JP2000147976A - Belt transport device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the transport performance to improve the quality by detecting traveling speed of a transfer transporting belt at a prescribed position, controlling the driving speed based on this detection result, and stabilizing the speed of the belt at every part. SOLUTION: Optical sensors 24a and 24b are respectively arranged at two section parting from the transfer part (a nip part between photosensitive drum and a transfer roller 20) by approximately 20 mm on the upstream side and the downstream side in the traveling direction, and arranged in nearly the center part in the direction orthogonal to the travel of the transfer belt 18. During the transport operation of the belt transport device, the belt transport speeds on the downstream side and the upstream side of the transfer roller 20 are respectively measured for the prescribed time by the optical sensors 14a and 14b. The fluctuation of the belt transport speed is caused by the rotary fluctuation of stepping motors 35 and 36, and the extension and contraction of the transfer belt 18 at the driving time however, the speed fluctuation range is enlarged by the extension and the contraction of the transfer belt 18. A CPU 26 controls the rotary speed of the stepping motors 35 and 36 by detecting the change in this speed fluctuation width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt conveying device used for a photoreceptor belt, a transfer belt, an intermediate transfer belt, and the like, and is applied to an image forming apparatus such as a copying machine, a facsimile, and a printer. Things.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus,
For example, there are a copying machine, a facsimile, a printer, and the like.

Hereinafter, a copying machine will be described as an example of an image forming apparatus provided with a belt conveying device according to the prior art.

FIG. 6 is a schematic sectional view of an image forming apparatus (copier) equipped with a belt conveying device according to the prior art.

First, the flow of a sheet (transfer paper P) on which an image is formed will be described.

In FIG. 6, an image formed by an image forming unit 2 that performs a known image forming process is transferred to a transfer sheet P stored in a cassette 1 that can be pulled out to the near side in the figure. Sent to the fixing device 4,
The image is fixed by the heat and pressure of the fixing device 4, and is discharged from a paper discharge port 7 by a paper discharge roller 6 to a copying machine main body 1 as an image forming apparatus.
It is discharged out of the machine of 05.

The transfer paper P discharged to the outside of the copying machine main body 105 enters the entrance 9 of the sheet separation device 8 and is discharged by the discharge roller 10 provided in the sheet separation device 8.
And is stacked on the paper discharge tray 11.

When reading a document image, the document is read by the exposure device 13 when the document is set on the pressure plate 12.

Then, the read image is transferred to the transfer paper P as a toner image by the image forming section 2 as described above.

When two or more copies of a plurality of originals are to be copied, the transfer paper P changes its course in the direction of the roller 14 by the flapper F, which is a paper conveyance path changing means in the sheet separation device 8, and discharges the paper. The paper is discharged onto the paper discharge tray 11 by the rollers 15.

The paper discharge tray 11 has a configuration in which a plurality of bins are stacked in multiple stages. The paper discharge tray 11 is indexed and moved in the direction of arrow A by a paper discharge tray driving means (not shown), and is discharged to each bin. The exit sides of the paper rollers 15 are made to coincide with each other and classified by the number of copies.

In the above, the front loading cassette 1, the transport unit 3, and the fixing device 4 are pulled out to the near side in a direction perpendicular to the plane of the drawing to maintain the apparatus and supply the transfer paper P.

Next, the transport unit 3 for transferring the image formed by the image forming unit 2 to the transfer paper P and transporting it to the fixing device 4 will be described.

In FIG. 6, the drive roller 16 and the tension roller 1 to which the drive is transmitted from the copying machine main body 105 are shown.
An endless transfer belt (transfer conveyance belt) 18 is stretched with a predetermined tension between the transfer belts 7.

The drive roller 16 and the tension roller 17 are rotatably supported by a side plate (not shown) of the transport unit 3 with a predetermined distance between the axes.

The transfer belt 18 has a base layer made of NBR rubber,
The surface layer is made of a fluorine-based rubber, and the volume resistivity is set to a high resistance of 1.0 × 10 ¹³ Ω.

The transfer belt 18 is in contact with a photosensitive drum 19 serving as an image carrier by being urged with a predetermined pressure by a transfer roller 20 disposed inside the transfer belt 18.

The transfer roller 20 is composed of a high-resistance EPDM rubber layer. A predetermined voltage is applied to the transfer roller 20 from a power supply device (not shown) to charge the surface of the transfer belt 18 to have a charge. .

When the transfer paper P comes into contact with the transfer belt 18 of the transport unit 3, it is attracted to the surface by electrostatic attraction and is transported.

The photosensitive drum 19 and the transfer roller 20
The image (toner image) formed on the photosensitive drum 19 by the image forming unit 2 is transferred onto the transfer paper P around the nip portion (transfer portion).

After the transfer, the transfer paper P is conveyed to the fixing device 4 while being adsorbed on the transfer belt 18.

[0022]

However, in the case of the above-described prior art, the following problems have occurred.

Since the transfer belt 18 is made of elastic rubber, it expands and contracts when the transfer belt 18 is driven, and the transfer speed of the surface of the transfer belt 18 varies depending on the location.

In particular, as shown in FIG. 5A, the transfer roller 20 is pressed and driven by the photosensitive drum 19 with the transfer belt 18 interposed therebetween, so that the belt easily expands and contracts.

The transfer roller 2 is moved faster than the outer peripheral speed V1 of the drum.
0 and the drive roller 16 has a low speed V2 (V1
> V2) The transfer paper P rises above the surface of the transfer belt 18 and forms a loop as shown in FIG.

As a result, the image formed on the surface of the transfer paper P is disturbed, or the transfer paper P hits the case of the cleaner 21 of the copying machine main body 105, resulting in a jam.

As shown in FIG. 5B, if the speed V3 between the transfer roller 20 and the tension roller 17 is lower than the outer peripheral speed V4 of the registration roller 22, (V4>
V3) The transfer paper P forms a floating loop as shown in the figure.

As a result, the charger 2 in the copier main body 105
Case 3 resulted in a jam and transfer paper P was stained.

Further, also at the time of transfer to the transfer paper P, since the outer peripheral speed of the photosensitive drum 19 is different from the speed of the transfer belt 18, transfer unevenness such as expansion and contraction of a transferred image occurs.

When the transfer paper P is separated from the photosensitive drum,
Drum separation failure of the transfer paper P due to a peripheral speed difference is likely to occur.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to stabilize the speed of each part of the belt to improve the transport performance and improve the quality. It is an object of the present invention to provide an improved belt conveying device and an improved image forming device.

[0032]

In order to achieve the above object, according to the present invention, there is provided a transfer / conveyance belt including a transfer portion onto which a toner image is transferred in a transfer path, and driving the transfer / conveyance belt. A driving unit, wherein a detecting unit for detecting a moving speed of the transfer conveying belt at a predetermined position is provided, and a driving speed of the driving unit is controlled based on a detection result of the detecting unit. It is characterized by becoming.

Therefore, it is possible to control the moving speed of the transfer / conveying belt at the position detected by the detecting means so as to be a desired speed.

A first drive unit and a first detection unit are arranged upstream of the transfer unit, and a second drive unit and a second detection unit are arranged downstream of the transfer unit. The driving speed of the first driving means may be controlled based on the detection result of the means, and the driving speed of the second driving means may be controlled based on the detection result of the second detection means.

Therefore, the speed can be controlled on the upstream and downstream sides of the transfer portion.

The transfer portion is a contact portion of the image carrier carrying the toner image to the transfer / transport belt, and the toner image carried on the surface of the image carrier is transferred toward the transfer / transport belt. Good.

The driving speed of the driving means or the driving speed of the image carrier may be controlled such that the moving speed of the transfer / conveying belt at a predetermined position is equal to the moving speed of the surface of the image carrier. .

In the image forming apparatus of the present invention,
The toner image is transferred onto the sheet while the sheet is conveyed by the transfer conveyance belt provided in the above-mentioned belt conveyance device, and then the toner image is fixed on the sheet.

Further, after a toner image is transferred onto a transfer / conveying belt provided in the above-mentioned belt conveying device, the toner image is further transferred onto a sheet, and the toner image is fixed onto the sheet. Features.

[0040]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

Referring to FIGS. 1 to 4, a belt conveying device and an image forming apparatus according to an embodiment of the present invention will be described.

FIG. 1 is a perspective view of a belt conveying device according to an embodiment of the present invention.

FIG. 2 is a sectional view of an image forming apparatus equipped with a belt conveying device according to an embodiment of the present invention.

FIG. 3 is an electric system diagram of the belt conveying device according to the embodiment of the present invention.

FIG. 4 is a graph showing the change over time of the belt speed of the belt conveying device according to the embodiment of the present invention.

In FIGS. 1 to 4, parts having the same role as in FIG. 6 referred to in the above description of the prior art are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1, reference numerals 24a and 24b denote optical sensors as detecting means having a laser light emitting element (LD) and a light receiving element (PIN photo) on the upper surface.

An optical sensor 24b as a first detecting means is disposed upstream of the transfer section, and an optical sensor 24a as a second detecting means is disposed downstream of the transfer section.

The laser is emitted from the laser light emitting elements of the optical sensors 24a and 24b toward the inner peripheral surface of the transfer belt (transfer and transfer belt) 18, and scattered light is received by the light receiving element.

The scattered light is converted into an analog signal having a Doppler frequency component proportional to the speed of the transfer belt 18.

This analog signal (Doppler raw signal) is amplified and transmitted to the CPU 26 installed in the image forming apparatus 5.

In the CPU 26, the transmitted analog signal is proportional to the speed of the transfer belt 18.
It is converted to an F / V signal.

Here, the laser irradiation is performed on the transfer belt 18.
Are irradiated vertically.

The base layer of the transfer belt 18 is milky white so that the laser is easily scattered after the transfer belt 18 is irradiated.

The optical sensors 24a and 24b are arranged at two locations approximately 20 mm upstream and downstream of the transfer portion (nip portion between the photosensitive drum 19 and the transfer roller 20), and are substantially at right angles to the transfer belt 18 in the direction perpendicular to the transfer direction. It is located at the center position.

The optical sensors 24a and 24b are fixed on a transfer roller support plate 25 holding the transfer roller 20.

Incidentally, a vibration isolator (not shown) or the like may be provided between the optical sensors 24a and 24b and the transfer roller support plate 25 so as not to transmit the vibration from the belt transport device 40 to the optical sensors 24a and 24b. preferable.

The transfer roller 20 has conductive bearings 27 at both ends.
The bearing 27 has a pin 28 as a center of rotation.

Power is supplied to the transfer roller 20 by the image forming apparatus 5.
A voltage is applied via a pin 28 from a voltage generator (not shown) provided therein.

The transfer roller 20 is urged vertically upward in the figure by a compression coil spring B to apply a charge to the transfer belt 18.

The transfer roller support plate 25 is
0 is hung between the rear plate 29 and the front plate 30, and the position is determined by inserting the pin 31 into a positioning hole (not shown) of the rear plate 29 and fixing the screw 32 to the front plate 30.

An insertion hole (not shown) is formed in the front side plate 30 to make it easy to insert the transfer roller support plate 25 from the front in the figure, so that the transfer roller support plate 25 can be easily attached and detached.

A stay 3 is provided between the front plate 30 and the rear plate 29.
3 is fixedly supported.

The transfer belt 18 is hung with a predetermined tension between an upstream drive roller 37 as a first drive unit and a downstream drive roller 38 as a second drive unit, and the surface of each roller and the inner surface of the transfer belt 18 are formed. The driving force is transmitted by the static friction force.

Upstream drive roller 37, downstream drive roller 38
Is a roller bearing 3 made of a non-conductive and highly slidable material fixed at both ends thereof to the front plate 30 and the rear plate 29.
4 rotatably supported.

The stepping motor 36,
35 is fixedly supported, and drive is transmitted to the upstream drive roller 37 and the downstream drive roller 38, respectively.

Next, a control operation of the belt conveying device 40 according to the embodiment of the present invention will be described.

During the transfer operation of the belt transfer device 40, the belt transfer speeds of the transfer roller 20 downstream and upstream of the transfer roller 20 are measured for a predetermined time by the optical sensors 24a and 24b.

FIG. 4 is a graph showing the fluctuation of the belt speed measured by the optical sensors 24a and 24b.

The fluctuation of the belt speed is determined by the stepping motor 3
The transfer belt 18 fluctuates due to rotation fluctuations of the transfer belts 5 and 36 and expansion and contraction of the transfer belt 18 during driving.

Here, since the speed fluctuation width of the stepping motors 35 and 36 is substantially constant, when the transfer belt 18 expands and contracts, the speed fluctuation width increases due to the expansion and contraction.

Therefore, in the present embodiment, the change in the speed fluctuation range is detected and the stepping motors 35 and 3 are detected.
6 is controlled.

The control method will be described below.

When the speed signals from the optical sensors 24a and 24b are within the preset upper and lower limits of the belt speed shown in FIG. 4, the rotation speeds of the stepping motors 35 and 36 are not changed and are not changed. To guess.

At this time, the average value of the belt speed fluctuation is
26, the drum driving motor 39 (FIG. 3) installed in the image forming apparatus 5 is controlled according to the average speed, and a peripheral speed of the photosensitive drum 19 equivalent to the average speed is obtained. To do.

The drum drive motor 39 drives not only the photosensitive drum 19 but also the registration roller 22 in FIG.

When the belt speed signal transmitted from the optical sensor 24a falls within the upper and lower limits of the belt speed shown in FIG. 4, and the speed signal of the optical sensor 24b deviates from the upper and lower limits, the rotation of the stepping motor 35 is started. The speed increase and deceleration control of the speed of the stepping motor 36 is performed without changing the number.

After the speed change, the belt speed is detected again by the optical sensors 24a and 24b. If the speed does not fall within the upper and lower limits shown in FIG. 4, the above speed control is repeated.

If so, the above control is performed.

When the belt speed signal transmitted from the optical sensor 24b falls within the upper and lower limits of the belt speed shown in FIG. 4, when the speed signal of the optical sensor 24a deviates from the upper and lower limits, the stepping motor 36 The speed of the stepping motor 35 is increased and decelerated while the rotation speed remains unchanged.

Then, the belt speed is detected again, and feedback control is performed in the same manner as described above.
If the speeds a and 24b fall within the upper and lower limits shown in FIG. 4, the drum drive motor 39 is controlled in accordance with the average value of the speeds as in the case of FIG. To match.

In this configuration, a laser Doppler speed sensor is used as the speed detecting means of the transfer belt 18, but the transport speed of the transfer belt 18 may be detected by using a reflection type photocoupler.

As a specific detection method, the transfer belt 1
In the non-image area of No. 8, a round hole is made, and the time for the round hole to pass is detected by two reflective photocouplers separated by a predetermined distance.

The transfer belt 1 is changed according to the variation of the passing time.
8 is controlled.

As described above, the moving speed of the transfer belt 18 at a predetermined position is detected, and the speed at the position is controlled so as to be a desired speed. it can.

In particular, the speed is controlled on the upstream side and on the downstream side of the nip portion (transfer portion) where the speed is likely to be uneven between the upstream and downstream sides, whereby the speed unevenness can be eliminated.

The driving speed of each part can be adjusted so that the moving speed of the transfer belt 18 is the same as the moving speed of the surface of the photosensitive drum 19 or the moving speed of the surface of the registration roller 22. Is prevented, stable transfer is enabled, and the quality of the formed image can be improved.

Further, since the sheet is prevented from being lifted, the occurrence of a jam can be reduced, and the transfer and separation can be reliably performed.

Since the expansion and contraction of the transfer belt 18 itself can be suppressed, the repetitive stress on the transfer belt 18 can be reduced, and the durability can be improved.

Since the surfaces of the photosensitive drum 19 and the transfer belt 18 move at the same speed, the sliding wear can be reduced, and the durability is improved.

In the above description, the transfer belt 1
8 describes a case in which a sheet is conveyed and applied to a belt for transferring a toner image onto the sheet.
The present invention is not limited to such a belt, and may be applied to a belt (an intermediate transfer belt or the like) for transferring a toner image directly onto a belt and then onto a sheet.

Even when applied to such a belt, the accuracy of the transfer position of the toner image can be improved, and the transfer performance of the transferred toner image is improved, which contributes to the improvement of the quality of the formed image.

[0093]

As described above, according to the present invention, the driving speed of the driving means is controlled based on the detection result of the detecting means for detecting the moving speed of the transfer / conveying belt at the predetermined position. The moving speed of the transfer conveyance belt can be set to a desired speed, and the conveyance performance is improved, and the quality is improved.

In addition, by controlling the driving speed on the upstream side and the driving speed on the downstream side of the transfer portion, unevenness in the transport speed is eliminated, and the transport performance is improved.

By controlling the moving speed of the transfer / conveying belt at a predetermined position to be equal to the moving speed of the surface of the image carrier, proper transfer becomes possible, which contributes to improvement of the quality of a formed image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration perspective view of a belt conveyance device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an image forming apparatus equipped with a belt transport device according to an embodiment of the present invention.

FIG. 3 is an electric system diagram of the belt transport device according to the embodiment of the present invention.

FIG. 4 is a graph showing a change over time of a belt speed of the belt conveyance device according to the embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a configuration of a belt conveyance device according to a conventional technique.

FIG. 6 is a schematic cross-sectional view of an image forming apparatus equipped with a transport device according to the related art.

[Explanation of symbols]

 2 Image Forming Unit 5 Image Forming Apparatus 18 Transfer Belt 19 Photosensitive Drum 24a, 24b Optical Sensor 26 CPU 35, 36 Stepping Motor 37 Upstream Drive Roller 38 Downstream Drive Roller 40 Belt Conveyor

Claims (6)

[Claims] 1. A belt conveyance device comprising: a transfer conveyance belt including a transfer section to which a toner image is transferred in a conveyance path; and a driving unit for driving the transfer conveyance belt. A belt conveying device, comprising: detecting means for detecting a moving speed at a position; and controlling a driving speed of the driving means based on a detection result of the detecting means. A first drive unit and a first detection unit disposed upstream of the transfer unit; and a second drive unit and a second detection unit disposed downstream of the transfer unit. The driving speed of the first driving means is controlled based on the detection result of the first detecting means, and the driving speed of the second driving means is controlled based on the detection result of the second detecting means. The belt conveyance device according to claim 1. 3. The transfer section is a contact section of an image carrier carrying a toner image to the transfer / transport belt, and the toner image carried on the surface of the image carrier is transferred toward the transfer / transport belt. The belt conveyance device according to claim 1, wherein the belt conveyance is performed. 4. The driving speed of the driving means or the driving speed of the image carrier is controlled so that the moving speed of the transfer / conveying belt at a predetermined position is equal to the moving speed of the surface of the image carrier. 4. The method according to claim 3, wherein
3. The belt transport device according to 1. 5. A toner image is transferred onto a sheet while transporting the sheet by a transfer transport belt provided in the belt transport device according to claim 1.
An image forming apparatus, wherein the toner image is fixed on a sheet. 6. A method according to claim 1, further comprising: transferring a toner image onto a transfer / conveying belt provided in the belt conveying device according to claim 1; and further transferring the toner image onto a sheet. An image forming apparatus for fixing the toner image on a sheet.