JP2020020949A - Fixing device, image forming apparatus, and image forming method - Google Patents

Abstract

To provide a fixing device and an image forming apparatus that can prevent adhesion of an opening portion during a fixing operation in a recording target medium in which two or more members are joined, such as a file wrapper and an envelope.SOLUTION: A fixing device 15 comprises: a fixing nip N that fixes a toner image to a recording target medium 33; conveying means that conveys the recording target medium 33 so that it passes through the fixing nip N; and control means 41 that controls the actuation of the conveying means. The conveying means includes a rotatable first conveying member 25 that is arranged close to the front side that is a surface of the recording target medium 33 on which a toner image is formed, and a rotatable second conveying member 29 that is arranged close to the back side of the recording target medium 33. The control means 41 controls the operation of the first conveying member 25 and second conveying member 29 such that the conveying members have the same linear velocity as each other during the conveyance of the recording target medium 33, and controls the operation of the first conveying member 25 and second conveying member 29 such that when the recording target medium 33 occupies a predetermined position during the passage through the fixing nip N, the linear velocity of either one of the first conveying member 25 or the second conveying member 29 exceeds the linear velocity of the other.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fixing device, an image forming apparatus, and an image forming method.

  2. Description of the Related Art Conventionally, a technique is known in which a toner image is fixed by heat or pressure on a recording medium formed by bonding two or more members, such as a wrapper or an envelope. In such a fixing technique, controlling the linear velocities on the front and back surfaces of the recording medium in accordance with various types of the recording medium is effective in accurately fixing the toner image to the recording medium. It is also known. Controlling the linear velocities of the front and back surfaces of the recording medium can be achieved by controlling the linear velocities of the rollers forming the fixing nip.

However, in a fixing device having such a configuration, when a recording medium to which two or more members, such as an envelope, are passed, a linear speed of each of the rollers constituting the roller pair changes. There has been a problem in that feeding, image disturbance, and wrinkling of conveyance occur.
In order to solve the above-mentioned problem, by appropriately setting the linear speeds of the fixing member and the pressing member constituting the roller pair during paper passing, a plurality of linear speeds can be obtained without deteriorating the life of the fixing member and the pressing member. A fixing device corresponding to a type of recording medium has been proposed (for example, refer to Patent Document 1).

However, in the conventional technology of fixing a toner image to a recording medium by applying heat and pressure, including the above-described technology, a recording medium to which two or more members such as envelopes and envelopes are joined is used. When passing the paper, the opening of the envelope or envelope is stuck due to heat or pressure, and it takes time to open the opening when enclosing other members with the recording medium on which the image has been formed. There is a problem that it takes.
The present invention solves the above-described problems, and in a recording medium to which two or more members such as envelopes and envelopes are joined, a fixing device capable of preventing sticking of an opening portion during a fixing operation, and An image forming apparatus is provided.

  The invention according to claim 1 includes a fixing nip for fixing a toner image on a recording medium, a conveying unit for conveying the recording medium to pass through the fixing nip, and a control unit for controlling an operation of the conveying unit. Wherein the transport unit includes a rotatable first transport member disposed on a front surface side of the recording medium on which the toner image is formed, and a rotatable first transport member disposed on the back surface side of the recording medium. A flexible second transport member, wherein the control means controls the operation of the first transport member and the second transport member so that the linear velocity is the same when transporting the recording medium; When the recording medium occupies a predetermined position during the passage through the fixing nip, the first conveying member or the second conveying member is moved such that the linear speed of one of the first conveying member and the second conveying member exceeds the other linear speed. The first transport member and the second transport member are moved. And controlling.

  According to the present invention, when the recording medium is conveyed, the control means controls the operation of the first conveyance member and the second conveyance member so that they have the same linear velocity, and a predetermined value is set while the recording medium passes through the fixing nip. When the position is occupied, since the operation of the first transport member and the second transport member is controlled such that the linear velocity of one of the first transport member and the second transport member exceeds the linear velocity of the other, The opening can be easily opened when an envelope is used as the recording medium, while preventing wrinkles from occurring in the recording medium.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a schematic diagram of a fixing device used in an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating behavior of an envelope at a fixing nip according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating wrinkles generated in an envelope. FIG. 3 is a schematic diagram illustrating a driving mechanism of the fixing device according to the embodiment of the present disclosure. FIG. 3 is a schematic diagram illustrating operation control of the fixing device according to the embodiment of the present disclosure. It is a block diagram of a control means used for one embodiment of the present invention.

FIG. 1 shows a color printer as an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the color printer 1 has a paper supply unit 3 having a plurality of paper supply trays 4 and 5 in which paper P as a recording medium is stored at a lower portion of an apparatus main body 2. An image forming section 6 for forming an image is provided above.
The image forming unit 6 includes image forming units 8Y, 8C, 8M, 8K each having a plurality of photosensitive drums 7Y, 7C, 7M, and 7K corresponding to respective colors of yellow, cyan, magenta, and black. And an intermediate transfer unit 13 having an intermediate transfer belt 12 which is a flexible intermediate transfer member wound around rollers 9, 10, and 11, and forming an electrostatic latent image on the outer peripheral surface of each photosensitive drum 7. A writing unit 14, a fixing device 15 for fixing the unfixed toner image T (see FIG. 2) on the paper P, and the like are provided. A paper transport path 16 including a plurality of transport roller pairs for transporting the paper P is formed between the paper feed unit 3 and the fixing device 15.

  The image forming units 8Y, 8C, 8M, and 8K include photoconductor drums 7Y, 7C, 7M, and 7K, a charging device, a developing device, a photoconductor cleaning device, and a static eliminator that are disposed around each photoconductor drum 7, respectively. , Each of which is configured to be detachable from the apparatus main body 2 individually. Each of the developing devices (not shown) contains yellow, cyan, magenta, and black toners, respectively. When the amount of each color toner in each developing device decreases, toner for replenishment is supplied from a toner bottle (not shown).

The intermediate transfer belt 12 is disposed to face each of the photosensitive drums 7, and is driven in a counterclockwise direction in FIG. 1 by driving any one of the rollers 9, 10, and 11 by a drive motor (not shown). You. Primary transfer rollers 17Y, 17C, 17M, and 17K as primary transfer units to which a transfer bias for primary transfer is applied are disposed inside the intermediate transfer belt 12 and at positions facing the respective photosensitive drums 7, respectively. Have been.
A belt cleaning device 18 that cleans the surface of the intermediate transfer belt 12 is provided at a position facing the roller 9. The intermediate transfer belt 12, each of the rollers 9, 10, 11, each of the primary transfer rollers 17, and the belt cleaning device 18 are integrally configured as a unit, and are configured to be detachable from the apparatus main body 2.

At a position facing the roller 11 via the intermediate transfer belt 12, a secondary transfer roller 19 as a secondary transfer unit to which a secondary transfer bias is applied is provided in a manner to contact the intermediate transfer belt 12. .
The optical writing unit 14 irradiates the light-modulated laser beam onto the surface of each photoconductor drum 7 to form an electrostatic latent image for each color corresponding to the surface of each photoconductor drum 7. In the present embodiment, the optical writing unit 14 is disposed below each image forming unit 8, and is configured so that laser irradiation is performed from below the apparatus to above the apparatus.

Next, the operation of the color printer 1 will be described.
When the image forming operation is started, each photosensitive drum 7 is rotationally driven clockwise by the operation of a driving unit (not shown), and the outer peripheral surface of each photosensitive drum 7 is given a predetermined polarity by each charging device (not shown). Is uniformly charged. The charged outer peripheral surface of each photoconductor drum 7 is irradiated with laser light from the optical writing unit 14, and an electrostatic latent image for each color is formed on the outer peripheral surface of each photoconductor drum 7. At this time, the image information to be exposed on each of the photosensitive drums 7 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The thus formed electrostatic latent image is visualized as a toner image by each color toner in each developing device when passing between each photosensitive drum 7 and each developing device.

When the intermediate transfer belt 12 travels counterclockwise by a driving force from a driving unit (not shown), the intermediate transfer belt 12 is formed on the outer peripheral surface of the photosensitive drum 7Y in the image forming unit 8Y occupying the most upstream position among the image forming units 8. The yellow toner image is primarily transferred onto the intermediate transfer belt 12 by the action of the primary transfer roller 17Y. The cyan toner image, magenta toner image, and black toner image formed in the other image forming units 8C, 8M, and 8K are superimposed and transferred on the primary-transferred yellow toner image. A full-color toner image is carried.
After the transfer of the toner image, the residual toner attached on the outer peripheral surface of each photoconductor drum 7 is removed from the outer peripheral surface of each photoconductor drum 7 by each photoconductor cleaning device. Each of the cleaned photosensitive drums 7 is subjected to a charge removing operation by a charge removing device, and the surface potential thereof is initialized to prepare for the next image formation.

  On the other hand, the paper P is fed from the paper feed tray 4 or the paper feed tray 5 by the rotation of the paper feed roller 20 or the paper feed roller 21 from the paper feed unit 3, and the fed paper P is fed into the paper transport path 16. It is. The fed sheet P is temporarily stopped at a pair of registration rollers 22 arranged on the upstream side of the secondary transfer roller 19 in the sheet transport direction. It is sent to the next transfer nip. At this time, a transfer voltage having a polarity opposite to the polarity of the toner charge of the toner image carried on the intermediate transfer belt 12 is applied to the secondary transfer roller 19, whereby the full-color toner image on the intermediate transfer belt 12 is And the secondary transfer is performed collectively.

The paper P on which the full-color toner image has been transferred is conveyed to the fixing device 15, and the full-color toner image on the paper P is melted and fixed on the paper P by the heat and pressure applied when passing through the fixing device 15. . The paper P on which the full-color toner image has been fixed is transported toward a discharge roller pair 23 disposed at the end of the paper transport path 16, discharged to the outside of the apparatus by the discharge roller pair 23, and disposed on the upper portion of the apparatus main body 2. The paper is discharged and stacked on the paper discharge tray 24 provided.
After transferring the full-color toner image onto the sheet P, the intermediate transfer belt 12 is cleaned of residual toner by a belt cleaning device 18 and is prepared for the next image formation.

  Next, the fixing device 15 will be described. As shown in FIGS. 1 and 2, the fixing device 15 includes a heat-resistant endless fixing belt 28 that is wound around a fixing roller 25, a heating roller 26, and a tension roller 27 and is driven to run. And a pressure roller 29 that is disposed in pressure contact with the fixing roller 25 through the fixing roller 25. The fixing belt 28 and the pressure roller 29 form a fixing nip N for fixing the unfixed toner image T on the sheet P to the sheet P, and the fixing toner image T1 is formed on the surface of the sheet P passing through the fixing nip. Is formed. The fixing device 15 is configured to be detachable from the apparatus main body 2.

  The fixing roller 25 and the heating roller 26 have their respective spindles rotatably supported by the casing 35 of the fixing device 15 so that the respective rotation center positions are fixed, and the interval between the respective axes is kept constant. ing. The tension roller 27 is disposed in a space inside the fixing belt 28 such that its peripheral surface is in contact with the inner peripheral surface of the fixing belt 28. A biasing force is applied to the tension roller 27 by the compression spring 30 in a direction of pressing the fixing belt 28 from the inside to the outside.

  The fixing roller 25 is made of an elastic material such as rubber, and the heating roller 26 is made of a hollow metal roller. Inside the metal roller 26, a heater unit 31 as a heating source including a pair of heating elements 31a and 31b extending in the axial direction of the heating roller 26 is provided. As the heating element, a halogen heater or another heater is used. The number of heaters constituting the heater unit 31 is not limited to two, and may be one or three or more. Further, a configuration may be employed in which the heating roller 26 is disposed outside the heating roller 26 as a heating source instead of inside, and heats the heating roller 26. The fixing roller 25 is driven to rotate by a motor 32, and the fixing belt 25 is driven to run counterclockwise in FIG. 2 with the rotation of the fixing roller 25, and the pressing roller 29 pressed against the fixing belt 28 is shown in FIG. In step 2, it is driven to rotate clockwise.

Next, a case where an envelope 33 is passed through the fixing device 15 instead of the paper P as a recording medium will be described. As shown in FIG. 3, the envelope 33 is formed by stacking two sheets of a front side sheet 33 a that is an image side and a back side sheet 33 b that is a non-image side when one-sided image is formed. Both ends in the axial direction of the fixing roller 25 and the leading end in the sheet conveying direction are glued together and have an opening that is opened only at the rear end in the sheet conveying direction.
When the envelope 33 moves through the fixing nip N, the linear velocity difference Δv between the linear velocities v1 and v2 between the surface 28a of the fixing belt 28 and the surface 29a of the pressure roller 29 is almost 0, and the unfixed toner image T is carried. The linear velocity vf2 of the back side paper 33b is passed as a linear velocity difference Δvf ≒ 0 with respect to the linear velocity vf1 of the front side paper 33a.

If there is a linear velocity difference Δv, when a recording medium having two or more members such as an envelope 33 overlapped on the fixing nip N and the end surfaces thereof are joined, the surface of the envelope 33 only reaches the central portion in the axial direction. The positional deviation accumulates between the side sheet 33a and the back side sheet 33b, and as a result, rib-like wrinkles 34 are generated on the surface of the envelope 33 as shown in FIG.
Although the wrinkles 34 do not occur in the envelope 33 that passes through the fixing nip N when the linear velocity difference Δv is almost 0, the two sheets, the front side paper 33a and the back side paper 33b, do not have any positional deviation. Due to the heating and pressurizing in the above, the opening 33c is brought into close contact. In many cases, the contents of the envelope 33 are inserted immediately after being discharged from the image forming apparatus. Therefore, if the opening 33c is stuck in close contact, the enclosing operation cannot be performed quickly.
Therefore, if a linear velocity difference Δv is arbitrarily generated in the vicinity of the opening 33c and a positional shift occurs so that the two sheets do not adhere to each other, the sticking of the opening 33c can be suppressed. Hereinafter, the configuration and operation of the present invention will be described.

FIG. 5 shows a driving mechanism of the fixing device 15. An input gear 36 is attached to the support shaft 25a of the fixing roller 25, and a drive gear 37 and a driven gear 38 mesh with the input gear 36, respectively. The driving gear 37 is connected to a motor 32 as driving means. The driving gear 37 rotates by receiving a rotational driving force from the motor 32, and the input gear 36 meshed with the driving gear 37 rotates, so that the fixing roller 25 is rotated. The fixing belt 28 is driven to rotate, and as a result, the fixing belt 28 is driven to run.
The driven gear 38 is attached to a support shaft 29 b of the pressure roller 29, and a one-way electromagnetic clutch 39 is interposed between the support shaft 29 b and the driven gear 38. In the one-way electromagnetic clutch 39, the inner ring portion is integrally connected to the support shaft 29b, and the outer ring portion is fixed to the driven gear 38. The one-way electromagnetic clutch 39 is turned on and off based on the electric signal. When the one-way electromagnetic clutch 39 is turned on, the transmission of the rotational force from the input gear 36 to the driven gear 38 is allowed, and the transmission of the rotational force from the driven gear 38 to the input gear 36 is performed. Cut off. This prevents the pressure roller 29 from slipping with respect to the fixing roller 25, and allows the rollers 25 and 29 to rotate in synchronization.

With the above-described configuration, the fixing roller 25 and the pressing roller 29 rotate in synchronization with each other, so that it is possible to prevent the fixing belt 28 and the fixing roller 25 from being hurt by friction with the pressing roller 29, and to reduce the durability of these members. Performance can be improved. Further, the provision of the one-way electromagnetic clutch 39 can absorb a difference in peripheral speed between the fixing belt 28 and the pressure roller 29, and can prevent the envelope 33 to be conveyed from having wrinkles 34.
On the other hand, when the one-way electromagnetic clutch 39 is off, the drive transmission from the input gear 36 to the driven gear 38 is not performed, and only the fixing roller 25 is driven to rotate. As a result, the pressure roller 29 is not driven and does not rotate synchronously with the fixing roller 25, so that a peripheral speed difference occurs between the fixing roller 25 and the pressure roller 29.

The operation of the fixing device 15 having the above-described configuration in the present invention will be described. Prior to the description of this operation, control means for controlling the operation of the fixing device 15 will be described.
As shown in FIG. 6, inside the fixing device 15, a sensor 40 for detecting the leading end of the conveyed envelope 33 is provided. When the sensor 40 detects the leading end of the envelope 33, the sensor 40 transmits a detection signal to a control unit 41 described later.
FIG. 7 is a control block diagram of the control means 41 used in one embodiment of the present invention. The control means 41, which comprises a well-known macro computer and has a CPU, a ROM, a RAM, and the like (not shown), controls the drive of the motor 32 and receives a detection signal from the sensor 40 to control the on / off of the one-way electromagnetic clutch 39.

  When the color printer 1 is activated and a print switch (not shown) is turned on, the motor 32 is driven by a command from the control means 41 and the one-way electromagnetic clutch 39 is turned on. As a result, the rotational force is transmitted from the input gear 36 to the driven gear 38, the fixing belt 28 is driven to run in the counterclockwise direction in FIG. 6, and the pressure roller 29 rotates in synchronization with the moving speed of the fixing belt 28. Driven. With this configuration, since the fixing belt 28 and the pressure roller 29 rotate in synchronization with each other, it is possible to prevent the fixing belt 28 and the fixing roller 25 from being damaged by friction with the pressure roller 29, and to reduce the durability of these members. Can be improved.

  Next, a case where the envelope 33 is used as a recording medium will be described. As shown in FIG. 2, the envelope 33 to which the unfixed toner image T has been transferred is sent into the casing 35 of the fixing device 15 and guided to the fixing nip N by the guide member 42 provided in the casing 35. . The control means 41 recognizes in advance the length L1 of the envelope 33 in the transport direction (see FIG. 6), and further determines the position of the envelope 33 in the fixing device 15 from the timing when the tip of the envelope 33 is detected by the sensor 40. We recognize that it is being transported. From the opening 33c, which is the rear end of the envelope 33, to the position of a predetermined length L2 (see FIG. 6), the control means 41 moves the one-way electromagnetic clutch 39 to the fixing nip N with respect to the envelope 33. Through.

At this time, since the one-way electromagnetic clutch 39 is turned on, the fixing belt 28 and the pressure roller 29 rotate synchronously, and there is no difference in peripheral speed between the fixing belt 28 and the pressure roller 29. The generation of wrinkles 34 on the envelope 33 can be effectively prevented.
When the control unit 41 recognizes that the portion from the rear end of the envelope 33 to the position L2 has passed the fixing nip N, the control unit 41 sends a command to turn off the one-way electromagnetic clutch 39. As a result, the rotational driving force from the input gear 36 is not transmitted to the driven gear 38, and only the fixing roller 25 is driven to rotate, and the pressure roller 29 is driven and rotated by the movement of the traveling fixing belt 28. A peripheral speed difference occurs between the pressure roller 29 and the pressure roller 29.

  As described above, when a peripheral speed difference occurs between the fixing roller 25 and the pressure roller 29 near the opening 33c of the envelope 33, the front side paper 33a and the back side paper 33b constituting the opening 33c of the envelope 33 are formed. And the sheet 33a, 33b in the opening 33c is prevented from sticking. In this configuration, the fixing roller 25 functions as a first conveying member, the pressure roller 29 functions as a second conveying member, and the one-way electromagnetic clutch 39 functions as a driving force transmitting unit.

According to the present invention, when the envelope 33 is conveyed, the control means 41 controls the operation of the fixing roller 25 and the pressure roller 29 so that they have the same linear velocity, and the envelope 33 passes through the fixing nip N. When the fixing roller 25 and the pressure roller 29 are occupied at a predetermined position, the operation speed of the fixing roller 25 and the pressure roller 29 is controlled so that the linear speed of the fixing roller 25 exceeds the linear speed of the pressure roller 29. , The opening 33c of the envelope 33 can be easily opened.
In the above-described embodiment, the configuration has been described in which the driving force from the driving gear 37 is transmitted to the fixing roller 25 via the input gear 36 and further transmitted to the pressure roller 29 via the driven gear 38. And transmitted to the fixing roller 25 via the driven gear 38.

  In the above embodiment, the fixing roller 25 serving as the first transport member and the pressure roller 29 serving as the second transport member are shown as control objects whose operations are controlled by the control unit 41. However, the object to be controlled by the control means 41 to which the present invention can be applied is not limited to this, and may be the discharge roller pair 23 shown in FIG. In this case, by controlling the operation of one of the discharge roller pairs 23 in the same manner as the fixing roller 25 and the other of the discharge rollers 23 in the same manner as the pressure roller 29, the same operation as in the above-described embodiment is achieved. The effect can be obtained.

  In the above-described embodiment and each modified example, an example in which a color printer is used as the liquid ejection device has been described. However, the present invention is not limited to this, and can be applied to a printer, a facsimile, a multifunction peripheral, and the like. . Further, in the present embodiment and the modified example, the configuration in which the envelope 33 is used as the recording medium on which an image is formed has been described. However, the recording medium is not limited to an envelope or a wrapper, and is thick paper, a postcard, an envelope, a plain paper. , Thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, OHP film, resin film, etc. You may.

  As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to such specific embodiments, and unless otherwise specified in the above description, the present invention described in the claims is not limited thereto. Various modifications and changes are possible within the scope of the gist. The effects described in the embodiments of the present invention merely exemplify the most preferable effects resulting from the present invention, and the effects according to the present invention are limited to those described in the embodiments of the present invention. is not.

1 Image Forming Apparatus 15 Fixing Device 23 Discharge Roller Pair 25 First Transport Member (Fixing Roller)
29 Second transport member (pressure roller)
32 Driving means (motor)
33 Recording medium (envelope)
33c Opening 39 Driving force transmission means (one-way electromagnetic clutch)
41 Control means N Fixing nip

JP 2011-191570A

Claims (7)

A fixing nip for fixing a toner image on a recording medium,
Conveying means for conveying the recording medium to pass through the fixing nip,
Control means for controlling the operation of the transport means,
The transport unit includes a rotatable first transport member disposed on a front surface side of the recording medium on which the toner image is formed, and a rotatable first transport member disposed on a back surface side of the recording medium. And two conveying members,
The control unit controls the operation of the first transport member and the second transport member so that the linear velocity becomes the same as each other when the recording medium is transported, so that the recording medium is passing through the fixing nip. When occupying a predetermined position, the first transport member and the second transport member are moved such that the linear velocity of one of the first transport member and the second transport member exceeds the linear velocity of the other. A fixing device that controls operation. The fixing device according to claim 1, wherein
A driving unit that rotationally drives one of the first transport member and the second transport member,
A driving force transmitting unit that can selectively take a transmitting state of transmitting the driving force of the driving unit to the other of the first conveying member or the second conveying member or a blocking state of blocking the driving force;
The fixing device according to claim 1, wherein the control unit switches the driving force transmission unit from the transmission state to the cutoff state at the predetermined position. The fixing device according to claim 1, wherein
The fixing device according to claim 1, wherein the first conveying member is a fixing member, and the second conveying member is a pressing member that presses the recording medium against the fixing member to form the fixing nip. The fixing device according to claim 1, wherein
A fixing member, a pressing member that presses the recording medium against the fixing member to form the fixing nip, a first roller and a second roller that are disposed downstream of the fixing nip in the recording medium conveyance direction. A discharge roller pair comprising a roller and
The fixing device according to claim 1, wherein the first transport member is the first roller, and the second transport member is the second roller. The fixing device according to any one of claims 1 to 4,
The fixing device according to claim 1, wherein the recording medium is a bag, and the predetermined position is a position corresponding to an opening of the bag.   An image forming apparatus comprising the fixing device according to claim 1. A fixing nip for fixing a toner image on a recording medium,
Transport means for transporting the recording medium to pass through the fixing nip,
The transport unit includes a rotatable first transport member disposed on a front surface side of the recording medium on which the toner image is formed, and a rotatable first transport member disposed on a back surface side of the recording medium. And two conveying members,
When the recording medium is conveyed, the first conveyance member and the second conveyance member are driven so as to have the same linear velocity, and the recording medium occupies a predetermined position while passing through the fixing nip. And operating the first transport member and the second transport member such that a linear velocity of one of the first transport member and the second transport member exceeds a linear velocity of the other. Image forming method.

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