JP5899782B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an inkjet image forming apparatus.

  A head array is configured by arranging a plurality of droplet discharge heads in a staggered manner, and a plurality of head arrays configured in this manner are arranged separately for each color so as to be orthogonal to the recording medium conveyance direction. Thus, an image forming apparatus having a line head array configuration that realizes image formation at high speed is known (see Patent Document 1 and the like).

  1 and 2 are diagrams showing a configuration example of a general head array 51. FIG. 1 is a perspective view, and FIG. 2 is a plan view.

  In FIG. 1 and FIG. 2, the droplet discharge head 501 is thermally coupled to the array base 502 by a droplet head mounting screw 503 and is attached so that the lower surface of the droplet discharge head 501 protrudes from the opening 504. A spring 505 is attached to the opening 504 of the array base 502, and the droplet discharge head 501 is spring-biased by the spring 505 in the vertical and horizontal directions within the surface of the array base 502. This is to absorb the expansion and contraction due to the temperature expansion of the droplet discharge head 501, and by allowing the droplet discharge head 501 to expand and contract in the biasing direction of the spring 505 due to a temperature change, thermal destruction due to thermal expansion is prevented. The Although only one droplet discharge head 501 is illustrated, the droplet discharge head 501 is similarly attached to all the openings 504.

  FIG. 3 is a diagram illustrating a configuration example of a general head array unit 5 including a plurality of head arrays 51.

  In FIG. 3, one end of the head array 51 is attached to a head array attachment frame 507 by an array base attachment screw 509 and the other end is spring-biased by a spring 508 attached to the head array attachment frame 507. This is to absorb the expansion and contraction due to the temperature expansion of the array base 502. By making the array base 502 expandable and contractible in the direction of the spring 508 due to a temperature change, the thermal destruction due to the thermal expansion is prevented.

  The image forming apparatus having the above-described line head array configuration can perform high-speed image formation because one line can be printed simultaneously. However, the landing position (ink droplets are recorded on paper or the like) due to the temperature difference of the head array. There has been a problem that the image quality is deteriorated due to the deviation of the position adhering to the medium.

  For example, when a user uses only a black (Bk) head array and prints only characters, only the black head array generates heat, and other head arrays that are not used for printing for full color (FC) There is no fever. Further, since the head array that is not used for printing is moved to a predetermined maintenance / recovery machine position and capped for the purpose of preventing ink drying on the nozzle surface, the temperature difference becomes more prominent.

  Therefore, when the user subsequently tries to form a full color image from black, the black head array is thermally expanded due to the heat generated by the droplet discharge head, and the head array for the full color that has not been used so far is used. A difference in thermal expansion occurs between the colors, and the landing positions between the colors shift, and a high-quality image cannot be obtained at the start of printing.

  FIG. 4 is a schematic diagram showing a case where the temperature (thermal expansion) between the two head arrays 51 attached to the head array attachment frame 507 is different. In FIG. 4, only the droplet discharge head 501 of the lower head array 51 is driven to generate heat, the temperature of the lower head array 51 becomes higher than that of the upper head array 51, and a thermal expansion difference is generated. Shows the case. The lower head array 51 is more thermally expanded than the upper head array 51, and the attachment positions of the droplet discharge head 501 and the array base 502 are the upper and lower sides in the horizontal direction and the vertical direction in the figure by the indicated dimensions. As a result, the landing positions are shifted. Since the droplet discharge head 501 and the array base 502 are thermally coupled to have the same temperature, a shift resulting from the shift of the droplet discharge head 501 and the shift of the array base 502 occurs at the landing position.

  FIG. 5 is a diagram showing an example of landing positions on the recording medium.

  FIG. 5A shows the landing positions when there is no deviation between the upper and lower head arrays 51 as shown in FIG. 3, and the solid line shows the ejected droplets of the upper head array 51, The broken lines indicate the discharged droplets of the lower head array 51, respectively. When there is no deviation, the landing positions of the upper and lower head arrays 51 coincide with each other, and image quality deterioration does not occur.

  As shown in FIG. 4, FIG. 5B shows the landing positions when there is a temperature difference between the upper and lower head arrays 51 and the lower head array 51 is thermally expanded and misaligned. Show. When a deviation occurs, a deviation occurs in the landing positions of the upper and lower head arrays 51, resulting in image quality deterioration.

  In order to solve such a problem, it is necessary to keep the temperature between the head arrays constant. Specifically, for example, a heater or the like is newly arranged to adjust the temperature of each head array to be uniform, or the head arrays are connected by a heat conducting member to make the temperature between the head arrays uniform. Can be considered.

  However, disposing a heater or the like for each head array leads to an increase in cost. Also, on the assumption that the head arrays move (move up and down and left and right from the printing position to move to a position once retracted from the transport path and capping), the head arrays are connected by a heat conducting member. Then, it becomes a complicated mechanical structure, and a space for moving the heat conduction member to be connected is also required.

  On the other hand, Patent Document 1 discloses a configuration in which head arrays are coupled by a thermal coupling member for the purpose of uniformizing thermal expansion between the head arrays. However, if the head array for each color does not have a moving mechanism, the connection with the heat conducting member can be simplified. However, the head arrays configured independently for each color are arranged apart from each other, and the head The case where the array itself moves is not considered, and the above-described problem cannot be solved.

  The present invention has been proposed in view of the above-mentioned conventional problems, and the object thereof is to make the temperature between all head arrays uniform without requiring a new heating mechanism or a complicated mechanical structure, An object of the present invention is to provide an image forming apparatus capable of preventing image quality deterioration.

In order to solve the above problems, in the present invention, a head array in which a plurality of droplet ejection heads for ejecting droplets onto a recording medium are arranged on an array base in a staggered manner, and the plurality of heads A head array unit configured by arranging the arrays so as to be orthogonal to the recording medium conveyance direction for each color, and a droplet discharge head for supplying a drive signal for causing the droplet discharge head to discharge droplets The droplet discharge head drive circuit is thermally coupled to the array base via a thermal resistance member, and the thermal energy generated by driving the droplet discharge head drive circuit is adjusted for the temperature of the head array. I am trying to use it.

  In the image forming apparatus according to the present invention, a driving circuit for the droplet discharge head is thermally coupled to the array base, and the thermal energy generated by driving the driving circuit is used for temperature adjustment of the head array. Without requiring a heating mechanism or a complicated mechanical structure, the temperature between all head arrays can be made uniform to prevent image quality deterioration.

FIG. 2 is a diagram (part 1) illustrating a configuration example of a general head array. FIG. 2 is a diagram (part 2) illustrating a configuration example of a general head array. FIG. 2 is a diagram (part 1) illustrating a configuration example of a general head array unit. FIG. 2 is a diagram (part 2) illustrating a configuration example of a general head array unit. It is a figure which shows the example of the landing position on a recording medium. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a configuration example (No. 1) of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a second diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the structural example of a head array unit. FIG. 2 is a diagram (part 1) illustrating a configuration example around a head array; FIG. 6 is a diagram (part 2) illustrating a configuration example around the head array; 3 is a diagram illustrating a configuration example of a control system of the image forming apparatus. FIG. It is a figure which shows the structural example of a head driver periphery. It is a figure which shows the structural example of a droplet discharge head drive circuit periphery. It is a figure which shows the example of a drive waveform. It is a flowchart (the 1) which shows the process example concerning the temperature adjustment in embodiment. It is a flowchart (the 2) which shows the process example concerning the temperature adjustment in embodiment.

  Hereinafter, preferred embodiments of the present invention will be described.

<Overall configuration>
6 and 7 are diagrams showing a configuration example of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a front view and FIG. 7 is a plan view.

  6 and 7, the illustrated image forming apparatus is a line type image forming apparatus, and the apparatus main body 1, a paper feed tray 2 on which paper P is stacked and fed, and printed paper P are discharged and stacked. A paper discharge tray 3, a transport unit 4 that transports the paper P from the paper feed tray 2 to the paper discharge tray 3, a head array unit 5 that discharges and prints droplets on the paper P transported by the transport unit 4, and printing A cleaning device 6 is provided as a maintenance / recovery mechanism that performs maintenance / recovery of each head of the head array unit 5 after completion or at a required timing.

  The apparatus main body 1 includes front and rear side plates and stays (not shown), and the paper P stacked on the paper feed tray 2 is fed to the transport unit 4 one by one by the separation roller 21 and the paper feed roller 22. Is done. The transport unit 4 includes a transport drive roller 41a and a transport driven roller 41b, and an endless transport belt 43 wound around the transport drive roller 41a and the transport driven roller 41b. A plurality of holes (not shown) are formed on the surface of the transport belt 43, and a suction fan 44 that sucks the paper P is disposed below the transport belt 43.

  Further, conveyance guide rollers 42a and 42b are respectively held on guides (not shown) on the conveyance driving roller 41a and conveyance driven roller 41b, and are in contact with the conveyance belt 43 by their own weight. The conveyance driving roller 41 a is rotated by a motor (not shown), so that the conveyance belt 43 rotates. The paper P is sucked onto the conveyance belt 43 by the suction fan 44 and is conveyed by the circular movement of the conveyance belt 43. The transport driven roller 41 b and the transport guide rollers 42 a and 42 b rotate following the transport belt 43. A head array unit 5 composed of a head array that discharges droplets to be printed on the paper P is disposed above the transport unit 4 so as to be movable in the arrow A direction. In addition, the head array unit 5 slides above the cleaning device 6 during the maintenance / recovery operation (cleaning).

  In the head array unit 5, four head arrays 51 a to 51 d including six droplet discharge heads arranged in a staggered pattern for discharging droplets are arranged over almost the entire width of the paper P at right angles to the transport direction of the paper P. Configured. That is, the first row head array 51a, the second row head array 51b, the third row head array 51c, and the fourth row head array 51d are arranged from the upstream side in the paper conveyance direction. Note that six droplet discharge heads per color constitute one line, but the number is not limited to six.

  The head arrays 51a to 51d can form an image for one line by discharging droplets of each color of yellow (Y), magenta (M), cyan (C), and black (K). . In the head array unit 5, distributors 52a to 52d, which are distributors for supplying ink of a required color to the head arrays 51a to 51d, are arranged above the head arrays 51a to 51d. A supply tube 53 connects between 51a to 51d. A sub tank 54 is disposed upstream of the distributors 52a to 52d, and ink is supplied to the droplet discharge heads of the head arrays 51a to 51d by a water head difference. Further, an ink main tank (not shown) is disposed on the upstream side of the sub tank 54, and ink is supplied to each through a supply tube.

  On the downstream side of the transport unit 4, a transport guide portion 7 that discharges the paper P to the paper discharge tray 3 is provided. The paper P guided and conveyed by the conveyance guide unit 7 is discharged to the paper discharge tray 3. The paper discharge tray 3 includes a pair of side fences 31 that regulate the width direction of the paper P and an end fence 32 that regulates the front end of the paper P.

  In the cleaning device 6 as the maintenance / recovery mechanism, the cleaning units 61 a to 61 d are arranged in a staggered manner corresponding to the head arrays 51 a to 51 d in the first to fourth rows of the head array unit 5. The notation of each part of the cleaning device 6 is the same as that of the head array unit 5. A suction pump (not shown) for sucking ink from the droplet discharge heads of the head arrays 51a to 51d is arranged below the respective cleaning means 61a to 61d.

  In this image forming apparatus, after the printing is finished, the ink is sucked from the nozzles while the droplet discharge heads of the head arrays 51a to 51d that discharge the droplets are capped by the cleaning units 61a to 61d, or the head When cleaning the ink adhering to the nozzle surfaces of the droplet ejection heads of the arrays 51a to 51d with the cleaning means 61a to 61d, the head arrays 51a to 51d are each independently in the direction of the arrow A in FIG. After moving, it moves in the direction of arrow B in FIG. 7 and is stopped above the cleaning device 6, and the cleaning means 61a to 61d are lifted to perform the cleaning operation (maintenance recovery operation) of the droplet discharge heads of the head arrays 51a to 51d. ) And capping operation. In short, only the head array (a part or all of the head arrays 51a to 51d) used for printing is arranged on the transport belt 43, and the head array not used for printing moves to the maintenance and recovery machine course and is capped. .

  FIG. 8 is a diagram showing a configuration example of the head array unit 5 including a plurality of head arrays 51, and is a plan view.

  FIG. 9 is a diagram showing a configuration example around each head array 51 constituting the head array unit 5, and shows one head array 51 shown in FIG. 8 in a longitudinal sectional view.

  8 and 9, the configuration of the head array 51 is the same as that shown in FIGS.

  In FIG. 8 and FIG. 9, the droplet discharge head drive circuit heat dissipation plate 511 of the droplet discharge head drive substrate 510 is connected to the droplet discharge head drive circuit heat dissipation plate 511 and the array base 502 by a heat dissipation plate mounting screw 514. Are attached in contact. A droplet discharge head drive circuit 512 for driving the droplet discharge head 501 is attached to the droplet discharge head drive circuit heat radiation plate 511 by thermal coupling with a drive circuit mounting screw 515. Specifically, the droplet discharge head drive circuit 512 is a circuit unit that constitutes a push-pull circuit with power transistors. The droplet discharge head drive circuit heat dissipation plate 511 is for heat dissipation of the push-pull circuit.

  FIG. 10 is a diagram showing another example of the configuration around the head array 51, and is shown in a longitudinal sectional view similar to FIG.

  In FIG. 10, the thermal coupling coefficient is controlled by the material of the heat resistance member 516 by attaching the droplet discharge head drive circuit heat radiation plate 511 and the array base 502 with the heat radiation plate mounting screw 514 via the heat resistance member 516. The saturation of the temperature rise of the head array 51 is suppressed. As a material of the heat resistance member 516, for example, an invar material or the like having a low thermal expansion coefficient and low thermal conductivity is used.

  8 to 10, the array base 502 or the droplet discharge head 501 is equipped with a temperature sensor as temperature information acquisition means. This temperature sensor includes a temperature detection element such as a thermistor. The temperature sensor measures the head array temperature or the droplet discharge head temperature, is A / D converted (converted from an analog signal to a digital signal), and transmits temperature information to a control system described later. The location of the temperature sensor is preferably in the vicinity of the array base 502 or the droplet discharge head 501, but if the temperature of the array base 502 or the droplet discharge head 501 can be estimated from information from the temperature sensor, the temperature sensor The installation location is not limited to this.

<Overview of overall control>
FIG. 11 is a diagram illustrating a configuration example of a control system of the image forming apparatus.

  11, a control unit 100 includes a CPU 101 that controls the entire image forming apparatus, a ROM 102 that stores programs executed by the CPU 101 and other fixed data, a RAM 103 that temporarily stores image data and the like, and a power source of the apparatus. An NVRAM (non-volatile memory) 104 for holding data even while being shut off, and an ASIC 105 for processing input / output signals for controlling the entire apparatus are provided. As for the ASIC 105, an image forming apparatus classified as a “high-speed machine” may be provided with a function responsible for a part of image processing.

  The control unit 100 also includes a host I / F 106 for transmitting / receiving data and signals to / from the host side, a head drive control unit 107 and a head driver 108 for driving and controlling the head array unit 5, and a head array unit. A head array unit moving motor driving unit 110 for driving the moving motor 109, a conveying belt moving motor driving unit 112 for driving the conveying belt moving motor 111 of the conveying belt 43, and a suction fan motor 116 for the suction fan 44 are provided. A suction fan motor driving unit 117 for driving, an environmental sensor 113 for detecting environmental temperature and / or environmental humidity, a paper sensor 200, a phase sensor 201, a temperature sensor 202 (temperature mounted on the array base 502 or the droplet discharge head 501) Sensor) and other sensors not shown And a like I / O 114 for inputting detection signals. The control unit 100 is connected to an operation panel 115 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 100 transmits print data including image data from the host side such as an information processing apparatus such as a personal computer (PC), an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera, via a cable or a network. Via the host I / F 106.

  Then, the CPU 101 reads out and analyzes the print data in the reception buffer included in the host I / F 106 and performs data rearrangement processing or the like (in some cases, part of image processing described later in some cases) by the ASIC 105. The image data is transferred to the drive control unit 107. Note that conversion of print data for image output into bitmap data (print raster data) may be performed, for example, by storing font data in the ROM 102, or image data may be bitmapped by a host-side printer driver. It is also possible to develop the bitmap data (print raster data) of the print data by developing the data, and then transfer the print raster data to this apparatus.

  Upon receiving the print raster data, the head drive control unit 107 sends the dot pattern data (print raster data) as serial data to the head driver 108 in synchronization with the clock signal, and outputs a latch signal at a predetermined timing. It is sent to the head driver 108.

  The head drive control unit 107 includes a ROM (can also be configured by the ROM 102) storing pattern data of a drive waveform (drive signal), and D / A for D / A converting the drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.

  The head driver 108 receives a clock signal from the head drive control unit 107 and serial data as image data, and a latch that latches the registration value of the shift register with a latch signal from the head drive control unit 107. Circuit, a level conversion circuit (level shifter) for changing the output value of the latch circuit, an analog switch array (switch means) whose on / off is controlled by the level shifter, and the like. By controlling, a required drive waveform included in the drive waveform is selectively applied to the actuator means of the head arrays 51a to 51d to drive the droplet discharge head, and the image data is printed to form a dot pattern line.

  The head drive control unit 107 generates a drive waveform (common drive waveform) composed of a plurality of drive pulses (drive signals) within one printing cycle, and outputs 2 bits corresponding to the print image. And a data transfer unit for outputting a clock signal, a latch signal (LAT), and droplet control signals (M0 to M3). The droplet control signals (M0 to M3) are signals for instructing opening / closing of an analog switch, which will be described later, of the head driver 108 for each droplet, and are waveforms to be selected in accordance with the printing cycle of the common drive waveform. The state transitions to the H level (ON), and when not selected, the state transitions to the L level (OFF).

<Droplet ejection head control>
FIG. 12 is a diagram illustrating a configuration example around the head driver 108.

  In FIG. 12, the head driver 108 includes a shift register 411 that inputs a transfer clock (shift clock) and serial image data (gradation data: 2 bits / CH) from the data transfer unit 402, and each register of the shift register 411. A latch circuit 412 for latching a value by a latch signal from the data transfer unit 402, a decoder 413 that decodes gradation data and droplet control signals M0 to M3 and outputs the result, and a logic level voltage signal of the decoder 413 Shifts to a level at which the analog switch 415 can operate, an analog switch 415 that is turned on / off (opened / closed) by the output of the decoder 413 provided through the level shifter 414, and passes through the analog switch 415 Drive waveform generator 4 And a voltage amplifier 416 that amplifies the common drive signal from 1.

  The output of the voltage amplification unit 416 is given to the droplet discharge head drive circuit 512 of the head array unit 5, and the output of the droplet discharge head drive circuit 512 is the selection electrode (individually) of the piezoelectric element 121 in the droplet discharge head 501. The common drive waveform from the drive waveform generation unit 401 is input. Accordingly, the analog switch 415 is turned on in accordance with the result of decoding the serially transferred image data (gradation data) and the droplet control signals M0 to M3 by the decoder 413, so that a required drive signal constituting the common drive waveform is obtained. Is passed (selected) and applied to the piezoelectric element 121.

  FIG. 13 is a diagram showing a configuration example around the droplet discharge head drive circuit 512.

  In FIG. 13, the voltage amplifying unit 416 amplifies the voltage to a value set on the circuit. The droplet discharge head drive circuit 512 drives the piezoelectric element 121 by amplifying current by push-pull connection of transistors connected in Darlington connection.

<Drive waveform>
FIG. 14 is a diagram illustrating an example of a drive waveform.

  Within one driving cycle (one printing cycle) determined by the pixel density and the paper conveyance speed, a non-ejection driving signal P0 that finely drives a nozzle meniscus that does not eject droplets in time series and droplets of ejection amount used for image formation A first driving waveform Pd including a plurality of first ejection driving signals (driving pulses) P1 to P3 for ejecting ink and a second ejection driving for ejecting droplets having an ejection amount smaller than the minimum ejection amount used for image formation. A drive waveform composed of a signal (drive pulse, second drive waveform) Pk is generated and output. Note that the second drive waveform can be composed of a plurality of second ejection drive signals in the same manner as the first drive waveform. Each of the drive signals P0 to P3 and Pk includes a waveform element that falls from the reference potential Ve and a waveform element that rises from the state after the fall. The waveform element in which the potential V of the drive signal falls from the reference potential Ve is a pull-in waveform element in which the piezoelectric element (not shown) contracts and the volume of the pressurized liquid chamber (not shown) expands. Further, the waveform element that rises from the state after the fall is a pressurization waveform element that expands the piezoelectric element and contracts the volume of the pressurized liquid chamber. That is, here, the drive signal P0 included in the first drive waveform Pd is a drive waveform that applies meniscus vibration without discharging droplets, and the drive signals P1 to P3, Pk included in the first and second drive waveforms are The drive waveform is such that the liquid chamber communicating with the nozzle of the droplet discharge head is expanded and then contracted to discharge the droplet.

  Then, for example, when performing fine driving by the droplet control signals M0 to M3 as shown in the drawing from the data transfer unit 402, the driving signal P0 is selected by the droplet control signal M0 (selected at the L level), and small. When a droplet (small dot) is formed, the drive signal P1 is selected by the droplet control signal M1, and when a large droplet (large dot) is formed, the drive signals P1 to P3 are selected by the droplet control signal M2 to perform idle ejection. Sometimes the drive signal Pk is selected by the droplet control signal M3 and applied to the piezoelectric element of the droplet discharge head. In addition, although it is set as two types of sizes, a small droplet and a large droplet here, the medium droplet of the magnitude | size between both can also be discharged, for example.

  FIG. 15 is a flowchart showing an example of processing related to temperature adjustment in the above embodiment.

  In FIG. 15, after receiving the print start command (step S11), the temperature information of each head array 51 is acquired by the temperature sensor 202 arranged in the vicinity of the array base 502 (step S12).

  The CPU 101 sets the temperature of the head array 51 having the maximum temperature as the reference temperature from the temperature information of each head array 51 (step S13), and the droplet discharge heads other than the head array 51 having the maximum temperature. The drive circuit 512 is operated and heated for a predetermined time (step S14). At this time, the drive waveform used to drive the droplet discharge head drive circuit 512 is a fine drive waveform that does not discharge droplets from the droplet discharge head 501.

  After the predetermined time has elapsed, the temperature information of each head array 51 is acquired again. When the set reference temperature is reached and the temperature difference disappears (Y in step S15), the operation of the droplet discharge head drive circuit 512 is stopped. (Step S16), the printing operation is started (Step S17).

  FIG. 16 is a flowchart showing another example of processing related to temperature adjustment in the above embodiment.

  In FIG. 16, during printing of the head array 51 used for printing, the CPU 101 acquires temperature information at specified time intervals (step S21), and constantly monitors the temperature information of each head array 51 (step S22). ). If the temperature difference between the head arrays 51 is within the allowable range (Y in step S22), the printing operation is continued (step S23).

  When a temperature difference exceeding the allowable range occurs between the head arrays 51 (N in Step S22), the temperature of the head array 51 used for printing is set to the reference temperature (Step S24).

  Next, the droplet discharge head drive circuit 512 of the head array 51 that is not used for other printing is driven and heated (step S25). At this time, the drive waveform used to drive the droplet discharge head drive circuit 512 is a fine drive waveform that does not discharge droplets from the droplet discharge head 501.

  Next, the set reference temperature is compared with the heated array base temperature (step S26), and it is determined whether the difference from the reference temperature is within an allowable range (step S27). If it is not within the allowable range (N in step S27), heating by driving the droplet discharge head drive circuit 512 (step S25) is continued.

  If the difference from the reference temperature is within the allowable range (Y in step S27), the driving of the head array 51 not used for printing is stopped (step S28).

  Thus, the temperature is adjusted so that the temperature between the head array 51 used for printing and the head array 51 not used for printing is the same.

  Therefore, when the user prints another image immediately and uses the head array 51 that has not been used for printing, the next image can be printed without waiting for the time to heat the head array 51.

<Summary>
As described above, according to the present embodiment, there are the following advantages.

  (1) A new heating mechanism or a complicated mechanical structure can be obtained by thermally coupling the drive circuit for the droplet discharge head with the array base and using the thermal energy generated by driving the drive circuit to adjust the temperature of the head array. It is not necessary to make the temperature between all the head arrays uniform and prevent image quality deterioration.

  (2) By conducting thermal coupling via a thermal resistance member, it is possible to moderately control the heat conduction from the drive circuit to the array base, and to prevent excessive heat conduction of the drive circuit to the array base. can do.

  (3) Before printing, temperature information of each head array is acquired by the temperature information detecting means mounted on each head array, and when there is a temperature difference between the head arrays, the drive circuit is driven. Thus, by performing control to make each head array uniform at a reference temperature, it is possible to eliminate the difference in thermal expansion between the head arrays.

  (4) During printing, the temperature of all head arrays is heated by using the heat generated by the drive circuit of the head array not used for other printing in accordance with the temperature of the head array used for printing. Since the difference is eliminated, when an image is formed using another head array, a printing operation can be performed immediately without preheating.

  (5) When heating the droplet discharge head, by switching to a fine driving waveform that does not discharge droplets and driving the piezoelectric elements of the droplet discharge head, it is possible to avoid using unnecessary image forming droplets. The temperature can be adjusted by driving the droplet discharge head.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments, various modifications and changes may be made to the embodiments without departing from the broad spirit and scope of the invention as defined in the claims. Obviously you can. In other words, the present invention should not be construed as being limited by the details of the specific examples and the accompanying drawings.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Paper feed tray 21 Separation roller 22 Paper feed roller 3 Paper discharge tray 31 Side fence 32 End fence 4 Transport unit 41a Transport drive roller 41b Transport driven roller 42a, 42b Transport guide roller 43 Transport belt 44 Suction fan 5 Head array Unit 51, 51a to 51d Head array 52, 52a to 52d Distributor 53 Supply tube 54 Sub tank 501 Droplet discharge head 502 Array base 503 Droplet head mounting screw 504 Opening 505 Spring 506 Array base mounting hole 507 Head array mounting frame 508 Spring 509 Array base mounting screw 510 Droplet discharge head drive substrate 511 Droplet discharge head drive circuit heat dissipation plate 512 Droplet discharge head drive circuit 513 Droplet discharge head nozzle surface 14 radiating plate mounting screw 515 driving circuit mounting screws 516 thermal resistance member 6 a cleaning device 61,61a~61d cleaning means 7 conveyance guide portion P sheet 100 controller 101 CPU
102 ROM
103 RAM
104 NVRAM
105 ASIC
106 Host I / F
DESCRIPTION OF SYMBOLS 107 Head drive control part 108 Head driver 109 Head array unit movement motor 110 Head array unit movement motor drive part 111 Conveyor belt movement motor 112 Conveyor belt movement motor drive part 113 Environmental sensor 114 I / O
115 Operation Panel 116 Suction Fan Motor 117 Suction Fan Motor Drive Unit 121 Piezoelectric Element 200 Paper Sensor 201 Phase Sensor 202 Temperature Sensor 401 Drive Waveform Generation Unit 402 Data Transfer Unit 411 Shift Register 412 Latch Circuit 413 Decoder 414 Level Shifter 415 Analog Switch 416 Voltage Amplification Part

JP 2007-196479 A

Claims (4)

A head array in which a plurality of droplet ejection heads for ejecting droplets onto a recording medium are arranged in a staggered pattern on an array base;
A plurality of head arrays each having a head array unit configured to be spaced apart from each other so as to be orthogonal to the recording medium conveyance direction;
A droplet discharge head drive circuit for supplying a drive signal for causing the droplet discharge head to discharge droplets,
The droplet discharge head drive circuit is thermally coupled to the array base via a thermal resistance member, and uses thermal energy generated by driving the droplet discharge head drive circuit to adjust the temperature of the head array. An image forming apparatus. The image forming apparatus according to claim 1 .
Temperature information acquisition means provided in each of the plurality of head arrays,
Prior to printing, each of the information from the plurality of temperature information acquisition means is compared, and if there is a temperature difference between the plurality of head arrays, the maximum temperature of the head array is set as a reference temperature. An image forming apparatus characterized in that the temperature between the plurality of head arrays is made uniform before printing by driving the droplet discharge head driving circuit of the other head array to adjust the temperature. The image forming apparatus according to claim 1 or 2,
Temperature information acquisition means provided in each of the plurality of head arrays,
During printing, each of the information from the plurality of temperature information acquisition means is compared, and if there is a temperature difference between the plurality of head arrays, the temperature of the head array used for printing is used as a reference. The temperature between the plurality of head arrays is made uniform before the next printing by setting the temperature and driving the droplet discharge head driving circuit of the head array that is not used for printing to adjust the temperature. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 3 ,
An image forming apparatus characterized in that a driving waveform used to drive the droplet discharge head driving circuit when adjusting the temperature of the head array is a fine driving waveform that does not discharge droplets from the droplet discharge head. .

Images