Image forming apparatus

Abstract

To provide an image forming apparatus that enables a more robust path design for transferring image data from the main unit control board to the head control board. [Solution] The image forming apparatus U according to the present invention comprises a plurality of head control units 22 that individually drive a plurality of recording heads 21, and a data transmission unit 11 that individually transfers image data to the plurality of head control units 22. Each of the plurality of head control units 22 is connected to the data transmission unit 11 by a separate first signal line L1, and each of the plurality of head control units 22 is connected to at least one other head control unit 22 by a separate second signal line L2. When transferring image data from the data transmission unit 11 to each of the plurality of head control units 22, the apparatus is configured to allow the use of a direct transfer method via the first signal line L1 and a detour transfer method via the second signal line L2.

Description

Technical Field

[0001] This disclosure relates to an image forming apparatus.

Background Art

[0002] An inkjet type image forming apparatus having a plurality of recording heads and performing image formation on a recording medium by ejecting ink from the plurality of recording heads is known.

[0003] In this type of image forming apparatus, generally, image data is transmitted from the main body side control board of the image forming apparatus to the head control board provided in each recording head. Then, in the head control board, the image forming operation is executed by controlling the ink ejection operation of each nozzle in the recording head corresponding to the image data. For example, refer to Patent Document 1 and Patent Document 2.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in this type of image forming apparatus, due to deterioration or disconnection of the signal line for transferring image data from the main body side control board to the head control board, or poor connection of the signal line, etc., the transfer of image data may not be carried out normally.

[0006] In such a case, repair of the image forming apparatus is required. Therefore, until the serviceman performs the repair work, the image forming apparatus becomes unusable, causing a problem of downtime for the user side.

[0007] Furthermore, in this type of image forming apparatus, high-speed serial interfaces such as V-by-One®, PCI Express®, and high-speed Ethernet are generally used when transferring image data from the main unit control board to the head control board. These types of interfaces are susceptible to noise, which can cause abnormalities such as data corruption and data loss.

[0008] In addition, when a scanning inkjet system is used in this type of image forming apparatus, the signal line may become bent depending on the position of the recording head. As a result, signal degradation may occur when transferring image data from the main unit control board to the head control board, and the transfer of image data may temporarily become impossible.

[0009] In such cases, it can lead to a degradation in the quality of the image formed on the recording medium.

[0010] This invention has been made in view of the above-mentioned problems. Specifically, the present invention aims to provide an image forming apparatus that can realize a more robust path design for transferring image data from the main unit control board to the head control board. [Means for solving the problem]

[0011] The main present invention that solves the aforementioned problems is: An inkjet-type image forming apparatus having multiple recording heads, which forms an image on a recording medium by ejecting ink from the multiple recording heads, Multiple head control units that drive each of the multiple recording heads individually, A data transmission unit that transfers image data to each of the aforementioned multiple head control units, Equipped with, Each of the aforementioned head control units is connected to the data transmission unit by a separate first signal line, and Each of the aforementioned head control units is connected to at least one other head control unit by a separate second signal line. When transferring the image data from the data transmission unit to each of the multiple head control units, the system is configured to allow the use of both a direct transfer method via the first signal line and a bypass transfer method via the second signal line. It is an image forming apparatus. [Effects of the Invention]

[0012] According to the image forming apparatus of the present invention, a more robust path design can be realized for transferring image data from the main unit control board to the head control board. [Brief explanation of the drawing]

[0013] [Figure 1] A diagram showing an example of the overall configuration of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This figure shows an example of the configuration of the control system of an image forming apparatus according to one embodiment of the present invention. [Figure 3] This figure shows an example of the configuration of a head control board according to one embodiment of the present invention. [Figure 4] This figure schematically illustrates the direct transfer method and the indirect transfer method when transferring image data from the data transmission unit to the head control board in an image forming apparatus according to one embodiment of the present invention. [Figure 5] A diagram showing an example of a detour route table according to one embodiment of the present invention. [Figure 6] A flowchart showing an example of the operation of the data transmission unit when performing data transfer of image data in an image forming apparatus according to one embodiment of the present invention. [Figure 7] This figure shows an example of a sequence of signal exchanges between the main control unit, data transmission unit, and head control board when performing data transfer of image data in an image forming apparatus according to one embodiment of the present invention. [Figure 8]A diagram showing an example of the configuration of packet data of image data when performing data transfer in the image forming apparatus according to Modification 1

Embodiments for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functions are denoted by the same reference numerals, and redundant description is omitted.

[0015] <Configuration of Image Forming Apparatus> Hereinafter, an example of the configuration of an image forming apparatus (hereinafter referred to as "image forming apparatus U") according to an embodiment of the present invention will be described.

[0016] FIG. 1 is a diagram showing an example of the overall configuration of the image forming apparatus U.

[0017] The image forming apparatus U includes an image forming apparatus main body (hereinafter abbreviated as "main body") 10 and head units 20Y, 20M, 20C, and 20K. Here, four head units 20Y, 20M, 20C, and 20K are provided corresponding to four colors of yellow, magenta, cyan, and black, respectively.

[0018] In the image forming apparatus U, the main body 10 conveys a recording medium P by a conveyance mechanism 10R (for example, a conveyance roller). Then, while conveying the recording medium P, the main body 10 forms a desired image on the recording medium P by discharging ink droplets from four head units 20Y, 20M, 20C, and 20K disposed so as to face the recording medium P.

[0019] The four head units 20Y, 20M, 20C, and 20K each have a similar configuration. The head units 20Y, 20M, 20C, and 20K include, for example, recording heads 21Y, 21M, 21C, and 21K, head control boards 22Y, 22M, 22C, and 22K, and head drive ICs 23Y, 23M, 23C, and 23K.

[0020] In the following, unless otherwise specified, the components will be collectively referred to as "head unit 20," "recording head 21," "head control board 22," and "head drive IC 23." Here, the head control board 22 corresponds to the "head control unit" of the present invention.

[0021] In the head unit 20, the recording head 21, the head control board 22, and the head drive IC 23 are, for example, integrally disposed within the housing of the head unit 20. More specifically, the recording head 21 and the head drive IC 23 are disposed within the housing of the head unit 20, and the head control board 22 is disposed to be attached to the housing.

[0022] The recording head 21 is, for example, an ink ejection mechanism that ejects ink using a piezoelectric method. The recording head 21 has, for example, a plurality of nozzles formed to face the transport surface. Inside the recording head 21, a plurality of pressure chambers and a plurality of piezoelectric elements that operate the plurality of pressure chambers are formed so as to communicate with each nozzle. Each piezoelectric element expands or contracts the pressure chamber according to the drive voltage supplied from the head drive IC 23, thereby ejecting ink from the nozzle.

[0023] The head control board 22 is an interface for receiving image data from the control board on the main unit 10 side (data transmission unit 11, described later). The head control board 22 passes the received image data to the head drive IC 23. The head drive IC 23 then generates drive signals to operate each nozzle of the recording head 21 based on the image data. The head control board 22 and the head drive IC 23 are wired together.

[0024] In the image forming apparatus U according to this embodiment, the recording head 21 is supported by the head support section 10T in such a manner that it can reciprocate in a direction perpendicular to the transport direction (hereinafter referred to as the scanning direction). The head support section 10T is configured, for example, to include guide rails that enable the recording head 21 to reciprocate along the scanning direction. That is, the image forming apparatus U according to this embodiment performs printing on the recording medium P using a scan-printing method.

[0025] <Configuration of the control system for an image forming apparatus> Figure 2 shows an example of the configuration of the control system of the image forming apparatus U. Figure 3 shows an example of the configuration of the head control board 22. Figure 4 is a schematic diagram illustrating the direct transfer method and the detour transfer method when transferring image data from the data transmission unit 11 to the head control board 22. Figure 5 shows an example of a detour route table.

[0026] In the image forming apparatus U according to this embodiment, a more robust path design is adopted as the signal path for transferring image data from the main body 10 (data transmission unit 11) to the head control board 22.

[0027] Specifically, the main unit 10 and the head units 20Y, 20M, 20C, and 20K are connected by separate normal transfer lines L1Y, L1M, L1C, and L1K. These signal lines are, for example, constructed using FPCs (Flexible Printed Circuits).

[0028] The normal transfer line L1Y is the main signal path for transferring Y-color image data from the data transmission unit 11 to the head control board 22Y. The normal transfer line L1M is the main signal path for transferring M-color image data from the data transmission unit 11 to the head control board 22M. The normal transfer line L1C is the main signal path for transferring C-color image data from the data transmission unit 11 to the head control board 22C. The normal transfer line L1K is the main signal path for transferring K-color image data from the data transmission unit 11 to the head control board 22K.

[0029] Furthermore, each of the head control boards 22Y, 22M, 22C, and 22K is connected to at least one other head control board 22 by bypass transfer lines L2a, L2b, and L2c. In the image forming apparatus U according to this embodiment, the head control board 22Y and the head control board 22M are connected by bypass transfer line L2a. The head control board 22M and the head control board 22C are connected by bypass transfer line L2b. The head control board 22C and the head control board 22K are connected by bypass transfer line L2c.

[0030] The bypass transfer line L2a is a secondary signal path for transferring image data from the data transmission unit 11 to the head control board 22Y or head control board 22M. Similarly, the bypass transfer line L2b is a secondary signal path for transferring image data from the data transmission unit 11 to the head control board 22M or head control board 22C. Furthermore, the bypass transfer line L2c is a secondary signal path for transferring image data from the data transmission unit 11 to the head control board 22C or head control board 22K. Here, the bypass transfer lines L2a, L2b, and L2c are formed by signal lines capable of bidirectional transmission.

[0031] In the following, unless otherwise specified, the normal transfer lines L1Y, L1M, L1C, and L1K will be collectively referred to as "normal transfer line L1." Similarly, unless otherwise specified, the bypass transfer lines L2a, L2b, and L2c will be collectively referred to as "bypass transfer line L2." Note that "normal transfer line L1" corresponds to the "first signal line" of the present invention, and "bypass transfer line L2" corresponds to the "second signal line" of the present invention.

[0032] Thus, in the image forming apparatus U, when transferring image data from the data transmission unit 11 to the head control board 22, both a direct transfer method via the normal transfer line L1 and a detour transfer method via the detour transfer line L2 are available.

[0033] Therefore, suppose the data transmission unit 11 attempts to transfer image data to the head control board 22Y using a direct transfer method. If a transmission error is detected at this time, the data transmission unit 11 can transfer the data to the head control board 22Y via another head control board 22, such as the head control board 22M, using a detour transfer method.

[0034] In the following, the "direct transfer method" will be described as the normal image data transfer method, and the "detour transfer method" will be described as the image data transfer method in abnormal situations.

[0035] In addition, both the direct transfer method via the normal transfer line L1 and the detour transfer method via the detour transfer line L2 transfer image data, for example, by serial transfer.

[0036] Furthermore, the main unit 10 and each head control board 22 are also connected by control signal lines (not shown) for the separate exchange of control signals. Examples of control signals exchanged between the main unit 10 and the head control boards 22 include, for example, error notifications (dotted arrows in Figure 3) and path switching commands (dash-dot arrows in Figure 3), which will be described later. In addition, the main unit 10 may also send synchronization signals to each head control board 22 via the control signal lines to synchronize their operation.

[0037] Next, we will explain the configuration of the main body 10 of the image forming apparatus U.

[0038] The main unit 10 comprises a main control unit 12 that centrally controls the operation of the entire image forming apparatus U, and a data transmission unit 11 that transfers image data to be printed to each head control board 22. The main control unit 12 and the data transmission unit 11 are housed within the casing of the main unit 10.

[0039] Furthermore, the main control unit 12 and the data transmission unit 11 are control boards that each include, for example, a CPU, ROM, RAM, input ports, and output ports. In other words, the functions of the main control unit 12 and the data transmission unit 11, which will be described later, are realized by the CPU referring to control programs and various data stored in the ROM and RAM, etc.

[0040] However, the main control unit 12 and the data transmission unit 11 may be composed of dedicated or general-purpose hardware such as a DSP, ASIC, or PLD, depending on the processing.

[0041] The main control unit 12 functions, for example, as a transport control unit 12a and an image processing unit 12b. The main control unit 12 also has a storage unit 12c that stores image data to be printed, which is input from an external computer M.

[0042] The transport control unit 12a, for example, drives the motors of the transport rollers constituting the transport mechanism 10R at a predetermined speed and timing to transport the recording medium P. The transport control unit 12a also operates the head unit 20 at a predetermined speed and timing by, for example, driving the motor that moves the head support section 10T (i.e., the guide rail).

[0043] Furthermore, the image processing unit 12b performs predetermined image processing on the image data input from the external computer M and stores the obtained image data in the storage unit 12c. This image processing includes correction processing to correct the image data, as well as color conversion processing, gradation correction processing, and pseudo-halftone processing.

[0044] The main control unit 12 moves the recording medium P and the head unit 20 using the transport control unit 12a. Then, in synchronization with these movements, it reads the image data processed by the image processing unit 12b from the storage unit 12c and transmits it to the data transmission unit 11.

[0045] The data transmission unit 11 functions as a transmission control unit 11a, a detection data addition unit 11b, a transmission error detection unit 11c, and a transfer method switching unit 11d. The data transmission unit 11 also has a storage unit 11e that stores a bypass route table when transferring image data using a bypass transfer method.

[0046] The transmission control unit 11a receives image data from the main control unit 12. The transmission control unit 11a then divides the image data into data corresponding to each head control board 22 and transmits the image data to each head control board 22 individually. Here, the transmission control unit 11a extracts frame data for each YMCK color from the image data relating to the color image. Then, from the frame data for each YMCK color, it transmits the image data of the corresponding color to the head control board 22 for each color.

[0047] When the transmission control unit 11a transmits image data to each head control board 22, for example, it divides the image data into line-based packet data. The transmission control unit 11a then adds an error detection code generated by the detection data addition unit 11b to the line-based packet data and transfers the data to the head control board 22.

[0048] Here, under normal conditions, the transmission control unit 11a sets the transfer path to transfer image data to each head control board 22 using the direct transfer method. On the other hand, if a transmission error occurs using the direct transfer method, the transmission control unit 11a sets the transfer path to transfer image data to the head control board 22 where the transmission error occurred using the detour transfer method. In this case, the transmission control unit 11a sets the transfer path based on a command to change the data transfer path from the transfer method switching unit 11d.

[0049] Furthermore, if a transmission error occurs using the direct transfer method, the transmission control unit 11a will change the data transfer path and then retransmit the same image data to the head control board 22 where the transmission error occurred using the detour transfer method.

[0050] The detection data addition unit 11b generates error detection data when transmitting image data (line-based packet data) from the data transmission unit 11 to each head control board 22. For example, a checksum or a CRC (Cyclic Redundancy Check) code can be used as the error detection data. In this embodiment, a CRC code is used as the error detection data.

[0051] When the data transmission unit 11 transfers image data to the head control board 22, the transmission error detection unit 11c determines a data transfer timeout based on the waiting time for the Ack signal from the head control board 22. If a timeout is detected, the transmission error detection unit 11c outputs a timeout notification to the transfer method switching unit 11d. In this embodiment, the head control board 22 (image data input unit 22a) is configured to send an Ack signal back to the data transmission unit 11 for each packet data line via the first signal line L1.

[0052] The transfer method switching unit 11d switches the transfer method when an image data transmission error is detected. In this embodiment, the transfer method switching unit 11d identifies a transmission error as occurring when it receives an error notification from the head control board 22 (error detection unit 22d). Furthermore, the transfer method switching unit 11d identifies a transmission error as occurring when it receives a timeout notification from the transmission error detection unit 11c.

[0053] Furthermore, the transfer method switching unit 11d receives error notifications from the head control board 22 (error detection unit 22d) via a control signal line connecting the data transmission unit 11 and the head control board 22.

[0054] The transfer method switching unit 11d changes the data transfer path for transferring image data to the head control board 22 where a transmission error has occurred, based on the bypass path table pre-set in the storage unit 11e.

[0055] The detour path table includes, for example, pre-configured detour paths in the event of a communication error in the head control board 22, associated with the identification information of the head control board 22 (see Figure 5).

[0056] Specifically, the detour route table is configured such that, for example, if a communication error occurs in the head control board 22Y, data transfer is performed via the head control board 22M and the detour transfer line L2a. Also, for example, if a communication error occurs in the head control board 22M, data transfer is performed via the head control board 22C and the detour transfer line L2b. Also, for example, if a communication error occurs in the head control board 22C, data transfer is performed via the head control board 22K and the detour transfer line L2c. Also, for example, if a communication error occurs in the head control board 22K, data transfer is performed via the head control board 22C and the detour transfer line L2c.

[0057] Figure 5 shows a configuration in which only one bypass route is set for bypass transfer to a single head control board 22. However, it is more desirable for two or more bypass routes to be set in the bypass route table for a single head control board 22. This makes it possible to reliably transfer image data from the data transmission unit 11 to the head control board 22 even if communication failures occur on multiple normal transfer lines L1. In such cases, the bypass route table may also store which of the set bypass routes should be prioritized.

[0058] Furthermore, it is desirable that the transfer method switching unit 11d stores in the storage unit 11e status information relating to the normal / abnormal state of the normal transfer line L1 and bypass transfer line L2 of each head control board 22 in association with the bypass route table. This makes it possible to select an appropriate bypass route even if a communication abnormality occurs in multiple head control boards 22. In addition, this allows the transmission control unit 11a to set a transfer route so that, once a transmission error is detected in a head control board 22, the image data is transferred using the bypass transfer method each time.

[0059] In other words, the change in the data transfer path is achieved when the transfer method switching unit 11d sends a bypass reception command and a retransfer command to the head control board 22, which is the target of the data transfer path change.

[0060] Specifically, the transfer method switching unit 11d transmits a detour reception command to the switching control unit 22f of the head control board 22 where a communication error has occurred. Then, the transfer method switching unit 11d transmits a retransfer command to the switching control unit 22f of the head control board 22 that has been set as the detour destination. These command signals are transmitted, for example, via control signal lines connecting the data transmission unit 11 and each head control board 22.

[0061] This causes the head control board 22 (switching control unit 22f) where a communication error has occurred to switch the destination for acquiring image data from the image data input unit 22a to the bypass image data input unit 22b. In addition, this causes the head control board 22 (switching control unit 22f) set as the bypass destination to output the image data input from the image data input unit 22a to the head control board 22 at the transfer destination via the bypass image data output unit 22c.

[0062] Next, the configuration of the head control board 22 will be explained (see Figure 3).

[0063] The head control board 22 includes an image data input unit 22a, a bypass image data input unit 22b, a bypass image data output unit 22c, an error detection unit 22d, a data distribution unit 22e, a switching control unit 22f, and an IF (interface) unit 22g.

[0064] The image data input unit 22a receives image data from the data transmission unit 11 on the main unit 10 via the normal transfer line L1. The image data input unit 22a then performs serial / parallel conversion on the image data received via the normal transfer line L1, for example. The image data after parallel conversion is then output to the data distribution unit 22e and the error detection unit 22d.

[0065] Furthermore, the image data input unit 22a also has the function of sending an Ack signal back to the data transmission unit 11 for each packet of line-based data when acquiring image data from the data transmission unit 11.

[0066] The bypass image data input unit 22b receives image data from the data transmission unit 11 on the main unit 10 side via the bypass transfer line L2. The bypass image data input unit 22b then performs serial / parallel conversion on the image data received via the bypass transfer line L2, for example. The image data after parallel conversion is then output to the data distribution unit 22e and the error detection unit 22d.

[0067] The bypass image data output unit 22c acquires image data from the data transmission unit 11 on the main unit 10 side via the bypass transfer line L2 when an abnormality occurs (i.e., when the bypass transfer method is in operation) from the data distribution unit 22e. The bypass image data output unit 22c then performs, for example, a parallel / serial conversion on the image data acquired from the data distribution unit 22e. The serially converted image data is then output to the head control unit 22, the retransmission destination, via the bypass transfer line L2.

[0068] The error detection unit 22d detects transmission errors by comparing the CRC code or checksum (in this embodiment, the CRC code) attached to the received image data. When using a CRC code, the error detection unit 22d calculates the CRC code from the image data as error detection data. The CRC code is the remainder when the bit sequence of the image data is divided by a predetermined generating polynomial. That is, the error detection unit 22d detects transmission errors by comparing the CRC code calculated from the image data with the CRC code attached to the received image data.

[0069] If the error detection unit 22d detects a transmission error, it notifies the data transmission unit 11 (in this case, the transfer method switching unit 11d) on the main unit 10 of the error. At this time, the error detection unit 22d may also notify the data transmission unit 11 of the error by adding the identification information of its own head control unit 22. The error notification from the error detection unit 22d to the data transmission unit 11 is performed, for example, via a control signal line connecting the data transmission unit 11 and each head control unit 22.

[0070] The data distribution unit 22e acquires image data transferred from the data transmission unit 11 from the image data input unit 22a or the bypass image data input unit 22b. The data distribution unit 22e then performs data distribution processing to either send the received image data to its downstream nozzle drive unit 22g or transfer it to another head control board 22 via the bypass image data output unit 22c.

[0071] Here, the operation of the data distribution unit 22e is changed under the control of the switching control unit 22f. Normally, the data distribution unit 22e acquires image data from the image data input unit 22a and sends the image data to the nozzle drive unit 22g which is downstream of it. On the other hand, if the data distribution unit 22e receives a bypass reception command from the switching control unit 22f, it switches the destination of the image data acquisition from the image data input unit 22a to the bypass image data input unit 22b. Also, if the data distribution unit 22e receives a retransmission command from the switching control unit 22f, it transfers the acquired image data to another head control board 22 via the bypass image data output unit 22c.

[0072] The switching control unit 22f changes the operation of the data distribution unit 22e based on a switching command (i.e., a detour reception command or a retransmission command) from the data transmission unit 11 (transfer method switching unit 11d) on the main unit 10 side. That is, when the switching control unit 22f receives a switching command from the data transmission unit 11, it switches the input port for receiving the image data. In other words, the switching control unit 22f changes the operation of the data distribution unit 22e from normal operation to either retransmission operation or detour reception operation in response to such a command signal.

[0073] Furthermore, if the head control board 22 has multiple bypass routes, information on which route to use may be added to the command signal from the transfer method switching unit 11d. The switching control unit 22f can then change the operation of the data distribution unit 22e according to such command signal.

[0074] The IF unit 22g receives image data from the data distribution unit 22e. The IF unit 22g then passes the image data it has received to the head drive IC 23.

[0075] Furthermore, the configuration of the head drive IC23 is the same as that of conventionally known configurations.

[0076] The head drive IC 23 receives, for example, image data from the head control board 22, a drive waveform (i.e., an analog voltage waveform) from the main control unit 12, and an ink ejection timing command signal. The head drive IC 23 determines which nozzles of the recording head 21 are to eject ink from according to the input image data. The head drive IC 23 then outputs a drive waveform to the nozzles of the recording head 21 to eject ink according to the ink ejection timing command signal, thereby performing ink ejection. For specific details of the head drive IC 23, please refer to, for example, Patent Document 2.

[0077] <Specific processing during data transfer of image data> Figure 6 is a flowchart showing an example of the operation of the data transmission unit 11 when transferring image data. Upon receiving image data from the main control unit 12, the data transmission unit 11 executes the process shown in the flowchart in Figure 6.

[0078] In step S1, the data transmission unit 11 divides the image data received from the main control unit 12 into image data corresponding to each head control board 22. Then, the data transmission unit 11 first starts transferring the Y-color image data to the head control board 22Y via the normal transfer line L1Y.

[0079] In step S1, the data transmission unit 11 divides, for example, the image data for the Y color into packet data for each line. Then, it adds the error detection code generated by the detection data addition unit 11b to the packet data and transmits it to the head control board 22Y.

[0080] In step S2, the data transmission unit 11 determines whether or not there is a communication abnormality in the normal transfer line L1Y. At this time, the data transmission unit 11 determines the communication abnormality based on whether or not a transmission timeout has been detected and whether or not an error notification has been received from the head control board 22Y.

[0081] If there is no communication error on the normal transfer line L1Y (S2: NO), the data transmission unit 11 completes the transfer of the image data via the normal transfer line L1Y and proceeds to step S5. On the other hand, if there is a communication error on the normal transfer line L1Y (S2: YES), the data transmission unit 11 proceeds to step S3.

[0082] In step S3, the data transmission unit 11 refers to the detour route table stored in the storage unit 11e. The data transmission unit 11 then switches the normal transfer line L1 used when transferring Y-color image data to the head control board 22Y (for example, L1Y ⇒ L1M).

[0083] Furthermore, at this time, the data transmission unit 11 sends a retransmission command to the switching control unit 22f of the head control board 22 (in this case, head control board 22M) that is the detour destination, according to the determined data transfer path. The data transmission unit 11 also sends a detour reception command to the switching control unit 22f of the head control board 22Y where the communication error occurred, according to the determined data transfer path.

[0084] In step S4, the data transmission unit 11 transfers the Y-color image data to the head control board 22M via the normal transfer line L1M. The head control board 22M then acquires the image data via the normal transfer line L1M. It then transfers the image data to the head control board 22Y via the bypass transfer line L2a. Once the data transmission unit 11 has transferred all the Y-color image data to the head control board 22Y in this manner, it proceeds to step S5.

[0085] The processing from step S5 onward is the same as the processing in steps S1 to S4. That is, in the subsequent steps S5 to S8, the data transmission unit 11 transfers image data for M color to the head control board 22M using the same processing as in steps S1 to S4. Then, in the subsequent steps S9 to S12, the data transmission unit 11 transfers image data for C color to the head control board 22C using the same processing as in steps S1 to S4. Then, in the subsequent steps S13 to S16, the data transmission unit 11 transfers image data for K color to the head control board 22K using the same processing as in steps S1 to S4.

[0086] Furthermore, after the transfer of image data to each head control board 22 is completed in this manner, the image data is simultaneously transferred from each head control board 22 to each head drive IC 23. Then, each head drive IC 23 synchronizes to eject ink from each recording head 21.

[0087] Figure 7 shows an example of a sequence of signal exchanges between the main control unit 12, the data transmission unit 11, and the head control board 22 when performing data transfer of image data.

[0088] First, the external computer M sends a print job execution command, along with image data converted into RIP data, to the main control unit 12 of the main unit 10 (Sa).

[0089] When the main control unit 12 receives a print job execution command, it instructs the data transmission unit 11 to perform the initial setup of the transfer line configuration (Sb). The data transmission unit 11 then notifies the head control board 22 of the transfer line information during the initial setup (Sc). In this case, the transfer line during the initial setup is the normal transfer line L1 (i.e., the direct transfer method). If there is already a normal transfer line L1 that is broken or otherwise unavailable, the notification is made so that the bypass transfer line L2 is set as the transfer line during the initial setup.

[0090] Next, the main control unit 12 sends a data transfer start command to the data transmission unit 11 (Sd), and then starts transmitting image data (Se). Then, as shown in Figure 6, the data transmission unit 11 transmits the image data to each head control board 22 in sequence upon receiving the image data from the main control unit 12 (Sf).

[0091] Here, the head control board 22 detects transmission errors in the image data received from the data transmission unit 11. If a transmission error is detected, the head control board 22 sends an error notification (Sg) to the data transmission unit 11.

[0092] If the data transmission unit 11 receives a normal transmission error notification from the head control board 22, it forwards the transmission error notification to the main control unit 12 (Sh), causing the main control unit 12 to retransmit the image data. At this time, the data transmission unit 11 also switches to a detour transmission method, sending a detour transmission command to the head control board 22 at the detour route destination, and also sending a detour reception command to the head control board 22 that experienced the transmission error (Si).

[0093] In this way, the image data is retransmitted from the main control unit 12 to the data transmission unit 11 (Sj). Then, the data transmission unit 11 transmits the image data to the head control board 22 that had a transmission error, using a detour transmission method according to the determined transfer path (Sk).

[0094] In the image forming apparatus U according to this embodiment, the image data is transferred to the head control board 22 using a detour transfer method when direct transfer of image data is not possible through this process.

[0095] <Effects> As described above, in this embodiment, An inkjet-type image forming apparatus having multiple recording heads, which forms an image on a recording medium by ejecting ink from the multiple recording heads, Multiple head control units that drive each of the multiple recording heads individually, A data transmission unit that transfers image data to each of the aforementioned multiple head control units, Equipped with, Each of the aforementioned head control units is connected to the data transmission unit by a separate first signal line, and Each of the aforementioned head control units is connected to at least one other head control unit by a separate second signal line. When transferring the image data from the data transmission unit to each of the multiple head control units, the system is configured to allow the use of both a direct transfer method via the first signal line and a bypass transfer method via the second signal line. An image forming apparatus was disclosed.

[0096] According to the image forming apparatus of this embodiment, when transferring image data from the main control board to the head control board, even if direct data transfer is not possible, data transfer can be performed using a bypass transfer method via a bypass signal line.

[0097] This makes it possible to suppress downtime even if the image forming apparatus requires repair due to a faulty signal line connecting the main control board and the head control board. Furthermore, it makes it possible to suppress image quality degradation even if the transfer of image data is temporarily not performed normally due to bending of the signal line or external noise.

[0098] (Variation 1) In the above embodiment, as an example of a method for switching the transfer method, a switching command is output from the data transmission unit 11 to the head control board 22 via a control signal line, thereby changing the distribution operation of the image data.

[0099] In the modified image forming apparatus U, a configuration is adopted in which destination address information is added to the image data in order to enable switching from a direct transfer method to a detour transfer method without using a switching command via a control signal line.

[0100] Figure 8 shows an example of the configuration of image data packet data when data transfer is performed in the image forming apparatus U according to this modified example.

[0101] In the image forming apparatus U according to this modified example, when the transmission control unit 11a transfers image data to each head control board 22, it adds destination address information corresponding to the identification information of the head control board 22 to the image data.

[0102] Furthermore, in the image forming apparatus U according to this modified example, the data distribution unit 22e of each head control board 22 is provided with a function to determine the destination of the image data acquired from the data transmission unit 11. That is, in this modified example, the data distribution unit 22e of each head control board 22 determines the destination of the received image data according to the destination address information attached to the image data. If the determined destination of the image data is one that was sent to itself, the data distribution unit 22e sends it to the subsequent nozzle drive unit 22g. On the other hand, if the data distribution unit 22e determines that the data was sent to another head control board 22, it retransmits it to that other head control board 22. In this embodiment, it is desirable that each head control board 22 has a storage unit that stores address data for determining the destination address information.

[0103] The image forming apparatus U according to this modified version is useful in that it can switch from a direct transfer method to a bypass transfer method even if a malfunction occurs in the control signal line.

[0104] (Modification 2) Although not explained in the above embodiment, it is desirable that the maximum transfer speed (maximum transfer bandwidth) of each direct transfer line L1 be at least twice the bandwidth required by the head control board 22 to transfer the amount of data requested per unit time.

[0105] For example, if an error occurs during transfer to the head control board 22Y, the data transmission unit 11 will send the image data for the head control board 22Y to the head control board 22Y via the direct transfer line L1M and the bypass transfer line L2a (see Figure 4). In this case, in order to maintain the print time throughput, the direct transfer line L1M must transfer the image data for the head control board 22Y and the image data for the head control board 22M at the same unit time as when the direct transfer line is functioning correctly (i.e., twice the transfer volume = twice the transfer speed is required). In other words, the direct transfer line L1M needs to have a speed bandwidth of more than twice the speed required for normal transfer.

[0106] Therefore, it is desirable that the maximum transfer speed (maximum transfer bandwidth) of each direct transfer line L1 be configured to have a bandwidth that allows for a transfer speed of at least twice the bandwidth required by the head control board 22 to transfer the amount of data per unit time.

[0107] (Variation 3) In the above embodiment, as an example of the multiple head control boards 22 that the image forming apparatus U has, a configuration in which four head control boards 22, one for each color, are used is shown.

[0108] However, the application of the path design for the image forming apparatus U according to the present invention is not limited to the head control board 22 for each color. For example, in recent years, with the increasing density and size of heads, image forming apparatus U has been developed that is equipped with multiple head control boards 22 corresponding to multiple nozzles arranged on the head, and drives the head with these multiple head control boards 22. That is, the path design for the image forming apparatus U according to the present invention is also applicable to multiple head control boards 22 provided to correspond to such multiple nozzles.

[0109] (Modification 4) In the above embodiment, when transferring image data from the data transmission unit 11 to each of the multiple head control boards 22, the transfer process is performed sequentially.

[0110] However, in realizing the image forming apparatus U according to the present invention, data may be transferred simultaneously from the data transmission unit 11 to each of the multiple head control boards 22.

[0111] (Variation 5) In the above embodiment, a scanning-type image forming apparatus was shown as an example. However, the image forming apparatus according to the present invention is also applicable to a one-pass type image forming apparatus (a system in which the head position is fixed and paper is transported and printed).

[0112] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. [Industrial applicability]

[0113] According to the image forming apparatus of the present invention, a more robust path design can be realized for transferring image data from the main unit control board to the head control board. [Explanation of Symbols]

[0114] U Image forming apparatus 10 Image forming apparatus main unit 10R Conveyor Mechanism 10T Head support section 11 Data transmission section 11a Transmission control unit 11b Data addition section for detection 11c Transmission error detection unit 11d Transfer method switching section 11e Storage section 12 Main Control Unit 12a Transport Control Unit 12b Image Processing Unit 12c storage section 20 Head Units 21 Recording head 22 Head control board 22a Image data input section 22b Bypass image data input section 22c Bypass image data output unit 22d Error detection unit 22e Data Distribution Unit 22f Switching Control Unit 22g IF part 23 Head drive IC L1Y, L1M, L1C, L1K Standard Transfer Lines L2a, L2b, L2c bypass transfer lines M External Computer P recording medium

Claims

1. An inkjet-type image forming apparatus having multiple recording heads, which forms an image on a recording medium by ejecting ink from the multiple recording heads, Multiple head control units that drive each of the multiple recording heads individually, A data transmission unit that transfers image data to each of the aforementioned multiple head control units, Equipped with, Each of the aforementioned head control units is connected to the data transmission unit by a separate first signal line, and Each of the aforementioned head control units is connected to at least one other head control unit by a separate second signal line. When transferring the image data from the data transmission unit to each of the multiple head control units, the system is configured to allow the use of both a direct transfer method via the first signal line and a bypass transfer method via the second signal line. Image forming apparatus.

2. The data transmission unit performs a first process of transferring the image data to the first head control unit among the plurality of head control units using the direct transfer method, If a transmission error is detected in the first process, the following steps are sequentially executed: a second process that transfers data to the first head control unit via the second head control unit among the plurality of head control units using the bypass transfer method; and a second process that transfers data to the first head control unit via the second head control unit among the plurality of head control units. The image forming apparatus according to claim 1.

3. Each of the aforementioned head control units has an error detection unit that detects a transmission error by comparing it with error detection data attached to the received image data. If the error detection unit detects a transmission error, it notifies the data transmission unit accordingly. The image forming apparatus according to claim 1.

4. The error detection data is a CRC code or a checksum. The image forming apparatus according to claim 3.

5. The data transmission unit includes a transfer method switching unit that switches the transfer method if a transmission error is detected during the data transfer of the image data. The transfer method switching unit, based on a pre-configured detour path table, changes the data transfer path for transferring the image data to the head control unit where the transmission error occurred. The image forming apparatus according to claim 1.

6. The transfer method switching unit changes the data transfer path based on status information relating to the normal / abnormal state of the first signal line and the second signal line connected to each of the plurality of head control units. The image forming apparatus according to claim 5.

7. After the data transmission unit has changed the data transfer path, it retransmits the same image data to the head control unit where the transmission error occurred, using the detour transfer method. The image forming apparatus according to claim 5.

8. Each of the aforementioned head control units has a switching control unit that, upon receiving a switching command from the data transmission unit, switches the input port for receiving the image data. The image forming apparatus according to claim 1.

9. Each of the aforementioned head control units determines the destination of the received image data based on the destination address information attached to the received image data, and either sends the image data to its own subsequent data processing unit or transfers it to another head control unit. The image forming apparatus according to claim 1.

10. In the direct transfer method via the first signal line and the detour transfer method via the second signal line, the image data is transferred by serial transfer. The image forming apparatus according to claim 1.

11. The maximum transfer bandwidth of the first signal line has a transfer speed that is at least twice the bandwidth required by the head control board to transfer the amount of data per unit time. The image forming apparatus according to claim 1.

Images