JP2002284399A - Sheet skew correcting / conveying apparatus, image forming apparatus and image reading apparatus provided with this apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reliably correct skew of a sheet without being affected by sheet thickness, material, and the like. A sheet skew correction conveyance device (5) causes a difference in sheet conveyance speed between a plurality of skew correction roller pairs (142a, 142b) when a CPU detects skew of a skew detection sensor (S1, S2). Active registration method and skew correction roller pair 142a, 142b
Is temporarily stopped and the leading edge of the sheet is received by the skew correction roller pairs 142a and 142b for a predetermined time, and the loop registration method is selectively performed based on the sheet information detected by the sheet thickness detection unit or the OHP sheet detection sensor. The skew correction of the sheet can be performed according to the thickness and type of the sheet, and the skew of the sheet can be reliably corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet skew correcting / conveying device for correcting a sheet conveyed obliquely to a straight direction, and a straight skew correcting / conveying device provided in a main body. The present invention relates to an image forming apparatus that forms an image on a sheet whose direction has been corrected, and an image reading apparatus that reads an image of a sheet that has been corrected and conveyed by a sheet skew correcting and conveying device.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine, a facsimile, a printer, and a multifunction peripheral thereof generally has a function of reading a document and a function of forming an image on a transfer material. However, some models have only a function of forming an image on a transfer material. Therefore, the image forming apparatus has at least a function of forming an image on a transfer material. Note that an image forming apparatus having a function of reading a document can be said to be an image reading apparatus.

When reading an original, the image forming apparatus cannot accurately read the original if the original is conveyed at an angle. Further, when an image is formed on a transfer material, if the transfer material is transported obliquely, the image is formed obliquely on the transfer material, and the appearance of the transfer material deteriorates.

For this reason, the image forming apparatus is provided with a document skew correcting / conveying device having a registration function for correcting (correcting) a document conveyed in an oblique direction to a straight direction. Further, there is provided a transfer material skew correcting / conveying device which corrects a transfer material conveyed in an oblique direction to a straight direction.

[0005] An original is a document such as an original sheet, a label, or the like.
A relatively thin object on which images such as characters, pictures, and symbols are formed. The transfer material refers to plain paper, a thin resin material which is a substitute for the plain paper, or a relatively thin material such as cardboard which can form an image. Documents, transfer materials, and the like are collectively referred to as sheets. Further, the document skew correction transport device and the transfer material skew correction transport device are collectively referred to as a sheet skew correction transport device. In addition, a state in which a sheet is conveyed at an angle is referred to as “skew”.

[0006] The registration function provided in the sheet skew correcting and conveying device includes a loop registration method and an active registration method.

In the loop registration method, the leading end of a sheet is brought into contact with the nip of a stopped roller pair to form a bend (loop) on the sheet, and the leading end of the sheet is pushed along the nip of the roller pair due to the elasticity of the sheet. This corrects skew.

In the active registration method, the sheet is not stopped at the time of registration,
The skew is corrected while the conveyance is continued.

The active registration method will be described in more detail. The active registration method is based on a sheet detection signal of a sensor when a leading edge of a sheet crosses two sensors disposed in a sheet conveying path in a direction substantially perpendicular to a sheet conveying direction and separated from each other. The skew of the leading edge of the sheet is detected, and the sheet conveyance speed of the two right and left registration roller pairs that are arranged in a direction substantially perpendicular to the sheet conveyance direction and coaxially separated, and rotate independently, The skew of the sheet is corrected by varying the amount of skew of the sheet.

That is, in the active registration system, the two registration rollers are individually rotated, so that the rotation speeds of two drive motors provided on both sides in the sheet conveying direction are controlled, and the sheet is skewed. The skew is corrected by making the conveying speed of one pair of registration rollers slower or faster than the conveying speed of the other pair of registration rollers according to the amount.

As described above, the active registration method corrects the skew without temporarily stopping the sheet conveyance, so that the sheet interval (between the sheets) is narrowed as compared with other methods, and the sheet conveyance efficiency is reduced. And the image forming speed can be substantially improved without increasing the image forming process speed in the image forming apparatus. Therefore, the active registration method can cope with high-speed operation in recent years in which image forming and image reading apparatuses tend to form images and read images at high speed.

[0012]

However, in order to correct the skew of the sheet by the active registration method, the rotational speeds of the drive motors provided on both sides in the sheet conveying direction are controlled so that the right and left sides are controlled. Since the sheet conveyance direction is controlled by the sheet conveyance speed difference between the two registration roller pairs, the sheet is twisted by an amount that changes the sheet conveyance direction. However, since the position of this twist varies depending on the shape of the sheet conveying path and the sheet size, even if an attempt is made to change the direction of the sheet, the guide plate is restricted and friction occurs between the sheet and the guide plate. In some cases, sheet correction cannot be performed reliably.

Further, in order to correct the skew of a sheet by the active registration method, a sheet for an overhead projector (hereinafter referred to as "OHP sheet") is used.
), Glossy paper, thick stiff paper, etc., may cause slippage (idling) of the registration roller pair during skew correction, and the skew correction accuracy of these papers may be reduced. In addition, a decrease in the skew correction accuracy causes a conveyance failure of the sheet, and is constrained by the thickness of the conveyable sheet and the type of the sheet.

On the other hand, in the case of the loop registration method, a space in which the sheet bends is provided around the registration roller to prevent a reduction in the correction accuracy of OHP paper, glossy paper, and stiff cardboard. Can be. However, in the case of the loop registration method, the sheet is temporarily stopped and then skew correction is performed. Therefore, compared with the active registration method, the sheet conveyance efficiency is poor, and the image forming apparatus has a low image forming process speed. Can not be raised.

According to the present invention, there is provided a sheet skew correcting / conveying device for selecting a loop registration method or an active registration method in accordance with the thickness, material, etc. of a sheet to surely correct sheet skew. An object of the present invention is to provide an image forming apparatus that forms an image on a sheet that has been transported straight, and an image reading apparatus that reads an image on a sheet that has been transported straight, comprising the sheet skew correction transport apparatus. I have.

[0016]

In order to achieve the above object, a sheet skew correcting / conveying apparatus according to the present invention comprises an information detecting means for detecting information on a conveyed sheet, and a skew direction of the sheet. Skew detection means for detecting the skew amount,
A plurality of sheet transporting units which are disposed apart from each other in a direction intersecting the transporting direction of the sheet and independently transport the sheet, and the plurality of sheets based on information regarding the sheet by the information detecting unit. Skew correction control means for individually controlling the sheet conveyance operation of the conveyance means to straighten the skew of the sheet, and wherein the skew correction detection means is such that the skew detection means A first skew correction operation that causes a difference in the sheet conveyance speeds of the plurality of sheet conveyance units when skew is detected, and the sheet conveyance unit suspends the sheet conveyance unit and moves the leading end of the sheet for a predetermined time to the sheet conveyance unit. And the second skew correction operation received by the information detecting means is selectively performed based on the information of the sheet detected by the information detecting means.

In the sheet skew correcting / conveying apparatus according to the present invention, the information detecting means is a thickness detecting means for detecting a thickness of the sheet, and the skew correcting control means is configured to control the sheet thickness to exceed a predetermined thickness. When not, the first skew correction operation is selected, and when the thickness exceeds the predetermined thickness, the second skew correction operation is selected.

The information detecting means of the sheet skew correcting / conveying device of the present invention is a thickness detecting means for detecting a thickness of the sheet, and the skew correcting control means detects whether the sheet has a skew. When the thickness is impossible, the sheet conveying operation of the sheet conveying means is stopped.

In the sheet skew correcting / conveying device of the present invention, the thickness of the sheet detected by the thickness detecting means may be:
When the thickness is such that the skew cannot be corrected, there is provided a notifying means for reporting that the correction is impossible.

The sheet skew correcting / conveying apparatus of the present invention further comprises a correcting operation setting means for inputting the value of the predetermined thickness.

The sheet skew correcting / conveying device of the present invention further comprises a correcting operation inhibition setting means for inputting a thickness value at which the skew cannot be corrected.

[0022] The thickness detecting means of the sheet skew correcting / conveying device of the present invention comprises: a pair of sheet conveying rotating members capable of pinching and conveying the sheet, and at least one of which can approach and separate from the other; A thickness detecting sensor for detecting a thickness of the sheet by detecting an amount of movement of the sheet transporting rotator capable of approaching and separating in the approaching / separating direction.

[0023] The information detecting means of the sheet skew correction conveying device of the present invention is a sheet discriminating means for detecting whether the sheet is a sheet for an overhead projector, and the skew correction control means includes: When the sheet is a sheet for an overhead projector, the second skew correction operation is selected.

[0024] The skew detecting means of the sheet skew correcting / conveying device of the present invention is provided with a plurality of sheets spaced apart in a direction intersecting the sheet conveying direction to detect a leading edge of the sheet. It has a detection sensor.

The sheet conveying means of the sheet skew correcting / conveying apparatus of the present invention is configured to convey the sheet while nipping and rotating the sheet.
It has a pair of rotating bodies.

In order to achieve the above object, an image forming apparatus according to the present invention forms an image on a sheet conveyed by the sheet skew correction device according to any one of the above-mentioned items, and a sheet skew correction device. Image forming means.

In order to achieve the above object, an image reading apparatus according to the present invention comprises: a sheet skew correcting / conveying apparatus according to any one of the above; and an image reading apparatus for reading an image on a sheet conveyed by the sheet skew correcting apparatus. Means.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a sheet skew correcting / conveying apparatus according to an embodiment of the present invention;

The sheet skew correcting / conveying device is provided not only in a copying machine but also in a main body of another image forming apparatus such as a facsimile, a printer, and a multifunction peripheral thereof. Further, the sheet skew correcting and conveying device is provided not only in the image forming apparatus but also in a main body of an apparatus for handling a sheet, for example, an image reading apparatus that reads an image formed on a sheet by an image reading unit (image reading unit). It has become. In addition, the sheet can be fed into the sheet punching section with the direction of the sheet aligned with the main body of the apparatus that punches the sheet.

Therefore, the device in which the sheet skew correction transporting device is incorporated is not limited to the main body of the image forming apparatus, but is provided in the main body of various devices for handling sheets, and is used for transferring originals, transfer materials, and the like. The skew of the sheet can be corrected.

(Copying Machine) In the schematic front sectional view of the copying machine shown in FIG.
And a printer unit 2 at the bottom. A sheet skew correcting and conveying device 5 is incorporated in the printer unit 2.

The configuration of the reader unit 1 will be described.

The reader unit 1 includes a platen glass 101 on which a document is loaded, a document pressure plate 102 for pressing the loaded document from above, a light source 103 for irradiating the image surface of the document, and a light source 1
03, a plurality of mirrors 104 for guiding reflected light from the image surface, and the lens 10
5. A photoelectric conversion / image processing unit 106 for performing photoelectric conversion of the reflected light from the original by the CCD 301 and performing various image processing on the obtained electric signal. The photoelectric conversion / image processing unit 106 has an image processing function of performing A / D conversion, shading correction, masking correction, scaling, LOG conversion, and the like on the photoelectrically converted electric signal.

The operation of the reader unit 1 will be described.

A user places an original on an original platen 101 on an original platen glass 101 so that an image surface thereof faces downward.
Press down on 1. The mirror stand 133 moves while illuminating the light with the light source 103 and scans the image surface of the document. The reflected light image from the image plane is transmitted to the CC of the photoelectric conversion / image processing unit 106 through a plurality of mirrors 104 and lenses 105.
An image is formed on D301, where it is photoelectrically converted into an electric signal. The image signal that has been converted into an electric signal is sent to the next printer unit 2 after being subjected to various image processing.

The configuration of the printer unit 2 will be described.

The printer unit 2 scans the surfaces of the laser drive unit 304, the laser element 108, and the photosensitive drum 112 with laser light, which converts an image signal sent from the reader unit 1 into a signal for driving a laser. It comprises a polygon scanner 109, an image forming section (image forming means) 6 including a photosensitive drum 112, and a fixing unit 120 disposed at the most downstream side in the transport direction of the transfer material.

The image forming section 6 includes a photosensitive drum 112 rotatably supported in the direction of an arrow, and a primary drum disposed around the photosensitive drum 112 substantially in the rotation direction to uniformly charge the surface of the photosensitive drum 112. Charger 113, developing device 110 for developing an electrostatic latent image on photosensitive drum 112, photosensitive drum 112
A transfer charger 119 for transferring the upper toner image onto a transfer material, and a cleaner 11 for removing transfer residual toner on the photosensitive drum 112
6. Cleaner blade 117, auxiliary charger 115 for removing charges, and pre-exposure lamp 114 for removing residual charges
And so on.

Further, the developing device 110 includes a developing roller 1.
11 are provided. The developing roller 111 develops a toner image on the photosensitive drum 112 by rotating in a direction opposite to the photosensitive drum 112. The pre-fixing belt 118 conveys the transfer material onto which the toner image has been transferred to the fixing unit 120. The fixing unit 120 heats and presses the transfer material while conveying the transfer material by the rotation of the fixing rollers 121 and 122 to fix the toner image on the transfer material. Transport roller 123
Is configured to discharge the transfer material after fixing to a paper discharge tray 126 outside the apparatus main body 4.

The paper feeder 150 for feeding the transfer material includes
Cassette paper feeder 124 and multi paper feeder 1
25. The cassette paper feed device 124 is
It has a transfer material transfer path, and includes a lower feed cassette 127, an upper feed cassette 128, a lower feed roller 129, an upper feed roller 130, and transfer rollers 131 and 132. The multi-sheet feeder 125 is a multi-tray 1
35, a paper feed roller 161, transport rollers 162 and 163, and the like. Since the transfer material feed path is straight, various transfer materials having different properties such as material and size are used for the image forming unit 6. Can be supplied.

The operation of the printer unit 2 will be described.

The paper feeding / conveying section 150 includes the cassettes 127, 1
28, and the transfer material P is supplied from the multi-sheet feeding device 125 to the sheet skew correcting / conveying device 5 described later. The sheet thickness detection roller pair 141 and the two skew correction roller pairs 142a and 142b of the sheet skew correction device 5 transport the transfer material P to the image forming unit 6. An OHP paper detection sensor (information detection means, sheet discrimination means) 143 for detecting OHP paper is arranged on the transport path on the upstream side of the paper thickness detection roller pair 141. One reflection-type and one transmission-type photosensor of the OHP paper detection sensor 143 are disposed, respectively.
By utilizing the fact that the OHP sheet transmits light, the CPU 306 determines whether or not the transfer material passing through the OHP sheet detection sensor 143 is the OHP sheet based on the logic of the output of the two sensors. I have. Paper thickness detection roller pair 14
1 detects the thickness of the transfer material. The two skew correction roller pairs 142a and 142b correct skew of the transfer material. This correcting operation will be described later.

The photosensitive drum 112 and the transfer charger 119 of the image forming section 6 transfer the toner image formed on the photosensitive drum 112 to a straightened transfer material. The pre-fixing belt 118 transfers the transfer material on which the toner image is transferred
Send to 0. The fixing device 120 fixes the toner image on the transfer material. Finally, the transport roller 123 discharges the transfer material on which the toner image has been fixed to the discharge tray 126.

The control relationship of the copying machine 3 will be described.

In the control block diagram of FIG. 2, the copying machine 3 is entirely controlled by a CPU (skew correction control means) 306.

The CPU 306 mainly controls the operation of each load in the copying machine 3, collects and analyzes information of sensors, and operates the operation unit 305, that is, the user interface, in addition to the image processing unit 107 and the laser driving unit 304. Is responsible for exchanging data with the

Further, the CPU 306 includes a ROM (not shown) in which programs for executing various sequences related to the above-described image forming sequence are stored, and rewritable data which needs to be temporarily or permanently stored. Is stored in the RAM. The RAM stores, for example, high-voltage setting values for the high-voltage control unit, various data, and image forming command information from the operation unit 305 (notification unit, correction operation limiting unit, correction operation inhibition setting unit). I have.

The operation unit 305 obtains information such as a copy magnification and a density setting value set by a user, and also stores information on the state of the image forming apparatus, for example, information on the number of images to be formed, whether or not an image is being formed, and jam. Is sent to the user to indicate the occurrence and location of the occurrence. The operation unit 305 automatically sets a specified value TSL of the sheet thickness of the active registration method and the loop registration method described later, and automatically switches between the active registration method and the loop registration method based on the specified value TSL. The user can set whether or not to make the setting. Further, the operation unit 305 allows the user to input information such as the thickness of the transfer material at the limit at which skew correction can be performed. When the skew correction cannot be performed, the operation unit 305 informs the user by displaying, warning, and the like. It also has a reporting function to report.

The CPU 306 drives each load in the copying machine and collects and analyzes information of sensors. A motor 316, a DC load 317 such as a clutch / solenoid, and various sensors 315 such as a photo-interrupter and a microswitch are arranged at various places inside the apparatus. That is, the driving of the motor 316 and the DC load 3
The transfer of the transfer material and the driving of each unit are performed by appropriately driving 17, and various sensors 315 monitor the operation thereof.

Therefore, the CPU 306 controls the various sensors 31
5, the motor control unit 310 controls each motor 316 via the motor driver 307, and at the same time, the DC load control unit 311 operates the DC load 317 such as a clutch / solenoid to perform an image forming operation. Is proceeding smoothly.

The various sensors 315 include an OHP paper sensor 143 for detecting OHP paper. Further, the CPU 306 sends various high-voltage control signals to a high-voltage control unit (not shown) so that the high-voltage unit can appropriately control the primary charger 113, the auxiliary charger 115, the transfer charger 119, and the developing roller 111 which are various chargers. High pressure is applied.

Further, the CPU 306 inputs the output signal of the thermistor inside the fixing device 120 and controls the driving of the fixing heater, so that the fixing device 120 has an optimum temperature necessary for fixing the toner image. 120 temperature control is also performed.

(Sheet skew straightening and conveying device) The sheet skew straightening and conveying device 5 includes a sheet thickness detecting section (information detecting means) 320 shown in FIG. 3, a skew correcting section 321 shown in FIG. .

The configuration of the paper thickness detecting section 320 will be described.

In FIG. 3, the paper thickness detecting section 320 includes a displacement amount detecting section 700, a pair of paper thickness detecting rollers (a pair of rotating sheet conveying members) 141, and the like. The irradiation light Li from the light emitting diode 708 of the displacement amount detection unit 700 is reflected on the reflection surface 14 which is the measurement surface of the upper roller 141a of the pair of paper thickness detection rollers 141.
1r, and is reflected by the light receiving position sensor 7 as reflected light Lr.
10 is incident. The lower roller 141b of the pair of paper thickness detecting rollers 141 is fixed so as not to move in the vertical direction in the figure, and the upper roller 141a is set in a free state. For this reason, the transfer material P is
a, 141b, the upper roller 141a moves up and down in the figure according to the thickness of the transfer material P.

Accordingly, the reflecting surface 141r moves up and down in accordance with the thickness of the transfer material P. When the transfer material P is thick, the reflection surface 141r moves upward and comes into contact with the light emitting diode 708. As a result, the position of the reflected light incident on the light receiving position sensor 710 changes according to the thickness of the transfer material P, and an analog signal 707, which is a thickness signal of the transfer material P, is input to the A / D converter 706.

Here, the lighting of the light emitting diode 708 and the light amount adjustment control are controlled by a signal 704 output from the sensor LED control unit 703 based on a control signal 701 from the CPU 306. The control signal 701 is A
The A / D conversion timing of the / D converter 706 is also controlled. A signal 705 corresponding to the digitized thickness of the transfer material P from the A / D converter 706 is sent to the CPU 306. The thickness of the transfer material P is calculated and calculated by the CPU 306. The light emitting sensor 710, the light receiving sensor 710, and the like constitute a thickness detection sensor.

Although the upper roller 141a of the sheet thickness detecting roller pair 141 moves up and down, the lower roller 141b may move up and down. Further, both the upper roller 141a and the lower roller 141b may move up and down. In these cases, the light emitting sensor 710 and the light receiving sensor 7 face the roller that moves up and down.
Of course, 10 is provided.

The operation of detecting the thickness of the transfer material P by the paper thickness detecting section 320 will be described with reference to the flowchart shown in FIG.

The calculation of the thickness of the transfer material is also performed by the CPU 3
06 is performed collectively. The transfer material P fed from the sheet feeder 150 through the sheet feed path is used as the sheet thickness detector 320.
And the detection of the thickness of the transfer material P is started (S90).
1). In order to collect data before the transfer material P reaches the paper thickness detection roller pair 141, the paper thickness detection roller pair 141 is
N is set (S902).

Here, the thickness of the transfer material P is, as described above,
Since it is determined by measuring the amount of displacement of the upper roller 141a of the pair of paper thickness detection rollers 141, it is possible to collect data when the pair of paper thickness detection rollers 141 does not sandwich the transfer material P. is necessary. Transfer material P
Is derived from the difference between the first data when the paper thickness detection roller pair 141 does not sandwich the transfer material P and the second data when the paper thickness detection roller pair 141 does.

For this reason, the first data when the transfer material P is not sandwiched therebetween is used as a reference when calculating the thickness of the transfer material P. The paper thickness detection roller pair 141 starts collecting data of the first data (Dr1, Dr2,..., Drn) before the transfer material P is sandwiched (S903).

At a relatively long time before the start of sheet feeding, a large amount of data is collected here, and from the viewpoint of improving the reliability of the data, the data for five rotations of the pair of sheet thickness detecting rollers 141 is obtained. Are collected (S904). When the paper thickness detection roller pair 141 makes five rotations, the collection of the first data before sandwiching the transfer material P is stopped, and the paper thickness detection roller pair 14 is stopped.
1, the supply of the transfer material P is started (S905).
Data collection is interrupted.

When the transfer material P reaches the pair of paper thickness detecting rollers 141 (S906), the second data (Dp1, Dp2,..., Dp) with the pair of paper thickness detecting rollers 141 sandwiching the transfer material P is provided.
The data collection of n) is started (S907). The data collection here is a data collection in a state where the paper thickness detecting roller pair 141 sandwiches the transfer material P, and is set to one rotation of the paper thickness detecting roller pair 141 (S908). This is because, when the transfer material P is sequentially conveyed from the paper thickness detection roller pair 141, data including a collision noise component generated when the transfer material P reaches the two skew correction roller pairs 142a and 142b is not used. That's why.

Therefore, the pair of paper thickness detecting rollers 141 to 141
Data of one rotation of the paper thickness detection roller pair is collected as a length equal to or less than the distance to the two skew feeding correction roller pairs 142a and 142b. When the paper thickness detection roller pair 141 makes one rotation, data collection in a state where the paper thickness detection roller pair 141 sandwiches the transfer material P ends, and (S903) to (S904).
And the average value of the n pieces of first data in a state before the paper thickness detecting roller pair 141 sandwiches the transfer material P collected in (S907)
To 14 of the paper thickness detection rollers collected in (S908).
The paper thickness value representing the thickness of the first transfer material P is determined by the difference K from the average value of the m pieces of second data in a state where 1 sandwiches the transfer material P (S909).

The transfer material P passes through the sheet thickness detection roller pair 141, and it is determined whether or not the transfer material P is the final transfer material P. The determination as to whether or not it is the final transfer material P is made by comparing the number of copies input by the user to the operation unit 305 with the number of sheets that have passed through the pair of paper thickness detection rollers 141.
If it is not the final transfer material P, paper thickness detection is performed for the second transfer material P (S910).

The first data of the second and subsequent transfer materials P before the paper thickness detection roller pair 141 sandwiches the transfer material is not collected because it is similar to the first data. Therefore, the paper thickness detection unit 320 suspends data collection until the transfer material P reaches the paper thickness detection roller pair 141. When the transfer material P reaches the paper thickness detection roller pair 141,
The paper thickness detection roller pair 141 starts collecting the second data with the transfer material P interposed therebetween. Thereafter, the above (S906) to (S910) are repeated. In (S910), when it is determined that the final transfer material P is the final transfer material P, when the final transfer material P passes through the paper thickness detection roller pair 141,
The sheet thickness detection roller pair 141 is turned off (S911).
Thus, the paper thickness detection operation ends (S912).

The configuration of the skew feeding correction unit 321 will be described.

As shown in FIG. 5, the skew feeding correction unit 321
A skew correction motor M5 and a skew correction motor M5 disposed on the left side from upstream to downstream in the transfer direction of the transfer material;
A skew correction roller pair 142a rotated by a skew detection sensor S1, a skew correction motor M6 disposed on the right side,
And a skew correction pair 142b rotated by a skew correction motor M6, a skew detection sensor S2, and a row detection sensor S1, S
A sensor processing unit 510 for amplifying or A / D converting two signal components and inputting detection information to the CPU 306;
A motor driver 511 for independently driving the skew correction motors M5 and M6 based on a control signal from the printer, and a paper thickness detection roller pair 141 (see FIG. 1) for supplying the transfer material P to the two skew correction roller pairs 142a and 142b. 1), skew correction unit 3
Entry detection sensor 14 for detecting entry of transfer material P into
4 and so on.

The two skew feeding correcting roller pairs 142
5, only one is shown in FIG. 5, but only one is shown in each of the upper and lower portions so as to sandwich the transfer material from the front and back.

A skew detecting sensor (sheet detecting means)
S1 and S2 constitute skew detecting means. further,
The skew feeding correction roller pairs 142a and 142b, the skew feeding correction motors M5 and M6, and the like constitute a sheet conveying unit.

The operation of the skew feed correction unit 321 will be described.

The operation of the skew feeding correcting unit 321 when the skew feeding correcting unit 321 is used as a loop registration method (second skew feeding correcting operation) will be described with reference to the flowchart of FIG.

The transfer material is supplied to the rollers 13
4, 163, and a sheet thickness detection roller pair 141 and the like are conveyed to the skew feeding correction unit 321. The CPU 306 stops driving the left and right skew correction motors M5 and M6 (S2).
01). When the entrance detecting sensor 144 disposed on the upstream side of the skew correction motors M5 and M6 in the transport direction of the transfer material detects the transfer material, the counter starts measuring time (S20).
2). The transfer material is conveyed to the skew correction roller pair 142.
a, 142b is abutted against the nip to form a loop (curved) to correct skew.

The CPU 306 determines the count value L of the counter.
A predetermined time CL required for the CNT to perform skew correction
Until the skew correction motors M5 and M6 are stopped (S203). When the count value LCNT reaches CL, the right and left skew correction motors M5 and M6 are simultaneously driven to convey the sheet (S204), and the skew correction using the loop registration method ends. After the skew correction is completed, the transfer material is straightened, and the two skew correction roller pairs 142
The toner image is transferred between the photosensitive drum 112 and the transfer charger 119 by a and 142b to transfer the toner image.
The time CL is set to a time necessary to correct the skew of the most skewed transfer material within a range in which the skew of the transfer material can be corrected.

The operation of the skew correction unit 321 when the skew correction unit 321 is used as an active registration method (first skew correction operation) will be described.

The skew feeding correcting unit 321 moves the skew feeding detecting sensors S1 and S while the pair of skew feeding correcting rollers 142a and 142b is nipping and rotating the transfer material. The skew direction R / L and the skew amount N are calculated by the CPU 306 by detecting the timing of the skew detection sensors S1 and S2.

The skew feed correction unit 321 is provided with a skew feed detection sensor S
The skew direction R / L is detected from the 1, S2 detection timing,
The time difference corresponding to the skew amount N is calculated by the CPU 306 by measuring the interval between the skew detection sensors S1 and S2 by a counter (not shown). And C
Under the control of the PU 306, skew correction is performed by accelerating or decelerating both or one of the skew correction motors M5 and M6 in a direction to eliminate the time difference. This skew correction control is completed before image formation is started.

The operation of the skew feeding correcting unit 321 according to the active registration method will be described in more detail with reference to the flowchart of FIG.

As described above, the skew correction by the active registration method is performed by selectively stopping, decelerating, or accelerating the skew correction motors M5 and M6 on the skew side (leading side).

First, the skew direction R / L and the skew amount N are calculated by the CPU 306 from the signals detected by the skew detection sensors S1 and S2 by the method described above (S801). Here, the skew amount N is obtained by converting a count value calculated from the difference between the detection timings of the skew detection sensors S1 and S2 into a pulse value corresponding to the movement amount per pulse of the skew correction motors M5 and M6. It is a value.

When the skew direction R / L is R (the right-hand side precedes skew), the skew amount N is supplied to the right motor CLK counter CNTR for counting the driving clocks of the skew correction motors M5 and M6, and the left motor 0 is loaded to the CLK counter CNTL to start counting (S803). Note that the skew direction R
If / L is not R, that is, L (the left side precedes skew), the right motor CLK counter CNTR is set to 0.
Is loaded into the left motor CLK counter CNTL with the skew amount N to start counting (S811). The subsequent control is similar to the control in which the skew direction R / L is switched to the right and left as compared with the case where the skew direction R / L is R.
And the control in the case of L is omitted.

When the skew direction R / L is R, the right motor drive table TBLR is set to −1 and the right skew correction motor M6
And at the same time, the table change TBL is incremented by 1 (S804). Here, the initial values of the right motor drive table TBLR and the left motor drive table TBLL before the correction control are TBLRi and TBBLi, respectively, and the initial value of the table change TBL is 0.

Right motor drive table TB reduced by one
LR indicates the right motor CLK counter CNTR and the left motor C
The process is continued until the difference of the LK counter CNTL becomes N-TBL (S805). Then, if the difference between CNTR and CNTL becomes N-TBL and the value is not N / 2, the right motor drive table TBLR is again reduced by -1, and the right skew correction motor M6 is further decelerated (S804). .

The deceleration of the right skew correction motor M6 is controlled by CNT.
Continue until the difference between R and CNTL becomes N / 2. When the difference between CNTR and CNTL becomes N / 2, the right motor drive table TBLR is incremented by one and the table change TBL is also one.
It increases (S807).

Until the difference between the right motor CLK counter CNTR and the left motor CLK counter CNTL becomes N-TBL, the right skew correction motor M6 is used in this right motor drive table.
Is driven. When the difference between CNTR and CNTL becomes N-TBL, it is determined whether or not the value is 0 (S809).
If not, the right motor drive table TBLR is incremented by one and the process is repeated until the difference between CNTR and CNTL becomes zero.

When the difference between CNTR and CNTL becomes 0, the right motor drive table TBLR and left motor drive table TBLL are changed to TBLRi and TBBLi, respectively, which are the initial values before the correction control, and the active registration method is used. The straightening control ends.

The sheet skew correcting / conveying device selects a loop registration method and an active registration method based on the thickness and material of the transfer material.
The transfer material is corrected.

Next, the sheet skew correcting / conveying device performs a loop registration method based on the thickness of the transfer material,
The operation of selecting the active registration method will be described with reference to the flowchart of FIG.

When the transfer material is conveyed, it is initialized in advance. Further, the CPU 306 reads the specified value TSL of the paper thickness set by the user in the operation unit 305, and determines the paper selection standard between the correction of the transfer material by the active registration method and the correction of the transfer material by the loop registration method. Set the specified value of thickness (S40)
0).

Next, it is determined whether or not the user is set to automatically switch between the active registration method and the loop registration method based on the specified value TSL (S401).

If automatic skew correction has not been set, the active registration method is selected (S404). If the automatic setting has been performed, the paper thickness is detected by the paper thickness detection unit 320, and the paper thickness T is calculated (S402). When the paper thickness T is equal to or smaller than the predetermined value TSL at which the correction control can be performed by the active registration method (S403), the skew correction is performed by the active registration method (S404). If the paper thickness T is larger than the default value TSL for which the correction control can be performed by the active registration method and is equal to or smaller than the default value TSH for which the correction control can be performed by the loop registration method (S40).
5), skew correction is performed by a loop registration method (S406).

If the paper thickness T exceeds the predetermined value TSH at which the correction control can be performed by the loop registration method (S405), the operation unit 305 or another display device such as a display (not shown) is displayed to the user. A warning is issued on the panel, and the driving of the skew correction motors M5 and M6 is stopped to stop the transfer of the transfer material (S407).

FIG. 9 is a flowchart showing the operation of the sheet skew correcting / conveying device for selecting a loop registration method or an active registration method based on whether or not the transfer material is OHP paper. It will be described based on.

The transfer material is conveyed, and reaches the two skew detection roller pairs 142a and 142b in the middle of the conveyance path.
The OHP paper detection sensor 143 (see FIG. 1)
It is detected whether the sheet is a P sheet (S501). Transfer material is OH
In the case of P, skew correction is performed by the loop registration method (S504). If the transfer material is not an OHP sheet, the sheet thickness is detected by the sheet thickness detection unit 320, and the sheet thickness T is calculated (S502).

The paper thickness T is larger than a predetermined value TSL which can be controlled by the active registration method and can be controlled by the loop registration method.
If not more than H (S503), skew correction is performed by the loop registration method (S504). When the paper thickness T is equal to or less than a predetermined value TSL at which the correction control can be performed by the active registration method (S505), the skew correction is performed by the active registration method (S50).
6).

If the paper thickness T exceeds the predetermined value TSH at which the correction can be controlled by the loop registration method (S505), the operation unit 305 or another display device such as a display (not shown) is displayed to the user. A warning is issued to the panel, and the driving of the skew correction motors M5 and M6 is stopped to stop the transfer of the transfer material (S507).

Next, the sheet skew correcting / conveying device performs an operation of selecting a loop registration method or an active registration method based on the thickness of the transfer material and whether or not the transfer material is OHP paper. This will be described with reference to the flowchart of FIG.

When the transfer material is conveyed, it is initialized in advance. Further, the CPU 306 reads the specified value TSL of the paper thickness set by the user in the operation unit 305, and determines the paper selection standard between the correction of the transfer material by the active registration method and the correction of the transfer material by the loop registration method. Set the specified value of thickness (S60)
0).

Next, the CPU 306 determines whether or not a setting has been made by the user to automatically switch between the active registration method and the loop registration method based on the specified value TSL (S6).
01).

Regardless of whether or not the automatic setting of the skew correction has been performed, when the transfer material is detected as an OHP sheet by the OHP sheet detection sensor 143 (see FIG. 1) (S601, S602, S603). , The loop registration method is selected (S608). If automatic transfer is not performed and the transfer material is not OHP paper (S601, S602), the active registration method is selected (S606).

When the automatic setting is performed and the transfer material is not OHP paper (S601, S603), the paper thickness detection unit 3
In step S60, the sheet thickness is detected, and the sheet thickness T is calculated.
4). If the paper thickness T is equal to or smaller than the predetermined value TSL at which the correction control can be performed by the active registration method (S60).
5), skew correction is performed by the active registration method (S606). If the paper thickness T is larger than the default value TSL that can be controlled by the active registration method and is equal to or smaller than the default value TSH that can be controlled by the loop registration method (S607), the skew correction is performed by the loop registration method. (S60
8).

If the paper thickness T exceeds the predetermined value TSH at which the correction can be controlled by the loop registration method (S607), the operation unit 305 or another display device such as a display (not shown) is displayed for the user. A warning is issued to the panel, the driving of the skew correction motors M5 and M6 is stopped, and the transfer of the transfer material is stopped (S609).

In any of the flowcharts described above, the default value TSL is input by the user to the operation unit 305, but is stored in advance in a ROM or RAM (not shown) connected to the CPU 306. You may. If the default value TSL is stored in advance, the flowchart of FIG. 8 starts from (S402). The flowchart in FIG. 10 starts from (S603).

The skew feeding correcting unit 321 described above is disposed downstream of the skew feeding detecting sensors S1 and S2 and the pair of skew feeding correcting rollers 142a and 142b as shown in FIG.
1, the skew detecting sensor S
1, S2 may be disposed downstream of the skew correction roller pair 142a, 142b.

In the case of the skew correction unit 322, when skew correction is performed by the active registration method,
Skew detection sensors S1 and S2 detect skew of the transfer material ahead of
Thereafter, according to the amount of skew, the skew correction roller pair 142a, 1
The rotation of 42b is controlled.

In the case of the skew correction unit 322, when skew correction is performed by the loop registration method,
In order to detect the skew of the transfer material ahead of the skew detection sensors S1 and S2, the skew correction roller pairs 142a and
2b can control the rotation stop time.
There is no need to stop the transfer material, and the skew of the transfer material can be corrected efficiently.

In the sheet skew correcting / conveying apparatus 5 of the present embodiment described above, when the CPU 306 detects skew of the skew detecting sensors S1 and S2, the sheet skew correction rollers 142a and 142b convey the sheet. An active registration method that causes a difference in speed, and a skew correction roller pair 142a, 142b in which the skew correction roller pairs 142a, 142b are temporarily stopped and the leading edge of the sheet is moved for a predetermined time.
And the loop registration method
Selective operation is performed based on the sheet information detected by the sheet thickness detection unit 320 or the OHP sheet detection sensor, so that the sheet can be skewed in accordance with the sheet thickness and type. Thus, the skew of the sheet can be reliably corrected.

Further, the sheet skew correcting / conveying apparatus 5 of the present embodiment detects the thickness of the sheet by the sheet thickness detecting section 320,
The CPU 306 selects the active registration method when the sheet thickness does not exceed the predetermined thickness, and selects the loop registration method when the sheet thickness exceeds the predetermined thickness. In addition, the sheet skew correcting operation according to the type can be performed, and the sheet skew can be reliably corrected.

Further, in the sheet skew correcting / conveying device 5 of the present embodiment, the sheet thickness is detected by the sheet thickness detecting section 320, and the sheet thickness is such that the skew cannot be corrected by the CPU 306. Sometimes, the skew correction roller pair 142
Since the sheet conveying operations a and 142b are stopped, excessive skew correction of the sheet is prevented, so that only the sheet whose skew has been corrected can be conveyed, and sheet jamming can be prevented. it can.

Further, in the sheet skew correcting / conveying device 5 of the present embodiment, the sheet thickness detected by the sheet thickness detecting section 320 is
When the thickness is such that the skew cannot be corrected, the operation unit 305 for notifying that the skew cannot be corrected is provided, so that the user can quickly remove the sheet whose skew cannot be corrected based on the notification information. Can be removed.

Further, the sheet skew correcting / conveying device 5 of the present embodiment has an operation unit 305 for inputting the value of the predetermined thickness.
, So you can freely select the active registration method and the loop registration method,
The skew of the sheet can be reliably corrected.

Further, since the sheet skew correcting / conveying device 5 of the present embodiment is provided with an operation section for inputting a thickness value at which skew cannot be corrected, it is possible to prevent unreasonable sheet skew correction. Thus, only the sheet whose skew has been corrected can be conveyed, and sheet jamming can be prevented.

Further, in the sheet skew correcting / conveying apparatus of this embodiment, the sheet thickness detecting section 320 includes a sheet thickness detecting roller pair capable of nipping and conveying a sheet, and at least one of which is capable of approaching and separating from the other. 141a and 141b, and a light emitting diode 708 and a light receiving position sensor 710 for detecting the amount of movement of the pair of paper pressure detecting rollers 141a in the approaching / separating direction to detect the thickness of the sheet. Since the thickness of the sheet can be detected while being conveyed, the thickness of the sheet can be reliably detected without lowering the sheet conveyance efficiency.

Further, the sheet skew correcting / conveying apparatus of the present embodiment has skew detecting sensors S1 and S2, and an OHP sheet detecting sensor 143 for detecting whether or not the sheet is a sheet for an overhead projector. Have and CPU
With the 306, the loop registration method is selected when the sheet is a sheet for an overhead projector. In the active registration, the OHP sheet that cannot reliably correct the skew of the sheet is reliably corrected. can do.

Further, the sheet skew correcting / conveying apparatus of the present embodiment is provided with a plurality of sheet detecting sensors which are disposed by the CPU 306 in a direction intersecting with the sheet conveying direction to detect the leading edge of the sheet. Because it has
The skew of the sheet can be reliably corrected.

The skew correcting and conveying device of the present embodiment corrects the skew of the sheet by the skew correcting roller pairs 142a and 142b which pinch and rotate the sheet to convey the sheet. Can be corrected while the sheet is being conveyed, so that the thickness of the sheet can be reliably detected without lowering the sheet conveying efficiency.

Further, the image forming apparatus of the present embodiment includes any one of the sheet skew correcting and conveying devices described above, and image forming means for forming an image on a sheet conveyed by the sheet skew correcting device. Therefore, an image can be formed on a sheet whose skew has been corrected, an image forming position on the sheet becomes accurate, and an image can be formed accurately at a desired position on the sheet.

Further, the image reading apparatus of the present embodiment
Any one of the above-described sheet skew correcting / conveying device and image reading means for reading an image on the sheet conveyed by the sheet skew correcting device are provided, so that the image of the sheet whose skew has been corrected can be read. And the image reading accuracy can be improved.

[0120]

According to the sheet skew correcting / conveying apparatus of the present invention, an active registration method or a loop registration method is selected according to the thickness of a sheet to be conveyed and the type of the sheet to straighten the sheet skew. Therefore, the restrictions on the conveyable sheet and the thickness can be relaxed, irrespective of the type and thickness of the sheet, reliable and stable skew correction can be performed, and the skew correction accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic front cross-sectional view of a copying machine, which is an image forming apparatus, provided with a sheet skew straightening and conveying device of the present invention in an apparatus main body.

FIG. 2 is a control block diagram of the copying machine shown in FIG.

FIG. 3 is a schematic diagram of a sheet thickness detection unit of the sheet skew correction and conveyance device.

FIG. 4 is a flowchart for explaining the operation of a sheet thickness detection unit of the sheet skew correction and conveyance device.

FIG. 5 is a schematic plan view of a skew correction unit of the sheet skew correction conveyance device.

FIG. 6 is a flowchart illustrating a case where the sheet skew correction conveyance device corrects a sheet skew by a loop registration method.

FIG. 7 is a flowchart illustrating a case where the sheet skew correction conveyance device corrects a sheet skew by an active registration method.

FIG. 8 is a flowchart illustrating a case where the sheet skew correction conveyance device corrects sheet skew based on the thickness of the sheet.

FIG. 9 is a flowchart illustrating a case where the sheet skew correction conveyance device corrects a sheet skew based on whether or not the sheet is an OHP sheet.

FIG. 10 is a flowchart illustrating a case where the sheet skew correction conveyance device corrects a sheet skew based on the thickness of the sheet and whether or not the sheet is an OHP sheet.

FIG. 11 is a schematic plan view of a skew correcting unit of another embodiment of the sheet skew correcting and conveying device.

[Explanation of symbols]

P Transfer material (sheet) S1 Skew detection sensor (Skew detection means) S2 Skew detection sensor (Skew detection means) 3 Copy machine (Image forming apparatus) 5 Sheet skew correcting and conveying device 6 Image forming unit (Image forming) 141) Paper thickness detection roller pair (sheet transport rotating body pair) 142a Skew correction roller pair (sheet transport means) 142b Skew correction roller pair (sheet transport means) 143 OHP paper detection sensor (information detection means, sheet discrimination means) ) 144 Entry detection sensor 305 Operation unit (notification unit, correction operation setting unit, correction operation inhibition setting unit) 306 CPU (skew correction control unit) 320 Paper thickness detection unit (information detection unit, thickness detection unit) 708 Issue diode ( Thickness detection sensor) 710 Light receiving position sensor (thickness detection sensor)

Claims (12)

[Claims] An information detecting unit configured to detect information on a conveyed sheet; a skew detecting unit configured to detect a skew direction and a skew amount of the sheet; A plurality of sheet transporting units that are disposed apart from each other in the direction to independently transport the sheet, and individually control sheet transporting operations of the plurality of sheet transporting units based on information about the sheet by the information detecting unit. And skew correction control means for straightening the skew of the sheet, wherein the skew correction control means detects a plurality of the sheets when the skew detection means detects skew of the sheet. A first skew correcting operation for causing a difference in the sheet conveying speed of the conveying unit,
A second skew correction operation in which the sheet conveying means is temporarily stopped and the leading edge of the sheet is received by the sheet conveying means for a predetermined time, selectively based on the information of the sheet detected by the information detecting means. A sheet skew straightening and conveying device characterized by performing. 2. The information detecting means is a thickness detecting means for detecting a thickness of the sheet, and the skew correction control means is configured to control the first skew when the thickness of the sheet does not exceed a predetermined thickness. 2. The sheet skew correcting and conveying apparatus according to claim 1, wherein the sheet skew correcting operation is selected, and the second skew correcting operation is selected when the sheet thickness exceeds the predetermined thickness. 3. The information detection means is a thickness detection means for detecting the thickness of the sheet, the skew correction control means, when the thickness of the sheet is a thickness that cannot correct the skew, 3. The sheet skew correcting and conveying apparatus according to claim 1, wherein the sheet conveying operation of the sheet conveying means is stopped. 4. When the thickness of the sheet detected by the thickness detecting means is a thickness that cannot be corrected for skew, there is provided a notifying means for notifying that the sheet cannot be corrected. The sheet skew correction conveying device according to claim 2 or 3. 5. The sheet skew correcting and conveying device according to claim 2, further comprising a correcting operation setting unit for inputting the value of the predetermined thickness. 6. The sheet skew correction conveyance device according to claim 3, further comprising a correction operation inhibition setting unit for inputting a value of a thickness in which the correction of the skew is impossible. 7. A pair of sheet conveying rotating bodies capable of sandwiching and conveying the sheet and at least one of which is capable of approaching and separating from the other, and the sheet conveying rotating mechanism capable of approaching and separating the sheet. The sheet skew according to any one of claims 2 to 6, further comprising: a thickness detection sensor configured to detect a thickness of the sheet by detecting an amount of movement of the body in the approaching / separating direction. Line straightening transport device. 8. The information detection unit is a sheet determination unit that detects whether the sheet is a sheet for an overhead projector, and the skew correction control unit is
The sheet skew correction transport device according to claim 1, wherein the second skew correction operation is selected when the sheet is a sheet for an overhead projector. 9. The skew detecting means includes a plurality of sheet detecting sensors that are disposed apart from each other in a direction intersecting the sheet conveying direction and detect a leading edge of the sheet. The sheet skew correcting / conveying device according to claim 1, wherein: 10. The sheet skew correcting and conveying apparatus according to claim 1, wherein the sheet conveying means has a pair of rotating bodies for nipping and rotating the sheet to convey the sheet. 11. The method according to claim 1, wherein
An image forming apparatus comprising: the sheet skew correction conveying device according to any one of the preceding items, and an image forming unit that forms an image on a sheet conveyed by the sheet skew correction device. 12. The method according to claim 1, wherein:
An image reading device, comprising: the sheet skew correcting / conveying device according to any one of the preceding items, and image reading means for reading an image on a sheet conveyed by the sheet skew correcting device.