JP5928178B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In recent years, technological development for reducing power consumption of image forming apparatuses has been advanced. For example, for the purpose of reducing standby power out of power consumed by the image forming apparatus, there is a technique for selectively turning off the power of a module in a standby state among a large number of modules constituting the image forming apparatus. Are known. Specific examples to which such a technique is applied include the following.

  The many modules constituting the image forming apparatus include an image processing unit that generates a drawing signal of a print image, an image forming unit that actually prints a print image on a sheet based on the drawing signal, and the like. The image processing unit includes an image control unit that generates print image data, a drawing unit that generates a print image drawing signal based on the print image data, a transmission element of the image control unit, and a reception element of the drawing unit And a differential transmission path for transmitting image data for printing to the. The image control unit and the drawing unit are each provided with a power supply unit that is controlled to be turned on / off independently of each other, and the drawing unit is controlled so that the power supply is turned off when waiting. Thereby, standby power is reduced.

  However, when the power of the drawing unit is turned off when the power of the image control unit is on, an unnecessary current flows in the differential transmission path from the image control unit in the on state to the drawing unit in the off state, There is a risk of damaging the receiving element installed in the drawing unit.

  In this connection, the power supply voltage supplied to the device is monitored, and when the power supply voltage falls below a predetermined threshold, it is determined that the power supply has been turned off, and the components of the device are informed that the power supply has been turned off. A technique for notification is known (see, for example, Patent Document 1 below). With reference to the technique described in Patent Document 1, the power supply voltage of the drawing unit is monitored, and when the power supply voltage falls below a predetermined threshold, the image control unit is notified that the power of the drawing unit is turned off. Can be considered. In response to this notification, the image control unit can prevent unnecessary current from flowing in the differential transmission path toward the drawing unit, for example, by cutting off the connection between the image control unit and the drawing unit. Conceivable.

  However, using a technique such as Patent Document 1, it is determined whether or not the power supply voltage of the drawing unit falls below a predetermined threshold value, and when the power supply voltage falls below the predetermined threshold value, the image control unit is notified accordingly. If the notification is made, there is a possibility that an unnecessary current will not be in time. As a result, an unnecessary current flows, and there is a problem that the receiving element of the drawing unit can be damaged. In addition, the power supply voltage of the drawing unit may be gradually lowered or suddenly lowered depending on the state of the connected load when the device is switched from the on state to the off state. There is also a problem that it is difficult to appropriately determine a threshold value related to voltage.

JP2011-224865A

  The present invention has been made in view of the above problems. Accordingly, an object of the present invention is to provide an image forming apparatus that reliably prevents unnecessary current from flowing in a differential transmission path from an image control unit to a drawing unit when the drawing unit is turned off.

  The above object of the present invention is achieved by the following means.

(1) An image control unit that generates image data for printing, a drawing unit that generates a drawing signal for a print image based on the image data for printing, and a pair of signal lines, and is installed in the image control unit A differential transmission path for transmitting the image data for printing from a transmitting element to a receiving element installed in the drawing unit, and an image forming unit for printing the print image on a sheet based on the drawing signal, the drawing unit comprises a power supply unit, the power supply unit, the image forming unit is turned on when printing is in progress, is turned off when the image forming unit is not in the print, the image control unit while the image forming unit for outputting a logic level 0 or 1 from the transmitting device in accordance with the printing image data when it is in said printing, said transmission device when said image forming unit is not in the print High impedance state To the image forming apparatus.

  (2) The image control unit is configured to output the image based on a print start signal that becomes active when the image forming unit starts printing and a print end signal that becomes active when the image forming unit finishes printing. The image forming apparatus according to (1), wherein the forming unit detects whether or not printing is in progress.

(3) said print start signal and the print end signal, the image forming apparatus described above SL (2), characterized in that become active each time period corresponding to one page of the print image.

(4) the print start signal and the print end signal, the image forming apparatus described above SL (2), characterized in that become active in each period corresponding to one or more lines of the printed image.

  (5) The power source unit of the drawing unit supplies a power source voltage by switching a power source voltage supplied by the power source unit of the image control unit. Any one of the above (1) to (4) The image forming apparatus described in 1.

  (6) The transmission element and the reception element are three-state buffers, and the image control unit uses the LVDS configured by the transmission element, the reception element, and the differential transmission path to the drawing unit for printing. The image forming apparatus according to any one of (1) to (5), wherein the image data is transmitted.

  According to the present invention, when the image forming unit is not printing, the image control unit puts the transmitting element in a high impedance state. Therefore, when the drawing unit is turned off, the image control unit sets the differential transmission path from the image control unit to the drawing unit. Unnecessary current can be reliably prevented from flowing. Therefore, it is possible to prevent the receiving element of the drawing unit from being damaged. In addition, since unnecessary current does not flow through the differential transmission path, power consumption of the image forming apparatus can be reduced.

1 is a schematic block diagram illustrating a functional configuration of an image forming apparatus according to a first embodiment of the present invention. It is a schematic block diagram which shows the functional structure of the image process part shown in FIG. 3 is a timing chart for explaining an example of the operation of the image control unit shown in FIG. 2. 6 is a timing chart for explaining another example of the operation of the image control unit shown in FIG. 2. It is a schematic block diagram which shows the functional structure of the image process part in the image forming apparatus of the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is a schematic block diagram showing a functional configuration of the image forming apparatus according to the first embodiment of the present invention.

  The image forming apparatus according to the present embodiment can be a copying machine, a facsimile, a printer, a multifunction machine, or the like. In the following, a copying machine is illustrated as an example of an image forming apparatus and its main configuration will be mainly described, and description of the same configuration as a conventional copying machine may be omitted.

  As illustrated in FIG. 1, the image forming apparatus 1 according to the present embodiment includes an image reading unit 10, an image processing unit 20, an image forming unit 30, an operation unit 40, a display unit 50, a communication interface 60, and a control unit 70. These components are connected to each other via a bus 80 so as to communicate with each other.

  The image reading unit 10 optically reads a document and acquires an image (for example, an RGB image) that is color-separated into a plurality of colors. The image reading unit 10 includes a light source, an optical system, an image sensor, and an analog / digital conversion circuit. In the image reading unit 10, the light source sequentially irradiates the original with light of each color (R, G, B). The optical system has a plurality of mirrors and an imaging lens, and the reflected light from the original is imaged on the image sensor through the mirror and imaging lens of the optical system. The image sensor reads reflected light corresponding to each color (R, G, B) for each line and generates an electrical signal according to the reflected light intensity from the document. The generated electrical signal is converted from an analog signal to a digital signal in an analog / digital conversion circuit, and transmitted to the image processing unit 20 as an image data signal.

  The image processing unit 20 generates print image data, and generates a print image drawing signal based on the print image data. The generated drawing signal is transmitted to the image forming unit 30. Details of the image processing unit 20 will be described later.

  The image forming unit 30 prints a print image on the paper supplied from the paper feed tray based on the drawing signal generated by the image processing unit 20. In the present embodiment, the image forming unit 30 prints a print image on paper by an electrophotographic process. More specifically, the image forming unit 30 charges the photosensitive drum, and forms an electrostatic latent image on the photosensitive drum by laser light based on the drawing signal generated by the image processing unit 20. Then, a toner image is formed by attaching toner to the electrostatic latent image on the photosensitive drum, the toner image on the photosensitive drum is transferred to a sheet by a transfer belt, and the toner image transferred to the sheet is transferred by a fixing roller. Fix by heating and pressing. The paper on which the toner image is fixed is discharged from the paper discharge tray.

  The operation unit 40 receives an instruction from the user and transmits the instruction to the control unit 70. The operation unit 40 includes an input device such as a push button switch or a touch panel. For example, the user instructs the image forming apparatus 1 to copy a document by pressing a push button switch of the operation unit 40.

  The display unit 50 displays setting contents related to printing processing by the image forming unit 30 and various messages for alerting the user. The display unit 50 includes, for example, a liquid crystal panel display, LEDs, and the like.

  The communication interface 60 is an interface for communicating with a client terminal connected to the image forming apparatus 1 via a network.

  The control unit 70 controls the image reading unit 10, the image processing unit 20, the image forming unit 30, the operation unit 40, the display unit 50, and the communication interface 60 to realize the function of the image forming apparatus 1 as a copying machine. In the present embodiment, the control unit 70 executes control to turn off the power of the module in the standby state in order to reduce standby power.

  The control unit 70 includes a CPU (Central Processing Unit) and a storage unit. The storage unit includes a hard disk drive, a ROM (Read Only Memory), and a RAM (Random Access Memory). A software program for controlling the image reading unit 10, the image processing unit 20, the image forming unit 30, the operation unit 40, the display unit 50, and the communication interface 60 is stored in the hard disk drive or ROM. The RAM is loaded when the software program is executed by the CPU and temporarily stores data such as various calculation results.

  Next, the image processing unit of the image forming apparatus according to the first embodiment of the present invention will be described in more detail with reference to FIG. FIG. 2 is a schematic block diagram showing a functional configuration of the image processing unit shown in FIG.

  The image processing unit 20 includes an image control unit 21, a drawing unit 22, and a differential transmission path 23. The image control unit 21 includes a power supply unit 211, a timing control unit 212, a transmission element 213, and a transmission control unit 214. The drawing unit 22 includes a power supply unit 221 and a receiving element 222. The transmitting element 213 and the receiving element 222 are electrically connected by a differential transmission path 23 having a pair of signal lines.

  The image control unit 21 generates print image data and transmits it to the drawing unit 22. The image control unit 21 generates print image data based on the image data signal received from the image reading unit 10. Since the configuration for generating the printing image data based on the image data signal is the same as the conventional configuration, the description thereof is omitted.

  The power supply unit 211 supplies power supply voltages VCCA and GNDA to each component of the image control unit 21 including the timing control unit 212, the transmission element 213, and the transmission control unit 214. The value of VCCA is positive and greater than the value of GNDA. Note that the image control unit 21 cannot predict when the reading of the document is started. Therefore, when the main power supply of the image forming apparatus 1 is turned on, the power supply unit 211 needs to be always turned on regardless of whether the image forming unit 30 is printing or not printing.

  The timing control unit 212 controls the output timing of printing image data. The timing control unit 212 receives the printing image data, the horizontal synchronization signal, and the vertical synchronization signal, and outputs the printing image data whose output timing is adjusted by the horizontal synchronization signal and the vertical synchronization signal. The print image data whose output timing is adjusted is transmitted to the input terminal of the transmission element 213.

  The transmission element 213 is, for example, a three-state buffer having a differential output terminal, an input terminal for inputting printing image data having a logic level 0 or 1, a differential output terminal for outputting printing image data, and an output And a control terminal for controlling. The transmission element 213 outputs the printing image data input to the input terminal to the differential output terminal according to the logic level applied to the control terminal, or the differential output terminal to high impedance (Hi-Z). Put it in a state. In this embodiment, when the logic level applied to the control terminal is 1, the printing image data input to the input terminal is output to the differential output terminal, and when the logic level applied to the control terminal is 0, the differential is performed. Set the output terminal to high impedance. The logic level 0 or 1 output from the differential output terminal of the transmission element 213 is transmitted to the differential input terminal of the reception element 222 via the differential transmission path 23.

  In the present embodiment, the image control unit 21 transmits image data for printing to the drawing unit 22 by LVDS (Low Voltage Differential Signaling) including a transmission element 213, a reception element 222, and a differential transmission path 23. However, the differential transmission method is not limited to LVDS, and other differential transmission methods may be used. By differentially transmitting the printing image data between the image control unit 21 and the drawing unit 22, it is possible to reduce the influence of noise on the printing image data. As a result, it is possible to increase the distance between the image control unit 21 and the drawing unit 22 as compared with the case of single-end transmission without differential transmission.

  The transmission control unit 214 generates a transmission control signal for controlling the output of the transmission element 213. The transmission control unit 214 inputs a print start signal and a print end signal, and outputs a transmission control signal based on the print start signal and the print end signal. Specifically, the transmission control signal becomes active during a period from when the print start signal becomes active until the print end signal becomes active. The generated transmission control signal is transmitted to the control terminal of the transmission element 213.

  The print start signal is a signal for notifying the start of printing of the image forming apparatus 30. For example, the image control unit 21 activates a print start signal based on a signal generated based on the operating state of each component such as the photosensitive drum, the fixing unit, and the conveyance unit of the image forming unit 30.

  The print end signal is a signal for notifying the end of printing of the image forming apparatus 30. The image control unit 21 counts the number of print image data output from the transmission element 213 and activates the print end signal when the predetermined number of data is reached. The predetermined number of data may be, for example, the number of data for one page of the print image or the number of data of two or more pages of the print image. Alternatively, the number of data corresponding to one or more lines of the print image may be used.

  As described above, the image control unit 21 performs image processing based on the print start signal that becomes active when the image forming unit 30 starts printing and the print end signal that becomes active when the image forming unit 30 finishes printing. It is detected whether or not the forming unit 30 is printing. Then, the image control unit 21 controls whether to output the printing image data or the high impedance to the drawing unit 22 based on the detection result.

  The drawing unit 22 generates a print image drawing signal based on the printing image data generated by the image control unit 21. In the present embodiment, in order to print a print image on a sheet by an electrophotographic process, the drawing unit 22 generates a light emission signal for forming an electrostatic latent image on a photosensitive drum as a drawing signal by laser light.

  The power supply unit 221 supplies power supply voltages VCCB and GNDB to each component of the drawing unit 22 including the receiving element 222. VCCB is a positive value and larger than the value of GNDB. The power supply unit 221 is on / off controlled independently of the power supply unit 211 of the image control unit 21. The power supply unit 221 is controlled by the control unit 70 so that the image forming unit 30 is turned off during a period other than the period during printing. When the power supply unit 221 is turned off, the power consumption of the image forming apparatus 1 is reduced.

  The receiving element 222 is, for example, a three-state buffer having a differential input terminal, and includes a differential input terminal for inputting print image data, an output terminal for outputting print image data, and a control terminal for controlling output. Prepare. The receiving element 222 outputs the print image data input to the differential input terminal to the output terminal according to the logic level applied to the control terminal. In this embodiment, when the logical level applied to the control terminal is 1, the printing image data input to the differential input terminal is output to the output terminal, and when the logical level applied to the control terminal is 0, the output terminal To the high impedance state.

  The image processing unit 20 of the present embodiment configured as described above has an image control unit 21 and a drawing unit 22, and the drawing unit 22 is controlled to be turned on / off independently of the power supply unit 211 of the image control unit 21. The power supply unit 221 is provided. In addition, the image processing unit 20 includes a differential transmission path 23 that transmits image data for printing from a transmission element 213 installed in the image control unit 21 to a reception element 222 installed in the drawing unit 22. The image control unit 21 outputs a logic level 0 or 1 from the transmission element 213 according to the image data for printing when the image forming unit 30 is printing, while the transmission element when the image forming unit 30 is not printing. Set 213 to a high impedance state.

  Hereinafter, the operation of the image control unit will be described with reference to FIGS. 3A and 3B. 3A is a timing chart for explaining an example of the operation of the image control unit shown in FIG. 2, and FIG. 3B is a timing chart for explaining another example of the operation of the image control unit shown in FIG.

  First, a case where the print start signal and the print end signal are activated every period corresponding to one page of a print image will be described with reference to FIG. 3A. One page of the printed image corresponds to a period from when the vertical synchronization signal is activated to when it is activated next. In the present embodiment, the horizontal synchronization signal and the vertical synchronization signal are low active signals.

  When the image forming unit 30 starts printing, the power of the drawing unit 22 that has been turned off in the standby state is turned on, and the print start signal becomes active (logic level 1). When the print start signal becomes active, the transmission control signal becomes active (logic level 1). The transmission control signal is kept active until the print end signal becomes active. When the transmission control signal is active, print image data is output from the differential output terminal of the transmission element 213 in accordance with the timing of the horizontal synchronization signal. Until the transmission control signal becomes active, the differential output terminal of the transmission element 213 is in a high impedance state. When the image forming unit 30 prints one page of print image, the print end signal becomes active and the transmission control signal becomes inactive (logic level 0). When the transmission control signal becomes inactive, the differential output terminal of the transmission element 213 enters a high impedance state. Then, the power of the drawing unit 22 is turned off and again enters a standby state.

  Next, a case where the print start signal and the print end signal become active every period corresponding to one or more lines of the print image will be described with reference to FIG. 3B. FIG. 3B shows a case where the print start signal and the print end signal become active every period corresponding to two lines of the print image. One line of the printed image corresponds to a period from when the horizontal synchronizing signal is activated to when it is activated next.

  When the image forming unit 30 starts printing, the power of the drawing unit 22 that has been turned off in the standby state is turned on, and the print start signal becomes active (logic level 1). When the print start signal becomes active, the transmission control signal becomes active (logic level 1). The transmission control signal is kept active until the print end signal becomes active. When the transmission control signal is active, print image data is output from the differential output terminal of the transmission element 213 in accordance with the timing of the horizontal synchronization signal. Until the transmission control signal becomes active, the differential output terminal of the transmission element 213 is in a high impedance state. When the image forming unit 30 prints the print image for two lines, the print end signal becomes active and the transmission control signal becomes inactive (logic level 0). When the transmission control signal becomes inactive, the differential output terminal of the transmission element 213 enters a high impedance state. Then, the power of the drawing unit 22 is turned off and again enters a standby state. In the example shown in FIG. 3B, the transmission element 213 enters a high impedance state every period corresponding to two lines of the print image.

  Thus, in the present embodiment, the image control unit 21 outputs the logic level 0 or 1 from the transmission element 213 according to the print image data when the image forming unit 30 is printing, while the image forming unit 30 When 30 is not printing, the transmitting element 213 is set to a high impedance (Hi-Z) state.

  As described above, the described image forming apparatus 1 of the present embodiment has the following effects.

  (A) When the image forming unit 30 is not printing, the image control unit 21 sets the transmission element 213 in a high impedance state. It is possible to reliably prevent unnecessary current from flowing through the transmission line 23. Therefore, it is possible to prevent the receiving element 222 of the drawing unit 22 from being damaged. In addition, since no unnecessary current flows through the differential transmission path 23, the power consumption of the image forming apparatus 1 can be reduced.

  (B) Since a configuration is locally added in the image processing unit 20 to prevent unnecessary current from flowing from the image control unit 21 to the drawing unit 22 in the differential transmission path 23, the power supply of the module in the standby state There is no need to change the control of the control unit 70 for selectively turning off the. Further, since it is detected whether or not the image forming unit 30 is printing based on an existing signal provided in the image forming apparatus 1 conventionally, a newly added configuration can be stopped on a small scale.

(Second Embodiment)
In the first embodiment, the case where the power supply unit of the drawing unit is configured to supply the power supply voltage independently of the power supply voltage supplied from the power supply unit of the image control unit has been described. On the other hand, in the second embodiment, a case will be described in which the power supply unit of the drawing unit is configured to supply the power supply voltage by switching the power supply voltage supplied by the power supply unit of the image control unit. The image forming apparatus according to the present embodiment is the first embodiment except that the power supply unit of the drawing unit supplies the power supply voltage by switching the power supply voltage supplied by the power supply unit of the image control unit. The configuration is the same as that of the image forming apparatus. In the following, in order to avoid duplication of explanation, explanation of the same configuration as that of the image forming apparatus of the first embodiment is omitted.

  FIG. 4 is a schematic block diagram illustrating a functional configuration of the image processing unit in the image forming apparatus according to the second embodiment of the present invention.

  As shown in FIG. 4, in the present embodiment, the power supply unit 211 of the image control unit 21 not only supplies the power supply VCCA and GNDA to each component of the image control unit 21 but also supplies the power supply voltage VCCA to the drawing unit 22. And GNDA.

  On the other hand, the power supply unit 221 of the drawing unit 22 includes a switching circuit, and by switching the power supply voltages VCCCA and GNDA input from the image control unit 21, each component of the drawing unit 22 including the receiving element 222 is switched. Supply power supply voltages VCCA and GNDA. The power supply unit 221 is on / off controlled independently of the power supply unit 211 of the image control unit 21. The power supply unit 221 is controlled by the control unit 70 so as to be turned off during a period other than the period during printing.

  As described above, the described image forming apparatus 1 according to the present embodiment has the following effects in addition to the effects of the first embodiment.

  (C) Since the power supply unit 221 of the drawing unit 22 switches the power supply voltages VCCCA and GNDA of the power supply unit 211 of the image control unit 21 and supplies the power supply voltage to each component of the drawing unit 22, the power supply unit 221. The circuit configuration can be simplified.

  As described above, the image forming apparatus of the present invention has been described in the embodiment. However, it goes without saying that the present invention can be appropriately added, modified, and omitted by those skilled in the art within the scope of the technical idea.

1 image forming apparatus,
10 image reading device,
20 image processing device,
21 Image control unit,
211 power supply,
212 timing control unit,
213 transmitting element;
214 transmission control unit,
22 Drawing part,
221 power supply unit,
222 receiving element,
23 differential transmission line,
30 Image forming unit,
40 operation unit,
50 display section,
60 communication interface,
70 Control unit.

Claims (6)

An image control unit for generating image data for printing;
A drawing unit that generates a drawing signal of a print image based on the print image data;
A differential transmission path comprising a pair of signal lines, and transmitting the printing image data from a transmission element installed in the image control unit to a reception element installed in the drawing unit;
An image forming unit that prints the print image on a sheet based on the drawing signal,
The drawing unit comprises a power supply unit,
The power supply unit is turned on when the image forming unit is printing, and is turned off when the image forming unit is not printing,
The image control unit, when said image forming unit is in said printing while outputting a logic level 0 or 1 from the transmitting device in accordance with the printing image data, the image forming unit is not in the print An image forming apparatus in which the transmitting element is placed in a high impedance state.   The image control unit is configured so that the image forming unit is activated based on a print start signal that becomes active when the image forming unit starts printing and a print end signal that becomes active when the image forming unit finishes printing. The image forming apparatus according to claim 1, wherein whether or not printing is in progress is detected. The image forming apparatus according to claim 2 , wherein the print start signal and the print end signal are activated every period corresponding to one page of the print image. The image forming apparatus according to claim 2 , wherein the print start signal and the print end signal are activated every period corresponding to one or more lines of the print image.   5. The image formation according to claim 1, wherein the power supply unit of the drawing unit supplies a power supply voltage by switching a power supply voltage supplied by the power supply unit of the image control unit. apparatus. The transmitting element and the receiving element are three-state buffers,
6. The image control unit according to claim 1, wherein the image control unit transmits the image data for printing to the drawing unit by LVDS configured by the transmission element, the reception element, and the differential transmission path. The image forming apparatus according to claim 1.

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