JP2012181464A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that successfully prevents the subsequent operation from being mistakenly executed in a state where lock operation of a belt lock, which is detachable to a body frame, has been remained forgotten.SOLUTION: A lock member is configured to be capable of switching a fixed state of a body frame of an image forming apparatus and a belt unit, between a lock state where the body frame and the belt unit are undetachably fixed and an unlock state where both of the two can be easily detached. Detection means detects whether the operation state of the lock member is the lock state or the unlock state. Notification means notifies the occurrence of trouble if the detection means detects that the lock member is in the unlock state.

Description

  The present invention relates to an image forming apparatus configured to form an image on a recording medium while conveying a sheet-like recording medium.

  As this type of image forming apparatus, those disclosed in Japanese Patent Application Laid-Open Nos. 2007-101728 and 2009-75402 are known. Such an image forming apparatus includes a belt unit that is detachable with respect to a main body frame constituting the apparatus main body. The belt unit includes a sheet conveying belt for conveying a sheet-like recording medium (paper) or an intermediate transfer belt for transferring a toner image to the recording medium. In the device disclosed in Japanese Patent Application Laid-Open No. 2007-101728, after the belt unit is placed at a predetermined position of the main body frame, the device user operates the lock member, so that both of them are securely fixed (locked). And the release (unlock) is performed.

  In this type of image forming apparatus, the lock member may be unlocked when the apparatus user performs apparatus maintenance. Here, when the apparatus user forgets the lock operation of the lock member and completes the maintenance (closes the cover or the like), various problems may occur.

  For example, when the cover is closed and the image forming operation is performed in the unlocked state, even if the normal operation is performed immediately after the start, there is a deviation in paper conveyance and electrostatic latent image development thereafter. Is normal. Alternatively, when the cover is closed in the unlocked state, members inside the apparatus main body interfere with each other to generate unnecessary frictional resistance, which may impair smooth operation.

  The present invention has been made to address such problems. That is, an object of the present invention is to satisfactorily prevent the following operation from being erroneously performed while the locking operation of the belt unit that is detachable from the main body frame is forgotten.

  The image forming apparatus of the present invention is configured to form an image on a recording medium while conveying the sheet-like recording medium. The image forming apparatus includes a main body frame, a belt unit, a plurality of image forming units, a lock member, a detection unit, and a notification unit. The main body frame is configured to support each part inside the image forming apparatus.

  The belt unit includes a belt, a plurality of belt conveyance rollers, and a belt unit frame. The belt unit frame is configured to be detachable from the main body frame. The plurality of belt conveyance rollers are rotatably supported by the belt unit frame. The belt is formed in an endless shape so as to form a closed curve in a side view. The plurality of belt conveyance rollers are provided to move the surface of the belt along the closed curve while supporting the belt.

  The image forming unit is provided to form an image on the recording medium, and includes, for example, a photosensitive drum. The plurality of image forming units are arranged in the main body frame along the surface of the belt (for example, along the horizontal direction). The plurality of image forming units may be configured to be exchangeable by being attached to and detached from the main body frame.

  The belt unit may be provided so as to convey the recording medium along the arrangement direction of the plurality of image forming units while carrying the recording medium on the surface of the belt.

  The belt unit may be disposed below the plurality of image forming units. The belt may be bridged in a substantially oval shape in a side view on the plurality of belt conveyance rollers.

  An upper cover that can be opened and closed with respect to the main body frame may be provided above the plurality of image forming units. In this case, specifically, for example, the upper cover is swingably supported at one end in the arrangement direction of the plurality of image forming units. The upper cover may be provided with an exposure unit for exposing the photosensitive drum.

  The lock member has an attachment / detachment switching portion and an operation portion. The attachment / detachment switching unit is configured to be able to switch a fixed state of the belt unit and the main body frame between a locked state in which the belt unit and the main body frame are fixed so as not to be detachable from each other and an unlocked state in which the belt unit and the main body frame are easily detached. The operation unit is a member operated to switch between the locked state and the unlocked state, and is formed integrally with the attachment / detachment switching unit. For example, the operation unit is provided so as to protrude toward the image forming unit.

  The attachment / detachment switching unit may have an engagement piece. The engaging piece is formed so as to engage with the main body frame in the locked state and to be disengaged from the main body frame in the unlocked state. Specifically, for example, the engagement piece is removably inserted into an engagement hole provided in the main body frame in the unlocked state, and the engagement piece in the main body frame is in the locked state. It is formed so as to engage with the peripheral portion of the engagement hole. In this case, the lock member is switched about the locked state and the unlocked state by rotating about the predetermined rotation center axis penetrating the engagement hole when the operation portion is operated. It is configured.

  The detection means is provided to detect an operation state of the lock member. Specifically, for example, when the engagement piece is provided to form a predetermined electric circuit on the main body frame side when engaged with the main body frame in the locked state, the detection is performed. The means is provided to detect the operation state based on the formation state of the electric circuit. The notification means is provided to notify an abnormality when the detection means detects that the operation state of the lock member is the unlocked state.

  In the image forming apparatus of the present invention having such a configuration, the detection unit detects whether the lock member is in the locked state or the unlocked state. The notification means notifies an abnormality when the detection means detects that the lock member is in the unlocked state. Therefore, it is possible to satisfactorily prevent the next operation from being erroneously performed while the unlocked state is maintained.

1 is a schematic diagram illustrating an overall configuration of a laser printer that is an image forming apparatus according to an embodiment of the present invention. It is a figure which expands and shows the structure of the periphery of the locking member shown by (ii) in FIG. It is a figure which shows the operation state of the locking member shown by FIG. It is the schematic which shows the structure for detecting the state of the locking member shown by FIG. FIG. 5 is a schematic view showing a modification of the configuration around the lock member shown in FIG. 4. It is the schematic which shows the other modification of the structure of the periphery of the locking member shown by FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

<Overall configuration of laser printer>
FIG. 1 is a schematic diagram showing the overall configuration of a laser printer 1 which is an image forming apparatus according to an embodiment of the present invention. Here, (i) in FIG. 1 shows a side sectional view of the laser printer 1. The laser printer 1 transports a sheet P, which is a sheet-like recording medium, along a sheet transport path PP (paper path) inside the laser printer 1 as a fine powdery dry developer on the sheet P. The non-magnetic one-component toner image (hereinafter referred to as “toner image”) is formed.

  In the following description, in (i) in FIG. 1, the direction in which the paper P is transported along the paper transport path PP (that is, the tangential direction at an arbitrary position of the paper transport path PP) is referred to as “paper transport direction. ". Further, the right side in the figure is referred to as “front side”, and the left side in the figure is referred to as “rear side”. Therefore, the left-right direction in FIG. Furthermore, the width direction of the laser printer 1, which is a direction perpendicular to the left-right direction and the up-down direction in FIG. Called. This paper width direction is a direction perpendicular to the paper transport direction and the thickness direction of the paper P. The paper width direction is also referred to as “main scanning direction”.

  Referring to (i) in FIG. 1, the laser printer 1 includes a transfer unit 2, a paper cassette 3, and an image forming unit 4. The transfer unit 2 is disposed above the paper cassette 3 and below the image forming unit 4.

  The image forming unit 4 includes a plurality of image forming units 4a (4Y, 4M, 4C, 4K) arranged horizontally along the front-rear direction in a side sectional view, and an image forming unit frame 4b that supports them. I have. That is, the plurality of image forming units 4Y, 4M, 4C, and 4K are arranged in this order in the paper transport direction. The image forming units 4Y, 4M, 4C, and 4K are configured to form toner images with yellow, magenta, cyan, and black toners, respectively.

  The image forming unit 4a includes a photosensitive drum 4c, a charger 4d, and a process cartridge 4e. The plurality of photosensitive drums 4c are provided in parallel to each other. The photosensitive drum 4c is a cylindrical member having a photosensitive layer formed on the outer peripheral portion thereof, and is rotatably supported by the image forming unit frame 4b. That is, the photosensitive drum 4c is driven to rotate about an axis parallel to the paper width direction, so that the electrostatic latent image carrying surface that is the peripheral surface thereof moves in a direction perpendicular to the paper width direction. Yes.

  The photosensitive drum 4c is disposed so as to face the transfer unit 2. That is, the plurality of photosensitive drums 4c are arranged so as to face portions that are formed horizontally along the front-rear direction in a side sectional view in the paper transport path PP. The charger 4d is attached to the image forming unit frame 4b at a position facing the electrostatic latent image carrying surface in order to uniformly charge the electrostatic latent image carrying surface.

  The process cartridge 4e is configured to be detachable from the image forming unit frame 4b. The process cartridge 4e contains toner of each color. The process cartridge 4e is mounted so as to face a portion of the photosensitive drum 4c opposite to the portion opposite to the sheet conveyance path, whereby an electrostatic latent image carrying surface that is a peripheral surface of the photosensitive drum 4c. The electrostatic latent image formed on the toner is developed with toner.

  The transfer unit 2, the paper cassette 3, and the image forming unit 4 (image forming unit frame 4 b) are configured to be detachable (easily detachable) from the main body 10 of the laser printer 1. In the present embodiment, the plurality of image forming units 4a (4Y, 4M, 4C, 4K) are integrally attached to and detached from the main body unit 10. Specifically, the main body unit 10 includes a main body frame 11. The main body frame 11 is a box-shaped member made of a metal plate, and is configured to detachably support the above-described units and the like, and to support other mechanism parts used for image formation in a fixed manner. Has been.

  The paper cassette 3 is provided below the main body 10 and is detachably attached to the main body 10 (main body frame 11) by sliding in the front-rear direction. In the paper cassette 3, a large number of sheet-like papers P are stored in a stacked state. The image forming unit frame 4 b is configured to be detachable from the main body frame 11 above the transfer unit 2.

  The transfer unit 2 corresponding to the “belt unit” of the present invention is disposed above the paper cassette 3 and below the image forming unit 4. The transfer unit 2 is configured to be attached and detached along the vertical direction with the image forming unit 4 (image forming unit frame 4 b) removed from the main body 10.

  (Ii) in FIG. 1 is a perspective view showing the external appearance of the main body frame 11 and the transfer unit 2 attached thereto. As shown in this figure, the main body frame 11 has a pair of transfer unit support tongues 11a. The transfer unit support tongue 11a is a flat plate-like member provided in parallel to the horizontal plane to support the transfer unit 2, and is formed integrally with the other parts of the main body frame 11 without seams.

  The main body frame 11 is covered with a casing 12. The casing 12 has an upper cover 12a that is opened and closed when the transfer unit 2 and the image forming unit 4 (process cartridge 4e) are attached and detached. The upper cover 12 a is supported so as to be rotatable (swingable) about a hinge 12 b provided at the rear end of the casing 12. The upper cover 12a is provided with a display unit 13 corresponding to the “notification means” of the present invention.

  In the main body 10, a paper feed unit 14, an exposure unit 15, a fixing unit 16, and a paper discharge unit 17 are provided. The paper feed unit 14 picks up the uppermost one of the many sheets P stacked in the sheet cassette 3, and transfers the picked up sheet P between the transfer unit 2 and the image forming unit 4. It is comprised so that it may convey toward.

  The exposure unit 15 generates a laser beam having a predetermined wavelength that is modulated in accordance with image information (ON / OFF is controlled) and irradiates the photosensitive drum 4c with the laser beam. 4 is provided on the upper cover 12a. The fixing unit 16 presses and heats the paper P on which the toner image is transferred at a position where the transfer unit 2 and the image forming unit 4 face each other, thereby fixing the toner image on the paper P. It is provided downstream of the position in the paper transport direction. The paper discharge unit 17 is provided on the downstream side of the fixing unit in the paper transport direction so as to discharge the paper P on which the toner is fixed through the fixing unit 16 to the outside of the main body unit 10.

<Detailed configuration of transfer unit>
The transfer unit 2 includes a transfer unit frame 20. The transfer unit frame 20 is a member made of a metal plate and formed in a substantially rectangular shape in plan view, and is configured to be detachable from the main body frame 11. At both ends of the transfer unit frame 20 in the paper width direction, the supported tongue pieces 20a are formed at positions facing the transfer unit support tongue pieces 11a at the upper side. When the transfer unit frame 20 is placed on the main body frame 11, the supported tongue piece 20a is provided so as to be in contact with the transfer unit support tongue piece 11a.

  As shown in (ii) in FIG. 1, a lock member 21 is detachably mounted at a position where the transfer unit supporting tongue piece 11a and the supported tongue piece 20a are stacked. The lock member 21 is configured to be able to switch the fixed state of the transfer unit 2 and the main body frame 11 between a locked state in which the transfer unit 2 and the main body frame 11 are fixed so as not to be detachable from each other, and an unlocked state in which the detachment is easy. Details of the configuration of the lock member 21 will be described later.

  The transfer unit 2 is provided so as to face each of the plurality of image forming units 4a (4Y, 4M, 4C, 4K) arranged as described above. The transfer unit 2 transfers the toner image from each image forming unit 4a to the paper P while transporting the paper P rearward along the position formed horizontally in the above-mentioned side sectional view in the paper transport path PP. Is configured to do. Specifically, the transfer unit frame 20 supports a plurality of transfer rollers 22, a pair of belt conveyance rollers 23, and a single sheet conveyance belt 24.

  The transfer roller 22 is disposed in parallel with the paper width direction and is supported so as to be rotatable about an axis parallel to the paper width direction. Further, the transfer roller 22 is connected to a predetermined power source (not shown) so that a predetermined bias voltage for electrostatically attracting toner to the paper P side is applied. The transfer roller 22 is provided so as to face the photosensitive drum 4c with the paper transport path PP interposed therebetween. That is, in the present embodiment, the same number of transfer rollers 22 as the number of image forming units 4a are formed horizontally along the front-rear direction in the side cross-sectional view in the paper transport path PP as described above. It is arranged along the place.

  One of the pair of belt conveyance rollers 23 is disposed further upstream in the paper conveyance direction than the transfer roller 22 facing the image forming unit 4Y located on the most upstream side. The other of the pair of belt transport rollers 23 is disposed further downstream in the paper transport direction than the transfer roller 22 facing the image forming unit 4K located on the most downstream side. The pair of belt conveyance rollers 23 are arranged in parallel with the paper width direction, and are supported rotatably about an axis parallel to the paper width direction. One or the other of the pair of belt transport rollers 23 is rotationally driven by a drive source such as a motor (not shown).

  The sheet conveying belt 24 is formed in an endless shape so as to form a closed curve in a side view, and is spanned between a pair of belt conveying rollers 23 so that the inner surface thereof is in contact with the peripheral surface of the transfer roller 22. ing. The outer surface of the portion of the sheet conveying belt 24 disposed along the plurality of transfer rollers 22 between the pair of belt conveying rollers 23 is a photoconductor provided in each of the image forming units 4Y, 4M, 4C, and 4K. It is provided so as to face the drum 4c across the paper transport path PP. Such a portion is laid in a substantially planar shape so as to constitute a portion that is formed horizontally along the front-rear direction in a side sectional view as described above in the paper transport path PP. The sheet conveying belt 24 is configured such that the outer surface of the sheet conveying belt 24 moves on a substantially elliptical track in a side sectional view by rotational driving of the pair of belt conveying rollers 23.

  As described above, the transfer unit 2 is configured to convey the sheet P along the arrangement direction of the plurality of image forming units 4 a while carrying the sheet P on the outer surface of the sheet conveying belt 24.

<Lock member>
FIG. 2 is an enlarged view showing a configuration around the lock member 21 shown in (ii) of FIG. Here, (i) in FIG. 2 is an enlarged perspective view of the lock member 21, and (ii) is an enlarged plan view of the transfer unit support tongue piece 11a and the supported tongue piece 20a to which the lock member 21 is attached. FIG.

  Referring to FIG. 2 below, the lock member 21 includes an operation unit 211 and a pair of attachment / detachment switching units 212. The operation unit 211 is a plate-like member that is operated to switch between the above-described locked state and unlocked state, and is formed integrally with the pair of attachment / detachment switching units 212. In the present embodiment, the lock member 21 is integrally formed of a conductive synthetic resin. As shown in FIG. 1, the operation unit 211 is provided so as to protrude toward the image forming unit 4. The attachment / detachment switching unit 212 is provided at the lower end of the operation unit 211 and at both ends in the width direction.

  The attachment / detachment switching unit 212 is inserted into an engagement hole H (see (ii) in the figure) provided so as to penetrate the transfer unit support tongue 11a and the supported tongue 20a, and the operation unit 211 is inserted. By being operated, the fixed state of the transfer unit frame 20 and the main body frame 11 can be switched between the locked state and the unlocked state. Specifically, the attachment / detachment switching unit 212 includes a leg portion 212a and an engagement piece 212b.

  The leg portion 212a is a rod-like member provided so as to extend downward from the lower end portion of the operation portion 211, and is formed to be elastically deformable. The engagement piece 212b is a plate-like member provided so as to extend in the horizontal direction from the upper portion of the leg portion 212a. In the present embodiment, the attachment / detachment switching unit 212 is formed symmetrically with respect to the rotation center axis C of the lock member 21 parallel to the vertical direction.

  FIG. 3 is a diagram illustrating an operation state of the lock member 21 illustrated in FIG. 2. As shown in FIG. 3, the engaging piece 212b is inserted into the engaging hole H in the unlocked state (see (i) in FIG. 3), and then the operating portion 211 is operated to rotate the above-mentioned rotation. It is formed so as to engage with a portion around the engagement hole H in the transfer unit support tongue 11a when it is locked by rotating around the central axis C (see (iii) in FIG. 3). ing. The pair of legs 212a is elastically deformed inward as shown in (ii) in FIG. 3 in an intermediate state between the locked state and the unlocked state, so that the locked state and the unlocked state are Are arranged so as to generate an operational click feeling.

<Detection mechanism>
FIG. 4 is a schematic diagram illustrating a configuration for detecting the state of the lock member 21 illustrated in FIG. 3. As shown in FIG. 4, in the present embodiment, in the main body frame 11, below the transfer unit support tongue 11a, other members in the main body frame 11 (for example, (i in FIG. ) Are provided with ground path members 501 and 502 which are metal plate-like members for grounding the fixing unit 16 and the like shown in FIG. The ground path member 501 is grounded. A gap 503 is provided between the ground path member 501 and the ground path member 502 so as to penetrate the attachment / detachment switching portion 212 of the lock member 21.

  As shown in FIG. 4, the lock member 21 is grounded by the pair of legs 212 a contacting the ground path member 501 and the ground path member 502 in the locked state (see (ii) in the figure). While the path member 501 and the ground path member 502 are electrically connected, the pair of legs 212a are separated from the ground path member 501 and the ground path member 502 in the unlocked state (see (i) in the figure). Thus, the electrical connection between the ground path member 501 and the ground path member 502 is cut off. A detecting unit 504 (for example, a current detecting unit) for detecting whether or not such an electrical connection is formed is interposed in an earth path constituted by the earth path member 501 and the earth path member 502.

<Operation / Effects of Configuration of Embodiment>
In such a configuration, the engagement piece 212b engages with a portion around the engagement hole H in the transfer unit support tongue piece 11a in the locked state, as shown in (iii) in FIG. Thereby, the transfer unit frame 20 (transfer unit 2) and the main body frame 11 are fixed favorably. At this time, as shown in FIG. 4 (ii), the pair of legs 212a abut against the ground path member 501 and the ground path member 502, respectively, so that the ground path member 501 and the ground path member 502 are An electrical connection is formed.

  On the other hand, in the unlocked state, as shown in FIG. 3I, the engagement between the engagement piece 212b and the portion around the engagement hole H in the transfer unit support tongue 11a is released. Is done. Thus, the transfer unit frame 20 (transfer unit 2) can be easily detached from the main body frame 11 (however, even in this state, the transfer unit 2 is placed on the main body frame 11). Is unchanged.) At this time, as shown in (i) in FIG. 4, the pair of legs 212 a is separated from the ground path member 501 and the ground path member 502, whereby the electrical connection between the ground path member 501 and the ground path member 502 is performed. Connection is broken.

  The detecting means 504 detects the operation state of the lock member 21 by detecting whether the electrical connection between the ground path member 501 and the ground path member 502 is formed or blocked. The detection result is displayed on the display unit 13 shown in (i) of FIG. Therefore, for example, when the upper cover 12a is about to be closed or an instruction to start an image forming operation is issued in the unlocked state, an error notification is given by the display unit 13.

  Therefore, according to this configuration, the operation unit 211 and the image forming unit 4 are effectively prevented from interfering with each other when the upper cover 12a is completely closed in the unlocked state. Alternatively, according to such a configuration, the image forming operation is performed in the unlocked state, so that an image forming defect such as a color shift caused by a minute positional shift of the transfer unit 2 with respect to the main body frame 11 during the image formation occurs. Is effectively prevented.

<Example of modification>
It should be noted that the above-described embodiments are merely examples of typical embodiments of the present invention that the applicant has considered to be the best at the time of filing of the present application. Therefore, the present invention is not limited to the above-described embodiment. Therefore, it goes without saying that various modifications can be made to the above-described embodiment within the scope not changing the essential part of the present invention.

  Hereinafter, some typical modifications will be exemplified. Needless to say, the modifications are not limited to those listed below. In addition, all or a part of the embodiments and modifications may be applied in combination with each other as appropriate within a technically consistent range. The present invention (especially those expressed functionally and functionally in the constituent elements constituting the means for solving the problems of the present invention) is based on the above-described embodiment and the description of the following modifications. Should not be interpreted as limited. Such a limited interpretation is unacceptable and improper for imitators, while improperly harming the applicant's interests (rushing to file under a prior application principle).

  The application target of the present invention is not limited to a laser printer capable of forming a multicolor image. For example, the present invention can be suitably applied to a so-called electrophotographic image forming apparatus such as a monochromatic laser printer and monochromatic and color copiers. The present invention can also be suitably applied to a developer supply apparatus in an image forming apparatus that does not use a photoreceptor (multi-stylus electrode system, ion flow system, toner jet system, etc.).

  The plurality of image forming units 4a (4Y, 4M, 4C, 4K) may be detachable individually instead of being integrally attached to and detached from the main body unit 10.

  The lock member 21 may be attached to the engagement hole H after the transfer unit 2 is placed on the main body frame 11 when the transfer unit 2 is attached to or detached from the main body frame 11. It may be mounted on the transfer unit frame 20 (supported tongue piece 20a) side.

  FIG. 5 is a schematic view showing a modification of the configuration around the lock member 21 shown in FIG. As shown in FIG. 5, the lock member 21 may be interposed in a power supply circuit for a transfer bias to the transfer roller 22. In this case, one of the pair of leg portions 212a of the lock member 21 is provided so as to contact the transfer roller shaft S in the locked state (see (ii) in the figure), and the other is attached to the main body frame 11. It is provided so as to abut on the provided power supply member 505.

  In such a configuration, the pair of leg portions 212a of the lock member 21 are separated from the transfer roller shaft S and the power supply member 505 in the unlocked state (see (i) in the figure). In this case, the power supply circuit for the transfer bias from the power supply member 505 to the transfer roller 22 is cut off. On the other hand, in the locked state (see (ii) in the figure), the pair of leg portions 212a of the lock member 21 abuts on the transfer roller shaft S and the power supply member 505, respectively. In this case, a power supply circuit for a transfer bias from the power supply member 505 to the transfer roller 22 is formed. The detection unit 504 detects whether the power supply circuit is formed or shut off.

  FIG. 6 is a schematic view showing another modification of the configuration around the lock member 21 shown in FIG. As shown in FIG. 6, the detection means 506 may be an optical detection means. In this case, as shown in FIG. 6, the detecting means 506 may also serve as a so-called “registration sensor” for detecting a registration mark for color misregistration correction.

  Specifically, as shown in FIG. 6, the detection means 506 is a peripheral surface of a portion of the paper transport belt 24 that is wound around the belt transport roller 23 and has a substantially semi-cylindrical shape. An end portion in the width direction is irradiated with a measurement beam (see a broken line in the figure), and the reflected light is detected.

  A swing lever 507 that is a member that swings about an axis parallel to the paper width direction is disposed in the vicinity of the detection unit 506. The swing lever 507 includes a first arm portion 507a, a blocking portion 507b provided at the tip of the first arm portion 507a, and a second arm portion 507c connected to the base end of the first arm portion 507a. Have. The swing lever 507 is supported so as to be swingable around a connection position between the first arm portion 507a and the second arm portion 507c.

  In the locked state (see (ii) in the drawing), the swinging lever 507 is biased by the leg portion 212a via the biasing spring 508 by the leg portion 212a, so that the blocking portion 507b becomes the above-described measuring beam. In the unlocked state (see (i) in the figure), the second arm portion 507c is released from the biased state, so that the blocking portion 507b becomes the above-described measurement beam. It is configured and arranged so as to be arranged at a blocking position for blocking the optical path.

  In such a configuration, the second arm portion 507c is biased by the leg portion 212a via the biasing spring 508 in the locked state (see (ii) in the figure), so that the position of the blocking portion 507b is as described above. This is a registration position that does not block the optical path of the measurement beam. At this time, the detection unit 506 can detect the reflected light. On the other hand, in the unlocked state (see (i) in the figure), the bias of the second arm portion 507c by the leg portion 212a is released, so that the position of the blocking portion 507b moves along the optical path of the measurement beam. It becomes the blocking position to block. At this time, the detection unit 506 cannot detect the reflected light. Therefore, the operation state of the lock member 21 is favorably detected based on the detection level by the detection unit 506.

  Instead of the paper conveying belt 24 in the above-described embodiment, an intermediate transfer belt or a photosensitive belt that can carry a toner image on the surface thereof may be used. In this case, the configuration of the process cartridge 4e and the paper feed unit 14, the arrangement of the fixing unit 16 and the paper discharge unit 17, and the form of the paper transport path PP based on these are appropriately changed from those in the above-described embodiment.

  Other modifications not specifically mentioned are naturally included in the technical scope of the present invention without departing from the essential part of the present invention. In addition, in each element constituting the means for solving the problems of the present invention, elements expressed functionally and functionally include the specific structures disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function. Furthermore, the contents of other applications and publications cited in this specification (including the specification and drawings) are included in a part of this specification, and are within a scope that is technically consistent as necessary. Can be incorporated by reference.

DESCRIPTION OF SYMBOLS 1 Laser printer 10 Main body part 11 Main body frame 11a Transfer unit support tongue piece 12 Casing 12a Upper cover 13 Display part 14 Paper feed part 15 Exposure part 16 Fixing part 17 Paper discharge part 2 Transfer unit 20 Transfer unit frame 20a Supported tongue piece 21 Lock member 211 Operation part 212 Attachment / detachment switching part 212a Leg part 212b Engagement piece 22 Transfer roller 23 Belt transport roller 24 Paper transport belt 4 Image forming unit 4a Image forming part 4b Image forming unit frame 4c Photosensitive drum 4d Charger 4e Process cartridge 501 Ground path member 502 Ground path member 503 Gap 504 Detection means 505 Power supply member 506 Detection means 507 Swing lever 507a First arm portion 507b Blocking portion 507c Second arm portion 508 Energizing spring H Engagement hole P For paper PP Transport path S transfer roller shaft

JP 2007-101728 A JP 2009-75402 A

Claims (11)

In an image forming apparatus configured to form an image on a recording medium while conveying a sheet-like recording medium,
A main body frame that supports each part inside the image forming apparatus;
A belt formed in an endless shape so as to form a closed curve in a side view, a plurality of belt transport rollers for moving the surface of the belt along the closed curve while supporting the belt, and the plurality of belts A belt unit having a belt unit frame configured to rotatably support the transport roller and to be detachable from the main body frame;
A plurality of image forming units arranged along the surface of the belt in the main body frame to form an image on the recording medium;
An attachment / detachment switching portion configured to be able to switch between a locked state in which the belt unit and the main body frame are fixed to each other so as not to be detachable and an unlocked state in which the belt unit and the main body frame can be easily detached, and the attachment / detachment switching portion are integrally formed. And an operation unit that is operated to perform switching between the locked state and the unlocked state, and a lock member,
Detecting means for detecting an operation state of the lock member;
An informing means for informing an abnormality when the detecting means detects that the operation state of the locking member is the unlocked state;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The image forming apparatus, wherein the operation unit is provided so as to protrude toward the image forming unit. An image forming apparatus according to claim 1 or 2, wherein
The attachment / detachment switching portion includes an engagement piece that engages with the main body frame in the locked state and is disengaged from the main body frame in the unlocked state. apparatus. The image forming apparatus according to claim 3,
The engagement piece is removably inserted into an engagement hole provided in the main body frame in the unlocked state, and a portion around the engagement hole in the main body frame in the locked state Formed to engage with,
The lock member is configured to switch between the locked state and the unlocked state by rotating about a predetermined rotation center axis penetrating the engagement hole when the operation unit is operated. An image forming apparatus. An image forming apparatus according to claim 3 or 4, wherein
The engagement piece is provided so as to form a predetermined electric circuit on the main body frame side when engaged with the main body frame in the locked state,
The image forming apparatus according to claim 1, wherein the detection unit is configured to detect the operation state based on a formation state of the electric circuit. An image forming apparatus according to any one of claims 1 to 5,
The plurality of image forming units are arranged along a horizontal direction,
The belt unit is disposed below the plurality of image forming units,
The image forming apparatus according to claim 1, wherein the belt is stretched between the plurality of belt conveying rollers in a substantially oval shape in a side view. The image forming apparatus according to claim 6.
An image forming apparatus, further comprising: an upper cover provided to be openable and closable with respect to the main body frame above the plurality of image forming units. An image forming apparatus according to claim 7,
The image forming apparatus, wherein the upper cover is swingably supported at one end in the arrangement direction of the plurality of image forming units. An image forming apparatus according to claim 7 or 8, wherein
The image forming unit includes a photosensitive drum,
An image forming apparatus according to claim 1, wherein the upper cover is provided with an exposure unit for exposing the photosensitive drum. An image forming apparatus according to any one of claims 1 to 9,
The image forming apparatus, wherein the plurality of image forming units are configured to be exchangeable by being attached to and detached from the main body frame. An image forming apparatus according to any one of claims 1 to 10,
The image forming apparatus, wherein the belt unit is provided so as to convey the recording medium along the arrangement direction of the plurality of image forming units while carrying the recording medium on the surface of the belt.

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