JP5091008B2 - Pressure sensor, head maintenance device, ink jet recording device, and maintenance method - Google Patents

Description

  The present invention relates to a pressure sensor, a head maintenance device, an inkjet recording device, and a maintenance method.

  In general, an ink jet recording apparatus sends an ink solution supplied from an ink tank to a head provided with a plurality of nozzles, and the ejection of the solution is controlled independently at the nozzles so that the solution is intermittently applied in the direction of the paper surface. Injection is performed. For example, a solution jetting method includes a mechanism in which a piezo element that is deformed by an electric current is disposed inside the nozzle and a piezoelectric element is deformed to push out the solution, or a thermal head that is heated by an electric current is disposed in the nozzle, A mechanism is known in which bubbles are generated inside and a solution is pushed out.

  In order to perform good printing, it is necessary to appropriately control and maintain the meniscus of the ink inside the nozzle and the amount of the solution ejected from the nozzle. For this reason, in the ink jet recording apparatus, head maintenance is performed to remove the thickened or solidified solution from the ink jet head. This is performed by a method in which the nozzle surface of the ink jet head is sealed with a cap portion having suction means, and the ink solution is sucked from the nozzle by a pump. At this time, a sealing member such as a rubber ring is interposed between the nozzle surface and the cap portion to avoid suction failure due to air mixing. However, if the adhesion between the nozzle surface and the sealing member cannot be obtained due to dust adhering to the nozzle surface or cracks generated in the sealing member, air is mixed in from the cap and the solution is normally sucked. There was a problem that printing failure or printing failure occurred despite the fact that the suction process was completed without any change and the suction process was performed.

Here, as a device for detecting the close contact between the head and the sealing member during the suction processing, Patent Document 1 proposes a recording apparatus provided with a pressure detection mechanism. In the recording apparatus described in Patent Document 1, a branch portion is provided at a part of the solution suction path, and a pressure sensor is provided at the tip. During normal solution suction, the inside of the channel from the cap to the solution suction mechanism is depressurized to a predetermined value, but if air is mixed, the inside of the channel is not depressurized to the predetermined value. According to this pressure sensor, the pressure inside the cap can be notified to the abnormality detection unit, and the abnormality detection unit can detect a pressure abnormality by comparing with a prescribed pressure during normal operation. For this reason, a solution suction failure can be detected.
JP-A-61-98543

  However, in the recording apparatus described in Patent Document 1, the pressure sensor is provided at the tip of a pipe branching from the solution flow path. The solution channel is a channel for the solution sucked from the nozzle, and the thickened or solidified solution flows through this channel. At this time, the thickened or solidified solution also flows into the pressure sensor provided at the end of the pipe branched from the solution flow path. When these solutions are deposited on the pressure detection unit of the pressure sensor and solidified, the pressure change in the solution flow path is not transmitted to the pressure detection unit. As a result, the sensitivity of the sensor is lowered, causing a malfunction that the pressure sensor cannot be detected even though the inside of the cap portion is depressurized to a predetermined value. In addition, a piezoelectric element is often used for the pressure detection unit. However, since the piezoelectric element is expensive, if a piezoelectric element is provided for each solution path, the apparatus cost increases.

  The present invention has been made in view of the above-described circumstances, and provides a pressure sensor, a head maintenance device, an ink jet recording apparatus, and an ink jet recording method that are unlikely to cause a malfunction due to a thickened or solidified solution and that can reduce costs. It is to provide.

  In order to solve the above problems, the present invention proposes the following means.

In the pressure sensor of the present invention, the lower surface of a solution jet head on which a plurality of nozzles are arranged is closed with a cap portion that can be sealed, and the suction portion sucks the solution from the nozzle by making the inside of the cap portion negative pressure A pressure sensor in a head maintenance device for detecting whether or not the inside of the cap portion has been depressurized to a predetermined pressure, and is provided in a part of an air flow path that opens the cap portion to the atmosphere. A branched portion, a bellows whose proximal end communicates with the branched portion, and whose tip moves in accordance with the pressure difference between the internal pressure and the atmospheric pressure of the atmospheric flow path, and a position detection unit that detects a change in the position of the tip of the bellows And a determination unit that receives a signal generated by the position detection unit and determines a suction failure, and the branching unit receives the solution that flows backward in the atmosphere channel during head maintenance. To When the said solution is characterized in that the partition wall to prevent the flow into the bellows-side is provided through the bifurcation.

According to this invention, when the solution is sucked from the nozzle, the inside of the cap portion is depressurized. Along with this, the atmospheric flow path communicating with the cap portion and the inside of the bellows are also decompressed. The bellows is deformed by the reduced pressure, and the tip moves. Then, the change in position is detected by the position detection unit, and it is determined whether or not the pressure is reduced to a predetermined value by the determination unit. Further, during the head maintenance, the solution may flow backward through the atmospheric flow path valve, but the flow into the subsequent portion is blocked by the partition provided at the branch portion. For this reason, only the atmosphere enters and leaves the bellows, and the solution cannot be fixed inside the bellows.

  In the pressure sensor of the present invention, the position detection unit includes a movable element having a base end connected to the tip of the bellows and having an optical path at the tip, a pair of light emitting units and a light receiving unit, and applies light to the optical path. And a photo sensor for detecting the movement of the moving element.

  According to this invention, when the internal pressure of the atmospheric flow path fluctuates, the mover provided at the tip of the bellows moves. At this time, the optical path provided in the moving element moves relative to the light emitting part, and light from the light emitting part is blocked by the moving element. Therefore, the light from the light emitting unit does not reach the light receiving unit. Accordingly, the movement of the moving element is detected by the photo sensor. Further, when the internal pressure of the atmospheric flow path returns to atmospheric pressure, the moving element returns to a specified position by the elastic restoring force of the bellows, and light from the light emitting part passes through the optical path to the light receiving part. Then, the return of the moving element is detected by the photo sensor.

  The pressure sensor of the present invention is characterized in that the branch portion is disposed above the cap portion.

  According to this invention, when the solution stored in the cap flows backward through the air flow path when the solution is sucked from the nozzle row using the cap portion, the upper limit of the liquid level is the same as that of the cap. The liquid surface does not reach the branch portion because the level is the same and the branch portion is provided above the cap.

  In the pressure sensor of the present invention, the bellows is characterized in that a reinforcing portion is formed at the top of the bent portion protruding outward.

  According to this invention, the top part of the bent part of the bellows is stronger than the other part, and when the inside of the bellows is decompressed, the bent part by the force applied from the top part in the axial direction of the bellows The deformation of is suppressed. Therefore, the deformation of the bellows occurs on the inclined surface of the bellows, and as a result, the bellows contracts efficiently in the axial direction.

A head maintenance device of the present invention includes a pressure sensor according to any one of claims 1 to 4 , a pump that sucks the solution, a motor that drives the pump, and a motor control unit that controls the motor. A solenoid that drives an atmospheric valve provided in the atmospheric flow path and a solenoid control unit that controls the solenoid are provided.

According to this invention, the head maintenance device determines a solution suction failure using the pressure sensor according to any one of claims 1 to 4 provided at the branch portion in the atmospheric flow path, The first control unit determines whether or not the maintenance operation can be continued, and the driving of the motor and the solenoid is controlled by the respective control units.

An ink jet recording apparatus of the present invention conveys a recording medium so as to pass through a head maintenance device according to claim 5 , a solution supply means for supplying a solution to the head, and a position facing the nozzle of the head. It is characterized by being mounted with a recording medium conveying means.

According to this invention, the ink jet recording apparatus is maintained with the head using the head maintenance apparatus according to claim 5 . At this time, the pressure sensor detects a reduced pressure state inside the cap portion due to the suction operation of the solution under maintenance.

The head maintenance method of the present invention is a head maintenance method using the head maintenance device according to claim 5 , wherein the lower surface of the head is sealed with the cap portion, and the inside of the cap portion is negatively pressurized. The step of sucking the solution from the nozzle, the step of determining a suction failure based on whether or not the internal pressure of the atmospheric flow path has been reduced to a predetermined pressure, and introducing the atmosphere into the cap portion The process is provided.

  According to the present invention, the pressure sensor detects the pressure reduction state inside the cap portion, and when the pressure is not reliably reduced, a suction failure is notified, thereby causing a manual or automatic cause of the failure by the user. Removal and re-suction are performed to achieve reliable suction operation.

  According to the present invention, it is possible to manufacture at a low cost by adopting a bellows as a main element of the pressure sensor. Further, a branch portion is provided in the atmospheric flow path instead of the solution flow path, and the pressure sensor By detecting the pressure inside the branch part of the atmospheric flow path, it is possible to prevent the solution from flowing into the pressure sensor and to avoid a decrease in sensor accuracy caused by the thickened or solidified solution. .

    An ink jet recording apparatus according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing a part of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing the pressure sensor of this embodiment. FIG. 3 is a perspective view showing the pressure sensor of the present embodiment.

  First, the overall configuration of the inkjet recording apparatus 100 will be described. As shown in FIG. 1, an ink jet recording apparatus 100 includes a solution ejecting mechanism 101 that ejects a solution onto a sheet P, a transport mechanism 102 that moves the solution ejecting mechanism 101 in the Y direction in the figure, and a solution ejecting recording medium. A recording medium conveying unit 103 that conveys the lower surface of the mechanism 101 in the X direction in the drawing and a head maintenance device 104 for performing maintenance of the solution ejection mechanism 101 are provided.

  The transport mechanism 102 is provided with a carriage motor 105. Further, a driving pulley 106 is connected to the carriage motor 105. The drive pulley 106 is supported on the inner surface on the right side of the rear wall 107 of the housing. A driven pulley 108 that is paired with the driving pulley 106 is rotatably supported on the left inner surface of the rear wall 107 of the inkjet recording apparatus 100.

  Further, a timing belt 109 is wound around the driving pulley 106 and the driven pulley 108. A carriage 110 is fixedly supported on the timing belt 109. The carriage is provided with an ink tank 111 and a head 112 for ejecting the solution.

  On the other hand, in the inkjet recording apparatus 100, a guide shaft 113 is installed in the horizontal direction of the housing. Further, the carriage 110 is inserted and supported by the guide shaft 113 so as to be guided in the axial direction of the guide shaft 113. Further, a maintenance position 114 is provided at the end of the guide shaft 113. Below the maintenance position 114, a head maintenance device 104 for the inkjet head is disposed. When the carriage 110 is at the maintenance position 114, the head maintenance device 104 vertically below the carriage 110 faces the head 112.

  Next, details of the head maintenance device 104 of the inkjet head according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the head maintenance device 104 is provided with a tank-shaped cap portion 202 that can contact the nozzle surface 201 of the head 112. A nozzle contact portion 203 that is in close contact with the nozzle surface is formed on the upper surface of the cap portion 202. The nozzle contact portion 203 is disposed so as to surround the nozzle row 204. The cap unit 202 is moved up and down by a link (not shown) so that the nozzle contact portion 203 is in close contact with the nozzle surface 201 of the inkjet head 112.

  The cap portion 202 is provided with an air introduction hole 205. One end of an air tube 206 that functions as an air flow path is connected to the outer end of the air introduction hole 205. Further, a branch portion 207 is connected to the other end of the air tube 206 so as to be positioned above the cap portion 202. The branching unit 207 branches the atmospheric flow path into a flow path where the solenoid valve 208 exists and a flow path where the pressure sensor 209 exists. Further, a partition 207a is provided at the branch 207 to prevent the solution flowing back through the air tube 206 during head maintenance from reaching the pressure sensor 209 through the branch 207 when the solution reaches the branch 207. Is formed.

  The solenoid valve 208 is provided with a valve seat 210, a valve body 211, and a solenoid 212, and the solenoid is connected to the valve body 211. The valve body 211 can reciprocate in the Z direction and can come into contact with the valve seat 210. A solenoid control unit 214 is connected to the solenoid 212.

  A solution suction hole 215 is formed in the cap portion 202. One end of an ink tube 216 serving as a flow path for the solution sucked from the nozzle is connected to the outer end of the solution suction hole 215, and the other end of the ink tube 216 is connected to a waste liquid tank 218 via a pump 217. A motor 219 for driving the pump is connected to the pump 217. A motor control unit 220 that controls driving of the motor 219 is connected to the motor 219.

  Next, details of the pressure sensor 209 will be described with reference to FIGS. The pressure sensor 209 includes a bellows 301. One end of a branching portion 207 is connected to the base end portion 302 of the bellows 301. The base end portion 302 is a fixed end fixed to the branch portion, and the tip end portion 303 is a free end that moves in accordance with the contraction of the bellows 301. Moreover, the front-end | tip part 303 of the bellows 301 is closed. A reinforcing portion 308 thicker than the slope portion 307 is formed at the top portion 306 of the bent portion 305 of the bellows portion 304 of the bellows 301. Further, a base end portion 321 of the mover 309 is fixed to the tip of the bellows 301.

  As shown in FIG. 3, a long hole 310 is formed in the moving element 309 along the axial center direction of the bellows 301, and the tip 312 of the twist preventing protrusion 311 is inserted into the long hole 310. A base end 313 of the twist preventing projection 311 is fixed to the fixing portion 314. A photosensor 317 including a light emitting unit 315 and a light receiving unit 316 is disposed below the base end 313 of the fixed unit 314. A moving element 309 is interposed between the light emitting unit 315 and the light receiving unit 316, and an optical path 318 is formed in the moving element 309. An optical axis 319 generated by the photosensor 317 passes through the optical path 318, and the optical axis 319 is blocked by the peripheral portion 320 of the optical path 318 when the movable element 309 moves relative to the photosensor 317.

  A spring hole 323 is formed at the tip 322 of the moving element 309. One end of a spring 324 is engaged with the spring hole 323. The other end of the spring 324 is locked to a locking portion (not shown).

  The overall operation of the ink jet recording apparatus of the present embodiment having the above-described configuration will be described with reference to FIGS. In the recording process by the inkjet recording apparatus 100, first, the paper P is supplied to the inkjet recording apparatus 100. Then, the carriage 110 starts reciprocating in the Y direction in the figure, and at this time, the solution in the ink tank 111 is ejected onto the paper P by the head 112. When the reciprocating operation of the carriage 110 is completed, the paper P is transported in the X direction in the drawing for printing the next line, and the process of ejecting the solution by the head 112 is similarly repeated.

  In the recording process, when the nozzle is partially or completely blocked due to the thickening or solidification of the solution, the solution is poorly jetted, and information on the area handled by the nozzle is missing on the paper P. Such an ejection failure is recognized by a nozzle sensor (not shown) provided in the inkjet recording apparatus 100 or a user's judgment, and the head maintenance process is started automatically or manually.

  When the head maintenance process is started, the carriage motor 105 is driven to rotate the driving pulley 106. The driven pulley 108 and the timing belt 109 are driven by this rotational force. A carriage is suspended and supported on the timing belt 109, and the carriage 110 is conveyed to the maintenance position 114 by the operation of the timing belt 109. The position of the carriage 110 is measured in real time by a carriage sensor (not shown). When the carriage 110 reaches the maintenance position 114, the carriage motor 105 is stopped by a signal generated by the carriage sensor, and the carriage 110 is stopped at the maintenance position 114. . At this time, the head 112 is positioned vertically above the head maintenance device 104.

  Next, the cap unit 202 provided in the head maintenance device 104 is lifted by a lifting device (not shown), contacts the nozzle surface 201 of the head 112 via the nozzle contact portion 203, and surrounds the nozzle row 204. Thus, the nozzle row 204 is sealed with the cap portion 202. Subsequently, the solenoid 212 is driven by the solenoid control unit 214, the valve body 211 comes into contact with the valve seat 210, and the atmospheric flow path is closed. Further, the motor 219 is driven by the motor control unit 220. Then, a suction force in the direction of the waste liquid tank 218 is generated inside a series of flow paths communicating from the air tube 206 to the ink tube 216 via the cap portion 202.

  Hereinafter, the operation of the pressure sensor 209 of the present embodiment will be described.

  If the close contact between the nozzle surface 201 and the nozzle contact portion 203 is complete, the inside of the series of flow passages becomes a negative pressure, and the solution is sucked from the nozzle row 204. Furthermore, since this suction force is similarly generated on all the inner walls of the series of flow paths, the bellows 301 is connected to the bellows 301 via the branch portion 207 connected to the air tube 206 in the same manner as the inside of the series of flow paths has a negative pressure. The internal space also becomes negative pressure.

  Bellows 301 receives a suction force from the inside toward branching portion 207. Since the front end portion 303 is closed inside the bellows 301, a force for contracting the bellows 301 is generated on the inner wall of the bellows 301. Since the reinforcing part 308 is formed in the bellows 301, the shrinkage | contraction of the circumferential direction is suppressed. Therefore, the bellows 301 contracts in the axial direction.

  When the bellows 301 contracts in the axial direction, the distal end portion 303 that is a free end approaches the proximal end portion 302 side with respect to the proximal end portion 302 that is a fixed end. Along with this, the mover 309 fixed to the tip of the bellows 301 also moves to the base end portion 302 side. Note that the movement of the moving element 309 is limited to a reciprocating motion by the torsion preventing protrusion 311 inserted into the elongated hole 310 formed in the moving element 309.

  Here, when the bellows 301 is not contracted, the optical axis 319 generated by the light emitting portion 315 of the photosensor 317 passes through the optical path 318 formed in the movable element 309, but the optical path is generated by the movement of the movable element 309. 318 also moves, and accordingly, the optical path 318 and the optical axis 319 shift. In this state, the optical axis 319 is applied to the peripheral portion of the moving element 309 and does not reach the light receiving unit 316. Then, a light path blocking signal is transmitted from the light receiving unit 316 to the detection circuit 325.

  The detection circuit 325 that has received the signal for blocking the optical path detects that the inside of the cap has been depressurized to a specified pressure, and proceeds to the air introduction step, which is the next step, assuming that the solution suction operation is being executed normally.

  In the air introduction process, the solenoid 212 is driven by the solenoid control unit 214, the contact between the valve body 211 and the valve seat 210 is released, and thereby the valve seat 210 is opened. Then, the atmosphere is introduced from the solenoid valve 208 toward the air tube 206 via the branch portion 207. Since the motor 219 is driven also in this step, suction in the direction of the waste liquid tank 218 is continued in a series of flow paths by the air tube 206, the cap unit 202, and the ink tube 216.

  However, since air continuously flows from the valve seat 210, the internal pressure in the series of flow paths is the same as the atmospheric pressure. At this time, in the pressure sensor 209, the contraction force in the axial direction of the bellows 301 disappears because the inside of the bellows 301 returns from the negative pressure to the atmospheric pressure. Next, the bellows 301 returns to its original shape by the elastic restoring force of the bellows 301 and the biasing force of the spring 324. Then, the optical path 318 provided in the moving element 309 returns to the position of the optical axis 319, and thus the optical axis 319 reaches the light receiving unit 316. Thereafter, the air introduction step is completed, the motor 219 is stopped by the motor control unit 220, and then the cap unit 202 is lowered by the lifting device, and the sealing of the nozzle row 204 of the cap unit 202 is released. After the descent of the cap unit 202 is completed, the process is taken over to the next process of the head maintenance, the resumption of the recording process, or the standby process.

  On the other hand, defective suction of the solution from the nozzle row 204 is caused by the introduction of air into the flow channel from at least a part of a series of flow channels including the air tube 206, the cap unit 202, and the ink tube 216, that is, the nozzle row 204. This occurs when the pressure for sucking the solution from the nozzle row 204 becomes insufficient due to the inflow of substances from other parts. This phenomenon occurs when a crack occurs in the air tube 206, the ink tube 216, the nozzle contact portion 203, or the like, and the nozzle contact portion is caused by dust adhered to the head 112 or a solution fixed around the nozzle row 204. This also occurs when there is a gap between 203 and the nozzle surface 201.

  When the suction failure occurs, the solenoid valve 208 is closed and the motor 219 is driven by the motor control unit 220, but the air continuously flows from the crack or the gap. The pressure inside is not reduced to the normal pressure. At this time, since the pressure within the bellows 301 is not reduced to the specified pressure, the force for contracting the bellows 301 is weak, and the amount of contraction of the bellows 301 in the axial direction is smaller than normal. Therefore, the moving amount of the moving element 309 is small, and the optical path 318 is not shifted to interrupt the optical axis 319. Therefore, an optical axis cutoff signal is not transmitted from the light receiving unit 316.

  Although the motor control unit 220 drives the motor 219, no signal for blocking the optical axis is transmitted from the light receiving unit 316, so the detection circuit 325 detects that the inside of the cap is not decompressed. Then, the detection circuit 325 transmits a signal indicating the occurrence of suction failure to a control unit (not shown). The control unit takes over from the suction process to an error processing process such as re-suction or suction stop, and returns to the normal process after the error processing is completed.

  As described above, according to the pressure sensor 209 according to the present embodiment, the bellows 301 is adopted as the main element of the pressure sensor 209, so that it can be manufactured at a low cost. 207, and further, a partition wall 207a is formed at the branching portion 207, and a pressure sensor 209 is connected to the tip of the partition wall 207, thereby preventing the solution from flowing into the bellows 301 and causing a thickened or solidified solution. It is possible to avoid a decrease in sensor accuracy.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

  For example, in the present embodiment, the pressure sensor 209 employs a configuration in which the base end portion 302 of the bellows 301 to the distal end portion 303 of the mover 309 are arranged on a straight line, but this is not a limitation. The bellows 301 may be bent and disposed within the elastic limit range.

  In the present embodiment, the spring 324 is employed as the biasing member. However, the present invention is not limited to this, and the elastic restoring force of the bellows 301 or the weight of the bellows may be used.

  Further, in the present embodiment, a configuration in which the branch portion 207 is integrally formed with the valve seat 210 is adopted, but the configuration is not limited thereto, and a configuration may be adopted in which a pipe line connected from the branch portion to the atmospheric valve is interposed.

  In this embodiment, the moving element 309 employs a configuration in which the elongated hole 310 and the optical path 318 are formed in a rectangular parallelepiped member. However, the present invention is not limited thereto, and a columnar or pyramidal member may be employed.

  In the present embodiment, the reinforcing portion 308 has a configuration formed of a thick member. However, the configuration is not limited thereto, and a configuration in which a reinforcing portion made of a material different from the material of the bellows 301 is formed. It may be adopted.

  In this embodiment, the photo sensor 317 is employed as the position detection unit. However, the present invention is not limited thereto, and a contact sensor may be employed.

1 is a perspective view showing a part of the configuration of an ink jet recording apparatus equipped with a pressure sensor according to an embodiment of the present invention. It is a block diagram which shows the head maintenance apparatus and pressure sensor of embodiment of this invention. It is a perspective view which shows the pressure sensor of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Inkjet recording apparatus 103 Recording medium conveyance means 104 Head maintenance apparatus 111 Ink tank (solution supply means)
112 Head 202 Cap portion 204 Nozzle array 206 Air tube (atmospheric flow path)
207 Branch 207a Partition 209 Pressure sensor 217 Pump (suction means)
208 Solenoid valve (atmospheric valve)
219 Motor (suction means)
214 Solenoid control part 220 Motor control part 301 Bellows 302 Base end part 303 Front end part 309 Mover 310 Long hole 311 Twist prevention protrusion 315 Light emitting part 316 Light receiving part 317 Photosensor (position detection part)
318 Optical path 319 Optical axis 325 Detection circuit P Paper (recording medium)

Claims (7)

The lower surface of the solution jetting head on which a plurality of nozzles are arranged is closed with a cap that can be sealed, and when the solution is sucked from the nozzle by suctioning the inside of the cap with negative pressure, the cap A pressure sensor in the head maintenance device for detecting whether or not the inside of the head has been depressurized to a predetermined pressure,
A branch part provided in a part of the atmospheric flow path that opens the cap part to the atmosphere, and a bellows whose proximal end communicates with the branch part, and whose tip moves according to the pressure difference between the internal pressure of the atmospheric flow path and the atmospheric pressure A position detection unit that detects a change in the position of the tip of the bellows, and a determination unit that receives a signal generated by the position detection unit and determines a suction failure ,
The branch portion is provided with a partition wall that prevents the solution flowing backward through the atmosphere flow path during head maintenance from flowing into the bellows side through the branch portion when the solution reaches the branch portion. a pressure sensor, characterized by being.   The position detecting unit includes a movable element having a base end connected to a tip end of the bellows and having an optical path, and a pair of a light emitting unit and a light receiving unit, and detects movement of the movable element by applying light to the optical path. The pressure sensor according to claim 1, further comprising a photosensor.   The pressure sensor according to claim 1, wherein the branch portion is disposed above the cap portion.   The pressure sensor according to any one of claims 1 to 3, wherein the bellows has a reinforcing portion formed at a top portion of the bent portion protruding outward.   5. The pressure sensor according to claim 1, a pump that sucks the solution, a motor that drives the pump, a motor control unit that controls the motor, and the atmospheric flow path. A head maintenance device comprising: a solenoid for driving the atmospheric valve; and a solenoid control unit for controlling the solenoid.   6. A head maintenance apparatus according to claim 5, a solution supply means for supplying the solution to the head, and a recording medium transport means for transporting a recording medium so as to pass through a position of the head facing the nozzle. An ink jet recording apparatus comprising:   A head maintenance method using the head maintenance device according to claim 5,
  Sealing the lower surface of the head with the cap, sucking the solution from the nozzle with a negative pressure inside the cap, and whether the internal pressure of the atmospheric flow path has been reduced to a predetermined pressure. A head maintenance method comprising: a step of determining a suction failure based on the above; and a step of introducing air into the cap portion.

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