JPH11327322A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent waviness so as to form an excellent image without causing any image defect by using a belt member and a sticking member constituted so that their water absorption or hygroscopic swelling coefficient are equal or approximate to each other. SOLUTION: A belt obtained by blending carbon black in polyimide, making the obtained substance film whose thickness is 0.1 mm and whose volume resistivity is 10<10> Ωcm and making it belt state is used as an intermediate transfer belt 30, and the hygroscopic swelling coefficient is 1×10<-4> /%RH. Then, polyimide whose width is 10 mm and whose thickness is 0.3 mm is used for a reinforcing tape 50 functioning as the sticking member 5 and the hygroscopic swelling coefficient is 0.8×10<-4> /%RH, which is approximate to that of the belt 30. In a copying machine equipped with the belt 30 constituted in such a way, the belt 30 is rotated while abutting on engaging plates 47 and 48 attached to two rolls 31 and 32, so that it is stably rotated without one-sided traveling and meandering.

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, a facsimile, and a multifunction peripheral thereof. The present invention relates to an image forming apparatus provided with an endless belt member that holds and conveys paper and the like.

[0002]

2. Description of the Related Art As an image forming apparatus of this type, for example, there is an intermediate transfer type color image forming apparatus using an intermediate transfer belt as a belt member. In this method, an intermediate transfer belt is stretched between a plurality of rolls so that the intermediate transfer belt contacts and rotates at a transfer portion of an image carrier (for example, a photosensitive drum) on which a toner image is formed by an electrophotographic process or the like. After the primary transfer of a plurality of toner images formed on the image carrier once to be superimposed on the same position of the intermediate transfer belt, the multiple toner images transferred on the intermediate transfer belt are Is collectively subjected to secondary transfer. Then, the multiple toner images transferred onto the paper are then fixed by a fixing device to become color images.

In addition, as an image forming apparatus provided with a belt member, a so-called tandem type color using a paper transport transfer belt that carries a paper and transports the paper so as to pass through transfer portions of a plurality of image forming units is used. There is also an image forming apparatus. This involves arranging a plurality of image forming units in order to individually form toner images of the respective color components, and stretching a paper transport transfer belt between a plurality of rolls so that the transfer belts of the image forming units come into contact with each other and rotate. Each of the toners formed in each image forming unit is transported so that the paper adsorbed and carried on the paper transporting transfer belt is passed through the transfer unit of each image forming unit. The images are transferred so as to be superimposed on the same paper sequentially, and finally fixed to form a color image.

[0004]

By the way, in a color image forming apparatus using a belt member 100 typified by such an intermediate transfer belt and a paper transport transfer belt, as shown in FIG. Adhesive member 120 may be attached to a part of the surface of 100, and when such adhesive member 120 is attached,
When environmental conditions surrounding the belt member 100 change (especially when the humidity becomes high), a swell E in which the belt surface is deformed so as to undulate may be generated in a peripheral belt member 100 region where the sticking member 120 is stuck. is there.

[0005] For example, as shown in FIG. 1, from the viewpoint of preventing the belt member 100 from running side-to-side or meandering, a part of a plurality of rolls that stretch the belt member 100 so that a predetermined tension is applied thereto. A disc-shaped regulating plate 130 for running while abutting one end of the belt member 100 is provided,
There is a case where a reinforcing tape 140 is attached for the purpose of reinforcement along the end of the belt member 100 applied to the regulating plate 130. In this case, if the belt member 100 is placed in an environment such as high humidity, the swell E may occur particularly around the reinforcing tape 140 of the belt member 100. It has also been confirmed that such undulations can occur even in an environment such as a high temperature.
Further, in addition to the above-described reinforcing tape, the sticking member 120 may be, for example, a detection mark detected by an optical sensor for extracting a reference signal used for controlling the running timing of the belt member 100 and the like. There are (a piece of film) 150, a joining tape 160 to be attached to a joint of the belt member 100, and the like. Even when each of these attaching members is attached, the undulation as described above is the same. May occur.

[0006] When any of these undulations has a sticking member on a part of the belt member 100 stretched in a state where a predetermined tension is applied between a plurality of rolls, the undulation is caused by sticking to the belt member. It is presumed that the wearing members are generated due to the difference in physical properties between each other.

[0007] In addition, the undulation generated due to the presence of such a sticking member, once generated, is left unattended. Then, when the humidity environment surrounding the belt member 100 returns to a normal state, Or the belt member 100
Even when the tension applied to the substrate is reduced or removed, it tends to remain without disappearing. In addition, such a undulation has a thickness of, for example, 0.3 mm as in the case of the above-described intermediate transfer belt or paper transport transfer belt.
When the thickness is extremely thin, such as below, there is also a tendency to occur remarkably.

When such undulation occurs, the smoothness of the belt member 100 is not maintained, so that the toner image is not normally transferred at a portion corresponding to the undulation portion and the image is lost. There is a problem in that image defects such as deviation or deviation, or variations in image density and color tone occur.

Japanese Patent Application Laid-Open No. 3-106736 discloses that, when a sheet conveying belt in a sheet conveying apparatus is left for a long period of time, permanent deformation of the belt is prevented, and image quality deterioration caused by the deformation is prevented. An image forming apparatus having a mechanism capable of reducing the tension applied to the belt in a multi-step manner when the belt is stopped compared to when the belt is rotated is disclosed.

However, in the image forming apparatus disclosed in this publication, since the tension applied to the sheet conveying belt is merely reduced at a specific time, the reinforcing tape such as the above-mentioned adhesive tape is applied to the conveying belt. When the member is attached, it is not expected to prevent the occurrence of undulation due to the presence of the sticking member, and once the undulation occurs, the undulation does not disappear and remains as described above. There is a strong possibility of doing it. Further, a mechanism for variably setting the tension applied to the belt member in the image forming apparatus may be configured and operated so as to operate based on information obtained by detecting environmental conditions such as humidity. In this case, the mechanism and the like become more complicated and expensive.

The present invention has been made in view of the above circumstances, and an object thereof is to generate a belt member to which an adhesive member is adhered when environmental conditions, particularly, humidity conditions fluctuate. An object of the present invention is to provide an image forming apparatus that can more easily and accurately prevent waviness that may occur and can form a good image without image defects caused by such waviness.

[0012]

An image forming apparatus according to the present invention includes a belt member which is stretched between a plurality of rolls, rotates, and holds and conveys at least a toner image or paper on an outer peripheral surface of the belt. In an image forming apparatus in which a sticking member is stuck to a partial region of a belt member, the belt member and the sticking member have the same or similar relationship in the water absorption rate or the coefficient of hygroscopic expansion of both. This is the one that is configured as described above.

In this means, the belt member is an intermediate transfer belt for holding and transporting the toner image as described above, or a paper transport transfer belt for holding and transporting the paper on which the toner image is transferred. Alternatively, for example, a paper transport belt for simply transporting paper may be used. The belt member mainly has a relatively small belt thickness.

The sticking member is not particularly limited as long as it is a member to be stuck to the belt member as needed, and is arbitrary. For example, a reinforcing tape as described above,
Such as a detection mark and a joining tape. This sticking member usually has a thickness substantially equal to that of the belt member. In the case of the sticking member having a thickness of several tens of times or more as compared with the thickness of the belt member, the above-described undulation hardly occurs. In addition, the sticking member is usually a member to be stuck to a non-image forming region on the outer peripheral surface side of the belt member, but may be a member to be stuck to a non-image forming region on the inner peripheral surface side of the belt member. Good.

[0015] The belt member and the sticking member are configured such that the water absorption rate or the coefficient of hygroscopic expansion of both of them is the same or approximate to each other.

Here, the water absorption rate is determined according to JIS K 6911.
/ 7209 is obtained by measuring according to a method in accordance with the measuring method, and is a percentage change in mass before and after immersion of the test piece in distilled water. In the measurement method of the JIS standard, a diameter of φ5
Although it is specified that a disk-shaped member having a thickness of 0 ± 1 mm and a thickness of 3 ± 0.2 mm is used, in the present invention, the belt member is relatively thin, and the condition of the thickness dimension of the above standard is satisfied. If it cannot be satisfied, the measurement is performed using a sample having the same volume and size as the disk-shaped sample of the above standard as a sample. On the other hand, the coefficient of hygroscopic expansion is the length of the sample in the longitudinal direction (MD) when the sample is placed in an environment in which the relative humidity is sequentially changed from 20% RH to 80% RH at a constant temperature (23 ° C.). The amount of change is measured and expressed as a unit “/% RH”.

Incidentally, the water absorption and the coefficient of hygroscopic expansion indicate the amount of water absorbed by the test piece as a percentage of the initial mass, whereas the coefficient of water absorption indicates the sample per unit humidity. Since the rate of change of the length is shown, the coefficient of humidity expansion is more suitable for showing the characteristics of the present invention when the problem of undulation is considered.

The approximate relationship between the water absorption and the coefficient of hygroscopic expansion means that in the case of the absorption, the respective water absorptions of the two members are in a relationship of about 1: 0.2 to 1: 1.5. ,
In the case of the coefficient of hygroscopic expansion, it means a relationship in which the coefficient of hygroscopic expansion of both members falls within a range of about ± 50%. For example, when the coefficient of hygroscopic expansion is specifically described with an example, when the coefficient of hygroscopic expansion of one member is 1 × 10 ⁻¹⁴ /% RH, the coefficient of hygroscopic expansion of the other member is about ± 5.
(0.5 to 1.5) × 10 ⁻¹⁴ /% R which is in the range of 0%
H refers to the relationship. In addition, the belt member and the sticking member,
It is more desirable that, in addition to the water absorption coefficient or the hygroscopic expansion coefficient, both of the thermal expansion coefficients have the same or similar relation to each other. Although the belt member and the sticking member having the above-mentioned physical properties are generally configured using the same material,
They may be formed using different materials.

According to such an image forming apparatus, since the water absorption or the coefficient of hygroscopic expansion of the belt member and the sticking member attached to the belt member are substantially the same, the belt member and the sticking member adhere to the belt member in an environment such as high humidity. Even in the case where the belt member and the sticking member are in contact with each other, the belt member and the sticking member show the degree of expansion (deformation) that are close to each other, so that distortion is less likely to occur between the two, and as a result, the belt member and the sticking member have The swell does not occur or hardly occurs in the part.

[0020]

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

Embodiment 1 [Overall Configuration and Operation of Apparatus] FIG. 1 is a schematic diagram showing a color copying machine having an intermediate transfer belt according to an embodiment of the present invention. The copying machine is roughly divided into an image reading section 1 for reading an image of a document, an image output section 2 for forming a toner image based on image information obtained by the image reading section 1 and outputting the toner image on a sheet. It is roughly constituted by.

In the image reading section 1, a document (not shown) placed on a platen 10 serving as a document table is placed on the platen 1
Light is emitted from a document illuminating lamp 11 that moves along the lower surface of the document 0, and reflected light from the document is incident on a charge-coupled device 15 such as a CCD via a moving mirror unit 12, a lens 13, and a fixed mirror 14. You. The charge-coupled device 15
The incident light is simultaneously decomposed into red (R), green (G), and blue (B) colors and converted into R, G, and B electric signals, and the electric signals are input to the image processing circuit 16. The image processing circuit 16 processes the electric signals of R, G, and B into image signals of respective colors of yellow (Y), magenta (M), cyan (C), and black (K), which have complementary colors. Store in image memory. When other functions such as a printer function are added to the copying machine, for example, an external input unit for inputting image information from an external device or the like may be provided. 1a in the figure indicates a platen cover or an automatic document feeder.

On the other hand, in the image output section 2, the optical writing control device 20 reads out the image signal stored in the image processing circuit 16 at a predetermined timing, and reads out the image signal from the optical beam writing device 21.
Output to The light beam writing device 21 modulates an input image signal into a light (laser) beam LB, deflects the laser beam LB by a polygon mirror 21a, and then rotates a photosensitive member as an image carrier that rotates in the direction of arrow a. Scanning is performed on the drum 22, whereby an electrostatic latent image corresponding to each color is written on the photosensitive drum 22. Reference numeral 23 in the drawing denotes a charger for uniformly charging the outer peripheral surface of the photosensitive drum 22 prior to writing the electrostatic latent image.

The electrostatic latent image written on the photosensitive drum 22 is transferred to a developing device 24 disposed around the photosensitive drum 22.
Is immediately developed. The developing device 24 is of a rotary type having four developing devices that respectively store and supply toners of yellow (Y), magenta (M), cyan (C), and black (K). The developing device containing the toner of the color corresponding to the latent image is rotated to a position facing the photosensitive drum 22 to supply the toner to the photosensitive drum 22 side.

The toner image formed on the photosensitive drum 22 in this manner is an intermediate belt member which is disposed so as to rotate in contact with or close to the transfer position (primary transfer portion) of the photosensitive drum 22. The primary transfer is electrostatically performed on the transfer belt 30. Reference numeral 25 in the drawing denotes a corona discharge type primary transfer device to which a bias voltage having a polarity opposite to that of the toner is applied, and reference numeral 26 denotes a toner that removes and adheres to the surface of the photosensitive drum 22 after the primary transfer. It is a cleaning device.

The intermediate transfer belt 30 is stretched around a driving roll 31 and a plurality of rotatable driven rolls 32, 33, and 34.
Are rotated at the same speed in the same direction (the direction of the arrow b) as the rotation direction. Multiple driven rolls (32-3
In 4), the roll 32 is a tension roll,
The intermediate transfer belt 30 is urged in the direction of arrow c by an urging mechanism such as a spring (not shown), thereby preventing the intermediate transfer belt 30 from bending. Reference numeral 35 in the figure denotes an electrode roll to which a bias voltage having the same polarity as that of the toner is applied to a support roll (backup roll) 33, and 36 is disposed so as to be able to come into contact with and separate from the support roll 33. A secondary transfer roller 37 that forms a nip portion between the intermediate transfer belt 3 and the intermediate transfer belt 3 (via the belt 30).
The cleaning device is disposed so as to be able to approach and separate from the belt 0 and removes toner and the like remaining on and attached to the belt 30. Incidentally, the secondary transfer roll 36 and the cleaning device 37 are used only when the secondary transfer is performed.
3 or the belt 30.

As a method of rotating the intermediate transfer belt 30, this copying machine employs a constant speed forward system in which the intermediate transfer belt 30 is rotated in one direction at a constant speed. A skip forward movement method in which the rotation speed is changed during transfer, or a reciprocating operation (quick return) method in which the primary transfer area on the belt is returned (returned) for repeated use may be adopted.

The toner image transferred onto the intermediate transfer belt 30 in this manner is fed to a sheet P fed to a nip portion (secondary transfer portion) between the secondary transfer roll 36 and the support roll 33.
Is secondarily transcribed. In this case, the paper P is
The paper feed roll 41
After the sheets are taken out one by one, the registration rolls 4 are passed through a paper conveyance path on which a plurality of conveyance roll pairs 42 are arranged.
3 and is sent to the nip at a predetermined timing by the registration roll 43. After the completion of the transfer, the surface of the intermediate transfer belt 30 is cleaned by a cleaning device 37 which comes into contact with the belt 30 in accordance with the execution time of the transfer.

The sheet P to which the toner image has been transferred from the intermediate transfer belt 30 is conveyed by a sheet conveying belt 44 disposed downstream of the secondary transfer section and sent to a fixing device 45, where the fixing device 45 is fixed. The toner image is fixed on the paper by being nipped and conveyed by a heating roll and a pressure roll rotating in a state of being pressed in the inside 45. As a result, a predetermined image is formed (copied) on the paper P.
The sheet P after the completion of the fixing is discharged to the outside of the apparatus by the discharge roller 46, and is stored on, for example, a storage tray (not shown).

In this copier, when a color copy (formation of a color image) is performed, first, a toner image of each color component is sequentially formed on the photosensitive drum 22 in accordance with the original image information. Each toner image is transferred so as to be sequentially superimposed on the same position (region) of the intermediate transfer belt 30 in the primary transfer section, and then the toner images multi-transferred onto the intermediate transfer belt 30 are transferred to the sheet P in the secondary transfer section. Are transferred collectively. On the other hand, when black-and-white copying (that is, formation of a single-color image) is performed, a single-color toner image of a desired color is formed on the photosensitive drum 22 and then transferred to the intermediate transfer belt 30 in the primary transfer unit. The single-color toner image on the intermediate transfer belt 30 is immediately transferred to the sheet P in the secondary transfer section.

[Detailed Structure Regarding Intermediate Transfer Belt] In this copying machine, as shown in FIGS. 2 and 3, as a measure for stabilizing the running of the intermediate transfer belt 30, a driving roll 31 and a tension roll 32 are used. Disc-shaped regulating plates 47 and 48 each having a diameter slightly larger than the diameter of each of the rolls 31 and 32 are attached to one end, and the side on which the regulating plates 47 and 48 are provided. A reinforcing tape 50 as an attaching member 5 is attached to the end of the intermediate transfer belt 30 along the edge of the belt over the entire circumference of the belt.

The intermediate transfer belt 30 is basically made by mixing an appropriate amount of a conductive agent such as carbon black with a base material made of various synthetic resins or rubber materials.
A sheet (film) having a thickness of about 0.15 mm is formed into an endless belt. Also,
The belt 30 has a volume resistivity of 10 ⁶ to 10 ¹⁶ Ω.
cm. As the synthetic resin material of the base material, polyimide, acrylic resin, polyvinyl chloride, polyester, polycarbonate or the like is used. Silicone rubber, acrylic rubber, urethane rubber, epichlorohydrin rubber, or the like is used as the rubber material of the base material.

In this embodiment, for example, the intermediate transfer belt 30 is prepared by mixing carbon black with polyimide to have a thickness of 0.1 mm and a volume resistivity of 10 ¹⁰ Ωcm.
A belt-shaped film is used. The intermediate transfer belt 30 has a coefficient of hygroscopic expansion of 1 × 10 ⁻⁴ /% RH and a coefficient of thermal expansion of 5 × 10 ⁻⁵ / ° C. Here, the coefficient of thermal expansion is measured using a thermomechanical analysis (TMA) measurement method.

The reinforcing tape 50 as the attaching member 5 is
Basically, a synthetic resin or rubber material is formed into a sheet (film) having a width of about 5 to 15 mm and a thickness of about 0.05 to 0.5 mm without containing other materials such as a conductive agent. Is used. As a synthetic resin material,
Polyimide, polyamide imide, polyether imide,
Polycarbonate, polyethylene terephthalate, polysulfone, polyethersulfone and the like are used. The reinforcing tape 50 is attached to the intermediate transfer belt 30 using a predetermined adhesive or the like.

In this embodiment, a reinforcing tape 50 made of polyimide having a width of 10 mm and a thickness of 0.3 mm is used. The coefficient of hygroscopic expansion of the reinforcing tape 50 made of polyimide is 0.8 × 10 ⁻⁴ /% RH.
This is similar to that of the intermediate transfer belt 30. The reinforcing tape 50 is formed by applying a synthetic resin-based adhesive to the back surface to a thickness of about 200 μm, and affixing the adhesive tape over the entire circumference along one end of the intermediate transfer belt 30.

In this embodiment, as shown in FIG. 2, the outer peripheral surface serving as a joint of the intermediate transfer belt 30 is made of the same carbon black-containing polyimide (0.1 mm in thickness) constituting the belt 30. Joining tape 51
Is attached as the attaching member 5. Further, at a predetermined position of the intermediate transfer belt 30, an optical detection mark (piece) 52 made of a small piece of aluminum plated on the surface side of the same polyimide film (tape) constituting the reinforcing tape 50 is attached. 5 is pasted. The polyimide 51 in the tape 51 and the mark 52 has a coefficient of hygroscopic expansion of 0.8 × 10 ⁻⁴ /% RH.
This is similar to that of the intermediate transfer belt 30.

The intermediate transfer belt 3 having such a configuration
0, the intermediate transfer belt 30 is
Engagement plates 47, 4 attached to book rolls 31, 32
Since it rotates while abutting on 8, it rotates stably without side running or meandering. As a result, image quality deterioration caused by the unstable running state of the intermediate transfer belt 30 is prevented, and good image formation is ensured.

Next, the following undulation test and image test were performed using the copying machine having the above-described configuration.

That is, as shown in FIG. 1 and FIG. 2, an image forming apparatus in which the intermediate transfer belt 30 is set to be stretched with a tension (tension) of 5 kgf is set to a room temperature and a normal humidity (20%).
Temperature, high humidity (30 ° C, 85%)
(RH) for 24 hours, and it was examined whether or not the intermediate transfer belt 30 was undulating. As a result, the belt 30 includes not only the peripheral portion of the reinforcing tape 50 but also the joining tape 51 and the detecting tape 5.
No undulation occurred in the periphery of No. 2 and in other belt areas.

Further, when the above-mentioned image forming apparatus was returned to the environment of normal temperature and normal humidity, and a color copy for a test was executed, the obtained color image was found to have image defects such as missing images, color misregistration and uneven color tone. As a result, a high-quality color image having no practical problem was obtained.

For comparison, as a reinforcing tape 50,
Instead of the polyimide of the above-described embodiment,
Width 10 made of polyethylene terephthalate (PET)
mm and a thickness of 0.2 mm
Then, the undulation test and the image test as described above were performed in the same manner. The reinforcing tape 50 made of PET has a coefficient of hygroscopic expansion of 1 × 10 ⁻⁵ /%.
RH.

As a result, PE of the intermediate transfer belt 30
It was confirmed that a swell having an amplitude (a difference in height between the uppermost portion and the lowermost portion) of about 2 to 3 mm was generated around the reinforcing tape 50 made of T. After that, when the temperature was returned to the environment of normal temperature and normal humidity or the tension applied to the intermediate transfer belt 30 was released, the undulation generated earlier did not disappear and remained. Further, when a test color copy is executed using the intermediate transfer belt 30 in a state in which the undulation occurs, the obtained image has an image missing (opening) in a portion corresponding to the undulating portion. It has been confirmed that this has occurred.

As described above, when two members made of the same polyimide, such as the intermediate transfer belt 30 of the present embodiment and the adhesive member 5 such as the reinforcing tape 50, are used, high humidity When the belt 30 is not undulated even when the environment is changed to the environment described above, when the sticking member 5 is replaced with a member made of, for example, polyethylene terephthalate as in the comparative example, high humidity etc. It can be seen that in the environment described above, undulation occurs in the belt 30 around the attaching member 5.

This is particularly due to the hygroscopic expansion of the intermediate transfer belt 30.
Tension coefficient K₃₀Swelling of the adhesive member 5 such as the reinforcing tape 50 and the like
Tension coefficient k₅₀Are substantially similar in the case of the present embodiment.
(The difference between the coefficients is 20%), while (K
₃₀= 1 × 10^-Four/% RH, K ₅₀= 0.8 × 10^-Four/
%), And to a certain extent in the case of the comparative example (K
₃₀Are the same, but K₅₀Is K₅₀= 1 × 10^-Five/% RH
Become this K₅₀Is about one digit compared to the previous embodiment
It is presumed that it is caused by different degrees. Chi
Incidentally, the thermal expansion of the intermediate transfer belt 30 and the attaching member 5
Regarding the number, any of the case of the present embodiment and the case of the comparative example
They also have a similar relationship.

Embodiment 2 A copy having the same configuration as in Embodiment 1 except that the coefficient of moisture expansion K ₅₀ of the reinforcing tape 50 made of polyimide in Embodiment 1 is changed to 0.5 × 10 ⁻⁴ /% RH. Machine.
In this case, the coefficient of hygroscopic expansion K of the intermediate transfer belt 30 is
_{The value 50} was set to the same value (1 × 10 ⁻⁴ /% RH) as in the first embodiment without any change.

When the same undulation test and image test as in Embodiment 1 were performed using this copying machine, a portion where an extremely small undulation of about 1 mm was found was slightly observed. In addition, the obtained image was good without a normal image dropout in the case of a copy having a low image density, but in the case of a copy having a high image density, a faint portion corresponding to the undulation was obtained. White spots occurred on the surface. From this, it has been found that when undulation of a level exceeding 1 mm occurs, image defects such as white spots are likely to occur. Further, the intermediate transfer belt 30 and the reinforcing tape 5
It is also found that if the respective hygroscopic expansion coefficients of 0 are close to each other so as to have a difference of at least 50% as in this embodiment, image defects such as white spots due to swelling are less likely to occur. did.

Next, waviness of occurrence rate when the hygroscopic expansion coefficient K ₃₀ of the intermediate transfer belt 30 is varied: was studied (the undulation amplitude height difference as described above). That is, in this test, the tension of the intermediate transfer belt 30 was 7 kg.
After leaving for 24 hours in an environment of 28 ° C. and 85% RH, the temperature was returned to normal temperature and normal humidity, and the amplitude of the undulation generated on the belt 30 was measured. As the reinforcing tape 50 of the attaching member 5, a tape made of PET exemplified as a comparative example of Embodiment 1 was used (the coefficient of moisture absorption expansion K50 of this tape ₅₀ is 1 × 10 ⁻⁵ /% RH. , Constant). On the other hand, by changing the physical properties of the polyimide constituting the intermediate transfer belt 30 (specifically, by changing the type and composition of the polymer particles), the moisture absorption expansion coefficient K ₃₀
Was appropriately changed. The results obtained in this test are shown in FIG.
Shown in

[0048] From the results of FIG. 4, the difference between the hygroscopic expansion coefficient K ₃₀ and hygroscopic expansion coefficient K ₅₀ of adhesive member 5 of the intermediate transfer belt 30 (0~0.5) × 10 ^-4 /% within the range When
An extremely small wave that does not cause swelling or causes no problem in practical use even if swelling occurs (the swelling amplitude is 1 m
m or less).

Other Embodiments As a measure for stabilizing the intermediate transfer belt 30 as shown in FIG. 5, instead of the structure of the first embodiment,
A belt-like running guide member (rib) 6 is attached to one end of the inner peripheral surface of the intermediate transfer belt 30 over the entire circumference of the belt, and the inner end of the guide member 6 is concentric with the end 31a of each of the rolls 31 to 34. The belt is rotated in a state where the belt is brought into contact with an engagement plate 49 attached to the intermediate transfer belt 30, and a reinforcing tape 53 is attached to the outer peripheral surface of the intermediate transfer belt 30 on the side to which the guide member is attached (adhering member). 5)
You may comprise so that it may stick.

Here, as the intermediate transfer belt 30, an endless (seamless type) belt made of the same material as that of the first embodiment is used. Also,
The guide member 6 is a belt-shaped member made of polyurethane rubber having a hardness of 70 ° and having a width of 5 mm and a thickness of 1 mm, which is adhered to the inner peripheral surface of one end of the intermediate transfer belt 30 using an epoxy adhesive. I have. Further, the engagement plate 49
A disk-shaped member made of polyacetal and having a center hole at the center and having a thickness of 2 mm is inserted from the shaft 38 of each roll through the center hole and fixed to the end of the roll.

As the reinforcing tape 53, a film-like material made of the same polyimide as that of the first embodiment and having a width of 10 mm and a thickness of 0.3 mm is used, and as shown in FIG. Is attached with a predetermined adhesive along the end of the. That is, the reinforcing tape 53 is disposed in a state where one half thereof vertically overlaps with the traveling guide member 6 and the other half thereof is extended in the center of the belt. The coefficient of hygroscopic expansion of the reinforcing tape 53 is 1.2 × 10 ⁻⁴ /% RH, which is similar to that of the intermediate transfer belt 30. In this embodiment, the bonding tape 51 and the detection mark 52 are not attached to the intermediate transfer belt 30 as in the first embodiment.

When such a measure for stabilizing the running of the intermediate transfer belt 30 is employed, the intermediate transfer belt 30 rotates while the running guide member 6 is abutted against the engaging plates 49 of the rolls 31 and 32. It rotates stably without side running or meandering. As a result, the image quality does not deteriorate due to the unstable running of the intermediate transfer belt 30,
Good image formation is possible.

When this traveling safety measure is adopted, the reinforcing tape 53 is adhered to the outer peripheral surface portion of the intermediate transfer belt 30 corresponding to the traveling guide member 6. The end is the traveling guide member 6
Is not bent at the center end Q of the belt. That is, when the reinforcing tape 53 is not provided, as illustrated in FIG. 7, the tension is applied to the intermediate transfer belt 30 from the roll 31 or the like in a direction perpendicular to the belt surface (the direction of the arrow in the figure). Since F is applied, the portion of the belt 30 to which the reinforcing tape 53 is attached is bent inward at the boundary Q (FIG. 2B). The stress concentrates on the bent portion of the belt so that the portion is easily damaged, and furthermore, the side surface of the traveling guide member 6 does not come into surface contact with the engagement plate 49, so that the belt is easily ridden. Occurs. In this regard, reinforcing tape 5
3 is provided, the boundary Q between the guide member 6 and the belt is reinforced by the reinforcing tape 53,
The durability against the stress concentrated on the boundary Q is improved,
It is difficult to bend.

Further, when the undulation test and the image test described above were conducted, no undulation was observed particularly in the intermediate transfer belt area and the like around the reinforcing tape 53, and the image quality deteriorated due to the undulation. No occurrence was observed. At this time, the traveling guide member 6 is connected to the belt 30.
Since it is sufficiently thicker than the tape or the tape 53, there is almost no expansion deformation due to high humidity, and it does not become a cause of undulation.

Such a reinforcing tape 53 is disposed so as to straddle at least the belt center side and the end side with respect to the belt center side end (corresponding to the boundary Q) of the traveling guide member 6. do it. Also, the reinforcing tape 53
If necessary, as shown in FIG. 6, the travel guide member 6 may have a cross-sectional shape in which the thickness near the belt center side end is thicker than other portions.

In the above-described embodiment, the apparatus provided with the intermediate transfer belt 30 has been described as an example. However, in addition to this, for example, the paper transport transfer belt 6 as shown in FIG.
0 device.

The image forming apparatus illustrated in FIG. 8 has four image forming units 3k, 3y, and 4k for forming toner images of black (K), yellow (Y), magenta (M), and cyan (C), respectively. 3m and 3c are arranged side by side in this order, and a tandem-type color in which a paper transport transfer belt 60 that transports the paper P so as to pass the paper P to the transfer section (transfer section of the photosensitive drum) of each image forming unit 3 is arranged. An image forming apparatus. Each of the image forming units 3 is a photosensitive drum 22 (k, y, m, c) that rotates in the direction of an arrow similarly to the copying machine according to the above-described embodiment.
And a charger 23 around the photosensitive drum 22.
A developing device 24 (for a single color), a transfer device 25, a cleaning device 26 and the like are arranged in this order. Further, a paper transport transfer belt 60 is stretched between a plurality of rolls 61, 62, 63, 64 so that the transfer belt of the image forming unit 3 comes into contact with the transfer unit and rotates in the direction of the arrow. . In FIG. 5, 45 is a fixing device, 65 is a paper suction roll, 66 is a static eliminator for the belt 50, and 67 is a belt 6
0 cleaning device. In this image forming apparatus, the sheet P conveyed from a sheet feeding unit (not shown)
Is transported so as to pass through the transfer section of each image forming unit 3 while being adsorbed and carried on the sheet transport transfer belt 60, so that each toner image formed by each image forming unit 3 is transferred onto the same sheet P. The image is transferred so as to be superimposed in order, and then, after being separated from the belt 60, the fixing device 4
5, the toner image on the sheet P is fixed to obtain a color image.

In the image forming apparatus having such a paper transport transfer belt 60, the belt 60 and the attaching member 5 (the reinforcing tapes 50, 5) to be attached to the belt are used.
3, the bonding tape 51, the detection mark 52, etc.) may be set so that the water absorption or the coefficient of moisture expansion is the same or approximated. As a result, similar to the intermediate transfer belt 30 in the above-described embodiment, unnecessary undulation does not occur in the peripheral portion of the attaching member 5 of the paper transport transfer belt 60, and a good color image without image leakage can be obtained. Obtainable.

[0059]

As described above, the image forming apparatus according to the present invention can be applied to the belt member around the portion where the sticking member is stuck even if the environmental condition, especially the humidity condition fluctuates. Swell is less likely to occur. And, the effect of preventing the occurrence of the undulation, as a belt member and a sticking member,
Since the water absorption rate or the coefficient of hygroscopic expansion of the two is obtained by using the one configured so as to have the same or similar relation to each other, the swell generated due to the sticking member causes unnecessary cost increase. Without this, it is possible to prevent the problem more simply and accurately. In addition, it is possible to prevent the occurrence of an image defect such as an image missing due to the undulation, and to form a good image.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main part showing a relationship between an intermediate transfer belt and an attaching member.

FIG. 3 is an explanatory diagram of a main part showing a relationship between an intermediate transfer belt and a roll.

FIG. 4 is a diagram showing the relationship between the expansion coefficient and the amplitude of undulation when the moisture absorption expansion coefficient of the intermediate transfer belt is changed.

FIG. 5 is an explanatory diagram of a main part of a relationship between an intermediate transfer belt and a roll of an image forming apparatus according to another embodiment of the present invention.

FIG. 6 is an explanatory view of a main part showing another example of a reinforcing tape.

FIG. 7 is an explanatory view of a main part showing a configuration example in the case where there is no reinforcing tape of FIG. 6 and a bending phenomenon.

FIG. 8 is a schematic diagram illustrating a configuration example of an image forming apparatus provided with a paper transport belt.

FIG. 9 is a perspective view of a main part showing undulations occurring in the prior art.

[Explanation of symbols]

5: sticking member, 30: intermediate transfer belt (belt member),
31, 32, 33, 34 ... multiple rolls, 50, 53 ...
Reinforcement tape, 51: joining tape, 52: detection mark, 60: paper transport belt (belt member), P: paper.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Takashi Kawabata 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (72) Inventor Yukio Hayashi 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A belt member which is stretched and rotated between a plurality of rolls, and which holds and conveys at least a toner image or a sheet on an outer peripheral surface of a belt, and a sticking member is provided in a partial region of the belt member. In the pasted image forming apparatus, the belt member and the adhering member are configured so that the water absorption or the coefficient of hygroscopic expansion of both of them is the same or approximate to each other. Characteristic image forming apparatus.