JP4721422B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image carrier on which a toner image is formed, a transfer device that transfers the toner image on the image carrier to a recording medium, a fixing device that fixes the toner image transferred to the recording medium, and a toner image A transfer device that removes transfer residual toner adhering to the image carrier after transferring the image and cleans the image carrier, and a reversing device that reverses the front and back of the recording medium that has passed through the fixing device. A single-side mode in which an image is formed only on one side of the recording medium, and a recording medium having a toner image transferred to one side and passed through the fixing device is sent to the reversing device to reverse the front and back of the recording medium. An image forming apparatus capable of selecting a duplex mode in which a toner image on an image carrier is transferred to the other surface of the recording medium, the toner image is fixed by the fixing device, and images are formed on both sides of the recording medium. About.

  An image forming apparatus of the above type configured as an electronic copying machine, a printer, a facsimile, or a complex machine of these is well known (see Patent Document 1). In this type of image forming apparatus, when the recording medium passes through the fixing device, the anti-offset liquid is applied to the surface of the fixing member in order to prevent the toner on the recording medium from moving to the fixing member of the fixing device. Is applied. Therefore, when the recording medium passes through the fixing device, a small amount of offset preventing liquid adheres to the recording medium. On the other hand, in this type of image forming apparatus, when the duplex mode is selected, the toner image is transferred from the image carrier, and the recording medium once passed through the fixing device is conveyed again to the image carrier, and the recording is performed. The other surface of the medium comes into contact with the image carrier, and the toner image on the image carrier is transferred to the other surface of the recording medium. At that time, since a small amount of the anti-offset liquid adheres to the recording medium once passed through the fixing device as described above, when the other surface of the recording medium comes into contact with the image carrier, the image is removed from the recording medium. A very small amount of offset prevention liquid is transferred to the carrier. In this manner, when the offset preventing liquid is gradually accumulated on the image carrier, the cleaning performance of the image carrier by the cleaning device is deteriorated.

JP 2003-66735 A

  An object of the present invention is to provide an image forming apparatus capable of preventing the deterioration of the cleaning performance of the image carrier by the cleaning apparatus or effectively suppressing the deterioration.

  In order to achieve the above object, the present invention adds a count value every time the duplex mode operation is executed and subtracts the count value every time the simplex mode operation is executed in the image forming apparatus of the format described at the beginning. In addition, when the count value is zero, a double-sided counter that does not subtract the count value even when the single-sided mode operation is performed is provided, and when the time for cleaning the image carrier by the cleaning device is defined as the cleaning time, An image forming apparatus is proposed in which the cleaning time when the count value of the counter reaches a predetermined value is set longer than the cleaning time when the count value is less than the predetermined value ( Claim 1).

  The image forming apparatus according to claim 1, wherein the cleaning device includes a cleaning brush that contacts the image carrier, and electrostatically transfers toner on the image carrier to the cleaning brush. Accordingly, it is advantageous that the image carrier is configured to be cleaned (claim 2).

  Further, in the image forming apparatus according to claim 1 or 2, it is advantageous that the image carrier is a belt body supported around a plurality of support rollers (claim 3).

  Further, in the image forming apparatus according to any one of claims 1 to 3, it is advantageous that the cleaning device is disposed on an upper portion of the image carrier (claim 4).

  According to the present invention, even if the anti-offset liquid adheres to the image carrier during the double-side mode operation, the anti-offset liquid can be effectively removed by the cleaning device, so that the cleaning performance of the image carrier by the cleaning device is deteriorated. It can be blocked or effectively suppressed.

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

  FIG. 1 is a schematic sectional view showing an example of an image forming apparatus, and FIG. 2 is an enlarged view showing a part of the configuration of FIG. The image forming apparatus shown here includes a photosensitive member 1 composed of an endless belt that is wound around a plurality of support rollers 2, 3, 4 and rotated in the direction of arrow A, and an image carrier configured as an intermediate transfer belt 5. Have a body. The intermediate transfer belt 5 is also wound around a plurality of support rollers 6, 7, 8, and 9 and is driven to rotate in the direction of arrow B. In this manner, the image carrier can be constituted by a belt body that is supported around a plurality of support rollers. The photoreceptor 1 has an organic photosensitive layer formed on the surface of a conductive belt substrate. Further, the photosensitive member portion wound around the support roller 4 is in contact with the surface of the intermediate transfer belt 5. Further, first to fourth developing devices 10K, 10C, 10M, and 10Y are arranged to face the photoreceptor 1, and black toner, cyan toner, magenta toner, and yellow toner are provided in the developing cases of the developing devices. Each toner is triboelectrically charged to a predetermined polarity, in the example shown, a negative polarity.

  During the image forming operation, the photosensitive member 1 and the intermediate transfer belt 5 are rotationally driven in the directions of arrows A and B, respectively, as described above. At this time, a high voltage is applied to the charging device including the charging roller 11 disposed to face the surface of the photosensitive member. Is applied. As a result, the photosensitive member 1 is uniformly charged to a predetermined polarity, in the illustrated example, a negative polarity. The surface of the charged photoreceptor is irradiated with light-modulated laser light L emitted from the exposure device 12, whereby an electrostatic latent image is formed on the photoreceptor 1. This electrostatic latent image is visualized as a black toner image by the first developing device 10K. The negatively charged toner is electrostatically transferred to the electrostatic latent image formed on the photosensitive member 1, and the latent image is visualized as a toner image.

  On the other hand, a primary transfer roller 13 is disposed in contact with a contact portion between the photosensitive member 1 and the intermediate transfer belt 5 or a back surface portion of the intermediate transfer belt in the vicinity thereof. A voltage having a positive polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 13, whereby the black toner image on the photoreceptor 1 is primarily transferred onto the intermediate transfer belt 5. The transfer residual toner adhering to the surface of the photoconductor after the toner image is transferred is removed by the cleaning device 14.

  In exactly the same manner as described above, an electrostatic latent image for a cyan image is formed on the photoreceptor 1, and this electrostatic latent image is visualized as a cyan toner image by the second developing device 10C. The toner image is primarily transferred to be superimposed on the black toner image on the intermediate transfer belt 5. In exactly the same manner, a magenta toner image and a yellow toner image are sequentially formed on the photosensitive member 1 by the third and fourth developing devices 10M and 10Y, and the respective toner images are first transferred onto the intermediate transfer belt 5. The toner images are sequentially primary-transferred over the toner images. In this manner, the formation of a toner image on the photoreceptor 1 and the primary transfer of the toner image to the intermediate transfer belt 5 are repeated four times, whereby a four-color superimposed toner image is formed on the intermediate transfer belt 5. Is done.

  On the other hand, at the lower part of the image forming apparatus main body, a paper feed cassette 15 containing a recording medium P made of, for example, transfer paper or a resin film, and a paper feed device 17 having a paper feed roller 16 are arranged. , The uppermost recording medium P is sent in the direction of arrow C. The fed recording medium is moved by a registration roller pair 18 at a predetermined timing between an intermediate transfer belt portion wound around the support roller 9 and a secondary transfer roller 19 which is an example of a transfer device placed on the intermediate transfer belt. Sent in between. At this time, a positive transfer voltage is applied to the secondary transfer roller 19, whereby the toner image on the intermediate transfer belt 5 is secondarily transferred to one surface of the recording medium P.

  The recording medium to which the toner image has been transferred is further conveyed upward and passes through the fixing device 20, and at this time, the toner image on the recording medium is melted and fixed by the action of heat and pressure. In this way, the recording medium on which the image is formed on one side is discharged as indicated by the arrow D to the paper discharge unit 21 constituted by the upper wall of the main body of the image forming apparatus. The transfer residual toner adhering to the intermediate transfer belt 5 after transferring the toner image is removed by the cleaning device 22 and the intermediate transfer belt 5 is cleaned.

  Here, the fixing device 20 of this example includes a fixing member composed of a fixing belt 25 that is wound around a fixing roller 23 and a heating roller 24 and is driven to rotate in the direction of arrow E, and a pressure that is in pressure contact with the fixing belt 25. The fixing belt 25 is heated by the heating roller 24. When the recording medium passes between the fixing belt 25 and the pressure roller 26, the toner image on the recording medium comes into contact with the fixing belt 25, and heat and pressure are applied to the toner image so that the toner image becomes a recording medium. To be established. At this time, in order to prevent an offset phenomenon in which the toner on the recording medium is transferred to the fixing belt, an anti-offset liquid made of, for example, silicone oil is applied to the surface of the fixing belt by a coating device (not shown). .

  As the fixing device, other appropriate types of devices can be used. For example, a fixing device having a fixing member made of a fixing roller and a pressure roller in pressure contact with the fixing member can be used. Also in this case, the recording medium carrying the toner image to be fixed on the recording medium passes between the heated fixing roller and the pressure roller. At this time, the toner image comes into contact with the fixing roller, and the toner image is It is fixed on the recording medium by the action of heat and pressure. Also in such a fixing device, in order to prevent the toner on the recording medium from moving to the fixing roller, an offset preventing liquid is applied to the surface of the fixing roller. As described above, any type of fixing device has a fixing member that comes into contact with the toner image to be fixed, and the fixing member is coated with the offset prevention liquid.

  As shown in FIG. 2, the cleaning device 22 for the intermediate transfer belt 5 is in contact with the cleaning brush 28 that is rotatably supported by the casing 27 and is also rotatably supported by the casing 27. And a blade 30 whose base end is fixedly supported by the casing 27 and whose tip edge is pressed against the metal roller 29. The casing 27 is supported by the image forming apparatus main body via a pin 31 so as to be swingable in the direction of arrow F.

  When the toner image on the intermediate transfer belt 5 passes through the cleaning device 22, the cleaning device 22 occupies a retreat position where the cleaning brush 28 is separated from the surface of the intermediate transfer belt 5, and remains on the intermediate transfer belt 5. During the cleaning operation for removing the transfer residual toner, the cleaning brush 28 occupies the cleaning position in contact with the surface of the intermediate transfer belt. At this time, the cleaning brush 28 and the metal roller 29 rotate in the directions indicated by arrows in FIG. 2, and a positive polarity voltage is applied to the metal roller 29.

  In FIG. 2, the transfer residual toner on the intermediate transfer belt that passes through the secondary transfer roller 19 toward the cleaning device 22 is schematically enlarged, and a reference symbol T is given to these toners. Are represented by + and-. Since a positive polarity charge is imparted to the toner on the intermediate transfer belt during the secondary transfer operation of the toner image, the transfer residual toner T is charged with a negative polarity which is the original charging polarity, and vice versa. There is a mixture of charged polarities. When the transfer residual toner T reaches the cleaning device 22, the negative polarity toner is electrostatically transferred to the cleaning brush 28, and the toner is further electrostatically collected on the surface of the metal roller 29, and then the blade 30. Is scraped off from the metal roller 29.

  On the other hand, the positively charged toner in the transfer residual toner T passes through the cleaning brush 28 without being transferred, and at this time, a positive charge is further given to the toner. When the positive polarity toner reaches the primary transfer portion, the toner is electrostatically transferred to the photoconductor 1 by the action of the positive polarity voltage applied to the primary transfer roller 13, and then for the photoconductor 1. Is removed from the surface of the photoreceptor 1 by the cleaning device 14.

  As described above, the image forming apparatus of this example includes the image carrier formed of the intermediate transfer belt 5 on which the toner image is formed, and the secondary transfer roller 19 that transfers the toner image on the image carrier to the recording medium P. A transfer device comprising: a fixing device 20 for fixing the toner image transferred to the recording medium P; and residual transfer toner adhering to the image carrier after the toner image is transferred; And a cleaning device 22 for cleaning. The cleaning device includes a cleaning brush that contacts the image carrier, and cleans the image carrier by electrostatically transferring toner on the image carrier to the cleaning brush. It is configured as follows. Of course, a transfer device, a fixing device, and a cleaning device other than those shown in the figure may be used.

  As described above, the mode for forming an image on only one side of the recording medium P is the single-sided mode, but the image forming apparatus of this example forms images on both sides of the recording medium in addition to this single-sided mode. It is configured so that the duplex mode can also be selected. Hereinafter, the double-side mode operation will be described.

  As shown in FIG. 1, the image forming apparatus of this example is provided with a reversing device 32 that reverses the front and back of the recording medium that has passed through the fixing device 20. As described above, the recording medium having the toner image transferred to one surface and passing through the fixing device 20 is sent to the reversing device 32 by switching the switching claw 35. The recording medium sent to the reversing device 32 is transported in the direction of arrow G by the transport roller pair 33. When the rear end of the recording medium reaches the transport roller pair 33, the switching claw 34 is switched and transported. The recording medium is conveyed in the direction of arrow H by the reverse rotation of the roller pair 33. In this way, the recording medium whose front and back are reversed is conveyed again to the registration roller pair 18, and is sent between the intermediate transfer belt 5 and the secondary transfer roller 19 by the rotation of the registration roller pair 18. In exactly the same manner, the toner image formed on the intermediate transfer belt 5 is transferred to the other surface of the recording medium by the action of the secondary transfer roller 19. Subsequently, the recording medium passes through the fixing device 20, and at this time, the toner image transferred to the other surface of the recording medium is fixed. The recording medium on which images are formed on both sides in this way is discharged to the paper discharge unit 21. Naturally, the transfer residual toner adhering to the intermediate transfer belt after the toner image on the intermediate transfer belt 5 is transferred to the other surface of the recording medium is also removed by the cleaning device 22 in the same manner as described above. It is.

  The configuration of the image forming apparatus described above is a basic configuration common to each specific configuration example described later. In the image forming apparatus having such a basic configuration, as described above, the single-side mode and the double-side mode can be selected. When the double-side mode is selected, the recording medium on which the toner image is transferred to one side After passing through the fixing device 20, the front and back are reversed by the reversing device 32, and again contact the intermediate transfer belt 5, and the toner image on the intermediate transfer belt 5 is transferred to the other surface of the recording medium. . At this time, since the anti-offset liquid is applied to the fixing belt 25, when the recording medium first passes through the fixing device 20, the anti-offset liquid adheres to the recording medium, and the recording medium is transferred again to the intermediate transfer. When coming into contact with the belt 5, the offset preventing liquid adhering to the recording medium moves to the intermediate transfer belt 5. For this reason, in the conventional image forming apparatus, the offset preventing liquid is gradually accumulated on the intermediate transfer belt, and the cleaning performance of the intermediate transfer belt by the cleaning device is unavoidable.

  Therefore, in the image forming apparatus of this example, the configuration described below is employed in order to eliminate the above-described problems.

  As described above, the time for cleaning the image carrier formed of the intermediate transfer belt 5 by the cleaning device 22 is referred to as a cleaning time. In the illustrated example, the cleaning time is the time during which the cleaning brush 28 contacts the surface of the intermediate transfer belt 5 and the transfer residual toner on the intermediate transfer belt is electrostatically transferred to the cleaning brush 28.

  First, in the first specific configuration example, the cleaning time in the double-side mode is set longer than the cleaning time in the single-side mode operation. More specifically, when the area where the toner image is formed on the intermediate transfer belt 5 is an image area, the image area after the toner image is transferred to the recording medium during the single-sided operation is used once for the cleaning brush 28. During the passage, the cleaning brush 28 is brought into contact with the surface of the intermediate transfer belt 5 to clean the surface of the intermediate transfer belt. On the other hand, during the duplex mode operation, the fur brush 28 is brought into contact with the surface of the intermediate transfer belt 5 while the image area after the toner image is transferred to the recording medium passes through the fur brush 28 at least twice. To clean the surface of the intermediate transfer belt. Such a cleaning operation of the cleaning device 22 will be referred to as a cleaning extension operation.

  According to the first specific configuration example described above, even when the offset prevention liquid adheres to the intermediate transfer belt 5 in the double-side mode, the cleaning time of the intermediate transfer belt 5 by the cleaning device 22 is long. In this case, the anti-offset liquid is not accumulated and the cleaning performance by the cleaning device 22 can be maintained.

  By the way, even when the duplex mode is selected, if the number of operations of the duplex mode is small, the amount of the anti-offset liquid adhering to the intermediate transfer belt 5 is small, so that the cleaning performance of the intermediate transfer belt 5 by the cleaning device 22 is reduced. Deterioration is not noticeable. Therefore, in the second specific configuration example, when the double-side mode operation is continuously executed a plurality of times, the cleaning time when the number of times of execution reaches a predetermined number of times is the number of times of execution. The cleaning time is set longer than the predetermined number of times. For example, when the duplex mode operation is continuously performed and the number of printed recording media obtained thereby is less than 50, the intermediate transfer belt 5 is cleaned by the cleaning device 22 for the cleaning time in the single-side mode. When the number of sheets becomes 50 or more, the cleaning device 22 performs the above-described cleaning extension operation every time the intermediate transfer belt 5 is cleaned by the cleaning device 22 during the double-side mode operation thereafter. It is configured to do. With this configuration as well, it is possible to prevent the cleaning performance of the intermediate transfer belt 5 from being deteriorated by the cleaning device 22, and it is possible to suppress a decrease in print productivity (the number of recorded recording media output per unit time) in the duplex mode. .

  By the way, in the single-sided mode, since the recording medium that has not passed through the fixing device 20 comes into contact with the intermediate transfer belt 5, the recording medium serves to remove the offset preventing liquid adhering to the intermediate transfer belt 5. Therefore, in the third specific configuration example, the count value is added every time the duplex mode operation is executed, and the count value is subtracted every time the simplex mode operation is executed, and the count value is zero. Is provided with a double-sided counter (not shown) that does not subtract the count value even when the single-sided mode operation is performed, and the cleaning time by the cleaning device 22 when the count value of the double-sided counter reaches a predetermined value. Is set to be longer than the cleaning time by the cleaning device 22 when the count value is less than the predetermined value. For example, when the predetermined value is set to 50 and the count value is less than 50, the cleaning device 22 is in the middle for the cleaning time during the single-sided mode operation both during the single-sided mode operation and during the double-sided mode operation. The transfer belt 5 is cleaned. On the other hand, when the count value reaches 50, each time the cleaning device 22 cleans the intermediate transfer belt 5, the cleaning device 22 executes the above-described cleaning extension operation. Therefore, according to this configuration, the cleaning device 22 does not perform the cleaning extension operation when, for example, the duplex mode is repeated 30 times, the simplex mode is 30 times, the duplex mode is 30 times, and the simplex mode is 30 times. For this reason, it is possible to prevent a decrease in print productivity during the duplex mode operation. Further, as described above, the count value of the double-sided counter in this configuration does not become negative. For example, when the duplex mode operation is continuously performed 10 times and then the duplex mode operation is continuously performed 20 times, the count value of the duplex counter is “0”.

  Next, in the fourth specific configuration example of this example, at the end of a series of duplex mode operations including one time, the cleaning time when the cleaning device 22 finally cleans the intermediate transfer belt 5 is earlier than that. The cleaning time is set longer than the cleaning time when the cleaning device 22 cleans the intermediate transfer belt 5. For example, when the double-side mode operation is performed ten times continuously, the surface of the intermediate transfer belt after the toner image on the intermediate transfer belt 5 is secondarily transferred to the other surface of the recording medium during the last double-side mode operation. Only when the cleaning device 22 performs cleaning, the cleaning device 22 performs the above-described cleaning extension operation. When the cleaning device 22 cleans the intermediate transfer belt 5 before that, the cleaning device 22 is short in the single-side mode. The intermediate transfer belt 5 is configured to be cleaned for the cleaning time. According to this configuration, it is possible to more reliably prevent a decrease in print productivity, and finally, the cleaning device 22 cleans the intermediate transfer belt 5 for a long time. Therefore, the cleaning device 22 cleans the intermediate transfer belt 5. It is possible to prevent the deterioration of performance from becoming remarkable. Further, in this configuration, even if the cleaning time of the last cleaning operation is longer than the cleaning time in the cleaning extension operation in each of the specific configuration examples described above, print productivity does not decrease.

  By the way, as described above, as a cleaning device for cleaning the intermediate transfer belt 5, various types of cleaning devices other than the illustrated type of device can be employed. For example, a cleaning device provided with a cleaning blade pressed against the surface of the intermediate transfer belt can be employed. According to such a cleaning device, it is possible to efficiently remove the offset prevention liquid adhering to the intermediate transfer belt. However, in the case of a cleaning device having a cleaning blade, the load fluctuation when the cleaning blade comes in contact with and separates from the surface of the intermediate transfer belt is large, and the amount of toner scattered during the contact and separation operation increases. Therefore, when such a cleaning device is disposed on the upper portion of the intermediate transfer belt 5, there is an unavoidable risk that toner scattered during the contact / separation operation of the cleaning blade may fall on and adhere to the intermediate transfer belt 5. In addition, if such a cleaning device is arranged on the upper portion of the intermediate transfer belt 5, there is an inevitable disadvantage that it becomes difficult to collect the toner removed from the intermediate transfer belt 5 by the cleaning device.

  On the other hand, if the cleaning member of the cleaning device that cleans the intermediate transfer belt is made of a member other than the cleaning blade, even if the cleaning device is arranged above the intermediate transfer belt as in the image forming apparatus of this example, The occurrence of malfunctions can be avoided. In the illustrated image forming apparatus, the cleaning device 22 has a cleaning member made up of the cleaning brush 28 that comes into contact with the intermediate transfer belt 5, so that there is no problem when the cleaning blade is used. However, according to the cleaning device using the cleaning member other than the cleaning blade, it is difficult to remove the anti-offset liquid adhering to the intermediate transfer belt as compared with the cleaning device using the cleaning blade. Therefore, by employing the above-described specific configuration examples, the offset preventing liquid can be effectively removed from the intermediate transfer belt even when a cleaning member other than the cleaning blade is used. Thus, the configuration according to the present invention can be applied particularly advantageously to an image forming apparatus having a cleaning device in which the cleaning member is made of a member other than the cleaning blade.

  The example in which the image carrier on which the toner image to be transferred to the recording medium is formed is the intermediate transfer belt 5 has been described above. However, in each configuration according to the present invention, the image carrier is, for example, a drum shape or The present invention can also be applied to an image forming apparatus that is composed of a single photosensitive member configured in a belt shape and directly transfers a toner image formed on the photosensitive member to a recording medium without using an intermediate transfer member. Furthermore, the present invention can be applied to image forming apparatuses that form toner images of different colors on a plurality of photoconductors and transfer the toner images to a recording medium directly or via an intermediate transfer member. it can. At that time, when the toner image on the photosensitive member is directly transferred to the recording medium, the photosensitive member constitutes the image carrier in the present invention, and the toner image on each photosensitive member is recorded via the intermediate transfer member. When transferring to a medium, the intermediate transfer member constitutes the image carrier in the present invention.

It is a schematic sectional drawing which shows an example of an image forming apparatus. It is a figure which expands and shows the one part structure shown in FIG.

Explanation of symbols

6, 7, 8, 9 Support roller 20 Fixing device 28 Cleaning brush 32 Reversing device P Recording medium T Transfer residual toner

Claims (4)

An image carrier on which a toner image is formed, a transfer device for transferring the toner image on the image carrier to a recording medium, a fixing device for fixing the toner image transferred to the recording medium, and after transferring the toner image A transfer device that removes transfer residual toner adhering to the image carrier and cleans the image carrier, and a reversing device that reverses the front and back of the recording medium that has passed through the fixing device. A one-sided mode in which an image is formed only on one side, and a recording medium having a toner image transferred to one side and passed through the fixing device is sent to the reversing device to reverse the front and back of the recording medium. An image forming apparatus capable of selecting a duplex mode in which a toner image on an image carrier is transferred to the other surface of the recording medium, the toner image is fixed by the fixing device, and an image is formed on both sides of a recording medium.
The count value is incremented every time the duplex mode operation is executed, and the count value is subtracted every time the simplex mode operation is performed. When the count value is zero, the count value is counted even if the simplex mode operation is performed. A double-sided counter that does not subtract and the time for cleaning the image carrier by the cleaning device is defined as the cleaning time, and the cleaning time when the count value of the double-sided counter reaches a predetermined value An image forming apparatus, wherein the value is set longer than a cleaning time when the value is less than a predetermined value. The cleaning device includes a cleaning brush that contacts the image carrier, and cleans the image carrier by electrostatically transferring toner on the image carrier to the cleaning brush. Image forming apparatus. The image forming apparatus according to claim 1, wherein the image carrier is a belt body supported by being wound around a plurality of support rollers. The image forming apparatus according to claim 1, wherein the cleaning device is disposed on an upper portion of the image carrier.

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