JP2005131928A - Recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a recorder in which registration gap of each image caused by local variation in the carrying speed of a recording medium can be corrected when images are recorded sequentially on the recording medium being carried by a plurality of recording means. <P>SOLUTION: Rotational speed of rolls 100YA-100KB for carrying a sheet P is detected by encoders 154YA-154KB to produce encoder pulse signals 156YA-156KB, and the forward end of the sheet P under carriage is detected by a sheet sensor 152 to produce a sensor signal 158. A print control section 160 controls print start timing of recording head arrays 42YA-42KB based on these signals. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recording apparatus, and more particularly, an inkjet recording apparatus that records an image by ejecting ink droplets from a recording head to a recording medium, and an output of a facsimile, a copier, a printer complex machine, a workstation, or the like having these functions. The present invention relates to a recording apparatus used as a device.

  In recent years, the spread of color documents in offices is remarkable, and various output devices have been proposed. In particular, a small-sized and low-cost inkjet method is used in various output devices.

  A recording head used in an ink jet system includes an energy generation unit, an energy conversion unit that converts energy generated by the energy generation unit into an ink discharge force, an ink discharge port that discharges an ink droplet by the ink discharge force, and an ink discharge port And an ink supply path for supplying ink. As the energy generation means, bubbles are generated by heating ink by means of discharging ink droplets using an electromechanical converter such as a piezo element or an electrothermal conversion element having a heating resistor, and the ink is generated by generating the bubbles. There are means for discharging droplets.

  In a recording head that uses an electrothermal conversion element, since the electrothermal conversion element is small, it is possible not only to arrange the ink discharge ports at a high density, but also to divert semiconductor integrated circuit manufacturing technology as its manufacturing technology. Therefore, it is possible to reduce the size of the recording head having a large number of high-precision ink discharge ports and to manufacture it at low cost.

  However, at present, a printing method called serial scan in which printing is performed one band at a time by reciprocating a recording head while conveying a recording medium is prevalent. This method is small and low in cost, but has a drawback that the printing speed is slow because the recording head needs to be scanned a plurality of times in order to form an image over the entire recording medium. In order to improve the printing speed, it is necessary to reduce the number of scans, and it is essential to lengthen the recording head. A non-scanning printing method performed by a recording head having a recording medium width has advanced this to the limit. This printing method is an ink jet recording apparatus having a recording head corresponding to a recording medium width in which a large number of ejection openings are arranged over a length substantially the same as the width of the recording medium. Recording is performed by moving.

  As described above, a so-called full-line head type ink jet recording apparatus has been proposed in which printing is performed while a recording medium is continuously conveyed by a non-scanning type recording head corresponding to the recording medium width. In such a full-line ink jet recording apparatus of the full line head type, a recording head of a plurality of colors (yellow (Y), magenta (M), cyan (C), black (K), etc.) for forming a color image is used. Are arranged along the conveyance direction of the recording medium, and ink droplets are sequentially ejected from the recording head of each color to the conveyed recording medium, and a color image is recorded by superimposing the images of each color on the recording medium. It is supposed to be configured.

  By the way, in the above-described ink jet recording apparatus, a roll conveying method in which a plurality of conveying rolls are arranged along a conveying direction (conveying path) and rotated to convey a recording medium, or a conveying belt wound around a driving roll. A belt conveyance system or the like is employed that is arranged along the conveyance direction and rotated. However, in the roll conveyance method, the conveyance speed of the recording medium fluctuates due to variations in the rotation speed of each conveyance roll, and in the belt conveyance method, due to component accuracy such as uneven thickness of the conveyance belt and roundness of the drive roll. And the image recording timing of the recording heads of the respective colors with respect to the recording medium is relatively shifted to cause a registration shift of the respective color images.

On the other hand, in the belt conveyance system, for example, the conveyance speed of the conveyance belt (conveyance means) is detected by a speed detector (speed detection means), and the control unit is based on the conveyance speed of the conveyance belt detected by the speed detector. A technique has been proposed in which the image recording timing of each recording head (each recording means) is adjusted by (timing adjusting means) so that the registration of each color image due to the unevenness of the thickness of the conveyor belt can be matched with high accuracy. (For example, refer to Patent Document 1).
JP-A-2-80269

  However, in the above-described conventional technology, the conveyance speed of only one portion of the conveyance belt is detected by a single detection unit (in the example of Patent Document 1, the recording head positioned on the most upstream side in the recording medium conveyance direction). Caused by partial belt slack, expansion / contraction, or belt vibration due to rotation unevenness of the drive roll, etc., which occurs at a position away from the detection location (upstream portion) (downstream in the recording medium conveyance direction in the example of Patent Document 1). The local speed fluctuation of the conveying belt cannot be detected. Therefore, there is a problem that the adjustment accuracy of the image recording timing of the recording head arranged away from the detection means is not improved so much and the registration deviation cannot be sufficiently improved.

  In addition, for example, in a configuration in which the number of recording heads is large and the conveyance path is long, the belt intermediate portion is supported by a plurality of rotating rolls in order to suppress the slackness of the elongated conveyance belt. In some cases, due to partial expansion and contraction of the conveyor belt between the rotating rolls, vibrations, etc., the speed near each winding portion of the conveying belt wound around each rotating roll (peripheral speed when the winding angle is large) Since the difference occurs and local fluctuation occurs in the conveyance speed of the recording medium, the above-described conventional technology cannot sufficiently correct the registration deviation due to the local fluctuation in the conveyance speed.

  Also, in the roll transport method, as described above, the rotational speed of each transport roll varies, so that a difference occurs in the peripheral speed of each transport roll, resulting in local fluctuations in the transport speed of the recording medium, resulting in registration deviation. Wake up. Therefore, it is necessary to improve the registration deviation due to this roll conveyance method.

  In the present invention, in consideration of the above facts, when images are sequentially recorded on a recording medium to be conveyed by a plurality of recording means, registration of each image that occurs due to local fluctuations in the conveyance speed of the recording medium It is an object of the present invention to provide a recording apparatus capable of correcting a shift and realizing high-quality image recording.

  In order to achieve the above object, the invention described in claim 1 is directed to a conveying unit that conveys a recording medium in a predetermined conveying direction, and an image with respect to the recording medium that is arranged and conveyed along the predetermined conveying direction. A plurality of recording means for sequentially recording the recording medium, and a detection signal generating means for detecting a front end of the recording medium that is disposed upstream of the plurality of recording means in the predetermined transport direction and generates a detection signal; A plurality of reference signal generating means disposed in the vicinity of at least two recording means of the plurality of recording means and detecting a recording medium conveyance speed of the conveying means to generate a reference signal; And a control means for controlling the image recording timing of at least one recording means arranged in the vicinity of each reference signal generating means based on each of the input detection signal and the plurality of reference signals. It is characterized by having, when.

  According to the first aspect of the present invention, image recording by the recording apparatus is performed by a plurality of recording units arranged along a predetermined transport direction on a recording medium transported in a predetermined transport direction by the transport unit. This is done by recording sequentially. As a result, a plurality of images recorded by a plurality of recording units are superimposed on the recording medium to form a multi-color or full-color image.

  In this image recording, the detection signal generating means arranged upstream of the plurality of recording means in the predetermined transport direction generates the detection signal when detecting the leading end of the transported recording medium. The plurality of reference signal generating means arranged in the vicinity of at least two recording means among the plurality of recording means respectively detect the recording medium conveyance speed of the conveying means at the arrangement location. Generate a reference signal. Then, the control means controls the image recording timing of at least one recording means arranged in the vicinity of each reference signal generating means based on each of the input detection signal and the plurality of reference signals.

  Regarding the image recording timing: T2, basically, the distance between the detection signal generating means and the recording means (design value): L1, the distance from the leading edge of the recording medium to the image recording start position (image data): L2, the recording medium The transport speed: V1, and the detection timing of the leading edge of the recording medium: T1 (T2 = (L1 + L2) / V1 + T1). In this case, for example, the control means records the transport means according to the input reference signal. When it is recognized that the medium transport speed (V2) matches the reference transport speed (V1) (V2 = V1), the recording means starts image recording at the reference image recording timing (T2), and When it is recognized that the recording medium conveyance speed of the conveyance means is slower than the reference conveyance speed (V2 <V1), the deceleration based on the reference signal is performed with respect to the reference image recording timing. In response to (−ΔV2), the image recording timing of the recording means is delayed (+ ΔT2), and when it is recognized that the recording medium conveying speed of the conveying means is higher than the reference conveying speed (V2> V1). For example, the image recording timing of the recording means is increased (−ΔT2) in accordance with the speed increase (+ ΔV) based on the reference signal with respect to the reference image recording timing. Such control is performed for each of at least one recording means arranged in the vicinity of each reference signal generating means. For example, the reference signal generating means is arranged in the vicinity of all the recording means. If so, the above-described control based on each reference signal generated by each reference signal generation unit can be performed on all the recording units.

  In this way, the recording medium conveyance speed with respect to the conveyance means is detected at a plurality of locations, and the image recording timing of the corresponding recording means is controlled according to the detection speed at each location, so that the conveyance speed of the recording medium is locally determined. The registration shift of each image caused by the fluctuation is corrected, and high-quality image recording can be realized.

  According to a second aspect of the present invention, in the recording apparatus according to the first aspect, the conveying unit is substantially opposed to the plurality of recording units and is adjacent to the plurality of recording units and the recording units along the predetermined conveying direction. A plurality of conveying rolls disposed between each of the plurality of conveying rolls, and a rotation driving unit that rotationally drives the plurality of conveying rolls, and the reference signal generating unit detects the rotation speed of the conveying rolls and detects the conveying rolls. Rotational speed detection means for generating the reference signal indicating the recording medium conveyance speed according to the above.

  In the invention according to claim 2, the plurality of transport rolls constituting the transport unit are respectively disposed in the vicinity of the plurality of recording units and between the recording units along a predetermined transport direction substantially facing the plurality of recording units. Then, the plurality of transport rolls are rotationally driven by the rotation driving means, whereby the recording medium is transported in the predetermined transport direction by the plurality of transport rolls.

  In such a roll conveyance system, the reference signal generation means is constituted by a rotation speed detection means that detects a rotation speed of the conveyance roll and generates a reference signal indicating a recording medium conveyance speed by the conveyance roll. As a result, even if there is a variation in the rotational speed of each transport roll and there is a difference in the peripheral speed of each transport roll and local fluctuations occur in the transport speed of the recording medium, a plurality of (at least two) transport rolls Rotational speed detection means provided in the apparatus detects the rotational speed of each transport roll, and generates a reference signal indicating the recording medium transport speed (deceleration / acceleration, etc. with respect to the reference transport speed) by the transport roll. Since the image recording timing of each recording unit corresponding to each reference signal is controlled by the unit, registration deviation of each image recorded by each recording unit can be accurately corrected.

  In addition, when the transporting unit is such a roll transporting system, a plurality of transporting rolls are arranged in the vicinity of the plurality of recording units and between the recording units, respectively, so that the respective opposing positions (conveying units) An empty space can be secured between the rolls). For example, when a maintenance mechanism or the like for maintaining the recording unit is arranged in the vicinity of the recording unit, the maintenance mechanism or the like can be easily arranged at a position facing the recording unit using the empty space.

  According to a third aspect of the present invention, in the recording apparatus according to the second aspect, the rotation driving means is a single drive source that rotationally drives the endless belt wound around the plurality of conveying rolls and the endless belt. It is characterized by providing these.

  In the invention according to claim 3, a plurality of transport rolls are driven by a single drive source via an endless belt, so that, for example, a plurality of transport rolls are driven by a plurality of drive sources. It is possible to suppress the influence of fluctuations in the recording medium conveyance speed by superimposing fluctuations in the speed of the drive source, and the recording medium can be conveyed at a more constant speed. In addition, if the endless belt is wound around the surface of the roll contacted by the recording medium of the transport roll, periodic fluctuations in speed can be suppressed even if there is runout due to the processing accuracy of the transport roll and the holding method. The conveyance speed of the recording medium by each conveyance roll can be kept at a more constant speed. In this way, the fluctuation in the conveyance speed that occurs when the recording medium is conveyed by a plurality of conveyance rolls is suppressed in advance by a mechanical configuration, so that the influence on the local fluctuation in the conveyance speed can be suppressed and electrically Registration deviation of each image to be performed can be corrected with higher accuracy.

  Since the recording apparatus of the present invention has the above-described configuration, when images are sequentially recorded on a recording medium to be conveyed by a plurality of recording units, each image generated when the conveyance speed of the recording medium varies locally is recorded. Registration deviation is corrected, and high-quality image recording can be realized.

  Hereinafter, an inkjet recording apparatus to which a recording apparatus according to an embodiment of the invention is applied will be described with reference to the drawings. In the first to third embodiments described below, a full-line head type ink jet recording apparatus that performs printing while continuously conveying a sheet by a non-scanning recording head corresponding to the sheet width will be described as an example.

(First embodiment)
As shown in FIG. 1, the inkjet recording apparatus 10 according to the first embodiment includes a transport mechanism 150 that transports the paper P in a predetermined paper transport direction (the arrow X direction in the drawing). Is arranged along the paper transport direction, and sequentially records images on the transported paper P. Four colors of yellow (Y), magenta (M), cyan (C), and black (K) are recorded. Recording heads 44Y, 44M, 44C, and 44K are provided. In the present embodiment, the recording heads 44Y to 44K are arranged in the order of Y, M, C, and K from the upstream side in the paper conveyance direction, and each of the recording heads 44Y to 44K includes a pair of recording head arrays 42A and 42B. (Recording head 44Y: Recording head array 42YA, 42YB / Recording head 44M: Recording head array 42MA, 42MB / Recording head 44C: Recording head array 42CA, 42CB / Recording head 44K: Recording head array 42KA, 42KB) Further, a paper detection sensor that detects the leading edge of the paper P to be transported and generates a detection signal (hereinafter referred to as a sensor signal) on the upstream side of the recording head array 42YA located at the uppermost stream in the paper transport direction. 152 is arranged.

  The conveyance mechanism 150 is substantially opposed to the recording head arrays 42YA to 42KB, and is disposed in the vicinity of the recording head array 42YA and between the recording head arrays 42YA to 42KB along the paper conveyance direction. , 100YB, 100MA, 100MB, 100CA, 100CB, 100KA, 100KB), and a drive source (rotation drive means) such as a drive motor (not shown) that rotationally drives these transport rolls 100YA to 100KB. By rotating 100 YA to 100 KB by a driving source, the paper P is transported in a predetermined paper transport direction by transport rollers 100 YA to 100 KB.

  Further, rotary encoders 154YA to 154KB (hereinafter simply referred to as encoders 154YA to 154KB) are provided on the transport rolls 100YA to 100KB. When the transport rolls 100YA to 100KB are rotationally driven, the encoders 154YA to 154KB detect the rotational speed of the transport rolls 100YA to 100KB and generate a pulse signal having a frequency proportional to the rotational speed (hereinafter referred to as an encoder pulse signal). To do. This encoder pulse signal becomes a reference signal indicating the sheet conveyance speed by the conveyance rolls 100YA to 100KB. The encoder pulse signals 156YA to 156KB generated by the encoders 154YA to 154KB and the sensor signal 158 generated by the paper detection sensor 152 are input to the print control unit 160.

  As shown in FIG. 2, the print control unit 160 includes a selection unit 162 and a print timing signal generation unit 164.

  The selection unit 162 receives encoder pulse signals 156YA to 156KB and a selection signal 166 from a personal computer (not shown) or the like directly connected to the inkjet recording apparatus 10 or connected to the network (hereinafter referred to as a PC). 162 selects an encoder pulse signal to be used for controlling the recording head arrays 42YA to 42KB from among the input encoder pulse signals 156YA to 156KB according to an instruction of the selection signal 166. In the present embodiment, the selection unit 162 instructs the recording head array 42YA to use the encoder pulse signal 156YA of the encoder 154YA and the recording head array 42YB to output the encoder pulse signal 156YB (remaining) according to the instruction of the selection signal 166. The same applies to the recording head arrays 42MA to 42KB of the recording head arrays 42MA to 42KB). For each of the recording head arrays 42YA to 42KB, the encoder pulse signals generated by the encoders 154YA to 154KB of the transport rolls 100YA to 100KB arranged in the vicinity are selected. To do.

  Note that the selection signal 166 for instructing the selection pattern as described above can be switched to a selection signal for instructing another selection pattern. For example, the user can arbitrarily select the signal from the operation screen of the PC. Can do.

  The encoder pulse signals 156YA to 156KB assigned to the recording head arrays 42YA to 42KB by the selection unit 162 and the sensor signal 158 are input to the print timing signal generation unit 164. The print timing signal generation unit 164 generates print timing signals 168YA to 168KB for controlling the printing start timing of the recording head arrays 42YA to 42KB based on the encoder pulse signals 156YA to 156KB and the sensor signal 158 that are selectively input. And output to the recording head arrays 42YA to 42KB.

For printing (image recording) timing T2, basically, the distance between the paper detection sensor 152 and the recording head array 42 (design value): L1, the distance from the paper leading edge to the printing start position (image data): L2, From the transport speed of the paper P: V1 and the detection timing of the leading edge of the paper: T1, the following formula is used.
[T2 = (L1 + L2) / V1 + T1]
Here, in the print timing signal generation unit 164, the frequency (F2YA to F2KB) of the encoder pulse signal (reference signal) matches the reference frequency (F1) (F2YA to F2KB = F1), and the encoder pulse signal is When it is recognized that the rotation speed (V2YA to V2KB) of the transport roll 100 shown matches the reference rotation speed (V1) (V2YA to V2KB = V1), the reference image recording timing (T2YA to T2KB) is used. Then, print timing signals (168YA to 168KB) for starting printing on the recording head array (42YA to 42KB) are generated.

  Further, when it is recognized that the frequency of the encoder pulse signal is lower than the reference frequency (F2YA to F2KB <F1) and the rotation speed of the transport roll 100 is slower than the reference rotation speed (V2YA to V2KB < V1) A print timing signal that delays the image recording timing of the recording head array (42YA to 42KB) according to the deceleration (−ΔV2YA to −ΔV2KB) based on the encoder pulse signal with respect to the reference image recording timing (+ ΔT2YA to + ΔT2KB). (168YA to 168KB) is generated.

  Further, when it is recognized that the frequency of the encoder pulse signal is higher than the reference frequency (F2YA to F2KB> F1) and the rotation speed of the transport roll 100 is higher than the reference rotation speed (V2YA to V1KB>). V1) Printing (−ΔT2YA to −ΔT2KB) for increasing the image recording timing of the recording head array (42YA to 42KB) according to the speed increase (+ ΔV2YA to + ΔV2KB) based on the encoder pulse signal with respect to the reference image recording timing A timing signal (168YA to 168KB) is generated.

  Further, the print timing signal generation unit 164 adds the print start timing correction included in the print timing signal 168YA to the print timing signal 168YA, and adds the print timing signal 168YA and the print timing signal 168YA to the print timing signal 168MA. The print timing signal 168YB (the print timing signal 168YB including the correction amount of the print timing signal 168YA) is added to the print start timing correction (the same applies to the remaining print timing signals 168MB to 168KB). The print timing signal 168 of the recording head array 42 arranged on the downstream side in the transport direction includes a print start timing compensation included in the print timing signals 168 of all the recording head arrays 42 arranged on the upstream side. Performs signal generating process to apply a minute.

  The recording head arrays 42YA to 42KB start printing on the conveyed paper P at the timing indicated by the input print timing signals 168YA to 168KB.

  Next, the image recording operation and action of the inkjet recording apparatus 10 according to the present embodiment will be described.

  In the image recording by the ink jet recording apparatus 10, as shown in FIG. 3, when the printing process is started in step 170, the driving source of the transport mechanism 150 is driven to rotate and the transport rolls 100YA to 100KB rotate to transport the paper P. Get ready. Here, the encoders 154YA to 154KB provided on the transport rolls 100YA to 100KB detect the rotational speeds of the transport rolls 100YA to 100KB, respectively, generate encoder pulse signals 156YA to 156KB, and output them to the selection unit 162 of the print control unit 160. To do.

  Further, in step 172, the selection unit 162 of the print control unit 160 selects a reference signal (encoder pulse signals 156YA to 156KB). In this step 172, as described above, the selection unit 162, in response to the instruction of the selection signal 166 input from the PC or the like, of the transport rolls 100YA to 100KB disposed closest to the upstream side with respect to the recording head arrays 42YA to 42KB, respectively. A selection is made to assign the encoder pulse signals 156YA to 156KB from the encoders 154YA to 154KB.

  Next, in step 174, the paper P is supplied to the transport mechanism 150, and transport is started in the predetermined transport direction by the transport rolls 100YA to 100KB (in the direction of arrow X in FIG. 1). When the leading edge of the conveyed paper P is detected by the paper detection sensor 152, the paper detection sensor 152 outputs a sensor signal 158 to the print timing signal generation unit 164 of the print control unit 160. The print timing signal generation unit 164 records each recording arranged closer to the downstream side in the transport direction than the encoders 101YA to 101KB based on each of the input sensor signal 158 and the selectively input encoder pulse signals 156YA to 156KB. The above-described print timing signals 168YA to 168KB for controlling the print start timing of the head arrays 42YA to 42KB are generated and output to the recording head arrays 42YA to 42KB.

  Subsequently, in step 176, the recording head arrays 42YA to 42KB start printing at the timing indicated by the input print timing signal on the paper P conveyed in the predetermined conveyance direction by the conveyance rolls 100YA to 100KB. . As the paper is conveyed, images of the respective colors are sequentially recorded on the paper P by the recording head arrays 42YA to 42KB, and a full color image is formed. Finally, when printing by the recording head arrays 42YA to 42KB is finished, the paper P is discharged to the paper discharge unit of the inkjet recording apparatus 10, and the printing process is finished in step 178.

  As described above, in the inkjet recording apparatus 10 of the present embodiment, in image recording, the sheet conveyance speed with respect to the conveyance mechanism 150 is detected in the vicinity of the recording head arrays 42YA to 42KB (eight positions) and detected at each position. By controlling the image recording timing of the corresponding recording head arrays 42YA to 42KB in accordance with the paper conveyance speed, the registration deviation of each image that occurs due to local fluctuation of the paper P conveyance speed is corrected. . Furthermore, in this embodiment, the registration error of each image can be corrected with higher accuracy by detecting the sheet conveyance speed in the vicinity of each of the recording head arrays 42YA to 42KB and controlling the image recording timing. Therefore, high quality image recording can be realized.

(Second Embodiment)
FIG. 4 shows an ink jet recording apparatus according to the second embodiment of the present invention. In the ink jet recording apparatus 200 according to the present embodiment, the same reference numerals are given to the same parts as those of the ink jet recording apparatus 10 according to the first embodiment, and the description thereof is omitted.

  As shown in FIG. 4, in the ink jet recording apparatus 200 of the present embodiment, among the eight transport rolls 100YA to 100KB constituting the transport mechanism 150, only four of the transport rolls 100YA, 100MA, 100CA, and 100KA are encoder 154YA. 154MA, 154CA, and 154KA are provided.

  Encoder pulse signals 156YA, 156MA, 156CA, and 156KA generated by the encoders 154YA, 154MA, 154CA, and 154KA are input to the print controller 160 by the rotation of the transport rolls 100YA, 100MA, 100CA, and 100KA, and the print control is performed. The selection unit 162 (see FIG. 2) of the unit 160 controls any of the encoder pulse signals 156YA, 156MA, 156CA, and 156KA to be input to the recording head arrays 42YA to 42KB according to the instruction of the selection signal 166. Select whether to use for. In the present embodiment, the selection unit 162 instructs the encoder pulse signal 156YA of the encoder 154YA for the recording head arrays 42YA and 42YB and the encoder pulse of the encoder 154MA for the recording head arrays 42MA and 42MB according to the instruction of the selection signal 166. The encoder pulse signals 156YA, 156MA, 156CA, and 156KA are arranged on the downstream side of the encoders 154YA, 154MA, 154CA, and 154KA, respectively, such as the signal 156MA (the same applies to the remaining recording head arrays 42CA to 42KB). Are assigned for printing timing control of the recording head arrays 42YA to 42KB. That is, the encoder pulse signals 156YA, 156MA, 156CA, and 156KA are assigned for each of Y, M, C, and K colors (for each recording head 44) of the recording head array 42.

  Then, the print timing signal generation unit 164 (see FIG. 2) of the print control unit 160 uses the input sensor signal 158 and the selectively input encoder pulse signals 156YA, 156MA, 156CA, and 156KA to record the head array 42YA˜ Print timing signals 168YA to 168KB for controlling the print start timing of 42KB are generated and output to the recording head arrays 42YA to 42KB.

  In addition, regarding the generation process of the print timing signals 168YA to 168KB and the image recording operation (see FIG. 3) by the ink jet recording apparatus 200 of the present embodiment, assignment of encoder pulse signals to the first embodiment and the recording head arrays 42YA to 42KB. Since the other points are the same, detailed description thereof is omitted.

  In the ink jet recording apparatus 200 of the present embodiment described above, in image recording, the detection of the paper conveyance speed with respect to the conveyance mechanism 150 is performed in the vicinity for each of the Y, M, C, and K colors of the recording head arrays 42YA to 42KB. (4 locations), which occurs when the transport speed of the paper P varies locally by controlling the image recording timing for each color of the recording head arrays 42YA to 42KB according to the paper transport speed detected at each location. Registration deviation for each color of the image is accurately corrected. In this embodiment, the number of encoders is reduced as compared with the first embodiment, so that the apparatus cost can be reduced.

(Third embodiment)
FIG. 5 shows an ink jet recording apparatus according to a third embodiment of the present invention. Note that in the inkjet recording apparatus 210 according to the present embodiment, the same reference numerals are given to common portions with the inkjet recording apparatus 10 according to the first embodiment, and description thereof is omitted.

  As shown in FIG. 5, in the ink jet recording apparatus 210 of the present embodiment, encoders 154YA and 154CA are provided on only two of the transport rolls 100YA and 100CA among the eight transport rolls 100YA to 100KB constituting the transport mechanism 150. It has been.

  Encoder pulse signals 156YA and 156CA generated by the encoders 154YA and 154CA are input to the print controller 160 by rotating the transport rolls 100YA and 100CA, and the selection unit 162 (see FIG. 2) of the print controller 160 is In response to an instruction from the selection signal 166, one of the encoder pulse signals 156YA and 156CA to be input is selected to be used for controlling the recording head arrays 42YA to 42KB. In the present embodiment, the selection unit 162 applies the encoder pulse signal 156YA of the encoder 154YA, the recording head arrays 42CA, 42CB, 42KA, and 42KB to the recording head arrays 42YA, 42YB, 42MA, and 42MB according to the instruction of the selection signal 166. On the other hand, encoder pulse signals 156YA and 156CA, such as encoder pulse signal 156CA of encoder 154CA, are used for printing timing control of four recording head arrays 42YA to 42KB arranged downstream of encoders 154YA and 154CA. Assigned. That is, the encoder pulse signals 156YA and 156CA are assigned to two colors Y, M, C, and K of the recording head array 42, respectively.

  The print timing signal generation unit 164 (see FIG. 2) of the print control unit 160 starts printing of the recording head arrays 42YA to 42KB in response to each of the input sensor signal 158 and the selectively input encoder pulse signals 156YA and 156CA. Print timing signals 168YA to 168KB for controlling the timing are generated and output to the recording head arrays 42YA to 42KB.

  In addition, regarding the generation process of the print timing signals 168YA to 168KB and the image recording operation (see FIG. 3) by the inkjet recording apparatus 210 of the present embodiment, assignment of encoder pulse signals to the first embodiment and the recording head arrays 42YA to 42KB. Since the other points are the same, detailed description thereof is omitted.

  In the ink jet recording apparatus 210 of the present embodiment described above, in image recording, the paper transport speed for the transport mechanism 150 is detected in the vicinity of the recording head arrays 42YA and 42CA (two locations), and the paper transport detected at each location. An image generated by locally varying the conveyance speed of the paper P by controlling the image recording timing for each of Y, M, C, and K of the recording head arrays 42YA to 42KB according to the speed. The registration deviation for each of the two colors Y, M, C, and K is corrected with high accuracy. In this embodiment, the number of encoders is reduced as compared with the first and second embodiments, thereby further reducing the apparatus cost.

  As described above, in the first to third embodiments, the case where the number and arrangement location of the encoders 154 are changed has been described as an example. However, these are not limited to the above-described embodiments. For example, the number and arrangement location of the encoders 154 can be appropriately selected depending on conditions such as required registration deviation correction accuracy, combinations of images to be corrected (for each color type, etc.), apparatus cost, and the like. The means for detecting the rotational speed of the transport roll 100 (rotational speed detecting means) is not limited to the rotary encoder that digitally detects the rotational speed as described above, but, for example, a potentiometer that detects it in an analog manner, or the like. Other means can also be used.

  Further, the conveying means for conveying the recording medium to which the present invention is applied is not limited to the roll conveying method as described above, and may be a belt conveying type conveying means. In the case of the belt conveyance method, for example, a plurality of rotating rolls arranged to suppress looseness of the belt intermediate portion of the conveying belt are provided with a rotation speed detecting means (reference signal generating means) such as a rotary encoder, and each rotating roll By detecting the rotation speed of the belt, the conveyance speed at a plurality of locations of the conveyance belt is detected, or separately from the above-described rotation roll, the rotation speed detection means is provided and the conveyance speed of the belt is directly detected by contacting the conveyance belt. A plurality of dedicated speed detection rolls are provided, and the rotation speed of each speed detection roll is detected to detect the conveyance speed at a plurality of locations on the conveyance belt, or along the conveyance direction (rotation direction) on the conveyance belt. To read markings, slits, etc. formed at predetermined intervals with a plurality of reference signal generating means comprising non-contact reflection type or transmission type photoelectric sensors, etc. Ri for detecting the conveying speed of the plurality of locations of the conveyor belt, by the like can be corrected misregistration due to local transport speed variation of the conveyor belt.

(Example)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the ink jet recording apparatus to which the recording apparatus according to this example is applied is based on the configuration of the ink jet recording apparatus described in the first embodiment, and includes parts common to the first embodiment. The same sign is attached.

(Overall configuration of inkjet recording apparatus)
First, the overall configuration of the ink jet recording apparatus will be briefly described.

  As shown in FIG. 6, the inkjet recording apparatus 10 of the present embodiment includes a sheet supply unit 12 that feeds out a sheet, a registration adjustment unit 14 that controls the attitude of the sheet, and a recording that forms an image on a sheet by ejecting ink droplets. The recording unit 20 includes a maintenance unit 18 that performs maintenance of the head unit 16 and the recording head unit 16, and a discharge unit 22 that discharges a sheet on which an image is formed by the recording unit 20.

  The sheet supply unit 12 includes a stocker 24 in which sheets are stacked and stocked, and a transport device 26 that transports the sheets one by one from the stocker 24 to the registration adjusting unit 14.

  The registration adjusting unit 14 includes a loop forming unit 28 and a guide member 30 that controls the posture of the paper. By passing through this portion, the skew is corrected using the stiffness of the paper and the conveyance timing is controlled. In this configuration, the recording unit 20 is entered.

  As for the recording unit 20, a sheet conveyance path for conveying a sheet between the recording head unit 16 and the maintenance unit 18 is configured. For the sheet conveyed continuously (without stopping) on the sheet conveyance path. Thus, ink droplets are ejected from the recording head unit 16 and an image is formed on the paper. The recording head unit 16 and the maintenance unit 18 are each unitized, and the recording head unit 16 is configured to be separable across the maintenance unit 18 and the sheet conveyance path. Therefore, in the case of paper jam, the jammed paper can be easily taken out. Since the recording unit 20 will be described later, detailed description thereof will be omitted.

  The paper discharge unit 22 stores the paper on which the image is formed by the recording unit 20 in the tray 32 via the paper discharge belt 31.

(Configuration of recording head)
Next, the recording head unit 16 will be described in detail with reference to FIGS. FIG. 7 is a schematic view of the recording head unit 16 as viewed from above (a plan view as viewed from above for easy correspondence with FIG. 13).

  As shown in FIG. 7, the recording head unit 16 has a paper width direction (arrow Y direction; hereinafter referred to as width direction) orthogonal to the paper transport direction (arrow X direction; hereinafter referred to as “transport direction”). The recording head array 42 having six unit recording heads 40 arranged at regular intervals is basically configured by arranging eight recording head arrays 42 at regular intervals in the paper transport direction.

  As shown in FIG. 8, the unit recording head 40 has nozzles 58 that eject ink on a nozzle surface 40A formed in a straight line, and ejects ink droplets by a well-known thermal ink jet method. In the present embodiment, the unit recording head 40 has a nozzle array density of 800 dpi and 800 nozzles, an ejection frequency of 7.56 kHz, and uses pigment ink.

  The recording head arrays 42A and 42B are formed by attaching six unit recording heads 40 to a common substrate 46, which will be described later, in a straight line so that the nozzle arrangement direction of the unit recording heads 40 coincides with the width direction. Yes.

  As shown in FIG. 9, each of the recording head arrays 42A and 42B has six unit recording heads 40 arranged at regular intervals. In the recording head arrays 42A and 42B, the arrangement of the unit recording heads 40 is arranged. Are arranged so as to be shifted from each other in the width direction, so that a part of the nozzle row of the unit recording head 40 has an overlapping region OL that overlaps between the recording head arrays 42A and 42B. By providing the overlap area OL in this way, it is possible to prevent an area that cannot be printed from occurring in the print area. That is, printing of one color on the paper is performed by ejecting ink droplets from the nozzles 58 of the unit recording heads 40 of the recording head array pairs 42A and 42B. In this embodiment, the combination of the pair of recording head arrays 42A and 42B is referred to as a recording head 44.

  In the recording head 44 of the present embodiment, the print area is 12 inches, which is set wider than the A3 short width (A4 long width) of 297 mm of the maximum paper width PW.

  The recording head 44 is configured so that yellow (Y), magenta (M), cyan (C), and black (K) are printed in this order from the upstream side in the transport direction, and full-color printing is possible. The reference numbers of the heads are distinguished by adding symbols Y, M, C, and K (as 44Y, 44M, 44C, and 44K) (see FIG. 7). Hereinafter, the same applies to other members.

  In FIG. 7, since the recording heads 44Y to 44K have the same configuration, reference numerals are given only to the components of the recording head 44Y, and reference numerals for the components of the other recording heads 44M to 44K are omitted. doing.

  In the recording head array 42A constituting the recording head 44, as shown in FIG. 10, six unit recording heads 40 are attached to a common substrate 46A extending in the paper width direction at a predetermined interval.

  That is, as shown in FIG. 9, the unit recording head 40 is attached to the common substrate 46A, so that the nozzle rows are arranged in the width direction.

  Further, in the recording head unit 16, three star wheels are arranged between the recording head arrays 42 along the transport direction, upstream from the most upstream recording head array 42YA, and downstream from the most downstream recording head array 42KB. Groups 72A to 72C are arranged (see FIG. 7). In the star wheel groups 72A to 72C, six star wheels 70 are pivotally supported at predetermined intervals with respect to three shafts 74A to 74C arranged continuously in the width direction. Each shaft 74A-74C is urged | biased by the conveyance roll 100 side mentioned later by the spring 75 at both ends. In addition, the regulating member 77 is arrange | positioned so that the displacement amount to the conveyance roll 100 side of the star wheel 70 may stop at the position which bites in slightly from the surface of the conveyance roll 100 (refer FIG. 11).

  Here, the space | interval of the width direction between star wheels 70 was 25.4 mm in the widest location. This is because 50 mm or less is desirable in order to suppress local floating and deformation of the paper.

  The force with which the star wheel 70 is pressed against the transport roll 100 by the spring 75 is 10 gf per piece. This is because if the pressing force is less than 5 gf, the sheet cannot be sufficiently pressed against the transport roll 100, and if it is greater than 30 gf, the star wheel 70 damages the sheet.

  As shown in FIG. 12A, the star wheel 70 includes a cylindrical resin holding body 76 in which a hole 74 is formed, and a stainless steel wheel 78 held by the holding body 76. .

  The holding body 76 includes a first member 76A that is reduced in diameter in the center in the axial direction so that the wheel can be inserted, and a second member 76B that fits in the reduced diameter portion and sandwiches the wheel 78 together with the first member 76A. ing. The wheel 78 has a large number of teeth 79 formed at regular intervals on the outer periphery. The tip shape of the teeth 79 is obtuse and R-shaped (see FIG. 12B). However, the contact area only needs to be as small as possible because it contacts the undried ink on the paper. Or an acute angle (see FIG. 12C).

  Further, in this embodiment, the thickness of the wheel 78 is 0.1 mm, and the thickness of the tip (tooth tip) is reduced to about 0.01 to 0.02 mm by taper processing. The wheel 78 is formed by simultaneously processing the outer shape and the tapered shape of the tip from a SUS631EH material by double-sided step etching, and has a water-repellent coating on the surface.

  In the recording head array 42 </ b> A, a star wheel 70 is arranged next to each unit recording head 40. The star wheel 70 is elastically pivotally supported via a leaf spring 73 at the tip of a support member 71 fitted to the common substrate 46 (see FIG. 11).

  In the recording head unit 16, a sheet detection sensor 152 is disposed on the upstream side of the recording head array 42YA and the star wheel 70 on the most upstream side in the transport direction and closer to one end in the width direction ( (See FIG. 7). In this embodiment, a reflection type photoelectric sensor using laser light is used for the paper detection sensor 152. If it is a laser type photoelectric sensor, (1) the presence or absence of the paper can be detected with high accuracy because the laser beam can be irradiated with a minute diameter of about several tens of μm, and (2) no load is applied to the paper itself because of non-contact detection. (It does not affect the paper conveyance speed) and (3) Since the response time is fast, the presence / absence of paper can be detected at high speed.

Further, when the paper detection sensor is arranged on the upstream side of the recording head, the following conditions must be satisfied.
[Time from detection of paper by sensor to start of ink ejection by recording head (TA) <time of paper movement between sensor and recording head (TB)]
For example, when the paper feed speed is A4 short width (210 mm), 60 ppm, 1200 dpi, the printing frequency is 10 kHz (= 100 μs), so TA = sensor response time (50 μs to 1 ms) + control under the above conditions. From the processing delay (˜200 μs), the time is approximately 250 μs to 1.2 ms. Therefore, the minimum distance required between the sensor and the recording head is about 210 mm / s × (250 μs to 1.2 ms) = 52.5 μm to 310 μm. In this embodiment, the distance between the paper detection sensor 152 and the recording head array 42YA is sufficiently larger than the minimum necessary distance in the above example, and the paper detection information by the paper detection sensor 152 is used for controlling the printing operation. There is no problem to do.

  In this embodiment, the sheet detection sensor 152 is disposed near one end in the width direction of the sheet conveyance path, but this is near the other end or near the center in the width direction of the sheet conveyance path. Is also possible. As for the location where the paper detection sensor 152 is disposed, when printing is performed on paper narrower than the width dimension of the paper conveyance path (in this embodiment, B5, A5 size, etc.), the paper is conveyed. It can be selected as appropriate according to the setting condition of the conveyance path, which is to be conveyed along which side end of the path or to be conveyed in the center of the sheet conveyance path.

  As a result, when the conveyed paper passes through the paper detection sensor 152, the paper detection sensor 152 detects the leading edge of the paper based on the change in the amount of reflected light of the irradiated laser light, and a sensor signal (detection signal) is detected at the detection timing. ) Is generated. The sensor signal is input to the print control unit 160 (see FIG. 2), and is used to control the print start timing of the recording head array 42 as described in the first embodiment.

(Maintenance department configuration)
The configuration of the maintenance unit 18 arranged to face the recording unit 20 will be described with reference to FIGS. 13 to 17 and FIG. FIG. 13 is a plan view of the maintenance unit 18 from the transport position.

  The maintenance unit 18 is disposed so as to face the recording unit 20 with the sheet conveyance position interposed therebetween, and a maintenance device 81 is disposed at a position facing each unit recording head 40 of the recording unit 20 as shown in FIG. . The maintenance device 81 includes a cap member 80 and a wiping member 88.

  As shown in FIG. 14, the cap member 80 is formed of a rectangular-shaped recess 8A having a depth of 8 mm and made of PBT resin. The cap member 80 is formed of silicone rubber (hardness 40 Hs) on the upper portion of the receiver 82. And an ink absorber 86 made of polypropylene and polyethylene disposed on the entire bottom surface of the recess 82A. Therefore, in the case of a dummy jet, which will be described later, ink droplets are ejected from the nozzles 58 of the unit recording heads 40 into the recesses 82A through the openings 84A of the cap member 80 and absorbed by the ink absorber 86. .

  Further, as shown in FIG. 15, the cap member 80 is unitized by attaching six cap members 80 respectively corresponding to the respective unit recording heads 40 constituting the recording head array 42 to the common substrate 300, and the elevating mechanism. 302 is configured to be able to approach and separate from the nozzle surface 40A of the unit recording head 40 integrally.

  The elevating mechanism 302 includes a drive motor 304 and an eccentric cam 308 that is attached to the drive shaft 306 of the drive motor 304 and is in contact with the lower surface of the common substrate 300. Accordingly, the eccentric cam 308 is rotated by driving the drive motor 304, and the common substrate 300 with which the eccentric cam 308 is in contact is moved closer to and away from the nozzle surface 40 </ b> A of the unit recording head 40.

  A spring 87 that adjusts the pressure contact force when pressed against the nozzle surface 40A is disposed below the cap member 80 (see FIG. 19). Therefore, at the time of a capping operation described later, the cap member 80 is raised and the rubber portion 84 is pressed against the nozzle surface 40A to seal the nozzle surface 40A including the nozzle 58, thereby preventing ink drying and preventing dust, dust, etc. Prevent adhesion. Further, during the wiping operation described later, the cap member 80 is lowered so that the wiping member 88 can be moved in the width direction.

  Further, wiping members 88 for cleaning the nozzle surfaces 40A of the unit recording heads 40 are disposed at positions adjacent to each other in the width direction of the cap members 80 (see FIGS. 14 and 15).

  As shown in FIG. 14, the wiping member 88 includes a holding member 90 having an approximately arch shape when viewed in the width direction, and a wiper 92 disposed on the holding member 90 and extending in the transport direction. It is what.

  The wiper 92 is made of a thermoplastic polymer resin (hardness 65Hs), has a width direction thickness W1 of 0.8 mm, a conveyance direction length L1 of 8 mm, and a height (free length) from the holding member 90 of 6 mm. .

  The holding member 90 is made of SUS material.

  The wiping member 88 was disposed at a position 1 mm from the end of the cap member 80 in the width direction.

  Further, as shown in FIG. 15, the wiping members 88 are unitized by attaching all wiping members 88 corresponding to the unit recording heads 40 constituting the recording head array 42 to the common substrate 310, and are moved by the moving mechanism 312. The unit recording head 40 is configured to be movable toward and away from the nozzle surface 40A of the unit recording head 40 and in the width direction.

  The moving mechanism 312 basically includes a slider 314 that supports the common substrate 310 so as to be movable in the width direction, a drive motor 316 that moves the common substrate 310 in the width direction on the slider 314, and a drive motor 318 that moves the slider 314 up and down. Configured. The slider 314 includes guides 320 provided at both ends in the transport direction and extending in the width direction, and the common substrate 310 guided by the guides 320 is movable in the width direction. Further, a convex portion 324 in which a rack 322 is formed is formed on one side surface of the common substrate 310 and meshes with a drive gear 326 of a drive motor 316 attached to the slider 314. Therefore, the common substrate 310 can be moved in the width direction on the slider 314 by driving the drive motor 316.

  Further, a convex portion 332 provided with a rack 330 extending in the vertical direction is formed below the slider 314, and the drive gear 334 of the drive motor 318 is engaged. Therefore, the slider 314 can be moved up and down by the drive motor 318. That is, the common substrate 310 and the wiping member 88 supported by the slider 314 are configured to move up and down integrally.

  As described above, the wiping member 88 is configured to be movable toward and away from the nozzle surface 40A by the moving mechanism 312 (up and down) and is movable in the width direction. That is, the wiping member 88 (wiper 92) is positioned at a position lower than the cap member 80 so as not to interfere with the conveyed paper at the home position (see FIG. 16A), but rises during wiping. Thus, wiping is performed by moving in the transport direction across the cap member 80 lowered from the home position (see FIG. 16C).

  In addition, guide members 94 are disposed on both sides of each cap member 80 in the width direction so that the recording portion 20 does not enter the recess 82A of the cap member 80 during sheet conveyance (see FIG. 14). The guide member 94 is made of SUS material, and as shown in FIG. 14, a horizontal portion 94A extending in the transport direction, two vertical portions 94B extending vertically downward from both ends of the horizontal portion 94A, and a horizontal portion It comprises guide portions 94C and 94D extending obliquely downward in the transport direction from both ends in the transport direction of the portion 94A.

  The horizontal portion 94A of the guide member 94 is disposed so as to face the star wheel 70 disposed between the unit recording heads (see FIGS. 7, 13, and 11). Accordingly, the paper to be conveyed is brought into contact with the guide member 94 (horizontal portion 94A) by the star wheel 70 at the printing position in the conveyance direction, and the paper that is deformed by ink adhesion or the like is kept at a certain distance from the nozzle surface 40A. It is a configuration (see FIG. 11).

  Subsequently, home positions (positions in a state in which no maintenance is performed on the unit recording head 40 during image printing) of each member constituting the maintenance device 81 will be described.

  The cap member 80 is disposed below the nozzle surface 40A of the recording head 40 so that the rubber portion 84 covers the entire nozzle surface 40A of the unit recording head 40 in plan view, and the opening of the rubber portion 84 in plan view. All the nozzles 58 of the unit recording head 40 are arranged in the portion 84A.

  In the wiping member 88, the tip of the wiper 92 is disposed below the nozzle surface 40A of the unit recording head 40, and the length of the wiper 92 in the longitudinal (conveyance) direction in plan view is the width in the conveyance direction of the nozzle surface 40A of the unit recording head 40. The wiper 92 is disposed at a position 1 mm away from the end in the width direction of the unit recording head 40 (a position that can be cleaned with respect to the width direction of the recording head).

  In the guide member 94, the uppermost surface of the horizontal portion 94A with which the sheet contacts is disposed below the nozzle surface 40A of the unit recording head 40, and the length of the horizontal portion 94A of the guide member 94 in the transport direction in plan view is the unit recording head 40. The uppermost surface of the horizontal portion 94A that contacts the sheet is disposed at a position 2 mm away from the end in the width direction of the unit recording head 40 at a position that can cover the nozzle surface 40A.

  Next, a configuration for conveying paper between the maintenance device 81 and the unit recording head 40 will be described.

  Conveying rolls 100 that transmit the driving force to the sheet and convey the sheet are respectively disposed between the cap members 80 adjacent to each other in the conveying direction in the maintenance unit 18 (see FIG. 13). The transport roll 100 is disposed corresponding to the positions where the star wheel groups 72A to 72C are disposed across the paper transport position (see FIG. 11), and is elastically pressed by the spring 75 to the transport roll 100 side. The paper is brought into contact with the transport roll 100 by the star wheels 70 of the star wheel groups 72 </ b> A to 72 </ b> C, and the driving force is transmitted from the transport roll 100.

  The transport roll 100 includes a small-diameter portion 100A that is pivotally supported by the casing 102, and a large-diameter portion 100B that is larger in diameter than the small-diameter portion 100A and abuts on the star wheel 70 (see FIG. 10). The transport roll 100 transmits a driving force to the paper through the large diameter portion 100B, and preferably has a large friction coefficient and is not easily worn. In this embodiment, the transport roll 100 is obtained by spray-coating a ceramic fine powder mainly composed of alumina on the surface of a metal (SUS303) roll having a diameter of 10 mm and satisfying the above conditions. This process is performed not only on the print area where the paper abuts on the large diameter portion 100B of the transport roll 100 but also on the non-print area where the flat belt 104 is stretched.

  In addition, in order to prevent the star wheel 70 from coming into contact with the surface of the transport roll 100 and deforming the cutting edge, the groove facing the star wheel 70 of the transport roll 100 has a width of 2 mm and a depth of 2 mm. 101 (see FIG. 11). Further, in order to prevent the sheet conveyance resistance from increasing due to an increase in the amount of entry of the star wheel 70 into the groove 101, a regulating member 77 that regulates the amount of entry of the star wheel 70 (see FIG. 11). Is provided.

  In addition, a total of eight encoders (rotary encoders) 154 are provided between the cap members 80 along the transport direction and on each of the transport rolls 100 on the upstream side of the cap member 80 on the most upstream side (see FIG. 13). ). The encoder 154 is located on one end side (the flat belt 104 winding side described later) of the transport roll 100, is coaxially disposed with the transport roll 100, and is attached to the casing 102. The tip of the rotating shaft 155 is the transport roll. 100 is connected to the end portion of the small diameter portion 100A. Accordingly, when the transport roll 100 is driven to rotate, the encoder 154 detects the rotational speed of the rotary shaft 155 together with the transport roll 100, and generates an encoder pulse signal having a frequency proportional to the rotational speed. The encoder pulse signal is input to the print control unit 160 (see FIG. 2), and is used to control the print start timing of the recording head array 42 as described in the first embodiment.

  As shown in FIG. 17, the drive mechanism for driving the transport roll 100 has a flat belt 104 wound around all the transport rolls 100 through idler rolls 110 and 112 from a drive shaft 108 of a single motor 106. Is. An idler roll 114 is disposed between adjacent transport rolls 100, and the flat belt is wound around each transport roll 100 (large diameter portion 100B).

  As shown in FIG. 18, in the transport roll 100, a flat belt 104 is wound around a non-printing area outside the printing area at a large diameter portion 100 </ b> B where the transported paper comes into contact. Such a flat belt 104 transmits the drive to the transport roll 100 without meshing teeth (with frictional force), and is particularly suitable without periodic speed fluctuations for each tooth. In addition, the flat belt 104 of this example is a 0.4 mm-thick polyurethane film coated on the surface (one side) of a base material woven with polyester fibers, which achieves both mechanical strength and high friction. Yes.

  Thus, by configuring the recording unit 20, in this embodiment, the nozzle surface-paper interval is designed to be 1.5 mm, and the paper is conveyed in the horizontal direction therebetween. Further, the maximum recording area (maximum paper width PW) to be printed is A3 short (A4 long). The process speed of the recording unit 20 is 240 mm / s, the printing resolution = 800 × 800 dpi, and the recording speed is 60 sheets per minute (in the case of A4LEF (Long Edge Feed)).

  Further, the configuration of the print control unit 160 in the ink jet recording apparatus 10 of the present embodiment, the generation process of the print timing signal by the print control unit 160 and the control of the print timing are the same as those in the first embodiment, and therefore detailed description thereof will be given. Is omitted.

  The operation of the inkjet recording apparatus 10 configured as described above will be described.

  Hereinafter, the printing operation and the maintenance operation (dummy jet, wiping, capping) will be sequentially described.

  First, the printing operation will be described.

  When a printing operation is performed, the paper is supplied from the paper supply unit 12, and the orientation and timing of the paper are controlled by the registration adjusting unit 14 and conveyed to the recording unit 20.

  On the other hand, in the recording unit 20, the motor 106 is driven, and the driving force is transmitted to all the transport rolls 100 via the flat belt 104.

  Accordingly, the paper that has reached the recording unit 20 is inserted between the transport roll 100 and the star wheel groups 72A to 72C that are located most upstream in the transport direction. At this time, since the star wheel 70 of the star wheel groups 72A to 72C biased by the spring 75 presses the paper against the transport roll 100, the transport force is reliably transmitted from the transport roll 100 to the paper, and the unit recording head at a constant speed. 40 is inserted at the bottom. Thereafter, the driving force is sequentially transmitted from the transport roll 100 disposed between the recording head arrays 42 and transported.

  At this time, since all the transport rolls 100 are driven by a single motor 106, the speed fluctuations of the plurality of drive sources are overlapped to change the paper transport speed as in the case of being driven by a plurality of drive sources. The influence is suppressed, and the sheet is conveyed at a more constant speed. In addition, periodic speed fluctuations that cause image defects that are easily visible on an image are often caused by tooth processing accuracy, etc., but driving force via the flat belt 104 (without engaging teeth). Therefore, the occurrence of the image defect is also prevented. Further, since the flat belt 104 is wound around the non-printing area of the large-diameter portion 100B with which the paper of the transport roll 100 abuts, the core runout caused by the processing accuracy of the transport roll 100 and the holding method (bearings, etc.) Even if there is, periodic speed fluctuations are suppressed, and the transport speed of the paper by each transport roll 100 can be kept at a more constant speed. Strictly speaking, in the configuration in which the idler roll 114 is arranged to increase the winding angle of the flat belt 104, periodic speed fluctuations caused by the processing accuracy and the holding method of the idler roll 114 occur, but the idler roll 114 is compared. It is easy to process at low cost and with high accuracy because it is small and can be made of a single material. On the other hand, the transport roll 100 is large in size and has a plurality of material configurations such as a cored bar and a covering material, so that it is difficult to process with high accuracy. Or it becomes a very expensive part. The surface friction drive system using the flat belt 104 has an effect that even if the radius and the rotation center of the transport roll 100 are somewhat varied, no periodic fluctuations caused by the radius or rotation center occur.

  Furthermore, since the star wheel groups 72A to 72C are divided into three in the width direction and the lengths of the respective shafts 74A to 74C are shortened, the deflection of the shafts 74A to 74C can be prevented, and a plurality of biased springs 75 are used. The star wheel 70 holds the paper evenly. Therefore, the driving force can be transmitted evenly to the paper.

  In particular, since the paper is pressed against the transport roll 100 by the star wheel 70, the driving force is reliably transmitted to the paper and can be transported at a constant speed. In particular, since the electrostatic adsorption method is not employed, the sheet can be stably conveyed regardless of the thickness or material of the sheet.

  Further, since the star wheel 70 is disposed between the unit recording heads 40 in the width direction and the guide member 94 is disposed at a position opposite to the star wheel 70, even at the printing (recording head array 42) position in the transport direction. The sheet can be prevented from being lifted, and the flatness of the sheet (a constant distance from the nozzle surface 40A) can be ensured.

  In other words, by arranging the star wheel 70 in this way, even if the maintenance device 81 such as the cap member 80 is disposed at a position facing the unit recording head 40, the flatness of the sheet (constant to the nozzle surface 40A). Distance) can be secured.

  On the other hand, when a print signal is input to each unit recording head 40 from the control unit of the apparatus with respect to the recording head unit 16, the heating element of the corresponding nozzle generates heat according to the printing signal, and is constant with respect to the nozzle surface 40A. Ink droplets are ejected from the nozzles on the paper that is being transported at a distance.

  Accordingly, printing is performed by the recording head array 42A, and then printing is performed by the recording head array 42B, thereby completing printing for one color in the corresponding portion of the sheet. Therefore, as the sheet is conveyed by the recording unit 20, printing is performed in the order of the recording heads 44Y, 44M, 44C, and 44K, and full-color printing is performed.

  In this way, flatness (a constant distance with respect to the nozzle surface) is ensured, and a high-quality image can be formed by performing printing on a sheet conveyed at a constant speed. In particular, since the flatness is always ensured by the star wheel 70 during the conveyance of the recording unit 20, it is possible to satisfactorily correct the deformation of the paper that occurs during printing on paper of various thicknesses, and the distance to the nozzle surface 40A is constant. Maintains high-quality printing.

  In particular, in the recording unit 20, the transport roll 100 is disposed between the recording head arrays 42, and is disposed upstream of the most upstream recording head array 42YA and downstream of the most downstream recording head array 42KB. In addition, since the plurality of transport rollers 100 are driven by a single drive source, the paper is reliably transported at a constant speed, and high-quality printing can be achieved.

  However, although the periodic change in the sheet conveyance speed is suppressed by the above-described mechanical configuration, if the flat belt 104 is partially loosened or the conveyance roll 100 has a large runout, the conveyance roll 100 is The rotation speed of each transport roll 100 may vary due to the vibration of the flat belt 104 caused by the rotation unevenness. For this reason, a difference occurs in the peripheral speeds of the respective transport rolls 100, local variations occur in the transport speed of the paper, and registration deviation occurs in the color image. In the case of the inkjet recording apparatus 10 of the present embodiment, the registration deviation caused by local fluctuations in the paper conveyance speed is performed by performing the electrical correction described in the first embodiment. Registration deviation can be accurately corrected. Therefore, high quality image recording can be realized.

  Next, the operation of the dummy jet will be described.

  The dummy jet is performed before the leading edge of the succeeding sheet arrives at the time of non-printing or whenever a predetermined number of sheets are printed during continuous printing of a plurality of sheets. That is, ink droplet ejection (so-called dummy jet) is performed from an arbitrary nozzle toward the cap member 80 among all the unit recording heads 40 constituting the recording heads 44Y to 44K. The dummy jet may be performed by all nozzles of all unit recording heads 40, or may be performed by selected unit recording heads 40 or all nozzles 58 of recording head array 42, and further, ink droplets are ejected for a predetermined time. Only the nozzle 58 that is not used may be used.

  For example, the distance between the nozzle surface 40A and the upper surface of the cap member 80 at the time of dummy jet for continuous printing of a plurality of sheets is set to 3 mm, and the leading end of the succeeding sheet is reached after passing the preceding sheet every 30 pages (A4). 500 drops are discharged from all nozzles at the previous timing.

  At this time, since the ink absorbing member 86 is disposed on the bottom surface of the concave portion 82A of the cap member 80, the discharged ink does not overflow or scatter from the concave portion 82A.

  For example, by ejecting ink droplets (dummy jet) from all nozzles of the unit recording head 40, it is possible to initialize the change in ejection performance due to drying of ink (particularly water-based ink, solvent ink). Also, even if the ink is oily ink or solid ink that hardly dries, it is possible to eliminate bubbles adhering to the ink flow path or the like inside the head by printing or to remove dust adhering to the nozzle surface. Ink droplet ejection performance can be initialized.

  Since the dummy jet can be performed without moving the recording head 44 or the cap member 80 during the printing of a plurality of sheets that are continuously printed (conveyed) as in this embodiment, the printing speed (production Improvement) is achieved. Further, the printing performance of the recording head 44 is maintained constant by the dummy jet, and high-quality printing is possible.

  Next, the wiping operation will be described.

  The wiping operation is performed before starting printing. The wiping member 88 of the maintenance unit 18 wipes the recording head 40 (nozzle surface 40A). A specific operation will be described based on the schematic diagram shown in FIG.

  First, the drive motor 304 of the lifting mechanism 302 shown in FIG. 15 is driven, and the common substrate 300 is lowered by the rotation of the eccentric cam 306. Further, the drive motor 318 of the moving mechanism 312 is driven, and the common substrate 310 supported by the slider 314 and the slider 314 is raised. That is, the six cap members 80 attached to the common substrate 300 are lowered from the home position (moved in a direction away from the recording head 40), and the six wiping members 88 attached to the common substrate 310 are moved to the home position. (Moves to the nozzle surface 40A side of the recording head 40) (see FIG. 16A → B).

  In the present embodiment, the cap member 80 descends to a position 6 mm from the nozzle surface 40A of the unit recording head 40, and the tip (upper end) of the wiper 92 of the wiping member 88 is 1.5 mm higher than the nozzle surface 40A (hereinafter referred to as “the nozzle surface 40A”). The contact amount is 1.5 mm).

  As a result, the holding member 90 of the wiping member 88 can move in the width direction across the cap member 80. Further, the wiper 92 of the wiping member 88 overlaps the nozzle surface 40A of the recording head 40 in the vertical direction (FIG. 16, arrow Z direction) (see FIG. 16B).

  In this state, by driving the drive motor 316 of the moving mechanism 312 shown in FIG. 15, the common substrate 310 moves in the width direction on the slider 314 via the rack 322 engaged with the drive gear 326. Accordingly, the wiping member 88 attached to the common substrate 310 moves in the width direction, and the wiper 92 of the wiping member 88 whose tip is positioned higher than the nozzle surface 40A is in sliding contact with the nozzle surface 40A of the unit recording head 40. Moving. As a result, dust, dried ink, and the like attached to the nozzle surface 40A are removed (see FIG. 16C). At this time, the wiping member 88 moves so as to straddle the lowered cap member 80.

  In this embodiment, since the wiper 92 is in sliding contact with the nozzle surface 40A while maintaining the contact amount of 1.5 mm, dirt attached to the nozzle surface 40A is reliably removed.

  Further, the wiping member 88 escapes from the lower portion of the nozzle surface 40A, and the movement of the wiping member 88 and the guide member 94 in the width direction is completed (see FIG. 16D). Subsequently, the common substrate 310, that is, the wiping member 88 is lowered by driving of the drive motor 318 of the moving mechanism 312 and moved to the height of the home position (see FIG. 16E).

  Subsequently, the common substrate 310, that is, the wiping member 88 is moved to the opposite side in the width direction by driving of the driving motor 318 of the moving mechanism 312 and returned to the home position (see FIG. 16F). Further, the wiping operation is completed by driving the drive motor 304 of the elevating mechanism 302 to raise the cap member 80 and returning it to the home position close to the nozzle surface 40A of the recording head 40 (see FIG. 16G). .

  Next, the capping operation will be described.

  The capping operation is performed when the non-printing state continues for a long time or when the power is turned off. Specifically, the common substrate 300 is raised by driving the drive motor 304 of the lifting mechanism 302 shown in FIG. 15, and the rubber portion 84 of the cap member 80 attached to the common substrate 300 is moved to the nozzle surface 40 </ b> A of the recording head 40. (See FIGS. 19A to 19B). As a result, the air tightness of the nozzle surface 40 (nozzle 58) is ensured, ink thickening and drying are prevented, and dust is prevented from adhering.

  Furthermore, as shown in FIG. 9, the recording head 44 of the present embodiment is configured by attaching recording head arrays 42A and 42B in which a plurality of short unit recording heads 40 are arranged to common substrates 46A and 46B, respectively. Therefore, the recording head 40 can be shared with an inexpensive device (recording head) produced in large quantities, and the recording head 40 capable of full width printing can be configured at a low price.

  Further, by attaching the recording head arrays 42A and 42B to the common substrates 46A and 46B, respectively, the configuration of the recording head arrays 42A and 42B is simplified, and the manufacture and the high-precision adjustment become easier. Further, there is an advantage that the configuration of the maintenance unit (cap member 80, wiping member 88) can be made common with that used in a short recording head. Furthermore, it becomes possible to arrange means (such as the star wheel 70 of this embodiment) for making the distance between the nozzle surface 40A and the paper constant by utilizing the gap (space) between the unit recording heads in the width direction, or There is an advantage that the degree of freedom in designing the arrangement of the cap member 80 and the like is increased.

  Further, in this embodiment, the cap member 80 is provided corresponding to the unit recording head 40, but one cap member 80 may be associated with the plurality of unit recording heads 40.

1 is a schematic configuration diagram illustrating a recording apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of a printing control part. 5 is a flowchart illustrating a printing operation and printing deviation correction by the recording apparatus. It is a schematic block diagram which shows the recording device which concerns on 2nd Embodiment of this invention. It is a schematic block diagram which shows the recording device which concerns on 3rd Embodiment of this invention. 1 is a schematic configuration diagram illustrating a recording apparatus according to an embodiment of the present invention. FIG. 3 is a schematic plan view of a recording head unit according to an embodiment of the present invention. 1 is a plan view of a unit recording head according to an embodiment of the present invention. FIG. 4 is a configuration explanatory diagram of a recording head array according to an embodiment of the present invention. It is a longitudinal cross-sectional view of the recording part which concerns on one Example of this invention. It is a principal part side view of the recording part which concerns on one Example of this invention. (A) is sectional drawing of a star wheel, (B) is a side view, (C) is a side view which concerns on another example. It is a schematic plan view of the maintenance part which concerns on one Example of this invention. It is a perspective view for demonstrating the principal part of the maintenance part which concerns on one Example of this invention. It is explanatory drawing of the raising / lowering mechanism and moving mechanism of a maintenance part which concern on one Example of this invention. (A)-(G) are wiping operation | movement explanatory drawings in the recording device based on one Example of this invention. FIG. 3 is an explanatory diagram of a drive mechanism of a recording apparatus according to an embodiment of the invention. It is a principal part top view explaining the paper conveyance mechanism which concerns on one Example of this invention. (A) and (B) are explanatory diagrams of a capping operation in a recording apparatus according to an embodiment of the present invention.

Explanation of symbols

10 Inkjet recording device (recording device)
40 unit recording head (recording means)
42A recording head array (recording means)
42B recording head array (recording means)
44 recording head 100 transport roll (transport means / transport roll)
104 Flat belt (conveying means / endless belt)
106 Motor (conveying means / drive source)
150 Conveying mechanism (conveying means)
152 Paper detection sensor (detection signal generating means)
154 Rotary encoder (reference signal generating means / rotational speed detecting means)
156 Encoder pulse signal (reference signal)
158 Sensor signal (detection signal)
160 Print Control Unit (Control Unit)
162 Selection Unit 164 Print Timing Signal Generation Unit 200 Inkjet Recording Device (Recording Device)
210 Inkjet recording apparatus (recording apparatus)

Claims (3)

Conveying means for conveying the recording medium in a predetermined conveying direction;
A plurality of recording means arranged along the predetermined transport direction and sequentially recording images on a transported recording medium;
A detection signal generating unit that is disposed upstream of the plurality of recording units in the predetermined transport direction and detects a front end of the transported recording medium to generate a detection signal;
A plurality of reference signal generating means arranged in the vicinity of each of at least two or more recording means of the plurality of recording means and detecting a recording medium conveyance speed of the conveying means to generate a reference signal;
Control means for controlling the image recording timing of at least one recording means arranged in the vicinity of each reference signal generating means based on each of the input detection signal and the plurality of reference signals;
A recording apparatus comprising: The conveying means includes a plurality of conveying rolls that are substantially opposed to the plurality of recording means and are arranged in the vicinity of the recording means and between the recording means along the predetermined conveying direction, and the plurality of conveying rolls. Rotational drive means for rotationally driving,
2. The recording according to claim 1, wherein the reference signal generating means is a rotational speed detecting means for detecting the rotational speed of the transport roll and generating the reference signal indicating the recording medium transport speed by the transport roll. apparatus.   The recording apparatus according to claim 2, wherein the rotation driving unit includes an endless belt wound around the plurality of transport rolls, and a single drive source that rotationally drives the endless belt.

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