JP2009160731A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate adjustment of an ink channel to suitably deform according to a temperature change. <P>SOLUTION: An ink is refilled from a sub-manifold flow channel 105a to a nozzle 108 side via an aperture 112. A diaphragm 151 which defines an inner wall surface of the aperture 112 is formed. A branch flow channel 141a is opposed to the aperture 112 holding the diaphragm 151 between. A pump which changes a pressure of the air in the branch flow channel 141a is equipped. The pump is controlled so as to change the pressure in the branch flow channel 141a on the basis of an ink temperature in the ink flow channel. Accordingly, the diaphragm 151 can be deformed to make a flow channel resistance of the aperture 112 large when the ink temperature is high, and to make the flow channel resistance of the aperture 112 small when the ink temperature is low. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet head that ejects ink.

  In an inkjet head in which an ejection port that ejects ink and an ink flow path that supplies ink to the ejection port are formed, the ejection characteristics of the ink may change depending on the temperature of the ink. For example, when the ink temperature increases, the ink viscosity decreases and the ink easily flows. Further, when the ink temperature is lowered, the ink viscosity is increased and the ink is difficult to flow.

  Japanese Patent Application Laid-Open No. 2004-228688 adjusts ink ejection characteristics by deforming an ink flow path according to ink temperature. In Patent Document 1, the wall portion of the flow path is constituted by a two-layer structure of a metal plate having a small linear expansion coefficient and a resin material having a large linear expansion coefficient. When the ink temperature changes, the wall portion is deformed due to the difference in linear expansion coefficient, and the flow path cross-sectional area changes. Patent Document 1 adjusts the ink ejection characteristics in this way.

JP 2006-306066 A

  By the way, the ability to refill ink into the ejection port side in the ink flow path after ink ejection may change depending on the ink temperature. For example, since the ink easily flows when the ink temperature becomes high, the ink is easily refilled. On the other hand, when the ink temperature becomes low, the ink does not easily flow, so the ink is difficult to be refilled. A change in ink ejection characteristics may occur due to a change in the ability to refill such ink.

  For example, if the ink flow path is designed so that the right amount of ink is refilled when the ink temperature is high, the amount of ink refilled when the ink temperature is low is insufficient. As a result, the amount of ink ejected from the ejection port may be insufficient. On the other hand, if the ink flow path is designed so that the right amount of ink is refilled when the ink temperature is low, the amount of ink refilled when the ink temperature is high becomes excessive. As a result, the amount of ink ejected from the ejection port may become excessive.

  Thus, by adopting Patent Document 1, it is conceivable to deform the ink flow path so that the ability to refill ink does not change according to temperature. However, in Patent Document 1, the ink flow path is deformed using the thermal expansion of the wall itself. In this case, how the wall portion is deformed by the temperature change of the ink is determined by the material and shape of the wall portion, the method of supporting the wall portion, and the like. For this reason, it is difficult to adjust so that the wall portion is appropriately deformed according to the temperature change.

  An object of the present invention is to provide an ink jet head that can be easily adjusted to appropriately deform an ink flow path in accordance with a temperature change.

  The inkjet head of the present invention includes an ejection port for ejecting ink, an ink channel for supplying ink to the ejection port, and an ejection for ejecting ink for ejecting ink from the ejection port to the ink in the ink channel. An actuator, a wall portion defining an inner wall surface of the ink flow path at a position separated from the ejection port along the ink flow path from a position where the ejection energy is supplied, and an ink in the ink flow path A temperature sensor that detects the temperature; and a flow path deforming unit that deforms the wall portion so that a cross-sectional area perpendicular to the flow direction of the ink flow path decreases as the temperature indicated by the detection result of the temperature sensor increases. ing.

  According to the ink jet head of the present invention, the temperature of the ink in the ink flow path is detected by the temperature sensor, and the wall portion of the ink flow path is deformed according to the temperature of the ink. The cross-sectional area of the ink flow path is reduced as the ink temperature increases. Accordingly, when the ink temperature is high and the ink viscosity is low, the ink easily flows, while the cross-sectional area of the ink flow path is small, so that it is difficult for the ink to flow to the ejection port. In addition, when the ink temperature is low and the ink viscosity is high, it becomes difficult for the ink to flow. On the other hand, since the cross-sectional area of the ink flow path becomes large, the ink easily flows. As described above, the performance of refilling the ink to the portion where the ejection energy is applied in the ink flow path can be appropriately adjusted according to the temperature change. In addition, since the wall portion is deformed based on the detection result of the ink temperature, if the configuration for deforming the wall portion is determined, how to change the deformation amount of the wall portion according to the detection result thereafter. It becomes a problem. For this reason, this invention is easy to adjust so that a wall part may be deform | transformed appropriately according to a temperature change compared with the case where a deformation | transformation amount is adjusted with the material of a wall part, a shape, the support method of a wall part, etc.

  In the present invention, the flow path deforming means may be configured such that a part of the inner wall surface is defined by the wall portion, the fluid chamber facing the ink flow path across the wall portion, and the wall portion is deformed. Pressure changing means for changing the pressure in the fluid chamber so as to control the pressure changing means so that the pressure in the fluid chamber increases as the temperature indicated by the detection result of the temperature sensor increases. It is preferable that pressure control means is further provided. According to this, since the wall portion is deformed by changing the pressure in the fluid chamber in contact with the wall portion, the flow path deforming means can be realized with a simple configuration by using, for example, a pump.

  In the present invention, the fluid chamber may be filled with a gas. According to this, the ink flow path can be deformed by changing the pressure of the gas in the fluid chamber.

  In the present invention, the wall portion is made of a ferromagnetic material, and the flow path deforming means generates an electromagnetic field that deforms the wall portion, and a current supply that supplies current to the electromagnet. A current supplied from the current supply means to the electromagnet so that a cross-sectional area perpendicular to the flow direction of the ink flow path decreases as the temperature indicated by the detection result of the temperature sensor increases. You may further provide the current control means to control. According to this, since the electromagnet is used for the deformation of the wall portion, the deformation amount of the wall portion can be easily adjusted by adjusting the current supplied to the electromagnet. Note that the control content of the current supply means includes changing the amount of current supplied to the electromagnet. The change in the amount of current includes stopping the supply of current to the electromagnet, or starting the supply of current from the state where the supply of current is stopped.

  Further, in the present invention, when no current is supplied to the electromagnet, the wall portion is bent in a direction opposite to the direction toward the ink flow path, and current is supplied to the electromagnet. It is preferable that a magnetic field is generated such that the wall portion is bent in a convex manner toward the ink flow path. According to this, since the wall portion is bent even when the magnetic field is not generated, the deformation amount of the wall portion when the magnetic portion is generated and the wall portion is bent in the reverse direction can be increased.

  In the present invention, the ejection actuator supplies the ejection energy by applying pressure to the ink in the ink flow path, and a part of the ink flow path includes the ejection actuator The throttle part may reflect a pressure wave generated when pressure is applied to the ink in the ink flow path, and the wall part may define at least a part of an inner wall surface of the throttle part. According to this, the cross-sectional area of the diaphragm portion changes according to the temperature change of the ink.

  Moreover, in this invention, it is preferable that the said wall part consists of a thin film-like member. According to this, a wall part can be made easy to bend.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic side view showing the overall configuration of the ink jet printer according to the first embodiment of the present invention. As shown in FIG. 1, the inkjet printer 101 is a color inkjet printer having four inkjet heads 1. The ink jet printer 101 has a control device 16, and the control device 16 controls the operation of each part of the ink jet printer 101. Further, the ink jet printer 101 is provided with a paper feed unit 11 on the left side in the drawing and a paper discharge unit 12 on the right side in the drawing.

  Inside the ink jet printer 101, a paper transport path is formed through which the paper P is transported from the paper feed unit 11 toward the paper discharge unit 12. A pair of feed rollers 5a and 5b for nipping and conveying the paper are arranged immediately downstream of the paper supply unit 11. The pair of feed rollers 5a and 5b are for feeding the paper P from the paper feeding unit 11 to the right in the drawing. In an intermediate portion of the paper conveyance path, two belt rollers 6 and 7, an endless conveyance belt 8 wound around the rollers 6 and 7, and an area surrounded by the conveyance belt 8 A belt conveyance mechanism 13 including a platen 15 disposed in a position facing the inkjet head 1 is provided. The platen 15 supports the conveyance belt 8 so that the conveyance belt 8 does not bend downward in a region facing the inkjet head 1. A nip roller 4 is disposed at a position facing the belt roller 7. The nip roller 4 presses the sheet P fed from the sheet feeding unit 11 by the feed rollers 5 a and 5 b against the outer peripheral surface 8 a of the transport belt 8.

  The conveyor belt 8 is driven by a conveyor motor (not shown) rotating the belt roller 6. Thereby, the conveyance belt 8 conveys the paper P pressed against the outer peripheral surface 8 a by the nip roller 4 toward the paper discharge unit 12 while being adhesively held. A weak adhesive silicon resin layer is formed on the surface of the conveyor belt 8.

  A peeling mechanism 14 is provided immediately downstream of the conveying belt 8 along the sheet conveying path. The peeling mechanism 14 is configured to peel the paper P adhered to the outer peripheral surface 8a of the conveyor belt 8 from the outer peripheral surface 8a and send it to the right paper discharge unit 12 on the left side in the drawing. .

  The four inkjet heads 1 are fixed side by side along the transport direction corresponding to four color inks (magenta, yellow, cyan, and black). That is, the ink jet printer 101 is a line printer. Each of the four inkjet heads 1 has a head body 2 at the lower end thereof. The head main body 2 has an elongated rectangular parallelepiped shape that is long in a direction orthogonal to the transport direction. Further, the bottom surface of the head main body 2 is an ink ejection surface 2a that faces the outer peripheral surface 8a. When the paper P transported by the transport belt 8 sequentially passes immediately below the four head bodies 2, ink of each color is ejected from the ink ejection surface 2a toward the upper surface of the paper P, that is, the printing surface. Thus, a desired color image can be formed on the printing surface of the paper P.

  Hereinafter, the inkjet head 1 will be described in more detail. FIG. 2 is a side view including a partial longitudinal section of the inkjet head 1.

  The inkjet head 1 has a reservoir unit 3 that supplies ink to the head body 2. An ink flow path 3 a is formed in the reservoir unit 3. An opening 3b of the ink flow path 3a is formed on the upper surface of the reservoir unit 3, and a plurality of openings 3c of the ink flow path 3a are formed on the lower surface of the reservoir unit 3. The opening 3 b communicates with the ink tube 31, and the opening 3 c communicates with a manifold channel 105 (described later) formed in the head body 2. The ink tube 31 communicates with an ink tank (not shown), and ink is supplied from the ink tank to the ink flow path 3a through the ink tube 31 and the opening 3b. The ink supplied into the ink flow path 3 a is further supplied to the head body 2.

  A temperature sensor 18 is installed in the ink flow path 3a. The temperature sensor 18 detects the temperature of the ink in the ink flow path 3 a and transmits the detection result to the control device 16. The control device 16 has a pressure control unit 17 (pressure control means). The pressure control unit 17 controls the operation of the pump 33 based on the detection result from the temperature sensor 18. The detailed control content of the pressure control unit 17 will be described later.

  In the reservoir unit 3, an air channel 3d is formed at a location where the ink channel 3a is not formed. An opening 3e of the air flow path 3d is formed on the upper surface of the reservoir unit 3, and an opening 3f of the air flow path 3d is formed on the lower surface of the reservoir unit 3. An air tube 32 communicates with the opening 3 e, and a pump 33 (pressure changing means) is connected to the air tube 32. The opening 3f communicates with an air flow path 141 described later formed in the head body 2. The pump 33 changes the pressure in the air flow path 141 of the head body 2 through the air tube 32 and the air flow path 3d. As the pump 33, various pumps such as a cylinder pump, a tube pump, and a roller pump can be used.

  Next, the head body 2 will be described with reference to FIGS. FIG. 3 is a plan view of the head body 2. FIG. 4 is an enlarged view of a region surrounded by a one-dot chain line in FIG. In FIG. 4, for convenience of explanation, the pressure chamber 110, the aperture 112, and the nozzle 108 that are to be drawn by broken lines below the actuator unit 21 are drawn by solid lines. FIG. 5 is a partial cross-sectional view taken along the line IV-IV shown in FIG.

  As shown in FIG. 3, the head body 2 includes a flow path unit 9 and an actuator unit 21. The inkjet head 1 further includes a driver IC (not shown) that generates a drive signal for driving the actuator unit 21. A signal from the driver IC is supplied to the actuator unit 21 through a flexible printed cable on which signal lines are wired. Note that the flexible printed cable is not shown in the drawing related to the first embodiment, but is shown as the flexible printed cable 41 in FIG. 7 related to the second embodiment.

  The head body 2 includes a flow path unit 9 and four actuator units 21 fixed to the upper surface 9 a of the flow path unit 9. As shown in FIG. 4, the flow path unit 9 includes an ink flow path including the pressure chamber 110 and the like, and an air flow path filled with air. The actuator unit 21 includes a plurality of actuators corresponding to the pressure chambers 110, and has a function of selectively applying ejection energy to the ink in the pressure chambers 110. Hereinafter, the ink flow path formed in the flow path unit 9 will be described.

  The flow path unit 9 has a rectangular parallelepiped shape. A total of ten ink supply ports 105 b are opened on the upper surface 9 a of the flow path unit 9 corresponding to the openings 3 c on the reservoir unit 3 side. As shown in FIGS. 3 and 4, a manifold channel 105 communicating with the ink supply port 105 b and a plurality of sub-manifold channels 105 a branched from the manifold channel 105 are formed inside the channel unit 9. . Each of the sub-manifold channels 105 a extends below the actuator unit 21 in parallel with the longitudinal direction of the channel unit 9. On the lower surface of the flow path unit 9, an ink ejection surface 2a in which the openings of a large number of nozzles 108 are arranged in a matrix is formed. A large number of pressure chambers 110 are also arranged in a matrix like the nozzles 108 on the fixed surface of the actuator unit 21 in the flow path unit 9.

  In the present embodiment, 16 rows of pressure chambers 110 arranged at equal intervals in the longitudinal direction of the flow path unit 9 are arranged in parallel to each other in the short direction. The number of pressure chambers 110 included in each pressure chamber row is arranged so as to gradually decrease from the long side toward the short side corresponding to the outer shape (trapezoidal shape) of the actuator unit 21 described later. Yes. The nozzle 108 is also arranged in the same manner.

  A plurality of apertures 112 constituting a part of the ink flow path from the sub-manifold flow path 105 a to each pressure chamber 110 are formed in the flow path unit 9. As shown in FIG. 4, the aperture 112 constitutes aperture rows 121 a to 121 p arranged in parallel to the longitudinal direction of the flow path unit 9. Among these, the aperture rows 121a to 121d are formed so as to be close to each other in a region where the sub manifold channel 105a is formed in a plan view. The aperture rows 121e to 121h, the aperture rows 121i to 121l, and the aperture rows 121m to 121p are also formed so as to be densely packed in the region where the sub-manifold channel 105a is formed in plan view.

  As shown in FIG. 5A, the flow path unit 9 includes a cavity plate 122, a base plate 123, an aperture plate 124, a supply plate 125, manifold plates 126, 127, 128, a cover plate 129, and a nozzle in order from the top. The plate 130 is composed of nine metal plates such as stainless steel. These plates 122 to 130 have a rectangular planar shape that is long in the main scanning direction.

  The cavity plate 122 is formed with a large number of through holes corresponding to the ink supply ports 105b and substantially rhombic through holes corresponding to the pressure chambers 110. In the base plate 123, a communication hole between the pressure chamber 110 and the aperture 112 and a communication hole between the pressure chamber 110 and the nozzle 108 are formed for each pressure chamber 110, and the communication between the ink supply port 105 b and the manifold channel 105 is formed. A hole (not shown) is formed. The aperture plate 124 is formed with a through hole serving as the aperture 112 for each pressure chamber 110 and a communication hole between the pressure chamber 110 and the nozzle 108, and a communication hole between the ink supply port 105 b and the manifold channel 105 (see FIG. (Not shown) is formed. In the supply plate 125, a communication hole between the aperture 112 and the sub manifold channel 105 a and a communication hole between the pressure chamber 110 and the nozzle 108 are formed for each pressure chamber 110, and the ink supply port 105 b and the manifold channel 105 are formed. A communication hole (not shown) is formed. In the manifold plates 126, 127, and 128, a communication hole between the pressure chamber 110 and the nozzle 108 for each pressure chamber 110, and a through-hole that is connected to each other at the time of stacking to form the manifold channel 105 and the sub-manifold channel 105a are formed. Has been. In the cover plate 129, a communication hole between the pressure chamber 110 and the nozzle 108 is formed for each pressure chamber 110. A nozzle 108 corresponding to each pressure chamber 110 is formed in the nozzle plate 130. On the lower surface of the nozzle plate 130, an opening 108a (discharge port) of the nozzle 108 is formed.

  By laminating these plates 122 to 130 in alignment with each other, the aperture 112 and the pressure chamber 110 are connected in the flow path unit 9 from the manifold flow path 105 to the sub manifold flow path 105a, and from the outlet of the sub manifold flow path 105a. A large number of individual ink flow paths 132 that reach the nozzle 108 are formed. Of these, the aperture 112 has a cross-sectional area in the direction perpendicular to the ink flow direction (the direction in which the individual ink flow path 132 extends) other than the nozzle 108 in the individual ink flow path 132, as shown in FIG. The smallest part.

  Next, the ink flow in the flow path unit 9 will be described. The ink supplied from the reservoir unit into the flow path unit 9 via the ink supply port 105b is branched from the manifold flow path 105 to the sub-manifold flow path 105a. The ink in the sub-manifold channel 105a flows into each individual ink channel 132 and reaches the nozzle 108 through the aperture 112 and the pressure chamber 110 functioning as a throttle.

  The actuator unit 21 will be described. As shown in FIG. 3, each of the four actuator units 21 has a trapezoidal planar shape, and is arranged in a staggered manner so as to avoid the ink supply ports 105b. Furthermore, the parallel opposing sides of each actuator unit 21 are along the longitudinal direction of the flow path unit 9, and the oblique sides of the adjacent actuator units 21 overlap each other in the width direction (sub-scanning direction) of the flow path unit 9. Yes.

  The actuator unit 21 has a laminated structure in which a plurality of piezoelectric sheets made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity are laminated. The piezoelectric sheet is a continuous flat plate having a size straddling a plurality of pressure chambers 110. An individual electrode (not shown) is arranged at a position facing the pressure chamber 110 on the upper surface of the uppermost piezoelectric sheet. A common electrode (not shown) formed on the entire surface of the uppermost piezoelectric sheet is disposed on the lower surface of the uppermost piezoelectric sheet.

  The common electrode is equally grounded in the region corresponding to all the pressure chambers 110. On the other hand, a drive signal from the driver IC is selectively input to the individual electrode. That is, in the actuator unit 21, a portion sandwiched between the individual electrodes and the pressure chambers 110 functions as individual actuators (injection actuators), and a plurality of actuators corresponding to the number of pressure chambers 110 are formed.

  Here, a driving method of the actuator unit 21 will be described. The piezoelectric sheet is polarized in the thickness direction, and the portion where the individual electrode is disposed functions as an active layer. In this active layer, when an electric field is applied to the piezoelectric sheet in the polarization direction with the individual electrode having a potential different from that of the common electrode, the electric field application portion of the piezoelectric sheet is distorted by the piezoelectric effect. For example, if the polarization direction is the same as the electric field application direction, the active portion contracts in a direction (plane direction) perpendicular to the polarization direction. That is, the actuator unit 21 is a so-called unimorph type actuator in which the uppermost piezoelectric sheet is a layer including an active portion and the lower piezoelectric sheet is an inactive layer. Since the piezoelectric sheet is fixed to the upper surface of the cavity plate 122 that defines the pressure chamber 110, a difference in distortion in the plane direction occurs between the electric field application portion of the uppermost piezoelectric sheet and the piezoelectric sheet below it. The entire piezoelectric sheet is deformed (unimorph deformation) so as to be convex toward the pressure chamber 110. As a result, pressure is applied to the ink in the pressure chamber 110 and ink droplets are ejected from the nozzle 108. That is, the pressure chamber 110 corresponds to a region in the individual ink flow path 132 where the ejection energy for ejecting ink from the opening 108a is supplied from the actuator unit 21 to the ink.

  Here, the individual ink flow path 132 is narrowed by arranging the aperture 112 between the pressure chamber 110 and the sub-manifold flow path 105a. That is, the aperture 112 corresponds to the throttle portion of the individual ink flow path 132. Therefore, when the pressure is applied to the pressure chamber 110, the ink in the individual ink flow path 132 can easily flow toward the nozzle 108 without flowing back to the sub manifold flow path 105a. Further, when ink droplets are ejected by a so-called fill before fire method, a pressure wave generated by applying a negative pressure to the ink in the pressure chamber 110 is reflected by the aperture 112. Then, a positive pressure is applied to the ink in the pressure chamber 110 in accordance with the timing at which the reflected wave reaches the pressure chamber 110. As described above, the aperture 112 also has a function of reflecting the pressure wave from the pressure chamber 110. Note that after ink droplets are ejected from the nozzle 108, the ink is refilled from the sub-manifold channel 105 a to the pressure chamber 110 through the aperture 112.

  Next, the air flow path formed in the flow path unit 9 will be described. As partially shown in FIG. 3, an air flow path 141 is formed in the flow path unit 9. The air flow path 141 is filled with air. An opening 141 b of the air flow path 141 is formed on the upper surface of the flow path unit 9. The opening 141b communicates with the opening 3f on the reservoir unit 3 side. The air flow path 141 branches into a plurality of branch flow paths 141a (fluid chambers) in a region (not shown) in the flow path unit 9. FIG. 4 shows a part of the branch channel 141a. The branch flow path 141a extends in parallel to the longitudinal direction of the flow path unit 9, and is arranged so as to overlap two adjacent aperture rows in plan view. For example, as shown in FIG. 4, one branch channel 141a overlaps the aperture rows 121i and 121j, and another branch channel 141a overlaps the aperture rows 121k and 121l. These branch flow paths 141a communicate with each other through a plurality of communication flow paths 141c. In FIG. 4, other branch flow paths 141 a are not shown for the sake of clarity, but the same applies to the aperture rows 121 a to 121 d, the aperture rows 121 e to 121 h, and the aperture rows 121 m to 121 p. The branch flow path 141a is formed in the positional relationship.

  As shown in FIG. 5A, the branch channel 141 a is formed in the base plate 123 so as to open on the lower surface of the base plate 123. A diaphragm 151 (wall portion) is installed between the branch channel 141 a and the aperture 112. The diaphragm 151 is a thin film member made of a resin material, a metal material, or the like, and is configured to be easily deformed as compared with other plates constituting the flow path unit 9. The diaphragm 151 has a shape including a region where the branch flow channel 141a and the aperture 112 overlap in a plan view. In addition, the space in the branch flow path 141a and the space in the aperture 112 are disposed between the base plate 123 and the aperture plate 124 so as to be completely separated. Accordingly, the diaphragm 151 defines a part of the inner wall surface of the aperture 112 and also defines a part of the inner wall surface of the branch flow path 141a. Further, the branch flow path 141a faces the aperture 112 with the diaphragm 151 interposed therebetween. The peripheral edge of the diaphragm 151 is securely bonded to one or both of the base plate 123 and the aperture plate 124. As a result, even if the diaphragm 151 is deformed, the ink does not flow out from the aperture 112 to the branch flow path 141a or air does not flow out from the branch flow path 141a to the aperture 112.

  The diaphragm 151 is configured to be deformed in accordance with the difference between the pressure in the branch flow path 141a and the pressure in the aperture 112. For example, when the pressure in the branch flow path 141a is equal to the pressure in the aperture 112, the diaphragm 151 is in a horizontally extending state as shown in FIG. On the other hand, when the pressure in the branch flow path 141a becomes larger than the pressure in the aperture 112, the state is bent in a convex manner toward the inside of the aperture 112 as shown in FIG. Therefore, in the state of FIG. 5B, the cross-sectional area of the aperture 112 is smaller than the state of FIG. 5A in the direction orthogonal to the ink flow direction (the direction along the individual ink flow path 132). That is, the flow path resistance of the aperture 112 in the state of FIG. 5B is larger than the flow path resistance of the aperture 112 in the state of FIG.

  By the way, as described above, after the ink is ejected from the nozzle 108, the ink is refilled through the aperture 112 from the sub manifold channel 105a to the pressure chamber 110. However, when the temperature of the ink flowing through the individual ink flow path 132 changes, the ability to refill ink from the sub-manifold flow path 105a to the pressure chamber 110 may change. This is because when the ink temperature changes, the viscosity of the ink changes accordingly. That is, the ink viscosity decreases as the ink temperature increases. As a result, the ink easily flows, so that the ink is easily refilled from the sub manifold channel 105a to the pressure chamber 110. On the other hand, the ink viscosity increases as the ink temperature decreases. This makes it difficult for the ink to flow, so that it is difficult to refill the ink from the sub-manifold flow path 105a to the pressure chamber 110.

  In addition, the ability to refill ink changes depending on the flow path resistance of the aperture 112. This is because if the flow path resistance is large, it becomes difficult for ink to flow, and if the flow path resistance is small, ink tends to flow. Therefore, for example, it is assumed that the shape and size of the aperture 112 are determined so that the flow path resistance of the aperture 112 has a certain value. Here, it is assumed that the value of the flow path resistance is adjusted so that an appropriate amount of ink is refilled when the ink reaches a certain temperature. In this case, if the temperature of the ink becomes higher than the certain temperature, the ink viscosity decreases and the ink easily flows, so that the refill amount becomes excessive. On the other hand, when the ink becomes lower than the certain temperature, the ink viscosity increases and the ink does not flow easily, so that the refill amount is insufficient.

  Therefore, in the present embodiment, the pressure control unit 17 controls the pump 33 as follows (see FIG. 2). The pressure control unit 17 holds control data in which the control amount of the pump 33 is associated with the ink temperature value. Based on the detection result from the temperature sensor 18, the control amount of the pump 33 corresponding to the ink temperature is acquired from the control data. The pressure control unit 17 controls the pump 33 based on the acquired control amount, and changes the pressure in the air flow path 141. On the other hand, when the pump 33 changes the pressure in the air flow path 141, the pressure in the branch flow path 141a also changes. As a result, the diaphragm 151 is deformed as shown in FIG. 5B, so that the aperture 112 is deformed and the flow path resistance of the aperture 112 changes. That is, the pump 33 and the air flow path 141 of the present embodiment constitute the flow path deforming means of the present invention that deforms the diaphragm 151 (wall portion) so that the cross-sectional area of the aperture 112 (ink flow path) changes. is doing.

  Here, the control data is adjusted by the pump 33 so that the pressure in the air flow path 141 increases as the ink temperature increases. That is, as the ink temperature is higher, the diaphragm 151 is deformed by the pressure in the branch flow path 141a, and the flow path resistance of the aperture 112 is adjusted to be increased. The flow path resistance of the aperture 112 preferably changes so that the ability to refill ink from the sub-manifold flow path 105a to the pressure chamber 110 is constant regardless of the change in ink temperature.

  Therefore, when the ink temperature is high and the ink viscosity is low, the pressure control unit 17 controls the pump 33 so that the flow of the aperture 112 is increased while the ink easily flows. Further, when the ink temperature is low and the ink viscosity is high, the pressure control unit 17 controls the pump 33 so that the flow resistance of the aperture 112 becomes small while the ink hardly flows. Thus, according to the present embodiment, control is performed such that the ability to refill ink from the sub-manifold flow path 105a into the pressure chamber 110 is less likely to change according to the ink temperature.

[Second Embodiment]
Hereinafter, a second embodiment which is an example of another embodiment of the present invention will be described. In the second embodiment, the description of the same configuration as that of the first embodiment will be omitted as appropriate. In addition, the same reference numerals as those used in the description of the first embodiment below indicate the same configurations as the configurations of the first embodiment.

  As shown in FIG. 6, the inkjet head 201 according to the second embodiment includes a reservoir unit 203 and a head main body 202. The reservoir unit 203 is formed with an ink flow path 3a as in the case of the reservoir unit 3, but is not provided with an air flow path. A temperature sensor 18 is provided in the ink flow path 3a, and the detection result is transmitted to the control unit 216. The inkjet head 201 includes an electromagnet 233 and a power supply unit 218 (current supply means) that supplies current to the electromagnet 233. The electromagnet 233 is installed on the upper surface of the head body 202. The power supply unit 218 can cause a current to flow through the electromagnet 233 or stop the current from flowing. In addition, the amount of current flowing through the electromagnet 233 can be adjusted. The control unit 216 includes a current control unit 217 (current control unit) that controls the current that the power supply unit 218 passes through the electromagnet 233. The current control unit 217 controls current supply from the power supply unit 218 to the electromagnet 233 based on the detection result from the temperature sensor 18.

  FIG. 7 is a plan view of the electromagnet 233 and the head main body 202. The ink jet head 201 has four electromagnets 233. The electromagnet 233 has a magnetic core 233b and a winding 233a wound around the magnetic core 233b. The magnetic core 233b has a prismatic shape whose upper and lower surfaces are horizontal. Both the upper surface and the lower surface of the magnetic core 233 b have the same shape as the planar shape of the actuator unit 21. The electromagnet 233 is installed above the head main body 202 so as to substantially overlap the actuator unit 21 in plan view. A flexible printed cable 41 that supplies a drive signal for driving the actuator unit 21 is connected to the upper surface of the actuator unit 21. The electromagnet 233 is disposed further above the flexible printed cable 41. When a current flows through the winding 233a, a magnetic field that penetrates the magnetic core 233b in the vertical direction is generated.

  FIG. 8 is a diagram corresponding to FIG. 5 of the first embodiment. In the flow path unit 209 of the second embodiment, an air flow path 141 and its branch flow path 141a are formed in the base plate 123 as in the first embodiment. However, in the second embodiment, the air flow path 141 does not communicate with a pump or the like and is open to the atmosphere. A diaphragm 251 is installed between the branch channel 141 a and the aperture 112. The shape, size, and arrangement of the diaphragm 251 are the same as those of the diaphragm 151. However, the diaphragm 251 is made of a ferromagnetic material, for example, 400 series SUS. On the other hand, in the flow path unit 209, other parts such as the cavity plate 122 and the base plate 123 are made of a material having no ferromagnetism, for example, 300 series SUS.

  Therefore, when a magnetic field is generated by passing an electric current through the electromagnet 233, the cavity plate 122 is not magnetized, but the diaphragm 251 is magnetized. As a result, the diaphragm 251 is attracted to the upper electromagnet 233, and as a result, as shown in FIG. 8B, the diaphragm 251 is bent convexly into the branch flow path 141a. When no magnetic field is generated from the electromagnet 233, the diaphragm 251 takes a horizontally extending state as shown in FIG.

  The current control unit 217 holds control data in which a current value flowing through the electromagnet 233 is associated with an ink temperature value. Based on the detection result from the temperature sensor 18, the current value corresponding to the ink temperature is acquired from the control data. The current control unit 217 controls the power supply unit 218 to supply the current having the acquired current value to the electromagnet 233. Accordingly, the diaphragm 251 is deformed as shown in FIG. 8B, the aperture 112 is deformed, and the flow path resistance of the aperture 112 is changed. That is, the power supply unit 218 and the electromagnet 233 of the present embodiment constitute the flow path deforming means of the present invention that deforms the diaphragm 251 (wall part) so that the cross-sectional area of the aperture 112 (ink flow path) changes. ing.

  Here, the control data is adjusted so that the current flowing through the electromagnet 233 increases as the ink temperature decreases. That is, the lower the ink temperature is, the stronger the magnetic field from the electromagnet 233 is, and the diaphragm 251 is greatly deformed, so that the flow path resistance of the aperture 112 is adjusted. The flow path resistance of the aperture 112 preferably changes so that the ability to refill ink from the sub-manifold flow path 105a to the pressure chamber 110 remains constant even if the ink temperature changes.

  Therefore, when the ink temperature is high and the ink viscosity is low, the ink can easily flow, while the current control unit 217 reduces the current flowing through the electromagnet 233 so that the flow path resistance of the aperture 112 is increased, or stops the current supply. To do. In addition, when the ink temperature is low and the ink viscosity is high, the ink does not flow easily, while the current control unit 217 increases or stops the current flowing through the electromagnet 233 so that the flow path resistance of the aperture 112 decreases. Restart current supply. As described above, according to the second embodiment, similarly to the first embodiment, the control for refilling the ink from the sub-manifold flow path 105a to the pressure chamber 110 is less likely to change according to the ink temperature. Is executed.

[Third Embodiment]
Hereinafter, a third embodiment which is an example of still another embodiment of the present invention will be described with reference to FIG. As in the second embodiment, the third embodiment uses an electromagnet 233 to deform the diaphragm. In the third embodiment, the description of the same configurations as those of the first and second embodiments is omitted as appropriate. In addition, the same reference numerals as those used in the description of the first and second embodiments below indicate the same configurations as those of the first and second embodiments.

  The head main body 302 of the third embodiment has a flow path unit 309. In the flow path unit 309, the base plate 323 does not have a structure corresponding to the air flow path 141 or the branch flow path 141a of the first and second embodiments. On the other hand, an air chamber 341 is formed in the supply plate 325 in the third embodiment. Unlike the first and second embodiments, the air chamber 341 does not communicate with the outside of the flow path unit 309 and constitutes a sealed space. The air chamber 341 is formed so as to overlap each aperture 112 in a plan view. Further, a rib portion 325a is formed between two apertures 112 adjacent to each other in plan view.

  A diaphragm 351 is installed between the air chamber 341 and the aperture 112. The diaphragm 351 is a thin film member made of a ferromagnetic material. The diaphragm 351 is disposed so as to straddle the plurality of apertures 112 as shown in FIG. The diaphragm 351 defines a part of the inner wall surface of the aperture 112 and also defines a part of the inner wall surface of the air chamber 341, and completely separates the space in the air chamber 341 and the space in the aperture 112. ing.

  The flow path unit 309 is configured as follows so that the diaphragm 351 is bent inward toward the air chamber 341 in a state where no magnetic field is generated from the electromagnet 233. The aperture plate 324 of the flow path unit 309 is formed of a material having a smaller expansion coefficient than the material forming the supply plate 325. Accordingly, the rib portion 324a facing the rib portion 325a with the diaphragm 351 interposed therebetween is configured to have a smaller linear expansion coefficient in the left-right direction in FIG. 9 than the rib portion 325a. Further, the rib portion 324a and the rib portion 325a are designed so that the widths in the left-right direction in FIG. 9 are equal to each other at a temperature sufficiently higher than the assumed usage environment of the present embodiment. It is glued.

  Therefore, in an actual use environment, the rib portion 325a contracts more than the rib portion 324a in the left-right direction of FIG. As a result, a bending moment is generated between the rib portion 325a and the rib portion 324a. This bending moment is a moment that causes the region sandwiched between the rib portion 325a and the rib portion 324a in the diaphragm 351 to bend upward and convex. Such a bending moment acts on the diaphragm 351 so as to bend downward toward a region adjacent to both ends of the rib portions 324a and 325a. As a result, the diaphragm 351 takes a state of being bent convexly into the air chamber 341 as shown in FIG.

  Further, the pressure in the air chamber 341 is adjusted to be equal to or smaller than the pressure on the aperture 112 side in such a bent state. For example, in the state in which the diaphragm 351 is bent as shown in FIG. 9A, the aperture 112 and the air chamber 341 are sealed so as to be at atmospheric pressure. Therefore, when the diaphragm 351 tries to bend into the aperture 112, the pressure in the air chamber 341 decreases, and thereby a force for pulling back into a state in which the diaphragm 351 is bent convexly into the air chamber 341 acts on the diaphragm 351. To do.

  As described above, the flow path unit 309 is configured such that the diaphragm 351 surely bends downward in a state where no magnetic field is generated from the electromagnet 233.

  In the third embodiment, the same current control unit 217 and power source unit 218 as those in the second embodiment are provided. The current control unit 217 controls the power supply unit 218 based on the detection result from the temperature sensor 18, and increases the current flowing through the electromagnet 233 when the ink temperature increases. As a result, as shown in FIG. 9B, the diaphragm 351 can be bent convexly into the aperture 112, and the flow path resistance of the aperture 112 can be increased. Therefore, also in the third embodiment, it is possible to execute control such that the ability to refill ink from the sub-manifold flow path 105a to the pressure chamber 110 is less likely to change according to the ink temperature.

  Further, according to the third embodiment, in a state where no magnetic field is generated by the electromagnet 233, the diaphragm 351 is bent convexly into the air chamber 341 as shown in FIG. When a magnetic field is generated by the electromagnet 233, the diaphragm 351 can be bent convexly into the aperture 112. Therefore, the diaphragm 351 can be greatly deformed as compared with the second embodiment, and the flow path resistance of the aperture 112 can be changed more greatly.

<Modification>
The above is a description of a preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the means for solving the problem. It is possible.

  For example, in each of the above-described embodiments, a diaphragm for deforming the individual ink flow path 132 is installed so as to determine the inner wall surface of the aperture 112. However, the diaphragm may be installed at any location as long as it is between the pressure chamber 110 and the sub manifold channel 105a.

  In the first embodiment, the air flow path 141 and the branch flow path 141a are filled with air, but a gas other than air or other fluid may be filled. For example, instead of filling only gas, a liquid may be injected.

  In each of the above-described embodiments, the temperature sensor 18 is installed in the ink flow path 3a of the reservoir unit 3, but may be installed in the ink flow path in the flow path unit.

  In the first embodiment, it is assumed that the pressure in the branch channel 141a is increased according to the ink temperature. In this case, the pressure may be continuously changed according to the ink temperature, or may be changed stepwise. When changing in stages, it may be two stages or three or more stages.

  Further, in the first embodiment, it is assumed that the diaphragm 151 is bent convexly toward the inside of the aperture 112 by increasing the pressure in the air flow path 141. However, by reducing the pressure in the air flow path 141, the diaphragm 151 may be bent convexly toward the branch flow path 141a. In this case, the pump 33 may be controlled so that the diaphragm 151 is bent more greatly as the ink temperature is lower.

  In the second and third embodiments, it is assumed that the current supplied to the electromagnet 233 is changed according to the ink temperature. In this case, the current may be continuously changed according to the ink temperature, or may be changed stepwise. When changing in stages, it may be two stages or three or more stages. For example, the control is executed such that the two states of a state in which no current is supplied to the electromagnet 233 and a state in which a constant current is supplied to the electromagnet 233 are switched based on whether or not the ink temperature exceeds a certain temperature. Also good.

1 is a schematic configuration diagram of an ink jet printer according to a first embodiment of the present invention. FIG. 2 is a side view including a partial longitudinal section of the ink jet head of FIG. 1. FIG. 2 is a plan view of the head body of FIG. 1. FIG. 4 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. 3. It is a fragmentary sectional view in alignment with the IV-IV line shown in FIG. It is a side view containing a partial longitudinal cross-section of the inkjet head of 2nd Embodiment. It is a top view of the electromagnet and head body of a 2nd embodiment. It is a fragmentary sectional view of the channel unit of a 2nd embodiment, and is a figure corresponding to Drawing 5 of a 1st embodiment. It is a fragmentary sectional view of the channel unit of a 3rd embodiment, and is a figure corresponding to Drawing 5 of a 1st embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Head main body 3 Reservoir unit 9 Flow path unit 16 Control apparatus 17 Pressure control part 18 Temperature sensor 33 Pump 101 Inkjet printer 108 Nozzle 108a Opening 110 Pressure chamber 112 Aperture 112 Each aperture 112 Aperture 132 Individual ink flow path 141 Air flow Path 141a Branch channel 151 Diaphragm 201 Inkjet head 202 Head body 203 Reservoir unit 209 Channel unit 216 Control unit 217 Current control unit 218 Power source unit 233 Electromagnet 251 Diaphragm 302 Head body 309 Channel unit 341 Air chamber 351 Diaphragm

Claims (7)

An ejection port for ejecting ink;
An ink flow path for supplying ink to the ejection port;
An ejection actuator that supplies ejection energy for ejecting ink from the ejection port to the ink in the ink flow path;
A wall portion defining an inner wall surface of the ink flow path at a position separated from the discharge port along the ink flow path from a position where the ejection energy is supplied;
A temperature sensor for detecting the temperature of the ink in the ink flow path;
An ink jet comprising: flow path deforming means for deforming the wall portion so that a cross-sectional area perpendicular to the flow direction of the ink flow path decreases as the temperature indicated by the detection result of the temperature sensor increases. head. The flow path deforming means is configured such that a part of an inner wall surface is defined by the wall part, a fluid chamber facing the ink flow path across the wall part, and the fluid chamber so that the wall part is deformed. Pressure changing means for changing the pressure,
2. The ink jet head according to claim 1, further comprising pressure control means for controlling the pressure changing means so that the pressure in the fluid chamber increases as the temperature indicated by the detection result of the temperature sensor increases. .   The inkjet head according to claim 2, wherein the fluid chamber is filled with a gas. The wall portion is made of a ferromagnetic material,
The flow path deforming means includes an electromagnet that generates a magnetic field that deforms the wall portion, and a current supply means that supplies a current to the electromagnet,
Current control means is further provided for controlling the current supplied from the current supply means to the electromagnet so that the cross-sectional area perpendicular to the flow direction of the ink flow path decreases as the temperature indicated by the detection result of the temperature sensor increases. The inkjet head according to claim 1, wherein the inkjet head is provided.   In a state where no current is supplied to the electromagnet, the wall portion bends in a direction opposite to the direction toward the ink flow path, and when the current is supplied to the electromagnet, the wall portion The ink-jet head according to claim 4, wherein a magnetic field is generated so as to bend toward the inside of the road. The ejection actuator supplies the ejection energy by applying pressure to the ink in the ink flow path;
A part of the ink flow path is a throttle part that reflects a pressure wave generated when the ejection actuator applies pressure to the ink in the ink flow path,
The inkjet head according to claim 1, wherein the wall portion defines an inner wall surface of at least a part of the throttle portion.   The ink-jet head according to claim 1, wherein the wall portion is made of a thin film member.

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