JP2007045111A - Transfer device and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet transfer device and a recording device which can be put into a low-noise and stable suction condition by optimizing sheet suction conditions. <P>SOLUTION: The transfer device, transferring recording mediums while sucking onto a platen, comprises a pressure detection means to detect pressure to suck a recording medium 43 transferred to the platen 45 and a platen suction means capable of lowering the pressure to suck the recording medium 43 to the platen 45 by information from the pressure detection means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conveying device that sucks and conveys a sheet and an ink jet recording apparatus including the conveying device.

  Conventionally, in an ink jet printer that performs printing using liquid or heat-meltable ink, in order to minimize the distance between the recording head that moves while ejecting the ink and the recording medium, and to improve the image quality, the distance is used. It is necessary to ensure a certain level. Further, it is necessary to prevent the recording medium from rubbing against the recording head.

  Therefore, some ink jet printers are provided with the conveying roller and a plate spring-like member at a position adjacent to the recording head to suppress deformation of the recording medium and keep the distance between the recording head and the recording medium constant. .

  However, if the recording medium is sandwiched between the conveying roller or a leaf spring-like member immediately after the ink is ejected from the recording head and attached to the recording medium, the surface of the recording medium or the inside of the recording medium may be damaged due to the nature of the ink. Before the ink is dried and solidified, a phenomenon occurs in which recorded characters and figures are deformed due to the contact of the rollers.

  For this reason, there is known a recording apparatus including a suction-type recording medium transport device that transports a recording medium from below the recording head along the holding surface of the recording unit by negative pressure due to air suction (see Patent Document 1).

  The suction-type recording medium transport device transports the recording medium along the holding surface of the recording unit by negative pressure due to air suction. Therefore, if the negative pressure is too large, the recording medium cannot be fed with high accuracy by the transport roller. . On the other hand, if the negative pressure in the recording portion is too small, the flatness of the recording medium cannot be maintained when the recording medium is curled in a high-temperature and high-humidity environment or the like, so that the image quality is degraded.

  In ink jet recording, if the distance between the recording head and the recording medium is kept short and constant, ink landing accuracy is improved and high image quality can be realized. For this reason, in the method of sucking and holding the recording medium, it is necessary to stably suck the negative pressure.

  In the suction recording medium transport device, the fan motor is driven to rotate the fan to generate a negative pressure. However, various suction pressure conditions are required depending on the type of the recording medium because of the demand for various recording media. Further, it is necessary to consider the occurrence of cockling or the floating of the recording medium due to curling or the like during recording conveyance.

  Therefore, in order to satisfy the suction pressure condition corresponding to the type of the recording medium, the suction setting condition is higher than the suction pressure substantially necessary for transporting the recording medium, such as the suction pressure setting in FIG. Is set to the highest value so as not to cause an abnormal conveyance of the recording medium.

JP 2002-127469 A

  In recent years, printers have been introduced into offices, and it has become an important issue to reduce printer noise. For this reason, as one of the noise sources, it is required to reduce the noise of the suction fan as much as possible. In order to meet this requirement, it is necessary to set a necessary minimum suction pressure for each recording medium.

  However, as described above, the conditions of the suction pressure have different characteristics for each recording medium, and there are many types. In order to suppress the floating of the recording medium under the minimum suction pressure condition corresponding to the recording medium, it has become difficult to cope with only a predetermined suction pressure as in the prior art.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a transport device and an ink jet recording apparatus that can achieve a stable suction state with low noise by optimizing the suction conditions of the sheet. .

  A representative means in the present invention for solving the above-described problems is a pressure detection for detecting a suction pressure of the recording medium to be conveyed to the platen in a conveying apparatus that conveys the recording medium while sucking the recording medium onto the platen. And a platen suction means capable of lowering the suction pressure of the recording medium to the platen by information from the pressure detection means.

  The present invention can always set the suction state to an optimum value when transporting the recording medium, and can realize quiet and highly accurate recording medium transportation without increasing the apparatus cost.

  Next, an ink jet recording apparatus provided with a transport apparatus according to an embodiment of the present invention will be described.

  FIG. 2 is an external view of the ink jet printer according to this embodiment. FIG. 2 shows a state where the front cover 103 is opened and the carriage 101 inside can be seen.

  An operation panel 102 is disposed in front of the right side of the apparatus. The operation panel 102 is provided with an input operation unit 102a such as various operation buttons and a display unit 102b which is a liquid crystal display here.

  FIG. 3 is an enlarged view of a drive-related portion of the carriage 101. A recording head 203 (here, four colors of yellow, magenta, cyan, and black) integrated with an ink cartridge is detachably mounted on the carriage 101. The carriage 101 is slidably held on the support shaft 205, and the rotational power of the carriage motor 201 is converted into the reciprocating motion of the carriage 101 via the belt 202.

  FIG. 4 shows a control hardware configuration example of the main part of the ink jet printer in the present embodiment. This configuration is roughly divided into a control block, an operation panel 102, a carriage motor 201, a transport motor 507, and a recording head 203. The control block includes a control unit 504 that can be configured by a CPU or the like, and the entire apparatus is controlled by a control program recorded in an internal ROM or the like.

  The control unit 504 uses the memory 501 as a temporary storage area for data and a storage area for work. It is preferable that at least the storage area for storing the status information (status parameter) of the abnormal carriage state related to the present embodiment is nonvolatile. The control unit 504 controls the carriage motor 201 via the motor driver 502. A pulse signal is output from the linear sensor 401 as the carriage 101 moves. Further, the control unit 504 recognizes the current position of the carriage 101 based on the count value and determines the ink ejection timing.

  Further, the control unit 504 drives the recording head 203 to eject ink at the determined ejection timing via the head driving unit 505 and according to the given recording data.

  The recording head 203 of the present embodiment energizes the electrothermal converter in response to a recording signal, and the ink is ejected by the growth and contraction of bubbles generated in the ink using film boiling generated in the ink by the thermal energy. The ink is ejected from the recording. In this way, by ejecting ink by growing and shrinking bubbles with thermal energy, it is possible to achieve ejection of a liquid with particularly excellent responsiveness.

  Further, the control unit 504 further drives the transport motor 507 via the motor driver 506 to transport the recording medium in a direction orthogonal to the carriage movement direction. The platen suction fan 516 is controlled by the fan drive circuit 515 when the recording medium is conveyed by the conveyance motor 507.

  Next, with reference to FIG. 5, the conveyance system which comprises the platen suction means in this embodiment is demonstrated.

  As will be described below, the platen suction means of this embodiment has pressure detection means for detecting the suction pressure to the platen 45 of the transported recording medium 43, and recording is performed based on information from the pressure detection means. The suction pressure of the medium to the platen 45 can be lowered.

  As shown in FIG. 5, a recording head 203 in which a plurality of ink ejection ports (not shown) for ejecting ink are formed, and the recording head 203 are mounted in the main scanning direction (arrow A). A carriage 101 that reciprocates in a direction perpendicular to the direction), a conveyance roller 44 and a pinch roller 42 that convey the recording medium in the direction of arrow A or arrow B while sandwiching the recording medium are disposed.

  The carriage 101 reciprocates in the main scanning direction while being guided by a guide rail 23 extending in the main scanning direction. Further, the pinch roller 42 rotates following the rotation of the conveying roller 44. The pinch roller 42 is attached to the pinch roller arm 46 and is urged so as to be pressed against the conveying roller 44 by a coil spring 47 connected thereto.

  Further, the printer is provided with a platen 45 on which a roll paper drawn portion or a cut paper (not shown) is placed as the recording medium 43. A large number of suction holes 45 a are formed in the platen 45. Each suction hole 45 a and a suction fan 516 are formed below the platen 45. The cut paper or roll paper placed on the platen 45 generates negative pressure on the platen 45 when the suction fan 516 is driven (rotated), whereby the recording medium 43 is sucked and adhered to the platen 45.

  Here, an outline of the operation of the ink jet printer in the present embodiment will be briefly described.

  Prior to using the printer shown in FIG. 2, the user sets a recording medium on the platen 45. The recording medium 43 is configured to be either a cut recording medium or a roll recording medium, but here, a description will be given using a cut recording medium.

  First, the front cover 103 is opened, and the pinch roller pressure lever (not shown) is released. Next, the recording medium 43 is set according to the reference on the platen 45. By setting the recording medium 43 at the reference position, the recording medium 43 is detected by a recording medium detection sensor (not shown) provided on the platen 45, and the recording medium is detected by the pinch roller 42 and the recording medium conveying roller 44. 43 can be sandwiched.

  The recording medium detection sensor is arranged behind the pinch roller 42 and the recording medium conveyance roller 43 with respect to the ejection direction of the recording medium 43, and the rear end of the recording medium 43 is separated from the recording medium detection sensor during recording. Even if the recording medium 43 is detached, the recording medium 43 can be held on the platen 45.

  The positional relationship with the nozzles of the recording head 203 is such that even if the rear end of the recording medium 43 is removed from the recording medium detection sensor during recording, the so-called “platen recording” does not occur.

  A suction fan 516 for attracting the recording medium 43 onto the platen 45 is provided inside the platen 45, and the platen 45 is provided with a plurality of suction holes 45a. When the recording medium 43 is detected by the recording medium detection sensor, the suction fan 516 operates and the recording medium 43 is attracted onto the platen 45. In this state, the pinch roller pressure lever is operated to sandwich the recording medium 43 between the pinch roller 42 and the recording medium conveying roller 44, and the front cover is closed.

  Next, after the recording medium 43 is set on the platen 45, loading of the recording medium 43 is started by a key operation on the operation panel 102. The loading of the recording medium 43 includes (1) positioning the leading and trailing edges of the recording medium 43 (detecting the length in the transport direction), (2) detecting the width of the recording medium 43, and (3) detecting skew.

  The trailing edge of the recording medium 43 is detected by the above-described recording medium detection sensor. In the detection of the trailing edge of the recording medium 43, the time when the recording medium 43 is transported in the ejection direction from the state in which the recording medium 43 is detected by the recording medium detection sensor and the recording medium 43 is not detected is determined. The rear end.

  The recording medium 43 is conveyed by driving a conveyance motor 507 connected to the recording medium conveyance roller 44. Detection of the leading end of the recording medium 43 is performed by a recording medium sensor (not shown) provided on the carriage 101. In order to detect the leading end position of the recording medium 43, the carriage 101 is first moved from the home position of the carriage 101 to above the recording medium. When the carriage 101 is moved onto the recording medium 43, the recording medium 43 can be detected by the recording medium sensor. In a state where the recording medium 43 is detected by the recording medium sensor, the recording medium 43 is conveyed in the direction opposite to the ejection direction. When the leading end of the recording medium 43 reaches the recording medium sensor, the recording medium sensor detects the state of “no recording”. The point in time when the recording medium is “absent” is the leading end portion of the recording medium 43.

  By detecting the trailing edge and the leading edge of the recording medium 43 described above, the length of the recording medium 43 in the transport direction can be known.

  The carriage-mounted recording medium sensor and the linear sensor 401 are used to detect the width and skew of the recording medium 43. When the linear sensor 401 detects one slit, the linear scale count value is incremented from 0 when the movement direction of the carriage 101 moves from the home position to the forward direction, and conversely when it moves in the backward direction. Decrement from the linear scale count value when the direction is reversed. Thereby, the position of the carriage 101 can be obtained based on the linear scale count value.

  Therefore, the width of the recording medium 43 is detected from the home position of the carriage 101 to the first end of the recording medium 43 (the point at which the output of the recording medium sensor changes from “no recording medium” to “present”). Is determined from the linear scale count value up to and the second end of the recording medium (the point at which the output of the recording medium sensor changes from “present” to “absent”). can do.

  When the setting and loading of the recording medium 43 are completed normally, the recording operation is started next. If the recording data has already been received from the host, the recording is started immediately. Otherwise, the recording is started after receiving the recording data from the host. The image is formed by repeating the reciprocating operation of the carriage 101 and the ejection of ink based on the linear scale timing taken in during the reciprocating operation, and the conveyance of the recording medium in accordance with the reciprocating operation cycle of the carriage 101.

  The recording head 203 mounted on the carriage 101 has a plurality of nozzles arranged in a direction orthogonal to the moving direction of the carriage 101, and each nozzle has a linear scale timing taken in by the movement of the carriage 101. Discharge corresponding to the recording data is performed.

  The recording mode includes bidirectional recording, unidirectional recording (forward recording, backward recording), multi-pass recording, and the like. Here, one-pass unidirectional recording (forward recording) will be described.

  Ink is ejected at the linear scale timing that is taken in when the carriage 101 moves in the forward direction, and ink is not ejected when the carriage 101 moves in the backward direction. Upon completion of the backward movement of the carriage 101, the transport motor 507 is moved to transport the recording medium for one band (here, “one band” corresponds to the length of a plurality of nozzle rows arranged in the recording head 203). Drive. By repeating this operation, an image is formed.

  FIG. 6 is a graph showing an example of the relationship between the area where the recording medium 43 blocks the platen 45 and the number of rotations of the suction fan 516 (when the driving conditions are fixed) in this embodiment.

  If the rotation speed (702) of the suction fan 516 when the blocking amount on the platen 45 is 100% is compared with the case where the blocking amount is reduced by about 5% (701), the rotation speed of the fan decreases by 1 Hz.

  As described above, it is possible to detect a change in the suction pressure of the recording medium on the platen 45 by detecting a change in the rotation speed of the suction fan 516 under any same driving condition. Therefore, the pressure detection means of the present embodiment detects the suction pressure by detecting the amount of change in the rotation state of the suction fan 516, whereby the floating state of the recording medium 43 can be detected.

  FIG. 7 illustrates an example of a current waveform when the suction fan 516 is driven (two-phase DC motor fan), and a method for detecting a rotation state of the fan motor from a driving current waveform will be described.

  In FIG. 7, a waveform (602) when the blocking amount of the platen 45 is 90% with respect to the current waveform when the blocking amount of the platen 45 by the recording medium 43 is 100% (601) is shown in the graph.

  The current waveform of the two-phase DC motor in FIG. 7 is a time (604) in which four similar waveforms (605) are generated while the suction fan 516 makes one rotation, and corresponds to a driving time for one rotation of the suction fan 516. This one repetition time (605) or four repetition times (604) are compared. The time difference (603) of ΔT can be detected when the platen blocking amount is 100% (601) and 90% (602) in FIG.

  FIG. 1 shows a circuit for detecting the motor rotation state from the drive current. It consists of a resistor 70 that converts the drive current of the suction fan 516, a low-pass filter 71 that reduces high-frequency noise in the voltage waveform, and a comparator 72 that detects the periodic component of the signal at an arbitrary signal level. Detects the rotation state.

  The rotational speed state of the suction fan 516 driven by the drive command signal 75 is detected by the rotational speed detection circuit 73 from the drive current waveform. A correction value calculation 74 of the drive command value is performed on the correction value of the suction fan 516 from the detected displacement amount of the rotation cycle. The suction fan 516 is brought into a normal rotation state by the drive signal 76 corrected with respect to the drive command signal 75, but the suction state is corrected.

  Next, the control sequence of this embodiment will be described. First, the setting of the suction fan rotation cycle reference value in the state where the suction state of the recording medium to be used first is normally sucked is acquired. The above initialization sequence will be described with reference to FIG. This sequence is performed by the initialization operation of the recording medium conveyance position before the start of recording.

  In FIG. 8, first, the platen suction fan 516 is turned on (S1), and then the rotation period T0 of the suction fan 516 in a state where the platen top is opened is measured (S2). Next, the recording medium is conveyed onto the platen (S3), and the rotation period TM of the suction fan 516 in the platen suction state is measured (S4). From the above measurement, it is determined that the suction is not correctly performed unless the rotation period TM in the suction state is shorter than the rotation speed T0 in the open state on the platen. That is, T0−TM> α (S5). However, α is a constant larger than 1 and determined by the platen mechanism.

  In the above case, it is determined that the suction state is correct, and the rotation period TR of the suction fan 516 with the correct suction pressure is stored in the memory as the reference rotation period.

  On the other hand, when the rotation cycle is T0−TM ≦ α, it is determined that the sheet is not sucked correctly on the platen, and the drive command value V is increased (S7). At this time, it is confirmed whether the drive command value is the maximum value, and the procedure for confirming the rotation speed of the suction fan 516 when the platen is opened is repeated again with the reset drive command value (S8). If the maximum value is exceeded, the process ends abnormally (S9).

  Next, a sequence for optimizing the suction state of the recording medium during the recording operation will be described with reference to the flowchart shown in FIG.

  The recording medium suction pressure during the recording operation is confirmed in real time for each recording medium transport operation. Before transporting the recording medium, the platen suction fan 516 is operating or turned on (S20). Here, the recording medium is conveyed onto the platen (S21), and the rotation period TM2 of the suction fan 516 is measured in a state where the recording medium is blocked on the platen 45. From the value of the rotation period TM2 and the reference rotation period TR, if TR ≧ TM2, it is determined that the fan is normal from the rotational speed of the fan (S23, S24).

  When the suction pressure decreases due to the floating of the recording medium, TR <TM2, and it is determined that the suction state is abnormal. At that time, the drive state of the suction fan 516 is corrected and controlled according to the correction value VH of the ink cartridge (S25).

  Correction value VH = V × ((TR−TM2) / TR)

  However, they are the reference drive command value V, the reference rotation period TR, and the measurement rotation period TM2.

  It is confirmed that the corrected drive command value VH is not the maximum voltage VMAX (S26), and the suction state setting sequence is performed again. On the other hand, if the drive command value VH exceeds the maximum value VMAX, the process ends abnormally (S27).

  Next, the control state of the suction pressure during the recording sequence in the present embodiment will be described with reference to FIG.

  The drive signal for the suction pressure required for the recording medium 43 requires a high suction pressure P1 at the beginning of conveyance of the recording medium as in the conventional case, but once the recording medium sucks, it can be sucked at the minimum suction pressure P3. It becomes possible. When the sheet is lifted from the platen 9 due to sheet characteristics during the recording operation, the conventional sheet suction pressure setting pattern predicts the lift during recording and sets the suction pressure P2. However, since the floating of the recording medium can be corrected in real time in this embodiment, the suction pressure P3 can be set to a lower suction pressure P3 at the initial stage during recording, and can be set to the suction pressure P2 after correction after detecting the suction pressure change.

  As described above, since the suction pressure can be set to an optimal value in more detail, the suction pressure of the recording medium can be accurately ensured while reducing fan noise. For this reason, it can be suitably used for a recording apparatus in which it is particularly desirable to minimize the distance between the recording head and the sheet, such as an ink jet recording apparatus.

  In the above-described embodiment, an example in which ink is ejected by thermal energy driven by a recording head in response to a signal is shown in the ink jet recording apparatus, but this need not be limited to thermal energy, and other mechanical Of course, the ink may be ejected by energy.

It is a block diagram which shows the structural example of the suction pressure control of a platen suction mechanism. 1 is an external view of an ink jet printer as an example of an image forming apparatus. FIG. 3 is an enlarged view showing a driving-related portion of a printer carriage. 2 is a block diagram illustrating a drive control configuration of the image forming apparatus. FIG. It is a figure which shows the conveyance mechanism side view of a printer. It is a graph which shows the relationship between the blockage state of a platen suction mechanism, and suction fan rotation speed. It is explanatory drawing of the drive current waveform of a suction fan. It is a flowchart which shows the setting method of a suction pressure reference value. It is a flowchart which shows the setting method of the platen suction pressure optimal value during recording. It is a graph which shows the outline | summary of the suction state in a printing sequence. It is a graph which shows the outline | summary of the suction pressure state in the conventional recording sequence.

Explanation of symbols

23… Guide rail
42… Pinch roller
43… Recording media
44… Conveying roller
45… Platen
45a… Suction hole
46… Pinch roller arm
47 Coil spring
70… Resistance
71… Low-pass filter
72… Comparator
73… Rotation speed detection circuit
74… Correction value calculation
75… Drive command signal
76… Drive signal
101 Carriage
102 ... Control panel
102a ... Input operation unit
102b ... Display section
103… Front cover
201 ... Carriage motor
202 ... belt
203… Recording head
205… support shaft
401… Linear sensor
501 ... Memory
502… Motor driver
504… Control unit
505 ... Head drive
506… Motor driver
507… Conveyance motor
515… Fan drive circuit
516… Platen suction fan

Claims (5)

In a transport device that transports a recording medium while sucking it onto the platen,
Platen suction means having pressure detection means for detecting the suction pressure to the platen of the recording medium being conveyed, and capable of reducing the suction pressure to the platen of the recording medium by information from the pressure detection means A conveying apparatus comprising: The platen suction means rotates a fan to generate a negative pressure to suck the recording medium into the platen, and the pressure detection means detects the amount of change in the rotation state of the fan to detect the suction pressure. The transport apparatus according to claim 1, wherein The conveyance device according to claim 2, wherein the rotational speed state of the fan is detected by a periodic change in a driving current of the fan. In an inkjet recording apparatus that performs recording by transporting a recording medium while sucking it onto a platen, and performing recording by scanning a recording head that discharges ink in a direction that intersects the conveyance direction of the recording medium.
An ink jet recording apparatus comprising the transport device according to claim 1 as a transport device for transporting the recording medium. 5. The ink jet recording apparatus according to claim 4, wherein the ink jet recording apparatus ejects ink by thermal energy or mechanical energy driven by the recording head according to a signal.