JPH1077152A - Curl correcting device, image forming device and curl detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a jam and a stain of a conveying guide, by detecting a curl direction and curl amount generated in a sheet, and correcting a curl in accordance with a detected result thereof. SOLUTION: A signal by a curl detection means 21, through a CPU and a mechanical controller, a curl correction means 24 is controlled, a curl is corrected. Relating to the curl detection means 21, for instance, in the case of generating an up facing curl in a recording sheet S, transition of detection time by an optical sensor 21a to 21c is ta < tb < tc, by detected time transition, a direction and amount of a curl, generated in the sheet S, can be detected. On the other hand, a movable member 24e of the curl correction means 24 is movably mounted in a vertical direction by a cam 24g rotated by a solenoid and a gear controlled by a controller. Consequently, in accordance with a curl amount of the recording sheet S, the movable member 24e is moved, reverse curl generation is performed in the sheet S conveyed along a peripheral surface of a conveying roller 24a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curl correcting device capable of correcting a curl on a sheet, an image forming apparatus using the same, and a curl detecting device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, or a facsimile machine, an electrophotographic recording system is often used. In this electrophotographic recording system, a sheet after toner transfer is fixed. The toner image transferred onto the sheet is fixed by applying heat and pressure to the sheet. Since the sheet may be curled by the application of the heat and the pressure, the sheet is conveyed along a conveyance guide curved in a direction opposite to the curl direction after the fixing process to remove the curl. In many cases, a curling correction mechanism is provided.

[0003] Today, an image forming apparatus that performs so-called double-sided recording, in which an image is formed on one side of a sheet, and the sheet is conveyed again to an image forming unit to form an image on the other side, is widely used. However, in this case, the curl correction is important because there is a possibility that a jam (paper jam) may occur if the sheet with the curl is conveyed to the image forming unit again after the fixing process.

[0004]

However, since the curl generated on the sheet differs depending on the type, size, thickness, and apparatus environment of the sheet, it is difficult to correct the curl according to the amount of curl generated on the sheet. Was. In particular, in a configuration in which the curl is corrected by the curvature of the conveyance guide curved in the direction opposite to the curl direction as described above, it is difficult to sequentially respond to the curl direction and curl amount generated in the sheet. .

[0005] The present invention is to solve the above problems,
An object of the present invention is to enable a curl correction device and an image forming apparatus using the same to correct the curl according to the curl state of a sheet. In the curl detecting device, the curl direction and curl amount of the sheet can be detected.

[0006]

A representative configuration according to the present invention for achieving the above object is a curl correction device for conveying a sheet and correcting a curl on the sheet.
Sheet conveying means for conveying the sheet, curl detecting means for detecting the curl of the conveyed sheet, curl correcting means for correcting the curl according to the curl detection amount by the curl detecting means, , Is characterized by having.

In the above arrangement, the direction and amount of curl generated on the sheet are detected by the curl detecting means.
By performing the correction by the curl correcting means according to the detection result, it is possible to accurately correct the curl generated in the sheet according to the type and size of the sheet and the environment of the apparatus. As a result, it is possible to effectively prevent the occurrence of jams and the occurrence of dirt on the transport guide and the like.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a curl detecting apparatus according to the present invention, a curl correcting apparatus using the same, and an image forming apparatus will be specifically described with reference to the drawings.

[First Embodiment] An image forming apparatus using a curl correcting apparatus according to a first embodiment will be described with reference to FIGS. FIG. 1 is an overall schematic explanatory view of the curl correcting device, FIG. 2 is an explanatory diagram showing a configuration of the curl detecting means and a curl detection signal, FIG. 3 is a structural explanatory view of the curl correcting means, and FIG. FIG. 1 is an overall schematic explanatory view of an image forming apparatus using an image forming apparatus.

Here, as the order of the description, first, the overall configuration of the image forming apparatus will be described, and then the configurations of the curl detecting device and the curl correcting device used by the image forming device will be described.

{Overall Description of Image Forming Apparatus} The image forming apparatus according to the present embodiment is a laser beam printer having a double-sided recording function based on an electrophotographic recording method. As shown in FIG. An image is formed on the sheet S by the image forming means B, the sheet S is conveyed to the fixing means C, and the image is fixed. I do. On the other hand, in the case of double-sided recording, the recording sheet S that has passed through the curl correction device D is conveyed again to the image forming means B, where the image is recorded on the other surface and then discharged.

The transport means A feeds the recording sheets S loaded and stored in the cassette 1 mounted on the bottom of the apparatus main body by the feed roller 2 as shown by the solid arrow in FIG. Is transferred to the image forming means B in synchronization with the image forming operation, and heat and pressure are applied when the sheet S after image formation is passed between the heating roller 4a and the pressure roller 4b constituting the fixing means C. Fix the image. The sheet S is conveyed to a later-described curl correction device D via a conveyance belt 5 and a discharge roller 6 to remove the curl. In the case of single-sided recording, the rotating tip of the flapper 7 is moved downward to discharge the sheet at the top of the device. Discharge to section 8.

On the other hand, in the case of double-sided recording, the rotating tip of the flapper 7 is moved upward, and the flapper 7 is conveyed to a re-sending path. The sheet S conveyed to the re-sending path is conveyed from the re-sending roller pair 9, 10 to the switchback rollers 11, 12 as shown by the dashed arrow in FIG. 4, and the conveying direction is switched back by the rollers 11, 12. Later, the sheet is again conveyed to the image forming means B by the re-feed rollers 13, 14, 15, 16 to record on the other surface and is discharged to the discharge section 8.

When an image signal is sent from the host computer, the image forming means B for forming an image on the recording sheet S adjusts the optical path of the laser light from the scanner 17 which emits light in response to the signal by the return mirror 18, The photosensitive drum 19 charged by charging means (not shown) is exposed to form an electrostatic latent image. The electrostatic latent image is developed with toner by developing means (not shown), and a transfer bias is applied to the transfer roller 20 while transferring the recording sheet S between the photosensitive drum 19 and the transfer roller 20. The toner image is transferred to a recording sheet S to record an image. The toner remaining on the photosensitive drum 19 after the transfer of the toner image is removed by a cleaning unit (not shown).

Description of the curl detecting device and the curl correcting device Next, the structure of the curl correcting device D for correcting the curl of the sheet S after passing through the fixing means C will be described.
As shown in FIG. 1, the curl detecting device 21 is a curl detecting device for detecting the curl state of the recording sheet S conveyed while being guided by the conveying guide plate 33, as indicated by an arrow. The curl is corrected by controlling the curl correcting means 24 via the signal from the CPU 21 and the mechanical controller 23.

As shown in FIG. 2A, the curl detecting means 21 includes a plurality of optical sensors 21a to 21a as sheet sensors.
c are provided in parallel in a direction intersecting (perpendicular to the present embodiment) with the sheet conveying direction, that is, in the thickness direction of the sheet, and are controlled by the time difference between the time when the sheet reaches each of the optical sensors 21a to 21c. The means is configured to detect the curl direction and the curl amount.

The three optical sensors 21a to 21c substantially cover the width of the sheet S and are arranged at equal intervals. Each of the optical sensors 21a to 21c includes a light emitting element and a light receiving element arranged with a sheet conveying path interposed therebetween, and sends a signal to the CPU 22 when the recording sheet S passes between the two elements. FIG. 2 (b) shows an example of the signal. In FIG. 2 (b), ta, tb and tc are the respective sensors.
21a to 21c indicate the time when the sheet is detected.

For example, as shown in FIG. 2A, when the recording sheet S is curled upward, the optical sensor 21
The transition of the detection time from a to 21c satisfies ta <tb <tc, as shown in FIG. If the sheet is curled in the opposite direction, the detection time transition is such that ta>tb> tc. Therefore, the direction of the curl occurring on the sheet S can be detected by the detection time transition (the order in which the optical sensors 21a to 21c detect the sheet).

The curl amount can also be detected by the difference between the detection times of the optical sensors 21a to 21c.
That is, the control means determines that the curl amount is large if the time difference is small, and that the curl amount is small if the time difference is large.

In this embodiment, the optical sensors 21a to 21c
Although an example using three sensors is shown, it is possible to detect the curl state if at least two sensors are used, and to detect a more detailed curl state by increasing the number of sensors. Is possible.

Next, the structure of the curl correcting means 24 for correcting curl according to the curl state detected by the curl detecting means 21 will be described.

As shown in FIG. 3, two auxiliary rollers 24b1 and 24b2 for pressing the recording sheet S are provided on the peripheral surface of the curl removing / conveying roller 24a. By being conveyed along the peripheral surface, a curvature in a direction opposite to the direction of the curl is given. The sheet pressing position of the two auxiliary rollers 24b1 and 24b2 with respect to the transport roller 24a can be changed.

That is, the auxiliary rollers 24b1 and 24b2 are
The support column 24c is rotatably supported on a shaft 24d, and is mounted on a movable member 24e. The movable member 24e is configured such that the auxiliary members 24b1 and 24b2 are pressed against the transport roller 24a by a pressing spring 24f. The movable member 24e is mounted so as to be movable in the vertical direction in FIG. 3 by a cam 24g rotated by a solenoid or gear (not shown) controlled by the controller 23.

For this reason, when the curl amount of the recording sheet S is small, as shown in FIG. 3A, the cam 24g is rotated to move the movable member 24e upward. As a result, the sheet conveyed along the peripheral surface of the conveying roller 24a is slightly curled. On the other hand, if the curl amount on the sheet S is large, as shown in FIG.
The movable member 24e is moved downward by rotating 24g. As a result, the auxiliary rollers 24b1 and 24b2 are
Along the transport roller 24a and the auxiliary roller 24a.
A large reverse curl is applied to the sheet S conveyed while being sandwiched between b1 and 24b2. In this way, appropriate curl correction is performed according to the curl amount.

In the curl correcting means 24 shown in FIG. 3, since the direction of the curl applied when the recording sheet S passes through the fixing means C is constant, the reverse curl direction is constant. The auxiliary rollers 24b1 and 24b2 are
By providing it below a, it is also possible to correct the curl according to the direction of the curl on the recording sheet S.

[Second Embodiment] Next, as a second embodiment, another example of the curl detecting means will be described with reference to FIG.

The curl detecting means according to this embodiment is the same as that shown in FIG.
As shown in (a), there is provided a first sensor 25 composed of a touch sensor that detects the passage of the curled recording sheet S passing through the fixing unit C, and is provided at a position separated from the sensor 25 by a predetermined distance. In addition, the light emitting element 26a
And a second sensor 26 provided with a light receiving element 26b.
Then, the time required for the recording sheet S to pass through the position of the first sensor 25 to pass through the position of the second sensor 26 is measured, and the curl amount is detected based on the time.

That is, as shown in FIG. 5B, assuming that the time when the recording sheet S has passed through the first sensor 25 is t1, if the sheet is conveyed at a constant speed, the uncurled sheet becomes the second sensor. The time to pass through 26 is t2. But,
When the sheet is curled, the time t3 until the sheet reaches the second sensor 26 becomes longer. Since the time t3 is longer as the curl amount is larger, the curl amount can be detected by detecting the time t3.

Third Embodiment Next, as a third embodiment, another example of the curl correcting means will be described with reference to FIG.

The curl correcting means according to this embodiment corrects according to the direction of the curl detected by the curl detecting means 21 of the first embodiment. In FIG. 6, 27
Is a variable conveyance guide rotatable in the direction of the arrow, 28 is a solenoid, 29 is a multi-stage adjustment gear, and 30 is a decurling conveyance roller, which is vertically movably mounted. Upper auxiliary rollers 31a and 31b, which can be pressed when the transport roller 30 moves upward,
Lower auxiliary rollers 32a and 32b that can be pressed when the transport roller 30 moves downward are provided.

The variable transport guide 27 and the transport roller
Numeral 30 is connected by a gear train (not shown), and when the rotating tip of the variable transport guide 27 is lowered, the transport roller 30 moves upward, and when the rotary tip of the variable transport guide 27 is raised, the transport roller 30 is rotated. Move downward.

In the above configuration, as shown in FIG. 6, when a sheet curled upward is conveyed, the curl detecting means 21 detects the direction and amount of curl. C
The PU 22 derives curl correction conditions according to the detection result, and sends the information to the mechanical controller 23. And
In response to an instruction from the controller 23, the solenoid 28 is driven to fix the multi-stage adjustment gear 29 at an arbitrary position. Then, the gear (not shown) of the rotating shaft of the variable conveyance guide 27 is rotated to a predetermined position to lower the variable conveyance guide 27, and at the same time, to move the conveyance roller 30 upward to make the upper auxiliary rollers 31a, 31b. And press against it.

In this state, the recording sheet S passes between the conveying roller 30 and the upper auxiliary rollers 31a and 31b through the upper path, and is curled downward at this time. The sheet S curled upward due to the canceling effect is to correct the curl.

On the other hand, when the curl is detected by the curl detecting means 21 to be downward, the curl on the sheet S is similarly corrected by performing the reverse operation.

Incidentally, even in this configuration, similarly to the first embodiment, the auxiliary rollers 31a, 31b, 32
The curl correction can be performed more finely by making the pressure contact position and pressure force of a and 32b variable.

In the above-described embodiment, the case where two sheet transport paths are provided has been described. However, the number of transport paths may be increased, or the transport path may be fixed and the curl removing transport roller 30 may be provided. Only one of them may be configured to be movable.

[Other Embodiments] In the above-described embodiment, an example is shown in which an electrophotographic recording system is used as an image forming means in an image forming apparatus. However, this is another recording system such as an ink jet recording system or a thermal transfer recording system. Of course, it is possible to use.

In the above-described embodiment, the case where the curl correcting device is used in the image forming apparatus has been described. However, the present invention can be similarly applied to a document reading device that conveys a sheet document and reads the image. .

[0039]

The present invention is constructed as described above.
The curl direction and amount of curl generated on the sheet are detected by the curl detecting device, and the curl is corrected by curl correcting means according to the detection result. It becomes possible to correct it appropriately. As a result, it is possible to effectively prevent the occurrence of jams and the occurrence of dirt on the transport guide and the like.

[Brief description of the drawings]

FIG. 1 is an overall schematic explanatory view of a curl correction device.

FIG. 2 is an explanatory diagram showing a configuration of a curl detection unit and a curl detection signal.

FIG. 3 is an explanatory diagram of a configuration of a curl correcting unit.

FIG. 4 is an overall schematic diagram of an image forming apparatus using the curl correction device.

FIG. 5 is an explanatory diagram illustrating a configuration of a curl detection unit according to a second embodiment.

FIG. 6 is an explanatory diagram of a configuration of a curl correcting unit according to a third embodiment.

[Explanation of symbols]

 A: Conveying means B: Image forming means C: Fixing means D: Curl correcting device S: Sheet 1: Cassette 2: Feeding roller 3: Registration roller pair 4a: Heating roller 4b: Pressure roller 5: Conveying belt 6: Discharge Roller 7 flapper 8 discharge unit 9,10 retransmission roller pair 11,12 switchback roller 13-16 retransmission roller 17 scanner 18 mirror 19 photosensitive drum 20 transfer roller 21 curl detection means 21a- 21c optical sensor 22 CPU 23 controller 24 curl correcting means 24a transport rollers 24b1 and 24b2 auxiliary roller 24c support 24d shaft 24e movable member 24f pressing spring 24g cam 25 first sensor 26 first 2 sensors 26a: light emitting element 26b: light receiving element 27: variable conveyance guide 28: solenoid 29: multi-stage adjustment gear 30: conveyance rollers 31a, 31b: upper auxiliary roller La 32a, 32 b ... lower auxiliary rollers 33 ... sheet guide

Claims (10)

[Claims] 1. A curl correction device that conveys a sheet to correct the curl attached to the sheet, comprising: a sheet conveyance unit for conveying the sheet; a curl detection unit for detecting the curl of the conveyed sheet; A curl correcting device for correcting the curl according to the amount of curl detected by the curl detecting device. 2. The curl detecting means according to claim 1, wherein at least two optical sensors are provided in parallel in a direction intersecting a sheet conveying direction, and a direction and a curl amount of the curl are determined based on a time difference at which the sheet arrives at each optical sensor position. The curl correction device according to claim 1, wherein the device is configured to detect the curl. 3. The curl correcting device according to claim 1, wherein said curl detecting means detects a curl amount based on a time difference of a sheet passing a predetermined distance. 4. The image forming apparatus according to claim 1, wherein the curl correcting unit is provided with at least two or more auxiliary rollers capable of pressing a sheet on a peripheral surface of the conveying roller, and is configured to be able to change a sheet pressing position of the auxiliary roller with respect to the conveying roller. Characteristic curl straightener. 5. The curl correcting device according to claim 1, wherein the curl correcting means is configured to be capable of changing a pressing position of the sheet against the peripheral surface of the transport roller in accordance with a curl direction of the sheet. 6. An image forming apparatus for conveying a sheet to form an image, an image forming means for forming an image on the sheet to be conveyed, and the curl straightening device according to claim 1. An image forming apparatus, comprising: a device; 7. The image forming means is of an electrophotographic recording type in which a developer is transferred to a sheet to form an image, and has a fixing means for heating the sheet on which the developer is transferred to fix the image. The image forming apparatus according to claim 6, wherein: 8. A conveying means for conveying a sheet, a plurality of sheet sensors arranged side by side in a thickness direction of the sheet conveyed by the conveying means, and a plurality of sheet sensors arranged in the order in which the plurality of sheet sensors detect the sheet. Control means for determining the direction of the curl; 9. A conveying means for conveying a sheet, a plurality of sheet sensors arranged side by side in a thickness direction of the sheet conveyed by the conveying means, and a difference between times when the plurality of sheet sensors respectively detect the sheets. Control means for determining the amount of curl of the sheet by using the curl detecting device. 10. A conveying means for conveying a sheet, a sheet sensor for detecting a sheet conveyed by the conveying means, and a control means for determining a curl amount of the sheet based on a time required for the sheet to pass through the sheet sensor. And a curl detection device comprising: