JP2825625B2 - Multi-stage paper feeder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, which has a plurality of paper feed containers in a housing, and a paper fed from these paper feed containers. The present invention relates to a sheet feeding and conveying device that is raised by a vertical conveying means and feeds the image to the image forming apparatus.

2. Description of the Related Art With the advance of space-saving OA equipment such as image forming apparatuses such as copying machines, laser printers, and facsimile machines, a paper feeder in which a plurality of paper feed cassettes or paper feed trays are vertically stacked is used as an image forming apparatus. An image forming apparatus which is formed separately from the main body and placed on the lower side of the image forming apparatus main body so as to reduce the installation area is gradually spreading.

Conventionally, this type of paper feeder, which is implemented and proposed, is disclosed in, for example, Japanese Utility Model Laid-Open No. 1-78629, but as shown in FIG. Paper cassette such as paper cassette or paper tray
The paper selectively fed from 302 and 303 is provided between the rollers and an elastic-conveying roller 304 made of elastic material and provided in the vertical direction facing the paper feeding end of these paper feeding containers and arranged according to the minimum size of the paper. In general, the sheet is conveyed upward through a vertical conveyance path constituted by the paired guide plates 305 and fed to the image forming apparatus main body.

Such a method of transporting a sheet by the frictional force of an elastic roller is widely used because of its simple structure.However, the friction coefficient of rubber used for the transport roller decreases with time, and slip due to generation of paper powder is caused. However, there is a drawback that paper is jammed at the connection between the roller and the guide plate due to the curl of the transfer paper in a high humidity environment.

Further, a simple paper feeder for a printing press which feeds paper from a plurality of vertically stacked paper feed trays to a recording unit by a single paper feed roller has been disclosed by the present applicant in Japanese Utility Model Application No. Hei.
Proposed by 78713. This paper feeder is
As shown in the figure, a transport mechanism having a single paper feed roller 306, a single paper feed tray elevating drive device 307, and a paper feed tray 308 raised and lowered by the paper feed tray elevating drive device 307 are provided. The paper feed tray 308 has a plurality of vertically stacked paper feed trays 309, 3
10 and each paper feed tray 309 except for the bottom 310 (1 in the figure).
(Only the stage is shown) indicates that the front end of the sheet bundle placed thereon in the paper feed direction is
It is slidable for a fixed distance between a position within the operation range of 306 and a position where the front end of the sheet retracts backward from the sheet feeding roller 306.

Therefore, the paper feed tray on which the paper to be fed is placed is held at a position where its front end is within the range of action of the paper feed rollers. When the sheet feed tray 308 is moved up by the single sheet feed tray elevating drive unit 307 and the sheet feed tray 308 is raised by the single sheet feed tray elevating drive device 307, the sheet feed tray above the sheet feed tray on which the paper to be fed The sheet bundle placed on the upper side rises behind the sheet bundle without contacting the sheet feeding roller, and the vicinity of the front end of the upper surface of the sheet bundle to be fed comes into pressure contact with the sheet feeding roller. The upper surface of the bundle comes to a predetermined position and stops. As a result, desired paper can be automatically fed by the paper feed roller.

However, this mechanism has a conventional one-tray-type paper feed tray and a paper feed tray that can slide in the paper feed direction. Loading paper is difficult due to layout,
In order to realize this, the paper feeding unit becomes large, and as a result, the entire printing press becomes large.

Also, each time the size and type of paper to be fed is changed, and each time the top position of the paper bundle in the cassette being fed falls below the allowable range, a paper feed tray equipped with a plurality of paper trays Since the paper board 308 must be moved in the vertical direction, there is a disadvantage that a large power is required.

By the way, as a conveying device for a sheet member or the like, an extremely novel conveying device that forms a charge density pattern alternating with an endless belt made of a dielectric material, and attracts and conveys the sheet member by an attraction force generated by this, has recently been developed. It has been proposed by the present applicant in Japanese Patent Application No. 1-117374.

 The principle of this transfer device is as follows.

As shown in FIG. 19, a belt 311 for feeding and conveying a sheet of transfer paper 310 or the like is rotatably held by a driving roller and a plurality of belt support rollers 312.
The belt 311 is an endless belt having a surface layer made of a dielectric material capable of holding electric charges and a back surface made of a semiconductor layer. Further, at least one supporting roller is grounded and is in contact with the back surface of the belt, and an alternating electric field (AHz) is applied from the high voltage power supply 313 to the roller 314 using the ground roller 312 as a counter electrode. Further, the belt 311 is moved at a constant speed Umm / s in the direction of the arrow by the driving roller, and the sheet pickup position is downstream of the contact position of the roller 314 with respect to the moving direction of the belt 311. ing. Therefore, the belt 311
Before the sheet is fed to the surface thereof, an AC voltage is applied from a high voltage power supply via a roller 314, whereby the charge density −σ, + σ is alternately applied to the surface of the belt 311 by U / Amm. , A stripe-shaped charge density pattern is formed. In the semiconductor layer on the back surface of the belt 311,
The charge of the opposite sign is induced by the charge density formed on the belt surface.

As shown in FIG. 20, an uneven electric field is formed in the vicinity of the surface of the belt 311 by the charge density pattern thus formed, and a force acting on a unit volume of the dielectric material serving as the sheet 310 by the electric field is as follows. Using Maxwell's stress tensor, expressed by the following formula, the sheet 310 is held by the force fx in the direction perpendicular to the sheet surface without being electrostatically attracted to the belt 311 and displaced, and carried along with the belt 311. Conveyed.

Assuming that the direction perpendicular to the sheet surface is x, the conveying direction is y, and the direction perpendicular to the conveying direction in the sheet surface is z, the component forces fx, fy in the x, y, and z directions of the force acting on the unit volume of the dielectric. , fz are as follows, respectively.

Maxwell's stress tensor is In the above equation, E is the electric field, D is the electric flux density,
x, y, and z indicate components in the respective directions.

The applied voltage may be obtained by superimposing a DC component on an AC voltage.

This adsorption principle is different from the generally known force of attracting charges of different signs, and the transfer paper can be adsorbed using the above-mentioned method without giving any charge to the transfer paper. For this reason, there is no influence on the transfer process even when used in the paper feeder of the electrostatic recording apparatus.

An example of the method of determining the attraction force of the sheet member conveying device and the measurement results are as follows.

As shown in FIG. 21, the A3 size plain paper 310 is fed to the transport belt, and when the contact length becomes 100 mm, a spring gauge is attached to the rear end of the paper, and the suction force is set as the tensile strength. It was measured. At this time, the adsorption area is 300 cm ² .

As shown in FIG. 22, the amplitude of the AC voltage is kept constant (4 kVp-
The suction force was measured by changing the applied frequency to p). As a result, in the present invention, when the period of the stripe shape was set to a range of 20 mm or less, a sufficient attraction force was obtained. Further, as shown in FIG. 23, as a result of measuring the attraction force while changing the applied voltage while keeping the applied frequency constant (26 Hz), a good attraction force was obtained at 2 kVp-p or more. At this time, it was found from the measurement of the surface potential that the charge density pattern was not formed on the belt at the applied voltage at which no attraction force was generated. For this reason, in order to generate the attraction force, at least an applied voltage higher than the charging start voltage is required.

The same applies to the case where the applied voltage is obtained by superimposing a DC component on an AC voltage or when a non-uniform alternating voltage is applied from a power supply that outputs a non-uniform alternating voltage.

However, in this proposal, there is no mention of a paper feeding method from a bundle of paper stacked on a paper feeding tray or the like.
It is thought that it is based on the conventional paper feed roller or the like, and in this regard, it is unlikely that the problem of the conventional paper feeder will be completely solved.

Although a paper feed tray is not provided in multiple stages, a single insulating endless belt feeds and transports the transfer paper from the paper feed unit of the copying machine, through the transfer unit, and to the insertion unit into the fixing device. A paper conveying apparatus of an electrophotographic copying machine which uses the apparatus is disclosed in, for example, JP-A-59-212856. The method of adsorbing transfer paper to the endless belt differs from the adsorption principle based on the formation of the charge density pattern described above, in which an insulative endless belt is charged using a charging means and electrostatically adsorbed by a potential difference from the transfer paper. However, as shown in FIG. 24,
The support roller 322 of the endless belt 321 provided facing the front end near the upper surface of the sheet bundle P placed in the sheet feed tray 320 is synchronized with the movement of the image area formed on the photoconductor 323,
The sheet is moved so as to be close to the sheet bundle P, and fed by bringing a feed roller 322a provided coaxially with the support roller 322 into contact with the sheet, and the fed sheet is adsorbed by an endless belt to be conveyed and transferred. Then, the toner image formed on the photoreceptor is transferred so that the leading end thereof coincides with the toner image, and is transported to the fixing unit 325.

According to this transporting method, it is possible to reliably transport the paper without causing a jam or the like, and it is possible to simplify the transport mechanism and reduce the cost. Further, since the conveying means and the paper do not come into frictional contact, paper dust is not generated or significantly reduced.

Also, JP-A-63-139846 discloses a paper feeding section of a copying machine,
The registration unit, the transfer unit, the fixing unit, and the paper discharge unit are connected in this order by one endless belt, and first, the endless belt is pressed against the copy paper held by the copy paper supply holding unit,
A paper transport device is disclosed in which a copy paper is carried out by a frictional force, is transferred to a transfer unit after registration, receives a transfer of a toner image from a photoconductor, is fixed in a fixing unit, and is discharged outside the machine. .

According to this apparatus, the movement of copy paper and each part of the copy machine,
Control of the transfer direction of the copy sheet can be performed more easily and reliably.

However, the above-described various apparatuses that perform paper feeding and conveyance using the endless belt are all applied to apparatuses that feed paper from a single paper feeding tray, and an object of the present invention. It is not conceivable to apply the present invention to a multi-stage paper feeding and conveying apparatus having a plurality of vertically arranged paper feeding containers.

Therefore, the present inventors have discussed the above-mentioned drawbacks of the conventional multi-stage paper feeder and the endless transport belt, in particular, a dielectric belt for forming a charge density pattern and sucking and transporting the paper, and a paper feeder and a transporter. In view of the advantage of the transport device constituted by one endless belt, a dielectric belt provided with a charge density pattern forming means is used, and a selected one of sheet storing means provided in multiple stages in the vertical direction is used. A multi-stage paper feeder capable of feeding paper and transporting the paper to an image forming apparatus installed on the apparatus has been separately proposed.

The multi-stage paper feeding and conveying device according to the proposal includes a plurality of recording paper storage means arranged in multiple stages in a vertical direction, and a paper supply for feeding recording paper one by one from any one of the storage means. Means for vertically transferring the sheet fed by the sheet feeding means to the image forming apparatus placed above the apparatus, and extending in the vertical direction so as to face the sheet feeding side of each of the accommodating means. And a vertical conveying means for conveying the paper to the recording paper stack, wherein the paper feeding means selectively contacts the front end of the upper surface of the uppermost sheet of the recording paper bundle stored in the plurality of recording paper storing means. A single paper supply unit that can be connected to the paper supply unit, and the paper supply unit and the vertical transport unit are extended over a roller group provided on the paper supply unit and a roller group provided on the apparatus frame. And a single endless conveyor bell circulated through a paper supply unit and a transfer unit to the image forming apparatus. And,
Means for forming a charge pattern for adsorbing recording paper to the endless transport belt.

Since the multi-stage paper feeder is configured as described above, the contact of the endless transport belt formed at a predetermined distance above the front end of the upper surface of the recording paper bundle stored in the selected recording paper storage means is achieved. In the area, the relative speed with respect to the recording paper bundle is changed to substantially zero, and the area contacts the front end of the upper surface of the recording paper bundle, and the uppermost sheet of the recording paper bundle has one charge pattern formed in advance in a range corresponding to the supporting range of the recording paper. The sheet is adsorbed, and is conveyed to a transfer section with the image forming apparatus by an endless conveying belt stretched seamlessly across the paper feeding unit and the rigid conveying means. Therefore, there is no possibility that a positional shift occurs between the recording paper and the transport belt, and since the relative speed of the transport belt at the time of paper feeding is substantially zero, paper dust is generated due to friction and slippage is caused due to a decrease in friction coefficient. Alternatively, there is no possibility of paper jam occurring at the connection between the conveying member and the guide member. Further, the paper feed unit is lowered to a position where it comes into contact with the upper surface of the recording paper bundle in each recording paper storage means, and sucks and feeds one topmost sheet, so that the recording paper storage means and the paper stored therein are There is no need to move the paper feeder in the vertical direction, and only the lifting and lowering of the lightweight paper feed unit is required, so that less power is required and the feeding operation becomes extremely light.

SUMMARY OF THE INVENTION As described above, the present invention provides a single sheet feeding unit on a recording sheet bundle in a selected sheet feeding cassette, and raises and lowers the sheet feeding operation. It is an object of the present invention to provide a multi-stage paper feeder having means for determining a position.

Means and Actions for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a multi-stage paper feeder having the above-mentioned separately proposed configuration, wherein the above-mentioned paper feed unit is used for storing recording paper to be fed during feeding. The lower surface of the endless transport belt in the paper feeding unit is always displaced to a position at a fixed distance from the upper surface of the recording paper bundle in accordance with the amount of recording paper loaded in the means, and the paper feeding operation is performed with this position as a home position. It is characterized by.

Since the home position is set in this way, even if the paper feeding position changes, the paper feeding unit can always perform the same operation from this position to feed paper.

As means for determining the home position, it is preferable that the paper feeding unit is provided with a recording paper bundle upper surface detecting means in the recording paper accommodation means.

Once each paper feed tray is selected and paper is fed, when recording paper is fed from the recording paper storage means, the recording paper bundle upper surface position data in the recording paper storage means is stored in the storage means. When feeding paper from the next recording paper storage means,
If the sheet bundle upper surface position data of the storage paper storage means stored in the storage means is used as the home position and the paper supply unit is directly moved to that position, even if the remaining amount of recording paper is small, it can be quickly moved, Feeding efficiency is improved.

The recording paper bundle upper surface position data in each of the recording paper storage means in the storage means is supplied to the recording paper storage means by an operation of replenishing the recording paper into each recording paper storage means and an operation of detaching the recording paper storage means from the apparatus main body. If the related data is initialized, a malfunction can be prevented.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

I. Schematic Description of Copying System FIG. 1 is a perspective view showing the appearance of a copying system provided with a multi-stage paper feeder (hereinafter referred to as a paper bank) according to the present invention, and FIG. FIG.

This copying system includes a copying machine body 50, a scanner (original reading device) 123, and a paper bank (hereinafter sometimes abbreviated as PB).
It is operated by an operation unit 601 provided on the 50 operation side.

The copier body 50 is a digital copier, and the scanner 123
The original placed on the contact glass 125 is the scanning optical system 1
The image is projected onto the CCD 130 via the optical disk 27 and read. The read image information signal is subjected to required image processing, and the laser light writing unit 1
The laser light input to and emitted from the rotating polygon mirror 5, f-
An image is formed on the photosensitive drum 11 via a writing optical system including a θ lens 7, a reflecting mirror 10, and the like, and optical writing is performed. A charging charger 12, the laser beam injection device, a developing unit 13, a transfer charger 14, a cleaning device 15, and a static elimination lamp 16 are arranged around the photoreceptor drum 11 in the order of rotation indicated by arrows. A toner image is formed on the photosensitive drum 11 by a photographic process. This toner image is transferred to the transfer paper fed to the transfer section under the action of the transfer charger 14. After the transfer, the transfer paper is separated from the photoreceptor drum and conveyed to the fixing device 18 where it is fixed and then discharged outside the machine, or when performing double-sided copying or composite copying, it is turned upside down as necessary and re-transferred to the transfer section. Paper is fed. In the illustrated copying machine, the endless transport belt 32 is used to take out the transfer paper from the paper feeding unit and transport the transfer paper to the transfer unit and the fixing unit. A flexible feed system using an attraction force based on a charge density pattern formed on a transport belt according to the theory is used, and first and second tandem tandem feeders are provided in a copying machine main body 50 in a feed direction. Paper cassette 41 that can be divided into two trays
In addition to the third to sixth paper feed trays 216, 217, 218, and 219 provided in the paper bank, which are symmetrical to the present invention, the manual paper can be manually fed from the manual paper feed unit 33.

Although the above-mentioned flexible feed system has been separately proposed and filed by the present inventors, the copying machine used in combination with the paper bank of the present invention is not limited to this, and it also has It is also possible to combine with an analog copying machine that performs exposure by forming an image of the reflected light directly on the photoreceptor.

II. Structure of Paper Bank Paper Bank 200 has a maximum loading capacity of 250
-Fifth three-tier trays 216, 217, 218 and a maximum loading capacity of 2000
It is composed of six sixth trays 219 and a single paper feeder. The third to fifth trays 216, 217, and 218 have the sheet feeding side end faces aligned with one vertical plane, and the sixth tray 219 projects the position of the sheet feeding side end face forward from the position of the sheet feeding side end face of the three-stage tray. Thus, the trays are installed in the housing, and each tray can be opened and closed by being pulled out to the near side and pushed into the back side when viewed from the operator.

Means for feeding the transfer paper from these paper feed trays and transporting the transfer paper to the transfer section to the image forming apparatus main body include:
Also in this case, the above-described conveying method of forming a charge density pattern on the dielectric endless belt and adsorbing the transfer paper is used.

As shown in FIG. 2 and FIG. 3, the sheet feeder is slidable on a slide rod 207 provided vertically across the entire height of the PB housing in opposition to the feed side end face of each sheet feed tray. A single paper supply unit 250 provided in the
And a single PB belt 201 spanned over a roller group provided between the side plates and between the PB side plates. As shown in FIG. 20, the PB belt 201 is a two-layer type, in which the surface layer is composed of a dielectric film (PET 50 μm), the lower layer is an aluminum endless belt, and is rotated by a driving roller and a plurality of supporting rollers. Freely supported. The volume resistance of this derivative was 10 ¹⁶ Ω · cm. roller
An alternating voltage of ± 2 kV and 26 Hz is applied to B212 from the high voltage power supply B. In addition, the PB belt 201 is moved at a constant speed of 130 mm / s by the driving roller 202 in the direction of the arrow, and the paper feeding position of the transfer paper is downstream of the contact position of the electrode of the roller B with respect to the moving direction of the PB belt. is there. Therefore, before the transfer paper is fed to the surface of the PB belt, a charge density pattern is formed on the surface of the belt at a period of 5 mm.

Referring to FIG. 3, the PB belt 201 is stretched around a PB driving roller 202, a belt tensioning roller 203, a roller A204, and a sheet feeding unit 250. Wires 206 are attached to the extension roller 203 on the near side and the back side, respectively, and the tension is applied to the PB belt 201 through the springs 205 by the mainspring spring 205 starting to the left. Also P
The B drive roller 202 is rotated counterclockwise in FIG. 3 by a PB belt drive motor 224 via gears 228 and 229 to drive the PB belt 201.

4 and 5 show the configuration of the paper feeding unit 250. FIG.
In addition, in order to show the outer side surface of the sheet feeding unit (pickup) rear side plate 223, FIG. A pickup roller 208, a shaft 246 of a bracket 245 that rotatably supports the belt variable speed rollers A209 and B210 at axially symmetric positions, a pickup auxiliary roller 211, and a roller C248 are provided between the pickup front side plate 222 and the pickup back side plate 223. It is mounted rotatably. Here, both ends of the pickup roller 208 are fixed to fixed points of a timing belt 236 stretched over pulleys 230 and 231, and are moved in a horizontal direction along slits 222a and 223a provided on both side plates 222 and 223 by a PB pickup drive motor 226. It is possible to move to. At the shaft end of this roller, a feeler 249 for determining a home position is attached,
Corresponding to this, near the left end of the slit 223a of the side plate 223 in FIG. 4, there is provided a PB pickup sensor 238 which is operated by the feeler 249 and detects that the pickup roller 208 is at the home position.

The interval between the side plates 222 and 223 is wider than the width of each paper feed tray, and a support member for mounting each paper feed tray is provided at a position before the pickup and not on the back side plates 222 and 223,
In addition, the paper feed side ends of the third to fifth paper feed trays are at positions where they do not catch on the pickup roller 208 at the home position.

At the end of the shaft of the pick-up roller 208, a bracket 244 for supporting the upper end of the paper bundle detection sensor 240 on the lower surface for detecting the upper end of the transfer paper bundle in the paper feed tray is attached. The paper bundle upper end detection sensor 240 detects that the paper supply surface of the PB belt has reached a height of 5 mm from the upper end of the paper bundle, and determines the home position of the paper supply operation for performing the paper supply operation from this position. Things.

The belt variable speed rollers A209 and B210 take up the PB belt 201 with these two rollers before starting the paper feeding operation and return the PB belt 201 wound up during the paper feeding operation to the PB belt. This is for controlling the speed of the belt 201 on the sheet feeding surface. The operations of winding and unwinding are as follows:
The rotation is performed by a PB belt variable speed motor 227, and a feeler 249 for detecting a home position position of the variable speed rollers A209 and B210 is attached to a rotating shaft 246 of brackets 244 and 245 supporting the two rollers 209 and 210. Correspondingly, a PB belt variable speed home position sensor 239 which is operated by the feeler at the home position is attached to the pickup rear side plate 223.

The roller C248 is for changing the transport direction of the paper fed from the paper feeding surface of the PB belt to the vertical direction, and the pickup auxiliary roller 211 serves to prevent the paper from peeling from the PB belt when changing the transport direction. You are.

The paper feeding unit 250 includes a PB front side plate 220 and a PB back side plate 221.
Further, it is slidably mounted via a bearing 247 on a sliding rod 207 mounted vertically near the front end in the paper feeding direction. Further, a shaft 233 is rotatably bridged between an upper portion and a lower portion between the PB front side plate 220 and the PB back side plate 221.Pulleys 232 are fixedly provided near both front and rear ends of the shaft 233, respectively. A timing belt 235 is wound around the pulley, and a pickup front side plate 222 and a pickup back side plate 223 are attached to the timing belt 235, respectively. One end of the upper shaft 233 is a PB unit drive motor 2.
It is connected to 25 drive shafts. With this configuration, by controlling the rotation of the shaft 233 by the PB unit drive motor 225, it is possible to control the vertical position of the sheet feeding unit 250.

For each of the paper feed trays 216 to 219, each tray open / close sensor 251 to 254 (see FIG. 2) is provided in the PB, and the open / close of the tray is detected. FIG. 6 (a) shows the third to fifth
Trays 216-218 are shown. L-shaped side fences 260 and 261 and an end fence 262 whose front ends are bent inward are attached to the bottom plate of the tray so that they can move in the directions of the arrows, and are fixed at positions that match the size of the sheet bundle. The four directions of the sheet bundle can be guided.

FIG. 6 (b) shows a sixth tray 219. On the bottom plate of the tray, side fences 264 and end fences 265 having the same shape as those of the three trays described above are provided so as to be movable in the direction of the arrow. It is possible to guide on four sides. Each tray is provided with a handle for pulling it out of the housing and pushing it in for feeding paper.

III. Description of Electrical System FIG. 7 is an overall electrical block diagram of the flexible feed system (FFS) of the copying system.

Reference numeral 401 denotes a main control board, in which a CPU, ROM, RA
It is composed of M, timer, I / O port, serial, etc. (It may be a one-chip CPU including these functions), and performs sequence control of the entire FFS. The FFS can be broadly divided into the main unit (upper) and the paper bank (lower).

The main body is roughly related to image formation, first tray, second tray, double-sided, transport, and other related functions.

Reference numeral 123 denotes a scanner unit, and a scanner control board 408
Performs transmission and reception of read image data and transmission and reception of commands and data. The description of the main body and the scanner section is omitted because they are not directly related to the present invention.

Next, the electrical system on the PB (paper bank) side will be described.

Reference numerals 224 and 225 denote a PB belt drive motor and its driver, which have a function of transporting the transfer paper to the main body. Here, a stepping motor is used.

225 and 425 are PB unit drive motors and drivers,
The unit is moving up and down. Reference numeral 237 denotes a PB unit sensor that performs position control based on the sensor.

226,423 are PB pickup motor and driver,
The transfer paper is picked up using a stepping motor. The PB pickup sensor 238 is a reference sensor for position control.

227 and 424 are PB belt variable speed motors and drivers,
The operation of temporarily stopping the belt to hold the transfer paper by suction is performed. 239 is a PB belt variable speed HP sensor for detecting the reference position.

Reference numeral 240 denotes a sheet bundle upper end detection sensor which detects a position up to the transfer sheet.

Reference numeral 243 denotes a high-voltage power supply (B), which absorbs transfer paper in the same manner as in (A).

A paper size sensor 426 detects paper sizes on the third, fourth, fifth, and sixth trays. Reference numerals 251, 252, 253, and 254 denote tray open / close sensors, which detect open / close of the tray.

IV. Description of operation display section The size and remaining amount of paper stored in each tray in this PB are determined by LC in the operation panel of the image forming apparatus main body.
Displayed on the paper display section of D (Liquid Crystal Display). First
FIG. 8 shows an example of the display unit. In this example,
The display unit 602 displays the size and remaining amount of paper stored in each paper feed tray including two paper feed trays in the image forming apparatus main body on the displays 613 to 681, respectively.

The amount of remaining paper is determined by the PB belt drive motor 22 as described later.
The determination is made based on the number of pulses from the home position of No. 4 until the paper bundle upper end detection sensor 240 of the paper supply unit 250 detects the upper end of the paper bundle in each paper supply tray.

In the example of FIG. 8, the A4 size of the sixth paper feed tray is selected. Also, by inputting the paper selection key 612,
The trays for feeding paper are sequentially selected, and the selected tray is displayed on the paper display unit 602.

V. Operation of Paper Bank The operation of the paper bank having the configuration described above will be described in detail below.

<Feeding Unit Up / Down> When the opening / closing operation of each tray is detected by the opening / closing sensors 251 to 254, the following initial operation is performed on the assumption that paper is supplied to the tray.

This equipment has a fixed four-stage paper feed tray and one movable paper feed unit 250. Even if the paper feed position changes due to the remaining amount of paper, the paper feed position is stored and the paper is fed at high speed. Tray can be changed.

After detecting the opening / closing of each of the trays from the third paper feed tray 216 to the sixth paper feed tray 219, if paper feed is selected for the first tray, the paper feed unit 250 moves to the highest point of the tray. It is moved up and down by the PB unit drive motor 225. Here, the uppermost point of each tray means that the maximum number of sheets that can be stacked on the third paper feed tray 216 to the fifth paper feed tray 218 is 250
Sheet, or about 5 mm above the height of the upper surface of the sheet bundle when the maximum number of sheets stacked on the sixth sheet tray 219 is 2,000, and the third to fifth sheet trays are 30 mm from the bottom plate and the sixth sheet tray. The paper tray is located at a position 205 mm from the bottom plate, which is the home position of each paper feed tray stage. The upper and lower home positions of the paper feeding unit 250 are the same as the home position of the uppermost third paper feeding tray 216, and are moved downward by the stepping motor 224 according to the number of step pulses of the stepping motor. Controlled. The vertical movement speed of the paper feed unit 250 at this time is 150 mm
At / sec., it moves up and down by forward and reverse rotation of the stepping motor. Paper feed unit from the home position of each paper tray
Reference numeral 250 denotes a paper upper end detection sensor 240 provided in the paper feeding unit 25.
Then, the paper feed belt stops at a position 5 mm from the upper edge of the detected paper. Then, the sheet feeding operation is repeated with that position as the home position of the sheet feeding operation.

Once each paper tray is selected and paper is fed, the paper feed unit is always
The 250 sheet feed position information is expressed as a pulse amount from the home position of the stepping motor as the main control board 401.
It is stored in the non-volatile RAM inside. This also gives
The remaining amount of paper in each paper feed tray can be determined. Then, the position is set as an initial position where the sheet feeding unit 250 starts sheet feeding next. If you select again, the paper feed unit 250 moves directly to the position 5 mm above the loaded paper below the home position of the tray and detected by the paper top sensor attached to the paper feed unit 250, and feeds it there. Is repeated as the home position. As a result, even when the remaining amount of paper is small, the paper feed tray can be changed quickly.

Further, if the paper is not detected by the paper bundle upper end detection sensor 240 at the paper feeding operation home position during continuous paper supply, the PB unit drive motor 225 feeds the paper to the position where the paper bundle upper end detection sensor 240 detects the paper. The sheet feeding is repeated by moving the unit 250 downward. As described above, the paper feeding unit 250 descends as the paper feeding progresses, and repeats the paper feeding process from the fixed paper feeding tray.

Note that malfunctions can be prevented by initializing the data stored in the nonvolatile RAM by a sheet feeding operation to each sheet feeding tray or a sheet feeding tray attaching / detaching operation.

<Sheet Selection> The operation of the sheet selection is shown in the flowchart of FIG. When a paper feed tray is selected by paper selection, it is determined whether this is the first paper feed after opening and closing the tray (STEP 1). In the first case, since the remaining amount of paper is not known and the paper feed position is not determined, since the paper load amount is already known at the uppermost position B of each tray, the last paper feed home position D at the last time Is set as the target position X of the paper feeding unit 250, the paper feeding unit 250 is moved up and down (SETP2). Here, the paper feed unit 25
The pickup roller 208 is already at the innermost home position of the moving range in the paper feeding unit 250 in preparation for the vertical movement of 0. When the sheet feeding unit 250 reaches the target position, the pickup roller 250 is extended in the sheet direction in preparation for sheet feeding. Next, the upper end of the sheet bundle is detected by the sheet bundle upper end detection sensor 240, and the unit is lowered so that the sheet feeding unit 250 goes to the home position of sheet feeding (STEP 3). For the second and subsequent times, this operation is not performed because the paper feed unit 250 has reached the last paper feed home position D of the last time.
At this time, the home position of the paper feeding is stored in the memory buffer D and used for the paper feeding operation. On the other hand, when the paper feed unit 250 reaches the home position for paper feed, the print OK indicator is turned on and copying is started. After that, ST
EP3 is repeated, and the sheet feeding unit 250 stores the position in the memory buffer D while descending.

<Pickup roller left and right> The pickup roller B208 of the paper supply unit 250 is used to attract paper in the tray to the PB belt 201 during paper supply.
It displaces with the PB belt 201 by 100 mm in the paper direction. On the other hand, when the sheet feeding unit 250 is moved in the vertical direction by selecting the sheet, the pickup roller B208 is moved to the right home position and retracted. The movement of the pickup roller B28 is performed by the PB pickup drive motor 226 attached to the sheet feeding unit 250 from the home position detected by the PB pickup sensor 238. The PB pickup drive motor 226 is a stepping motor, whose position is controlled according to the number of pulses.

<Paper Feeding Interval> Since the paper bank 200 feeds paper from a fixed paper feed tray using a paper feed unit 250 that can move in the vertical direction, the paper feeding position differs depending on the paper feed stage and the paper stacking amount. The transport timing from the paper feed timing to the main body is calculated as follows. The PB belt 201 is transported at a constant speed of 130 mm / sec by a PB belt drive motor 224 of a stepping motor, and the paper after the operation of the PB belt variable speed motor 227 is 130 mm / se.
conveyed in c. The transport distance changes depending on the vertical position of the sheet feeding unit, which is determined by the number of steps N from the home position of the PB unit drive motor 225. Since the PB unit drive motor 225 moves 0.2 mm in one step, the transport path L of each tray is represented by L = N × 0.2 + P. Here, P is a fixed distance depending on the paper feed tray, 200 mm for the third to fifth paper feeds, and 120 mm for the sixth paper feed.
This difference depends on the transport distance in the horizontal direction. Therefore, the transport time T is represented by T = L / 130. The total of the transport time T and the paper feed time is the time required for feeding the first sheet, and the continuous paper feed from the second sheet becomes irrelevant to the transport time T. Further, the continuous paper feed interval may be repeated at a constant interval, and A4 size printing can be repeated at 3 seconds / cycle to print at 20 PPM.

<Paper Feeding Operation> The paper feeding operation will be described with reference to the operation transition diagrams of FIGS. 10 (a), (b), (c) and FIGS. 11 (a), (b), (c).
In the present embodiment, the deceleration / stop mechanism of the PB belt 201 includes 2
One using two belt variable speed rollers A209 and B210 is used. FIGS. 9 (a), (b) and (c) show the case of feeding from the third tray 216 to the fifth tray 218, and FIGS. 10 (a), (b) and (c) show the sixth tray. This is the case of paper feeding from 219.

The paper feed unit 250 feeds the position detected by the paper upper end sensor attached to the paper feed unit 250 at a point 5 mm above the upper surface of the stacked paper bundle below the home position of the tray as the home position of the paper feed operation. Repeat the operation. At this time, the flat portion of the PB belt 201 stretched between the pickup roller 208 and the roller 248 is 5 mm from the upper end of the sheet bundle.
Located on top. Next, the pit-up roller B208 is displaced by entraining the PB belt 201 by 100 mm in the paper direction from the home position in order to attract the paper in the tray to the PB belt 21 during paper feeding.

In order to attract one top sheet of paper on the tray to the PB belt 201, a charge pattern is formed on the PB belt 201 by a roller B212 in synchronization with the sheet feeding timing by an amount corresponding to the sheet size before feeding.

Lower the paper feed unit 250 by 5 mm and set a PB belt on the upper edge of the paper.
Contact 201. At this time, the above-mentioned belt transmission mechanism is operated so that the displacement speed of the PB belt 201 on the paper contact surface is made zero. The operation of the belt transmission mechanism will be described later in detail. This is performed to improve the adsorptivity of the stopped paper in order to suck and convey only the top sheet of the stopped paper, and reduce the conveyance speed of the PB belt 201 to a speed of 130 mm / sec or less. They may be brought into contact with each other and sucked and conveyed.

In the case of paper feeding from the third tray 216 to the fifth tray 218,
Since the paper is adsorbed from the leading edge of the paper and transports the paper in the horizontal direction between the rollers 248, the paper bundle is moved while the relative displacement speed of the PB belt 201 with respect to the tray on the paper contact surface is set to zero using a belt speed change mechanism. The paper feed unit 250 is raised to the home position of the paper feed operation at a point 5 mm above the upper surface.

After that, after the S-shaped bending by the belt transmission mechanism is released, the PB belt 201 becomes straight in the vertical conveyance section, and
Moves at a constant speed of 130 mm / sec by the B belt drive motor 224
It is attracted to the PB belt 201 and is transported at a predetermined speed at a constant speed.

The winding means of the belt speed change mechanism is operated between the sheets of the continuous feeding in which the conveyed sheet has passed through the belt speed change mechanism to prepare for the deceleration in the next paper feed stroke. At this time,
The PB belt 201 between the rollers 208 and 248 of the paper feeding unit is accelerated, but at this point, the belt is not in contact with the paper, and there is no problem.

On the other hand, in the case of paper feeding from the sixth tray 219, the paper is sucked from a position about 20 mm from the leading edge of the paper, and the belt C is used to transport the paper vertically by the roller C248.
First, the sheet is conveyed horizontally leftward. That is, the sheet feeding unit 250 is raised to the home position of the sheet feeding operation at a point 5 mm above the sheet of paper while the relative displacement speed of the PB belt 201 with respect to the tray on the sheet contact surface is set to a minus value. As described above, even in the case of the sixth sheet feeding, the PB belt
And paper feeding and conveyance can be stably performed.

<Belt shifting operation of paper feed unit> Two belt variable speed rollers shown in FIGS. 10 and 11
A shift operation using A209 and B210 will be described.

The two belt variable speed rollers A209 and B210 have a diameter of 8 mm, a distance between roller centers of 12 mm, and a PB belt variable speed motor at the center.
At 228, the PB belt 201 is wound up and released. The operation
Figure 12 shows. As a result, the belt movement amount 1 when the PB belt is not being conveyed is equal to the belt variable speed rollers A209 and B210.
When the rotation angle of is represented by θ (rad), it is approximated by the following equation.

1 = 2rθ + 12 (1-cos θ) From the relationship θ = ωt, the displacement velocity v is expressed by this time derivative, and v = 2rω + 12ωsinωt. Here, ω is the angular velocity of rotation, and r is the winding radius of the belt variable speed rollers A209 and B210.

130mm to stop the PB belt 201 at the paper feed contact surface
/ sec. at a constant speed, and the paper feed unit 250 is 150mm / se
When descending in c., the PB belt 201 is 280 mm / s
By moving the motor at ec. and setting v to 280 mm / sec. to cancel this, the above equation shows the angular speed ω at the time and the rotational position, that is, the driving speed of the PB belt variable speed motor 228. On the other hand, in the case of paper feeding from the sixth tray 219, the PB belt 201 on the paper contact surface is displaced by 20 mm in the minus direction while raising the paper feeding unit 250 to the home position of the paper feeding operation at a point 5 mm above the paper. The time is 5 (mm) / 150 (mm / sec.) = 0.033 (sec.), And the linear velocity in the reverse direction of the PB belt at that time is 20 mm / 0.033 sec. = 600 mm / sec. The PB belt 201 is driven at a constant speed of 130 mm / sec., And when the sheet feeding unit 250 moves up at 150 mm / sec.
The belt 201 is similarly obtained by setting v to 580 mm / sec so as to cancel the winding at 600 + 130-150 = 580 mm / sec.

The PB belt variable speed motor 228 is constituted by a stepping motor, and a timer value corresponding to the driving speed of the PB belt variable speed motor 228 with respect to the time obtained as described above is stored in the ROM in the main control board 401 in advance. Speed control of PB belt variable speed motor 228, while calling it,
And control of forward / reverse rotation.

On the other hand, in preparation for deceleration in the next paper feeding process, the winding operation of the belt speed change mechanism between the papers of the continuous feeding in which the conveyed paper has passed through the belt speed change mechanism is usually about 150 mm between the A4 size paper. Therefore, the PB belt variable speed motor 228 may perform the winding operation at a constant speed.

Next, a belt transmission mechanism having another configuration will be described with reference to FIGS.
This will be described with reference to the drawings.

In this variable mechanism, two fixed rollers 650 and 651 and one displacement roller 652 are used.

FIG. 13 shows the case where paper is fed from the third tray 216 to the fifth tray 218, and FIG. 14 shows the case where paper is fed from the sixth tray 219. The paper feeding surface of the PB belt 201 and the behavior of the paper are the same as those shown in FIGS.

The displacement roller 652 is driven by a PB belt variable speed motor 227
The PB belt 201 is displaced by moving in a horizontal direction between the two fixed rollers 650 and 651, and the speed of the sheet feeding surface of the PB belt 201 is adjusted.

The time when the paper feeding unit 250 descends a distance of 5 mm at 150 mm / sec. Is 5 mm / 150 mm / sec. = 0.033 sec. Displace in the minus direction of 280 mm / sec so as to cancel the displacement of sec. Since this is performed at 0.033 sec., The displacement amount at that time is 280 mm / sec. × 0.033 sec. = 9.3 mm, and the speed of the displacement roller 652 is 280 (mm / sec.) / 2 = 140 (mm / sec.). With a displacement of 9.3mm / 2 = 4.7mm, it can be moved to the left at a constant speed.

Similarly, the displacement of the sixth tray 219 in the minus direction during paper feeding is the speed of the displacement roller 652 at 290 mm / sec.
Move at a constant speed to the left with mm.

The speed change operation is performed by constant speed control with a total displacement of 14.4 mm when the axis of the fixed rollers 650 and 651 is to the right of the axis of the displacement roller 652.

<Feeding Timing> The feeding timing when the transmission having the configuration shown in FIGS. 13 and 14 is used will be described. FIG. 15 shows a timing chart of the control of the sheet feeding operation. FIG. 15 shows a case where A3 size paper is continuously fed from the third sheet feeding tray. FIG.
6 is an example of a timing chart in the case of performing continuous sheet feeding of A4 landscape size.

In FIG. 15, the PB belt drive motor 224 is turned on to perform constant-speed rotation. Next, the voltage power supply B243 is operated according to the sheet feeding timing. This start timing is based on the PB belt
A value calculated from the linear velocity of the charge pattern forming position of the PB belt 201 is programmed in advance so that a charge pattern is formed upstream of the sheet feeding unit at a position where the sheet 201 is adsorbed, and in this example, This value is about 1.48 sec. Before the suction operation. The same applies to paper feeding from the fourth and fifth paper feeding trays. It differs only in the case of paper feeding from the sixth paper feeding tray. Next, prior to the sheet feeding operation, the PB belt variable speed motor 227 is rotated forward, and the displacement roller 652 is made to stand by in the right direction. At the paper feed timing, the PB unit drive motor 225 is rotated forward, and simultaneously the PB belt variable speed motor 227 is rotated at a high speed, and the speed of the PB belt 2001 on the paper suction surface is set to zero, and the PB belt 201 is placed on the upper surface of the paper. Make contact. Further, the PB belt variable speed motor 227 is further rotated in the reverse direction to retract the displacement roller 652 to the left, and the PB belt 201 is vertically conveyed. The paper fed and conveyed is fed to the PB paper feed sensor 51
(See Fig. 2) for about 3.2 seconds. High voltage power supply B24
The operation end timing of the PB belt 201 during the continuous operation period
Since the acceleration and deceleration operations described above have occurred, the operation is the same as the case where the constant speed operation is performed by subtraction, and the operation is performed only for a period of 3.2 sec. When the charge pattern changes at the linear velocity of the PB belt 201 at the formation position, that is, when the PB variable speed motor 227 is operating, the frequency applied by the high-voltage power supply B243 is set so that the charge pattern cycle of the PB belt 201 is constant. Is changing. When the charge pattern formed last becomes effective, when the linear velocity of the PB belt 201 at the charge pattern formation position is equal to or less than zero,
The operation of the high-voltage power supply B243 is arbitrary, and is turned off in this example.

In FIG. 16, the basic operation is the same as in FIG. The sixth sheet feeding includes a displacement operation of the suction surface of the PB belt 201 in the minus direction. When the PB unit driving motor 225 is rotated in the reverse direction, the PB variable speed motor 227 is further rotated at a higher speed, and the sheet feeding surface linear speed is −600 mm / sec. The operation timing of the high-voltage power supply B243 is about 1.98 sec.before suction because the layout is different from that of other paper feed trays.Because it is A4 size, it operates while the PB belt 201 at the charge pattern forming position moves at high speed Stop.

As described above, the PB belt 201 having the same length as the paper size
The PB belt 201 can be attracted to and conveyed to the charge pattern forming position with the PB belt 201 stopped.

In the case where the sheet is thin and light, the sheet can be sufficiently conveyed if a charge pattern is formed in a portion corresponding to an appropriate range in front of the sheet according to its weight.

<Transfer of transfer paper from the PB side to the main body> Transfer of the transfer paper from the PB side to the main body uses the transfer belt.
By making the transport speed of the PB belt equal, smooth transfer without slack or pulling can be achieved. This can be realized by setting the linear velocity of the PB belt to 120 mm / s since the main body side is 120 mm / s. However, in this example, a case will be described in which the linear velocity of the PB belt is set to 130 mm / s in order to increase the productivity on the PB side. (When PB belt linear velocity> transfer belt linear velocity) This is because moving roller 29 is moved from PB belt 201 to transfer belt 3
When the transfer paper is transferred to 2 in FIG. 2, the speed of the transfer belt can be increased by moving from left to right in the same manner as the transmission shown in FIG. Apparently, they come into contact at a relative speed of zero, are attracted and conveyed by the charge pattern, and the delivery is completed.

Effects As described above, according to the present invention, the same operation is always performed regardless of the amount of recording paper, even when the amount of recording paper changes even when paper is fed from any of the paper cassettes provided in multiple stages in the vertical direction. Paper can be fed.

In addition, by storing the data of the upper surface position of the recording paper bundle at the time of the previous paper feeding of each paper feeding tray in the storage means, even when the remaining amount of the recording paper in each paper feeding tray is small, it can be moved quickly and the paper feeding efficiency can be improved. The effect is obtained for improvement.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external appearance of an example of a copying system having a multi-stage paper feeder according to the present invention, FIG. 2 is a side sectional view showing a schematic configuration of each component, and FIG. FIGS. 4 and 5 are a perspective view and a plan view, respectively, showing the arrangement of the sheet feeding unit and the endless belt of the embodiment of the multi-stage sheet feeding / conveying apparatus, and FIGS. ),
(B) is a perspective view showing a paper feed tray other than the lowermost paper feed tray and a lowermost paper feed tray of the multi-stage paper feeder, FIG. 7 is an overall electrical block diagram of a flexible feed system of the above-mentioned copying system, and FIG. FIG. 9 is a plan view showing an example of a paper display unit of the paper feed tray, FIG. 9 is a flowchart showing a flow of a paper feed selection operation, and FIGS. 10 (a), (b) and (c) show paper feeds other than the lowest. FIG. 11 (a), (b), (c) are similar diagrams for the lowermost sheet feeding tray, and FIG. 12 is a belt variable speed of the sheet feeding section. FIGS. 13 and 14 are explanatory diagrams for explaining the operation of the roller, FIG. 13 and FIG. 14 are explanatory diagrams for explaining the operation of the belt transmission mechanism of another configuration, and FIG. 15 and FIG. 17 and 18 are timing charts showing the configuration of a conventional multi-stage paper feeder. A side cross-sectional showing views, FIG. 19 through FIG. 23 is an explanatory view illustrating the principle of the transfer device for suction conveyance the sheet by forming a charge density pattern derivatives belt,
FIG. 24 is a cross-sectional view showing an example of a conventional apparatus in which sheet feeding and conveyance are performed by one endless belt. 11 Photoconductor drum 32 Endless transport belt 41 Paper cassette 50 Copier (image forming device) 123 Scanner 200 Multi-stage paper transport device (paper bank, PB) 201 PB Belts (endless transport belts) 202, 203, 204, 208, 248 Roller groups 209, 210, 227 Endless transport belt variable speed means 212, 243 Charge pattern forming means 216, 217, 218, 219 Paper feed tray (recording paper storage means) 220, 221 PB side plates 222, 223 Pickup side plate 224 …… PB belt drive motor 225 …… PB unit drive motor 226 …… PB pickup drive motor 237 …… PB unit HP sensor 238 …… PB pickup sensor 239 …… PB belt variable speed HP sensor 240 …… Detection of recording paper bundle upper surface Sensor 250 Paper feed unit (paper feed means) 251,252,253,254 Paper feed tray open / close sensor 260,261,263,264 Side fence 262,265 End fence 650,651,652 Endless Transmission belt variable speed means

──────────────────────────────────────────────────続 き Continued on the front page (72) Kazushige Taguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Kazunori Sakauchi 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) B65H 1/00-3/68

Claims (4)

(57) [Claims] 1. A plurality of recording paper storage means arranged in multiple stages in a vertical direction; a paper supply means for feeding recording paper one by one from an arbitrary one of the storage means; A vertical transport unit that extends in the vertical direction to face the paper supply side, and transports the recording paper fed by the paper feed unit to a transfer unit to an image forming apparatus mounted on the upper side of the apparatus. A multi-stage sheet feeding and conveying device, wherein the sheet feeding means is a single sheet feeding means capable of selectively abutting on a front end of a top surface of an uppermost sheet of recording paper bundles accommodated in the plurality of recording paper accommodation means. A paper feed unit, and the paper feed unit and the vertical transport unit are wound around a roller group provided in the paper feed unit and a roller group provided in an apparatus frame, and a paper feed unit is provided. A single endless transport belt that is rotated via a transfer section to the image forming apparatus; Means for forming an electric charge pattern for adsorbing recording paper, wherein at the time of feeding, the paper feeding unit is adapted to feed paper according to the amount of recording paper loaded in the recording paper storage means to be fed. Wherein the lower surface of the endless conveyor belt is always displaced to a position at a fixed distance from the upper surface of the recording paper bundle, and the sheet feeding operation is performed with this position as a home position. 2. The sheet feeding unit according to claim 1, wherein said sheet feed unit is provided with a recording sheet bundle upper surface detecting means in said recording sheet accommodating means.
3. The paper feeding and conveying device according to 1. 3. A means for determining the home position, wherein when recording paper is fed from the recording paper storage means, the recording paper bundle upper surface position data in the recording paper storage means is stored in the storage means. When paper is fed from the recording paper storage means, the top position data of the paper bundle of the recording paper storage means stored in the storage means is set as the home position, and the paper supply unit is directly moved to that position. The sheet feeding / conveying device according to claim 1. 4. The recording paper bundle upper surface position data in each of the recording paper storage means in the storage means is provided by a recording paper replenishing operation into each of the recording paper storage means and a detachment operation of the recording paper storage means from the apparatus main body. 4. The sheet feeding and conveying device according to claim 3, wherein data relating to the recording sheet storage unit is initialized.