JP4766609B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof. In particular, the image formed on the image carrier is primarily transferred to form an image on the intermediate transfer member, and the image on the intermediate transfer member is secondarily transferred to finally form the image on the transfer material. The present invention relates to an image forming apparatus.

  In the image forming apparatus, an electrostatic latent image is formed by charging and writing on the image bearing member as the drum-shaped or belt-shaped image bearing member rotates, and then the toner is attached by the developing device. In this way, a visible toner image is formed, and the toner image is directly transferred to form an image on a transfer material such as paper or an OHP film. For example, indirectly via a belt-like intermediate transfer member. To form an image on a transfer material.

  In the latter, an image formed on an image carrier such as a photoconductor is primarily transferred using a primary transfer body such as a primary transfer roller, and the image is then transferred onto an intermediate transfer body such as an intermediate transfer belt. Using a secondary transfer member such as a secondary transfer roller formed and in contact with the intermediate transfer member, the image on the intermediate transfer member is secondarily transferred to finally transfer the image onto a transfer material such as paper. Was forming.

In such an image forming apparatus, in a multi-colored one,
1) Images of different colors are sequentially formed on one image carrier, and the images are sequentially primary-transferred, and these images are superimposed to form a multicolor color image on the intermediate transfer member. What is called a revolver type or a rotary type that forms a multicolor image on a transfer material by performing a secondary transfer in a batch,
2) A plurality of image forming stations are provided along the intermediate transfer member, and images of different colors are formed on the respective image carriers at the respective image forming stations, and these images are sequentially transferred while running on the intermediate transfer member. By performing primary transfer, a multicolor image is formed on the intermediate transfer member, and the image is secondarily transferred collectively using the secondary transfer member to form a multicolor image on the transfer material. There is what is called a tandem type.

  In this type of image forming apparatus used for multicolor image formation including full color, it is required to achieve stabilization of image quality including color reproducibility. As a method for meeting this requirement, as disclosed in Patent Document 1 below, a density detection pattern image, so-called patch pattern, is formed on an intermediate transfer member, and the patch pattern is optically detected by an optical detection means. And various types of parameters used for image forming conditions are feedback-controlled based on the read result.

  In feedback control, the amount of toner that forms the patch pattern formed on the intermediate transfer member is measured by an image density detection sensor that is an optical detection means, and if the measurement result does not satisfy the predetermined condition, the predetermined condition is satisfied. Various parameters such as writing output characteristics, charging characteristics of the image carrier, charging characteristics that affect the adhesion of toner in the developer, and development bias characteristics that control the amount of toner adhesion are adjusted so as to be matched.

  The patch pattern formed on the intermediate transfer member is formed larger than the detection range by the optical detection means. Then, measurement is performed on a portion where the output from the optical detection means is saturated, that is, a portion where the patch pattern is formed over the entire detection range of the optical detection means, and the amount of toner adhesion is calculated based on the detection result. The calculated toner adhesion amount is used for discrimination with respect to a predetermined density, or the timing at which each color patch pattern is formed is calculated, and the calculated patch pattern formation timing is Or used for discrimination for matching the image forming position of each color.

  As a density control method by measuring the density of a patch pattern, there is one disclosed in Japanese Patent Application Laid-Open No. 2002-132097. Regarding image position control (positional deviation causing color misregistration) by detecting the position of a patch pattern, There is one disclosed in Japanese Patent No. 2642351.

  By the way, the patch pattern is formed at a constant density in an area that does not overlap the starting edge of the next image forming area, separately from the original image forming area. Therefore, when a patch pattern is formed for density measurement or position detection, the patch pattern as an untransferred image is transferred to the secondary transfer body at the secondary transfer nip formed by contacting the secondary transfer body with the intermediate transfer body. Then, there is a problem that the toner transferred to the secondary transfer member adheres to the back surface of the transfer material that passes through the secondary transfer nip and stains the back surface of the transfer material.

  For this reason, in order to eliminate such a problem that the back surface of the transfer material is soiled, conventionally, when a patch pattern is formed, when the patch pattern passes through the secondary transfer nip, the secondary transfer member is removed from the intermediate transfer member. It was controlled to release. That is, as shown in the flowchart of FIG. 17, when the image formation is started in S1, if the process control timing is determined in S2, the secondary transfer of the secondary transfer body is separated in S3 after the secondary transfer of the normal image is completed. The image forming conditions of the patch pattern are changed as necessary at S4, and a patch pattern is created at S5. Next, when the detection of all the patch patterns is completed in S6, the detection result of the patch pattern is fed back to the control in S7. Next, in S8, the secondary transfer member is brought into contact, and the process proceeds to S9. If there is a job to continue image formation, the process returns to S1, and if not, the process ends.

  If it is not the process control timing in S2, the secondary transfer bias is switched to the opposite polarity and rotated in the state in which the secondary transfer member is in contact with the intermediate transfer member between the transfer materials in S10, and the secondary transfer member is rotated. After performing cleaning for adhering the adhered toner to the intermediate transfer member, the process proceeds to S10. Similarly, if there is a job for image formation, the process returns to S1, and if not, the process is terminated. In the case of such a method, for example, when a four-tone pattern for each color is created, a pattern layout as shown in FIG. 18 is obtained.

  In FIG. 18, reference numeral 1 denotes a belt-like intermediate transfer member, 2 denotes a normal image forming region thereof, 3 denotes a roller-like secondary transfer member, and 4 denotes an optical detection unit supported by a support member 5. Py1, Py2, Py3, and Py4 are yellow four-tone patch patterns formed on the intermediate transfer body 1, and Pc1 and Pc2 are cyan four-tone patch patterns that are subsequently formed on the intermediate transfer body 1. It is a part.

JP-A-10-161388 JP 2002-123052 A JP 2003-167394 A

  When the configuration for canceling the secondary transfer process is used as described above when detecting the patch pattern, for example, when a secondary transfer roller is used as the secondary transfer member as disclosed in Patent Document 2, The next transfer roller comes in contact with and separates from the intermediate transfer member. For this reason, since it is necessary to set the time required for the contact / separation operation, the conveyance interval of the transfer material that is the target of the secondary transfer is widened.

  Specifically, the timing is as shown in FIG. For this reason, in the conventional method, in order to prevent the influence on the image, the image formation is performed after the secondary transfer body is contacted and separated, which causes a great downtime.

  Further, when the secondary transfer member used for the secondary transfer is brought into contact with and separated from, the vibration due to the operation is generated in the intermediate transfer member, and as a result, the patch pattern executed in a state where the secondary transfer process is released. The optical relationship with the optical detection means at the time of density detection, that is, the optical distance is disturbed, which causes density detection errors.

  To eliminate such problems, stop the process related to image formation after the image formation process, separate the rollers in this state, and then start the process related to image formation again to detect the density of the patch pattern. It is conceivable to eliminate the influence of vibration generated on the intermediate transfer member. However, with this method, the elapsed time due to process stop and restart becomes prominent, and the user's standby time may increase. In particular, as disclosed in Patent Document 2 and Patent Document 3, when the optical detection means is disposed facing the extended portion of the intermediate transfer member, the influence of the vibration of the intermediate transfer member is greatly generated.

  By the way, when a secondary transfer roller is used as the secondary transfer body in order to solve the problem of soiling the back surface of the transfer material, a cleaning device for removing toner attached to the secondary transfer roller may be provided. However, in this case, since a separate cleaning device is provided, there are problems in terms of space saving and miniaturization, which hinders cost reduction.

  On the other hand, since the patch pattern provides information regarding the image for each color, it is necessary to form all of the patch pattern before the secondary transfer is started. When the start of transfer is accelerated, there is a possibility that a patch pattern of the final color is not formed, and an appropriate patch pattern forming condition is hindered in relation to the start of secondary transfer. There is a bug.

  Accordingly, an object of the present invention is to reduce the time required for detecting a patch pattern that provides information that contributes to the image forming conditions and to increase the accuracy, and to affect the detection accuracy in view of the problems in the conventional image forming apparatus described above. Another object of the present invention is to provide a small and low-cost image forming apparatus that can suppress the vibration of the intermediate transfer member and can reliably form all the patch patterns for each color.

According to the first aspect of the present invention, a toner image formed on an image carrier such as a drum-shaped photosensitive member is primarily transferred to form an image on an intermediate transfer member such as an intermediate transfer belt, and the intermediate transfer member. Forming a secondary transfer body such as a secondary transfer roller provided in contact with the secondary transfer of the image on the intermediate transfer body and finally forming an image on a transfer material such as paper or OHP film In the device
When the width of the intermediate transfer member is A, the width of the secondary transfer member is B, and the width of the transfer material passing between them is C, which is orthogonal to the direction in which the transfer material is conveyed, the relationship of A>B> C age,
A patch pattern forming region is provided in a region where the secondary transfer member does not contact the intermediate transfer member,
With optical detection means for detecting the patch pattern formed in the patch pattern formation region ,
The intermediate transfer member is an intermediate transfer member belt formed of an endless belt, and is wound around a secondary transfer member facing member such as a secondary transfer backup roller facing the secondary transfer member. The secondary transfer body is arranged with the center in the width direction of
A roller-shaped contact portion is provided on both outer sides in the width direction of the secondary transfer body, with a patch pattern formation region interposed therebetween and pressed against each end portion in the width direction of the intermediate transfer body .

  Then, at an appropriate timing, a patch pattern is formed in the patch pattern formation region of the intermediate transfer member, and the patch pattern is detected by the optical detection means to detect the image density and position, and the writing output characteristics, charging of the image carrier Various image forming parameters such as characteristics, charging characteristics that affect the adhesion of toner in the developer, and development bias characteristics that control the amount of toner adhesion are feedback controlled.

An intermediate transfer member, which is an intermediate transfer belt, is applied symmetrically to the secondary transfer member facing member, and the secondary transfer member is contacted symmetrically with respect to the intermediate transfer member, and the width of the secondary transfer member. The abutting portions are pressed against each end in the width direction of the intermediate transfer member with the patch pattern forming area sandwiched on both outer sides in the direction, and the secondary transfer member rotates together with the secondary transfer member facing member as the intermediate transfer member runs. .

According to a second aspect of the invention, in the image forming apparatus according to claim 1, comprising a displacement prevention member along the opposite edges of the intermediate transfer member is an intermediate transfer belt, the secondary and the displacement prevention member An intermediate transfer member is provided around the secondary transfer member facing member in contact with both end faces of the transfer member facing member. Then, when the intermediate transfer member that is the intermediate transfer member belt is run, the misalignment prevention members provided along both end edges of the intermediate transfer member are applied to both end surfaces of the secondary transfer member facing member, and the secondary transfer member facing member The intermediate transfer member that is wound around is prevented from shifting in the width direction and being offset.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , in the traveling direction of the intermediate transfer member, the secondary transfer member is formed downstream of the secondary transfer nip formed in contact with the intermediate transfer member. An optical detection means such as a reflective photosensor is provided at the position. When the patch pattern is formed in the patch pattern formation region of the intermediate transfer member, the patch pattern after passing through the secondary transfer nip is detected by the optical detection means.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the secondary transfer body is supported by a cover such as an exterior cover that is provided in the image forming apparatus main body so as to be freely opened and closed. It is characterized by comprising. When the cover is opened with respect to the image forming apparatus main body, the secondary transfer member supported by the cover is separated from the intermediate transfer member.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the intermediate transfer member is wound around a plurality of rollers to form a unit configuration, and the intermediate transfer unit includes an optical detection unit. It is characterized by comprising. In the intermediate transfer unit, the intermediate transfer member and the optical detection means are assembled to the same member.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the intermediate transfer member has a unit configuration, and a cover that contacts the intermediate transfer unit when the intermediate transfer unit is closed is provided with an image. The forming apparatus main body is provided so as to be openable and closable, and is provided with an optical detection means such as a reflective photosensor supported by the cover. When the cover is closed, the intermediate transfer unit is brought into contact with the intermediate transfer unit, and a position between the cover supporting the optical detection means and the intermediate transfer unit provided with the intermediate transfer member is positioned.

  According to the first aspect of the present invention, the patch pattern forming area is provided in the area where the secondary transfer body does not contact the intermediate transfer body, and the patch pattern is formed in the patch pattern forming area. Even if the secondary transfer body is not contacted / separated, the patch pattern formed on the intermediate transfer body is not likely to adhere to the secondary transfer body, and the time required for detecting the patch pattern is as much as the secondary transfer body is contacted / separated. A small and low-cost image forming apparatus capable of improving the accuracy, suppressing the vibration of the transfer body that affects the detection accuracy, and further reliably forming all the patch patterns for each color is provided. be able to.

In addition , the intermediate transfer member, which is an intermediate transfer belt, is symmetrically wound around the secondary transfer member facing member, and the secondary transfer member is symmetrically contacted with the intermediate transfer member, so that the intermediate transfer member does not run. Since the secondary transfer member rotates together with the secondary transfer member facing member, the pressing load applied to the intermediate transfer member, which is an intermediate transfer belt, is evenly distributed to the left and right to prevent the intermediate transfer member from shifting in the width direction, It is possible to prevent the image quality from deteriorating by eliminating misalignment and the like and by eliminating the occurrence of abnormal images such as slip marks.

According to the invention of claim 2, when traveling middle between transfer member against the displacement prevention member provided along the opposite edges of the intermediate transfer member to the opposite end faces of the secondary transfer member opposing member, secondary Since the intermediate transfer member that is hung around the transfer member is prevented from being displaced, similarly, the intermediate transfer member is prevented from being displaced, color misregistration, etc. are eliminated, and abnormal images such as slip marks are not generated. A decrease can be prevented.

According to the invention described in claim 1, pressurized strong point, across the patch pattern formation region in both widthwise outer secondary transfer member, pressed against the contact portion in the width direction each end of the intermediate transfer member, the intermediate Since the secondary transfer member is rotated together with the secondary transfer member facing member even when the transfer member is running, the intermediate transfer member is similarly prevented from being displaced, color misregistration, etc., and abnormal images such as slip marks are generated. It is possible to prevent the image quality from being degraded. In particular, because the width direction both end portions of the intermediate transfer member to which the toner does not adhere Ru pressing the contact portion to prevent slippage, it is also possible to eliminate the occurrence of image defects due to secondary transfer failure due to slip.

According to the invention of claim 3, when forming a patch pattern in the patch pattern formation region of the medium between the transfer member, so to detect a patch pattern after passing through the secondary transfer nip by the optical sensing means, optical sensing means Therefore, it is possible to provide image information with high accuracy at the downstream position of the secondary transfer nip.

According to the invention of claim 4, when the cover is opened with respect to images forming apparatus main body, since separating the secondary transfer member which supports at its cover from the intermediate transfer member, transfer material transport by opening the cover The path can be opened to facilitate the jam processing at the secondary transfer position.

According to the invention of claim 5, in the middle between the transfer unit, since assembling the intermediate transfer member and the optical detection means on the same member, variations in the distance between the patch pattern and the optical detection means on the intermediate transfer member This makes it possible to detect image information stably.

According to the invention of claim 6, contacts the intermediate transfer unit when closing the cover, and a cover for supporting the optical detection means, since the positioning between the intermediate transfer unit to provide an intermediate transfer member Further, it is possible to reduce the variation in the distance between the patch pattern on the intermediate transfer member and the optical detection means and to enable stable image information detection. Further, since the optical detection means is supported by the cover, the dirt on the optical detection means can be easily cleaned by opening the cover, thereby facilitating maintenance.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic configuration of an internal mechanism in a tandem type full-color image forming apparatus. Reference numeral 100 in the figure denotes an image forming apparatus main body.

  In the image forming apparatus main body 100, four image forming stations 10y, 10c, 10m, and 10b of yellow, cyan, magenta, and black are arranged in a tandem manner along an intermediate transfer belt 15 of an intermediate transfer unit 50 described later. . Each image forming station is provided with photoreceptors 11y, 11c, 11m, and 11b, which are drum-shaped image carriers, around which charging devices 12y, 12c, 12m, and 12b, developing devices 14y, 14c, 14m, and 14b, Primary cleaning devices 17y, 17c, 17m, 17b and the like are provided.

  As the photoconductors 11y, 11c, 11m, and 11b rotate clockwise in the drawing, first, a bias voltage is applied by the charging devices 12y, 12c, 12m, and 12b to uniformly charge the surface. Next, writing is performed by irradiating laser light Ly, Lc, Lm, and Lb from a common writing device 13 based on an image signal sent from a host or the like, respectively, on the photoreceptors 11y, 11c, 11m, and 11b. An electrostatic latent image is formed. After that, each developing device 14y, 14c, 14m, 14b attaches toner to visualize the electrostatic latent image, and forms each color single color image on the photoreceptors 11y, 11c, 11m, 11b.

  Then, the endless belt-shaped intermediate transfer belt 15 travels counterclockwise in the drawing in contact with the photoreceptors 11y, 11c, 11m, and 11b, and the primary transfer rollers 16y, 16c, 16m, and 16b that are primary transfer bodies. The primary color images of the respective colors on the photoreceptors 11y, 11c, 11m, and 11b are transferred onto the intermediate transfer belt 15 as an intermediate transfer body in order from cyan, and the transfer images are superimposed to form a full color image on the intermediate transfer belt 15. Form.

  The intermediate transfer belt 15 is formed of an endless belt, and is wound around a secondary transfer backup roller 51, a cleaning backup roller 52, and a tension roller 53, which are secondary transfer member facing members. The photosensitive drums 11y, 11c, 11m, and 11b are provided with primary transfer rollers 16y, 16c, 16m, and 16b opposite to each other through the intermediate transfer belt 15. Further, around the intermediate transfer belt 15, the secondary cleaning device 18 is opposed to the cleaning backup roller 52 via the intermediate transfer belt 15, and is a secondary transfer body opposed to the secondary transfer backup roller 51. A secondary transfer roller 25 is provided. As a result, the intermediate transfer unit 50 that is detachable from the image forming apparatus main body 100 is configured.

  On the other hand, the feeding roller of the paper feeding device 20 is rotated at an appropriate timing, the transfer material N is fed out from the paper feeding cassette 21 in the image forming apparatus main body 100, and conveyed through the transfer material conveyance path 23 to be paired with the registration rollers 24. Stop in the middle. Then, the pair of registration rollers 24 are rotated in synchronization with the full color image on the intermediate transfer belt 15, and the full color image is secondarily transferred onto the transfer material N by the secondary transfer roller 25. After that, the transfer material N after full color image transfer is conveyed upward as it is through the transfer material conveyance path 23, and the unfixed transfer toner is fixed to the transfer material N when passing through the fixing nip of the fixing device 22. After the image is formed on the transfer material N, the image is discharged by the discharge roller 26 and stacked on the paper discharge stack device 27 on the image forming apparatus main body 100.

  The photoreceptors 11y, 11c, 11m, and 11b after the completion of the primary transfer are cleaned by the primary cleaning devices 17y, 17c, 17m, and 17b to remove the transfer residual toner and are initialized. The intermediate transfer belt 15 after the completion of the secondary transfer is cleaned by the secondary cleaning device 18 to remove the transfer residual toner and is initialized.

  Reference numerals 28y, 28c, 28m, and 28b in the figure denote toner bottles for the respective colors that supply toner to the respective color developing devices 14y, 14c, 14m, and 14b.

  In the illustrated image forming apparatus, a secondary transfer nip formed by contacting the intermediate transfer belt 15 with a secondary transfer roller 25 as a secondary transfer body in the running direction of the intermediate transfer belt 15 as an intermediate transfer body. Is provided with a reflection type photosensor 30 as an optical detection means. Further, a backup roller 31 is provided inside the intermediate transfer belt 15 so as to face the reflective photosensor 30. In a small image forming apparatus, it is often difficult in terms of layout to dispose the reflective photosensor 30 upstream of the secondary transfer nip. Therefore, as in this example, the reflective photosensor 30 is disposed at a downstream position of the secondary transfer nip.

FIG. 2 shows an enlarged configuration of the yellow image forming station 10y.
As shown in FIG. 2, a primary transfer roller 16y and a primary cleaning device 17y are provided around a drum-shaped photoconductor 11y via a charging device 12y, a developing device 14y, and an intermediate transfer belt 15. A drive motor 34 is connected to the developing device 14 y via the control unit 33. Although not shown, the other cyan, magenta, and black image forming stations 10c, 10m, and 10b also differ only in the color of the toner used, and the yellow image forming station 10y shown in FIG. It is exactly the same as the configuration.

  FIG. 3 is a block diagram for explaining the configuration of the control unit 33 provided in the image forming apparatus main body 100.

  As shown in the figure, the control unit 33 is a microcomputer provided with a CPU 35 using a ROM for executing a sequence program for image formation and arithmetic processing, and a RAM 36 using a nonvolatile memory as a data storage unit. It consists of The input / output unit via an interface (not shown) includes a developing device 14y, 14c, 14m, 14b, a writing device 13, a paper feeding device 20, a registration roller 24, a primary transfer roller 16y, 16c, 16m, 16b. 16, a reflective photosensor 30 is connected.

  The reflection type photosensor 30 has a configuration capable of outputting a signal corresponding to the light reflectance from the intermediate transfer belt 15. Of the diffused light detector or the regular reflection light detector, the reflection type photosensor 30 is formed on the surface of the intermediate transfer belt 15. What can obtain the difference between the amount of reflected light and the amount of reflected light from a reference pattern image described later as a sufficient output value is used. In this example, a regular reflection type that is advantageous for detecting black toner and an edge of a toner pattern of all colors and a diffusion type that is advantageous in being able to detect a high density portion of color toner are used in combination.

  The controller 33 is turned on at a predetermined timing such as when a main power (not shown) is turned on, when waiting after a predetermined time has elapsed, when outputting a predetermined number of prints, or after waiting for a predetermined number of prints. The image forming performance in each of the developing devices 14y, 14c, 14m, and 14b, that is, the image forming performance such as the image density is tested.

  Specifically, when this predetermined timing comes, first, the photoreceptors 11y, 11c, 11m, and 11b are uniformly charged while rotating. With respect to this charging, unlike the uniform charging (for example, −700 V) during normal printing, the potential is gradually increased. Then, visible image processing by the developing devices 14y, 14c, 14m, and 14b, that is, development is performed while forming an electrostatic latent image for the reference pattern image by scanning with the laser beam L from the writing device 13.

  By this development, bias development pattern images of each color, so-called patch patterns, are formed on the photoreceptors 11y, 11c, 11m, and 11b. At the time of development, the control unit 33 performs control so that the value of the developing bias applied to the developing sleeve in each developing device 14y, 14c, 14m, 14b is gradually increased.

  FIG. 4 shows the positional relationship between the intermediate transfer belt 15, the secondary transfer roller 25, and the reflective photosensor 30 supported by the support member 37.

  As shown in FIG. 4, the intermediate transfer belt 15 is provided so that the normal image forming regions 38 are arranged without being overlapped with an interval in the running direction indicated by an arrow in the drawing. The width of the intermediate transfer belt 25, which is an intermediate transfer member, and the width of the secondary transfer roller 25, which is a length in the direction orthogonal to the traveling direction of the intermediate transfer belt 15, are B, When the width of the transfer material N passing through the secondary transfer nip between them is C, which is the same as the width of the normal image forming region 38, the relationship of A> B> C is established.

  In addition, a patch pattern forming region is provided in a region of the intermediate transfer belt 15 where the secondary transfer roller 25 does not contact, that is, a region AB. The patch pattern Py, Pc, Pm, Pb is formed in the patch pattern formation region, and the reflection type photosensor 30 described above is provided so as to detect the patch patterns Py, Pc, Pm, Pb. Thus, even when the patch patterns Py, Pc, Pm, and Pb are formed, the secondary transfer roller 25 is not soiled with untransferred toner.

  Specifically, the patch patterns Py, Pc, Pm, and Pb are 15 mm long × 10 mm wide and are formed with a gap of 5 mm. Thus, the lengths occupied by the patch patterns Py, Pc, Pm, and Pb on the intermediate transfer belt 15 are 15 mm × 4 + 5 mm × 3 = 75 mm, respectively. The patch patterns Py, Pc, Pm, and Pb are different from the toner images of the respective colors formed during the printing process, and are not overlapped with each other on the intermediate transfer belt 15 to be detected by the reflective photosensor 30. Transcribed to line up. By such a transfer procedure, one pattern block composed of patch patterns Py, Pc, Pm, and Pb of each color is formed on the intermediate transfer belt 15.

  Further, the intermediate transfer belt 15 that is an intermediate transfer member is formed as an endless belt, and is wound around a secondary transfer backup roller 51 that is a secondary transfer member facing member that faces the secondary transfer roller 25 that is a secondary transfer member. Then, the secondary transfer roller 25 is arranged so that the widthwise centers of the secondary transfer backup roller 51 coincide with each other. This is to prevent the intermediate transfer belt 15 from being shifted toward the end by pressing the secondary transfer roller 25 evenly to the left and right. If the center of the secondary transfer roller 25 is biased toward the end instead of the center of the intermediate transfer belt 15, the pressure of the intermediate transfer belt 15 changes at both ends, and the belt traveling path is shortened on the higher pressure side. The force to pull the belt will increase.

  FIG. 5 shows the installation state of the photoconductors 11y, 11c, 11m, and 11b around the intermediate transfer unit 50.

  As shown in FIG. 5, L1 = 100 mm is set between the photoconductors 11y, 11c, 11m, and 11b. The length (L3) of the region where the patch patterns Py, Pc, Pm, Pb are formed is 75 mm. Further, the distance from the center of the photoreceptor 11b forming the patch pattern Pb of the final color to the tension roller 53 around which the intermediate transfer belt 15 is wound, and the tension roller 53 to the secondary transfer roller 25, in other words, the secondary color. The distance to the secondary transfer nip with the transfer backup roller 51 is both L2 = 75 mm.

  The above-described patch patterns Py, Pc, Pm, and Pb of the respective colors are detected in their light reflection amounts when passing through a position facing the reflective photosensor 30 as the intermediate transfer belt 15 moves endlessly, and are described as electrical signals. To the control unit 33. The control unit 33 calculates the light reflectance of each patch pattern Py, Pc, Pm, Pb based on the data sequentially output from the reflective photosensor 30, and stores it in the RAM 36 as density pattern data. Each patch pattern Py, Pc, Pm, Pb that has passed through the position facing the reflective photosensor 30 is cleaned by the cleaning device 18.

  FIG. 6 shows a flowchart when image density detection and position detection are performed using a patch pattern in the illustrated image forming apparatus.

  When image formation is started in S11, if it is determined in S12 that the process control timing has been reached, the switch to the patch pattern creation conditions is immediately performed in S13 without performing secondary transfer separation, and in S14, the patch pattern Py, Pc, Pm, and Pb are created, all patch patterns are detected in S15, and process control is performed in S16. Thereafter, the process proceeds to S17. If there is a job to continue image formation, the process returns to S11, and if not, the process ends.

  If the process control timing is not reached in S12, the secondary transfer bias is switched to the reverse polarity and the secondary transfer roller 25 is idled while the secondary transfer roller 25 is in contact with the intermediate transfer belt 15 between the transfer materials in S18. After performing cleaning for adhering the toner adhering to the roller 25 to the intermediate transfer belt 15, the process proceeds to S17, and similarly, if there is a job for image formation, the process returns to S11, and if not, the process is terminated.

  FIG. 7 shows a part of the pattern layout at this time, and FIG. 8 shows a timing chart. In FIG. 7, reference numeral 15 is an intermediate transfer belt, 38 is a normal image forming area, 25 is a secondary transfer roller, and 30 is a reflection type photosensor supported by a support member 37. Py1, Py2, Py3, and Py4 are yellow four gradation patch patterns formed on the intermediate transfer belt 15, and Pc1, Pc2, Pc3, and Pc4 are cyan four gradations that are subsequently formed on the intermediate transfer belt 15. Pm1 is a part of a magenta four-tone patch pattern formed on the intermediate transfer belt 15 subsequently.

  Here, since the image forming conditions are switched, specifically, the charging potential and the developing bias are switched for creating a patch pattern, it is not possible to create a normal image with different image forming conditions. For this reason, although the down time shown in FIG. 8 occurs, the down time can be reduced to about 1/3 in a four gradation pattern as can be seen from comparison with the conventional FIG.

FIG. 9 shows another example timing chart.
In this example, the image formation conditions at the time of patch pattern image formation, specifically, the charging potential and the development bias are the same as those at the time of normal image formation, and the patch pattern is formed by switching only the write conditions. As shown in FIG. 9, the timing chart at this time can be imaged in parallel with the normal image, so that no downtime occurs. FIG. 7 shows the layout of this pattern formation.

  In the above-described example, as shown in FIG. 10, the intermediate transfer belt 15 is wound around the secondary transfer backup roller 51, and the secondary transfer roller 25 is pressed against the intermediate transfer belt 15 so as to sandwich the secondary transfer nip. And the transfer material N is conveyed through the secondary transfer nip. When the width of the intermediate transfer belt 15 is A, the width of the secondary transfer roller 25 is B, and the width of the transfer material N is C, the relationship of A> B> C is established and the secondary transfer of the intermediate transfer belt 15 is performed. A patch pattern formation region is provided in a region where the roller 25 does not contact, and the patch pattern P is formed in the patch pattern formation region.

  At this time, as shown in FIG. 10, for example, the intermediate transfer belt 15 is provided with a misregistration prevention member 40 by sticking a guide tape along both end edges. The secondary transfer belt 15 is provided with the position shift prevention member 40 in contact with both end surfaces 51 a of the secondary transfer backup roller 51 and wound around the secondary transfer backup roller 51. As a result, when the intermediate transfer belt 15 travels, the intermediate transfer belt 15 that hangs around the secondary transfer backup roller 51 is shifted in the width direction by applying the position shift prevention member 40 to both end surfaces 51a of the secondary transfer backup roller 51. To prevent it.

  By the way, as shown in FIG. 11, at this time, the patch pattern formation region is sandwiched between both sides of the secondary transfer roller 25 in the width direction and pressed against each end portion in the width direction of the intermediate transfer belt 15. A unit 42 may be provided. Then, the patch pattern forming region is sandwiched between both sides of the secondary transfer roller 25 in the width direction, the abutting portions 42 are pressed against the respective end portions in the width direction of the intermediate transfer belt 15, and the secondary transfer roller 15 is not traveled. The secondary transfer roller 25 is rotated together with the transfer backup roller 51. Accordingly, it is possible to prevent the intermediate transfer belt 15 from being displaced, to eliminate color misregistration and the like, and to prevent the occurrence of abnormal images such as slip marks, thereby preventing deterioration in image quality. In particular, the contact portion 42 is pressed against both ends in the width direction of the intermediate transfer belt 15 to which no toner adheres, so that slip can be prevented and occurrence of image failure due to secondary transfer failure due to slip can be eliminated. .

  In order to prevent the intermediate transfer belt 15 from detaching, it is conceivable to increase the belt tension. However, the load on the intermediate transfer belt 15 is increased, curling occurs, and an abnormal image is caused. For this reason, it is not preferable to raise the tension too much. Further, in the above example, the secondary transfer roller 25 is rotated by being rotated along with the intermediate transfer belt 15, but as shown in FIG. Since the area is formed, the secondary transfer roller 25 is prevented from slipping by the toner or the transfer material N and causing a problem on the image.

12 and 13 show an example in which two reflective photosensors 30 are arranged.
In the above-described example, one reflection type photosensor 30 is arranged. However, as shown in FIGS. 12 and 13, the reflection type photosensor 30 is supported by the support member 37 in two places, both of which are secondary to the patch pattern. You may arrange | position so that the transfer roller 25 may not contact | abut. With this configuration, it is possible to increase the speed of pattern detection, and it is also possible to perform alignment control by detecting the amount of misregistration of each color on both sides. In the example shown in FIG. 12, a pattern for alignment is created first, and then a solid density pattern is created. FIG. 13 shows a state in which each color 4-gradation pattern is imaged in parallel.

FIG. 14 shows a schematic configuration near the secondary transfer position in another image forming apparatus.
As can be seen from this figure, also in this example, the image forming area width is designed to be larger than the maximum transfer size width, the width of the intermediate transfer belt 15 (direction perpendicular to the running direction) is set to A, and the intermediate transfer belt 15 On the other hand, when the total width of the area where the secondary transfer roller 25 abuts is B and the maximum width of the transfer material N is C, the relationship of A>B> C is established, and the patch pattern is formed so that the secondary transfer roller 25 does not abut. A patch pattern P is formed in the region (A-B), and the reflective photosensor 30 is provided outside the transfer material conveyance path 23 facing the secondary transfer backup roller 51.

  Further, here, the secondary transfer roller 25 is supported and provided by a cover 44 that can be freely opened and closed in the image forming apparatus main body 100. Then, when the cover 44 is opened with respect to the image forming apparatus main body 100 in the direction of the arrow in the figure, the secondary transfer roller 25 supported by the cover 44 is separated from the intermediate transfer belt 15, and the transfer is performed by opening the cover 44. The material conveyance path 23 is opened to facilitate the jam processing at the secondary transfer position.

  Further, since the image forming apparatus main body 100 and the cover 44, that is, the secondary transfer roller 25 are provided separately from the image forming apparatus main body 100 side as described above, if the secondary transfer roller 25 is provided with a cleaning mechanism. The waste toner tank needs to be provided separately from the image forming apparatus main body 100, and there is a problem that extra cost, space, and labor are required. However, in this example, since the patch pattern P is formed in the patch pattern forming region where the secondary transfer roller 25 does not contact, there is no possibility that the toner forming the patch pattern P adheres to the secondary transfer roller 25. Since it is not necessary to provide a cleaning mechanism for cleaning the transfer roller 25, such a problem can be solved.

FIG. 15 shows a DD cross section of FIG.
As illustrated, the cover 44 can be opened in the direction of the arrow. The patch pattern P can be formed on the outer side in the width direction of the transfer material conveyance path 23 and the secondary transfer roller 25, and the reflection type photosensor 30 can also be arranged at a position where it does not interfere.

  The reflective photosensor 30 needs to keep the distance from the opposing intermediate transfer belt 15 within a predetermined range. This is because the amount of light reflected by the reflective photosensor 30 varies depending on this distance and appears as a detection error. Therefore, in the example shown in FIGS. 14 and 15, the intermediate transfer belt 15 is wound around a plurality of rollers 51 to 53 to form a unit configuration and supported by the unit side plate 46 of the intermediate transfer unit 50. Is provided with a reflective photosensor 30. In the intermediate transfer unit 50, the intermediate transfer belt 15 and the reflective photosensor 30 are assembled to the unit side plate 46, which is the same member. Thereby, variation in the distance between the patch pattern P on the intermediate transfer belt 15 and the reflective photosensor 30 can be reduced, and stable image information detection can be performed.

FIG. 16 shows another support configuration of the reflective photosensor 30.
In the illustrated example, the intermediate transfer belt 15 has a unit configuration, and a cover 44 that abuts the intermediate transfer unit 50 when it is closed is provided in the image forming apparatus main body 100 so as to be openable and closable. A photosensor 30 is provided. Then, when the cover 44 is closed, the intermediate transfer unit 50 comes into contact with the cover 44 that supports the reflective photosensor 30 and the intermediate transfer unit 50 provided with the intermediate transfer belt 15 is positioned.

  That is, the reflective photosensor 30 is supported by the cover 44 in the same manner as the secondary transfer roller 25. However, if the cover 44 is simply supported, the distance from the intermediate transfer belt 15 cannot be kept constant as described above. For this reason, in this example, the cover 44 is provided with a positioning contact member 47 for maintaining the distance between the reflective photosensor 30 and the secondary transfer roller 25. The positioning abutting member 47 abuts against the unit side plate 46 when the cover 44 is closed to maintain the distance, and the intermediate transfer unit 50 and the secondary transfer roller 25 are positioned abutting against the unit side plate 46. Since the position is determined by the contact of the member 47, the distance between the reflective photosensor 30 and the intermediate transfer belt 15 can be easily maintained.

  Further, since the reflective photosensor 30 of this example opens and closes together with the cover 44, when the reflective photosensor 30 becomes dirty with scattered toner or the like, the cover 44 is opened and cleaned so that the user can easily perform maintenance. Is possible.

In addition, the process conditions of each member used in the above example are as follows.
An organic photoreceptor (OPC) is used for the photoreceptors 11y, 11c, 11m, and 11b. For the charging devices 12y, 12c, 12m, and 12b, a charging roller is used in proximity to or in contact with the photosensitive member so that uniform charging of -200 to -2000 (V) can be performed. An electrostatic latent image is formed on the photoconductors 11y, 11c, 11m, and 11b using the laser beams Ly, Lc, Lm, and Lb corresponding to the document image.

  A negatively chargeable toner is used and negative-positive development is performed, whereby the electrostatic latent image is subjected to visible image processing to form a toner image. As the intermediate transfer belt 15, a thermosetting resin having a thickness of 0.10 mm, a width of 266 mm, and an inner peripheral length of 796 mm is used, and the moving speed is set to 150 mm / sec. Further, a misalignment prevention member 40 having a width of 5 mm and a height of 2.5 mm is sewn on both sides of the back surface of the intermediate transfer belt 15. The maximum transfer paper size is LT longitudinal paper, and the maximum length in the width direction is 216 mm.

  Based on the above conditions, the volume resistivity of the entire intermediate transfer belt 15 is 107 to 1012 Ωcm. The volume resistivity is the result of applying a voltage of 100 V for 10 seconds using the measurement method described in JIS K 6911. Further, the surface resistivity of the intermediate transfer belt 15 was 109 to 1014 Ω / □ as measured by a resistance measuring instrument “High Lester IP” manufactured by Mitsubishi Oil Corporation. The surface resistivity can be measured by the surface resistance measuring method described in JIS K 6911, in addition to using the above resistance measuring instrument. As the secondary transfer roller 25, a roller made of urethane foam resin having a diameter of 26 mm and a width of 226 mm was used.

1 is a schematic configuration diagram of an internal mechanism in a tandem type full-color image forming apparatus. It is an enlarged block diagram of the yellow imaging station. FIG. 3 is a block diagram for explaining a configuration of a control unit provided in the image forming apparatus main body. FIG. 4 is a positional relationship diagram of the intermediate transfer belt, a secondary transfer roller, and a reflective photosensor. FIG. 5 is a diagram illustrating a state where a photoconductor is installed around the intermediate transfer unit. 6 is a flowchart when performing image density detection and position detection using a patch pattern in the image forming apparatus. It is a figure which shows a part of pattern layout of a patch pattern. It is a timing chart of the example. It is a timing chart of another example. It is a block diagram of a secondary fixing nip position. FIG. 6 is a configuration diagram of another secondary fixing nip position. FIG. 5 is a positional relationship diagram of an intermediate transfer belt, a secondary transfer roller, and a reflective photosensor in an example in which two reflective photosensors are arranged. FIG. 10 is a positional relationship diagram of an intermediate transfer belt, a secondary transfer roller, and a reflective photosensor in another example in which two reflective photosensors are arranged. FIG. 6 is a schematic configuration diagram in the vicinity of a secondary transfer position in another image forming apparatus. It is DD sectional drawing of FIG. It is another support block diagram of a reflection type photosensor. It is a flowchart when performing density detection and position detection of an image using a conventional patch pattern. It is a pattern layout diagram of a conventional patch pattern. It is a timing chart of the example.

Explanation of symbols

11y, 11c, 11m, 11b Photoconductor (image carrier)
15 Intermediate transfer belt (intermediate transfer member)
25 Secondary transfer roller (secondary transfer body)
30 Reflective photosensor (optical detection means)
40 Position shift prevention member 42 Contact portion 44 Cover 50 Intermediate transfer unit 51 Secondary transfer backup roller (secondary transfer member facing member)
51a Secondary transfer backup roller end face 100 Image forming apparatus main body N Transfer material P, Py, Pc, Pm, Pb Patch pattern

Claims (6)

The image formed on the image carrier is primarily transferred to form an image on the intermediate transfer member, and the secondary transfer member provided in contact with the intermediate transfer member is used to transfer the image on the intermediate transfer member to the secondary transfer member. In an image forming apparatus that transfers and finally forms an image on a transfer material,
When the width of the intermediate transfer member is A, the width of the secondary transfer member is B, and the width of the transfer material passing between them is C, the relationship of A>B> C is established.
A patch pattern forming region is provided in a region of the intermediate transfer member where the secondary transfer member does not contact,
With optical detection means for detecting the patch pattern formed in the patch pattern formation region ,
The intermediate transfer body is formed of an endless belt, and is wound around a secondary transfer body facing member facing the secondary transfer body, and the widthwise centers of the secondary transfer body facing member are aligned with each other. Place the secondary transfer member,
Abutting portions are provided on both outer sides in the width direction of the secondary transfer body, with the patch pattern forming regions being sandwiched and pressed against each end in the width direction of the intermediate transfer body.
An image forming apparatus. A misalignment preventing member is provided along both edges of the intermediate transfer member, and the misalignment preventing member is brought into contact with both end surfaces of the secondary transfer member facing member, and the intermediate transfer member is placed on the secondary transfer member facing member. The image forming apparatus according to claim 1 , wherein the image forming apparatus is provided by being wound around. In the running direction of the intermediate transfer body, to a position downstream of the secondary transfer nip formed by contact with the secondary transfer member to the intermediate transfer member, characterized by comprising the optical sensing means, according to claim 1 or the image forming apparatus according to 2. Characterized in that it comprises supporting the secondary transfer member by a cover provided openably in the image forming apparatus main body, an image forming apparatus according to any one of claims 1 to 3. Wherein characterized in that the intermediate transfer unit to provide an intermediate transfer member comprises said optical detection means, the image forming apparatus according to any one of claims 1 to 4. 2. The image forming apparatus main body includes a cover that abuts on an intermediate transfer unit that provides the intermediate transfer member when the image forming apparatus is closed, and the optical detection unit is supported by the cover. 5. The image forming apparatus according to any one of 4 to 4 .

Images