JP2019105698A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus including a developing device that can be reduced in price and size. An image forming apparatus includes an image carrier 17 that rotates with an electrostatic latent image formed thereon, a developing device 21 that develops the electrostatic latent image into a developer image, and the developer image that carries the image carrier. And a transfer device for transferring from the body to the paper. The developing device 21 has a developing roller 37 that carries a developer on its surface and rotates, and a regulating member 71 that faces the developing roller 37 with a predetermined gap therebetween and regulates the layer thickness of the carried developer. And a guide member 73 that opposes the image carrier 17 and the transfer device and guides the paper to a transfer area where the developer image is transferred from the image carrier to the paper. The restriction member 71 and the guide member 73 are provided integrally. [Selection] Figure 2

Description

  The present invention relates to an image forming apparatus provided with a developing device for developing an electrostatic latent image formed on an image carrier with a developer.

  In an electrophotographic image forming apparatus such as a printer or a multifunction peripheral, an image carrier on which an electrostatic latent image is formed, a developing device for developing the electrostatic latent image into a developer image, and a developer image on paper And a transfer device for transferring. Depending on the structure of the image forming apparatus, the sheet may be conveyed to the transfer area where the image carrier and the transfer device face each other through the lower side of the developing device. Patent Document 1 and Patent Document 2 describe an image forming apparatus in which a conveyance guide is provided in a developing device in order to convey a sheet to a transfer area smoothly.

  On the other hand, the developing device is provided with a developing roller which carries and rotates a developer on the surface, and a regulating member which regulates the layer thickness of the developer carried by the developing roller. As disclosed in Patent Document 3, the rotation direction of the image carrier and the rotation direction of the development roller are reversed in the development region where the image carrier and the development roller face each other and the electrostatic latent image is developed into a developer image. Also in the counter developing system, a regulating blade (regulating member) for regulating the layer thickness of the developer is provided on the upstream side of the developing area in the rotational direction of the developing roller.

JP, 2014-48314, A JP, 2015-99224, A JP, 2016-4160, A

  With the price reduction and miniaturization of the image forming apparatus in recent years, the price reduction and miniaturization of the developing device are also progressing. As described above, when the conveyance guide and the regulating member are provided in the developing device, there is a problem that the developing device becomes large.

  An object of the present invention is to provide an image forming apparatus provided with a developing device capable of achieving price reduction and miniaturization in consideration of the above-mentioned circumstances.

  In order to solve the above problems, an image forming apparatus according to the present invention comprises: an image carrier that rotates with an electrostatic latent image formed thereon; a developing device that develops the electrostatic latent image into a developer image; An image forming apparatus including a transfer device for transferring the image carrier to the sheet, wherein the developing device includes a developing roller that carries a developer on its surface and rotates, and a predetermined distance between the developing roller and the developing roller. The control member for controlling the layer thickness of the carried developer is opened and opposed, and the image carrier and the transfer device are opposed, and the developer image is transferred from the image carrier to the sheet And a guide member for guiding a sheet to a region, wherein the restriction member and the guide member are integrally provided.

  In the image forming apparatus according to the present invention, the rotational direction of the image carrier and the developing roller in a development area where the image carrier and the developing device face each other and the electrostatic latent image is developed on the developer image. It may be characterized in that the direction of rotation is opposite to the direction of rotation of.

  In the image forming apparatus of the present invention, the regulating member may be characterized in that a bias voltage having the same polarity as the bias voltage to the developing roller is applied.

  In the image forming apparatus of the present invention, the regulation member may be reinforced by an auxiliary member along the width direction of the sheet.

  In the image forming apparatus of the present invention, the leading end of the regulating member on the developing roller side may be bent to the downstream side in the rotation direction of the developing roller.

  In the image forming apparatus of the present invention, the developing device may have a developing housing in which the developing roller is accommodated, and the guide member may be supported by the lower surface of the developing housing.

  According to the present invention, since the regulating member for regulating the layer thickness of the developer layer and the guide member for guiding the sheet to the transfer region are integrated, the number of parts can be reduced and the developing device can be miniaturized.

FIG. 1 is a view schematically showing an internal structure of a printer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a developing device according to an embodiment of the present invention. FIG. 13 is a cross-sectional view showing a first modified example of the regulating member in the developing device according to the embodiment of the present invention. FIG. 18 is a cross-sectional view showing a second modified example of the regulating member in the developing device according to the embodiment of the present invention. FIG. 21 is a cross-sectional view showing a third modification of the regulating member in the developing device according to the embodiment of the present invention.

  Hereinafter, the image forming apparatus of the present invention will be described with reference to the drawings.

  First, the overall configuration of a printer as an image forming apparatus will be described with reference to FIG. FIG. 1 is a front view schematically showing the internal configuration of the printer. In the following description, the left side of the sheet of FIG. 1 is referred to as the front side of the printer. Fr, Rr, L, R, U, and Lo of each figure show the front side, the rear side, the left side, the right side, the upper side, and the lower side of the printer, respectively.

  The apparatus main body 2 of the printer 1 includes a sheet feeding cassette 3 in which the sheet S is stored, a sheet feeding device 5 that feeds the sheet S from the sheet feeding cassette 3, and an image forming unit 7 that forms a toner image on the sheet S. A fixing device 9 for fixing a toner image to a sheet S, a sheet discharging device 11 for discharging the sheet S, and a sheet discharge tray 13 for receiving the sheet S discharged are provided.

  The sheet feeding cassette 3 is accommodated in the lower part of the apparatus main body 2 and is attached and detached along the front-rear direction. The sheet feeding device 5 is disposed above the front end of the sheet feeding cassette 3. The image forming unit 7 is disposed behind the sheet feeding device 5 and above the sheet feeding cassette 3. The fixing device 9 is disposed behind the image forming unit 7. The sheet discharge device 11 is disposed above the fixing device 8. The paper discharge tray 13 is formed on the upper surface of the apparatus main body 2.

  The image forming unit 7 includes a photosensitive drum 17 as an image carrier, a charging device 19, a developing device 21, a transfer roller 23 as a transfer device, a cleaning device 25, an exposure device 27, a toner container 29 and ,have. The photosensitive drum 17 rotates in the clockwise direction in FIG. The charging device 19, the developing device 21, the transfer roller 23, and the cleaning device 25 are sequentially arranged around the photosensitive drum 17 along the rotation direction of the photosensitive drum 17. Specifically, the charging device 19 is disposed above the photosensitive drum 17, the developing device 21 is disposed in front of the photosensitive drum 17, the transfer roller 23 is disposed below the photosensitive drum 17, and the cleaning device 25 is disposed. It is disposed in the rear of the photosensitive drum 17.

  In the apparatus main body 2, a conveyance path P of the sheet S is formed from the sheet feeding device 5 to the sheet discharging device 11 through the image forming unit 7 and the fixing device 9. The conveyance path P is turned upward and backward from the paper feeding device 5, extends rearward through the image forming unit 7, passes through the fixing device 9, and is curved upward toward the paper ejection device 11. In the image forming unit 7, the conveyance path P is directed substantially horizontally to the transfer region N 1 where the photosensitive drum 17 and the transfer roller 23 face each other through the lower side of the developing device 21.

  Next, the image forming operation will be described. In the image forming unit 7, after the photosensitive drum 17 is charged by the charging device 19, the photosensitive drum 17 is exposed by the exposure device 27 based on the image data. Thus, an electrostatic latent image is formed on the surface of the photosensitive drum 17. The electrostatic latent image is developed by the developing device 21 and a toner image is carried on the surface of the photosensitive drum 17. Toner is supplied to the developing device 21 from the toner container 29.

  On the other hand, the sheet S accommodated in the sheet feeding cassette 3 is fed to the conveyance path P by the sheet feeding device 5 and conveyed to the image forming unit 7. In the transfer area N1 of the image forming unit 7, the toner image carried on the surface of the photosensitive drum 17 is transferred onto the sheet S by the transfer roller 23. The sheet S on which the toner image has been transferred is conveyed on the conveyance path P, and the toner image is fixed on the sheet S by the fixing device 9. The sheet S on which the toner image is fixed is discharged from the discharge device 11 to the discharge tray 13.

  Next, the developing device 21 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the developing device. The developing device 21 includes a developing housing 31, a first stirring screw 33, a second stirring screw 35 and a developing roller 37 accommodated in the developing housing 31, and a restricting / guide member 39 supported by the developing housing 31. ing.

  The developing housing 31 is a member having a flat hollow portion that is long in the rotational axis direction of the photosensitive drum 17 (the left-right direction of the printer 1), and accommodates a two-component developer including a carrier and a toner. In the development housing 31, a first stirring chamber 41 and a second stirring chamber 43 along the rotational axis direction of the photosensitive drum 17 are formed side by side in the front-rear direction. A partition wall 45 divides the first stirring chamber 41 and the second stirring chamber 43 from each other. Passage openings (not shown) are formed in the partition wall 45 at both ends in the rotational axis direction of the photosensitive drum 17.

  The first stirring chamber 41 is disposed on the side far from the photosensitive drum 17. A toner supply port 47 is formed on the upper surface of the first stirring chamber 41. The toner is supplied from the toner container 29 to the first stirring chamber 41 through the supply port 47. The bottom wall 41 a of the first stirring chamber 41 is curved downward in a convex semicircular shape as viewed from the axial direction of the rotation axis of the photosensitive drum 17.

  The second stirring chamber 43 is disposed closer to the photosensitive drum 17. The second stirring chamber 43 is formed longer in length in the front-rear direction than the first stirring chamber 41, and the stirring screw storage chamber 51 and the developing roller storage chamber 53 along the rotational axis direction of the photosensitive drum 17 are They are formed side by side in the front-rear direction. The stirring screw storage chamber 51 is adjacent to the first stirring chamber 41 via the partition wall 45. The developing roller accommodating chamber 53 is disposed on the photosensitive drum 17 side.

  The bottom wall 51 a of the agitating screw storage chamber 51 is curved in a semicircular shape convex downward when viewed from the axial direction of the rotation shaft of the photosensitive drum 17.

  An opening 55 is formed in the developing roller storage chamber 53 so as to face the photosensitive drum 17 and open obliquely downward and backward. The bottom wall 53 a of the developing roller accommodating chamber 53 is curved downward in a convex shape of a quarter arc when viewed from the axial direction of the rotation axis of the photosensitive drum 17. At the tip of the bottom wall 53a, that is, at the lower end of the opening 55, a lower edge portion 57 which is bent downward from the bottom wall 53a is formed.

  The first stirring screw 33 is accommodated in the first stirring chamber 41 and rotates in the counterclockwise direction in FIG. The second stirring screw 35 is accommodated in the stirring screw storage chamber 51 of the second stirring chamber 43, and rotates in the clockwise direction in FIG. 2 opposite to the first stirring screw 33. As the first stirring screw 33 and the second stirring screw 35 rotate, the developer is stirred while being transported between the first stirring chamber 41 and the second stirring chamber 43 through the passage port of the partition wall 45. And the toner is charged. When the amount of toner stored in each chamber decreases, the toner is replenished from the toner container 29 through the supply port 47.

  The developing roller 37 has a cylindrical sleeve 61 and a cylindrical magnet roller 63 housed inside the sleeve 61. The sleeve 61 is formed of a nonmagnetic material. The magnet roller 63 has a plurality of magnetic poles along the circumferential direction, and the developer is held on the surface of the sleeve 61 by the magnetic force of each magnetic pole.

  The developing roller 37 is accommodated in the developing roller accommodating chamber 53 of the second stirring chamber 43, and a part thereof is exposed from the opening 55. The sleeve 61 is connected to a drive source (not shown) and rotates clockwise in FIG. That is, in the development region N2 where the developing roller 37 and the photosensitive drum 17 face each other, the photosensitive drum 17 and the developing roller 37 rotate in the opposite direction. Further, a DC voltage or a bias potential in which an AC voltage is superimposed on the DC voltage is applied to the sleeve 61. The magnet roller 63 is accommodated inside the sleeve 61 and fixed to the developing housing 31 so that each magnetic pole is disposed at a predetermined position.

  The regulating and guiding member 39 is a plate-like member elongated in the rotational axis direction of the photosensitive drum 17. The restricting / guide member 39 has a restricting portion 71 and a guide portion 73. The restricting portion 71 is a restricting member that restricts the layer thickness of the developer held by the developing roller 37, and has a rectangular shape elongated in the rotational axis direction of the photosensitive drum 17. The guide portion 73 is a guide member for guiding the sheet S transported along the transport path P to the transfer area N1, and is bent forward substantially at the lower edge of the regulating portion 71. The guide portion 73 includes, in order from the lower edge of the regulating portion 71, a lower horizontal portion 73a extending substantially horizontally forward, an inclined portion 73b inclined obliquely upward from the lower horizontal portion 73a, and a front portion from the inclined portion 73b. And an upper horizontal portion 73c extending substantially horizontally. The lower horizontal portion 73a extends toward the transfer region N1.

  The regulating and guiding member 39 is formed of, for example, a sheet metal material having a thickness of 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, sufficient strength may not be secured, and if it exceeds 0.5 mm, the cost is increased. Preferably, the regulating and guiding member 39 is formed of a magnetic material.

  The restricting portion 71 is fixed to the outer surface (rear surface) of the lower edge portion 57 of the developing housing 31 with a screw B at a predetermined interval in the rotational axis direction of the photosensitive drum 17. That is, the restricting portion 71 is disposed on the upstream side of the developing area N2 in the rotation direction of the developing roller 37. The tip of the regulating portion 71 slightly protrudes from the lower edge portion 57 of the developing roller storage chamber 53 into the developing roller storage chamber 53. Between the tip of the regulating portion 71 and the developing roller 37, a constant gap G is provided along the rotational axis direction of the photosensitive drum 17. The guide portion 73 extends below the bottom walls 53a, 51a, 41a of the developing housing 31, and the upper horizontal portion 73c is between the first stirring chamber 41 and the second stirring chamber 43, and the bottom wall 41a and the bottom wall 51a It is fixed with a screw B in between. A bias potential equivalent to the bias potential applied to the sleeve 61 is applied to the regulating member 71.

  The developing operation of the developing device 21 having the above configuration will be described. The developer contained in the first stirring chamber 41 and the second stirring chamber 43 of the developing housing 31 is between the first stirring chamber 41 and the second stirring chamber 43 by the first stirring screw 33 and the second stirring screw 35. The toner is charged while being conveyed while being conveyed. The developer containing charged toner is held on the sleeve 61 by the magnetic poles of the magnet roller 63 and is conveyed by the rotation of the sleeve 61. The layer thickness of the held developer is regulated to a constant thickness when passing through the gap G between the tip of the regulating portion 71 of the regulating and guiding member 39 and the developing roller 37.

  The developer layer whose layer thickness is thus restricted is conveyed to the development region N2 by the rotation of the sleeve 61. In the development area N2, toner is supplied to the electrostatic latent image by the potential difference between the sleeve 61 and the photosensitive drum 17, and the electrostatic latent image is developed into a toner image.

  On the other hand, when the sheet S conveyed to the image forming unit 7 is conveyed along the conveyance path P below the developing device 21, the sheet S is guided to the transfer region N1 along the guide portion 73 of the restricting and guiding member 39 . In the transfer area N1, the toner image formed on the surface of the photosensitive drum 17 is transferred to the sheet S.

  Among the toners held by the developing roller 37, the toner not supplied to the electrostatic latent image is returned to the second stirring chamber 43, and is conveyed by the second stirring screw 35 in the direction away from the developing roller 37. , Mixed again with the carrier.

  As described above, according to the present invention, the regulating and guiding member 39 integrates the regulating portion 71 for regulating the layer thickness of the developer layer and the guide portion 73 for guiding the sheet S to the transfer area N1. Therefore, the number of parts can be reduced and the development housing 31 can be miniaturized. Further, by applying the present invention to a counter developing method in which the developing roller 37 rotates in the direction opposite to the rotating direction of the photosensitive drum 17 in the developing region N2, the above effect can be effectively exhibited. Further, the developing device 21 and the transfer area N1 are arranged in the lateral direction along the transport direction, and the layer thickness of the developer layer is regulated by the regulating portion 71 on the upstream side of the development area N2 in the rotation direction of the developing roller 37 Therefore, if the guide portion 73 is supported on the lower surface of the developing housing 31, the sheet S can be stably transported to the transfer area N1.

  Furthermore, since the bias potential is applied to the regulating and guiding member 39, when the sheet S conveyed along the conveyance path P contacts the guide portion 73, the static electricity of the sheet S is removed. Therefore, the sheet S can be stably transported as compared with the case where the transport guide is float. Further, when the regulating and guiding member 39 is formed of a magnetic material, magnetic lines of force generated from the magnet roller 63 can be concentrated on the regulating portion 71, so that the layer thickness of the developer held by the developing roller 37 is regulated. You can increase your strength.

  Next, with reference to FIG. 3, a first modified example of the restricting and guiding member 39 will be described. FIG. 3 is a cross-sectional view of the developing device.

  In this example, the auxiliary sheet metal 81 is fastened together to the restricting portion 71 of the restricting / guide member 39. The auxiliary sheet metal 81 is formed of, for example, the same material as the regulating and guiding member 39. The auxiliary sheet metal 81 is fastened to the outer surface (rear surface) of the regulating portion 71 with a screw B at a predetermined interval in the rotational axis direction of the photosensitive drum 17.

  By providing the auxiliary sheet metal 81 as described above, the strength of the restricting portion 71 can be increased and the bending can be reduced without significantly increasing the cost. Therefore, the accuracy of the gap G can be improved, and the durability of the restricting and guiding member 39 can be improved.

  Next, with reference to FIG. 4 and FIG. 5, the second modified example and the third modified example of the regulating and guiding member 39 will be described. 4 and 5 are cross-sectional views of the developing device.

  In the example shown in FIG. 4, the restricting portion 71 is formed to be higher than the height of the lower edge portion 57, and the tip end portion 71a protruding from the lower edge portion 57 is bent so as to curve downward. Further, in the example shown in FIG. 5, the tip end portion 71 a protruding from the lower edge portion 57 is bent substantially at the rear to the rear.

  By bending the tip end portion 71 a of the restricting portion 71 as described above, the strength of the restricting portion 71 can be increased and the bending can be reduced. Therefore, the accuracy of the gap G can be improved, and the durability of the restricting and guiding member 39 can be improved.

  Further, although the two-component developing type developing device has been described in the present embodiment, the present invention is also applicable to a one-component developing type developing device.

  Furthermore, since the above description of the embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, there may be various technically preferable limitations. The technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the components in the embodiment of the present invention described above can be appropriately replaced with existing components and the like, and various variations are possible including combinations with other existing components, The description of the embodiments of the present invention described above does not limit the contents of the invention described in the claims.

1 Printer (image forming device)
17 Photosensitive drum (image carrier)
21 Development device 23 Transfer roller (transfer device)
31 developing housing 37 developing roller 39 regulating and guiding member 71 regulating portion (regulating member)
71a tip 73 guide (guide member)
81 Auxiliary member

Claims (6)

An image carrier rotating with an electrostatic latent image formed thereon, a developing device for developing the electrostatic latent image into a developer image, and a transfer device for transferring the developer image from the image carrier to a sheet of paper An image forming apparatus comprising:
The developing device is
A developing roller that carries and rotates a developer on the surface;
A restricting member which opposes the developing roller at a predetermined interval to restrict the layer thickness of the carried developer;
And a guide member for guiding the sheet to a transfer area where the developer image is transferred from the image carrier to the sheet, with the image carrier and the transfer device facing each other.
The image forming apparatus, wherein the restriction member and the guide member are integrally provided.   The rotation direction of the image carrier and the rotation direction of the developing roller are opposite in a development region where the image carrier and the developing device face each other and the electrostatic latent image is developed into the developer image. The image forming apparatus according to claim 1,   The image forming apparatus according to claim 1, wherein a bias voltage having the same polarity as the bias voltage to the developing roller is applied to the regulating member.   The image forming apparatus according to any one of claims 1 to 3, wherein the restriction member is reinforced by an auxiliary member along a width direction of the sheet.   The image forming apparatus according to any one of claims 1 to 4, wherein a leading end portion of the regulating member on the developing roller side is bent to the downstream side in the rotation direction of the developing roller. The developing device is
It has a developing housing in which the developing roller is accommodated,
The image forming apparatus according to any one of claims 1 to 5, wherein the guide member is supported by the lower surface of the developing housing.

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