Image recording device

Abstract

To solve the problem that when a spread spectrum is applied, in transmitting printing data, a clock for data transfer and a printing timing signal to a print head, periodic modulation occurs on the printing timing signal as well, which deteriorates an image quality.SOLUTION: A spread spectrum is not applied to a signal that influences an image quality but the spread spectrum is applied to a signal that does not influence an image quality. An image recording device comprises a controller that generates print image data that are transmitted to a print head, a transmission clock that transmits the print image data, and a discharge timing signal for the print head, which is mounted with a plurality of clock generators that generate clocks acting as a reference for operation of the controller. A spread spectrum is applied to image data inside the controller and a clock acting as a reference for operation of a block that generates the image data transmission clock, and a spread spectrum is not applied to a clock that is inputted to a block that generates a printing timing signal inside the controller.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an EMI countermeasure method for an inkjet printhead. [Background technology]

[0002] An inkjet recording device ejects ink droplets from nozzles arranged on a recording head, forming dots on recording paper to form a recorded image. One type of inkjet recording device is a line printer, in which a print head having nozzles arranged in a line is fixed, and the recording medium is transported perpendicular to the print head, ejecting ink droplets to form a recorded image.

[0003] In order to eject the desired ink droplets at the desired positions on the paper, the printer's built-in controller must send printing data and signals that determine the timing of ejection to the print head that ejects the ink. Printing data is usually sent using a clock signal (CLK) that transfers data, and a data signal (DATA) that is synchronized with that clock signal. The ejection timing signal is a signal (LT) generated by an encoder or other device installed on the transport motor that transports the recording paper, and is a signal that is synchronized with the transport of the recording paper.

[0004] Here, print head I / F signals such as CLK / DATA / LT signals sent to the print head are often transmitted via cables such as FFC due to the physical distance constraints between the controller and print head. In this case, the transmission of high-speed CLK / DATA signals via FFC can cause unwanted radiation (EMI) problems. The EMI problem becomes more pronounced as the frequency of the CLK / DATA signals increases and as the number of signals increases.

[0005] One possible way to combat EMI is to apply spread spectrum (SS) to the clock input to the module inside the control controller that generates the head I / F signal. SS is a technology that reduces EMI by slightly varying the frequency of the clock signal to lower the peak value of the frequency spectrum of the clock signal. Patent Literature 1 proposes a technology that applies SS to the signal that transmits print data and the clock signal of the stepping motor that controls the polygon mirror. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-95789 Summary of the Invention [Problem to be solved by the invention]

[0007] The conventional techniques have the following problems to be solved.

[0008] In conventional technology, SSC is applied not only to the signals that transmit print data, but also to the clock that controls the motor. However, in the case of a line printer like this, SSC is applied to the transport motor that transports the recording paper, and SSC is also applied to the encoder signal installed on the transport motor, which results in SSC being applied to the LT signal generated from the encoder signal. If SSC were applied to the LT signal, periodic modulation would occur in the intervals of the ejection timing signal, which could cause periodic unevenness in the image formed on the recording paper, leading to a decrease in print quality.

[0009] Therefore, in order to solve the above problems, an object of the present invention is to reduce EMI without degrading the print quality of images printed on recording paper. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention has the following configuration.

[0011] That is, the image recording apparatus of the present invention comprises a print head which forms an image, print image data which is sent to the print head, a transmission clock for sending the print image data, and a controller which generates a timing signal which defines the ejection timing of the print head, the image recording apparatus has a plurality of clock oscillators which generate clocks which serve as a reference for operation of the controller, has a function of applying spectrum spreading to the clock oscillators which input to a block within the controller which generates a transmission clock for sending image data, and does not apply spectrum spreading to the clock generator which inputs to a block within the controller which generates the print timing. [Effects of the Invention]

[0012] By applying this patented technology, SSC is applied only to the high-speed signals between the printer and the print head that affect EMI, and not to the signals that affect image quality, thereby achieving both EMI reduction and image quality. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a control block diagram of the inkjet recording apparatus of the present patent. [Figure 2] FIG. 2 is a control block diagram of the inkjet recording apparatus of the present patent. [Figure 3] FIG. 2 is a detailed diagram of the recording control unit of the present patent. [Figure 4] FIG. 2 is an explanatory diagram of signals between a print head and the printer; DETAILED DESCRIPTION OF THE INVENTION

[0014] The control unit of the inkjet recording device including the image reading device in this patent will be described. Figures 1 and 2 are control block diagrams of the inkjet recording device. The control unit 13 is communicably connected to a higher-level device (DFE) HC2, and the higher-level device HC2 is communicably connected to a host device HC1.

[0015] In the host device HC1, manuscript data that is the source of the recorded image is generated or saved. Here, the manuscript data is generated in the form of an electronic file such as a document file or an image file. This manuscript data is transmitted to the host device HC2, which converts the received manuscript data into a data format usable by the control unit 13 (for example, RGB data that expresses an image in RGB). The converted data is transmitted from the host device HC2 to the control unit 13 as image data, and the control unit 13 starts a recording operation based on the received image data.

[0016] In this embodiment, the control unit 13 is roughly divided into a main controller 13A and an engine controller 13B. The main controller 13A includes a processing unit 131, a storage unit 132, an operation unit 133, an image processing unit 134, a communication I / F (interface) 135, a buffer 136, and a communication I / F 137.

[0017] The processing unit 131 is a processor such as a CPU, which executes programs stored in the storage unit 132 and controls the entire main controller 13A. The storage unit 132 is a storage device such as a RAM, a ROM, a hard disk, or an SSD, which stores programs and data executed by the CPU 131, and also provides a work area for the CPU 131. The operation unit 133 is an input device such as a touch panel, a keyboard, or a mouse, which receives instructions from a user.

[0018] The image processing unit 134 is, for example, an electronic circuit having an image processing processor. The buffer 136 is, for example, a RAM, a hard disk, or an SSD. The communication I / F 135 communicates with the upper device HC2, and the communication I / F 137 communicates with the engine controller 13B. In FIG. 4, the dashed arrows illustrate the flow of image data processing. Image data received from the upper device HC2 via the communication I / F 135 is accumulated in the buffer 136. The image processing unit 134 reads the image data from the buffer 136, performs predetermined image processing on the read image data, and stores the image data again in the buffer 136. The image data after image processing stored in the buffer 136 is transmitted from the communication I / F 137 to the engine controller 13B as print data to be used by the print engine.

[0019] 2, the engine controller 13B includes control units 14, 15A to 15D, and acquires detection results and controls the drive of the sensors and actuators 30 to 33 provided in the inkjet recording apparatus 1. Each of these control units includes a processor such as a CPU, a storage device such as a RAM or a ROM, and an interface with external devices. Note that the division of the control units is an example, and some of the controls may be executed by multiple, further subdivided control units, or conversely, multiple control units may be integrated and their control contents may be executed by a single control unit.

[0020] The engine control unit 14 controls the entire engine controller 13B. The recording control unit 15A converts the recording data received from the main controller 13A into a data format suitable for driving the inkjet recording heads, such as raster data. The recording control unit 15A controls the ejection of each recording head 30.

[0021] The transport control unit 15B controls the sensor / actuator group 31 to transport the recording medium, and the reading control unit 15C controls the sensor / actuator group 32 including the image sensor and light source when reading an image.

[0022] The reliability control unit 15C controls the ink supply unit, the recovery unit that recovers the print head, and the like.

[0023] Each control unit is synchronously controlled via the LAN 34 inside the device.

[0024] The print control unit will now be described in detail with reference to Figure 3. The print control unit includes a print head control board 300 and a print head 307.

[0025] The print head control board contains a print head controller 301 and a print head power supply control unit 302. The print head controller 301 outputs ejection data (head data), a transfer clock (head data transfer clock) that transfers that head data, and a signal that specifies the timing of ejection. The print head power supply control unit 302 controls the power supplied to the print head. Print data, transfer clock, and ejection timing signals are often sent to the print head via a cable such as an FFC, which often causes EMI problems.

[0026] The print head controller 301 will now be described. The print head controller 301 may be an ASIC or an FPGA. The print head controller 301 includes a print head data generation unit 303 and an ejection timing generation unit 304. The print head data generation unit 303 processes the image data input from the main controller into a data format that can be ejected by the print head, and sends this to the print head in synchronization with a CLK signal also generated by the print head generation unit 303. The ejection timing generation unit generates the timing for the print head to eject based on a signal synchronized with media transport from the transport control unit (for example, a signal from an encoder installed on the transport motor), and sends this to the print head.

[0027] As mentioned above, the print head controller 301 and print head 307 are physically far apart and are connected by a cable such as an FFC, and when high-speed signals pass through this cable, the cable acts as an antenna, causing EMI problems. For this reason, one possible way to reduce EMI is to apply SSC to the signals between the print head controller and print head.

[0028] The relationship between the head data, head data transfer clock, and ejection timing signal is shown in Figure 4. The ejection timing signal for the print head is generated based on the transport reference signal input from the transport control unit. In Figure 4, the transport reference signal is shown at the 1200 dpi end and the ejection timing signal at 9600 dpi, but the resolution does not necessarily have to be as shown in Figure 4. The head data is sent to the print head in synchronization with the head data transfer clock during the ejection timing signal (a signal in 9600 dpi units in Figure 4). Since all the data must be sent during the ejection timing signal, the faster the transport speed, the higher the frequency of the head data transfer clock, which is detrimental to EMI. The head data received by the print head is ejected in synchronization with the ejection timing signal.

[0029] As mentioned above, applying SSC to signals between the print head (head data signal, head data transfer clock signal, and ejection timing signal) can be expected to reduce EMI, but SSC causes periodic fluctuations in the signals between the print head. For example, if SSC has a modulation period of 30 kHz and a modulation amount of 1%, a 1% modulation will be applied to the frequency of the reference clock that generates signals between the print head and the print head at a 30 kHz period. With regard to the head data and head data transfer clock, this is not a problem as long as the SSC is within a range that does not affect print head operation, but if the ejection timing signal fluctuates periodically, unevenness synchronized with the modulation period can occur in the image formed on the recording media, and this unevenness can affect image quality.

[0030] For this reason, in this embodiment, as shown in Figure 3, oscillators 305 and 306 are provided for the head data control unit and the ejection timing generation unit, respectively. The oscillators 305 and 306 output clocks that serve as the reference for the operation of each block, and the head control unit and the ejection timing generation unit operate based on these clocks. As mentioned above, applying SSC to the clock input to the print head data generation unit is not a problem as long as the print head operates normally. However, applying SSC to the clock input to the ejection timing generation unit would cause unevenness synchronized with the SSC modulation period to occur in the image formed on the recording medium, so SSC should not be applied to the clock input to the ejection timing generation unit. Therefore, oscillator 305, which can apply SSC, is connected to the print head generation unit 303, and oscillator 306, which does not apply SSC, is connected to the ejection timing generation unit. As explained in Figure 4, while the head data transfer clock is a high-speed clock signal, the ejection timing signal is a low-speed signal output in 1200 dpi increments. Therefore, even if SSC is not applied, there is no problem from the perspective of EMI.

[0031] When SSC is applied to the head data control unit, the frequency of the head data transfer clock is modulated and periodically reduced. However, because the head data must be sent within the interval between ejection timing signals, the SSC modulation amount must be such that the data can be sent even if the frequency is reduced by SSC.

[0032] By using the configuration of this patent, SSC is applied only to signals between the printer and the print head that affect EMI, making it possible to achieve both EMI reduction and image quality. [Explanation of symbols]

[0033] HC1 host device HC2 host device 13 Control Unit 13A Main Controller 13B Engine Controller 131 Processing section 132 Storage section 133 Operation section 134 Image processing section 135 Communication I / F (Interface) 136 buffers 137 Communication I / F

Claims

1. an image recording device comprising: a print head for forming an image; and a controller for generating print image data to be sent to said print head, a transmission clock for sending the print image data, and a timing signal for determining the ejection timing of said print head; said controller has a plurality of clock oscillators for generating clocks that serve as a reference for the operation of said controller; said image recording device has a function of applying spectrum spreading to the image data inside said controller and the clock generated by said clock oscillators that is input to a block that generates the transmission clock for sending the image data; and said image recording device does not apply spectrum spreading to the clock generated by the oscillator that is input to the block that generates the print timing inside said controller.

2. an image recording device comprising: a print head for forming an image; a controller for generating print image data to be transmitted to the print head; a transmission clock for transmitting the print image data; and a timing signal for determining the ejection timing of the print head; the controller has a plurality of clock oscillators for generating clocks that serve as a reference for the operation of the controller; the image data within the controller and the clock generated by the clock oscillator that is input to a block that generates the transmission clock for transmitting the image data have a function of applying spectrum spread to the clock generated by the clock oscillator that is input to a block that generates the print timing within the controller; and the clock generated by the oscillator that is input to the block that generates the print timing within the controller does not have spectrum spread applied to it; and the image recording device described in claim 1 is characterized in that the amount of frequency modulation of the spectrum spread applied to the transmission clock for transmitting the print image data is an amount of modulation that allows head data to be sent within the print timing interval determined by the timing signal.

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