JPH0912172A - Endless belt deviation prevention mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] An endless belt deviation prevention mechanism that enables stable recording material conveyance by preventing waviness and wrinkles from occurring on the recording material conveyance surface during belt deviation control. To provide. [Structure] Three rollers (belt suspension tension member) 2,
A detection ring (belt deviation detection member) 8 rotatably supported at one end of one of the rollers 3 and 4 (deviation correction roller) 3, and the detection ring 8 and a portion of the endless belt 1 hanging on the detection ring 8. When the rotational torque acts on the detection ring 8 by the frictional force, the rotational movement of the detection ring 8 is converted into a linear movement to displace the end portion of the deviation correction roller 3 in a predetermined direction. In the deviation prevention mechanism, the detection ring 8 and the displacement means are arranged on the deviation correction roller 3 other than the recording material conveyance surface, and the detection ring 8 is arranged outside the recording material conveyance area. According to the present invention, it is possible to prevent waviness and wrinkles of the endless belt 1 from occurring on the recording material conveying surface during the deviation control of the endless belt 1, and it is possible to stably convey the recording material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt deviation prevention mechanism provided in a recording material conveying device having an endless belt which is stretched between at least three belt suspension tension members.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus which has adopted an electrophotographic system or an electrostatic recording system for an image forming process, a cylindrical photosensitive drum is used as an image carrier, and the periphery of the photosensitive drum is charged. A well-known type is one in which peripheral devices such as a container, an exposure unit, a developing unit, a cleaning unit, and a recording material conveying mechanism (recording material conveying unit) are arranged.

By the way, in recent years, in order to further improve the functions of the photosensitive drum, the recording material conveying mechanism, etc., an endless belt using a photoconductor instead of the photosensitive drum is adopted, or an endless belt is used as the recording material conveying mechanism. An image forming apparatus that employs is developed.

In the image forming apparatus using the endless belt for the photosensitive member and the transfer material conveying mechanism as described above, many functions can be improved, but there are drawbacks peculiar to the belt mechanism. A means for suppressing the deviation of the endless belt with respect to the reference trajectory or the meandering of the endless belt during a certain driving is indispensable.

Factors causing the positional deviation due to the one-sided movement of the endless belt include parallelism and twist between members that suspend and suspend the endless belt, but there is a limit to improving the accuracy of these members. However, it is difficult to prevent the endless belt from moving toward the side by improving the accuracy.

Therefore, conventionally, the following method has been adopted as a means for correcting these defects when the endless belt is offset or meandered. (1) One of a plurality of roller members that electrically detects the deviation of the endless belt and holds the endless belt
A method in which one end on one side is moved up and down with a solenoid or stepping motor to move the endless belt in the direction to return it to the normal position. (2) A method in which the diameter of at least one roller member that holds the endless belt is set to be larger than the end portions of the roller member at the central portion in the axial direction so that the roller member has a crown shape as a whole. (3) A method of providing a deviation regulating rib on the endless belt.

[0007]

However, all of the above conventional methods have the following problems.

That is, in the above method (1), since the vertical movement of the roller member necessary for producing the artificial deviation of the endless belt is performed by using an electric component such as a solenoid or a stepping motor, the entire apparatus is Causes an increase in size and cost.

Further, in the above method (2), the roller member is formed into a crown shape so that the endless belt is positively distorted to generate an internal stress difference, thereby suppressing deviation of the endless belt. Therefore, it is necessary to use an endless belt made of a material having sufficient elasticity. In addition, since the so-called permanent deformation of the endless belt due to creep strain is prevented while utilizing the strain generated in the endless belt, for example, when a rubber belt is used as the endless belt, the elasticity of low rubber hardness as described above is used. It is necessary to use a material with abundant materials, and the thickness of the material must be set so as to satisfy the mechanical strength. Therefore, when the method (2) is applied to a photoreceptor belt or the like, the belt surface is distorted and the image is deformed, and when it is applied to the transfer material transport belt, the thickness of the transport belt is increased. I have to set a large transfer current in order to be
When forming a color image, color misregistration occurs, which is inappropriate in any case.

Further, in the above method (3), since the thrust force generated in the endless belt is received by the end face of the guide rib to suppress the deviation of the endless belt, the accuracy of the guide rib provided in the endless belt is reduced. Will determine the accuracy of the movement speed control of the endless belt. However, it is technically difficult to attach the guide ribs to the endless belt with high precision, so that it is difficult to control the moving speed of the endless belt with high precision, and therefore it is not suitable for mass production.

The present invention has been made in view of the above problems. An object of the present invention is to cause waviness and wrinkles of an endless belt during belt deviation control on a recording material conveying surface or an image exposure surface and an image transfer surface. It is an object of the present invention to provide an endless belt deviation preventing mechanism which can prevent the occurrence of the occurrence of the recording medium and can stably convey the recording material or perform image exposure and image transfer.

[0012]

In order to achieve the above object, the invention according to claim 1 is a recording material conveying apparatus having an endless belt which is stretched between at least three belt suspension tension members. A mechanism provided, wherein a belt deviation detection member rotatably supported on at least one end of at least one belt suspension tension member, and friction between the belt deviation detection member and an endless belt portion hanging on the belt deviation detection member When a rotational torque acts on the belt deviation detection member by a force, the rotational movement of the belt deviation detection member is replaced with a linear movement to displace the end portion of the belt suspension tension member in a predetermined direction. In the endless belt deviation prevention mechanism, the belt deviation detection member and the displacement means are arranged on a belt suspension tension member other than the recording material conveyance surface, Characterized in that the serial belt deviation detecting member from the recording material conveying region arranged outside.

According to a second aspect of the present invention, in the first aspect of the invention, the recording material conveying device having the endless belt is for transferring an image formed on at least one image carrier to the recording material. A transfer belt, the belt deviation detecting member and the displacing means are arranged on a belt suspension tension member that is not on the same plane as the image transfer area, and the belt deviation detecting member is arranged outside the image area. Is characterized by.

Further, the invention according to claim 3 is a mechanism provided in a recording material conveying device having an endless photosensitive belt which is hung between at least four belt suspension tension members and rotates, A belt deviation detecting member rotatably supported on at least one end of one belt suspension tension member, and the belt deviation detecting member is rotated by the frictional force between the belt deviation detecting member and the endless belt portion hanging on the belt deviation detecting member. In an endless belt deviation prevention mechanism having a displacement means for displacing the rotational movement of the belt deviation detection member with a linear movement when torque is applied to displace the end portion of the belt suspension tension member in a predetermined direction, The belt deviation detecting member and the displacing means are arranged on a belt suspension tension member that is not flush with the image exposure area and the image transfer area, and Characterized in that a belt close detection member outside the image area.

[0015]

According to the present invention, the belt deviation detecting member and the displacing means are provided on the belt suspension tension member other than the recording material conveying surface or the belt suspension tension member which is not flush with the image exposure and image transfer area. In addition, since the belt deviation detection member is arranged outside the image area, it is possible to prevent wrinkles and wrinkles of the endless belt from occurring on the recording material conveyance surface or the image exposure surface and the image transfer surface during the belt deviation control. It is possible to stably convey the recording material or perform image exposure and image transfer.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a schematic perspective view of a transfer belt having a belt deviation preventing mechanism according to the present invention, FIG. 2 is a schematic sectional view of a color copying machine having the transfer belt, and FIG. FIGS. 4 and 5 are perspective views for explaining the operation of the belt deviation prevention mechanism according to the present invention.

The color copying machine shown in FIG. 2 employs an electrophotographic image forming process. In the color copying machine, four uniformly charged photosensitive drums 5a, 5 are used.
The rotating polygon mirror 6 and the reflecting mirrors a ₁ , a ₂ ,
_{a 3, b 1, b 2} , b 3, c 1, c 2, c 3, d 1, d 2
, D ₃ form latent images of images to be copied, and the latent images are developed by the developing devices 7a, 7b, 7c, 7d and converted into visible images, and the visible images are transferred by the recording material conveying means and the transfer belt. It is conveyed by a certain endless belt 1 and transferred onto a recording material (not shown).

By the way, the endless belt 1 is formed, for example, by coating a high resistance material layer such as polytetrafluoroethylene or polyethylene terephthalate on the surface of a conductive rubber. As shown in detail in FIG. Is wound around the drive roller 2 on the downstream side, the deviation correction roller 3 and the driven roller 4 on the upstream side, which constitute the belt suspension tension member, and moves in the direction of arrow K1. Both ends of each of these rollers 2, 3 and 4 are rotatably held between bearings (not shown) and are arranged substantially in parallel.

The drive roller 2 is composed of a metal roller having a rubber layer having a large friction coefficient on its surface layer, and its diameter is set to 10 to 30 mm. It is driven to rotate at speed.

The deviation correction roller 3 is for correcting defects such as deviation and meandering that occur in the endless belt 1, which is constantly urged by the tension spring 12 in the direction in which the endless belt 1 is stretched. There is. One end of the rotation shaft of the deviation correction roller 3 is supported by a rocking bearing 9 via a detection ring 8 so as to be vertically swingable, and the other end is rotatably supported by a bearing (not shown). There is.

Further, the driven roller 4 is composed of a metal roller such as SUS, and its both end bearings are fixed at predetermined positions. A fixed guide may be used instead of the driven roller 4.

When the drive roller M is rotationally driven in the direction of the arrow (counterclockwise) in FIG. 1 by the drive source M, the frictional force between the outer peripheral surface of the drive roller 2 and the inner peripheral surface of the endless belt 1. The driving force is transmitted to the endless belt 1, and the endless belt 1 is rotationally driven between the three members of the drive roller 2, the driven roller 4, and the deviation correction roller 3 in the counterclockwise direction of arrow K1 in FIG.

Now, the detection ring 8 will be described.

The detection ring 8 is concentrically and rotatably provided on the shaft portion of the deviation correction roller 3 on the side of the rocking bearing 9, and the inner end surface thereof is almost in contact with the end surface of the deviation correction roller 3 on the front end side. The correction roller 3 and the correction roller 3 have substantially the same diameter.
On the outer end surface of the detection ring 8, a cylindrical control belt winding portion 11 having an outer diameter smaller than that of the deviation correction roller 3 is provided integrally with and coaxially with the detection ring 8. Then, the front end portion of the endless belt 1 suspended by the deviation correction roller 3 is hooked on the detection ring 8.

By the way, as shown in FIG. 3, the detection ring 8 is arranged outside the image area. still,
It is desirable that the material of the detection ring 8 has a high friction coefficient, and for example, PPS mixed with silicone rubber is used.

As shown in FIG. 2, a control belt 10 is provided between the control belt winding portion 11 and a stationary locking portion (for example, a side plate (not shown)).
One end (lower end) 10a of 0 is the control belt winding unit 1
The other end portion (lower end portion) 10 b is fixed to the outer surface of 1 and is locked to the locking portion 13. The control belt 10 is made of a material that is flexible and has a small tensile elongation. Further, the winding direction of the control belt 10 with respect to the control belt winding portion 11 is set to the direction in which the control belt 10 is wound around the control belt winding portion 11 by the rotation torque due to the rubbing between the detection ring 8 and the endless belt 1. Has been done.

Next, the operation of the deviation prevention mechanism will be described.

In the rotational driving process of the endless belt 1, as shown in FIG. 4, the endless belt 1 has moved toward the rear end side direction B in the width direction.
Width (hang amount) W of the front end side of the detection ring 8
Is small, the frictional force between the endless belt 1 and the detection ring 8 is small, and therefore the rotational torque T acting on the detection ring 8 is also small. Therefore, the force F for pulling down the front end side of the deviation correction roller 3 by the tension spring 12 is larger than the winding force of the control belt 10 of the control belt winding portion 11 by the rotation torque T, and the deviation correction roller 3 has a larger force. As shown by the solid line in FIG. 4, the front end side hits and is received by the lower limit stopper member 13, and further lowering is prevented.

That is, the front end side of the deviation correction roller 3 is displaced downward D by using a bearing (not shown) on the rear end side as a fulcrum, and this displacement causes the deviation correction roller 3 with respect to the axes of the driving roller 2 and the driven roller 4. Twist occurs in the front. As a result, the endless belt 1 returns and moves in the front end side direction A in the width direction thereof.

As the endless belt 1 returns in the direction A, the hanging width W of the endless belt 1 with respect to the detection ring 8 increases, and the frictional force between the endless belt 1 and the detection ring 8 increases. The rotational torque T that acts also increases.

As described above, the control belt winding force of the winding portion 11 increases due to the increase of the rotation torque T, and the deviation correction roller 3 is pulled up by the winding of the control belt 10 of the winding portion 11. When the force becomes larger than the pulling down force F by the tension spring 12, the control belt 10
Is taken up by the take-up portion 11, whereby the front end side of the deviation correction roller 3 is pulled up against the tension spring 12 and displaced upward U.

Then, due to the increase of the rotational torque T of the detection ring 8, the pulling force on the front end side of the deviation correction roller 3 due to the winding of the control belt 10 of the winding portion 11 is larger than the pulling down force F by the tension spring 12. Continues, the front end side of the deviation correction roller 3 hits and is received by the upper limit stopper member 14 as shown by the solid line in FIG.
Further pulling is blocked.

That is, the front end side of the deviation correction roller 3 is displaced upwards U by using the bearing on the rear end side as a fulcrum, and this displacement causes the deviation correction roller 3 to move forward and rearward with respect to the axes of the driving roller 2 and the driven roller 4. Twisting opposite to the case shown in FIG. 4 occurs. In this state, the endless belt 1 returns and moves in the front end side direction B in the belt width direction.

As the endless belt 1 returns in the direction B, the hanging width W of the endless belt 1 with respect to the detection ring 8 decreases, and the frictional force between the endless belt 1 and the detection ring 8 decreases. Ring 8
The rotational torque T that acts on is also reduced.

Due to the decrease in the rotational torque T, the winding unit 1
The control belt winding force of No. 1 is reduced,
Deflection correction roller 3 by winding control belt 10 of No. 1
When the pulling down force F by the tension spring 12 becomes larger than the pulling up force on the front end side of the control belt 10, the front end side of the deviation correction roller 3 is pulled down while the control belt 10 is rewound on the winding section 11 and moves downward D. It will be displaced.

Due to the decrease in the rotation torque T of the detection ring 8, the pull-down force F of the tension spring 12 continues to be larger than the pull-up force of the front end side of the deviation correction roller 3 due to the winding of the control belt 10 of the winding portion 11. Then, the front end side of the deviation correction roller 3 hits and is received by the lower limit stopper member 13 as shown by the solid line in FIG. 4, and further pulling is prevented. In this state, the endless belt 1 returns and moves in the direction B on the back end side in the belt width direction.

That is, the rotational torque T acts on the detection ring 8 due to the frictional force with the endless belt 1, and the rotational torque T changes depending on the size of the hanging width W of the endless belt 1 with respect to the detection ring 8. The larger the loop width W of the belt 1 is, the larger the rotation torque T of the detection ring 8 is, and the control belt winding force of the winding portion 11 is increased.

Then, the winding force and the tension spring 12
The front side of the deviation correction roller 3 is displaced up and down U and D depending on the magnitude of the pulling force F of the endless belt 1, whereby the deviation directions A and B of the endless belt 1 are controlled.

Thus, in the process of displacing the front end side of the deviation correcting roller 3 to the upper U or the downward D, the pulling force F by the tension spring 12 on the front end side of the deviation correcting roller 3 and the winding portion. There is a case where the control belt winding force of 11 causes the deviation correction roller 3 to be balanced with the pulling force on the front end side. At this time, the deviation correction roller 3 becomes stationary at a position in equilibrium near the endless belt 1, and the endless belt 1 stops its deviation movement and rotates at a fixed position.

When the above two forces are not balanced,
The front end side of the deviation correction roller 3 moves up and down within a regulated range between the upper limit stopper 14 and the lower limit stopper 13, and the endless belt 1 also rotates while reciprocating in the A and B directions within a certain range. To do.

In this embodiment, the detection ring 8 and the deviation correction roller 3 are connected to the photosensitive drums 5a to 5 which are transfer / conveyance surfaces.
Since it is arranged on the side opposite to d, it is possible to construct a simple deviation prevention mechanism that does not cause waviness or wrinkles on the transfer / transport surface.

Further, since the portion of the endless belt 1 that is hooked on the detection ring 8 receives the biasing force of the endless belt 1 and the frictional force between the detection ring 8 and the endless belt 1 that opposes it, the endless belt 1 is damaged. It is also possible that wrinkles may occur in this, but since the detection ring 8 is arranged outside the image area as shown in FIG. 3, it is possible to always provide a good transfer surface.

As described above, according to this embodiment, it is possible to provide the endless belt 1 having a good transfer area, and particularly in the formation of a color image, an image of excellent quality without color misregistration is obtained. be able to.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. 6 is a schematic sectional view of a laser beam printer provided with a deviation prevention mechanism according to the present invention, and FIG. 7 is a side view of a photoconductor belt unit. In these drawings, the same elements as those shown in FIGS. 1 and 2 are shown. Are denoted by the same reference numerals.

In the laser beam printer shown in FIG. 6, a photoconductor belt unit 20 having an endless photoconductor belt 21 is provided in the main body 40 of the apparatus, and a charger 22 is provided around the photoconductor belt unit 20. Each device for executing the electrophotographic process, such as the developing device 23, the transfer charger 24, and the cleaning device 25, is provided. Further, a paper feed cassette 26 is arranged above the developing device 23, and a plurality of recording materials P are stacked and accommodated in the paper feed cassette 26.

Thus, in the present laser beam printer, when the recording material P is fed from the paper feeding cassette 26 by the paper feeding roller 27, the recording material P is registered by the registration roller 28.
Then, the sheet is conveyed to the upper side of the photosensitive belt 21 at a proper timing.

The photoconductor belt 21 includes four belt support rollers 29, 30, 31, 3 whose both shaft ends are rotatably supported by side plates (not shown) of the photoconductor belt unit 20.
9 is stretched between 9 and rotated in the direction of the arrow in the figure, the surface thereof is uniformly charged by the charging charger 22, and the laser beam L from the optical scanning device 32 is emitted to cause the photoconductor belt. An electrostatic latent image is formed on 21.

The electrostatic latent image is visualized as a toner image by toner when passing through the developing device 23, and the toner image is conveyed to the upper side of the photosensitive belt 21 and the lower surface of the recording material P is conveyed. It is transferred to the side by the transfer charger 24. Then, the recording material P on which the toner image is transferred
Is guided by a conveyance guide 33 to a fixing device 34, where the toner image is fixed by the fixing device 34, and then discharged onto a discharge tray 37 via a discharge roller 35 and a discharge guide 36. It

Details of the photosensitive belt unit 20 will be described with reference to FIG.

In the photoconductor belt unit 20, the belt supporting roller 29 functions as a driving roller, the belt supporting rollers 31 and 39 function as driven rollers, and the belt supporting roller 30 functions as a deviation correcting roller. Similarly, the detection ring 8 is arranged outside the image area at one end of the deviation correction roller 30. Here, the charging charger 22 and the cleaning blade 38 provided in the vicinity of the deviation correction roller 30 are mounted on the rocking bearing 9 via a side plate (not shown).
By connecting the above with the above and linking them with the vertical movement of the deviation correction roller 30, the respective functions of charging and cleaning are not hindered.

Thus, also in this embodiment, as is apparent from FIG. 7, even if the deviation correction roller 30 moves up and down for deviation control, the exposure surface and the transfer surface on the photosensitive belt 21 are stable. To do. Further, as in the case of the first embodiment, the portion of the photoconductor belt 21 that is hooked on the detection ring 8 may be wrinkled or damaged. An exposed surface and a transfer surface can be provided.

Therefore, it is possible to obtain a simple and inexpensive mechanism for preventing the deviation of the photosensitive belt 21, which can provide a high quality image without image distortion.

[0054]

As is apparent from the above description, according to the present invention, the belt deviation detecting member and the displacing means are not connected to the belt suspension tension member other than the recording material conveying surface or the image exposure and image transfer area. Since the belt suspension tension member is provided on the same surface, and the belt deviation detection member is arranged outside the image area, waviness and wrinkles of the endless belt at the time of controlling the belt deviation causes the recording material conveyance surface or the image exposure surface. In addition, it is possible to prevent the occurrence of occurrence on the image transfer surface, and it is possible to obtain an effect that stable conveyance of the recording material or image exposure and image transfer are possible.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a transfer belt including a belt deviation prevention mechanism according to a first exemplary embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a color copying machine including a belt deviation prevention mechanism according to the first embodiment of the present invention.

FIG. 3 is a plan view of a transfer belt including a belt deviation prevention mechanism according to the present invention.

FIG. 4 is a perspective view illustrating the operation of the belt deviation prevention mechanism according to the first exemplary embodiment of the present invention.

FIG. 5 is a perspective view illustrating the operation of the belt deviation prevention mechanism according to the first embodiment of the present invention.

FIG. 6 is a schematic sectional view of a laser beam printer including a deviation prevention mechanism according to a second embodiment of the present invention.

FIG. 7 is a side view of a photoconductor belt unit including a deviation prevention mechanism according to a second exemplary embodiment of the present invention.

[Explanation of symbols]

1 Endless Belt (Transfer Belt) 2,29 Drive Roller (Belt Suspension Member) 3,30 Deviation Correction Roller (Belt Suspension Member) 4,31,39 Driven Roller (Belt Suspension Member) 8 Detection ring (belt deviation detection member) 10 Control belt (displacement means) 11 Control belt winding section (displacement means) 12 Tension spring (displacement means) 21 Photoconductor belt (endless belt)

Claims (3)

[Claims] 1. A mechanism provided in a recording material conveying device having an endless belt that is stretched between at least three belt suspension tension members, and at least one end of at least one belt suspension tension member. Belt deviation detection member rotatably supported on the belt deviation detection member and the belt deviation detection member when a rotational torque acts on the belt deviation detection member due to a frictional force between the belt deviation detection member and the endless belt portion hanging on the belt deviation detection member. Of the endless belt deviation prevention mechanism having a displacement means for displacing the rotational movement of the belt movement with a linear movement to displace the end portion of the belt suspension tension member in a predetermined direction, the belt deviation detection member and the displacement means being recorded. It is arranged on a belt suspension tension member other than the material conveying surface, and the belt deviation detection member is arranged outside the recording material conveying area. Deviation prevention mechanism of the endless belt, characterized. 2. A recording material conveying device having the endless belt is composed of a transfer belt for transferring an image formed on at least one image carrier to a recording material, and the belt deviation detecting member and the displacing means are provided. 2. The endless belt deviation preventing mechanism according to claim 1, wherein the belt deviation detecting member is arranged on a belt suspension tension member that is not flush with the image transfer area, and the belt deviation detecting member is arranged outside the image area. 3. A mechanism provided in a recording material conveying device having an endless photosensitive belt which is stretched between at least four belt suspension tension members, the mechanism comprising at least one belt tension tension member. Of the belt deviation detection member rotatably supported on at least one end of the belt deviation detection member and the belt deviation detection member when the rotational torque acts on the belt deviation detection member by the frictional force between the belt deviation detection member and the endless belt portion hanging on the belt deviation detection member. An endless belt deviation prevention mechanism having a displacement means for displacing the rotational movement of the deviation detection member with a linear movement to displace the end of the belt suspension tension member in a predetermined direction, wherein the belt deviation detection member and the displacement The means is disposed on a belt suspension tension member that is not on the same surface as the image exposure area and the image transfer area, and the belt deviation detection member is an image area. Endless belt deviation preventing mechanism, wherein more that provided outside.