DEVELOPMENT DEVICE AND IMAGE FORMING APPARATUS

A development device includes a developer carrier, a housing, a layer thickness regulating member and an attachment member. The developer carrier carries a developer developing an electrostatic latent image formed on an image carrier, the developer carrier rotating around an axis. The housing stores the developer carrier and the developer, and has an opening through which the developer carrier is exposed. The layer thickness regulating member is disposed so as to form a gap between the layer thickness regulating member and the developer carrier and regulates a layer thickness of the developer carried on the developer carrier. The attachment member is made of a material has the same thermal expansion property as the layer thickness regulating member. The layer thickness regulating member is fixed to the attachment member using only an adhesive.

INCORPORATION BY REFERENCE

This application is based on and claims the benefit of priority from Japanese patent application No. 2019-027750 filed on Feb. 19, 2019, which is incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to a development device which develops an electrostatic latent image by a toner and an image forming apparatus including the development device.

A development device using a two-component developer is provided with a development blade facing a development sleeve to regulate a layer thickness of the developer on the development sleeve. A blade gap (a gap between the development sleeve and the development blade) is conventionally adjusted by putting a thickness gauge between the development blade and the development sleeve and fastening the development blade by a screw while adjusting the gap between the development sleeve and the development blade. However, in recent years, as a size of the toner becomes small for high image quality, the developer layer on the development roller is required to be thin, and the tolerance of the blade gap tends to be severe because of necessity for narrowing the blade gap.

Conventionally, because fastening by the screw causes slight waving, warpage and deformation of the development blade, a fine adjustment of the blade gap by fastening the screw requires a considerable skill. Then, a technique to adjust the blade gap is discussed. For example, there is a configuration that the both end portions (corresponding to the non-image forming area) of the development blade are fastened to the development housing with a screw while the portion corresponding to the image forming area is fixed with an adhesive. Alternatively, there is another configuration that the gap setting member made of resin is pressed against the development sleeve at both the end portions (corresponding to the non-image forming area) of the development blade to adjust the gap.

However, in the case where the development blade is directly adhered to the development housing, distortion or peeling of the adhesive may occur owing to a difference in coefficient of thermal expansion between the development housing (made of resin, conventionally) and the development blade (made of metal, conventionally). In the case where the resin gap setting member is used, considering the tolerance of resin product and the attachment tolerance, the tolerance of the blade gap at the time of mass production is limited to about ±0.1, and if the tolerance is required to be lower than that, the yield becomes very bad. Additionally, there is a possibility that when abrasion powder of the resin product is mixed with the developer, an output image may be adversely affected.

SUMMARY

In accordance with an aspect of the present disclosure, a development device includes a developer carrier, a housing, a layer thickness regulating member and an attachment member. The developer carrier carries a developer developing an electrostatic latent image formed on an image carrier. The developer carrier rotates around an axis. The housing stores the developer carrier and the developer, and has an opening through which the developer carrier is exposed. The layer thickness regulating member is disposed so as to form a gap between the layer thickness regulating member and the developer carrier and regulates a layer thickness of the developer carried on the developer carrier. The attachment member is made of a material has the same thermal expansion property as the layer thickness regulating member. The layer thickness regulating member is fixed to the attachment member using only an adhesive.

In accordance with an aspect of the present disclosure, an image forming apparatus includes the development device develops the electrostatic latent image.

DETAILED DESCRIPTION

Hereinafter, a printer1(an example of an image forming apparatus) and a development device16according to on embodiment of the present disclosure will be described with reference to the drawings. FIG. is a front view schematically showing an inner structure of the printer1. In the following description, a near side (a front side) of a paper surface ofFIG. 1is defined to be a front side of the printer1, and a left-and-right direction is defined based on a direction in which the printer1is viewed from the front side. In each figure, U, Lo, L, R, Fr and Rr respectively show an upper side, a lower side, a left side, a right side, a front side and a rear side.

The printer1includes a box-shaped casing2. In the casing2, a sheet feeding device3which feeds a sheet S to a conveyance path6, an image forming part4which forms a toner image on the sheet S, a fixing device5which fixes the toner image on the sheet S and a discharge part7which discharges the sheet S on which the toner image is fixed.

The image forming part4includes a photosensitive drum21, a charging device22, an exposure device9, a developer container12, a development device16, an intermediate transferring belt41, a primary transferring roller42, a secondary transferring roller11and a cleaning device23. The photosensitive drum21is driven to be rotated. The charging device22charges the photosensitive drum21. The exposure device9emits laser light based on an image data to the photosensitive drum21to form an electrostatic latent image on the photosensitive drum21. The developer container12supplies a developer containing a toner to the development device16. The development device16develops the electrostatic latent image by the toner to form a toner image. The intermediate transferring belt41is wound around a drive roller and a driven roller. The primary transferring roller42transfers the toner image to the intermediate transferring belt41. The secondary transferring roller11transfers the toner image on the intermediate transferring belt41to the sheet S. The cleaning device23cleans the surface of the photosensitive drum21. The printer1is provided with four sets of the photosensitive drum21, the charging device22, the exposure device9, the developer container12, the development device16, the primary transferring roller42and the cleaning device23, and configured to form a color image using the toners of four colors. The present disclosure may be applied to an image forming apparatus which forms an image using the toner of one color, or the toners of three or five or more colors.

Next, an image forming operation of the printer1will be described. When the printer1receives an image data from an exterior computer or the like, the sheet S is fed to the conveyance path6from the sheet feeding device3. Additionally, on the surface of the charged photosensitive drum21, an electrostatic latent image is formed by the exposure device9based on the image data. The developer is supplied to the housing31from the developer container12, and then agitated by the screws33. The two screws33convey the developer in opposite directions to circulate the developer in the housing31. The developer is carried on the magnetic roller32by magnetic force between the carrier and the magnetic roller32. The toner contained in the carried developer is carried on the electrostatic latent image by a potential difference between the magnetic roller32and the photosensitive drum21. As a result, the toner image is formed.

The toner images formed on the photosensitive drums21are overlapped and transferred on the intermediate transferring belt41by the primary transferring rollers42. The toner image transferred on the intermediate transferring belt41is transferred on the sheet S by the secondary transferring roller11, and then fixed on the sheet S by the fixing device5. The sheet S on which the toner image is fixed is discharged to the discharge part7.

Next, with reference toFIG. 2toFIG. 5, a development blade34(an example a layer thickness regulating member) will be described.FIG. 2is a perspective view showing the development device16.FIG. 3is a perspective view showing the development device16before the development blade34is attached.FIG. 4is a sectional view showing the development device16.FIG. 5is a sectional view showing the development device16before the development blade34is attached.

The development device16includes a development sleeve37(an example of a developer carrier), the housing31, the development blade34(an example of a layer thickness regulating member) and an attachment member35. The development sleeve37carries the developer. The housing31stores the development sleeve37and the developer, and has an opening56through which the development sleeve37is exposed. The development blade34is disposed so as to face the development sleeve37via a gap, and regulates a layer thickness of the developer carried on the development sleeve37. The attachment member is made of the same type of material as the development blade34, and fixed to the housing31. The development blade34is fixed to the attachment member35using an adhesive G.

The magnetic roller32is covered with the development sleeve37. The development sleeve37is made of non-magnetic material, and formed into a cylindrical shape. The development sleeve37is supported by the housing31in a rotatable manner in a predetermined direction.

The housing31is formed into a box-like shape whose longitudinal direction is along the front-and-rear direction. The magnetic roller32and the two screws33are disposed inside the housing31parallel to each other with their axial directions along the front-and-rear direction. The two screws33are disposed in the bottom portion of the housing31side by side in the left-and-right direction, and the magnetic roller32is disposed above the right screw33. The housing31has the opening56on a right side of the magnetic roller32. The outer circumferential face of the magnetic roller32exposed through the opening56faces the outer circumferential face of the photosensitive drum21via a predetermined gap. Between the housing31and the developer container2, a supply path (not shown) for the developer is provided. The developer is a two-component developer containing a toner and a carrier, for example.

The development blade34is an approximately rectangular plate-shaped member whose longitudinal direction is along the front-and-rear direction, and has the same length as the development sleeve37in the front-and-rear direction.

The attachment member35is a member to which the development blade34is adhered. The attachment member35is a plate like member having the same size as the development blade34, and fastened to the housing31with a screw or the like below the opening56. The attachment member35is made of the same type of material as the development blade34. The same type of material as the development blade34shows the same material as the development blade34or a material in which a difference of a coefficient of thermal expansion between the development blade34and the attachment member35is within a predetermined range, such as stainless steel. The development blade34is adhered to the attachment member35using the adhesive G, and the upper end portion of the development blade34faces the outer circumferential face of the development sleeve37of the magnetic roller32via a predetermined distance.

As shown inFIG. 5, the attachment member35has a recess36on the face (the right face) facing the development blade34, and the recess36is formed within a range at least corresponding to the electrostatic latent image in the axial direction of the development sleeve37. The adhesive G is applied to the recess36. The range corresponding to the electrostatic latent image is a range of the outer circumferential face of the photosensitive drum21facing the region where the electrostatic latent image can be formed. In the example shown in the figure, three groove-shaped recesses36having a V-shaped cross section are formed along the front-and-rear direction. The recess36is formed by engraving, for example.

The adhesive G is preferably a hot-melt adhesive. By controlling the temperature of the hot-melt adhesive, the solidifying time can be adjusted depending on a working time. Additionally, the peeling and the re-adhering are possible by heating.

The blade gap is adjusted by positioning the development blade34while measuring the distance of the gap between the development blade34and the development sleeve37using a high resolution CCD camera40, for example. The adjustment of the development gap may be performed manually or automatically by a robot.

According to the development device16according to the above described embodiment, the development blade34is adhered to the attachment member35using the adhesive G, so that distortion hardly occurs on the development blade34compared with a case where it is fastened by a screw or the like. Additionally, the attachment member35is made of the same type of material as the development blade34so that the torsion of the development blade34and the peeling of the adhesive hardly occur due to the difference of the coefficient of thermal expansion between the attachment member35and the development blade34, compared with a case where the attachment member35is made of the different type of material as the development blade34. Therefore, according to the development device16of the present embodiment, it becomes possible to adjust the blade gap easily even if the required tolerance is severe.

According to the development device16of the present embodiment, the attachment member35has the recess36within the range at least corresponding to the electrostatic latent image in the axial direction of the development sleeve37, and the adhesive G is applied to the recess36. Therefore, the adhesive G hardly leaks to a side of the development sleeve37compared with a case where the recess36is not provided.

According to the development device16of the present embodiment, a hot-melt adhesive is used as the adhesive G, so that the adjustment of the solidifying time of the adhesive and the peeling and re-adhering of the adhesive by heating become possible. Therefore, it becomes possible to adjust the blade gap correctly compared with a case where an adhesive other than the not-melt adhesive is used.

The above embodiment may be modified as follows.

The recess36may be formed in the attachment member35by any machining method.FIG. 6andFIG. 7are sectional views showing the development device16of the modified example. The example inFIG. 6shows the recess36aformed by half punching (half blanking). The example inFIG. 7shows the bead shaped recess36bformed by press machining.

The above embodiment shows an example in which the present disclosure is applied to the development device16including the development sleeve37as an example of a developer carrier. However, the developer carrier is not limited to the development sleeve37. For example, the present disclosure may be applied to a touch down type development device which supplies the toner to the photosensitive drum21from the magnetic roller32via the development roller. In this case, the development roller is used as the developer carrier.

FIG. 8is a sectional view showing the development device16of the modified example. As shown in the figure, the development blade34may have a protrusion38on the face (the left face) facing the attachment member35, and the protrusion38corresponds to the recess36of the attachment member35. The protrusion38has a thickness smaller than a depth of the recess36, and a length in the upper-and-lower direction shorter than a length of the recess36in the upper-and-lower direction. A difference in the length between the protrusion38and the recess36is an adjustment allowance at the adjusting of the blade gap. According to the configuration, it becomes possible to position the development blade34easily before adhering.

The adhesive G may be applied to the portion other than the recess of the attachment member, in addition to the recess. For example, the adhesive may be applied to the lower portion or the lateral portion of the recess. In a case where a plurality of recesses is formed, the adhesive may be applied between the adjacently disposed recesses.