Cover opening and closing mechanism and image forming apparatus

A cover opening and closing mechanism includes a first cover member having a first sheet placing surface and a second cover member having a second sheet placing surface. The first cover member has a first engagement part at a distal end of the first sheet placing surface, the second cover member has a second engagement part at a distal end of the second sheet placing surface so that the first sheet placing surface is flush with the second sheet placing surface. During a process in which the first cover member swings in a close direction, a first contact part of the first cover member, which is other than the first sheet placing surface, contacts to a second contact part of the second cover member, which is other than the second sheet placing surface, before the first engagement part contacts to the second engagement part.

CROSS REFERENCE

The present application is related to, claims priority from and incorporates by reference Japanese Patent Application No. 2013-222402, filed on Oct. 25, 2013.

TECHNICAL FIELD

The present invention relates to a cover opening and closing mechanism that is provided with a plurality of external covers and the like, and further relates to an image forming apparatus such as a copying machine, a printer or a facsimile that is provided with the cover opening and closing mechanism.

BACKGROUND

Conventionally, an image forming apparatus, such as a copying machine, a printer or a facsimile, that uses an electrophotographic method is provided with a photosensitive drum as an image carrier, a charging device that charges the photosensitive drum to a predetermined polarity and potential, an exposure unit that forms an electrostatic latent image on the charged photosensitive drum, a development unit that develops the electrostatic latent image as a toner image using a toner, a transfer unit that transfers the toner image to a transfer material such as a sheet, a fuser unit that fuses the toner image on the transfer material, and the like. Further, in order to allow paper jam release, insertion and removal of each unit, and the like to be easily performed, the image forming apparatus is configured in such a manner that a plurality of external covers are mounted rotatable about respective supporting point parts and interior of the image forming apparatus can be accessed from each direction (for example, see Patent Document 1).

However, in an image forming apparatus having the above-described configuration, since the respective external covers rotate about the respective supporting point parts, when the respective covers are closed, it is difficult to ensure rigidity that prevents a gap due to an external force from occurring in a joining portion between the external covers and to maintain a good appearance.

The present invention includes a first cover member that swings between open and close positions about a first rotation point, and a second cover member that swings about a second rotation point in conjunction with opening and closing of the first cover member. The first cover member has a first contact part that is in contact with the second cover member and a first engagement part that engages with a second engagement part of the second cover member. In a process in which the first cover member rotates from an open position to a close position, after the first contact part and the second cover member become in contact with each other, the first engagement part engages with the second engagement part.

According to the present invention, opening and closing of the first and second cover members are performed in conjunction with each other, and at a stage where the first cover member is closed, rigidity of a joining portion of the respective cover members can be ensured.

DETAILED DESCRIPTION OF EMBODIMENTS

First Embodiment

FIG. 1illustrates a schematic configuration diagram for describing a main part configuration of an image forming apparatus1of a first embodiment that is provided with a cover opening and closing mechanism of the present invention.

As illustrated inFIG. 1, the image forming apparatus1is internally provided with: four large units, that is, image forming units2K,2Y,2M,2C (which may be simply referred to as the image forming units2when it is not necessary to particularly distinguish between them) that respectively print black (K), yellow (Y), magenta (M) and cyan (C) images; transfer rollers10K,10Y,10M,10C (which may be simply referred to as the transfer rollers10when it is not necessary to particularly distinguish between them) that respectively oppose the image forming units2K,2Y,2M,2C; a transfer unit27that includes a carrying belt18, a belt driven roller16and a belt drive roller17, the carrying belt18carrying a recording sheet35in an endless manner; a sheet cassette24for placing therein a plurality of the recording sheets35and sequentially feeding out the recording sheets; a sheet feeding roller11for separating and feeding out one by one the recording sheets35from the sheet cassette24by simultaneously using a separation tongue piece and the like; a first carrying roller pair13and a first entrance sensor12thereof; a second carrying roller pair15and a second entrance sensor14thereof; a writing sensor21; a fuser unit28that includes a fuser roller19that internally has a heating element such as a halogen lamp and fuses developer onto the recording sheet35by applying heat and pressure to the recording sheet35, and a fuser backup roller20; an ejection sensor22; an ejection roller pair23that ejects the recording sheet35after fusion; and an ejection tray31on which the recording sheets35that are ejected by the ejection roller pair are stacked.

The image forming units2K,2Y,2M,2C are respectively configured by LED heads3K,3Y,3M,3C (which may be simply referred to as the LED heads3when it is not necessary to particularly distinguish between them), photosensitive drums4K,4Y,4M,4C (which may be simply referred to as the photosensitive drums4when it is not necessary to particularly distinguish between them), charging rollers5K,5Y,5M,5C (which may be simply referred to as the charging rollers5when it is not necessary to particularly distinguish between them), development rollers6K,6Y,6M,6C (which may be simply referred to as the development rollers6when it is not necessary to particularly distinguish between them), toner tanks7K,7Y,7M,7C, development blades8K,8Y,8M,8C, and toner supply sponge rollers9K,9Y,9M,9C.

As will be described later, a top cover41(or first cover member) covering an internal configuration is arranged on an upper portion of the image forming apparatus1. The top cover41is fixedly held by an inner plate42, which is rotatably held by a supporting point part43(first rotation point) on an apparatus body, and allows the apparatus to be opened and closed from above to replace an internal component and the like. As described above, with respect to movable or removable configuration elements such as the top cover41, a portion of the image forming apparatus1excluding those movable or removable configuration elements may be referred to as an image forming apparatus body.

Further, although not illustrated inFIG. 1, motors for rotating various rollers, rollers on carrying paths that are laid at a distance equal to or less than a minimum recording sheet interval, a solenoid for carrying path switching, and the like are provided. In particular, as the motors, as will be described later in description ofFIG. 2, a sheet feeding motor811for mainly rotating the sheet feeding roller11, a carrying motor812for rotating the carrying roller pairs13,15, a carrying belt motor801for rotating the belt drive roller17, a fuser motor793for rotating the fuser roller19, the fuser backup roller20and the ejection roller pair23, and a K-ID motor781, a Y-ID motor782, an M-ID motor783and a C-ID motor784for respectively independently driving the image forming units2K,2Y,2M,2C are provided.

With respect to X, Y and Z axes inFIG. 1, the X-axis is taken in a carrying direction when the recording sheet35passes through the image forming units2K,2Y,2M,2C; the Y-axis is taken in a rotation direction of the photosensitive drums4K,4Y,4M,4C (to be described later); and the Z-axis is taken in a direction orthogonal to the X and Y axes. Further, when the X, Y and Z axes are illustrated in other drawings (to be described later), the directions of these axes indicate common directions. That is, the X, Y and Z axes in each of the drawings indicate arrangement directions when illustrated portions in the each of the drawings configure the image forming apparatus1illustrated inFIG. 1. Here, it is assumed that the image forming apparatus1is arranged in such a manner that the Z axis is along a substantially vertical direction.

FIG. 2illustrates a block diagram illustrating a main part configuration of a control system that controls main part operation of the image forming apparatus1.

InFIG. 2, an image formation controller700is configured by a microprocessor, a ROM, a RAM, an input and output port, a counter, a timer and the like, and receives print data and a control command from a host device to perform sequence control of a whole printer part and to perform a print operation. An I/F controller710transmits printer information to the host device, and analyzes a command input from the host device and processes data received from the host device. A reception memory720stores data received from the host device for each color based on control of the I/F controller710. An operation part701is provided with an LED for indicating a state of the image forming apparatus1and a switch for providing an instruction from a user to the image formation controller700.

Various sensors702include a plurality of sensors (the first entrance sensor12, the second entrance sensor14, the writing sensor21, the ejection sensor22, and the like) for detecting a carrying position of the recording sheet35. Outputs of the respective sensors are input to the image formation controller700. An image data editing memory730is a memory for editing as image data the print data input via the I/F controller710from the host device, that is, for receiving the print data that is temporarily stored in the reception memory720and editing the printed data into image data for transmitting to the LED heads3(FIG. 1), and storing the edited image data.

A charging voltage controller740performs control for charging surfaces of the photosensitive drums4by applying voltages to the charging rollers5in the image forming units2(FIG. 1) according to an instruction from the image formation controller700. The charging voltage controller740divides control tasks according to the respective colors and has a K-charging voltage controller, a Y-charging voltage controller, an M-charging voltage controller and a C-charging voltage controller, which respectively control voltages applied to the K-charging roller5K, the Y-charging roller5Y, the M-charging roller5M and the C-charging roller5C.

A head controller750performs control for causing the LED heads3(FIG. 1) to irradiate the charged surfaces of the photosensitive drums4with light to expose the surfaces according to the image data stored in the image data editing memory730. The head controller750divides control tasks according to the respective colors and has a K-head controller, a Y-head controller, an M-head controller and a C-head controller, which respectively perform controls for transmitting the image data at predetermined timings to the K-LED head3K, the Y-LED head3Y, the M-LED head3M and the C-LED head3C.

A development voltage controller760performs control for applying voltages to the development rollers6in the image forming units2for attaching toners to electrostatic latent images that are generated by the LED heads3on the surfaces of the photosensitive drums4(FIG. 1). For this reason, the development voltage controller760has a K-development voltage controller, a Y-development voltage controller, an M-development voltage controller and a C-development voltage controller, which respectively control voltages applied to the K-development roller6K, the Y-development roller6Y, the M-development roller6M and the C-development roller6C.

A transfer voltage controller770performs control for receiving an instruction from the image formation controller700to apply voltages to the transfer rollers10(FIG. 1) for transferring toner images generated on the surfaces of the photosensitive drums4(FIG. 1) to the recording sheet35that is a recording medium. For this reason, the transfer voltage controller770has a K-transfer voltage controller, a Y-transfer voltage controller, an M-transfer voltage controller and an C-transfer voltage controller, which respectively control voltages applied to the K-transfer roller10K, the Y-transfer roller10Y, the M-transfer roller10M and the C-transfer roller10C and sequentially superimpose and transfer the respective toner images that are generated on the surfaces of the photosensitive drums4to the recording sheet35.

An image formation drive controller780performs control for receiving an instruction from the image formation controller700to drive the photosensitive drums4, the charging rollers5and the development rollers6that are provided in the image forming units2(FIG. 1). For this reason, the image formation drive controller780has a K-ID motor controller, a Y-ID motor controller, an M-ID motor controller and a C-ID motor controller, which respectively drive and control the K-ID motor781, the Y-ID motor782, the M-ID motor783and the C-ID motor784of the respective image forming units.

A fuser controller790is a controller for fusing a toner image that has been transferred to the recording sheet35, receives an instruction from the image formation controller700and a detection temperature from a fuser thermistor791that is for measuring a predetermined temperature of the fuser unit28(FIG. 1), and controls fusing temperature by turning ON and OFF voltage application to the heating element792(seeFIG. 1) that is built in the fuser unit28. Further, at a stage where temperature of the fuser unit28has risen to the predetermined temperature, the fuser controller790rotationally drives and controls the fuser motor793for rotating the fuser roller19, the fuser backup roller20and the ejection roller pair23.

A carrying belt drive controller800rotationally controls, according to an instruction from the image formation controller700, the carrying belt motor801that rotates the belt drive roller17that drives the carrying belt18of the transfer unit27(FIG. 1). A sheet feeding and carrying drive controller810rotationally drives and controls, according to an instruction from the image formation controller700, the sheet feeding motor811for rotating the sheet feeding roller11(FIG. 1) that feeds the recording sheet35and the carrying motor812for rotating the first carrying roller pair13and the second carrying roller pair15that carry the recording sheet35.

A print operation of the image forming apparatus1in the above-described configuration is described next.

The image formation controller700illustrated inFIG. 2receives via the I/F controller710a control command and print data that are transmitted from the host device and, upon receiving a print instruction from the host device, instructs the sheet feeding and carrying drive controller810about a predetermined carrying speed and causes the sheet feeding roller11illustrated inFIG. 1to rotate to feed out one sheet of the recording sheet35from the sheet cassette24and to carry the recording sheet35to the first carrying roller pair13.

The first entrance sensor12in the middle of the way is provided for such a purpose that whether or not the sheet feeding roller11has normally performed sheet feeding is detected and, when the sheet feeding roller11has not normally performed the sheet feeding, the sheet feeding operation is performed again; and for such a purpose that, after a leading edge position of the recording sheet35is detected, by controlling a driving timing of the first carrying roller pair13, the leading edge of the recording sheet35is butted against the first carrying roller pair13to eliminate a skew of the recording sheet35.

Thereafter, the recording sheet35that has been carried to the first carrying roller pair13is carried by the second carrying roller pair15to the image forming unit2K. The image forming units2K,2Y,2M,2C start rotation of the rollers at substantially the same time as the start of the sheet feeding. At this time, negative voltages (about −1000 V), which the image formation controller700instructs the charging voltage controller740to apply, are applied to the charging rollers5K,5Y,5M,5C, and the surfaces of the photosensitive drums4K,4Y,4M,4C are charged. Toners that are used in printing are supplied from the toner tanks7K,7Y,7M,7C via the sponge rollers9K,9Y,9M,9C to the development rollers6K,6Y,6M,6C, and the toners on the development rollers6K,6Y,6M,6C are formed into thin layers by the development blades8K,8Y,8M,8C and are frictionally charged.

Further, the belt drive roller17rotates at the same time as the start of the rotation of the photosensitive drums4K,4Y,4M,4C, and the carrying belt18moves at a speed same as a circumferential speed of each of the photosensitive drums4. The recording sheet35is further carried by the second carrying roller pair15and the writing sensor21is turned on. After a predetermined period of time has elapsed since the leading edge of the recording sheet35is detected here, the LED head3K starts exposure to form an electrostatic latent image on the photosensitive drum4K.

A toner image according to the electrostatic latent image that is formed here is formed on the photosensitive drum4K by the development roller6K. At the time when the recording sheet35reaches between the photosensitive drum4K and the transfer roller10K, a positive voltage (about 3000 V) is applied to the transfer roller10K, the toner image on the photosensitive drum4K is attracted to the recording sheet35side, and transfer to the recording sheet35is performed.

The image forming units2Y-2C of the other colors also sequentially similarly superimpose and transfer toner images of the respective colors. The recording sheet35to which the toner images of the respective colors are transferred is heated and pressed between the fuser roller19and the fuser backup roller20, and fusion of the transferred toner images to the recording sheet35is performed. After the fusion, after the leading edge of the recording sheet35turns on the ejection sensor22that is for monitoring heater jamming and for detecting a medium length after fusion, the recording sheet35is ejected by the ejection roller pair23and is placed in the ejection tray31.

(Configuration of Cover Opening and Closing Mechanism)

Next, a cover opening and closing mechanism of the image forming apparatus1according to the present invention is described below.

FIG. 3illustrates an external perspective view of the image forming apparatus1.FIG. 4illustrates an external perspective view of a top cover unit40when the top cover unit40is locked to a front unit45.FIG. 5illustrates a standalone external perspective view of the top cover unit40.FIG. 6illustrates an external perspective views of a top cover41.FIG. 7illustrates an external perspective view of the top cover41, viewed from another angle.FIG. 8illustrates an external perspective view of an ejection cover unit60.FIG. 9illustrates an external perspective view of the ejection cover unit60, viewed from another angle.

FIG. 3illustrates a state in which the top cover unit40that is arranged in the upper portion of the image forming apparatus1is closed. As illustrated inFIG. 5, the top cover unit40has the top cover41as a first cover member that is made of plastic resin and configures a part of external covering of the image forming apparatus1, and the inner plate42that is made of a metal plate and is arranged on an inner side of the top cover41and is integrally fixed to the top cover41by a plurality of screws.

On two sides on left and right of the inner plate42, a pair of supporting point parts43L,43R (of which only43L is illustrated in the drawings, and which may be referred to as the supporting point part43when it is not necessary to particularly distinguish between them) as a first rotation point that form a rotation shaft for rotatably holding the top cover unit40on the body of the image forming apparatus1are formed in a manner coaxially protruding leftward and rightward.

As illustrated inFIG. 1, the pair of the supporting point parts43L,43R are respectively held by the body of the image forming apparatus1on a rotation axis line parallel to the Y-axis on a back side (plus side of the X-axis) of the image forming apparatus1. Further, between the inner plate42and the body of the image forming apparatus1, a biasing member such as a torsion spring is interposed. As a result, the top cover41is rotatable about the supporting point part43between an open position (to be described later) and a close position illustrated inFIG. 3, and is biased in an opening direction.

As illustrated inFIG. 5, on a rotation front end side of the inner plate42, a pair of opening parts44L,44R are formed.FIG. 10is for describing a lock mechanism of the top cover unit40that is due to the opening part44L and a lock bar46provided on the front cover45.

As illustrated inFIG. 10, at a position where a claw part47of the lock bar46can be fitted into the opening part44L of the inner plate42by rotation to allow the top cover41to be engaged at the close position, a supporting point part48of the lock bar46is rotatably held by the front unit45(FIG. 4) that is fixed on the body of the image forming apparatus1. The lock bar46is biased in an arrow A direction, in which the claw part47fits into the opening part44L of the inner plate42, by a biasing member such as torsion spring interposed between the lock bar46and the front unit45.

Therefore, to unlock the top cover41that is engaged at the close position by the lock mechanism, the lock bar46in an engaging position (illustrated by a solid line inFIG. 10), where the claw part47of the lock bar46is fitted into the opening part44L of the inner plate42to engage the top cover41to the close position, is moved by an operator against a biasing force to a release position (illustrated by a solid line inFIG. 10), where the claw part47is disengaged from the opening part44L of the inner plate42. Here, the lock mechanism of the opening part44L is described. The same lock mechanism is also provided for the opening part44R.

As illustrated inFIGS. 6 and 7, the top cover41has: an outer frame part50that is arranged in a substantially square shape; a sheet placing surface51(or first sheet placing surface) having a shaft side end part52that is formed in a manner slightly curved downwardly from a front end side (minus side of the X-axis) of the outer frame part50toward the supporting point part43(rotation shaft; seeFIGS. 4 and 5) and is parallel to a rotation axial direction; rib-shaped left and right contact parts53L,53R (which may be referred to as the contact parts53(or first contact part) when it is not necessary to distinguish between them), as a first contact part, that are continuously formed on a pair of side wall parts that are formed in a perpendicular direction between an upper portion of the outer frame part50and left and right ends of a curved portion of the sheet placing surface51, and extend more than the shaft side end part52toward a shaft direction; and an opening49surrounded by a shaft side upper end part54(seeFIG. 4) of the outer frame part50, the shaft side end part52and the left and right contact parts53L,53R.

Next, with reference toFIGS. 8 and 9, the ejection cover unit60is described. The ejection cover unit60, together with the top cover41, is a part of the external covering of the image forming apparatus1that is made of plastic resin, and is configured by an ejection frame62and an ejection cover61as a second cover member. As illustrated inFIG. 3, when the ejection cover unit60is provided on the body of the image forming apparatus1, the ejection cover unit60is positioned at the opening49portion of the top cover41. As will be described later, the ejection cover unit60is configured in such a manner that in conjunction with an opening and closing operation of the top cover41, the ejection cover61opens and closes between an open position (to be described later) and a close position illustrated inFIGS. 8 and 9. As will be described later, when the top cover41and the ejection cover61are in the close position, the opening49of the top cover41is blocked by the ejection frame62and the ejection cover61.

The ejection frame62is provided with a regulatory wall part63that faces a trailing edge side in an ejection direction of the recording sheet35that is ejected from the image forming apparatus1and is placed on the sheet placing surface51, a pair side wall parts64L,64R that extend from two left and right end parts of the regulatory wall part63to a downstream side (minus side of the X-axis) of sheet ejection direction, and a fixed bottom part65that similar extends in the same direction from a lower end part of the regulatory wall part63. Further, on outer sides of the side wall parts64L,64R and at positions near front ends of the fixed bottom part65, left and right posts66L,66R (which may be referred to as the posts66when it is not necessary to particularly distinguish between them), as a second rotation supporting point, are respectively formed in a manner protruding outwardly.

The ejection cover61is provided with a sheet placing surface71(or second sheet placing surface) that is formed in a flat plate shape, and a pair of side surface parts72L,72R that extend in a perpendicular direction from two left and right end parts of the sheet placing surface71and respectively oppose the side wall parts64L,64R of the ejection frame62on outer sides of the side wall parts64L,64R. Further, on outer sides of the side surface parts72L,72R and at positions near the fixed bottom part65side of the sheet placing surface71, a pair of shaft holes73L,73R are formed into which the pair of the posts66L,66R are respectively rotatably fitted.

Further, on two end parts on a front end side (opposite to the side where the shaft holes73L,73R are formed) of the sheet placing surface71, a receiving part67L in contact with the left side contact part53L of the top cover41and a receiving part67R in contact with the contact part53R of the top cover41are formed (the receiving parts67L,67R may be referred to as the receiving parts67when it is not necessary to particularly distinguish between them). The receiving parts67correspond to a second contact part.

Therefore, the ejection cover61is rotatably held by the ejection frame62and is configured rotatable between a close position, at which, as illustrated inFIG. 8, the fixed bottom part65of the ejection frame62and the sheet placing surface of the ejection cover61are flush with and adjacent to each other, and an open position, at with, as illustrated inFIG. 13to be described later, the regulatory wall part63and the sheet placing surface71oppose each other. Further, the ejection cover61is biased in an arrow B direction (FIG. 8), which is an opening direction, by a torsion spring68(FIG. 13) as a biasing member that is interposed between the ejection cover61and the ejection frame61and, in a natural state, is maintained at the open position as illustrated inFIG. 13. The open position is illustrated inFIG. 16Awith reference Q1.

FIG. 11illustrates a state in which the ejection cover unit60is arranged at a predetermined position of the image forming apparatus1and the top cover41is locked at the close position by the lock mechanism. As illustrated inFIG. 11, in this case, an upper end part of the regulatory wall part63of the ejection cover unit60is flush with the shaft side upper end part54(FIG. 4) of the opening49of the top cover41; the left and right contact parts53L,53R of the top cover41and the left and right side wall parts64L,64R of the ejection frame62are flush with each other; and a front end part74formed in the rotation axial direction of the ejection cover61overlaps on an upper side with the shaft side end part52(FIG. 7) of the top cover41so that the sheet placing surface71of the ejection cover61in the close position and the sheet placing surface51of the top cover41are flush with each other. Further, in this case, as will be described later, the contact parts53L,53R of the top cover41and the receiving parts67L,67R of the ejection cover61are in a state of being in contact with each other.

Next, relation between the top cover41and the ejection cover61during opening and closing of the top cover41is further explained.

FIG. 12illustrates state in which, in the cover opening and closing mechanism of the present embodiment, the top cover41and the ejection cover61are both in the open position.FIG. 13illustrates an enlarged view of the ejection cover unit60illustrated inFIG. 12.FIGS. 14 and 15illustrate external perspective views illustrating a positional relation between the top cover41and the ejection cover61in a process in which the top cover41is closed.FIGS. 16A-18Dillustrate operation explanatory diagrams of the top cover41and the ejection cover61in the process in which the top cover41is moving toward the close position (P3).

FIGS. 16A and 16Billustrate operation explanatory diagrams illustrating a state viewed from a minus side of the Y-axis in which the contact part53R of the top cover41and the receiving part67R of the ejection cover61become in contact with each other during a process in which the top cover41is moving to be closed.FIG. 16Aillustrates, using solid lines, respective states of the top cover41at four places from a rotation position P0, which is the open position, to a rotation position P3, which is the close position, when the top cover41rotates in directions of arrows D, E about the supporting point part43(equivalent to a rotation shaft).FIG. 16Aalso illustrates, using solid lines, respective states of the ejection cover61at three places from a rotation position Q1at the open position to a rotation position Q3at the close position, when the ejection cover61rotates in directions of arrows B, C about the post66(equivalent to a rotation shaft).

As illustrated inFIG. 16, when the top cover unit40(FIG. 12) is rotated, for example, by an operator, from a state (state ofFIG. 12) in which the top cover41and the ejection cover61are at the rotation positions P0and Q1, which are both the open positions, in the arrow E direction against the biasing force so as to be closed, along with this rotation, the top cover41illustrated inFIG. 16rotates in the arrow E direction from the rotation position P0, which is equivalent to the open position, to the rotation position P3, which is equivalent to the close position. Due to a bias force toward direction B, the ejection cover61is positioned at rotation position Q1with a normal state.

In the rotation process in the arrow E direction, at the rotation position P1, the contact part53R of the top cover41becomes in contact with the receiving part67R of the ejection cover61in the rotation position Q1(the open position), and thereafter, the ejection cover61rotates in the arrow C direction against the biasing force thereof. After the contact part53R of the top cover41and the receiving part67R of the ejection cover61become in contact with each other at the rotation position P1of the top cover41, and until the close position P3, an area where the contact part53R of the top cover41and the receiving part67R of the ejection cover61can be in contact with each other gradually increases and a contact state is ensured. These contact lengths d1to d3of the area are illustrated inFIG. 16B. The contact length d1corresponds to the open position P1. The contact length d2corresponds to the position P2, and the contact length d3corresponds to the close position P3. This is because in a situation where the open position (rotation position P1) of the ejection cover61at the start of the engagement is inclined more toward a counterclockwise direction than a vertically upward direction, the rotation shaft (supporting point part43, or first rotation point) of the top cover41is at least positioned more on a plus side of the X-axis than the rotation shaft (post66or second rotation point) of the ejection cover61. A shortest distance L0between the supporting point part43and the post66is illustrated inFIG. 18B. A distance in X-direction is with Lx, and a distance in Z-direction is with Lz as shown inFIG. 18A.

Here, the relation between the contact part53R of the top cover41and the receiving part67R of the ejection cover61is described. However, the contact part53L of the top cover41and the receiving part67L of the ejection cover61, which are the other sides of the pairs, are configured to have a similar relation and similarly interact with each other.

FIG. 17illustrates an operation explanatory diagram illustrating a relation between the shaft side end part52of the top cover41and the front end part74of the ejection cover61when the top cover41and the ejection cover61are respectively in the rotation positions P1, Q1.FIG. 14illustrates an external perspective view of the top cover unit40illustrating a state in this case.

As illustrated in these figures, at the stage where the contact part53of the top cover41and the receiving part67of the ejection cover61begin to be in contact with each other, the shaft side end part52of the sheet placing surface51of the top cover41and the front end part74of the sheet placing surface71of the ejection cover61are still in a separated state.

FIG. 18Aillustrates an operation explanatory diagram illustrating a state viewed from the minus side of the Y-axis in which the shaft side end part52of the sheet placing surface51of the top cover41and the front end part74of the sheet placing surface71of the ejection cover61oppose (engage) each other during a process in which the top cover41is closed.FIG. 18Aillustrates, using solid lines, respective states of the top cover41at four places from the rotation position P0, which is the open position, to the rotation position P3, which is the close position, when the top cover41rotates in the directions of the arrows D, E about the supporting point part43(equivalent to a rotation shaft).

FIG. 18Aalso illustrates, using solid lines, respective states of the ejection cover61at three places from the rotation position Q1at the open position to the rotation position Q3at the close position, when the ejection cover61rotates in the directions of the arrows B, C about the posts66(equivalent to a rotation shaft). The rotation positions P0-P3, Q1-Q3are common to the respective rotation positions indicated using the same reference numeral symbols illustrated inFIG. 16.FIG. 18Billustrates a partial enlarged view of a rectangular surrounding portion M inFIG. 18A; andFIG. 18Cillustrates a partial enlarged view of a rectangular surrounding portion M inFIG. 18A.

InFIG. 18A, a movement path PT52as a first movement path is a movement path of the shaft side end part52of the sheet placing surface51of the top cover41, and a movement path PT74as a second movement path is a movement path of the front end part74of the sheet placing surface71of the ejection cover61. As described above, in the process in which the top cover41rotates from the open position in the arrow E direction, the contact part53of the top cover41becomes in contact with the receiving part67of the ejection cover61at the rotation position P1, and thereafter, along with the rotation of the top cover41in the arrow E direction, the ejection cover61rotates in the arrow C direction.

The rotation position P2is a rotation position of the top cover41when the shaft side end part52of the top cover41reaches a cross point XP1of the movement paths PT52, PT74. As the movement paths PT52, PT74illustrate, the shaft side end part52of the top cover41moves on an outer side of an arc of the movement path PT74of the front end part74of the sheet placing surface71until the top cover41reaches the rotation position P2, and, after passing the rotation position P2, moves on an inner side of the arc of the movement path PT74until reaching the rotation position P3(close position). The front end part74of the sheet placing surface71extends in a radial direction with respect to the rotation shaft (post66) of the ejection cover61.

As illustrated inFIG. 18B, the configuration is provided in such a manner that, in the process in which the top cover41is closed, a bent part52aas a first engagement part of the shaft side end part52of the top cover41reaches the cross point of the movement paths PT52, PT74first, and thereafter, the front end part74of the sheet placing surface71of the ejection cover61reaches the cross point XP1. A clearance between the bent part52aand the front end part74that occurs at the stage where the top cover41reaches the rotation position P2is T1. Further, in this case, the sheet placing surface51of the top cover41and the sheet placing surface71of the ejection cover61are substantially flush with each other.

Therefore, as illustrated inFIG. 18B, a cross section of the shaft side end part52of the top cover41has a crank-like step part with respect to the sheet placing surface51. The bent part52aof the shaft side end part52is displaced toward a downstream side in the direction in which the top cover41is closed (in the arrow E direction), with respect to the sheet placing surface51and further, as illustrated inFIG. 17, with respect to the contact part53, and extends toward the supporting point part43(equivalent to the rotation shaft). On the other hand, as illustrated inFIG. 17, the front end part74as a second engagement part of the sheet placing surface71of the ejection cover61is positioned on an upstream side in the direction in which the ejection cover61is closed (in the arrow B direction), with respect to the receiving part67.

When the top cover41further rotates from the rotation position P2in the arrow E direction, the bent part52aof the top cover41and the front end part71of the ejection cover61that is positioned on a more upstream side than the bent part52ain the direction in which the ejection cover61is closed (in the arrow B direction) begin to overlap in a tangential direction of the arc of the movement path PT74of the front end part74of the sheet placing surface71.

At the stage where the top cover41reaches the rotation position P3corresponding to the close position of the top cover unit40, as illustrated inFIG. 18C, the bent part52aof the top cover41and the front end part71of the ejection cover61are formed in such a manner that the bent part52aand the front end part71overlap for a required amount and oppose (engage) each other across a gap w.FIG. 15illustrates an external perspective view of the top cover unit40illustrating a state in this case.

In order for the movement paths PT52, PT74to cross each other, it is necessary to offset the rotation shaft (post66) of the ejection cover61with respect to the rotation shaft (supporting point part43) of the top cover41. However, in the situation where the cross point is set to the rotation position Q2at which the ejection cover61is inclined in the counterclockwise direction more than the vertically upward direction, this condition is satisfied when the rotation shaft (supporting point part43) of the top cover41is at least positioned more on the plus side of the X-axis (on the side away from the cross point XP1) than the rotation shaft (post66) of the ejection cover61. Here, in order to obtain a sufficient crossing angle and a sufficient overlap amount between the bent part52aof the top cover41and the front end part74of the ejection cover61, a distance Lx parallel to the X-axis (distance in a horizontal direction) between the rotation shaft (supporting point part43) and the rotation shaft (post66) is set.

When the top cover41reaches the rotation position P3, the top cover unit40is in the close position and, as described above, is locked at this close position by fitting the claw part47of the lock bar46(FIG. 10) provided on the front cover45into the opening part44of the inner plate42. On the other hand, as illustrated inFIG. 16, the ejection cover61remains at the rotation position Q3, which is the close position, in a state in which the receiving part67of the ejection cover61presses against the contact part53of the top cover41, by the biasing force due to the torsion spring68(FIG. 13).

Therefore, in the state in which the top cover unit40is in the close position, the outer periphery of the top cover unit40is supported by a side cover80(FIG. 3) of the body of the image forming apparatus1and the front unit45. In particular, a rotation front end part side of the top cover unit40that is in a position farthest from the rotation shaft (supporting point part43) is supported by the front unit45. Therefore, a high rigidity is obtained.

On the other hand, in the state in which the ejection cover61is in the close position, when the ejection cover61is subjected to, for example, a force F in a downward direction (the arrow C direction illustrated inFIG. 16) as illustrated by an arrow F as illustrated inFIG. 11, the ejection cover61tends to rotate in the same direction against the biasing force. However, as can be seen fromFIG. 18C, the front end part74of the ejection cover61is in contact with the bent part52aof the shaft side end part52of the top cover41and the rotation in the same direction is inhibited. As a result, even when the ejection cover61is subjected to an external force, the state in which the sheet placing surface51of the top cover41and the sheet placing surface71of the ejection cover61are flush with each other is maintained.

Comparison Example

FIGS. 19-23Billustrate reference diagrams of a cover opening and closing mechanism that is described as comparative example.FIG. 19illustrates a state in which an ejection cover unit560is arranged at a predetermined position of an image forming apparatus and a top cover541is locked at a close position by a lock mechanism.FIG. 20illustrates an external perspective view of the ejection cover unit560.FIG. 21illustrates an external perspective view of the top cover unit540, viewed obliquely from below.

In the cover opening and closing mechanism as the comparative example, similar to the cover opening and closing mechanism of the first embodiment, the top cover unit540is formed by a top cover541and an inner plate542, which are integrated, and, on the inner plate542, a supporting point part543is formed as a rotation shaft when the inner plate542is rotatably held on a body of the image forming apparatus.

An ejection cover561of the ejection cover unit560is rotatably held using a post566that is formed on an ejection frame562as a rotation shaft, is biased in an opening direction by a torsion spring568, and, similar to the cover opening and closing mechanism of the first embodiment, opens and closes in conjunction with opening and closing of the top cover unit540.FIG. 20illustrates a state in which the ejection cover561is closed against a biasing force of the torsion spring568.

A pair of contact parts553are formed on the top cover541. Similar to the cover opening and closing mechanism of the first embodiment, the pair of the contact parts553are respectively in contact with a pair of receiving parts567that are formed on the ejection cover561and open and close the ejection cover561that is biased in the opening direction.

FIG. 22illustrates an operation explanatory diagram illustrating a state viewed from the minus side of the Y-axis in which the contact parts553of the top cover541the receiving parts567of the ejection cover561become in contact with each other during a process in which the top cover541is closed.FIG. 22illustrates, using solid lines, respective states of the top cover541at a rotation position P0, which is an open position, and at a rotation position P3, which is a close position, when the top cover541rotates about the supporting point part543(equivalent to a rotation shaft).FIG. 22also illustrates, using solid lines, respective states of the receiving parts567of the ejection cover561at a rotation position Q0, which is an open position, and at a rotation position Q3, which is a close position, when the ejection cover561rotates about the posts566(equivalent to a rotation shaft).

As illustrated inFIG. 22, when the top cover unit540(FIG. 21) is rotated, for example, by an operator, from a state in which the top cover541and the ejection cover561are at the rotation positions P0and Q1, which are both the open positions, so as to be closed, along with this rotation, the top cover541rotates from the rotation position P0, which is equivalent to the open position, to the rotation position P3, which is equivalent to the close position. During this rotation, the contact parts553of the top cover541press against the receiving parts567of the ejection cover561, and the ejection cover561is rotated against the biasing force thereof to the rotation position Q3, which is the close position.FIG. 19illustrates a state when the top cover541and the ejection cover561are both closed.

FIG. 23Aillustrates an operation explanatory diagram illustrating a state viewed from the minus side of the Y-axis in which a shaft side end part552of the top cover541and a front end part574of the ejection cover561oppose (engage) each other during a process in which the top cover541is closed.FIG. 23Aillustrates, using solid lines, respective states of the top cover541at the rotation position P0, which is the open position, and at the rotation position P3, which is the close position, when the top cover541rotates about the supporting point part543(equivalent to a rotation shaft).

FIG. 23Aalso illustrates, using solid lines, respective states of the ejection cover561at a rotation position Q0, which is the open position, and at the rotation position Q3, which is the close position, when the ejection cover561rotates about the posts566(equivalent to a rotation shaft). The rotation positions P0-P3, Q1-Q3are common to the respective rotation positions indicated using the same reference numeral symbols illustrated inFIG. 22.FIG. 23Billustrates an enlarged view of a rectangular surrounding portion inFIG. 23A.

InFIG. 23A, a movement path of the shaft side end part552of the top cover541and a movement path of the front end part574of the ejection cover561are indicated using dotted lines. As described above, in the process in which the top cover541rotates in the closing direction, along with the rotation of the top cover541in the closing direction, the ejection cover561rotates in the closing direction.

As the respective movement paths illustrate, the shaft side end part552of the top cover541and the front end part574of the ejection cover561cross each other in the respective rotation processes, and while crossing each other, the ejection cover561and the top cover541reach the close positions.FIG. 19illustrates a state when the top cover541and the ejection cover561are both closed, andFIG. 23Billustrates a partial enlarged view of the shaft side end part552of the top cover541and the front end part574of the ejection cover561in this case.

As illustrated inFIG. 23B, a sheet placing surface551of the top cover541and a sheet placing surface571of the ejection cover561are substantially flush with each other, and a bent part574athat is formed in a crank-like shape overlaps, on a downstream side in the closing direction of the top cover541, with the front end part552of the top cover541.

When the top cover541reaches the rotation position P3, similar to the above-described cover opening and closing mechanism of the first embodiment, the top cover unit540is locked to the close position and, as illustrated inFIG. 22, the ejection cover561remains at the rotation position Q3, which is the close position, in a state in which the receiving parts567of the ejection cover561press against the contact parts553of the top cover541, due to the biasing force of the torsion spring568(FIG. 20).

Therefore, in the cover opening and closing mechanism of the comparative example, as illustrated inFIG. 19, in a state in which the ejection cover561is in the close position, when the ejection cover561is subjected to, for example, a downward force F as illustrated by an arrow F, as illustrated by dotted lines inFIG. 23A, the ejection cover561rotates in the same direction against the biasing force and a gap Wp occurs in a joining portion of the top cover541and the ejection cover561.

As described above, according to the cover opening and closing mechanism of the present embodiment, when the top cover41is in the close position in which the top cover41is closed, the front end part74of the ejection cover61is positioned on a more upstream side (the arrow B direction) in the direction in which the ejection cover61is closed than the bent part52aof the shaft side end part52of the top cover41. Therefore, even when an external force is applied to the front end part74of the ejection cover61, rotation is restricted by the bent part52aof the top cover41, so that a gap does not occur in the joining portion and a good appearance is obtained.

Second Embodiment

FIG. 24illustrates state in which, in a cover opening and closing mechanism that is adopted by a second embodiment based on the present invention, a top cover141(or first cover member) and an ejection cover61(or second cover member) are both in open positions.FIG. 25illustrates an external perspective view of a top cover unit140, viewed obliquely from above when the top cover unit140is turned upside down.FIG. 26illustrates a partial enlarged view of a portion surrounded with dotted lines inFIG. 25.FIGS. 27-29Billustrate operation explanatory diagrams of the top cover141and the ejection cover61in a process in which the top cover141is closed.

The image forming apparatus that adopts this cover opening and closing mechanism is mainly different from the above-described image forming apparatus that adopts the cover opening and closing mechanism of the first embodiment illustrated inFIG. 12in that guide ribs190are provided at three places including two end parts and a central part of a shaft side end part152of a sheet placing surface151(FIGS. 29A and 29B) of the top cover141. Therefore, for the image forming apparatus that adopts this opening and closing mechanism, parts that are in common with the above-described image forming apparatus1of the first embodiment are denoted using the same reference numeral symbols, or are omitted from the drawings and their description is omitted, and differences are mainly described. Further, a main part configuration of the image forming apparatus of the present embodiment, excluding the top cover141, is in common with the main part configuration of the image forming apparatus1of the first embodiment illustrated inFIG. 1. Therefore,FIG. 1is referenced as needed.

FIG. 27illustrates an operation explanatory diagram illustrating a state viewed from the minus side of the Y-axis in which the contact part53R of the top cover141and the receiving part67R of the ejection cover61become in contact with each other during the process in which the top cover141is closed.FIG. 27illustrates, using solid lines, respective states of the top cover141at four places from the rotation position P0, which is the open position, to the rotation position P3, which is the close position, when the top cover141rotates in the directions of the arrows D, E about the supporting point part43(equivalent to a rotation shaft).FIG. 27also illustrates, using solid lines, respective states of the ejection cover61at three places from the rotation position Q1at the open position to the rotation position Q3at the close position, when the ejection cover61rotates in the directions of the arrows B, C about the posts66(equivalent to a rotation shaft).

As illustrated inFIG. 27, when the top cover unit140(FIG. 24) is rotated, for example, by an operator, from a state (state ofFIG. 12) in which the top cover141and the ejection cover61are at the rotation positions P0and Q1, which are both the open positions, in the arrow E direction against the biasing force so as to be closed, along with this rotation, the top cover141illustrated inFIG. 27rotates in the arrow E direction from the rotation position P0, which is equivalent to the open position, to the rotation position P3, which is equivalent to the close position.

In the rotation process in the arrow E direction, at the rotation position P1, the contact part53R of the top cover141becomes in contact with the receiving part67R of the ejection cover61in the rotation position Q1(the open position), and thereafter, the ejection cover61rotates in the arrow C direction against the biasing force thereof.

Here, the relation between the contact part53R of the top cover141and the receiving part67R of the ejection cover61is described. However, the contact part53L of the top cover141and the receiving part67L of the ejection cover61, which are the other sides of the pairs, are configured to have a similar relation and similarly interact with each other.

FIG. 28illustrates an operation explanatory diagram illustrating a relation between the shaft side end part152of the top cover141and the front end part74of the ejection cover61when the top cover141and the ejection cover61are respectively in the rotation positions P1, Q1.

As illustrated inFIG. 28, at the stage where the contact part53of the top cover141and the receiving part67of the ejection cover61begin to be in contact with each other, the shaft side end part152of the sheet placing surface151of the top cover141and the front end part74of the sheet placing surface71of the ejection cover61are still in a separated state.

FIG. 29Aillustrates an operation explanatory diagram illustrating a state viewed from the minus side of the Y-axis in which the shaft side end part152of the sheet placing surface151of the top cover41and the front end part74of the sheet placing surface71of the ejection cover61oppose (engage) each other during the process in which the top cover141is closed.FIG. 29Aillustrates, using solid lines, respective states of the top cover141at four places from the rotation position P0, which is the open position, to the rotation position P3, which is the close position, when the top cover141rotates in the directions of the arrows D, E about the supporting point part43(equivalent to a rotation shaft).

FIG. 29Aalso illustrates, using solid lines, respective states of the ejection cover61at three places from the rotation position Q1at the open position to the rotation position Q3at the close position, when the ejection cover61rotates in the directions of the arrows B, C about the posts66(equivalent to a rotation shaft). The rotation positions P0-P3, Q1-Q3are common to the respective rotation positions indicated using the same reference numeral symbols illustrated inFIG. 16.FIG. 29Billustrates a partial enlarged view of a rectangular surrounding portion inFIG. 29A.

InFIG. 29A, a movement path PH152is a movement path of a front end part191of the guide rib190that is formed on the shaft side end part152of the sheet placing surface151of the top cover141, and the movement path PT74is the movement path of the front end part74of the sheet placing surface71of the ejection cover61. In the embodiment, the shaft side end part152may be considered as a first engagement part of the invention, and the front end part191of the guide rib190may be defined as a part of the side end part152, corresponding to the first engagement part. As described above, in the process in which the top cover141rotates from the open position in the arrow E direction, the contact part53of the top cover141engages with the receiving part67of the ejection cover61at the rotation position P1, and thereafter, along with the rotation of the top cover141in the arrow E direction, the ejection cover61rotates in the arrow C direction. The contact part53corresponds to a first contact part, and the receiving part67corresponds to a second contact part.

Here, conditions for forming the shaft side end part152of the top cover141are the same as conditions for forming the shaft side end part52of the top cover41of the first embodiment. As illustrated inFIGS. 26,29A and29B, the guide rib190is a plate-shaped member that is provided on the shaft side end part152is on a side of the arrow E direction (direction in which the top cover141is closed) of the shaft side end part152of the top cover141and extends in the same direction. The front end part191of the guide rib190is arranged closer to the supporting point part43than a front end part of a bent part152ais, and a linear guide side192is formed from the front end part of the bent part152ato the front end part191.

The rotation position P2′ is a rotation position of the top cover141when the front end part191of the guide rib190of the top cover141reaches a cross point of the movement paths PT152, PT74. As the movement paths PT152, PT74illustrate, the front end part191of the guide rib190of the top cover141moves on an outer side of an arc of the movement path PT74of the front end part74of the sheet placing surface71until the top cover141reaches the rotation position P2′, and, after passing the rotation position P2′, moves on an inner side of the arc of the movement path PT74until reaching the rotation position P3(close position). The cross point means an intersection formed by two front ends of the top cover141and the ejection cover61. In this view, the cross point inFIG. 29Acan be considered as a first cross point (XP1).

The configuration is provided in such a manner that, in the process in which the top cover141is closed, the bent part152aof the shaft side end part152of the top cover141reaches the cross point of the movement paths PT152, PT74first, and thereafter, the front end part74of the sheet placing surface71of the ejection cover61reaches the cross point. A clearance between the bent part152aand the front end part74that occurs at the stage where the front end part191of the guide rib190reaches the rotation position P2′ first is T2. Further, in this case, the sheet placing surface151of the top cover141and the sheet placing surface71of the ejection cover61are substantially flush with each other.

Therefore, as illustrated inFIG. 29B, a cross section of the shaft side end part152of the top cover141has a crank-like step part with respect to the sheet placing surface151. The bent part152aof the shaft side end part152is displaced toward a downstream side in the direction in which the top cover141is closed (in the arrow E direction), with respect to the sheet placing surface151and further, as illustrated inFIG. 28, with respect to the contact part53, and extends toward the supporting point part43(equivalent to the rotation shaft). On the other hand, as illustrated inFIG. 28, the front end part74as a second engagement part of the sheet placing surface71of the ejection cover61is positioned on an upstream side in the direction in which the ejection cover61is closed (in the arrow B direction), with respect to the receiving part67.

When the top cover141further rotates from the rotation position P2′ in the arrow E direction, first the guide rib190of the top cover141, followed by the bent part152aof the top cover141, and the front end part71of the ejection cover61that is positioned on a more upstream side (the arrow B direction) in the direction in which the ejection cover61is closed than the guide rib190and the bent part152a, begin to sequentially overlap in a tangential direction of the arc of the movement path PT74of the front end part74of the sheet placing surface71. At the stage where the top cover141reaches the rotation position P3, which is the close position, as illustrated inFIG. 29B, the bent part152aof the top cover141and the front end part71of the ejection cover61are formed in such a manner that the bent part152aand the front end part71overlap for a required amount and oppose (engage) each other across a gap w.

Here, when the above-described rotation position P2of the first embodiment that is illustrated inFIG. 18Aand the rotation position P2′ of the present embodiment are compared, as illustrated inFIG. 29A, the rotation position P2′ is moved to the arrow D side of the rotation position P2by an amount by which the front end part191of the guide rib190is arranged closer to the supporting point part43than the front end part of the bent part152a.

Therefore, a clearance T2between the bent part152aand the front end part74at the rotation position P2′ of the top cover141is ensured to be larger than the above-described clearance T1between the bent part52aand the front end part74in the first embodiment that is illustrated inFIG. 18B. Here, the clearance is a measure of allowance when the front end part74of the ejection cover61is displaced in the arrow C direction (direction in which the ejection cover61is closed), for example, as illustrated by dotted lines inFIG. 29A, due to warping or deformation. The larger the clearance is, the more the allowance increases.

For example, even when the ejection cover61is deformed as illustrated by the dotted lines inFIG. 29A, in the process in which the top cover141further rotates from the rotation position P2′ in the arrow E direction, the front end part74of the ejection cover61becomes in contact with the linear guide side192of the guide rib190and is guided to the bent part152aof the top cover141. At the stage where the top cover141reaches the rotation position P3, which corresponds to the close position of the top cover unit140, the front end part74of the ejection cover61remains at the rotation position Q3in a state in which the deformation is corrected. Thus, the front end part74of the ejection cover61can be prevented from being positioned more on the arrow C side than the shaft side end part152of the top cover141.

When the top cover141reaches the rotation position P3, the top cover unit140is in the close position and, as described above, is locked at this close position by fitting the claw part47of the lock bar46(FIG. 10) provided on the front cover45into the opening part44of the inner plate42. On the other hand, as illustrated inFIG. 27, the ejection cover61remains at the rotation position Q3, which is the close position, in a state in which the receiving part67of the ejection cover61presses against the contact part53of the top cover141, by the biasing force due to the torsion spring68(FIG. 13).

On the other hand, in the state in which the ejection cover61is in the close position, when the ejection cover61is subjected to, for example, a force F in a downward direction (the arrow C direction illustrated inFIG. 27) as illustrated by an arrow F as illustrated inFIG. 11, the ejection cover61tends to rotate in the same direction against the biasing force. However, as illustrated inFIGS. 29A and 29B, the front end part74of the ejection cover61is in contact with the bent part152aof the shaft side end part152of the top cover141and the rotation in the same direction is inhibited. As a result, even when the ejection cover61is subjected to an external force, the state in which the sheet placing surface151of the top cover141and the sheet placing surface71of the ejection cover61are flush with each other is maintained.

As described above, according to the cover opening and closing mechanism of the present embodiment, when the top cover141is in the close position in which the top cover141is closed, the front end part74of the ejection cover61is positioned on a more upstream side (the arrow B direction) in the direction in which the ejection cover61is closed than the bent part152aof the shaft side end part152of the top cover141. Therefore, even when an external force is applied to the front end part74of the ejection cover61, rotation is restricted by the bent part152aof the top cover141, so that a gap does not occur between the overlapping portions and a good appearance is obtained.

Further, even in the state in which front end part74of the ejection cover61is deformed in the direction in which the ejection cover61is closed due to warping or deformation, since the top cover unit140is closed while the front end part74is in contact with the guide side192of the guide rib190, the opening and closing operation of the top cover unit140becomes more smooth.

In the above-described embodiments, examples are described in which the present invention is applied to an image forming apparatus as a printer. However, the present invention is not limited to this, but can also be applied to image forming apparatuses such as a copying machine and a facsimile, and further to apparatuses in other fields.

Additional Descriptions

In this application, front ends often mean distal ends that are positioned at the farthest portions from rotational axes.

Specs, Preferred Ranges and Formulas of Embodiment

In this section, specs and preferred ranges of the specs are described. As shownFIG. 16A, the first engagement path (PT52) of the first engagement part (52) has first engagement radius R52around the first rotation point (43). The second engagement path (PT74) of the second engagement part (74) has second engagement radius R74.FIG. 16Aillustrates that the first contact path (PT53) of the first contact part (53) has first contact radius R53and the second contact path (PT67) of the second contact part (67) has second contact radius R67, both of which swing around the second rotation point (66). The distances between the two rotation points (43and66) are referred with Lx in X direction and Lz in Z direction. Lx and Lz are respectively horizontal and vertical inFIG. 18A. The direct distance is referred by L0shown inFIG. 18D.

The first engagement path (PT52, PT152) and the second engagement path (PT74) intersect. The point is defined as a first cross point (XP1). The first cross point may be defined as a point where a distal end of the first sheet placing surface (51) comes to contact to the second sheet placing surface (71). Without a guide rib, the first cross point is illustrated inFIG. 18B. With a guide rib, the first cross point is illustrated inFIG. 29A.

Regarding the first and second contact parts (53,67), the first contact path (PT53) and the second contact path (PT67) intersect. The point is defined as a second cross point (XP2). The second cross point may be defined as a point where a distal end of any part other than the second sheet placing surface (71) comes to contact to any part other than the first sheet placing surface (71).

The contact lengths between the first contact part and the second contact part are referred by d1to d3according to the positions, seeFIG. 16B. Rotation angles of the first engagement part (52) are referred by θ1and θ2. Rotation angle θ1corresponds to an angle that is measured from open position P1to middle P2. Rotation angle θ2corresponds to an angle that is measured from middle position P2to close position P3. Rotation angles of the second engagement part (74) are referred by θ3and θ4. Rotation angle θ3corresponds to an angle that is measured from open position P1to middle P2. Rotation angle θ4corresponds to an angle that is measured from middle position P2to close position P3.

A first height difference (H1) is defined as a height gap between the first engagement path (PT52) and the second engagement path (PT74). The gap is measured on a vertical line (VL) passing through the second rotation point (66), seeFIG. 18DA second height difference (H2) is defined as another height gap between the first contact path (PT53) and the second contact path (PT67). The gap is measured on a vertical line (VL) passing through the second rotation point (66), seeFIG. 16B.

=As one example, actual specs of the above elements are shown below.

In order to compact the mechanism, it is preferred that the first rotation point is positioned above the second rotation point in Z-direction (or vertical direction). Also, the radius R67is preferably smaller than the radius R53.

In order that a rotation load of the second cover member (61) is less likely to affect a rotation load of the first cover member (41) at a timing of the second contact part (67)'s contact to the first contact part (53), it is preferred that length Lx is less than radius R53. Also, first height difference H1is greater than zero.

In order to intersect the first and second embodiment paths (PT52, PT74), it is preferred to satisfy the formula below:
R67>R53−L0, and
R74<R52<R53.

In order to obtain a space for engagements, it is preferred to satisfy the formulas below:
H1>H2,
θ3>θ4,
θ1>θ2.

Further, length Lx is preferably ranged within 30% to 70% of radius R53. Length Lz is preferably ranged within 5% to 30% of length Lx. Radius R67is preferably ranged within 60% to 90% of radius R53. Radius R74is preferably ranged within 60% to 91% of radius R52.