JP2006021894A - Paper stacked condition detecting device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an paper stacked condition detecting device using one detecting means for detecting the stacked condition of paper on each discharge tray of an image forming device having a plurality of discharge trays, and to provide the image forming device. <P>SOLUTION: The image forming device 1 comprises an image forming device body 6 including a paper supply part 2, an image forming part 3, and a paper discharge part 4, the discharge trays 7, and an elevation drive part 8. Herein, the paper stacked condition detecting device 5 including the non-contact type detecting means is provided near the paper discharge part 4 of the image forming device body 6, instead of the discharge trays 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet stacking state detection apparatus and an image forming apparatus.

  An electrophotographic image forming apparatus mounted on a copying machine, a printer, a facsimile, or the like is provided at a lower portion of the apparatus, and includes a sheet supply unit that stores sheets and a sheet supplied from the sheet supply unit via a conveyance path. An image forming unit that records an image on the sheet, a sheet discharge unit that discharges the sheet on which the image is recorded by the image forming unit, and a discharge tray that stores the sheet discharged from the sheet discharge unit. Is done.

  According to the image forming apparatus, high-quality monochrome or color images can be easily recorded. Therefore, the image forming apparatus is indispensable in all fields. Increasing year by year.

  For example, as a sheet of an image forming apparatus, conventionally, a standard product determined by a manufacturer of the image forming apparatus has been mainly used. However, with the diversification of industrial products, while cost reduction is desired, paper for image forming apparatuses that are less expensive than standard products have come to the market and become widely used. ing. Such low-priced paper includes many papers that are poor in quality and are likely to cause a jam in the image forming apparatus and irregularities on the discharge tray. Recently, as part of energy saving, there is a case where an image is recorded again on the back side of a sheet on which an image is recorded once. In that case, it is also easy for a conveyance jam to occur, and the paper is greatly curled after image recording, which may hinder the discharge to the discharge tray. Therefore, in a recent image forming apparatus, one of the problems is that image formation can be continued without hindrance even if the paper is deteriorated or reused.

  In order to solve such a problem, there has been proposed an image forming apparatus including a detection unit for detecting a stacking state of sheets on a discharge tray. For example, a paper stacking device including a stacking state detection unit that detects a stacking state of sheets discharged to a discharge tray, and a control unit that determines whether paper discharge is continued or stopped based on detection information of the stacking state detection unit Has been proposed (see, for example, Patent Document 1). FIG. 8 is a cross-sectional view schematically showing the configuration of the paper stacking apparatus 100 disclosed in Patent Document 1. As shown in FIG.

  The sheet stacking device 100 is disposed on a side surface of the image forming apparatus main body 100, supports a plurality of discharge trays 101 and 102, supports a discharge tray 101, and includes a distance measurement sensor 103 on a lower surface thereof. A tray support member 105 that is disposed on a side surface of the forming apparatus 100 and supports the discharge tray 102 is configured.

  The paper P on which an image is recorded is discharged from the image forming apparatus main body 110 to the discharge trays 101 and 102 via a pair of discharge rollers 106 and 107 included in the image forming apparatus main body 110. The stacking state of the paper P discharged to the discharge tray 102 on the discharge tray 102 is detected by a distance measuring sensor 103 built in the lower surface of the tray support member 104. An example of the distance measuring sensor 103 is an optical reflective sensor having a detection distance of 40 to 300 mm. It is designed so that the output voltage from the distance measuring sensor 103 is read from an input port of a CPU (not shown) and the detection distance can be determined by the level of the voltage value. For example, when the paper P is normally stacked on the discharge tray 102, the distance between the distance measuring sensor 103 and the paper surface is w1, and w1 does not change rapidly. On the other hand, when the paper P is discharged in a curled state, the distance between the distance measuring sensor 103 and the paper surface is w2 that is remarkably shorter than the normal w1, thereby detecting an abnormal stacking of the paper P.

  However, since the distance measuring sensor 103 is built in the lower surface of the tray support member 104 in the paper stacking apparatus 100, the stacking state of the paper P on the discharge tray 102 can be detected, but the paper P on the discharge tray 101 can be detected. There is a drawback that the loading state cannot be detected. When the detection unit is provided on the lower surface of the tray support member 104 as in the paper stacking apparatus 100, an image forming apparatus having a plurality of discharge trays has a plurality of discharge trays corresponding to the respective discharge trays. It is necessary to provide detection means.

JP 2003-26370 A

  An object of the present invention is an image forming apparatus including a plurality of discharge trays, a sheet stacking state detection device capable of detecting a stacking state of sheets on each discharge tray by one detection unit, and an image including the sheet stacking state detection device. A forming apparatus is provided.

The present invention is close to one side surface of an image forming apparatus main body that includes a sheet supply unit that supplies a sheet on which an image is recorded, an image forming unit that records an image on the sheet, and a sheet discharge unit that discharges a sheet on which an image is recorded. A plurality of discharge trays which are provided so as to be movable up and down with respect to the image forming apparatus main body, wherein the paper stacking unit detects a paper stacking state in the discharge tray for storing the paper discharged from the image forming apparatus main body by the paper discharge unit. In the state detection device,
Including at least one detection means;
The detection means is
Provided inside the image forming apparatus body,
A sheet stacking state detection device that detects the stacking state of sheets on a discharge tray when a predetermined discharge tray reaches a predetermined position by using the raising and lowering of the discharge tray.

Further, in the paper stacking state detection device of the present invention, the above-mentioned detection means is
It is provided in the vicinity of the paper discharge portion and at a position facing the paper loaded on the discharge tray through a light transmissive member or a light transmission hole provided on one side surface of the image forming apparatus main body.

  Furthermore, the sheet stacking state detection apparatus of the present invention is characterized in that the detecting means is a non-contact distance measuring sensor.

Furthermore, in the paper stacking state detection device according to the present invention, the above-described detection means includes:
A storage unit that stores a predetermined reference value; a comparison unit that compares the detected value with the reference value; and a determination unit that determines a loading state according to the output of the comparison unit;
The loading state detected by the detection means is
The present invention is characterized in that the maximum stacking capacity of sheets determined in advance for each discharge tray has been reached or the sheet is abnormally discharged to the discharge tray.

The present invention also provides an image forming apparatus main body including a sheet supply unit that supplies a sheet on which an image is recorded, an image forming unit that records an image on the sheet, and a sheet discharge unit that discharges a sheet on which an image is recorded. A plurality of discharge trays that are provided close to one side surface of the apparatus main body and store sheets discharged from the image forming apparatus main body by the paper discharge unit, and the plurality of discharge trays are driven up and down with respect to the image forming apparatus main body. In an image forming apparatus capable of switching a discharge tray that is to store paper discharged from the image forming apparatus main body by moving up and down a plurality of discharge trays by the lift driving unit.
Further, the image forming apparatus includes any one of the above-described sheet stacking state detection devices.

Furthermore, the image forming apparatus of the present invention includes a position detection unit that detects the raising and lowering positions of the discharge trays arranged at the uppermost and / or lowermost stages of the plurality of discharge trays,
Tray recognition means for recognizing a predetermined discharge tray from a plurality of discharge trays according to the detection output of the position detection means;
In response to the output of the tray recognition means, a paper stacking state on a predetermined discharge tray is detected by a paper stacking state detection device, and in response to the detection output, a paper supply unit, an image forming unit, a paper discharge unit, and a lift drive unit And a control means for controlling the operation of at least one part.

  According to the present invention, in the image forming apparatus in which a plurality of discharge trays are provided on one side surface of the image forming apparatus main body including the paper supply unit, the image forming unit, and the paper discharge unit, the detection unit is disposed inside the image forming apparatus main body. Then, a sheet stacking state detection device is provided that detects the stacking state of sheets on the discharge tray when a predetermined discharge tray reaches a predetermined position by using the raising and lowering of the discharge tray.

  By using the paper stacking state detection device of the present invention, it is possible to detect the paper stacking state on the plurality of discharge trays by at least one detection unit, and it is not necessary to provide a detection unit for each discharge tray. This contributes to simplification of the structure of the apparatus and reduction of manufacturing costs.

  According to the invention, the above-mentioned detection means is provided in the discharge tray near the paper discharge portion of the image forming apparatus main body and through the light transmitting member or the light transmitting hole provided on one side surface of the image forming apparatus main body. By providing the sheet to be loaded at the position facing it, it is possible to efficiently detect the sheet stacking state of all the discharge trays without hindering the movement of the discharge tray, and the internal structure of the image forming apparatus main body is simplified. Is easy.

  In addition, according to the present invention, by using a non-contact distance measuring sensor as the detection means, it is possible to always accurately detect the sheet stacking state on the discharge tray without being affected by the movement operation of the discharge tray. . Note that in a discharge tray of a type having a function of sorting by shifting the stacking position in the horizontal direction, it is possible to prevent deterioration of stacking property (alignment property) due to contact between the paper and the detection means.

  Further, according to the present invention, the detection unit further includes a storage unit, a comparison unit, and a determination unit to detect a state in which the maximum load amount of paper determined for each discharge tray has been reached or an abnormal discharge state of the paper to the discharge tray. By doing so, the sheet is further discharged to the discharge tray in the maximum loaded state or the abnormal discharge state, and it is possible to prevent the sheet from being bent, discharged from jamming, or dropped from the discharge tray.

  According to the present invention, there is provided an image forming apparatus including the above-described sheet stacking state detecting device and having a plurality of discharge trays. In the image forming apparatus, by including the paper stacking state detection device of the present invention, the internal structure is simplified, the manufacturing cost is reduced, and a series of image forming operations of paper supply, image formation, and paper discharge are delayed. Can be implemented smoothly.

  According to the invention, the image forming apparatus of the invention incorporates a position detection means for detecting the raising / lowering position of the discharge tray and a tray recognition means for recognizing a predetermined discharge tray according to the detection output of the position detection means. Further, in response to an output of the tray recognition means, a paper stacking state on a predetermined discharge tray is detected by a paper stacking state detection device, and in response to the detection output, a paper supply unit, an image forming unit, a paper discharge unit, and By incorporating a control means for controlling the operation of at least one part of the raising / lowering drive section of the discharge tray, it is possible to quickly determine whether image formation and paper discharge can be continued based on the detection result of the detection means. For example, if there is no conveyance jam in the image forming apparatus and there is a stacking abnormality on the discharge tray, the image formation is temporarily interrupted, the discharge tray is moved to another discharge tray, and the image is formed. Can be resumed. This is particularly advantageous when printing a large amount of one image.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to a first embodiment of the present invention. 2 is a cross-sectional view showing a state in which the elevating / lowering discharge tray 7 described later is raised from the reference position in FIG. 1 in the image forming apparatus shown in FIG.

  The image forming apparatus 1 is an electrophotographic image forming apparatus that forms a single color image or a multicolor image on a sheet based on image data transmitted from the outside. When forming a multicolor image, image formation corresponding to image data is performed using four colors obtained by adding black to yellow, magenta, and cyan which are three subtractive primary colors obtained by color separation of a multicolor image. .

  An image forming apparatus 1 stores a sheet on which an image is recorded and supplies a sheet to an image forming unit 3 described later, and an image forming unit that records an image on a sheet fed from the sheet supplying unit 2 3. Paper stacking unit 4 that discharges a sheet on which an image is recorded in the image forming unit 3 and a sheet stacking unit that is provided in the vicinity of the sheet discharging unit 4 and that detects the stacking state of the image-recorded sheets stored in the discharge tray 7 The image forming apparatus main body 6 including the state detection device 5 and the image forming apparatus main body 6 are provided close to one side surface 6a of the image forming apparatus main body 6 so as to be vertically movable with respect to the image forming apparatus main body 6. It includes a discharge tray 7 for storing image-recorded paper discharged to the outside of the apparatus main body 6, and a lifting drive unit 8 that drives the discharge tray 7 to be movable up and down with respect to the image forming apparatus main body 6. Is done.

  The paper supply unit 2 is provided so as to face the pickup roller 12, a paper cassette 10 that stores paper, a pickup roller 12 that takes out the paper in the paper cassette 10 one by one, and a plurality of papers are provided by the pickup roller 12. When the sheet is taken out, the sheet feeding roller 13 that separates and feeds one sheet and the sheet that is provided along the sheet conveying path P1 and is taken out from the sheet cassette 10 by the pickup roller 12 or the sheet feeding roller 13 are fed. And a conveying roller 14 for feeding to the image forming unit 3. The paper cassette 10 is a tray for storing paper such as plain paper, color copy paper, and OHP film. The replenishment of the paper to the paper cassette 10 is performed by pulling out the paper cassette 10 to the front side (operation side) of the image forming apparatus main body 6.

  In the paper supply unit 2, the paper in the paper cassette 10 is taken out from the paper cassette 10 one by one by the pickup roller 12 or the paper feed roller 13, and passes through the paper conveyance path P 1 by the conveyance roller 14 to the image forming unit 3. Be sent.

  In the present embodiment, as indicated by a two-dot chain line, one or more of the paper supply units 2 a having the same configuration as the paper supply unit 2 are provided on the lower surface and / or side surface of the image forming apparatus main body 6. it can.

  The image forming unit 3 includes an image forming unit 20, an intermediate transfer unit 21, a secondary transfer unit 22, a cleaning unit 23, and a fixing unit 24. Further, among the units constituting the image forming unit 3, the secondary transfer unit 21 and the fixing unit 24 are provided along the sheet conveyance path P <b> 2 together with the conveyance roller 15 and the registration roller 25.

  The image forming unit 20 forms an electrostatic latent image corresponding to image data of each hue and develops the electrostatic latent image to form a toner image of each color. An image forming unit 20a for forming a toner image, an image forming unit 20b for forming a toner image corresponding to cyan image data, an image forming unit 20c for forming a toner image corresponding to magenta image data, and a black color image data. An image forming unit 20d that forms a toner image corresponding to the image data is included.

  The image forming unit 20a includes a photosensitive drum 26a, a charging roller 27a provided so as to face the peripheral surface of the photosensitive drum 26a, an exposure unit 28, a developing device 29a, and a cleaning unit 30a. The The photosensitive drum 26a is supported so as to be rotatable in the direction of an arrow 31, and includes a cylindrical or columnar conductive substrate (not shown) and a photoconductive layer formed on the surface of the conductive substrate. Is done. The charging roller 27a charges the peripheral surface of the photosensitive drum 26a to a predetermined polarity and potential. Instead of the charging roller 27a, a brush type charger, a charger type charger or the like can be used. The exposure unit 28 includes a laser irradiation means 32 made of, for example, a semiconductor laser, a polygon mirror 33, and reflection mirrors 34a, 34b, 34c, and 34d. The laser light emitted from the laser irradiation means 32 based on the image information is modulated by the polygon mirror 33 based on the image data of each color. Among these, the laser beam modulated based on the yellow color image data is reflected by the two reflecting mirrors 34a, and is irradiated onto the peripheral surface of the photosensitive drum 26a charged to a predetermined polarity and potential. An electrostatic latent image based on the image data is formed. The developing device 29a is provided so as to be in contact with the peripheral surface of the photosensitive drum 26a, and the yellow toner filled therein is statically formed on the surface of the photosensitive drum 26a based on the yellow image data. The electrostatic latent image is supplied to the electrostatic latent image and developed into a yellow toner image. The cleaning unit 30a removes and collects the yellow toner remaining on the peripheral surface after the yellow toner image on the peripheral surface of the photosensitive drum 26a is primarily transferred to the intermediate transfer unit 21.

  According to the image forming unit 20a, while rotating the photosensitive drum 26a in the direction of the arrow 31, first, the peripheral surface of the photosensitive drum 26a is charged by the charging roller 27a, and the charged unit is charged by the exposure unit 28. An electrostatic latent image is formed on the surface, and the developing device 29a develops the electrostatic latent image into a yellow toner image. The yellow toner image is primarily transferred to the intermediate transfer belt 35 of the intermediate transfer unit 21, and then the photosensitive drum 26a. A cycle in which the yellow toner image remaining on the peripheral surface is removed and collected by the cleaning means 30a is repeatedly executed.

  Since the image forming units 20b, 20c, and 20d have a similar structure to the image forming unit 20a except that the color of the toner to be used is different, the same reference numerals are given, and yellow is added at the end of each reference numeral. Instead of “a” indicating “b”, “b” indicating cyan, “c” indicating magenta, or “d” indicating black is added, and description thereof is omitted. The image forming units 20a, 20b, 20c, and 20d are arranged in a line in this order in the moving direction (sub-scanning direction) of the intermediate transfer belt 35. In addition, in the exposure unit 28 of the image forming unit 20d, the reflection mirror 34d that reflects the laser beam modulated based on the black color image information and irradiates the peripheral surface of the photosensitive drum 26d is another image forming unit 20a. , 20b, and 20c, there is only one.

  The intermediate transfer unit 21 includes an intermediate transfer belt 35, a driving roller 36, a driven roller 37, and intermediate transfer rollers 38a, 38b, 38c, and 38d.

The intermediate transfer belt 35 is stretched between the driving roller 36 and the driven roller 37 to form a loop-shaped movement path. The intermediate transfer belt 35 is formed endlessly using a film such as a resin film. Although there is no restriction | limiting in particular in the thickness, Preferably it is about 100-150 micrometers. The resistance value is not particularly limited, but is preferably 10 ¹¹ to 10 ¹² Ω · cm. When the resistance value is within this range, during intermediate transfer, the intermediate transfer belt 35 can be provided with a sufficient charge for the intermediate transfer, and the means for neutralizing the intermediate transfer belt 35 after passing through each transfer position. There is no need to provide. The outer peripheral surface 35a of the intermediate transfer belt 35 faces the photosensitive drums 26a, 26b, 26c, and 26d in this order. Intermediate transfer rollers 38a, 38b, 38c, and 38d are disposed at positions facing the photosensitive drums 26a, 26b, 26c, and 26d with the intermediate transfer belt 35 interposed therebetween. A position of the intermediate transfer belt 35 facing the photosensitive drums 26a, 26b, 26c, and 26d is an intermediate transfer position.

  The intermediate transfer rollers 38a, 38b, 38c, and 38d are provided so as to be in pressure contact with the inner peripheral surface of the intermediate transfer belt 35 and to be rotatable about its axis, for example, a metal shaft body and a surface of the shaft body And a conductive layer to be coated. The shaft body is made of, for example, stainless steel. The diameter is not particularly limited, but is preferably 8 to 10 mm. The conductive layer is formed of a conductive elastic body or the like. As the conductive elastic body, those commonly used in this field can be used, and examples thereof include EPDM, foamed EPDM, foamed urethane and the like containing a conductive material such as carbon black. A high voltage is uniformly applied to the intermediate transfer belt 35 by the conductive layer.

  The intermediate transfer rollers 38a, 38b, 38c, and 38d are respectively opposite to the normal direction of the photosensitive drums 26a, 26b, 26c, and 26d with respect to the axes of the photosensitive drums 26a, 26b, 26c, and 26d. Be energized. Further, the intermediate transfer rollers 38a, 38b, 38c, and 38d are charged with toner charge polarity in order to transfer toner images formed on the surfaces of the photosensitive drums 26a, 26b, 26c, and 26d onto the intermediate transfer belt 35. A reverse polarity intermediate transfer bias is applied by constant voltage control. As a result, yellow, cyan, magenta, and black toner images formed on the photosensitive drums 26a, 26b, 26c, and 26d are sequentially transferred onto the outer peripheral surface 35a of the intermediate transfer belt 35 and transferred. A multicolor toner image is formed on the outer peripheral surface 35a. However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, an image corresponding to the hue of the input image data among the image forming units 20a, 20b, 20c, and 20d. A toner image is formed only in the forming unit. For example, when a monochrome image is formed, a toner image is formed only in the image forming unit 20 d corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface 35 a of the intermediate transfer belt 35.

  In the present embodiment, since the intermediate transfer bias amount applied to the intermediate transfer belt 35 is constant, all of the intermediate transfer rollers 38a, 38b, 38c, and 38d are used regardless of the monochrome image formation or the full-color image formation. Is applied with an intermediate transfer bias. Accordingly, the intermediate transfer rollers 38a, 38b, 38c, and 38d are always in contact with the intermediate transfer belt 35. This further improves the transfer accuracy. In this embodiment, a brush-like intermediate transfer member can be used instead of the intermediate transfer roller.

  According to the intermediate transfer unit 21, the toner images of the respective colors formed by the image forming units 20a, 20b, 20c, and 20d are transferred onto a predetermined position of the outer peripheral surface 35a of the intermediate transfer belt 35 and transferred onto the outer peripheral surface 35a. A multicolor toner image is formed.

  The secondary transfer unit 22 includes a secondary transfer roller 39. The secondary transfer roller 39 transfers the toner image formed on the outer peripheral surface 35 a of the intermediate transfer belt 35 onto the paper fed from the paper supply unit 2, and the driving roller 36 via the intermediate transfer belt 35. The intermediate transfer belt 35 is provided so as to be in pressure contact with the outer peripheral surface 35a of the intermediate transfer belt 35 with a predetermined nip pressure and to be rotatable around its axis. Similar to the intermediate transfer roller 38, the secondary transfer roller 39 is, for example, a metal shaft made of stainless steel or the like, and an EPDM formed on the surface of the metal shaft and containing a conductive material such as carbon black, And a conductive layer made of foamed EPDM, foamed urethane rubber or the like. In order to maintain the nip pressure between the secondary transfer roller 39 and the intermediate transfer belt 35 at a predetermined value, one of the secondary transfer roller 39 or the drive roller 36 is formed of a hard material such as metal, and the other is It is preferable that at least the surface is an elastic roller made of a soft material (elastic rubber, foamable resin, etc.). In the secondary transfer unit 22, the intermediate transfer belt 35 is formed on the outer peripheral surface 35 a of the intermediate transfer belt 35 in the image forming unit 3 by the rotation of the intermediate transfer belt 35 at the contact position between the intermediate transfer belt 35 and the secondary transfer roller 39. The toner image is conveyed, and at the same time, the sheet is conveyed from the sheet supply unit 2 to the contact position between the intermediate transfer belt 35 and the secondary transfer roller 39 via the conveyance roller 14 b and the registration roller 25, and is transferred to the secondary transfer roller 39. By applying a high voltage having a polarity opposite to the charging polarity of the toner, the toner image is transferred from the outer peripheral surface 35a of the intermediate transfer belt 35 to the surface of the sheet. The sheet on which the toner image is transferred is fed to the fixing unit 24.

  The registration roller 25 applies the sheet fed from the sheet feeding unit 2 via the sheet conveyance path P2 to the intermediate transfer belt 35 and the secondary transfer roller 39 at a timing synchronized with the rotation of the intermediate transfer belt 35. Lead to close position. Therefore, the registration roller 25 stops rotating when the operations of the photosensitive drums 26a, 26b, 26c, 26d, the intermediate transfer belt 35, and the like are started, and the sheet supplied prior to the rotation of the intermediate transfer belt 35 has a leading edge. The movement in the paper conveyance path P1 is stopped in a state where it is in contact with the registration roller 25. Thereafter, the registration roller 25 is a position where the intermediate transfer belt 35 and the secondary transfer roller 39 are in pressure contact with each other, and the front margin portion of the toner image formed on the front end portion of the sheet and the outer peripheral surface 35 a of the intermediate transfer belt 35. Rotation starts at the timing of facing each other.

  The cleaning unit 23 is for removing the toner remaining on the outer peripheral surface 35 a of the intermediate transfer belt 35 after the toner image is transferred to the paper in the secondary transfer unit 22, and is in contact with the intermediate transfer belt 35. A cleaning blade 40 that scrapes off toner remaining on the outer peripheral surface 35a of the intermediate transfer belt 35, and a toner storage container 41 that stores toner scraped off by the cleaning blade 40. As the cleaning blade 40, those commonly used in this field can be used, and examples thereof include a blade made of an elastic metal material (for example, elastic stainless steel). According to the cleaning unit 23, toner remaining on the outer peripheral surface 35 a of the intermediate transfer belt 35 without being transferred to the paper is scraped off by the cleaning blade 40, and the scraped toner is stored in the toner storage container 41. .

  The fixing unit 24 is for receiving the supply of the paper on which the toner image is transferred from the secondary transfer unit 22 and fixing the toner image on the paper. A heating roller 42 for bringing the toner into a molten state, and a pressure roller 43 that is in contact with the heating roller 42 and is rotatably driven, and applies pressure to the toner in the molten state to fix the toner on the paper. According to the fixing unit 24, the sheet on which the toner image is transferred in the secondary transfer unit 22 is heated and pressed by the heating roller 42 and the pressure roller 43, and the toner is melted and fixed to the sheet. Is fixed on the paper.

  In the image forming unit 3, the toner image formed on the outer peripheral surface 35 a of the intermediate transfer belt 35 in the image forming unit 20 is transferred to and fixed on the sheet fed from the sheet supply unit 2. The paper on which the toner image has been fixed and image formation has been completed is fed to the paper discharge unit 4 by the transport roller 44.

  The paper discharge unit 4 includes discharge rollers 45 and 46 and conveyance rollers 48 and 49 that are rotatably supported. The transport rollers 48 and 49 are provided along the paper transport path P3.

  Among these rollers, the discharge roller 45 can be rotated in both forward and reverse directions, and is driven in the forward rotation direction when discharging the image-recorded paper to the discharge tray 50 provided on the upper surface of the image forming apparatus main body 6. The sheet is discharged to the discharge tray 50. At this time, the image-recorded paper is a paper on which an image is formed on one side or both sides. Further, the discharge roller 45 is driven in the reverse direction at the time of double-sided image formation in which an image is formed on the other side of the sheet having an image formed on one side, and the sheet having the image formed on one side is transferred to the transport roller 48. To the paper conveyance path P3. In that case, the discharge roller 45 is driven in the forward rotation direction until the rear end of the sheet passes through the fixing unit 24, and then is driven in the reverse direction with the rear end of the sheet being sandwiched, thereby feeding the sheet to the sheet conveyance path. Guide into P3. As a result, the sheet on which the image is formed on only one side during the double-sided image formation is guided to the sheet conveyance path P2 with the front and back surfaces and the front and rear ends reversed.

  The discharge roller 46 discharges the image-recorded paper on which an image is formed on one side or both sides in the image forming unit 3 to the discharge tray 7.

  According to the paper discharge unit 4, the image-recorded paper on which the image is formed in the image forming unit 3 is discharged to a discharge tray 7 provided outside the image forming apparatus main body 6 or a discharge tray 50 provided on the upper surface thereof.

  The sheet stacking state detection device 5 detects the stacking state of the image-recorded sheets stored in the discharge trays 7 and 50, and includes detection means 51 and 52, a storage unit (not shown), a comparison unit, and a determination unit. Consists of including. The storage unit stores a reference value determined in advance from the measurement results obtained by the detection means 51 and 52, and the comparison unit includes the reference value, the detection value obtained from the measurement results obtained by the detection means 51 and 52, and the reference value. The determination unit determines the sheet stacking state of the discharge trays 7 and 50 according to the output of the comparison unit.

  The detecting means 51 detects the stacking state of the image-recorded sheets on the discharge tray when the predetermined discharge tray reaches a predetermined position by using the elevation of the discharge tray 7. The detection means 51 is an image-recorded sheet that is stacked on the discharge tray 7 above the discharge roller 46 in the image forming apparatus main body 6 through a light transmission hole 53 formed on one side surface 6 a of the image forming apparatus main body 6. It is provided to face. The detection means 51 irradiates the light 55 to detect the stacked state of the image-recorded sheets on the discharge tray 7.

  The detection means 52 detects the stacked state of the image-recorded sheets on the discharge tray 50, and the light formed on the one side surface 6 b of the image forming apparatus body 6 above the discharge roller 45 in the image forming apparatus body 6. It is provided so as to face the image-recorded paper loaded on the discharge tray 50 through the transmission hole 54. The detection unit 52 irradiates the light 56 and detects the stacked state of the image-recorded sheets on the discharge tray 50.

  Although various sensors can be used for the detection means 51 and 52, a non-contact type distance measuring sensor can be preferably used. The non-contact type distance measuring sensor measures the distance to the paper (exactly the paper surface) loaded on the discharge trays 7 and 50 by irradiating the paper with light and displays it as an output voltage. FIG. 3 shows the relationship between the distance (cm) to the reflector (here, the paper stacked on the discharge tray 7) and the output power (V) displayed at each distance in the non-contact type distance measuring sensor. It is a graph. The change in the output voltage displayed by the distance measuring sensor is very weak when the distance changes to the extent that one sheet is stacked. Therefore, if the change in the output voltage exceeds a predetermined value, it is determined that there is a stacking abnormality. Is set as follows. Here, for example, when the distance to the reflector is 20 cm (output power around 0.8 V), the discharge tray 7 is in an empty state in which no sheets are stacked, and the distance to the reflector is about 15 cm (output power 1). Is set such that the paper stacking state of the discharge tray 7 is full. Furthermore, it is set so that it is determined that a loading abnormality has occurred when the change in the output voltage is 0.1 V or more.

  FIG. 4 is a cross-sectional view showing one form of detection of abnormal paper stacking on the discharge tray by the distance measuring sensor. A distance measuring sensor, which is a detection means 51 provided above the discharge roller 46 inside the image forming apparatus main body 6, is the uppermost stage through a light transmission hole 53 formed on one side surface 6 a of the image forming apparatus main body 6. Light 55 is irradiated to the paper P stacked on the discharge tray 7b one level below the discharge tray 7a. When the sheet P is not folded or bent and is normally stacked on the discharge tray 7b, an output power change of 0.1 V or more does not occur, so a stacking abnormality is not detected. However, if the sheet Pn is bent on the discharge tray 7b, the distance between the distance measuring sensor and the sheet P1 is instantaneously shortened, and the output voltage changes by 0.1 V or more, so that it is detected as a stacking abnormality. When a stacking abnormality is detected, the image formation is interrupted and the paper P1 is removed from the discharge tray 7b, and then the image formation is resumed, or the image formation is interrupted and the discharge tray 7 is moved up and down to remove the discharge tray. After the change, image formation is resumed. If the discharge tray is changed as in the latter case, image formation can be continuously performed without removing the paper Pn. For example, when the operator is not near the image forming apparatus 1, a large amount of a single image is printed. This is particularly advantageous.

  The discharge tray 7 is provided close to one side surface 6a of the image forming apparatus main body 6 and is vertically movable with respect to the image forming apparatus main body 6. The discharge tray 7 includes two or more discharge trays. Further, a discharge tray stopper 57 is provided below the one side surface 6a of the image forming apparatus main body 6 to prevent the discharge tray 7 from being lowered more than necessary.

  The elevating drive unit 8 includes an elevating motor 60, a pulley 61 provided on the output shaft of the elevating motor 60, a deceleration pulley 62 that is supported so as to be rotatable around its axis, and a pulley 61 and a deceleration pulley 62. A belt 63 stretched between, a hanging pulley 64, and a suspended pulley 64 and a deceleration pulley 62 are stretched between one end and wound around a small diameter portion of the deceleration pulley 61, and the other end is fixed. And a belt 65 fixed to the root portion 66 of the elevating tray 7e. According to the elevating drive unit 8, when the elevating motor 60 rotates in the normal rotation direction (counterclockwise in the figure), the belt 65 is wound around the small diameter portion of the deceleration pulley 61, and the discharge tray 7 is raised. Conversely, when the lifting motor 60 rotates in the reverse direction (clockwise in the figure), the belt 65 is fed out from the small diameter portion of the deceleration pulley 61 and the discharge tray 7 is lowered.

  Furthermore, in the image forming apparatus 1 according to the present embodiment, a control device 70 is disposed above the image forming unit 3 inside the image forming apparatus main body 6.

  FIG. 5 is a block diagram showing electrical connection between the detection means 51 and 52, the control device 70, and its output control unit.

  In the image forming apparatus main body 6, in addition to the distance measuring sensors which are the detection means 51 and 52, other sensors (non-detection) for detecting a paper jam or the like provided in the discharge tray position detection sensor 67 and the paper transport paths P1 to P3. Is provided). A detection result of the paper stacking state of the discharge tray 7 is input as an electric signal from the distance measuring sensor to the control device 70 provided in the image forming apparatus main body 6. Further, a detection result indicating which of the plurality of discharge trays 7 is at the position of the sheet discharge hole of the image forming apparatus main body 6 is input from the discharge tray position detection sensor 67 as an electrical signal. Based on these detection results, the control device 70 includes the discharge tray lifting / lowering motor 60 included in the discharge tray lifting / lowering means 8, the sheet supply unit 2, the image forming unit 3, and the sheet transport paths P <b> 1 to P <b> 3 in the image forming apparatus main body 6. An electric signal is sent to a motor other than the discharge tray lifting / lowering motor 60 (for example, a paper transport motor), a solenoid, etc. provided in the above, and the discharge tray 7 is moved up and down, the paper is fed by the paper supply unit 2, and the image is formed in the image forming unit 3. Control of paper conveyance in the paper conveyance paths P1, P2, and P3 is performed. In FIG. 1 and FIG. 2, illustration of electrical wiring connecting the control device 70 to each sensor, motor, solenoid and the like is omitted.

  FIG. 6 is a flowchart showing a procedure for detecting the sheet stacking state on the discharge tray 7a by the detecting means 51. At this time, the detection means 51 includes a distance measuring sensor, a storage unit, a comparison unit, and a determination unit.

  Step S0 is a start of detection of the paper stacking state in the discharge tray 7a. The upper end to the lower end in the transport direction of the paper Pn is normally discharged to the discharge tray 7, and the upper end in the transport direction of the next paper Pn + 1 does not come out from the paper discharge port of the image forming apparatus main body 6 at all.

At this time, the storage unit of the detection unit 51 irradiates the surface of the paper Pn with light from the distance measuring sensor, the output power V ₀ (V, reference value) that is the distance from the distance measuring sensor to the surface of the paper Pn, and the discharge. A voltage value of 1.0 V, which is a reference value for determining that the loading amount of the tray 7a and the remaining trays has reached the maximum loading amount, is stored.

Step S1 is a step of irradiating the surface of the paper Pn + 1 newly discharged to the discharge tray 7a with light from the distance measuring sensor and outputting the distance from the distance measuring sensor to the surface of the paper Pn + 1 as the voltage V ₁ (V). .

Step S2 is a step of storing the output voltage V ₁ (V, detection value) obtained in step S1 in the storage unit.

Step S3 compares the output voltage V ₀ (reference value) with the output voltage V ₁ (detection value) in the comparison unit of the detection means 51, and the difference between the output voltage V ₀ and the output voltage V ₁ in the determination unit. Is a step of determining whether or not the absolute value is 0.1 V or less. If it exceeds 0.1V, the process proceeds to step S4, and if it is 0.1V or less, the process proceeds to step S5.

  Step S4 is a step of determining that a stacking abnormality has occurred, and proceeds to step S7 where the image forming operation is terminated.

Step S5, the determination of the detection means 51, a comparison of the reference value 1.0V of the output power _{V 1} and the maximum load capacity is the step of determining whether less 1.0V or higher or 1.0V . If the output power V ₁ is less than 1.0V, the process proceeds to step S6, if it is more than 1.0V, the sheet stacking amount of the discharge tray 7a is judged to have reached the maximum load, terminating the image forming operation Therefore, the process proceeds to step S7.

Step S6, the storage unit, the output voltages V ₁ is a detected value, and stores the replaced the output voltage V ₀ is a reference value, then the process proceeds to step S1, and repeats the subsequent steps.

  In step S7, the image forming operation is terminated and new image formation is started as necessary.

  When the process proceeds from step S5 to step S7, the image forming operation is terminated due to a stacking abnormality. The loading abnormality may be notified to the operator by the control device 70 and display means such as an operation screen and a warning sound. The operator can remove the sheet Pn + 1 causing the stacking abnormality detection from the discharge tray 7a, cancel the error display on the operation screen, and restart image formation from step S0. Further, after canceling the error display on the operation screen, the operator can change the discharge tray 7a to another discharge tray 7b by lifting and lowering the discharge tray 7 without removing the paper Pn + 1, and can restart image formation from step S0. Further, according to the setting of an operation control program given in advance for image forming operation control of the control device 70, the operator automatically switches to another discharge tray 7b without canceling the error and restarts image formation from step S0. You can also

  If the process has proceeded from step S6 to step S7, the image forming operation has ended normally with the discharge tray 7a being full, so the image formation may be ended as it is. In that case, the operator may be notified of the exhaust tray 7a being full in the same manner as described above by an operation screen, a warning sound, or the like. Further, when printing the same image, the operator can automatically or automatically switch to another discharge tray 7b, and image formation can be restarted from step S0.

  FIG. 7 is a flowchart showing one mode of switching the discharge tray 7 based on the detection result of the paper stacking state on the discharge tray 7 by the detection means 51. The detection means 51 includes a distance measuring sensor, a storage unit, a comparison unit, and a determination unit. As described above, the storage unit stores a voltage value of 1.0 V, which is a reference value for determining that the paper stacking state of the discharge tray 7 is maximum (full).

  In step T0, image formation by the image forming apparatus 1 is started. The image-recorded paper on which the image is recorded is discharged and stacked on, for example, a discharge tray 7b that is a lower stage of the uppermost tray 7a of the discharge tray 7.

  In step T1, the distance sensor of the detection means 51 measures the paper stacking amount of the discharge tray 7b as an output voltage, stores the output power in the storage unit, and the output power is 1.0 V or higher or 1 in the comparison unit. Compare if it is less than 0V. The determination unit makes a determination according to the output of the comparison unit. If the output voltage is less than 1.0 V, the process proceeds to step T2, and if the output voltage is 1.0 V or more, the process proceeds to step T3.

  In step T2, the image formation is continued, the discharge of the image-formed paper to the discharge tray 7b is continued, and the process returns to step T1.

  In step T3, based on the detection result that the paper stacking amount of the discharge tray 7b is full by the determination unit of the detection unit 51, an operation panel (not shown) provided on the upper surface of the image forming apparatus main body 6 is attached to the discharge tray. The switching is displayed and the process proceeds to step T4.

  In step T4, a discharge tray for discharging and stacking image-recorded sheets is selected. For example, the discharge tray 7 is lowered, and the distance measuring sensor of the detection means 51 outputs the sheet stacking state of the discharge tray 7a that is the uppermost tray as a voltage, and the output voltage (detection value) is 1.0 V or more. In the comparison unit, the determination unit determines the sheet stacking state of the discharge tray 7a according to the output of the comparison unit. If the output voltage is less than 1.0 V, it is determined that the discharge tray 7a is not full, and the process proceeds to step T5. If it is 1.0 V or more, it is determined that the discharge tray 7a is full, and the process proceeds to step T6. When no paper is stacked on the discharge tray 7a, the output voltage from the distance measuring sensor is stored in the storage unit and compared with the detection value in the comparison unit, and the output voltage when there is no paper stack differs from the detection value. In this case (that is, when the output tray 7a is not full but already recorded paper is already loaded), there is a possibility that papers with different images may be mixed. A so-called empty discharge tray without a flow may be selected.

  In step T5, image formation is continued in the same manner as in step T2, paper is discharged and stacked on the discharge tray 7a, and the process returns to step T4.

  In step T6, based on the detection result by the detection means 51 that the sheet stacking capacity of the discharge tray 7a is full, the discharge tray 7 is raised, the discharge tray 7a is set as the first level, and the discharge trays 7an after the nth level. The paper stacking state (n is an integer of 3 or more) is determined in the same manner as in step T4. If the output voltage from the distance measuring sensor is less than 1.0 V, the discharge tray 7an is not full, and the process proceeds to step T7. If it is 1.0 V or more and the discharge tray 7an is full, the process proceeds to step T8.

  In step T7, image formation is continued in the same manner as in steps T2 and T5, the sheets are discharged and stacked on the discharge tray 7an, and the process returns to step T6.

  In step T8, the detection tray 51 further raises the discharge tray 7 based on the detection result that the sheet stacking amount of the discharge tray 7an is full, and the sheet stacking state of the lowermost discharge tray of the discharge tray 7 is changed to step T8. Judgment is made in the same manner as T4. If the output voltage from the distance measuring sensor is less than 1.0 V, the lowermost discharge tray is not full, and the process proceeds to step T9. If it is 1.0 V or more and the lowermost discharge tray is full, the process proceeds to step T10.

  In step 9, image formation is continued in the same manner as steps 2, 5, and 7, the sheets are discharged and stacked on the lowermost discharge tray, and the process returns to step 8.

  In step T10, based on the detection result indicating that the sheet stacking amount of the entire discharge tray 7 has reached the maximum stacking amount by the detecting unit 51, printing of the image is stopped, and the operation status operation on the upper surface of the image forming apparatus main body 6 is performed. The panel displays that all the trays of the discharge tray 7 are full, emits a warning sound as necessary, and notifies the operator.

  In the present invention, as shown in FIGS. 6 and 7, when the discharge tray 7 reaches the maximum stacking amount or exhibits a stacking abnormality, the image forming is not stopped simply as in the prior art, but the discharge trays are sequentially arranged. By switching. The image formation can be continued without stopping until the lowermost tray is full.

  The image forming apparatus 1 of the present embodiment is an intermediate transfer type single-color / multiple-color image forming apparatus having a plurality of image forming units, but is not limited thereto, and is a direct transfer type full-color image forming apparatus, image A color image forming apparatus having one or two forming units, a monochrome image forming apparatus, or the like may be used.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a state where a discharge tray is raised in the image forming apparatus illustrated in FIG. 1. It is a graph which shows the relationship between the distance (cm) to a reflective body in a ranging sensor, and output electric power (V). It is sectional drawing which shows one form of detection of the paper stacking abnormality by a non-contact type distance measuring sensor. It is a block diagram which shows the electrical connection of a detection means, a control apparatus, and its output control part. 6 is a flowchart illustrating a procedure for detecting a paper stack state by a distance measuring sensor. 3 is a flowchart showing control of discharge tray switching in the image forming apparatus shown in FIG. 10 is a cross-sectional view schematically illustrating a configuration of a paper stacking device disclosed in Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper supply part 3 Image forming part 4 Paper discharge part 5 Paper stacking state detection apparatus 6 Image forming apparatus main body 6a, 6b One side surface of the image forming apparatus main body 7, 7a, 7b, 50 Discharge tray 8 Lifting drive part DESCRIPTION OF SYMBOLS 10 Paper cassette 12 Pickup roller 13 Paper feed roller 14, 15, 44, 48, 49 Conveyance roller 20, 20a, 20b, 20c, 20d Image forming unit 21 Intermediate transfer unit 22 Secondary transfer unit 23 Cleaning unit 24 Fixing unit 25 Resistor Rollers 26a, 26b, 26c, 26d Photosensitive drums 27a, 27b, 27c, 27d Charging rollers 28 Exposure units 29a, 29b, 29c, 29d Developing devices 30a, 30b, 30c, 30d Cleaning means 31a, 31b, 31c, 31d 32 laser Projection means 33 Polygon mirrors 34a, 34b, 34c, 34d Reflective mirror 35 Intermediate transfer belt 35a Intermediate transfer belt outer peripheral surface 36 Drive roller 37 Driven roller 38, 38a, 38b, 38c, 38d Intermediate transfer roller 39 Secondary transfer roller 40 Cleaning blade 41 Toner storage container 42 Heating roller 43 Pressure roller 45, 46 Discharge roller 51, 52 Detection means 53, 54 Light transmission hole 55, 56 Light 57 Discharge tray stopper 60 Lifting motor 61 Pulley 62 Deceleration pulley 63, 65 Belt 64 Drooping Pulley 66 Root 70 Control device

Claims (6)

An image forming apparatus close to one side surface of an image forming apparatus main body including a sheet supply unit that supplies a sheet on which an image is recorded, an image forming unit that records an image on the sheet, and a sheet discharge unit that discharges a sheet on which an image is recorded A sheet stacking state detection device that detects a stacking state of sheets in a plurality of discharge trays that are movable up and down with respect to a main body, and that stores sheets discharged from a main body of an image forming apparatus by a sheet discharge unit. ,
Including at least one detection means;
The detection means is
Provided inside the image forming apparatus body,
A sheet stacking state detection device that detects the stacking state of sheets on a discharge tray when a predetermined discharge tray reaches a predetermined position by using the raising and lowering of the discharge tray. The detection means is
2. The apparatus according to claim 1, wherein the sheet is provided near a sheet discharge portion and facing a sheet loaded on a discharge tray through a light transmitting member or a light transmitting hole provided on one side surface of the image forming apparatus main body. The paper loading state detection device described.   2. The paper stacking state detecting apparatus according to claim 1, wherein the detecting means is a non-contact distance measuring sensor. The detection means is
A storage unit that stores a predetermined reference value; a comparison unit that compares the detected value with the reference value; and a determination unit that determines a stacking state of the discharge tray according to an output of the comparison unit;
The loading state detected by the detection means is
The paper stacking state detection according to any one of claims 1 to 3, wherein the paper stacking state detection state is a state in which a maximum stacking amount of sheets predetermined for each discharge tray has been reached or an abnormal discharge state of sheets to the discharge tray. apparatus. An image forming apparatus main body including a paper supply unit that supplies paper on which an image is recorded, an image forming unit that records an image on the paper, and a paper discharge unit that discharges the paper on which the image is recorded, and one side of the image forming apparatus main body A plurality of discharge trays for accommodating sheets discharged from the image forming apparatus main body by the paper discharge unit, and a lift drive unit that drives the plurality of discharge trays to be movable up and down relative to the image forming apparatus main body. In the image forming apparatus capable of switching the discharge tray to accommodate the paper discharged from the image forming apparatus main body by raising and lowering the plurality of discharge trays by the lifting drive unit,
An image forming apparatus, further comprising: the sheet stacking state detection device according to claim 1. Furthermore, position detecting means for detecting the raising and lowering positions of the discharge trays arranged at the uppermost and / or lowermost stages of the plurality of discharge trays;
Tray recognition means for recognizing a predetermined discharge tray from a plurality of discharge trays according to the detection output of the position detection means;
In response to the output of the tray recognition means, a paper stacking state on a predetermined discharge tray is detected by a paper stacking state detection device, and in response to the detection output, a paper supply unit, an image forming unit, a paper discharge unit, and a lift drive unit The image forming apparatus according to claim 5, further comprising a control unit that controls an operation of at least one portion of the image forming apparatus.

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