JP3377149B2 - Paper transport device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device for conveying sheets such as copying machines and facsimiles. In particular,
The present invention relates to a sheet which is sucked and conveyed by negative pressure.

[0002]

2. Description of the Related Art Conventionally, the above-described sheet conveying device has been used, for example, in an electrostatic copying machine to convey a sheet, to which an image has been transferred and which has been peeled off from a photoconductor, to an image fixing section. , Has the following configuration. That is, the paper transport device includes an endless transport belt stretched between two rollers. A plurality of holes are evenly formed throughout the conveyor belt, and a duct provided between both rollers and the conveyor belt to suck air from the holes, and a suction fan that sucks air from the duct. Is equipped with. The suction fan sucks the air in the vicinity from the hole of the conveyor belt,
The paper can be sucked onto the conveyor belt. The sheet is conveyed in this suction state.

The following techniques are known in order to achieve more stable transportation. The sheet conveying device of the copying machine described in JP-A-1-104560 changes the suction force of the suction fan according to the size and quality of the sheet. The change in the suction force of the suction fan is performed by switching a plurality of suction fans or changing the rotation speed of the suction fan, and the suction force is increased when a small sheet is conveyed.

In the sheet conveying apparatus described in JP-A-5-278894, the duct is divided into a small portion on the upstream side and a large portion on the downstream side along the sheet conveying direction of the conveying belt. A separate suction fan was provided in the section. In this case, since the suction force on the upstream side can be increased, the sheet can be stably conveyed even when the sheet sent from the image forming unit is curled.

[0005]

However, in the above-described conventional sheet conveying apparatus, if there is a portion on the conveying belt where the sheet is not placed, air also flows in from that portion, so that the sheet is not placed. The suction force of the placed part is not sufficient. Therefore, when the end portion of the paper is being placed on the conveyor belt, the suction force is not sufficient, and the curled paper is likely to cause conveyance failure.

Further, although the above-mentioned technique can increase the suction force, it is not preferable in terms of cost and space because a plurality of suction fans are required or it is necessary to use suction fans having a large capacity. Further, even if a plurality of suction fans are installed, as in the above-described conventional paper conveying device, air flows in from a portion on the conveying belt where the paper is not placed, so that the suction force is effectively reduced. Can't be strong. Therefore, stable sheet conveyance is difficult.

Further, the above technique requires a plurality of suction fans, which is not preferable in terms of cost and space. Therefore, an object of the present invention is to solve the above-mentioned technical problems and to provide a sheet conveying apparatus capable of stably conveying a sheet with a smaller number of suction fans.

[0008]

In order to achieve the above object, a sheet conveying device according to a first aspect of the present invention has a placing surface on which a sheet is placed, and the placing surface is movable in the conveying direction. In a sheet conveying device including a member and a suction unit that sucks a sheet placed on the placement surface onto the placement surface, the suction unit includes a plurality of small holes formed on the placement surface. , Below the mounting surface
Suction port provided on the and suction force generation connected to the suction port
Means, the small hole facing the suction port, the air flow direction
The size of the overlapping part changes with the movement of the mounting surface
Is arranged so that the sheet is placed on the placement surface by the suction means.
Air flow in the area where the small hole and the suction port overlap
Move the transport member so that the size in the passing direction becomes smaller.
Change the suction force according to the transport condition of the paper .
Paper is placed only on the part of the transport member where small holes are placed.
The plurality of small holes are arranged in the carrying direction .

With the above arrangement, when placed on the mounting surface sheet, the conveyance condition requiring suction force, the sheet is strongly attracted to the mounting surface by the suction means strengthening the suction force, stable Can be transported. Further, since the suction force is strengthened when necessary, the suction means does not always require a large suction force and does not have to increase its ability .

That is, even if the suction force generating means has the same ability, if the size of the overlapping portion of the small hole and the suction port in the air flow direction becomes small, the suction force by the air passing therethrough becomes strong. Further, since the suction force can be increased when the sheet is placed on the placing surface, the sheet can be stably placed.

A sheet conveying device according to a second aspect is the first aspect.
In the paper transporting device described above, the suction port includes a part on the upstream side and a part on the downstream side in the paper transporting direction, which are partitioned from each other, and the suction means is configured when the paper is placed on the placement surface. It is characterized in that the downstream side portion of the suction port is closed.

According to the above construction, when the downstream side portion of the suction port is closed, the flow of air passing through the relatively upstream side portion becomes strong, and the suction force at the upstream side portion can be strengthened .

[0013]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing an internal cross section of a copying machine to which the sheet conveying apparatus of this embodiment is applied. Referring to FIG. 1, the present copying machine 1 exposes and scans an original placed on a transparent original placing plate 20 inside a main body 10 of the copying machine, and reflects light from the original on a photosensitive drum 41. Optical system 30 for guiding the image, a photoconductor drum 41 for forming a latent image according to the light from the optical system 30, and a developing device for visualizing the electrostatic latent image formed on the photoconductor drum 41. An image forming unit 40, which includes 43, transfers a visualized image onto a sheet, and a fixing device 51 that heats and fixes the toner image transferred onto the sheet. And a sheet conveying section 50 for discharging the sheet.

As the image forming section 40, a charging charger 42, a developing device 43, a transfer charger 44 and a cleaning device 45 are arranged in this order around a photosensitive drum 41. The image forming unit 40 forms an electrostatic latent image by forming a document image on the outer peripheral surface of the photosensitive drum 41 uniformly charged by the charging charger 42, and then the electrostatic latent image is developed by the developing device 43. The toner image is visualized, the toner image is transferred to the sheet by the transfer charger 44, and the residual toner is collected by the cleaning device 45.

The paper transport unit 50 guides the paper feed tray 52 that stores paper, a paper feed roller 54 that feeds the paper in the paper feed tray 52 one by one, and the paper that is fed from the paper feed roller 54. Guide plate 55 and roller pair 56 for
And a registration roller 58 that sends the sheet conveyed by the sheet feeding / conveying path 57 to the image forming unit 40 at a predetermined timing, and the fixing device 51 that fixes the sheet on which the image is transferred by the image forming unit 40. It has a sheet conveying device 59 for conveying the sheet to the sheet, the fixing device 51, and a sheet discharge conveying path 60 for discharging the sheet on which the toner image is fixed by the fixing device 51 to the discharge tray 53.

As will be described later in detail, the sheet conveying device 59 applies a suction force to the sheet so that the curled sheet can be stably conveyed. Therefore, as a suction force generating means, a fan device 66 for sucking the paper,
And a duct 65 for guiding air to the fan device 66. The paper carrying device of the present invention is applied to the paper carrying device 59.

FIG. 2 is a partially sectional front view of the main part of the sheet conveying device 59. FIG. 3 is a plan view of a main part of the paper transport device 59. The sheet conveying device 59 includes a roller 61 that is rotatably supported, a rotatable roller 62 that is arranged in parallel with the roller 61 with a predetermined distance, and a roller 62 that is a conveying member that places a sheet on the upper surface. Endless conveyor belt 63 stretched around the roller and roller 61
And an origin sensor 7 for detecting a predetermined position of the conveyor belt 63.
0 and a position detection device 68 for detecting the rotation angle of the roller 61.
And a motor 67 for driving the roller 61. In addition, the conveyor belt 63 is
And a drive unit that drives the conveyor belt 63 while controlling the position of the conveyor belt 63. Further, the paper transport device 59 includes a casing 64 arranged between the rollers 61 and 62 and the transport belt 63.

The motor 67 is connected to the roller 61 via a speed reducer 69 such as a gear. As the motor 67, a servo motor having good controllability is used so that the position of the conveyor belt 63 can be accurately controlled as described later. As a mechanism for driving the conveyor belt 63, the rollers 62,
A roller 61, a motor 67, and a speed reducer 69 are provided. The structure of the driving mechanism is not limited to the above,
It suffices if the conveyor belt 63 can be driven.

When the motor 67 is driven, the roller 61 is rotationally driven in a predetermined direction, for example, counterclockwise in FIG.
Accordingly, the conveyor belt 63 is moved in a predetermined direction, for example, as shown in FIG.
Is driven counterclockwise (arrow 71). At this time, the moving direction of the upper portion of the conveyor belt 63 is the predetermined conveying direction. The detecting means for detecting the position of the conveyor belt 63 is composed of the position detecting device 68 and the origin sensor 70. The origin sensor 70 allows the conveyor belt 63
It is possible to detect an arbitrary position of the conveyor belt 63 from the output of the position detection device 68 based on the detected position.

The position detecting device 68 is a rotary encoder connected to the roller 61. This rotary encoder has a rotatable rotary shaft for detection that is connected to an object to be detected, and for each rotation of a predetermined rotary angle of the rotary shaft for detection,
Output a predetermined pulse signal. Therefore, by counting the number of pulses of the output signal, the rotation angle of the detection rotation shaft can be detected from the above-described predetermined rotation angle. The rotation shaft for detection is connected coaxially with the roller 61.

The origin sensor 70 is a photo sensor provided near the conveyor belt 63, detects a detection hole (not shown) of the conveyor belt 63, and outputs a signal. Since the detection hole is opened at a predetermined position of the conveyor belt 63, by counting the output of the rotary encoder from the time when the detection signal is detected, the position of the conveyor belt 63 is set to the predetermined position as a reference. Can be accurately detected. The detection hole may also be used as a small hole 63a described later.

The driving means for driving the conveyor belt 63 while controlling its position is constituted by combining the above-mentioned mechanism for driving the conveyor belt 63 and the detecting means for detecting the position. The driving means is not limited to the above configuration. For example, a stepping motor or the like capable of position control may be used without using the rotary encoder. Also,
The detection of the position of the conveyor belt 63 is performed in order to match the paper conveyance timing with the position of the conveyor belt 63.
By appropriately setting the predetermined position detected by the origin sensor 70, the conveyance belt 63 may be driven in synchronization with the conveyance timing of the sheet.

The conveying belt 63 has an outer peripheral surface on the upper side in a state of being stretched between the rollers 61 and 62 as a sheet placing surface, has a width capable of placing the sheet, and has a plurality of small belts at predetermined positions. A hole 63a is formed. The small holes 63a are circular holes having a predetermined size and are regularly arranged at predetermined intervals. Further, the small hole 63a has a size of a portion facing the suction port 64b and overlapping in the air circulation direction, which is described later, and at a predetermined time point, the overlapping portion on the upstream side and the overlapping portion on the downstream side. Differently from each other, they are collectively arranged on the conveyor belt 63 as follows. Therefore, the size of the overlapping portion changes as the transport belt 63 moves.

That is, the small hole 63a of the conveyor belt 63
The position of the portion where is placed is set to a predetermined position of the conveyor belt 63, and the paper is placed on this. The portion where the small holes 63a are arranged is located at one place of the conveyor belt 63 and is not formed at the other portion. For example, the portion where the small holes 63a are arranged is within the range indicated by the alternate long and short dash line B in FIG. 3, and is formed within the range indicated by the leader line A in the direction along the surface of the conveyor belt 63.

The size of the portion in which the small holes 63a are arranged is set within the range of the size of the paper placed on the conveyor belt 63. Further, the shape of the portion in which the small holes 63a are arranged is a rectangle corresponding to the shape of the sheet, and is set according to the mounting posture. For example, the sides of the rectangle are arranged so as to be parallel or orthogonal to the edge of the conveyor belt 63. The shape is not limited to a rectangle, and various modifications can be considered as described later.

The arrangement of the small holes 63a is such that the conveyor belt 6
3 are arranged in a line at a predetermined interval along a direction orthogonal to the moving direction, and a plurality of these lines are arranged at a predetermined interval in the moving direction. In addition, the position of the small holes 63a in the direction orthogonal to the moving direction is the same as that of the small holes 63 in the adjacent row.
It is set to be in the middle of the position of a. Therefore,
A large number of small holes 63a can be arranged at narrow intervals, and the entire sheet can be sucked uniformly, as will be described later.

In order to suck the paper, one end of the duct 65 is connected to the casing 64, and the fan device 66 is provided at the other end of the duct 65 as shown in FIG. By these, a suction air passage for guiding the air sucked from the small holes 63a is formed. The casing 64 is formed in a hollow box shape, and allows air to flow inside. The casing 64 is arranged close to its upper surface along a lower surface of an upper portion of the conveyor belt 63 (a portion whose moving direction coincides with the conveying direction). On the rear surface of the casing 64, a connection port 64a to which one end of the duct 65 is connected is formed, and on the upper surface of the casing 64,
The suction port 64b is formed.

The suction port 64b is arranged at the central portion of the conveyor belt 63 in the width direction so as to face it. Also, the suction port 6
4b is formed in a rectangular shape having one side parallel to the transport direction of the transport belt 63, the size of the casing 64 in the transport direction, and the small hole 63 in the width direction of the transport belt 63.
It is narrower than the portion where a is arranged. The shape is not limited to a rectangle, and various modifications can be considered as described later.

The suction air passage is from the small hole 63a to the suction port 64.
b, the space inside the casing 64, the connection port 64a (arrow F1 in FIG. 2), and the duct 65 (arrow F in FIG. 3).
2), reaching the fan device 66. Also, the small hole 63a
And the suction port 64b cooperate with each other to form a suction opening for sucking an object to be sucked. The fan device 66 drives a fan for blowing air to blow air by driving the built-in motor.

As described above, when the fan device 66 is rotationally driven, the air in the duct 65 is sucked and a negative pressure is generated. Along with this, the air flows from the small holes 63a through the suction air passage. Therefore, the paper near the small hole 63a is
It is drawn to the small holes 63a along with the flow of air. The sheet sucked up closes the small hole 63a. A negative pressure is generated in the closed small hole 63a, and the sheet is pressed against the conveying belt 63 by the atmosphere and conveyed.

By the way, the smaller the size of the flow path of the suction air passage, for example, the smaller the opening area in the direction orthogonal to the air flow direction, the harder it is for air to flow, the stronger the air flow, and the stronger the suction force. Also, negative pressure is likely to occur. In the present invention, by limiting the size of the suction air passage as follows, a sufficiently large suction force is generated without increasing the capacity of the fan device 66.

That is, when the conveyor belt 63 moves,
Since the position of the small hole 63a also changes, the relative positional relationship between the small hole 63a and the suction port 64b also changes. Therefore, since the size of the overlapping portion of the small hole 63a and the suction port 64b, which is the size of the suction opening, also changes, when the overlapping portion is small, the suction airflow is larger than when it is large. It becomes difficult for the air in the passage to flow, the negative pressure in the duct 65 becomes strong, and a large suction force is generated.

Specifically, the suction force changes as follows. That is, when the portion of the transport belt 63 without the small holes 63a faces the suction port 64b, the sucked air flows into the suction port 64b through the gap between the transport belt 63 and the casing 64. Then, the conveyor belt 63 is driven to move the portion of the portion where the small holes 63a are arranged,
The part on the downstream side in the transport direction (the part on the left side in FIG. 3) is
When facing the portion of the suction port 64b on the upstream side in the transport direction (the portion on the right side in FIG. 3), the small holes 63a that face each other.
The air flows into the suction air passage from the overlapping portion of the suction port 64b and the suction port 64b. Since the overlapped portion at this time is only the above portion and is small, a strong suction force works here.
As will be described later, at this time, the downstream end of the sheet can be placed, so that the sheet can be sucked onto the transport belt 63 with a strong suction force. Even a curled sheet sent from 40 can be stably placed.

Further, as the conveyor belt 63 moves, the overlapping portion of the small holes 63a and the suction port 64b facing each other gradually becomes larger. When the portion of the conveyor belt 63 in which the small holes 63a are arranged is positioned so as to cover the entire suction port 64b (the state of FIG. 3), the portion of the small hole 63a and the suction port 64b that face each other overlap each other. The size is maximized, and the suction force is weakened to an appropriate strength, so that the sheet can be sucked as a whole and stably conveyed.

As described above, since the suction force can be changed in accordance with the transport state, for example, the suction force at the beginning of placing the sheet can be made stronger and weakened later, an excessive suction force acts on the sheet. It is possible to surely suck the paper while preventing this, and the paper is not wrinkled. Further, the copying machine 1 includes a control section 80 for controlling the operation of the entire copying machine 1 and also for controlling each section of the sheet conveying device 59, and an operation key (not shown) including a start key for starting an image copying operation. ) And.

The control section 80 includes a microcomputer and controls each section according to a program stored in RAM, ROM or the like. The control unit 80 includes a position detection device 68,
Various sensors such as the origin sensor 70 and operation keys are connected,
Based on these detection signals and command signals, the motor 67, the fan device 66, etc. connected to the control unit 80 are driven.

The control unit 80 controls each unit so as to obtain a change in the suction force according to the above-described sheet conveyance state. That is, the control unit 80 reduces the size of the overlapping portion of the small hole 63a and the suction port 64b in the air flow direction when the paper is placed on the placement surface of the transport belt 63, and The conveyor belt 63 is moved so that the paper can be placed on the reduced overlapping portion.

The operation of the sheet conveying device 59 of the present invention will be described below. The paper transporting device 59 has a transport belt 63 in advance.
Has been moved to a predetermined position. This position is a position where the origin sensor 70 can detect a signal. In addition, the fan device 6
6 has stopped. The copying machine 1 starts the image copying operation when the start key is pressed. That is, the optical system 3
0 starts the illumination scanning of the original, and the paper transport unit 50 sends out a predetermined paper to the image forming unit 40. The paper is sent out with the timing adjusted by the registration rollers 58 so that the electrostatic latent image formed on the photosensitive drum 41 is transferred to the paper. In synchronization with this, the motor 67 is driven at a predetermined speed, and the conveyor belt 63 moves. Further, the fan device 66 is driven to suck the air. Then, when the portion of the transport belt 63 on the downstream side of the portion where the small holes 63a are arranged begins to overlap with the suction port 64b, the leading end portion of the sheet sent from the image forming unit 40 is
The conveyor belt 63 is driven so as to cover the portion of the conveyor belt 63 on the upstream side of the paper conveyor 59, in synchronization with its position. At this time, as described above, the sheet is strongly attracted to the conveyor belt 63 and is stably placed. In this way, the suction force can be increased according to the transport state during the placing operation that requires the strong suction force. After that, the conveyor belt 63 moves at a predetermined speed, and the paper is sent to the fixing unit 51.

The fan unit 66 is driven at the same timing when the paper is conveyed, and is stopped at other times. Therefore, the conveyor belt 63
It is not sucked by the casing 64 by the suction force generated by driving the fan device 66, and the driving resistance of the conveyor belt 63 is also reduced. It also saves energy. In this way, since the air can strongly flow from the suction air passage that passes through the small hole 63a on the upstream side of the suction air passage that passes through the small hole 63a on the downstream side of the sheet conveying device 59, the air can flow to the upstream side accordingly. A certain sheet can be strongly sucked. Further, the suction force can be increased according to the transport state in which the suction force is required at the time of placement. Therefore, the paper can be reliably placed on the conveyor belt 63 and can be stably conveyed.

Further, since a part of the suction air passage is limited and the suction force from the remaining part is strengthened, the suction force of the fan device 66 does not have to be increased. Further, the suction force of the fan device 66 does not have to be always large because the suction force is strengthened when the suction force is required according to the transport state such as when the sheet is placed. Also does not have to be large.

In other words, even a smaller-sized fan can obtain the same or higher performance than the conventional one. Therefore, by using a small fan, it is cheaper and
Space saving, power saving, and noise reduction can be achieved. Next, a second embodiment of the present invention will be described. Figure 4
[FIG. 4] is a plan view of the conveyor belt 63 and shows the same position as in FIG. 3. In this embodiment, the arrangement of the small holes 63a of the conveyor belt 63 is different from that in the first embodiment. That is, in the portion of the conveyor belt 63 where the small holes 63a are arranged, the downstream side is small and the upstream side is large. Therefore, the small hole 63a and the suction port 64
The size of the portion overlapping with b is smaller when the sheet is placed, compared to the first embodiment. Therefore, the suction force also becomes stronger, and the paper can be sucked more reliably.

Next, a third embodiment of the present invention will be described. FIG. 5 is a plan view of the conveyor belt 63 and shows the same position as in FIG. Also in this embodiment, the way of arranging the small holes 63a of the conveyor belt 63 is different from that of the first embodiment. That is, the small hole 63a of the conveyor belt 63
In the portion where is arranged, the downstream side is small, the intermediate portion is large, and the upstream side is small. Therefore, the small hole 6
The size of the overlapping portion of 3a and the suction port 64b is smaller than that of the first embodiment when a sheet is placed. Therefore, the suction force is further strengthened, and a stable sheet can be placed. Further, as compared with the second embodiment, the small holes 63a are increased in the middle portion, so that even a short sheet in the conveying direction can be widely sucked in the width direction of the sheet and can be stably conveyed.

The position of the portion where the small holes 63a are arranged in the second and third embodiments described above corresponds to the portion on which the sheet is placed, as in the first embodiment. It is set. Next, a fourth embodiment of the present invention will be described. FIG. 6 is a plan view of the casing 64. In the present embodiment, the shape of the suction port 64b is different from that of the first embodiment. That is, the downstream side is large and the upstream side is small along the transport direction, and the openings are substantially triangular. Further, the upstream end portion 64g is formed to have a size capable of ensuring a predetermined opening area. Therefore, the suction port 6
Since the upstream side of 4b is small, the size of the overlapping portion of the small hole 63a and the suction port 64b when the sheet is placed is smaller than that in the first embodiment. Therefore, the suction force is further strengthened, and a stable sheet can be placed.

Next explained is the fifth embodiment of the invention. FIG. 7 is a plan view of the casing 64. In this embodiment, the inside of the casing 64 is different from that of the first embodiment. That is, in the casing 64, the chamber 64c that does not communicate with the connection port 64a and the connection port 64a
Chambers 64d, 64e, 64f communicating with a are defined. The chamber 64d is on the upstream side in the transport direction and is narrowly divided in the central portion in the width direction. The chambers 64e and 64f are
It is located on the downstream side and is broadly divided in the width direction. The chambers 64c, 64d, 64e, 64f define a suction port 64b. Therefore, the air flowing in from the portion where the small hole 63a and the suction port 64b overlap with each other passes through the chamber 64d when the sheet is placed, and the suction air passage becomes narrow. Therefore, even when the small holes 63a are arranged as shown in the first embodiment, the portion facing the chamber 64c does not serve as the suction air passage, and the suction air passage when the sheet is placed is ,
It is smaller than that of the first embodiment. Therefore,
The suction force also becomes stronger, and the paper can be placed securely. Further, when the transport belt 63 moves and reaches the downstream side, air also flows in through the chambers 64e and 64f that are widened in the sheet width, and can be stably sucked in the entire sheet width.

Next explained is the sixth embodiment of the invention. FIG. 8 is a plan view of the casing 64. In this embodiment, the inside of the casing 64 is different from that of the first embodiment. Further, the transport belt 63 is formed with small holes 63a uniformly over the entire circumference. That is, in the casing 64, the chamber 64 that does not communicate with the connection port 64a is provided.
c and chambers 64d and 64e communicating with the connection port 64a are partitioned. The chamber 64d is on the upstream side in the transport direction and is narrowly divided in the central portion in the width direction. Room 64e
Is located on the downstream side and is broadly partitioned in the width direction. The chambers 64c, 64d, 64e define a suction port 64b. Further, as an opening / closing means capable of opening / closing this communicating portion, in a portion communicating with the connection port 64a of the chamber 64e,
A valve 85 driven by the solenoid 84 is provided. The solenoid 84 is connected to the control unit 80 and opens and closes the valve 85 at a predetermined timing.

When the valve 85 is closed, air is no longer sucked through the chamber 64e. Therefore, the flow of air passing through the chamber 64d on the upstream side becomes relatively strong, and the suction force from the suction air passage passing through the chamber 64d can be strengthened. The valve 85 is closed when a sheet is placed, and opened after a predetermined time such that the sheet reaches the middle of the conveyor belt 63. By thus limiting the downstream side of the suction air passage, the suction force on the upstream side can be increased without increasing the capacity of the fan device 66. Further, the suction force can be changed according to the conveyance state of the paper. Therefore, when the sheet is placed, the suction force can be increased for reliable transport, and thereafter, the sheet can be stably transported with an appropriate suction force. Further, in this case, the fan device 66 may be constantly driven and the motor 67 may not be position-controlled, and simple control can be performed.

In the embodiment of the present invention, the small holes 63a of the conveyor belt 63 are not formed in any portion other than the portion on which the paper is placed .

Further, the shapes of the suction port 64b and the small hole 63a,
The arrangement is not limited to the above specific example. In short, at a certain point, the small hole 63a on the downstream side in the sheet conveying direction and the suction port 64b overlap with each other in the air flow direction so that the overlapped portion is smaller than the overlapped portion on the upstream side. It suffices if the small holes 63a are arranged in the conveyor belt 63. In addition, various design changes can be made without changing the gist of the present invention.

[0049]

According to the first aspect of the present invention, the suction force can be changed according to the sheet conveyance state.
In the conveyance state that requires suction force, the sheet can be stably conveyed by the strong suction force. Further, since the suction force is strengthened as necessary, the suction means does not always require a large suction force and does not have to increase its ability.

For example, when a sheet is placed on the placing surface,
The suction force is increased, and the paper can be placed stably.

According to the second aspect of the invention, the suction force of the upstream side portion can be increased by closing the downstream side portion of the suction port .

[Brief description of drawings]

FIG. 1 is a front cross-sectional view of a schematic configuration of a copying machine to which a sheet conveying device according to a first embodiment of the present invention is applied.

FIG. 2 is a partial cross-sectional front view of a main part of the above-described sheet conveying device.

FIG. 3 is a plan view of a main part of the paper transport device of FIG.

FIG. 4 is a plan view of a conveyor belt according to a second embodiment of the present invention.

FIG. 5 is a plan view of a conveyor belt according to a third embodiment of the present invention.

FIG. 6 is a plan view of a casing according to a fourth embodiment of the present invention.

FIG. 7 is a plan sectional view of a casing according to a fifth embodiment of the present invention.

FIG. 8 is a plan sectional view of a casing according to a sixth embodiment of the present invention.

[Explanation of symbols]

59 Paper transport device 63 Conveyor belt (conveyor member) 63a small hole 64b suction port 64d upstream part 64e Downstream part 66 Fan device (suction force generation means) 80 Control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-70787 (JP, A) JP-A-64-38369 (JP, A) Actually open 2-2-7633 (JP, U) Actually open 54- 99283 (JP, U) Actual development Sho 60-44054 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B65H 5/22 G03G 15/00 518

Claims (2)

(57) [Claims] 1. A transport member having a loading surface on which a sheet is loaded, the loading surface being movable in the transport direction, and suction for sucking a sheet loaded on the loading surface onto the loading surface. And a plurality of small holes formed on the placement surface,
Suction port provided below the surface and the suction port connected to the suction port.
And a small hole facing the suction port and overlapping in the air flow direction.
Arranged so that the size of the minute changes with the movement of the mounting surface
The suction means absorbs the small holes when the paper is placed on the placement surface.
The size in the air flow direction of the part that overlaps with the outlet is small
Kunar so on, to move the conveying member, and by changing the attraction force according to the transport state of the sheet, only the portion of the conveying member disposed in the small holes, the sheet is placed al
In this paper transport device , a plurality of small holes are arranged in the transport direction . 2. The sheet transporting apparatus according to claim 1, wherein the suction port is partitioned from each other on the upstream side in the sheet transporting direction.
And a portion on the downstream side, the suction means is configured to remove the suction port when the sheet is placed on the placement surface.
A paper conveyance device characterized in that the downstream side portion is closed .