JP2010208231A - Printer and ejection control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the conveying speed of a belt with more accuracy by eliminating an error resulting from the thickness unevenness of the belt and eccentricity of a roller shaft which are superimposed on the measured conveying speed of the belt. <P>SOLUTION: This printer includes a laser Doppler speedometer 311 detecting the moving speed of a surface directly under ejection of an ink head and the angular speed of rotation of a driven roller as the belt surface moving speed in the conveyor belt 160, and a driven side encoder 310. The printer further includes a speed ratio computing part 401 extracting speed ratio data (profile data) having a frequency corresponding to a speed ratio, as belt profile data and roller profile data from the accumulated data of the temporal variation of the measured speed ratio; a storage part 332 storing the profile data; and a correction control part 331 controlling each image forming timing by a head unit 110 to reduce a positional deviation between a plurality of images on the conveyor belt 160 based on each profile data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing apparatus having a plurality of ink heads that form a plurality of images so as to overlap each other on a recording sheet on a conveyance belt, and a discharge control method thereof.

  In recent years, in order to improve the recording speed, a line head type ink jet recording apparatus in which recording heads are arranged in the entire width direction of the recording paper has been proposed. This is because the recording paper is transported using an endless transport belt, and a plurality of ink heads that form different monochrome images arranged along the transport direction are sequentially passed through each recording medium. A color image can be obtained by superimposing single color images.

  Here, in a printing apparatus, it is necessary to reliably eject ink to a target position of a recording medium. In particular, in a line head type printing apparatus, ink is ejected while a recording medium is being conveyed. The compatibility between the medium conveyance state and the ink discharge timing is important. For this reason, conventionally, for example, there is a control method for keeping the rotational speed of the driving roller constant by keeping the rotational angular speed of a gear that transmits the rotational driving force generated by the motor to the driving roller constant.

  However, since the driving roller and the driven roller around which the conveyance belt is wound are eccentric, there is a problem that the conveyance speed of the print medium by the conveyance belt is changed due to the eccentricity of the roller. If the moving speed of the conveyor belt is not maintained at a constant speed in this way, each monochrome image is formed on a recording medium by a plurality of ink heads, and when these colors are superimposed, the transfer position of each monochrome image is A so-called “landing deviation” occurs which is relatively shifted. When such landing deviation occurs, for example, a fine line image formed by overlapping a plurality of color images looks blurred, or a black character image formed in a background image formed by overlapping a plurality of color images White spots may occur around the outline of the.

  In order to prevent such landing deviation, for example, there is a technique disclosed in Patent Document 1. In the technique disclosed in Patent Document 1, an encoder is attached to a driven roller, and a ratio between an actual rotation angle with respect to the transport belt moving distance and a detected rotation angle of the driven roller obtained by the encoder in the meantime is stored in advance as an angle ratio. The ink ejection timing is corrected based on the detected signal interval of the encoder and the angle ratio according to the rotation angle of the driven roller, thereby preventing landing deviation on the recording medium.

Japanese Patent Laid-Open No. 2008-23943

  However, in the technique disclosed in Patent Document 1, the correction data described above is calculated in real time as ratio data based on the encoder signal. For this reason, there is a problem in that the calculation process for calculating the moving speed of the belt directly under each ink head is complicated, the amount of extra memory used increases, and the landing deviation cannot be corrected accurately due to a calculation delay. . In addition, in real-time data calculation, there is a problem that the maximum amount when the deviation is accumulated cannot be predicted, and when the maximum amount is unacceptable, the entire image is displaced.

  The present invention has been made in view of the above problems. In a printing apparatus equipped with a conveyance mechanism that conveys a sheet by a conveyance belt, the correction data is accumulated data of the speed ratio, thereby reducing the calculation processing burden. It is another object of the present invention to provide a printing apparatus and a discharge control method thereof that can prevent landing deviation at the time of printing with high accuracy.

  In order to solve the above-described problems, the present invention provides an endless transport belt that is stretched between a plurality of support rollers, a driving unit that rotates the support roller to move the transport belt endlessly, In a printing apparatus having a plurality of ink heads that form a plurality of images so as to overlap each other on the recording paper, a conveyance speed measuring unit that measures a movement speed at two arbitrary measurement points on the conveyance belt or the support roller; A belt speed extraction unit that extracts belt profile data having a frequency corresponding to the moving speed of the conveying belt from accumulated data obtained by accumulating temporal fluctuations of the moving speed at each measurement point measured by the conveying speed measuring unit; From the time variation of the moving speed at each measurement point measured by the transport speed measuring means, A roller speed extraction unit for extracting roller profile data having a number, a storage unit for storing the extracted belt profile data and roller profile data, and measuring the moving speed at one of two measurement points during the printing process. Print control means for correcting the result based on the belt profile data and the roller profile data and controlling the timing of image formation by the ink head so that the positional deviation between the plurality of images on the conveyor belt is reduced; The ink head forms a plurality of images on the recording material in accordance with the print control means.

In another aspect of the present invention, an endless transport belt stretched between a plurality of support rollers, a drive unit that rotates the support roller to move the transport belt endlessly, and a recording medium on the transport belt. An ink head ejection control method in a printing apparatus having a plurality of ink heads that form a plurality of images so as to overlap each other.
(1) a conveyance speed measurement step for measuring a movement speed at two arbitrary measurement points on the conveyance belt or the support roller;
(2) Belt profile data having a frequency corresponding to the moving speed of the conveying belt is extracted from accumulated data obtained by accumulating temporal fluctuations of the moving speed at each measurement point measured in the conveying speed measuring step. A speed extraction step of extracting roller profile data having a frequency corresponding to the rotation speed of the support roller from the temporal variation of the moving speed at the point;
(3) During the printing process, the moving speed of any one of the two measuring points is measured, and the measurement result is corrected based on the belt profile data and the roller profile data, and the position between the plurality of images on the conveyor belt. And a print control step for controlling the timing of image formation by the ink head so as to reduce the deviation.

  According to these inventions, the moving speed of two measuring points on the conveyor belt is detected, and this is used as the profile of the conveyor belt and the support roller that drives the conveyor belt. That is, in the present invention, the speed fluctuation caused by the thickness unevenness in the entire circumference of the conveyor belt and the speed fluctuation caused by the eccentricity of the support roller are measured in advance and stored as belt profile data and roller profile data. Remember it. In the actual printing process, the moving speed of one of the two measuring points is measured, and the profile data is reflected in this measurement result, and the printing timing is changed so that the printing position is not shifted due to the fluctuation of the conveying belt speed. The landing deviation can be eliminated.

  In particular, in the present invention, since the accumulated data is obtained by accumulating fluctuations in the speed ratio, the speed ratio with respect to the reference point can be obtained for the entire belt, and the arithmetic processing can be simplified. That is, in order to eliminate the landing deviation, it is necessary to calculate an absolute positional deviation based on the appropriate landing position, but the instantaneous measurement values at the two measuring points on the belt are the two measuring points. Therefore, when the landing deviation is corrected, an absolute speed fluctuation with respect to a predetermined reference point must be calculated. In the present invention, relative speed fluctuations are accumulated from a predetermined reference value and profiled as accumulated data in advance as absolute speed fluctuations, so that it is possible to reduce the processing load during printing execution.

  Further, according to the present invention, the speed ratio with respect to the reference point can be obtained for each point on the belt by treating the data as the accumulated data in which the fluctuation of the speed ratio is accumulated. It is possible to immediately grasp the deviation of the maximum amount accumulated in the entire belt, which cannot be predicted from data obtained by calculating the ratio in real time. As a result, for example, in the inspection at the time of factory shipment, it is possible to easily and quickly discriminate a product whose maximum deviation exceeds an allowable range.

  Further, in the present invention, since the belt profile data and the roller profile data are stored and used as separate file data, for example, when only the transport belt is exchanged, only the belt profile data is newly created, It can be installed in the printing apparatus, can be dealt with by work / operation only at the installation site of the printing apparatus, and the maintenance work can be facilitated.

  More specifically, the conveyance belt and its support roller are in a mechanical relationship, and errors due to their component characteristics and accuracy affect each other, and one error greatly affects the whole. Therefore, when the conveyor belt and the support roller have the same profile, for example, when only the conveyor belt is replaced, the mechanical relationship between the replaced conveyor belt and the existing support roller is changed. It will be necessary to inspect again and reflect it in the profile. In this case, it is not possible to cope with the work only at the installation site of the printing apparatus, and the burden of the maintenance work increases.

  In the above invention, the belt speed extraction unit and the roller speed extraction unit calculate the accumulated data by accumulating the temporal variation of the speed ratio at each measurement point as the temporal variation of the moving speed at each measurement point. It is preferable to extract belt profile data and roller profile data from the frequency corresponding to.

  In this case, when generating the belt profile data and the roller profile data, the ratio of errors can be stopped within a certain range by using the speed ratio at two measurement points as a parameter and the accumulated data. All the speeds can be handled with one type of profile. As a result, according to the present invention, even in a printing apparatus in which the belt conveyance speed fluctuates in accordance with the resolution and the printing mode, the size of the profile data is reduced and the conveyance belt is moved directly below each ink head. The speed can be calculated simply, and an increase in memory capacity and processing delay can be avoided.

  In the above invention, when any two measuring points are the first measuring point and the second measuring point, the moving speed of the first measuring point is the moving speed of the surface of the conveyor belt, and the second measuring point. Is the rotation speed of the support roller, and the belt speed extraction unit and the roller speed extraction unit define the moving speed at an arbitrary time at the first measurement point as a reference speed, and after a predetermined time has elapsed at the first measurement point. It is preferable to calculate the speed ratio of each point with respect to the reference speed over the entire circumference of the belt.

  In this case, since the speed ratio with the passage of time is accumulated with respect to the reference speed at the reference point, the speed ratio with respect to the reference point can be obtained for the entire belt. It can be handled as an absolute speed fluctuation from a constant reference speed, and the landing deviation can be appropriately eliminated.

  In the above invention, the roller speed extraction unit extracts the roller profile data based on the frequency corresponding to the rotation period of the support roller from the temporal variation of the moving speed of each measurement point, and the belt speed extraction unit It is preferable to extract the belt profile data by calculating the frequency corresponding to the rotation period of the belt as the eccentric component of the support roller and removing the eccentric component of the support roller from the frequency corresponding to the moving speed of the conveying belt.

  In this case, the roller profile data and the belt profile data can be acquired from one measurement result without increasing the amount of measurement of the moving speed at the measuring point, and the burden at the time of profile creation can be reduced. it can.

  In the above invention, when any two measuring points are the first measuring point and the second measuring point, the moving speed of the first measuring point is the moving speed of the surface of the conveyor belt, and the second measuring point. Is a rotation speed of the support roller, and the conveying speed measuring means for the first measuring point is a non-contact measuring apparatus that is detachably attached to the printing apparatus and optically measures the moving speed of the conveying belt surface. Preferably there is.

  In this case, when measuring the first measurement point at the time of profile creation, a device that optically measures the surface of the belt profile can be used as this measurement device. Since the belt profile is created at a low frequency, for example, at the time of factory shipment, it is unnecessary to incorporate an expensive measuring device such as an optical sensor only for that purpose, which unnecessarily increases the manufacturing cost. Will be. In the present invention, the manufacturing cost can be reduced by attaching the optical measuring device only when creating the belt profile and removing the measuring device after creating the profile. Examples of the optical measuring device include a laser Doppler velocity measuring device that measures the velocity of an object by measuring a change in wavelength between incident light and reflected light based on a relative velocity with the object. is there.

  According to the present invention, in a printing apparatus having a conveyance mechanism that conveys paper by a conveyance belt, correction data is accumulated data of a speed ratio, thereby reducing memory usage and calculation processing load, and landing at the time of printing. Deviation can be prevented with high accuracy.

It is a block diagram which shows the outline | summary of the conveyance path | route in the printing apparatus which concerns on embodiment. It is a functional block diagram which shows the module regarding the discharge timing control of the head unit which concerns on embodiment. In an embodiment, it is a functional block diagram showing the relation between the processing in the arithmetic processing unit and the printing / conveying drive unit in the printing apparatus. It is a functional block diagram which shows the module regarding the profile generation which concerns on embodiment. It is explanatory drawing which shows typically the function and operation | movement of profile generation which concern on embodiment. It is explanatory drawing regarding correction | amendment of an encoder signal at the time of controlling the discharge timing of the ink which concerns on embodiment. It is a flowchart figure which shows the procedure at the time of the production | generation of the profile data which concerns on embodiment. It is a flowchart figure which shows the procedure of the correction process with respect to the speed ratio accumulation data which concerns on embodiment. It is a graph which shows accumulation data calculation of the speed ratio which concerns on embodiment.

(Overall configuration of printing device)
Embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a diagram illustrating an outline of a conveyance path in the printing apparatus 100 according to the present embodiment. In this embodiment, the printing apparatus 100 includes a plurality of ink heads on which a large number of nozzles are formed, discharges black or color ink from each ink head, performs printing in line units, and prints on a recording medium on a conveyance belt. An ink-jet line color printer that forms a plurality of images so as to overlap each other will be described as an example.

  As shown in FIG. 1A, the printing apparatus 100 is an apparatus that forms an image on the surface of a recording medium conveyed on an annular conveyance path, and the conveyance path is a paper feed system conveyance path FR that supplies the recording medium. And a normal path CR from the paper feed system conveyance path FR through the head unit 110 to the paper discharge path DR, and a reverse path SR branched and connected to the normal path CR.

  In the paper feed system conveyance path FR, as a paper feed mechanism for supplying the recording medium, a side paper feed stand 120 disposed outside the side surface of the housing and a plurality of paper feed trays (inside the housing) 130a, 130b, 130c, and 130d) and a paper feed driving unit 183 that transports paper in the paper feed path. In addition, a paper discharge port 140 is provided as a paper discharge mechanism for discharging the printed recording medium.

  The recording medium fed from one of the side paper feed tray 120 and the paper feed tray 130 is transported along a paper feed system transport path FR in the housing by a driving mechanism such as a roller, and the recording medium It is guided to the resist portion R which is the reference position of the head portion. A head unit 110 including a plurality of ink heads is provided further on the registration direction R in the transport direction side. The recording medium is image-formed line by line with ink ejected from each ink head while being conveyed at a speed determined by printing conditions by a conveying belt 160 provided on the opposite surface of the head unit 110.

  The printed recording medium is further conveyed on the normal route CR by a driving mechanism such as a roller. In the case of single-sided printing in which printing is performed only on one side of the recording medium, the paper is directly discharged to the paper discharge port 140 through the paper discharge path DR, and is discharged as a tray for the paper discharge port 140. It is loaded on the table 150 with the printing surface facing down. The paper discharge table 150 has a tray shape protruding from the housing, and has a certain thickness. The sheet discharge table 150 is inclined, and the recording medium discharged from the sheet discharge port 140 is naturally arranged and overlapped by a wall formed at a position below the inclination.

  On the other hand, in the case of double-sided printing in which printing is performed on both sides of the recording medium, the front surface (the first printed surface is “front surface” and the next printed surface is “back surface”). Without being guided to the side, it is further transported in the housing and sent out to the reversing path SR. For this reason, the printing apparatus 100 is provided with a switching mechanism 170 for switching the transport path for backside printing, and the recording medium that has not been sent to the discharge path by the switching mechanism 170 is drawn into the reversing path SR.

  In the reversal path SR, the recording medium is delivered from the normal path CR, and so-called switchback is performed in which the recording medium is reversed by reciprocating the recording medium. Then, it is returned to the normal route CR via the switching mechanism 172 by a driving mechanism such as a roller, is fed again through the registration portion R, and the back side is printed by the same procedure as the front side. Thereafter, the recording medium on which the back side is printed and images are formed on both sides is guided to the paper discharge port 140 through the paper discharge route DR and discharged, and the paper discharge is provided as a receiving base of the paper discharge port 140. It is loaded on the table 150.

  In the present embodiment, switchback at the time of duplex printing is performed using a space provided in the paper discharge tray 150. The space provided in the paper discharge tray 150 is configured to be covered so that the recording medium cannot be removed from the outside during switchback. As a result, it is possible to prevent the user from accidentally pulling out the recording medium during the reversing operation. Further, the paper discharge tray 150 is originally provided in the printing apparatus 100, and by performing switchback using the space in the paper discharge tray 150, a separate switchback is provided in the printing apparatus 100. There is no need to provide space. Therefore, an increase in the size of the housing can be prevented. Furthermore, since the paper discharge path and the reverse path are not shared, the switchback process and the discharge of other recording media can be performed in parallel.

  In the printing apparatus 100, the recording medium that has been printed on one side is also re-fed to the registration portion R that is the reference position of the leading portion of the fed recording medium. For this reason, a junction point where the conveyance path of the newly fed recording medium and the refeed path where the recording medium for backside printing is circulated is merged is formed immediately before the registration portion R. Is done. Then, the registration unit R sends out the recording medium in the vicinity of the merging point between the paper feeding system conveyance path FR and the normal path CR.

  In the present embodiment, the path on the sheet feeding mechanism side is defined as the sheet feeding system conveyance path FR, and the other paths are defined as the conveyance paths based on the merging point. This transport path is annular, and includes the normal path CR and the reverse path SR as described above. FIG. 1B is a diagram schematically showing the sheet feeding system conveyance path FR, the normal path CR, and the reverse path SR. In the figure, the number of rollers constituting the drive unit is omitted as appropriate.

  In the paper feed system conveyance path FR, the side paper feed driving unit 220 for feeding paper from the side paper feed tray 120 and the paper feed from the paper feed trays 130 (130a, 130b, 130c, 130d) are provided. A tray 1 driving unit 230a, a tray 2 driving unit 230b,. Thus, a sheet feeding unit for feeding the recording medium to the registration unit R is configured.

  Further, any of the driving units (tray 1 driving unit 230a, tray 2 driving unit 230b...) In the above-described paper feeding system conveyance path FR includes a driving mechanism composed of a plurality of rollers or the like. Are taken one by one and conveyed in the direction of the registration portion R. Each drive unit can be driven independently, and necessary drive unit operations are performed in accordance with a paper feed mechanism that feeds paper.

  In addition, a plurality of transport sensors are arranged in the paper feed system transport path FR so that a transport jam in the paper feed system transport path FR can be detected. That is, each conveyance sensor is a sensor that detects the presence or absence of a recording medium or the leading edge of the recording medium. For example, a plurality of conveyance sensors are arranged at appropriate intervals on a conveyance path, and a conveyance sensor provided on the paper feeding side is provided. If the conveyance sensor on the conveyance direction side does not detect the recording medium within a predetermined time after detecting the recording medium, it can be determined that a conveyance jam has occurred.

  Among these conveyance sensors, a registration sensor in front of the registration unit R that sends out the recording medium measures the size of the recording medium being conveyed, and, for example, the recording medium being passed based on the passing speed and the passing time of the recording medium. When a conveyance sensor does not detect a recording medium within a predetermined time after measuring the size of the paper or driving the side paper feed drive unit 220, the tray 1 drive unit 230a, etc., a paper jam (paper feed error) has occurred. It can be judged.

  The normal path CR forms a part of the circulation transport path, and is a path from the paper feed transport path FR that supplies the recording medium to the paper discharge path DR through the head unit 110, and the recording is performed on the normal path CR. An image is formed on the upper surface of the medium. The normal path CR includes a registration driving unit 240 that guides the recording medium to the registration unit R, a belt driving unit 250 that drives the endless movement of the conveyance belt 160 provided on the opposite surface of the head unit 110, and a conveyance direction side. The first upper surface transport driving unit 260 and the second upper surface transport driving unit 265, which are sequentially arranged, the upper surface discharge driving unit 270 that guides the printed recording medium to the paper discharge port 140, and the recording medium is pulled into the reverse path SR for back surface printing Driving means are provided. Each drive unit includes a drive mechanism composed of one or a plurality of rollers or the like, and conveys the recording medium one by one along the conveyance path. Each drive unit can be driven independently, and necessary drive unit operations are performed in accordance with the conveyance status of the recording medium.

  In addition, a plurality of transport sensors are arranged on the normal route CR so that a transport jam in the normal route CR can be detected. Further, it is possible to confirm that the recording medium is appropriately conveyed also in the resist portion R. In the normal route CR, a conveyance sensor is provided corresponding to the drive unit, and it is possible to specify in which drive unit of the normal route CR the conveyance jam has occurred.

  The reversing path SR is branched and connected to the normal path CR, the recording medium is transferred from the normal path CR, and the recording medium is reciprocated (switched back) to return to the normal path CR to reverse the front and back of the recording medium. The reversing path SR is provided with a reversing drive unit 281 and a refeed driving unit 282 for reversing the recording medium and leading it to the junction. The reversing path SR can be transported at a speed different from that of the normal path CR, and when taking over the recording medium from the normal path CR, it is accelerated or decelerated, and the stop time at the time of switchback is extended or shortened. Can be.

  In the present embodiment, after a certain recording medium is fed, the next recording medium is not fed after waiting for the recording medium to be printed and discharged. Before the recording medium is discharged, the subsequent recording medium is fed and can be continuously printed at a predetermined interval. Therefore, in normal scheduling at the time of duplex printing, a space is secured in advance so as to secure a position where the recording medium returned from the reversing path SR is inserted when feeding the recording medium on the front surface. Thereby, in this apparatus, printing on the front surface and printing on the back surface can be performed in parallel, and half the productivity can be ensured with respect to single-sided printing.

  The conveyor belt 160 is wound around a driving roller 161 and a driven roller 162 disposed at the front end and the rear end of the surface facing the head unit 110, and rotates and moves in the clockwise direction in FIG. . Further, on the upper surface of the transport belt 160, ink heads of four colors are arranged side by side along the belt moving direction, and a head unit 110 that forms a color image so as to overlap a plurality of images is opposed to the head unit 110. Yes.

  Furthermore, as illustrated in FIG. 1A, the printing apparatus 100 includes an arithmetic processing unit 330. The arithmetic processing unit 330 is configured by a processor such as a CPU or DSP (Digital Signal Processor), memory, hardware such as other electronic circuits, software such as a program having the function, or a combination thereof. Various functional modules are virtually constructed by appropriately reading and executing a program, and various functional modules for processing related to image data, operation control of each unit, and user operations are constructed by each constructed functional module. Process. In addition, an operation panel 340 is connected to the arithmetic processing unit 330, and an instruction and a setting operation by a user can be received through the operation panel 340.

(Discharge timing control)
Control of the ejection timing in the head unit 110 described above is also performed by the arithmetic processing unit 330. FIG. 2 is a functional block diagram illustrating modules relating to ejection timing control of the head unit 110 in the arithmetic processing unit 330. FIG. 3 illustrates processing in the arithmetic processing unit 330 and a printing / conveying drive unit in the printing apparatus 100. It is a functional block diagram which shows the relationship. The “module” used in the description refers to a functional unit that is configured by hardware such as an apparatus or a device, software having the function, or a combination thereof, and achieves a predetermined operation. .

  As shown in FIG. 2, the control unit 300 includes a correction control unit 331, a storage unit 332, a discharge control unit 333, a drive control unit 334, and a system control unit 335, and includes belt profile data and The roller profile data is transferred from the storage unit 332 to the correction control unit 331, and the correction control unit 331 corrects the output of the encoder.

  The storage unit 332 is a memory device that records generated belt profile data and roller profile data, and includes a storage memory 332b that stores belt profile data and a storage memory 332a that stores roller profiles. In the present embodiment, the belt profile data and the roller profile data are generated in advance by the external profile generation device 400 or the like, and are stored in the storage memories 332a and 332b by being installed at the time of factory shipment.

  Based on the belt profile data and roller profile data stored in the storage unit 332, the correction control unit 331 is input from the driven encoder 310 so that the positional deviation between the plurality of images on the conveyance belt 160 is reduced. This is a module that corrects the detected signal and inputs it to each ejection control unit 333.

  In the present embodiment, the correction control unit 331 includes a belt profile correction control unit 331a and a roller profile correction control unit 331b. The belt profile correction control unit 331a is a module that corrects a detection signal from the driven encoder 310 based on the belt profile data, and corrects a speed variation caused by a belt thickness unevenness component. On the other hand, the roller profile correction control unit 331b is a module that corrects the detection signal from the driven encoder 310 based on the roller profile data, and mainly corrects the speed fluctuation due to the eccentric component of the driven roller. In this embodiment, the driven roller is selected as the target of the roller profile that records the eccentric component of the driven roller, but other support rollers such as the eccentricity of the encoder and the driving roller are also targeted. Can do.

  The belt profile correction control unit 331a receives the belt home position signal detected by the belt HP sensor 312 that detects one mark (reference mark) in one circumference of the belt together with the detection signal from the driven encoder 310. Entered. On the other hand, the roller profile correction control unit 331b receives the detection signal corrected by the belt profile correction control unit 331a and the roller home position signal detected by the roller HP sensor 313 that detects one rotation of the roller. .

  The ejection control unit 333 is a print control unit that controls the timing of image formation by the head unit 110 based on the corrected detection signal. The head unit 110 performs recording according to the control by the ejection control unit 333. A plurality of images are formed on the medium 10.

  The system control unit 335 is a central processing unit that controls the operation of each module in the control unit 300. In addition to image processing during printing, the system control unit 335 controls the operation of each drive unit in the transport path through the drive control unit 334. . In addition, the system control unit 335 also functions as a communication interface that performs communication with the outside and an interface that transmits and receives data to and from the operation panel 340.

(Discharge timing control method during printing)
The ejection timing control using the profile data generated in this way is performed according to the following procedure. FIG. 3 is a block diagram schematically showing the operation during the printing process. Here, it is assumed that the roller profile data and the belt profile data are already stored in the storage memories 332a and 332b as independent profile data in the storage unit 332, respectively.

  First, when the printing process is started, the stored roller profile data and belt profile data are read from the storage memories 332a and 332b, respectively, and input to the correction control unit 331.

  Next, when the printing process is started, the angular velocity detected by the driven encoder 310 is input, the moving speed of the conveyor belt is measured (S201), and the discharge control of the head unit 110 is controlled based on the measurement result. Do. In this discharge control, the correction control unit 331 is driven on the driven side so that the positional deviation between the plurality of images on the transport belt 160 is reduced based on the roller profile data and the belt profile data stored in the storage unit 332. The encoder detection signal input from the encoder 310 is corrected (S202, S203) and input to the discharge control unit 333.

  In this correction, the correction value in the belt profile data is read in accordance with the rotation period of the conveyor belt 160 based on the home position signal, and the encoder detection input from the driven encoder 310 as shown in FIG. The signal is advanced or delayed according to the correction value so that the positional deviation (landing deviation) between the plurality of images on the conveying belt 160 is adjusted and input to the ejection control unit 333. . The ejection control unit 333 controls the timing of image formation by the head unit 110 based on the corrected encoder detection signal (S204), and the head unit 110 ejects ink according to the control by the ejection control unit 333. Then, a plurality of images are formed on the recording medium.

  In this embodiment, in order to eliminate the landing deviation, it is necessary to calculate an absolute positional deviation based on the appropriate landing position as indicated by Δd in FIG. Since the instantaneous measurement value at is a relative speed fluctuation between these two measurement points, it is necessary to calculate an absolute speed fluctuation with respect to a predetermined reference point when correcting the landing deviation. In the present embodiment, the speed ratio between two measurement points at each time point is accumulated, and Δd, which is an absolute positional deviation at each time point, is stored in advance as a profile.

(Profile generator)
In the present embodiment, the belt profile data and roller profile data described above are generated using the profile generation device 400 and installed in the storage unit 332. FIG. 4 is an explanatory diagram showing a schematic configuration of the profile generation device 400. As shown in FIG. 4A, the profile generation apparatus 400 is an external apparatus that is temporarily connected to the printing apparatus 100 when the printing apparatus 100 is manufactured, before factory shipment, during maintenance, and the like. 400a and PC400b are roughly comprised.

  The LDV device 400a is a device that measures the moving speed of an object in a non-contact manner with a laser Doppler speedometer 311 that is a transport speed measuring means. The LDV apparatus 400a includes a laser Doppler speedometer 311 attached to the upper surface of the transport belt 160, and a follower. A driven encoder 310 provided on the roller 162, a belt home position sensor 312 that detects one rotation of the conveyor belt 160, and a roller HP sensor 313 that detects one rotation of the driven roller 162 are connected to each other. The input signal is acquired and passed to the PC 400b as the profile generation device while being synchronized.

  The PC 400b is an arithmetic processing unit provided with a CPU, and can be realized by a general-purpose computer such as a personal computer or a dedicated device specialized in functions. By executing software on the CPU, a profile data generation device Function as. Specifically, the PC 400b as the profile data generation apparatus includes a speed ratio calculation unit 401, a data processing unit 402, and a data memory 403 as shown in FIG.

  The speed ratio calculation unit 401 is a module that calculates the temporal variation of the speed ratio at each measurement point by the belt speed extraction unit 401b and the roller speed extraction unit 401a. Specifically, the belt speed extraction unit 401b and the roller speed The extraction unit 401a measures the moving speed at two arbitrary measurement points set on the conveyor belt 160 or on its driving means (drive motor, support roller, etc.) by the speed measuring means. In the present embodiment, the two arbitrary measurement points are the first measurement point and the second measurement point, and the movement speed of the first measurement point is the movement speed of the surface of the conveyance belt immediately below the center of the ink head. The second measuring point is the rotational speed (angular speed) of the driven roller 162.

  In this embodiment, the speed measuring means for the first measuring point is a non-contact measuring device that optically measures the moving speed of the surface of the conveyor belt. In this embodiment, a laser Doppler velocimeter 311 is used. . The laser Doppler velocimeter 311 is a speed measuring unit that optically measures the moving speed of the surface of the conveyor belt 160. Specifically, the laser Doppler velocimeter 311 measures the change in wavelength between incident light and reflected light depending on the relative speed with the object. The speed of the object is measured by measuring. The laser Doppler speedometer 311 is detachably provided to the printing apparatus 100. As a result, the laser Doppler velocimeter 311 can be installed only at the time of creating profile data, and the manufacturing cost can be reduced without incorporating an expensive measuring device in the image forming apparatus.

  On the other hand, the speed measuring means for the second measuring point uses a driven encoder 310 that measures the rotational speed of the driven roller 162. The belt speed extraction unit 401b and the roller speed extraction unit 401a extract the speed data of the conveyor belt and the roller from the moving speed measured by the laser Doppler velocimeter 311 and the detection signal of the driven encoder 310, respectively. Here, in the present embodiment, the second measuring point is the rotational speed of the driven roller 162, and the influence of the driving force of the motor or the like that rotates the driving roller 161, for example, the speed unevenness due to the driving force and the slipping of the belt or the like. For example, the difference between the belt behavior and the measurement result by the encoder is reduced. The present invention is not limited to this, and the second measuring point may be the rotational speed of the drive roller 161, and a drive-side encoder may be used as a means for measuring the rotational speed of the drive roller 161.

  In this embodiment, as shown in FIG. 4, the detection signal from the laser Doppler velocimeter 311 and the detection signal from the driven encoder 310 are input to the speed ratio calculation unit 401. In addition, the speed ratio calculation unit 401 includes a belt HP sensor 312 that detects one mark (reference mark) on one circumference of the belt and a roller HP sensor that detects one mark (reference mark) on one circumference of the roller. Each home position signal detected at 313 is input.

  The data processing unit 402 is a module that performs processing such as averaging and digitization on the speed ratio data. The data memory 403 is a memory device that records pulse width data measured by the laser Doppler velocimeter 311 and a detection signal from the driven encoder 310 as speed data.

  The speed ratio calculation unit 401 then calculates the time ratio of the speed ratio at each measurement point based on the moving speed of the conveyor belt surface detected by the laser Doppler speedometer 311 and the rotational angular speed detected by the driven encoder 310. The fluctuation is calculated, and belt profile data and roller profile data are extracted from the frequency corresponding to the calculated speed ratio.

  These profile data are sent from the data processing unit 402 to the data memory 403 through the data bus. The data memory 403 is a storage unit that stores belt profile data and roller profile data. The stored belt profile data and roller profile data are transmitted to the printing apparatus 100 via the communication interface 404 and the like.

  The operation at the time of the generation processing of the belt profile data and the roller profile data by the profile generating apparatus 400 having such a configuration will be described in detail. FIG. 5 is a block diagram schematically showing an operation procedure when generating a belt profile.

  First, the temporal variation of the speed ratio at each measurement point is calculated by the belt speed extraction unit 401b and the roller speed extraction unit 401a. Specifically, the belt speed extracting unit 401b and the roller speed extracting unit 401a measure the moving speed at two arbitrary measurement points set on the transport belt or the driving unit thereof by the speed measuring unit (S101 and S102). . Specifically, the moving speed of the first measuring point is determined by measuring the change in the wavelength of incident light and reflected light with respect to the surface of the conveyor belt 160 that is an object by using a laser Doppler velocimeter 311. The speed of the measuring point is the rotational speed of the driven roller 162.

  The speed ratio calculation unit 401 calculates a speed ratio based on the belt moving speed optically measured by the laser Doppler speedometer 311 with respect to the rotational speed of the driven encoder 310 and the angular speed from the laser Doppler speedometer 311. (S103) Then, the temporal variation of the moving speed is recorded as a profile by recording the temporal variation of these speed ratios (S105 and S104).

  Here, the temporal fluctuation of the moving speed includes a speed fluctuation caused by uneven thickness in the entire circumference of the conveyor belt and eccentricity of the support roller. The belt speed extracting unit 401b extracts belt profile data having a frequency corresponding to the moving speed of the conveying belt from the temporal variation of the moving speed, and the roller speed extracting unit 401a is a time of the moving speed at each measurement point. The roller profile data having a frequency corresponding to the rotation speed of the support roller is extracted from the dynamic variation. In this embodiment, speed ratio data is recorded as data for one belt revolution.

  In this embodiment, the timing for acquiring the belt profile data and the roller profile data is the factory shipment. However, the acquisition timing is not limited to the time of shipment from the factory, and it can be triggered by a change in environment, a change with time, or a maintenance.

(Operation during profile generation)
An operation at the time of profile generation in the profile generation apparatus 400 according to the present embodiment having the above configuration will be described. FIG. 7 is a flowchart showing an operation when generating a profile.

  First, the profile generation device 400 detects signals from each sensor and encoder. Specifically, a detection signal from the laser Doppler speedometer 311 and a detection signal from the driven encoder 310 are input to the speed ratio calculation unit 401. Further, the home position signal detected by the belt HP sensor 312 and the roller HP sensor 313 is input to the speed ratio calculation unit 401. Thus, the moving speed for each pulse of the encoder around the belt is measured (S301, S401).

  Next, speed ratio data of the moving speed having a frequency corresponding to the speed fluctuation of the conveyor belt 160 from the ratio of the moving speed and the rotational angular speed detected by the laser Doppler speedometer 311 and the driven encoder 310 in the speed ratio calculation unit 401. Is extracted (S302, S402).

And the roller speed extraction part 401a extracts roller profile data from the time fluctuation | variation of the moving speed of each measuring point based on the frequency corresponding to the rotation period of a support roller. The belt speed extraction unit 401b calculates a frequency corresponding to the rotation period of the driven roller 162 as an eccentric component of the driven roller 162, and removes the eccentric component of the support roller from the frequency corresponding to the moving speed of the conveyance belt. Then, belt profile data is extracted.
Specifically, the roller speed extraction unit 401a divides the period data for one rotation of the roller from the calculated speed fluctuation ratio data of each pulse, and averages the period data for one rotation of the belt (S403). Thereby, the eccentric component of the roller is calculated (S404). Then, the eccentric processing component of the roller is subjected to data processing in the data processing unit 402 to generate roller profile data (S405).

  Similarly to the above, the belt speed extraction unit 401b calculates speed ratio data of the moving speed having a frequency corresponding to the speed fluctuation of the transport belt 160 (S301, S302). Thereafter, the eccentric component of the roller calculated earlier is removed from the frequency corresponding to the speed ratio data, and the thickness unevenness component of this belt is calculated (S303). The belt thickness unevenness component is processed by the data processing unit 402 to generate belt profile data (S304).

  The calculated roller profile data and belt profile data are sent from the data processing unit 402 to the data memory 403 through the data bus, and the data memory 403 stores the received belt profile data. As described above, the roller profile data and the belt profile data are stored in the data memory 403 as independent profile data.

(Cumulative profile data)
Furthermore, in the present embodiment, cumulative data is calculated when calculating the speed ratio in steps S302 and S402 described above. FIG. 8 is a flowchart showing a procedure for generating profile cumulative data.

  First, in the calculation of accumulated data, an arbitrary point such as HP is set as a reference point, and speed ratio data for each pulse of the encoder is acquired in order to obtain a speed ratio with respect to this reference point over the entire circumference of the conveyor belt 160 (S501). ), The values of the respective speed ratios are sequentially accumulated and calculated (S502).

  Specifically, the angular velocity at the rotation angle of the driven encoder 310 at an arbitrary time (t) is defined as ωt, and the velocity of the belt surface at the point measured by the LDV 311 at ωt is defined as Vt, and one of these two points is measured. The speed ratio at the other measuring point with respect to is the relative speed ratio Vt / ωt.

  Specifically, the speed of the belt surface at a point measured by the LDV 311 at a certain moment is set as a reference speed VA, and the moving speed of the conveyor belt 160 wound around the driven encoder 310 at that time is set as VB. Further, the belt moving speed VB at the point of the driven encoder 310 at an arbitrary time (t) is VB = ωt × Rt, where Rt is the rotation radius at that time. This change in Rt is a change in the thickness of the belt in the driven encoder 310 over time, and is obtained as VB / ωt = Rt. Here, if the expansion and contraction of the conveyor belt 160 is ignored, VA = VB, and the belt surface measured by the LDV 311 at an arbitrary time (t) is the speed Vt. Therefore, VA = VB = Vt and Vt / The relationship ωt = Rt is obtained. Therefore, by maintaining the thickness unevenness Rt at an arbitrary time as a profile, the VA at that moment can be corrected based on ωt, and landing deviation can be eliminated.

Then, as shown in the table below, the speed ratio at the reference point on the conveyor belt 160 (for example, the home position at t = 0) is set to the reference speed ratio V0 / ω0 = R0, and along the circumferential direction of the conveyor belt 160. The speed ratio Rt at each time is sequentially multiplied and accumulated, and the speed ratio Ct of each point with respect to the reference point is calculated over the entire circumference of the conveyor belt 160.

  After the speed ratio cumulative data is calculated in this manner, various data processing such as zero correction is performed on the cumulative data. FIG. 9 is a graph showing the accumulated speed ratio. Here, in FIG. 9, the X axis represents the position of one round of the belt with an arbitrary correction reference point as the zero point, and the Y axis represents the speed ratio value with respect to the reference point. At the intersection (origin), the ratio value is 1. 9A is a plot of ratios (R0, R1, R2,... Rn) at the measurement points in Table 1, and FIG. 9B is an accumulation corresponding to each plot in FIG. Values (C0, C1, C2,... Cn) are plotted. Further, FIG. 9C is corrected so that all the plots in FIG. 9B become 0 or more.

  In the zero correction in step S503, first, as shown in FIG. 9A, the speed ratio at each point is set to a speed ratio 1 (= R0) on the basis of an arbitrary measurement point on the conveyor belt or its driving means. When the instantaneous speed ratios (R1, R2,... Rn) are sequentially multiplied and accumulated, as shown in FIG. 9B, data in which the speed ratios are accumulated is calculated.

  In the accumulated data calculated in this way, if there is negative data, all data is 0 as shown in FIG. The data is corrected so as to be as described above (S503). Data processing is performed in this way, and the accumulated data of the speed ratio is set as belt profile data (S504).

  The accumulated data of the speed ratio in the belt profile data calculated in this way is stored in the storage unit 332 of the printing apparatus 100 at the time of shipment, and is used as a belt profile at the time of printing.

(Action / Effect)
According to the printing apparatus 100 according to the present embodiment as described above, during the printing process, the moving speed at any two arbitrary measurement points is measured, and the measurement result is extracted and stored in advance as belt profile data and By controlling the timing of each image formation by the ink head based on the roller profile data, it is possible to change the printing timing so as not to cause a printing position shift due to fluctuations in the conveyance belt speed, and to eliminate landing deviation.

  Further, in the present embodiment, since the accumulated data is obtained by accumulating the speed ratio fluctuation, the speed ratio with respect to the reference point can be obtained for the entire belt, and a series of behaviors associated with the circulation of the belt is shown in FIG. As shown in FIG. 5, it is possible to handle the amount of change as an absolute change with the reference point as the origin, and the arithmetic processing can be simplified. That is, in order to eliminate the landing deviation, it is necessary to calculate an absolute positional deviation based on the appropriate landing position as indicated by Δd in FIG. 6, but momentarily at two measurement points on the belt. Since the measured value is a relative speed fluctuation between these two measurement points, an absolute speed fluctuation with respect to a predetermined reference point must be calculated when correcting the landing deviation. In the present embodiment, the speed ratio between two measurement points is accumulated, and Δd at each time point is stored as a profile in advance, so that it is possible to reduce the calculation processing burden at the time of printing execution.

  Furthermore, in this embodiment, the speed ratio with respect to the reference point can be obtained for each point on the belt by treating the accumulated speed ratio as accumulated data, and the instantaneous speed at each point on the belt can be obtained. It is possible to immediately grasp the deviation of the maximum amount accumulated in the entire belt, which cannot be predicted from data obtained by calculating the ratio in real time.

  More specifically, by making the belt profile data cumulative data, the speed ratio at each point on the belt as shown in FIG. 11C can be obtained as a sine curve with the reference point as the origin. By finding the maximum amplitude of the sine curve, it is possible to immediately grasp the maximum amount of deviation accumulated in the entire belt. As a result, for example, in the inspection at the time of factory shipment, it is possible to easily and quickly discriminate a product whose maximum deviation exceeds an allowable range.

  In this embodiment, since the belt profile data and the roller profile data are stored and used as separate file data as correction data, for example, when only the transport belt is replaced, only the belt profile data is used. Can be created and installed in the printing apparatus 100, and can be handled only by work / operation at the installation site of the printing apparatus 100, thereby facilitating maintenance work.

  Further, in the present embodiment, the belt speed extraction unit 401b and the roller speed extraction unit 401a calculate the temporal variation of the speed ratio at each measurement point, and the belt profile data and the roller profile from the frequency corresponding to the calculated speed ratio. Since the data is extracted, when the profile is generated, the ratio of the speeds at the two measuring points is used as a parameter, so that the ratio of errors can be kept within a certain range, and each type of profile supports all speeds. can do. As a result, even for printing devices in which the belt moving speed fluctuates according to the resolution and printing mode, the profile data size is reduced, and the transport belt moving speed is simply calculated directly under each ink head. It is possible to avoid an increase in memory capacity and processing delay.

  Furthermore, in this embodiment, roller profile data is extracted based on the frequency corresponding to the rotation period of the driven roller 162, and the eccentric component of the driven roller 162 is removed from the frequency corresponding to the moving speed of the conveyor belt. Because belt profile data is extracted, roller profile data and belt profile data can be acquired from a single measurement result without increasing the amount of movement speed measured at the measurement point, reducing the burden of profile creation. can do.

  In the present embodiment, the moving speed of the first measuring point is the moving speed of the surface of the conveyor belt, the second measuring point is the rotational speed of the support roller, and the speed measuring means for the first measuring point is: Since the laser Doppler speedometer 311 provided detachably with respect to the printing apparatus is used, the laser Doppler speedometer 311 can be connected to the printing apparatus 100 only when the belt profile is created, and can be removed after the profile creation, which is expensive. There is no need to incorporate a speedometer in the printing apparatus, and the manufacturing cost of the printing apparatus can be reduced.

CR: Normal path DR: Paper discharge path FR: Paper feed system transport path R ... Registration section SR ... Reverse path 10 ... Recording medium 100 ... Printing device 110 ... Head unit 120 ... Side paper feed stand 130 ... Paper feed tray 140 ... Discharge Paper outlet 150 ... Discharge stand 160 ... Conveying belt 161 ... Drive roller 162 ... Driving roller 170,172 ... Switching mechanism 183 ... Paper feed drive unit 220 ... Side feed drive unit 230a, 230b ... Tray drive unit 240 ... Registration drive unit 250 ... belt drive unit 260 ... first upper surface conveyance drive unit 265 ... second upper surface conveyance drive unit 270 ... upper surface discharge drive unit 281 ... reverse drive unit 282 ... refeeding drive unit 300 ... control unit 310 ... driven side encoder 311 ... Laser Doppler speedometer (LDV)
312 ... Belt home position sensor 313 ... Roller home position sensor 330 ... Arithmetic processing unit 331 ... Correction control unit 331a ... Belt profile correction control unit 331b ... Roller profile correction control unit 332 ... Storage units 332a, 332b ... Storage memory 333 ... Discharge control Unit 334 ... Drive control unit 335 ... System control unit 340 ... Operation panel 400 ... Profile generation device 400a ... LDV device 400b ... PC
401 ... Speed ratio calculation unit 401a ... Roller speed extraction unit 401b ... Belt speed extraction unit 402 ... Data processing unit 403 ... Data memory 404 ... Communication interface

Claims (6)

An endless conveyor belt stretched between a plurality of support rollers;
Driving means for rotating the support roller to move the conveyor belt endlessly;
In a printing apparatus having a plurality of ink heads that form a plurality of images so as to overlap each other on a recording sheet on the conveyance belt,
A conveying speed measuring means for measuring a moving speed at two arbitrary measuring points set on the conveying belt or the support roller;
A belt speed extraction unit for extracting belt profile data having a frequency corresponding to the moving speed of the conveying belt from accumulated data obtained by accumulating temporal fluctuations of the moving speed at each measurement point measured by the conveying speed measuring unit; ,
A roller speed extraction unit that extracts roller profile data having a frequency corresponding to the rotation speed of the support roller from temporal variation of the moving speed at each measurement point measured by the conveyance speed measuring unit;
A storage unit for storing the extracted belt profile data and the roller profile data;
During the printing process, the moving speed of any one of the two measurement points is measured, and the measurement result is corrected based on the belt profile data and the roller profile data, and the interval between the plurality of images on the conveyor belt is corrected. Printing control means for controlling the timing of image formation by the ink head so that the positional deviation of
The printing apparatus, wherein the ink head forms the plurality of images on the recording material in accordance with a print control unit.   The belt speed extraction unit and the roller speed extraction unit calculate the accumulated data by accumulating the temporal variation of the speed ratio at each measurement point as the temporal variation of the moving speed at each measurement point. The printing apparatus according to claim 1, wherein the belt profile data and the roller profile data are extracted from a frequency corresponding to. When the two arbitrary measuring points are the first measuring point and the second measuring point, the moving speed of the first measuring point is the moving speed of the surface of the conveyor belt, and the second measuring point Is the rotational speed of the support roller,
The belt speed extraction unit and the roller speed extraction unit are:
The moving speed at an arbitrary time at the first measuring point is set as a reference speed,
The speed ratio after elapse of a predetermined time at the first measuring point is a relative speed ratio,
The printing apparatus according to claim 2, wherein the relative speed ratio is sequentially accumulated on the reference speed, and the speed ratio of each point with respect to the reference speed is calculated over the entire circumference of the belt. The roller speed extraction unit extracts the roller profile data based on a frequency corresponding to a rotation period of the support roller from a temporal change in the moving speed of each measurement point.
The belt speed extraction unit calculates a frequency corresponding to a rotation period of the support roller as an eccentric component of the support roller and removes an eccentric component of the support roller from a frequency corresponding to a moving speed of the transport belt. The printing apparatus according to claim 1, wherein the belt profile data is extracted. When the two arbitrary measuring points are the first measuring point and the second measuring point, the moving speed of the first measuring point is the moving speed of the surface of the conveyor belt, and the second measuring point Is the rotational speed of the support roller,
The conveying speed measuring means for the first measuring point is a non-contact measuring apparatus that is detachably provided to the printing apparatus and optically measures the moving speed of the surface of the conveying belt. The printing apparatus according to claim 1. An endless conveyor belt stretched between a plurality of support rollers;
Driving means for rotating the support roller to move the conveyor belt endlessly;
A discharge control method for an ink head in a printing apparatus having a plurality of ink heads for forming a plurality of images on a recording medium on the conveyor belt so as to overlap each other.
A conveyance speed measurement step for measuring a movement speed at two arbitrary measurement points set on the conveyance belt or the support roller;
Belt profile data having a frequency corresponding to the moving speed of the conveying belt is extracted from accumulated data obtained by accumulating temporal fluctuations of the moving speed at each measurement point measured in the conveying speed measuring step, and each measurement is performed. A speed extraction step of extracting roller profile data having a frequency corresponding to the rotational speed of the support roller from the temporal variation of the moving speed at the point;
During the printing process, the moving speed of any one of the two measurement points is measured, and the measurement result is corrected based on the belt profile data and the roller profile data, and the interval between the plurality of images on the conveyor belt is corrected. And a printing control step for controlling the timing of image formation by the ink head so that the positional deviation of the printing head becomes small.