Image forming device

Abstract

Depending on the communication method, external noise may cause image data communication to be improper. If image data communication is not performed properly, the image data may be corrupted, which may affect latent image formation. In view of the above-mentioned problems, the present invention aims to reduce the risk of data communication not being performed properly in an image forming apparatus that performs data communication via serial communication. The output unit outputs an enable signal after the power supply supplies power to the conversion unit, and the reset unit resets the conversion unit after the output unit outputs the enable signal.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with a transmitting device, a receiving device, a transmitting / receiving device, and a transmitting / receiving system. [Background technology]

[0002] In electrophotographic printers, a method is generally known in which a latent image is formed by exposing a photosensitive member to light using an exposure head having light-emitting elements such as LEDs.

[0003] Furthermore, in recent years, the data volume has increased due to the high image quality of image forming devices, and a configuration for transmitting data at high speed is required. Patent Document 1 discloses a configuration for performing high-speed communication by transmitting image data via serial communication. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-217654 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described communication method, there is a possibility that image data communication may not be performed properly due to external noise, and if image data communication is not performed properly, the image data may be corrupted, which may affect latent image formation.

[0006] In view of the above-mentioned problems, an object of the present invention is to reduce the risk of data communication not being performed properly in an image forming apparatus that performs data communication via serial communication. [Means for solving the problem]

[0007] The image forming apparatus of the present invention comprises a rotating photosensitive body, an exposure head arranged along the rotational axis of the photosensitive body and having a plurality of light-emitting elements that emit light to expose the photosensitive body, a generation unit that generates image data that controls the turning on and off of the plurality of light-emitting elements and outputs it as serial data, a conversion unit that receives the image data that is serial data output by the generation unit and converts it into parallel data, a drive unit that drives the plurality of light-emitting elements based on the image data that is parallel data converted by the conversion unit, a reset unit that resets the conversion unit to an initial state, an output unit that outputs an enable signal indicating that the conversion unit is in a state where it can receive the serial data, and a power supply that supplies power to the conversion unit, wherein the output unit outputs the enable signal after the power supply supplies power to the conversion unit, and the reset unit resets the conversion unit after the output unit outputs the enable signal. [Effects of the Invention]

[0008] SUMMARY OF THE INVENTION An object of the present invention is to reduce the possibility that data communication will not be performed normally in an image forming apparatus that performs data communication by serial communication. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Figure 2] FIG. 3 is an explanatory diagram of the arrangement of a photosensitive drum and an exposure head. [Figure 3] FIG. [Figure 4] Block diagram of the image controller and printed circuit board. [Figure 5] 5 is a timing chart relating to signals that control a light-emitting element driving unit. [Figure 6] 10 is a flowchart showing job execution process control. [Figure 7] 4 is a flowchart showing job execution process control of the image processing apparatus in this embodiment. [Figure 8] 1 is a conceptual diagram of an operation in the first embodiment. [Figure 9] Multiple color retraining timing relationships. [Figure 10] FIG. 10 is a conceptual diagram of an operation in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Example 1] The electrophotographic image forming apparatus of this embodiment will be briefly described. The overall configuration of the apparatus is shown in Figure 1. This image forming apparatus is composed of a scanner unit 100, an image creating unit 103, a fixing unit 104, a paper feed / transport unit 105, and a printer control unit (not shown) that controls these units.

[0011] The scanner unit 100 illuminates a document placed on a platen, optically reads the document image, and converts the image into an electrical signal to create image data. The image-creating unit 103 rotates and drives the photosensitive drum 102, charging the photosensitive drum 102 with a charger 107. The exposure head 106 emits light according to the image data, and the light emitted from the chip surfaces of the light-emitting element group arranged along the rotation axis of the photosensitive drum 102 is focused on the photosensitive drum 102 to form an electrostatic latent image. The developer 108 develops the electrostatic latent image formed on the photosensitive drum 102 with toner. The developed toner image is transferred onto paper transported on a transfer belt 111. The image-creating unit has four image-creating units that perform the above-mentioned series of electrophotographic processes (charging, exposure, development, transfer), and are arranged in the order of cyan (C), magenta (M), yellow (Y), and black (K) to form a full-color image. The four imaging units sequentially perform magenta, yellow, and black imaging operations after a predetermined time has elapsed since the start of imaging at the cyan station. The paper feed / transport unit 105 feeds paper from a pre-selected paper feed unit—inside paper feed units 109a and 109b, external paper feed unit 109c, or manual paper feed unit 109d—and transports the paper to registration rollers 110. The registration rollers 110 transport the paper onto a transfer belt 111 at the timing when the toner image formed by the imaging unit 103 is transferred onto the paper. Opposite the transfer belt 111 is an optical sensor 113, which detects the position of a test chart printed on the transfer belt 111 to calculate the amount of color misregistration between the stations. The calculated amount of color misregistration is reported to an image controller (not shown), which corrects the image position for each color. This control ensures that a full-color toner image is transferred onto the paper without color misregistration. The fixing unit 104 is composed of a combination of rollers and has a built-in heat source such as a halogen heater. It melts and fixes the toner on the paper onto which the toner image has been transferred from the transfer belt 111 using heat and pressure, and then discharges the paper outside the image forming apparatus using paper discharge rollers 112.

[0012] Next, we will explain the exposure head 106 that exposes the photosensitive drum 102. Figures 2(a) and 2(b) are diagrams showing the arrangement of the exposure head 106 with respect to the photosensitive drum 102. The exposure head 106 is made up of a light-emitting element group 201, a printed circuit board 202 on which the light-emitting element group 201 is mounted, a rod lens array 203, and a housing 204 to which the rod lens array 203 and the printed circuit board 202 are attached, and is fixed so that light emitted from the light-emitting element group 201 is imaged on the photosensitive drum 102. In other words, the light-emitting element group 201 corresponds to a plurality of light-emitting units.

[0013] FIG. 3(a) is a diagram showing the surface of the printed circuit board 202 on which the light-emitting element groups 201 are arranged, opposite the surface on which the light-emitting element groups 201 are mounted (hereinafter referred to as the light-emitting element non-mounting surface). FIG. 3(b) is a diagram showing the surface of the printed circuit board 202 on which the light-emitting element groups 201 are mounted (hereinafter referred to as the light-emitting element mounting surface). The light-emitting element group 201 is configured by arranging multiple light-emitting elements 602 (602-1 to 602-n). The multiple light-emitting elements 602 may be inorganic LEDs or organic EL elements. The light-emitting elements are arranged at a pitch of a predetermined resolution in the longitudinal direction of the chip. In this embodiment, the pitch between adjacent light-emitting elements in the longitudinal direction of the chip is a pitch of 1200 dpi (approximately 21.16 μm). The light-emitting element group 201 is arranged with n=14173 light-emitting elements 602. As a result, an image corresponding to an image width of approximately 300 mm in the longitudinal direction of the photosensitive drum 102 can be formed. The number and pitch of the light emitting elements in this embodiment are merely examples, and the number, pitch and arrangement of the light emitting elements may be other values.

[0014] On the surface of the printed circuit board 202 where the light emitting elements are not mounted, a serial-parallel conversion control unit 720, a light emitting element driving unit 400, and a connector 305 are arranged.

[0015] The serial-parallel conversion control unit 720 has a function of restoring input serial data to parallel data. A control signal for controlling the light-emitting element driving unit 400 is input as serial data to the serial-parallel conversion control unit 720 from an image controller unit (not shown) via a connector 305. The serial-parallel conversion control unit 720 supplies the restored parallel data to the light-emitting element driving unit 400. Note that power necessary for the operation of the printed circuit board 202 is also supplied to the printed circuit board 202 via the connector 305.

[0016] 4 is a block diagram showing the configuration of the image controller unit 700 and the printed circuit board 202. In this embodiment, data communication between the image controller unit 700 and the printed circuit board 202 is performed by clock-embedded serial communication.

[0017] Image controller unit 700 has the function of generating and transmitting signals for controlling light emitting element drive unit 400 to printed circuit board 202 in response to instructions from the printer control unit. Image controller unit 700 includes CPU 703, image data generation unit 701, communication control unit 702, parallel-serial conversion unit 710, and differential driver 711.

[0018] The image data generation unit 701 generates signals for controlling the light emission of the light emitting element drive unit 400 in response to instructions from the printer control unit. Specifically, the image data generation unit 701 performs dithering processing at a predetermined resolution on image data received from the scanner unit 100 or from outside the image forming apparatus to generate image data. In this embodiment, dithering processing is performed at a resolution of 1200 dpi in the chip longitudinal direction (main scanning direction) and 1200 dpi in the rotation direction of the photosensitive drum 102 (sub-scanning direction) in accordance with the pitch of the light emitting elements. In this embodiment, the image data is binary and represents on and off. Note that the image data is not limited to binary data and may be multi-valued data.

[0019] The communication control unit 702 outputs the image data generated by the image data generation unit 701 based on rotational speed information of the photosensitive drum 102. That is, in this embodiment, the resolution in the rotational direction of the photosensitive drum 102 is 1200 dpi. Therefore, the communication control unit 702 outputs the image data as a data signal 707 at the timing when the surface of the photosensitive drum 102 moves by 1200 dpi. Furthermore, the communication control unit 702 generates a clock signal 705, a synchronization signal 706 indicating the start timing of communication data, and a data signal 707 for setting the register of the light-emitting element driving unit 400. Furthermore, when the CPU 703 requests that the light-emitting element driving unit 400 send a register setting value, the communication control unit 702 operates to send register setting data.

[0020] The image data and register setting data are transmitted via a common signal line. Therefore, header information may be added to the beginning of the data signal 707 so that the image data and the register setting data can be distinguished from each other. Furthermore, in this embodiment, the communication control unit 702 simultaneously transmits a synchronization signal 706 so that the beginning of the data to be transmitted can be identified.

[0021] 5(a) and 5(b) are timing charts showing the state of communication of various signals. Fig. 5(a) is a diagram showing the operation when image data is transmitted from the communication control unit 702.

[0022] While the communication control unit 702 is transmitting the data signal 707, the clock signal 705 continues to toggle. When the synchronization signal 706 goes high, a header indicating that the data signal 707 is image data is transmitted, and image data for the light-emitting elements 602 is transmitted. When transmission of image data for all the light-emitting elements 602 is complete, all signals become low until the next transmission begins. This is repeated in accordance with the speed at which the surface of the photosensitive drum 102 moves in the rotational direction, at a timing at which the sub-scanning resolution becomes 1200 dpi, thereby transmitting the image.

[0023] 5(b) is a diagram showing the operation of the communication control unit 702 transmitting register setting data. While the communication control unit is transmitting the data signal 707, the clock signal 705 continues to toggle. When the synchronization signal 706 goes high, a header indicating the register data is transmitted in the data signal 707, and the register setting value is transmitted. This changes the setting information for the drive current that drives the light emitting element 602, and changes the light intensity.

[0024] The parallel-serial converter 710 converts the signal output from the communication control unit 702 into a serial signal and outputs it. More specifically, the parallel-serial converter 700 converts each of the clock signal 705, synchronization signal 706, and multi-bit data signal 707 into a serial signal and outputs it. The differential signal driver 711 converts the serial signal output from the parallel-serial converter 710 into a differential signal 712 and outputs it to the printed circuit board 202.

[0025] In this embodiment, an example is shown in which data is transferred between the image controller unit 700 and the printed circuit board 202 using one set of differential signals, but two or four sets may be used depending on the required transfer speed.

[0026] 3, and includes a serial-to-parallel conversion control unit 720, a light-emitting element driving unit 400, a light-emitting element group 201, and a connector 305. The serial-to-parallel conversion control unit 720 further includes a differential signal receiver 721, a clock recovery unit 723, and a serial-to-parallel conversion unit 724.

[0027] Differential signal 712 output from differential signal driver 711 is input to printed circuit board 202 via the on-board transmission path, cable, and connector 305, and is then received by differential signal receiver 721 and converted to a normal single-ended signal. The signal converted to single-ended is input to clock recovery unit 723, and the clock superimposed on the serial signal is restored by clock recovery unit 723. The signal converted to single-ended by differential receiver 721 is also input to serial-parallel conversion unit 724, and data is sampled using the clock restored by clock recovery unit 723, converted to a parallel signal, and output. In other words, clock recovery unit 723 corresponds to a restoration unit.

[0028] The parallel signal output from the parallel-to-serial conversion unit 724 is the same as the signal before serialization output from the communication control unit 702. Specifically, a clock signal 725, a synchronization signal 726, and a data signal 727 are output to the light-emitting element driving unit 400.

[0029] Here, a certain time (delay) is required for a signal to pass through the parallel-to-serial conversion unit 710 and the serial-to-parallel conversion unit 724. The delay varies depending on the implementation form and the transmission path between chips, but in a single system with a fixed implementation form and transmission path, the delay is approximately constant regardless of the data being transferred.

[0030] A drive signal 401 is supplied from the light emitting element drive unit 400 to each light emitting element of the light emitting element group 201, and light emission is controlled by this.

[0031] The clock recovery unit 723 also outputs a lock signal 704. In order to recover the clock signal superimposed on the serial signal, it is necessary to adjust the phase and frequency of the clock signal. The lock signal 704 is a signal that indicates that the phase and frequency adjustment for recovering the clock signal has been completed. The lock signal 704 is input to the parallel-to-serial conversion unit 710 and the CPU 703.

[0032] Next, the operation of the lock signal 704 will be described. First, immediately after the image forming apparatus is powered on, the clock recovery unit 723 is not locked. At this time, the parallel-to-serial conversion unit 710 transmits a communication training signal to the clock recovery unit 723 to lock the clock recovery unit 723. At this time, the serial-to-parallel conversion control unit 720 is powered on (not shown) to receive the communication training signal. Thereafter, in order to output the communication training signal from the parallel-to-serial conversion unit, the CPU 703 transmits an enable signal 708 to the parallel-to-serial conversion unit 710, turning on an enable signal that starts serial communication. In other words, the CPU 703 corresponds to an output unit. This enables the parallel-to-serial conversion unit 710 to transmit the communication training signal. When the clock recovery unit 723 has completed clock regeneration, the clock recovery unit 723 sets the lock signal to low level, thereby notifying the parallel-to-serial conversion unit 710 and the CPU 703 that image data transfer is possible.

[0033] The operation from the initial training to transmitting image data will be described in detail with reference to the flowchart of FIG. 6 and FIG.

[0034] Fig. 6 is a flowchart showing job execution process control of the image processing apparatus. Note that each step in the flowchart of Fig. 6 is executed by the CPU 703, and each process is performed by controlling each element of the image processing apparatus under the control of the CPU 703.

[0035] In S1101, it is determined whether the image forming apparatus has received a print job. When the image processing apparatus is powered on in S1101, the image processing apparatus waits to receive a print job. If the image processing apparatus has received a print job in S1101, the process proceeds to S1102.

[0036] In S1102, in order to receive a communication waveform from the parallel-to-serial conversion unit 710, the power supply to the serial-to-parallel conversion control unit 720 is turned on, and power is supplied to the serial-to-parallel conversion unit 720.

[0037] In S1103, serial communication is enabled.

[0038] In S1104, initial communication training of the serial communication unit is started. This is performed by the parallel-serial conversion unit 710 and the serial-parallel conversion control unit 720. When the initial communication training is completed, the lock signal 704 goes low, and this is notified to the parallel-serial conversion unit 710 and the CPU 703. After this, it becomes possible to transfer image data via the serial communication unit.

[0039] In S1105, it is determined whether the initial training of the serial communication unit has been completed. If the initial communication training of the serial communication unit has been completed, the process proceeds to S1106.

[0040] In S1106, the CPU 703 performs a register setting operation. The communication control unit 702 performs an operation to transmit the register setting data of the light emitting element driving unit 400 in response to an instruction from the CPU 703, thereby setting setting information of the drive current for driving the light emitting element 602.

[0041] In S1107, the image data generation unit 701 generates the image data described above. As a result, image data with a resolution corresponding to the resolution of the image to be formed is generated. In this embodiment, image data with a resolution of 1200 dpi is generated for both the main scanning and sub-scanning directions to be printed.

[0042] In S1108, the generated image data is output at predetermined intervals. The communication control unit 702 is controlled to output the generated image data at predetermined intervals based on speed information of the movement of the surface of the photosensitive drum 102 in the rotational direction. The data output from the communication control unit 702 is supplied to the light-emitting element driving unit 400 via the parallel-to-serial conversion unit 710 and the serial-to-parallel conversion unit 724. Then, under the control of the light-emitting element driving unit 400, each light-emitting element emits light, thereby forming an image for each line. By performing this operation up to the last line, an image for one page is formed.

[0043] In S1109, it is determined whether the line transmitted in S1108 is the last line. If it is not the last line, the process returns to S1108 and repeats image transmission, and if it is the last line, the process proceeds to S1110.

[0044] In S1110, processing is performed to stop the light emission of the light emitting element group 201. In S1110, after the image data of the last line is output, white data is output and the light emission of the light emitting element group 201 is stopped.

[0045] In S1111, it is determined whether a series of printing operations has been completed. If there is a next page, serial communication is enabled and turned off in S1112, and then the process returns to S1102 and repeats the same processing to perform continuous printing operations. If there is no next page, the process returns to S1101 and waits again for the reception of a print job.

[0046] Figure 8(a) shows the operation during the flow shown in Figure 6. The serial-parallel conversion control unit 720 is powered on, and the parallel-serial conversion unit 710 serial communication enable is turned ON. After that, initial training is completed, and it can be seen that image data is being transferred correctly. However, before serial communication is enabled ON, the impedance of the serial communication terminal is high and the voltage is not yet determined (Hi-Z state). When the serial communication terminal is in the Hi-Z state, it is an unstable state in which the terminal voltage changes significantly with even a slight change in current. Therefore, when the serial communication terminal is in the Hi-Z state, it is susceptible to influences such as large changes in terminal voltage due to disturbances such as noise.

[0047] For example, consider a case where the serial communication terminal is in a Hi-Z state and is affected by noise while power is being supplied to the serial-parallel conversion control unit 720. In this case, it may cause the serial-parallel conversion control unit 724 to malfunction, making it impossible to set registers or transmit image data correctly.

[0048] FIG. 8(b) shows the timing when noise affects the image formation and when an image formation defect occurs. As shown in FIG. 8(b), when serial communication is enabled and power is supplied to the serial-parallel conversion control unit 720, noise entering the serial communication unit may cause the serial-parallel conversion unit 724 to malfunction. After that, initial training is performed after serial communication is enabled and the lock signal transitions to the locked state after the training is complete. However, the serial-parallel conversion unit 724 is malfunctioning due to noise before the training, and the serial-parallel conversion unit 724 is unable to properly transmit image data, resulting in an abnormal image.

[0049] Therefore, in this embodiment, training is performed at a timing when the influence of disturbances due to noise has sufficiently disappeared after enable is turned on. In other words, before setting the register, the serial-parallel conversion control unit 724 is reset and training is performed. By performing the above processing, it becomes possible to output correct image data even if the influence of noise occurs before serial communication is enabled on.

[0050] FIG. 7 is a flowchart showing the job execution process control of the image processing apparatus in this embodiment.

[0051] S1201 to S1205 are the same as S1101 to S1105 shown in FIG. 6, so the description will be omitted.

[0052] In S1206, the serial-to-parallel conversion unit 724 is reset. Resetting the serial-to-parallel conversion unit 724 means sending a reset signal 713 from the CPU 703 to the serial-to-parallel conversion unit 724. In other words, the CPU 703 corresponds to the reset unit. When the serial-to-parallel conversion unit 724 receives the reset signal 713, it enters its initial state. By sending a reset signal to the serial-to-parallel conversion unit 724 and returning it to its initial state, it is possible to return the serial-to-parallel conversion unit 724 to its normal state even if it is malfunctioning due to noise while the enable is OFF.

[0053] In S1207, training is performed again. The CPU 703 instructs the parallel-serial conversion unit 710 to perform training again. Figure 8(c) shows how image formation occurs when training is performed again. Figure 8(c) shows a case where noise is mixed into the serial communication unit while serial communication is enabled and OFF, causing the serial-parallel conversion unit 724 to malfunction. After noise is mixed into the serial communication unit, a reset signal 724 is used to return the serial-parallel conversion unit 724 to its initial state. Training is then performed again on the serial-parallel conversion unit 724, and serial communication is re-established, returning the serial-parallel conversion unit 724 to its normal state. As a result, register settings and image data can be transmitted normally even if there is a risk of being affected by noise during the enable-OFF period.

[0054] In S1208, it is determined whether the training has been completed again. If the training has been completed again, the process proceeds to S1209.

[0055] The processing in S1209 to S1215 is the same as the processing in S1106 to S1112 shown in FIG. 6, and therefore the description thereof will be omitted.

[0056] While the above method has been described for processing a single color, similar processing is required for all four colors in an image forming apparatus that forms color images. Figure 9 shows the timing of re-training for each of the four YMCK colors. The training flow for each color is the same as the flow shown in Figure 7. However, the start timing of training is controlled to prevent overlapping of the training periods for each color. As shown in Figure 9, initial training for yellow begins according to the flow shown in Figure 7. After initial training for yellow is completed, initial training for magenta begins, and similarly, initial training for cyan and black begins. At this time, to prevent overlapping of the training periods for each color, the start timing of magenta training is delayed relative to the start timing of yellow training. Similarly, the start timing of cyan training is delayed relative to the start timing of magenta training, and the start timing of black training is delayed relative to the start timing of cyan training. During training communication, data signals toggle at high speed, increasing the intensity of radiated noise. Therefore, if the training periods for each color overlap, the intensity of radiated noise increases even further. Therefore, the start timing of training is controlled to prevent overlapping of the training periods for each color. Once the initial training for black is complete, retraining for yellow begins according to the flow in Figure 7. As with the initial training, retraining for magenta, cyan, and black is also controlled so that the training periods for each color do not overlap.

[0057] As described above, when forming a color image and performing training for each color, the data signals from the training communication can become a source of noise and potentially cause malfunction of the serial-to-parallel converter 724. However, by adjusting the timing of the training periods for each color so that they do not overlap, it is possible to strengthen the resistance of the serial-to-parallel converter 724 for each color to malfunction due to noise using the method described above.

[0058] [Example 2] In the first embodiment, initial training starts at the same time as serial communication enable 708 is turned ON, but in the second embodiment, an example is shown in which the timing of initial training can be arbitrarily executed asynchronously with serial communication enable 708. When the timing of initial training can be arbitrarily determined, as shown in Fig. 10, after serial communication enable 708 is turned ON, a reset signal 713 for resetting the serial-parallel conversion unit 724 is sent to the serial-parallel conversion unit 724. By performing initial training after that, it is possible to omit the re-training performed in the first embodiment. As a result, the same effects as those of the first embodiment can be obtained in the second embodiment. [Explanation of symbols]

[0059] 102 Photosensitive drum 602 Light-emitting element 106 Exposure head 703 CPU

Claims

1. A rotating photoreceptor; an exposure head including a plurality of light emitting units arranged along the rotation axis direction of the photosensitive member and emitting light to expose the photosensitive member; a generation unit that generates image data for controlling the lighting and extinguishing of the plurality of light-emitting elements and outputs the image data as serial data; a conversion unit that receives the image data, which is serial data output by the generation unit, and converts it into parallel data; a driver that drives the plurality of light-emitting units based on image data that is parallel data converted by the converter; a reset unit that resets the conversion unit to an initial state; an output unit that outputs an enable signal indicating that the conversion unit is in a state where it is possible to receive the serial data; a power source that supplies power to the conversion unit; Equipped with the output unit outputs the enable signal after the power supply supplies power to the conversion unit; the reset unit resets the conversion unit after the output unit outputs the enable signal; An image forming apparatus characterized by:

2. the generating unit outputs the image data, which is serial data, after the resetting unit resets the converting unit.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. 2. The image forming apparatus according to claim 1, wherein the generating unit superimposes a clock signal for driving the converting unit on the serial data and outputs the superimposed clock signal.

4. 4. The image forming apparatus according to claim 3, further comprising a restoration unit that restores a clock signal superimposed on the serial data.

5. 2. The image forming apparatus according to claim 1, wherein the plurality of light emitting units are organic EL units.

Images