JP2020163723A - Liquid discharge unit - Google Patents

Abstract

To provide a liquid discharge unit comprising a cooling structure which can substantially equally cool plural liquid discharge devices.SOLUTION: A cooling structure defines: plural cooling channels 33 which circulate a cooling liquid, and each of which is thermally connected to each of plural liquid discharge devices; plural supply channels 34 which are connected to one ends of the plural cooling channels 33 respectively; supply manifold channels 311, 312 which are connected to the plural supply channels 34 on an upper side with respect to the plural liquid discharge devices, and distribute the cooling liquid to the plural supply channels 34; plural recovery channels 35 which are connected to the other ends of the plural cooling channels 33 respectively; and recovery manifold channels 321, 322 which are connected to the plural recovery channels 35 on an upper side with respect to the plural liquid discharge devices, and merge the cooling liquids from the plural recovery channels 35. A cross sectional area of the supply manifold channel is smaller than a cross sectional area of the recover manifold channel.SELECTED DRAWING: Figure 2

Description

The present invention relates to a liquid discharge unit.

An image recording device is used in which a liquid such as ink is discharged to a medium such as paper via a liquid ejection device, and an image is recorded on the medium by this. Liquid discharge devices generally include a number of pressure chambers, each containing a liquid, nozzles fluidly connected to each of the pressure chambers, actuators for applying pressure to the liquid in the desired pressure chamber, and actuators. It includes a control unit that controls the drive.

The liquid discharge by the liquid discharge device is performed by the control unit driving an actuator to apply pressure to the liquid in a desired pressure chamber. As a result, the liquid in the pressure chamber to which the pressure is applied is discharged from the corresponding nozzle and forms an image on a medium such as paper.

As one form of an image recording device including a liquid discharge device, a device including a liquid discharge unit having a plurality of liquid discharge devices and simultaneously discharging droplets from a plurality of liquid discharge devices is known. Regarding such an image recording device, it has been proposed to cool a plurality of liquid discharge devices with a coolant in order to suppress heat generation of the liquid discharge device due to continuous use for a long time (Patent Document 1).

JP-A-2007-237486

The heat generated in the control unit of the liquid discharge device is transferred to the liquid flowing through the pressure chamber or the like, and may cause a change in the characteristics of the liquid. For example, when the liquid is ink, the density and viscosity of the ink change. Therefore, in an image forming apparatus that uses a plurality of liquid ejection devices at the same time, if the plurality of liquid ejection devices cannot be cooled uniformly, for example, the density and viscosity of the ink inside will differ for each liquid ejection device. If image formation is performed in such a state, the quality of the formed image may deteriorate. It is hard to say that the structure of Patent Document 1 can uniformly cool a plurality of liquid discharge devices.

An object of the present invention is to provide a liquid discharge unit having a cooling structure capable of cooling a plurality of liquid discharge devices more evenly.

According to the first aspect of the present invention,
Multiple liquid discharge devices, each of which discharges liquid,
A liquid discharge unit having a cooling structure for cooling the plurality of liquid discharge devices with a cooling liquid.
The cooling structure
A plurality of cooling channels through which the coolant flows, each of which is thermally connected to each of the plurality of liquid discharge devices.
A plurality of supply channels, each of which is connected to one end of the plurality of cooling channels,
A supply manifold flow path that is connected to the plurality of supply flow paths above the plurality of liquid discharge devices and distributes the cooling liquid to the plurality of supply flow paths.
A plurality of recovery channels, each of which is connected to the other end of the plurality of cooling channels,
A recovery manifold flow path that is connected to the plurality of recovery flow paths above the plurality of liquid discharge devices and that merges the cooling liquids from the plurality of recovery flow paths is defined.
A liquid discharge unit having a cross-sectional area of the supply manifold flow path smaller than the cross-sectional area of the recovery manifold flow path is provided.

In the liquid discharge unit of the first aspect, the cross-sectional area of each of the plurality of supply flow paths may be smaller than the cross-sectional area of the supply manifold flow path. According to this aspect, since the flow velocity of the liquid becomes larger in the supply flow path, the bubbles sent from the supply manifold flow path to the supply flow path can be efficiently pushed downstream.

In the liquid discharge unit of the first aspect, the cross-sectional area of each of the plurality of supply channels and the cross-sectional area of each of the plurality of recovery channels may be equal. According to this aspect, the member constituting the supply flow path and the member constituting the recovery flow path can be used as a common member, the manufacturing process can be simplified, and the manufacturing cost can be reduced.

In the liquid discharge unit of the first aspect, the cross-sectional area of the recovery manifold flow path may be twice or more the cross-sectional area of the supply manifold flow path. According to this aspect, the cooling liquid of the supply manifold flow path can be more evenly distributed to the plurality of cooling flow paths, and the cooling liquid of the plurality of cooling flow paths can be more evenly flowed into the recovery manifold flow path. Can be done. Therefore, the plurality of liquid discharge devices can be cooled more evenly.

In the liquid discharge unit of the first aspect, the recovery manifold flow path is included in the first recovery manifold flow path connected to a part of the recovery flow paths and the plurality of recovery flow paths. A second recovery manifold flow path connected to some other flow path may be included, and the supply manifold flow path, the first recovery manifold flow path, and the second recovery manifold flow path are in the first direction in the horizontal plane. The supply manifold flow path may extend along the above, and the supply manifold flow path is provided between the first recovery manifold flow path and the second recovery manifold flow path in the second direction orthogonal to the first direction in the horizontal plane. You may. Further, the cooling structure includes a supply port for flowing the cooling liquid toward the upstream end of the supply manifold and a recovery port for flowing the cooling liquid from the recovery manifold while arranging vertically with the supply port. Further, the supply port and the collection port may be provided on the upstream end side of the supply manifold flow path in the first direction, and may be the same as the supply manifold flow path in the second direction. It may be provided at a position. In this embodiment, since the length (flow path resistance) of the branch path connecting the supply port and the recovery port to each manifold flow path (supply manifold flow path, recovery manifold flow path) can be set equally, the flow rate of the coolant can be set to the same value. The 1 recovery manifold flow path and the 2nd recovery manifold flow path can be made equal, and it is possible to prevent the cooling response force from becoming uneven.

In the liquid discharge unit of the first aspect, the plurality of liquid discharge devices form a first row arranged in a predetermined direction in a horizontal plane and a second row parallel to the first row along the predetermined direction. The supply manifold flow paths may be arranged in a staggered pattern, and the supply manifold flow paths may extend between the first row and the second row in parallel with the first row and the second row. In this aspect, a space can be secured above the liquid discharge device, and the space can be effectively utilized. In addition, in this specification and the present invention, "parallel" also includes a substantially parallel state in which one is inclined by a predetermined angle, which is greater than 0 ° and less than 5 ° with respect to the other.

In the liquid discharge unit of the first aspect, the recovery manifold flow path is a supply manifold flow path that sandwiches at least one of the plurality of liquid discharge devices by the recovery manifold flow path and the supply manifold flow path. It may extend in parallel. In this aspect, a space can be secured above the liquid discharge device, and the space can be effectively utilized.

The liquid discharge unit of the first aspect may further include a plurality of liquid flow path members connected to each of the plurality of liquid discharge devices and supplying the liquid to each of the liquid discharge devices. Further, in the liquid discharge unit of the first aspect, the supply flow path and the recovery flow path connected to each of the plurality of cooling flow paths are inclined upward with respect to the vertical direction and extend upward to the supply manifold flow. It may be connected to the path and the recovery manifold flow path, or the supply flow path and the recovery flow path may be inclined so that the distance between them increases as the direction increases upward, and the plurality of liquid flows may be connected to each other. The road member may be arranged so as to extend upward from the liquid discharge device and pass between the supply manifold flow path and the recovery manifold flow path. In this aspect, the liquid discharge unit can be miniaturized by arranging the liquid flow path member by effectively utilizing the space above the liquid discharge device.

The liquid discharge unit of the first aspect may further include a holding member that integrally holds the plurality of liquid discharge devices. According to this aspect, since the configuration including a plurality of liquid discharge devices can be maintained and managed as one unit, it becomes easy to perform the positioning and replacement in the printer.

In the liquid discharge unit of the first aspect, the cooling structure may include a pump connected to the supply manifold flow path and the recovery manifold flow path. According to this aspect, the cooling liquid can be efficiently flowed by the pump, and the plurality of liquid discharge devices can be cooled more uniformly.

According to the liquid discharge unit of the present invention, a plurality of liquid discharge devices can be cooled more evenly by the cooling structure.

FIG. 1 is a diagram showing a schematic configuration of a printer of the embodiment. FIG. 2 is a perspective view of the inkjet head unit according to the embodiment of the present invention. FIG. 3 is a perspective view showing an inkjet head, a spacer, and a cooling member that is a part of a cooling structure. FIG. 4 is a plan view of the flow path unit. FIG. 5 is a cross-sectional view taken along the line VV of FIG. FIG. 6A is a plan view of the inkjet head unit according to the embodiment of the present invention. FIG. 6B is a side view of the inkjet head unit according to the embodiment of the present invention. FIG. 7 is a diagram showing the shape of the flow path to be analyzed in the simulation analysis for examining the relationship between the cross-sectional area of the supply manifold flow path and the cross-sectional area of the recovery manifold flow path. 8 (a) and 8 (b) are tables showing the results of simulation analysis for examining the relationship between the cross-sectional area of the supply manifold flow path and the cross-sectional area of the recovery manifold flow path. 9 (a) and 9 (b) are graphs showing the results of simulation analysis for examining the relationship between the cross-sectional area of the supply manifold flow path and the cross-sectional area of the recovery manifold flow path. FIG. 10A is a plan view of an inkjet head unit according to a modification of the present invention. FIG. 10B is a side view of the inkjet head unit of the modified example of the present invention.

[Embodiment]
The inkjet head unit (liquid ejection unit) 100 of the embodiment of the present invention and the printer 1000 including the same will be described with reference to FIGS. 1 to 10.

<Printer 1000>
As shown in FIG. 1, the printer 1000 mainly includes four inkjet head units 100, a platen 500, a pair of transfer rollers 601 and 602, and a housing 900 for accommodating them. An ink tank 700 and a control device CONT are further provided inside the housing 900.

In the following description, the direction in which the pair of transfer rollers 601 and 602 are lined up, that is, the direction in which the paper P is conveyed during image formation is referred to as the "paper feed direction" of the printer 1000 and the inkjet head unit 100. Regarding the "paper feed direction", the upstream side in the direction in which the paper P is conveyed is called the "paper feed side", and the downstream side is called the "paper discharge side". Further, the direction in the horizontal plane orthogonal to the paper feed direction, that is, the direction in which the rotation axes of the transport rollers 601 and 602 extend is called the "paper width direction", and the direction orthogonal to the "paper feed direction" and the "paper width direction" is " Called "up and down". In the description of the flow path in the present specification, the "upstream side" and "downstream side" mean the upstream side and the downstream side in the direction in which the liquid flows inside.

Each of the four inkjet head units 100 is a mechanism for ejecting ink for image formation, and is supported by the support 100a at both ends in the paper width direction. In the present embodiment, the four inkjet head units 100 are configured to eject inks of four colors different from each other. These four colors are, for example, cyan, magenta, yellow and black. The specific structure and function of each of the inkjet head units 100 will be described later.

The platen 500 is a plate-shaped member that supports the paper P from the opposite side (lower side) of the inkjet head unit 100 when the ink is ejected from the inkjet head unit 100 toward the paper P. The width of the platen 500 in the paper width direction is larger than the width of the largest paper on which the image can be recorded by the printer 1000.

The pair of transfer rollers 601 and 602 are arranged so as to sandwich the platen 500 in the paper feed direction. The pair of transport rollers 601 and 602 feed the paper P to the paper ejection side in the paper feed direction in a predetermined manner when the inkjet head unit 100 forms an image on the paper P.

The ink tank 700 is an accommodating portion for accommodating the ink ejected by the inkjet head unit 100, and is divided into four so as to accommodate four colors of ink. The ink tank 700 is connected to the sub tank 810 (FIG. 6B) above the inkjet head unit 100 via the ink flow path member 800, and the sub tank 810 is connected to the inkjet head unit via the ink flow path member 820. It is connected to 100. Inside the ink flow path member 820, an ink supply path 821 for sending ink from the sub tank 810 to the inkjet head unit 100 and an ink recovery path 822 for returning ink from the inkjet head unit 100 to the sub tank 810 are defined. Has been done.

The control device CONT controls each part of the printer 1000 as a whole, and causes the paper P to form an image or the like.

<Inkjet head unit 100>
Next, the inkjet head unit 100 will be described.

As shown in FIG. 2, the inkjet head unit 100 includes a holding member 10, ten inkjet heads 20 integrally supported by the holding member 10, and a cooling structure 30 for cooling the ten inkjet heads 20.

The holding member 10 is a rectangular plate-shaped member in a plan view in which the paper width direction is the longitudinal direction and the paper feed direction is the lateral direction. Both ends of the holding member 10 in the longitudinal direction are supported portions supported by the support 100a.

The ten inkjet heads 20 are integrally held by the holding member 10 by being arranged inside a plurality of openings (not shown) of the holding member 10.

The ten inkjet heads 20 are arranged in a staggered pattern along the paper width direction in a plan view (FIG. 6A). Specifically, of the 10 inkjet heads, 5 inkjet heads 20 are linearly arranged at equal intervals in the paper width direction to form the first row L1. The remaining five inkjet heads 20 are arranged linearly at equal intervals in the paper width direction on the paper ejection side of the first row L1 in the paper feed direction to form the second row L2. The inkjet heads 20 forming the second row L2 are arranged so as to be offset in the paper feed direction with respect to the inkjet heads 20 forming the first row L1. As a result, the inkjet head 20 is positioned without a gap in the paper width direction of the holding member 10.

<Inkjet head 20>
As shown in FIG. 3, each of the plurality of inkjet heads 20 includes a flow path unit 21, a piezoelectric actuator 22, and a discharge control unit 23.

The flow path unit 21 is formed with a flow path CH (FIG. 4) for distributing and discharging the ink from the sub tank 810 at an appropriate position. As shown in FIG. 5, the flow path unit 21 has a laminated structure in which the diaphragm 21A, the plates 21B to 21I, and the nozzle plate 21J are laminated in this order from the top, and each of the plates 21B to 21I and the nozzle plate 21J. The flow path CH is formed by removing a part of.

As shown in FIGS. 4 and 5, the flow path CH comprises a plurality of individual flow path ICHs arranged in the paper feed direction and the paper width direction, and a plurality of inks supplied from the sub tank 810 via the ink supply path 821. It mainly includes a distribution flow path DCH that distributes to the individual flow path ICH. The flow path CH further includes an ink supply port PI ₂₁ that connects the ink supply path 821 and the distribution flow path DCH, and an ink recovery port PO ₂₁ that connects the ink recovery path 822 and the distribution flow path DCH.

A plurality of individual flow path ICHs arranged in the paper width direction form an individual flow path row L _ICH . One distribution flow path DCH is provided for each of the four individual flow path rows _LICH , and one ink supply port PI ₂₁ and one ink recovery port PO ₂₁ are provided for each distribution flow path DCH. It is provided. In the present embodiment, eight individual flow path rows _LICH are formed in the paper feed direction, and two distribution flow paths DCH, two ink supply ports PI ₂₁ , and two ink recovery ports PO ₂₁ are formed.

As shown in FIG. 5, each of the plurality of individual flow path ICH includes a throttle flow path 1, a pressure chamber 2, a descender flow path 3, and a nozzle 4 along the upstream side to the downstream side of the ink flow.

The throttle flow path 1 is formed by removing a part of the plates 21C and 21D, and is connected to the distribution flow path DCH at the upstream end and to the pressure chamber 2 at the downstream end.

The pressure chamber 2 is a space for applying pressure by the piezoelectric actuator 22 to the ink, and is formed by removing a part of the plate 21B. The upper surface of the pressure chamber 2 is formed by the diaphragm 21A. The plan view shape of the pressure chamber 2 is an oval shape that is long in the paper feed direction (FIG. 4), and the throttle flow path 1 is connected in the vicinity of one arc portion and the descender flow path 3 is connected in the vicinity of the other arc portion. There is.

The descender flow path 3 is a flow path for flowing the ink of the pressure chamber 2 to the nozzle 4, and is formed by coaxially providing circular through holes in each of the plates 21C to 21I. The descender flow path 3 extends in the vertical direction from the pressure chamber 2 toward the nozzle 4.

The nozzle 14 is a minute opening for ejecting ink toward the paper P, and is formed on the nozzle plate 21J.

The two ink supply ports PI ₂₁ and the two ink recovery ports PO ₂₁ are alternately arranged in the vicinity of one end in the paper width direction of the flow path unit 21 along the paper feed direction.

As shown in FIG. 5, each of the two ink supply ports PI ₂₁ is formed by providing through holes coaxially in each of the diaphragm 21A and the plates 21B to 21D. The ink supply port PI ₂₁ is connected to the ink supply path 821 via the ink supply port PI ₄₀ and PI ₃₃ on the upper side, and is connected to the distribution flow path DCH on the lower side.

Each of the two ink recovery ports PO ₂₁ is formed by providing through holes coaxially in each of the diaphragm 21A and the plates 21B to 21D, similarly to the ink supply port PI ₂₁ . The ink recovery port PO ₂₁ is connected to the ink recovery path 822 via the ink recovery port PO ₄₀ and PO ₃₃ on the upper side, and is connected to the distribution flow path DCH on the lower side.

Each of the two distribution flow paths DCH is formed by removing a part of the plates 21E to 21H.

Each of the two distribution flow paths DCH is a substantially U-shaped flow path in a plan view, and is connected to the ink supply port PI ₂₁ at the upstream end and to the ink recovery port PO ₂₁ at the downstream end. Specifically, each of the two distribution flow paths DCH has a first straight line portion DCH 1 extending linearly from the ink supply port PI ₂₁ toward one side in the paper width direction, and a paper width direction from the ink recovery port PO _21. It has a second straight line portion DCH 2 extending linearly toward one side, and a connecting portion DCH 3 extending in the paper feed direction and connecting the first straight line portion DCH 1 and the second straight line portion DCH 2.

The upper surface of the first straight portion DCH1 of distribution channel DCH, on the upper surface of the second linear portion DCH2, throttle channel 1 of the corresponding two of the plurality of individual flow channels of the individual channels column _{L ICH} ICH is, the sheet width direction It is connected in a staggered pattern along.

As shown in FIG. 5, the piezoelectric actuator 22 includes a first piezoelectric layer 221 provided on the upper surface of the flow path unit 21, a second piezoelectric layer 222 above the first piezoelectric layer 221 and first piezoelectric layers 221 and first piezoelectric layer 221. It is composed of a common electrode 223 sandwiched between the two piezoelectric layers 222 and a plurality of individual electrodes 224 provided on the upper surface of the second piezoelectric layer 222.

The first piezoelectric layer 221 is provided on the upper surface of the diaphragm 21A so as to cover all of the plurality of individual flow path ICHs formed in the flow path unit 21. A common electrode 223 is provided on the upper surface of the first piezoelectric layer 221 so as to cover almost the entire upper surface of the first piezoelectric layer 221. On the upper surface of the common electrode 223, the first piezoelectric layer 221 and the common electrode 223 are provided. A second piezoelectric layer 222 is provided so as to cover the entire area.

The common electrode 223 is grounded via wiring (not shown) and is always held at the ground potential.

Each of the plurality of individual electrodes 224 has a substantially rectangular planar shape with the paper feed direction as the longitudinal direction. The plurality of individual electrodes 224 are provided on the upper surface of the second piezoelectric layer 222 so as to be located above the pressure chambers 2 of the plurality of individual flow paths ICH (FIG. 5). Each of the plurality of individual electrodes 224 is aligned so as to be located above the central portion of the corresponding pressure chamber 2.

In the structure in which the first piezoelectric layer 221 and the second piezoelectric layer 222, the common electrode 223, and the plurality of individual electrodes 224 are arranged as described above, among the second piezoelectric layer 222, the common electrode 223 and the plurality of individual electrodes 224 The portion sandwiched between the two becomes the active portion 222a polarized in the thickness direction.

The discharge control unit 23 mainly includes a holding plate 231, an FPC (Flexible Printed Circuits, flexible printed circuit board) 232 wound around the holding plate 231 and two driver ICs 233 mounted on the FPC232.

A plurality of contacts (not shown) are formed on the portion of the FPC232 located on the lower surface 231d side of the holding plate 231. Two driver ICs 233 are mounted on the portion of the FPC232 located on the upper surface 231u side of the holding plate 231.

The discharge control unit 23 is arranged on the upper surface of the piezoelectric actuator 22 so that each of the plurality of contacts of the FPC 232 is electrically connected to each of the plurality of individual electrodes 224 of the piezoelectric actuator 22. As a result, each of the plurality of individual electrodes 224 of the piezoelectric actuator 22 is connected to the driver IC 233 via the FPC232. Further, the driver IC 233 is connected to the control unit CONT via a wiring (not shown).

<Cooling structure 30>
The cooling structure 30 is a structure for cooling the inkjet head 100 using a coolant (refrigerant), and includes the first and second supply manifolds 311 and 312, and the first and second recovery manifolds 321 and 322. The cooling member 33 thermally connected to each of the ten inkjet heads 20, the ten supply pipes 34 connecting the first and second supply manifolds 311 and 312 and the cooling member 33, and the first and second supply pipes 34. It mainly includes 10 recovery pipes 35 that connect the recovery manifolds 321 and 322 and the cooling member 33.

In the present specification and the present invention, "thermally connected" to another member does not necessarily mean that they are in direct contact with each other, and they are in contact with each other or in a manner in which heat exchange is possible. It means that they are in close proximity.

The cooling structure 30 further includes a coolant tank 36, a connection pipe 371 and a flow diversion pipe 372 that connect the first and second supply manifolds 311 and 312, and the coolant tank 36, and the first and second recovery manifolds 321. It includes a connecting pipe 381 and a merging pipe 382 that connect the 322 and the refrigerant tank 36, and a coolant pump 39 provided in the middle of the connecting pipe 371.

The first and second supply manifolds 311 and 312 are arranged above the holding member 10 and the plurality of inkjet heads 20. The first and second supply manifolds 311 and 312 are linear circular tubes extending in the paper width direction, respectively, and are formed of a nylon tube or the like as an example.

The upstream ends 311a and 312a of the first and second supply manifolds 311 and 312 are connected to the diversion pipe 372. The downstream ends 311b and 312b of the first and second supply manifolds 311 and 312 are closed. Inside the first and second supply manifolds 311 and 312, the first and second supply manifold flow paths 311C and 312C that linearly extend from the upstream ends 311a and 312a to the downstream ends 311b and 312b are defined.

As shown in FIG. 6A, the first and second supply manifolds 311 and 312 have the first row L1 and the second row L2 between the first row L1 and the second row L2 of the inkjet head 20. They are arranged in parallel. The first and second supply manifolds 311 and 312 are provided at positions different from those of the inkjet head 20, that is, positions that do not overlap with the inkjet head 20 in a plan view. As a result, the space above the inkjet head 20 can be effectively used. In the present embodiment, the ink flow path member 820 extending between the sub tank 810 and the inkjet head 20 is arranged in this space (FIG. 6 (b)).

The cross-sectional shapes of the first and second supply manifold flow paths 311C and 312C defined inside the first and second supply manifolds 311 and 312 are circular, and the cross-sectional areas are A [mm ² ], respectively. The length of the first and second supply manifold flow paths 311C and 312C is, for example, about 300 [mm] to 330 [mm].

The first and second recovery manifolds 321 and 322 are arranged above the holding member 10 and the plurality of inkjet heads 20. The first and second recovery manifolds 321 and 322 are linear circular tubes extending in the paper width direction, respectively, and are formed of a nylon tube or the like as an example.

The upstream ends 321a and 322a of the first and second recovery manifolds 321 and 322 are closed, and the downstream ends 321b and 322b of the first and second recovery manifolds 321 and 322 are connected to the merging pipe 382. Inside the first and second recovery manifolds 321 and 322, first and second recovery manifold flow paths 321C and 322C extending linearly from the upstream ends 321a and 322a to the downstream ends 321b and 322b are defined.

As shown in FIG. 6A, the first collection manifold 321 is arranged parallel to the first row L1 on the paper feed direction feeding side of the first row L1 of the inkjet head 20, and the second collection manifold 322. Is arranged in parallel with the second row L2 on the paper feed direction discharge side of the second row L2 of the inkjet head 20. That is, the first recovery manifold 321 sandwiches the first row L1 of the inkjet head 20 together with the first supply manifold 311 in the paper feed direction, and the second recovery manifold 322 and the second supply manifold 312 sandwich the first row L1 of the inkjet head 20. The row L2 is sandwiched in the paper feed direction.

The first and second recovery manifolds 321 and 322 are provided at positions different from those of the inkjet head 20, that is, positions that do not overlap with the inkjet head 20 in a plan view. As a result, the space above the inkjet head 20 can be effectively used.

The cross-sectional shapes of the first and second recovery manifold flow paths 321C and 322C defined inside the first and second recovery manifolds 321 and 322 are circular, respectively. The cross-sectional areas of the recovery manifold flow paths 321C and 322C are twice the cross-sectional areas A [mm ² ] of the first and second supply manifold flow paths 311C and 312C, that is, 2A [mm ² ]. The length of the first and second recovery manifold flow paths 321C and 322C is, for example, about 300 [mm] to 330 [mm].

As shown in FIG. 3, each of the cooling members 33 is a thick plate-shaped member having a substantially square plan view. As an example, each of the cooling members 33 may be made of a material having high thermal conductivity such as aluminum.

Inside each of the cooling members 33, a cooling flow path 33C having a substantially U-shape in a plan view is formed. The cooling flow path 33C includes an inflow portion 33C1 extending downward from the upper surface 33u of the cooling member 33, a first cooling portion 33C2 extending downward from the downstream end of the inflow portion 33C1 to one side in the paper width direction, and a downstream of the first cooling portion 33C2. A connecting portion 33C3 extending from the end in the paper feed direction, a second cooling portion 33C4 extending from the downstream end of the connecting portion 33C3 to the other side in the paper width direction, and a cooling member 33 extending upward from the downstream end of the second cooling portion 33C4. The outflow portion 33C5 reaching the upper surface 33u is included. The upstream end of the inflow portion 33C1 is the upstream end 33Ca of the cooling flow path 33C, and the downstream end of the outflow portion 33C5 is the downstream end 33Cb of the cooling flow path 33C.

Note that FIG. 3 shows a cooling member 33 attached to the inkjet head 20 included in the first row L1. The shape of the cooling member 33 attached to the inkjet head 20 included in the second row L2 is the same as this, but in the cooling flow path 33C, the downstream end 33Cb in FIG. 3 is the upstream end, and the upstream end 33Ca is the downstream end. Become.

The cross-sectional shape of the cooling flow path 33C is circular, and the cross-sectional area is smaller than the cross-sectional area A [mm ² ] of the first and second supply manifold flow paths 311C and 312C. The length from the upstream end 33Ca to the downstream end 33Cb of the cooling flow path 33C is, for example, about 70 [mm] to 80 [mm].

Each of the cooling members 33 is provided with two ink supply ports PI ₃₃ and two ink recovery ports PO ₃₃ adjacent to the cooling flow path 33C in the paper width direction. The two ink supply ports PI ₃₃ and the two ink recovery ports PO ₃₃ are alternately arranged along the paper feed direction.

Each of the cooling members 33 is fixedly connected to each of the flow path units 21 of the inkjet head 20 via the spacer 40. The spacer 40 is a plate-shaped member having a substantially square view in a plan view, and has a rectangular through hole 40A in a plan view that penetrates most of the spacer 40, and two ink supply ports PI ₄₀ and 2 adjacent to the through hole 40A in the paper width direction. It has two ink recovery ports PO ₄₀ . The two ink supply ports PI ₄₀ and the two ink recovery ports PO ₄₀ are alternately arranged along the paper feed direction.

In a state where the cooling member 33 is connected to the flow path unit 21 via the spacer 40, the piezoelectric actuator 22 and the discharge control unit 23 are housed inside the through hole 40A of the spacer 40, and the driver IC 233 of the cooling member 33 It abuts on the lower surface 33d. As a result, the driver IC 233 is thermally connected to the cooling member 33 and the cooling flow path 33C. More specifically, one of the driver IC 233 is located at a position overlapping the first cooling unit 33C2 in a plan view, and the other driver IC 233 is located at a position overlapping the second cooling unit 33C4 in a plan view. It abuts on the lower surface 33d.

When the cooling member 33 is connected to the flow path unit 21 via the spacer 40, the two ink supply ports PI ₂₁ of the flow path unit 21, the two ink supply ports PI 40 of the spacer ₄₀ , and the cooling member 33 The two ink supply ports PI ₃₃ of the above are overlapped in a coaxial manner to define an ink supply port PI (FIG. 2) extending vertically. Similarly, two ink recovery port _{PO 21} of the passage unit 21, two ink recovery port _{PO 40} of the spacer 40, two ink recovery ports _{PO 33} of the cooling member 33 overlap coaxially ink recovery port extending in the vertical The PO (FIG. 2) is defined.

Five supply pipes 34 are provided for the first supply manifold 311 and five for the second supply manifold 312, respectively. Each of the supply pipes 34 is a linear circular pipe, and is formed of a nylon tube or the like as an example. A supply flow path 34C is defined inside each of the supply pipes 34.

Each upstream end 34a of the supply pipe 34 provided for the first and second supply manifolds 311 and 312 is the first at equal intervals along the extending direction of the first and second supply manifolds 311 and 312. , Connected to the second supply manifolds 311 and 312. Each upstream end 34a is connected to the peripheral surfaces of the first and second supply manifolds 311 and 312 below the upper and lower centers of the first and second supply manifolds 311 and 312. The supply pipe 34 located on the most downstream side of the first and second supply manifolds 311 and 312 is the first and second supply manifolds 311 and 312 at the downstream ends 311b and 312b of the first and second supply manifolds 311 and 312. It is connected to the.

The five supply pipes 34 provided for the first supply manifold 311 extend from the connection portion with the first supply manifold 311 to the paper feed side and downward in the paper feed direction orthogonal to the first supply manifold 311. , Is connected to a cooling member 33 fixed to the inkjet head 20 constituting the first row L1. Specifically, the downstream ends 34b of the five supply pipes 34 are connected to the upstream ends 33Ca of the five cooling flow paths 33C. The five supply pipes 34 provided for the second supply manifold 312 extend from the connection portion with the second supply manifold 312 to the paper discharge side and downward in the paper feed direction orthogonal to the second supply manifold 312. , It is connected to the cooling member 33 fixed to the inkjet head 20 constituting the second row L2. Specifically, the downstream ends 34b of the five supply pipes 34 are connected to the upstream ends 33Ca of the five cooling flow paths 33C.

The cross-sectional shape of the supply flow path 34C is circular, and the cross-sectional area is smaller than the cross-sectional area A [mm ² ] of the first and second supply manifold flow paths 311C and 312C, and is the same as the cross-sectional area of the cooling flow path 33C. is there. The length from the upstream end 34a to the downstream end 34b of the supply flow path 34C is, for example, about 75 [mm] to 85 [mm].

Five recovery pipes 35 are provided for the first recovery manifold 321 and five for the second recovery manifold pipe 322. Each of the recovery tubes 35 is a linear circular tube, and is formed of a nylon tube or the like as an example. A recovery flow path 35C is defined inside each of the recovery pipes 35.

The downstream ends 35b of the recovery pipes 35 provided for the first and second recovery manifolds 321 and 322 are the first at equal intervals along the extending direction of the first and second recovery manifolds 321 and 322. , It is connected to the peripheral surface of the second recovery manifolds 321 and 322. Each downstream end 35b is connected to the peripheral surfaces of the first and second recovery manifolds 321 and 322 below the upper and lower centers of the first and second recovery manifolds 321 and 322. Of the recovery pipes 35, the recovery pipes 35 located on the most upstream side of the first and second recovery manifolds 321 and 322 are the first and first recovery pipes 35 at the upstream ends 321a and 322a of the first and second recovery manifolds 321 and 322. 2 It is connected to the recovery manifolds 321 and 322.

The five collection pipes 35 provided for the first collection manifold 321 extend from the connection portion with the first collection manifold 321 to the paper ejection side and downward in the paper feed direction orthogonal to the first collection manifold 321. , Is connected to a cooling member 33 fixed to the inkjet head 20 constituting the first row L1. Specifically, the upstream ends 35a of the five recovery pipes 35 are connected to the downstream ends 33Cb of the five cooling flow paths 33C. The five collection pipes 35 provided for the second collection manifold 322 extend from the connection portion with the second collection manifold 322 to the paper feed side and downward in the paper feed direction orthogonal to the second collection manifold 322. , It is connected to the cooling member 33 fixed to the inkjet head 20 constituting the second row L2. Specifically, the upstream ends 35a of the five supply pipes 35 are connected to the downstream ends 33Cb of the five cooling flow paths 33C.

The cross-sectional shape of the recovery flow path 35C is circular, and the cross-sectional area is smaller than the cross-sectional area A [mm ² ] of the first and second supply manifold flow paths 311C and 312C, and is the same as the cross-sectional area of the cooling flow path 33C. is there. The length from the upstream end 35a to the downstream end 35b of the recovery flow path 35C is, for example, about 75 [mm] to 85 [mm].

The upstream end 311a of the first supply manifold 311 and the upstream end 312a of the second supply manifold 312 are connected to the diversion pipe 372, respectively. Further, the downstream end 321b of the second recovery manifold 321 and the downstream end 322b of the second recovery manifold pipe 322 are connected to the merging pipe 382, respectively. The upstream end (supply port) 372a of the diversion pipe 372 and the downstream end (collection port) 382b of the confluence pipe 382 are arranged side by side in the vertical direction at the same position in the paper feed direction.

The diversion pipe 372 is connected to the coolant tank 36 via the connecting pipe 371, and the merging pipe 382 is connected to the coolant tank 36 via the connecting pipe 381. The coolant pump 39 is provided in the middle of the connecting pipe 371 in the present embodiment, but is not limited to this, and the coolant can be sent from the coolant tank 36 to the cooling flow path 33C at an arbitrary position. Can be arranged as

The supply path for sending the cooling liquid from the coolant tank 36 to the plurality of cooling members 33 is composed of the connecting pipe 371, the diversion pipe 372, the first and second supply manifolds 311 and 312, and the plurality of supply pipes 34. .. Further, a recovery path for returning the cooling liquid from the plurality of cooling members 33 to the coolant tank 36 is composed of a plurality of recovery pipes 35, first and second recovery manifolds 321 and 322, a merging pipe 382, and a connecting pipe 381. To.

<Image formation method>
Image formation on paper P using the printer 1000 and the inkjet head unit 100 is performed as follows.

First, the paper P in the paper feed tray (not shown) is fed to the paper feed side of the transport roller 601 and is fed onto the platen 500 by the transport roller 601. The plurality of inkjet heads 20 of the inkjet head unit 100 continuously eject ink droplets on the paper P fed in the paper feed direction by the transport rollers 601 and 602, and form an image on the paper P. The paper P on which the image is formed is fed to the paper ejection side of the transport roller 602 and ejected to a paper ejection tray (not shown).

The ejection of ink droplets using the inkjet head 20 is performed by applying pressure to the ink in a predetermined pressure chamber 2 (referred to as “target pressure chamber”) using the piezoelectric actuator 22. Specifically, first, the driver IC 233 applies a drive potential to the individual electrodes 224 corresponding to the target pressure chamber via the FPC 232 under the instruction of the control device CONT. As a result, an electric field parallel to the polarization direction is generated in the active portion 222a sandwiched between the individual electrode 224 to which the driving potential is applied and the common electrode 223, and the active portion 222a contracts in the horizontal direction orthogonal to the polarization direction. .. As a result, the diaphragm 21A above the target pressure chamber vibrates, pressure is applied to the ink in the target pressure chamber, and droplets of ink are ejected from the nozzle 4 communicating with the pressure chamber 2 via the descender flow path 3. To.

Further, the inkjet head unit 100 and the printer 1000 of the present embodiment use the cooling structure 30 to cool the driver IC 233 and eventually the inkjet head 20 during the image formation.

Specifically, the coolant pump 39 is driven to transfer the low-temperature coolant held in the coolant tank 36 to the connecting pipe 371, the diversion pipe 372, the first and second supply manifolds 311 and 312, and the supply pipe 34. It flows to the cooling flow path 33C of a plurality of cooling members 33 through. As a result, heat exchange is performed between the coolant flowing through the cooling flow path 33C and the driver IC 233 thermally connected to the cooling flow path 33C, the temperature of the driver IC 233 decreases, and the temperature of the coolant increases. To do. The cooled liquid whose temperature has risen is returned to the coolant tank 36 via the recovery pipe 35, the first and second recovery manifolds 321 and 322, the merging pipe 382, and the connecting pipe 381, and is cooled by a cooling device (not shown). To.

The inkjet head unit 100 and the printer 1000 of the present embodiment cool the driver IC 233 by using the cooling mechanism 30 in this way. As a result, the heat of the driver IC 233 is transferred to the ink in the flow path unit 21, and it is suppressed that the characteristics of the ink are changed (for example, changes in density and viscosity), and that the quality of the formed image is deteriorated. ..

<Cross-sectional area of supply manifold flow path and recovery manifold flow path>
In the inkjet head unit 100 of the present embodiment, the cross-sectional areas of the first and second supply manifold flow paths 311C and 312C are A [mm ² ], and the cross-sectional areas of the first and second recovery manifold flow paths 321C and 322C are , Twice that, 2A [mm ² ]. In other words, the cross-sectional area of the first and second supply manifold flow paths 311C and 312C is 1/2 of the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C. This feature has the following significance.

The first and second supply manifold flow paths 311C and 312C are arranged above the inkjet head 20. Therefore, in order to discharge the air bubbles mixed in the cooling liquid in the first and second supply manifold flow paths 311C and 312C, the supply flow path 34C extending downward from the first and second supply manifold flow paths 311C and 312C It is necessary to send the bubbles and let the bubbles flow through the cooling flow path 33C to the first and second recovery manifold flow paths 321C and 322C.

However, since the air bubbles receive buoyancy and go upward, when the flow velocity of the coolant flowing in the first and second supply manifold flow paths 311C and 312C is small, the air bubbles that try to go upward are extended downward. It is difficult to flush it into the supply flow path 34C. In this case, air bubbles inside the first and second supply manifold flow paths 311C and 312C may stay in the first and second supply manifold flow paths 311C and 312C. Then, when the amount of stagnant air bubbles increases, the uniform distribution of the cooling liquid from the first and second supply manifold flow paths 311C and 312C to the five supply flow paths 34C is hindered by the air bubbles. Specifically, for example, the first and second supply manifold flow paths 311C, by gathering air bubbles in the vicinity of the downstream ends 311b and 312b of the first and second supply manifolds 311 and 312 to obstruct the flow of the coolant. More coolant flows through the supply channel 34C connected to the upstream side of the 312C, and the coolant flows through the supply channel 34C connected to the downstream side of the first and second supply manifold channels 311C and 312C. The phenomenon of decreasing can occur. As a result, the coolant cannot be evenly sent to the plurality of cooling flow paths 33C, and it becomes difficult to evenly cool the plurality of inkjet heads 20.

Therefore, for the first and second supply manifold flow paths 311C and 312C, it is preferable to reduce the cross-sectional area to increase the flow path resistance and increase the flow velocity of the coolant flowing inside. As a result, bubbles can be efficiently sent to the supply flow path 34C by the cooling liquid having a high flow velocity.

On the other hand, the cooling liquid flows into each of the first and second recovery manifold flow paths 321C and 322C from the plurality of recovery flow paths 35C. At the confluence point where the coolant flows from the recovery flow path 35C to the first and second recovery manifold flow paths 321C and 322C, turbulence is generated and the cooling flows through the first and second recovery manifold flow paths 321C and 322C. Pressure loss occurs in the liquid. When the pressure loss is large, the speed of the flow from the upstream side to the downstream side in the first and second recovery manifold flow paths 321C and 322C decreases, or the flow stagnates.

Specifically, for example, due to turbulence at the confluence of a certain recovery flow path 35C and the first and second recovery manifold flow paths 321C and 322C, from the upstream side of the confluence point to the downstream side of the confluence point. The flow can be blocked. As a result, in the recovery flow path 35C that joins the first and second recovery manifold flow paths 321C and 322C on the upstream side of the confluence point, the cooling liquid whose temperature has risen due to heat exchange with the driver IC 233 is the first and first. 2 The recovery manifold flow path 321C and 322C cannot flow, and the recovery flow path 35C is stagnant. As described above, if the discharge of the cooling liquid whose temperature has risen is obstructed in a part of the cooling flow paths 33C, it becomes difficult to uniformly cool the plurality of inkjet heads 20.

Therefore, it is preferable to increase the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C to suppress the occurrence of turbulence and pressure loss. As a result, the flow of the coolant from the upstream side to the downstream side can be maintained.

In the present embodiment, in view of the above two points, the cross-sectional area of the first and second supply manifold flow paths 311C and 312C is halved of the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C. .. As a result, in the first and second supply manifold flow paths 311C and 312C, the flow velocity of the coolant becomes relatively large, and the bubbles are satisfactorily swept away. Further, in the first and second recovery manifold flow paths 321C and 322C, the pressure loss due to the turbulent flow becomes relatively small, and the coolant efficiently flows to the downstream side.

As a result, the coolants of the first and second supply manifold channels 311C and 312C flow evenly into the five supply channels 34C and the five cooling channels 33C without being hindered by the bubbles, and the first row. The five inkjet heads 20 in L1 and the second row L2 are cooled evenly. Further, the coolant whose temperature has risen due to heat exchange with the driver IC 233 in the five cooling channels 33C is not hindered by turbulence, and the first and second recovery manifold channels 321C from the five recovery channels 35C It flows evenly into 322C and is returned to the coolant tank 36. That is, the cooling liquid is supplied and recovered to the 10 cooling flow paths 33C substantially evenly, and the 10 inkjet heads 20 are cooled substantially evenly.

The cross-sectional area of the first and second supply manifold flow paths 311C and 312C is not limited to 1/2 of the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C, and the first and second recovery manifolds It may be smaller than the cross-sectional area of the flow paths 321C and 322C. Further, the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C may be twice or more the cross-sectional area of the first and second supply manifold flow paths 311C and 312C. The reason for this is as follows.

The inventor of the present invention has the size of the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C with respect to the size of the cross-sectional area of the first and second supply manifold flow paths 311C and 312C. The following simulation was performed in order to examine whether it is preferable to have.

In the simulation, as shown in FIG. 7, a linear main flow path M and a flow path C having five branch flow paths B1 to B5 connected to the main flow path M at equal intervals were analyzed. The cross-sectional shape of the main flow path M is circular, and the cross-sectional area is 0.25S [mm ² ], 1.00S [mm ² ], 2.00S [mm ² ], 2.25S [mm ² ], 4.00S [ There are 5 types of mm ² ]. Here, S [mm ² ] is a desired cross-sectional area of the first and second supply manifold flow paths 311 and 312 set by the present inventor based on various conditions such as the flow path length.

The distance between the branch flow paths B1 to B5 was set to [70 mm], and the branch flow path B5 was connected to one end of the main flow path M. The length of each of the branch flow paths B1 to B5 was set to 80 [mm]. The cross-sectional shape of the branch flow paths B1 to B5 was circular, and the diameter thereof was 1/2 of the diameter of the cross-sectional shape of the main flow path M. The ends of the branch flow paths B1 to B5 opposite to the ends connected to the main flow path M were set to open to the atmosphere.

8 (a) and 9 (a) are the results of simulation analysis, and a liquid having a viscosity equivalent to that of the coolant flows in from the end portion M1 of the main flow path M at a rate of 1000 [cc / min]. The flow rate of the liquid flowing into each of the branch flow paths B1 to B5 when the flow rate is increased is shown for each cross-sectional area of the main flow path M.

As shown in FIG. 8A, when the cross-sectional area of the main flow path M is 1.00 S [mm ² ], the inflow amount (= 217.9) into the branch flow path B1 having the largest inflow amount of liquid. The difference between [cc / min]) and the inflow amount (= 188.9 [cc / min]) into the branch flow path B5 where the inflow amount of the liquid is the smallest is 29.0 [cc / min]. In this case, it can be said that the liquid flows into the branch flow paths B1 to B5 almost evenly.

On the other hand, when the cross-sectional area of the main flow path M is 0.25 S [mm ² ], the inflow amount to the branch flow path B1 having the largest inflow amount of liquid (= 324.7 [cc / min]). The difference between this and the inflow amount (= 133.4 [cc / min]) into the branch flow path B5, which has the smallest inflow amount of liquid, is as large as 191.3 [cc / min]. In this case, 2.4 times or more of the inflow amount into the branch flow path B5 located on the most downstream side of the main flow path M flows into the branch flow path B1 located on the most upstream side of the main flow path M. Therefore, it cannot be said that the liquid flows into the branch flow paths B1 to B5 almost evenly.

On the other hand, when the cross-sectional area of the main flow path M is 2.25 S [mm ² ] and when it is 4.00 S [mm ² ], the inflow amount to the branch flow path having the largest inflow amount of liquid is used. The difference from the inflow amount to the branch flow path where the inflow amount of the liquid is the smallest is 20.8 [cc / min] and 45.0 [cc / min], respectively. In these cases as well, it can be said that the liquid flows into the branch flow paths B1 to B5 almost evenly.

From the above simulation results, the cross-sectional area S [mm ² ] of the first and second supply manifold flow paths 311 and 312 set by the inventor of the present invention sends the cooling liquid to the plurality of cooling flow paths 33C almost evenly. It was confirmed that it is the optimum value for. That is, when the cross-sectional area of the first and second supply manifold flow paths 311 and 312 is smaller than S [mm ² ], the pressure loss due to the flow path resistance becomes large, and the coolant is evenly distributed to the plurality of cooling flow paths 33C. It tends to be difficult to send. On the other hand, if the cross-sectional area of the first and second supply manifold flow paths 311 and 312 is made larger than S [mm ² ], the above-mentioned retention of air bubbles becomes a problem. Such an optimum cross-sectional area S [mm ² ] can be appropriately set by a person skilled in the art based on the shape of the flow path, the viscosity of the liquid flowing through the flow path, the flow rate, and the like.

8 (b) and 9 (b) are the results of simulation analysis, and a liquid having a viscosity equivalent to that of the coolant is collected from the end M1 of the main flow path M at a rate of 1000 [cc / min]. In this case, the flow rate of the liquid flowing into the main flow path M from each of the branch flow paths B1 to B5 is shown for each cross-sectional area of the main flow path M.

As shown in FIG. 8B, when the cross-sectional area of the main flow path M is 2.00 S [mm ² ], the inflow amount from the branch flow path B1 having the largest amount of liquid outflow to the main flow path M ( = 230.9 [cc / min]) and the inflow amount (= 177.7 cc / min) from the branch flow path B5, which has the least amount of liquid outflow, to the main flow path M (= 177.7 cc / min), the difference is 53.2 [cc / min]. min]. In this case, it can be said that the liquid flows almost evenly from the branch flow paths B1 to B5.

When the cross-sectional area of the main flow path M is 1.00 S [mm ² ], the inflow amount (= 297.0 [cc / min]) from the branch flow path B1 having the largest outflow amount of liquid and the liquid The difference from the inflow amount (= 135.5 cc / min) from the branch flow path B5 having the smallest outflow amount is 161.5 [cc / min]. This degree of variation is the lower limit at which it can be considered that the liquid is flowing in from the branch flow paths B1 to B5 almost evenly.

On the other hand, when the cross-sectional area of the main flow path M is 0.25 S [mm ² ], the inflow amount from the branch flow path having the largest liquid outflow amount and the branch flow path having the smallest liquid outflow amount. The difference from the inflow amount from is as large as 580.5 [cc / min]. In this case, the amount of inflow from the branch flow path located on the upstream side of the main flow path M is small, and it cannot be said that the liquid flows almost evenly from the branch flow paths B1 to B5.

Conversely, if the cross-sectional area of the main flow channel M is 2.25 × S [mm ^2], and if it is 4.00S [mm ^2] is the inflow from outflow of liquid largest branch channel The difference between the amount and the inflow amount from the branch flow path where the outflow amount of the liquid is the smallest is as small as 39.2 [cc / min] and 48.7 [cc / min], respectively. In these cases, it can be said that the liquid flows almost evenly from the branch flow paths B1 to B5.

From the above simulation results, the optimum cross-sectional area of the first and second recovery manifold flow paths 321 and 322 for recovering the cooling liquid from the plurality of cooling flow paths 33C is the first and second supply manifolds. flow path 311C, the cross-sectional area of 312C as S [mm ^2], said at least have the S [mm ^2] or more, S [mm ^{2] 2} times or more, i.e., 2S and is preferably [mm ^2] or more ..

The main effects of the inkjet head unit 100 of this embodiment are summarized below.

In the inkjet head unit 100 of the present embodiment, the first and second supply manifold flow paths 311C, 312C, and the plurality of supply flow paths 34C are connected to the plurality of cooling flow paths 33C thermally connected to the plurality of inkjet heads 20. The coolant is supplied in parallel via. That is, the cooling liquid that has not undergone heat exchange with the inkjet head 20 is sent in parallel to all of the plurality of cooling flow paths 33C. Therefore, the plurality of inkjet heads 20 can be cooled more evenly.

In the inkjet head unit 100 of the present embodiment, the cross-sectional area of the first and second supply manifold flow paths 311C and 312C is smaller than the cross-sectional area of the first and second recovery manifold flow paths 321C and 322C. Therefore, in the first and second supply manifold flow paths 311C and 312C, air bubbles can be efficiently discharged by the flow of the cooling liquid having a relatively large flow velocity, and in the first and second recovery manifold flow paths 321C and 322C, the bubbles can be efficiently discharged. , The generation of turbulent flow can be suppressed, and the stagnation of the coolant flow due to pressure loss can be suppressed. As a result, the supply of the cooling liquid to the plurality of cooling flow paths 33C and the recovery of the cooling liquid from the plurality of cooling flow paths 33C can be performed more evenly, and the plurality of inkjet heads 20 can be cooled more evenly. Can be done.

In the inkjet head unit 100 of the present embodiment, since the cross-sectional area of the supply flow path 34C is smaller than the cross-sectional area of the first and second supply manifold flow paths 311C and 312C, the coolant is supplied from the first and second supply channels. Accelerates as it flows from the manifold flow paths 311C and 312C into the supply flow path 34C. Further, the coolant flows in the supply flow path 34C at a flow velocity even higher than the flow velocity in the first and second supply manifold flow paths 311C and 312C. As a result, the bubbles can be efficiently washed away.

In the inkjet head unit 100 of the present embodiment, the cross-sectional area of the recovery flow path 35C is equal to the cross-sectional area of the supply flow path 34C. Therefore, the flow velocity of the liquid in the supply flow path 34C can be maintained, and the air bubbles can be efficiently pushed out to the first and second recovery manifold flow paths 321C and 322C. Further, by making the supply pipe 34 and the recovery pipe 35 the same member, the manufacturing process can be simplified and the manufacturing cost can be reduced.

[Modification example]
In the above embodiment, the following modifications can also be used.

The inkjet head unit 100 of the above embodiment includes a first supply manifold 311 and a second supply manifold 312, but the inkjet head unit 100 may include only one supply manifold 313 (FIG. 10A). ).

In this embodiment, the supply manifold 313 is arranged between the first row L1 and the second row L2 in parallel with the first row L1 and the second row L2 of the inkjet head 20. The supply manifold 313 has five supply pipes 34 connected to cooling members 33 fixed to the inkjet heads 20 forming the first row L1 and cooling fixed to the inkjet heads 20 forming the second row L2. Five supply pipes 34 connected to the member 33 are connected.

Further, the inkjet head unit 100 may have one supply manifold and one recovery manifold, and may have three or more supply manifolds and / or three or more recovery manifolds. The number and arrangement of the supply manifold and the recovery manifold can be appropriately changed according to the number and arrangement of the inkjet heads 20 included in the inkjet head unit 100. Further, at least one of the supply manifold and the recovery manifold may be arranged directly above the inkjet head 20 so as to overlap each other in a plan view.

The inkjet head unit 100 of the above embodiment has 10 inkjet heads 20, but is not limited to this. The inkjet head unit 100 may include at least two inkjet heads 20.

In the above embodiment, the cross-sectional area of the cooling flow path 33C, the cross-sectional area of the supply flow path 34C, and the cross-sectional area of the recovery flow path 35C are the same, and the first and second supply manifold flow paths 311C and 312C are disconnected. Smaller than the area, but not limited to this. The cross-sectional area of the cooling flow path 33C, the cross-sectional area of the supply flow path 34C, and the cross-sectional area of the recovery flow path 35C may be different from each other. Make any one or more of the cross-sectional area of the cooling flow path 33C, the cross-sectional area of the supply flow path 34C, and the cross-sectional area of the recovery flow path 35C larger than the cross-sectional area of the first and second supply manifold flow paths 311C and 312C. May be good.

In the above embodiment, the cross-sectional shape of the first and second supply manifold flow paths 311C and 312C, the cross-sectional shape of the first and second recovery manifold flow paths 321C and 322C, the cross-sectional shape of the cooling flow path 33C, and the cross-sectional shape of the supply flow path 34C. The cross-sectional shape of the above and the cross-sectional shape of the recovery flow path 35C are both circular. However, the cross-sectional shape of each flow path is not limited to this, and is arbitrary such as a rectangle, a square, and a polygon. Further, the cross-sectional shapes of the respective flow paths may be different from each other.

In the above embodiment, the driver IC of the inkjet head 20 is brought into contact with the cooling member 33 of the cooling structure 30, but the present invention is not limited to this. The driver IC may be arranged in any manner in which heat exchange is performed with the coolant flowing through the cooling flow path 33C of the cooling member 33.

As long as the features of the present invention are maintained, the present invention is not limited to the above-described embodiment, and other modes considered within the scope of the technical idea of the present invention are also included within the scope of the present invention. Is done.

According to the liquid discharge unit of the present invention, a plurality of liquid discharge devices can be cooled evenly to perform good image formation.

10 Holding member 20 Ink head 30 Cooling structure 311 1st supply manifold 312 2nd supply manifold 321 1st recovery manifold 322 2nd recovery manifold 33 Cooling member 34 Supply pipe 35 Recovery pipe 36 Coolant tank 39 Coolant pump 100 Ink head unit 500 Platen 601, 602 Conveying roller 700 Ink tank 800 Ink flow path member 900 Housing 1000 Printer

Claims (10)

Multiple liquid discharge devices, each of which discharges liquid,
A liquid discharge unit having a cooling structure for cooling the plurality of liquid discharge devices with a cooling liquid.
The cooling structure
A plurality of cooling channels through which the coolant flows, each of which is thermally connected to each of the plurality of liquid discharge devices.
A plurality of supply channels, each of which is connected to one end of the plurality of cooling channels,
A supply manifold flow path that is connected to the plurality of supply flow paths above the plurality of liquid discharge devices and distributes the cooling liquid to the plurality of supply flow paths.
A plurality of recovery channels, each of which is connected to the other end of the plurality of cooling channels,
A recovery manifold flow path that is connected to the plurality of recovery flow paths above the plurality of liquid discharge devices and that merges the cooling liquids from the plurality of recovery flow paths is defined.
A liquid discharge unit whose cross-sectional area of the supply manifold flow path is smaller than the cross-sectional area of the recovery manifold flow path. The liquid discharge unit according to claim 1, wherein the cross-sectional area of each of the plurality of supply flow paths is smaller than the cross-sectional area of the supply manifold flow paths. The liquid discharge unit according to claim 1 or 2, wherein the cross-sectional area of each of the plurality of supply channels is equal to the cross-sectional area of each of the plurality of recovery channels. The liquid discharge unit according to any one of claims 1 to 3, wherein the cross-sectional area of the recovery manifold flow path is at least twice the cross-sectional area of the supply manifold flow path. The recovery manifold flow path is connected to a first recovery manifold flow path connected to a part of the plurality of recovery flow paths, and to another part of the recovery flow paths. Including the second recovery manifold flow path
The supply manifold flow path, the first recovery manifold flow path, and the second recovery manifold flow path extend along the first direction in the horizontal plane.
The supply manifold flow path is provided between the first recovery manifold flow path and the second recovery manifold flow path in the second direction orthogonal to the first direction in the horizontal plane.
The cooling structure
A supply port for circulating the coolant toward the upstream end of the supply manifold,
A recovery port that is vertically aligned with the supply port and that allows the coolant to flow from the recovery manifold is further defined.
The supply port and the collection port are provided on the upstream end side of the supply manifold flow path in the first direction, and are provided at the same position as the supply manifold flow path in the second direction. The liquid discharge unit according to any one of the items to 4. The plurality of liquid discharge devices are arranged in a staggered manner along the predetermined direction so as to form a first row arranged in a predetermined direction in a horizontal plane and a second row parallel to the first row.
The liquid discharge unit according to any one of claims 1 to 5, wherein the supply manifold flow path extends between the first row and the second row in parallel with the first row and the second row. The liquid according to claim 6, wherein the recovery manifold flow path sandwiches at least one of the plurality of liquid discharge devices between the recovery manifold flow path and the supply manifold flow path and extends in parallel with the supply manifold flow path. Discharge unit. A plurality of liquid flow path members connected to each of the plurality of liquid discharge devices and supplying the liquid to each of the liquid discharge devices are further provided.
The supply flow path and the recovery flow path connected to each of the plurality of cooling flow paths are inclined in the vertical direction and extend upward to be connected to the supply manifold flow path and the recovery manifold flow path. Ori
The supply flow path and the recovery flow path are inclined so that the distance between them increases as they move upward.
Any one of claims 1 to 7, wherein the plurality of liquid flow path members are arranged so as to extend upward from the liquid discharge device and pass between the supply manifold flow path and the recovery manifold flow path. The liquid discharge unit described in the section. The liquid discharge unit according to any one of claims 1 to 8, further comprising a holding member for integrally holding the plurality of liquid discharge devices. The liquid discharge unit according to any one of claims 1 to 9, wherein the cooling structure includes a pump connected to the supply manifold flow path and the recovery manifold flow path.

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