surfaces. By applying a voltage between the two external electrodes, the piezoelectric element member is displaced. The liquid discharge head according to this embodiment obtains the ink discharge pressure by using the displacement in the thickness direction of the piezoelectric element member. Then, the piezoelectric element members were divided by a dicing saw at a pitch of about 85 μm to form individual piezoelectric elements 21, and then the FPC cable 27 was joined to the side surfaces of the piezoelectric elements 21.

  The nozzle plate 12 and the vibration plate 13 are manufactured by an electroforming method, and are positioned with high accuracy with the flow path plate 11 in which a through portion to be a liquid chamber 16 is formed by etching a silicon substrate, and each is laminated with an epoxy adhesive. Fixed. Furthermore, the diaphragm 13, the piezoelectric element 21, and the epoxy resin frame member 23 were bonded and fixed with an epoxy adhesive, and the liquid discharge head was assembled.

  Next, the filter unit 3 was manufactured by fixing a filter 32 made of a sintered body of a SUS wire rod having a filtration accuracy of 10 μm to a transparent PC filter case 30 by heat fusion. As shown in FIG. 2, supply ports 33 and bubble discharge ports 36 are formed at both ends of the filter case 30 of the filter unit 3. The first space 31A on the upper side of the filter 32 had a width of 4 mm, a length of 30 mm, and a height of 1.5 mm on the supply port 33 side and 0.5 mm on the bubble discharge port 36 side. The second space 31B below the filter 32 has a width of 4 mm, a length of 30 mm, and a height of 1 mm on the supply port 33 side and 2 mm on the bubble discharge port 36 side.

  The head tank 4 was a structure having a volume of about 7 cc, with one surface of a box-shaped case body 62 formed of polyethylene resin sealed with a flexible film-like member 63. The flexible film-like member 63 has a low-density polyethylene on the inner surface, nylon on the outer surface, and a thickness of 80 μm. A compression spring 64 is disposed in the ink containing portion 61. As the compression spring 64, a spiral spring having a generated force of about 20 to 60 gf with respect to a displacement of 6 mm was used. Detection electrodes 76 and 77 made of metal pins as replenishment completion sensors are provided by press-fitting at the top of the top surface of the ink container 61 of the head tank 4. In addition, an air release hole 69 composed of a through hole having a diameter of about 2 mm was formed in the vicinity of the same portion, and an air release mechanism 70 urged by a spring 74 and normally closed was provided. Further, an introduction path 75 composed of a hole having a diameter of about 0.5 mm was formed at a position slightly above the metal pins 76 and 77 in the upper part of the head tank 4, and a supply tube 83 having an inner diameter of 1 mm was connected to that portion. The other end of the supply tube 83 was connected to the ink cartridge 81 via the piston pump 82. As the ink cartridge 81, a bag-shaped cartridge made of an aluminum vapor deposition film was used.

  Further, a resin lever part as a displacement member 66 is applied to the outer surface of the flexible film-like member 63 of the head tank 4 by a spring (not shown) to apply the flexible film-like member 63 to the inside with a force of about 5 to 10 g. It was provided so as to press. On the detection piece 66a side of the displacement member 66, a detection sensor 68 composed of a transmission type photosensor for detecting the displacement of the displacement member 66 is disposed.

  Each connecting portion of the head tank 4, the filter unit 3, and the frame member 23 of the liquid discharge head 2 is sealed with seal members 41 to 43 made of O-rings having a wire diameter of φ1 with fluororubber having a rubber hardness of 70 degrees, and filling evaluation Went.

  First, using the head unit 1 in a dry state where no liquid was passed through, the atmosphere release mechanism 70 was opened and the supply pump 82 was operated, and ink was injected until the impedance between the electrodes 76 and 77 changed. When the filling state inside the filter chamber 31 is confirmed through the case 30 of the transparent filter unit 3, the first space 31A above the filter 32 is neatly filled with ink, and the second space 31B below the filter 32 is filled in the second space 31B. There was a little ink only in the vicinity of the supply port 33.

  Next, when the surface of the nozzle plate 12 was sealed with a rubber cap and sucked for 5 seconds at a pressure of about 60 kPa, the second space 31B below the filter 32 was completely filled with ink. After the ink was filled up again and the atmosphere release mechanism 70 was closed, about 0.6 cc of ink was discharged by cap suction and the surface of the nozzle plate 12 was wiped with EPDM rubber. A meniscus could be formed.

  Next, the same filling evaluation was performed with the filter unit 3 once cleaned with the cleaning liquid containing the surfactant. As in the previous case, a good filling state could be obtained. Further, when the head unit 1 was mounted on a printer as an image forming apparatus and printing evaluation was performed, good printing quality could be obtained.

  For comparison, the same evaluation was performed with the filter unit of the comparative example that does not have the bubble discharge port 36 described in FIG. 4. As a result, good filling quality was obtained in the dry state, but the inside was washed and wetted. In the case of the above condition, a large amount of air remains in the first space 31A above the filter 32.

<Example 2>
In the head tank 104 of FIG. 10, one surface of a box-shaped case main body 162 formed of polyethylene resin is sealed with a flexible film-like member 163 to form a structure having a volume of about 7 cc. The flexible film-like member 163 was previously formed into a substantially mountain shape with low-density polyethylene on the inner surface, nylon on the outer surface, and a thickness of 80 μm, and joined by heat fusion. A compression spring 164 is disposed in the ink storage portion 161 of the head tank 104. As the compression spring 164, a spiral spring having a generated force of about 20 to 60 gf with respect to a displacement of 6 mm was used.

  A hole communicating with the filter unit 103 is formed on the bottom surface of the head tank 104, and a partition 178 is formed inside the ink supply path 179 so that ink is supplied from an upper portion in the ink storage portion 161. The structure. Further, a tube 83 is connected to the upper portion of the head tank 104, an ink cartridge 81 is connected via a piston pump 82, and an ink supply system is provided. Details regarding the ink supply system are the same as in the first embodiment, and a description thereof will be omitted.

  Further, similarly to the first embodiment, a displacement member 166 is provided on the outer surface of the flexible film-like member 163 on the side surface of the head tank 104, and a detection sensor comprising a transmission type photosensor that detects the displacement of the displacement member 166. 168 was placed.

  The filter unit 103 connected to the head tank 104 uses a transparent filter case 130 made of PC so that the filling state can be confirmed, and the shape of the built-in filter 132 and filter chamber 131 is the filter 32 and filter of the first embodiment. Same as chamber 31. However, the bubble outlet 136 does not communicate with the inside of the head tank 104 but has a shape extending upward to a position substantially equal to the top surface of the head tank 104. A pair of SUS electrodes 186 and 187 having a diameter of 1 mm were press-fitted and provided at the upper end opening of the bubble discharge port 136 and a position 15 mm below. In addition, a normally-closed air release valve 180 that seals the inside of the head tank 104 from outside air by providing a silicone rubber seal member 183 in close contact with the upper opening surface of the bubble discharge port 136 is provided. The seal member 183 is normally closed by a spring 184 with a force of about 100 gf, and is configured to open when the actuator 185 made of a solenoid operates.

  Then, the liquid discharge head 2, the filter unit 103, and the head tank 104, which are the same as those in the first embodiment, are sealed with a seal member made of silicone rubber having a rubber hardness of 40 degrees and made of an O-ring having a wire diameter of φ1, and a filling evaluation is performed. It was.

  First, the actuator 185 of the liquid discharge head unit 101 was driven, the air release valve 180 of the filter unit 103 was opened, the position of the displacement member 166 in this state was detected using the detection sensor 168, and the position was stored. Next, the supply pump 82 was operated, ink was injected until the impedance between the electrode pairs 186 and 187 changed, and the atmosphere release valve 180 was closed.

  When the filling state inside the filter chamber 131 is confirmed through the filter case 130 of the transparent filter unit 103, the first space 131A above the filter 132 is cleanly filled with ink, and the second space 131B below the filter 132 is filled with the ink. There was a little ink only in the vicinity of the supply port 133.

  Next, when the surface of the nozzle plate 12 was sealed with a rubber cap and sucked for 5 seconds at a pressure of about 60 kPa, the second space 131B below the filter 132 was completely filled with ink. Thereafter, the supply pump 82 was moved again until the displacement member 166 moved to the previously stored position, and the ink was filled up to the full level. Next, about 0.6 cc of ink was discharged by cap suction, and when the surface of the nozzle plate 12 was wiped with EPDM rubber, a meniscus could be formed cleanly on the nozzle 14.

  Further, when the liquid discharge head unit 101 was mounted on a printer and printing evaluation was performed, good printing quality could be obtained.

Next, an example of an image forming apparatus equipped with the liquid discharge head unit according to the present invention will be described with reference to FIGS. 12 is a schematic side view for explaining the outline of the mechanism of the image forming apparatus, and FIG.
The image forming apparatus includes an apparatus main body 201, a paper feed tray 202 for loading paper loaded in the apparatus main body 201, and a sheet on which an image is recorded (formed) by being detachably mounted on the apparatus main body 201. A paper discharge tray 203 for stocking is provided. Furthermore, a cartridge loading unit 204 for loading an ink cartridge as a first liquid storage unit is provided at one end of the front surface of the apparatus main body 201 (side of the paper supply / discharge tray unit).

  The cartridge loading unit 204 contains a plurality of recording liquids (inks) that are different color materials, such as black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink. Ink cartridges (main tanks) 210k, 210c, 210m, and 210y (referred to as “ink cartridges 210” when the colors are not distinguished) are recording liquid cartridges as the first liquid storage means. It can be inserted and inserted from the rear side to the rear side.

  The carriage 233 is slidably held in the main scanning direction by a main guide rod 231 and a sub guide rod 232 horizontally mounted on the left and right main side plates 221A and 221B constituting the frame 220, and a timing belt is supported by a main scanning motor (not shown). And moving and scanning in the direction indicated by the arrow (carriage main scanning direction).

  The carriage 233 includes a recording head 234 including four liquid ejection heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), and a plurality of ink ejection ports. Are arranged in a direction crossing the main scanning direction (paper feeding direction), and the ink droplet ejection direction is directed downward.

  The liquid discharge head constituting the recording head 234 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator using an electrostatic force, an electrostatic actuator using an electrostatic force, and the like provided as pressure generating means for generating a pressure for discharging a droplet can be used.

  In addition, the carriage 233 is provided with a head tank 235 for each color, which is a second liquid storage unit for supplying each color ink to each recording head 234. A filter unit (filter unit) 236 according to the present invention is interposed between the head tank 235 and the recording head 234, and the recording head 234, the filter unit 236, and the head tank 235 constitute a liquid discharge head unit according to the present invention. It is configured.

  As described above, each color head tank 235 is supplementarily supplied with ink of each color from the ink cartridge 210 mounted in the cartridge loading unit 204 via the supply tube 237 having flexibility of each color. The cartridge loading 204 is provided with a supply pump unit 224 which is a liquid feeding means for feeding ink in the ink cartridge 210. The supply tube 237 is held on the front stay 229 by a holding member 238 in the middle.

  On the other hand, as a paper feeding unit for feeding the paper 242 stacked on the paper stacking unit (pressure plate) 241 of the paper feed tray 202, a half-moon roller (feeding) that separates and feeds the paper 242 one by one from the paper stacking unit 241. A separation pad 244 made of a material having a large coefficient of friction is provided opposite to the sheet roller 243 and the sheet feeding roller 243, and the separation pad 244 is urged toward the sheet feeding roller 243 side.

  In order to feed the sheet 242 fed from the sheet feeding unit to the lower side of the recording head 234, a guide member 245 for guiding the sheet 242, a counter roller 246, a conveyance guide member 247, and a tip pressure roller. And a conveying belt 251 which is a conveying means for electrostatically attracting the fed paper 242 and conveying it at a position facing the recording head 234.

  The conveyor belt 251 is an endless belt, and is configured to wrap around the conveyor roller 252 and the tension roller 253 so as to circulate in the belt conveyance direction (sub-scanning direction). In addition, a charging roller 256 that is a charging unit for charging the surface of the transport belt 251 is provided. The charging roller 256 is disposed so as to come into contact with the surface layer of the conveyor belt 251 and to rotate following the rotation of the conveyor belt 251. Further, a guide member 257 serving as a platen portion is disposed on the back side of the conveying belt 251 corresponding to the printing area by the recording head 234.

  The transport belt 251 rotates in the belt transport direction when the transport roller 252 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 242 recorded by the recording head 234, a separation claw 261 for separating the paper 242 from the transport belt 251, a paper discharge roller 262, and a paper discharge roller 263 are provided. A paper discharge tray 203 is provided below the paper discharge roller 262.

  A double-sided unit 271 is detachably attached to the back surface of the apparatus main body 201. The duplex unit 271 takes in the paper 242 returned by the reverse rotation of the transport belt 251, reverses it, and feeds it again between the counter roller 246 and the transport belt 251. The upper surface of the duplex unit 271 is a manual feed tray 272.

  Further, as shown in FIG. 13, a maintenance / recovery mechanism 281 including a recovery means for maintaining and recovering the nozzle state of the recording head 234 is disposed in the non-printing area on one side of the carriage 233 in the scanning direction. Yes.

  The maintenance / recovery mechanism 281 includes cap members (hereinafter referred to as “caps”) 282a to 282d (hereinafter referred to as “caps 282” when not distinguished) for capping each nozzle surface of the recording head 234, and nozzle surfaces. A wiper blade 283 that is a blade member for wiping the ink, and an empty discharge receiver 284 that receives liquid droplets for discharging the liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid. ing. Here, the cap 282a is a suction and moisture retention cap, and the other caps 282b to 282d are moisture retention caps.

  Then, the waste liquid of the recording liquid generated by the maintenance / recovery operation by the maintenance / recovery mechanism 281, the ink discharged to the cap 282, the ink attached to the wiper blade 283 and removed by the wiper cleaner (not shown), and the empty ejection receiver 284 are empty. The discharged ink is discharged and stored in a waste liquid tank (not shown).

  Further, as shown in FIG. 13, in the non-printing area on the other side in the scanning direction of the carriage 233, idle ejection is performed to eject liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. An empty discharge receiver 288 for receiving the droplets at the time is arranged, and this empty discharge receiver 288 is provided with an opening 289 along the nozzle row direction of the recording head 234 and the like.

  In the image forming apparatus configured as described above, the paper 242 is separated and fed one by one from the paper feed tray 202, and the paper 242 fed substantially vertically upward is guided by the guide 245, and the transport belt 251 and the counter roller The leading end is guided by the conveying guide 247 and pressed against the conveying belt 251 by the leading end pressing roller 249, and the conveying direction is changed by about 90 °.

  At this time, a charging voltage pattern in which an alternating voltage is applied so that a positive output and a negative output are alternately repeated from the AC bias supply unit of the control unit (not shown) to the charging roller 256, that is, an alternating voltage is applied to the conveying belt 251. That is, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction which is the circumferential direction. When the sheet 242 is fed onto the conveyance belt 251 charged alternately with plus and minus, the sheet 242 is attracted to the conveyance belt 251, and the sheet 242 is conveyed in the sub scanning direction by the circumferential movement of the conveyance belt 251.

  Therefore, by driving the recording head 234 according to the image signal while moving the carriage 233, ink droplets are ejected onto the stopped paper 242 to record one line, and after the paper 242 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 242 has reached the recording area, the recording operation is finished and the paper 242 is discharged onto the paper discharge tray 203.

  Further, during printing (recording) standby, the carriage 233 is moved to the maintenance / recovery mechanism 281 side, the recording head 234 is capped by the cap 282, and the nozzles are kept in a wet state to prevent ejection failure due to ink drying. . Further, the recording liquid is sucked from the nozzle by a suction pump (not shown) with the recording head 234 capped with the cap 282 (referred to as “nozzle suction” or “head suction”), and the thickened recording liquid and bubbles are discharged. Perform recovery action. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 234 is maintained.

  As described above, since the image forming apparatus includes the liquid discharge head unit according to the present invention, even if the filter is enlarged by increasing the length of the recording head, the bubble discharging property and the ink filling property are good. Thus, high-quality images can be stably formed at high speed.

  In the above embodiment, the liquid ejection head unit according to the present invention has been described as an example applied to an image forming apparatus. However, the present invention is not limited to this and can be applied to all liquid ejection apparatuses. Further, the present invention is also applicable to a liquid discharge apparatus and an image forming apparatus that use a liquid other than a recording liquid, for example, a liquid discharge head that is used in a liquid discharge apparatus or an image forming apparatus that discharges a DNA sample, resist, pattern material, or the like as described above. can do.

It is explanatory drawing explaining the structure of the liquid discharge head unit which concerns on 1st Embodiment of this invention. FIG. 2 is a cross-sectional explanatory view taken along line AA in FIG. 1. It is explanatory drawing with which it uses for description of an effect | action of the head unit. It is explanatory drawing explaining the structure of the unit of the head of a comparative example. It is explanatory drawing with which it uses for description of an effect | action of the head unit of the comparative example. It is explanatory drawing explaining the structure of the liquid discharge head unit which concerns on 2nd Embodiment of this invention. It is principal part plane explanatory drawing of FIG. It is explanatory drawing with which it uses for description of the ink filling operation | movement with respect to the head unit. It is a cross-sectional explanatory drawing similarly. It is explanatory drawing explaining the structure of the liquid discharge head unit which concerns on 3rd Embodiment of this invention. It is principal part plane explanatory drawing of FIG. FIG. 3 is a schematic side view illustrating an outline of a mechanism unit as an example of an image forming apparatus in which the liquid discharge head unit according to the present invention is mounted. Similarly, it is an explanatory plan view of the main part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 101 ... Liquid discharge head unit 2 ... Liquid discharge head 3, 103 ... Filter unit 4, 104 ... Head tank (ink reservoir)
DESCRIPTION OF SYMBOLS 11 ... Flow path plate 12 ... Nozzle plate 13 ... Vibration plate 14 ... Nozzle 16 ... Liquid chamber (discharge chamber)
DESCRIPTION OF SYMBOLS 17 ... Fluid resistance part 18 ... Communication part 21 ... Piezoelectric element 23 ... Frame member 24 ... Common liquid chamber 30, 130 ... Filter case 31, 131 ... Filter chamber 31A, 131A ... 1st space 31B, 131B ... 2nd space 32, 132: Filter 36, 136 ... Bubble discharge port 61, 161 ... Ink storage portion 234 ... Recording head (liquid ejection head)
235 ... Head tank (sub tank)
236 ... Filter unit

Claims (7)

In a liquid discharge head unit comprising a liquid discharge head for discharging liquid droplets and a filter unit having a filter chamber in which a filter for filtering the liquid supplied to the liquid discharge head is incorporated.
The liquid discharge head unit, wherein the filter chamber is provided with a space for generating a liquid flow in the longitudinal direction of the filter on the upstream side of the filter, and a bubble discharge path facing the space. A liquid discharge head that discharges liquid droplets, a filter unit having a filter chamber in which a filter for filtering the liquid supplied to the liquid discharge head is built, and a liquid storage unit that is connected to the filter unit and stores the liquid A liquid ejection head unit comprising:
In the filter chamber, a space for generating a liquid flow in the longitudinal direction of the filter is formed on the upstream side of the filter, and a bubble discharge path facing the space is provided, and a discharge side opening of the bubble discharge path is formed in the liquid storage portion. A liquid discharge head unit characterized by facing.   3. The liquid discharge head unit according to claim 2, wherein the liquid storage portion is provided with an air release means for opening and closing the communication between the inside and the atmosphere.   4. The liquid discharge head unit according to claim 2, wherein the bubble discharge side opening in the liquid storage part of the bubble discharge path is provided at a position higher than the liquid supply port from the liquid storage part to the filter part. A liquid discharge head unit.   5. The liquid discharge head unit according to claim 1, wherein a space upstream of the filter in the filter chamber has a flat structure, and a bubble discharge path is provided at one end of the space. Liquid discharge head unit.   6. The liquid discharge head unit according to claim 1, wherein a liquid supply port to the liquid discharge head is formed in the filter portion on a substantially opposite side across the bubble discharge path and the filter. A liquid discharge head unit. An image forming apparatus comprising the liquid discharge head unit according to claim 1.

Images