JP2633077B2 - Image forming device - Google Patents

Description

The present invention relates to a method for forming an image on an image carrier, and transferring the image to a recording material conveyed by a conveyance unit that moves endlessly. The present invention relates to an image forming apparatus, for example, an electrophotographic image forming apparatus, particularly to form images of different colors on a plurality of image carriers such as an electrophotographic photosensitive member,
The present invention can be suitably applied to a color electrophotographic apparatus of a type in which the images are sequentially transferred onto the same recording material.

[Conventional technology]

Conventionally, an image forming apparatus that includes a plurality of image forming sections, forms toner images of different colors in each image forming section, and sequentially superimposes and transfers the toner images to the same recording material, a so-called,
Various color image forming apparatuses have been proposed, and among them, a color copying apparatus based on a multicolor electrophotographic system has been widely used.

An example of such a color electrophotographic copying apparatus will be briefly described with reference to FIG. 5. First, second, third and fourth image forming sections Pa,
Pb, Pc and Pd are juxtaposed. The image forming department Pa, Pb, Pc
And Pd are provided with dedicated image carriers, in this example, electrophotographic photosensitive drums 1a, 1b, 1c and 1d.

On the outer peripheral side of the photosensitive drums 1a, 1b, 1c and 1d, latent image forming sections 2a, 2b, 2c and 2d, developing sections 3a, 3b, 3c and 3d and cleaning sections 5a, 5b, 5c and 5d are respectively arranged. You.

Further, below the image forming units Pa, Pb, Pc, and Pd, a transport belt 8 that transports a recording material is disposed, and inside the transfer belt 8, transfer discharge units 4a, 4b, 4c, and 4d are provided with the respective photosensitive drums 1a, 1b, 1c,
Each is arranged corresponding to 1d.

In such a configuration, first, a latent image of black component color in image information is formed on the photosensitive drum 1a of the first image forming unit Pa by the latent image forming unit 2a. The latent image is converted into a visible image by the black toner of the developing unit 3a, and the black toner image is transferred from the recording material cassette 60 to the recording material 6 sent from the recording material cassette 60 through the registration roller 13 by the transport belt 8 at the transfer unit 4a. You.

On the other hand, while the black image is being transferred to the recording material 6 as described above, a magenta component color latent image is formed in the second image forming unit Pb, and subsequently, the magenta toner The image is transferred to a predetermined position on the recording material 6 when the recording material 6 that has been transferred by the first image forming unit Pb is carried into the transfer unit 4b.

Hereinafter, yellow and cyan images are formed by the third and fourth image forming units Pc and Pd in the same manner as described above, and the yellow and cyan colors are transferred to predetermined positions on the same recording material 6. Is done.

When such an image forming process is completed, the multicolor image fixed on the recording material by the fixing unit 7 is obtained from the image on the recording material. On the other hand, the photosensitive drums 1a, 1b, 1c,
In 1d, the residual toner is removed by the cleaning units 5a, 5b, 5c, and 5d, and is prepared for the subsequent latent image formation.

In the image forming apparatus as described above, generally, both ends of a dielectric resin film sheet such as a polyethylene terephthalate resin film sheet, a polyfluorovinylidene resin film sheet, or a polyurethane resin film sheet are used as a recording material conveying belt. Those that are overlapped and joined to form an endless shape are often used. This is because a seamless type belt having no seams is difficult to manufacture and very expensive, which is very disadvantageous in cost.

In the case of using a belt having such a seam, if transfer is performed on a recording material at a location corresponding to the seam, only the seam has a difference in physical properties from other portions, so that transfer omission occurs or the seam becomes convex. Otherwise, image defects such as image disturbance due to strong contact with the photosensitive drum occur.

Therefore, during preliminary rotation prior to image formation, a mechanism for detecting this seam portion is provided, and this seam portion is detected,
For example, there is a method of avoiding the above problem by carrying the recording material into the belt immediately after the seam portion passes through the portion carrying the recording material into the belt.

[Problems to be solved by the invention]

However, in the above-described conventional example, if the position of the seam portion on the transport belt is detected before the actual image formation, and then the actual image forming operation is started, the worst case is that the transport belt makes one round. Has a disadvantage that the pre-rotation prior to the image formation is prolonged and the so-called first copy time is prolonged without entering the image forming operation. In addition, the life of these components is shortened because the conveyor belt and those that operate simultaneously with the operation of the conveyor belt, such as the photosensitive drum and the fixing device, are operated extra by pre-rotation prior to image formation. There was also a disadvantage.

[Means for solving the problem]

An object of the present invention is to provide an image forming apparatus which has solved the above-mentioned conventional disadvantages.

That is, according to the present invention, which achieves the above object, there is provided an image forming method in which an image formed on a moving image carrier is transferred onto a recording material conveyed by a conveying means moving endlessly to form an image on the recording material. In the apparatus, the transporting unit has a joint, and moves in a moving direction of the image carrier from an image forming position of the image carrier toward an upstream from a transfer position of the image carrier with respect to a moving direction of the transporting unit. At a position separated by a distance obtained by adding a first distance to a transfer position and a second distance corresponding to a length of the recording material in the moving direction of the recording material,
Detecting means for detecting a seam of the conveying means is provided, and after the moving of the conveying means is started, the conveying means
When the detecting means does not detect a seam of the conveying means within the moving time, the image forming operation on the image carrier is started.

The present invention can further exert its effects by applying this configuration to the image carrier on the most upstream side of a plurality of image forming sections.

〔Example〕

Hereinafter, an embodiment of the image forming apparatus according to the present invention will be described 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. 4, the present invention is embodied in a color electrophotographic copying machine similar to that described in connection with FIG.

That is, in the present embodiment, the image forming apparatus is
A plurality of image forming units Pa, Pb, Pc, and Pd are arranged therein, and a driving roller 11, a driven roller 12, a tension roller 6, and a seam wound around the rollers are provided below the image forming unit. A conveying means including a conveying belt 8 having a total circumference of about 1600 mm is provided.
It is moved endlessly at the speed of sec. In the present embodiment, the transport belt 8 is formed by joining polyurethane resin film sheets by an ultrasonic fusion method. In this embodiment, a polyurethane resin is used, but a synthetic resin film such as a PVDF (polyvinylidene fluoride) resin, a PET (polyethylene terephthalate) resin, a PEN (polyethylene naphtholate) resin, a polycarbonate resin, a polyethersulfon resin, or the like. Is also preferably used.
Also, it goes without saying that the fusion method is not limited to the ultrasonic fusion, and other methods may be used.

In FIG. 4, the registration stroke 13 is on the right side of the conveyor belt 8.
Is arranged.

The first, second, third and fourth image forming units Pa, Pb, Pc and Pd arranged in parallel above the conveyor belt 8 are photosensitive drums 1a,
1b, 1c and 1d, and chargers 15a, 15b, 15c and 15d are provided on the upper left side of each of the photosensitive drums 1a, 1b, 1c and 1d.

Laser beam scanners 16a, 16b, 16c, and 16d are provided on the photosensitive drums 1a, 1b, 1c, and 1d, respectively. These laser beam scanners 16a, 16b, 16c, 16d
Is composed of a semiconductor laser, a polygon mirror, an fθ lens, etc., receives an input of an electric digital image signal, and applies a laser beam modulated according to the signal to the chargers 15a, 15b,
The photosensitive drum 1 is located between 15c, 15d and the developing units 3a, 3b, 3c, 3d.
It is formed so as to scan in the generatrix directions of a, 1b, 1c, and 1d to expose them.

When an image forming operation start signal is input to the image forming apparatus shown in the present embodiment, the photosensitive drum 1a starts rotating in the direction of the arrow, and receives uniform charging by the charger 15a, and thereafter,
A laser beam modulated by an image signal corresponding to the black component image of the original image is written by the laser beam scanner 16a to form a latent image. Next, the developing device 3a
As a result, the latent image is developed by the toner in the developing device 3a, and a toner image is formed on the photosensitive drum 1a.

On the other hand, the recording material 6 in the recording material cassette 60 is taken out of the recording material cassette 60 by the pick-up roller 9 and sent to the registration roller 13. The recording material 6 once stopped by the registration roller 13 is fed by the registration roller 13 onto the transport belt 8 which has already started rotating and moving at a timing with the toner image formed on the photosensitive drum 1a. The recording material 6 fed onto the conveyor belt 8 at a time is transferred to a transfer section of the image forming section Pa by a transfer charger.
4a, the transfer charging is applied from the back side of the conveyor belt 8,
The toner image on the photosensitive drum 1a is transferred.

This process is similarly performed in the remaining image forming units Pb, Pc, and Pd, and a magenta toner image, a yellow toner image,
The cyan toner images are sequentially transferred and superimposed on the recording material 6.
The color order is not limited to this embodiment.

The recording material 6 on which all the transfer has been completed is separated from the conveyance belt 8 while being subjected to AC static elimination by a separation charger 61 almost immediately above the roller 12 at the left end of the conveyance belt 8, and is sent to the fixing unit 7. After the toner image on the recording material 6 is fixed to the recording material by heat in the fixing unit 7, the toner image is discharged from the discharge port 14 to the outside of the apparatus main body 10.

The above is an outline of the overall operation of the image forming apparatus to which the present invention is applied. Next, a detailed description will be given of the main part of the present invention with reference to FIG.

When the distance from the image exposure position E, which is the latent image forming position of the photosensitive drum 1a, to the transfer position T along the rotation direction of the photosensitive drum 1a is ET, the distance from the transfer position T to the upstream side with respect to the moving direction of the transport belt is substantially equal. The point that goes up by the distance of ET, that is, ET
It relates to the moving direction of the conveyor belt from point B which is TB. The maximum paper size to be used, a point S approximately 420 mm away from the point S, which is substantially equal to the longitudinal length of the A3 size paper in this embodiment, ie, B
The seam 81 of the conveyor belt 8 is located at the point S where S420 mm is
The sensor 17 for detecting is provided.

In the present embodiment, a polyurethane resin is used as the transport belt 8, and when joined by using an ultrasonic fusion method, the seam portion becomes thicker or changes in composition than other surrounding portions. Or Therefore, in the present embodiment, an optical sensor is used as the sensor 17 described above.

Since the seam portion 81 exhibits a different spectral transmittance and a different spectral reflectance from the surrounding portion for the above-described reason, the seam portion 81 can be detected by an optical sensor.
It is needless to say that a mark indicating the seam portion may be provided near the seam portion 81, and the mark may be detected by a sensor. In this case, it goes without saying that not only an optical sensor but also a magnetic sensor, an electric sensor, a mechanical sensor, or the like can be suitably used as the sensor.

Further, in the present embodiment, the registration rollers 13 are arranged such that the distance from the point A at which the recording material is fed to the conveyance belt is ABCA when the nip portion of the roller pair is point C.

Now, when a signal indicating the start of operation in the image forming apparatus having the above configuration is input, the photosensitive drums 1a, 1b, 1c, 1
d, the paper feed mechanism, and the transport belt 8 each start operating in the direction of the arrow. In the paper feed mechanism, after the recording material 6 is taken out from the recording material cassette 60 and conveyed to the registration roller 13, the movement of the registration roller 13 is temporarily stopped by the operation of the registration roller 13, and a standby state is established at the registration roller 13. .

On the other hand, the sensor 17 located at the point S continues to detect the passage of the seam portion 81 from the time when the conveyance belt starts operating. At this time, a signal indicating that the signal has not been detected is stored in a storage device of a control unit (not shown). The distance l
When the seam section 81 by the sensor 17 within the time (420 mm) by the conveyor belt corresponds to the time to move is not detected (this time is T ₁₎ is rapidly operates the resist roller 13, the recording material 16 And irradiates the point E on the photosensitive drum 1a with a light image to start forming a latent image. At this time, as described above, the seam portion 81 does not exist between the point B and the point S.

Thereafter, the point on the conveyor belt 8 that has been in the point B to the time T ₁ (the point to X) is, when it came to the point A, so is disposed a resist roller 13 to keep the ABCA relationship: Then, the leading end of the recording material 6 exactly coincides with the point X on the transport belt, and the recording material 6 is sent onto the transport belt. Further, when the point X on the transport belt 8 reaches the point T which is the transfer position on the photosensitive drum 1a, the ETTB
Is maintained at the transfer position T, the toner image formed on the photosensitive drum 1a is transferred just in conformity with the leading end of the recording material 6 at the point X, and the toner image is transferred onto the recording material 6. Is formed.

Further, when the detection of the seam portion 81 is started by the sensor 17 and the seam portion 81 is detected by the sensor 17 before the time corresponding to the distance l (420 mm) has elapsed, the detection is not performed at the time of the detection. The signal indicating that the seam portion stored in the storage device of the illustrated control means has not passed is reset once, and the detection of the seam portion is started again from this time, and the same method as described above is used. Image formation is performed.

When an image was formed using the image forming apparatus having the above-described configuration, the first copy time was the worst case, and for example, (the entire belt circumference-l × 2) ÷ (belt Moving speed) = (1600-420 x 2) / 100 = 7.6 It is possible to reduce 7.6 seconds from the above formula, and on average, ((A) Expected value of the movement distance of the belt when the seam part does not pass while the sensor 17 is detecting the seam part. (B) The belt movement when the seam part passes while the seam part is being detected by the sensor 17 (Expected value of moving distance) It became possible to reduce about 2.1 sec from the above formula.

Further, the effect of improving the service life of the transport belt, the photosensitive drum, the fixing device, and the like was also obtained.

Conventionally, the first copy time is the maximum and minimum, for example, (the entire belt circumference) / (the belt movement speed) = 16
00 ÷ 100 = 16, resulting in 16 seconds being different, giving the user a very unnatural feeling,
According to the present embodiment, also for this problem, 1 ÷ (movement speed of the belt) = 420 ÷ 100 = 4.2, and the difference is only 4.2 seconds, so that the unnatural feeling as described above can be eliminated.

In the present embodiment, the point C is determined so that the distance between the nip portion C of the registration roller 13 and the point A at which the recording material 6 is fed to the conveyor belt 8 is CAAB.
It goes without saying that the point C may be set so as to be AB. In this case, the operation start of the registration roller 13 may be delayed by a time corresponding to the distance (AB) -the distance (CA).

 Next, a second embodiment will be described with reference to FIG.

In the present embodiment, in addition to the configuration described in the first embodiment, the length in the conveyance belt moving direction during conveyance of the A4 size paper from point B toward the upstream side in the movement direction of the conveyance belt 8. The sensor 18 is provided at a point S 'which is approximately 210 mm away from the point 1' which is substantially equal to the distance l '. Then, the sensors 17 and 18 can be selectively used.

According to the present embodiment, when the length of the recording material selected and instructed by the operator in the transport belt moving direction during the transportation of the recording material is larger than the A4 size paper and is equal to or less than the A3 size paper (maximum paper size), the sensor 17 is used. Is used, and in the case of A4 size paper or less, the joint is detected using the sensor 18. When an image forming operation was performed in the same manner as in the first embodiment, when a recording material having a size of A4 size paper or less was passed, the first copy time was worse in the worst case than in the related art. When calculated by the equation shown in the first embodiment, 1
It was possible to reduce the time by 1.8 seconds, and on average, by the same calculation, it was possible to reduce the time by about 5.5 seconds, and even better results were obtained.

 Further, a third embodiment will be described with reference to FIG.

In the present embodiment, in addition to the configuration described in the first embodiment, a sensor moving member (not shown) that can change the position of the sensor 17 according to the size of the recording material to be passed is provided. is there. A distance approximately equal to the length of the sensor 17 in the conveying belt moving direction during the conveyance of the recording material 6, for example, 171 at a point S "where BS" = l "if the length is l", and BS if the length is 11 " = L
Moved and placed as 172.

When an image forming operation was performed in the above-described configuration in the same manner as in the first and second embodiments, a sensor was provided for each recording material to be passed.
Since the 17 positions can be changed, it was confirmed that the smaller the recording material, the less the waste and the greater the effect of reducing the first copy time.

Although the first, second and third embodiments have all described the image forming apparatus having a plurality of image carriers, the present invention is directed to a case where a recording material is conveyed by a conveyance belt to one image carrier. It may be applied to the image forming apparatus described above.

〔The invention's effect〕

As described above, according to the present invention, the sensor that detects the seam of the conveying means such as the conveyance belt is used to detect the seam at a predetermined distance, for example, a moving time corresponding to the distance corresponding to the longitudinal direction of the maximum recording material. The image forming operation for the image carrier such as the photosensitive drum is started when the image is not continuously detected, so that the first copy time can be reduced and the life of the parts such as the conveying means, the image carrier, and the fixing device can be improved. It has become possible.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a main part of an image forming apparatus embodying the present invention, FIG. 2 is a schematic cross-sectional view showing a main part of an image forming apparatus according to another embodiment of the present invention, and FIG. FIG. 4 is a schematic cross-sectional view illustrating a main part of an image forming apparatus according to still another embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating the overall configuration of the image forming apparatus embodying the present invention. FIG. 1a, 1b, 1c, 1d: Photoconductor drum (image carrier) 6: Recording material 8: Conveying belt (conveying means) 11, 12: Driving roller 13: Registration rollers 17, 18, 171, 172 …… Sensor (detection means) 81 …… Seam of the conveyor belt

Claims (8)

(57) [Claims] An image forming apparatus for transferring an image formed on a moving image carrier to a recording material conveyed by a conveying means moving endlessly to form an image on the recording material, wherein the conveying means Has a seam, and a first direction from the image forming position of the image carrier to the transfer position along the moving direction of the image carrier toward the upstream from the transfer position of the image carrier with respect to the moving direction of the conveying means. And a detecting means for detecting a seam of the conveying means at a position separated by a distance obtained by combining the distance of the recording medium with a second distance corresponding to the length of the recording material in the moving direction of the recording material. Starting the movement of the image carrier, when the detecting means does not detect a seam of the conveying means within a time period in which the conveying means moves the second distance, an image forming operation for the image carrier is started. Image forming equipment . 2. The image forming apparatus according to claim 1, wherein the second distance corresponds to a length of a recording material having a maximum size used in the image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the arrangement position of said detection means can be changed according to the size of a recording material to be used. 4. The detecting means has a plurality of detecting sections, and selects and uses one of the plurality of detecting sections in accordance with the size of a recording material, and uses the detecting section to select the transporting means. The image forming apparatus according to claim 1, wherein a seam is detected. 5. The image forming apparatus according to claim 1, wherein the image forming position of the image carrier is a latent image forming position with respect to the image carrier. 6. The image forming apparatus according to claim 5, wherein the image forming operation is a latent image forming operation on the image carrier. 7. The image forming apparatus has a plurality of image forming units in which a plurality of image carriers are juxtaposed along a moving direction of the recording material, and a transfer position of the image carriers is the most upstream side thereof. The image forming apparatus according to claim 1, wherein the image forming apparatus is a transfer position. 8. The image forming apparatus according to claim 7, wherein images of different colors are formed in said plurality of image forming sections, respectively, and these images are superimposedly transferred onto the same recording material to form a color image.