JP6031957B2 - Ink jet head and image forming apparatus - Google Patents

Description

The present invention relates to an inkjet head and an image forming apparatus .

In general, an inkjet image forming apparatus includes an inkjet head provided with a plurality of nozzles. The plurality of nozzles are provided along a predetermined direction to form a nozzle row.
Also, inkjet heads such as image forming apparatuses using phase transition inks whose ink viscosity changes significantly with temperature, thermal type image forming apparatuses that discharge ink with bubbles generated in the ink by heating the ink, etc. In some image forming apparatuses, ink is heated. Each component constituting the inkjet head of such an image forming apparatus undergoes expansion due to heating, that is, thermal expansion. Such thermal expansion may cause warpage of the substrate in the ink jet head, and thus measures against warpage are applied to the substrate of the ink jet head. As an inkjet head in which countermeasures against warping of the substrate are taken, for example, an inkjet head using a substrate in the inkjet head as a multilayer structure and a reinforcing material (for example, Patent Document 1), a plurality of substrates in consideration of thermal expansion An ink jet head (for example, Patent Document 2) is known.

JP 2007-30283 A JP 2006-21434 A

By the way, if there is a difference in the degree of expansion between the two side surfaces facing each other across the nozzle row, a difference occurs in the amount of change in length along the nozzle row direction on each of the two side surfaces as shown in FIG. As a result, warpage called BOW occurs in the nozzle row. Such warpage of the nozzle row causes a shift in the landing position of the ink ejected from each nozzle. Therefore, it is necessary to reduce the warpage of the nozzle row in order to improve the accuracy of the ink landing position. Here, as a simple method for minimizing the warp, there is a method in which each configuration of the inkjet head existing at a position facing each other across the nozzle row is plane-symmetric. This is because, if each configuration is plane-symmetric, the coefficient of thermal expansion is generally uniform, so that it is difficult for differences to occur due to the expansion of the two side surfaces.
However, in recent years, along with the progress of miniaturization of inkjet heads due to the miniaturization of inkjet image forming apparatuses and the reduction in the interval between nozzles, the plane-symmetric arrangement of each configuration of the inkjet head across the nozzle rows Has become difficult. Specifically, the substrate 203 including the wiring 202 to the ejection unit 201 having each nozzle forming the nozzle row, and the holding unit 204 that holds the substrate above the ejection unit 201 are the minimum in the inkjet head 200. In this case, as shown in FIG. 11, the holding unit 204 is provided at a position shifted from the center L in the width direction of the inkjet head 200 according to the thickness of the substrate. In this case, in the ejection unit 201, the side surface on which the holding unit 204 is provided is alleviated by the holding unit 204, while the side surface on the opposite side is not relaxed by the holding unit 204. In addition, since the degree of heat radiation by the holding unit 204 is non-uniform, the amount of change due to the expansion of the two side surfaces becomes non-uniform, causing the nozzle array to warp.

An object of the present invention is to provide an ink jet head and an image forming apparatus capable of preventing warpage of a nozzle row.

An ink jet head according to a first aspect of the present invention includes an ink discharge portion having an ink discharge surface in which a plurality of nozzles that discharge ink are arranged along a predetermined direction, and wiring connected to the ink discharge portion. a substrate, a first holding portion for holding said substrate, said plurality of said ink discharge portion having a second opening for the nozzle and the first aperture and the ink discharge portion to expose the connecting the wiring inside A frame having a cylindrical second holding portion that is accommodated and held , and a connection portion that connects the first holding portion and the second holding portion, and is in a direction along the ink ejection surface. Te, and when the direction orthogonal to the predetermined direction and a width direction, the first holding portion is provided in the front Symbol offset from the center of the front Symbol width direction of the second holding portion position, the connecting portion If the in the second holding portion second Connection surface for connecting the opening side of the surface, the is characterized in that it is arranged symmetrically with respect to the center in the width direction of the second holding portion.

  A second aspect of the present invention is the ink jet head according to the first aspect, wherein the connection surface is located at the center in the width direction.

A third aspect of the present invention is the ink jet head according to the first or second aspect, wherein the shape of the connection portion is plane-symmetric with respect to the center in the width direction.

Invention of Claim 4 is an inkjet head as described in any one of Claim 1 to 3, Comprising: The said flame | frame WHEREIN: The site | part which connects the said connection part and the said 1st holding | maintenance part, and the said connection part And at least one of the parts connecting the second holding part is provided, and is provided between at least one of the parts and between the first holding part and the second holding part. It has the gap formed.

Invention of Claim 5 is an inkjet head as described in any one of Claim 1 to 4, Comprising: The said flame | frame WHEREIN: The site | part which connects the said connection part and the said 1st holding | maintenance part, and the said connection part And a plurality of portions for connecting the second holding portion to each other .

A sixth aspect of the present invention is the ink jet head according to any one of the first to fifth aspects, further comprising a heating unit that heats ink existing in the ink discharge unit.
A seventh aspect of the present invention is the inkjet head according to any one of the first to sixth aspects, wherein the substrate is disposed closer to the center in the width direction than the first holding portion. It is characterized by.
The invention according to an eighth aspect is the inkjet head according to any one of the first to seventh aspects, wherein the ink ejection portion includes an inkjet head chip having the ink ejection surface, and the inkjet head chip. And a manifold that is provided on a side surface adjacent to the ink discharge surface and stores ink to be supplied to the inkjet head chip.
The invention according to claim 9 is the inkjet head according to any one of claims 1 to 8, wherein the first holding part is a side on which the second opening of the second holding part is provided. Placed in
The connection portion connects an end of the first holding portion on the second holding portion side and the second holding portion.
A tenth aspect of the present invention is an image forming apparatus including the inkjet head according to any one of the first to ninth aspects.

  According to the present invention, warpage of the nozzle row can be prevented.

1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a perspective view which shows the main structures of an inkjet head. FIG. 3 is an exploded perspective view of the ink jet head shown in FIG. 2. It is a schematic sectional drawing of a 2nd holding | maintenance part. FIG. 3 is a schematic diagram of an ink ejection surface viewed from below. It is a flowchart which shows an example of the flow of the process which concerns on the operation control by a control part. It is a figure which shows a flame | frame. FIG. 7A is a perspective view. FIG. 7B is a cross-sectional view when the frame is cut along the XZ plane at the position of the line W shown in FIG. It is the schematic which shows an example in which the some heating part was provided in each of the two side surfaces of a 2nd holding | maintenance part. It is the schematic which shows an example of the connection part which connects the 1st holding | maintenance part 10a and the 2nd holding | maintenance part 10b in three or more places. It is the schematic which shows the example which the curvature produced in the nozzle row. It is a figure which shows the example in which the flame | frame was provided in the position shifted | deviated from the center of the width direction of an inkjet head.

  Embodiments of the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention.
The image forming apparatus 100 is an image forming apparatus that forms an image by ejecting ink. The image forming apparatus 100 includes, for example, an image acquisition unit 110, an image processing unit 120, an image forming unit 130, a detection unit 140, an operation display unit 150, a control unit 160, and the like. Each unit included in the image forming apparatus 100 is connected by a bus B.

The image acquisition unit 110 acquires image data corresponding to an image formed on the recording medium by the image forming apparatus 100.
Specifically, for example, the image acquisition unit 110 is connected so as to be able to transmit data with an external device or a network interface card (NIC) that is communicably connected with an external device, although illustration is omitted. Image data is acquired from a connected external device. As an external device, for example, an image reading apparatus that optically reads a sheet or the like to generate and output image data, a computer that transmits image data to the image forming apparatus 100, and a recording apparatus on which image data is recorded And a reading device for reading a recording medium on which image data is recorded.

The image processing unit 120 performs various image processing on the image data acquired by the image acquisition unit 110.
Specifically, the image processing unit 120 includes, for example, an integrated circuit such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and performs image processing according to functions implemented on the integrated circuit. I do. As image processing performed by the image processing unit 120, for example, color conversion processing such as conversion of an RGB image into a CMYK image, gradation conversion processing such as conversion of a color image into a monochrome image, and a preset number of screen lines Examples thereof include screen processing for converting an image into halftone dots.

The image forming unit 130 forms an image on a recording medium based on the image data that has been subjected to image processing by the image processing unit 120.
Specifically, the image forming unit 130 includes, for example, a conveyance unit that pulls out and conveys a recording medium, a carriage that includes a plurality of inkjet heads 1 that discharge ink to the recording medium conveyed by the conveyance unit, and image data. Accordingly, it includes a drive unit that drives the inkjet head 1 and the carriage, a discharge unit that discharges the recording medium on which the image is formed, a supply unit that supplies ink to the inkjet head 1, a cleaning unit that cleans the inkjet head 1, and the like. . A plurality of inkjet heads 1 are provided in the carriage. FIG. 1 illustrates the configuration of one inkjet head 1 that operates under the control of the control unit 160, and the configuration of other inkjet heads 1 and other image forming units. The illustration of each component 130 is omitted.

The detection unit 140 performs an operation related to detection of the arrangement of a plurality of ink droplets.
Specifically, for example, although not illustrated, the detection unit 140 includes an imaging device provided to image the recording surface of the recording medium, and ink is ejected from the inkjet head 1 of the image forming unit 130. The recording surface of the recording medium is imaged and the captured image is output to the control unit 160.

The operation display unit 150 performs various inputs and display outputs related to the operation of the image forming apparatus 100.
Specifically, the operation display unit 150 includes, for example, a touch panel type input display device, up / down / left / right movement keys and various function keys for performing various selection operations and feed operations, although not shown. Then, a signal corresponding to a user operation input is output to the control unit 160. The operation display unit 150 displays various display contents related to the operation of the image forming apparatus 100 on the input display device under the control of the control unit 160.

  For example, the control unit 160 has a CPU, a RAM, a ROM, and the like (not shown), and reads and executes various software programs, data, and the like corresponding to the processing contents from a recording device such as a ROM. Various processes related to the operation of the image forming apparatus 100 are performed.

Next, the inkjet head 1 will be described.
FIG. 2 is a perspective view showing the main configuration of the inkjet head 1. FIG. 3 is an exploded perspective view of the inkjet head 1 shown in FIG.
The inkjet head 1 has a housing 2 and wiring 3 extending from the housing 2. The housing 2 includes a frame 10 having each configuration relating to ink ejection, such as the drive substrate 11, and a cover 20 that covers the drive substrate 11 and the like held by the frame 10.
Hereinafter, the direction along the standing direction of the cover 20 with respect to the frame 10 is the Z direction, the direction perpendicular to the Z direction and the direction along the longitudinal direction of the frame 10 is the Y direction, and the direction perpendicular to the Z direction and the Y direction is X. It is written as direction. For convenience, the direction in which the wiring 3 extends from the cover 20 among the directions along the Z direction is defined as the upper direction, and the opposite direction, that is, the direction in which ink is ejected from the inkjet head 1 is defined as the lower direction.

The frame 10 includes a first holding unit 10a that holds the drive substrate 11, a second holding unit 10b that holds an inkjet head chip 12, which will be described later, and a connection unit 10c that connects the first holding unit 10a and the second holding unit 10b. Have.
Specifically, in the frame 10, the first holding unit 10 a guides the back side of the plate surface of the driving substrate 11 on the upper side to hold the driving substrate 11, and the second holding unit 10 b on the lower side has the inkjet head chip 12 or the like. Holding. And the connection part 10c is provided so that it may be located between the 1st holding | maintenance part 10a and the 2nd holding | maintenance part 10b. In the present embodiment, the connection portion 10c supports the lower end side of the drive substrate 11, but this is an example and the present invention is not limited to this.
The frame 10 is made of, for example, a metal such as aluminum. However, the frame 10 is an example and is not limited thereto, and any material can be used as the material of the frame 10 as appropriate.

The cover 20 is provided so as to cover the configuration of the frame 10 above the second holding portion 10b.
Specifically, the cover 20 is, for example, a resin molded in a box shape. The cover 20 has an open box-like surface, abuts against the second holding portion 10b of the frame 10 on the opened one surface side, and is bonded to the frame 10 at the abutting portion. Thereby, the cover 20 covers the structure above the 2nd holding | maintenance part 10b among each structure which the flame | frame 10 has, such as the drive board | substrate 11. FIG.

  The wiring 3 is a flexible printed circuit board, for example, and extends from above the cover 20. The wiring 3 has one end 3a connected to the drive substrate 11 and the other end connected to the control unit 160 via the connector 3b. That is, the wiring 3 connects the inkjet head 1 and the control unit 160.

Next, each configuration relating to ink ejection of the frame 10 will be described.
FIG. 4 is a schematic cross-sectional view of the second holding portion 10b.
FIG. 5 is a schematic view of the ink ejection surface viewed from below.
The frame 10 includes an inkjet head chip 12 that ejects ink from a plurality of nozzles 12a provided along a predetermined direction (Y direction).
The inkjet head chip 12 includes, for example, a plurality of nozzles 12a provided on an ink ejection surface along the XY plane, an actuator (not shown) that drives each of the nozzles 12a, and ink for introducing ink to the plurality of nozzles 12a. An inlet 12b and the like are provided. The inkjet head chip 12 has a convex portion 12c that protrudes upward from the upper portion thereof, and engages with a concave portion 10d provided upward inside the second holding portion 10b so that the second holding portion 10b can be engaged with the second holding portion 10b. Retained. The inkjet head chip 12 is connected to the drive substrate 11 via the flexible printed circuit board F. The drive substrate 11 has various circuits, wirings, and the like related to ink ejection by the inkjet head chip 12.
In addition, the nozzle 12a in FIG. 5 is based on schematic illustration, and is illustrated with a larger diameter than actual. The actual diameter of the nozzle 12a is determined according to the diameter of the ejected ink.
FIG. 5 shows the inkjet head chip 12 having a plurality of nozzles 12a provided in a line along the Y direction, but this is an example and the present invention is not limited to this. For example, the inkjet head chip 12 may have a plurality of nozzle rows along the Y direction.

The inkjet head chip 12 is provided so as to be sandwiched between the two manifolds 13 and 14.
Specifically, the two manifolds 13 and 14 are provided at positions facing each other across the inkjet head chip 12 in the X direction. The two manifolds 13 and 14 are made of, for example, resin and have a box-like shape by sandwiching the inkjet head chip 12, and a conduction path for conducting ink is formed inside thereof. The conduction path formed by the two manifolds 13 and 14 functions as an ink supply path that guides the ink supplied via the connecting portion 15 to the ink inlet 12 b of the inkjet head chip 12.
Although not shown, more specifically, the connecting portion 15 and the manifold 14 are connected, and ink is guided to the space between the manifold 13 and the inkjet head chip 12 through the manifold 14, whereby the ink is introduced into the ink inlet 12 b. Is supplied.

The ink used in the present embodiment is an ink whose fluidity greatly changes when heated, and is heated by the heaters 16 a and 16 b in the ink jet head chip 12 and in the vicinity of the ink jet head chip 12.
Specifically, each of the heaters 16a and 16b is a heating wire provided in a plate shape, and is provided so as to sandwich the plurality of nozzles 12a. More specifically, the heaters 16a and 16b are provided at positions facing each other across the inkjet head chip 12 and the two manifolds 13 and 14 in the X direction.
The heaters 16a and 16b are connected to the control unit 160 via connection lines 16c and 16d extending upward. More specifically, the heater 16a and the connection line 16c are connected, and the heater 16b and the connection line 16d are connected, whereby the heaters 16a and 16b are individually connected to the control unit 160. The heaters 16a and 16b operate individually under the control of the control unit 160, and heat the inks existing in the two manifolds 13 and 14 and the inkjet head chip 12 by heating the two manifolds 13 and 14, respectively.
The two side surfaces 10e and 10f of the second holding portion 10b on which the heaters 16a and 16b and the heaters 16a and 16b are provided are provided along the YZ plane. That is, the two side surfaces 10e and 10f of the heaters 16a and 16b and the second holding portion 10b are along the arrangement direction of the plurality of nozzles 12a.

Further, the inkjet head 1 has a temperature detection unit 17 for detecting the temperature of the ink existing in the inkjet head chip 12.
Specifically, the temperature detection unit 17 is a thermistor, for example, and is provided between the manifold 13 and the inkjet head chip 12 to detect the temperature of ink in the ink inlet 12b as shown in FIG. To do.

  As shown in FIGS. 2 to 5, a plate-like chip holding plate 18 along the XY plane is provided on substantially the same plane as the ink ejection surface where the plurality of nozzles 12 a are arranged along the Y direction. It is done. A lower end portion of the inkjet head chip 12 provided with the plurality of nozzles 12 a is provided so as to be exposed downward from a hole provided in the chip holding plate 18.

  The inkjet head 1 is connected to the supply unit via the connection unit 15. The ink supplied from the supply unit is guided to the ink inlet 12b through the two manifolds 13 and 14. The ink guided to the ink inlet 12b and the ink existing in the two manifolds 13 and 14 are heated to a predetermined temperature by the operation of the heaters 16a and 16b. The ink is heated to a predetermined temperature and has fluidity suitable for ejection. The ink jet head chip 12 then ejects ink onto each recording medium from each of the plurality of nozzles 12a under the control of the control unit 160.

Next, processing related to control by the control unit 160, in particular, operation control of the heaters 16a and 16b will be described.
The control unit 160 controls each operation of the heaters 16a and 16b based on a predetermined operation algorithm so that the ink existing in the inkjet head chip 12 has a predetermined temperature. Here, the operation algorithm calculates in advance the coefficient of thermal expansion of the frame 10 to be heated in accordance with the operation of the heaters 16a and 16b, particularly the coefficient of thermal expansion of each of the two side surfaces 10e and 10f of the second holding unit 10b. This is based on the measured measurement results. The coefficient of thermal expansion is based on, for example, various physical factors related to the two side surfaces 10e and 10f, such as the correlation between the temperature and volume of aluminum, which is the material of the frame 10, and the shape of each part of the frame 10. Measured. In addition, the operation algorithm sets the ink in the inkjet head chip 12 to a predetermined temperature and, based on the measurement result of the coefficient of thermal expansion of the frame 10, the two side surfaces 10 e and 10 f of the second holding portion 10 b of the frame 10. It is determined that each of the heaters 16a and 16b is operated so that the degree of expansion of each is equal. That is, the controller 160 controls the heater so that the degree of expansion of each of the two side surfaces 10e and 10f of the frame 10 is equal based on the thermal expansion coefficient of each of the two side surfaces 10e and 10f of the frame 10 acquired in advance. The operation of each of 16a and 16b is controlled.

Further, the control unit 160 detects the arrangement of a plurality of ink droplets ejected from the plurality of nozzles 12a during image formation, and controls the operation of each of the heaters 16a and 16b based on the detection result.
Specifically, the control unit 160 first, among the plurality of ink droplets included in the captured image output from the detection unit 140, the plurality of inks ejected from the plurality of nozzles 12 a of the one inkjet head 1. Extract droplets. Next, the control unit 160 detects a row formed by the arrangement of the extracted plurality of ink droplets. That is, the detection unit 140 and the control unit 160 of the present embodiment detect the arrangement of a plurality of ink droplets ejected from the plurality of nozzles 12a in cooperation.
The technique related to the extraction of ink droplets included in a captured image and the specification of the direction of a row formed by a plurality of ink droplets is a well-known technique and will not be described in detail.

  The arrangement of the plurality of ink droplets forming the row corresponds to the arrangement of the plurality of nozzles 12a ejecting the plurality of inks. Further, the plurality of nozzles 12a are provided so as to be arranged along the Y direction. For these reasons, if the second holding portion 10b of the inkjet head 1 is not warped, a row formed by a sequence of a plurality of ink droplets is along the Y direction.

  The control unit 160 determines whether or not the plurality of ink droplet columns extracted from the captured image is a column along the Y direction. Here, when it is determined that the plurality of ink droplet rows are arranged in the Y direction, the control unit 160 controls the operation of the heaters 16a and 16b based on a predetermined operation algorithm. maintain. That is, as long as the second holding unit 10b of the inkjet head 1 is not warped, the control unit 160 determines the two side surfaces of the frame 10 based on the thermal expansion coefficients of the two side surfaces 10e and 10f of the frame 10 acquired in advance. The operation of each of the heaters 16a and 16b is controlled so that the degree of expansion of each of 10e and 10f is equal.

  On the other hand, when it is determined that the plurality of ink droplet rows are not aligned in the Y direction, the control unit 160 causes the heater 16a, Each operation of 16b is controlled.

Here, warping occurring in the frame 10 when a plurality of ink droplet rows are not arranged in the Y direction will be described.
The second holding portion 10b of the inkjet head 1 has a relatively large amount of change on one side with respect to a volume change due to expansion of each of the two side faces 10e and 10f of the frame 10, particularly a change in length in the Y direction. When the amount of change in the side surface is relatively small, warping occurs so as to swell toward one surface side.

  As described above, the control unit 160 controls the operation of each of the heaters 16a and 16b so that the degree of expansion of each of the two side surfaces 10e and 10f of the frame 10 is equal based on a predetermined operation algorithm. doing. However, since the temperature in the inkjet head chip 12 changes sequentially due to various factors such as the operation status of each nozzle and the degree of new ink inflow, there is a difference in the amount of change due to expansion between the two side surfaces 10e and 10f. The possibility of occurrence is non-zero. For this reason, when there is a difference in the amount of change between the two side surfaces 10e and 10f, the second holding portion 10b of the inkjet head 1 may be warped. The warp of the second holding unit 10b of the ink jet head 1 causes warpage in the row due to the arrangement of the plurality of nozzles 12a, and appears as warpage in the row due to the arrangement of the plurality of ink droplets on the recording medium. . In this case, the control unit 160 controls the operations of the heaters 16a and 16b so that the difference in the amount of change in the length of the two side surfaces 10e and 10f in the Y direction caused by the expansion of the two side surfaces 10e and 10f of the frame is reduced. This reduces or eliminates warping.

Specifically, when it is determined that the plurality of ink droplet columns are not aligned in the Y direction, the control unit 160 warps the plurality of ink droplet columns. Is determined. In this case, the control unit 160 determines whether the plurality of ink droplet rows in the captured image are warped so as to draw an arc on either side of the two side surfaces 10 e and 10 f of the frame 10. Then, based on the determination result of the warp direction, the control unit 160 reduces the temperature of the side surface of the two side surfaces 10e and 10f of the frame 10 on the side where the plurality of ink droplet rows form an arc. The operation of each of the heaters 16a and 16b is controlled so as to increase the temperature of the opposite side surface or both. That is, the control unit 160 turns off the side heater on the side where a row of ink droplets forms an arc and lowers the temperature to reduce the volume of the side, thereby reducing the side heater on the opposite side. By turning on and increasing the temperature to increase the volume of the side surface or both, the difference in the amount of change in the length of the two side surfaces 10e and 10f in the Y direction is reduced, and the warp of the second holding portion 10b is reduced. Let go. The controller 160 also controls the heater 16a so that the temperature of the ink existing in the inkjet head chip 12 is a predetermined temperature even during operation control of the heaters 16a and 16b for eliminating the warp of the second holding unit 10b. , 16b are controlled.
The operation control for detecting the warp and eliminating the warp may be performed a plurality of times. For example, the control unit 160 detects the arrangement of a plurality of ink droplets at predetermined time intervals during image formation, and each operation of the heaters 16a and 16b for reducing and eliminating the warp when the warp is detected. Control may be performed.
The control unit 160 individually performs the above-described detection and operation control of the heaters 16 a and 16 b for the plurality of inkjet heads 1.

Next, an example of a process flow related to operation control by the control unit 160 will be described with reference to a flowchart of FIG.
First, the control unit 160 controls the operation of the heaters 16a and 16b by a predetermined operation algorithm based on the thermal expansion coefficients of the two side surfaces 10e and 10f of the frame 10 acquired in advance (Step S1), and the inkjet head The ink in the chip 12 is heated.
Next, the temperature detection unit 17 detects the temperature of the ink in the inkjet head chip 12 (step S <b> 2), and the temperature detection result is output to the control unit 160. The controller 160 determines whether or not the ink in the inkjet head chip 12 has a predetermined temperature based on the temperature detection result (step S3). Here, when it is determined that the ink in the inkjet head chip 12 is not at the predetermined temperature (step S3: NO), the process proceeds to step S1. On the other hand, when it is determined that the ink in the inkjet head chip 12 has a predetermined temperature (step S3: YES), the control unit 160 assumes that image formation is ready and performs image formation based on the image data. Perform (step S4). Even after the image formation is started, the control unit 160 continues the operation control of the heaters 16a and 16b by a predetermined operation algorithm based on the thermal expansion coefficients of the two side surfaces 10e and 10f of the frame 10 acquired in advance. .

After starting the image formation, the control unit 160 detects the arrangement of the plurality of ink droplets ejected from the plurality of nozzles 12a based on the image captured by the detection unit 140 (step S5). Then, the control unit 160 determines whether or not the arrangement of the plurality of ink droplets is warped in the Y direction (step S6). Here, when it is determined that the arrangement of the plurality of ink droplets has warped in the Y direction (step S6: YES), the control unit 160 sets the heaters 16a and 16b for eliminating the warp. Operation control is performed (step S7). Specifically, the controller 160 lowers the temperature of the side surface on the opposite side of the two side surfaces 10e and 10f of the frame 10 by lowering the temperature of the side surface on which the row of ink droplets draws an arc. The operation of each of the heaters 16a and 16b is controlled so as to raise or both.
Thereafter, the control unit 160 determines whether or not the image formation has been completed (step S8). If it is determined that the image formation has not been completed (step S8: NO), the process proceeds to step S5. That is, the controller 160 continuously detects the arrangement of a plurality of ink droplets at predetermined time intervals during image formation, and each of the heaters 16a and 16b for eliminating the warp when the warp is detected. Control the operation. On the other hand, when it is determined that the image formation is finished (step S8: YES), the control unit 160 finishes the heating of the ink by the operation of the heaters 16a and 16b and finishes the process.
If it is determined in step S6 that the arrangement of the plurality of ink droplets does not warp in the Y direction (step S6: NO), the process proceeds to step S8.

Next, the connection part of the frame 10 and the expansion of the frame 10 will be described.
FIGS. 7A and 7B are diagrams illustrating the frame 10. FIG. 7A is a perspective view, and FIG. 7B is a cross-sectional view when the frame 10 is cut along the XZ plane at the position of the line W shown in FIG. 7A.
The frame 10 has a gap 10g formed between the first holding part 10a and the second holding part 10b. The gap 10g illustrated in FIG. 7A is a gap located between the two connection portions 10c and 10c provided on both lower ends in the Y direction of the first holding portion 10a, but is an example. However, the present invention is not limited to this, and may be provided as a gap between a plurality of connecting portions.

  The first holding unit 10a is provided at a position shifted from the center line L1 in the X direction of the second holding unit 10b. Specifically, as shown in FIG. 7B, the first holding unit 10a passes through the center of the width D1 in the X direction of the second holding unit 10b and is on the center line L1 orthogonal to the ink ejection surface. On the other hand, it is provided at a position shifted to one side (for example, the right side shown in FIG. 7B) along the X direction.

  For example, the first holding unit 10a is provided at a position shifted to one side along the X direction by an amount corresponding to the thickness in the X direction of the drive substrate 11 with respect to the center line L1. Thereby, the thickness in the X direction of the first holding part 10a and the structure on the upper side of the frame 10 including the drive substrate 11 held by the first holding part 10a can be made substantially equal to the center line L1. . On the other hand, if the first holding portion 10a is provided on the center line L1, the structure on the upper side of the frame 10 is provided at a position that is biased to one of the X directions, so that the second holding portion 10b etc. The width of the entire inkjet head 1 including the X direction becomes larger. That is, in the inkjet head 1 of the present embodiment, the first holding portion 10a is provided at a position shifted from the center line L1 in the X direction of the second holding portion 10b, so that the width in the X direction becomes more compact. ing.

Further, the connection surfaces of the connection portion 10c and the second holding portion 10b are arranged symmetrically with respect to the center in the X direction.
Specifically, as illustrated in FIG. 7B, the connection portion 10c has, for example, the center of the width D2 in the X direction of the connection surface with the second holding portion 10b in the X direction of the second holding portion 10b. It is provided so as to coincide with the center line L1. That is, the connection surface of the connection portion 10c with the second holding portion 10b is located at the center in the X direction.

If the first holding part 10a provided at a position shifted from the center line L1 in the X direction of the second holding part 10b is extended downward as it is and provided integrally with the second holding part 10b, Among the two holding portions 10b, a stress in the contraction direction by the first holding portion 10a acts upon expansion of one side where the first holding portion 10a exists across the center line L1. On the other hand, in this case, the stress in the contraction direction by the first holding portion 10a does not act on the other side of the second holding portion 10b where the first holding portion 10a does not exist across the center line L1. In addition, in this case, since heat radiation by the first holding portion 10a works more strongly on the one side where the first holding portion 10a exists, a difference in heat dissipation performance occurs between the one side and the other side. For these reasons, the second holding portion 10b in this case has non-uniform expansion due to temperature changes such as heating on one side and the other side across the center line L1. That is, in this case, the respective portions of the second holding portion 10b that are located opposite to each other across the center line L1 have different degrees of expansion and contraction in the Y direction accompanying a temperature change. Therefore, in this case, the second holding portion 10b warps in the Y direction by causing one side to expand more significantly with respect to the other side and vice versa. Here, the inkjet head chip 12 held by the second holding unit 10b inside the second holding unit 10b also warps due to the stress caused by the warp of the second holding unit 10b, and as a result, along the Y direction. The nozzle row of the plurality of nozzles 12a provided is warped.
On the other hand, the connection part 10c of the inkjet head 1 of this embodiment has the connection surface with the 2nd holding | maintenance part 10b located in the center of the X direction of the 2nd holding | maintenance part 10b. Thereby, the stress by the 1st holding | maintenance part 10a will be added on the centerline L1 of the 2nd holding | maintenance part 10b via the connection part 10c. Moreover, also when heat dissipation by the 1st holding | maintenance part 10a arises, the heat of both sides will be transmitted from the center of the 2nd holding | maintenance part 10b substantially equally. For these reasons, the influence of the first holding portion 10a on the both side portions becomes substantially equal in relation to the expansion of the both side portions of the second holding portion 10b existing at positions facing each other across the center line L1. Therefore, since the warp of the second holding portion 10b due to the structure of the frame 10 can be prevented, the warp of the nozzle row by the plurality of nozzles 12a can be prevented.

  As described above, according to the image forming apparatus 100 of the present embodiment, the heaters 16a and 16b are configured so as to reduce the difference between the length changes in the Y direction of the two side surfaces 10e and 10f caused by the expansion of the two side surfaces 10e and 10f of the frame. Since the warpage of the frame 10 due to expansion can be reduced and eliminated, the warpage of the nozzle array due to the difference in the degree of expansion of the two side surfaces 10e and 10f can be reduced and eliminated. .

  Further, each of the heaters 16a and 16b is equalized based on the thermal expansion coefficient of each of the two side surfaces 10e and 10f of the frame 10 so that the degree of expansion of each of the two side surfaces 10e and 10f of the frame 10 is equal. Since the operation of each of the heaters 16a and 16b is controlled, the degree of heating can be based on the thermal expansion coefficient of each of the two side surfaces 10e and 10f of the frame 10, so that the expansion can be performed more reliably. The warpage of the frame 10 due to the above can be prevented, and the warpage of the nozzle row due to the difference in the degree of expansion of the two side surfaces 10e, 10f can be prevented.

  In addition, since the operation of each of the heaters 16a and 16b is controlled based on the arrangement of a plurality of ink droplets detected during image formation, it flexibly responds to changes in the amount of heat generated in the inkjet head 1 during image formation. The warpage of the frame 10 can be reduced and eliminated by the operation control of the heaters 16a and 16b, and the warpage of the nozzle row due to the difference in the degree of expansion of the two side surfaces 10e and 10f can be reduced and eliminated.

  In addition, since the operation of each of the heaters 16a and 16b is controlled so that the temperature of the ink in the inkjet head chip 12 becomes a predetermined temperature, the temperature of the ink ejected from the inkjet head 1 is set to the predetermined temperature. Can do. That is, by setting the temperature of the ink suitable for ejection determined based on the characteristics exhibited by the ink ejected from the inkjet head 1 to the predetermined temperature, the temperature suitable for ejection of the ink can be achieved.

  In addition, since the connection surface of the second holding portion 10b of the connecting portion 10c is located at the center in the width direction, the first holding is performed with respect to each portion of the second holding portion 10b that is opposed to the center line L1. Since the influence of the stress and heat radiation by the part 10a can be made substantially uniform, the warp of the second holding part 10b due to the stress can be prevented, and the warp of the nozzle row by the plurality of nozzles 12a can be prevented. . Further, since the first holding portion 10a can be shifted from the center in the width direction after preventing the nozzle row from warping, the thickness of the drive substrate 11 is taken into consideration when designing the frame 10. Since the position in the width direction of the 1 holding part 10a can be determined, it is possible to achieve both prevention of warpage of the nozzle row and miniaturization of the inkjet head 1.

  Further, since the frame 10 has a gap 10g formed between the first holding part 10a and the second holding part 10b, the expansion and contraction accompanying the thermal expansion between the first holding part 10a and the second holding part 10b is possible. Since the difference in degree can be absorbed by the gap 10g, transmission of stress in the X direction from the first holding unit 10a to the second holding unit 10b can be prevented. That is, the warp of the second holding portion 10b due to the stress can be prevented more reliably, and the warpage of the nozzle row by the plurality of nozzles 12a can be prevented.

  Further, since the heaters 16a and 16b for heating the ink existing in the ink jet head chip 12 and the like are provided, even if the ink is heated by the ink jet head 1, the second due to the stress accompanying the expansion of the first holding portion 10a. Warpage of the holding portion 10b can be prevented, and warpage of the nozzle row by the plurality of nozzles 12a can be prevented.

  The embodiment of the present invention should be considered that the embodiment disclosed this time is illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

For example, in the above embodiment, the detection unit 140 and the control unit 160 are provided separately from the inkjet head 1, but this is an example and the present invention is not limited to this.
For example, the inkjet head 1 may be provided with detection means for detecting the arrangement of the plurality of nozzles 12a or the arrangement of the plurality of ink droplets ejected from the plurality of nozzles 12a. As a specific example, a configuration that functions as a strain sensor that detects strain in the Y direction of the inkjet head 1, such as a load cell, is provided in the inkjet head 1, and warpage of a nozzle row by a plurality of nozzles 12 a is detected by the configuration. Etc.
In addition, the operation control of each of the heaters 16a and 16b may be performed independently by the inkjet head 1. In this case, a configuration (for example, an IC chip or the like) that functions as a control unit that performs operation control of each of the heaters 16a and 16b is provided on the drive substrate 11, for example.

Further, the detection unit 140 in the above embodiment is provided to detect the arrangement of a plurality of ink droplets ejected on the recording medium, but is not limited to this example. For example, the arrangement of the plurality of nozzles 12 a may be detected by using an imaging device provided as an imaging device for imaging the ink ejection surface of the inkjet head 1 as the detection unit 140.
Further, in the above embodiment, the detection unit 140 and the control unit 160 cooperate to function as detection means, but this is an example and the present invention is not limited to this. For example, a processing unit that performs processing for detecting a row formed by a sequence of a plurality of ink droplets from a captured image may be provided in the detection unit 140, and a processing result by the processing unit may be output to the control unit 160. Good.

  In the above-described embodiment, the heaters 16a, 16a, and 16c detect the arrangement of a plurality of ink droplets ejected from the plurality of nozzles 12a during image formation, and arrange the plurality of ink droplets along the Y direction. Although each operation | movement of 16b is controlled, it is an example and is not restricted to this. For example, in the pre-measurement operation for determining an operation algorithm for controlling the operation of the heaters 16a and 16b, warpage of the arrangement of the plurality of nozzles 12a or the arrangement of the plurality of ink droplets that may occur during image formation. The degree may be detected. In this case, feedback control for preventing the warpage is included in the operation algorithm. That is, the control unit 160 controls the operation of the heaters 16a and 16b based on the operation algorithm, thereby preventing warpage that may occur during image formation without performing detection using the detection unit 140 during image formation. can do. In this case, since the preliminary measurement work is performed, the thermal expansion coefficient of each of the two side surfaces 10e and 10f of the frame 10 can be considered at the same time.

  In the above-described embodiment, each of the heaters 16a and 16b is one heating unit, but is an example and is not limited thereto. For example, a plurality of temperature changing means may be provided on each of the two side surfaces 10e and 10f. In this case, as a plurality of temperature changing means, for example, as shown in FIG. 8, a plurality of heating units (for example, shown in FIG. 8) are provided on each of the two side surfaces 10e, 10f of the second holding unit 10b along the Y direction. Heating units 16h, 16i, 16j, 16k, etc.) are provided. And the control part 160 controls each of the several heating part provided in each side separately. Thereby, each operation control of the heaters 16a and 16b can be performed more finely, so that the warpage of the frame 10 due to the expansion can be reduced, eliminated, and prevented more reliably, and the expansion of the two side surfaces 10e and 10f can be prevented. It is possible to reduce, eliminate and prevent the warpage of the nozzle row due to the difference in degree.

  In the above, a heater is used as the temperature changing means, but this is an example and the present invention is not limited to this. For example, a thermoelectric element that heats or cools the frame, such as a Peltier element, may be used as the temperature changing means. In this case, when there is a difference in the degree of expansion of the two side surfaces 10e and 10f of the frame 10, a process for cooling the side surface on the side where the degree of expansion is relatively large is added. The degree of expansion can be equalized, and the warp of the frame 10 can be reduced, eliminated, or prevented by more flexible temperature control means operation, and the nozzles due to the difference in the degree of expansion of the two side surfaces 10e and 10f Row warping can be reduced, eliminated, or prevented.

  In the above embodiment, the inkjet head chip 12 sandwiched between the two manifolds 13 and 14 is provided inside the second holding portion 10b of the frame 10. However, this is only an example and the present invention is not limited thereto. It is not something that can be done. For example, the components provided inside the frame 10 and the second holding portion 10b of the frame 10, such as the frame 10, the inkjet head chip 12, the two manifolds 13 and 14, the heaters 16a and 16b, are not necessarily independent components. Alternatively, a part or all of the configuration may be one. In addition, the ink supply path to the inkjet head chip 12 is not limited to that by the manifolds 13, 14, and the like, and any specific form may be used as long as ink can be supplied to the plurality of nozzles 12 a.

  Moreover, in said embodiment, although the flame | frame 10, especially the 2nd holding | maintenance part 10b is described as a structure which the expansion | swelling accompanying the heating by the heaters 16a and 16b produces, it is an example and is not restricted to this. For example, when the frame 10 and the manifolds 13 and 14 provided outside the inkjet head chip 12 are omitted, and only the inkjet head chip 12 and the heaters 16a and 16b are provided, the configuration in which expansion due to heating occurs is an inkjet head. It becomes two side surfaces of the chip 12. Similarly, when there is no physical restriction of the inkjet head chip 12 by the frame 10, such as when there is a gap between the two side surfaces of the inkjet head chip 12 and the two side surfaces of the frame 10, expansion due to heating similarly occurs. The resulting configuration is two sides of the inkjet head chip 12. In this case, the control unit 160 controls the operations of the heaters 16a and 16b so that the difference in the amount of change in length between the two side surfaces of the inkjet head chip 12 is reduced.

  In the above embodiment, ink heated before ejection is used, but this is an example and the present invention is not limited to this. For example, ink that does not require heating before ejection may be used. In this case, the control unit 160 controls the operation of temperature changing means such as the heaters 16a and 16b in order to reduce, eliminate, and prevent warpage of the nozzle row.

Moreover, the connection part 10c shown to Fig.7 (a), (b) is an example, and is not restricted to this, The connection surface of a connection part and the 2nd holding | maintenance part 10b is symmetrical with respect to the center of the width direction. It suffices if they are arranged.
Specifically, for example, the first holding unit 10a and the second holding unit 10b may be connected at three or more locations as in the connection unit 10h illustrated in FIGS. 9A and 9B. The connection part 10h shown to Fig.9 (a), (b) is toward the 2nd holding | maintenance part 10b side from each of the two base parts 10i and two base parts 10j which were connected with the 1st holding | maintenance part 10a, and the base part 10i. A leg portion 10k that extends and connects the base portion 10i and the second holding portion 10b, and extends from each of the base portions 10j so as to be bifurcated in the X direction toward the second holding portion 10b side. Leg portions 10l and 10m connecting the base portion 10j and the second holding portion 10b. Here, the bifurcated leg portion 10l and the leg portion 10m are in a plane-symmetrical relationship with respect to the center line L1 in the X direction. The base portions 10i and 10j and the leg portions 10k have a plane-symmetric shape with respect to the center line L1 in the X direction. Furthermore, the leg 10k has a connection surface with the second holding part 10b located at the center in the width direction of the second holding part 10b.
By connecting the 1st holding | maintenance part 10a and the 2nd holding | maintenance part 10b in three or more places like the connection part 10h, the intensity | strength of a connection part can be ensured more reliably. Accordingly, it is possible to more easily solve technical problems in the process of manufacturing the frame, such as securing the strength of the frame required when integrally molding the frame, and to provide the inkjet head 1 at a lower cost. Can do. Further, since the connecting portion 10h is provided so as to be plane-symmetric with respect to the center line L1 in the X direction of the second holding portion 10b, the degree of expansion of the two side surfaces 10e and 10f is more reliably made substantially equal. be able to.
Note that the frame 10 may include only one of the connection portion including the base portion 10i and the leg portion 10k and the connection portion including the base portion 10j and the leg portions 10l and 10m illustrated in FIGS. 9A and 9B. Good. Further, the connection unit may connect the first holding unit 10a and the second holding unit 10b at one place.

Further, in the above embodiment, the case where the first holding unit 10a applies stress in the contraction direction and performs heat dissipation with respect to the expansion of the second holding unit 10b is described as an example, but the present invention is not limited thereto. Not a thing. For example, even when the first holding unit 10a expands due to heat generated by the drive substrate 11 and the first holding unit 10a applies stress in the expanding direction to the second holding unit 10b, the connection unit and the second Since the connection surface of the holding portion 10b is arranged symmetrically with respect to the center in the width direction, warping due to the stress can be prevented. In this case, heat may be transferred from the first holding unit 10a to the second holding unit 10b, but the connection surface between the connection unit and the second holding unit 10b is the center in the width direction. Since the heat is transmitted substantially evenly to both side portions of the second holding portion 10b, warpage due to heat transfer imbalance can be prevented.
As described above, the connection surface between the connecting portion and the second holding portion 10b has a width with respect to the warp caused by the difference in the amount of heat and the degree of expansion of the both sides of the first holding portion 10a and the second holding portion 10b. Warpage can be prevented by being arranged symmetrically with respect to the center of the direction.

  In addition, the drive substrate 11 in the above embodiment includes various circuits, wirings, and the like related to ink ejection by the inkjet head chip 12, but this is an example and the present invention is not limited thereto. For example, the drive substrate 11 may function only as a wiring.

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Housing | casing 10 Frame 10a 1st holding | maintenance part 10b 2nd holding | maintenance part 10c Connection part 11 Drive substrate 12 Inkjet head chip 12a Nozzle 16a, 16b Heater

Claims (10)

An ink discharge section having an ink discharge surface in which a plurality of nozzles for discharging ink are arranged along a predetermined direction;
A substrate including wiring connected to the ink ejection unit;
A first holding portion for holding said substrate, said plurality of said ink discharge portion having a second opening for the nozzle and the first aperture and the ink discharge portion to expose the connecting the wiring accommodated therein a second holding portion cylindrical holding a frame having a connecting portion for connecting the said first holding portion and the second holding unit,
With
When the width direction is a direction along the ink discharge surface and perpendicular to the predetermined direction,
The first holding portion is provided in the front Symbol offset from the center of the front Symbol width direction of the second holding portion position,
Said connecting portion, said connecting surface for connecting a surface of the second opening side of the second holding portion, characterized by being arranged symmetrically with respect to the center in the width direction of the second holding portion An inkjet head.   The inkjet head according to claim 1, wherein the connection surface is located at a center in the width direction. The inkjet head according to claim 1, wherein the shape of the connection portion is plane-symmetric with respect to the center in the width direction. The frame is provided with a plurality of at least one of a portion connecting the connecting portion and the first holding portion and a portion connecting the connecting portion and the second holding portion, and at least a plurality of at least one of the plurality of portions 4. The inkjet head according to claim 1, further comprising a gap formed between the portions and between the first holding portion and the second holding portion. 5. The said frame is provided with the site | part which connects the said connection part and the said 1st holding | maintenance part, and the site | part which connects the said connection part and the said 2nd holding | maintenance part, respectively. The inkjet head as described in any one of these.   The inkjet head according to claim 1, further comprising a heating unit that heats ink existing in the ink discharge unit. The inkjet head according to claim 1, wherein the substrate is disposed at a position closer to the center in the width direction than the first holding portion. The ink ejection unit includes an inkjet head chip having the ink ejection surface, and a manifold that is provided on a side surface adjacent to the ink ejection surface of the inkjet head chip and stores ink to be supplied to the inkjet head chip. The inkjet head according to any one of claims 1 to 7, wherein: The first holding portion is disposed on the side of the second holding portion where the second opening is provided,
The inkjet head according to any one of claims 1 to 8, wherein the connecting portion connects an end portion of the first holding portion on the second holding portion side and the second holding portion. An image forming apparatus comprising the inkjet head according to claim 1.

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