JP2010128070A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that improves the accuracy of detection by preventing relative displacement between a detected object and a detector for detecting a test pattern. <P>SOLUTION: The image forming apparatus includes a test pattern forming means for forming a test pattern P for inspecting image characteristics, on the surface of an image carrier 2; test pattern detectors 29, 30 for detecting the test pattern P; and an image forming condition correcting means for correcting image forming conditions based on the detection result of the test pattern P. The test pattern detectors 29, 30 are constituted integrally with a secondary transfer device 12. The test pattern P formed on the image carrier 2 is transferred to an intermediate transfer body 10, and the test pattern P on the intermediate transfer body 10 is transferred to the secondary transfer device 12. The test pattern P transferred to the secondary transfer device 12 is detected by the test pattern detectors 29, 30. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these.

  There is a widely known method for controlling image forming conditions by detecting a test pattern formed on a photoreceptor or an intermediate transfer belt with a detection device and inferring image density and position information from the detection data of the test pattern. (For example, refer to Patent Document 1). As a detection device for detecting a test pattern, a reflection type optical sensor is generally used. The reflective optical sensor includes a light emitting element and a light receiving element, and light emitted from the light emitting element is reflected by a detection target having a test pattern, received by the light receiving element, and converted into a signal. By reading the change in the signal, the information of the test pattern can be inferred.

The optical sensor is set so that the output signal on the surface (background portion) of the photoconductor or intermediate transfer belt without a test pattern is a reference. For this reason, when using an optical sensor, it is used after performing calibration at the initial stage, every use, or at an appropriate timing. There are various calibration methods depending on the system to be used. For example, when a predetermined output signal is set as a reference, the input signal of the sensor is adjusted so that the output signal is obtained. Specifically, the control parameter (here, LED current) of the light emitting element is adjusted so that the output of the background portion becomes a predetermined output signal. Then, under the same LED current, the density and position information can be detected when the output of the background portion and the test pattern are present or not, or by detecting the output difference between a plurality of different test patterns.
JP 2007-121943 A

  In the calibration operation, as one of determining the reflective optical sensor characteristic value, there is a relative positional relationship between the optical sensor and the object to be detected. If the relative positional relationship between the optical sensor and the object to be detected is deviated, it appears as a signal difference, which may lead to erroneous detection. Even if the positional relationship deviates, it is possible to avoid erroneous detection by performing a calibration operation, but there remains a concern that the calibration operation cannot be performed in the first place.

  When explaining based on the above example, the LED current value of the light emitting element is adjusted so that the output of the background portion becomes a predetermined output signal, but within the specification range of the LED current that the element has, Adjustment may not be possible. This is particularly remarkable in the case of a regular reflection optical sensor. In many image forming apparatuses, an appropriate value is obtained with a large sensor output in order to increase the sensitivity of the sensor. However, if the positional relationship between the specular reflection optical sensor and the object to be detected is not appropriate (the detection distance) Sensor output or sensor angle decreases). Then, the LED current is increased to obtain a predetermined output. However, if the degree of output decrease is large, the amount of increase in the LED current increases and the specification upper limit of the LED element may be exceeded. Also, such a phenomenon is likely to occur when the detected portion is a curved surface rather than a flat surface, and more likely to occur as the curvature of the detected portion is smaller.

  In order to eliminate the detection error caused by the relative positional deviation between the optical sensor and the object to be detected, it is important to firmly fix the positions of the optical sensor and the object to be detected. However, modules (photoreceptors and intermediate transfer units) that are detected objects so far are often handled as replacement parts, and in order to avoid replacing the optical sensor with each detected object, The detected object and the optical sensor could not be configured integrally. For this reason, the object to be detected as a replacement part is positioned and attached to the image forming apparatus main body to improve the accuracy of the relative position of the object to be detected with respect to the optical sensor. Due to the accumulation of mechanical tolerances such as dimensional errors and mounting errors, there has been a limit to accurately positioning the object to be detected.

  The present invention has been made in view of the problems of the related art, and can improve detection accuracy by preventing relative displacement between a detection device that detects a test pattern and an object to be detected. An object is to provide a possible image forming apparatus.

  The invention of claim 1 comprises a plurality of image carriers, charging means for charging the surface of the image carrier, exposure means for exposing the surface of the image carrier to form an electrostatic latent image, and the image Development means for supplying a developer to the electrostatic latent image formed on the surface of the carrier to make a visible image, and a primary transfer device for primary transfer of the visible image formed on the surface of the image carrier to the intermediate transfer member And a secondary transfer device for secondary transfer of the visible image on the intermediate transfer body to a recording medium, wherein a test pattern for inspecting image characteristics is formed on the surface of the image carrier In the image forming apparatus comprising: a test pattern forming unit that performs detection; a test pattern detection device that detects the test pattern; and an image formation condition correction unit that corrects an image formation condition based on a detection result of the test pattern. And a test pattern formed on the image bearing member is transferred to the intermediate transfer member, and the test pattern on the intermediate transfer member is transferred to the secondary transfer device. The test pattern transferred to the secondary transfer device is detected by the test pattern detection device.

  Since the test pattern detection device is configured integrally with the secondary transfer device, the relative positions of the test pattern detection device and the secondary transfer device are fixed. As a result, the distance, angle (orientation), etc. of the test pattern detection device with respect to the test pattern transferred to the secondary transfer device can be made constant, and detection accuracy can be improved.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the secondary transfer device includes a secondary transfer rotating body disposed in pressure contact with the intermediate transfer body, and the secondary transfer An image forming apparatus configured to transfer a visible image on the intermediate transfer body to the recording medium when the recording medium is passed through a pressure contact portion between the rotating body and the intermediate transfer body. The test pattern formed on the intermediate transfer member is transferred to a non-image transfer region excluding the image transfer region of the intermediate transfer member, and the test pattern on the intermediate transfer member is transferred to the surface of the secondary transfer rotator. Is.

  Since the transfer of the test pattern to the intermediate transfer member is transferred to the non-image transfer region excluding the image transfer region of the intermediate transfer member, the test pattern is not erroneously transferred to the recording medium. Further, the secondary transfer rotator can be disposed in a state of being in constant contact (pressure contact) with the intermediate transfer member. Accordingly, since it is not necessary to bring the secondary transfer rotator into contact with or separated from the intermediate transfer member, it is possible to prevent a decrease in image quality due to vibration or the like associated with the contact and separation operation.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a portion to which the test pattern of the secondary transfer device is transferred is configured with a member having a high glossiness.

  Thereby, it is possible to satisfactorily detect the test pattern transferred to the secondary transfer device.

  A fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, further comprising a cleaning device that cleans the test pattern on the secondary transfer device after detecting the test pattern. Is.

  Thereby, it is possible to prevent the test pattern formed in the next step from being transferred on the test pattern remaining on the secondary transfer apparatus. Further, it is possible to prevent the recording medium from being soiled by the test pattern remaining on the secondary transfer device.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a cover member for blocking or opening the detection surface of the test pattern detection device is provided.

  By blocking the detection surface of the test pattern detection device with the cover member when not in use, it is possible to prevent foreign matter from adhering to the detection surface and becoming dirty.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the cover member is arranged in a non-contact manner on the detection surface in a state where the detection surface is blocked by the cover member. .

  Since the cover member is disposed in a non-contact manner on the detection surface in a state where the cover member is cut off, the possibility of damaging the detection surface by the cover member can be eliminated.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, a raised cleaning member is provided on the cover member, and the cleaning member is moved to the detection surface when the cover member is shut off or opened. It is comprised so that it may slide-contact with.

  As the cover member is shielded / opened, the cleaning member is brought into sliding contact with the detection surface, so that the dirt attached to the detection surface by the cleaning member can be wiped off. Thereby, it becomes possible to maintain the detection function of a test pattern detection apparatus favorably.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the test pattern includes a density detection pattern for detecting an image density and a shift in an image position. This is a misregistration detection pattern.

  Since the detection accuracy of the density detection pattern and the position shift detection pattern can be improved, the accuracy of image density correction and position shift correction is also improved.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the test pattern detection device is an optical sensor.

  By applying an optical sensor conventionally used as a test pattern detection device, there is an advantage that it can be controlled in the same sequence.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the second aspect, the secondary transfer rotator is a secondary transfer roller, and the detection direction of the optical detection device is set to the center of the secondary transfer roller. It is set to go to.

  As a result, it is possible to detect efficiently while suppressing the power supplied to the test pattern detection apparatus.

  The image forming apparatus of the present invention does not use an image carrier or an intermediate transfer member, which is often configured to be detachable from the image forming apparatus main body, as a detection object, but a secondary transfer apparatus fixed to the image forming apparatus main body. Since the detection object is used, it is possible to prevent the relative positional deviation between the detection of the test pattern detection apparatus and the secondary transfer apparatus as the detection object, and the detection accuracy can be improved.

  FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus according to the present invention. The image forming apparatus of the present invention shown in FIG. 1 includes four process units 1Y, 1C, 1M, and 1BK. Each process unit 1Y, 1C, 1M, 1BK is configured to be detachable from the image forming apparatus main body 100.

  The process units 1Y, 1C, 1M, and 1BK have the same configuration except that they contain toners of different colors of yellow, cyan, magenta, and black corresponding to the color separation components of the color image. Therefore, the configuration of one process unit 1Y will be described as an example.

  In FIG. 2, a process unit 1Y includes a photoconductor 2 as an image carrier, a charging unit 3 for charging the surface of the photoconductor 2, and a developing unit 4 for supplying toner (developer) to the surface of the photoconductor 2. A cleaning means 5 for cleaning the surface of the photoreceptor 2 and a lubricant application means 6 for applying a lubricant to the surface of the photoreceptor 2 are provided.

  The charging unit 3 includes a charging roller 3a configured by covering a conductive cored bar with a medium-resistance elastic layer as a charging member. The charging roller 3a is connected to a power source (not shown) and is applied with a predetermined voltage. Further, the charging roller 3a is provided with a charging cleaning member 3b for cleaning in contact with the surface of the charging roller 3a.

  The developing unit 4 includes a developing sleeve 4 a having a magnetic field generating unit therein at a position facing the photoconductor 2. Below the developing sleeve 4a, two screws 4b for pumping the toner and the magnetic carrier to the developing sleeve 4a while stirring are disposed. Furthermore, a doctor blade 4c for leveling the developer to a predetermined thickness on the developing sleeve 4a is disposed to face the surface of the developing sleeve 4a.

  The cleaning means 5 includes a cleaning blade 5a made of rubber which is an elastic body. The cleaning blade 5a is disposed so as to abut on the surface of the photoreceptor 2 with a predetermined contact pressure. The cleaning unit 5 includes a toner conveying screw 5b that conveys toner or the like removed by the cleaning blade 5a to a collecting unit (not shown).

  The lubricant application means 6 includes a solid lubricant 6b housed in a fixed case, and a brush roller 6a that scrapes off the solid lubricant 6b and applies it to the photoreceptor 2. The solid lubricant 6b is urged toward the brush roller 6a by a pressing member 6c such as a compression spring.

  Referring to FIG. 1 again, an exposure device 7 as an exposure means for exposing the surface of the photosensitive member 2 is disposed below each process unit 1Y, 1C, 1M, 1BK. On the other hand, an intermediate transfer unit 8 is disposed above the process units 1Y, 1C, 1M, and 1BK. The intermediate transfer unit 8 has an intermediate transfer belt 10 constituted by an endless belt. The intermediate transfer belt 10 is stretched around four rollers 25, 26, 27, and 28 including a driving roller and a driven roller, and is configured to be able to run in the direction of arrow A in the figure. Further, the intermediate transfer unit 8 includes a belt cleaning device 21 for cleaning the surface of the intermediate transfer belt 10.

  The image forming apparatus primarily transfers a toner image formed on each photoconductor 2 to the intermediate transfer belt 10 and performs a secondary transfer of the toner image on the intermediate transfer belt 10 to a recording medium such as paper. A secondary transfer device. The primary transfer device includes four primary transfer rollers 11Y, 11C, 11M, and 11BK, and each primary transfer roller 11Y, 11C, 11M, and 11BK is an inner peripheral surface of the intermediate transfer belt 10 at a position facing the photoreceptor 2 respectively. Is in pressure contact. Thus, the four photoconductors 2 are in pressure contact with the outer peripheral surface of the intermediate transfer belt 10, and a primary transfer nip is formed at each pressure contact portion.

  The secondary transfer device includes a secondary transfer roller 12 disposed at a position facing one roller 25 that stretches the intermediate transfer belt 10. The secondary transfer roller 12 is in pressure contact with the outer peripheral surface of the intermediate transfer belt 10 and forms a secondary transfer nip at the pressure contact portion.

  A recording medium storage unit 13 that stores a recording medium S such as paper or an OHP sheet is disposed below the image forming apparatus main body 100. The recording medium accommodating portion 13 is provided with a supply roller 14 for carrying out the recording medium S and the like.

  In the image forming apparatus main body 100, a conveyance path R for guiding the recording medium S upward from the recording medium accommodating portion 13 is disposed. A pair of registration rollers 15 a and 15 b are disposed on the upstream side (lower side in the drawing) of the transport path R in the transport direction with respect to the secondary transfer roller 12. In addition, the fixing device 16 is disposed downstream of the secondary transfer nip in the conveyance direction of the conveyance path R (upward in the drawing). The fixing device 16 includes, for example, a fixing roller 17 having a heating source therein, and a pressure roller 18 pressed against the fixing roller 17. A fixing nip is formed at a pressure contact portion between the fixing roller 17 and the pressure roller 18.

  A pair of discharge rollers 19a and 19b are disposed at the downstream end of the transport path R in the transport direction. In addition, a stock unit 20 on which the recording medium S is loaded is formed with the upper surface of the image forming apparatus main body 100 being recessed inward.

The basic operation of the image forming apparatus will be described below with reference to FIG.
In FIG. 2, the photosensitive member 2 is rotated in the direction of the arrow in the figure, and the surface of the photosensitive member 2 is charged to a uniform high potential by the charging roller 3a. Next, a laser beam is irradiated onto the surface of the photosensitive member 2 from the exposure device 7 (see FIG. 1) based on the image data, and the potential of the irradiated portion is lowered to form an electrostatic latent image.

  At this time, the developing unit 4 mixes the toner charged from a toner bottle (not shown) with the magnetic carrier by the two screws 4b and pumps it up to the developing sleeve 4a while stirring. The developer composed of toner and magnetic carrier pumped up by the screw 4b is regulated to a predetermined developer layer thickness by the doctor blade 4c, and is carried on the developing sleeve 4a. The developing sleeve 4 a supplies toner to the surface of the photoconductor 2 while rotating in the same direction at a position facing the photoconductor 2. As a result, the toner is electrostatically transferred to the portion of the electrostatic latent image formed on the surface of the photoreceptor 2 to form a toner image (visible image).

  The operation of the yellow process unit 1Y has been described above with reference to FIG. 2, but the toner image forming operation in the other process units 1M, 1C, and 1BK is the same.

  When a toner image is formed on the photosensitive member 2 in each process unit 1Y, 1M, 1C, 1BK, a constant voltage or a constant voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11Y, 11M, 11C, 11BK. A current-controlled voltage is applied to form a transfer electric field in the primary transfer nip. Then, in the primary transfer nip, the toner image on each photoconductor 2 is primarily transferred so as to overlap the intermediate transfer belt 10.

  After the primary transfer process, a lubricant is applied to the surface of the photoreceptor 2 by a rotating brush roller 6a, and toner remaining on the photoreceptor 2 is removed by a cleaning blade 5a (FIG. 2). The toner or the like removed by the cleaning blade 5a is conveyed to a collecting unit (not shown) by the toner conveying screw 5b.

  On the other hand, in the recording medium accommodating portion 13 shown in FIG. 1, the recording medium S accommodated is sent out to the transport path R by rotating the supply roller 14. The sent recording medium S is temporarily stopped by the registration rollers 15a and 15b.

  Further, a voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 12 to form a transfer electric field in the secondary transfer nip. Alternatively, a similar transfer electric field may be formed by applying a voltage having the same polarity as the charging polarity of the toner to the roller 25 facing the secondary transfer roller 12. Thereafter, the driving of the registration rollers 15a and 15b is resumed, and the recording medium S is sent to the secondary transfer nip in synchronism with the toner image on the intermediate transfer belt 10. Then, the toner image on the intermediate transfer belt 10 is secondarily transferred collectively onto the recording medium S by a transfer electric field formed in the secondary transfer nip. Further, after the secondary transfer, the toner remaining on the surface of the intermediate transfer belt 10 is removed by the belt cleaning device 21, and the removed toner is collected in a waste toner container (not shown).

  The recording medium S to which the toner image has been transferred is conveyed to the fixing device 16. The recording medium S sent to the fixing device 16 is heated and pressurized when passing through the fixing nip between the fixing roller 17 and the pressure roller 18, and the toner image is fixed on the recording medium S. Thereafter, the recording medium S is discharged to the stock unit 20 by the discharge rollers 19a and 19b.

Hereafter, the characteristic part of this invention is demonstrated.
An image forming apparatus according to the present invention includes a test pattern forming unit that forms a test pattern for inspecting image characteristics, a test pattern detecting device that detects the test pattern, and an image forming condition based on the result of the detected test pattern. Image forming condition correcting means for correcting the above.

FIG. 3 is a perspective view of main parts of the image forming apparatus shown in FIG. In the figure, the same reference numerals as those in FIG. 1 denote the same members.
A symbol P shown in FIG. 3 is a test pattern. The illustrated test pattern P is a misalignment detection pattern (line pattern) for detecting misalignment of the image position, but it is also possible to form a density detection pattern (tone pattern) for detecting the image density. It is.

  The method for forming the test pattern P is basically the same as the above-described image forming operation, and is formed on the surface of the photoreceptor 2 at a predetermined timing according to an instruction from a control unit of an image forming apparatus (not shown). That is, the test pattern forming means includes the process units 1Y, 1M, 1C, and 1BK shown in FIG. 1, the exposure apparatus 7, and the control unit that controls these.

  The test pattern P formed on each photoconductor 2 is transferred onto the intermediate transfer belt 10 at the primary transfer nip where the photoconductor 2 and the intermediate transfer belt 10 are in pressure contact, and then transferred onto the intermediate transfer belt 10. The pattern P is configured to be transferred to the secondary transfer roller 12 at a secondary transfer nip where the intermediate transfer belt 10 and the secondary transfer roller 12 are in pressure contact with each other.

  In the image forming apparatus of the present invention, the test pattern P is transferred to both ends of the intermediate transfer belt 10 in the width direction. Specifically, as shown in the plan view of the intermediate transfer belt 10 in FIG. 4, the test pattern P is transferred to a non-image transfer area excluding the image transfer area B of the intermediate transfer belt 10. The image transfer area B here is an area including the maximum area where the image on the photoconductor 2 can be transferred in the surface area of the intermediate transfer belt 10. Accordingly, the non-image transfer area refers to an area on both ends of the intermediate transfer belt 10 relative to the image transfer area B and an area between the image transfer areas B. In FIG. 4, the test pattern P is transferred to both ends of the intermediate transfer belt 10 from the image transfer region B, but may be transferred between the image transfer regions B.

  In addition, it is desirable that at least a portion of the secondary transfer roller 12 to which the test pattern P is transferred is formed of a member having high glossiness (or reflectance). In this embodiment, the glossiness of the portion (both ends) where the test pattern P of the secondary transfer roller 12 is transferred is greater than the glossiness of the portion (both ends) where the test pattern P of the intermediate transfer belt 10 is transferred. Set high.

  Further, as shown in FIG. 3, the two reflection type optical sensors 29 and 30 as the test pattern detecting device have both end portions of the rotating roller portion 12b of the secondary transfer roller 12 to which the test pattern P is transferred. It is arrange | positioned facing. The optical sensors 29 and 30 can be appropriately selected from known optical sensors for test pattern detection used in conventional image forming apparatuses. Each optical sensor 29, 30 is integrally fixed to the secondary transfer roller 12 via a support member 31. Specifically, the support member 31 includes a longitudinal main body portion 31a to which the optical sensors 29 and 30 are attached, and two leg portions 31b extending from both ends of the main body portion 31a. The secondary transfer roller 12 is attached to both ends of the non-rotating shaft portion 12a.

  As shown in FIG. 5, the detection direction D of the optical sensor 29 (30) is directed toward the center O of the secondary transfer roller 12 in order to efficiently detect the supplied power (LED current). It is preferable to set to.

  As shown in FIG. 3, the image forming apparatus of the present invention includes a cleaning device 32 that cleans the secondary transfer roller 12. The cleaning device 32 includes, for example, a cleaning roller 32 a that contacts the surface of the roller portion 12 b of the secondary transfer roller 12. As the cleaning device 32, it is preferable to apply an electrostatic cleaning means in that the number of parts is reduced.

  The image forming condition correcting unit is configured by a control unit of the image forming apparatus. The control unit is configured to optimally control image forming conditions (parameters) such as a developing bias, a charging bias, and a laser exposure power based on data obtained by detecting the test pattern P.

FIG. 6 shows a second embodiment of the present invention.
In the first embodiment of the present invention, the secondary transfer roller 12 is employed as the secondary transfer rotating body pressed against the intermediate transfer belt 10. However, in the second embodiment, the secondary transfer roller 12 is replaced with a secondary transfer roller 12. A next transfer belt 33 is employed. Specifically, the secondary transfer device according to the second embodiment includes an endless secondary transfer belt 33 stretched around two rollers 34 and 35. By feeding the recording medium S to the secondary transfer nip where the secondary transfer belt 33 and the intermediate transfer belt 10 are in pressure contact, the toner image on the intermediate transfer belt 10 is secondarily transferred to the recording medium S. ing.

  Similarly to the above, the image forming apparatus according to the second embodiment also includes two optical sensors 29 and 30 as test pattern detection apparatuses. Each of the optical sensors 29 and 30 is integrally fixed to a roller 34 that stretches the secondary transfer belt 33 via a support member 31. Similarly to the above, the support member 31 has a longitudinal main body 31a to which the optical sensors 29 and 30 are attached, and two leg portions 31b extending from both ends of the main body portion 31a. 31b is attached to both ends of the shaft portion 34a where the roller 34 does not rotate. In FIG. 6, the optical sensors 29 and 30 are arranged so as to detect the surface of the secondary transfer belt 33 that is stretched around the roller 34, but the rollers 34 and 35 of the secondary transfer belt 33 are arranged. It is also possible to configure so as to detect a portion that is not stretched by. Further, as in the first embodiment, a cleaning device for cleaning the surface of the secondary transfer belt 33 may be provided (not shown).

  Further, the image forming apparatus according to the second embodiment has an image based on a test pattern forming unit that forms a test pattern P for inspecting image characteristics and the result of the test pattern P detected by the optical sensors 29 and 30. Image forming condition correcting means for correcting the forming conditions is provided. Since the configuration for forming and transferring the test pattern P is the same as that of the first embodiment, description thereof is omitted.

FIG. 7 shows a third embodiment of the present invention.
The image forming apparatus according to the third embodiment includes a cover member 36 that blocks or opens the detection surface 29a (30a) on which the lens of the optical sensor 29 (30) is disposed. The cover member 36 is disposed in a non-contact manner with respect to the detection surface 29a (30a) in a state where the detection surface 29a (30a) is blocked.

  Further, a cleaning member 37 may be provided on the cover member 36 as in the fourth embodiment of the present invention shown in FIG. The cleaning member 37 is disposed in contact with the detection surface 29a (30a) in a state where the detection surface 29a (30a) is blocked by the cover member 36. For example, the cleaning member 37 is preferably a brushed member that does not damage the detection surface 29a (30a).

  In the embodiment shown in FIGS. 7 and 8, the configuration other than the configuration described above is configured in the same manner as in the first embodiment, and thus the description thereof is omitted.

The test pattern detection operation in the image forming apparatus of the present invention will be described below.
In FIG. 3, first, a test pattern P is formed on the surface of each photoconductor 2 in accordance with an instruction from a control unit (not shown). The test pattern P formed on each photoconductor 2 is transferred onto the intermediate transfer belt 10 at the primary transfer nip where the photoconductor 2 and the intermediate transfer belt 10 are pressed. Next, the test pattern P transferred onto the intermediate transfer belt 10 is transferred to the secondary transfer roller 12 at the secondary transfer nip where the intermediate transfer belt 10 and the secondary transfer roller 12 are in pressure contact.

  The transfer condition of the test pattern P from the intermediate transfer belt 10 to the secondary transfer roller 12 is desirably set to be equal to the transfer condition when the image on the intermediate transfer belt 10 is secondarily transferred to the recording medium S. However, when it is difficult to transfer the toner image and the test pattern P satisfactorily, for example, the central side (the side on which the toner image is transferred) and the end side (the test pattern) of the intermediate transfer belt 10 are used. The transfer conditions may be different, for example, by providing different bias application devices on the side where P is transferred.

  Thereafter, the test pattern P transferred onto the secondary transfer roller 12 is detected by the two optical sensors 29 and 30. When at least a portion of the secondary transfer roller 12 to which the test pattern P is transferred is formed of a member having a high glossiness (or reflectance), the test pattern P can be detected satisfactorily. is there. Then, based on the positional deviation or density change of the image obtained from the detection data of the test pattern P, the control unit (image forming condition correcting unit) optimally corrects the image forming condition.

  Further, after the detection by the optical sensors 29 and 30 is performed, the test pattern P on the secondary transfer roller 12 is removed by the cleaning roller 32a. Thereby, it is possible to prevent the test pattern P formed in the next step from being transferred on the test pattern P remaining on the secondary transfer roller 12. Further, it is possible to prevent the recording medium S from being soiled by the test pattern P remaining on the secondary transfer roller 12.

  Further, since the test pattern P is transferred to the intermediate transfer belt 10, the test pattern P is transferred to the non-image transfer area excluding the image transfer area B of the intermediate transfer belt 10 (see FIG. 4). There is no accidental transcription. In addition, the secondary transfer roller 12 can be disposed in a state in which the secondary transfer roller 12 is always in contact (pressure contact) with the intermediate transfer belt 10. Therefore, since it is not necessary to bring the secondary transfer roller 12 into and out of contact with the intermediate transfer belt 10, it is possible to prevent the image quality from being deteriorated due to vibrations caused by the contact and separation operation.

  Note that the transfer of the test pattern P to the secondary transfer roller 12 may be performed simultaneously with the transfer of the toner image to the recording medium S or may not be performed simultaneously. However, if there is a possibility that both simultaneous transfer and non-simultaneous transfer are performed depending on the timing, the secondary transfer is performed by the thickness of the recording medium S when the recording medium S passes through the secondary transfer nip and when it does not pass through the secondary transfer nip. Since the transfer nip changes, the test pattern P may not be transferred well. Therefore, it is also effective to prevent the transfer failure of the test pattern P by changing the transfer conditions in each case.

  Further, in the case of the image forming apparatus including the secondary transfer belt 33 shown in FIG. 6, the detection operation is the same as that described above except that the test pattern P is transferred from the intermediate transfer belt 10 to the secondary transfer belt 33.

  7 and 8, the detection surface 29a (30a) of the optical sensor 29 (30) is blocked by the cover member 36 when not in use. It is possible to prevent the paper dust and toner scattered in 30a) from adhering and becoming dirty. In addition, since the cover member 36 is disposed in a non-contact manner with respect to the detection surface 29a (30a), there is no possibility of damaging the detection surface 29a (30a).

  As shown in FIG. 8, when the cleaning member 37 is provided on the cover member 36, the cleaning member 37 comes into sliding contact with the detection surface 29 a (30 a) as the cover member 36 is shielded / opened. Thereby, the dirt adhering to the detection surface 29a (30a) can be wiped off by the cleaning member 37. This makes it possible to maintain the detection function of the optical sensor 29 (30) well. Note that frictional charging may occur when the cleaning member 37 contacts the detection surface 29a (30a). Since the detection surface 29a (30a) is triboelectrically charged, there is a risk that toner that scatters in a charged state may be attracted to the detection surface 29a (30a) and become contaminated. Therefore, the material of the detection surface 29a (30a) and the cleaning member 37 The material may be made of a material that is not frictionally charged or a material that is charged to a polarity opposite to the charged polarity of the scattered toner.

  As described above, according to the image forming apparatus of the present invention, since the optical sensors 29 and 30 are integrally formed in the secondary transfer device, the optical sensors 29 and 30 and the secondary transfer roller 12 as a detection object. Alternatively, the relative position with the secondary transfer belt 33 can be fixed. By fixing this relative position, the distance and angle (orientation) of the optical sensors 29 and 30 with respect to the test pattern P can be made constant, and the detection accuracy can be improved.

  That is, in the present invention, the secondary transfer device fixed to the image forming apparatus main body is detected without using the photosensitive member 2 and the intermediate transfer belt 10 that are often configured to be detachable from the image forming apparatus main body as detection objects. Therefore, the relative displacement between the test pattern detection device (optical sensor) and the detection target (secondary transfer device) can be prevented, and the detection accuracy can be improved.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. It is a schematic block diagram which expands and shows a process unit. FIG. 2 is a perspective view of a main part of the image forming apparatus. 2 is a plan view of an intermediate transfer belt. FIG. It is a side view of an optical sensor and a secondary transfer roller. It is a principal part perspective view of the image forming apparatus which concerns on 2nd Embodiment of this invention. It is a principal part side view of the image forming apparatus which concerns on 3rd Embodiment of this invention. It is a principal part side view of the image forming apparatus which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Photoconductor 3 Charging means 4 Developing means 7 Exposure apparatus 10 Intermediate transfer belt 11Y, 11M, 11C, 11BK Primary transfer roller 12 Secondary transfer roller 29 Optical sensor 29a Detection surface 30 Optical sensor 30a Detection surface 32 Cleaning device 36 Cover Member 37 Cleaning member B Image transfer area D Detection direction

Claims (10)

A plurality of image carriers, charging means for charging the surface of the image carrier, exposure means for exposing the surface of the image carrier to form an electrostatic latent image, and formed on the surface of the image carrier. A developing means for supplying a developer to the electrostatic latent image to form a visible image, a primary transfer device for primarily transferring the visible image formed on the surface of the image carrier to the intermediate transfer member, and the intermediate transfer member on the intermediate transfer member. An image forming apparatus including a secondary transfer device that secondarily transfers the visible image of the image to a recording medium,
A test pattern forming means for forming a test pattern for inspecting image characteristics on the surface of the image carrier, a test pattern detecting device for detecting the test pattern, and correcting the image forming condition based on the test pattern detection result In the image forming apparatus provided with the image forming condition correcting means to
The test pattern detection device is configured integrally with the secondary transfer device, and the test pattern formed on the image carrier is transferred to the intermediate transfer member, and the test pattern on the intermediate transfer member is transferred to the secondary transfer device. An image forming apparatus configured to be transferred to a transfer device, wherein the test pattern detection device detects a test pattern transferred to the secondary transfer device. The secondary transfer device has a secondary transfer rotator disposed in pressure contact with the intermediate transfer member, and a recording medium is passed through a pressure contact portion between the secondary transfer rotator and the intermediate transfer member. An image forming apparatus configured to transfer a visible image on the intermediate transfer member to a recording medium,
The test pattern formed on the image carrier is transferred to a non-image transfer area excluding the image transfer area of the intermediate transfer body, and the test pattern on the intermediate transfer body is transferred to the surface of the secondary transfer rotator. The image forming apparatus according to claim 1, wherein   The image forming apparatus according to claim 1, wherein a portion to which the test pattern of the secondary transfer device is transferred is configured with a member having high glossiness.   The image forming apparatus according to claim 1, further comprising a cleaning device that cleans the test pattern on the secondary transfer device after detecting the test pattern.   5. The image forming apparatus according to claim 1, further comprising a cover member configured to block or open a detection surface of the test pattern detection apparatus.   The image forming apparatus according to claim 5, wherein the cover member is disposed in a non-contact manner on the detection surface in a state where the detection surface is blocked by the cover member.   7. The image forming apparatus according to claim 5, wherein a raised cleaning member is provided on the cover member, and the cleaning member is slidably contacted with the detection surface in accordance with a shutting / opening operation of the cover member. .   The image forming apparatus according to claim 1, wherein the test pattern is a density detection pattern for detecting an image density and a position shift detection pattern for detecting a shift of an image position.   The image forming apparatus according to claim 1, wherein the test pattern detection device is an optical sensor.   The image forming apparatus according to claim 2, wherein the secondary transfer rotator is a secondary transfer roller, and the detection direction of the optical detection device is set to be directed toward the center of the secondary transfer roller.

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