JP2000038232A - Belt conveyor device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt conveyor device which prevents the elongation and deformation of an endless belt stretched and arranged rotatably and does not increase warming up time for strating the next image formation beyond necessity and an image forming device using the same. SOLUTION: In a belt conveyor device which consists of an endless belt member 1 stretched and supported on a plurality of rotatable roller members 2 and conveys an object to be supported on the belt member 1 by turning it, an environment sensor 3 detecting environment information around the belt member 1, a variable tension means 4 changing tensile force of the belt member 1, and a control means 5 reducing or releasing tensile force given to the belt member 1 by the variable tension means 4 under the condition in which the environment information detected by the environment sensor 3 when the belt member 1 stops the turning exceeds a set value specified in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt conveying device for rotating a belt member for carrying an image, a belt member for conveying a sheet and the like, and an image forming apparatus using the same.
In particular, the present invention relates to a belt transport device of a type in which the belt member is stretched and supported by a plurality of rolls, and an improvement of an image forming apparatus using the belt transport device.

[0002]

2. Description of the Related Art As a conventional intermediate transfer type image forming apparatus, for example, a photosensitive drum on which a toner image corresponding to an electrostatic latent image is formed, and a toner image on the photosensitive drum are intermediately transferred. An intermediate transfer belt, a primary transfer device for transferring the toner image on the photosensitive drum to the intermediate transfer belt, and a secondary transfer device for collectively secondary transferring the toner image transferred on the intermediate transfer belt to paper A device having a transfer device is known (see, for example, JP-A-5-323704).

In this type of image forming apparatus, from the viewpoint of forming a high-quality image without disturbance such as image unevenness, white spots, and distortion, the intermediate transfer belt has a toner image bearing surface of the intermediate transfer belt. It is important to be smooth,
Conventionally, an endless intermediate transfer belt has been stretched and supported by a plurality of rolls to maintain smoothness.

[0004]

When the intermediate transfer belt is stretched by a plurality of rolls as described above, a predetermined tension acts on the intermediate transfer belt and a stress is applied. While the intermediate transfer belt rotates, this stress is not particularly problematic because the stress is dispersed throughout the intermediate transfer belt. However, when the intermediate transfer belt is left standing for a long time with the rotation stopped, the stress is reduced. Concentration occurs near the roll support portion of the transfer belt, and the winding tendency of the intermediate transfer belt occurs near this portion. If the stress exceeds the allowable stress of the material forming the intermediate transfer belt, the intermediate transfer belt will be elongated. Such a phenomenon is particularly noticeable in a high-temperature environment.

If the surroundings change to a high-temperature environment or a high-humidity environment while the rotation of the intermediate transfer belt is stopped, the intermediate transfer belt expands and expands with an increase in temperature and humidity. And However, in the roll supporting portion, the elongation of the intermediate transfer belt is limited because the roll and the intermediate transfer belt are in close contact with each other, and therefore, an internal stress is generated at the contact portion of the intermediate transfer belt. Further, due to the close contact between the roll and the back surface of the intermediate transfer belt, a difference in the amount of belt elongation occurs between the front and back surfaces of the belt, and the internal stress causes permanent plastic deformation of the intermediate transfer belt (corrugated shape having a maximum width of about 2.5 mm). (Swell) occurs.

In such a situation, even if the intermediate transfer belt is stretched by a plurality of rolls, the generated undulation cannot be eliminated, and therefore, the smoothness of the toner image bearing surface of the intermediate transfer belt is reduced. As a result, the image cannot be maintained and the formed image is disturbed.

Therefore, in order to solve such technical problems, for example, as an first means, in an electrophotographic apparatus using an intermediate transfer belt, one of a plurality of rolls over which the intermediate transfer belt (Japanese Patent Laid-Open No. 4-119371) has been proposed in which a solenoid is provided in such a manner that the solenoid is moved in a direction to release the tension acting on the intermediate transfer belt when the power supply of the apparatus is cut off.

However, when the above-mentioned first means is applied, tension is always applied to the intermediate transfer belt while the power of the apparatus is turned on. If the environment is suddenly changed to a high-temperature environment or a high-humidity environment in a state where the intermediate transfer belt is stopped or the rotation of the intermediate transfer belt is stopped, the above-described plastic deformation of the intermediate transfer belt may not be able to be avoided.

[0009] As a second means, a swing member swinging at the time of rotation and stop of the transfer belt stretched and rotated between the rollers, and the transfer belt is always rotated at the start of rotation in accordance with the swing operation. A transfer belt support mechanism having a biasing member for applying tension and releasing the tension when the transfer belt stops rotating (see JP-A-63-188175);
As a third means, an electrophotographic printing apparatus provided with an endless belt for electrostatically adsorbing and transferring a transfer body, wherein a mechanism for releasing or reducing a tension applied to the endless belt during a non-printing operation is provided. (JP-A-3-179476)
And the like) have been proposed. In these cases, unlike the first means, when the rotation of the intermediate transfer belt is stopped even during power-on, the tension applied to the intermediate transfer belt is always released or reduced. Therefore, it may be effective in solving the above problems.

However, in the above-mentioned second and third means, the tension is released or reduced even under an environmental condition in which there is no possibility of plastic deformation of the intermediate transfer belt, and the unnecessary tension release (reduction) is also performed. It will be done. In such an embodiment, the tension applied to the intermediate transfer belt must be restored every time image formation is to be started. Then, when the tension is restored, a shift in the width direction of the intermediate transfer belt occurs, so that it takes time to correct this shift. Tension release (reduction)
Therefore, there is a technical problem that an extra warm-up time is required for correcting the displacement.

Incidentally, such technical problems are not limited to the intermediate transfer belt. For example, the paper successively passes through a photoreceptor belt used as an image carrier or a transfer portion of a plurality of image forming units. A sheet conveying belt of an image forming apparatus of a type having a sheet conveying belt to be transferred, and sequentially transferring each color component toner image formed by each image forming unit to a sheet on the sheet conveying belt, and transferring the transferred sheet to a fixing device. The same can occur for a paper transport belt to be transported or a fixing belt of a fixing device using a belt member.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problem, and appropriately adjusts the tension at the time of stopping rotation of an endless belt rotatably stretched and arranged according to environmental conditions. Provided is a belt conveying device that prevents elongation and deformation of an endless belt by controlling, and does not unnecessarily increase a warm-up time for starting the next image formation, and an image forming apparatus using the same. Things.

[0013]

That is, as shown in FIG. 1, the present invention comprises an endless belt member 1 stretched and supported by a plurality of rotatable roll members 2. An environment sensor 3 for detecting environmental information around the belt member 1, a tension varying means 4 for varying the tension of the belt member 1, and a belt member. Control means 5 for reducing or canceling the tension applied to the belt member 1 by the tension varying means 4 under the condition that the environment information from the environment sensor 3 exceeds a predetermined set value at the time of the rotation stop of 1. It is characterized by.

In such technical means, the belt member 1 which is the object of the present invention may be of any material and structure. For example, a semiconductive or dielectric electrostatic attraction belt that conveys a sheet such as paper, an image carrying belt made of a photoconductor or a dielectric carrying a toner image, etc., and a toner image carried on the image carrier An intermediate transfer belt or a fixing belt for fixing a sheet such as a sheet carrying a toner image may be used.

The environmental information detected by the environmental sensor 3 may be appropriately selected from various types of environmental information that may cause the deformation of the belt member 1. For example, the deformation of the belt member 1 due to creep or the like may be selected. From the viewpoint of prevention, it is sufficient to detect at least one of the ambient temperature information and the humidity information. Also, from the viewpoint of preventing deformation of the belt member 1 due to a sudden environmental change. For example, at least one of ambient temperature change information and humidity change information over time may be detected. Further, the timing at which the environment sensor 3 detects the environmental information may be appropriately selected, and the detection may be performed when the rotation of the belt member 1 is stopped. Alternatively, the detection may always be performed.

Further, as long as the tension varying means 4 is capable of varying the tension of the belt member 1, its structure and arrangement may be appropriately selected. Here, from the viewpoint of simplification and downsizing of the device configuration, the tension varying means 4 is attached to one of the plurality of roll members 2 and the tension is varied by moving the roll member 2. It is preferable to configure.

The control means 5 controls the tension changing means 4 to operate the belt member 1 under the condition that the environment information from the environment sensor 3 exceeds a predetermined value when the belt member 1 is stopped.
May be appropriately selected as long as it is controlled so as to reduce or cancel the tension applied to the substrate.

When a functional member other than the roll member 2 (for example, a primary transfer unit to be described later) is brought into contact with the belt member 1, the tension changing means 4 gives the belt member 1 by the control means 5. Even if the tension is reduced or released, as long as another functional member is in contact with the belt member 1, the belt member 1 may be plastically deformed at the contact portion. Therefore, from the viewpoint of preventing plastic deformation of the belt member 1 at the contact portion, the control unit 5 contacts the belt member 1 when the tension varying unit 4 reduces or cancels the tension applied to the belt member 1. It is preferable to control the other functional members to be moved in a direction in which the tension of the belt member 1 is reduced or released.

Further, the above-mentioned belt conveying device is, for example,
A photoreceptor belt used as an image carrier, and a paper transport belt through which paper is sequentially passed at each transfer site of the plurality of image forming units. Each color component toner image formed by each image forming unit is transferred onto the paper transport belt. Paper transfer belt for an image forming apparatus of the type that transfers images sequentially to different types of paper, a paper transfer belt for transporting the transferred paper to a fixing device, or a copying machine or printer using a fixing belt of a fixing device using a belt member. It is preferably applied to an image forming apparatus such as an image forming apparatus. In particular, the image forming apparatus includes an image carrier on which a toner image corresponding to image information is carried, and an endless belt member stretched and supported by a plurality of rotatable roll members. An intermediate transfer belt opposed to the image carrier, a primary transfer unit for sequentially transferring the toner image on the image carrier onto the intermediate transfer belt, and a transfer onto the intermediate transfer belt; In an image forming apparatus including a secondary transfer unit that collectively transfers the held toner images onto a recording medium, and a belt cleaner that cleans a residue on the intermediate transfer belt after the secondary transfer, an image forming apparatus including: An environmental sensor for detecting environmental conditions; a tension varying means for varying the tension of the intermediate transfer belt; and a tension sensor under a condition in which environmental information from the environmental sensor exceeds a preset value when the rotation of the intermediate transfer belt is stopped. It is preferable to apply the present invention to an intermediate transfer body type image forming apparatus including a control unit for reducing or canceling the tension applied to the belt member by the variable unit.

In the image forming apparatus of the intermediate transfer type, the primary transfer means, the secondary transfer means and the belt cleaner are arranged in contact with the intermediate transfer belt, for example, when the primary transfer means is constituted by a transfer roll. In some types, even if the tension applied to the intermediate transfer belt by the tension changing means is reduced or released by the control means,
As long as the primary transfer means, the secondary transfer means, and the belt cleaner are in contact with the intermediate transfer belt, there is a possibility that the intermediate transfer belt is plastically deformed at each contact portion. From the viewpoint of preventing the plastic deformation of the intermediate transfer belt at such a contact portion, the control unit controls the primary transfer unit and the secondary transfer unit when the tension varying unit reduces or cancels the tension applied to the intermediate transfer belt. It is preferable to control the transfer means and the belt cleaner so that the tension applied to the intermediate transfer belt is reduced or released.

Next, the operation of the above technical means will be described. In FIG. 1, under the condition that the rotation of the belt member 1 stretched over the plurality of roll members 2 is stopped and the environment information from the environment sensor 3 exceeds a predetermined set value, The tension varying means 4 reduces or cancels the tension applied to the belt member 1. For this reason, the tension of the belt member 1 is released under an environmental condition in which the belt member 1 may be deformed, so that the deformation of the belt member 1 is prevented. On the other hand, the tension of the belt member 1 is not released under the environmental condition in which the belt member 1 is not likely to be deformed, so that the warm-up time for starting the next image formation is not unnecessarily increased.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. Embodiment FIG. 2 shows a schematic configuration of a color image forming apparatus (a color electrophotographic copying machine in the present embodiment) in which an embodiment of the belt conveying device according to the present invention is incorporated. In the figure,
Reference numeral 11 denotes a photosensitive drum (latent image carrier),
With the rotation in the direction, an electrostatic latent image corresponding to the image information is formed on the surface by a well-known electrophotographic process such as a charging device 12 and an exposure device (not shown, an exposure beam is denoted by reference numeral 13). You. Around the photosensitive drum 11, developing devices 14 corresponding to each color of black (Bk), yellow (Y), magenta (M), and cyan (C) are provided.
17 are provided, and the electrostatic latent image formed on the photosensitive drum 11 is developed by any of the developing units 14 to 17 to form a toner image T. Note that reference numeral 19
Is a drum cleaner that collects residual toner that has not been primarily transferred.

Reference numeral 20 denotes an intermediate transfer belt disposed in contact with the surface of the photosensitive drum 11, and is stretched over a plurality of (four in the present embodiment) rolls 21 to 24 and is indicated by an arrow B direction. To rotate. Here, the intermediate transfer belt 20 has a volume resistivity of 10 ⁶ to 10 ¹⁵ Ω · cm by containing an appropriate amount of carbon black or the like in a resin such as polyimide, polycarbonate, polyester, polypropylene, or polyethylene terephthalate or various rubbers. The thickness is set to, for example, 0.1 mm. Further, reference numeral 21 denotes a driven roll, 22 denotes a driving roll of the intermediate transfer belt 20, 23 denotes a tension roll for controlling the tension of the intermediate transfer belt 20, and 24 denotes an opposing roll (backup roll) for secondary transfer.

The tension roll 23 is provided with a tension varying device 27 that varies the tension applied to the intermediate transfer belt 20 by supporting and moving the tension roll 23. In the present embodiment, as shown in FIG. 3, the tension varying device 27 includes a pair of roll support members 71 that rotatably support the rotating shafts 23 a at both ends of the tension roll 23, and a pair of the roll support members 7.
And a swing mechanism 70 for swinging the swing mechanism 1.

Here, the roll support member 71 is slidably fitted in a concave groove (not shown) formed in a frame member 78 provided outside the roll support member 71. The movement direction is restricted only to the direction of arrow C and the opposite direction. In the present embodiment, the following is employed as the swing mechanism 70. That is, the stepping motor 77 is fixed to the frame member 78 and the bracket 73
Is rotatably mounted. One end of a spring 72 is attached to the other end of the tension roller 23 shaft support portion of the roll support member 71, and the other end of the spring 72 is attached to a free rotation end of the bracket 73. Further, the rotation shaft 73 of the bracket 73
A gear 74 is coaxially fixed to a, and a gear 75 meshing with the gear 74 and a gear 76 fixed coaxially with the rotation shaft of the stepping motor 77 mesh with each other.

Further, in the present embodiment, a primary transfer device (this embodiment) is provided on a portion (primary transfer position) of the intermediate transfer belt 20 facing the photosensitive drum 11 and on the back side of the intermediate transfer belt 20. In this embodiment, a primary transfer roll 18 is provided, and by applying a voltage having a polarity opposite to the charging polarity of the toner to the primary transfer roll 18, the photosensitive drum 11
The upper toner image is electrostatically attracted to the intermediate transfer belt 20.

Further, a secondary transfer device 40 is provided at a secondary transfer position of the intermediate transfer belt 20 facing the conveyance path of the sheet P as a recording material. And a counter roll (back-up roll) 24 disposed on the back surface side of the intermediate transfer belt 20 and serving as a counter electrode of the secondary transfer roll 25. Have been.
In the present embodiment, the secondary transfer roll 25 is grounded, and a bias having the same polarity as the charged polarity of the toner is stably applied to the backup roll 24 via the power supply roll 26. The secondary transfer roll 25 has a cleaning blade 2 made of, for example, urethane rubber.
8 is attached.

Further, a belt cleaner 41 is provided downstream of the secondary transfer device 40 for removing the toner T remaining on the intermediate transfer belt 20 without being transferred onto the paper P.

In the present embodiment, the paper transporting system feeds the paper P from the paper tray 50 to a feed roll 51.
The sheet P is sent to the secondary transfer position at a predetermined timing after the positioning is once stopped by the registration roll (registration roll) 52, and the sheet P after the secondary transfer is not illustrated. The sheet is guided to a conveyance belt 53 via a sheet conveyance guide, and is conveyed to a fixing device 54 by the conveyance belt 53. Further, in the present embodiment, as shown in FIG. 4, the secondary transfer roll 25 and the belt cleaner 41 are disposed so as to be able to freely contact and separate from the intermediate transfer belt 20 by contacting / separating devices 104 and 105 including actuators and the like. When a color image is formed, these members are separated from the intermediate transfer belt 20 until the toner image before the final color passes through the secondary transfer roll 25 and the belt cleaner 41.

Further, in this embodiment, as shown in FIG. 4, a tension control system 100 for controlling the tension applied to the intermediate transfer belt 20 is provided. In FIG.
Reference numeral 1 denotes a rotation detection sensor provided on the drive roll 22 of the intermediate transfer belt 20 to detect the rotation state of the intermediate transfer belt 20; 102a, a temperature sensor for detecting the ambient temperature;
2b is a humidity sensor for detecting the surrounding humidity, 103 is a contact / separation device for retracting the primary transfer roll 18 from the intermediate transfer belt 20, 104 is a contact / separation device for retracting the secondary transfer roll 25 from the intermediate transfer belt 20, and 105 is A contact / separation device for retracting the belt cleaner 41 from the intermediate transfer belt 20 and a control device 106 for controlling them.

FIG. 5 is a block diagram of the control system 100. In the figure, a belt rotation signal 111 from a rotation detection sensor 101, a temperature signal 112 from a temperature sensor 102a, and a humidity signal 113 from a humidity sensor 102b.
Is input to the CPU 122 via the input interface 121, and then the CPU 122 executes a control program (program for executing the image forming process, the belt driving monitoring process, and the belt stopping control process) stored in the ROM 123 in advance. After performing appropriate data processing with the RAM 124, the belt tension control signal 131 is sent to the tension varying device 27 via the output interface 125.
The primary transfer roll position control signal 132 is supplied to the contact / separation device 103 of the primary transfer roll 18, and the secondary transfer roll position control signal 133 is supplied to the contact / separation device 104 of the secondary transfer roll 25.
, And a belt cleaner position control signal 134 is sent to the contact / separation device 105 of the belt cleaner 41, respectively.

Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. More specifically, if the electrostatic latent image written on the photosensitive drum 11 corresponds to, for example, yellow image information, the electrostatic latent image is yellow (Y).
The toner is developed by the developing device 15 containing the toner, and a yellow toner image T is formed on the photosensitive drum 11. Then, the unfixed toner image T formed on the photosensitive drum 11
Is transferred from the photosensitive drum 11 to the surface of the intermediate transfer belt 20 by a transfer electric field formed by the primary transfer roll 18 at a primary transfer position where the photosensitive drum 11 and the intermediate transfer belt 20 are in contact with each other.

At this time, when forming a monochrome image,
The toner image T primarily transferred to the intermediate transfer belt 20 is immediately secondary-transferred. However, when a color image in which toner images of a plurality of colors are superposed is formed, the photosensitive drum 1
The process of forming the toner image on the surface 1 and the primary transfer of the toner image is repeated by the number of colors. For example, when a toner image in which four color toner images are superimposed is formed, black, yellow,
Magenta and cyan toner images T are formed, and these toner images T are sequentially primary-transferred onto the intermediate transfer belt 20 in order.
On the other hand, the intermediate transfer belt 20 rotates at the same cycle as the photosensitive drum 11 while holding the first primary-transferred black toner image T, and the yellow and magenta And a cyan toner image T are formed.

The toner image T primarily transferred to the intermediate transfer belt 20 in this manner is conveyed to a secondary transfer position as the intermediate transfer belt 20 rotates. On the other hand, the sheet P is supplied to the secondary transfer position by the registration roll 52 at a predetermined timing. After the toner image before the final color on the intermediate transfer belt 20 has passed, the secondary transfer roll 25 comes into contact with the intermediate transfer belt 20 at a predetermined timing, and the secondary transfer roll 25 nips the paper P against the backup roll 24. I do.

Then, the toner image T carried on the intermediate transfer belt 20 is moved to the secondary transfer position by the action of the transfer electric field formed between the secondary transfer roll 25, which is the secondary transfer device 40, and the backup roll 24. Is transferred to the sheet P. The sheet P on which the toner image T is transferred is conveyed to the fixing device 54 by the conveying belt 53, and the toner image is fixed. On the other hand, the toner remaining on the intermediate transfer belt 20 after the transfer is cleaned by the belt cleaner 41 in contact with the intermediate transfer belt 20 after the toner image before the final color on the intermediate transfer belt 20 has passed.

Here, the tension is applied to the intermediate transfer belt 20 as follows. 3, when the stepping motor 77 rotates in the direction D in the drawing, the brackets 73,
Rotates in the direction D ′ about the rotation shaft 73a. The spring 72 is extended with the movement of the bracket 73, and at the same time, moves the roll support member 71 in the direction of arrow C.
At this time, the tension roll 23 attached to the end of the roll support member 71 moves in a direction to press the intermediate transfer belt 20 from the inside, and the intermediate transfer belt 20 is stretched with a predetermined tension. On the other hand, the reduction of the tension applied to the intermediate transfer belt 20 is achieved by rotating the stepping motor 77 in the direction E in the drawing to move the bracket 73 in the E ′ direction and moving the tension roll 23 in the direction opposite to the direction of the arrow C. This is done by letting

The variable tension system of the intermediate transfer belt 20 is a system in which a solenoid or the like is connected to the tension roll 23 to directly move (in this case, the moving distance becomes several mm and the tension applied to the intermediate transfer belt 20 is completely reduced). The bracket 73 is temporarily moved by several meters as compared with
Even when the intermediate transfer belt 20 is moved by m, the movement distance is slightly absorbed by the extension of the spring 72, so that a state where a slight tension is applied to the intermediate transfer belt 20 can be maintained. Therefore, it is preferable that the lateral displacement of the intermediate transfer belt 20 can be minimized even when the tension is restored.

In the present embodiment, the temperature and humidity are measured by the temperature sensor 102a and the humidity sensor 102b at an arbitrary fixed time. Then, using the measurement results of the temperature and the humidity, as shown in FIG. 6, a belt driving time monitoring process is executed while the intermediate transfer belt 20 is driven, while the belt is stopped while the intermediate transfer belt is stopped. The stop control process is executed. Hereinafter, each process will be described.

(1) Belt Drive Monitoring Process FIG. 7 is a flowchart of the belt drive monitoring process. When the intermediate transfer belt 20 is driven, first, it is checked whether the tension applied to the intermediate transfer belt 20 is reduced. If the tension is reduced, the belt tension varying device 27 is used. Intermediate transfer belt 20
To correct the lateral displacement of the intermediate transfer belt 20 (position correction). At the same time, the primary transfer roll 18 that has been separated from the intermediate transfer belt 20 is returned to a predetermined position in contact with the intermediate transfer belt 20 by using the contact and separation device 103. On the other hand, if the tension applied to the intermediate transfer belt 20 is not reduced, the process proceeds to the next step.

Next, the temperature Tn is taken in, and the temperature Tn taken in and the temperature Tn + taken in next to this Tn are taken.
The calculation of the difference between 1 and 1 is performed. At this time, Tn + 1−T
If n is larger than a predetermined temperature difference ΔT, this temperature Tn is held as a reference temperature Tx.
Thereafter, the temperature Tn + 2 taken in after the Tx and Tn + 1
Is calculated, and if Tn + 2−Tx is larger than a predetermined allowable temperature difference T, the intermediate transfer belt 2
When the rotation of 0 is stopped, a tension reduction command to reduce the tension is issued, and the process returns to FIG. 6 while holding this command until the intermediate transfer belt 20 stops. On the other hand, Tn + 1
-When Tn is equal to or less than the specified temperature difference ΔT, and Tn + 2−
If Tn is equal to or smaller than the allowable temperature difference T, the process returns to FIG. In the present embodiment, the specified temperature difference ΔT is 2 ° C.
The allowable temperature difference T is set to 5 ° C.

Further, in the belt drive monitoring process in the present embodiment, humidity is monitored simultaneously with temperature (see FIG. 7). In the present embodiment, the specified humidity difference ΔM is set to 10%, and the allowable humidity difference M is set to 20%. Further, in the present embodiment, the temperature Tn and the humidity Mn are separately and independently monitored, and when at least one of the temperature and the humidity exceeds the allowable value, a command to reduce the tension of the intermediate transfer belt 20 is issued. Is issued.

(2) Belt Stop Control Process FIG. 8 is a flowchart of a belt drive monitoring process. When the driving of the intermediate transfer belt 20 is stopped,
First, while the intermediate transfer belt 20 is being driven (during the belt drive monitoring process), it is checked whether a tension reduction command has been issued, and if the tension reduction command has been issued, the belt tension can be varied. The tension applied to the intermediate transfer belt 20 is reduced by the device 27. At the same time, the primary transfer roll 18, the secondary transfer roll 25, and the belt cleaner 41, which have been in contact with the intermediate
3, 3, and 105 are retracted from the intermediate transfer belt 20. On the other hand, if the tension release command for the intermediate transfer belt 20 has not been issued, the process directly proceeds to the next step.

Next, the temperature Tn is captured, and the captured temperature Tn is compared with a predetermined allowable temperature Tmax. At this time, when the temperature Tn is higher than the allowable temperature Tmax, the tension applied to the intermediate transfer belt 20 is reduced by the tension changing device 27, and at the same time, the primary transfer roll 18, the secondary transfer roll 25, and the belt cleaner 41 are The transfer belt 20 is retracted. However, if the tension applied to the intermediate transfer belt 20 has already been reduced, that state is maintained. In the present embodiment, the allowable temperature Tmax is set to 25 ° C. This is the lower limit of the temperature at which the elongation or deformation of the intermediate transfer belt 20 is likely to occur, and is determined by various physical properties of the intermediate transfer belt 20.

On the other hand, if the taken-in temperature Tn is lower than the predetermined allowable temperature Tmax, the taken-in temperature Tn and the taken-in temperature next to the taken-in temperature Tn are used in the same manner as in the belt drive monitoring process. The calculation of the difference from the temperature Tn + 1 is performed. At this time, if Tn + 1−Tn is larger than a predetermined temperature difference ΔT, this temperature T
n is held as the reference temperature Tx. Thereafter, a difference between the Tx and the temperature Tn + 2 taken in after the Tn + 1 is calculated. If Tn + 2−Tx is larger than a predetermined allowable temperature difference T, the tension varying device is used. 27 reduces the tension applied to the intermediate transfer belt 20, and at the same time, the primary transfer roll 18, the secondary transfer roll 25, and the belt cleaner 41.
Is withdrawn from the intermediate transfer belt 20. However, if the tension applied to the intermediate transfer belt 20 has already been reduced, that state is maintained.

On the other hand, if Tn + 1−Tn is equal to or smaller than the specified temperature difference ΔT, it is checked whether the tension applied to the intermediate transfer belt 20 has been reduced. Then, a process of determining whether or not to return the tension is executed (hereinafter, referred to as a belt tension return process). That is, the temperature Tn and the predetermined return temperature Tm
and if the temperature Tn is lower than the return temperature Tmin, the tension applied to the intermediate transfer belt 20 is restored by the belt tension varying device 27, and at the same time, the primary transfer roll separated from the intermediate transfer belt 20 is removed. 18 is a contact / separation device 1
03 is returned to a predetermined position in contact with the intermediate transfer belt 20. In the present embodiment, the return temperature Tmin is set to 15 ° C. This is the intermediate transfer belt 20
This is a temperature at which elongation or deformation of the intermediate transfer belt hardly occurs, and is a value determined by various physical properties of the intermediate transfer belt 20. Also,
If the tension applied to the intermediate transfer belt 20 has not been reduced, or if the tension applied to the intermediate transfer belt 20 has been reduced but the temperature Tn is equal to or lower than the return temperature Tmin, the operation returns to the position shown in FIG. .

Further, in the control process at the time of stopping the belt according to the present embodiment, control based on humidity as well as temperature is performed (see FIG. 8). In the present embodiment,
The allowable humidity Mmax is 70% and the return humidity Mmin is 30%.
% Are set respectively. Further, in the present embodiment, the temperature Tn and the humidity Mn are separately and independently monitored, and when at least one of the temperature and the humidity exceeds the allowable value, the tension applied to the intermediate transfer belt 20 is reduced. Is to be reduced.

In the present embodiment, when the power of the image forming apparatus is turned off, the tension applied to the intermediate transfer belt 20 is reduced by the tension varying device 27 without fail.
The primary transfer roll 18, the secondary transfer roll 25, and the belt cleaner 41 are retracted from the intermediate transfer belt 20 by respective contacting / separating devices 103, 104, and 105.

As described above, in the present embodiment, the temperature difference and the humidity difference are monitored during the driving of the intermediate transfer belt 20, and the temperature difference or the humidity difference is set to a predetermined allowable temperature difference or allowable humidity. If the difference is exceeded, the intermediate transfer belt 2
0, the tension applied to the intermediate transfer belt 20 is reduced immediately after the rotation of the intermediate transfer belt 20 is stopped.
Zero elongation and deformation are reliably prevented.

While the driving of the intermediate transfer belt 20 is stopped, the temperature and the humidity and the temperature difference and the humidity difference are monitored, and when the temperature or the humidity exceeds a predetermined allowable temperature or humidity. Also, when the temperature difference or the humidity difference exceeds a predetermined allowable temperature difference or allowable humidity difference, the tension applied to the intermediate transfer belt 20 is reduced. And deformation are reliably prevented.

Further, when the driving of the intermediate transfer belt 20 is stopped and the tension applied to the intermediate transfer belt 20 is reduced, the temperature or the humidity is reduced.
When the temperature falls below the return temperature Tmin or the return humidity Mmin, the warm-up time for starting the next image formation is reduced by that amount.

On the other hand, under environmental conditions where the intermediate transfer belt 20 is not likely to be deformed or stretched, the tension applied to the intermediate transfer belt 20 is not released.
The warm-up time for starting the next image formation is not unnecessarily increased.

In the belt driving monitoring process according to the present embodiment, the temperature difference and the humidity difference are monitored from the viewpoint of coping with environmental fluctuations during the driving of the intermediate transfer belt. Instead, a tension reduction command may be issued when the temperature or humidity exceeds the allowable temperature Tmax or the allowable humidity Mmax. In the belt driving monitoring process, the temperature, the humidity, the temperature difference, and the humidity difference may be used in an appropriate combination.

Further, in the belt stop control process of the present embodiment, the tension return process is executed when a predetermined condition is satisfied. However, this process may be omitted.

Furthermore, in the belt stop control process of the present embodiment, the temperature, humidity, temperature difference and humidity difference are monitored. However, the present invention is not limited to this. It only needs to monitor one.

[0055]

As described above, according to the present invention,
By appropriately controlling the tension at the time of rotation stop of the rotatably stretched belt member in accordance with environmental conditions, the belt member may be stretched or deformed under environmental conditions in which the belt member may be stretched or deformed. Reduce or release tension,
Under the environmental conditions where the belt member is not likely to be stretched or deformed, the tension of the belt member is not reduced or the releasing operation is not executed. It is possible to prevent unnecessary warm-up time from increasing unnecessarily.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a belt conveying device according to the present invention.

FIG. 2 is an explanatory diagram showing an outline of an intermediate transfer type color image forming apparatus incorporating a belt transport device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a control system of the color image forming apparatus according to the embodiment.

FIG. 4 is an explanatory diagram illustrating an outline of a variable tension device of an intermediate transfer belt of the color image forming apparatus according to the embodiment.

FIG. 5 is a block diagram illustrating a control system of the color image forming apparatus according to the embodiment.

FIG. 6 is a flowchart illustrating a tension control process of the color image forming apparatus according to the embodiment.

FIG. 7 is a flowchart showing a belt driving monitoring process.

FIG. 8 is a flowchart illustrating a belt stop control process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Belt member, 2 ... Roll member, 3 ... Environmental sensor, 4
... tension varying means, 5 ... control means, 11 ... photosensitive drum,
18 primary transfer device (primary transfer roll), 20 intermediate transfer belt, 21 driven roll, 22 drive roll, 23
... tension roll, 24 ... backup roll, 25
... secondary transfer roll, 27 ... variable tension device, 41 ... belt cleaner, 100 ... control system, 102a ... temperature sensor, 1
02b: Humidity sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Hayashi 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. (72) Inventor Nobuo Hyakutake 2274 Hongo, Ego-shi, Kanagawa Fuji Xerox Co., Ltd. (72) Inventor Masao Okubo 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Yoko Miyamoto 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. 3F049 AA10 BB04 BB06 BB12 LA02 LB03

Claims (7)

[Claims] 1. A belt transport device comprising an endless belt member stretched and supported by a plurality of rotatable roll members, and transporting an object carried on the belt member while rotating the belt member. An environment sensor for detecting environmental information around the circumstance, a tension varying means for varying the tension of the belt member, and a condition in which the environmental information from the environmental sensor exceeds a predetermined set value when the rotation of the belt member is stopped. A belt transport device, comprising: a control unit configured to reduce or cancel the tension applied to the belt member by the tension varying unit. 2. The belt conveyance device according to claim 1, wherein the environment sensor detects at least one of temperature information and humidity information as environment information. 3. The belt conveying device according to claim 1, wherein the environment sensor detects at least one of temperature change information and humidity change information over time as environment information. Transport device. 4. The belt conveying device according to claim 1, wherein the control unit controls another functional member that contacts the belt member when the tension varying unit reduces or cancels the tension applied to the belt member. A belt conveying device for moving a belt member in a direction in which the tension of the belt member is reduced or released. 5. An image forming apparatus comprising the belt conveying device according to claim 1. 6. An intermediate member comprising an image carrier for carrying a toner image corresponding to image information, and an endless belt member stretched and supported by a plurality of rotatable roll members, and disposed opposite to the image carrier. A transfer belt, a primary transfer means for sequentially transferring the toner image on the image carrier onto the intermediate transfer belt, and a secondary transfer means for transferring the toner image transferred and held on the intermediate transfer belt to a recording medium at a time. An image forming apparatus including a belt cleaner for cleaning a residue on the intermediate transfer belt after the secondary transfer, an environment sensor for detecting an environmental condition around the intermediate transfer belt, and a tension for varying a tension of the intermediate transfer belt. A variable means for reducing or canceling the tension applied to the intermediate transfer belt by the tension variable means under a condition in which environmental information from an environment sensor exceeds a predetermined value when the rotation of the intermediate transfer belt is stopped. An image forming apparatus comprising: 7. The image forming apparatus according to claim 6, wherein
In the type in which the primary transfer unit, the secondary transfer unit, and the belt cleaner are arranged in contact with the intermediate transfer belt, the control unit is configured to reduce or cancel the tension applied to the intermediate transfer belt by the tension variable unit. An image forming apparatus, wherein a primary transfer unit, a secondary transfer unit, and a belt cleaner are moved in a direction in which a tension applied to an intermediate transfer belt is reduced or released.