Patent Publication Number: US-2012038943-A1

Title: Document reading apparatus, document size determining method and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the priority of U.S. Provisional Application No. 61/372,438, filed on Aug. 10, 2010, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a document reading apparatus to read a document, a document size determining method to determine a document size, and an image forming apparatus including the document reading apparatus. 
     BACKGROUND 
     Hitherto, an image forming apparatus such as an MFP includes a scanner unit and a printer unit. The scanner unit reads a document, the image data read by the scanner unit is processed, and the printer unit prints. Besides, the image forming apparatus includes an auto document feeder (ADF), and the scanner unit reads a document fed by the ADF or reads a document placed on a document table. 
     In a document reading apparatus of related art, in order to determine the size of a document placed on the document table, plural sensors are arranged below the document table. In order to detect plural documents different in size, such as A3 or A4, all of the plural sensors are in a turned-on state at the time of use of the image forming apparatus. 
     However, when all the sensors are turned on to determine the size of the document, there is a defect that power consumption increases, and an improvement for achieving power saving is required. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural view showing an image forming apparatus including a document reading apparatus of an embodiment. 
         FIG. 2  is a plan view showing the arrangement of sensors to detect A-series and B-series documents in the embodiment. 
         FIG. 3  is a view showing a determination matrix of A-series and B-series document sizes in the embodiment. 
         FIG. 4  is a flowchart showing the operation of a determination process of A-series and B-series document sizes in the embodiment. 
         FIG. 5  is a block diagram showing a control system of the image forming apparatus in the embodiment. 
         FIG. 6  is a plan view showing the arrangement of sensors to detect LT-series documents. 
         FIG. 7  is a view showing a determination matrix of LT-series document sizes. 
         FIG. 8  is a flowchart showing the operation of a determination process of LT-series document sizes. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a document reading apparatus includes plural sensors that are arranged to face a document table and detect a document placed on the document table, a sensor drive unit to power on a first sensor among the plural sensors and to power on a next sensor in a previously set sequence according to a detection result of the first sensor, a size determination unit to determine a size of the document based on a detection result of the document obtained by the powered-on sensor, and a control unit that, when the size determination unit determines the size of the document before all of the plural sensors are powered on, stops power supply to a remaining sensor. 
     Hereinafter, an image forming apparatus including a document reading apparatus of an embodiment will be described with reference to the drawings. Incidentally, the same part in the respective drawings is denoted by the same reference numeral. 
       FIG. 1  is a structural view showing the image forming apparatus. The image forming apparatus  10  is, for example, a MFP (Multi-Function Peripherals) as a compound machine, a printer, a copying machine or the like. The following description is made while the MFP is used as an example of the image forming apparatus  10 . 
     A transparent document table  12  is provided at an upper part of a main body  11  of the MFP  10 , and an auto document feeder (ADF)  13  is openably and closably provided over the document table  12 . Besides, an operation panel  14  is provided at an upper part of the main body  11 . The operation panel  14  includes various operation keys  141  and a touch panel display unit  142 . 
     A scanner unit  15  is provided below the document table  12  of the MFP  10 . The scanner unit  15  reads an image of a document fed by the ADF  13  or a document placed on the document table  12 . The scanner unit  15  includes a first carriage  16  and a second carriage  17 . 
     The first carriage  16  includes a light source  161  to expose and scan a document, and light from the light source  161  is irradiated to the document. The light reflected by the document is reflected by a reflecting mirror  162 . The second carriage  17  includes mirrors  171  and  172  to reflect the light reflected by the reflecting mirror  162 , and the light reflected by the mirror  172  is guided to a CCD  19  through a lens  18 . The CCD  19  is an image sensor. The reflected light from the document is photoelectrically converted by the CCD  19 , and an electric signal from the CCD  19  is subjected to image processing, so that image data is generated. 
     Incidentally, when the scanner unit  15  reads the document fed by the ADF  13 , the position of the first carriage  16  is fixed to an illustrated position (below the ADF  13 ), and the second carriage  17  is located at a position close to the first carriage  16 . When the scanner  15  reads the document placed on the document table  12 , the first carriage  16  and the second carriage  17  are moved in parallel to the document table  12 , and the scanner unit  15  reads the document placed on the document table  12 . 
     A printer unit  20  is provided inside the main body  11 . The printer unit  20  includes a photoconductive drum, a laser and the like, processes the image data read by the scanner unit  15  or image data generated by a PC (Personal Computer) or the like, and forms an image on a recording medium. Incidentally, in the following, the description is made while a sheet S is used as an example of the recording medium. 
     The printer unit  20  includes, for example, plural image forming units below a transfer belt  21  along the upstream side to the down stream side. The image forming unit scans and exposes the surface of a photoconductive drum  22  with a laser beam from the laser  30 , and forms an electrostatic latent image on the photoconductive drum  22 . A charging charger  23 , a developing unit  24 , a primary transfer roller  25 , a cleaner  26 , a blade  27  and the like are arranged around the photoconductive drum  22 . 
     The charging charger  23  uniformly charges the whole surface of the photoconductive drum  22 . The developing unit  24  includes a mixer to agitate a developer and a developing roller to which a development bias is applied, and supplies the toner of two-component developer including toner and carrier to the photoconductive drum  22  by the developing roller. The cleaner  26  uses the blade  27  and removes the remaining toner on the surface of the photoconductive drum  22 . 
     A toner image on the photoconductive drum  22  is transferred to the transfer belt  21  by the primary transfer roller  25 , and the toner image transferred to the transfer belt  21  is transferred to the sheet S by a secondary transfer roller  28 . The toner image transferred to the sheet S is fixed by a fixing unit  29 . The fixing unit  29  includes a fixing roller and a pressure roller, and the sheet S passes through between the fixing roller and the pressure roller, so that the toner image on the sheet S is fixed to the sheet S. 
     When a color image is formed, the printer unit  20  includes plural image forming units of black, magenta, cyan, yellow and the like. Incidentally, the structure of the printer unit  20  is not limited to the above example, and there are various systems. 
     Plural cassettes  31  to  34  to contain sheets of various sizes are provided at a lower part of the main body  11 . Incidentally, the number of the cassettes is not limited to four. A conveyance roller  35  to convey the sheet S taken out from each of the cassettes  31  to  34  to the printer unit  20  is provided between the secondary transfer unit  28  and the cassettes  31  to  34 . The sheet S on which the toner image is fixed by the fixing unit  29  and the image formation is completed is discharged to a paper discharge part  37  by a paper discharge roller  36 . 
     In the document reading apparatus, in order to detect the size of a document placed on the document table  12 , plural sensors are arranged below the document table  12 , and the size of the document is determined based on the detection results of the respective sensors. In the related art, since all of the plural sensors are operated to determine the document size, the power consumption increases. 
     In the document reading apparatus of the embodiment, the plural sensors to detect a document are powered on in a previously set sequence, and the size of the document is determined based on the detection result of each sensor, so that the power saving is achieved. 
     Hereinafter, the arrangement of plural sensors to detect a document will be described. 
       FIG. 2  is a plan view showing the arrangement of sensors S 1  to S 5  used for determining the sizes of eight kinds of A-series and B-series documents (A3, A4, A5, B4, B5, A4-R, B5-R, A5-R), and shows positions of the sensors S 1  to S 5  when the document table  12  is seen from right above. Each of the sensors S 1  to S 5  includes a light-emitting element and a light-receiving element. The light-emitting element irradiates light to a document, and the light-receiving element receives the light reflected by the document, so that the presence or absence of the document is detected. 
     When a corner point as a positioning reference when a document is placed on the document table  12  is X, the sensor S 1  is located at a position farthest from the corner point X, and the sensor  2  is located at a position next farthest from the corner point X. The sensor S 4  and S 5  are located at positions close to the corner point X. 
     That is, the sensor S 1  is located at the lower right end of an A4 document, the sensor S 2  is located at the right end center of a B5-R document, and the sensor S 3  is located at the lower right end of a B5 document. The sensor S 4  is located the lower right end of an A5 document, and the sensor S 5  is located at the lower right end of an A5-R document. 
     The sensor S 1  detects the presence or absence of the A4 and A3 documents, and the sensor S 2  detects the presence or absence of the B5-R document. The sensor S 3  detects the presence or absence of the B4 and B5 documents, and the sensor S 4  detects the presence or absence of the A4-R and A5 documents. The sensor S 5  detects the presence or absence of the A5-R document. 
       FIG. 3  is a view showing a logical matrix of document size determination based on the detection results of the respective sensors S 1  to S 5 . In  FIG. 3 , a state where a sensor is on and there is a document is “0”, and a state where a sensor is off and there is no document is “1”. For example, when all the sensors S 1  to S 5  are determination is made that there is no document, and when all the sensors S 1  to S 5  are “0”, the document size is determined to be A3. 
     In  FIG. 3 , with respect to the A-series and B-series document sizes, the five sensors S 1  to S 4  detect nine kinds of document sizes including the state where there is no document. In some sensors, the number of times where “0” occurs is small. The lower part of  FIG. 3  shows a frequency when the sensors S 1  to S 5  become “0”. The frequency of the sensor S 1  is 2, the frequencies of the sensors S 2  and S 3  are 4, and the frequencies of the sensors S 5  and S 6  are 6. 
     In the embodiment, from  FIG. 3 , attention is paid to the fact that the frequency of the sensor S 1  is lowest, and when the document size is determined, the sensor S 1  is first powered on. With respect to the other sensors, determination is made based on the state of the sensor S 1  as to whether or not the other sensors are powered on. 
     Hereinafter, timings when the sensors S 1  to S 5  are powered on and the operation of the determination process of the document size will be described along the flowchart of  FIG. 4 . 
     In  FIG. 4 , at Act A 0 , determination of a document size starts, and at Act A 1 , the sensor S 1  is powered on. At Act A 2 , the sensor S 1  starts to detect the presence or absence of a document. At Act A 3 , determination is made as to whether or not the sensor S 1  is on. When the sensor S 1  is on and is “0”, at Act A 4 , the sensor S 2  is powered on, and at Act A 5 , the sensor S 2  starts to detect the presence or absence of the document. At Act A 6 , determination is made as to whether or not the sensor S 2  is on. When the sensor S 2  is on and is “0”, at Act A 7 , the document size is determined to be A3. At Act A 6 , when the sensor S 2  is not on and is “1”, at Act A 8 , the document size is determined to be A4. 
     That is, since the sensor S 1  is on only when the document size is A3 or A4, the state of the sensor S 2  is detected, and when the sensor S 2  is on, the document size is determined to be A3, and when the sensor S 2  is off, the document size is determined to be A4. Accordingly, when the document size is A3 or A4, only the sensor S 1  and the sensor S 2  are powered on, and the other sensors S 3  to S 5  are not powered on. Accordingly, the power consumption can be reduced. 
     At Act A 3 , when the sensor S 1  is off and is “1”, at Act A 9 , the sensor S 3  is powered on, and at Act A 10 , the sensor S 3  starts to detect the presence or absence of a document. At Act A 11 , determination is made as to whether or not the sensor S 3  is on. When the sensor S 3  is on and is “0”, at Act A 12 , the sensor S 2  is powered on, and at Act A 13 , the sensor S 2  starts to detect the presence or absence of a document. At Act A 14 , determination is made as to whether or not the sensor S 2  is on. When the sensor S 2  is on and is “0”, at Act A 15 , the document size is determined to be B4. At Act A 14 , when the sensor S 2  is not on and is “1”, at Act A 16 , the document size is determined to be B5. 
     That is, since the sensor S 1  is off when the document size is other than A3 or A4, the state of the sensor S 3  is further detected. When the sensor S 3  is on and is “0”, the document size is B4 or B5. Accordingly, the state of the sensor S 2  is further detected, and when the sensor S 2  is on and is “0”, the document size is determined to be B4, and when the sensor S 2  is off, the document size is determined to be B5. 
     Accordingly, when the document size is A3, A4, B4 or B5, only the sensors S 1 , S 2  and S 3  are powered on, and the other sensors S 4  and S 5  are not powered on. 
     At Act A 11 , when the sensor S 3  is off and is “1”, at Act A 17 , the sensors S 4 , S 5  and S 2  are powered on, and at Act A 18 , the sensors S 4 , S 5  and S 2  start to detect the presence or absence of a document. At Act A 19 , determination is made as to whether or not all the sensors S 1  to S 5  are off. When all the sensors S 1  to S 5  are off and are “1”, at Act A 20 , determination is made that there is no document. 
     At Act A 19 , when all the sensors A 1  to A 5  are not off, advance is made to Act A 21 , and the document size is determined from the on or off states of the sensors S 4 , S 5  and S 2 . 
     That is, when the sensors S 1  and S 3  are off and one of the sensors S 4 , S 5  and S 2  is on and is “0”, the document size is one of A5, A5-R, B5-R and A4-R. Accordingly, the document size (A5, A5-R, B5-R, A4-R) is determined in accordance with the logical matrix shown in  FIG. 3 . 
     As described above, when the document size is determined, the two sensors of the sensor S 1  and the sensor S 2  located at the positions far from the corner point X are first powered on, so that at least the document sizes of A4 and A3 can be determined. Since the use frequency of the A3 or A4 size document is high, when determination can be made as to whether the size is A3 or A4, the remaining sensors S 3  to S 5  are not required to be powered on. Accordingly, power saving at the time of determination of the document size can be achieved. 
     When the document size is neither A3 nor A4, the sensors S 1 , S 2  and S 3  are powered on, so that the B4 and B5 documents having next higher use frequency can be determined. In this way, the sensor far from the corner point X is first powered on, and the document size is determined, and when the size can not be determined, the sensor located at the position close to the corner point X is powered on. Accordingly, the power consumption can be reduced. 
       FIG. 5  is a block diagram showing a control system of the image forming apparatus  10 . In  FIG. 5 , a main control unit  100  includes a CPU  101 , a ROM  102 , a RAM  103 , a size determination unit  104  and an image processing unit  105 . 
     The CPU  101  controls the image forming apparatus  10  in accordance with a control program stored in the ROM  102 . Besides, the main control unit  100  controls the operation of the scanner unit  15  and the printer unit  20  in response to the user&#39;s operation of the operation panel  14 . The RAM  103  is used for temporarily storing control data, or is used for arithmetic operation at the time of control. 
     The size determination unit  104  determines the size of a document based on the detection results of the sensors S 1  to S 5 . The image processing unit  105  performs a process, such as magnification conversion, on the image data read by the scanner unit  15 . When the determined document size is different from the sheet size to be used, the image processing unit  105  can set to change the magnification of the image data to be printed and to perform an image processing. 
     The operation panel  14  includes the plural keys  141  and the display unit  142  used also as the touch panel, and gives various instructions for image formation. For example, the instruction for the number of copies is given by using the keys  141 , and the instruction for the sheet size or magnification is given by operating the touch panel of the display unit  142 . The execution of the copy or the like is started by the operation of a start key. 
     Besides, the main control unit  100  is connected to a sensor drive unit  110 . The sensor drive unit  110  controls power supply to the sensors S 1  to S 5  under the control of the CPU  101 . The sensors S 1  to S 5  are powered on in the sequence shown in the flowchart of  FIG. 4 . The detection results (0, 1) of the sensors S 1  to S 5  are sent to the main control unit  100 , and the size determination unit  104  determines the size of the document according to the detection results of the sensors S 1  to S 5  and in accordance with the flowchart of  FIG. 4 . 
     The main control unit  100  controls the sensor drive unit  110 , and when the size determination unit  104  can determine the document size before all the sensors S 1  to S 5  are powered on, the remaining non-power-on sensors are not powered on. 
     Besides, from the determination result of the size determination unit  104 , the main control unit  100  controls so that a sheet having the same size as the document size is taken out one by one from the corresponding cassette among sheets contained in the cassettes  31  to  34 , and is conveyed to the printer unit  20 . Alternatively, a sheet having the size specified by the user is taken out one by one from the corresponding cassette, and is conveyed to the printer unit  20 . Accordingly, the main control unit  100  functions also as a selection unit to select the cassette according to the document size. 
     For example, when the user sets a document on the document table  12  and performs a copy operation without specifying the sheet size, the size determination unit  104  of the main control unit  100  determines the document size based on the results detected by the sensors S 1  to S 5 . Then, the cassette ( 31  to  34 ) containing sheets having the same size as the document size is selected, and the sheet S is taken out one by one from the corresponding cassette, and is conveyed to the printer unit  20 . The image processing unit  105  outputs the image data of the document read by the scanner unit  15  while the size is made the same as the sheet size, and the printer unit forms an image on the sheet S. 
     When the user sets a document on the document table  12 , and specifies the sheet size (for example, when the document size is A3 and the specified sheet size is A4), a sheet having the specified size is taken out from the cassette ( 31  to  34 ) and is conveyed to the printer unit  20 . The size determination unit  104  determines the document size based on the results detected by the sensors S 1  to S 5 . When the document size is different from the specified sheet size, the image processing unit  105  changes the magnification of the image data read by the scanner unit  15  and prints the data on the sheet S. For example, when the document size is A3 and the size of the sheet S specified by the user is A4, the data is reduced and is printed. Of course, when the user specifies the sheet or the copy magnification, printing is performed on the specified sheet and with the specified magnification. 
     As a result of the determination of the document size by the size determination unit  104 , when the sheet having the corresponding size is not contained in the cassettes  31  to  34 , the main control unit  100  displays, on the display unit  142  of the operation panel  14 , the warning that there is no sheet having the same size as the document. 
     Although  FIG. 1  shows the image forming apparatus  10  including the four cassette  31  to  34 , actually, as shown in  FIG. 3 , there are eight kinds of document sizes. Thus, sheets corresponding to all documents can not be contained in the cassettes  31  to  34 . Accordingly, when the sheet having the same size as the document is not contained in the cassettes  31  to  34 , the warning is displayed. 
       FIG. 6  is a plan view showing the arrangement of sensors S 6  to S 9  to detect six kinds of LT-series documents (LD, LT, LG, ST, LT-R, ST-R). A sensor S 6  is located at the lower right end of an LT document, a sensor S 7  is located at the right end center of an LG document, and a sensor S 8  is located at the lower right end of an ST document. Besides, the sensor S 9  is located at the lower right end of an ST-R document. 
     The sensor S 6  detects the presence or absence of the LD and LT documents, and the sensor S 7  detects the presence or absence of the LG document. The sensor S 8  detects the presence or absence of the LT-R and the ST documents, and the sensor S 9  detects the presence or absence of the ST-R document. 
       FIG. 7  is a view showing a determination matrix of document size based on the detection results of the respective sensors S 6  to S 9 . In  FIG. 7 , for example, when all the sensors S 6  to S 9  are “1”, determination is made that there is no document, and when all the sensors S 6  to S 9  are “0”, the document size is determined to be LD. 
     Hereinafter, timings when the sensors S 6  to S 9  are powered on and the operation of the determination process of the document size will be described along the flowchart of  FIG. 8 . 
     In  FIG. 8 , at Act A 30 , determination of the document size starts, and at Act A 31 , the sensor S 6  is powered on. At Act A 32 , the sensor S 6  starts to detect the presence or absence of the document. At Act A 33 , determination is made as to whether or not the sensor S 6  is on. When the sensor S 6  is on and is “0”, at Act A 34 , the sensor S 7  is powered on, and at Act A 35 , the sensor S 7  starts to detect the presence or absence of a document. At Act A 36 , determination is made as to whether or not the sensor S 7  is on. When the sensor S 7  is on and is “0”, at Act A 37 , the document size is determined to be LD. At Act A 36 , when the sensor S 7  is not on and is “1”, at Act A 38 , the document size is determined to be LT. 
     That is, since the sensor S 6  is on only when the document size is LD or LT, the state of the sensor S 7  is detected, and when the sensor S 7  is on and is “0”, the document size is determined to be LD, and when the sensor S 7  is off, the document size is determined to be LT. Accordingly, when the document size is LD or LT, only the sensor S 6  and the sensor S 7  are powered on, and the other sensors S 8  and S 9  are not powered on. Accordingly, power consumption can be reduced. 
     Besides, at Act A 33 , when the sensor S 6  is off and is “1”, at Act A 39 , the sensor S 7  is powered on, and at Act A 40 , the sensor S 7  starts to detect the presence or absence of a document. At Act A 41 , determination is made as to whether or not the sensor S 7  is on. When the sensor S 7  is on and is “0”, the document size is determined to be LG. 
     That is, since the sensor S 6  is off when the document size is other than LD or LT, the state of the sensor S 7  is further detected. When the sensor S 7  is on and is “0”, the document size is determined to be LG. Accordingly, when the document size is LD, LT or LG, only the sensors S 6  and S 7  are powered on, and the other sensors S 8  and S 9  are not powered on. 
     Besides, at Act A 41 , when the sensor S 7  is off and is “1”, at Act A 43 , the sensors S 8  and S 9  are powered on, and at Act A 44 , the sensors S 8  and S 9  start to detect the presence or absence of a document. At Act A 45 , determination is made as to whether or not all the sensors S 6  to S 9  are off. When all the sensors S 6  to S 9  are off and are “1”, at Act A 46 , determination is made that there is no document. 
     At Act A 46 , when all the sensors S 6  to S 9  are not off, advance is made to Act A 47 , and the document size is determined from the on or off states of the sensors S 8  and S 9 . That is, when the sensor S 6  and S 7  are off, and one of the sensors S 8  and S 9  is on and is “0”, the document size is one of LT-R, ST-R and ST. Thus, the document size (LT-R, ST-R and ST) is determined in accordance with the logical matrix shown in  FIG. 7 . 
     As stated above, when the LT-series document sizes are determined, the two sensors of the sensor S 6  and the sensor S 7  located at the positions far from the corner point X are first powered on, so that at least the document sizes of LD, LT and LG can be determined. Since the use frequency of the document of LD, LT or LG size is high, when the size of LD, LT or LG can be first determined, power saving at the time of determination of the document size can be achieved. When the document size is not LD, LT or LG, the sensors S 8  and S 9  arranged at the positions close to the corner point X are powered on, so that the other document size can be determined. 
     Incidentally, when the LT-series document sizes are detected, in the block diagram shown in  FIG. 5 , the sensors S 1  to S 5  have only to be replaced by the sensors S 6  to S 9 . The size determination unit  104  determines the document size in accordance with the flowchart of  FIG. 7 . 
     According to the embodiment described above, when the document size is determined, the plural sensors are powered on in the previously set sequence, so that the power consumption is reduced and the determination can be made. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel apparatus and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatus and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.