JP2003312891A - Sheet number detecting method, sheet number detecting apparatus, sheet feeding apparatus, and image forming apparatus provided with the sheet feeding apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To accurately detect a small number of sheets regardless of the type of sheets such as recording paper. SOLUTION: A surface (lower surface) of one side of the recording paper P is heated by a heater 11, a temperature of the other surface (upper surface) is detected by a temperature detector 12, and the temperature of the detected temperature is determined. The controller 50 calculates the number of sheets of recording paper P sandwiched between the heater 11 and the temperature detector 12 by calculation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the number of paper sheets, a device for detecting the number of paper sheets,
The present invention relates to a sheet feeding device capable of detecting the number of sheets and an image forming apparatus including the sheet feeding device.

[0002]

2. Description of the Related Art Conventionally, an apparatus for detecting whether the conveyed medium is one sheet or plural sheets when a conveyed medium such as paper is conveyed is disclosed in, for example, Japanese Patent Laid-Open No. 2000-34037.
It is described in Japanese Patent Publication No. This apparatus is provided with a visible light emitting element and a visible light receiving element, and an infrared light emitting element and an infrared light receiving element, which form a pair, respectively, and provides a first signal according to the intensity of light received by the visible light receiving element. And a infrared light receiving circuit that outputs a second signal in accordance with the intensity of light received by the infrared light emitting element, and inputs the first signal and the second signal. When the calculated value is equal to or less than the threshold value indicating the superposition of the transport media, it is determined that the number of the transport media transported is one, and if it exceeds the threshold, the sheet number identifying circuit determines that the multiple transport media are transported. I am trying to do it. Further, the detection of the number of recording sheets (paper sheets) used in the sheet feeding device of the conventional image forming apparatus is, for example, to detect whether or not there is a recording sheet on the recording sheet stacking unit, It is common to detect roughly the number of recording papers such as 50 or more and 100 or more. further,
Japanese Patent Laid-Open No. 8-48439 also uses an infrared light emitting device and a light receiving device which are arranged to face each other across a sheet to be conveyed,
An apparatus is described in which double feeding is detected by a change in the amount of light transmitted through a sheet passing therethrough.

[0003]

However, in the above-mentioned apparatus for detecting a conveyed medium, the conveyed medium is one.
Since it is a device that only detects whether the number of sheets or a plurality of sheets, even if this device is applied to, for example, a sheet feeding device of an image forming apparatus, the number of sheets is temporarily set on the recording sheet stacking unit of the sheet feeding device. If a number of recording papers are stacked, it may not be possible to accurately detect the number of recording papers. Further, inconvenience may occur in the case of detecting whether or not there is a recording sheet on the recording sheet stacking means or detecting roughly the number of recording sheets such as 50 sheets or more and 100 sheets or more. That is, in recent years, image forming apparatuses such as copiers and printers have become colorized and image formation has been accelerated, so that, for example, as shown in FIG. 9, an intermediate transfer belt 91, which is a large image carrier, is mounted. The intermediate transfer belt 9
A plurality of (five in the example of FIG. 9) images G _{1 to} G ₅ can be carried on one sheet at a time, and the conveyance path length must be shortened to shorten the first print time. The distance to the transfer part is shortened.

In such an image forming apparatus, if it is not possible to accurately detect the remaining number of recording sheets stacked on the bottom plate 96 serving as the recording sheet stacking means of the sheet feeding tray 95, the remaining number of sheets is transferred intermediately. When the number of images that can be carried on the belt 91 at one time is smaller than the number of images that can be carried at one time, the number of images that exceeds the remaining number of images may be formed and carried on the intermediate transfer belt 91. In this case, the cleaning device removes all the extra images that could not be transferred to the recording paper, resulting in a completely unproductive operation and waste of toner. Further, since a large amount of toner is collected by cleaning the extra image, the load on the cleaning device also increases. Specifically, in the case of the example shown in FIG. 9, five sheets of images G _{1 to} G ₅ can be carried on the intermediate transfer belt 91, while from the paper feed tray 95 to the transfer section 94. If there are only 3 sheets of recording paper (P _{1 to} P ₃ ) in the sheet, it is impossible to transfer the image of 2 sheets of 5−3 = 2 sheets to the recording sheet, so that the image is erased by the cleaning device. Will be done.

The formation of such an extra image can be prevented if the remaining number of recording papers in the paper feed tray can be accurately detected. However, in a conventional device that detects the number of recording papers by a change in the amount of light transmitted through the recording papers by using an infrared light emitting device and a light receiving device that are arranged to face each other across the recording papers (papers), Depending on the type, it was not possible to detect the correct number of recording papers. That is, in the case where the recording paper is a recording paper that transmits almost all light, such as OHP paper, or conversely, a recording paper that transmits almost no light, such as light-shielding paper, the light transmitted through the paper as described above is used. Even if an attempt was made to detect the number of recording papers due to the change in the light amount, it could not be detected accurately. The present invention has been made in view of the above problems, and makes it possible to accurately detect the number of a small number of paper sheets regardless of the type of paper sheets such as recording paper. With the goal.

[0006]

In order to achieve the above object, the present invention heats one side surface of a paper sheet, detects the temperature of the other side surface, and detects whether the detected temperature is high or low. Thus, there is provided a method for detecting the number of sheets, which detects the number of sheets. In the method of detecting the number of sheets, the heating of the sheets and the detection of the temperature of the surface on the other side are performed every time the sheets stacked on a plurality of sheets are fed, and the sheet feeding operation is performed. It is preferable that the temperature change per sheet is obtained from the change in the detected temperature for each, and the number of sheets of a plurality of sheets is corrected by the temperature change. Further, the heating means for heating the surface of one side of the paper sheet, the temperature detection means for detecting the temperature of the surface of the other side of the paper sheet, and the temperature detected by the temperature detection means A unit for calculating the number of sheets is provided to configure a sheet number detecting device. The heating means and the temperature detection means may be arranged to face each other in the vertical direction with respect to the surface of the paper sheet.

Further, in a paper feeding device having a stacking means for stacking a plurality of paper sheets and a paper feeding means for feeding the paper sheets stacked on the stacking means, the paper is loaded on the stacking means. The heating means for heating the surface on one side of the plurality of paper sheets, the temperature detecting means for detecting the temperature of the surface on the other side of the paper sheet, and the high and low of the temperature detected by the temperature detecting means. There is also provided a sheet feeding device provided with a unit for calculating the number of sheets stacked on the stacking unit. In the sheet feeding device, heating of the sheets and detection of the temperature of the surface on the other side are performed every time the sheets stacked on a plurality of sheets are fed one by one,
A means for calculating the temperature change due to the thickness of each sheet by the change of the detected temperature for each sheet feeding operation and correcting the number of the plurality of sheets stacked on the stacking unit by the temperature change is provided. It is good to provide. Further, a moving means for moving the heating means and the temperature detecting means in the same direction in the same direction along the surface of the paper sheet is provided, and the moving means is detected each time the temperature of the paper sheet stacked on the stacking means is detected. Is preferably driven to move the heating means and the temperature detecting means by an appropriate amount in the above direction. The stacking means has a bottom plate on which paper sheets are stacked and rotatable, and the bottom plate rotates until the paper sheet reaches a constant paper feed start position for each paper feeding operation, and heats the bottom plate. Either the means or the temperature detecting means may be attached.
At least one of the heating means and the temperature detecting means in the paper sheet feeding direction may be the paper feeding start position. An image forming apparatus provided with the above-mentioned number-of-sheets detecting device or a sheet feeding device, which has an image carrier capable of carrying a plurality of visible images, and when the number of detected sheets is less than a predetermined number, the image is formed. Provided is an image forming apparatus provided with means for preventing formation of a visible image on a carrier.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a sheet number detecting apparatus for carrying out the sheet number detecting method according to the present invention. This paper sheet number detection device is a heater 11 which is a heating means including a heater for heating one surface (lower surface) of the recording paper P which is a paper sheet,
A temperature detector 12 which is a temperature detecting means for detecting the temperature of the other surface of the recording paper P, and a control which is a means for calculating the number of the recording paper P based on the temperature detected by the temperature detector 12. And a device 50. The heater 11 and the temperature detector 12 are arranged so as to face each other with the recording paper P sandwiched therebetween. And that heater 1
1 and the temperature detector 12 may be of a contact type that contacts the surface of the recording paper P, or may be a non-contact type that does not contact the surface of the recording paper P. The positional relationship between the heater 11 and the temperature detector 12 may be reversed from the example shown in FIG.

In this paper sheet number detecting device, the heater 11 heats one surface (lower surface) of the recording paper P, and the temperature detector 12 measures the temperature of the other surface (upper surface). The number of recording sheets P is detected and the number of sheets of recording paper P is detected according to the detected temperature level.
Then, the number of recording sheets P sandwiched by the temperature detector 12 is calculated. The control device 50 includes a central processing unit (CPU) having various determination and processing functions, a ROM that stores each processing program and fixed data, a RAM that is a data memory that stores the processing data, and an input / output circuit (I / I). O) and a microcomputer, which inputs a signal corresponding to the detected temperature from the temperature detector 12. Then, based on the input information, the number of recording sheets P sandwiched between the heater 11 and the temperature detector 12 is calculated. The calculation of the number of recording papers performed by the microcomputer is performed by using Expression 1. Here, T: temperature detected by the temperature detector T ₁ : temperature of the heater T ₀ : initial temperature (ambient temperature) by the temperature detector erf: error function n: number of recording sheets x: thickness of recording sheet k: Thermal conductivity of recording paper t: Heating time

[0010]

[Equation 1]

FIG. 2 is a diagram showing the temperature change due to the difference in the number of recording sheets when T ₁ = 100 ° C. and T ₀ = 25 ° C. Here, if the heating time is set to a fixed value, the relationship between the number of recording sheets and the detected temperature of the recording sheets can be obtained. FIG. 3 is a diagram showing the relationship between the number of recording sheets and the temperature output. Based on this diagram, the number of recording sheets is determined by the following algorithm. That is, when the output is less than A, it is determined that the number of recording sheets is 5 or more. Output is B
If it is less than A, it is determined that the number of recording sheets is four. When the output is less than C and more than B, it is determined that the number of recording sheets is three. When the output is less than D and not less than C, the number of recording sheets is determined to be two. When the output is less than E and more than D, it is determined that the number of recording sheets is one. When the output is E or more, it is determined that the number of recording sheets is zero. The outputs A to E are numerical values set in advance by experiments or calculations, and are arbitrarily changed depending on environmental factors, types of recording paper, and other variable factors.

As described above, the paper sheet number detecting device heats one surface of the recording paper and detects the temperature of the other surface, and the smaller the number of recording papers, the better the heat conduction. By taking advantage of the fact that the temperature on the temperature detection side rises, the more the number of recording papers, the poorer the heat conduction and the lower the temperature on the temperature detection side. Since the detection is performed, it is not affected by the transmittance of the recording paper as in the case of detecting the number of recording papers from the change in the amount of light transmitted through the recording paper. Therefore, even if the recording paper transmits almost all the light like OHP paper, or conversely, even if it is the recording paper that hardly transmits light like the light-shielding paper, it is possible to accurately detect the number of sheets. .

FIG. 4 is a schematic configuration diagram showing an embodiment of a sheet feeding device according to the present invention, and the portions corresponding to those in FIG. 1 are designated by the same reference numerals. The paper feeding device 4 includes a heater 11 that heats one surface (a lower surface in the example of FIG. 4) of a plurality of recording sheets P stacked on a bottom plate 5 that is a stacking unit, and the recording sheets P. A temperature detector 12 for detecting the temperature of the surface on the other side, and a controller 50 'serving as a means for calculating the number of recording sheets P stacked on the bottom plate 5 according to the level of the temperature detected by the temperature detector 12. Is provided. Further, the paper feeding device 4 is a pickup roller 6 which is a paper feeding means for feeding the recording paper P stacked on the bottom plate 5 in the counterclockwise direction in FIG. When a plurality of recording paper sheets P are printed, a separating roller (not shown) including a feed roller and a reverse roller for separating the recording paper sheets P into one sheet is provided. The bottom plate 5 is rotatably supported at the left end in FIG. 1 by the paper feeding tray 22, and with the recording paper P placed thereon, the left end is used as a fulcrum. It can be rotated in the direction of arrow B.
The bottom plate 5 rotates every time the paper feed operation is performed by the pickup roller 6 until the recording paper P stacked on the bottom plate 5 reaches a constant paper feed start position. The rotation of the bottom plate 5 is pushed up by a raising lever which is provided on the lower side of the bottom plate 5 and which is turned upward by a drive source such as a motor (not shown), and the recording paper feeding end side (the right end in FIG. Side) rises. The heater 11 is fixed to the bottom plate 5. Therefore, the heater 11 ascends along with the rotation of the bottom plate 5 while being in contact with the lower surface of the bundle of recording papers P, and
The positional relationship with the recording paper P is always maintained.

For feeding paper from the paper feeding device 4, the recording paper P stacked on the bottom plate 5 is picked up by picking up the recording paper P located at the uppermost position as the bottom plate 5 rotates upward.
It is performed by ascending to a position where the pickup roller 6 comes into contact with the pickup roller 6 and rotating in that state. Further, the control device 50 ′ of this paper feeding device picks up the recording papers P stacked on the bottom plate 5 one by one in order to heat the recording paper and detect the temperature of the other surface (upper surface). Is performed every time the sheet feeding operation is performed, the temperature change due to the thickness per recording sheet is obtained from the change in the detected temperature for each sheet feeding operation, and the plurality of recording sheets stacked on the bottom plate 5 are obtained by the temperature change. It also functions as a means for correcting the number of sheets. Then, every time the controller 50 'feeds the recording paper loaded by a plurality of sheets by heating the recording paper by the heater 11 and detecting the temperature of the other surface by the temperature detector 12, Recording paper for controlling the number of plural recording papers on the bottom plate 5 by obtaining the temperature change per recording paper by the change of the detected temperature for each paper feeding operation. Perform the number detection method. The control device 50 'stores a central processing unit (CPU) having various determination and processing functions similar to those of the control device 50 shown in FIG. 1, a ROM storing each processing program and fixed data, and processing data. It has a microcomputer including a RAM as a data memory and an input / output circuit (I / O), and the microcomputer inputs a signal corresponding to the detected temperature from the temperature detector 12. Then, the number of recording sheets P on the bottom plate 5 is corrected based on the input information.

The number detection process performed by the microcomputer of the control unit 50 'is basically the same as the number detection unit for sheets, which has been described with reference to FIG. 1, but the detection temperature changes for each sheet feeding operation. It is different in that the number detection is made more accurate by incorporating. In the correction for detecting the number of recording sheets, when the pickup roller 6 performs the paper feeding operation, the number of recording sheets stacked on the bottom plate 5 is decreased by one, but the detection detected by the temperature detector 12 at that time. When the temperature change is large, for example, as shown in FIG. 5, when the output at a certain point is less than b and less than a, but less than d during the next sheet feeding operation, and more than c, the temperature conduction is low. It is determined that the recording paper (heat is not easily transmitted) is used, and the number of recording papers on the bottom plate 5 is corrected (determined as one). According to this paper feeding device, since the surface temperature of the recording paper P on the bottom plate 5 is detected by the temperature detector 12 every time the paper feeding operation is performed,
The temperature change per sheet of recording paper can be known accurately. Thereby, even if the type of recording paper is not known in advance, the number of recording papers on the bottom plate 5 can be accurately detected.

FIG. 6 is an overall block diagram showing an example of a color image forming apparatus provided with the paper feeding device of FIG. In this color image forming apparatus, an image forming section 20 is arranged at the substantially center of the apparatus main body 1, and a sheet feeding section 2 having a plurality of sheet feeding trays 22 is arranged immediately below the image forming section 20. It should be noted that another paper feeding device can be added to the paper feeding unit 2 if necessary. A reading unit 23 for reading a document is provided above the image forming unit 20 and the image forming unit 2 is provided.
No. 0 of FIG. 6 is provided with a discharged paper storage unit 24 on the left side, and the discharged paper storage unit 24 stores the recorded recording paper P having an image formed thereon. The image forming unit 20 is provided with a belt-shaped intermediate transfer belt 25 which is stretched between a plurality of rollers and rotates in the arrow A direction.
As shown in the drawing, drum-shaped photoconductors 26Y, 26M, 26C, and 26K, which form four image forming units, are arranged in parallel around each other.

Around each of the photoconductors, each charging device 62 for charging the surface of the photoconductor, and each of the electrostatic latent images formed on the surface of the photoconductor are visualized with toner of each color. A developing device 63 and cleaning devices 64 for removing and collecting residual toner remaining on each photoconductor after transferring the toner image (visible image) on each photoconductor to the intermediate transfer belt 25 are provided. The photoconductors 26Y, 26M, 26C, 26 of the image forming unit 20 are provided above the image forming unit 20.
K is provided with an exposure device 7 that irradiates a laser beam corresponding to each color image information to form a latent image thereon.
Further, a registration roller 33 is provided on the upstream side of the recording sheet conveyance of the image forming section 20, and a fixing device 28 is provided on the downstream side of the recording sheet conveyance of the image forming section 20.
Thus, the skew of the recording paper is corrected, and the paper is fed in time with the image on the photoconductor. Further, the toner image transferred onto the recording paper is fixed by the fixing device 28. On the downstream side of the fixing device 28, a paper discharge roller 41 for discharging the recording paper, which has passed through the fixing device 28, onto the paper discharge storage section 24 is provided. In FIG. 6, the reference numeral 3 indicates that the original is automatically placed on the contact glass 31.
It is an automatic document feeder that conveys documents to the top.

When the color image forming apparatus starts a full-color image forming operation, the photoconductors 26Y, 26M, 26 charged by the charging devices 62 of the image forming section 20 are charged.
The charged surfaces on C and 26K are exposed by the exposure device 7 to yellow (Y), magenta (M), cyan (C), and black (B).
K) is exposed by the operation light corresponding to each color, and a latent image is formed there. Each photoconductor 26 by the exposure device 7
Writing to Y, 26M, 26C and 26K is performed by the reading unit 2
The image of the original set on the contact glass 31 provided in FIG. 3 is read and scanned by reciprocal movement of the reading traveling bodies 32a and 32b including the original illuminating light source and the mirror in the horizontal direction in FIG. This is performed based on the image information read as an image signal in the CCD 35 installed behind the lens 34. Ie CCD
The image signal read by 35 is digitized and image-processed. Based on the image-processed signal, the laser diode in the exposure device 7 emits light to cause the photoconductor 26
Each surface of Y, 26M, 26C, and 26K is exposed to form an electrostatic latent image on it. At that time, the light from the laser diode reaches each photoconductor through a polygon mirror and a lens.

In this way, the photoconductors 26Y, 26
The latent images formed on M, 26C and 26K are
Toner images are developed by the developing devices 63 corresponding to the four colors of yellow (Y), magenta (M), cyan (C), and black (BK). As for the toner image, the yellow image on the photoconductor 26Y is first shown in FIG.
Is transferred onto the intermediate transfer belt 25 which is rotating in the direction of arrow A, and when the yellow image is moved to the position of the photoconductor 26M, the magenta image is superposed and transferred thereon. To do. When the portion to which the magenta image is transferred moves to the position of the photoconductor 26C, the cyan image is superposed and transferred thereon, and the part to which the cyan image is transferred is the position of the photoconductor 26K. When it moves to, the black image is overlaid and transferred.

The four-color superposed image of yellow, magenta, cyan and black is the intermediate transfer belt 2.
When the transfer roller 51 moves to a certain transfer position by the rotation of 5, the transfer roller 51 collectively transfers the recording paper fed in synchronism with the timing. In this way, this color image forming apparatus performs an image forming process in which the intermediate transfer belt 25 rotates once to form one color image. And the intermediate transfer belt 2
After the four-color superposed toner images on 5 are collectively transferred to the recording paper, the toner remaining on the intermediate transfer belt 25 is removed and collected by the intermediate transfer cleaning device 52. The recording paper on which the toner image has been fixed and which has passed through the fixing device 28 is discharged to the discharged paper storage unit 24 by the paper discharge roller 41 when the recording paper is for single-sided image formation. Further, when a double-sided image forming instruction is issued, the recording paper is arranged below the image forming unit 20 by the branch claw 43 provided on the conveyance path between the fixing device 28 and the paper discharge roller 41. The image is formed on the second surface by being fed to the double-sided device 29, inverted, conveyed again to the registration roller 33, and then discharged onto the discharged paper storage unit 24 by the paper discharge roller 41 after the image is formed on the second surface. It

On the other hand, the paper feed unit 2 for feeding recording paper is provided with the paper feed device 4 described in FIG. 4 for each paper feed stage. As described above, according to this color image forming apparatus, it is possible to accurately detect the number of recording sheets stacked on the bottom plate 5 regardless of the type of recording sheets. As a result, the number of recording sheets remaining on the bottom plate 5 is compared with the number of visible images that can be carried on the intermediate transfer belt 25, and when the number of recording sheets on the bottom plate 5 is small, the image formation is stopped. The toner image (visual image) is controlled not to be transferred onto the intermediate transfer belt 25. Therefore, waste of toner can be prevented. Further, when the toner images more than the number of recording sheets remaining on the bottom plate 5 are formed on the intermediate transfer belt 25, a large amount of the excessively formed toner images are formed by the intermediate transfer cleaning device 52. Although a large load is applied to the intermediate transfer cleaning device 52 for erasing, it can be prevented. When the number of recording sheets detected by the temperature detector 12 shown in FIG. 4 is smaller than a predetermined number (the number of visible images that can be carried on the intermediate transfer belt 25), the visible images are formed on the intermediate transfer belt 25. Although not shown in FIG. 6, the central processing unit (CP) having various judgment and processing functions is provided as a means for not performing this.
U) and R storing each processing program and fixed data
OM and RA which is a data memory for storing processed data
A control device having a microcomputer including M and an input / output circuit (I / O) functions.

FIG. 7 is a schematic block diagram similar to FIG. 4 showing an embodiment of the paper feeding device in which the position of the temperature detector is set to the position of the pickup roller, and the parts corresponding to those in FIG. I am doing it. The sheet feeding device according to this embodiment is shown in FIG.
With respect to the paper feeding device described in the above, the position of the temperature detector 12 in the recording paper feeding direction (the direction of arrow G) is made to substantially coincide with the position of the pickup roller 6 which is the recording paper feeding start position. Only different. In this way, the temperature detector 1
The position 2 of the recording paper feeding direction is substantially the same as the recording paper feeding start position by the pickup roller 6. As a result, the bundle of recording papers P stacked on the bottom plate 5 is rotated upward as it is fed, and the angle of the upper surface of the recording paper P located at the uppermost position is changed. However, the contact position of the temperature detector 12 with the upper surface of the recording paper continues to be maintained at a substantially constant position. Therefore, the temperature detection accuracy of the temperature detector 12 is increased, and the detection accuracy of the number of recording sheets is improved. In addition, the heater 11 is arranged at a position where the temperature detector 12 of FIG.
When the temperature detector 12 is arranged on the bottom plate 5 side, the heater 11 may be substantially aligned with the position of the pickup roller 6.

FIG. 8 is a schematic block diagram similar to FIG. 7, showing an embodiment of a paper feeding device provided with moving means for moving the heater and the temperature detector along the surface of the recording paper in the same direction and by the same amount. Therefore, the portions corresponding to those in FIG. 7 are denoted by the same reference numerals. The sheet feeding device according to this embodiment is provided with moving means 60 for moving the heater 11 and the temperature detector 12 in the same direction (direction of arrow C) along the surface of the recording paper by the same amount, and the bottom plate 5'is provided with the moving means 60. The heater 11 is driven by driving the moving means 60 each time the temperature of the stacked recording papers P is detected (may be every paper feeding operation).
The temperature detector 12 is moved in the direction of arrow C by an appropriate amount, for example, a distance equal to or larger than the width W of the heater 11. In this paper feeding device, the heater 11 is connected to the lower support member 65.
The temperature detector 12 is fixed to one end of the upper support member 66.
It is fixed at one end. And the lower support member 6
5 is engaged with the guide portion 66a of the upper support member 66 and is movable in the vertical direction in FIG.
Is urged upward in FIG. In addition, the bottom plate 5'is provided with a long hole 5 for allowing the heater 11 to move in the direction of arrow C.
a is formed.

Thus, the heater 11 and the temperature detector 12
Is fixed to the lower support member 65 and the upper support member 66, and the lower support member 65 is biased toward the upper support member 66 by the spring 67, so that the bundle of recording paper P is placed on the bottom plate 5 '. When the heater 11 and the temperature detector 12 are set so that they are stacked and sandwiched between them in the vertical direction, the heater 11 contacts the lower surface of the recording paper, and the temperature detector 12 contacts the upper surface of the recording paper. Therefore, the heater 11 and the temperature detector 12 have a minimum distance according to the number of recording sheets P on the bottom plate 5 '. By the way, the recording paper P on the bottom plate 5 '
Since the recording paper P is heated by the heater 11 when the number of sheets of paper is detected, in the case of such a number of sheets detection method, when the number of sheets of paper is detected again, the temperature of the recording paper P is lowered to some extent. I have to wait. That is, as a result of actual measurement,
It was confirmed that the temperature of the recording paper returns to its original value several seconds after the heating by the heater 11 is stopped. However, in the case of a paper feeding device that can continuously feed paper at high speed,
As described above, it becomes necessary to detect the next number of recording sheets before the temperature of the recording sheets returns to the original temperature.

Therefore, in the paper feeding device according to this embodiment, the moving means 60 is driven to heat each time the temperature detector 12 detects the temperature of the recording paper P stacked on the bottom plate 5'as described above. The temperature sensor 11 and the temperature detector 12 in the direction of arrow C,
An appropriate amount is moved to a range that is not affected by the temperature of the portion heated by the heater 11. The heater 11 and the temperature detector 12 moved by the moving means 60.
May perform reciprocating motion so as to return to the original location when the original location returns to the original temperature after performing the paper feeding operation to some extent. According to this paper feeding device, since it is possible to detect the next number of sheets without waiting for the temperature of the recording sheet that has risen when the number of sheets is detected by heating the recording sheet, the next sheet number can be detected. It can also handle paper operations. Therefore, the number of recording sheets can be accurately detected even if the sheet feeding interval is shortened to improve the speed. The embodiments of the sheet number detecting device and the sheet feeding device according to the present invention, and the image forming apparatus including the sheet feeding device have been described above. For detecting the number of recording sheets respectively used therein, The heater 11 and the temperature detector 12 may be arranged to face each other in the vertical direction with respect to the surface of the recording paper. By doing so, the heat from the heater 11 moves to the temperature detector 12 in the shortest time, so that the temperature detector 12 can respond to the change in the number of recording sheets.
The difference in height of the detected temperature at the point becomes large. Thereby, the number of recording sheets can be detected with high accuracy.

[0026]

As described above, if the sheet number detecting device and sheet feeding device according to the present invention and the sheet number detecting method are implemented, one side surface of the sheet is heated. Then, since the number of the small number of paper sheets can be detected by detecting the temperature of the surface on the other side, light is transmitted to the paper sheets to detect the number of paper sheets. As in the case, it is not affected by the transmittance of the paper sheet. Therefore, OHP
The number of sheets can be accurately measured even if the sheet has a high transmitted light rate such as a sheet, and the number of sheets can be accurately detected even if the sheet has a low transmitted light rate. Further, according to the image forming apparatus provided with the paper feeding device, even when a large image carrier capable of carrying a plurality of images at a time is provided,
Since it is possible to form an image according to the exact number of sheets on the stacking unit, carelessly forming an image on the image carrier that is larger in number than the number of sheets on the stacking unit. At this time, it is possible to prevent an unproductive operation of erasing an excessive image that cannot be transferred to the sheet by a cleaning device. As a result, waste of toner can be prevented and the burden on the cleaning device can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an embodiment of a sheet number detecting apparatus for carrying out a sheet number detecting method according to the present invention.

FIG. 2 is a diagram showing a temperature change due to a difference in the number of recording papers when T ₁ = 100 ° C. and T ₀ = 25 ° C.

FIG. 3 is a diagram showing the relationship between the number of recording sheets and temperature output.

FIG. 4 is a schematic configuration diagram showing an embodiment of a sheet feeding device according to the present invention.

FIG. 5 is a diagram showing a relationship between the number of recording sheets and a temperature output when a recording sheet having low temperature conduction is used.

6 is an overall configuration diagram showing an example of a color image forming apparatus including the paper feeding device of FIG.

FIG. 7 is a schematic configuration diagram similar to FIG. 4, showing an embodiment of a sheet feeding device in which a temperature detector is located at a pickup roller position.

FIG. 8 is a schematic configuration diagram similar to FIG. 7, showing an embodiment of a sheet feeding device provided with a moving unit that moves the heater and the temperature detector along the surface of the recording paper in the same direction and by the same amount.

FIG. 9 is a schematic diagram for explaining a problem when a larger number of images than the remaining number of recording sheets are carried on the intermediate transfer belt.

[Explanation of symbols]

4: Paper feeder 5: Bottom plate (loading means) 6: Pickup roller (paper feeding means) 11: heater (heating means) 12: Temperature detector (temperature detecting means) 50, 50 ': control device 60: means of transportation P: Recording paper (paper sheets)

Claims (10)

[Claims] 1. A paper sheet is heated on one side, the temperature of the other side surface is detected, and the number of the paper sheets is detected based on the detected temperature level. How to detect the number of paper sheets. 2. The method for detecting the number of paper sheets according to claim 1, wherein the heating of the paper sheets and the temperature detection of the surface on the other side are performed by feeding the paper sheets stacked one by one. It is performed every operation, and the temperature change per sheet is obtained by the change in the detected temperature for each sheet feeding operation, and the number of the plurality of sheets is corrected by the temperature change. How to detect the number of paper sheets. 3. A heating means for heating the surface of one side of the paper sheet, a temperature detecting means for detecting the temperature of the surface of the other side of the paper sheet, and a temperature detecting means for detecting the temperature of the temperature detecting means. And a means for calculating the number of sheets according to the height of the sheet. 4. The sheet number detecting device according to claim 3, wherein the heating unit and the temperature detecting unit are arranged to face each other in the vertical direction with respect to the surface of the paper sheet. 5. A paper feeding device comprising a stacking means for stacking a plurality of paper sheets and a paper feeding means for feeding the paper sheets stacked on the stacking means, wherein the stacking means stacks the paper sheets. By heating means for heating the surface on one side of the plurality of paper sheets, temperature detecting means for detecting the temperature of the surface on the other side of the paper sheets, and by the high and low of the temperature detected by the temperature detecting means. And a means for calculating the number of sheets stacked on the stacking means. 6. The sheet feeding device according to claim 5, wherein the heating of the sheets and the detection of the temperature of the surface on the other side are performed every time the sheets stacked on a plurality of sheets are fed one by one. Then, the temperature change due to the thickness per sheet is obtained from the change in the detected temperature for each sheet feeding operation, and the temperature change corrects the number of the plurality of sheets stacked on the stacking unit. A sheet feeding device, characterized in that it is provided with a means for performing. 7. The paper feeding device according to claim 5, further comprising moving means for moving the heating means and the temperature detecting means in the same direction in the same direction along the surface of the paper sheet, respectively.
Paper feeding characterized in that the moving means is driven every time the temperature of the paper sheets stacked on the stacking means is detected to move the heating means and the temperature detecting means by an appropriate amount in the direction. apparatus. 8. The stacking means has a bottom plate on which paper sheets are stacked and rotatable, and the bottom plate rotates until a constant paper feed start position is reached for each paper feeding operation. The sheet feeding device according to claim 5, wherein one of the heating unit and the temperature detecting unit is attached to the bottom plate. 9. The sheet feeding device according to claim 8, wherein at least one of the heating unit and the temperature detecting unit is set at a position in the sheet feeding direction as the sheet feeding start position. 10. An image forming apparatus comprising the sheet number detecting device according to any one of claims 1 to 4 or the sheet feeding device according to claim 5. An image carrier capable of carrying a visible image is provided, and means is provided for preventing formation of a visible image on the image carrier when the number of detected sheets is less than a predetermined number. An image forming apparatus characterized by.