JP4392306B2 - Document feeder for image forming apparatus and image forming apparatus provided with the same - Google Patents

Description

  The present invention relates to a document feeder of an image forming apparatus, and an image forming apparatus including such a document feeder.

  In recent years, an image forming apparatus having a copying function has been mainly provided with an automatic document feeder (ADF) for feeding a document to a document reading position. The ADF is arranged to oppose the document reading unit provided at the upper part of the main body, and has a document placing unit, and the documents placed on the document placing unit are one by one in the document reading unit. Paper is fed to the original reading position.

  A conventional ADF having a lift plate on which a document is set and can be moved up and down in the stacking direction has already been proposed. The lift plate normally stands by at a lower position when a document is not set, and can stand by at an upper position where the leading end of the document contacts the paper feed roller when the document is set.

  As such an ADF, there is known a type in which the lift plate rises after the start button of the main body unit instructing reading of the document is pushed, but the lift plate rises after pushing the start button. It takes time to start printing.

  In view of this, a type has been proposed in which the lift plate is raised immediately after placing a document to prepare for a printing operation. In this case, the document reading is started immediately after the start button is pressed.

In addition, there exists a technique shown by patent documents 1 thru | or 4 as a thing relevant to the above techniques, for example.
JP 11-237770 A Japanese Patent Laid-Open No. 11-352608 JP 2000-95359 A Japanese Patent Laid-Open No. 2000-60067

  However, in the conventional ADF, the leading edge of the document is in contact with the paper feed roller without any gap, so that the document that has been set once is reset (reset) or the document is added later and loaded. It becomes difficult to do.

  SUMMARY OF THE INVENTION An object of the present invention is to make it easy to add or reset a document in an image forming apparatus capable of reducing the time required from a printing instruction to a printing operation.

A document feeding device according to a first aspect is a document feeding device of an image forming apparatus for feeding a document toward a document reading position, and includes a document placement unit, a sheet feeding unit, an upper limit sensor, And a detecting means and a lift plate driving section. The document placement unit has a lift plate on which a document can be placed and which can move up and down in the document stacking direction. The paper feed unit is disposed at an upper interval with respect to the lift plate disposed at the lowermost position, and is movable upward following the force received from below by the lift plate. The upper limit sensor detects that the lift plate has moved up and the document on the lift plate has pushed up the paper feed unit. The detecting means can detect an upward pressure on the paper feeding unit in a state where the upper limit sensor detects that the paper feeding unit has been pushed up . The lift plate driving unit lowers the lift plate so that a space is formed between the document placed on the document placement unit and the paper feed unit when an upward pressure on the paper feed unit is detected. .

  In this apparatus, when the lift plate is raised in a state where the document is set, the lift plate can be fed in a state in which the lift plate is in contact with the paper feed unit through the document or the paper feed unit is pushed up (paper feedable state). Thus, there is no gap between the document and the paper feeding unit. In this state, if an attempt is made to add another document and another document is pushed between the already set document and the lift plate, the paper feed unit is pushed upward, and the lift is detected when this is detected. The board goes down. As a result, a space is generated between the document and the paper feed unit, and the document can be easily added or reset.

  Therefore, here, it is possible to add or reset a document as necessary while shortening the time from the print instruction to the start of printing.

  In the present invention, the movement of the lift plate is not limited to the parallel movement in the stacking direction. For example, the lift plate moves on the rear end portion (upstream side in the transport direction) of the lift plate as a fulcrum. This also includes vertical movements. Therefore, the term “above or below” includes not only the vertical direction but also an oblique direction if it is above or below the reference position. Further, the force on the sheet feeding unit includes, for example, a pressure on the sheet feeding unit.

  According to a second aspect of the present invention, there is provided the document feeder according to the first aspect, wherein the detecting means is a pressure sensor capable of detecting an upward pressure with respect to the paper feeding unit.

  In this apparatus, specifically, the lift plate is lowered by detecting the pressure acting on the sheet feeding unit by the pressure sensor.

  The document feeder according to a third aspect is the apparatus according to the second aspect, wherein the pressure sensor can detect the magnitude of the pressure. The lift plate driving unit lowers the lift plate by a distance corresponding to the magnitude of the pressure detected by the pressure sensor.

  In order to add a large number of thick originals, a considerable space is required between the lift plate and the paper feed unit. When such a document is added, a large pressure is applied to the paper feed unit. Therefore, in this apparatus, an appropriate space is formed between the lift plate and the paper feeding unit by changing the lowered width of the lift plate according to the magnitude of the pressure.

  According to a fourth aspect of the present invention, there is provided the document feeder according to any one of the first to third aspects, wherein the lift plate driving unit further detects the force acting on the lift plate and then further lifts the lift plate. The lift plate is raised when a predetermined time has elapsed without detecting the force acting upward.

  In this apparatus, when a document is not added for a predetermined time and a force on the sheet feeding unit is not detected, the lift plate that is lowered is basically raised so that the sheet can be fed.

  An image forming apparatus according to a fifth aspect includes the document feeder of the image forming apparatus according to any one of the first to fourth aspects, and a main body having a document reading unit and an image forming unit. The document reading unit is arranged to face the document feeding device and reads image information of the document. The image forming unit forms an image based on the image information read by the document reading unit.

  Since this image forming apparatus is provided with the above document feeder, it is possible to add or reset a document if necessary while shortening the time from the start of printing to the actual start. Become.

  According to the present invention, it is possible to add or reset a manuscript as necessary while shortening the time from the print instruction to the start of printing.

[Entire configuration of image forming apparatus]
1 and 2 show an image forming apparatus 1 in which an embodiment of the present invention is adopted.

  The image forming apparatus 1 is a multifunction machine having functions as a copying machine, a printer, a facsimile machine, and a scanner, and includes a main body 13 and an ADF 11.

  The main body 13 includes a document reading unit 21, an operation panel 23, an image forming unit 25, a control unit 27, a memory 28, and another input / output unit 29.

The document reading unit 21 is for reading an image of a document on a document table (not shown).
It is provided on the upper part of the main body 13 so as to oppose the ADF 11.

  The operation panel 23 includes a plurality of operation keys 23a and a display unit 23b configured with a touch panel type liquid crystal display. The plurality of operation keys 23a include a start key for instructing printing and a numeric keypad for inputting numerical values.

  The image forming unit 25 forms an image based on the image information read by the document reading unit 21, and includes a photosensitive drum and a charging device, an exposure device, a developing device, a transfer device, and the like disposed around the photosensitive drum. And a fixing device (both not shown) arranged on the downstream side thereof.

  The control unit 27 includes a microcomputer including a CPU and the like, and controls input / output units such as the ADF 11 and the document reading unit 21. The control unit 27 has a timer function and counts a predetermined time described later.

  The memory 28 includes a RAM and a ROM, and stores various control programs executed by the control unit 27.

  The main body unit 13 includes, as another input / output unit 29, a communication unit for communication with an externally connected device such as a personal computer or a facsimile, a sheet feeding unit that feeds sheets one by one from a sheet feeding cassette, The image forming unit 25 further includes a paper discharge unit (none of which is shown) that discharges the paper on which the image is formed.

[Configuration of document feeder]
As shown in FIGS. 2 and 3, the ADF 11 is a device for feeding a document toward the document reading position R, and includes a document placement unit 31, a paper feed unit 32, a pressure sensor (detection means). ) 33, a lift plate driving unit 35, and a document discharge tray 37.

  The document placing unit 31 includes a lift plate 41, an upper limit sensor 43, a lower limit sensor 45, and a document set detection sensor 47.

  The lift plate 41 is a plate-like member on which a document can be placed, and can be moved to the upper limit in the sheet stacking direction by the lift plate driving unit 35.

  The upper limit sensor 43 is a sensor for stopping the lift plate 41 from rising at a predetermined position, and is composed of an optical sensor. The upper limit sensor 43 is optically detected and stopped when the lift plate 41 rises and a document on the lift plate 41 pushes up a paper feed roller 51 (described later).

  The lower limit sensor 45 is a sensor for detecting that the lift plate 41 has been lowered to the lowest position.

  The document set detection sensor 47 is a sensor for detecting that a document is set on the lift plate 41, and includes a light emitting unit 47a and a light receiving unit 47b, and the document blocks light emitted between them. Thus, it is detected that the document is set.

  The paper feed unit 32 is for feeding a document on the lift plate 41, and includes a paper feed roller (paper feed unit) 51 and a separation roller 53.

  The sheet feeding roller 51 is disposed at an upper interval with respect to the lift plate 41 disposed at the lowest position, and is positioned at a lower position by its own weight in a free state, but receives a force from below by the lift plate 41. Following the above, it is configured to be movable upward. As a result, when the lift plate 41 is in a feedable state, the paper feed roller 51 comes into contact with the leading end of the document set on the lift plate 41, and when the start button is pressed, the paper feed roller 51 is moved to the document reading position R. Documents can be fed to the front.

  The separation roller 53 is used to prevent a double feed by feeding a document fed by the paper feed roller 51.

  The pressure sensor 33 can detect the magnitude of the upward pressure on the paper feed roller 51. Specifically, when an attempt is made to add more documents to the document on the lift plate 41 that is ready to feed or to reset a document already set on the lift plate 41, The pressure that pushes up 51 can be detected.

  The lift plate drive unit 35 is for moving the lift plate 41 up and down, and includes a stepping motor, a rack and pinion mechanism, and the like. The lift plate 41 is variously controlled by the control unit 27. Specifically, as soon as a document is set on the lift plate 41, the lift plate 41 is raised, and when pressure is detected by the pressure sensor 33 in a state where paper can be fed, it corresponds to the size. The lift plate 41 is lowered by the lowering width. Further, the lift plate driving unit 35 raises the lift plate 41 when a predetermined time (for example, about several seconds) elapses without further pressure being detected in a state where the lift plate 41 is lowered (standby state).

  The document discharge tray 37 is a place where a document read at the document reading position R is discharged.

[Operation of Image Forming Apparatus]
Next, an example of the operation of the image forming apparatus 1 will be described with reference to FIG.

  In the image forming apparatus 1, when the lift plate 41 is in a paper feedable state, the pressure on the paper feed roller 51 is detected by, for example, adding a document to a document already set on the lift plate 41. Then (S1), the lift plate 41 begins to fall (S2), and when the lift plate 41 descends to a predetermined position (a lower position corresponding to the magnitude of pressure) and enters a standby state (S3), The descent stops (S4). As a result, a space is formed between the document and the paper feed roller 51, and the document can be added or reset.

  When a predetermined time elapses after the lift plate 41 enters the standby state (S5), the lift plate 41 rises (S6), and when the lift plate 41 rises to the upper limit position (S7), the lift plate 41 stops rising (S8). ).

  According to the image forming apparatus 1 described above, when the lift plate 41 is in a feedable state and pressure is detected when another document is added, a space is formed between the lift plate 41 and the feed roller 51. Arise. This makes it easy to add and reset documents. Therefore, according to this apparatus 1, it is possible to add or reset an original as necessary while shortening the time from the print instruction to the start of printing.

[Other Embodiments]
(A) The configuration of various sensors of the ADF is not limited to the above. For example, the lower limit switch may not be provided.

  (B) In the control unit, a part of the command system may be arranged in the ADF, and in this case, the predetermined time may be counted by the command system in the ADF.

  (C) The lowering of the lift plate may be stopped when the detected pressure is lowered to some extent, for example, instead of the lowering width corresponding to the magnitude of the pressure.

  (D) The document feeder of the present invention can also be applied to a double-sided readable type having a reversal function.

1 is a diagram illustrating an image forming apparatus in which an embodiment of the present invention is employed. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus. FIG. 2 is a longitudinal sectional view showing a document feeding device of the image forming apparatus. 6 is a flowchart for explaining the operation of the document feeder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Automatic document feeder 13 Main-body part 21 Document reading part 25 Image forming part 31 Document mounting part 33 Pressure sensor (detection means)
35 Lift plate drive unit 41 Lift plate

Claims (5)

A document feeder of an image forming apparatus for feeding a document toward a document reading position,
An original placement unit having a lift plate on which the original can be placed and movable up and down in the stacking direction of the original;
A sheet feeding unit that is arranged at an upper interval with respect to the lift plate arranged at the lowest position, and that is movable upward following the force received from below by the lift plate;
An upper limit sensor for detecting that the lift plate is raised and the document on the lift plate pushes up the paper feed unit;
Detection means capable of detecting an upward force on the paper feed unit in a state where the upper limit sensor detects that the paper feed unit has been pushed up ;
A lift plate that lowers the lift plate so that a space is formed between the document placed on the document placement portion and the paper feed portion when an upward force on the paper feed portion is detected A drive unit;
Document feeder with The document feeder according to claim 1, wherein the detection unit is a pressure sensor capable of detecting an upward pressure with respect to the sheet feeding unit. The pressure sensor can detect the magnitude of the pressure,
The lift plate driving unit lowers the lift plate by a distance corresponding to the magnitude of the pressure detected by the pressure sensor;
The document feeder according to claim 2. The lift plate driving unit moves the lift plate when a predetermined time elapses after a force acting on the lift plate is detected without detecting a force acting on the lift plate. The document feeder of the image forming apparatus according to claim 1, wherein the document feeder is raised. An original document feeder of the image forming apparatus according to any one of claims 1 to 4,
A document reading unit disposed opposite to the document feeding device and configured to read image information of the document; and an image forming unit configured to form an image based on the image information read by the document reading unit. The main body,
An image forming apparatus.

Images