JP2011112660A - Document feeding device, and image forming apparatus mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document feeding device which uses a general purpose member as a control part, thereby allowing an increase in the cost and size thereof to be suppressed, and also performs a stable document feeding operation. <P>SOLUTION: The document feeding device 30 includes a CPU 57 of a document feeding control part 55. Signals are input to each of two sensors; a document length detection sensor 34 and a conveying state detection sensor 38 which are branched from one output signal line 57b extending from the output port 57a which is one output part to output control signals, and the CPU 57 selectively receives the signals output from the document length detection sensor 34 and the conveying state detection sensor 38. Thereby, the number of output ports of the CPU 57 to output the control signals to the two sensors is reduced to one. Consequently, the CPU 57 is used as a general purpose CPU. Further a compact CPU having a relatively small number of output ports is used among the general purpose CPUs. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a document conveying apparatus applicable to an image forming apparatus represented by a copying machine or a facsimile. The present invention also relates to an image forming apparatus equipped with the document conveying device.

  An image forming apparatus such as a copying machine or a facsimile usually includes a document conveying device that automatically sends a plurality of documents to a document reading unit. The document transport device separates the documents one by one from the uppermost layer of the document stack stacked on the document placement tray, and sends the document toward the document reading unit. The original is read by the original reading unit, and then is discharged to an original discharge tray provided on the most downstream side of the original conveyance path.

  There are a roller supply method and a suction supply method as a mechanism of a paper feed unit that sends out a document to the outside of the document placing tray in the document conveying device, and the roller supply method is generally widely used. In the roller supply method, the pickup roller contacts the uppermost layer of the original bundle and delivers the original to the paper feed roller on the downstream side in the transport direction, and the original is sent out one by one to the outside of the original placement tray.

  There are several types of document conveying devices, such as bringing the uppermost layer of the document bundle into contact with the pickup roller, feeding the document from the document loading tray, and switching the document conveying direction when reading the image data on both sides of the document. Some have a motor. The document transport device also detects the length of the document in the transport direction, detects the width of the document perpendicular to the transport direction, detects the presence or absence of a document on the document tray, and brings the uppermost layer of the document bundle into contact with the pickup roller. Some of them have a plurality of sensors such as upper limit detection.

  In order to improve the operability, the document conveying apparatus often includes a control unit that controls functional members such as the plurality of motors and the plurality of sensors. An example of such a document conveying device can be seen in Japanese Patent Application Laid-Open No. 2004-133620.

Japanese Patent Laying-Open No. 2005-263452 (page 4-5, FIGS. 1 and 2)

  A control CPU used in a control unit that controls a large number of functional members (controlled members) of the document conveying apparatus requires a corresponding number of output ports. If a specially designed CPU that is sufficiently designed to sufficiently satisfy the number of output ports is used, there is a high possibility that the cost of the document conveying apparatus will increase. However, if a general-purpose CPU is used as the control CPU, there is a possibility that the output ports will be insufficient.

  Although a method of compensating for the shortage of the number of output ports by configuring a circuit using a plurality of general-purpose CPUs can be considered, there is a possibility that an increase in cost cannot be avoided because a CPU and many other additional parts are required. In addition, the occupied area of the control board related to the circuit configured using these components becomes wider, and there is a possibility that the size of the document conveying apparatus is increased.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above points. By using as few and as few general-purpose members as possible as a control unit, it is possible to perform a stable document conveying operation while increasing costs and suppressing an increase in size. An object of the present invention is to provide a document conveying device capable of performing the above. It is another object of the present invention to provide an image forming apparatus equipped with such a document conveying device.

  In order to solve the above problems, the present invention provides a document conveying apparatus in which a single output signal line extending from a single output unit that outputs a control signal is branched to input a signal to each of a plurality of controlled members. The control part which selects and receives the signal output from this to-be-controlled member was decided to be provided.

  According to this configuration, information branched from one place of the output unit of the control unit, signals are input to the plurality of controlled members, and information output from any of the plurality of controlled members is employed.

  Further, in the document conveying apparatus having the above-described configuration, a plurality of filter circuits that allow signals of different frequencies to pass therethrough are provided, and a plurality of signal lines obtained by branching one output signal line extending from the output unit are connected to the plurality of filters. A filter unit connected to the plurality of controlled members via each circuit is provided.

  According to this configuration, even when signals are simultaneously output to a plurality of controlled members from one place of the output unit of the control unit, the controlled members to which signals are input are selected by the filter circuit.

  In the document conveying device having the above-described configuration, the plurality of controlled members are sensors related to the form and / or state of the document.

  Further, in the document conveying apparatus having the above-described configuration, a document placing tray for stacking and storing documents, a document size detecting sensor for detecting a document size on the document placing tray, and a document transported from the document placing tray. A conveyance state detection sensor for detecting a conveyance state, the control unit for controlling the document size detection sensor and the conveyance state detection sensor, and first and second filter circuits that allow signals having different frequencies to pass therethrough are provided, One of the two signal lines branched from one output signal line extending from the output unit of the control unit is connected to input to the document size detection sensor via the first filter circuit, and the other is connected to the first signal line. And the filter unit connected to input to the conveyance state detection sensor via a two-filter circuit.

  According to this configuration, one output signal line extending from the control unit that controls the document size detection sensor and the conveyance state detection sensor is branched and connected to be input to each of the two sensors.

  In the document conveying apparatus having the above-described configuration, the document size detection sensor is a document length detection sensor that detects the length of the document in the conveyance direction. According to this configuration, one signal line extending from the control unit is branched and connected to each of the document length detection sensor and the conveyance state detection sensor, and the control unit controls them.

  In the present invention, the document conveying device is mounted on the image forming apparatus.

  According to the configuration of the present invention, the output portion (output port) of the CPU that outputs a control signal to a plurality of controlled members, that is, sensors, can be provided at one location. As a result, as few general-purpose members as possible, that is, general-purpose CPUs can be used as the control unit. Of the general-purpose CPUs, a small CPU with relatively few output ports can be employed.

  In addition, by providing the filter unit, the control unit may not need to perform time-sharing control of the input port that receives a signal output from the controlled member. Furthermore, by making the frequencies of the drive signals of the plurality of controlled members different, it is not necessary to provide a signal frequency switching circuit.

  Therefore, it is possible to provide a document conveying device capable of performing a stable document conveying operation while suppressing an increase in cost and an increase in size. Further, it is possible to provide a highly reliable image forming apparatus equipped with such a document conveying device.

1 is a schematic vertical sectional front view of an image forming apparatus equipped with an original conveying apparatus according to an embodiment of the present invention. FIG. 2 is a schematic block diagram illustrating a configuration of the image forming apparatus in FIG. 1. FIG. 2 is a schematic vertical sectional front view of the document conveying device of FIG. 1. FIG. 3 is a detailed block diagram illustrating a partial configuration of the document conveying device in FIG. 2. 6 is a flowchart illustrating an operation related to document conveyance.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, an image output operation of an image forming apparatus equipped with an original conveying apparatus according to an embodiment of the present invention will be described while explaining the outline of the structure with reference to FIGS. FIG. 1 is a schematic vertical sectional front view of the image forming apparatus, and FIG. 2 is a schematic block diagram showing the configuration of the image forming apparatus. In FIG. 1, solid arrows indicate the paper conveyance path and conveyance direction, and alternate long and short dash arrows indicate the laser beam L.

  As shown in FIG. 1, a paper feed cassette 3 is disposed below the inside of the main body 2 of the image forming apparatus 1. The paper feed cassette 3 stores and accommodates paper P such as cut paper before printing. The sheets P are separated and sent one by one toward the upper left of the sheet feeding cassette 3 in FIG. The paper feed cassette 3 can be pulled out horizontally from the front side of the main body 2.

  A first paper transport unit 4 is provided in the main body 2 and on the left side of the paper feed cassette 3. The first paper transport unit 4 is formed substantially vertically along the left side surface of the main body 2. Then, the first paper transport unit 4 receives the paper P sent out from the paper feed cassette 3 and transports it to the transfer unit 5 vertically upward along the left side surface of the main body 2.

  A manual paper feed unit 6 is provided above the paper feed cassette 3 and on the right side, which is the side opposite to the left side of the main body 2 where the first paper transport unit 4 is formed. In the manual paper feed unit 6, paper of a size that is not in the paper feed cassette 3, or paper that is to be manually fed, such as thick paper and OHP sheets, is placed.

  A second paper transport unit 7 is provided on the left side of the manual paper feed unit 6. The second paper transport unit 7 is located immediately above the paper feed cassette 3, extends substantially horizontally from the manual paper feed unit 6 to the first paper transport unit 4, and joins the first paper transport unit 4. The second paper transport unit 7 receives the paper fed from the manual paper feed unit 6 and transports the paper to the first paper transport unit 4 substantially horizontally.

  On the other hand, a document conveying device 30 is mounted on the upper surface of the main body 2 of the image forming apparatus 1, and an image reading device 8 is mounted in the main body 2 below the main body 2. When a user copies a document, the document on which images such as characters, figures, and patterns are drawn is stacked on the document conveying device 30 or placed on a contact glass (not shown) on the upper surface of the image reading device 8. To do. The document conveying device 30 separates and sends out the documents one by one, and the image reading device 8 reads the image data. For the original on the contact glass, image data is read by scanning light within the image reading device 8.

  The reading of the document image, that is, the start of image formation is executed using the operation panel 9 provided on the front side of the image reading device 8 at the upper part of the main body 2. The user can input and set printing conditions such as the paper size used for printing, enlargement / reduction, and presence / absence of double-sided printing from the operation panel 9.

  Information on the image data of the document is sent to the exposure device 10 disposed above the second paper transport unit 7 and in the center of the main body 2. The exposure apparatus 10 irradiates the image forming unit 11 with laser light L controlled based on the image data.

  An image forming unit 11 and a transfer unit 5 are provided above the first paper transport unit 4 and on the left side of the exposure apparatus 10. In the image forming unit 11, an electrostatic latent image of a document image is formed by the laser light L emitted by the exposure device 10, and a toner image is developed from the electrostatic latent image. The toner is supplied to the image forming unit 11 from a toner container 12 provided above the exposure device 10. The toner image formed by the image forming unit 11 is transferred by the transfer unit 5 to the pre-printing paper P sent in synchronization by the first paper transport unit 4.

  A fixing device 13 is provided above the transfer unit 5. The paper P carrying the unfixed toner image in the transfer unit 5 is sent to the fixing device 13, and the toner image is heated and pressed by the heat roller and the pressure roller to be fixed.

  A sheet guide device 14 is provided above the fixing device 13. The paper P discharged from the fixing device 13 is discharged from the paper guide device 14 to the in-body paper discharge portion 15 provided in the image forming apparatus 1 when double-sided printing is not performed.

  The discharge port portion from which the paper P is discharged from the paper guide device 14 toward the in-body paper discharge portion 15 serves as a switchback portion 16. When duplex printing is performed, the switchback unit 16 switches the transport direction of the paper P discharged from the fixing device 13. Then, the paper P passes through the paper guide device 14 and is sent downward through a double-sided printing paper conveyance path 17 provided on the left side of the fixing device 13 and on the left side of the transfer unit 5, and again the first paper conveyance unit. 4 is sent to the transfer section 5.

  Further, the image forming apparatus 1 includes a main control unit 18 composed of a CPU 19 and other electronic components (not shown) in the main body 2 as shown in FIG. The main control unit 18 uses the CPU 19 as a central processing unit, and includes a document conveying device 30, an image reading device 8, an image forming unit 11, a fixing device 13 and the like based on programs and data stored and input in the storage unit 20. A series of image forming operations are realized by controlling the elements. Further, the main control unit 18 receives a condition setting related to the operation of the image forming apparatus 1 by the user from the operation panel 9.

  Next, the structure of the document conveying device 30 of the image forming apparatus 1 will be described with reference to FIGS. 3 and 4 in addition to FIG. FIG. 3 is a schematic vertical sectional front view of the document conveying device, and FIG. 4 is a detailed block diagram showing a partial configuration of the document conveying device. Note that solid arrows in the document conveyance device 30 in FIG. 3 indicate the document conveyance path and conveyance direction.

  As shown in FIG. 3, the document conveying device 30 includes a document placing tray 31, a lift plate 32, a document feeding unit 40, and a document discharge tray 33.

  The document placing tray 31 is provided on the upper portion of the document conveying device 30. Documents can be stacked and stacked on the document tray 31 from above. The document placing tray 31 is configured to be inclined downward from upstream to downstream in the document conveying direction, that is, from right to left in FIG.

  A document length detection sensor 34 is provided upstream of the document loading tray 31 in the document transport direction. The document length detection sensor 34 is a document size detection sensor, and detects the length of the document in the conveyance direction. The document length detection sensor 34 is composed of, for example, a reflection-type optical sensor. The document length detection sensor 34 emits light upward from the placement surface of the document placement tray 31, that is, toward the document, and receives the reflected light. The length in the conveyance direction is detected.

  A document width detection device 35 is provided on the downstream side of the document tray 31 in the document transport direction. The document width detection device 35 detects the width of the document that is perpendicular to the conveyance direction. The document width detection device 35 includes a movable side plate 35a and a document width identification substrate 35b. The movable side plate 35a has an electrical contact (not shown) in the document placement tray 31, protrudes upward from the placement surface, and is slidable in the document width direction. The document width identification substrate 35b is fixed in the document placement tray 31, and is arranged so that the electrical contact of the movable side plate 35a contacts a document width identification pattern (not shown) provided on the upper surface thereof. When a document is placed on the document placement tray 31 and the movable side plate 35a is brought into contact with the side edge of the document, the electrical contacts that move in the document width direction together with the movable side plate 35a slide on the document width identification pattern. The width detection device 35 detects the document width.

  The lift plate 32 is provided at the most downstream portion of the document placing tray 31. The lift plate 32 is composed of a plate-like member that extends along the placement surface of the document placement tray 31 and extends in the document transport direction and the document width direction. The lift plate 32 is provided so as to be rotatable in a vertical plane along the document conveying direction with a substantially horizontal support shaft 32a provided at the upstream portion as a center and a downstream end as a free end. The lift plate 32 is rotated and displaced about a support shaft 32a by a drive mechanism (not shown) using, for example, a solenoid when supplying the document, and the downstream end of the document stacked on the document loading tray 31 is located above the lift plate 32. It is urged upward so as to come into contact with the disposed paper feeding mechanism 42.

  A document placement detection sensor 36 is provided at the most downstream portion of the lift plate 32. The document placement detection sensor 36 detects whether or not a document is placed on the document placement tray 31. The document placement detection sensor 36 is constituted by, for example, a reflection type optical sensor, and irradiates light upward from the document placement surface of the lift plate 32, that is, toward the document, and receives the reflected light to place the document. It is detected whether it is placed.

  The document feeder 40 includes a document supply port 41 and a paper feed mechanism 42 at the downstream end of the document placement tray 31. The paper feed mechanism 42 includes a pickup roller 42a and a paper feed belt 42b. The paper feed mechanism 42 separates the originals stacked on the original placement tray 31 brought into contact with the pickup roller 42a by the lift plate 32 one by one from the uppermost layer, and the original feed section through the original supply port 41 by the paper supply belt 42b. It supplies toward the inside of 40. A first document transport path 43 extends toward the inside of the document feeding unit 40 on the downstream side of the document supply port 41.

  A document upper limit detection sensor 37 is provided at the pickup roller 42 a of the paper feed mechanism 42. The document upper limit detection sensor 37 detects that the uppermost layer of the document bundle lifted by the lift plate 32 is in contact with the pickup roller 42a and reaches the paper feed position. The document upper limit detection sensor 37 is composed of, for example, a transmissive optical sensor, and the light emitted from the light emitting portion toward the light receiving portion is shielded by a shielding plate (not shown) that moves up and down together with the pickup roller 42a. It detects that the document has reached the paper feed position.

  A conveyance state detection sensor 38 is provided immediately downstream of the paper feed mechanism 42. The conveyance state detection sensor 38 detects the conveyance state of the original, that is, the occurrence of double feeding in which the original is overlapped and sent out. The conveyance state detection sensor 38 is configured by an ultrasonic sensor in which an ultrasonic transmission unit 38a and a reception unit 38a each incorporating a piezoelectric material such as piezoelectric ceramic are arranged to face each other with the first document conveyance path 43 therebetween. ing. The conveyance state detection sensor 38 detects whether or not double feeding has occurred by identifying the strength of ultrasonic waves that attenuate as the document passes.

  A registration roller pair 44 is provided downstream of the conveyance state detection sensor 38. The registration roller pair 44 corrects the oblique feed and feeds it at a suitable timing so that accurate reading can be performed on the document going to the document reading unit 45.

  The tip of the first document conveyance path 43 reaches the bottom surface of the document conveyance device 30, and a document reading unit 45 is provided at this position. Further, following the first document conveyance path 43, a second document conveyance path 46 extends from the position of the document reading unit 45. The document sent to the document reading unit 45 moves from the first document transport path 43 to the second document transport path 46 further downstream, that is, the position of the document reading unit 45 in FIG. 3 from the left to the right. In the middle, the image data of the first surface, which is the lower surface, is read by the image reading device 8 (see FIG. 1) of the main body 2 provided therebelow.

  A document switching unit 47 is provided downstream of the document reading unit 45 in the second document transport path 46. When it is necessary to read the image data on both the front and back sides of the document, the document that has reached the document switching unit 47 is distributed above the second document transport path 46. Then, the conveyance direction is changed to the opposite direction at the document reversing section 48 that follows the document conveyance direction downstream side. The document whose transport direction has been changed passes through the upper side of the document switching unit 47 and is sent to the first document transport path 43 on the upstream side of the document reading unit 45, and the image data on the second surface is read again by the document reading unit 45.

  In addition to the method of reading the image data on both the front and back sides of the document by the document reading unit 45, the first document transport path 43 is provided with a box-shaped contact image sensor 49 provided immediately upstream of the document reading unit 45. There is also a method for reading image data on two sides. According to this, when the document passes through the area of the first document transport path 43 from the document supply port 41 to the position of the document reading unit 45, the image data on the second surface is first detected by the contact image sensor 49 first. The document reading unit 45 reads the image data on the first surface. Therefore, it is possible to read the image data on both the front and back sides of the document by only transporting the first document transport path 43 and the second document transport path 46 once without switching the document transport direction by the document reversing unit 48. .

  A document discharge port 50 is provided downstream of the document switching unit 47 and downstream of the second document transport path 46. The document whose image has been read is discharged from the document discharge port 50 to the document discharge tray 33.

  The document discharge tray 33 is provided below the document placement tray 31, and these trays are configured in two upper and lower stages. The document discharged to the document discharge tray 33 can be taken out from the front side of the document conveying device 30.

  With the above configuration, the document conveying device 30 separates the documents stacked on the document placing tray 31 one by one and feeds them into the document feeding unit 40, and the document reading unit 45 or the contact image sensor 49 reads the image data of the document. Then, it is discharged to the document discharge tray 33.

  Further, since the document conveying device 30 conveys the document from the document placing tray 31 to the document discharge tray 33 in order to read the image data of the document, as shown in FIG. Unit 55 and storage unit 56.

  The first motor 51 is used to raise and lower the lift plate 32, the second motor 52 is used for paper feeding operation by the paper feeding mechanism 42, and the third motor 53 is a fourth motor for general document transportation in the document feeding unit 40. 54 is used to switch the document transport direction in the document reversing unit 48.

  The document conveyance control unit 55 includes a CPU 57 and other electronic components (not shown), and is a control device that controls the document conveyance device 30 based on control by the main control unit 18. The document conveyance control unit 55 uses the CPU 57 as an arithmetic processing unit, and the program, data, document length detection sensor 34, and conveyance state detection sensor stored in the storage unit 20 or the storage unit 56 according to a control command from the main control unit 18. The first motor 51 to the fourth motor 54 are controlled on the basis of information from sensors such as 38 to convey the original.

  Further, as shown in FIG. 4, a filter unit 60 is provided between the document conveyance control unit 55, the document length detection sensor 34, and the conveyance state detection sensor 38. The filter unit 60 includes a first filter circuit 61 and a second filter circuit 62.

  One output signal line 57b connected to an output port 57a that is an output unit of the CPU 57 of the document conveyance control unit 55 is branched into two on the way and input to the first filter circuit 61 and the second filter circuit 62, respectively. Connected to do. Further, signal lines are connected so that signals are input to the document length detection sensor 34 via the first filter circuit 61 and to the conveyance state detection sensor 38 via the second filter circuit 62. The output signal lines 34 a and 38 a of the document length detection sensor 34 and the conveyance state detection sensor 38 are connected to input ports 57 c and 57 d of the CPU 57.

  Here, the reflection type optical sensor used for the document length detection sensor 34 may be affected by disturbance light such as a fluorescent lamp. Therefore, for example, by changing the frequency of the clock signal at regular intervals or by discontinuously transmitting, the document conveyance control unit 55 sends the clock signal at a frequency that is not easily affected by disturbance light, and detects the document length. The light emitting part of the sensor 34 is controlled to emit light in pulses. The first filter circuit 61 is a band-pass filter that passes a clock signal having a frequency for operating the document length detection sensor 34 as described above.

  As described above, the conveyance state detection sensor 38 is a so-called ultrasonic sensor that uses ultrasonic waves to detect the conveyance state of a document. For example, the document conveyance control unit 55 outputs a clock signal every time a predetermined number of the drive clocks are counted, so that the frequency of the clock signal input to the transmitter 38a of the ultrasonic sensor is, for example, several hundred kHz. Yes. The second filter circuit 62 is a band-pass filter that passes a clock signal having a frequency for operating the conveyance state detection sensor 38 as such an ultrasonic sensor.

  Next, the document conveying operation in the document conveying device 30 will be described with reference to FIG. 5 in addition to FIGS. FIG. 5 is a flowchart showing an operation related to document conveyance.

  When the power is turned on (start in FIG. 5), the document conveyance control unit 55 of the document conveyance device 30 starts outputting a clock signal having a frequency for the document length detection sensor 34 to the output port 57a (step #). 101). As a result, the clock signal passes through the first filter circuit 61 but does not pass through the second filter circuit 62. Therefore, the clock signal is input only to the document length detection sensor 34 to operate the sensor.

  Subsequently, the document conveyance control unit 55 validates the input from the document length detection sensor 34, invalidates the input from the conveyance state detection sensor 38 (step # 102), and selects signals output from these controlled members. And accept. The document conveyance control unit 55 maintains this state until the document is properly placed on the document placement tray 31 after the power is turned on (No in step # 103).

  The placement of the document on the document placement tray 31 is detected by the document placement detection sensor 36, and the detection information is transmitted to the document conveyance control unit 55 (Yes in Step # 103). Subsequently, the document conveyance control unit 55 determines the document size based on information from the document length detection sensor 34 and the document width detection device 35 (step # 104). Information relating to the document size is transmitted to the main control unit 18 by the document conveyance control unit 55, and is used for selection of printing paper. Then, the document conveyance control unit 55 determines whether or not the start key of the operation panel 9 has been pressed (step # 105).

  When the start key is pressed (Yes in step # 105), the document conveyance control unit 55 starts outputting a clock signal having a frequency for the conveyance state detection sensor 38 to the output port 57a (step # 106). As a result, the clock signal passes through the second filter circuit 62 but does not pass through the first filter circuit 61. Therefore, the clock signal is input only to the conveyance state detection sensor 38 to operate the sensor.

  Subsequently, the document conveyance control unit 55 invalidates the input from the document length detection sensor 34, validates the input from the conveyance state detection sensor 38 (step # 107), and selects signals output from these controlled members. And accept. The document conveyance control unit 55 maintains this state until the document placement detection sensor 36 no longer detects a document, that is, until there is no document on the document placement tray 31.

  Subsequently, the document conveyance control section 55 performs document double feed detection using the conveyance state detection sensor 38 (step # 108). When double feeding is detected (Yes in step # 108), the document conveyance control unit 55 stops document conveyance (step # 109). Then, the document conveyance control unit 55 or the main control unit 18 notifies that a double feed error has occurred using the operation panel 9 (step # 110), and prompts the user to process the document in the double feed state. The document feeder 30 is not usable until the double feed error is resolved (end in FIG. 5).

  On the other hand, when the double feed of the original is not detected (No in Step # 108), the double feed detection and the original transport are repeated until the original on the original placement tray 31 runs out (Step # 108 and Step # 111).

  Then, when the document placement detection sensor 36 does not detect a document, that is, when there is no document on the document placement tray 31 (No in step # 110), the document conveyance control unit 55 returns to the initial state. That is, output of a clock signal having a frequency for the document length detection sensor 34 to the output port 57a is started (step # 101).

  In this way, the output port of the CPU 57 of the document conveyance control unit 55 that outputs control signals to the two sensors of the document length detection sensor 34 and the conveyance state detection sensor 38 can be provided in one place. As a result, a general-purpose CPU can be used as the CPU 57. Of the general-purpose CPUs, a small CPU with relatively few output ports can be employed.

  In addition, by providing the filter unit 60, the CPU 57 can eliminate the need for time-sharing control of the input port that receives the signal output from the sensor. Further, by making the frequencies of the drive signals of the two sensors different from each other, there is no need to provide a signal frequency switching circuit.

  Therefore, it is possible to provide a document conveying device 30 capable of performing a stable document conveying operation while suppressing an increase in cost and an increase in size. Further, it is possible to provide a highly reliable image forming apparatus 1 equipped with such a document conveying device 30.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, in the above-described embodiment of the present invention, the image forming apparatus 1 mounted with the document conveying device 30 has been described as an example of an image forming apparatus for monochrome printing using only black toner. The image forming apparatus is not limited to such a model, but includes an intermediate transfer belt and can form an image by superimposing a plurality of colors, or a tandem type or rotary rack type image forming apparatus for color printing. It does not matter.

  Further, the plurality of controlled members that branch the output signal line 57b extending from the output port 57a of the CPU 57 and input signals are not limited to the document length detection sensor 34 and the conveyance state detection sensor 38. These sensors may be combined, or the first motor 51 to the fourth motor 54 may be combined. Further, as a method of branching the output signal line 57b, it may be branched so that signals are input to three or more controlled members.

  The present invention can be used in all document conveying apparatuses used in copying machines and the like.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body 30 Document conveying apparatus 31 Document loading tray 32 Lift plate 33 Document discharge tray 34 Document length detection sensor (controlled member, document size detection sensor)
38 Conveyance state detection sensor (controlled member)
40 Document Feeding Section 55 Document Feed Control Section (Control Section)
57 CPU
57a Output port (output unit)
57b Output signal line 60 Filter unit 61 First filter circuit 62 Second filter circuit

Claims (6)

  A control unit that branches one output signal line extending from one output unit that outputs a control signal, inputs a signal to each of the plurality of controlled members, and selects and receives signals output from the plurality of controlled members An original conveying apparatus comprising:   A plurality of filter circuits for passing signals of different frequencies are provided, and a plurality of signal lines obtained by branching one output signal line extending from the output unit are connected to the plurality of controlled lines via the plurality of filter circuits. The document conveying apparatus according to claim 1, further comprising a filter unit connected to the member.   The document conveying apparatus according to claim 1, wherein the plurality of controlled members are sensors relating to a form and / or state of a document. A document tray for stacking and storing documents;
A document size detection sensor for detecting a document size on the document tray;
A conveyance state detection sensor for detecting a conveyance state of a document conveyed from the document placement tray;
The controller for controlling the document size detection sensor and the conveyance state detection sensor;
First and second filter circuits that pass signals of different frequencies are provided, and one of the two signal lines obtained by branching one output signal line extending from the output unit of the control unit is the first signal line. The filter unit connected to input to the document size detection sensor via a filter circuit, and the other connected to input to the conveyance state detection sensor via the second filter circuit;
The document conveying apparatus according to claim 1, further comprising:   5. The document conveyance device according to claim 4, wherein the document size detection sensor is a document length detection sensor that detects a length in the document conveyance direction.   An image forming apparatus comprising the document conveying device according to claim 1.

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