Image forming apparatus

Abstract

To provide an image forming apparatus that facilitates cleaning or replacement of a cleaning jig for cleaning a light receiving surface of density detection means by allowing insertion and withdrawal of the cleaning jig into and from an image forming apparatus body.SOLUTION: An image forming apparatus comprises: an image forming unit that forms toner images; an image carrier that carries the toner images; and at least one density detection means that has a light receiving surface optically reading the toner images and constantly opposing the image carrier. The image forming apparatus transfers the toner images on the image carrier to a recording material for printing. The image forming apparatus has a cleaning jig for cleaning the density detection means, and an insertion and withdrawal port for inserting and withdrawing the cleaning jig into and from an apparatus body. The cleaning jig is provided with a cleaning part in contact with the light receiving surface, and can be inserted into the apparatus body from the insertion and withdrawal port and reciprocated to clean the light receiving surface. After the cleaning of the light receiving surface, the cleaning jig is taken out from the inside of the apparatus body.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] As image forming apparatuses, copiers, printer apparatuses, facsimile apparatuses, etc. that use an electrophotographic method are well known. In this type of image forming apparatus, the density characteristics of printed images are likely to vary depending on the usage environment, characteristic variations of the developing cartridge and photosensitive drum, etc. Therefore, many color image forming apparatuses have image density control means.

[0003] The image density control means generally forms patches of each color on an intermediate transfer belt, and measures the density of these patches with a density sensor to determine image forming conditions (correction control) for obtaining a toner image with a desired density.

[0004] However, if the density sensor is soiled by toner or the like inside the image forming apparatus and its photosensitivity deteriorates, there is a risk of detection error. Therefore, a technique is used in which a shutter (shielding member) for opening and closing the opening of the density sensor is provided to protect the density sensor from dirt such as toner (see, for example, Patent Documents 1 and 2).

Summary of the Invention

Problems to be Solved by the Invention

[0005] Recent image forming apparatuses have been accelerating, and particularly perform real-time data writing, so it is necessary to read with a density sensor during image formation. Therefore, there is a problem that the timing for closing the shutter is short and the effect of providing the shutter is not great.

[0006] Also, from the viewpoint of improving productivity, the linear speeds of rollers, belts, etc. have become even faster, and along with that, the scattering of toner inside the apparatus has become even worse. Therefore, the density sensor is also easily soiled, and there is a need to frequently clean or replace the cleaning member for cleaning the sensor.

[0007] Therefore, the present invention aims to provide an image forming apparatus that allows for easy cleaning or replacement of a cleaning jig for cleaning the light-receiving surface of a density detection means, by making the cleaning jig removable from the main body of the image forming apparatus. [Means for solving the problem]

[0008] The above problem is solved by an image forming apparatus comprising: an image forming unit that forms a toner image; an image carrier that holds the toner image; and at least one density detection means having a light-receiving surface for optically reading the toner image that is always facing the image carrier, wherein the image forming apparatus transfers the toner image on the image carrier to a recording material for printing, and further comprises a cleaning jig for cleaning the density detection means and an insertion / removal port for inserting and removing the cleaning jig from the apparatus body, wherein the cleaning jig has a cleaning part that contacts the light-receiving surface, is inserted into the apparatus body through the insertion / removal port and moves back and forth to clean the light-receiving surface, and after cleaning the light-receiving surface, the cleaning jig is removed from the apparatus body. [Effects of the Invention]

[0009] The image forming apparatus of the present invention allows the cleaning jig (and cleaning member) to be easily cleaned or replaced by making the cleaning jig removable from the apparatus body. Therefore, the cleaning capacity of the cleaning member can be maintained at a certain level or higher. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the overall configuration of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of the intermediate transfer belt and concentration sensor, as seen from the direction of arrow A in Figure 1. [Figure 3] This is a schematic diagram showing a configuration for cleaning a concentration sensor according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing a configuration for cleaning a concentration sensor according to a modified example of the present invention. [Figure 5]This is a schematic plan view of the concentration sensor and guide member as seen from the direction of arrow B in Figure 4. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the attached drawings. Figure 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to one embodiment of the present invention. This image forming apparatus 1 is a color laser printer, and in the center of the printer body, along the tension direction of the intermediate transfer belt 30, four image forming sections 4Y, 4C, 4M, and 4K are arranged side by side. Each image forming section 4Y, 4C, 4M, and 4K has the same configuration except that it contains different colored developers corresponding to the color separation components of a color image: yellow (Y), cyan (C), magenta (M), and black (K).

[0012] Specifically, each image-forming unit 4Y, 4C, 4M, and 4K that constitutes the image station is equipped with a drum-shaped photoreceptor 5 as a latent image carrier, a charging device 6 for charging the surface of the photoreceptor 5, a developing device 7 for supplying toner to the surface of the photoreceptor 5, and a cleaning device 8 for cleaning the surface of the photoreceptor 5. In Figure 1, color codes are assigned only to the photoreceptor 5, charging device 6, developing device 7, and cleaning device 8 of the black image-forming unit 4K, while codes are omitted for the other image-forming units 4Y, 4C, and 4M.

[0013] Below the image-forming sections 4Y, 4C, 4M, and 4K, an exposure device 9 is provided to expose the surface of the photoreceptor 5. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflective mirror, etc., and irradiates the surface of each photoreceptor 5 with laser light Lb based on the image data.

[0014] A transfer device 3 is positioned above the image-forming sections 4Y, 4C, 4M, and 4K. The transfer device 3 comprises an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, and a secondary transfer roller 36 as secondary transfer means. Furthermore, the transfer device 3 includes a secondary transfer backup roller 32, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35.

[0015] The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, the rotational drive of the secondary transfer backup roller 32 causes the intermediate transfer belt 30 to travel (rotate) in the direction indicated by the arrow in the figure.

[0016] Furthermore, a density sensor 50, which is an optical density detection means, is positioned on the intermediate transfer belt 30 at a location where measurement is possible. This density sensor 50 detects the density of the toner image formed on the surface of the intermediate transfer belt 30. Details of the density sensor 50 will be described later.

[0017] Each of the four primary transfer rollers 31 forms a primary transfer nip by sandwiching the intermediate transfer belt 30 between itself and each photoreceptor 5. Furthermore, the printer's power supply is connected to each primary transfer roller 31, and a predetermined direct current (DC) and / or alternating current (AC) voltage is applied to each primary transfer roller 31.

[0018] The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 between itself and the secondary transfer backup roller 32 to form a secondary transfer nip. Similar to the primary transfer roller 31, the secondary transfer roller 36 is also connected to the printer's power supply, and a predetermined direct current (DC) and / or alternating current (AC) voltage is applied to the secondary transfer roller 36.

[0019] The belt cleaning device 35 has a cleaning brush and a cleaning blade arranged to contact the intermediate transfer belt 30. On the upper part of the printer main body, a bottle storage part 2 is provided, and four toner bottles 2Y, 2C, 2M, and 2K containing replenishing toner are detachably mounted in the bottle storage part 2. As is well known, a supply path is provided between each toner bottle 2Y, 2C, 2M, 2K and each developing device 7, and toner is supplied from each toner bottle 2Y, 2C, 2M, 2K to each developing device 7 through this supply path.

[0020] On the other hand, on the lower part of the printer main body, a paper feed tray 10 for housing the paper P as a recording material, a paper feed roller 11 for discharging the paper P from the paper feed tray 10, and the like are provided. Here, the recording material includes, in addition to plain paper, thick paper, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, OHP sheets, and the like. Also, as is well known, a manual paper feed mechanism may be provided.

[0021] Inside the printer main body, a conveyance path R for passing the paper P from the paper feed tray 10 through the secondary transfer nip and discharging it outside the device is arranged. In the conveyance path R, upstream of the position of the secondary transfer roller 36 in the paper conveyance direction, a pair of registration rollers 12 as conveyance means for conveying the paper P to the secondary transfer nip are arranged.

[0022] Also, downstream of the position of the secondary transfer roller 36 in the paper conveyance direction, a fixing device 20 for fixing the unfixed toner image transferred to the paper P is arranged. Further, downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R, a pair of paper discharge rollers 13 for discharging the paper P outside the device are provided. Also, on the upper surface part of the printer main body, a paper discharge tray 14 for stacking the paper P discharged outside the device is provided.

[0023] The basic operation of the printer according to this embodiment is as follows. When the image forming operation is started, each photosensitive member 5 in each image forming unit 4Y, 4C, 4M, 4K is rotationally driven clockwise in the figure, and the surface of each photosensitive member 5 is uniformly charged to a predetermined polarity by the charging device 6. Laser light Lb is irradiated from the exposure device 9 onto the surface of each charged photosensitive member 5, and an electrostatic latent image is formed on the surface of each photosensitive member 5. At this time, the image information exposed to each photosensitive member 5 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. Thus, toner is supplied by each developing device 7 to the electrostatic latent image formed on each photosensitive member 5, and the electrostatic latent image is visualized as a toner image (visible image).

[0024] Also, when the image forming operation is started, the secondary transfer backup roller 32 is rotationally driven counterclockwise in the figure, and the intermediate transfer belt 30 is circulated in the direction indicated by the arrow in the figure. Then, a voltage controlled by a constant voltage or constant current having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 31. Thereby, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 31 and each photosensitive member 5.

[0025] Thereafter, as each photosensitive member 5 rotates, when the toner images of each color on the photosensitive member 5 reach the primary transfer nip, the toner images on each photosensitive member 5 are sequentially superimposed and transferred onto the intermediate transfer belt 30 by the transfer electric field formed in the primary transfer nip. Thus, a full-color toner image is carried on the surface of the intermediate transfer belt 30. Also, the toner on each photosensitive member 5 that could not be completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. The surface of each photosensitive member 5 is then discharged, and the surface potential is initialized.

[0026] In the following explanation, the term "image carrier" is used to refer to a concept that includes the photoreceptor 5 and the intermediate transfer belt 30. An "image carrier" refers to a configuration that has the function of carrying the toner image developed from the latent image created by the optical scanning system. For example, in an image forming apparatus that transfers a toner image from a photoreceptor to a printing target such as paper, the photoreceptor itself corresponds to the "image carrier." Also, in an image forming apparatus that transfers a toner image from a photoreceptor to a printing target via a transfer belt, the photoreceptor and the transfer belt correspond to the "image carrier."

[0027] At the bottom of the image forming apparatus 1, the paper feed roller 11 starts rotating, and the paper P is fed from the paper feed tray 10 to the transport path R. The paper P fed to the transport path R is timed by the registration roller 12 and sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage with the opposite polarity to the toner charge polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip.

[0028] Subsequently, as the intermediate transfer belt 30 travels around the circuit, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip, the transfer electric field formed at that nip transfers the toner image on the intermediate transfer belt 30 onto the paper P all at once. At this time, any remaining toner on the intermediate transfer belt 30 that was not transferred to the paper P is removed by the belt cleaning device 35, and the removed toner is transported to a waste toner container located inside the printer body for collection.

[0029] Subsequently, the paper P is transported to the fuser unit 20, where the fuser unit 20 fixes the toner image on the paper P to the paper P. Then, the paper P is discharged from the device by the paper output roller 13 and stored on the paper output tray 14.

[0030] The above description concerns the image formation operation when forming a full-color image on paper P. However, it is also possible to form a monochrome image using one of the four image formation units 4Y, 4C, 4M, or 4K, or to form a two-color or three-color image using two or three image formation units.

[0031] In this embodiment, the configuration shown in Figure 1 will be used as an example, but the present invention is not limited to this configuration of an image forming apparatus. As the image forming apparatus, you can use one that directly transfers an image from the photoreceptor 5 to a printed material, one that has only a single-color developing apparatus, one that uses two or three image forming units to form a two-color or three-color image, or one that has five or more developing apparatuses, etc.

[0032] Figure 2 is a schematic cross-sectional view of the intermediate transfer belt and the density sensor as seen from the direction of arrow A in Figure 1. The density sensor 50 has a light-emitting part that emits detection light that irradiates the surface of the intermediate transfer belt 30, and a light-receiving surface 50a that detects (optically reads) the reflected light from the toner image on the surface of the intermediate transfer belt 30 due to this detection light.

[0033] Meanwhile, density detection patch areas 40 are formed on the surface of the intermediate transfer belt 30. Each density sensor 50 detects the density of each color in these patch areas 40, and these detection results are reflected in the image formation conditions (correction control).

[0034] Furthermore, the region where these patch portions 40 are formed may be a region outside the area on the intermediate transfer belt 30 where the normal toner image is formed. Also, the number of times the patch portions 40 are formed may be every predetermined number of image formations, or every predetermined time from the start of image formation. A well-known configuration can be used for such image density control.

[0035] Incidentally, as can be seen from Figure 2 and the aforementioned Figure 1, the density sensor 50 is positioned in close proximity to the surface of the intermediate transfer belt 30. Therefore, if the sensor surface (especially the light-receiving surface 50a) becomes contaminated with foreign matter such as scattered toner, dust, or paper dust, the amount of light transmitted through the sensor surface will change, which may prevent accurate density detection.

[0036] In contrast, for example, Patent Document 3 discloses a configuration in which the sensing surface of the sensor is rubbed with a cleaning member (nonwoven fiber containing silicone oil). However, since the removal of dirt from the cleaning member itself is not considered, there was a problem that the sensor dirt could not be removed after prolonged use.

[0037] Therefore, in this embodiment, the cleaning jig for cleaning the light-receiving surface of the density sensor is made removable from the main body of the image forming apparatus, allowing for easy cleaning or replacement, and enabling the density sensor to be cleaned with a clean cleaning jig.

[0038] Figure 3 is a schematic diagram showing a configuration for cleaning a concentration sensor according to one embodiment of the present invention. The image forming apparatus 1 of this embodiment has a cleaning jig 60 for cleaning the concentration sensor 50 (its light-receiving surface 50a) and an insertion / removal port 70 for inserting and removing the cleaning jig 60 from the apparatus body. Furthermore, the concentration sensor 50 of this embodiment does not have a shutter (shielding member) to shield its light-receiving surface 50a, and the light-receiving surface 50a is always facing the surface of the intermediate transfer belt 30.

[0039] The cleaning jig 60 is, for example, a plate-shaped member with a cleaning member 60a attached to one side thereof. The cleaning member 60a contacts the light-receiving surface 50a of the concentration sensor 50 to clean it. Nonwoven fabric can be used as the material for the cleaning member.

[0040] The insertion / removal port 70 is an opening provided on the side of the image forming apparatus 1, through which the user can insert the cleaning jig 60 into the apparatus body. Furthermore, by moving the cleaning jig 60 back and forth after inserting it into the apparatus body, the cleaning member 60a can be rubbed against the light-receiving surface 50a of the density sensor 50, thereby cleaning it.

[0041] After cleaning is complete, the user removes the cleaning jig 60 from the main body of the device and stores it. At this time, the soiled cleaning component 60a may also be cleaned and / or replaced.

[0042] Furthermore, it is desirable to provide a cover that can be opened and closed at the insertion / removal port 70, so that the cover can be opened when necessary (for example, when cleaning).

[0043] Thus, in this embodiment, the image forming apparatus 1 allows the cleaning jig 60 to be inserted into and removed from the apparatus body, making it easy to clean or replace the cleaning jig 60 (and the cleaning member 60a). Therefore, the cleaning capacity of the cleaning member 60a can be maintained at a certain level or higher.

[0044] (modified version) Figure 4 is a schematic diagram showing a configuration for cleaning a concentration sensor according to a modified example of the present invention. This modified image forming apparatus has a guide member 80 provided between the intermediate transfer belt 30 and the concentration sensor 50.

[0045] This guide member 80 is parallel to the light-receiving surface 50a of each density sensor 50, and as shown in Figure 5, at least the portion facing each light-receiving surface 50a is open (opening 80a).

[0046] In this modified example, the cleaning jig 60 is placed on the guide member 80, and its reciprocating movement is guided by the guide member 80. Therefore, the light-receiving surface 50a of the density sensor 50 can be cleaned stably and easily.

[0047] Such guide members 80 may be flat plate-shaped members or wire-shaped members. However, in either case, at least the portion facing each light-receiving surface 50a is left open.

[0048] Furthermore, if the light-receiving surface 50a of the concentration sensor 50 becomes charged, dirt is more likely to adhere to it. Therefore, it is desirable to apply a liquid (for example, distilled water) that has properties to prevent static charge buildup to the contact area between the cleaning member 60a and the light-receiving surface 50a. In this case, cleaning can be performed without charging the concentration sensor 50 (and the light-receiving surface 50a), which is advantageous.

[0049] The present invention has been described in detail above using embodiments. These embodiments are examples and can be modified in various ways without departing from the spirit of the invention. For example, embodiments and modified examples may be combined.

[0050] Alternatively, the density sensor 50 (or its light-receiving surface 50a) may be positioned to always face the photoreceptor 5, thereby detecting the density of a density-detecting patch formed on the surface of the photoreceptor 5. In this case as well, the density sensor 50 (or its light-receiving surface 50a) can be cleaned using the configuration described in the previous embodiment (such as the insertion / removal port provided on the main body of the device and the cleaning jig). [Explanation of Symbols]

[0051] 1. Image forming apparatus 2 Bottle storage section 2Y, 2M, 2C, 2K toner bottles 3. Transfer device 4Y, 4M, 4C, 4K image creation section 5 Photoreceptor 6. Charging device 7. Developing device 8 Cleaning device 9. Exposure apparatus 10 Paper feed tray 11 Paper feed roller 12 Registroller 13 Paper output roller 14. Paper output tray 20 Fixing device 30 Intermediate transfer belt 31 Primary Transfer Roller 32 Secondary transfer backup roller 33 Cleaning backup roller 34 Tension Roller 35 Belt cleaning device 36 Secondary transfer roller 40 Patch area 50 Concentration Sensor 50a Photosensitive surface 60 Cleaning jigs 60a Cleaning member 70 Insertion / removal slots 80 Guide member 80a opening P Paper (recording material) [Prior art documents] [Patent Documents]

[0052] [Patent Document 1] Japanese Patent Publication No. 2013-174755 [Patent Document 2] Japanese Patent Publication No. 2006-208645 [Patent Document 3] Japanese Patent Application Publication No. 11-161123

Claims

1. An image forming unit that forms a toner image, An image carrier that holds the aforementioned toner image, The light-receiving surface for optically reading the toner image comprises at least one density-detecting means that is always facing the image carrier, In an image forming apparatus that transfers the toner image on the image carrier onto a recording material for printing, A cleaning jig for cleaning the concentration detection means, It has an insertion / removal port for inserting and removing the cleaning jig into the main body of the device, The cleaning jig comprises a cleaning section that contacts the light-receiving surface, and is inserted into the main body of the device through the insertion / removal opening and moves back and forth to clean the light-receiving surface. An image forming apparatus characterized in that, after cleaning the light-receiving surface, the cleaning jig is removed from the main body of the apparatus.

2. A guide member is provided between the image carrier and the density detection means, and has an opening in at least the portion of the density detection means facing the light-receiving surface, The image forming apparatus according to claim 1, characterized in that the reciprocating movement of the cleaning jig is guided by the guide member.

3. The image forming apparatus according to claim 2, characterized in that the guide member is parallel to the light-receiving surface of each of the density detection means.

4. The image forming apparatus according to claim 2, characterized in that the guide member is in the shape of a flat plate.

5. The image forming apparatus according to claim 2, characterized in that the guide member is wire-shaped.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that when the light-receiving surface is cleaned, a liquid having properties that prevent static charge is applied to the contact portion between the cleaning part and the light-receiving surface.

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