Patent Publication Number: US-2022234350-A1

Title: Liquid Ejecting Head And Liquid Ejecting Apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-009363, filed on Jan. 25, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a liquid ejecting head and a liquid ejecting apparatus. 
     2. Related Art 
     A flow path through which a liquid flows is formed inside a liquid ejecting head that ejects a liquid such as an ink. The liquid ejecting head includes a temperature sensor that detects a temperature of the liquid in the flow path. In JP-A-2020-142379, a substrate in which the flow path is defined is provided with an opening communicating with the flow path. A temperature detection element is disposed on a metal plate that seals this opening. 
     Since a flow velocity of the liquid decreases in a region in contact with an inner wall surface of the flow path, a temperature of the liquid in the vicinity of the inner wall surface tends to be lower than a temperature of the liquid flowing in the center of the flow path away from the inner wall surface. For this reason, when the temperature of the liquid in the flow path is detected from an outer wall surface on a side opposite to the inner wall surface, there has been a risk of decreased accuracy of temperature detection of the liquid. 
     SUMMARY 
     According to an aspect of the present disclosure, a liquid ejecting head includes: a nozzle for ejecting a liquid; a flow path member in which a flow path communicating with the nozzle is formed and which has an inner wall surface defining the flow path and an outer wall surface on a side opposite to the flow path with respect to the inner wall surfaces; and a temperature sensor disposed on a part of the outer wall surface and detecting a temperature of the liquid in the flow path. The flow path includes a narrowed region having a narrow width in a second direction orthogonal to a first direction in a direction in which the flow path extends. The temperature sensor is disposed on a portion of the outer wall surface that forms the narrowed region. 
     According to another aspect of the present disclosure, a liquid ejecting apparatus includes: the liquid ejecting head as described above; and a liquid storage portion storing the liquid supplied to the liquid ejecting head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating a configuration of a liquid ejecting apparatus according to a first embodiment. 
         FIG. 2  is an exploded perspective view illustrating a liquid ejecting head. 
         FIG. 3  is a bottom view of the liquid ejecting head. 
         FIG. 4  is a schematic view illustrating a flow path of an ink of the liquid ejecting apparatus. 
         FIG. 5  is a plan view illustrating a temperature sensor and wiring lines. 
         FIG. 6  is a sectional view illustrating the temperature sensor and a protrusion portion and is a view illustrating a cross section in a flow direction of the ink. 
         FIG. 7  is a sectional view illustrating the temperature sensor and the protrusion portion and is a view illustrating a cross section orthogonal to the flow direction of the ink. 
         FIG. 8  is a sectional view illustrating the protrusion portion when viewed in a Z-axis direction. 
         FIG. 9  is a perspective view illustrating an example of a flow path formed inside a flow path structure. 
         FIG. 10  is a sectional view illustrating a temperature sensor and a narrowed region of a liquid ejecting head according to a second embodiment. 
         FIG. 11  is a schematic view illustrating a configuration of a liquid ejecting apparatus according to a third embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, a mode for carrying out the present disclosure will be described with reference to the drawings. However, dimensions and scales of each portion in each drawing are appropriately different from actual dimensions and scales. In addition, since embodiments to be described below are suitable specific examples of the present disclosure, various technically preferable limitations are added, but the scope of the present disclosure is not limited to these forms unless it is stated in the following description that the present disclosure is particularly limited. 
     In the following description, three directions that intersect each other may be described as an X-axis direction, a Y-axis direction, and a Z-axis direction. The X-axis direction includes an X1 direction and an X2 direction, which are directions opposite to each other. The X-axis direction is an example of a third direction. The Y-axis direction includes a Y1 direction and a Y2 direction, which are directions opposite to each other. The Y-axis direction is an example of a first direction. The Z-axis direction includes a Z1 direction and a Z2 direction, which are directions opposite to each other. The Z1 direction is a downward direction, and the Z2 direction is an upward direction. The Z1 direction is the direction of gravity. The Z-axis direction is an example of a second direction. In addition, in the present specification, “upper” and “lower” are used. “Upper” and “lower” correspond respectively to “upper” and “lower” in a normal use state of a liquid ejecting apparatus  1 . 
     The Z-axis direction is a direction in a vertical direction. The X-axis, the Y-axis, and the Z-axis directions are typically orthogonal to each other, but are not limited thereto. The Z-axis direction is not limited to the vertical direction. 
       FIG. 1  is a schematic view illustrating a configuration of the liquid ejecting apparatus  1  according to a first embodiment. The liquid ejecting apparatus  1  is an ink jet printing apparatus that ejects an ink, which is an example of a “liquid”, as droplets onto a medium PA. The liquid ejecting apparatus  1  is a serial type printing apparatus. The liquid ejecting apparatus  1  includes a plurality of liquid ejecting heads  10 . The liquid ejecting head  10  ejects the ink toward the medium PA while moving in a width direction of the medium PA. The medium PA is typically printing paper. Note that the medium PA is not limited to printing paper, and may be a printing target of any material, such as a resin film or cloth. 
     As illustrated in  FIG. 1 , the liquid ejecting apparatus  1  includes a liquid container  2  that stores the ink. Examples of a specific aspect of the liquid container  2  include a cartridge that is attachable to and detachable from the liquid ejecting apparatus  1 , a bag-shaped ink pack formed of a flexible film, and an ink tank that can be replenished with the ink. Note that any appropriate type of the ink may be stored in the liquid container  2 . The liquid container  2  is an example of a liquid storage portion. 
     The liquid container  2  includes a first liquid container  2   a  and a second liquid container  2   b . A first ink is stored in the first liquid container  2   a . A second ink of a type different from that of the first ink is stored in the second liquid container  2   b . For example, the first ink and the second ink are inks of colors different from each other. Note that the first ink and the second ink may be the same type of ink. 
     The liquid ejecting apparatus  1  includes a control unit  3 , a medium transport mechanism  4 , a carriage  5 , and a carriage transport mechanism  6 . The control unit  3  controls an operation of each element of the liquid ejecting apparatus  1 . The control unit  3  includes, for example, a processing circuit, such as a central processing unit (CPU) or a field programmable gate array (FPGA), and a storage circuit, such as a semiconductor memory. Various programs and various data are stored in the storage circuit. The processing circuit realizes various forms of control by executing the program and appropriately using the data. 
     The medium transport mechanism  4  is controlled by the control unit  3  to transport the medium PA in a transport direction DM. The medium transport mechanism  4  includes a transport roller that transports the medium PA and a motor that rotates the transport roller. Note that the medium transport mechanism  4  is not limited to having a configuration using the transport roller, and may have, for example, a configuration using a drum or an endless belt that transports the medium PA in a state in which the medium PA clings onto an outer peripheral surface thereof by an electrostatic force or the like. 
     The plurality of liquid ejecting heads  10  are mounted on the carriage  5 . The carriage transport mechanism  6  is controlled by the control unit  3  to reciprocate the carriage  5  in the width direction of the medium PA. The carriage transport mechanism  6  may include, for example, an endless belt laid over a plurality of rollers spaced apart from each other in the width direction of the medium PA. Note that the liquid container  2  may be configured to be mounted on the carriage  5  and be transported together with the plurality of liquid ejecting heads  10 . 
       FIG. 2  is an exploded perspective view illustrating the liquid ejecting head  10 .  FIG. 3  is a bottom view of the liquid ejecting head  10 . The liquid ejecting head  10  includes a plurality of head chips  11  provided with nozzles N, a holder  12  holding the head chips  11 , a flow path structure  13  in which a flow path of the ink is formed, a relay substrate  14  disposed on an upper portion of the flow path structure  13 , and a connector  15  provided on the relay substrate  14 . 
     As illustrated in  FIG. 3 , the plurality of head chips  11  are disposed at a bottom portion of the liquid ejecting head  10 . The plurality of head chips  11  are held by the holder  12 . The head chip  11  is provided with a plurality of nozzles N that eject a liquid. The nozzles N are arranged in a predetermined direction to constitute nozzle rows  16 . A plurality of nozzle rows  16  are provided so as to correspond to types of inks. 
     As illustrated in  FIG. 2 , the flow path structure  13  is disposed on the holder  12 . The flow path through which the ink flows is formed in the flow path structure  13 . The flow path structure  13  includes a plurality of flow path substrates  17 . The plurality of flow path substrates  17  are laminated in a plate thickness direction. For example, grooves and openings are formed in the flow path substrates  17 . The flow paths are formed by these grooves and openings. 
     The liquid ejecting apparatus  1  employs an ink circulation method that circulates the ink. The flow path structure  13  is provided with ink supply ports  18  for introducing the ink into the flow path structure  13  and ink discharge ports  19  for discharging the ink from the flow path structure  13 . 
     In addition, a temperature sensor  20  is disposed on the upper portion of the flow path structure  13 . Details will be described later. 
     The relay substrate  14  covers the upper portion of the flow path structure  13 . The relay substrate  14  is provided with a plurality of electrical wiring lines. The head chips  11  and the temperature sensor  20  are electrically coupled to the electrical wiring lines provided on the relay substrate  14 . 
     The connector  15  projects upward from the relay substrate  14 . The connector  15  is electrically coupled to an external electrical component of the liquid ejecting head  10 . The head chips  11  and the temperature sensor  20  are electrically coupled to the control unit  3  via the connector  15 . 
       FIG. 4  is a schematic view illustrating a flow path  30  of an ink of the liquid ejecting apparatus  1 . In  FIG. 4 , the flow path  30  through which one type of ink flows is illustrated. The flow path  30  of the ink is provided for each type of ink. The liquid container  2 , a pump  31 , a heater  32 , filters  33 , and common liquid chambers  34  are coupled to the flow path  30 . The flow path  30  includes a supply flow path  35  and a collection flow path  36 . The supply flow path  35  is a flow path for supplying the ink from the liquid container  2  to the common liquid chamber  34 . The collection flow path  36  is a flow path for collecting the ink from the common liquid chamber  34  in the liquid container  2 . 
     The pump  31  is coupled to the downstream of the liquid container  2  and transfers the ink stored in the liquid container  2 . The heater  32  is coupled to the downstream of the pump  31  and heats the ink to a predetermined temperature. Note that the heater  32  may be configured to heat the ink stored in the liquid container  2 . By adjusting a temperature of the ink, the ink viscosity can be adjusted. The liquid container  2 , the pump  31 , and the heater  32  are disposed outside the liquid ejecting head  10 . The liquid container  2 , the pump  31 , and the heater  32  may be mounted on, for example, the carriage  5 . The liquid container  2 , the pump  31 , and the heater  32  are coupled to the supply flow path  35 . 
     The ink flows through the supply flow path  35 , passes through the ink supply port  18 , and is introduced into the flow path inside the flow path structure  13 . The flow path inside the flow path structure  13  is branched into a plurality of portions and is coupled to the plurality of head chips  11 . The head chip  11  is provided with the common liquid chamber  34 . The ink introduced into the head chip  11  is stored in the common liquid chamber  34 . A part of the ink stored in the common liquid chamber  34  is ejected from the nozzles N. 
     The filter  33  is provided upstream of the common liquid chamber  34  in the flow path inside the flow path structure  13 . The ink that has passed through the filter  33  is supplied to the common liquid chamber  34 . The filter  33  removes foreign matter and air bubbles mixed in the ink. 
     The ink that is not ejected from the nozzles N in the ink stored in the common liquid chamber  34  is collected in the liquid container  2 . The ink discharged from the common liquid chamber  34  flows through the flow path inside the flow path structure  13 , passes through the ink discharge port  19 , and is discharged outside the flow path structure  13 . The ink discharged from the ink discharge port  19  flows through the collection flow path  36  and is collected in the liquid container  2 . As described above, the ink is circulated. 
     The head chip  11  includes the common liquid chamber  34 , pressure chambers  37 , piezoelectric actuators  38 , and the nozzles N. A plurality of pressure chambers  37  are coupled to the common liquid chamber  34 . The piezoelectric actuator  38  and the nozzle N are provided for each of the plurality of pressure chambers  37 . The pressure chamber  37  enables the common liquid chamber  34  and the nozzle N to communicate with each other. The ink in the common liquid chamber  34  flows into the pressure chamber  37 . 
     The piezoelectric actuator  38  is electrically coupled to the control unit  3 . The piezoelectric actuator  38  is controlled and driven by the control unit  3 . The piezoelectric actuator  38  deforms wall surfaces of the pressure chamber  37  to change the volume of the pressure chamber  37  interior. As a result, the piezoelectric actuator  38  ejects the ink in the pressure chamber  37  from the nozzle N. Note that the liquid ejecting head  10  may be configured to include other driving elements, such as heat generating elements, instead of the piezoelectric actuators  38 . 
     The temperature sensor  20  detects a temperature of the ink flowing through a flow path  35   b  inside the flow path structure  13 . The temperature sensor  20  detects the ink in the flow path  35   b  downstream of the ink supply port  18 . Note that the temperature sensor  20  may detect a temperature of the ink in the flow path  35   b  downstream of the filter  33 . The temperature sensor  20  may detect a temperature of the ink in a flow path  35   a  upstream of the ink supply port  18 . In addition, the temperature sensor  20  may detect a temperature of the ink in flow paths  36   a  and  36   b  downstream of the common liquid chamber  34 . 
     The temperature sensor  20  is disposed on the upper portion of the flow path structure  13  as illustrated in  FIG. 2 . The temperature sensor  20  is disposed on the flow path substrate  17  disposed on the uppermost side.  FIG. 5  is a plan view illustrating the temperature sensor  20  and wiring lines  21 . The temperature sensor  20  is electrically coupled to the wiring lines  21  formed on a flexible substrate  22 . In addition, an electronic component  24 , such as a capacitor is electrically coupled to the wiring lines  21 . The flexible substrate  22  is coupled to the connector  15 . The temperature sensor  20  is electrically coupled to the control unit  3 . The temperature sensor  20  is electrically coupled to the wiring lines  21  via coupling terminals  23  provided on the flexible substrate  22 . 
       FIG. 6  is a sectional view illustrating the temperature sensor  20  and a protrusion portion  80  and is a view illustrating a cross section in a flow direction of the ink.  FIG. 7  is a sectional view illustrating the temperature sensor  20  and the protrusion portion  80  and is a view illustrating a cross section orthogonal to the flow direction of the ink.  FIG. 8  is a sectional view illustrating the protrusion portion  80  when viewed in the Z-axis direction. In  FIGS. 6 to 8 , arrows indicating the flow direction of the ink are illustrated. In  FIGS. 6 to 8 , the ink flows substantially in the Y1 direction. 
     As illustrated in  FIGS. 6 and 7 , the temperature sensor  20  detects a temperature of the ink in a flow path  51  of the flow path structure  13 . The flow path structure  13  includes the plurality of flow path substrates  17  as described above. The plurality of flow path substrates  17  include flow path substrates  17 A and  17 B. The flow path substrate  17 A is laminated on the flow path substrate  17 B. A thickness direction of the flow path substrates  17 A and  17 B corresponds to the Z-axis direction. The flow path substrate  17 A is disposed in the Z2 direction of the flow path substrate  17 B. The flow path substrate  17 A is an example of a first flow path substrate, and the flow path substrate  17 B is an example of a second flow path substrate. The flow path  51  is, for example, a part of the supply flow path  35   b.    
     The flow path structure  13  has inner surfaces  60  that define the flow path  51  and an outer surface  70  on a side opposite to the flow path  51  with respect to the inner surfaces  60 . The inner surface  60  is an example of an inner wall surface, and the outer surface  70  is an example of an outer wall surface. The outer surface  70  is a surface on an outer side of the flow path structure  13  that does not constitute the flow path  51 . 
     The inner surfaces  60  include inner surfaces  61  and  62 . The inner surfaces  61  and  62  are spaced apart from each other in the Z-axis direction. In the Z-axis direction, a region between the inner surfaces  61  and  62  constitutes the flow path  51 . The inner surfaces  60  include inner surfaces  63  and  63 , as illustrated in  FIGS. 7 and 8 . The inner surfaces  63  and  63  are spaced apart from each other in the X-axis direction. In the X-axis direction, a region between the inner surfaces  63  and  63  constitutes the flow path  51 . The inner surfaces  61  and  63  are formed on the flow path substrate  17 A. The inner surface  62  is formed on the flow path substrate  17 B. The flow path substrate  17  is made of, for example, a resin. 
     As illustrated in  FIG. 6 , an opening  52  passing through the flow path substrate  17 A in the Z-axis direction is formed in the flow path substrate  17 A. The opening  52  communicates with the flow path  51 . The opening  52  is formed upward from the flow path  51 . The flow path structure  13  includes a sealing portion  50  that covers the opening  52 . The sealing portion  50  includes the above-mentioned flexible substrate  22  and sealing plates  53  and  54 . A thickness direction of the flexible substrate  22  and the sealing plates  53  and  54  corresponds to the Z-axis direction. 
     The sealing plate  53  is disposed at a position closest to the opening  52  in the Z-axis direction. The sealing plate  53  covers the opening  52  from above. The sealing plate  54  is disposed in the Z2 direction of the sealing plate  53 . The flexible substrate  22  is disposed in the Z2 direction of the sealing plate  54 . The sealing plate  54  functions as a reinforcing plate reinforcing the flexible substrate  22 . 
     A metal or a ceramic can be used as a material for the sealing plates  53  and  54 . It is preferable to use a metal or a ceramic having high thermal conductivity as the material for the sealing plates  53  and  54 . As the metal, for example, stainless steel or aluminum can be used. The number of sealing plates  53  and  54  included in the sealing portion  50  is not limited to two, and may be one or may be three or more. The sealing portion  50  is not limited to including the flexible substrate  22 . The flexible substrate  22  and the sealing plates  53  and  54  may be adhered to each other by, for example, an adhesive having high thermal conductivity. 
     The sealing portion  50  includes an inner surface  50   a  and an outer surface  50   b  spaced apart from each other in the Z-axis direction. The inner surface  50   a  is a surface, in the Z1 direction, of the sealing plate  53  positioned on the most Z1 direction side in the sealing portion  50 . The inner surface  50   a  is included in the inner surface  60  that defines the flow path  51 . The outer surface  50   b  is a surface, in the Z2 direction, of the flexible substrate  22  positioned on the most Z2 direction side in the sealing portion  50 . The outer surface  50   b  is included in the outer surface  70 . The temperature sensor  20  is installed on the outer surface  50   b  of the sealing portion  50 . The temperature sensor  20  may be adhered to the sealing portion  50  by, for example, an adhesive having high thermal conductivity. When the sealing portion  50  does not include the flexible substrate  22 , the temperature sensor  20  may be installed on the sealing plate  54 . In this case, the temperature sensor  20  is electrically coupled to the flexible substrate  22  existing in the vicinity of the temperature sensor  20 . 
     The flow path structure  13  includes the protrusion portion  80  protruding into the flow path  51  from the inner surface  62  toward the temperature sensor  20 . The protrusion portion  80  is positioned in the Z1 direction of the opening  52 . The protrusion portion  80  includes a slope  81 , a top surface  82 , and a slope  83 . The slope  81  is an example of a first slope. The slope  81  includes a surface disposed upstream of the temperature sensor  20  in the Y-axis direction. Most of the slope  81  is disposed upstream of the temperature sensor  20 . A part of the slope  81  may be disposed so as to overlap the temperature sensor  20  when viewed in the Z-axis direction. 
     The slope  81  is inclined with respect to the inner surface  62  when viewed in the X-axis direction. An inclination angle θ of the slope  81  with respect to the inner surface  62  is, for example, 45°. The inclination angle θ of the slope  81  may be, for example, 50° or less. The inner surface  62  is an example of a reference plane, and is a surface along the X-axis direction and the Y-axis direction. 
     A position P 1  of the slope  81  is the most upstream position of the slope  81 . A position P 2  of the slope  81  is the most downstream position of the slope  81 . The position P 2  is located at a position closer to the temperature sensor  20  than the position P 1  is, in the Z-axis direction. The position P 1  is an example of a first position of the first slope. The position P 2  is an example of a second position of the first slope. The slope  81  is inclined so that the position P 2  on the downstream is closer to the temperature sensor  20  in the Z-axis direction than the position P 1  on the upstream is. 
     The top surface  82  is a surface in the Y-axis direction when viewed in the X-axis direction. The top surface  82  is disposed downstream of the slope  81 . In the protrusion portion  80 , the top surface  82  is a surface closest to the temperature sensor  20 . The top surface  82  may be linearly formed or may be curved when viewed in the X-axis direction. The top surface  82  is disposed so as to overlap the temperature sensor  20  when viewed in the Z-axis direction. 
     The slope  83  is disposed downstream of the top surface  82 . The slope  83  includes a surface disposed downstream of the temperature sensor  20  in the Y-axis direction. Most of the slope  83  is disposed downstream of the temperature sensor  20 . A part of the slope  83  may be disposed so as to overlap the temperature sensor  20  when viewed in the Z-axis direction. The slope  83  is inclined with respect to the inner surface  62  when viewed in the X-axis direction. An inclination angle of the slope  83  with respect to the inner surface  62  is, for example, 45°. The inclination angle of the slope  83  with respect to the inner surface  62  may be 50° or less. The slope  83  may have the same inclination angle as the slope  81  or may have an inclination angle different from that of the slope  81 . 
     A position P 3  of the slope  83  is the most upstream position of the slope  83 . A position P 4  of the slope  83  is the most downstream position of the slope  83 . The position P 3  is located at a position closer to the temperature sensor  20  than the position P 4  is, in the Z-axis direction. The slope  83  is inclined so that the position P 4  on the downstream is further from the temperature sensor  20  in the Z-axis direction than the position P 3  on the upstream is. 
     The flow path  51  includes a narrowed region  55  having a narrow width in the Z-axis direction. The narrowed region  55  includes a region between the top surface  82  of the protrusion portion  80  and the inner surface  50   a  of the sealing portion  50  in the Z-axis direction. A width W 1  of the narrowed region  55  is smaller than a width W 2  of the flow path  51 . The width W 1  is a distance between the top surface  82  and the inner surface  50   a  in the Z-axis direction. The width W 2  is a distance between the inner surface  61  and the inner surface  62  in the Z-axis direction. 
     The temperature sensor  20  is disposed on a portion forming the narrowed region  55 . The portion forming the narrowed region  55  includes a portion of the outer surface  70  that overlaps the narrowed region  55  when viewed in the Z-axis direction intersecting the flow direction of the ink. The portion forming the narrowed region  55  includes a position of the outer surface  50   b  of the sealing portion  50  that overlaps with the top surface  82  when viewed in the Z-axis direction. The “flow direction of the ink” mentioned here is the Y-axis direction, and is a direction along the top surface  82  when viewed in the X-axis direction. In addition, the flow direction of the ink may be a direction orthogonal to a lamination direction of the flow path substrates  17 . In addition, the “flow direction of the ink” may be a direction in which the flow path  51  which is a flow path detected by the temperature sensor  20  and includes the narrowed region  55  extends, when viewed in the Z-axis direction in a direction in which the temperature sensor  20  is laminated with respect to the outer surface  70 . 
     A height H 1  of the protrusion portion  80  corresponds to, for example, a length equal to 50% of the width W 2  of the flow path  51 . The height H 1  of the protrusion portion  80  is a distance between the inner surface  62  and the top surface  82  in the Z-axis direction. The height H 1  of the protrusion portion  80  may be 30% or more and less than 70% of the width W 2  of the flow path  51 . The height H 1  of the protrusion portion  80  may be 45% or more and 55% or less of the width W 2  of the flow path  51 . In addition, the width W 1  may be 50% or more and less than 95% of the width W 2 . 
     A virtual plane F 1  extending along the slope  81  overlaps the temperature sensor  20  when viewed in the X-axis direction. An inclination angle of the virtual plane F 1  with respect to the inner surface  62  is the same inclination angle θ as the slope  81 . 
     The flow path substrate  17 A includes a slope  56  disposed upstream of the temperature sensor  20  in the Y-axis direction and a slope  57  disposed downstream of the temperature sensor  20  in the Y-axis direction. The slope  56  is an example of a second slope. The slope  56  is spaced apart from the slope  81  in a normal direction U 1  of the slope  81 . 
     A position P 5  of the slope  56  is the most upstream position of the slope  56 . A position P 6  of the slope  56  is the most downstream position of the slope  56 . The position P 6  is disposed at a position closer to the temperature sensor  20  than the position P 5  is, in the Z-axis direction. The position P 5  is an example of a first position of the second slope. The position P 6  is an example of a second position of the second slope. The slope  56  is inclined so that the position P 6  on the downstream is closer to the temperature sensor  20  in the Z-axis direction than the position P 5  on the upstream is. 
     A position P 7  of the slope  57  is the most upstream position of the slope  57 . A position P 8  of the slope  57  is the most downstream position of the slope  57 . The position P 7  is disposed at a position closer to the temperature sensor  20  than the position P 8  is, in the Z-axis direction. The slope  57  is inclined so that the position P 8  on the downstream is further from the temperature sensor  20  in the Z-axis direction than the position P 7  on the upstream is. 
     The slope  56  is disposed in the Y2 direction of the opening  52 , and the slope  57  is disposed in the Y1 direction of the opening  52 . The opening  52  is long in the Y-axis direction. A length W 3  of the opening  52  in the Y-axis direction is greater than a length W 4  of the opening  52  in the X-axis direction. The phrase “long in the Y-axis direction” means that the length W 3  in the Y-axis direction is longer than the length W 4  in the X-axis direction. The length W 3  is a length between the position P 6  and the position P 7  in the Y-axis direction. The length W 4  is a length between an inner surface  52   a  and an inner surface  52   b  in the X-axis direction. The inner surface  52   a  and the inner surface  52   b  are surfaces that define the opening  52 , are spaced apart from each other in the X-axis direction, and are extend in the Y-axis direction and the Z-axis direction. 
     The length W 3  of the opening  52  in the Y-axis direction is greater than a length W 5  of the protrusion portion  80  in the Y-axis direction. The length W 5  is a length between the position P 1  and the position P 4  in the Y-axis direction. 
     As illustrated in  FIGS. 7 and 8 , the flow path  51  is also formed on both sides of the protrusion portion  80  in the X-axis direction. The protrusion portion  80  has side surfaces  84  and  84  that are spaced apart in the X-axis direction. The side surfaces  84  face the inner surfaces  63  in the X-axis direction. Regions between the inner surfaces  63  and the side surfaces  84  are also included in the flow path  51 . 
     As illustrated in  FIG. 7 , in a cross section orthogonal to the Y-axis direction, a cross-sectional area S 1  of the flow path close to the temperature sensor  20  from the top surface  82  is greater than the sum of cross-sectional areas S 2  and S 3  of the flow path  51  far from the temperature sensor  20  from the top surface  82 . In  FIG. 7 , a cross section, orthogonal to a Y axis, of the flow path  51  cut so as to pass through the temperature sensor  20  and the top surface  82  is illustrated. In  FIG. 7 , a virtual line L 1  extending in the X-axis direction along the top surface  82  is illustrated by a two-dot chain line. The cross-sectional area S 1  is a region located in the Z2 direction with respect to the virtual line L 1  in a cross section of the flow path  51 . The cross-sectional area S 2  is a region positioned in the Z1 direction with respect to the virtual line L 1  in the cross section of the flow path  51 , and is a region positioned in the X1 direction of the protrusion portion  80 . The cross-sectional area S 3  is a region positioned in the Z1 direction with respect to the virtual line L 1  in the cross section of the flow path  51 , and is a region positioned in the X2 direction of the protrusion portion  80 . The cross-sectional area S 1  is greater than the sum of the cross-sectional areas S 2  and S 3 . 
     In addition, a width W 6  of the protrusion portion  80  in the X-axis direction is greater than a width W 7  of the temperature sensor  20  in the X-axis direction. The width W 6  of the protrusion portion  80  in the X-axis direction is smaller than a width W 8  of the flow path  51  in the X-axis direction. The width W 8  of the flow path  51  in the X-axis direction is a length between the inner surfaces  63  and  63  in the X-axis direction. The width W 6  of the protrusion portion  80  formed on the flow path substrate  17 B is narrower than a distance between the inner surfaces  63  and  63  formed on the flow path substrate  17 A. As a result, a defect that the protrusion portion  80  cannot be disposed between the inner surfaces  63  and  63  when the flow path substrates  17 A and  17 B are laminated is prevented. 
     In such a liquid ejecting apparatus  1 , the temperature of the ink flowing in the flow path  51  is detected by the temperature sensor  20  disposed on the outer surface  50   b  of the sealing portion  50 . Information on the temperature of the ink detected by the temperature sensor  20  is input to the control unit  3 . The control unit  3  may calculate the ink viscosity based on the temperature of the ink flowing in the flow path  51 . The control unit  3  can control the piezoelectric actuator  38  according to the ink viscosity to adjust an ejection amount of the ink, or control the heater  32  to adjust the temperature of the ink supplied to the liquid ejecting head  10 . 
     According to the liquid ejecting apparatus  1 , since the protrusion portion  80  protruding from the inner surface  62  toward the temperature sensor  20  in the Z2 direction is provided, a flow of the ink flowing in the flow path  51  can be brought to the temperature sensor  20  in the Z-axis direction. The temperature of the ink flowing inside the flow path  51  is higher in a portion close to the center than a portion far from the center, in the cross section orthogonal to the flow direction of the ink. In the liquid ejecting apparatus  1 , since a flow near the center can be brought closer to the temperature sensor  20  in the cross section of the flow path  51 , detection accuracy of the temperature of the ink by the temperature sensor  20  can be improved. 
     In the liquid ejecting apparatus  1 , since the slope  81  is provided upstream of the protrusion portion  80 , it is easy to bring the flow of the ink toward the temperature sensor  20  while suppressing an increase in pressure loss of the ink. In addition, in the liquid ejecting apparatus  1 , since the slope  83  is provided downstream of the protrusion portion  80 , the flow of the ink can be returned from the temperature sensor  20  toward the Z1 direction while suppressing an increase in pressure loss of the ink. 
     In the liquid ejecting apparatus  1 , the opening  52  is formed in the Z2 direction of the protrusion portion  80 , and the opening  52  is long in the Y-axis direction. It is easy to bring the flow of the ink toward the temperature sensor  20  when the length of the opening  52  in the Y-axis direction is great as compared to the case when the length the opening  52  in the Y-axis direction is small. When the length of the opening  52  in the Y-axis direction is small, the flow of the ink in the Y-axis direction at a position close to the temperature sensor  20  becomes short, such that it is difficult to bring the flow of the ink close to the temperature sensor  20 . When the length W 3  of the opening  52  in the Y-axis direction is great, the flow of the ink in contact with the inner surface  50   a  of the sealing portion  50  can be lengthened. As a result, the flow of the ink can be brought closer to the temperature sensor  20 , such that detection accuracy of the temperature of the ink by the temperature sensor  20  can be improved. 
     In the liquid ejecting apparatus  1 , when viewed in the X-axis direction, the virtual plane F 1  extending along the slope  81  of the protrusion portion  80  overlaps the temperature sensor  20 . Since such a slope  81  is provided, the ink flowing along the slope  81  is brought to a position close to the temperature sensor  20 . For that reason, the detection accuracy of the temperature of the ink by the temperature sensor  20  can be improved. 
     In the liquid ejecting apparatus  1 , the inclination angle θ of the slope  81  with respect to the inner surface  62  is 45°. As a result, the flow of the ink can be brought closer to the temperature sensor  20  while suppressing pressure loss upstream of the protrusion portion  80 . 
     In the liquid ejecting apparatus  1 , the slope  56  disposed upstream of the temperature sensor  20  in the Y-axis direction and spaced apart from the slope  81  in the normal direction U 1  of the slope  81  is formed. As a result, the ink flows along the slope  56 , and thus, it is easy to bring the ink to a position closer to the temperature sensor  20  while suppressing pressure loss upstream of the temperature sensor  20 . For that reason, the detection accuracy of the temperature of the ink by the temperature sensor  20  can be improved. 
     In the liquid ejecting apparatus  1 , the temperature sensor  20  is installed on the outer surface  50   b  of the sealing portion  50  that seals the opening  52 . A total thickness of the sealing portion  50  including the flexible substrate  22  and the sealing plates  53  and  54  laminated in the Z-axis direction is smaller than that of the flow path substrate  17 A. By installing the temperature sensor  20  on such a thin sealing portion  50 , it is possible to allow the temperature sensor  20  to approach the ink in the flow path  51 . 
     When the opening  52  is provided in the Z-axis direction intersecting the Y-axis direction in which the flow path  51  extends, there is a risk that stagnation will occur in the flow of the ink. When the stagnation occurs in the opening  52 , there is a risk of the decreased accuracy of the temperature of the ink detected by the temperature sensor  20 . However, in the liquid ejecting apparatus  1 , since the protrusion portion  80  is provided in the Z1 direction of the opening  52 , the flow of the ink can be brought to a position closer to the opening  52 . Therefore, the flow of the ink in the opening  52  can be increased, such that the stagnation of the flow of the ink in the opening  52  can be suppressed. As a result, the detection accuracy of the temperature of the ink by the temperature sensor  20  can be improved. 
     In the liquid ejecting apparatus  1 , since the flow path substrate  17  is made of the resin, a manufacturing cost of the flow path structure  13  can be reduced and a weight of the liquid ejecting head  10  can be reduced. When the flow path substrate  17  is made of the resin, a thickness of the flow path substrate  17  becomes great, but by providing the opening  52  in the flow path substrate  17  and sealing the opening  52  with the sealing portion  50  having a small thickness, thermal resistance from the flow path  51  to the temperature sensor  20  can be decreased. Further, by including the sealing plates  53  and  54  made of the metal or the ceramic in at least a part of the sealing portion  50 , the thermal resistance from the flow path  51  to the temperature sensor  20  can be further decreased. 
     In the liquid ejecting apparatus  1 , the length W 3  of the opening  52  in the Y-axis direction is greater than the length W 5  of the protrusion portion  80  in the Y-axis direction. As a result, it is easy to bring the ink into the opening  52  while suppressing an increase in resistance in the flow path  51  in the vicinity of the protrusion portion  80 . 
     In the liquid ejecting apparatus  1 , the protrusion portion  80  is formed on a side opposite to the opening  52  in the Z-axis direction. When the opening  52  is positioned at an upper portion, it is easy for air bubbles to stay, but since the protrusion portion  80  is formed below the opening  52 , the flow of the ink flowing into the opening  52  is increased, such that the staying of the air bubbles in the opening  52  can be suppressed. Since the air bubbles flow due to the flow of the ink flowing into the opening  52 , the staying of the air bubbles in the opening  52  is suppressed. 
     In the liquid ejecting apparatus  1 , in the cross section orthogonal to the Y-axis direction, the cross-sectional area S 1  of the flow path  51  close to the temperature sensor  20  from the top surface  82  is greater than the cross-sectional areas S 2  and S 3  of the flow path  51  far from the temperature sensor  20  from the top surface  82 . As a result, resistance of the flow path closer to the temperature sensor  20  can be made smaller than resistance of the flow path further from the temperature sensor  20 . For that reason, it is easy for the ink to flow to a side closer to the temperature sensor  20 , such that a flow rate of the ink flowing near the temperature sensor  20  can be increased. As a result, it is possible to suppress the staying of the air bubbles in the opening  52  and improve the detection accuracy of the temperature of the ink by the temperature sensor  20 . 
       FIG. 9  is a perspective view illustrating an example of the flow path  51  formed inside the flow path structure  13 . In  FIG. 9 , shapes of the flow paths  35   b ,  36   b , and  51  formed inside the flow path structure  13  are illustrated. The flow path structure  13  includes the plurality of flow path substrates  17 . In  FIG. 9 , the flow path structure  13  and the flow path substrates  17  are not illustrated. The flow paths  35   b ,  36   b , and  51  are formed by grooves, through holes, faces in contact with these grooves and through holes, or the like, provided in the flow path substrates  17 . The flow paths  35   b  are supply flow paths  35   b  in the flow path structure  13  and allow the ink supply ports  18  and the common liquid chambers  34  to communicate with each other. The flow paths  36   b  are collection flow paths  36   b  in the flow path structure  13 , and allow the common liquid chambers  34  and the ink discharge ports  19  to communicate with each other. The flow path  51  is a flow path in the vicinity of the temperature sensor  20 , and is included in, for example, the supply flow path  35   b . The supply flow paths  35   b  are provided with the filters  33 . 
     The temperature sensor  20  is disposed on the opening  52  that communicates with the flow path  51 . Note that in  FIG. 9 , the sealing portion  50  that seals the opening  52  is not illustrated. The protrusion portion  80  is formed below the opening  52 , as described above. In the liquid ejecting apparatus  1 , the temperature sensor  20  can be installed with respect to such a flow path  51  to detect the temperature of the ink flowing in the flow path  51 . 
     In  FIG. 9 , the flow paths  35   b  and  36   b  are provided for each type of ink. Only one temperature sensor  20  may be provided in the flow path structure  13  or a plurality of temperature sensors  20  may be provided in the flow path structure  13  according to the type of ink. 
     Next, a disposition of a temperature sensor  20  of a liquid ejecting head  10 B according to a second embodiment will be described with reference to  FIG. 10 .  FIG. 10  is a sectional view illustrating the temperature sensor  20  and a narrowed region  55 B of the liquid ejecting head  10 B according to the second embodiment. In the liquid ejecting head  10 B, an installation surface of the temperature sensor  20  is disposed below an inner surface  61  that defines a flow path  51 B, in the Z-axis direction. 
     A recess portion  25  recessed toward the inside of the flow path  51 B in the Z1 direction is formed on an outer wall surface of a flow path substrate  17 A of the liquid ejecting head  10 B. The recess portion  25  is recessed in the flow path  51 B in the Z1 direction. An opening  52  communicating with the flow path  51 B is formed at a bottom portion of the recess portion  25 . The opening  52  is covered with a sealing portion  50 . 
     An inner surface  50   a  and an outer surface  50   b  of the sealing portion  50  are disposed in the Z1 direction with respect to the inner surface  61  in the Z-axis direction. The outer surface  50   b , which is an installation surface on which the temperature sensor  20  is disposed, is disposed at a position close to the top surface  82  of the protrusion portion  80  in the Z-axis direction. 
     The liquid ejecting head  10 B according to the second embodiment as described above also has an action effect similar to that of the liquid ejecting head  10  according to the first embodiment. In the liquid ejecting head  10 B, the recess portion  25  is formed and the temperature sensor  20  is disposed at a position close to the protrusion portion  80 , and thus, the temperature sensor  20  is disposed at a position close to the center of a flow of an ink in a cross section of the flow path  51 B. For that reason, the detection accuracy of the temperature of the ink by the temperature sensor  20  can be improved. Note that in the present embodiment, the protrusion portion  80  protruding from the inner surface  62  may not be provided. 
     Next, a liquid ejecting apparatus  1 B according to a third embodiment will be described with reference to  FIG. 11 .  FIG. 11  is a schematic view illustrating a configuration of the liquid ejecting apparatus  1 B according to the third embodiment. The liquid ejecting apparatus  1 B is a line head type printing apparatus. The liquid ejecting apparatus  1 B includes a plurality of liquid ejecting heads  10 B. The plurality of liquid ejecting heads  10 B are arranged in a predetermined direction to constitute a line head  90 . The plurality of liquid ejecting heads  10 B are arranged in, for example, a width direction of the medium PA. 
     An ink stored in a liquid container  2  is supplied to the liquid ejecting head  10 B via a circulation mechanism  7 . The circulation mechanism  7  supplies the ink to the liquid ejecting head  10 B and collects the ink discharged from the liquid ejecting head  10 B. The circulation mechanism  7  supplies the collected ink to the liquid ejecting head  10 B again. The circulation mechanism  7  includes a flow path for supplying the ink to the liquid ejecting head  10 B, a flow path for collecting the ink discharged from the liquid ejecting head  10 , a sub-tank for storing the collected ink, a pump for transferring the ink, and the like. 
     The liquid ejecting head  10 B includes a flow path structure in which a flow path through which the ink flows is formed, similar to the liquid ejecting head  10  according to the first embodiment described above. The flow path structure includes a plurality of flow path substrates, and the flow paths are formed by grooves, holes, surfaces, and the like, formed in the flow path substrates. The liquid ejecting head  10 B includes a temperature sensor  20  that detects a temperature of the ink in the flow path. A protrusion portion protruding into the flow path is formed on the flow path substrate. The temperature sensor  20  is disposed at a position facing the protrusion portion with the flow path interposed therebetween. 
     The liquid ejecting apparatus  1 B according to the third embodiment as described above also has an action effect similar to that of the liquid ejecting apparatus  1  described above. A configuration of the liquid ejecting head  10 B may be the same as that of the liquid ejecting head  10  or may be different from that of the liquid ejecting head  10 . 
     Next, a liquid ejecting head  10  according to a first modification will be described. The liquid ejecting head  10  according to the first modification is different from the liquid ejecting heads  10  according to the above-described embodiments in that the opening  52  is provided upstream of the filter  33  and the temperature sensor  20  is installed at a position corresponding to the opening  52 . The opening  52  is covered with the sealing portion  50  as in the above-described embodiments, and the temperature sensor  20  is installed on the outer surface  50   b  of the sealing portion  50 . 
     The liquid ejecting head  10  according to the first modification as described above also has an action effect similar to that of the liquid ejecting head  10  described above. In the liquid ejecting head  10  according to the first modification, since the temperature sensor  20  is installed with respect to the flow path downstream of the filter  33 , the temperature sensor  20  can detect the temperature of the ink at a position closer to the nozzle N. In other words, the temperature sensor  20  can detect the temperature of the ink at a position close to the piezoelectric actuator  38 . In addition, a configuration in which it is difficult for the air bubbles to stay in the opening  52  provided in a direction opposite to the direction of gravity with respect to the flow path  51  is realized by the protrusion portion  80 . As a result, influence of the air bubbles staying and growing in the opening  52  downstream of the filter  33  on discharge from the nozzle N can be suppressed and the piezoelectric actuator  38  can be controlled according to the temperature of the ink at a position close to the piezoelectric actuator  38 , such that high-precision printing can be realized. 
     Next, a liquid ejecting head  10  according to a second modification will be described. The liquid ejecting head  10  according to the second modification is different from the liquid ejecting heads  10  according to the above-described embodiments in that the temperature sensor  20  is provided at an inlet port of the flow path structure  13 . The inlet port is, for example, the ink supply port  18 . The inlet port of the flow path structure  13  is, for example, a tubular body, and a tube is coupled to this inlet port. An ink flowing in the tube passes through the inlet port and flows into the flow path inside the flow path structure  13 . 
     In the second modification, the temperature sensor  20  is installed on an outer surface of the tubular body constituting the inlet port. Also in the liquid ejecting head  10  according to the second modification as described above, a protrusion portion that protrudes into the flow path toward the temperature sensor  20  is provided. The liquid ejecting head  10  according to the second modification as described above also has an action effect similar to that of the liquid ejecting apparatus  1  described above. 
     Note that the above-described embodiments merely show typical embodiments of the present disclosure, the present disclosure is not limited to the above-described embodiments, and various modifications and additions can be made without departing from the gist of the present disclosure. 
     In the above-described embodiment, the narrowed region  55  in which a width of the flow path is small in the Z-axis direction has been described by way of example, but a direction in which the width of the flow path is small is not limited to the Z-axis direction, and the narrowed region  55  may be a narrowed region having a narrow width in another direction intersecting the flow direction of the ink. The flow direction of the ink in the vicinity of the temperature sensor  20  is not limited to the Y-axis direction, and may be the Z-axis direction or the X-axis direction. For example, when the flow direction of the ink is the Z-axis direction, the protrusion portion may be provided in the X1 direction of the flow path, and the temperature sensor  20  may be disposed in the X2 direction of the flow path. 
     In the above-described embodiment, a case where the temperature sensor  20  is disposed in the Z2 direction with respect to the flow path  51  has been described by way of example, but a direction in which the temperature sensor  20  is disposed is not limited to the Z2 direction, and may be the Z1 direction, the X1 direction, the X2 direction, or any other direction. Similarly, a direction in which the protrusion portion  80  protrudes is not limited to the Z2 direction, and the protrusion portion  80  may protrude in any other direction. The protrusion portion  80  is only required to be able to bring the flow of the ink to a position close to the temperature sensor  20 . 
     In addition, in the above-described embodiment, the opening  52  has been covered from the outside of the flow path using the sealing plate  53 , but the sealing plate may be disposed so as to cover the opening  52  from the inside of the flow path. In addition, the opening communicating with the flow path may not be formed. For example, a thickness of a portion of the flow path substrate  17  in contact with the flow path may be reduced, and the temperature sensor  20  may be installed in this portion. 
     In addition, in the above embodiment, as illustrated in  FIGS. 6 and 7 , the flow path  51  has been formed by the flow path substrates  17 A and  17 B, but the flow path  51  may be formed by one flow path substrate  17  or may be formed by three or more flow path substrates  17 . For example, a third flow path substrate  17  may be disposed between the flow path substrate  17 A and the flow path substrate  17 B. The flow path  51  may be formed by the inner surface  61  of the flow path substrate  17 A, an opening formed in the third flow path substrate  17  and passing through the third flow path substrate  17  in a plate thickness direction, and the inner surface  62  of the flow path substrate  17 B. In addition, the flow path  51  may be configured by an inner surface  61  of the flow path substrate  17 A and a groove of the flow path substrate  17 B. 
     In addition, the temperature sensor  20  may be installed on an outer surface of a pipe through which the ink flows or a sealing portion may be provided at a portion coupling the pipes to each other and the temperature sensor  20  may be installed on an outer surface of the sealing portion. 
     The liquid ejecting apparatus described by way of example in the above-described embodiments can be adopted in various apparatuses such as a facsimile apparatus or a copying machine, in addition to an apparatus dedicated to printing. However, a use of the liquid ejecting apparatus is not limited to the printing. For example, a liquid ejecting apparatus that discharges a solution of a coloring material is used as a manufacturing apparatus that forms a color filter of a display apparatus such as a liquid crystal display panel. In addition, a liquid ejecting apparatus that discharges a solution of a conductive material is used as a manufacturing apparatus that forms a wiring line or an electrode of a wiring board. In addition, a liquid ejecting apparatus that discharges a solution of an organic matter relating to a living body is used as a manufacturing apparatus that manufactures, for example, a biochip.