JPH08305112A - Image forming device - Google Patents

Abstract

PURPOSE: To prevent an image defect which is caused by a level difference made at the joint of a carrying belt. CONSTITUTION: The joint is made so that it is inclined to a vertical line L in the direction of the movement of the carrying belt 8, and when the joint 8a passes rollers 11, 12, and 76, the belt is made to move onto them gradually and move apart from them gradually. This reduces speed irregularities and vibration and, therefore, prevents image quality deterioration such as color slippage and density irregularities.

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 for forming an image on an image carrier and transferring the image onto a sheet-shaped transfer material conveyed by a conveying means, for example, an electrophotographic image. Forming apparatus, in particular, a multi-transfer type color electrophotographic copying machine or printer apparatus that forms images of different colors on a plurality of image carriers, which are electrophotographic photoconductors, and sequentially transfers the images onto the same transfer material. Can be suitably applied to.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus is provided with a plurality of image forming units, each image forming unit forms a toner image of a different color, and these toner images are sequentially transferred onto the same recording material. Various color image forming apparatuses have been proposed. Among them, a color copying apparatus using a multicolor electrophotographic system is widely used.

An example of this color electrophotographic copying apparatus is shown in FIG.
A brief description will be given based on. The main body of the color electrophotographic copying apparatus includes first, second, third and fourth image forming portions P.
a, Pb, Pc, and Pd are arranged in parallel. Image forming unit Pa,
Pb, Pc and Pd respectively include electrophotographic photosensitive drums 1a, 1b, 1c and 1d as dedicated image carriers.

The photosensitive drums 1a, 1b, 1c and 1d have latent image forming portions 2a, 2b, 2c and 2d, developing portions 3a, 3b, 3c and 3d, cleaning portions 5a and 5b on their outer peripheral sides.
5c and 5d are arranged, respectively.

Further, the image forming portions Pa, Pb, Pc,
A transport belt 8 for transporting the recording material to each transfer position is disposed below Pd so as to be revolvable by a drive roller 8a and a driven roller 8b, and a transfer discharge portion 4a corresponding to each photosensitive drum is provided therein. 4b, 4c, and 4d are arranged.

With such a configuration, first, the first image forming portion Pa
A latent image of a cyan component color is formed on the photosensitive drum 1a based on the image information read from an image reader (not shown) by the latent image forming unit 2a. The latent image is formed on the developing unit 3a.
The developer having the cyan toner is used to form a visible image, and the cyan toner image is transferred to the recording material cassette 60 at the transfer portion 4a.
The recording material 6 is fed from the recording medium 6 and further transferred to the recording material 6 by the conveyor belt 8 via the registration rollers 13.

On the other hand, while the cyan image is being transferred onto the recording material as described above, a latent image of a magenta component color is formed in the second image forming portion Pb, and subsequently, a magenta toner image is formed in the developing portion 3b. When the recording material 6 that has been transferred by the first image forming portion Pa is carried into the transfer portion 4b, the recording material 6 is transferred onto a predetermined position of the recording material 6 in an overlapping manner.

Thereafter, the third and fourth methods are performed in the same manner as above.
The image forming units Pc and Pd form images of yellow and black, respectively.
The black color is further transferred and transferred to a predetermined position.

When such an image forming process is completed, the image on the recording material is fixed on the recording material 6 by the fixing section 7.
Complete a multicolor image.

On the other hand, each of the photosensitive drums 1a after the transfer is completed,
1b, 1c, 1d are cleaning units 5a, 5b, 5
Residual toner is removed by c and 5d, and the toner is prepared for the subsequent latent image formation.

By the way, the conveyor belt 8 is a film made of a dielectric resin such as a polyethylene terephthalate resin (PET sheet) or a polyvinylidene fluoride resin film sheet or a polyurethane resin film sheet. However, an endless shape or a so-called seamless belt having no joint is used.

[0012]

However, it is difficult to manufacture the seamless belt among the above-mentioned conventional examples, and the productivity,
There is a big problem in terms of cost.

The so-called seam belt having a seam has the following problems.

First, there is a problem of a step due to joining. Currently, as a joining method, there are adhesive joining using an adhesive or heat welding by heat, and it is considered that heat welding by ultrasonic waves is particularly excellent in terms of joining strength and the like. However, even in this case, the step due to the superposition of the film sheets cannot be eliminated, and this step causes a problem.

In the conventional example, the thickness t = 1 as the conveyor belt.
If a film sheet of about 50 μm is used, 10
A step difference of about 0 μm occurs. When this portion passes through the drive roller 8a and the driven roller 8b, minute rotation unevenness and vibration (shock) occur. As a result, the image being transferred is disturbed, resulting in color misregistration and density unevenness, which deteriorates the image quality.

Further, when transfer is carried out while holding the recording material at a position corresponding to the seam, the transfer electric field is different from the surrounding because the part of the transfer material overlapping the seam has different physical characteristics from its surroundings. Image disturbance occurs, and as a result, an image defect occurs as an image, which is line-shaped density unevenness corresponding to the joint portion.

Therefore, in order to prevent the occurrence of the density unevenness as described above, the recording material is not placed on the seam portion, the use is started from the position where the seam is formed, and the conveyor belt is set to an integral multiple of the paper size used. It is proposed to do so.

Further, a method has been proposed in which the recording material is not placed on the joint portion, and the joint portion is detected to adjust the timing at which the recording material is placed on the conveyor belt.

As the detecting means, (a) a method of forming a hole in the conveyor belt and detecting its position by a transmission type photosensor, (b) printing or taping with different reflectance on the surface of the conveyor belt, There is a method of detecting the position thereof by a reflection type photo sensor, but the above method has the following problems.

As for (a), when the hole is wound around the roller, bending stress is concentrated on the peripheral portion of the hole, leading to destruction, and scattered toner scattered from the hole enters the conveyance belt and adheres to the transfer charger. As a result, there is a problem that the image quality is deteriorated and the drive roller and the conveyor belt are slipped.

Regarding (b), there is a problem that the printing is scraped off due to long-term use of the apparatus and becomes undetectable, or the taping is peeled off and becomes undetectable.

Therefore, an object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of an image defect due to a stepped portion of a joint portion of a conveyor belt.

Another object of the present invention is to prevent damage and slippage of the conveyor belt, deterioration of image quality due to scattered toner, and the like.
It is an object of the present invention to provide an image forming apparatus provided with a joint portion detecting means capable of accurately detecting the joint portion of a conveyor belt over a long period of time.

[0024]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
At least one image carrying means for forming a visible image on the surface via the latent image forming means and the developing means, and a transfer material carrying means for carrying the transfer material on which the visible image is transferred are provided, and these image carrying means are provided. And at least one of the transfer material transporting means and a plurality of transport rollers arranged substantially parallel to each other with a predetermined distance, and carrying and transporting the visible image or the transfer material by being stretched over these transport rollers. And an endless belt member for forming an image, wherein the endless belt member has a joint portion formed to be inclined with respect to a line perpendicular to the moving direction of the endless belt member. .

The inclination of the seam from the vertical line is 1
It is preferably 0 to 20 mm.

According to another aspect of the present invention, at least one image carrying means for forming a visible image on the surface via a latent image forming means and a developing means, and a transfer material on which the visible image is transferred are conveyed. And a transfer material transporting means, and at least one of the image carrying means and the transfer material transporting means is provided with a plurality of transport rollers which are arranged substantially parallel to each other with a predetermined distance therebetween, and which are hung on these transport rollers. An image forming apparatus that has an endless belt member that carries and conveys the visible image or the transfer material, and forms an image,
The endless belt member has a seam portion having a step, and in order to detect the position of the seam portion, a seam portion detection portion provided immediately upstream of the seam portion and detection for detecting the seam portion detection portion. An image forming apparatus is provided which comprises:

The joint detecting portion is a detecting marking, and preferably includes an adhesive layer, a light reflecting layer, and a transparent protective film layer, and their total thickness is 100 μm or less.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. Prior to describing the main part of the present invention, the overall operation of the image forming apparatus will be described.

Referring to FIG. 6, the present invention is embodied in a color electrophotographic copying machine similar to that described in connection with FIG.

That is, in this embodiment, the image forming apparatus includes a plurality of image forming sections Pa, Pb, Pc, P in the apparatus body 10.
d is disposed below the image forming unit, and has a driving roller 12, a driven roller 11 and a tension roller 76, and an entire circumference 10 having a seam wound around these rollers.
Conveying means composed of a conveying belt 8 of 00 mm is provided. The conveyor belt 8 is moved endlessly at a speed of 100 mm / sec in the arrow direction.

In this embodiment, as the conveyor belt 8, a polyurethane resin film sheet spliced by an ultrasonic fusion method is used. In addition, in the present embodiment, a synthetic resin film such as PVDF (polyvinylidene fluoride) resin, PET (polyethylene terephthalate) resin, PEN (polyethylene naphthalate) resin, polycarbo resin, and polyether sulfone resin using polyurethane resin is also used. It is preferably used. Needless to say, the fusion method is not limited to ultrasonic fusion and other methods may be used.

The first, second, third and fourth image forming portions Pa, Pb, Pc and Pd arranged in parallel above the conveyor belt 8 have photosensitive drums 1a, 1b, 1c and 1d. Chargers 15a, 15b, 15c and 15d are provided above the drums 1a, 1b, 1c and 1d, respectively.

The photosensitive drums 1a, 1b, 1c and 1d have laser beam scanners 16a, 16b and 1 above them.
6c and 16d are provided, respectively. The laser beam scanners 16a, 16b, 16c, 16d are composed of semiconductor lasers, polygon mirrors, fθ lenses, etc., receive an input of an electric digital image signal, and charge the laser beam modulated corresponding to the signal with the chargers 15a, 15b. 1
5c and 15d and the developing devices 3a, 3b, 3c and 3d are formed to scan in the generatrix direction of the photosensitive drums 1a, 1b, 1c and 1d to expose them.

When an image forming operation start signal is input to the image forming apparatus shown in this embodiment, the photosensitive drum 1a starts rotating in the direction of the arrow and is uniformly charged by the charger 15a, and thereafter, With the laser beam scanner 16a,
The laser light modulated by the image signal corresponding to the black component image of the original image is written to form a latent image. Next, the latent image is developed by the toner in the developing device 3a by the developing device 3a, and a black toner image is formed on the photosensitive drum 1a.

On the other hand, the recording material 6 as the transfer material in the recording material cassette 60 is taken out from the recording material cassette 60 by the pickup roller 9 and sent to the registration roller 13 provided near the driving roller 11. The recording material 6 once stopped by the registration roller 13 is sent by the registration roller 13 onto the conveyor belt 8 which has already started to rotate at a timing with the toner image formed on the photosensitive drum 1a. Timing belt 8
The recording material 6 sent to the upper side is transfer-charged from the back side of the conveyor belt 8 by the transfer charger 4a at the transfer portion of the image forming portion Pa, and the black toner image on the photosensitive drum 1a is transferred.

In this step, the remaining image forming portions Pb, Pc,
The same process is performed for Pd, and the magenta toner image, the yellow toner image, and the cyan toner image are sequentially transferred and transferred onto the recording material 6. The color order of the toner images is not limited to this embodiment.

The recording material 6 on which all the transfer has been completed is separated from the conveyor belt 8 while being subjected to AC static elimination by the separation charger 61 just above the driven roller 12 at the left end portion of the conveyor belt 8 and sent to the fixing portion 7. Be done. Recording material 6 at fixing unit 7
The upper toner image is fixed on the recording material by heat and then discharged from the discharge port 14 to the outside of the apparatus main body 10.

The above is the main sequence in the case of forming an image, but when obtaining a high image quality by a plurality of multiple transfer steps, the balance of each image quality is important. Therefore, for example, a preparatory operation such as attaching and adjusting a potential sensor to each of the photosensitive drums and performing static elimination and cleaning of the transfer belt in advance are often performed. This is called a pre-rotation sequence.

On the other hand, cleaning means 8 for the conveyor belt 8
0 is mainly a blade system and a brush system. Since the former has less vibration during cleaning, there is less waffle, and even if it is always in contact, it does not significantly affect image unevenness. After the image is output, cleaning is performed by the post-rotation sequence so that the toner adhering to the conveyor belt is not fused by leaving it.

The above is the overall outline of the image forming apparatus to which the present invention is applied. Next, the main part of the present invention will be described in detail.

Embodiment 1 An embodiment of the conveyor belt according to the present invention will be described with reference to FIGS. 1 and 2. As shown in both figures, the conveyor belt 8
Is wound around the driving roller 11, the driven roller 12, and the tension roller 76 as described above, and has the joint portion 8a. The seam portion 8a is formed by inclining by W from a line L perpendicular to the moving direction of the conveyor belt indicated by an arrow.

Further, in the present embodiment, the recording material is sucked and conveyed on the conveyor belt 8 avoiding the joint portion, and W = 10 to 2 so that the recording material is smaller than the continuous conveying distance.
It is set to 0 mm.

In this embodiment, the driving roller 12 has a diameter of 50 mm, and the driven roller 11 and the tension roller 76 both have a diameter of 20 mm.

Since the joint portion 8a in the conventional example is formed perpendicular to the moving direction of the conveyor belt, when the joint portion 8a passes through the above-mentioned rollers, the step (about 1
00 μm) and the effect of rigidity, speed unevenness and vibration occur with respect to the movement of the conveyor belt 8. For this reason,
In the image forming apparatus as in this embodiment, color misregistration or density unevenness occurs on an image, which causes image deterioration.

In this embodiment, since the seam portion 8a is formed so as to be inclined by L with respect to the moving direction of the conveyor belt 8, when passing through each roller, it gradually climbs on the roller and gradually separates from the roller. Therefore, the speed unevenness and the vibration (shock) described above are alleviated, so that the image quality deterioration such as the color shift and the density unevenness is prevented.

Further, the cleaning blade 80a as a cleaning means for the conveyor belt 8 shown in FIG.
Even when overcoming, the overcoming is gradually performed, and the bounce due to the joint portion is suppressed, and the cleaning performance is improved.

The above-mentioned dimensions are not limited to this, and the effects of the present invention can be achieved even if they are determined by various conditions.

Embodiment 2 Next, an embodiment of the position detecting means for the joint portion 8a according to the present invention will be described.

The outline of the position detecting means is to detect the detecting portion 8b printed or taped on the conveyor belt 8 by the reflection type photosensor 20 and feed back the position to the apparatus. It is excellent in terms of destruction and toner stains compared to the means for opening and detecting.

That is, in the conventional detecting means, when the printing or taping detecting portion is on the surface of the conveyor belt, it is brought into contact with the photosensitive drum or the cleaning means of the conveyor belt 8 described above, and when it is on the rear surface of the conveyor belt. There is a problem in that the above-mentioned contact with the rollers causes the chip to be scraped off or peeled off, resulting in defective detection of the seam.

The embodiment of the present invention is embodied as shown in FIGS. 2 shows a case where the detection unit 8b is formed on the front surface of the conveyor belt 8, and FIG. 3 shows a case where the detection unit 8b is formed on the rear surface of the conveyance belt 8.

In each case, the detecting portion 8b is arranged on the upstream side continuous with the joint portion 8a, and the reflection type photosensor (seam detecting sensor) 20 is installed on the side of the detecting portion 8b, and the detecting portion 8b and other The position is detected by the change in the reflectance with respect to the part and is fed back to the device. The apparatus is controlled by the above-mentioned detection signal so that the recording material is not stacked on the joint portion 8a.

Next, an example of the control will be described with reference to the flow chart of control shown in FIG.

As shown in the figure, when a copy signal is input, the above-described pre-rotation sequence starts, and at the same time, the recording material and its size T _W are detected. During this pre-rotation sequence, the value S = 1 of the joint belt joint detection sensor 20
When turned on, the paper feed clock is set to C = 0. There are various possible paper feed clocks such as a drum rotation speed, a clock timer using a crystal oscillator in the main body, and the number of drive motor pulses on the conveyor belt. In this embodiment, the drum rotation speed used for controlling the potential of the drum is used. A DD motor having a good wower characteristic is also used as the conveyor belt driving motor that also serves as the internal clock. The value of the paper feed clock C indicated by the internal clock in the figure corresponds to the drum clock of the main body and is a value that increases in units of 0.01 seconds, but when the sensor S = 1, C = 0. Becomes

On the other hand, after the pre-rotation of the recording material, the recording material 6 is fed from the paper feeding cassette 60 by the pickup roller 9 in FIG. 6, hits the registration roller, forms a loop, and stops once. Then, at the same time that the value of C of the paper feed clock becomes equal to the timing T ₁ of the first sheet of the recording paper 6 calculated by the carrying timing control means, the registration roller rotates and the paper is fed and carried onto the carrying belt. To be done.

The feeding timing T _N at this time is shown in FIG.
It is shown in the explanatory diagram of. This is the case where the peripheral length of the conveyor belt 8 in the printer shown in FIG. 6 is 1000 mm. In FIG. 5, a _n indicates that the n-th recording material is held, and b _n indicates that the n-th recording material is not placed.

As shown in FIG. 5, when the recording material of A4 is held and conveyed with a paper interval of 100 mm, the belt end portion is in the paper interval b ₄ in the first round, so that image unevenness does not occur. However, since there is an end in a ₇ of the 7th sheet on the second round and a ₁₀ of the 10th sheet on the 3rd round, a seam streak appears in the image.

Therefore, as shown in FIG. 5, in the case of A4, the paper feed clock C is set to C = 0 for each belt revolution,
A seam always comes into the _space between the sheets b _4i (i = belt rotation speed). However, in the case of, the process speed is a factor that determines the continuous copy speed by the sheet interval b + the sheet size a, but is the factor that is determined by the belt peripheral length / the number of sheets per one cycle. For example, 15 sheets per minute, A
Assuming that 4 can be output, 12 rotations per belt rotation
Seconds, 4 seconds per sheet.

When the belt circumference is simply set to the recording material size or an integral multiple of the recording material size and the paper interval, even if the belt peripheral length is gradually deviated due to the accumulation of errors such as mechanical accuracy or clock accuracy. Since the clock correction (C = 0) is performed for each rotation as in the embodiment, the malfunction can be suppressed.

For example, as shown in FIG. 5, even if the belt rotation speed is slightly slower than the drum rotation speed, the seam portion can be retained in the paper interval b ₄ .

Further, FIG. 5 shows the case where A3 paper is passed in this apparatus. Incidentally, as shown in FIG. 5, when the timing of A4 size is adjusted, a ₂ is deposited on the end of the belt.

As described above, when the feeding timing T _N is calculated in FIG. 4 and the recording material detection result is A4 (T
₁ , T ₂ , T ₃ ,) = (1.20, 4.92, 8.6
4), in case of A3 (T ₁ , T ₂ ) = (0.36, 6.4)
8).

Since the gist of the present invention is not the above-described control but the method of forming the detection portion 8b, the control method is various including the above-mentioned control method as an example.

Here, a method of forming the detecting portion 8b will be described. As shown in FIGS. 2 and 3, the detection portion 8b is formed on the conveyor belt 8 by utilizing the step of the joint portion 8a of the conveyor belt 8.

As shown in FIG. 2, both the case where the detecting portion 8b is formed on the front surface of the conveyor belt 8 and the case where the detecting portion 8b is formed on the rear surface of the conveyor belt 8 as shown in FIG. The detection unit 8b is provided immediately upstream of the seam portion 8a protruding in the moving direction. Thereby, the detection unit 8
Since b does not protrude from the conveyor belt 8 in the moving direction, it is effective for the problems such as shaving and peeling as described above. Particularly, in terms of durability and the like, it is possible to provide a detection means without detection failure.

Further, as the structure of the detecting section 8b, the one in which an adhesive layer is formed on the surface of the conveyor belt 8, a reflective layer is formed on the adhesive layer, and a protective film layer is formed on the adhesive layer is highly reliable. It is desirable that the reflective layer has a reflectance sufficient to be discriminated from the surface of the conveyor belt 8, and the protective film is specifically made of PET to prevent stains such as toner and scratches on the reflective layer. Have the effect of.

In the above embodiment, the endless conveyor belt as the endless conveyor of the recording material has been described. However, as is well known, the present invention is also applicable to an image forming apparatus using a belt-shaped photoreceptor as an image carrier. Needless to say, can be applied.

[0068]

As described above, since the endless belt member has the seam formed so as to be inclined with respect to the vertical line with respect to the moving direction of the endless belt member, the seam has uneven speed and vibration when passing through each roller. (Impact) can be prevented, and therefore image deterioration such as color misregistration and density unevenness can be prevented, and a good image can be obtained.

According to another aspect of the present invention, the endless belt member has a joint having a step, and a joint provided immediately upstream of the joint for detecting the position of the joint. By having a part detection part and a detection means for detecting the joint part detection part, the position detection of the joint part avoids problems such as destruction of the endless belt member due to long-term use and toner contamination, Problems such as abrasion and peeling can be avoided, and it is possible to provide an image forming apparatus equipped with a reliable and durable detection unit.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a conveyor belt according to the present invention.

FIG. 2 is a cross-sectional view showing a joint detection unit of the conveyor belt of FIG.

FIG. 3 is a cross-sectional view showing a modified example of a joint detection unit of the conveyor belt of FIG.

FIG. 4 is a flowchart showing an example of control of the image forming apparatus by detecting a seam.

FIG. 5 is an explanatory diagram of a feeding timing showing an example of control of the image forming apparatus by detecting a seam.

FIG. 6 is a schematic sectional view showing the overall configuration of the image forming apparatus of the present invention.

FIG. 7 is a conceptual diagram showing a conventional image forming apparatus.

[Explanation of symbols]

 1a to 1d Photosensitive drum (image bearing means) 3a to 3d Developing device (developing means) 6 Recording material (transfer material) 8 Conveying belt (endless belt member) 8a Joint portion 8b Detection marking (joint portion detecting portion) 11 Followed roller ( Conveying roller 12 Drive roller (conveying roller) 16a to 16d Latent image forming means 20 Reflective photosensor (detecting means) 76 Tension roller (conveying roller)

Claims (4)

[Claims] 1. At least one image carrying means for forming a visible image on the surface via a latent image forming means and a developing means, and a transfer material carrying means for carrying a transfer material on which the visible image is transferred. At least one of the image carrying means and the transfer material carrying means is provided with a plurality of carrying rollers arranged substantially parallel to each other with a predetermined distance, and the visible image or An image forming apparatus for forming an image, comprising an endless belt member carrying and conveying a transfer material, wherein the endless belt member has a joint portion formed to be inclined with respect to a vertical line with respect to a moving direction thereof. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the joint portion has an inclination of 10 to 20 mm from the vertical line. 3. At least one image carrying means for forming a visible image on the surface through a latent image forming means and a developing means, and a transfer material carrying means for carrying a transfer material to which the visible image is transferred. At least one of the image carrying means and the transfer material carrying means is provided with a plurality of carrying rollers arranged substantially parallel to each other with a predetermined distance, and the visible image or An image forming apparatus for forming an image, comprising an endless belt member for carrying and transferring a transfer material, wherein the endless belt member has a joint portion having a step, and the joint portion for detecting the position of the joint portion. An image forming apparatus, comprising: a joint portion detecting portion provided immediately upstream of the joint portion; and detecting means for detecting the joint portion detecting portion. 4. The joint detection portion is a detection marking, which includes an adhesive layer, a light reflection layer, and a transparent protective film layer, and has a total thickness of 100 μm or less. Image forming device