JP2001031289A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten an inter-sheet distance of carrying sheets while carrying a passable sheet and a nonpassible sheet by constituting so as to switch a sheet detecting sensor for detecting the passing of the sheet rear end according to a kind of sheet. SOLUTION: A sheet detecting sensor 114 is composed of a transmissive light sensor to judge that a sheet can pass when output of the sheet detecting sensor 114 is an ON state and that the sheet cannot pass in an OFF state when the sheet carried from a separating roller 113 passes. Since the sheet detecting sensor 114 cannot be used as a sheet detecting sensor when the sheet can pass, a lever sensor 115 being a contact type detecting sensor for knowing the passing of the sheet by detecting the positional change when rotating the sheet by abutting to a lever, is arranged on the downstream side of the sheet detecting sensor 114. When using the lever sensor 115, an apparent sheet passing distance is extended by a difference distance B of a position shown by a continuous line and a broken line. When carrying a nonpassible sheet, small inter-paper distance control is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for conveying a special sheet.

[0002]

2. Description of the Related Art Conventionally, in sheet feeding and conveyance control used in an image forming apparatus represented by a copying machine,
As means for detecting the presence or absence of a sheet and the passage of a sheet,
A method has been adopted in which a lever is provided on a transport path and the operation of the lever is detected. However, this type of detection means requires a space for the lever to operate, and has the disadvantage that the apparent distance from when the sheet is detected to when the sheet is not detected is increased. there were.

[0003] This drawback does not cause a problem if the space between the conveyed sheets has a certain margin or more.
When narrowing the interval between sheets in order to improve productivity, it has become a problem that cannot be ignored. In order to solve this problem, a transmission type or reflection type optical sensor has been used as necessary.

[0004]

However, if an optical sensor is used as a means for detecting the presence or absence or passage of a sheet as described above, it is possible to detect when a transparent sheet such as an OHP sheet is conveyed. There was a problem of not being able to do so.

Accordingly, the present invention provides a copier in which small sheet gap control is performed to shorten the sheet gap of a sheet to be conveyed, and achieves both high productivity when conveying both types of transparent sheets and non-transparent sheets. It is an object of the present invention to provide an image forming apparatus having the above configuration.

[0006]

In order to solve the above-mentioned problems, a typical configuration of an image forming apparatus according to the present invention includes image forming means for forming an image on a sheet, conveying means for conveying the sheet, At least two sheet detection sensors for detecting the presence or absence or passage of a sheet, and a sheet type detection sensor for detecting a type of the sheet, wherein the sheet detection sensor is provided in accordance with a detection result of the sheet type detection sensor Is selected, and the conveyance of the sheet is controlled by the selected sheet detection sensor.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an image forming apparatus according to the present invention will be described with reference to the drawings. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a control block diagram in the image forming apparatus, FIG. 3 is a block diagram of an image processing unit, and FIG.
Is a block diagram of an image memory unit, FIG. 5 is a configuration diagram of an external I / F processing unit, FIG. 6 is a diagram showing an operation unit, FIGS. 7 and 8 are diagrams showing display examples of a display panel, and FIG. FIG. 10 is a flow chart for explaining an image forming operation. In the present embodiment, a description will be given using a copying machine having an image reading unit and an image forming unit as an image forming apparatus.

(Entire Apparatus Configuration) An image forming apparatus 1 shown in FIG. 1 includes an automatic document feeder 2 for continuously conveying a sheet for reading an image, a deck 3 for feeding a sheet for recording an image, and an image recording apparatus for recording an image. And a post-processing device 4 for performing a predetermined process on the discharged sheet.

The image forming apparatus 1 has a platen glass 10 including a scanner 11, a document certification lamp 12, scanning mirrors 13 to 15, and the like at an upper portion. Scanner by motor not shown
11 is reciprocally scanned in a predetermined direction, a document certificate lamp 12 irradiates a light beam on a document placed on the platen glass 10, and the reflected light is transmitted through a lens 16 via scanning mirrors 13 to 15 to cause a CCD sensor 17 to scan. Image.

The CCD sensor 17 converts the formed image into an electric signal and sends it to the exposure control unit 18. The exposure control unit 18 is provided with a laser oscillator and a polygon scanner, and irradiates the photosensitive drum 21 of the image forming unit 20 with a laser beam 19 modulated by performing predetermined image processing described later. Around the photosensitive drum 21, a primary charger 22, a developing unit 23, a transfer charger 24, a separation charger 25, a cleaning device 26, and a pre-exposure lamp 27 are arranged.

In the image forming unit 20, the photosensitive drum 21 is charged by a motor (not shown) to a sensing potential, and is charged to a desired potential by a primary charger 22, and then irradiated with a laser beam 19 from an exposure control unit 18 to form an electrostatic latent image. Is formed. The electrostatic latent image formed on the photosensitive drum 21 is developed by the developing device 23 and is visualized as a toner image.

On the other hand, a sheet as a recording medium is loaded on the upper cassette 28 and the lower cassette 31 in a lower portion of the image forming apparatus 1 and is sent out by pickup rollers 29 and 32. Each of the fed sheets has a separation roller pair 3
Separated one by one by 0, 33
4 transports to the transport belt 34.

The sheets are also supplied from a deck 3 provided on the side of the apparatus. The deck 3 can store, for example, 4000 sheets, and the lifter 50 is configured to rise according to the amount of stacked sheets, and to always contact the feed roller 51. The upper portion of the deck 3 has a manual feeding portion 52 capable of storing about 100 sheets.

The toner image visualized by the transfer charger 24 is transferred to the sheet fed from the cassette 28, 31 or the deck 3. After the transfer, the photosensitive drum 21 is cleaned of residual toner by the cleaning device 26, and residual charge is removed by the pre-exposure lamp 27. The sheet after the transfer is separated from the transport belt 34, the toner image is recharged by pre-fixing chargers 35 and 36, sent to a fixing device 37, and pressurized.
The toner is fixed by heating, and is discharged by a discharge roller 38.

A discharge flapper 39 for switching the transport path is provided downstream of the discharge roller 38. The discharge flapper 39 switches between the case of discharging to outside the apparatus and the side of re-feeding. When the paper is discharged outside the apparatus, the paper is discharged to the post-processing device 4 by a discharge roller 40 provided near the discharge flapper 39.

The re-feeding is performed to process double-sided recording and multiplex recording. After the sheet whose transport path has been switched to the re-feeding side by the discharge flapper 39 passes through the feed roller 41, the reverse path 44 or the lower transport path 45 is switched by the multiplex flapper 42 which switches the transport path for double-sided recording and multiplex recording.
Leading to.

When performing double-sided recording, the sheet is guided to the reversing path 44 by the multiplex flapper 42, and after the rear end of the sheet passes through the multiplex flapper 42, the rotation direction of the reversing roller 43 is reversed, and the sheet is reversed. It is transported to the transport path 45. On the other hand, when performing multiplex recording, the sheet is directly conveyed to the lower conveyance path 45 by the multiplex flapper 42. The sheets conveyed to the lower conveyance path 45 are stacked on a re-feeding tray 46, and the sheets are re-supplied one by one from below via a path 48 by a re-feeding roller 47.
Re-sent to 21.

When the sheet is inverted and discharged to the post-processing device 4, the sheet on which the image is formed is first conveyed to a reversing path 44, and after the rear end of the sheet passes the feed roller 41, the reversing roller 43 To reverse the sheet and return
Discharge the sheet by 40.

The post-processing device 4 staples and punches the sheets discharged from the image forming apparatus 1, and stacks the discharged sheets one by one on the processing tray 53 for alignment. When the discharge of a part of the image formation is completed, the sheet bundle is subjected to processing such as stapling, and then the discharge tray 54,
Discharge to 55. The discharge trays 54 and 55 are controlled to move up and down by a motor (not shown), and the discharge tray used before the start of the image forming operation moves to a position corresponding to the processing tray 53.

(Apparatus Control Configuration) FIG. 2 is a control block diagram in the image forming apparatus 1. The image forming apparatus 1 includes a CPU 60 for performing basic control and a ROM 6 in which a control program is written.
1, having a RAM 62 or the like which is a memory for performing processing,
An input / output port 63 is connected to the CPU 60 via an address bus and a data bus. The input / output port 63 is connected to various load devices such as a motor and a clutch for controlling the image forming apparatus 1 and input devices such as a sensor for detecting a position of a sheet.

The CPU 60 controls input / output sequentially through the input / output port 63 according to the absence of the ROM 61, and executes an image forming operation. The operation unit 5 is connected to the CPU 60, and controls a display unit and a key input unit of the operation unit 5. The operator instructs the CPU 60 to switch the image forming mode and display through the key input unit, and the CPU 60 displays the state of the image forming apparatus 1 and the operation mode setting by key input. The CPU 60 is connected to an image processing unit 64 that processes a signal converted into an electric signal by the CCD sensor 17 and an image memory unit 65 that stores a processed image.

(Image Processing Unit) Referring to FIG.
64 will be described in detail. As shown in the figure, through the lens 16
The document image formed on the CCD sensor 17 is input as black luminance data, and is converted into an analog electric signal by the CCD sensor 17. The converted image information is input to an analog signal processing unit (not shown),
After dark level correction, etc., the A / D converter 66
Performs shading correction (correction of variations in a sensor for reading a document and orientation characteristics of a document illumination lamp).

Thereafter, the image information is input to the Log conversion unit 67. The Log conversion unit 67 stores an LUT (Look Up Table) for converting the input density data into density data, and outputs a data value corresponding to the input memory address by outputting the data value. And converts the luminance data into density data. After that, the image is scaled to a desired magnification by the scaling processing unit 68 and input to the γ correction unit 69. When outputting the density data, the γ correction unit 69 performs conversion using an LUT in consideration of the characteristics of the printer, and adjusts the output according to the density value set by the operation unit 5.

Thereafter, the data is input to the binarizing unit 70. Binarization section
At 70, the standing density data is binarized and the density is 0 or 2
It becomes 55. 8-bit image data is binarized to 0 or 1
The image data is converted into 1-bit image data, and the amount of image data stored in the memory is reduced. However, when the image is binarized, the number of gradations of the image is changed from 256 to 2 gradations. Therefore, image data having a large number of halftones such as a photographic image generally has a remarkable deterioration in image quality. Therefore, it is necessary to perform pseudo halftone expression using binary data. Here, an error diffusion method is used as a method of pseudo-halftone expression using binary data.

In the error diffusion method, if the density of a certain image is larger than a certain threshold, it is determined that the density data is 255. In this method, a difference between data and binarized data is distributed to surrounding pixels as an error signal.
The distribution of the error is performed by multiplying a weight coefficient on a matrix prepared in advance by the error generated by the binarization, and adding the result to surrounding pixels. As a result, the average density value of the entire image is stored, and the halftone can be represented in a pseudo binary manner. The binarized image data is sent to the image memory unit 65 and accumulated.

The image data input from the computer via the external I / F processing unit 71 is sent to the image memory unit 65 as it is for processing by the external I / F processing unit 71 as binary image data. The image memory section 65 has a high-speed page memory and a hard disk as a large-capacity memory capable of storing a plurality of page image data. The plurality of image data stored in the hard disk are output in an editing mode specified by the operation unit 5 of the image forming apparatus 1, for example, in an order according to a sorting instruction.

Also, image data of a document once stored in the hard disk can be read and output a plurality of times. Thus, a plurality of sets of images can be formed, and the same role as a sorter having a plurality of bins can be performed. The image data output from the image memory unit 65 is sent to a smoothing unit 73 in the printer unit 72. The smoothing unit 73 complements the data so that the line end of the binarized image becomes smooth, and outputs the image data to the exposure control unit 18. The exposure controller 18 forms an electrostatic latent image on the photosensitive drum 21 according to the image data as described above.

(Image Memory Unit) The image memory unit 65 will be described in detail with reference to FIG. The image memory unit 65 writes a binary image from the external I / F processing unit 71 and the image processing unit 64 via a memory controller 75 to a page memory 74 composed of a memory such as a DRAM, and writes the image to the printer unit 72. Start reading
The compression unit 76 accesses the hard disk 77, which is a large-capacity storage device, for image input / output while compressing and expanding data. The memory controller 75
A DRAM refresh signal is generated, and access to the page memory 74 from the external I / F processing unit 71, the image processing unit 64, and the hard disk 77 is adjusted. Further, in accordance with an instruction from the CPU 60, it controls a write address to the page memory 74, a read address from the page memory 74, a read direction, and the like. As a result, the CPU 60 arranges a plurality of original images in the page memory 74 to lay out the
72, a function of cutting out and outputting only a part of an image, and an image rotation function.

(External I / F Processing Unit) Referring to FIG.
The configuration of the processing unit 71 will be described. As described above, the external I / F processing unit 71 fetches the binary image data of the reader unit 84 into the external I / F processing unit 71 via the image memory unit 65, and also receives the external I / F via the image memory unit 65. The binary image data from the F processing unit 71 is output to the printer unit 72 to form an image.
The external I / F processing unit 71 includes a core unit 78 and a facsimile unit 79, a hard disk 80 for storing communication image data of the facsimile unit 79, a computer interface unit 81 connected to the computer 9, a formatter unit 82, an image memory unit.
Has 83.

The facsimile unit 79 is connected to a telephone line via a modem (not shown), and receives facsimile communication data from the telephone line and transmits facsimile communication data to the telephone line. The facsimile unit 79 stores a facsimile image on the hard disk 80 and performs processing, such as performing facsimile transmission at a specified time or transmitting image data in response to a specified password inquiry from a partner. Thus, once the image is transferred from the reader unit 84 to the facsimile unit 79 and the facsimile hard disk 80 via the image memory unit 65, the image is transmitted again without using the reader unit 84 and the image memory unit 65. Can be.

The computer interface section 81 is an interface section for performing data communication with an external computer, and includes a local area network (hereinafter referred to as a LAN), a serial I / F, a SCSI I / F, and a Centronics I / F for inputting data to a printer. F and so on. Via this I / F, the statuses of the printer unit 72 and the reader unit 84 are notified to the computer 9, an image read by the reader unit 84 is transferred to the computer 9 by an instruction of the computer, and image data is transmitted from the computer 9. Or receive it.

Since the image data notified from the computer 9 via the computer interface unit 81 is described in a dedicated printer code, the formatter unit 82
Converts the code into raster image data for forming an image in the printer unit 72 via the image memory unit 65. The formatter unit 82 develops the raster image data in the image memory unit 83. The image memory unit 83 is used as a memory in which the formatter unit 82 expands raster image data, or when the image of the reader unit 84 is sent to an external computer via the computer interface unit 81 (image scanner function). , Image memory section
It is also used when the image data sent from 65 is once expanded in the image memory unit, converted into the format of data to be sent to the computer 9, and sent out from the computer interface unit 81.

The core unit 78 controls and manages data transfer among the facsimile unit 79, the computer interface unit 81, the formatter unit 82, the image memory unit 83, and the image memory unit 65. Thus, when the external I / F processing unit 71 has a plurality of image output units, even if there is only one image transfer path to the image memory unit 65, exclusive control and priority control under the management of the core unit 78 are performed. Control is performed and image output is performed.

(Operation Unit) The image forming apparatus 1 will be described with reference to FIG.
The operation unit 5 for setting the copying operation and the like will be described.
In FIG. 6, a power switch 85 is provided on the operation unit 5, and a power lamp 86 is turned on and off in accordance with the ON / OFF switching of the power supply. The ten keys 87 are used to set the number of images to be formed and to input numerical values for mode setting, and are used to input a telephone number on the facsimile setting screen. Similarly, a clear key 88 for clearing the settings input with the ten keys 87, a reset key 89 for returning the set number of image formation and operation mode, and a selected feeding stage to a specified value, a start key 90 for starting an image forming operation, an image A stop key 91 for stopping the forming operation is provided. An LED 90a is provided at the center of the start key 90 to indicate whether an image can be formed. The LED 90a lights up in green when image formation is possible, and lights up in red when image formation is not possible.

When the guide key 92 is depressed and another key is depressed, a description of a function which can be set by that key is displayed on the display panel 95. To release the guide display, the guide key 92 is pressed again. By pressing the user setting key 93, the user can change the settings of the image forming apparatus. The settings that can be changed by the user include, for example, the time until the settings are automatically cleared, the setting of the mode default value when the reset key 89 is pressed, and the like. When the interrupt key 94 is pressed during the image forming operation, the other image forming operations are stopped, and the image can be formed without using the automatic document feeder 2.

The display panel 95 is composed of a liquid crystal or the like, and the display contents are changed according to the setting mode in order to facilitate detailed mode setting. Further, the surface of the display panel 95 is a touch sensor, and a mode can be set by touching a displayed key. FIG. 6 shows an example of a copy operation mode setting screen. For example, a paper selection key 96 for selecting a sheet stage sets which of the cassettes 28 and 31 is to be fed, and a magnification setting key 97 to 100
Sets the copy magnification of the copy operation. Advanced mode key 101
When is pressed, a screen for setting the mode of the application function such as the multiplexing operation, the reduced layout mode, the cover page, and the slip sheet mode is displayed on the display panel 95 as shown in FIG. 7, and these can be set.

A two-sided operation setting key 102 is a "one-sided mode" for performing duplex output from a one-sided original, a "two-sided mode" for performing dual output from a two-sided original, and a "one-sided output for two sheets from a two-sided original" The setting of three types of double-sided mode of "two-sided mode" is performed. The sort key 103 sets the operation mode of the post-processing device 4 and sets the output paper sorting mode using the image memory. In addition to the normal display, if the display key mode cannot be set, the display line is displayed as a dotted line (shaded) to indicate that the key cannot be operated. Has become.

In the example shown in FIG. 6, the contents of the set copy operation and the current operation state are displayed above the display panel 95. Further, at the upper left of the display panel 95, there is a display indicating which screen of this function screen is in each of the function modes to be described later. In the figure, a setting screen of “copy A” is shown. Instead of displaying characters, symbols indicating each mode may be used. Further, below the display panel 95, the operation state of another function mode to be described later is displayed in a range that can be displayed in one line, and in the drawing, it is indicated that the copy B is being output to the printer unit 72. I have.

A key that can be changed by the user is provided next to the application mode key 101 in the display panel 95, and up to two function keys that can be set on the application mode setting screen can be registered. By displaying the application mode setting key at the position shown in the figure, the registered mode setting can be performed more easily. These keys are collectively referred to as registration keys, and their settings will be described with reference to FIG.

FIG. 8A is a screen for setting items of the first registration key 105. This screen is displayed by pressing the user setting key 93 and then selecting the setting of the registration key 1 in the setting item. Select an item on the screen shown in Fig. 8 (a) and press the OK key 10.
By pressing 4, the function displayed on the first registration key can be selected. In this way, as shown in FIG. 8B, the first registration key 105 and the second registration key 106 are selected and displayed on the display panel 95.

In FIG. 6, a function switching key 10 is used to change the display on the display panel 95 for setting various functions such as a copying operation and a system operation using the image forming apparatus 1.
7 to 110, specifically, copy A key 107, copy B key 10
8. A fax key 109 and a printer key 110 are provided. These keys are composed of translucent buttons, and have display lamps such as LEDs (not shown) inside, and when these keys are pressed, the lamps inside the keys corresponding to the operation screen are turned on. ing. As for the lamp inside each key, only the selected key lights up,
The other keys are controlled to be turned off.

On the right of each key, green LEDs 107b-11
0b is arranged, and the operation status of each function is represented by LED lighting control. For example, the LED 108b of the copy B key 108 is controlled to be turned off while the copy B is in the standby state, and is controlled to blink when the copy B is in the output operation as in the example of FIG. Is stored, and the lighting is controlled when the image formation of the copy B is not performed. Similarly, for example, LED10 of Faxski 109
In 9b, the flashing is controlled during the communication operation, the image formation, and the reading operation, and the lighting control is performed when the facsimile unit 79 has a fax image on the hard disk 80.

Red LEDs 107a-11 are located to the left of each key.
0a is arranged to indicate that the above-mentioned situation of each function has occurred by lighting control. For example, the LED 108a of the copy B is controlled to blink when the copy B is interrupted due to no paper or a jam occurs. At this time, by pressing the copy B key 108 and switching the display panel 95 to copy B, the display panel
The status of copy B is displayed at 95, and the details of the status can be confirmed. These function switching keys can be pressed at any time regardless of the operation status of each function, and the display panel 95 can be switched.

Therefore, when the copy A function and the copy B function can be switched as in this embodiment, the keys outside the display panel 95 such as the reset key 89, the start key 90, the stop key 91, etc. The keys 107 to 110 are operated for the function selected. For example, even if the stop key is pressed while the copy A operation screen is displayed in FIG. 6, the image forming operation cannot be stopped for the copy B output operation. To stop the image forming operation of the copy B, the user can stop by pressing the stop key 91 after pressing the copy B key 108. The data set by the user setting key 93 is held in each of the modes in which the copy A and copy B operation units are selected, and the setting operation can be performed independently.

(Sheet Conveying Control) Next, with respect to the sheet conveying control according to the feature of the present invention, the control when the sheet is fed from the manual feeding section 52 will be described. Fig. 9 (a) shows the manual feeding section
FIG. 52 is an enlarged configuration view of FIG. 52, in which sheets stacked on a sheet stacking tray 111 are fed by a pickup roller 112, and separated and fed one by one by a separation roller 113.

On the downstream side of the separation roller 113, a sheet type detection sensor 114 for identifying the type of the conveyed sheet is provided. The sheet detection sensor 114 is configured by a transmission type optical sensor, and when the sheet conveyed from the separation roller 113 passes, the output of the sheet detection sensor 114 is in an ON state (a state where light is transmitted).
If it is, it can be determined that the sheet is transmissive (such as an OHP sheet), and if it is in the OFF state (a state that blocks light), it can be determined that the sheet is non-transmissive. Further, the sheet detection sensor 114 can be used as a sheet detection sensor when the sheet is non-transparent, and thus is used as a second detection sensor as described later.

Further, a lever sensor 115, which is a contact-type first detection sensor, is provided downstream of the sheet detection sensor 114. The lever sensor 115 detects passage of the sheet by detecting a change in the position of the sheet when the sheet is rotated by contacting the lever. As shown in FIG. 9B, the lever sensor 115 includes a lever 116 rotatably supported and a photo interrupter 117. When the sheet passes, it comes into contact with the lever 116 and rotates from the position shown by the solid line to the position shown by the broken line. Then, the optical path of the photo-interrupter 117 at the end 116a of the lever 116 is interrupted, and the passage of the sheet is detected. As described above, when the lever sensor 115 is used, the apparent sheet passing distance is extended by the difference distance B between the position indicated by the solid line and the position indicated by the broken line.

Therefore, in the present embodiment, sheet conveyance control is performed as shown in FIG. First, the start key for image formation
The process waits until 90 is pressed (S1), and when the copy key is pressed, feeding of the manual feeding unit 52 is started (S2).
Then, the control waits until the contact-type lever sensor 115 detects the leading edge of the sheet (S3).
It is detected whether the type of the sheet is an OHP sheet or not (S4).

If the sheet is an OHP sheet, the trailing edge detection sensor flag is set as a lever sensor (S
5) Otherwise, the rear end detection sensor flag is set to the optical sensor (S6). Next, the means for detecting the passage of the trailing edge of the sheet is switched based on the trailing edge detection sensor flag described above (S7). If the trailing edge detection sensor flag is a lever sensor, the control waits until the lever sensor 115 detects the trailing edge of the sheet (S8). If the trailing edge detection sensor flag is an optical sensor, the sheet detecting sensor 114 determines the trailing edge of the sheet. Wait for detection (S9).

Further, it is determined whether or not the type of the sheet is an OHP sheet (S10). If the type is an OHP sheet, the inter-paper distance is set wider than a normal interval (S11). The interval is set to a normal short interval (S12), and the feeding of the next sheet is waited for a time corresponding to the sheet interval.

That is, considering the transport of the OHP sheet, the sheet detection sensor 114 of the optical sensor cannot be used as a means for detecting the trailing edge of the sheet.
The contact type lever sensor 115 will be used. However, when the lever sensor 115 is used, as shown in FIG. 9B, the lever 116 rotates after the rear end of the sheet S passes and the lever operates until the lever sensor 115 is turned off. A detection loss occurs for the distance. Therefore, if the sheet is conveyed at an interval shorter than this distance, the lever remains in the ON state, and it becomes impossible to detect the sheet rear end.

Therefore, in the present invention, as a means for detecting the passage of the rear end of the sheet, the lever sensor 115 is used in the case of an OHP sheet, and the sheet detection sensor 114 which is an optical sensor is used in the case of other sheets. By doing
When a sheet other than the OHP sheet is conveyed, it is possible to perform small sheet interval control for further shortening the sheet interval.

Thereafter, it is determined whether the set number of sheets has been completed (S13). If the set number has been completed, the flow returns to step S2 to feed the next sheet.

Further, in this embodiment, the type of sheet is automatically detected by the sensor. However, the type of sheet can be designated in advance from the operation unit, and the sheet detection sensor can be selectively used based on the designation.

[0055]

As described above, according to the image forming apparatus of the present invention, the sheet detection sensor for detecting the passage of the trailing edge of the sheet is switched according to the type of the sheet. Since both types of transparent and non-transparent sheets can be conveyed, the distance between the conveyed sheets can be shortened.
An image forming apparatus that achieves both productivity and compatibility with various types of sheets can be provided.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a control block diagram in the image forming apparatus.

FIG. 3 is a block diagram of an image processing unit.

FIG. 4 is a block diagram of an image memory unit.

FIG. 5 is a configuration diagram of an external I / F processing unit.

FIG. 6 is a diagram illustrating an operation unit.

FIG. 7 is a diagram illustrating a display example of a display panel.

FIG. 8 is a diagram illustrating a display example of a display panel.

FIG. 9 is a diagram illustrating a configuration of a feeding unit.

FIG. 10 is a flowchart illustrating an image forming operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Automatic original feeder 3 ... Deck 4 ... Post-processing apparatus 5 ... Operation part 9 ... Computer 10 ... Platen glass 11 ... Scanner 12 ... Original certification lamp 13-15 ... Scanning mirror 16 ... Lens 17 ... CCD Sensor 18 Exposure control unit 19 Laser beam 20 Image forming unit 21 Photoconductor drum 22 Primary charger 23 Developing unit 24 Transfer charger 25 Separation charger 26 Cleaning device 27 Pre-exposure lamp 28 Upper cassette 29… Pickup roller 30… Separation roller pair 31… Lower cassette 32… Pickup roller 33… Separation roller pair 34… Conveyer belt 35… Charger before fixing 36… Charger before fixing 37… Fixer 38… Discharge roller 39… Discharge flapper 40… Discharge roller 41… Feed roller 42… Multiple flapper 43… Reversing roller 44… Reversing path 45… Lower conveying path 46… Refeed tray 47… Refeed roller 48… 50 Lifter 51 Feed roller 52 Manual feed unit 53 Processing tray 54 Eject tray 55 Eject tray 60 CPU 61 ROM 62 RAM 63 I / O port 64 Image processing unit 65 Image memory Section 66 A / D conversion section 67 Log conversion section 68 Magnification processing section 69 Gamma correction section 70 Binarization section 71 External I / F processing section 72 Printer section 73 Smoothing section 74 Page memory 75 ... Memory controller 76 ... Compression unit 77 ... Hard disk 78 ... Core unit 79 ... Facsimile unit 80 ... Hard disk 81 ... Computer interface unit 82 ... Formatter unit 83 ... Image memory unit 84 ... Reader unit 85 ... Power switch 86 ... Power lamp 87 ... Numeric keys 88… Clear key 89… Reset key 90… Start key 90a… LED 91… Stop key 92… Guide key 93… User setting key 94… Key 95… Display panel 96 Paper selection key 97-100… Magnification setting key 101… Application mode key 102… Duplex operation setting key 103… Sort key 104… OK key 105… First registration key 106… Second registration key 107… Copy A key 108… Copy B key 109 ... Fax key 110 ... Printer key 111 ... Sheet loading tray 112 ... Pickup roller 113 ... Separation roller 114 ... Sheet detection sensor 115 ... Lever sensor 116 ... Lever 116a ... End 117 ... Photo interrupter

Claims (5)

[Claims] 1. An image forming means for forming an image on a sheet, a conveying means for conveying a sheet, at least two sheet detection sensors for detecting the presence or absence or passage of a sheet, and an apparatus for detecting a type of the sheet An image having a sheet type detection sensor, wherein the sheet detection sensor is selected according to a detection result of the sheet type detection sensor, and sheet conveyance is controlled by the selected sheet detection sensor. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the selected sheet detection sensor is used as a unit that detects passage of a trailing edge of the sheet. 3. The at least two sheet detection sensors are a contact-type first detection sensor and a second detection sensor including a transmission type or reflection type optical sensor, wherein the sheet type detection sensor is the sheet type. 2. The image forming apparatus according to claim 1, wherein when detecting that the sheet is transparent, the first detection sensor is selected to control the conveyance of the sheet. 4. The sensor according to claim 3, wherein the second detection sensor and the sheet type detection sensor are the same sensor.
The image forming apparatus as described in the above. 5. The image forming apparatus according to claim 1, wherein a conveyance interval of the sheet is changed according to a detection result of the sheet type detection sensor.