JP2003173089A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten copying time by making the start of warm-up for the stabilization of a transfer belt fast. <P>SOLUTION: In a color copying machine 1 having a photoreceptor drum 9 on which a toner image corresponding to image information is held and an intermediate transfer belt 31 comprising freely rotational roll members and a belt member stretched and supported by the roll members, a tension control means 62 is provided. The tension control means 62 applies tension to the intermediate transfer belt 31 by the drive of a belt pressure release lever 52 when a human-body detection sensor 60 judges that a human body is near the sensor or when data are input through an operation panel 70. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a FAX, and more particularly to an image forming apparatus using an intermediate transfer member.

[0002]

2. Description of the Related Art Conventionally, as an intermediate transfer type image forming apparatus, as disclosed in, for example, Japanese Patent Application Laid-Open No. 5-323704, a photosensitive drum on which a toner image corresponding to an electrostatic latent image is formed, An intermediate transfer belt on which the toner image on the photoconductor drum is intermediately transferred, a primary transfer device that transfers the toner image on the photoconductor drum to the intermediate transfer belt, and toner transferred on the intermediate transfer belt. 2. Description of the Related Art A device that includes a secondary transfer device that secondarily transfers an image onto a sheet is known.

[0003]

The intermediate transfer belt needs to have a smooth toner image bearing surface in order to obtain a high-quality image free from irregularities such as image unevenness, white spots, and distortion. It was stretched and supported by a plurality of rolls to hold it. However, while the intermediate transfer belt was rotating, the stress was distributed over the entire belt, so there was no particular problem.However, if the intermediate transfer belt was left for a long time with the rotation stopped, the stress would be intermediate. Concentration occurred near the roll support portion of the transfer belt, and a curl was generated on the intermediate transfer belt in this vicinity.

In order to solve this problem, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open No. 119371, one in which a solenoid is provided on one of a plurality of rolls around which an intermediate transfer belt is provided, and the solenoid is moved in a direction to release tension each time the power of the apparatus is cut off, Proposed. However, this method is used when the power is always on,
When the fluctuation of the usage environment is small, the tension acting on the intermediate transfer belt is not released, and thus the plastic deformation of the intermediate transfer belt as described above cannot be avoided.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 2000-382232, the tension applied to the belt is released or reduced every time the rotation of the intermediate transfer belt is stopped based on the environmental information of the environmental sensor. The method to be done is proposed. However, in this method, the tension applied to the intermediate transfer belt is rapidly returned at the same time when the image formation is started, so that the state of the intermediate transfer belt is not stable and there is a possibility that the transfer position may be displaced. Further, in order to correct this misalignment, it takes a long time to warm up the intermediate transfer belt such as idling, so that even if the start button is pressed, it takes time to start image formation and a long copying time is required.

An object of the present invention is to shorten the copy time by accelerating the start of warming up for stabilizing the transfer belt.

[0007]

According to a first aspect of the present invention, there is provided an image carrier on which a toner image corresponding to image information is carried, and an intermediate transfer belt. The intermediate transfer belt is provided with a plurality of rotatable members. In an image forming apparatus having a roll member and a belt member stretched and supported by the roll member, a human body detection sensor for detecting whether an operator is nearby, and a tension acting on the intermediate transfer belt in response to the human body detection sensor. And a tension control means for varying the tension,
When the human body detection sensor determines that a person is nearby, the tension control means drives the tension varying means to apply tension to the intermediate transfer belt.

According to the first aspect of the present invention, when the operator approaches the image forming apparatus, the human body detection sensor provided in the apparatus determines that the operator is nearby. Then, when the signal from the sensor is input to the control unit, the tension varying means is driven to apply tension to the intermediate transfer belt, and then the belt is rotated to stabilize the belt, and the operator presses the start button. The image formation is started by. Therefore,
The warm-up of the intermediate transfer belt can be performed by using the time from when the operator approaches the image forming apparatus to when the start button is pressed. Therefore, the stabilization of the intermediate transfer belt can be accelerated, and the copy time can be shortened.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the human body detection sensor determines that a person is not near the tension control means during the image forming operation, At that time, the tension of the intermediate transfer belt is not released, and the tension of the intermediate transfer belt is released within a predetermined time after completion of the image forming operation.

According to the invention described in claim 2, claim 1
While exhibiting the same effect as the invention described in, the human body detection sensor during the image forming operation does not release the tension when it is determined that a person is not nearby, and after the image forming operation is completed,
The tension of the intermediate transfer belt is released after a predetermined time has elapsed. Therefore, even if the operator leaves the image forming apparatus during the image forming operation, the signal from the human body detection sensor is ignored, so that the tension of the intermediate transfer belt is not changed during the image forming operation.

According to a third aspect of the present invention, there is provided an image carrier on which a toner image corresponding to image information is carried, and an intermediate transfer belt composed of a belt member stretched and supported by a plurality of rotatable roll members. The image forming apparatus includes an operation panel for inputting information and a tension changing means for changing the tension of the intermediate transfer belt. It is characterized in that a tension control means for giving a tension is provided.

According to the third aspect of the invention, tension is applied to the intermediate transfer belt in conjunction with data input from the operation panel. Therefore, the warm-up of the intermediate transfer belt can be performed by utilizing the time from the input of data to the operation panel to the pressing of the start button.

According to a fourth aspect of the present invention, the tension control means drives the tension varying means to apply tension to the intermediate transfer belt, and at the same time, idles the intermediate transfer belt by a predetermined distance.

In the invention described in claim 4, the same effect as the invention described in claims 1 to 3 is obtained, and at the same time as the tension is applied to the intermediate transfer belt, the idling is started at the same time. Faster stabilization can be achieved.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a color copying machine 1 according to the present invention, and FIG.
FIG. 3 is an enlarged schematic configuration diagram of an image forming unit 3 of the color copying machine 1.

As shown in FIG. 1, a color copying machine 1 has an image forming section 3, a color image reading section (hereinafter referred to as “color scanner”) 5, a sheet feeding cassette 6 and a manual sheet feeding tray 8. The paper unit 7 and a control unit (not shown) for controlling the driving of the paper unit 7 and the like.

The color scanner 5 reads the color image information of the original for each color-separated light of red, green, and blue (hereinafter referred to as "R", "G", and "B"), and an electrical image signal is read. Convert to. Then, with the intensity levels of the R, G, and B color-separated image signals obtained by the color scanner 5 as a reference, color conversion processing is performed by an image processing unit (not shown), and black, cyan, magenta, yellow (hereinafter,
Image data of “Bk”, “C”, “M”, and “Y”) are obtained.

As shown in FIG. 2, the image forming section 3 includes a photosensitive drum 9 as an image carrier, a charging charger 11 as a charging means, a photosensitive blade cleaning device 17 including a cleaning blade 13 and a fur brush 15, and a developing unit. The revolver developing unit 21, the intermediate transfer unit 23, and the secondary transfer unit 25 are provided as means.

The writing optical unit 19 also converts the color image data from the color scanner 5 into an optical signal, and corresponds to the image of the original on the surface of the photosensitive drum 9 uniformly charged by the charging charger 11. Laser light L
Is irradiated to perform optical writing, and an electrostatic latent image is formed on the surface of the photosensitive drum 9. This writing optical unit 19
Is, for example, a semiconductor laser as a light source, a laser emission drive control unit, a polygon mirror 33 and a rotation motor 3 thereof.
5, f / θ lens 37, reflection mirror 39 and the like.

The revolver developing unit 21 includes a Bk developing machine 21a using Bk toner, a C developing machine 21b using C toner, an M developing machine 21c using M toner, a Y developing machine 21d using Y toner, and a half unit. It is composed of a developing revolver driving unit (not shown) that rotates clockwise.

Each of the developing machines 21a to 21d installed in the revolver developing unit 21 is a developing agent carrier which rotates by bringing the developing agent into contact with the surface of the photosensitive drum 9 to develop an electrostatic latent image. It is composed of sleeves 22a to 22d and a developing sleeve drive unit (not shown) for rotating them.

In this embodiment, each of the developing machines 21a-2a
The toner in 1d is negatively charged by stirring with the ferrite carrier, and the developing sleeves 22a to 22d are also charged.
Is applied with a developing bias power source (not shown) as a developing bias applying means, a developing bias voltage in which a negative DC voltage Vdc (DC component) and an AC voltage Vac (AC component) are superimposed is applied, and the developing sleeves 22a to 22d are exposed. The metal base layer of the body drum 9 is biased to a predetermined voltage.

In the standby state of the color copying machine 1, the revolver developing unit 21 is stopped at the home position where the Bk developing machine 21a is located at the developing position, and when the start key is pressed, reading of the original image data is started. Based on the color image data, optical writing by the laser light L, that is, electrostatic latent image formation starts (hereinafter, the electrostatic latent image based on the Bk image data is referred to as “Bk electrostatic latent image”. C, M,
The same applies to Y).

In order to enable development from the tip of the Bk electrostatic latent image, the rotation of the Bk developing sleeve is started before the tip of the electrostatic latent image reaches the Bk developing position to start the Bk electrostatic latent image. Is developed with Bk toner. Then, the developing operation of the Bk electrostatic latent image is continued, but when the rear end of the Bk electrostatic latent image passes the Bk developing position, the revolver developing is promptly performed until the developing machine of the next color reaches the developing position. The unit 21 rotates.

The intermediate transfer unit 23 includes an intermediate transfer belt 31 stretched around a plurality of rollers which will be described later.
Around the intermediate transfer belt 31, there are a secondary transfer belt 37 which is a transfer material carrier of the secondary transfer unit 25, a secondary transfer bias roller 39 which is a secondary transfer charge giving means, and an intermediate transfer body cleaning means. Belt cleaning blade 41, lubricant applying brush 4 as a lubricant applying means
3 and the like are arranged so as to face each other.

The intermediate transfer belt 31 includes a primary transfer bias roller 45, a belt drive roller 47, a belt tension roller 49, a secondary transfer counter roller 51, a cleaning counter roller 53, and a ground roller 55, which are primary transfer charge applying means. It is stretched. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 45 is grounded.

In the present embodiment, as shown in FIG. 3, one end of a tension spring 50 is connected to the belt tension roller 49 of the intermediate transfer belt 31, and the belt pressure release lever 52 is connected to the other end. Has been done. The belt pressure release lever 52 is rotatable around a fulcrum 52a. When the belt pressure release lever 52 rotates in the direction E in the figure, the tension spring 50 is compressed and the belt tension roller 49 causes the intermediate transfer belt 31 to move. Is moved from the inner side in a pressing direction, and the intermediate transfer belt 31 is stretched with a predetermined tension.

On the other hand, when the belt pressure release lever 52 rotates in the F direction in the figure, the tension spring 50 is extended and the belt tension roller 49 moves the intermediate transfer belt 31.
Is moved inward, and the tension of the intermediate transfer belt 31 is released. The driving operation of the belt pressure release lever 52 is controlled by the tension control means 62 according to the response of the human body detection sensor 60.

The primary transfer bias roller 45 is supplied with a transfer bias controlled to a predetermined current or voltage by a primary transfer power source 57 controlled to a constant current or a constant voltage according to the number of superposed toner images. It has been applied. Also,
The intermediate transfer belt 31 is driven in the arrow B direction by a belt driving roller 47 which is rotationally driven by a driving motor (not shown).

At a transfer portion (hereinafter referred to as “primary transfer portion”) 30 for transferring the toner image on the photosensitive drum 9 to the intermediate transfer belt 31, a primary transfer bias roller 45 and an earth roller 55 are used to transfer the intermediate transfer belt 31 to the photosensitive member. The photosensitive drum 9 is stretched by pressing it against the drum 9 side.
A nip portion 32 having a predetermined width is formed between the intermediate transfer belt 31 and the intermediate transfer belt 31.

The lubricant coating brush 43 is for polishing zinc stearate 44 as a lubricant formed in a plate shape and applying the polished fine particles to the intermediate transfer belt 31. The lubricant coating brush 43 is configured to be adjacent to the intermediate transfer belt 31, and is controlled so as to come into contact with the intermediate transfer belt 31 at a predetermined timing.

Secondary transfer belt 3 of secondary transfer unit 25
7 is stretched around three support rollers 59, 613, 63, and the stretched portion between the support rollers 59, 63 can be pressed against the secondary transfer counter roller 51. One of the three support rollers 59, 61, 63 is a drive roller that is rotationally driven by a drive unit (not shown), and the drive roller drives the secondary transfer belt 37 in the direction indicated by arrow C in the figure. .

The secondary transfer bias roller 39 is a secondary transfer means and is disposed so as to sandwich the intermediate transfer belt 31 and the secondary transfer belt 37 between the secondary transfer opposing roller 51 and the constant current control. A secondary transfer power supply 65 applies a transfer bias of a predetermined current. In addition, a position where the secondary transfer belt 37 and the secondary transfer bias roller 39 are in pressure contact with the secondary transfer counter roller 51 (a position indicated by a solid line in FIG. 2) and a position where they are separated (a position indicated by a chain line in FIG. 2). In order to obtain the above, a separation / contact mechanism (not shown) that drives the support roller 59 and the secondary transfer bias roller 39 in the direction of arrow D is provided.

Further, reference numeral 67 in FIG. 2 denotes a registration roller pair, which is provided between the intermediate transfer belt 31 and the secondary transfer belt 37 sandwiched between the secondary transfer bias roller 39 and the secondary transfer counter roller 51. Transfer paper P, which is a transfer material, is fed at the timing of.

In the portion of the secondary transfer belt 37, which is stretched on the support roller 63 on the fixing roller pair 27 side, a transfer paper charge eliminator 69 which is a transfer material charge eliminator, and a belt which is a transfer material carrier charge eliminator. The antistatic charger 71 faces. Further, a cleaning blade 73, which is a transfer material carrying member cleaning means, is in contact with a portion of the secondary transfer belt 37 which is stretched around the lower support roller 61 in the drawing.

The transfer paper charge eliminator 69 removes electric charges held on the transfer paper P so that the transfer paper P can be satisfactorily separated from the secondary transfer belt 37 by the strength of the transfer paper P itself. To do. The belt charge removal charger 71 removes charges remaining on the secondary transfer belt 37. In addition, the cleaning blade 73
Is to remove and clean the adhering substances adhering to the surface of the secondary transfer belt 37.

Next, the operation of this embodiment will be described based on the above-mentioned configuration. In the color copying machine 1, when the image forming cycle is started, the photosensitive drum 9 is rotated in the direction indicated by the arrow A by the drive motor (not shown), and the intermediate transfer belt 31 is moved by the belt drive roller 47 and is indicated by the arrow B. It is rotated around. With the rotation of the intermediate transfer belt 37, Bk toner image formation, C toner image formation, M toner image formation, and Y toner image formation are primarily transferred by a transfer bias by a voltage applied to the primary transfer bias roller 45. Finally, toner images are formed in the order of Bk, C, M, and Y on the intermediate transfer belt 31.

For example, Bk toner image formation is performed as follows. The charging charger 11 uniformly charges the surface of the photoconductor drum 9 with a negative charge to a predetermined potential by corona discharge. Then, the writing optical unit 19 performs raster exposure with laser light based on the Bk color image signal. When this raster image is exposed, in the exposed portion of the surface of the photosensitive drum 9 which is initially uniformly charged, the charge proportional to the amount of exposure light disappears and a bk electrostatic latent image is formed.

When the negatively charged Bk toner of the Bk developing sleeve 22a of the Bk developing device 21a comes into contact with the Bk electrostatic latent image, the toner is attached to the portion of the photosensitive drum 9 where the charge remains. However, the toner is adsorbed to the portion having no electric charge, that is, the exposed portion, and Bk similar to the electrostatic latent image.
A toner image is formed. The Bk toner image formed on the photosensitive drum 9 is transferred to the surface of the intermediate transfer belt 31 that is in constant contact with the photosensitive drum 9 and is being driven at a constant speed.

On the side of the photoconductor drum 9, the Bk image forming process is followed by the C image forming process, the reading of the C image data by the color scanner 5 is started at a predetermined timing, and the laser light writing by the C image data is performed to expose the C image data. A C electrostatic latent image is formed on the surface of the body drum 9.

Then, after the trailing edge of the previous Bk electrostatic latent image has passed and before the leading edge of the C electrostatic latent image has arrived, the revolver developing unit 21 is rotated to perform C developing. The machine 21b is set to the developing position, and the C electrostatic latent image is developed with C toner.

Thereafter, the development of the C electrostatic latent image area is continued,
When the rear end of the C electrostatic latent image passes, the revolver developing unit 21 is rotated like the case of the Bk developing machine 21a, and the next M developing machine 21c is moved to the developing position. This step is also completed before the leading edge of the next M electrostatic latent image reaches the developing position.

On the intermediate transfer belt 31, the toner images of Bk, C, M and Y which are sequentially formed on the photosensitive drum 9 are formed.
The images are sequentially aligned and transferred on the same surface. As a result, a toner image in which a maximum of four colors are superimposed is formed on the intermediate transfer belt 31.

At the time when this image forming operation is started, the transfer paper P is fed from the transfer paper cassette 6 or the manual feed tray 8 and is waiting at the nip of the registration roller pair 67.
Secondary transfer opposing roller 51 and secondary transfer bias roller 3
When the front end of the toner image on the intermediate transfer belt 31 reaches the secondary transfer portion where the nip is formed by 9, the registration roller pair 67 is driven so that the front end of the transfer paper P coincides with the front end of this toner image. Then, registration of the transfer sheet P and the toner image is performed.

Then, the transfer paper P is superposed on the toner image on the intermediate transfer belt 31 and passes through the secondary transfer portion. At this time, the four-color superposed toner images on the intermediate transfer belt 31 are collectively transferred onto the transfer paper by the transfer bias by the voltage applied to the secondary transfer bias roller 39 by the secondary transfer power supply 65.

On the other hand, the surface of the photoconductor drum 9 after the belt transfer is cleaned by the photoconductor cleaning device 17 and uniformly discharged by the charge eliminating lamp 18. Further, the toner remaining on the surface of the intermediate transfer belt 31 after the toner image is transferred onto the transfer paper P is cleaned by the belt cleaning blade 41 which is pressed against the intermediate transfer belt 31 by a separation / contact mechanism (not shown).

At the time of repeat copying, the operation of the color scanner 5 and the image formation on the photosensitive drum 9 are 1
Following the image forming process for the fourth color (Y) of the second sheet, the process proceeds to the image forming process for the first color (Bk) of the second sheet at a predetermined timing. Further, in the intermediate transfer belt 31, the second Bk toner image is formed in the area cleaned by the belt cleaning blade 41 on the front surface after the batch transfer process of the first four-color superimposed toner image onto the transfer paper. To be transferred to the belt. After that, the same operation as the first sheet is performed.

The copy mode for obtaining a full-color copy of four colors has been described above.
In the case of the two-color copy mode, the same operation as described above is performed for the designated color and the number of times.

In the single-color copy mode, only the developing machine of the predetermined color of the revolver developing unit 21 is brought into the developing operation state until the predetermined number of sheets are finished, and the belt cleaning blade 41 is pressed against the intermediate transfer belt 31. The copy operation is performed with the position kept as it is.

Next, the control timing of the belt tension acting on the intermediate transfer belt 31 of the color copying machine 1 in the present embodiment will be described. FIG. 4 shows the control timings of the “human body detection sensor signal”, the “tension varying means signal”, and the “intermediate transfer belt operation” from the top.

When the operator approaches the color copying machine 1, the human body detection sensor 60 outputs a human body detection sensor signal to the tension control means 62. Then, in response to a signal from the tension control means 62, the belt pressure release lever 52 presses the tension spring 50 around the fulcrum 52a, and applies tension to the intermediate transfer belt 31. Further, tension is applied to the intermediate transfer belt 31, and at the same time, the driving roller 47 is driven to start idling of the intermediate transfer belt 31.

When the start key is pressed after a predetermined time has elapsed, the image forming operation is started as described above. Although the operator may leave the color copying machine 1 during the image forming operation, the signal from the human body detection sensor 60 is ignored during the image forming operation.

When the image forming operation is completed and the operation of the intermediate transfer belt 31 is stopped, the signal from the human body detection sensor 60 is turned off (when it is determined that the operator is not near), and then it is constant. After a lapse of time (n seconds), the belt pressure release lever 52 rotates in the release direction (F direction), the tension spring 50 is extended, and the belt tension roller 49 is released.
Is moved inward, and the tension of the intermediate transfer belt 31 is released. When the signal from the human body detection sensor 60 is already OFF when the operation of the intermediate transfer belt 31 is finished, a certain time has elapsed (msec) after the operation of the intermediate transfer belt 31 is finished. The tension acting on the intermediate transfer belt 31 is released.

As described above, according to the present embodiment, when the operator approaches the color copying machine 1, a signal is sent from the human body detection sensor 60 to the tension control means 62, and the signal from the tension control means 62 is sent. In response to this, tension is applied to the intermediate transfer belt 31. At the same time, the rotation of the intermediate transfer belt 31 is started. Therefore, it is possible to stabilize the intermediate transfer belt 31 by using the time from the reception of the signal from the human body detection sensor 60 to the start of image formation. it can.

Next, another embodiment will be described. In the description, the same parts as those described above are designated by the same reference numerals, and the description thereof will be omitted.

In the second embodiment, the human body detection sensor 60 in FIG. 3 is replaced with the operation panel 70. As described above, in the first embodiment, the human body detection sensor 60 provided in the color copying machine 1 receives the fact that the operator is approaching the color copying machine 1 and receives the belt pressure release lever 52. The tension is applied to or released from the intermediate transfer belt 31 by driving the. In the second embodiment, in response to the operator's operation on the operation panel 70, the tension is applied to or released from the intermediate transfer belt 31. Here, in the operation of the operation panel 70, the operation by the start key is excluded.

Color copier 1 in the second embodiment
The control timing of the belt tension acting on the intermediate transfer belt 31 will be described. FIG. 5 shows the timings of the “printer data signal”, the “tension varying means signal”, and the “intermediate transfer belt operation” from the top.

When data is input on the operation panel 70 of the color copying machine 1, a data signal is output to the tension control means 62. Then, in response to a signal from the tension control means 62, the belt pressure release lever 52 presses the tension spring 50 around the fulcrum 52a, and applies tension to the intermediate transfer belt 31. Further, tension is applied to the intermediate transfer belt 31 and the driving roller 47 is driven to start idling of the intermediate transfer belt 31.

When the image forming operation is completed and the operation of the intermediate transfer belt 31 is stopped, the belt pressure releasing lever 52 rotates in the releasing direction (F direction) after a lapse of a certain time (n seconds later).
The tension spring 50 is extended, the belt tension roller 49 is moved inward, and the intermediate transfer belt 31
Tension is released.

As described above, according to the second embodiment, at the same time when the data signal is input through the operation panel 70,
Tension is applied to the intermediate transfer belt 31 to
Since the rotation of No. 1 is started, the time from when the data is input to when the image formation is started is used.
Can be stabilized.

Next, an embodiment in which the present invention is applied to an electrophotographic color copying machine 100 which is an image forming apparatus will be described with reference to the drawings. 6 and 7 are schematic diagrams of the image forming unit 105 of the electrophotographic color copying machine 100 according to the third embodiment.

The image forming section 105 includes a photosensitive drum 11
0, a charging device 120, a developing device 130 for each color, and the like are provided. In addition, an intermediate transfer belt 150, a fixing device 160, and the like are provided around the image forming unit 105. The structure is almost the same as that of the above-described device except that the number of the photosensitive drums 110 is four and the structure of the rollers around the intermediate transfer belt 150 is different.

As shown in FIG. 7, the intermediate transfer belt 150 is provided with a belt tension roller 170, a tension spring 180, and a belt pressure release lever 190, which have the same construction as that shown in FIG. Then, a signal is transmitted to the control unit 210 in response to the human body detection sensor 200 provided in the electrophotographic color copying machine 100 to apply or release tension to the intermediate transfer belt 150. The control timing (see FIG. 4 and FIG. 5) is the same as the above description, and will be omitted.

As described above, the photosensitive drum 110
If the number of the intermediate transfer belt 150 is four, the intermediate transfer belt 150 is in contact with many members and the belt circumference is often long, so that the intermediate transfer belt 150 may be in an unstable state. There is a possibility that a main scanning shift will occur with the application or release of tension. Therefore, according to the present invention, it is possible to more effectively stabilize the intermediate transfer belt 150 as compared with the first embodiment or the second embodiment described above.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, although the color copying machine 1 has been described as an example in the above-described embodiment, it may be related to a printer, a FAX, or the like. Further, as the device for applying or releasing the tension to the intermediate transfer belt 31, the belt pressure release lever 52 connected to the tension spring 50 is used.
The present invention is not limited to this, and a method of connecting a tension roller 49 to a solenoid or the like to apply or release tension to the intermediate transfer belt 31 may be used.

[0066]

According to the first aspect of the invention, the warm-up of the intermediate transfer belt can be performed by utilizing the time from when the operator approaches the image forming apparatus to when the start button is pressed. Therefore, the stabilization of the intermediate transfer belt can be accelerated, and the copy time can be shortened.

According to the invention described in claim 2, the same effect as the invention described in claim 1 is obtained, and even if the operator is separated from the image forming apparatus during the image forming operation, the human body detection sensor Since the signal is ignored, the tension of the intermediate transfer belt is not changed during the image forming operation.

According to the third aspect of the invention, the warm-up of the intermediate transfer belt can be performed by utilizing the time from the input of the operation panel to the pressing of the start button.

According to the invention described in claim 4, the same effects as those of the invention described in claims 1 to 3 are obtained, and at the same time as the tension is applied to the intermediate transfer belt, the idling is started at the same time. Fast stabilization can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a color copying machine showing an embodiment of an image forming apparatus.

FIG. 2 is a schematic configuration diagram of an image forming unit of a color copying machine.

FIG. 3 is an enlarged configuration diagram showing an intermediate transfer belt of the color copying machine of FIG.

FIG. 4 is a diagram showing a control timing of belt tension acting on the intermediate transfer belt.

FIG. 5 is a diagram showing a control timing of belt tension acting on an intermediate transfer belt in another embodiment.

FIG. 6 is a schematic configuration diagram showing an electrophotographic color copying machine in another embodiment.

FIG. 7 is an enlarged structural view of the intermediate transfer belt in FIG.

[Explanation of symbols]

1 Color copier (image forming device) 9 Photoconductor drum (image carrier) 31 Intermediate transfer belt 52 Belt pressure release lever (tension varying means) 60 Human body detection sensor 62 Tension control means 70 Operation panel

Claims (4)

[Claims] 1. An intermediate transfer belt comprising an image carrier on which a toner image corresponding to image information is carried, and a plurality of rotatable roll members, and a belt stretched and supported by the roll members. In an image forming apparatus having a member, a human body detection sensor for detecting whether or not an operator is near, a tension variable means and a tension control means for varying the tension acting on the intermediate transfer belt in response to the human body detection sensor are provided. An image forming apparatus comprising a human body detection sensor, wherein the tension control means drives the tension varying means to apply tension to the intermediate transfer belt when it is determined that a person is nearby. 2. The tension control means, when the human body detection sensor determines that a person is not near during the image forming operation,
The image forming apparatus according to claim 1, wherein the tension of the intermediate transfer belt is not released at that time, and the tension of the intermediate transfer belt is released within a predetermined time after completion of the image forming operation. 3. An image forming apparatus comprising: an image carrier, which carries a toner image corresponding to image information; and an intermediate transfer belt, which comprises a belt member stretched and supported by a plurality of rotatable roll members. Is equipped with an operation panel for inputting the data and a tension varying means for varying the tension of the intermediate transfer belt, and a tension control means for applying a tension to the intermediate transfer belt in conjunction with data input from any operation panel other than the start button. An image forming apparatus characterized by being provided. 4. The tension control means drives the tension varying means to apply tension to the intermediate transfer belt, and at the same time, idles the intermediate transfer belt by a predetermined distance. The image forming apparatus described in 1.