JPH06149110A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent image irregularities in an unfixed toner image by preventing the leading edge of a paper sheet from colliding with the surface of a thermal roller 50. CONSTITUTION:This image forming device is provided with an image forming part including an imaging unit, etc., a fixing/carrying device 16 fixing a toner image formed on the surface of the paper sheet by the image forming part, a carrying guide 45 and a lower entering guide 49. The carrying guide 45 has prescribed surface resistivity and guides the paper sheet from the image forming part to the side of the fixing/carrying device 16. The lower entering guide 49 is a member for guiding the carried form between the thermal roller 50 and a pressure roller 51 and has the surface resistivity lower than that of the carrying guide 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an image forming apparatus, and more particularly to
The present invention relates to an image forming apparatus having a conveying unit that forms an image with a magnetic toner on a surface of a sheet and conveys the sheet to a fixing unit.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a facsimile machine, a toner image is transferred onto a sheet in an image forming section,
The toner image on the paper is fixed in the fixing unit. Therefore, the sheet on which the unfixed toner image is formed is conveyed by the conveying section between the image forming section and the fixing device.

When a sheet having an unfixed toner image formed on its surface is conveyed to the fixing section, it is necessary to prevent the unfixed toner image from being disturbed (image dust). For this reason, 1-59
In Japanese Patent No. 581, the surface resistivity of the guide member arranged on the downstream side of the conveyor belt is 1 × 10 ⁶ ohms or more and 1 × 10 ⁹ or more.
It is shown to be set within the range of ohms or less. In such an apparatus, since the guide member that guides the conveyance of the sheet has a predetermined electric resistance, the electric charge charged on the sheet does not suddenly escape, so that the carrying force of the unfixed toner image on the sheet is increased. It is ensured and the dust of the image can be suppressed.

[0004]

In the prior art as described above, since the guide member for guiding the paper to the nip of the fixing roller has a predetermined electric resistance, it has the same polarity as the electric charge charged on the paper. The electric charge easily charges the guide member. In this case, the leading edge of the sheet sent to the surface of the guide member may float up from the guide member due to the electric repulsive force. Then, the leading edge of the sheet may not be guided to the nip position of the fixing roller, and the leading edge of the sheet may collide with the surface of the heat roller. When the leading edge of the paper collides with the surface of the heat roller, the impact causes the unfixed toner image on the surface of the paper to be disturbed.

An object of the present invention is to prevent the leading edge of the sheet guided by the guide member from colliding with the surface of the fixing roller and prevent the unfixed toner image from being disturbed.

[0006]

An image forming apparatus according to the present invention fixes an unfixed toner image formed on a sheet surface by an image forming section for forming an image with magnetic toner on the sheet surface. The fixing unit includes a fixing unit, a conveying unit, and an entrance guide member. The transport unit includes a transport guide member that has a predetermined surface resistivity and that guides the sheet from the image forming unit to the fixing unit. The entrance guide member is a member for guiding the sheet conveyed by the conveying unit to the fixing portion, and has a smaller surface resistivity than the conveyance guide member.

[0007]

In the image forming apparatus according to the present invention, the toner image is formed on the surface of the sheet in the image forming section, the sheet is conveyed to the fixing section by the conveying means including the conveying guide member, and further, the fixing section is fixed by the entrance guide member. Will be guided to. At this time, since the transport guide member has a predetermined surface resistivity, charges accumulated on the sheet on the transport guide member do not suddenly escape, and image dust can be prevented. Further, the approach guide member has a smaller surface resistivity than the transport guide member, and therefore the approach guide member is less likely to be charged. Therefore, the electric repulsive force generated between the sheet and the entrance guide member can be reduced, and the sheet can be prevented from floating on the entrance guide member and colliding with the roller or the like that constitutes the fixing unit. Therefore, the disturbance of the toner image on the sheet surface due to the impact at the time of collision can be suppressed.

In an apparatus in which the sheet conveying path is curved downward, the sheet conveying speed in the fixing unit is made faster than the sheet conveying speed in the image forming unit, so that the leading edge of the sheet is conveyed to the fixing unit. Then, the sheet is separated from the entry guide member, and it is possible to prevent the electric charge accumulated in the sheet from rapidly escaping through the entry guide member.
Therefore, the surface resistivity of the approach guide member can be made extremely small, and the electric repulsive force generated between the sheet and the approach guide member can be further reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overall Structure FIG. 1 is an external perspective view of a facsimile apparatus to which an embodiment of the present invention is applied, and FIG. 2 is a schematic vertical sectional view of the structure. As shown in these drawings, the present apparatus is provided with a reading unit 1 arranged at an upper portion for reading image information of a document, and an output unit 2 arranged at a substantially central portion of the apparatus for forming received image information on a sheet surface. And a paper feed unit 3 which is arranged at the bottom of the apparatus and supplies paper to the output unit 2.

The reading section 1 has a document table 5 on which a document is placed.
And a document transport section 6 for transporting the document, and a document discharge tray 7 for storing the document discharged from the document transport section 6. An image information reading sensor 8 for reading the image information of the original is arranged in the original conveying section 6. An operation panel 9 having various keys and a display unit is arranged on the upper surface of the device. Furthermore, a handset 10 is arranged on top of the device. The output unit 2 includes an imaging unit 11 including a photosensitive drum and a developing unit 14 including a developing roller 12 and a toner cartridge 13.
And an image according to the received information
Laser device 15 for forming on the photosensitive drum surface of
And a fixing and conveying device 16 for fixing the toner image formed on the surface of the paper by the imaging unit 11. A paper discharge tray 17 is provided on the downstream side of the fixing and conveying device 16. The paper feeding unit 3 is a paper feeding cassette 21 that is detachable from an opening 20 provided at the bottom of the apparatus body, and a paper feeding device that feeds paper from the paper feeding cassette 21 and supplies the paper to the output unit 2. 22 and 22. The sheet feeding device 22 has a registration roller 23 for controlling the sheet feeding timing.

The apparatus main body is divided into an upper case 25 and a lower case 26, and the upper case 25 has a hinge portion 27.
It can be freely opened and closed with respect to the lower case 26. In the upper case 25, the reading unit 1 and the imaging unit 11, the developing unit 14, and the laser device 15 of the output unit 2 are included.
Are mounted, and the lower case 26 is provided with the fixing / conveying device 16 of the output unit 2 and the paper feeding unit 3.

Image Unit and Conveyance Section FIG. 3 is an enlarged view of the imaging unit 11 and the fixing conveyance device 16 of the output section 2. The imaging unit 11 has a unit case 30. A mounting flange portion 31 protruding upward is formed on the upper portion of the unit case 30. A long hole 31a that is long in the vertical direction is formed in the mounting flange portion 31, and the hole 31a is locked to a pin 32 provided on the body frame side.
With such a configuration, the imaging unit 11 can move in the vertical direction within a predetermined range. On the other hand, the lower portion of the unit case 30 is formed with a locking portion 33 protruding downward. The locking portion 33 is locked to a pin 34 provided on the main body frame side to lock the imaging unit 30.
The vertical positioning of is performed. A photosensitive drum 35 is rotatably attached to the end of the imaging unit 11 on the developing roller side. Further, a cleaning blade 36 for removing the toner remaining on the surface of the photosensitive drum 35 is provided on the side of the photosensitive drum 35. The toner removed from the surface of the photoconductor drum 35 by the cleaning blade 36 is stored in the storage portion 37 in the unit case 30.

Below the photosensitive drum 35, a transfer roller 40 for transferring the toner image formed on the photosensitive drum 35 onto a sheet is arranged. The transfer roller 40 is
It is rotatably supported by the frame on the lower case 26 side. A main charging device 41 for charging the surface of the photoconductor drum 35 is arranged above the photoconductor drum 35. As described above, the imaging unit 11, the developing unit 14, the transfer roller 40, and the main charging device 41 constitute an image forming unit that forms a toner image on the surface of the paper. In this embodiment, the photosensitive drum 35 is negatively charged, the toner has a positive charge, and the sheet is negatively charged by the transfer roller 40.

A transport guide 45 for guiding a sheet having a toner image formed on its surface toward the fixing transport device 16 is disposed downstream of the image forming portion in the sheet transport direction. As shown in FIG. 4, the conveyance guide 45 is continuous with a lower entry guide 49 fixed to the base 48 of the fixing conveyance device 16, and the conveyance path formed by both members 45 and 49 is curved downward. is doing. The transport guide 45 is made of antistatic resin. A resin having a surface resistivity of 10 ¹² Ω is used as the antistatic resin. Also, the lower approach guide 4
No. 9 is formed of a zinc-treated steel plate and has a surface resistivity of 1
Those having a resistance of less than 0 ⁷ Ω and a resistance of about 10 ² Ω are used. An intermediate frame 46 is arranged above the transport guide 45 and close to the imaging unit 11. The intermediate frame 46 is made of, for example, an iron plate material and serves as a conductor. The intermediate frame 46 is in contact with the imaging unit 11 via the flange portion 46b, and is grounded via another frame. In this intermediate frame, notches 46a are formed at two end portions in the width direction of the conveyed sheet.

Fixing / Conveying Device The fixing / conveying device 16 has, as shown in FIGS. 3 and 4, a heat roller 50 having a heater 50a therein and a pressure roller 51 which can be pressed against the heat roller 50. is doing. A conductive polytetrafluoroethylene (PTFE) resin is applied to the surface of the heat roller 50, and its surface resistivity is 10 ⁶ Ω. A fixing upper housing 52 is arranged on the side and above the heat roller 50 so as to cover the heat roller 50. The upper fixing housing 52 is made of a heat resistant resin having a heat resistant temperature of about 200 ° C. such as polybutylene terephthalate (PBT), extends in the axial direction of the heat roller 50, and is attachable to and detachable from a lower fixing housing (not shown). . Further, the lower fixing housing is provided with rollers 50, 51.
It is fixed to a pair of fixing frames 53 provided at both ends in the axial direction. In the center of the upper wall of the fixing upper housing 52,
A groove 52a is formed along the roller axial direction, and a mounting member 54 is detachably inserted into this groove 52a.
The mounting member 54 has a recess 54a at the center, and a cleaning member 55 for cleaning the surface of the heat roller 50 is attached to the lower end thereof.

Further, on the side wall 52b of the fixing upper housing 52 on the paper discharge side, two cutouts 52c are formed in the roller axial direction.
Are formed. A pin-shaped support portion 56 is formed in the notch 52c, and a peeling claw 57 is formed on the support portion 56.
Is rotatably supported. The peeling claw 57 is the support portion 5.
6, the fulcrum portion 57a, the peeling portion 57b extending from the fulcrum portion 57a toward the heat roller 50, and the fulcrum portion 57a.
From the side wall 52b to the outside of the lever portion 57c. The peeling portion 57b is pressed against the surface of the heat roller 50 by a torsion spring 58. Also, the lever portion 57c
Extends from the notch 52c so as to be exposed to the outside of the side wall 52b. When the fixing upper housing 52 is attached or detached,
As shown in FIG. 4, the operator attaches the lever portion 57c to the side wall 52.
By pushing to the b side, the peeling portion 57b at the tip is separated from the surface of the heat roller 50.

With such a peeling claw 57, the paper wound around the heat roller 50 can be peeled from the surface of the heat roller 50 with a very simple mechanism. Moreover, when the fixing upper housing 52 is attached or detached at the time of parts replacement, the tip of the peeling claw 57 can be reliably separated from the surface of the heat roller 50 by gripping the lever portion 57c, and the heat at the time of parts replacement, etc. Damage to the surface of the roller 50 can be avoided.

As shown in FIGS. 3 and 5A, pressure contact release levers 65 made of polyphenylene sulfide (PPS) resin or the like are arranged at both ends of the heat roller 50 in the axial direction. The heat roller 50 is rotatably supported by the fixing frame 53 by the bearing portion 65 a of the pressure release lever 65. A pinion gear 69 for driving the heat roller 50 is attached to the back side (right side in FIG. 5A) of the heat roller 50. The pinion gear 69 is formed of a synthetic resin material such as a polyamide-imide resin having a heat insulating property.

The heater 50a is arranged inside the heat roller 50 along the axial direction of the heat roller 50. Heater 5
As shown in FIG. 5 (b), the heat distribution characteristic of 0a is such that by changing the winding density, the amount of heat generated is large on the front side, low on the middle side, higher than the middle side on the back side, and lower than the front side. It has become the amount. The reason for setting such heat distribution characteristics is that the two heat insulating members of the bearing portion 65a and the pinion gear 69 are mounted on the back side, so that the heat diffusion action is weaker than that on the front side, and uniform heat distribution is achieved. This is because the surface temperature on the back side becomes higher than that on the front side when heated by a heater having thermal characteristics. In addition, in this type of device, cooling is performed by a fan, but the direction of the cooling air of the fan is usually the front side as indicated by the arrow in order to prevent hot air from blowing to the operator side. From the back. Therefore, since the temperature of the cooling air is low on the front side, the cooling effect is high, and on the back side, the cooling effect is low. Therefore, if the heat distribution characteristics are uniform, the surface temperature on the back side becomes higher than that on the front side. Considering these points, the heat generation amount on the front side is set higher than that on the back side. Thereby, the temperature unevenness on the surface of the heat roller 50 is reduced.

On the other hand, the pressure roller 51 has its shaft 61 supported by the fixing frame 53 via a bearing 62 and a spring 63. A protrusion 62 a that protrudes upward is formed on the upper portion of the bearing 62. The bearing 62 is movable up and down with respect to the frame 53, and is constantly urged toward the heat roller 50 by a spring 63. The pressure release lever 65, the bearing 62, and the spring 63 are arranged at both ends in the roller axial direction.

The pressure contact release lever 65 is concentrically and rotatably mounted on the heat roller 50. The pair of press contact release levers 65 includes a bearing portion 65a that supports the heat roller 50, a cam portion 65b formed in a part of the bearing portion 65a, and an L-shaped lever that extends from the bearing portion 65a toward the image forming portion. Part 65
and c. This pressure release lever 65 is
A spring 66, one end of which is locked to the fixing frame 53, urges it counterclockwise in FIG. When the imaging unit 11 is mounted on the apparatus, the tip of the lever portion 65c is notched by the notch 46 of the intermediate frame 46.
It passes through a and is in contact with the bottom surface of the unit case 30 of the imaging unit 11, whereby the lever portion 65c
Is rotated clockwise against the biasing force of the spring 66. In this state, the cam portion 65b is separated from the bearing protrusion 62a of the pressure roller 51. For this reason,
The pressure roller 50 is pressed against the heat roller 51 by a spring 63.

As shown in FIGS. 6 and 7, two notches 70a and 70b are formed in the side wall 52d of the fixing upper housing 52 on the image forming portion side, and the notch 70 is formed.
A locking portion 71 is formed between a and 70b. The thermal fuse 7 is inserted so that the locking portion 71 passes inside the housing.
2 is locked, and both ends of the thermal fuse 72 are screwed to the outer surface of the housing side wall 52d. Although not shown, an electric wire connected to the internal heater 50a of the heat roller 50 is connected to the screw stopper. Upper entry guides 52e and 71a are formed at the lower end of the side wall 52d and the locking portion 71 so that the supplied sheet is guided between the heat roller 50 and the pressure roller 51. With such a configuration, when the thermal fuse 72 is arranged close to the heat roller 50, the gap between the two can be easily and accurately adjusted.

Further, as shown in FIGS. 4 and 6, a notch 70c is formed in a part of the side wall 52d of the upper fixing housing 52 on the sheet introduction side. The mounting member 73 is fixed to the side wall 52d formed with the notch 70c with a screw. A thermistor 74 is fixed to the lower end of the mounting member 73. The thermistor 74 is an element for detecting the surface temperature of the heat roller 50. The temperature data detected by the thermistor 74 is input to a temperature control circuit (not shown), whereby the heater 50 inside the heat roller 50 is heated.
The power supplied to a is controlled, and the surface temperature of the heat roller 50 is controlled to be 185 ° C.

A fixing cover 59 is mounted on the side of the side wall 52d of the upper fixing housing 52 on the sheet introduction side.
The fixing cover 59 is formed of a resin material such as polyethylene terephthalate (PET) having a higher heat resistance temperature than the upper fixing housing 52. The fixing cover 59 is a member for covering the screw for mounting the mounting member 73, the screw for mounting the thermal fuse 72, and the wiring 60 connected to the thermal fuse and the thermistor. The fixing cover 59 is arranged in parallel with the side wall 52d with a predetermined gap from the side wall 52d, and is provided between the fixing frames 53 before and after the apparatus. The upper part and the lower part of the fixing cover 59 are respectively locked in locking notches provided in the upper fixing housing 52. The fixing cover 59
A plurality of ribs 59a are provided in a predetermined range in the vertical direction on the lower side of the thermistor 74 on the back side opposite to the heat roller 50.

In such a structure, the heat roller 50 becomes abnormally high in temperature for some reason, and when the fixing upper housing 52 exceeds the heat resistant temperature, the side wall 52d is thermally deformed so as to spread outward. As a result, the mounting member 73 and the thermistor 74 also move in a direction away from the heat roller 50. When the thermistor 74 is separated from the heat roller 50, the thermistor 74 is heated even though the heat roller 50 is at a high temperature.
Detects temperature data lower than the actual surface temperature of the heat roller 50. However, in this embodiment, since the rib 59a of the fixing cover 59 is disposed on the back side of the thermistor 74, even if the side wall 52d deforms and the thermistor 74 tries to deform outward, the deformation is restricted by the rib 59a. The position of the thermistor 74 is maintained at the almost initial position.

Even when the upper fixing housing 52 is thermally deformed, an air layer (gap) as a heat insulating layer is interposed between the side wall 52d and the fixing cover 59, so that the fixing cover 59 is deformed together with the side wall 52d. There is no such thing. Further, since the fixing cover 59 is made of a resin material having higher heat resistance than the upper fixing housing 52, the fixing cover 59 has less thermal deformation than the side wall 52d.

Further, the rib 59a of the fixing cover 59 is provided.
Since the deformation of the locking portion 71 to which the thermal fuse 72 is locked is restricted, the thermal fuse 72 can be prevented from separating from the surface of the heat roller 50, and the thermal fuse 72 is melted at a desired temperature to generate electric power. Can be stopped. As shown in FIGS. 3 and 6, the intermediate frame 46
Also extends above the fixing / conveying device 16, and the fixing / conveying device 1
A partition frame 47 for partitioning 6 and the upper part thereof is configured. The partition frame 47 has both left and right side portions inclined upward so that the portion directly above the mounting member 54 is the lowest, and the inclined surfaces 47a and 47b and the inclined surface 47 are formed.
a, 47b and a collecting portion 47c on which water droplets adhering to them are concentrated.

As shown in FIGS. 3 and 4, a pair of discharge rollers 75 and 76 are arranged on the downstream side of the fixing and conveying device 16. The upper roller 75 is fixed to the drive shaft 77 supported by the fixing frame 53, and is formed of an elastic body such as rubber or sponge. On the other hand, the lower roller 76
Are rotatably supported by a fixing lower housing (not shown). The lower roller 76 is made of, for example, polyacetal (P
It is made of a resin such as OM) and has a hardness higher than that of the upper roller 75. As shown in FIGS. 8 and 9, a plurality of U-shaped grooves 76a are formed on the outer peripheral surface. The lower roller 76 has, for example, an outer diameter of 12 mm,
Groove 7 with a roughly cylindrical shape with an inner diameter of 4.3 mm and a thickness of 8 mm
6a has a width dimension of 1.2 mm and has an equal angular interval of 24 ° of 15 mm.
It is provided individually. In addition, as shown enlarged in FIG.
The angle α formed between the groove end surface and the outer peripheral surface of the groove 76a is set to 90 ° or less.

In such a configuration, the lower roller 76 is shown in FIG.
When the sheet is discharged by rotating in the direction of arrow A, the upper roller 75 is elastically deformed so that a part thereof bites into the groove 76a and pushes the sheet into the groove 76a. Then, the trailing edge of the sheet gradually enters the groove 76a as the sheet rotates, and the sheet is reliably delivered to the discharge tray side. Figure 10
As shown in FIG. 7, a mechanism for releasing the driving force of the discharge rollers 75 and 76 is provided further behind the fixing frame 53 at the rear of the apparatus. This mechanism will be described.

A drive gear 78a is fixed to the heat roller 50 on the rear end side of the apparatus. The upper roller 7 of the discharge roller
A driven gear 78b is fixed to the end of the drive shaft 77 to which 5 is fixed. The drive gear 78a and the driven gear 78b are connected by an intermediate gear 78c. The intermediate gear 78c is attached to the intermediate shaft 79. The intermediate shaft 79 is rotatably supported by a bearing 86 that can move up and down with respect to the fixing frame 53. The bearing 86 is constantly urged downward by the spring 87.

On the other hand, the shaft 61 of the pressure roller 51 is engaged with a long hole 88a formed at one end of the releasing arm 88. The release arm 88 is rotatably attached to the fixing frame 53 by a pin 89. Further, an inclined surface 88b is formed at the other end of the release arm 88, and the inclined surface 88b can contact the intermediate shaft 79. With such a configuration, when the release arm 88 is rotated clockwise in FIG. 10, the inclined surface 88b causes the intermediate shaft 79 to rotate.
Can be pushed upward to release the meshing between the intermediate gear 78c and the driven gear 78b.

Paper Conveying System Next, the conveyance of the paper will be described with reference to the schematic diagram of the conveying system shown in FIG. In this example, the sheet conveyance system is composed of a registration roller 23, a conveyance guide 45, a lower entry guide 49, fixing roller pairs 50 and 51, and discharge roller pairs 75 and 76 from the upstream side in the sheet conveyance direction. . In addition,
The photosensitive drum 35 and the transfer roller 40 are not in contact with each other.
The guide surface of the transport guide 45 is concave. Therefore, the sheet sent from the photoconductor drum 35 is bent on the upper surface of the conveyance guide 45 and is guided between the heat roller 50 and the pressure roller 51 along the lower entry guide 49. And
After the leading edge of the sheet enters the fixing roller pair 50, 51, the fixing roller pair 5 is compared with the conveyance speed of the sheet sent by the registration roller 23 so that the sheet is not bent.
The conveyance speed of the paper fed by 0, 51 is set high. Here, the transport speed of the registration roller 23 and the pair of fixing rollers 50 and 51 will be described in detail.

Here, each symbol is set as shown in FIG. o: intersection of the outer periphery of the photoconductor drum 35 and the line connecting the centers of the photoconductor drum and the transfer roller 40 a: contact point between the upper registration roller and the lower registration roller b: point on the conveyance guide 45 c: lower entry guide 49 point d: contact point between heat roller 50 and pressure roller 51 la (mm): distance between oa l '(mm): (distance between ob) + (distance between bc) +
(Distance between cds) l (mm): Distance between ods L (mm): Total length of paper used vd (mm / s): Peripheral speed of photoconductor drum Under the above conditions, the deflection of the paper is (l ' -L) (mm)
Therefore, the leading end of the paper is fixed by the fixing roller pair 50,
Immediately after entering 51, the trailing edge of the paper is the registration roller 23.
Set each transport speed so that it disappears before exiting. The peripheral speed vf of the fixing roller pair 50, 51 for this purpose is obtained as follows.

The time required from immediately after the leading edge of the sheet enters the pair of fixing rollers 50 and 51 to when the trailing edge of the sheet exits the registration roller 23 is calculated by (L-1'-la) / vd. Therefore, the deflection (l′−
The peripheral speed vf (mm) of the fixing roller pair required to eliminate
/ s) relational expression is

[0035]

[Equation 1]

As a result,

[0037]

[Equation 2]

[0038] As a result, the fixing roller pair 50,
The peripheral speed of 51 is equal to the peripheral speed of the registration roller 23 (L-l-l
It can be seen that it is desirable to set in a range of a) / (L-1'-la) times or more and without affecting the image unity magnification. Specific examples of the transport system are shown below. Total length of paper L = 297 mm, distance between photoconductor drum and registration roller la = 45 mm Linear distance between photoconductor drum and fixing roller pair l = 99 mm Distance including paper deflection between photoconductor drum and fixing roller pair l ′ = 100 mm, the required peripheral speed vf of the fixing roller pair is vf = {(297-99-45) / (297-100-45)} vd = (153/152) .vd = 1.0066vd, It can be seen that the peripheral speed of the registration roller should be 1.0066 times.

Therefore, the diameter of the registration roller 23 and the reduction ratio of the gear train forming the power transmission system between the registration roller 23 and the fixing roller pair 50, 51 are adjusted to adjust the peripheral speed of the registration roller and the fixing roller pair. Adjust so that the peripheral speed is almost equal. Then, when the heat roller 50 is formed, the outer diameter dimension is adjusted so that the conveyance speed of the fixing roller is 1.0066 times as high as the conveyance speed of the registration roller.

Fixing / Conveying Device Attachment Structure The fixing / conveying device 16 is attached to the apparatus main body by attaching the fixing frames 53 (see FIG. 12) arranged at both ends thereof to the attaching frames 80 as shown in FIG. The fixing frame 53 has a first hook portion 81 at its lower end.
And a second hook portion 82, and a flange portion 83 on the side portion on the discharge side. The mounting frame 80 includes a mounting portion 80e on which the fixing frame 53 is mounted and a vertical portion 80d.
And have. The first hook portion 81 of the fixing frame 53
Has a protruding portion 81a protruding toward the image forming portion, and its upper end has a curved shape. The first hook portion 81 is inserted into the notch 80a formed in the mounting frame 80. Here, as shown in FIG.
As shown in FIG. 7, the locking portion 80b protruding into the notch 80a
Is formed, and the protruding portion 81a of the first hook portion 81 can be locked to the locking portion 80b. The locking portion 80b can be elastically deformed by a predetermined amount. The dimension t1 between the upper surface of the protruding portion 81a and the lower end surface of the fixing frame 53.
And the plate thickness t0 of the mounting frame 80 are as follows: t0> t1 (for example, t0 = 1.2 mm, t1 = 1.
15 mm). Therefore, when the first hook portion 81 is locked to the locking portion 80b, the tip of the locking portion 80b is elastically deformed upward.

On the other hand, the second hook portion 82 has a protruding portion 82a protruding toward the first hook portion 81 side. Protruding part 8
The upper surface of 2a is an inclined surface 82b whose tip is inclined downward. The second hook portion 82 is provided on the mounting frame 80 side.
A notch 80c is formed corresponding to the. Notch 80
The size of c is such that the entire first hook portion 82 can be inserted. Further, the base end of the inclined surface 82b and the fixing frame 5
3 The dimension t2 between the lower end surface and the plate thickness t of the mounting frame 80
The relationship with 0 is: t0 <t2 (for example, t0 = 1.2 mm, t2 = 1.
3 mm).

The vertical portion 80d is the mounting frame 80.
Is bent upward from the end of the mounting portion 80e. A screw hole 84 is formed in the vertical portion 80d so that the flange portion 83 of the fixing frame 53 can be attached with a screw 85. Here, as shown by the alternate long and short dash line in FIG. 13, when the fixing and conveying device 16 is mounted on the mounting frame 80 and the second hook portion 82 is in contact with the end surface of the notch 80c of the mounting frame 80, A slight gap t3 (for example, 0.1 to 0.1) is formed between the vertical portion 80d.
0.5 mm) is set to open.

When the fixing and conveying device 16 having such a fixing frame 53 is mounted on the mounting frame 80 of the main body of the apparatus, first, both hook portions 81 and 8 of the fixing frame 53 are attached.
2 is inserted into the notches 80a and 80c of the mounting frame 80. In this state, when the fixing frame 53 is moved to the right in FIG. 15, the protruding portion 82a of the second hook portion 82 is formed.
Is guided downward by the contact between the inclined surface 82b and the end surface of the notch 80c. Further, the first hook portion 81 is guided so that the projecting portion 81a extends under the locking portion 80b. In this manner, the fixing / conveying device 16 can be temporarily fixed in the vertical direction simply by moving the fixing frame 53 in the horizontal direction.

In the temporarily fixed state, a gap t3 is formed between the vertical portion 80d of the mounting frame and the flange portion 83 of the fixing frame 53. In this state, screws 85
When is screwed into the screw hole 84 and tightened, the flange portion 83 bends and comes into close contact with the vertical portion 80d. The fixing conveyance device 16 is firmly fixed to the mounting frame 80 by the bending force of the flange portion 83.

By using the fixing frame 53 and the mounting frame 80 as described above, even when the fixing frame 53 cannot be fixed by screws from above in the mounting direction, the fixing frame 53 can be easily positioned and securely fixed. In the embodiment having such a configuration, the imaging unit 11 is not mounted at the time of product shipment, for example. In this case, as shown in FIG. 15, the pressure contact release lever 65
The lever portion 65c can pass through the notch 46a of the intermediate frame 46 and rotate upward. Therefore, the lever portion 65c is rotated counterclockwise in FIG. 15 by the biasing force of the spring 66. In this state, the cam portion 65b of the pressure release lever 65 contacts the bearing protrusion 62a of the pressure roller 51, and pushes the bearing 62 and the pressure roller 51 downward against the urging force of the spring 63. As a result, the pressure roller 51 is separated from the heat roller 50, and the pressure contact between the two rollers 50, 51 is released.

On the other hand, when installing this facsimile apparatus, the upper case 25 is opened and the imaging unit 11 is mounted. When the upper case 25 is closed with the imaging unit 11 attached, the lever portion 65c of the press contact release lever 65 is pushed downward by the bottom surface of the case 30 of the imaging unit 11, as shown in FIG. Then, the pressure contact release lever 6 is resisted against the biasing force of the spring 66.
5 rotates clockwise in FIG. 3, and the cam portion 65b separates from the bearing protrusion 62a of the pressure roller 51. Then, the pressure roller 51 is pushed upward by the spring 63, and the rollers 50 and 51 come into pressure contact with each other.

Further, the lever portion 65 of the pressure contact release lever 65
The bottom of the imaging unit 11 is pushed upward by c. Then, the locking portion 33 of the unit case 30 hits the pin 34, and reliable positioning is performed. Further, when the imaging unit 11 is replaced, the upper case 25 is opened and the pressing by the lever portion 65c is released, so that the gap between the photosensitive drum 35 and the developing roller 12 can be increased. Therefore, the imaging unit 1
It is possible to avoid a collision between the developing roller 12 and the photoconductor drum 35 when attaching / detaching.

In this way, the heat roller 50 and the pressure roller 51 can be automatically brought into pressure contact with each other as the imaging unit 11 is mounted, and the heat roller 50 and the pressure roller 51 are installed in comparison with the case where a spacer or the like is used as in the conventional apparatus. The time can be shortened, and problems due to erroneous operation can be resolved. Further, since the rotation center of the pressure contact release lever 65 is aligned with the axis center of the heat roller 50, the rotation center axis for the lever 65 is unnecessary, and the mechanism for releasing the pressure contact is simplified. Further, since the pressure contact is released by the rotating operation, if the slope of the cam portion 65b is made gentle, the pressure contact can be released with a small force.

When the paper is jammed at the fixing and conveying device 16 portion, the upper case 25 is opened as shown in FIG. In this case, the imaging unit 11
Since the bottom surface of the unit case 30 is separated from the tip of the lever portion 65c of the pressure contact release lever 65, the pressure contact release lever 6 is released as in the case where the imaging unit 11 is not attached.
5 rotates counterclockwise in FIG. 16, and the cam portion 65b
The pressing roller 51 is separated from the heat roller 50 by pressing. When the pressure roller 51 is further separated from the heat roller 50, the release arm 88 locked to the shaft 61 of the pressure roller 51 is rotated clockwise in FIG. Then, the inclined surface 88b formed at the upper end of the release arm 88 pushes the intermediate shaft 79 upward. Thereby, the intermediate gear 78c
Moves upward against the biasing force of the spring 87. Therefore, the intermediate gear 78c and the driven gear 78b are disengaged from each other, and the upper discharge roller 75 can freely rotate.

In such a state, the paper jammed by the fixing and conveying device 16 can be easily taken out from either the inside or outside of the device. Moreover, the mechanism for making the discharge upper roller 75 in the free state is a simple mechanism, and is inexpensive as compared with the case where the electromagnetic clutch or the one-way clutch is provided. Further, since it is not necessary to provide the discharge upper roller 75 on the upper case 25 side to release the pressure contact, it is possible to dispose the discharge roller irrespective of the fulcrum of rotation of the case, and the degree of freedom in design is increased.

Image Forming Operation and Conveying Operation When the facsimile device receives information, the laser device 15 forms an electrostatic latent image on the surface of the photosensitive drum 35 in accordance with the received content. This electrostatic latent image is visualized as a toner image by the developing unit 14. The toner image is transferred onto the surface of the supplied paper by the transfer roller 40.

The sheet is guided to the fixing and conveying device 16 side by the conveying guide 45. At this time, the positively charged residual toner is stored in the storage portion 37 of the imaging unit 11. On the other hand, the sheet that has passed the transfer roller 40 is charged with the opposite polarity to the toner. Here, if the transport guide 45 is formed of a good conductor, the electric charge of the paper suddenly escapes via the transport guide 45, and the carrying force of the unfixed toner on the paper is lost. Therefore, the image on the surface of the paper is disturbed during the transportation. However, in this embodiment, the transport guide 4
Since No. 5 is formed of the antistatic resin having the surface resistivity as described above, the electric charge of the paper is gradually removed through the transport guide 45. Therefore, the disturbance of the unfixed toner image can be suppressed. In particular, in this embodiment, since the distance of the transport guide 45 is long, by setting the surface resistivity to the above-mentioned value, it is possible to prevent the image from being disturbed due to the escape of charges even during the transport.

The residual toner accommodated in the accommodating portion 37 of the unit case 30 is positively charged. Moreover, since the intermediate frame 46 is grounded, the intermediate frame 46 is negatively charged by electrostatic induction. Further, as described above, since the negative charges of the paper on the transport guide 45 gradually escape, the electric attraction of the paper with respect to the residual toner in the accommodating portion 37 becomes small, and the paper is prevented from rolling up. it can. Therefore, stable transportation can be performed.

The sheet conveyed as described above is fed into the upper fixing housing 52 and the upper engaging guide 52 of the locking portion 71.
e, 71a and the lower entry guide 49, and is guided between the heat roller 50 and the pressure roller 51. here,
Since the surface resistivity of the lower approach guide 49 is very small as described above (10 ² Ω), the electric charge at the leading edge of the sheet is removed via the lower approach guide 49. For this reason, it is possible to prevent the lower entry guide 49 and the sheet from electrically repelling and colliding the leading edge of the sheet with the outer periphery of the heat roller 50.

Here, the leading edge of the paper is the pair of fixing rollers 50 and 5.
In the state where the sheet is nipped at 1, the sheet is bent downward along the surface of the conveyance guide 45. When the sheet starts to be conveyed by the pair of fixing rollers 50 and 51, the conveying speed of the pair of fixing rollers 50 and 51 is set to the registration roller 2 as described above.
Since the paper is conveyed at a speed higher than the conveyance speed of 3, the deflection of the paper is gradually reduced, and the trailing edge of the paper is moved to the registration roller 2
It disappears when leaving 3.

Here, the leading edge of the paper is the fixing roller pair 50, 5.
When the sheet is nipped at 1, the sheet is fed at a high transport speed as described above, and therefore the sheet after the leading edge portion is fed to the lower entry guide 49.
Away from the top surface of. As a result, the charges in the image forming area of the sheet are not removed through the lower entry guide 49,
The toner holding power of the paper does not suddenly weaken. Therefore, it is possible to prevent image dust due to the lower approach guide 49.

If the sheet is bent when the trailing edge of the sheet is separated from the registration rollers 23, the sheet jumps up due to the waist of the sheet, and the sheet is misaligned in the image forming section to cause image distortion. There is. However, in this embodiment, when the trailing edge of the sheet is separated from the registration roller 23, the bending of the sheet is almost eliminated, so that the deviation of the sheet in the image forming unit can be prevented.

Between the pair of fixing rollers 50 and 51, the paper is heated while being sandwiched by a predetermined pressure, and the toner image on the surface is fixed. In such a fixing operation, the paper usually contains a large amount of water, and the heat roller 50 is temperature-controlled to 150 ° C. or higher.
Water vapor is generated from the paper just after passing 0. When this steam contacts the partition frame 47 when the inside of the machine is not sufficiently warmed, dew condensation occurs on the surface of the partition frame 47. Water droplets generated by dew condensation are concentrated on the collecting portion 47c above the mounting member 54 along the inclined surfaces 47a and 47b of the partition frame 47. Then, the water drops that have fallen from the collecting portion 47c are collected in the concave portion 54a of the mounting member 54.

The concave portion 54a of the mounting member 54 is the heat roller 50.
Is close to. Therefore, when the printing operation is continued, the water in the recess 54a is evaporated by the heat of the heat roller 50. At this time, since the inside of the machine is sufficiently warm, even if steam comes into contact with the partition frame 47 again, dew condensation does not occur. In this case, if the concave portion 54a of the mounting member 54 has a capacity capable of accommodating the maximum amount of dew condensation, it is possible to prevent water droplets from falling onto other portions such as the surface of the paper, and suppress the disturbance of the image due to water droplets. be able to. Further, since the partition frame 47 and the mounting member 54 are used, a special member such as a hygroscopic material is unnecessary.

The sheet for which the fixing operation has been completed is peeled off from the heat roller 50 by the peeling claw 57, and is further discharged onto the discharge roller 7.
The sheet is discharged onto a sheet discharge tray by 5,76. At this time, as shown in FIG.
Enter into 6a. In this case, since the groove end surface of the groove 76a has an acute angle with respect to the outer peripheral surface, the rear end of the sheet further enters the inside of the groove 76a as the lower roller 76 rotates. Therefore, the paper is reliably delivered to the paper discharge tray 17.
Further, since the outer peripheral surface of the lower roller 76 is a curved surface having a circular arc, it is possible to prevent the paper from being damaged.

Other Embodiments (a) In the above embodiment, the lever portion 65c of the pressure contact release lever 65 is directly contacted with the bottom surface of the case of the imaging unit 11, but it may be contacted with another member. . In the embodiment shown in FIGS. 17 and 18, the shutter member 90 is movably arranged below the intermediate frame 46. The shutter member 90 is supported by guides 91a and 91b provided on the lower surface of the intermediate frame 46,
It is movable in the roller axis direction of the heat roller 50.
The shutter member 90 has a cutout 4 in the intermediate frame 46.
A pair of notches 90a having substantially the same size are formed at positions corresponding to 6a. Therefore, at the position shown in FIG. 18, the notch 46a of the intermediate frame 46 and the notch 90a of the shutter member 90 are aligned with each other, and the lever portion 65c can pass through these notches 46a, 90a. is there. On the other hand, a projecting portion 90b that projects upward is formed at one end of the shutter member 90. When the imaging unit 11 is attached to the apparatus main body, the end of the imaging unit 11 contacts the protrusion 90b of the shutter member 90, which moves the shutter member 90 in the arrow direction of FIG. As a result, the notch 46a of the intermediate frame 46 and the notch 90a of the shutter member 90 are displaced, and the lever portion 65c abuts the shutter member 90 and cannot rotate upward.

In this state, as shown in FIG. 17, the cam portion 65b of the pressure contact release lever 65 is separated from the bearing protrusion 62a of the pressure roller 51, and the pressure contact between the rollers 50 and 51 is allowed. When the rigidity of the imaging unit 11 is low, when the lever portion 65c of the pressure contact release lever 65 is directly brought into contact with the imaging unit 11 as in the above embodiment, the imaging unit 11 may be bent by the spring force of the spring 66. Imaging unit 1
When 1 is bent, it adversely affects image formation. However, in the embodiment shown in FIGS. 17 and 18, the lever portion 65c hits the shutter member 90, and the imaging unit 11
Does not hit directly. Therefore, the imaging unit 1
Even when the rigidity of No. 1 is low, the pressure contact of the heat roller 50 and the pressure roller 51 can be automatically released without adversely affecting the image formation.

(B) Another embodiment of the peeling claw is shown in FIGS.
Shown in 1. In this embodiment, a notch 92b is formed in the side wall 92a on the downstream side of the upper fixing housing 92. A substantially L-shaped support member 93 is fixed to the side wall 92a. The lower portion 96 of the support member 93 has a cutout 92b.
And extends into the fixing upper housing 92. In the lower portion 96 of the support member 93, the peeling claw 95 is provided to the fixing portion 96a (area A1) in the downstream half of the supporting member 93 via the adhesive 94.
The base end of is bonded. Further, the extension portion 96b (area A2) of the upstream half is arranged with the peeling claw 95 with a predetermined gap.

The peeling claw 95 is made of a heat-resistant resin sheet material such as polyimide, and its lower surface facing the paper is coated with fluorine resin. The peeling claw 9
The upper surface of No. 5 needs to be adhered to the fixed portion 96a, and thus is not coated. Also, the peeling nail 9
The thickness of 5 is preferably 70 μm to 250 μm. The tip of the peeling claw 95 elastically contacts the surface of the heat roller 50. The tip of the peeling claw 95 is tapered, and the tip portion is formed in an arc shape. Therefore, the tip of the peeling claw 95 comes into contact with the surface of the heat roller 50 at one place, and even if the mounting posture of the peeling claw 95 is displaced, the paper can be smoothly peeled from the heat roller 50.

In such an embodiment, the paper wound around the heat roller 50 is peeled off by the peeling claw 95 and conveyed to the discharge roller side. At this time, the heat roller 5 of the peeling claw 95
The pressure contact force against 0 is the fulcrum P due to the end of the fixed portion 96a.
It is determined according to the length from 1 to the tip and can be set relatively small. Therefore, wear of the heat roller 50 can be reduced, and the life of the heat roller 50 can be extended.

On the other hand, when peeling a strong paper or when a paper jam occurs, the peeling claw 95 is pushed upward, and the peeling claw 95 is pushed.
The middle portion of the contact point abuts on the fulcrum P2 which is the end portion of the extension portion 96b. In this case, the elastic force of the peeling claw 95 is determined according to the relatively short length from the fulcrum P2 to the tip.
A relatively large force is required to deform the above. That is, in the peeling claw 95 and the supporting member 93,
It is possible to increase the resistance force against the roll-up of the peeling claw 95 without increasing the pressure contact force so much.

Further, since the lower surface of the peeling claw 95 is coated with fluorine, contamination of the peeling claw 95 by toner or paper powder is reduced, and stable peeling performance can be obtained for a long period of time. (C) FIGS. 22 to 24 show still another embodiment of the peeling claw. In this embodiment, the lower portion 100a of the support member 100 is
However, it is formed in an inverted V shape as shown in FIG. 23, and the center is higher by a distance H than both ends. And
The peeling claw 101 also has an inverted V shape along the lower portion 100a of the support member 100. Further, as shown in FIG. 24, the peeling claw 101 has a tapered tip, and the tip is formed in an arc shape. The peeling claw 101 is attached such that the contact angle (angle with respect to the tangent m) β to the heat roller 50 is in the range of 5 ° <β <45 °.

In such an embodiment, the peeling claw 101 is
Since the central portion is formed to be curved so as to be higher, the elastic force of the peeling claw 101 pushed toward the heat roller 50 side becomes larger than the elastic force of the peeling claw 101 in the direction away from the heat roller 50. It is possible to increase the resistance force against the roll-up of the peeling claw 101 without increasing the pressure contact force of the heat roller 50.

Further, the peeling claw 101 has an angle β (5 ° <β <
Since it is in contact with the heat roller 50 at 45 °, the paper can be smoothly separated from the heat roller 50 even when the paper is thick. The shape of the peeling claw 101 is not limited to the example shown in FIG. 23, and may be curved in an arc shape, for example.

(D) In the above embodiment, the pressure contact release lever is rotated by pressing the imaging unit 11 or the like. However, as shown in FIG. 25, it may be rotated by using a drive mechanism such as a motor. May be. In the example shown in FIG. 25, the pressure contact releasing member 105 also functions as a bearing that supports the heat roller 50. A cam portion 105a for pressing the protruding portion 62a of the bearing 62 of the pressure roller 51 is formed on a part of the outer periphery thereof. A gear portion 105b is formed on a part of the outer circumference. On the other hand, a motor 107 is fixed to the fixing frame 106, and a worm gear 109 is connected to the shaft tip of the motor 107 via a joint 108. The worm gear 109 meshes with the gear portion 105b of the pressure contact releasing member 105.

In this case, the pressure contact releasing member 105 can be rotated around the heat roller 50 by rotating the motor 107 and rotating the worm gear 109. Therefore, the pressure roller 51 can be separated from the heat roller 50 by rotating the pressure contact releasing member 105 to bring the cam portion 105a into contact with the bearing protrusion 62a of the pressure roller 51.

In such an embodiment, a lever or the like is unnecessary, and the heat roller 50 and the pressure roller 51 can be easily pressed and released in a very narrow space. (E) As shown in FIG. 26, the recess 54 a of the mounting member 54
You may form the hole 54b in the bottom part of this. In such an embodiment, the water drops that have fallen into the recess 54a pass through the hole 54b and permeate into the cleaning member 55. Since the cleaning member 55 is in contact with the surface of the heat roller 50, the cleaning member 55 has a high heat and the water evaporates in a short time.

(F) In the above embodiment, the thermal deformation of the upper fixing housing 52 to which the thermistor 74 is attached is restricted by the fixing cover 59 and its rib 59a.
As shown in the schematic view of FIG. 27, the mounting member 110 may be formed of a shape memory alloy to suppress the movement of the thermistor 74. That is, in the embodiment shown in FIG. 27, the attachment member 110 is attached to the side wall 52d of the upper fixing housing 52 with the screw 111. The mounting member 110 is made of a shape memory alloy, and the thermistor 74 is fixed to the lower end of the mounting member 110.

In this embodiment, below the heat resistant temperature of the upper fixing housing 52, as shown in FIG. 27, the mounting member 110 is linear, and the thermistor 74 fixed to the lower end thereof contacts the heat roller 50. There is. On the other hand, when the side wall 52d is deformed to the outside as shown in FIG. 28 due to an abnormal temperature rise, the mounting member 110 has the shape stored in advance. That is, the tip is deformed so as to approach the heat roller 50 side so as to cancel the deformation of the side wall 52d. As a result, even if the side wall 52d is deformed outward, the thermistor 74 can be kept in contact with the heat roller 50. Therefore, the surface temperature of the heat roller 50 can be accurately detected and normal temperature control can be performed.

(G) Another example of the driving force releasing mechanism of the discharge roller portion is shown in FIG. In this example, the drive shaft 77 to which the discharge upper roller 75 is fixed can be moved up and down. That is, the drive shaft 77 is rotatably supported by the bearing 115,
The bearing 115 can move up and down with respect to the fixing frame 53. The bearing 115 is constantly urged downward by the spring 116. On the other hand, in the fixing frame 53,
The release arm 117 is attached so as to be rotatable around the pin 118. Long holes 1 are provided at both ends of the release arm 117.
17a and 117b are formed respectively, and the long hole 11
The shaft 61 of the pressure roller 51 is locked to 7a, and the drive shaft 77 of the discharging upper roller 75 is locked to the other long hole 117b.

In this embodiment, when the shaft 61 is pushed downward to release the pressure contact of the pressure roller 51, the release arm 117 rotates clockwise about the pin 118. Then, the drive shaft 77 locked to the upper end of the release arm 117 is lifted upward against the biasing force of the spring 116. As a result, the sandwiching of the sheet sandwiched between the discharge rollers 75 and 76 by a jam or the like is released, and the jam processing can be easily performed from inside or outside the apparatus.

Also in this case, the discharge roller pair 75, which has an inexpensive structure as compared with the electromagnetic clutch and the one-way clutch,
The driving force of 76 can be released. (H) In the above embodiment, the surface resistivity of the transport guide 45 and the lower approach guide 49 was described, but the transport guide 4
5, the relationship between the surface resistivity of the lower entrance guide 49 and the surface resistivity of the heat roller 50 is preferably: conveyance guide ≧ lower entrance guide ≧ heat roller. At this time, the surface resistivity of each member is within the range of 10 ⁷ to 10 ¹⁴ Ω. For example, the transport guide 45 and the lower approach guide 49 are formed of an antistatic resin to have surface resistivities of 10 ¹² Ω and 10 ¹¹ Ω, respectively, and the surface of the heat roller 50 is coated with conductive PTFE to reduce its surface resistivity. It may be set to 10 ⁸ Ω.

In this case, as the paper is conveyed, the electric charge on the paper is gradually removed and abrupt movement of the electric charge is suppressed, so that the dustiness of the toner image on the paper can be suppressed. (I) In the above-described embodiment, the heat distribution characteristic of the heater 50a is such that the amount of heat generation is high on the front side and low on the back side, but the heat distribution characteristic of the heater 50a is made uniform, and as shown in FIG. The endothermic layer 50 may be formed on the front side region 50b of the inner peripheral surface of 50 by applying, for example, a black paint having heat absorption and heat resistance. The region 50b may be a region on the front side of the pinion gear 69. This allows
The heat transfer efficiency in the region 50b is higher than that in the unpainted portion, and the temperature rise in the unpainted portion can be prevented. Therefore, unevenness of the surface temperature of the heat roller 50 is reduced.

(J) In order to reduce the unevenness of the surface temperature of the heat roller 50, the heater 50a may be arranged so as to be offset toward the front side as shown in FIG. In this case, the calorific value on the front side does not substantially change or increases, but the calorific value on the back side decreases. Therefore, the temperature unevenness on the surface of the heat roller 50 is reduced. (K) In FIG. 32 showing still another embodiment, a heater 50a having a uniform heat distribution characteristic is used. In this case, the heat roller 50 is extended to the front side, and heat insulation similar to that of the pinion gear 69 is performed there. A collar 68 having characteristics is attached. In this case, the heat balance of the heat roller 50 is the same on the back side and the front side. Further, by disposing the pinion gear 69, the collar 68, and the bearing portion formed of a heat insulating member on the back side and the front side, it is possible to suppress heat loss due to heat radiation at both ends of the heat roller 50. Therefore, it is possible to reduce the temperature unevenness on the surface of the heat roller 50 and prevent the temperature inside the machine from rising due to heat radiation from both ends.

[0080]

As described above, according to the present invention, since the surface resistivity of the entrance guide member for guiding the sheet to the fixing portion is made smaller than that of the upstream conveyance guide member, the sheet being conveyed is conveyed. It is possible to prevent the electric charge from rapidly escaping from the surface of the sheet and prevent the unfixed toner image on the sheet surface from being disturbed. Moreover, it is possible to avoid a collision between the fixing roller and the like and the sheet when the sheet enters the fixing unit, and it is possible to prevent the image from being disturbed due to the collision.

[Brief description of drawings]

FIG. 1 is an external perspective view of a facsimile device to which an embodiment of the present invention is applied.

FIG. 2 is a schematic configuration diagram of a vertical cross section of FIG.

FIG. 3 is a front view of an image forming unit and a fixing / conveying device of the apparatus.

FIG. 4 is a partial vertical cross-sectional configuration diagram of a fixing and conveying device.

FIG. 5 is a diagram showing heat distribution characteristics of a heat roller and an internal heater.

FIG. 6 is a vertical cross-sectional configuration diagram of a fixing / conveying device.

FIG. 7 is a perspective view of a thermal fuse mounting portion of the fixing and conveying device.

FIG. 8 is a perspective view of a lower roller of the fixing and conveying device.

FIG. 9 is an enlarged partial view of the lower roller.

FIG. 10 is a diagram showing a driving force releasing mechanism for a pair of discharge rollers.

FIG. 11 is a schematic diagram of a paper transport system.

FIG. 12 is a partial front view of the frame of the fixing / conveying device.

FIG. 13 is a sectional view of a mounting frame of the fixing / conveying device.

FIG. 14 is a perspective partial view of a frame attachment portion of the fixing / conveying device.

FIG. 15 is a front view of the fixing and conveying device at the time of product shipment.

FIG. 16 is a front view of the fixing / conveying device during a jam process.

FIG. 17 is a partial front view of a fixing / conveying device according to another embodiment.

FIG. 18 is a partial side view of FIG.

FIG. 19 is a vertical cross-sectional configuration diagram of a fixing / conveying device according to still another embodiment.

20 is an enlarged partial view of FIG.

21 is a bottom view of the peeling claw of FIG. 20. FIG.

FIG. 22 is an enlarged partial view of a fixing / conveying device according to still another embodiment.

FIG. 23 is a side view of FIG. 22.

FIG. 24 is a bottom view of FIG. 23.

FIG. 25 is a front partial view of a fixing / conveying device according to still another embodiment.

FIG. 26 is a vertical cross-sectional configuration diagram of a fixing / conveying device according to still another embodiment.

FIG. 27 is a schematic configuration diagram of another embodiment of the thermistor mounting portion.

FIG. 28 is a diagram showing how the embodiment shown in FIG. 27 is deformed at a high temperature.

FIG. 29 is a view showing another embodiment of the driving force releasing mechanism of the discharge roller.

FIG. 30 is a diagram showing another example of the heat roller.

FIG. 31 is a view showing still another embodiment of the heat roller.

FIG. 32 is a view showing still another embodiment of the heat roller.

[Explanation of symbols]

 11 Imaging Unit 14 Developing Unit 16 Fixing and Conveying Device 23 Registration Roller 45 Conveying Guide 49 Lower Entry Guide 50 Heat Roller 51 Pressure Roller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daisuke Hayashi 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (2)

[Claims] 1. An image forming unit for forming an image with magnetic toner on a sheet surface, a fixing unit for fixing an unfixed toner image formed on the sheet surface by the image forming unit, and a predetermined surface resistivity. Compared to a conveyance unit including a conveyance guide member that guides the sheet from the image forming unit to the fixing unit side, and the conveyance guide member that guides the sheet conveyed by the conveyance unit to the fixing unit. And an entrance guide member having a small surface resistivity. 2. The conveyance guide member and the entrance guide member are arranged so that a sheet conveyance path formed by them is curved downward, and the image forming unit conveys a sheet at a predetermined conveyance speed. 2. The image according to claim 1, wherein the fixing unit has a pair of sheet conveying surfaces that sandwich a sheet and convey the sheet at a speed higher than a sheet conveying speed by the conveying unit of the image forming unit. Forming equipment.