JPH0480141A - Multiple stage sheet feeding and transferring device - Google Patents

Abstract

PURPOSE:To achieve suction of a forward end part of a recording sheet securely at the time of feeding it by setting an electric charge pattern forming range to be a predetermined range from the front part of the recording sheet corresponding to the weight of the recording sheet. CONSTITUTION:An electric charge pattern forming range formed by an electric charge pattern forming means 212 is set to be a range equivalent to the range of a recording sheet sucked and transferred, and this recording sheet is sucked to an endless belt from its forward end to its back end securely to be transferred without peeling. At this time, when the recording sheet is a thin and light paper, an electric charge pattern is formed at a part equivalent to a predetermined range of the front part of the sheet corresponding to its weight, so the recording sheet is held sufficiently to be transferred.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is placed under an image forming apparatus, has a plurality of paper feed containers in a housing, and receives paper fed from these paper feed containers. The present invention relates to a paper feed conveyance device that is raised by a vertical conveyance means to feed the paper to the image forming apparatus.

With the progress in space saving of OA equipment such as image forming devices such as copiers, laser printers, and facsimile machines, paper feed conveyance devices in which multiple paper feed cassettes or paper feed trays are stacked vertically have been introduced. Devices that are made separately from the main body of the image forming apparatus and placed below the main body of the image forming apparatus to reduce the installation area are gradually becoming popular.

This type of paper feeding and conveying device that has been implemented and proposed in the past is disclosed in, for example, Japanese Utility Model Application Publication No. 1-78629, and as shown in FIG. Paper selectively fed from paper feed stands 302 and 303 such as a plurality of paper feed cassettes or paper feed trays are provided vertically facing the paper feed ends of these paper feed containers, and are arranged to match the minimum size of the paper. A transport roller 304 made of an elastic material and a pair of guide plates 30 provided between the rollers.
Generally, the paper is conveyed upward through a vertical conveyance path configured by 5 and fed to the main body of an image forming apparatus.

This method of conveying paper using the frictional force of elastic rollers is widely used because of its simple structure, but it is prone to slipping due to a decrease in the coefficient of friction of the rubber used in the conveying roller over time and the generation of paper dust. However, there is a drawback that paper jams occur at the connection between the roller and the guide plate due to curling of the transfer paper in a high humidity environment.

In addition, the present applicant has proposed a paper feeding device for a printing press that has a simple structure in which paper is fed from a plurality of vertically stacked paper feeding trays to a recording section using a single feeding roller. 7
No. 8713. As shown in FIG. 18, this paper feeding device includes a conveying mechanism section having a single paper feeding roller 306, a single paper feeding tray elevating/lowering/parking device 307, and the paper feeding tray elevating/lowering cantering device 307. The paper feed tray 308 has a plurality of paper feed trays 309 and 310 that are stacked in the vertical direction. (shows only one stage) indicates the position where the leading edge of the stack of sheets placed on the above is within the action range of the sheet feeding roller 306 of the sheet feeding roller transport mechanism section and the leading edge of the sheet is individually moved in the sheet feeding conveyance direction. It is capable of sliding for a certain distance from a position where it is retreated rearward from the paper feed roller 306.

Therefore, hold the paper tray on which the paper you are trying to feed is placed in a position where its front end is within the action range of the paper feed roller, and hold the paper tray above it so that its front end is within the action range of the paper feed roller. When the paper feed tray 308 is moved back to a position away from the paper feed tray 306 and raised by the single paper feed tray elevating device M307, the paper feed tray above the paper tray on which the paper to be fed is placed and the The paper stack placed on top of the stack rises behind it without contacting the paper feed roller, and the front edge of the top surface of the paper stack to be fed comes into pressure contact with the paper feed roller, and a known upper limit detection sensor detects the paper stack. The east upper surface of the paper comes to a predetermined position and stops. Thereby, desired paper can be automatically fed by the paper feed roller.

However, with this mechanism, a paper feed tray that can slide in the paper feeding direction is installed on top of the conventional one-tray paper feed tray, so a large amount of paper, such as 1000 sheets, can be stored on one paper feed tray. Stacking paper is difficult due to the layout, and if you try to achieve this, the paper feed section will become larger,
As a result, the entire printing press becomes larger.

In addition, each time the size and type of paper to be fed changes, and each time the top position of the paper stack in the cassette falls below the allowable range, the Since the paper table 308 must be moved in the vertical direction, there is a drawback that a large amount of power is required.

By the way, there is an extremely novel conveyance device for conveying sheet members, etc., in which alternating charge density patterns are formed on a dielectric endless belt, and the generated attraction force attracts and conveys sheet members. Recently, the present applicant has proposed a method in Japanese Patent Application No. 1-117374.

The principle of this conveyance device is as follows.

As shown in FIG. 19, a belt 311 for feeding and conveying a sheet of transfer paper or the like 310 is rotatably held by a drive roller and a plurality of belt support rollers 312. Further, the belt 311 is an endless belt whose surface layer is a dielectric material capable of retaining charges and whose back surface is a semiconductor layer. At least one support roller is grounded and is in contact with the back surface of the belt, and an alternating electric field (A Hz) is applied from a high voltage power source 313 to the roller 314 with the ground roller 312 as a counter electrode. Furthermore, the belt 311 is moved in the direction of the arrow at a constant speed Um/s by the drive roller, and the sheet pick amplifier position is downstream of the contact position of the roller 314 in the moving direction of the belt 311. It has become. Therefore, before the sheet is fed onto the surface of the belt 311, a high voltage power source is applied to the roller 311.
An alternating current voltage is applied via 4, which causes the belt 3 to
1], charge densities −σ and 10σ are alternately U/A
A striped charge density pattern arranged at a period of mm is formed. Charges of opposite signs are induced in the semiconductor layer on the back surface of the belt 311 due to the charge density formed on the belt surface.

As shown in FIG. 20, due to the charge density pattern formed in this way, an unequal electric field is formed near the surface of the belt 311, and the force exerted by this electric field on a unit volume of the dielectric material, which is the sheet 310, is as follows. Using Maxwell's stress tensor, it is expressed by the following equation, and the sheet 310 is electrostatically attracted to the belt 311 and held without shifting due to the force fx in the direction perpendicular to the sheet surface, and is carried by the belt 311. transported.

When the direction perpendicular to the sheet surface is X, the transport direction is y, and the direction perpendicular to the transport direction within the sheet surface is 2, the component forces in each direction of X+3'+Z of the force acting on the unit volume of the dielectric material fx, fy, fz are respectively as follows.

Maxwell's stress tensor is therefore.

In addition, in the above formula, E is the electric field, D is the electric flux density, and the subscript x
, y, and z indicate components in respective directions.

The applied voltage may be an AC voltage with a DC component superimposed thereon.

This attraction principle differs from the generally known force of attraction between charges of opposite signs, and the transfer paper can be attracted using the above-described method without applying a valley charge to the transfer paper. For this reason, even when used in a paper feed conveyance device of an electrostatic recording device, there is no effect on the transfer process.

An example of a method for measuring the suction force of this sheet member conveying device and the measurement results is as follows.

As shown in Fig. 21, A3 size plain paper 310 is fed to the conveyor belt, and when the contact length reaches Loom, a spring gauge is attached to the trailing edge of the paper, and the suction force is expressed as tensile strength. It was measured. The adsorption area at this time is 300 d.

As shown in Figure 22, the amplitude of the AC voltage is kept constant (4kV
pp), and the adsorption force was measured by changing the applied frequency. From this, in the present invention, sufficient adsorption force was obtained when the period of the stripe shape was set to a range of 20 m or less. Also, the second
As shown in Figure 3, the adsorption force was measured by changing the applied voltage while keeping the applied frequency constant (26Hz).
Good adsorption power was obtained above pp. Furthermore, it was found from measuring the surface potential that no charge density pattern was formed on the belt at the applied voltage at which no adsorption force was generated. From this, in order to generate adsorption force, at least an applied voltage equal to or higher than the charging start voltage is required.

The same applies when the applied voltage is an alternating current voltage with a direct current component superimposed on it, or when a non-uniform alternating voltage is applied from a power source that applies a non-uniform alternating voltage.

However, this proposal makes no mention of the method of feeding paper from a stack of paper stacked on a paper feed tray, etc., and appears to be based on the assumption that conventional paper feed rollers, etc., will be used. However, it is not believed that the problems of the conventional paper feeding and conveying device described above will be completely solved.

Although it does not have multiple paper feed trays, it uses a single insulated endless belt to feed and transport the transfer paper from the paper feed section of the copying device, through the transfer section, and to the insertion section of the fixing device. A paper conveying device for an electrophotographic copying machine using the above method is disclosed, for example, in Japanese Patent Application Laid-Open No. 59-212856. The method of attracting the transfer paper to the endless belt is different from the above-mentioned attraction principle based on the formation of a charge density pattern, in which the insulating endless belt is charged using a charging means, and the transfer paper is electrostatically attracted due to the potential difference between the belt and the transfer paper. However, as shown in FIG. 24, a support roller 322 of an endless belt 321 is formed on a photoreceptor 323, which is provided opposite to the front end of the upper surface of a stack of sheets P placed in a paper feed tray 320. In synchronization with the movement of the image area, the feed roller 322a provided coaxially with the support roller 322 is brought into contact with the paper and fed, and the fed paper is fed. The toner image is attracted and conveyed by an endless belt, and the toner image formed on the photoreceptor is transferred by the transfer section 324 so that the leading edge coincides with the toner image, and then conveyed to the fixing section 325.

With this conveyance method, it is possible to realize reliable conveyance of paper without the risk of jamming, etc., and at the same time, it is possible to simplify the conveyance mechanism and reduce costs. Further, since there is no frictional contact between the conveying means and the paper, paper dust is not generated or is significantly reduced.

Furthermore, Japanese Patent Application Laid-Open No. 63-139846 discloses that the paper feeding section, registration section, transfer section, fixing section, and paper ejection section of a copying machine are connected in this order with one endless belt, and the endless belt is first connected to the copying paper. The copy paper is brought into pressure contact with the copy paper held in the supply holding section, and the copy paper is carried out by frictional force. After registration, the copy paper is transported to the transfer section where the toner image is transferred from the photoreceptor, fixed at the fixing section, and sent out of the machine. A paper conveyance device configured to eject the paper is disclosed.

According to this device, it is possible to more easily and reliably control the movement of the copy paper and each part of the copy machine, as well as the transport direction of the copy paper.6 However, by using the above-mentioned endless belt, The various conveyance devices are all applicable to those that feed paper from a single paper feed tray, and the present invention aims at a multi-stage system in which a plurality of paper feed containers are provided in the vertical direction. Application to a paper feed conveyance device is unthinkable.

Therefore, the present inventors solved the above-mentioned drawbacks of the conventional multi-stage sheet feeding and conveying device, and solved the problem by combining an endless conveying belt, particularly a dielectric belt that forms a charge density pattern and attracts and conveys paper, and a sheet feeding section and a conveying section. In consideration of the advantages of a conveying device configured with an endless book belt, a dielectric belt equipped with a charge density pattern forming means is used to collect sheets one by one from a selected one of paper storage means provided in multiple stages in the vertical direction. We have separately proposed a multistage paper feeding and conveying device that can feed paper and convey it to an image forming device installed on top of the device.

The multistage paper feeding and conveying device according to the proposal includes a plurality of recording paper storage means arranged in multiple stages in the vertical direction, and a paper feeder that feeds recording paper one sheet at a time from any one of the storage means. and a means for delivering recording paper fed by the paper feeding means to an image forming apparatus placed on the upper side of the apparatus, the recording paper being extended in the vertical direction facing the paper feeding side of each of the storage means. In a multi-stage sheet feeding conveyance system having a rigid conveying means for conveying the sheets to the plurality of recording sheet storage means, the sheet feeding means selectively contacts the front edge of the top surface of the uppermost paper of the stack of recording sheets accommodated in the plurality of recording sheet storage means. It has a single paper feed unit that can be contacted, and the paper feed unit and the rigid conveying means are connected to a group of rollers provided in the paper feed unit and a group of rollers provided in the machine frame of the device. a single endless conveyance belt which is rotated via a paper feed section and a delivery section to the image forming apparatus; a means for forming a charge pattern for adhering recording paper to the endless conveyance belt; and means for changing the speed of the endless conveyor belt within the paper unit.

Since this multi-stage sheet feeding and conveying device is configured as described above, the endless conveying belt formed at a position a predetermined distance above the front end of the upper surface of the stack of recording sheets stored in the selected recording sheet storage means comes into contact with The relative speed to the recording paper stack is changed to approximately zero, and the area contacts the front edge of the upper surface of the paper stack, and the topmost sheet of the recording paper stack is attracted to the charge pattern formed in advance on the endless conveyor belt, and the sheet is fed. The image forming apparatus is transported to a delivery section with the image forming apparatus by an endless transport belt stretched seamlessly over the unit and the rigid transport means. therefore.

There is no risk of misalignment between the recording paper and the conveyor belt, and since the relative speed of the conveyor belt during paper feeding is approximately zero, there is no risk of paper dust generation due to friction, slipping due to a decrease in the coefficient of friction, or There is also no possibility of paper jamming occurring at the connection between the conveyance member and the guide member. In addition, the paper feeding unit descends to a position where it contacts the upper east surface of the recording paper in each recording paper storage means, and sucks and feeds the topmost sheet of paper, so that the paper feeding unit and the paper stored therein are Since there is no need to move the sheet vertically and only the lightweight sheet feeding unit needs to be raised and lowered, less power is required and the feeding operation becomes extremely light.

Problems to be Solved by the Invention However, if the formation area of the charge pattern formed in advance on the endless belt before paper feeding is shifted from the recording paper carrying range, or the pattern formation area is small with respect to the recording paper. If it is too large, reliable suction and conveyance of the recording paper cannot be expected, and if it is too large, power will be wasted. SUMMARY OF THE INVENTION An object of the present invention is to provide a multistage paper feeding and conveying device in which the formation area of a charge pattern is optimal.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a multi-stage sheet feeding and conveying device having a separately proposed configuration, in which a charge pattern is formed on an endless conveying belt according to the size of recording paper. It is characterized in that the area is controlled so that it corresponds to the area of the recording paper that is attracted and conveyed on the conveyor belt.

However, if the recording paper is a light paper, it is not necessary to form a charge pattern over the entire area corresponding to the area of the recording paper, but rather to an appropriate area at the front of the area of the recording paper depending on its weight. Control may be performed so that a charge pattern is formed in the region.

Since the charge pattern forming area is set to correspond to the range of the recording paper that is attracted and conveyed as described above, the paper is surely attracted to the endless belt from the leading edge to the trailing edge and is conveyed without peeling off. Ru.

However, if the paper is thin and light, it is sufficient to hold and transport the paper simply by forming a charge pattern on a portion corresponding to an appropriate range at the front of the paper depending on its weight.

Embodiments of the present invention will be described in detail below with reference to the drawings.

1. General description of the copying system Fig. 1 is a perspective view showing the external appearance of a copying system equipped with a multistage paper feeding and conveying device (hereinafter referred to as a paper bank) according to the present invention, and Fig. 2 shows the configuration of its component equipment. FIG.

This copying system consists of a copying machine main body 50, a scanner (original reading device) 123, and a paper bank (hereinafter sometimes abbreviated as PB), and these devices are installed on the operation side of the copying machine main body 50. It is operated by the operating unit 601 that is displayed.

The copying machine main body 50 is a digital copying machine, and the scanner 12
The original placed on the contact glass 125 of No. 3 is projected onto the CCD 130 via the reading optical system 127 and read.

The read image information signal is subjected to necessary image processing and input to the laser beam writing section 1, and the emitted laser beam is sent to a writing optical system consisting of a rotating polygon mirror 5, an f-theta lens 7, a reflection [10, etc.] An image is formed on the photosensitive drum 11 via the system, and optical writing is performed. A charger 12, the laser beam incident position, a developing device 13, a transfer charger 14, a cleaning device 15, and a static elimination lamp 16 are arranged around the photosensitive drum 11 in the rotational direction indicated by the arrow. A toner image is formed on the photoreceptor drum 11 by a photographic process. This toner image is transferred to a transfer sheet fed to a transfer section under the action of a transfer charger 14. After the transfer, the transfer paper is conveyed to a device 18 consisting of a photoreceptor drum, fixed thereon, and then discharged to the outside of the machine. Alternatively, when performing double-sided copying or composite copying, the paper is turned over as necessary and placed in the transfer section. The paper will be re-fed. In the illustrated copying machine, an endless conveyor belt 32 is used to take out the transfer paper from the paper feed section and convey it to the transfer section and the fixing section, and the above-mentioned method is used to attract the transfer paper to the endless conveyance belt 32. A flexible feed system is used that utilizes the adsorption force created by the charge density pattern formed on the conveyor belt according to theory, and as a paper feeding means,
A paper feed cassette 41 that can be divided into two trays, a first and a second tray, in tandem in the paper feeding direction in the copying machine main body 50, and third to third trays that are stacked vertically in the paper bank, which is the name of the invention. In addition to having six paper feed trays 216, 217, 218, and 219, it is also possible to manually feed paper from a manual paper feed section 33.

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

■ Structure of the paper bank The paper bank 200 has three trays 216, 217, 21.8, 3rd to 5th, each with a maximum loading capacity of 250 sheets, and a 6th tray 219 with a maximum loading capacity of 2000 sheets. It consists of a single paper feeding and conveying device. The third to fifth trays 216, 217, and 218 have their paper feed side end faces aligned with one vertical plane, and the sixth tray 219 has its paper feed side end faces aligned with the paper feed side end faces of the three trays. The trays are installed in the housing so as to protrude further forward, and each tray can be opened and closed by pulling it out toward the front and pushing it toward the back when viewed from the operator.

The means for feeding the transfer paper from these paper feed trays and transporting the transfer paper to the main body of the image forming apparatus is to form a charge density pattern on the aforementioned dielectric endless belt. A conveyance method is used that adsorbs the transfer paper.

As shown in FIGS. 2 and 3, the paper feeding and conveying device is slidable on a sliding rod 207 that is vertically provided across the entire height of the PB housing, facing the paper feeding side end surface of each paper feeding tray. A single paper feed unit 25o provided in the paper feed unit 250, and a single PB belt 201 stretched over a group of rollers provided between the side plates of the paper feed unit 250 and between the PB side plates. .

As shown in FIG. 20, the PB belt 201 is a two-layer type with a surface layer made of a dielectric film (PE750μ
m) The lower layer is constructed as an endless belt made of vapor-deposited aluminum, and is rotatably supported by a drive roller and a plurality of support rows.

The volume resistance of this dielectric was set to 101r'Ω·■. Roller B212 is supplied with ±2kV, 26Hz from high voltage power supply B.
An alternating voltage of is applied. In addition, PB belt 201
is set at a constant speed of 130 in the direction of the arrow by the drive roller 202.
The transfer paper moves at a speed of mm+/s, and the paper feeding position of the transfer paper is downstream from the contact position of the electrode of roller B with respect to the moving direction of the PB belt. 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 ann.

To explain with reference to FIG. 3, the PB belt 201 is
It is stretched over the BN moving roller 202, belt tension roller 203, roller A 204, and paper feeding unit 250.

The tension roller 203 has wires 206 on the front side and the back side, respectively.
is installed, and the mainspring spring 205 is connected via this.
The PB belt 201 is stretched to the left in the figure.
tension is applied to. Also, PB [moving roller 202].

The PB belt is rotated counterclockwise in FIG.
The BB belt 01 is being driven.

The configuration of the paper feeding unit 250 is shown in FIGS. 4 and 5.

In order to show the outer surface of the paper feeding unit (pickup) back side plate 223, FIG. 4 is shown with the right and left sides reversed from FIG. 3. Between the pickup front side plate 222 and the pickup back side plate 223, the shaft 246 of the bracket 245, the pickup auxiliary roller 211, and the roller c248 that rotatably support the pickup roller 208 and belt variable speed rollers A209 and B210 in axially symmetrical positions are installed. It is rotatably mounted. Here, pick up roller 208
Both ends of are fixed to fixed points of a timing belt 236 that is stretched around pulleys 230 and 231, and are moved from the PB pickup assist motor 226 to the left and right along the slits 222a and 223a provided in the side plates 222 and 223. It is movable. At the shaft end of this roller,
A tweeter 249 is attached to determine the home position, and correspondingly the slit 2 of the side plate 223
In FIG. 4 of 23a, near the left end is the tweeter 2.
A PB pickup sensor 238 is provided which is activated by 49 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 the support member on which each paper feed tray is placed is provided at a position in front of the pickup and at a position where it does not overlap the back side plates 222 and 223, and The paper feed side ends of the third to fifth paper feed trays are
It is located at a position where it does not hang over the pickup roller 208 at the home position.

Further attached to the shaft end of the pickup roller 208 is a bracket 244 that carries a paper stack upper end detection sensor 240 on its lower surface for detecting the upper end of the transfer paper stack in the paper feed tray. This paper stack top edge detection sensor 240 is for detecting when the PBB belt paper feeding surface has come to a height of 5III11 from the top of the paper stack, and determining the home position of the paper feeding operation from which the paper feeding operation is performed from this position. It is.

Belt variable speed roller A209. B210 winds up the PBB belt 01 with these two rollers in advance before starting the paper feeding operation, and by returning the wound PBB belt 01 during the paper feeding operation, the paper feeding surface of the PBB belt 01 is This is to control the speed of. This winding and unwinding operation is performed by a PBB belt variable speed motor 227, and a variable speed roller A209. A tweeter 249 is attached to detect the home position of the B210, and a PBB belt shift home position sensor 239 that is operated by this tweeter at the home position is attached to the back side plate 223 of the pickup. .

The roller C248 is for changing the conveying direction of the paper fed from the PBB belt paper feeding surface to the vertical direction, and the pickup auxiliary roller 211 is for changing the conveying direction of the paper from the PBB belt paper feeding surface to the PBB belt paper feeding surface.
Its role is to prevent the BB belt paper from peeling off.

The paper feeding unit 250 is slidably attached to the PB front side plate 220 and the PB back side plate 221 via a bearing 247 on a sliding rod 207 vertically attached near the front end in the paper feeding direction. In addition, the PB front plate 220 and the PB
Shafts 233 are provided at the upper and lower parts between the rear side plate 221 and the rear side plate 221, respectively.
A pulley 232 is fixedly installed near both the front and rear ends of this shaft 233, and a timing belt 235 is stretched between the upper and lower pulleys. A rear side plate 223 is attached to each side. One end of the upper shaft 233 is connected to the PB unit assist motor 2.
25 is connected to the movement axis. With this configuration, by controlling the rotation of the shaft 233 by the PB unit drive motor 225, the vertical position of the sheet feeding unit 250 can be controlled.

Tray opening/closing sensors 251 to 254 (see FIG. 2) are provided in the PB for each of the paper feed trays 216 to 219, and detect opening and closing of the trays. FIG. 6(a) shows third to fifth trays 216 to 218. At the bottom of the tray, L-shaped side fences 260° 261 and end fences 262 with the front ends folded inward are installed so that they can move in the directions of the arrows, and are fixed at positions that match the size of the paper stack. By doing so, it is possible to guide the paper stack on all four sides.

Further, a sixth tray 219 is shown in FIG. 6(b). On the bottom plate of the tray, there are side fences 264 and end fences 265 that have the same shape as those of the three trays mentioned above.
is provided so as to be movable in the direction of the arrow, and by fixing it at a position that matches the paper size, it becomes possible to guide the paper on all four sides. Each tray is provided with a handle for pulling it out from the housing and pushing it in to replenish paper.

(2) Description of Electrical System FIG. 7 is a block diagram of the entire electrical system of the flexible feed system (FFS) of this copying system.

401 is the main control board, inside is CPU, RO
It consists of M, RAM, timer, I10 port, serial, etc. (one-chip CPU that includes these functions).
) Performs sequence control for the entire FFS.

FFS can be broadly divided into the main body side (upper part) and the paper bank side (lower part).

The functions on the main body side can be roughly divided into those related to image formation, those related to first tray, those related to second tray, those related to duplexing, those related to conveyance, and those related to other.

123 is a part of the scanner, and the scanner control board 4
08 transfers read image data and sends and receives commands and data. Since the main body side and a part of the scanner are not directly related to the present invention, explanations thereof will be omitted.

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

224 and 225 are drivers for the PB belt assist motor, which has the function of conveying the transfer paper to the main body side.
Here, a stepping motor is used.

225.425 is a PB unit drive motor and driver, which moves the unit up and down.

237 is a PB unit sensor, and position control is performed using this as a reference.

Reference numerals 226 and 423 indicate a PB pickup motor and driver, which uses a stepping motor to pick up the transfer paper. PB pickup sensor 238
is the reference sensor for position control.

Reference numerals 227 and 424 designate an FBB belt variable speed motor and driver, which temporarily stop the belt in order to attract and hold the transfer paper. 239 detects the reference position with a PB belt variable speed HP sensor.

Reference numeral 240 is a paper stack upper end detection sensor that detects the position up to the transfer paper.

243 is a high voltage power source (B), which attracts the transfer paper similarly to (A).

A paper size sensor 426 detects the paper size on the 3rd, 4th, and 5°6 trays. 251,252.253,
A tray opening/closing sensor 254 detects opening/closing of the tray.

■, Explanation of the operation display section The size of the paper stored in each feedable tray in the book PB and the remaining amount of paper can be determined using the L button in the operation panel of the image forming apparatus main body.
Displayed on the paper display section of the CD (liquid crystal display). FIG. 18 is a diagram showing an example of the display section. In this example, the display unit 602 displays the size of paper stored in each stage of paper feed trays including two paper feed trays in one image forming apparatus main body, and the remaining amount of paper on displays 613 to 681, respectively. Ru.

The remaining amount of paper is determined by the PBB belt drive motor 2, as described later.
The determination is made based on the number of pulses it takes from the home position of No. 24 until the top end detection sensor 240 of the paper bundle in the paper feed unit 250 detects the top end of the paper stack in each paper feed tray.

In the example of FIG. 8, A4 size is selected for the sixth paper feed tray. In addition, the paper selection key 612 is operated manually to sequentially select trays for feeding paper, and the selected tray is displayed on the paper display section 602.

(2) Operation of Paper Bank The operation of the paper bank having the configuration described above will be explained in detail below.

<Upper and Lower Paper Feeding Units> When the opening/closing operation of each tray is detected by the opening/closing sensors 251 to 254, it is assumed that the tray has been replenished with paper, and the following initial operation is performed.

This device is equipped with four fixed paper feed trays and one movable paper feed unit 250, and even if the paper feed position changes depending on the amount of remaining paper, it memorizes the paper feed position and feeds paper at high speed. Trays can be changed.

After detecting the opening and closing of each of the trays from the third paper feed tray 216 to the sixth paper feed tray 219, if a certain tray is selected to feed paper first, the paper feed unit 250 moves to the top position of that tray. The PB unit parking assistance motor 225 is moved in the vertical direction.

Here, the highest point of each tray is the third paper feed tray 21
Maximum number of sheets loaded on the 6th to 5th paper feed trays 218 is 250 sheets,
Or the maximum number of sheets loaded on the sixth paper tray 219 is 2000.
Approximately 5 m above the height of the top surface of the paper stack when stacked,
The positions of the third to fifth paper feed trays are 30 m from the bottom plate, and the sixth paper feed tray is 205 m from the bottom, which are the home positions of each paper feed tray stage. Also,
The upper and lower home positions of the paper feed unit 250 are the same as the home positions of the third paper feed tray 216 at the top, and from there the position is controlled downward by the stepping motor 224 according to the number of step pulses of the stepping motor. Ru. At this time, the vertical movement speed of the paper feeding unit 250 is 150+s/see, and the sheet feeding unit 250 moves vertically by forward and reverse rotation of the stepping motor. From the home position of each paper feed tray, the paper feed unit 250 descends until it is detected by the paper top edge detection sensor 240 provided in the paper feed unit 25, and the paper feed belt stops at a position five points from the detected paper top edge. do. Then, the paper feeding operation is repeated using this as the home position for the paper feeding operation.

-Once each paper feed tray is selected and paper is fed,
Even if the selected paper feed tray is changed, the paper feed unit 25 is always
The paper feed position information of 0 is determined by the main control board 401 as the amount of pulses from the home position of the stepping motor.
The memory is stored in unused RAM within the memory. This also makes it possible to determine the remaining amount of paper in each paper feed tray. Then, this position is set as the initial position at which the paper feeding unit 250 next starts feeding paper. When selected again, the paper feed unit 250 is placed 5 m above the loaded paper below the home position of that tray.
The paper feeding unit 250 moves directly to the position detected by the paper upper end sensor attached to the paper feeding unit 250, and repeats the paper feeding operation using that point as the Baum position for the paper feeding operation. This allows the paper feed tray to be quickly changed even when there is little remaining paper.

Furthermore, when the paper is no longer detected by the paper stack top edge detection sensor 240 at the paper feeding operation home position during continuous paper feeding, the PB unit supporting motion motor 225 feeds the paper until the paper is detected by the paper stack top edge detection sensor 240. paper unit 2
50 downward and repeat paper feeding. As described above, as paper feeding progresses, the paper feeding unit 250 repeats the process of feeding paper from a fixed paper feeding tray while descending.

Incidentally, malfunctions can be prevented by initializing the data stored in the nonvolatile RAM by feeding paper to each paper feed tray or by attaching/detaching the paper feed trays.

<Paper feed selection> The operation of paper feed 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 that tray (STEPI).

If this is your first time, the remaining amount of paper is not known and the paper feeding position cannot be determined, so the top position B of each tray is used, and from the second time onwards, the paper loading amount is already known, so the last paper feeding home position is set. is set as the target position X of the paper feeding unit 250 and compared with the current position of the paper feeding unit 250.

Move the paper feed unit 250 up and down (STEP 2).

Here, in preparation for the vertical movement of the paper feed unit 250, the pickup roller 208 is already at the innermost home position of the movement range within the paper feed unit 250. When the paper feeding unit 250 reaches the target position, the pickup roller 250 is moved toward the paper in preparation for paper feeding. Next, the upper end of the paper stack is detected by the paper stack upper end detection sensor 240, and the unit is lowered so that the paper feed unit 250 goes to the paper feeding home position (STEP 3). From the second time onwards, the paper feed unit 250 is set to the last paper feed home position ID from the previous time.
has been reached, so this action is not performed.

At that time, the paper feeding home position is stored in the memory buffer D and used for the paper feeding operation. On the other hand, the paper feed unit 250
When the paper reaches the paper feeding home position, the print OK display is turned on and copying is started. Thereafter, 5TEP3 is repeated during paper feeding, and the paper feeding unit 250 stores its position in the memory buffer D while descending.

<Pickup roller left and right> The pickup roller B2O3 of the paper feed unit 250 is
In order to cause the paper in the tray to be attracted to the PBB belt 01 during paper feeding, it is displaced along with the PBB belt 01 by 100 m in the paper direction. On the other hand, depending on the paper selection, the paper feed unit 250
When moving the pickup roller B2O in the vertical direction,
3 to the right to the home position and evacuate. The movement of the pickup roller B28 starts from the home position detected by the PB pickup sensor 238.
The PB pickup parking assistance motor 226 attached to the paper feed unit 250 operates. The position of the PB pickup auxiliary motor 226 is controlled by a stepping motor according to the number of pulses.

<Paper Feed Interval> Since the paper bank 200 feeds paper from a fixed paper feed tray with a vertically movable paper feed unit 250, the paper feed position varies depending on the paper feed stage and the amount of paper loaded. The transport timing from the paper feeding timing to the main body is calculated as follows. PBB belt 01 is a stepping motor PB belt auxiliary motor 224130 m/se
After the PB belt variable speed morph 227 has operated, the paper is transported at a speed of 130 wm/sec. The conveyance distance changes depending on the vertical position of the paper feeding unit, and is determined by the number of steps N from the home position of the PB unit assist motor 225. Since the PB unit auxiliary motor 2251 moves by 0.2 nn in steps, the transport bus L for each tray is expressed as L=NX0.2+P. Here, P is a distance fixed by the paper feed tray, which is 200 m++ for the third to fifth paper feeds and 120 m for the sixth paper feed, and this difference depends on the horizontal transport distance. Therefore, the transport time T is.

It is expressed as T=L/130. The sum of the conveyance time T and paper feeding time is the time required to feed the first sheet, and continuous sheet feeding from the second sheet onwards has nothing to do with this conveyance time T. Furthermore, the continuous paper feeding interval can be set by repeating the paper feeding operation at regular intervals, and A4
It is possible to print at 20 PPM by repeating the size at 3 seconds/cycle.

<Paper Feeding Operation> The sheet feeding operation will be explained based on the operation transition diagrams shown in FIGS. 10(a), (b), and (C) and FIGS. 11(a), (b), and (c).

In this embodiment, the deceleration and stopping mechanism for the PBB belt 01 uses two belt variable speed rollers A209 and B210.

FIGS. 9(a), (b), and (c) are different from FIG. 10(a) when paper is fed from the third tray 216 to the fifth tray 218.
(b) and (c) are cases where paper is fed from the sixth tray 219.

The paper feeding unit 250 feeds paper at a position detected by a paper top edge sensor attached to the paper feeding unit 250, which is located 5IIIl above the top surface of the stack of stacked papers below the home position of the tray, as the home position for paper feeding operation. Repeat the action. At this time, the flat part of the PBB belt 01 stretched between the pickup roller 208 and the roller 248 is located 5 m+ above the east upper end of the sheet. Next, the bit up roller B2O3 moves the paper in the tray to P during paper feeding.
In order to attract the paper to the BB belt 1, the PBB belt 01 is carried along and displaced by 100 m1 from the home position in the paper direction.

In order to adsorb the topmost sheet of paper on the tray to the PB belt 20, prior to paper feeding, the roller B212 moves the PB belt 20 by an amount corresponding to the paper size in synchronization with the paper feeding timing.
1 to form a charge pattern.

Lower the paper feed unit 250 by 5 mm and place the PB on the top edge of the paper.
The belt 201 is brought into contact. At this time, the above-mentioned belt transmission mechanism is used to operate 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 explained in detail later. This is done to improve the suction ability in order to attract and convey only the topmost sheet of paper that is stopped. They may be brought into contact and transported by suction.

When paper is fed from the third tray 216 to the fifth tray 218, the paper is attracted from the leading edge, and in order to convey the paper horizontally by the amount up to the roller 248, a belt speed change mechanism is used to transfer the PB of the paper contact surface. While keeping the relative displacement speed of the belt 201 with respect to the tray at zero, the paper feeding unit 250 is raised to the home position of the paper feeding operation at a point 5+m+ above the east upper surface of the paper.

Thereafter, after the S-shaped curvature caused by the belt transmission mechanism is released, the vertical conveyance section of the PB belt 201 becomes straight, and the paper is moved at 130 WI/se by the PB belt parking motor 224.
c, and is attracted to the PB belt 201 which is driven at a constant speed, and is transported at a constant speed at a predetermined speed.

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

On the other hand, when paper is fed from the sixth tray 219, the paper is attracted from a position approximately 20+m+ from the leading edge, and the roller C24
In step 8, in order to convey the paper vertically, the belt transmission mechanism is used to first convey the paper horizontally to the left. That is, while keeping the relative displacement speed of the paper contact surface of the PB belt 201 with respect to the tray negative, the paper feeding unit 250 is moved to the home position of the paper feeding operation at the point of the upper five fields of paper.
to rise. As described above, even in the case of the sixth paper feed, the leading edge of the paper can be attracted to the PB belt 201.

Paper feeding and conveyance can be performed stably.

<Belt speed change operation of paper feeding section> A speed change operation using the two belt variable speed rollers A209 and B210 shown in FIGS. 10 and 11 will be described.

The two belt variable speed rollers A209 and B210 have a diameter of 81111, a distance between roller centers of 12 mm, and a PB at the center.
The PB belt 201 is wound and released by the belt variable speed motor 228. The operation is shown in FIG. As a result, the belt movement amount l when the PB belt is not conveyed is determined by changing the rotation angle of the belt variable speed rollers A209 and B210 by θ.
(rad), it is approximated as shown in the following equation.

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

In order to stop the PB belt 201 at the paper feed contact surface, 1
When the paper feeding unit 250 is driven at a constant speed of 30 on/sec and descends at 150 on/sec, P
The B belt 201 moves at a speed of 280 mm/see on the paper feed contact surface, and to cancel this movement, the V is moved at a speed of 280 mm/see.
, the angular velocity ω at time and rotational position, that is, the driving speed of the PB belt variable speed motor 228 can be determined from the above equation.

On the other hand, in the case of paper feeding from the sixth tray 219, the paper upper part 5
While raising the paper feeding unit 250 to the home position of the paper feeding operation at point III,
The time to displace the B belt 201 by 20 m1 in the negative direction is 5 (m+)/150 (+m+/sec, ) = 0.0
33 (see, ), and the linear velocity of the PBB belt in the opposite direction at that time is 20 m/0, 033 sec, = 60
0m/sec.

The PBB belt 01 is driven at a constant speed of 13Qm/sec, and the paper feed unit 250 is driven at a constant speed of 150m/s.
ec, the PBB belt 01 is at the paper feed contact surface, 600+130-150=580++w++/see.

To release the winding, rotate ■ at 580wn/sec.
You can obtain the same result by setting it to .

The PBB belt variable speed motor 228 is composed of a stepping motor, and the PBB belt speed change motor 228 is configured as a stepping motor.
A timer value corresponding to the drive speed of the belt variable speed motor 228 is stored in advance in the ROM in the main control board 401, and while the timer value is called up, the PBB belt variable speed motor 2 is controlled.
28 speed control and forward/reverse control.

On the other hand, in preparation for deceleration in the next paper feeding process, the winding operation of the belt speed change mechanism between sheets of continuous feeding after the conveyed paper has passed through the belt speed change mechanism section is 1 Normally, the paper distance of about 150 m + n for A4 size paper. Due to the fact that PBB
The belt speed change motor 228 may perform winding operation at a constant speed.

Next, regarding belt transmission mechanisms with other configurations, Section 13.1
This will be explained based on Figure 4.

In this changing mechanism, two fixed rollers 650, 651 and 1
Two displacement rollers 652 are used.

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 the paper is fed from the sixth tray 219. The paper feeding surface of the PBB belt 01 and the behavior of the paper are similar to those shown in FIGS. 1 and 11.

The displacement roller 652 is moved horizontally between the two fixed rollers 650 and 651 by the PBB belt variable speed motor 227 to displace the PBB belt 01.
This is to adjust the speed of the first paper feeding surface.

The time it takes for the paper feed unit 250 to descend a distance of 5 m at 150 mn/see is: 5 m + / 150 wn/sec = 0.033 sec
At step c, the paper feed surface is displaced by 280 m1sec in the negative direction so as to cancel out the 150 on/see displacement of the paper feed surface due to the constant speed drive and the lowering of the paper feed unit 250. This is done for 0.033sec, so the displacement amount at that time is 280+w/sec, X O,033sec, =
9, 3+e+n, and the speed of the displacement roller 652 is 280 (+m/see, ) / 2 = 140 (
I/see, ) Displacement amount: 9.3m/2=4.7m It is sufficient to move at a constant speed to the left.

Similarly, the displacement of the sixth tray 219 in the negative direction during paper feeding is the speed of the displacement roller 652 of 290 m/5ec1.
, moves to the left at a constant speed with a displacement of 9.7■.

The speed change operation begins when the axes of the fixed rollers 650 and 651 are to the right of the axes of the displacement roller 652, at a total speed of 14.
The displacement amount is 4m, and it is carried out by constant velocity control.

<Paper Feed Timing> The paper feed timing when the transmission device having the configuration shown in FIGS. 13 and 14 is used will be explained. The timing chart for controlling the paper feeding operation is shown in Fig. 15, when A3 size paper is continuously fed from the third paper feed tray, and Fig. 16 is when A4 horizontal size paper is continuously fed from the sixth paper feed tray. This is an example of a timing chart when performing the following.

In Fig. 15, the PB belt assistance motor 224○N
Rotate at a constant speed. Next, the voltage power source B243 is operated in accordance with the paper feeding timing.

This start timing is programmed in advance with a value calculated from the linear velocity of the charge pattern forming position of the PBB belt 01 so that the charge pattern is formed upstream of the paper feed section at the position where the paper is attracted to the PBB belt 01. In this example, this value is approximately 1.48 seconds before the suction operation.

The same applies to the case of paper feeding from the fourth and fifth paper feeding trays. It differs only when paper is fed from the sixth paper feed tray. Next, prior to the sheet feeding operation, the PBB belt variable speed motor 227 is rotated in the forward direction, and the displacement roller 652 is kept waiting in the right direction.

At the paper feeding timing, the PB unit drive motor 22
5 in the forward direction, and at the same time, the PB belt variable speed motor 227 is rotated in the reverse direction at high speed to bring the speed of the PB belt 2001 on the paper feeding suction surface to zero and bring the PB belt 201 into contact with the upper surface of the paper. Moreover, the PB belt variable speed motor 227 is further reversed, the displacement roller 652 is retracted to the left, and the PB belt 201 is vertically conveyed. The fed and conveyed paper is passed through the PB paper feed sensor 51 (see Figure 2) provided in the paper feed path of the main body.
It is detected for about 3.2 seconds. The operation end timing of the high voltage power supply B243 is the PB belt 20 during the continuous operation period.
Since the acceleration and deceleration operations of 1 have occurred, the result is the same as when a constant velocity operation is performed by subtraction, and the operation is performed for a period of 3.2 seconds. In addition, when the charge pattern changes with 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 adjusted so that the charge pattern period of the PB belt 201 is constant. is changing. Since the last formed charge pattern becomes effective, when the linear velocity of the PB belt 201 at the charge pattern formation position is less than zero, the high voltage power source B243 is optionally operated, and is turned off in this example.

In FIG. 16, the basic operation is the same as in FIG. 15. The sixth sheet feeding includes a displacement operation of the suction surface of the PB belt 201 in the negative direction, and the PB unit support motor 2
25, the PB variable speed motor 227 is reversed at a higher speed to achieve a sheet feeding surface linear velocity of -600 no/see. The operation timing of the high-voltage power supply B243 is approximately 1.98 seconds for suction because the layout is different from other paper feed trays.
ec.

Since it is A4 size, the PB belt 201 at the charge pattern forming position stops operating during high-speed movement.

With the above, the PB belt 20 has a length equal to the paper size.
The PB belt 201 can be attracted to and conveyed to the charge pattern forming position of No. 1 in a stopped state.

Note that if the paper is thin and light, it can be transported sufficiently by forming a charge pattern on a portion corresponding to an appropriate range on the front of the paper depending on its weight.

<Transfer paper is received and transferred from the PB side to the main body side> Transfer paper is received and transferred from the PB side to the main body side by making the transport speed of the transfer belt and the PB belt the same, so that it is received smoothly without slack or tension. can be handed over. This means that the main body side is 1
Since it is 20m/s, the PB belt linear speed is 120mm/s.
This can be achieved by doing However, in this example, in order to increase the productivity on the PB side, the PB belt linear speed was set to 130+m+/s.
The case will be explained below. (When PB belt linear speed>transfer belt linear speed) This is done by moving the moving roller 29 from left to right in FIG. 2 when transferring the transfer paper from the PB belt 201 to the transfer belt 32. The speed of the transfer belt can be increased using the same principle as the speed change device shown in Figure 13. The transfer belt and paper contact each other at an apparent relative speed of zero, are attracted by the charge pattern, are conveyed, and then the receiver completes the transfer. do.

As described above, according to the present invention, recording paper can be reliably attracted to the endless conveyance belt and then fed and conveyed. or,
Since the charge pattern is formed in an appropriate range from the front of the recording paper depending on the weight of the recording paper, the front edge of the recording paper is reliably attracted during paper feeding, and the front end of the paper is Since the area corresponding to the weight of the area is adsorbed on the endless belt and conveyed, there is no problem even if the charge formation area is reduced, and highly reliable feeding ability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the appearance of an example of a copying system equipped with a multi-stage paper feeding and conveying device 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 side view showing the arrangement of the paper feeding unit and the endless belt of the embodiment of the multi-stage paper feeding and conveying device, and FIG. ), (
b) is a perspective view showing the paper feed trays other than the bottom stage of the multi-stage paper feed conveyance device and the bottom paper feed tray, FIG. 7 is an overall electrical block diagram of the flexible feed system of the copying system, and FIG. A plan view showing an example of the paper display section of a paper feed tray, FIG. 9 is a flowchart showing the flow of paper feed selection operation, and FIGS. 10 (a), (b), and (c) are paper feed trays other than the lowest one. 11(a), (b), and (c) are similar diagrams for the lowest paper feeding tray, and FIG. 12 shows the belt variable speed roller of the paper feeding section. 13 and 14 are explanatory diagrams explaining the operation of a belt transmission mechanism with other configurations,
15 and 16 are timing charts showing the sequence of operation timings of each device during paper feeding, respectively; FIGS. 17 and 18 are side sectional views showing an example of the configuration of a conventional multistage paper feeding and conveying device; Figures 19 to 23 are explanatory diagrams explaining the principle of a conveying device that forms a charge density pattern on a dielectric belt to attract and convey paper, and Figure 24 shows that paper is fed and conveyed using a single endless belt. FIG. 2 is a sectional view showing an example of a conventional device. 11... Photosensitive drum 32... Endless conveyor belt 41... Paper feed cassette 50... Copying machine (image forming device) 123...
...Scanner 200...Multi-stage paper feed conveyance device (paper bank, PB) 201...PBB belt endless conveyance belt) 20
2.203, 204, 208, 248... Roller group 209.210, 227... Endless conveyor belt variable speed means 212.243... Charge pattern forming means 21
6.217,218,219...Paper feed tray (
Recording paper storage means) 220.221...PB side plate 222.223...Pickup side plate 224.
...PB belt auxiliary motor 225...P
B unit parking motor 226...PB pickup parking assistance motor 237...PB unit HP sensor 238...PB pickup sensor 239...
...PB belt variable speed HP sensor 240...
... Recording paper stack top surface detection sensor 250 ... Paper feeding unit (paper feeding means) 251, 252, 253, 254.
... Paper tray open/close sensor 260.261, 263, 264 ... Site fence 262.265 ... End fence 650.6
51,652... Endless Conveyor Belt Variable Speed Means Agent Patent Attorney Takehisa Ito (I) [Six-color resistance] Figure 20 Procedural amendment (method) % formula % 1. Indication of the case 1990 Patent Application No. 194427 2. Name of the invention 4. Agent address 4-chome Yotsuya, Shinjuku-ku, Tokyo 25 No. 5 No. 5, date of amendment order October 30, 1990 6゜Drawing subject to amendment 7, content of amendment Figures 22 and 23 will be replaced.

Claims (2)

[Claims] (1) A plurality of recording paper storage means arranged in multiple stages in the vertical direction, a paper feeding means for feeding recording paper one sheet at a time from any one of the storage means, and a feeding means for each of the abovementioned storage means. and a vertical conveying means that extends in the vertical direction facing the paper side and conveys the recording paper fed by the paper feeding means to a delivery section for the image forming apparatus placed on the upper side of the apparatus. A multi-stage paper feeding and conveying device, wherein the paper feeding means is a single paper feeder that can selectively abut the front edge of the top surface of the uppermost sheet of the stack of recording sheets accommodated in the plurality of recording paper storage means. unit, the paper feeding unit and the vertical conveyance means are spanned between a roller group provided in the paper feeding unit and a roller group provided in the device frame, and the paper feeding unit and the above-mentioned image A single endless conveyor belt rotated via a delivery section to a forming device, a means for forming a charge pattern for adhering recording paper to the endless conveyor belt, and an endless conveyor belt in a paper feed unit. and a means for changing the speed, according to the size of the recording paper, a region of the charge pattern formed on the endless conveyor belt is attracted to the endless conveyor belt and is conveyed within the range of the recording paper. A paper feeding and conveying device characterized in that it is controlled to have an area corresponding to . (2) If the recording paper is light paper, instead of the range of the recording paper in claim 1, the area corresponds to an appropriate range in front of the range of the recording paper that is attracted to the conveyor belt according to its weight. A paper feeding and conveying device characterized in that it is controlled so that a charge pattern is formed on the paper.