JP2008120567A - Sheet conveyor and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet conveyor capable of performing the correct sheet conveyance control by detecting a sheet at the roller nip position, and an image forming device using the same. <P>SOLUTION: The sheet conveyor for conveying a sheet by rotating a roller member has a retard 7 in which a roller part 7a abutted on the sheet is rotated by the rotation of a roller shaft 7b, and a sheet detection sensor 17 for detecting the sheet to be conveyed. The sheet detection sensor 17 is located between the roller shaft 7b and the abutted part on the sheet by the roller part 7a in the radial direction of the rotation of the retard roller 7, and arranged in an area without the roller part 7a in the roller axial direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet by rotation of a roller member, and an image forming apparatus such as a copying machine and a printer using the sheet conveying apparatus.

  2. Description of the Related Art Conventionally, for example, an image forming apparatus such as a copying machine using an electrophotographic system uses a roller member to convey a sheet such as paper that is a medium for printing.

  The conveyance speed when printing on the sheet is called the image forming speed, the time when the sheet is fed from the sheet stacking section is called the feeding speed, etc., in order to shorten the time to discharge the printed sheet after feeding, Increased feeding is performed to increase the feeding speed when feeding and transporting rather than holding an image.

  In addition, in order to correct the sheet posture (skew, misalignment, etc.) during transport, the leading edge of the transported sheet abuts against the roller nip, and the sheet spacing is reduced by transporting multiple sheets. In order to ensure, control to decelerate or stop the conveyance speed is performed.

  Thus, in order to control the conveyance of the sheet, it is necessary to provide a sheet detection sensor for the position of the conveyed sheet in the sheet conveyance path (sheet path). As a sensor used for sheet detection, for example, as shown in FIG. 6, there is a flag sensor type that detects the leading edge of a sheet S conveyed by a roller pair 100 by swinging a flag 101 (Patent Document 1). In addition to the flag sensor, there is a photo sensor type that detects passage of a sheet by blocking light.

  The sensor arranged on the sheet path detects that the leading edge or the trailing edge of the sheet has passed, and determines the position of the sheet. If the detection at the set conveyance timing is not possible, it is determined that a conveyance abnormality such as a sheet jam has occurred. In addition, in order to control the distance between the two sheets before and after being conveyed, the sheet conveying speed is changed by changing the conveying roller speed according to a predetermined detection timing, and the sheet interval is set. Conventionally, control to bring the value close to the value has been performed.

JP-A-10-59582

  However, since conventionally used sheet detection sensors are a single flag sensor type or a photo sensor type, it has been difficult to arrange structurally and continuously.

  Further, as a method of separating the sheets one by one in the feeding unit that feeds the sheets from the sheet stacking unit, a feeding roller that rotates in the sheet feeding direction and a retard roller that rotates in the direction to return the sheet There is a retard system composed of a pair of rollers. In such a retard separation system, the sheet position in the vicinity of the retard roller nip tends to become unstable, and acceleration / deceleration control is indispensable during conveyance downstream thereof. Therefore, it is desirable that the separation state of the sheet between the nips of the roller pair can be accurately detected.

  However, there is no space for arranging the sensor between the nips of the pair of retard rollers, and a sheet detection sensor cannot be provided. For this reason, it is impossible to detect the sheet separation state between the nips, and the acceleration / deceleration control downstream of the nip is a control that also takes into account variations in the separation unit, which is an obstacle to high productivity. .

  Although the conventional flag sensor type and photo sensor type have been used as close as possible to the nip of the roller pair, the presence of a sheet near the nip can be detected because a single sensor cannot be placed continuously. However, it was difficult to determine an accurate position.

  As described above, conventionally, only a small number of sheet detection points, such as one or two, can be arranged between the conveyance roller and the conveyance roller downstream thereof. As a result, since the sheet detection points are limited, it is difficult to perform transport control with higher accuracy.

  Further, if a sensor using an inorganic semiconductor such as a conventional line sensor is used, continuous detection is possible, but it is difficult to arrange the sensor between the roller shafts of a roller pair because of its large size. Furthermore, it cannot be placed in a bent path or where the transport path is not thick, which hinders downsizing of the apparatus and is difficult to realize.

  In addition, as a demand for feeding / conveying control, it is required to support more media than conventional media. There is a demand for higher productivity than before. The transport path length has also become shorter. Due to such multi-media support, the factors of variation increase, and with higher productivity, more dense sheet-to-sheet conveyance is required. By shortening the path, the conventional acceleration / deceleration control space is eliminated. ing.

  The present invention has been made in view of the above points, and an object of the present invention is to detect a sheet at a sheet nip position by a rotating body and perform accurate sheet conveyance control and an image using the same. A forming apparatus is provided.

  In the sheet conveying apparatus for conveying a sheet by rotating the rotating member, a typical means in the present invention for solving the above-described problem is a rotating member in which a contact rotating portion that contacts the sheet is rotated by rotation of a rotating shaft. And a sheet detection sensor for detecting the conveyed sheet, wherein the sheet detection sensor is in contact with the sheet by the rotation shaft and the contact rotation portion in the rotational radius direction of the rotating member. It is characterized in that it is arranged in a region where there is no abutting rotation part in the rotation axis direction of the rotation member.

  In the present invention, in a region where there is no contact rotation part, the sheet detection sensor is disposed between the rotation shaft and the sheet nip position by the contact rotation part, thereby detecting the position of the sheet near the sheet nip. can do. For this reason, it is possible to perform denser sheet conveyance control than before.

  Next, a sheet conveying apparatus according to an embodiment of the present invention will be described together with an image forming apparatus including the sheet conveying apparatus.

[First Embodiment]
FIG. 1 is an explanatory diagram of a main part of an image forming apparatus including a sheet conveying device according to the first embodiment of the present invention.

{Image forming device}
First, the overall configuration of an image forming apparatus using a sheet conveying apparatus will be described together with an image forming operation. In this image forming apparatus A (in this embodiment, a laser beam printer), the image forming unit 1 is arranged at the upper part, and the sheet conveying apparatus B is arranged at the lower part. That is, as shown in FIG. 1, the image forming means 1 irradiates the photosensitive drum 3 with laser light based on image information from the optical system 2 to form an electrostatic latent image, and this latent image is formed using toner. Develop to form a toner image.

  A sheet conveying apparatus B that feeds the sheet S in the feeding cassette 4 to the image forming unit 1 includes a pickup roller 5, a feed roller 6, and a retard roller 7, and the sheet S stacked on the feeding cassette 4 is 1 Pick up one by one and feed it to the main unit.

  The sheet S sent from the sheet conveying apparatus B is fed from the conveying roller pair 8 to the registration roller pair 9, and is conveyed to the transfer unit with the posture of the sheet S adjusted. Then, the toner image formed on the photosensitive drum 3 in the transfer portion is transferred to the sheet S by applying a voltage to the transfer roller 10. The sheet S is guided by the guide plate 11 and conveyed to the fixing unit. This fixing means includes a pressure roller 12 and a fixing roller 13 incorporating a heater, and applies heat and pressure to the passing sheet material to fix the transferred toner image on the sheet S. The sheet S is discharged to the discharge unit 15 by the discharge roller pair 14 to complete the image formation.

{Sheet conveying device}
Next, the sheet conveying apparatus B will be described with reference to FIGS. The sheet conveying apparatus B according to the present embodiment separates and feeds the sheets S picked up by the pickup roller 5 one by one by a retard roller pair.

  The retard roller pair includes a feed roller 6 and a retard roller 7. The feed roller 6 is rotationally driven in a sheet feeding direction (counterclockwise direction in FIG. 1) by driving means in the apparatus main body. The retard roller 7 is rotationally driven in a direction (counterclockwise direction in FIG. 1) for returning the sheet S to a direction opposite to the conveying direction by a driving means in the apparatus main body via a torque limiter (not shown). As a result, the uppermost sheet is separated from the other sheets, conveyed to the conveying roller pair 8, and further conveyed to the image forming unit.

  Here, as shown in FIG. 2, the feed roller 6 and the retard roller 7 both have roller portions (contact rotation portions) 6a and 7a that contact the sheet and apply a conveying force to roller shafts (rotation shafts) 6b. , 7b is configured as a roller member (rotating member) divided in the axial direction. That is, in the roller axis direction, there is a region where the roller portions 6a and 7a are not present, and the roller shafts 6b and 7b having a smaller diameter than the roller portions 6a and 7a are exposed in the region.

  A sheet detection sensor 17 is provided for detecting a sheet at the nip position of the retard roller pairs 6 and 7. The sheet detection sensor 17 is disposed between the roller shafts 6b and 7b of the retard roller pair. Therefore, the sheet detection sensor 17 has a thin sheet shape. As shown in FIG. 2, the sheet detection sensor 17 is a region where there is no roller portion 7 a in the rotational axis direction of the retard roller 7, and the roller shaft 7 b and the roller portion in the rotational radius direction of the retard roller 7. It arrange | positions between the contact parts with the sheet | seat by 7a.

  Here, the sheet detection sensor 17 according to the present embodiment will be specifically described. The sheet detection sensor 17 of the present embodiment is a sheet-like sensor having an optical sensor layer in which a plurality of photoelectric conversion elements are continuously arranged in the sheet conveyance direction. As shown in FIG. 3, the sheet-like sensor is disposed from the upstream side to the downstream side in the sheet conveying direction with the roller nip portion of the retard roller pair 6, 7 as the center.

  In recent years, a sheet-like scanner using an organic compound semiconductor as a photoelectric conversion element has been developed. In this example, reading pixels 61, which are minute optical sensors (photoelectric conversion elements) configured by combining an organic transistor and an organic photodiode on a plastic film, are arranged in a matrix in a row direction and a column direction. The organic photodiode is configured to generate a current when light hits the photosensor.

  FIG. 4A is a schematic diagram for explaining the circuit configuration of the sheet detection sensor 17 in which the organic semiconductor photosensors are arranged in a matrix, and FIG. 4B is a schematic explanatory diagram for explaining the circuit configuration of each photosensor. is there.

  In the figure, one column of read pixels 61 arranged in the column direction is connected to a word line 63, and the word line 63 is connected to a column decode line 67 via a word line selector 70.

  The read pixels 61 arranged in a row in the row direction are connected to a bit line 64, and the bit line 64 is connected to a row decode line 69 via a bit line selector 71.

  A current value of a predetermined read pixel 61 is read by addressing the column decode line 67 and the row decode line 69. By reading the current value of the reading pixel 61, it is possible to detect the conveyed sheet position.

  In the present embodiment, the optical sensor is composed of an organic semiconductor. For this reason, it is possible to form an optical sensor and a peripheral circuit on a conveyance guide or a sheet-like member by using, for example, a precision printing technique. Moreover, it can be used as a sensor having a thickness (height) of several millimeters or less. For this reason, the distance between the roller surface and the roller shaft surface is generally 5 mm or less. However, the sheet detection sensor 17 of this embodiment has a roller shaft of one roller and a contact portion between the roller portion and the sheet. It is possible to arrange between. The sheet detection sensor 17 is fixed to a fixing member such as a conveyance guide in order to maintain a distance from the conveyed sheet S.

  Since the sheet detection sensor 17 can continuously arrange a large number of optical sensors, the number of sheet detection lines can be selectively formed. Therefore, it is possible to easily form a one-line sensor array continuously in the sheet conveying direction.

  Further, since the sheet detection sensor 17 has a thin sheet shape, even if the sheet conveyance path is S-shaped or bent, the sheet detection sensor 17 can be arranged along the shape. Therefore, the sheets can be detected continuously along the sheet conveyance path.

  The sheet detection sensor 17 detects the sheet position by detecting the leading edge or the trailing edge of the conveyed sheet with the optical sensor. And since it is arrange | positioned between roller axis | shafts 6b and 7b, the position of the sheet | seat in the roller nip vicinity which was not able to be detected conventionally can be detected.

  And since the said optical sensor is arrange | positioned continuously, the position of a sheet | seat edge is detected continuously and the position change of the conveyed sheet | seat is caught with time.

  As described above, since the position of the sheet can be continuously detected at the roller nip, the leading edge of one sheet is detected, and the sensed sheet conveyance speed is compared with the sheet conveyance speed calculated by the roller rotation speed. Can do. Therefore, when there is a deviation between the two, it is determined that the conveyance is abnormal, and slip detection can be performed.

  As a result, high productivity of sheet conveyance can be realized in correspondence with multiple media. Furthermore, since the sensor is a sheet-like sensor, the installation space can be reduced, and the apparatus can be downsized.

{Sheet detection and sheet conveyance control}
As described above, the sheet conveying apparatus of the present embodiment can detect a sheet in the retard roller nip. And it has a speed changing means for changing the rotation speed of the roller member such as the feed roller 6 according to the sheet detection signal of the sheet detection sensor 17.

  Next, sheet conveyance control based on the sheet detection result will be described.

  Since the sheet conveying apparatus B of the present embodiment uses the retard separation method, the separated sheet leading edge may protrude beyond the retard roller nip as shown in FIG. 5 due to variations in the separation state. Conventionally, when the sheet is fed again, the leading edge position of the sheet is unclear and causes a conveyance failure such as a collision with a preceding sheet downstream. It was necessary to secure the space between the sheets.

  In contrast, the sheet conveying apparatus of the present embodiment can accurately detect the separation state by disposing the sheet-like sheet detection sensor 17 in the vicinity of the retard roller nip as described above. That is, it is possible to detect how much the leading edge of the sheet has protruded from the retard roller nip. For this reason, when the sheet that has jumped out from the retard roller nip is fed again, the feed roller 6 is fed so that the sheet is conveyed at a timing at which the distance between the preceding sheet and the preceding sheet is maintained or at a feeding conveyance speed according to the detection result. The rotation speed can be controlled.

  As a result, it is possible to omit the complicated control on the downstream side in the sheet conveyance direction as in the prior art, and further, it is possible to omit the conveyance path length necessary for the control. For this reason, it is possible to reduce the size of the apparatus and increase the productivity by reducing the space between sheets.

  For example, if the nominal value for control is that the sheet starts from the position of the feeding cassette 4, if the leading end of the sheet is near the retard roller nip at the feeding operation start timing, the feeding start timing from the nominal position is determined. Also, the feeding start timing is delayed by the difference in arrival time to the sheet leading edge position. As a result, the distance between the preceding sheet and the preceding sheet can be maintained at a constant distance. Further, instead of delaying the feed start timing, the transport speed may be slowed so as to reach a designated position that is a certain transport distance.

  Further, as shown in FIG. 5, the sheet conveying apparatus B of the present embodiment is a sheet-shaped sheet detection sensor 17, and therefore, from the upstream side in the sheet conveying direction to the downstream side of the conveying roller pair 8 relative to the retard roller pairs 6 and 7. It can arrange | position along the conveyance path | route bent to the side. In addition, the sheet conveyance speed can be detected by continuously detecting the sheet position therebetween.

  Therefore, it is possible to detect both the input conveyance speed of the sheet entering the nip of the retard roller pair 6 and 7 and the sheet conveyance speed sent out from the retard roller pair 6 and 7. From this detection result, the accuracy of sheet acceleration / deceleration control and the like can be improved by feedback control of the rotation speed of the feed roller 6.

  For example, normally, in the vicinity of the nip of the retard roller pair 6, 7, the transport speed of the sheet S fed by the feed roller 6 is slightly faster than the input transport speed of the sheet entering the nip of the retard roller 6, 7 pair. Set. Conversely, if the input conveyance speed is faster than the speed at which the sheet is sent out, there is a possibility that the sheet will be delayed.

  Accordingly, the sheet detection sensor 17 compares the input conveyance speed with the sheet conveyance speed sent by the feed roller 6, and the feed roller 6 is set so that the sheet conveyance speed fed by the feed roller 6 is faster than the input conveyance speed. Control the drive.

  Thereby, it is possible to keep a constant distance between the preceding sheet and the sheet. At this time, the input conveyance speed is increased, and if the conveyance speed of the sheet S does not reach the set value even when a certain input conveyance speed is reached, it is determined as a conveyance defect.

  As described above, the sheet detection sensor 17 continuously detects the sheet position to detect the actual sheet conveyance speed, and by changing the roller drive accordingly, it is possible to convey the sheet with high accuracy. Is possible.

[Other Embodiments]
In the above-described embodiment, the sheet-like sheet detection sensor 17 is disposed between the retard roller pairs 6 and 7 on the retard roller 7 side. However, this may be arranged on the feed roller 6 side.

  In the embodiment described above, an example in which the sheet detection sensor 17 is disposed between the roller shafts of the retard roller pairs 6 and 7 has been described. However, the sheet detection sensor 17 is not limited to a pair of rollers. For example, the sheet detection sensor 17 conveys the sheet with only one roller so that the separation roller and the friction pad come into contact with each other to separate and feed the sheet. It can also be arranged in a sheet conveying device. In this case, the same effect as that of the above-described embodiment can be obtained.

  Further, the above-described sheet detection sensor 17 can be arranged in the same manner even when a rotating member such as a belt or a roller is used as a sheet conveying unit as well as a roller member, and the same effect as the above-described embodiment. Can be obtained.

  Further, the sheet detection sensor 17 may include a plurality of photoelectric conversion elements arranged in one line in the sheet conveyance direction or a plurality of lines.

3 is a configuration explanatory diagram of a main part of an image forming apparatus including a sheet conveying device. FIG. It is a cross-sectional explanatory drawing of the roller axial direction which shows arrangement | positioning of a retard roller pair and a sheet | seat detection sensor. It is a cross-sectional explanatory drawing of the roller rotation radial direction which shows arrangement | positioning of a retard roller pair and a sheet | seat detection sensor. It is a schematic diagram explaining the circuit structure of the sheet | seat detection sensor using an organic semiconductor. FIG. 3 is a cross-sectional explanatory view of a sheet conveying device in which a sheet detection sensor is bent and arranged. It is explanatory drawing of the sheet | seat detection structure concerning a prior art.

Explanation of symbols

A ... Image forming apparatus B ... Sheet conveying apparatus S ... Sheet 1 ... Image forming means 2 ... Optical system 3 ... Photosensitive drum 4 ... Feed cassette 5 ... Pickup roller 6 ... Feed roller 6a, 7a ... Roller part 6b, 7b ... Roller shaft 7 ... retard roller 8 ... conveying roller pair 9 ... registration roller pair
10 Transfer roller
11… Guide plate
12… Pressure roller
13… Fixing roller
14… discharge roller pair
15… discharge section
16 Roller member
17… Seat detection sensor
61… Reading pixel
63… Word line
64… bit line
67 ... Column decode line
69… Line decode line
70… Word line selector
71… Bit line selector

Claims (12)

In a sheet conveying apparatus that conveys a sheet by rotating a rotating member,
A rotating member that rotates a contact rotating portion that contacts the sheet by rotation of the rotation shaft;
A sheet detection sensor for detecting the conveyed sheet;
Have
The sheet detection sensor is between the rotating shaft and a contact portion of the sheet by the contact rotating portion in the rotational radius direction of the rotating member, and the contact rotation in the rotating shaft direction of the rotating member. A sheet conveying apparatus, wherein the sheet conveying apparatus is disposed in a region having no portion. The sheet conveying apparatus according to claim 1, wherein the sheet detection sensor is a sheet-like sensor having an optical sensor layer in which a plurality of photoelectric conversion elements are continuously arranged in a sheet conveying direction. 2. The sheet detection sensor according to claim 1, wherein the sheet detection sensor is a sheet-like sensor having an optical sensor layer in which a plurality of photoelectric conversion elements are continuously arranged in a sheet conveyance direction and a direction intersecting the sheet conveyance direction. Sheet conveying device. 4. The sheet conveying apparatus according to claim 2, wherein the photoelectric conversion element is continuously arranged on at least one of an upstream side or a downstream side of the rotating member in a sheet conveying direction. 5. 5. The sheet conveying apparatus according to claim 2, wherein the plurality of photoelectric conversion elements are arranged along the bent sheet conveying path in the sheet detection sensor. The sheet conveying apparatus according to claim 1, wherein the sheet detection sensor continuously detects a position of a conveyed sheet. The sheet conveying apparatus according to claim 6, further comprising a speed changing unit that changes a rotation speed of the rotating member in accordance with a sheet detection signal of the sheet detection sensor. The sheet according to claim 6, wherein when there is a deviation between the sheet conveyance speed detected by the sheet detection sensor and the sheet conveyance speed calculated from the rotation speed of the rotating member, it is determined that the sheet conveyance is abnormal. Conveying device. The sheet conveying apparatus according to claim 6, wherein the sheet conveying timing or the sheet conveying speed is changed according to a sheet leading end position detected by the sheet detecting sensor. The rotation speed of the rotating member is changed by comparing a sheet input conveying speed to the rotating member detected by the sheet detection sensor and a sheet conveying speed by the rotating member. Item 8. The sheet conveying apparatus according to Item 7. The sheet conveying apparatus according to any one of claims 2 to 10, wherein the photoelectric conversion element is a combination of an organic transistor and an organic photodiode. In an image forming apparatus that conveys a sheet to form an image,
A sheet conveying device according to any one of claims 1 to 11,
An image forming means for forming an image on the conveyed sheet;
An image forming apparatus comprising:

Images