Charging device and image forming apparatus

Abstract

To reduce the possibility that a photoreceptor drum is not appropriately charged due to a contact state of a contact part between a shaft part of a charging roller and a support member.SOLUTION: The two support members 133 and 33-2 are conductive members that respectively support both ends of the conductive shaft portion 31a of the charging roller 31 and respectively support both ends of the conductive shaft portion 32a of the cleaner roller 32. The conductive elastic member 34 biases the two support members 1,33 and 33-2. A predetermined voltage is applied to the conductive shaft 31a of the charging roller 31 via at least one of the two elastic members 34 and at least one of the two support members 133 and 33-2, and both ends of the conductive shaft 31a of the charging roller 31 are electrically connected via the conductive shaft 32a of the charging roller 31 and the two support members 133 and 33-2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a charging device and an image forming apparatus. [Background technology]

[0002] An image forming apparatus includes a photosensitive drum and a charging device that charges the photosensitive drum. The charging device includes a charging roller that charges the photosensitive drum and a cleaning roller that cleans the charging roller. The charging roller is rotatably supported by a first support member, and the cleaning roller is rotatably supported by a second support member. An elastic member is provided between the first support member and the second support member (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-12261 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in electrophotographic image forming devices, a high voltage (DC voltage or AC voltage) is applied to the conductive shaft of the charging roller, which increases the potential of the charging roller and charges the photosensitive drum.

[0005] When a high voltage is applied to the conductive shaft of the charging roller from an external high-voltage power supply, the high-voltage power supply is electrically connected to the support member for the shaft of the charging roller, and the high voltage is applied via the contact point between the shaft of the charging roller and the support member. Therefore, if the contact condition at the contact point becomes poor, a sufficiently high voltage may not be applied to the shaft of the charging roller, and the surface of the photosensitive drum may not be sufficiently charged to the target voltage.

[0006] For example, if the contact condition at the contact point between one end of the shaft of the charging roller and the support member becomes poor, a high voltage is applied to the other end of the shaft of the charging roller via the elastic member and the cleaning roller.In this case, in the above-mentioned image forming apparatus, the high voltage is applied via the contact point between one first support member and one elastic member, the contact point between one elastic member and one second support member, the contact point between one second support member and the shaft of the cleaning roller, the contact point between the shaft of the cleaning roller and the other second support member, the contact point between the other second support member and the other elastic member, the contact point between the other elastic member and the other first support member, and the contact point between the other first support member and the other end of the shaft of the charging roller, so there is a possibility that a sufficiently high voltage will not be applied to the charging roller due to poor contact or contact resistance.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a charging device and an image forming apparatus that reduce the possibility of the photosensitive drum not being properly charged due to the contact state of the contact point between the shaft portion of the charging roller and the support member. [Means for solving the problem]

[0008] The charging device according to the present invention includes a charging roller having a conductive shaft portion, a cleaning roller having a conductive shaft portion and cleaning the charging roller, two support members that support both ends of the conductive shaft portion of the charging roller and also support both ends of the conductive shaft portion of the cleaning roller, and two conductive elastic members that bias the two support members, respectively. A predetermined voltage is applied to the conductive shaft portion of the charging roller via at least one of the two elastic members and at least one of the two support members, and both ends of the conductive shaft portion of the charging roller are electrically connected via the conductive shaft portion of the cleaning roller and the two support members.

[0009] An image forming apparatus according to the present invention includes the above-described charging device and a photosensitive drum, and the charging device charges the photosensitive drum. [Effects of the Invention]

[0010] According to the present invention, a charging device and an image forming apparatus are provided that reduce the possibility that a photosensitive drum will not be properly charged due to the contact state of the contact point between the shaft of the charging roller and the support member.

[0011] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a side view showing a part of the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of various devices around the photosensitive drum 1a in FIG. [Figure 3] FIG. 3 is a diagram showing the configuration of the charging device according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing the configuration of a charging device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] Embodiment 1

[0015] Fig. 1 is a side view showing a part of the internal mechanical configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in Fig. 1 is a device having an electrophotographic printing function, such as a printer, facsimile machine, copier, or multifunction machine.

[0016] The image forming apparatus of this embodiment has a tandem color developing device. This color developing device has photosensitive drums 1a-1d, exposure devices 2a-2d, and developing devices 3a-3d for each color. The photosensitive drums 1a-1d are photosensitive bodies for four colors: cyan, magenta, yellow, and black. The exposure devices 2a-2d are devices that irradiate the charged photosensitive drums 1a-1d with laser light, thereby exposing the photosensitive drums 1a-1d and forming electrostatic latent images. The exposure devices 2a-2d each have a laser diode as a source of laser light and optical elements (lenses, mirrors, polygon mirrors, etc.) that guide the laser light to the photosensitive drums 1a-1d, and irradiate the photosensitive drums 1a-1d with light to form electrostatic latent images on the photosensitive drums 1a-1d.

[0017] Toner containers filled with toner of four colors, cyan, magenta, yellow, and black, are connected to the developing devices 3a to 3d. A developing bias is applied to each of the developing devices 3a to 3d, and based on the potential difference between the developing devices 3a to 3d and the photosensitive drums 1a to 1d, the toner supplied from the toner container is applied to the electrostatic latent images on the photosensitive drums 1a to 1d by a developing roller, thereby performing development (forming a toner image).

[0018] Magenta development is performed by photosensitive drum 1a, exposure device 2a, and developing device 3a, cyan development is performed by photosensitive drum 1b, exposure device 2b, and developing device 3b, yellow development is performed by photosensitive drum 1c, exposure device 2c, and developing device 3c, and black development is performed by photosensitive drum 1d, exposure device 2d, and developing device 3d.

[0019] The intermediate transfer belt 4 is an image carrier that carries the toner images transferred from the photosensitive drums 1a to 1d, and is an endless (i.e., circular) intermediate transfer body. The intermediate transfer belt 4 is stretched around a drive roller 5, and rotates by the driving force of the drive roller 5 from the contact position with the photosensitive drum 1d toward the contact position with the photosensitive drum 1a. In other words, the toner image obtained by adhering toner to the electrostatic latent image is primarily transferred onto the intermediate transfer belt 4.

[0020] The secondary transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4, and performs a second transfer of the toner image on the intermediate transfer belt 4 onto the paper. The paper onto which the toner image has been transferred is then conveyed to a fixing device 9, where the toner image is fixed onto the paper.

[0021] The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove toner remaining on the intermediate transfer belt 4 after the secondary transfer of the toner image to paper. Note that a cleaning blade may be used instead of the roller 7 having a cleaning brush.

[0022] Sensor 8 is a reflective optical sensor that detects toner on intermediate transfer belt 4, and in order to detect the toner concentration during calibration, it irradiates light onto intermediate transfer belt 4 and detects the reflected light. During calibration, sensor 8 irradiates light onto a predetermined area through which a test toner pattern formed on intermediate transfer belt 4 passes, detects the reflected light, and outputs an electrical signal according to the amount of light detected.

[0023] Fig. 2 is a diagram showing an example of various devices in the vicinity of the photosensitive drum 1a in Fig. 1. Note that Fig. 2 shows various devices in the vicinity of the photosensitive drum 1a, but the same configuration is also applied to the peripheries of the photosensitive drums 1b to 1d.

[0024] As shown in FIG. 2, in addition to the developing device 3a, a charging device 21 and a cleaning device 22 are provided around the photosensitive drum 1a. The charging device 21 charges the photosensitive drum 1a with a charging bias of a specified voltage. The charging device 21 has a charging roller 31 that contacts the photosensitive drum 1a, and charges the photosensitive drum 1a with the charging roller 31. The cleaning device 22 has a cleaning blade 22a that contacts the photosensitive drum 1a, and collects residual toner on the photosensitive drum 1a. In addition, a primary transfer roller 23 is provided at a position facing the photosensitive drum 1a with the intermediate transfer belt 4 interposed therebetween.

[0025] The developing device 3a includes a housing 11, an agitating screw 12, a magnetic roller 13, and a developing roller 14. A toner container (not shown) is connected to the developing device 3a, and toner is supplied from the toner container to the housing 11 through a supply port (not shown). Within the housing 11, a two-component developer containing toner and a carrier is agitated by the agitating screw 12. A magnetic material is used for the carrier.

[0026] The magnetic roller 13 holds a two-component developer in a brush-like form on its surface and supplies the toner in the two-component developer to the developing roller 14. The toner in the two-component developer moves to the developing roller 14 in response to the voltage difference between the magnetic roller 13 and the developing roller 14.

[0027] The developing roller 14 holds the toner transferred from the magnetic roller 13 on its surface as a thin toner layer. A developing bias is applied to the developing roller 14, and the toner layer formed on the surface of the developing roller 14 is transferred to the photosensitive drum 1a by the voltage of the photosensitive drum 1a relative to the developing roller 14 (the difference between the developing bias and the surface potential of the photosensitive drum 1a). In other words, the developing roller 14 holds the toner with the developing bias and causes the toner to adhere to the electrostatic latent image.

[0028] Fig. 3 is a diagram showing the configuration of the charging device according to embodiment 1. For example, as shown in Fig. 3, in addition to a charging roller 31, charging device 21 includes a cleaning roller 32, two support members 33-1 and 33-2, two elastic members 34, a power distribution member 35, and a case 36 made of insulating resin.

[0029] The charging roller 31 has a conductive shaft portion 31a and a roller rubber portion 31b, and is arranged approximately parallel to the photosensitive drum 1a, with the roller rubber portion 31b in contact with the photosensitive drum 1a, and charges the photosensitive drum 1a while rotating.

[0030] The cleaning roller 32 has a conductive shaft portion 32a and a roller sponge portion 32b, and is arranged approximately parallel to the charging roller 31, with the roller sponge portion 32b in contact with the charging roller 31 (roller rubber portion 31b), and cleans the surface of the charging roller 31 (roller rubber portion 31b) as it rotates.

[0031] The support members 33-1 and 33-2 rotatably support both ends of the conductive shaft portion 31a of the charging roller 31, and also rotatably support both ends of the conductive shaft portion 32a of the cleaning roller 32. The support members 33-1 and 33-2 are conductive members, and in this case, are resin bushings. Note that to ensure smooth rotation of the charging roller 31 and the cleaning roller 32 and to maintain conductivity at the contact points between the support members 33-1 and 33-2 and the conductive shaft portions 31a and 32a, conductive grease is applied to the contact points between the support members 33-1 and 33-2 and the conductive shaft portions 31a and 32a.

[0032] The two elastic members 34 are conductive members that come into contact with the two support members 33-1 and 33-2, respectively, and urge the support members 33-1 and 33-2 toward the photosensitive drum 1. For example, the elastic members 34 are metal coil springs.

[0033] In the first embodiment, one elastic member 34 is disposed between the support member 33-1 and the power distribution member 35, one end of the elastic member 34 contacts the support member 33-1, and the other end of the elastic member 34 contacts the power distribution member 35, and the support member 33-1 and the power distribution member 35 are electrically connected via the elastic member 34. The other elastic member 34 is disposed between the support member 33-2 and the case 36 (the protrusion 36a of the case 36), and one end of the elastic member 34 contacts the support member 33-2, and the other end of the elastic member 34 contacts the protrusion 36a.

[0034] Based on this configuration, a predetermined voltage is applied from a high-voltage power supply (not shown) to the conductive shaft portion 31a of the charging roller 31 via one of the two elastic members 34 and one of the two support members 33-1, 33-2. In addition, both ends of the conductive shaft portion 31a of the charging roller 31 are electrically connected to the conductive shaft portion 32a of the cleaning roller 32 via the two support members 33-1, 33-2.

[0035] Moreover, the power distribution member 35 is, for example, a plate-shaped or wire-shaped conductive member that is arranged along the inner wall of the case 36 and, in the first embodiment, is in contact with one of the two elastic members 34. For example, the power distribution member 35 is a stainless steel plate-shaped member or wire.

[0036] In this embodiment, the photosensitive drums 1a to 1d and the charging roller 31 are arranged substantially perpendicular to the front panel of the image forming apparatus, and the power distribution member 35 is arranged on the rear side of the image forming apparatus, as shown in FIG. 3, for example, and a predetermined high voltage is applied from the rear side.

[0037] Next, the operation of the charging device according to the first embodiment will be described.

[0038] In the charging device 21, a predetermined voltage from a high-voltage power supply is applied to the power distribution member 35. If there is no poor contact between the conductive shaft portion 31a of the charging roller 31 and the support member 33-1, the voltage is applied to the conductive shaft portion 31a of the charging roller 31 via the elastic member 34 and the support member 33-1.

[0039] On the other hand, even if there is poor contact between the conductive shaft portion 31a of the charging roller 31 and the support member 33-1, the voltage is applied to the conductive shaft portion 31a of the charging roller 31 via the elastic member 34, the conductive shaft portion 32a of the cleaning roller 32, and the support member 33-2. At this time, because the end of the conductive shaft portion 31a of the charging roller 31 and the end of the conductive shaft portion 32a of the cleaning roller 32 are supported by the same support member 33-1 or support member 33-2, there are fewer contact points on the circuit before the voltage is applied to the conductive shaft portion 31a of the charging roller 31, and the contact resistance at the contact points can be kept low.

[0040] In this way, a stable voltage is applied to the charging roller 31, so that fluctuations in the potential of the photosensitive drums 1a to 1d due to poor contact are suppressed.

[0041] As described above, according to the first embodiment, the charging roller 31 includes the conductive shaft portion 31a, and the cleaning roller 32 includes the conductive shaft portion 32a and cleans the charging roller 31. Two support members 33-1 and 33-2 support both ends of the conductive shaft portion 31a of the charging roller 31 and also support both ends of the conductive shaft portion 32a of the cleaning roller 32. A conductive elastic member 34 biases the two support members 33-1 and 33-2. The two support members 33-1 and 33-2 are conductive members. A predetermined voltage is applied to the conductive shaft portion 31a of the charging roller 31 via at least one of the two elastic members 34 and one of the two support members 33-1 and 33-2, and both ends of the conductive shaft portion 31a of the charging roller 31 are electrically connected via the conductive shaft portion 32a of the cleaning roller 32 and the two support members 33-1 and 33-2.

[0042] This ensures a circuit through the cleaning roller 32 to the conductive shaft portion 31a of the charging roller 31 with small contact resistance, reducing the possibility that the photosensitive drums 1a to 1d will not be properly charged due to the contact state at the contact point between the shaft portion 31a of the charging roller 31 and the support member 33-1.

[0043] Embodiment 2

[0044] 4 is a diagram showing the configuration of a charging device according to embodiment 2. In embodiment 2, for example, as shown in FIG.

[0045] In the second embodiment, the power distribution member 41 is, for example, a plate-like or wire-like conductive member that extends along the charging roller 31 and the cleaning roller 32 and is in contact with both of the two elastic members 34. For example, the power distribution member 41 is a stainless steel plate-like member or wire. As shown in FIG. 4, one end of each elastic member 34 is in contact with one of the support members 33-i (i = 1 or 2), and the other end of each elastic member 34 is in contact with the power distribution member 35. A predetermined voltage is applied to the power distribution member 41 from a high-voltage power supply, and the predetermined voltage is applied to the conductive shaft portion 31a of the charging roller 31 via the power distribution member 35, the two elastic members 34, and the two support members 33-1 and 33-2.

[0046] Next, the operation of the charging device according to the second embodiment will be described.

[0047] In the second embodiment, if there is no poor contact between the conductive shaft portion 31a of the charging roller 31 and the support members 33-1 and 33-2, the voltage is applied to the conductive shaft portion 31a of the charging roller 31 via the elastic member 34 and the support members 33-1 and 33-2.

[0048] On the other hand, even if there is poor contact between conductive shaft portion 31a of charging roller 31 and one of support members 33-1 and 33-2, the voltage is applied to conductive shaft portion 31a of charging roller 31 via elastic member 34 and support member 33-1 or support member 33-2. At this time, because the end of conductive shaft portion 31a of charging roller 31 and the end of conductive shaft portion 32a of cleaning roller 32 are supported by one support member 33-1 or support member 33-2, even if the above-mentioned poor contact occurs, the number of contact points until the above-mentioned voltage is applied to conductive shaft portion 31a of charging roller 31 remains small, and contact resistance at the contact points can be kept small.

[0049] The other configurations and operations of the charging device and image forming apparatus according to the second embodiment are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0050] As described above, according to the second embodiment, a predetermined voltage is applied to the conductive shaft portion 31a of the charging roller 31 via both of the two elastic members 34 and both of the two support members 33-1 and 33-2, and both ends of the conductive shaft portion 31a of the charging roller 31 are electrically connected to the conductive shaft portion 32a of the cleaning roller 32 and the two support members 33-1 and 33-2.

[0051] This ensures two circuits from the power distribution member 41 to the conductive shaft portion 31a of the charging roller 31, so that even if poor contact occurs in the support member 33-i or the elastic member 34, the photosensitive drums 1a to 1d are less likely to be properly charged due to that poor contact.

[0052] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, it is intended that such changes and modifications be included within the scope of the claims. [Industrial Applicability]

[0053] The present invention is applicable to, for example, a charging device of an image forming apparatus. [Explanation of symbols]

[0054] 21 Charging device 31 Charging roller 31a Conductive shaft 32 Cleaning roller 32a Conductive shaft 33-1, 33-2 Support member 34 Elastic member 35,41 Power distribution components

Claims

1. a charging roller having a conductive shaft portion; a cleaning roller having a conductive shaft portion for cleaning the charging roller; two support members that support both ends of the conductive shaft portion of the charging roller and also support both ends of the conductive shaft portion of the cleaning roller; two conductive elastic members that bias the two support members, respectively; the two support members are conductive members, a predetermined voltage is applied to the conductive shaft portion of the charging roller via at least one of the two elastic members and at least one of the two support members; both ends of the conductive shaft portion of the charging roller are electrically connected via the conductive shaft portion of the cleaning roller and the two support members; A charging device characterized by:

2. Further comprising an electrically conductive current distribution member; the power distribution member is in contact with both of the two elastic members; a predetermined voltage is applied to the conductive shaft portion of the charging roller via the power distribution member, the two elastic members, and the two support members; 2. The charging device according to claim 1, wherein:

3. The charging device according to claim 1 or 2; a photosensitive drum; the charging device charges the photosensitive drum; An image forming apparatus comprising:

Images