JP7196562B2 - Image reader, printer, image forming system - Google Patents

Description

The present invention relates to an image reader, a printer, and an image forming system.

As an image reader, there is one that reads a detection image applied to a sheet material.

Conventionally, an upstream conveying roller pair and a downstream conveying roller pair for conveying a sheet material to an image reading means are arranged upstream and downstream of the reading means, respectively, and the downstream conveying roller pair is separated from the image reading means. The sheet material is conveyed and read by the side conveying roller pair, and when the leading edge of the sheet material reaches the downstream conveying roller pair, the upstream conveying roller pair is separated and the sheet material is conveyed by the downstream conveying roller pair. A reading device is known that attempts to keep the conveying speed of the sheet material constant by doing so (Patent Document 1).

JP 2005-067821 A

However, in the configuration disclosed in Japanese Patent Application Laid-Open No. 2002-200011, the separation of the pair of upstream conveying rollers and the pressing contact of the pair of downstream conveying rollers are performed while reading is performed by the reading means. There is a problem that it fluctuates and reading accuracy decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to improve reading accuracy.

In order to solve the above problems, an image reading device according to claim 1 of the present invention includes:
reading means for reading the detection image formed on the sheet;
an upstream reading/conveying rotor pair arranged upstream of the reading means in the sheet conveying direction and conveying the sheet;
at least one pair of upstream conveying rotators disposed on the upstream side in the sheet conveying direction of the pair of upstream reading and conveying rotators for conveying the sheet toward the pair of upstream reading and conveying rotators;
At least one of the pair of upstream conveying rotating bodies is provided such that at least one of the rotating bodies can come into contact with and separate from the other rotating body,
The pair of upstream conveying rotators is separated after the leading edge of the sheet reaches the pair of upstream reading conveying rotators and before the leading edge of the sheet reaches the reading position by the reading means.
It was configured.

According to the present invention, reading accuracy can be improved.

1 is a schematic explanatory diagram of an image reading device according to a first embodiment of the present invention; FIG. FIG. 4 is a schematic explanatory diagram for explaining a reading operation in the same embodiment; FIG. 11 is a schematic explanatory diagram similarly used for explaining the reading operation; FIG. 5 is a schematic explanatory diagram of an image reading device according to a second embodiment of the present invention; FIG. 4 is a schematic explanatory diagram for explaining a reading operation in the same embodiment; FIG. 10 is a schematic explanatory diagram of an image reading device according to a third embodiment of the present invention; FIG. 11 is a schematic explanatory diagram of an image reading device according to a fourth embodiment of the present invention; FIG. 4 is a schematic explanatory diagram for explaining a reading operation in the same embodiment; FIG. 11 is a schematic explanatory diagram of an image reading device according to a fifth embodiment of the present invention; 1 is a schematic configuration diagram of an example of a printing device that configures an image forming system according to the present invention; FIG. FIG. 4 is a schematic diagram showing an installation mode of a reading device and a position reference member in the same detection apparatus; FIG. 8 is an explanatory diagram of an example of a pattern as a detection mark for image position adjustment, which is similarly formed on the sheet P; FIG. 11 is an explanatory diagram schematically showing types of image correction in the same manner; FIG. 4 is an explanatory diagram of an example of an upstream separating means for an upstream conveying rotor pair (conveying roller pair) that constitutes the image reading apparatus;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic explanatory diagram of an image reading device according to the embodiment.

The image reading device 2 includes a reading means 21 for reading a detection mark M (detection mark M1 at the leading edge is shown in FIG. 1) which is an image for detection on the sheet P. As shown in FIG.

An upstream reading/conveying roller pair 22 (22A, 22B), which is a pair of upstream reading/conveying rotating members for conveying the sheet P, is arranged on the upstream side of the reading means 21 in the sheet conveying direction. Further, downstream side reading/conveying roller pair 23 (23A, 24B), which is a pair of downstream reading/conveying rollers when sheet P is conveyed, is disposed downstream of reading means 21 in the sheet conveying direction.

The image reading device 2 is disposed on the upstream side in the sheet conveying direction of the upstream reading and conveying roller pair 22, and is an upstream conveying rotating member pair that conveys the sheet P toward the upstream reading and conveying roller pair 22. A roller pair 24 (24A, 24B) is provided. At least one upstream conveying roller pair 24 is sufficient, but a plurality of them may be arranged along the conveying direction.

The upstream-side conveying roller pair 24 (24A, 24B) includes one conveying roller (driven roller) 24B that can come into contact with and separate from the other conveying roller (drive roller) 24A. An upstream separating means 26 is provided for contacting and separating the driven roller 24B of the upstream conveying roller pair 24 from the other conveying roller 24A.

Further, the image reading device 2 is arranged downstream of the downstream reading and conveying roller pair 23 in the sheet conveying direction, and receives the sheet P conveyed from the downstream reading and conveying roller pair 23 and conveys it downstream. A pair of downstream conveying rollers 25 (25A, 25B), which is a pair of rotating bodies, is provided. At least one downstream transport roller pair 25 is sufficient, but a plurality of roller pairs may be arranged along the transport direction.

In the downstream side transport roller pair 25 (25A, 25B), one transport roller (driven roller) 25B is provided so as to be able to contact and separate from the other transport roller (drive roller) 25A. A downstream separating means 27 is provided for contacting and separating the driven roller 25B of the downstream conveying roller pair 25 from the conveying roller 25A.

Next, the read operation in this embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 and 3 are schematic explanatory diagrams for explaining the same operation.

When reading the detection mark M1 on the sheet P, as shown in FIG. 2A, the sheet P is conveyed toward the upstream reading conveying roller pair 22 at a conveying speed V by the upstream conveying roller pair 24, for example. The upstream reading conveying roller pair 22 conveys the sheet P to the reading position S by the reading means 21, as shown in FIG. 2(b).

Here, after the sheet P reaches the upstream side reading conveying roller pair 22 and before the leading edge of the sheet P reaches the reading position S by the reading means 21, the driven roller 24B of the upstream side conveying roller pair 24 is moved to the upstream side. It is separated from the conveying roller 24A by the separating means 26 .

Here, T1 is the time from when the sheet P reaches the upstream reading conveying roller pair 22 until the start of separation of the driven roller 24B, and T2 is the time until the separation is completed (separation time). When the conveying speed of P is V, the distance L1 between the upstream reading conveying roller pair 22 and the reading position S is set so as to satisfy the relationship of L1>V.times.(T1+T2).

In this case, in order to reduce the speed fluctuation due to the shock when the driven roller 24B is separated, it is preferable to set the distance L1 in consideration of the margin.

Further, when a plurality of upstream transport roller pairs 24 are arranged, all the driven rollers 24B of the upstream transport roller pairs 24 upstream of the upstream reading transport roller pair 22 by at least the maximum length of the sheet P are It is preferable to separate them.

At this time, as shown in FIG. 2(c), the sheet P is conveyed only by the upstream reading conveying roller pair 22 with respect to the reading means 21. tug-of-war can be avoided.

As a result, the sheet P can be conveyed with high accuracy, and the conveying direction coordinates of the detection marks can be detected with high accuracy.

Next, when reading the detection mark M2 on the trailing edge side of the sheet P, as shown in FIG. , the driven roller 25B of the downstream conveying roller pair 25 is separated from the conveying roller 25A.

In this case, when a plurality of downstream side transport roller pairs 25 are arranged, all the driven rollers 24B of the downstream side transport roller pairs 25 downstream of the reading position S by the maximum length of the sheet P or more should be separated. is preferred.

At this time, as shown in FIG. tug-of-war can be avoided.

As a result, the sheet P can be conveyed with high accuracy, and the conveying direction coordinates of the detection marks can be detected with high accuracy.

After that, when the reading of the trailing edge of the sheet P is completed, the driven roller 25B of the downstream side transport roller pair 25 is brought into pressure contact (contact) with the transport roller 25 as shown in FIG. 3(c).

At this time, it is necessary to press the downstream reading conveying roller pair 23 before the trailing edge of the sheet P is pulled out.

Therefore, the distance L2 between the downstream side reading conveying roller pair 23 and the reading position S is the time T3 from when the trailing edge of the sheet P reaches the reading position until the downstream side conveying roller pair 23 starts contacting. When the time required for contact (pressure contact) is T4 and the sheet conveying speed is V, the relationship is L2>V.times.(T3+T4).

As a result, the sheet P can be conveyed by the downstream conveying roller pair 25 before the trailing edge of the sheet P passes through the downstream reading conveying roller pair 23, and high reading accuracy can be achieved.

Also, the contact of the downstream side transport roller pair 23 can be started before the trailing edge of the sheet P reaches the reading position S. FIG. In this case, when the time required for the trailing edge of the sheet P to reach the reading position S after the start of contact is -T3, the relationship T3+T4>0 is established.

In other words, the time T3 may be a negative value, but T3+T4>0 so that the conveying speed does not fluctuate due to pressure contact (contact) while the trailing edge of the sheet P is being read.

In this manner, the detection image provided on the sheet P can be read with high accuracy.

Next, a second embodiment of the invention will be described with reference to FIG. FIG. 4 is a schematic explanatory diagram of the image reading device according to the embodiment.

In this embodiment, the downstream side reading conveying roller pair 23 (23A, 23B) is provided such that one reading conveying roller (driven roller) 23B can come into contact with and separate from the other reading conveying roller (drive roller) 23A. there is A downstream reading/conveying separating means 28 is provided to bring the driven roller 23B of the downstream reading/conveying roller pair 23 into contact with and separate from the conveying roller 23A.

Next, the read operation of this embodiment will be described with reference to FIG. FIG. 5 is a schematic explanatory diagram for explaining the same operation.

In this embodiment, as shown in FIG. 5A, the distance Lm1 from the leading edge of the sheet P to the downstream end of the detection mark M1 in the sheet conveying direction is greater than the distance L2 between the reading means 21 and the downstream reading conveying roller pair 23. is large (lm1>L2).

That is, when Lm1>L2, the leading edge of the sheet P reaches the downstream read-conveying roller pair 23 before the detection mark M1 passes the reading position S by the reading means 21, and the upstream reading-conveying roller pair 22 alone, the sheet P cannot be conveyed.

Therefore, in this case, as shown in FIGS. 5A and 5B, before the leading edge of the sheet P reaches the downstream reading conveying roller pair 23, the driven roller 23B of the downstream reading conveying roller pair 23 is pushed. separate the

Thereby, when the detection mark M1 passes the reading position S by the reading means 21, the sheet P can be conveyed only by the upstream reading conveying roller pair 22, and highly accurate reading can be performed.

Next, a third embodiment of the invention will be described with reference to FIG. FIG. 6 is a schematic explanatory diagram of the image reading device according to the embodiment.

In the present embodiment, the distance L1 between the upstream reading and conveying roller pair 22 and the reading position S by the reading means 21, the distance Lm1 from the leading end of the sheet P to the downstream end of the detection mark M1 in the sheet conveying direction, and the device of the sheet P The minimum length Lmin in which the paper can be passed is in the relationship of Lmin>(Lm1+L1).

In this manner, the upstream read-conveying roller pair 22 and the downstream reading-conveying roller pair 23 are arranged so that (Lm1+L1) is greater than the minimum sheet length Lmin that can be passed through the apparatus.

In this case, after the detection mark M1 is detected, before the trailing edge of the sheet P leaves the upstream reading and conveying roller pair 22, the downstream reading and conveying roller pair 23 is brought into contact with the sheet P, and the sheet P after the mark detection is detected. can be reliably transported downstream. Detection of the detection mark M1 can be reliably performed on all sheets having a length equal to or longer than the length Lmin.

Next, a fourth embodiment of the invention will be described with reference to FIG. FIG. 7 is a schematic explanatory diagram of the image reading device according to the embodiment.

In this embodiment, the pair of upstream read-conveying rollers 22 (22A, 22B) includes one reading-conveying roller (driven roller) 22B which can come into contact with and separate from the other reading-conveying roller (drive roller) 22A. there is Further, an upstream reading/conveying separating means 29 is provided for bringing the driven roller 22B of the upstream reading/conveying roller pair 22 into contact with and separating from the conveying roller 22A.

Next, the read operation of this embodiment will be described with reference to FIG. FIG. 8 is a schematic explanatory diagram for explaining the same operation.

In this embodiment, as shown in FIG. 8A, the distance Lm2 from the trailing edge of the sheet P to the upstream edge of the detection mark M2 in the sheet conveying direction is equal to the distance L1 between the reading means 21 and the upstream reading conveying roller pair 22. (lm2>L1).

That is, when Lm2>L1, the detection mark M1 passes the reading position S by the reading means 21 before the trailing edge of the sheet P passes through the pair of reading and conveying rollers 22 on the upstream side. The sheet P cannot be conveyed only by the conveying roller pair 23 .

Therefore, in this case, as shown in FIGS. 8A and 8B, before the detection mark M1 passes the reading position S by the reading means 21, the driven roller 22B of the upstream reading conveying roller pair 22 is moved. Separate.

Accordingly, when the detection mark M2 passes the reading position S by the reading means 21, the sheet P can be conveyed only by the downstream reading conveying roller pair 23, and highly accurate reading can be performed.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic explanatory diagram of the image reading device according to the embodiment.

In this embodiment, the distance L2 between the reading position S by the reading means 21 and the downstream reading conveying roller pair 23, the distance Lm2 from the trailing end of the sheet P to the upstream end of the detection mark M2 in the sheet conveying direction, The minimum length Lmin of paper that can be passed through the device is configured to have a relationship of Lmin>(Lm2+L2).

In this way, the upstream read-conveying roller pair 22 and the downstream reading-conveying roller pair 23 are arranged so that (Lm2+L2) is larger than the minimum sheet length Lmin that can be passed through the apparatus.

In this case, even if the upstream read-conveying roller pair 22 is separated before detecting the detection mark M2, the downstream reading-conveying roller pair 23 continues to convey the sheet P downstream while detecting the detection mark M2. be able to. As a result, the detection mark M2 can be reliably detected on all sheets P having a length equal to or longer than the length Lmin.

Although the pair of conveying rotators and the pair of reading and conveying rotators have been described as roller pairs, one or both of the rotators may be formed of an endless belt or the like. In addition, one conveying rotator and one reading conveying rotator pair are arranged so as to be able to contact and separate from the other conveying rotator and the other reading conveying rotator pair. It is also possible to adopt a configuration in which the conveying rotor pair moves to make contact and separate.

Next, an example of a printing apparatus that constitutes the image forming system according to the present invention will be described with reference to FIG. FIG. 10 is a schematic configuration diagram of the printing apparatus.

A printing apparatus (image forming system) 1 includes a paper discharge unit 102, a cooling unit 103, a drying unit 104, an image forming unit 105 as an image forming apparatus, a registration unit 106, a pre-coating unit 107, and a paper feed unit. a unit 108;

The sheet feeding unit 108 accommodates a sheet P to be processed (an object to be transported), and supplies the sheet P to the imaging unit 105 or the like in the subsequent stage. Examples of the sheet P include, but are not limited to, a sheet P (transfer paper). Anything is fine. In the present embodiment, the sheet P on which an image is to be formed is the object to be processed (conveyed object). transported object).

The pre-coating unit 107 coats a pre-coating liquid onto the sheet P, which is a processing target (transported object) supplied from the paper feed unit 108 . As a result, it is possible to allow the ink to be applied by the image forming unit 105 to different sheets P as well. A configuration without the pre-coating unit is also possible.

A registration unit 106 is a unit that adjusts the transport timing and position of the sheet P with respect to the image forming unit 105 .

The image forming unit 105 is an inkjet type printing means, and forms an image by ejecting ink onto the sheet P. FIG. The image forming unit 105 can form on the sheet P an output image instructed to be printed by a user and detection marks M1 and M2 as detection images. Note that the image forming unit 105 may be an electrophotographic printing unit instead of the inkjet printing unit.

The drying unit 104 has a role of drying the ink adhering to the sheet P by the image forming unit 105 and making it familiar.

A cooling unit 103 cools the sheet P heated by the drying unit 104 .

In the case of single-sided printing, the cooling unit 103 sends the sheet P on which the image is formed to the subsequent paper ejection unit 102 . On the other hand, the cooling unit 103 sends the image-formed sheet P to the reversing path 109 in the case of double-sided printing.

The reversing path 109 reverses the front side and the back side of the sheet P by switching back the sent sheet P and conveys it. The sheet P transported by the reversing path 109 is transported again to the image forming unit 105, the image forming unit 105 forms an image on the opposite side of the previous sheet, and the drying unit 104 and the cooling unit 103 dry and cool the sheet. It is sent to the subsequent discharge unit 102 as a printed matter.

The paper discharge unit 102 receives the paper discharge of the sheet P on which the image is formed through the image forming unit 105 , the drying unit 104 and the cooling unit 103 .

In addition, the image forming unit 105 detects the edge of the conveyed sheet P and the position of an image recorded on the sheet P in order to correct the relative position between a plurality of reading devices and for each pixel of one reading device. A detection device 200 is provided which includes an image reading device according to the present invention.

The detection apparatus 200 includes a reading device 201 as reading means and a position reference member 202 .

The reading device 201 can be realized by, for example, a CIS (Contact Image Sensor) in which a plurality of imaging elements (CMOS image sensors) are arranged in a line. The reading device 201 receives reflected light from an object to be read and outputs an image signal. Specifically, the reading device 201 sets the conveying position of the sheet P on which an image is formed by the image forming unit 105 and the image forming position on the sheet P as the reading target. Further, the reading device 201 uses the position reference member 202 as a reading target.

A CIS applied to the reading device 201 is generally known to have a configuration in which a required effective reading length in the main scanning direction is secured by arranging a plurality of sensor chips having a plurality of pixels in the main scanning direction.

The position reference member 202 does not function as an absolute position reference when expansion/contraction occurs due to the influence of heat generation of peripheral members, etc., resulting in deterioration of position detection accuracy. Therefore, the position reference member 202 is made of a material that has a linear expansion coefficient lower than that of the substrate of the reading device 201 and that expands and contracts due to the influence of the ambient temperature in position detection so small that it can be ignored.

In this embodiment, the position reference member 202 is made of glass in consideration of the assumed temperature change range and linear expansion coefficient. Note that the material of the position reference member 202 is not limited to this, and quartz glass or the like is preferably used in order to achieve highly accurate medium position detection when the temperature change range of the reading device 201 is wide. be.

Next, the detection device 200 will be described with reference to FIG. FIG. 11 is a schematic diagram showing an installation mode of a reading device and a position reference member in the detection apparatus.

The position reference member 202 is composed of a position reference member 202a and a position reference member 202b. The position reference member 202 (202a, 202b) is provided on a rotating member (revolver) 203 that is rotationally driven by a motor 204. As shown in FIG. The position reference member 202 (202a, 202b) is moved by a rotating member 203 that is rotated at a constant speed by a motor 204. As shown in FIG. The position reference member 202a and the position reference member 202b are switched along with the rotation of the rotating member 203, and arranged on the facing surface of the reading device 201 at a predetermined timing.

The rotating member 203 is also provided with a reading background 205 used for detecting the edge of the conveyed sheet P and the position of an image recorded on the sheet P, for example. The position reference member 202 and the reading background 205 are selectively switched to a position facing the reading device 201 by rotating the rotating member 203 driven by the motor 204 .

Further, the position reference member 202 (202a, 202b) is rotated in order to detect the mounting inclination of the reading device 201 in the sub-scanning direction. This is for reading the scale, which is a reference pattern including lines extending in a predetermined direction and arranged on the reference member 202 (202a, 202b).

In FIG. 11, the position reference member 202 (202a, 202b) is attached to the rotating member 203 so that the position reference member 202 (202a, 202b) is moved at a constant speed in the sub-scanning direction, but the present invention is not limited to this. No. For example, the position reference members 202 (202a, 202b) may be provided so as to be linearly movable.

Next, an example of a pattern as a detection mark as a detection image for image position adjustment formed on the sheet P will be described with reference to FIG.

The printing device 1 has an adjustment mode for adjusting the image position. When the adjustment mode is selected automatically or manually, the printer 1 forms detection marks, which are images for detection, near the four corners of the sheet P by the inkjet head (detection mark addition unit) provided in the image forming unit 105. L-shaped patterns a, b, c, and d are formed. The center positions of the patterns a, b, c, and d are a0, b0, c0, and d0, respectively. The patterns a and b are formed on the leading end side of the sheet P in the conveying direction and correspond to the detection mark M1. The patterns c and d are formed on the rear end side of the sheet P in the conveying direction and correspond to the detection marks M2.

The sheet P on which the patterns a, b, c, and d are formed passes through an ink drying process by the drying unit 104 and a cooling process of the sheet P by the cooling unit 103, and is conveyed to the detection device 200 in the reversing path 109. FIG.

The detection device 200 includes a CIS (color image sensor) provided extending in the width direction as a reading device 201 . As described above, the detection device 200 includes a plurality of upstream read-conveying roller pairs 22 for conveying the sheet P, a downstream reading-conveying roller pair 23, and an upstream read-conveying roller pair 23, which are arranged upstream and downstream of the reading device 201 serving as reading means. A conveying roller pair 24, a downstream conveying roller pair 25, and the like are provided. Further, as described in the first to third embodiments, the upstream separating means 26, the downstream separating means 27, the downstream reading conveying separating means 28, and the upstream reading conveying separating means 29 are provided as required.

The detecting device 200 optically reads the edges and patterns a, b, c, and d of the sheet P conveyed by the plurality of conveying rollers with the reading device 201 with the reading background 205 facing the reading device 201 .

A CPU (mark coordinate calculation unit) provided in the printing apparatus 1 calculates the coordinates (H0, V0, etc.) of the center position of the pattern (detection mark center position) on the sheet P based on the reading result.

A pattern such as a cross, rectangle, or straight line may be used instead of the pattern shown in FIG. Further, in the present embodiment, the head for ejecting the output image is used as the detection mark adding section, but a dedicated head for adding the detection mark may be provided separately from the head for ejecting the output image.

Next, image correction will be described with reference to FIG. FIG. 13 is an explanatory diagram schematically showing types of image correction.

The CPU (correction value calculation unit) of the printing apparatus 1 calculates the amount of deviation (correction value) of the calculated center position of the pattern from the target position, and adjusts the pattern from the print head so that the pattern is formed at the target position. Correct the ink ejection timing and position.

As shown in FIG. 13, the printing apparatus 1 of the present embodiment corrects the image position by performing registration correction (that is, correction for moving the image position in parallel in the width direction of the sheet P or in the transport direction), magnification correction, and skew correction. , keystone correction, or other correction, but not limited to this.

In the printing apparatus 1, the sheet P expands, contracts, or deforms due to the printing process and the post-printing drying process, and the positions of the images formed on the front and back sides of the sheet P may shift from each other.

Therefore, it is preferable to align the image positions on the front surface and the back surface of the sheet P using the correction method.

When aligning the image positions of the front and back, the CPU of the printing device 1 performs pattern printing on the front side, drying, cooling, reading of the pattern on the front side, pattern printing on the back side, drying, cooling, and reading of the pattern on the back side in this order. . Then, based on the results of reading the patterns on the front and back sides, the timing and position of ink ejection from the print head are corrected so that the positions of the images on the front and back sides match each other. As a result, it is possible to prevent the image positions on the front side and the back side from being shifted from each other.

Next, an example of the spacing means that constitutes the image reader will be described with reference to FIG. FIG. 14 is an explanatory diagram of an example of an upstream separating means for the upstream conveying rotor pair (conveying roller pair).

The upstream separating means 26 is connected to an arm 41 that rotatably supports the rotation shaft of the driven roller 24B of the upstream conveying roller pair 24, and to a rotation fulcrum 42 of the arm 41 to rotate the arm 41 around the rotation fulcrum 42. and a motor 43 for driving.

The motor 43 rotates the arm 41 clockwise to separate the driven roller 24B from the transport roller 24A (driving roller). Further, the motor 43 rotates the arm 41 counterclockwise to bring the driven roller 24B into contact with the transport roller 24A.

Although the upstream separating means 26 is described here, the downstream separating means 27, the downstream reading/conveying/separating means 28, and the upstream reading/conveying/separating means 29 can be configured in the same manner. In addition, although the motor is used as the drive source for the spacing means, the spacing means can also be configured using a cam, solenoid, link, or the like.

Thus, by providing the image reading device according to the present invention, it is possible to print a highly accurate image.

1 Printing device (image forming system)
2 image reading device 21 reading means 22 upstream reading conveying roller pair 23 downstream reading conveying roller pair 24 upstream conveying roller pair 25 downstream conveying roller pair 26 upstream separating means 27 downstream separating means 28 downstream conveying separating means 29 Upstream conveying/separating means 200 detector P sheet

Claims (16)

reading means for reading the detection image on the sheet;
an upstream reading/conveying rotor pair arranged upstream of the reading means in the sheet conveying direction and conveying the sheet;
at least one pair of upstream conveying rotators disposed on the upstream side in the sheet conveying direction of the pair of upstream reading and conveying rotators for conveying the sheet toward the pair of upstream reading and conveying rotators;
At least one of the pair of upstream conveying rotating bodies is provided such that at least one of the rotating bodies can come into contact with and separate from the other rotating body,
The pair of upstream conveying rotators is separated after the leading edge of the sheet reaches the pair of upstream reading conveying rotators and before the leading edge of the sheet reaches the reading position by the reading means. An image reading device characterized by: a pair of downstream reading/conveying rotators arranged downstream of the reading means in the sheet conveying direction for conveying the sheet;
At least one pair of downstream conveying rotators disposed on the downstream side in the sheet conveying direction of the pair of downstream reading and conveying rotators for receiving the sheet conveyed from the pair of downstream reading and conveying rotators and conveying the sheet downstream. and including
At least one of the pair of downstream conveying rotating bodies is provided such that at least one of the rotating bodies can contact and be separated from the other rotating body,
2. The image reading apparatus according to claim 1, wherein the downstream conveying rotor pair is separated before the detection image on the trailing edge side of the sheet reaches a reading position by the reading means. . reading means for reading the detection image formed on the sheet;
a pair of downstream reading/conveying rotators arranged downstream of the reading means in the sheet conveying direction for conveying the sheet;
At least one pair of downstream conveying rotators disposed on the downstream side in the sheet conveying direction of the pair of downstream reading and conveying rotators for receiving the sheet conveyed from the pair of downstream reading and conveying rotators and conveying the sheet downstream. and including
At least one of the pair of downstream conveying rotating bodies is provided such that at least one of the rotating bodies can contact and be separated from the other rotating body,
The image reading device, wherein the pair of downstream conveying rotators are separated before the detection image on the trailing edge side of the sheet reaches a reading position by the reading means. The distance L1 between the pair of upstream reading and conveying rotors and the reading position by the reading means is such that separation of the pair of upstream conveying rotors starts when the leading edge of the sheet reaches the pair of upstream reading and conveying rotors. T1 is the time until separation, T2 is the time from the start of separation to the completion of separation, and V is the conveying speed of the sheet. 3. The image reader according to 1 or 2. A plurality of pairs of upstream conveying rotors are arranged,
Among the plurality of pairs of upstream conveying rotators, all the pairs of upstream conveying rotators whose distance to the reading position by the reading means is shorter than the maximum length of the sheet to be conveyed are spaced apart. 5. The image reader according to any one of claims 1, 2 and 4. At least one of the pair of downstream reading and conveying rotating bodies is provided such that at least one of the rotating bodies can come into contact with and separate from the other rotating body,
When the distance Lm1 from the leading edge of the sheet to the downstream end of the detection image in the sheet conveying direction is longer than the distance L2 from the reading position of the reading means to the pair of downstream reading conveying rotating members, the downstream reading conveying rotation 3. An image reader according to claim 2, wherein the body pairs are spaced apart. 7. The image reading apparatus according to claim 6, wherein the pair of downstream reading and conveying rotators is separated before the leading edge of the sheet reaches the pair of downstream reading and conveying rotators. The distance L1 between the pair of upstream reading/conveying rotating bodies and the reading position by the reading means, the distance Lm1, and the minimum length Lmin of the sheet that can be passed through the device are in a relationship of Lmin>(Lm1+L1). 8. The image reader according to claim 6 or 7, characterized by: A plurality of downstream conveying rotor pairs are arranged,
The pair of downstream conveying rotators whose distance to the reading position by the reading means is shorter than the maximum length of the sheet, among the plurality of pairs of conveying rotators, are separated from each other. Item 9. The image reader according to any one of Items 2, 3, 6, 7 and 8. At least one of the pair of upstream reading and conveying rotating bodies is provided such that at least one of the rotating bodies can come into contact with and separate from the other rotating body,
When the distance Lm2 from the trailing end of the sheet to the upstream end of the detection image in the sheet conveying direction is longer than the distance L1 between the pair of upstream reading and conveying rotating bodies and the reading means, the upstream reading and conveying 3. The image reader according to claim 2, wherein the pair of rotating bodies are spaced apart. 11. The image reading apparatus according to claim 10, wherein said upstream reading/conveying rotor pair is separated before said image for detection reaches a reading position by said reading means. 10. The distance L2 between the reading position by the reading means and the pair of downstream reading and conveying rotators, the distance Lm2, and the minimum length Lmin of the sheet have a relationship of Lmin>(Lm2+L2). 12. The image reader according to 11. The distance L2 between the downstream reading and conveying rotor pair and the reading position by the reading means is the distance from when the trailing edge of the sheet reaches the reading position to when the downstream conveying rotor pair starts contacting. Claims 2, 3, 10, 11, and 11, characterized in that a relationship of L2>V.times.(T3+T4) is established, where T3 is the time from contact start to contact completion, T4 is the time from contact start to contact completion, and V is the sheet conveying speed. 13. The image reader according to any one of 12. Before the trailing edge of the sheet reaches the reading position, the pair of downstream conveying rotators start contacting each other, and the time taken for the trailing edge of the sheet to reach the reading position after the contact is started is −T3. 14. The image reading apparatus according to claim 13, wherein the relationship is T3+T4>0. A printing apparatus comprising the image reading apparatus according to any one of claims 1 to 14. an image reader according to any one of claims 1 to 14;
and an image forming apparatus that forms an image on the sheet.

Images