Image forming apparatus

Abstract

To provide an image forming apparatus capable of moving a developing unit according to the pressure of a pressure spring without increasing the size of the apparatus.SOLUTION: When the developing unit 24 moves from the separation position to the developing position, a force receiving portion 4011 that receives a reactive force of a force applied to the developing unit 24 along with the pressure of the pressure spring 229 is provided on the rail side 401a of the developer tray 401. The developing unit 24 receives a reaction force from the force receiving portion 4011, and the force applied from the photosensitive drum 2 and the force applied from the force receiving portion 4011 are balanced. As a result, the position of the developing unit 24 relative to the developing tray 401 with respect to the left-right direction, which is roughly determined before the pressing by the pressing spring 229, is determined during the pressing by the pressing spring 229. Since the force receiving portion 4011 is located inside the outer shapes of the developing unit 24 and the developer tray 401, the developing unit 24 can move between the separation position and the developing position without increasing the size of the apparatus to secure a large space between the developing unit 24 and the photosensitive drum 2.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus using electrophotographic technology, such as a printer, a copying machine, a facsimile machine, or a multifunction machine. [Background technology]

[0002] In an image forming device, an electrostatic latent image formed on a photosensitive drum is developed into a toner image by a developer carried on a developing sleeve. A predetermined gap (called an SD gap) is maintained between the photosensitive drum and the developing sleeve along the rotational axis of the photosensitive drum for development. The developing unit with the developing sleeve can be inserted into or removed from the device body for replacement or maintenance by sliding along rails provided in the device body.

[0003] The developing unit is also provided so as to be movable between a developing position where it is close to the photosensitive drum to develop an electrostatic latent image, and a spaced position away from the photosensitive drum (Patent Document 1). In the device described in Patent Document 1, the developing unit is attached to the developing rail and is guided by a guide mechanism to move from the spaced position (second position) to the developing position (first position) in accordance with pressure from a pressure spring. The guide mechanism has a guide hole formed at the point where the developing unit of the device main body hits, and an engagement pin provided in the developing unit that is engageable with the guide hole. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-133760 Summary of the Invention [Problem to be solved by the invention]

[0005] Recent image forming devices use an LED array exposure device, in which multiple light-emitting elements such as LEDs are arranged along the rotational axis of the photosensitive drum, as the exposure device that forms an electrostatic latent image on the photosensitive drum. Since it is preferable to position the LED array exposure device close to the photosensitive drum, it is typically positioned between the development unit and the drum unit. In conventional image forming devices, there is a risk that the engagement pin may come into contact with the exposure device when inserting the development unit. To prevent the engagement pin from coming into contact with the exposure device, it is necessary to ensure a large space between the development unit and the drum unit. However, this conventional approach results in an increase in the size of the device, which is contrary to the recent demand for miniaturization and has been difficult to adopt.

[0006] In view of the above-mentioned problems, the present invention aims to provide an image forming apparatus in which the developing unit can move from the separated position to the developing position in accordance with the pressure of the pressure spring, without having to increase the size of the apparatus in order to secure a large space between the developing unit and the photosensitive drum. [Means for solving the problem]

[0007] An image forming apparatus according to one embodiment of the present invention includes an apparatus main body, an image carrier capable of carrying a toner image, a first support section that supports the image carrier with respect to the apparatus main body, and a developer carrier capable of carrying a developer, the developer carrier being movable within the apparatus main body between a first position where the developer carrier and the image carrier face each other with a predetermined gap so that an electrostatic latent image on the image carrier can be developed with the developer carried on the developer carrier, and a second position where the developer carrier and the image carrier are spaced apart by a distance greater than the predetermined gap; a first abutment section that is provided on the first support section and abuts against the developing unit in a first direction perpendicular to a tangent direction of the image carrier at a position where the developer carrier and the image carrier are closest to each other; and a first abutment section that is provided in the apparatus main body and that at the first position forms an angle with the first direction of 90° or more and 180° or more. a second abutment portion that abuts against the developing unit in a second direction in a range of less than 10°; a second support portion that is provided in the device main body and supports the developing unit so that it can be inserted in a predetermined insertion direction; and a pressure means that pressurizes the second support portion so that the developing unit is pressed in the direction in which it abuts against the first abutment portion and the second abutment portion, wherein the second support portion has a force receiving portion that receives a reaction force of a force applied to the developing unit as the pressure is applied by the pressure means when the developing unit moves from the second position to the first position, and the force receiving portion is located inside the outer contours of the developing unit and the second support portion when viewed from the insertion direction when the developing unit is supported by the second support portion. [Effects of the Invention]

[0008] According to the present invention, an image forming apparatus can be provided in which the developing unit can move from the separated position to the developing position in accordance with the pressure of the pressure member, without having to enlarge the apparatus in order to ensure a large space between the developing unit and the image carrier. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an external perspective view showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. [Figure 3] FIG. 2 is a schematic diagram showing the image forming apparatus when the development unit is in the separated position. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 4 is a perspective view showing the bottom surface of the exposure unit. [Figure 7] FIG. [Figure 8] FIG. 4 is an enlarged view showing the front cover and inner door in an open state. [Figure 9] FIG. 4 is an enlarged view showing the state in which the drum unit is removed. [Figure 10] FIG. 4 is an enlarged view showing a state in which the development unit is removed. [Figure 11] FIG. 2 is a cross-sectional view showing a developing unit, a drum unit, and an exposure unit. [Figure 12] 1A is a front view showing the developing unit and the drum unit when the developing unit is in the developing position, and FIG. 1B is a front view showing the developing unit and the drum unit when the developing unit is in the separated position. [Figure 13] FIG. [Figure 14] FIG. 2A is a schematic diagram showing a first state of the contact / separation mechanism, and FIG. 2B is a schematic diagram showing a second state of the contact / separation mechanism. [Figure 15] FIG. 4 is a perspective view of the developing unit for explaining the support points of the developing unit. [Figure 16] FIG. 2A is a perspective view showing a state in which the drum unit is attached to the apparatus main body, and FIG. 2B is a perspective view showing a state in which the drum unit and the developing unit are attached to the apparatus main body. [Figure 17] FIG. 3 is a cross-sectional view showing the developing unit and the contact / separation mechanism. [Figure 18] 6A and 6B are diagrams showing the relationship of forces acting on the developing unit due to pressure applied by a pressure spring. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Image forming device> The present embodiment will be described below. First, an overview of the image forming apparatus of the present embodiment will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the image forming apparatus 100 of the present embodiment is a so-called internal discharge type image forming apparatus. That is, the image forming apparatus 100 includes an apparatus main body 100A and an original reading device 200 that reads image information from an original, and an output tray 21 that stacks sheets (recording materials) discharged from the apparatus main body 100A is formed between the apparatus main body 100A and the original reading device 200. The image forming apparatus 100 forms a toner image on a sheet in accordance with an image signal sent from the original reading device 200 or an external device (not shown) such as a personal computer.

[0011] The device main body 100A has an operation unit 46 disposed on the front side, which has a display unit capable of displaying various information and keys for inputting various information in response to user operation. In this specification, the side from which a developing unit (described later) removably mounted in the device main body 100A can be inserted and removed from the outside by a user is referred to as the "front (front)," and the opposite side is referred to as the "rear (back)." In addition, the left side when viewing the image forming device 100 from the front is referred to as the "left," and the right side when viewing the image forming device 100 from the front is referred to as the "right."

[0012] Apparatus main body 100A is made up of a front plate provided on the front side, a rear plate provided on the rear side, stays connecting these front and rear plates, pillars supporting the front plate, and other metal plates, and is covered by an exterior cover that constitutes the exterior of image forming apparatus 100. As exterior covers, front cover 101, multiple cassette covers 103, and upper front cover 104 are arranged on the front side. In addition, side covers 105 and 106 are arranged on the left and right side sides, and a rear cover 325 is arranged on the rear side.

[0013] As shown in FIGS. 2 and 3, the image forming apparatus 100 includes four image forming units 1Y, 1M, 1C, and 1K that form toner images in four colors: yellow (Y), magenta (M), cyan (C), and black (K). FIG. 2 shows a case where the developing unit 24 is in a developing position (first position) where it can develop an electrostatic latent image on the photosensitive drum 2. FIG. 3 shows a case where the developing unit 24 is in a spaced position (second position) away from the photosensitive drum 2. Note that the image forming units 1Y, 1M, 1C, and 1K that form toner images of each color are substantially identical in configuration, and therefore, in FIGS. 2 and 3, only the magenta image forming unit 1M is designated by a reference numeral, and the description will be given using the image forming unit 1M as an example.

[0014] The image forming section 1M includes a drum unit 23, a developing unit 24, and an exposure unit 4 (see FIG. 3). The drum unit 23 and the developing unit 24 are each provided so as to be insertable into and removable from the front side of the apparatus main body so as to be guided in the direction of the rotation axis of the photosensitive drum 2 that rotates around a rotation axis. The drum unit 23 includes the cylindrical photosensitive drum 2 as an image carrier, a charging roller 3 that charges the photosensitive drum 2, and a drum cleaner unit (not shown).

[0015] The developing unit 24 as a developing device includes a developing container 30 that contains a developer containing a magnetic carrier and non-magnetic toner, a developing sleeve 5 that is disposed in the developing container 30 and is capable of carrying the developer that supplies the toner to the photosensitive drum 2 to form a toner image, and a conveying screw 7 that conveys the toner while stirring it, and supplies the toner to the developing sleeve 5. Between the drum unit 23 and the developing unit 24 that are arranged adjacent to each other, an exposure unit 4 is disposed as an exposure section that exposes the surface of the photosensitive drum 2 to light to form an electrostatic latent image.

[0016] An intermediate transfer belt unit 8 is disposed above the image forming stations 1Y to 1K. The intermediate transfer belt unit 8 has four primary transfer rollers 6 disposed opposite the photosensitive drums 2 of each color, and one endless intermediate transfer belt 9. Toner bottles 22Y to 22K containing replenishment toner to be supplied to the developing units 24 are provided above the intermediate transfer belt unit 8 so as to be detachable from a toner supply mechanism (not shown). The toner supply mechanism supplies the appropriate amount of toner from the toner bottles 22Y to 22K to each developing unit 24 of the corresponding image forming stations 1Y to 1K at the appropriate time. Sheet cassettes 12A and 12B containing sheets S are disposed below the image forming stations 1Y to 1K.

[0017] <Image formation process> Next, the image forming process on the sheet S in the image forming apparatus 100 will be described. In each of the image forming units 1Y to 1K, the surface of the photosensitive drum 2, which is driven to rotate by a motor (not shown), is uniformly charged by a charging roller 3 pressed against the photosensitive drum 2. Thereafter, an exposure unit 4, which is driven based on a signal of image information, irradiates the surface of the photosensitive drum 2 with light, and an electrostatic latent image is formed on the surface of the photosensitive drum 2. The electrostatic latent image formed on the photosensitive drum 2 is developed into a toner image by a developing unit 24. The developing unit 24 develops the electrostatic latent image on the photosensitive drum 2 (on the image carrier) into a toner image using toner contained in a developer.

[0018] In the developing unit 24, a high voltage is applied to the cylindrical developing sleeve 5 as a developer carrier, and the toner, which is charged by the stirring of the conveying screw 7, is uniformly coated on the surface of the developing sleeve 5. The conveying screw 7 is rotated at a relatively high speed compared to the rotational speed of the developing sleeve 5 and the photosensitive drum 2, and as a result, the toner is evenly coated on the surface of the developing sleeve 5.

[0019] The toner image on the photosensitive drum 2 is primarily transferred from the photosensitive drum 2 to the intermediate transfer belt 9 by applying a primary transfer voltage to a primary transfer roller 6 disposed opposite the image forming units 1Y to 1K with the intermediate transfer belt 9 interposed therebetween. A drum cleaner unit (not shown) collects residual toner remaining on the photosensitive drum 2 after the primary transfer.

[0020] Inside the apparatus main body 100A of the image forming apparatus 100, a sheet transport path for transporting the sheet S from bottom to top is provided on the right side. Arranged on this sheet transport path from bottom to top are a supply roller pair 13, a registration roller pair 15, a secondary transfer outer roller 16, a fixing unit 19, and a discharge roller pair 20. The secondary transfer outer roller 16 abuts against the secondary transfer inner roller 10, which is arranged inside the intermediate transfer belt 9, with a predetermined pressure across the intermediate transfer belt 9, thereby forming a secondary transfer nip portion 17.

[0021] Sheets S stored in sheet cassettes 12A and 12B are supplied one by one from either sheet cassette 12A or 12B to a sheet conveying path by driving supply roller pair 13 at a predetermined control timing. The sheet S supplied by supply roller pair 13 is conveyed to registration roller pair 15 arranged midway along the sheet conveying path. The registration roller pair 15 then performs skew correction and timing correction on the sheet S, and the sheet S is sent to secondary transfer nip portion 17. Secondary transfer nip portion 17 is formed by a secondary transfer inner roller 10 and a secondary transfer outer roller 16 that face each other across intermediate transfer belt 9, and is a nip portion that transfers a toner image from intermediate transfer belt 9 onto sheet S by applying a predetermined pressure and secondary transfer voltage.

[0022] The image formation processes for each color, which are processed in parallel by the image forming units 1Y to 1K for each color described above, are performed in a timed manner to sequentially superimpose the image onto the toner image of the color that was primarily transferred onto the intermediate transfer belt 9 upstream in the movement direction. As a result, a full-color toner image is formed on the intermediate transfer belt 9 and is transported to the secondary transfer nip portion 17. At the secondary transfer nip portion 17, the timing of the sheet S and the full-color toner image coincides, and secondary transfer is performed in which the toner image is transferred from the intermediate transfer belt 9 to the sheet S. The sheet S is then transported to the fuser 19, where the fuser 19 applies heat and pressure to fix the toner image to the sheet S. After passing through the fuser 19, the sheet S is transported to the discharge roller pair 20, and is discharged onto the discharge tray 21 by the discharge roller pair 20.

[0023] In this embodiment, the drum unit 23 and the developing unit 24 deteriorate due to repeated image formation processes and require replacement or maintenance. The drum unit 23 and the developing unit 24 are in the form of cartridges so that the user can easily insert and remove them from the apparatus main body 100A for replacement or maintenance. Figure 3 shows the arrangement of the drum unit 23, the developing unit 24, and the exposure unit 4 when inserting and removing the drum unit 23 and the developing unit 24.

[0024] 3, when inserting or removing the drum unit 23 or the developing unit 24, the developing unit 24 and the exposure unit 4 are in a separated position (second position) separated from the photosensitive drum 2, unlike the state shown in FIG. 2. This is because if the developing unit 24 and the exposure unit 4 are in a state close to the photosensitive drum 2 when inserting or removing the drum unit 23 or the developing unit 24, dynamic interference during insertion or removal of the drum unit 23 or the developing unit 24 could damage the photosensitive drum 2, the developing sleeve 5, or the lens array 52 described below. For this reason, the user is allowed to separate the developing unit 24 and the exposure unit 4 from the photosensitive drum 2 before inserting or removing the drum unit 23 or the developing unit 24.

[0025] <Exposure unit> Next, the exposure unit 4 will be described with reference to Fig. 3 and Fig. 4 to Fig. 6. As shown in Fig. 4, the exposure unit 4 has a mounting substrate 50, a plurality of light-emitting elements 51 arranged on one side of the mounting substrate 50 in the direction of the rotation axis of the photosensitive drum 2 (main scanning direction), and a lens array 52 in which a plurality of lenses that transmit light emitted from the light-emitting elements 51 are arranged. The light-emitting elements 51 are, for example, light-emitting diodes (light emitting diodes) or organic electroluminescence (EL) elements. The lens array 52 has a plurality of lenses arranged in the arrangement direction of the light-emitting elements 51, and the lens array 52 focuses light emitted from the plurality of light-emitting elements 51 onto the surface of the photosensitive drum 2.

[0026] A plurality of light-emitting elements 51 and a plurality of lenses are arranged on the mounting substrate 50 and the lens array 52, respectively, across the exposure range in the rotation axis direction of the photosensitive drum 2. Therefore, as shown in Fig. 5, the mounting substrate 50 and the lens array 52 are formed in a shape that extends along the rotation axis direction of the photosensitive drum 2. The mounting substrate 50 and the lens array 52 are held in a housing 54. The housing 54 is required to have high rigidity, and in this embodiment, sheet metal such as a galvanized steel plate or a cold-rolled steel plate bent to have a substantially U-shaped cross section is used.

[0027] The housings 54 further include housing support members 55 formed with a generally U-shaped cross section, which are provided integrally with the opening of the U-shape of the housings 54. As shown in Fig. 6, an opening 55A that communicates between the inside and outside of the housing support member 55 is formed in the bottom of the housing support member 55 at a position facing the back surface of each housing 54 opposite the front surface of the mounting substrate 50. As described above, the exposure unit 4 is configured as an integrated exposure head by the mounting substrate 50 on which the plurality of light-emitting elements 51 are mounted, the lens array 52 in which the plurality of lenses are arranged in parallel, the housings 54, and the housing support members 55.

[0028] Next, the insertion and removal of the drum unit 23 and the developing unit 24 into the apparatus main body 100A will be described with reference to Figures 7 to 10. As shown in Figure 7, the image forming apparatus 100 is equipped with inner doors 102Y, 102M, 102C, and 102K (hereinafter collectively referred to as "inner door 102") that cover the front sides of both the drum unit 23 and the developing unit 24 mounted in the apparatus main body 100A. The inner door 102 is a necessary member for protecting the drum unit 23, the developing unit 24, and the exposure unit 4, and for making it difficult for the photosensitive drum 2 to be exposed to light outside the image formation process, and is disposed in a position facing the front of the image forming sections 1Y to 1K so as to be able to open and close.

[0029] As will be described in detail later, the developing unit 24 is moved toward and away from the photosensitive drum 2 by a contact / separation mechanism that is linked to the operation of opening the inner door 102. Note that Figures 8 to 10 show a state in which only the drum unit 23 and the inner door 102K that are provided in the black image forming section 1K and that open and close to insert and remove the developing unit 24 are open.

[0030] A front cover 101 is provided on the front side of the image forming apparatus 100 so as to be able to be opened and closed freely. The front cover 101 is provided in front of the inner door 102 in the direction of the rotation axis of the photosensitive drum 2. The front cover 101 is an exterior cover that constitutes the external appearance of the image forming apparatus 100, covering the entirety of the multiple inner doors 102 lined up in the left-right direction when closed.

[0031] For example, replacement of the drum unit 23 or the developing unit 24 included in the black image forming unit 1K is performed by the user in the following procedure. The user opens the front cover 101 as shown in FIG. 7, and then opens the inner door 102K as shown in FIG. 8, thereby removing the drum unit 23 from the apparatus main body 100A with the developing unit 24 spaced apart from the photosensitive drum 2 (see FIG. 9). Alternatively, the user can remove the developing unit 24 from the apparatus main body 100A with the developing unit 24 spaced apart from the photosensitive drum 2 (see FIG. 10). The user then inserts a new drum unit 23 or developing unit 24, closes the inner door 102K, and then closes the front cover 101, thereby completing the replacement of the drum unit 23 or developing unit 24.

[0032] <Developing unit contact / separation mechanism> The developing unit 24 is intended to be detachable and replaceable from the apparatus main body 100A. Therefore, the configuration and operation for attaching and detaching the developing unit 24 will be described with reference to FIGS. 11 to 13. First, as shown in FIG. 11, the developing unit 24 is disposed with the developing sleeve 5 facing the photosensitive drum 2 with a predetermined gap (SD gap) between them. Because this SD gap is minute, if the developing unit 24 or the drum unit 23 is pulled out forward from the apparatus main body 100A in this state, there is a possibility that the photosensitive drum 2 or the developing sleeve 5 will be scratched by friction. Therefore, the developing unit 24 or the drum unit 23 is attached or detached only after they are separated by a sufficient distance to prevent friction between them.

[0033] Therefore, in this embodiment, a contact / separation mechanism 400, which will be described later, is provided to move the developing unit 24 closer to and away from the drum unit 23. When removing any of the units, the contact / separation mechanism 400 moves the developing unit 24 away from the drum unit 23. When inserting any of the units into the apparatus main body 100A, the contact / separation mechanism 400 also moves the developing unit 24 away from the drum unit 23, and after insertion, the developing unit 24 moves closer to the drum unit 23.

[0034] As shown in FIG. 3, the drum units 23 and developing units 24 for each color are arranged side by side in the left-right direction within the apparatus main body 100A. Therefore, the direction in which the developing units 24 are moved toward and away from each other is approximately vertical in this embodiment, as shown in FIGS. 12(a) and 12(b). In FIG. 12(a), the developing sleeve 5 and the photosensitive drum 2 face each other with a predetermined gap, and the developing unit 24 is positioned at a developing position where the electrostatic latent image on the photosensitive drum 2 can be developed with the developer carried on the developing sleeve 5. In contrast, in FIG. 12(b), the developing sleeve 5 and the photosensitive drum 2 are spaced apart by more than the predetermined gap, and in this embodiment, the developing unit 24 is positioned at a separated position where the developing unit 24 or the drum unit 23 can be detached.

[0035] Next, the configuration of the contact / separation mechanism 400 that contacts and separates the developing unit 24 will be described with reference to FIGS. 13 to 14(b). As shown in FIG. 13, the contact / separation mechanism 400 includes a developing tray 401 and a link mechanism 410. The developing tray 401, which serves as a second support, is disposed at a position on the apparatus main body 100A where the developing unit 24 is attached. The developing tray 401 has rails 401a and 401b extending in the front-rear direction, and is capable of supporting the developing unit 24 as it slides along the rails 401a and 401b. The rails 401a and 401b are provided on the developing tray 401 so as to face each other in the width direction (left-right direction) and allow the developing unit 24 to slide with a loose fit. That is, the rails 401a and 401b are members that guide the developing unit 24 during insertion and removal. The distance between the rails 401a and 401b is set larger than the distance between the engaged portions of the developing unit 24 so that the user can smoothly insert and remove the developing unit 24.

[0036] 14(a) and 14(b), the link mechanism 410 has a slide member 411, a first rotation shaft 412, and a second rotation shaft 413. The slide member 411 is disposed so as to be movable relative to the developing tray 401 in the insertion / removal direction. The first rotation shaft 412 rotatably supports the inner door 102 at the upstream end of the slide member 411 in the insertion direction (from front to rear in this case) in which the developing unit 24 can be inserted. The second rotation shaft 413 rotatably supports the inner door 102 at a position spaced apart from the first rotation shaft 412 with respect to the apparatus main body 100A.

[0037] The developing tray 401 is disposed above the slide member 411, facing it. The upper surface of the slide member 411 is formed by a first surface 414 that is higher in the vertical direction, a second surface 415 that is lower than the first surface 414, and an inclined surface 416 that connects the first surface 414 and the second surface 415. The first surface 414 is located upstream of the second surface 415 in the insertion direction, and the inclined surface 416 is inclined in a direction that increases as it moves upstream in the insertion direction. On the other hand, a protruding portion 402 that protrudes downward is provided on a portion of the lower surface of the developing tray 401 that faces the upper surface of the slide member 411. The side surface of the protruding portion 402 on the upstream side in the insertion direction is inclined upward as it moves upstream in the insertion direction. The developing tray 401 is movable up and down due to the engagement between the protruding portion 402 and the upper surface of the slide member 411.

[0038] For example, when the developing unit 24 is in the developing position shown in Fig. 12(a), the protruding portion 402 of the developing tray 401 rides on the first surface 414 of the slide member 411, as shown in Fig. 14(a). In this state, the inner door 102 is closed so as to cover the developing unit 24.

[0039] When the inner door 102 is opened to remove the developing unit 24 from this state, the inner door 102 rotates about the second rotation shaft 413, and the slide member 411, which is connected to the inner door 102 by the first rotation shaft 412, is pulled out in the direction of arrow E in FIG. 14(b). That is, the slide member 411 moves upstream in the insertion direction. At this time, the protrusion 402 slides down the inclined surface 416 of the slide member 411 and moves onto the second surface 415. Then, the developing tray 401 moves downward in the direction of arrow F in FIG. 14(a). As a result, the developing unit 24 supported by the developing tray 401 also moves downward to the separated position shown in FIG. 12(b). Therefore, this movement in the direction of arrow F separates the developing unit 24 from the drum unit 23. The user removes the developing unit 24 from the developing tray 401 in the state shown in FIG. 14(b) for replacement.

[0040] Then, the user places a new developing unit 24 on the developing tray 401 in the state shown in FIG. 14(b) and inserts it to a predetermined position along the rails 401a (see FIG. 13) extending in the insertion direction. Before closing the inner door 102, the user fastens the inserted developing unit 24 to the developing tray 401 with, for example, a shoulder screw to prevent the developing unit 24 from moving in the insertion / removal direction. When the user then closes the inner door 102, the slide member 411 moves downstream in the insertion direction, and the inclined surface 403 of the protruding portion 402 of the developing tray 401 engages with the inclined surface 416 of the slide member 411, causing the protruding portion 402 to ride from the second surface 415 onto the first surface 414. This causes the developing tray 401 to move in the direction opposite to the direction of arrow F, i.e., upward. As a result, the developing unit 24 supported by the developing tray 401 also moves upward. At that time, the developing unit 24 rotates in accordance with the pressure of the developing tray 401 by a pressure spring 229 (see FIG. 11), which will be described later, so that the developing sleeve 5 moves toward the photosensitive drum 2. When the inner door 102 is closed, the state shown in FIG. 12(a) is reached, in which access to both the developing unit 24 and the drum unit 23 is not possible, and therefore, it is possible to prevent a user from accidentally removing either unit.

[0041] <Developing unit positioning configuration> Next, the positioning configuration of the developing unit 24 will be described using FIGS. 15 to 16(b) with reference to FIGS. 11, 12(a), and 12(b). FIG. 15 is a perspective view of the developing unit 24 shown to explain the support points of the developing unit. FIG. 16(a) is a perspective view showing the inside of the apparatus main body 100A when the drum unit 23 is installed but the developing unit 24 is not installed. FIG. 16(b) is a perspective view showing the inside of the apparatus main body 100A when the drum unit 23 and the developing unit 24 are installed. Note that FIG. 11 schematically shows the direction in which the pressure spring 229 presses the developing unit 24 when the developing unit 24 is positioned at the development position, and the support points that support the developing unit 24.

[0042] As shown in FIG. 15, the developing unit 24 has two bearings 250 that rotatably support both end portions of the developing sleeve 5. Each of the two bearings 250 has a first abutment portion 251 on the side where the developing sleeve 5 is exposed from the developing container 30 (i.e., the side facing the photosensitive drum 2). The developing unit 24 also has at least three second abutment portions 260, four in this embodiment. The four second abutment portions 260 are formed near the four corners of the upper surface of the developing container 30. In this embodiment, an engagement pin 154 is provided on the downstream end surface of the developing unit 24 in the insertion direction so as to protrude downstream.

[0043] On the other hand, as shown in FIG. 16(a), the drum unit 23 has two bearings 270 provided as first support portions that rotatably support the photosensitive drum 2 relative to the case 214 of the drum unit 23. The two bearings 270 have first contact portions 271 on the sides facing the developing sleeve 5. Since the drum unit 23 is supported by the apparatus main body 100A while attached to the apparatus main body 100A, the two bearings 270 support the photosensitive drum 2 relative to the apparatus main body 100A via the case 214. The two first contact portions 271 provided on the two bearings 270 can also be said to be provided on the apparatus main body 100A. In this embodiment, the two first contact portions 271 form a first positioning portion 272 that positions the developing unit 24 in a first direction, which will be described later.

[0044] 16(a), at least three second contact portions 280 are provided on the upper surface of the space in the apparatus main body 100A into which the developing unit 24 is inserted, and in this embodiment, four are provided. In this embodiment, the four second contact portions 280 form second positioning portions 281 that position the developing unit 24 in a second direction, which will be described later. Furthermore, a screw hole 291 into which a screw 290, such as a stepped screw, is formed at the upstream end in the insertion direction of a developing tray 401 that is supported by the apparatus main body 100A and on which the developing unit 24 is supported, so that the supported developing unit 24 can be fastened to the developing tray 401 by the screw 290, which will be described later.

[0045] When the developing unit 24 is inserted into the apparatus main body 100A from the state shown in FIG. 16(a) and positioned at the developing position, the state shown in FIG. 16(b) is achieved. In this state, the two first abutting portions 251 (X1, X2) on the developing unit 24 abut against the two first contact portions 271 (X1, X2) on the drum unit 23. In this embodiment, by appropriately setting the outer shapes of the bearing portions 250, 270, when the two first abutting portions 251 abut against the two first contact portions 271 at the first position, a predetermined gap (SD gap) is formed between the developing sleeve 5 and the photosensitive drum 2.

[0046] Furthermore, at least three of the four second abutting portions 260 (Z1, Z2, Z3, Z4) on the developing unit 24 side abut against at least three of the four second abutting portions 280 (Z1, Z2, Z3, Z4) on the apparatus main body 100A side. If there is no distortion in the developing unit 24, the apparatus main body 100A, or the drum unit 23, the four second abutting portions 260 will abut against the four second abutting portions 280, respectively.

[0047] As a result, the developing unit 24 is positioned as shown in FIG. 11. Here, the points where the developing unit 24 is supported by the two first abutting portions 251 abutting against the two first contact portions 271 are defined as support points X1 and X2 in the first direction. Furthermore, the points where the developing unit 24 is supported by the four second abutting portions 260 abutting against the four second contact portions 280 are defined as support points Z1, Z2, Z3, and Z4 in the second direction. Note that while support points Z1, Z2, Z3, and Z4 are described as such for ease of explanation, the support points in the second direction are any three of these points. In other words, the posture of the developing unit 24 is maintained if it is supported by at least three support points, so it is sufficient for the developing unit 24 to abut at three or more points, and it may be supported at any three or more of the four points.

[0048] Here, the first direction supported by the support points X1 and X2 is a direction perpendicular to the tangent direction of the photosensitive drum 2 at the position where the developing sleeve 5 and the photosensitive drum 2 are closest to each other at the development position, that is, the direction of arrow X in FIG. 11. This first direction is a direction in which a predetermined gap (SD gap) is formed between the photosensitive drum 2 and the developing sleeve 5, and in this embodiment, the first direction (X direction) is defined as a direction connecting the center O1 of the developing sleeve 5 and the center O2 of the photosensitive drum 2. Therefore, the developing unit 24 is supported at two points in the first direction by the two first abutment portions 271 of the first positioning portion 272 (one of the positioning portions).

[0049] The second direction supported by any three of the support points Z1, Z2, Z3, and Z4 is a direction in which the angle θ1 with respect to the first direction is in the range of 90° or more and less than 180° at the first position. Here, the angle between the first direction and the second direction is the following angle. That is, it is the angle between the portion of the first direction from the developing sleeve 5 toward the photosensitive drum 2 relative to the position where the first direction and the second direction intersect, and the portion of the second direction from the position where the developing unit 24 intersects toward the second contact portion 280. In other words, it is the angle in the counterclockwise direction from the first direction in FIG. 11. In this embodiment, the second direction is the direction indicated by the arrow Z in FIG. 11, which forms an angle of 90° with the first direction (X direction). Therefore, the first direction and the second direction in this embodiment are perpendicular to each other. Therefore, the developing unit 24 is supported at three points in the second direction by any three of the four second contact portions 280 of the second positioning portion 281 (the other positioning portion).

[0050] <Developing unit pressure structure> Next, the pressure application configuration of the developing unit 24 will be described with reference to FIG. 11. The developing unit 24 is pressed in the direction of arrow P in FIG. 11 by a pressure spring 229 serving as a pressure applying means. The direction of arrow P is the direction in which the developing unit 24 contacts two first contact portions 271 (first positioning portions 272) and at least three second contact portions 280 (second positioning portions 281). In other words, the X- and Z-direction components of the pressure application direction of the pressure spring 229 are directed to contact three of the X-direction support points X1 and X2 and the Z-direction support points Z1, Z2, Z3, and Z4. Therefore, the pressure application direction of the pressure spring 229 is a direction in which the angle θ2 with respect to the first direction (X direction) is greater than 0° and less than 90°. Similar to the angle θ1 described above, the angle between the pressure application direction and the first direction is an angle measured counterclockwise from the first direction in FIG. 11.

[0051] Furthermore, the developing unit 24 is movable in this direction, as will be described later. Therefore, the spring force (pressure) of the pressure spring 229 is set taking into consideration at least the gravity of the developing unit 24. Note that one pressure spring 229 is provided near each end of the developing tray 401 in the insertion direction, and presses the developing unit 24 together with the developing tray 401. For this reason, in this embodiment, the spring force of the pressure spring 229 is set taking into consideration the gravity of the developing tray 401 as well as the gravity of the developing unit 24.

[0052] <Developing unit guide mechanism> Next, the guide configuration of the developing unit 24 will be described with reference to FIG. 11 and FIGS. 12(a) and 12(b). As shown in FIG. 12(a), the developing unit 24 is guided by a guide mechanism 150 serving as a guide means within the apparatus main body 100A (inside the apparatus main body) at least from the separated position to just before the developing position. In this embodiment, the guide mechanism 150 is provided in an area overlapping the developing unit 24 when viewed from the insertion direction. The guide mechanism 150 has a guide hole 151 formed in the apparatus main body 100A and an engagement pin 154 provided in the developing unit 24 as an engagement portion engageable with the guide hole 151. The guide hole 151 is formed long in the vertical direction and includes a first guide portion 152 having a narrow widthwise (left-right) spacing between its middle and lower ends, and a second guide portion 153 located above the first guide portion 152 and having a wider widthwise spacing than the first guide portion 152.

[0053] The first guide portion 152 guides the developing unit 24 from the separated position in a direction approaching the photosensitive drum 2. In this embodiment, it guides the developing unit 24 in the vertical direction. The second guide portion 153 guides the developing unit 24, which has been guided by the first guide portion 152 and pressed by the pressure spring 229, so that it abuts against two of the first abutment portions 271 before abutting against at least three of the second abutment portions 280.

[0054] The engagement pin 154 protrudes from the downstream end surface in the insertion direction of the developing unit 24, which moves integrally with the developing tray 401 inside the apparatus main body 100A (see FIG. 15), and engages with the first guide portion 152 and the second guide portion 153 to guide the developing unit 24. The second guide portion 153 is formed so that when the developing unit 24 abuts against the two first abutment portions 271 and then is further pressed by the pressure spring 229, the second guide portion 153 abuts against at least three second abutment portions 280 in a state where it is disengaged from the engagement pin 154. For this reason, the second guide portion 153 has a wider widthwise spacing than the first guide portion 152, and is formed so that a portion of the side edge on the drum unit 23 side gradually inclines more toward the X direction than the first guide portion 152 as it approaches the Z direction.

[0055] The developing unit 24 is guided from the separated position to the developing position as follows. First, the developing unit 24, which is in the separated position, is moved upward by the aforementioned contact / separation mechanism 400. At this time, the developing unit 24 is guided in a substantially vertical direction by the engagement between the engagement pin 154 and the first guide portion 152, as shown in FIG. 12(b). At this time, the developing unit 24 is pressed in the direction of arrow P by the pressure spring 229 (see FIG. 11), but is guided in a substantially vertical direction by the engagement between the engagement pin 154 and the first guide portion 152 and the substantially vertical component force of the pressure spring 229.

[0056] As the developing unit 24 moves further upward, the engagement pin 154 moves from the first guide portion 152 to the second guide portion 153. Then, due to the pressure of the pressure spring 229, the two first abutment portions 251 of the developing unit 24 are guided in a direction in which they abut against the two first abutment portions 271 of the drum unit 23. As described above, the second guide portion 153 has a wider widthwise spacing than the first guide portion 152, and is formed so that part of its side edge is gradually inclined in the widthwise direction (to the right) more than the first guide portion 152. Therefore, the developing unit 24 is guided in the X direction by the engagement between the engagement pin 154 and the second guide portion 153 and the X-direction component force of the pressure spring 229, and the two first abutment portions 251 abut against the two first abutment portions 271.

[0057] However, at this time, the developing unit 24 is not in contact with at least three of the second contact portions 280. From this state, the developing unit 24 is further pressurized by the pressure spring 229, so that the developing unit 24 is guided by the two first contact portions 271, and the engagement pin 154 moves away from the second guide portion 153. That is, the bearing portion 250, which is provided with the two first abutment portions 251, moves along the outer circumferential surface of the bearing portion 270, which is provided with the two first contact portions 271, so that the developing unit 220 moves further upward while being supported at two points. Then, as shown in FIG. 12(a), the developing unit 24 comes into contact with any three of the four second contact portions 280. That is, the developing unit 24 is guided in the Z direction by the engagement between the first abutment portion 251 and the first contact portion 271 and the Z-direction component force of the pressure spring 229, and the three second abutment portions 260 abut against the three second contact portions 280.

[0058] As a result, the developing unit 24 is positioned at the development position and is supported in the X direction by two support points X1 and X2 and in the Z direction by any three support points Z1, Z2, Z3, and Z4. In this way, the developing unit 24 is positioned, and a predetermined gap (SD gap) is formed between the developing sleeve 5 and the photosensitive drum 2.

[0059] Before closing the inner door 102, the user screws the screw 290 into the screw hole 291 on the upstream side in the insertion direction, and fastens the developing unit 24 to the developing tray 401 with the engagement pin 154 engaged with the guide hole 151 on the downstream side in the insertion direction. This restricts movement of the developing unit 24 relative to the developing tray 401 in the Y direction (the insertion direction of the developing unit 24), which is perpendicular to the X and Z directions. In this embodiment, before closing the inner door 102, i.e., before moving in response to the pressure of the pressure spring 229, the developing unit 24 has its left-right position determined on the downstream side in the insertion direction because the engagement pin 154 is engaged with the guide hole 151, whereas its left-right position on the upstream side in the insertion direction is roughly determined but not fixed. Therefore, the developing unit 24 can move left-right between the rails 401a and 401b on the upstream side in the insertion direction, starting from the engagement pin 154.

[0060] As described above, the developing unit 24 moves from the separated position to the developing position in response to the pressure of the pressure spring 229. The developing unit 24 is supported in the X direction by two support points X1 and X2 and in the Z direction by three support points Z1, Z2, Z3, and Z4. Positioning the developing unit 24 in this manner creates a predetermined gap (SD gap) between the developing sleeve 5 and the photosensitive drum 2. However, if the developing unit 24 supported by the developing tray 401 can move left and right on the upstream side in the insertion direction, the developing unit 24 cannot be positioned as described above due to the relationship between the forces acting on the developing unit 24 as a result of pressure applied by the pressure springs 229, one on the upstream side and one on the downstream side in the insertion direction. Therefore, in this embodiment, the developing unit 24 is provided with a protrusion 444, as shown in FIGS. 11, 16(b), and 17.

[0061] 11 and 17, the protruding portion 444 as a contact portion protrudes from the engaged portion 30a of the developing unit 24, which is provided on the bottom surface of the developing container 30 in the insertion direction, toward the rail 401a as a rail portion of the developing tray 401. The engaged portion 30a is provided to engage with the rail 401a and guide the developing unit 24 when the developing unit 24 is inserted or removed. As shown in FIG. 16(b), the protruding portion 444 is provided in a partial range on the upstream side (front side) of the engaged portion 30a in the insertion direction. As shown in FIG. 11, when the developing unit 24 is in the development position, the protruding portion 444 is in contact with the force receiving portion 4011 of the rail 401a.

[0062] On the other hand, when the developing unit 24 is in the separated position, the engaged portion 30a has some play with respect to the rail 401a, and therefore the protruding portion 444 is not necessarily in contact with the force receiving portion 4011 of the rail 401a. As the developing unit 24 is rotated from the separated position to the developing position by the pressure spring 229, the protruding portion 444 transitions to a contact state in which it is in contact with the force receiving portion 4011 of the rail 401a. As will be described later, when the developing unit 24 moves from the separated position to the developing position, the force receiving portion 4011 receives a reaction force to the force applied to the developing unit 24 as a result of the pressure of the pressure spring 229. Also, as shown in FIG. 17 , the force receiving portion 4011 is located inside the outer shapes of the developing unit 24 and the developing tray 401 when viewed from the insertion direction of the developing unit 24 with the developing unit 24 supported by the developing tray 401.

[0063] 18 is a schematic diagram showing the relationship of the forces acting on the developing unit 24 in response to pressure from the pressure spring 229 when the protruding portion 444 is in contact. As shown in FIG. 18, a reaction force 709 is applied to the developing unit 24 from the first contact portion 271 in response to pressure from the pressure spring 229, and a reaction force 705 is received by the force receiving portion 4011 of the rail 401a of the developing tray 401 with which the protruding portion 444 comes into contact. Furthermore, reaction forces 706 and 707 acting on the developing unit 24 from the second contact portion 280 (Z1, Z2, Z3, Z4) in response to pressure from the pressure spring 229 are received by a reaction force 708 at the contact point between the developing unit 24 (specifically, the developing container 30) and the developing tray 401. As a result, the forces acting on the developing unit 24 in response to the pressure from the pressure springs 229 on the upstream and downstream sides in the insertion direction are balanced, and the left-right and up-down positions of the developing unit 24 are determined. As a result, the developing unit 24 is positioned as shown in FIG.

[0064] As described above, in this embodiment, the rail 401a of the developing tray 401 is provided with a force receiving portion 4011 that receives a reaction force of the force applied to the developing unit 24 due to the pressure of the pressure spring 229 when the developing unit 24 moves from the separated position to the developing position. The force receiving portion 4011 of the rail 401a balances the force applied from the first contact portion 271 and the force applied from the force receiving portion 4011. As a result, the lateral position of the developing unit 24 relative to the developing tray 401, which was rough before the pressure spring 229 applied pressure, is determined when the pressure spring 229 applies pressure. Because the force receiving portion 4011 is located inside the outer shape of the developing unit 24 and the developing tray 401, the developing unit 24 can move from the separated position to the developing position without enlarging the device to ensure a large space between the developing unit 24 and the drum unit 23. Furthermore, the positioning of the exposure unit 4 is not obstructed.

[0065] In the above-described embodiment, the guide mechanism 150 for guiding the developing unit 24 is configured to engage the guide hole 151 with the engagement pin 154, but this is not limiting and the developing unit 24 may be guided by another mechanism. For example, the positional relationship between the guide hole and the engagement pin may be reversed, the guide hole 151 may be a groove instead of a hole, and the engagement pin 154 may have another shape such as a rib. [Explanation of symbols]

[0066] 2...image carrier (photosensitive drum), 4...exposure section (exposure unit), 5...developer carrier (developing sleeve), 24...developing unit, 51...light emitting element, 52...lens array, 100...image forming apparatus, 100A...apparatus main body, 150...guide means (guide mechanism), 152...first guide section, 153...second guide section, 154...engagement section (engagement pin), 229...pressure means (pressure spring), 250...bearing section, 270...first support section (bearing section), 271...first contact section, 280...second contact section, 401...second support section (developing tray), 401a...rail section (rail), 4011...force receiving section

Claims

1. A device body, an image carrier capable of carrying a toner image; a first support portion that supports the image carrier relative to the apparatus main body; a developing unit having a developer carrier capable of carrying a developer, the developing unit being movable within the device main body between a first position where the developer carrier and the image carrier face each other with a predetermined gap so that an electrostatic latent image on the image carrier can be developed with the developer carried on the developer carrier, and a second position where the developer carrier and the image carrier are spaced apart from each other by a distance greater than the predetermined gap; a first contact portion provided on the first support portion and contacting the developing unit in a first direction perpendicular to a tangential direction of the image carrier at a position where the developer carrier and the image carrier are closest to each other at the first position; a second contact portion provided in the apparatus main body, the second contact portion contacting the developing unit at the first position in a second direction that forms an angle with the first direction in a range of 90° or more and less than 180°; a second support portion provided in the apparatus main body and supporting the developing unit so that the developing unit can be inserted in a predetermined insertion direction; a pressure applying unit configured to apply pressure to the second support portion so that the developing unit is pressed in a direction in which the developing unit contacts the first contact portion and the second contact portion, the second support portion has a force receiving portion that receives a reaction force to a force applied to the developing unit in association with the application of pressure by the pressure applying means when the developing unit moves from the second position to the first position, the force receiving portion is located inside the outer contours of the developing unit and the second support portion when viewed from the insertion direction in a state in which the developing unit is supported by the second support portion. An image forming apparatus characterized by:

2. a guide means provided at a position overlapping the developing unit as viewed from the insertion direction, the guide means guiding the developing unit within the device main body at least between the second position and just before the first position; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. the second support portion has a rail portion that guides the developing unit along the insertion direction, the developing unit has a contact portion that comes into contact with the rail portion in response to pressure applied by the pressure applying means when the developing unit moves from the second position to the first position, the force receiving portion is provided on the rail portion and comes into contact with the contact portion; 3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. an exposure unit including a plurality of light-emitting elements that emit light and a lens array having a plurality of lenses that focus the light emitted from the light-emitting elements onto the surface of the image carrier, and exposing the image carrier to light to form an electrostatic latent image; the image carrier and the developing unit are arranged adjacent to each other in the main body of the apparatus, the exposure unit is disposed between the image carrier and the developing unit; 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. Two first contact portions are provided on the support portion, At least three second contact portions are provided on the device body.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

6. the guiding means includes a first guiding portion that guides the developing unit from the second position in a direction approaching the image carrier, and a second guiding portion that guides the developing unit, which has been guided by the first guiding portion and pressed by the pressing means, so that the developing unit abuts on the two first abutment portions before abutting on the at least three second abutment portions.

6. The image forming apparatus according to claim 5,

7. the guiding means has engaging portions that are provided on the developing unit or on a member that moves integrally with the developing unit and that engage with the first guiding portion and the second guiding portion, respectively, to guide the developing unit; the second guide portion is formed so as to come into contact with the at least three second contact portions in a state in which the engagement with the engaging portion is released when the developing unit comes into contact with the two first contact portions and is then further pressed by the pressing means.

7. The image forming apparatus according to claim 6, wherein the image forming apparatus is a recording medium.

8. the developer bearing member is a cylindrical developing sleeve, the developing unit rotatably supports both end portions of the developing sleeve and has two bearing portions that respectively abut on the two first abutment portions; 8. The image forming apparatus according to claim 5, wherein the image forming apparatus is a recording medium.

9. the image carrier is a cylindrical photosensitive drum, the first direction is a direction connecting the center of the developing sleeve and the center of the photosensitive drum; 9. The image forming apparatus according to claim 8,

Images