Image forming apparatus

Abstract

To provide an image forming apparatus with high accuracy for faulty connection testing. [Solution] The image forming apparatus comprises a recording head and a control board for controlling the recording head. The control board includes a control unit that generates print data and inspection data for determining connection problems between the recording head and the control board, and a transmission unit that transmits the print data and inspection data as differential signals to the recording head. The recording head includes a receiving unit that receives the print data and inspection data, and a determination unit that determines the connection problems from the received inspection data. The transmission unit and the receiving unit are equipped with switching means that can swap clock signals and data signals for transferring print data and inspection data.

Description

Technical Field

[0006]

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] An inkjet recording apparatus having a configuration in which a recording head mounted on a carriage can be detached by a user is known. In an inkjet recording apparatus having such a configuration, when the user mounts the recording head, there may be a problem of poor contact at the contact between the recording head and the carriage. Therefore, conventionally, it is known to provide a connection failure inspection (see Patent Document 1).

Prior Art Documents

Patent Documents

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

Means for Solving the Problems

[0007] According to the present invention, it is possible to provide an image forming apparatus with high accuracy for faulty connection inspection. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing the exterior of an inkjet recording device. [Figure 2] This is a block diagram showing the configuration of the control unit of an inkjet recording device. [Figure 3] This is a block diagram showing the configuration of the connection between an inkjet recording device and a recording head. [Figure 4] This is a conceptual diagram of the signals used during connection failure testing. [Figure 5] This is a flowchart illustrating connection failure testing. [Figure 6] This is a timing chart of signals used during connection failure testing. [Figure 7] This is an internal configuration diagram of the LVDS transmitter and receiver. [Figure 8] This is a logical table of selectors. [Figure 9] This flowchart provides a detailed explanation of the connection failure testing process. [Modes for carrying out the invention]

[0009] Embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of each component of the embodiments described below may be appropriately changed depending on the configuration and various conditions of the recording device to which the present invention is applied. The scope of the present invention is not limited to the embodiments described below.

[0010] In this specification, "record" (sometimes referred to as "print") refers not only to cases where meaningful information such as text and figures is formed, but also to cases where images, patterns, etc. are formed on a recording medium, or where the medium is processed, regardless of whether it is meaningful or not. Furthermore, it also refers to cases where images, patterns, etc. are formed on a recording medium, or where the medium is processed, regardless of whether it is made apparent in a way that humans can perceive visually.

[0011] Furthermore, the term "recording medium" refers not only to paper, which is commonly used in recording devices, but also to a wide range of materials that can accept ink, such as cloth, plastic film, metal plates, glass, ceramics, wood, and leather.

[0012] Furthermore, "ink" (sometimes referred to as "liquid") should be interpreted broadly, similar to the definition of "record (print)" above. Therefore, it refers to a liquid that, when applied to a recording medium, can be used to form images, patterns, designs, etc., or to process the recording medium, or to process the ink (for example, to solidify or insolubilize the colorants in the ink applied to the recording medium).

[0013] Figure 1(a) is a perspective view showing the external appearance of the inkjet recording device (recording device), and Figure 1(b) is a perspective view showing the recording device in Figure 1(a) with the top cover removed. As shown in Figure 1(a), a manual feed slot 88 is provided on the front of the recording device 2, and a roll paper cassette 89 that can be opened and closed to the front is provided below it. The recording medium is supplied into the recording device 2 from the manual feed slot 88 or the roll paper cassette 89. The recording device 2 comprises a device body 94 supported by two legs 93, a stacker 90 for stacking the discharged recording medium, and an upper cover 91 that can be opened and closed, is transparent, and allows the interior to be seen. On the right side of the device body 94, there is an operation unit 12, an ink supply unit, and an ink tank.

[0014] As shown in Figure 1(b), the recording device 2 includes a transport roller 70 for transporting the recording medium in the direction of arrow B (sub-scanning direction), and a carriage 4 guided and supported so as to be able to reciprocate in the width direction of the recording medium (direction of arrow A, main scanning direction). The recording device 2 further includes a carriage motor (not shown) and a carriage belt (hereinafter referred to as the belt) 270 for reciprocating the carriage 4 in the direction of arrow A, and a recording head 11 mounted on the carriage 4. It also includes a suction-type ink recovery unit 9 for supplying ink and resolving ink ejection problems caused by clogging of the ejection port of the recording head 11. The recording head 11 is detachable from the carriage 4, and can be reattached or replaced with a new recording head in case of improper mounting.

[0015] In this recording device, the carriage 4 is equipped with an inkjet recording head (hereinafter referred to as "recording head") 11 consisting of four heads corresponding to four color inks, in order to perform color recording on the recording medium. Specifically, the recording head 11 consists of, for example, a K head that ejects K (black) ink, a C head that ejects C (cyan) ink, an M head that ejects M (magenta) ink, and a Y head that ejects Y (yellow) ink. Each head is provided with a nozzle (not shown) for ejecting ink.

[0016] When recording an image on a recording medium with the above configuration, the conveyance roller 70 conveys the recording medium to a predetermined recording start position. After that, by repeating the operation of scanning the recording head 11 in the main scanning direction by the carriage 4 and the operation of conveying the recording medium in the sub-scanning direction by the conveyance roller 70, recording on the entire recording medium is performed.

[0017] That is, the carriage 4 moves in the direction of arrow A shown in Fig. 1(b) by the belt 270 and a carriage motor (not shown), and thus an image is recorded on the recording medium. When the carriage 4 is returned to the position (home position) before being scanned, the recording medium is conveyed in the sub-scanning direction (the direction of arrow B shown in Fig. 1(b)) by the conveyance roller, and then the carriage is scanned again in the direction of arrow A in Fig. 1. In this way, recording of an image, characters, etc. on the recording medium is performed. Further, by repeating the above operation, when the recording of one sheet of the recording medium is completed, the recording medium is discharged into the stacker 90, and the recording of one sheet is completed.

[0018] Fig. 2 is a block diagram showing the configuration of the control circuit of the recording apparatus 2 and the circuit built in the recording head attached to the recording apparatus. In the present embodiment, data is transmitted and received by a differential signal system between the printer control unit 218 connected via the LVDS line 224 and the circuit built in the recording head. For other communication paths, namely, between the printer control unit 218 - signal sequence determination unit 222 and between the printer control unit 218 - head information storage unit 223, data transmission is performed by an I2C bus in a single-ended format.

[0019] The printer control unit 218 corresponding to the control board includes a CPU 201, a RAM 202, a ROM 203, an image processing unit 20, a HDD 205, a host interface 206, a printer engine 207, an operation display unit 209, a general-purpose I / O controller 👁️‍🗨️, a system bus 211, a data generation unit 227, an LVDS transmission unit 219, and a recording head communication unit 220.

[0020] The CPU 201 controls the entire recording device 2. The CPU 201 controls the operation of the entire recording device 2 by executing operation control programs stored in RAM 202 or ROM 203. Specifically, it controls the image processing unit 204, which converts print job data received from the host computer (hereinafter referred to as the host) into image data for output to the recording medium, the operation display unit 209, and the general-purpose I / O controller 210. The CPU 201 also controls the transfer of image data generated by the image processing unit 204 to the printer engine 207. Furthermore, the CPU 201 controls the transmission of connection test data (inspection data) generated by the data generation unit 227 from the LVDS transmission unit 219 to the LVDS reception unit 221 in the recording head 11 via the LVDS line 224. The recording head communication unit 220 then determines the quality of the recording head connection based on the connection test signal pattern matching result received from the signal arrangement determination unit 222. Details of this operation will be described later.

[0021] RAM202 includes RAM devices and a RAM controller that manages access to the RAM devices. The RAM devices function as work memory for executing operation control programs run on CPU201, and as buffer memory for storing various intermediate data generated during the printing process. In addition, they function as buffer memory for temporarily storing various data (print job data and various control data) transmitted and received between the host and the system.

[0022] ROM203 includes a ROM device and a ROM controller that controls access to the ROM device. The ROM device is a non-volatile memory that stores operation control programs executed by the CPU201, various data for recording control, and various screen data for display on the LCD provided in the operation display unit 209. ROM203 outputs the stored information to the system bus 211 according to instructions from the CPU201. The operation control programs include various programs, such as the control program for the printer engine 207.

[0023] The image processing unit 204 performs color space conversion, gamma correction, and quantization using error diffusion on the image data transmitted from the host as print job data, in order to generate binary image data that can be output by the printer engine.

[0024] HDD205 includes a Serial ATA hard disk drive and a bridge unit for connecting the system bus 211 and the Serial ATA interface of the hard disk drive. HDD205 operates as a large-capacity external storage device for recording device 2 and stores and saves print job data received from the host via the host interface (I / F) 206.

[0025] The host interface 206 connects the recording device 2 and the host (not shown), and enables data transmission and reception between them. Print job data received from the host computer via the host interface 206 is stored in the RAM 202 via the system bus 211. The host interface 206 uses serial communication methods such as USB or network communication methods such as 1000Base-TX.

[0026] The printer engine 207 receives the binary image data generated by the image processing unit 204 and stored in the RAM 202 sequentially.

[0027] The head information storage unit 223 includes a ROM device and a ROM controller that controls access to the ROM device. The ROM device is a non-volatile memory that stores information on the time constant, which is determined from the resistance (resistive component) and parasitic capacitance (capacitive component) inherent in the data transmission line of the recording head 11. This time constant is the time constant in the LVDS line 224 when the recording head is actually mounted on the image forming apparatus, and is measured at the time of shipment. For example, an image forming apparatus for measuring the time constant is prepared. The recording head is mounted on the prepared image forming apparatus, and data communication is performed between the image forming apparatus and the recording head. At this time, the time required for the rising edge of the transmitted signal (time constant) is measured using a measuring instrument. After that, the measured time constant is recorded in the head information storage unit 223.

[0028] The data generation unit 227 stores the data in the RAM 202 during connection failure testing. In this embodiment, the data is stored in the RAM 202, but other memory or recording means may be used. The data generation unit 227 generates a new clock signal and a connection failure testing signal based on the time constant information of the recording head 11.

[0029] Here, we will explain the connection failure test of the recording head performed by the inkjet recording device using Figures 3 and 4.

[0030] As shown in Figure 3, when the user mounts the recording head 11 onto the carriage 4, it is electrically connected to the printer control unit 218 of the recording device via the carriage 4 through contacts A to H on the recording head. The recording head 11 is supplied with the power necessary for its operation via a flexible flat cable (FFC, not shown) and the carriage 4.

[0031] A clock signal is transmitted from the LVDS transmission unit 219 to the recording head 11 via the carriage 4 through the CLK+ and CLK- clock lines in the LVDS line 224. Print data is also transmitted to the recording head 11 via the carriage 4 through the data lines DATA0+ / DATA0- to DATA2+ / DATA2-. The print data includes ink ejection nozzle data containing information about the nozzles that eject ink, and heat data containing information necessary for heating the heater. In this embodiment, the print data is transmitted using three pairs of data lines, but the number of data line pairs increases or decreases in accordance with the required specifications of the recording device, as the frequency of the clock signal and the print data increase or decrease accordingly.

[0032] The LVDS transmitter 219 transmits a clock signal and a signal for fault detection to the LVDS receiver 221 via the LVDS line 224 during fault detection testing. Note that termination resistors are connected in parallel between the CLK+CLK- line and the DATAx+ / DATAx-(x=0,1,2) line, as shown in Figure 3. In this embodiment, the resistance values ​​of termination resistors 301-304 are 100Ω, but these values ​​may be changed as appropriate.

[0033] The LVDS receiver 221 has the function of receiving print data transmitted by the LVDS transmitter 219 via the LVDS line 224 when recording. In addition, during connection failure testing, the LVDS receiver 221 receives the connection failure testing clock signal and connection failure testing signal transmitted from the LVDS transmitter 219.

[0034] The signal array determination unit 222 latches the value of the connection failure test signal at the rising and falling edges of the connection failure test clock signal read by the LVDS receiver unit 221. This connection failure test signal contains predetermined information in 1-byte units. In this embodiment, as shown in Figure 4, within a predetermined trigger period (trigger signal 401, interval from 1 to 2), the start command ~ print data ~ CRC check (normal signal form 402) becomes a single data form. Here, during connection failure testing, the LVDS transmitter unit 219 transmits only the start command (connection test signal 403). If the connection is normal, the LVDS receiver unit 221 receives the start command (connection test signal 403) and expects subsequent print data ~ CRC command. However, since the CRC command does not arrive by trigger signal 401 2, the error flag becomes "1" (error flag 404 when the connection is good). The default value of the error flag is "0", and it is reset to "0" after the value of the error flag is transmitted. On the other hand, in the event of a connection failure, the start command itself is not read by the LVDS receiver 221, so the error flag remains unchanged at "0" (error flag 405 in the case of a connection failure).

[0035] The connection failure test for the recording head is performed according to the above procedure. Note that this embodiment is just one example of a connection failure test, and connection tests may be performed by appropriately modifying the resistance, signal patterns, etc., of multiple recording heads.

[0036] Figure 7 shows the internal configuration of the LVDS transmitter 219 and the LVDS receiver 221. The LVDS transmitter 219 includes a selector 701 and transmit LVDS buffers 702-705. The selector 701 has four input lines (input 0, input 1, input 2, input 3), four output lines (output 0, output 1, output 2, output 3), and a 2-bit switching signal as an input / output signal. CLK, DATA0, DATA1, and DATA2 are connected to inputs 0, 1, 2, and 3, respectively. The signals output from outputs 0, 1, 2, and 3 change according to the value of the switching signal according to the logic table of the selector 701, as shown in the upper part of Figure 8. Here, the switching signal is controlled by the CPU 201. The transmit LVDS buffers 702-705 convert the input signals into LVDS signals.

[0037] The LVDS receiver 221 includes receiving LVDS buffers 706-709, a selector 710, and a decoder 711. The receiving LVDS buffers 706-709 convert signals input as LVDS signals. The selector 710 has four input lines (input 0, input 1, input 2, input 3), four output lines (output 0, output 1, output 2, output 3), and a 2-bit switching signal as an input / output signal. Signal lines output from the receiving LVDS buffers 706-709 are connected to inputs 0, 1, 2, and 3, respectively. The signals input to the input lines change depending on the value input to the switching signal of selector 701 inside the LVDS transmitter 219. However, by making the value of the switching signal input to selector 710 the same as the value input to the switching signal of selector 701, the signals output from output 0, output 1, output 2, and output 3 become CLK, DATA0, DATA1, and DATA2, respectively. The signals output from outputs 0, 1, 2, and 3 are based on the logic table of selector 710 shown at the bottom of Figure 8.

[0038] The switching signal input to the selector 710 is output from the decoder 711. The decoder 711 is equipped with an I2C bus interface and shares the I2C bus used for communication between the printer control unit 218 and the head information storage unit 223. This connection configuration makes it possible to control the decoder 711 from the printer control unit 218 without increasing the number of signal lines between the printer control unit 218 and the recording head 11. Two bits of serial data are set to the decoder 711, and the set value is output as a switching signal to the selector 710.

[0039] Figure 5(a) is a flowchart showing the connection failure inspection process that is automatically executed when the recording head is mounted on the carriage if any of contacts C to H are faulty in the prior art. Figure 5(b) is a flowchart showing the connection failure inspection process that is automatically executed when the recording head is mounted on the carriage if any of contacts C to H are faulty in this embodiment. This process is executed by the CPU 201 based on a control program stored in the ROM 203.

[0040] Figure 6 is a timing chart of signals used for faulty connection testing. Here, section A represents the time concept of the dotted line section and corresponds to section 2A. In other words, section 2A is twice the length of section A.

[0041] Assuming that only contact D in Figure 3 is faulty, an example of misjudgment that may occur when fault detection is performed using a high-speed fault detection signal similar to that used for print data, as in the conventional technology, will be described. When the recording head 11 is mounted to the recording device, the CPU 201 generates a fault detection signal as S1. Specifically, the data generation unit 227 generates a start command (in this embodiment, the signal sequence is "1010") which is a fault detection signal having a frequency equivalent to a clock signal (CLK+ signal S301, CLK- signal S302) of a predetermined frequency.

[0042] Subsequently, the process proceeds to S2, where the CPU 201 transmits connection failure test signals from the LVDS transmitter 219 to the LVDS receiver 221 for each of the DATAx+ / DATAx- (x=0, 1, 2) on the LVDS line 224. At this time, for DATA1+ / DATA1- and DATA2+ / DATA2-, which have no contact failures, the DATA+ signal S304 and DATA- signal S305, which are LVDS signals with appropriate amplitudes, are propagated. On the other hand, for DATA0+ / DATA0-, which have a contact failure at contact D, if there is no parasitic capacitance in the circuit built into the recording head and the time constant is 0, the potential of the termination resistor 302 becomes equal during differential voltage reading. As a result, as shown in S306(b), the signal sequence of the DATA differential signal is determined to be "0000". Since the error flag remains at 0, the value of the error plug is notified to the printer control unit 218 (S3), and the printer control unit 218 determines that the recording head is not properly connected (S4).

[0043] Next, consider the case where parasitic capacitance exists in the circuitry built into the recording head, causing the time constant to exceed a certain value. In this case, the potential of the termination resistor 302 will not be equipotential when reading the differential voltage. As a result, a differential voltage is generated as in S306(c), and when determining 1 and 0 in the signal sequence, it exceeds the threshold, and despite the connection failure, it may be judged as "1010" as in S306(a), which is a differential signal when there is no connection failure. As a result, the error flag is set to "1", the value of the error plug is notified to the printer control unit 218 (S3), and the printer control unit 218 determines that the recording head is connected well (S4). As described above, conventional connection failure testing can sometimes result in false detections even when there is a connection failure.

[0044] Next, in this embodiment, the frequency of the connection failure inspection signal is set lower than the frequency of the print data signal, and the procedure for performing a connection failure inspection that can identify where in the LVDS line 224, including CLK, a connection failure has occurred will be explained. In this connection failure inspection, the case where only contact D in Figure 3 is faulty is assumed. When the recording head 11 is mounted to the recording device, as S10, the CPU 201 reads the frequency information of the recording head's internal circuit. Specifically, the CPU 201 reads the time constant information provided by the resistance value and parasitic capacitance inherent in the data transmission line, which is recorded in the head information storage unit 223. In this embodiment, the time constant information is stored in the RAM 202, but other memory or other devices may be used as long as the information can be temporarily stored. Also, in this embodiment, the time constant information is pre-stored in the head information storage unit 223, measured and recorded when the recording head 11 is shipped, but it may be recorded again as needed.

[0045] Following S10, in S20, the CPU 201 generates a clock signal of a predetermined frequency and a connection failure inspection signal in the data generation unit 227 based on the time constant information stored in the RAM 202. In this embodiment, the frequency of the print data is 100 MHz and the time constant τ is 5.0 nsec. Also, the frequency f0 of the generated clock signal (CLK+ signal S307, CLK- signal S308) and connection failure inspection signal (DATA+ signal S310, DATA- signal S311) is 50 MHz.

[0046] If the frequency of the connection failure test signal is fixed and set without varying the time constant for each recording head, the test time will be longer. Therefore, it is preferable to vary the frequency of the connection failure test signal according to the time constant of each recording head, from the viewpoint of shortening the connection failure test time.

[0047] Following S20, as S30, the CPU 201 transmits clock signals (CLK+ signal S307, CLK- signal S308) from the LVDS transmitter 219 to the LVDS receiver 221 via CLK+ / CLK- on the LVDS line 224. Specifically, as in S307 and S310, and S308 and S311, the phase of the DATA is delayed by 90°, and S310 and S311 are transmitted to the LVDS receiver via DATAx+ / DATAx- (x=0, 1, 2) on the LVDS line 224.

[0048] Figure 9 is a flowchart showing the detailed connection failure inspection process in S30. First, CPU201 performs a connection test without swapping the CLK signal and the DATA signal (S901). Next, CPU201 checks whether all of DATAx+ / DATAx-(x=0, 1, 2) were determined to be connection failures based on the results of the connection test performed in S901 (S902). If the result in S902 is no, the process proceeds to S903; if all are determined to be connection failures, the process proceeds to S904. In S903, since there is at least one DATA signal that has been determined to have a normal (good) connection status, CPU201 determines that the connection status of CLK and the DATA signals that have not been determined to be connection failures is normal. After that, the process ends.

[0049] In S904, CLK and DATA0 are swapped, that is, switching signal 2'b01 is set for selectors 701 and 710, and the CPU 201 performs a connection test again. After that, the CPU 201 determines whether or not DATA1 had a connection problem based on the results of the connection test performed in S904 (S905). If the connection status of DATA1 is determined to be normal in S905, the process proceeds to S906. On the other hand, if the connection status of DATA1 is determined to be poor, the process proceeds to S909.

[0050] In S905, if the connection status of DATA1 is normal, it can be determined that the connection status of the original DATA0 and DATA1 is normal because communication between CLK (the original DATA0) and DATA1 is normal. On the other hand, in S901, since all DATA is determined to be unconnected, it can be determined that CLK is unconnected. Next, the CPU201 determines whether or not DATA2 was unconnected based on the results of the connection test performed in S904 (S906). If the connection status of DATA2 is normal, the process proceeds to S907; if the connection status of DATA2 is unconnected, the process proceeds to S908.

[0051] If the connection status of DATA2 is normal, then communication between CLK (the original DATA0) and DATA2 is normal, and therefore the connection status of DATA2 can be determined to be normal. For this reason, CPU201 determines that CLK has a connection failure and determines that the connection status of all DATA is normal (S907). After that, processing is terminated.

[0052] If the connection status of DATA2 is poor, then communication between CLK (original DATA0) and DATA2 is not occurring properly. Since S905 determines that the connection status of CLK (original DATA0) is normal, it can be determined that DATA2 has a connection problem. Therefore, in S908, CPU201 determines that CLK and DATA2 have connection problems, and that the connection status of DATA0 and DATA1 is normal. The process then terminates.

[0053] In S909, similar to S906, CPU201 determines whether DATA2 had a connection problem based on the results of the connection test performed in S904. If the connection status of DATA2 is normal in S909, the process proceeds to S910; otherwise, the process proceeds to S911.

[0054] In S909, if the connection status of DATA2 is normal, then communication between CLK (the original DATA0) and DATA2 is normal, and therefore the connection status of the original DATA0 and DATA2 can be determined to be normal. On the other hand, in S905, DATA1 is determined to have a connection problem, so DATA1 can be determined to have a connection problem. Furthermore, even though the connection status of DATA0 and DATA2 is normal, in S901 all DATA is determined to have a connection problem, so CLK can also be determined to have a connection problem. Therefore, CPU201 determines that CLK and DATA1 have connection problems, and that the connection status of DATA0 and DATA2 is normal (S913). After that, the process terminates.

[0055] On the other hand, in S911, CLK and DATA1 are swapped, that is, switching signal 2'b10 is set for selectors 701 and 710, and CPU201 performs a connection test again. Based on the results of the connection test in S911, CPU201 determines whether or not DATA2 was poorly connected (S912). If the connection status of DATA2 is normal, the process proceeds to S913; if the connection status of DATA2 is poor, the process proceeds to S914.

[0056] If the connection status of DATA2 is normal, then communication between CLK (the original DATA1) and DATA2 is normal, and therefore the connection status between the original DATA1 and DATA2 can be determined to be normal. On the other hand, even though the connection status of DATA1 and DATA2 is normal, S905 and S909 determine that DATA1 and DATA2 have connection problems, so it can be determined that DATA0, which was transmitting CLK during the test, has a connection problem. Furthermore, even though the connection status of DATA1 and DATA2 is normal, S901 determines that all DATA has connection problems, so it can be determined that CLK also has a connection problem. Therefore, CPU201 determines that CLK and DATA0 have connection problems, and that the connection status of DATA0 and DATA2 is normal (S913). After that, the process is terminated.

[0057] If the connection status of DATA2 is poor, it is determined that at least one of CLK and DATA0, at least one of CLK and DATA1, and at least one of CLK and DATA2 are poorly connected (S902). It is also determined that at least one of DATA0 and DATA1 is poorly connected (S905). Furthermore, it is determined that at least one of DATA0 and DATA2 is poorly connected (S909), and at least one of DATA1 and DATA2 is poorly connected (S912). Based on the above determination results, CPU201 determines that at least three of CLK, DATA0, DATA1, and DATA2 are poorly connected (S914). After that, the process terminates.

[0058] In the processing of S40, assuming that the connection status of the recording head 11 is normal (good), it is assumed that the signal sequence received in S30 matches the start command (in this embodiment, "1010") set in the head information storage unit 223. In this case, print data ~ CRC command following the start command is expected, but since the CRC command is not received between predetermined triggers, the error flag is set to "1", and the CPU 201 sends the value of the error flag to the printer control unit 218. Note that at this time, the connection failure inspection signal at the termination resistor 226 received by the LVDS receiving unit 221 is S312(a).

[0059] On the other hand, in the processing of S40, if the connection state of the recording head 11 is poor, for example, if contact D shown in Figure 4 is poorly connected, the connection failure signal at the termination resistor 226 received by the LVDS receiver 221 will be "0000" as in S312(b). Therefore, it will not be recognized as a start command, and the error flag will remain "0".

[0060] In S50, if the error flag value "1" set in S40 is transmitted to the printer control unit 218 within a predetermined time, the printer control unit 218 determines that the recording head 11 is connected to the LVDS line 224. On the other hand, if the printer control unit 218 does not receive the error flag value "1" within a predetermined time, the printer control unit 218 determines that the recording head 11 is not connected to the LVDS line 224. Thus, according to this embodiment, highly accurate connection failure testing can be performed in a short time.

[0061] This embodiment includes the following configuration.

[0062] (Composition 1) An image forming apparatus comprising a recording head and a control board for controlling the recording head, The control board receives the print data and A control unit that generates inspection data for determining a connection failure between the recording head and the control board, The system includes a transmitting unit that transmits the print data and the inspection data as differential signals to the recording head, The recording head comprises a receiving unit that receives the print data and the inspection data, and a determination unit that determines the connection failure from the received inspection data. An image forming apparatus characterized in that the transmitting unit and the receiving unit are equipped with switching means capable of switching between a clock signal and a data signal for transferring the print data and the inspection data.

[0063] (Configuration 2) The image forming apparatus according to Configuration 1, wherein the frequency at which the transmitting unit transmits the inspection data is lower than the frequency at which the transmitting unit transmits the print data.

[0064] (Composition 3) The image forming apparatus according to configuration 1 or 2, wherein the recording head is equipped with a storage unit in which frequency information corresponding to the time constant due to the resistive and capacitive components of the data line is pre-set.

[0065] (Composition 4) Between the control unit and the recording head, there is a data line different from that of the transmitting unit and the receiving unit. The image forming apparatus according to configuration 3, wherein the control unit reads the frequency information from the storage unit.

[0066] (Composition 5) The image forming apparatus according to configuration 4, wherein the switching means is controlled via a data line different from that of the transmitting unit and the receiving unit.

[0067] (Composition 6) The image forming apparatus according to any one of configurations 3 to 5, wherein the frequency used when transmitting the inspection data by the transmitting unit is determined by the frequency information.

Claims

1. An image forming apparatus comprising a recording head and a control board for controlling the recording head, The control board receives the print data and A control unit that generates inspection data for determining a connection failure between the recording head and the control board, The system includes a transmitting unit that transmits the print data and the inspection data as differential signals to the recording head, The recording head comprises a receiving unit that receives the print data and the inspection data, and a determination unit that determines the connection failure from the received inspection data. An image forming apparatus characterized in that the transmitting unit and the receiving unit are equipped with switching means capable of switching between a clock signal and a data signal for transferring the print data and the inspection data.

2. The image forming apparatus according to claim 1, wherein the frequency at which the transmitting unit transmits the inspection data is lower than the frequency at which the transmitting unit transmits the print data.

3. The image forming apparatus according to claim 1, wherein the recording head is equipped with a storage unit in which frequency information corresponding to the time constant due to the resistive and capacitive components of the data line is pre-set.

4. Between the control unit and the recording head, there is a data line different from that of the transmitting unit and the receiving unit. The image forming apparatus according to claim 3, wherein the control unit reads the frequency information from the storage unit.

5. The image forming apparatus according to claim 4, wherein the switching means is controlled via a data line different from that of the transmitting unit and the receiving unit.

6. The image forming apparatus according to claim 3, wherein the frequency used when transmitting the inspection data by the transmitting unit is determined by the frequency information.

Images