JP4206854B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium.

Image forming apparatuses such as copiers and printers include an open / close cover that can be opened and closed with respect to the main body of the image forming apparatus for paper jam processing and process cartridge replacement.
As an image forming apparatus of this type, a heating roller and a pressure roller (fixing device) provided for fixing a toner image on a sheet are separated from each other in conjunction with the opening and closing cover. There is known an image forming apparatus that can easily remove a jammed paper while being sandwiched between a heating roller and a pressure roller (for example, Patent Document 1).
JP 2002-189377 A

  However, since the urging force is applied to the heating roller and the pressure roller in the direction in which they are pressed against each other, it is necessary to hold the opening / closing cover against this urging force in order to keep the opening / closing cover fully open. The workability of removing the jammed paper was poor.

  Further, when the opening / closing cover is displaced in the opening direction, the urging force is applied to the opening / closing cover. The opening / closing cover is opened until there is enough space to enter, and when this gap is formed, an operation may be performed in which the opening / closing cover is fully opened by putting a hand in the gap and grasping the end of the opening / closing cover. In this case, there is a problem that it takes time to open the opening / closing cover because the opening / closing cover must be opened by grasping a portion other than this end until the end of the opening / closing cover is grasped.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that facilitates opening an opening / closing cover and an operation performed by fully opening the opening / closing cover.

  The image forming apparatus according to claim 1, wherein the image forming apparatus according to claim 1 is provided in a fixing mechanism for fixing the toner image on the paper by pressing the paper on which the toner image is formed. A pressing member for generating a pressing force in the fixing mechanism by being urged by the fixing mechanism, and a cover that is disposed on the front side of the main body of the image forming apparatus and that can be opened to the front side with the lower side as a fulcrum. The process unit for forming the toner image on the paper is opened and closed to be attached to and detached from the process unit mounting portion facing the paper transport path inside the image forming apparatus, and covers the process unit mounting portion in the closed state. An opening / closing cover, a link mechanism for displacing the pressing member in a direction opposite to the pressing force against the biasing force of the biasing means in linkage with an opening operation of the opening / closing cover; A holding means for holding the open state of the open / close cover against the biasing force of the biasing means, and an open force that acts in the opening direction of the open / close cover are generated on the open / close cover in the fully closed state. An initial opening force generating means; and a lock mechanism that can resist the opening force of the initial opening force generating means and that can lock the open / close cover in the fully closed state and can be unlocked by a predetermined operation. Features.

  According to the image forming apparatus configured as described above, the lock is released when the operator performs a predetermined operation on the lock mechanism when the open / close cover is fully closed. When the lock is released, the opening / closing cover is opened according to the opening force by the opening force of the initial opening force generating means. After that, when the operator displaces the opening / closing cover further in the opening direction against the urging force by the urging means, the holding means holds the opening state of the opening / closing cover against the urging force. .

  For this reason, the opening / closing cover is opened according to the opening force by a predetermined unlocking operation on the locking mechanism, and a gap is formed between the opening / closing cover and the image forming apparatus main body. The operator can perform an operation of putting the hand in the gap and grasping the end of the opening / closing cover to fully open the opening / closing cover, so that the opening operation of the opening / closing cover is facilitated. Further, since the open state is maintained even if the operator does not hold down the opening / closing cover, the process cartridge can be easily replaced and a paper jam can be handled.

Further, at the time of unlocking, the opening / closing cover may be opened to a position corresponding to the magnitude of the opening force of the initial opening force generating means, but if the opening force of the initial opening force generating means fluctuates, The opening position of the opening / closing cover will fluctuate. Accordingly, as described in claim 1 , the biasing means biases the opening / closing cover when the opening / closing cover is displaced beyond a preset intermediate position from the fully closed state, and the pressing force Is preferably larger than the opening force.

  According to the image forming apparatus configured as described above, the opening / closing cover is opened to the preset intermediate position by the opening force, and when the intermediate position is exceeded, a pressing force larger than the opening force is applied. Release by stops in the middle position.

For this reason, the fluctuation | variation of the open position of an opening-and-closing cover by the fluctuation | variation of opening force can be suppressed.
In the image forming apparatus according to claim 1, further as described in claim 2, wherein the cover is preferably provided with a sheet tray which is mounted for insertion of the sheet into the image forming apparatus.

  According to the image forming apparatus configured as described above, the weight of the opening / closing cover is increased by the weight of the paper tray. Therefore, when the opening / closing cover is displaced in the opening direction against the urging force of the urging means. The operator can reduce the force for opening the opening / closing cover by the weight of the paper tray, and can facilitate the operation of the opening / closing cover.

In the image forming apparatus according to claim 1 or 2 , it is preferable that the link mechanism and the press contact member are configured to be separable as described in claim 3 .
According to the image forming apparatus configured as described above, when the pressure contact member is replaced, the pressure contact member can be easily replaced without removing the link mechanism.

In the image forming apparatus according to any one of claims 1 to 3, further as described in claim 4, in conjunction with the opening and closing of the cover, detachable process unit in the image forming apparatus main body A process-side drive shaft for receiving a driving force for performing the operation of each part from the apparatus main body side, and a main-body side drive shaft for transmitting a rotational force applied from a drive source on the apparatus main body side to the drive shaft. Switching means for switching between connection and release, a movable member that reciprocates along the opening / closing direction of the opening / closing cover in conjunction with the operation of the switching means, and the opening / closing cover in conjunction with reciprocation of the movable member Detecting means for detecting an open / closed state, and the initial opening force generating means may comprise a spring attached to the switching means or the movable member.

  According to the image forming apparatus configured as described above, the springs used in the switching unit and the detecting unit can be used in the initial opening force generating unit, so that the parts constituting the image forming apparatus can be saved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In this embodiment, a laser printer will be described as an example of the image forming apparatus.
First, the overall configuration of the laser printer of this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the laser printer, and FIG. 2 is a sectional side view of the main part showing the configuration of the laser printer.

  A laser printer 1 shown in FIG. 1 has a substantially box-shaped main body case 2, and a display panel 3 is disposed on the upper surface of the main body case 2. The display panel 3 is provided with a liquid crystal display, and displays the operating state of the laser printer 1 with characters and graphics. Further, the display panel 3 is provided with operation switches such as printing start and printing stop, and various operations are performed by pressing these switches.

  A paper feed cassette 4 is disposed below the main body case 2, and the paper feed cassette 4 can store a plurality of sheets and is configured to be inserted into and withdrawn from the main body case 2. The paper stored in the paper feed cassette 4 is conveyed to the image forming unit 5 (FIG. 2) in the main body case 2, and after a predetermined image is printed by the image forming unit 5, the paper is discharged onto the paper discharge tray 6. Is done.

  Further, a cover release button 8 is disposed on the upper surface of the main body case 2, and is configured such that when the cover release button 8 is pressed, the engagement between the main body case 2 and the open / close cover 7 is released.

  A link mechanism 110 (on the side surface of a main body frame (not shown) that supports the opening / closing cover 7 on the front side is linked with opening of the opening / closing cover 7 and release of pressure contact of a pressure roller 37 described later). A switching mechanism 200 (see FIG. 6) for switching between connection and release of a developing roller driving shaft and a developing roller driving gear 250, which will be described later, is attached to the other side surface.

Next, the structure of the laser printer 1 of this embodiment is demonstrated based on FIG.
As shown in FIG. 2, in the laser printer 1 of the present embodiment, a paper feed cassette 4 that is detachably inserted into the main body case 2 is disposed below the main body case 2, and a spring (not shown) is provided in the inside thereof. A support plate 11 biased upward is provided.

Above the support plate 11, a supply roller 13 that separates the recording sheets held in a stacked manner on the support plate 11 one by one and supplies them in the direction of the image forming unit 5 is disposed.
On the recording paper conveyance path from the supply roller 13 to the image forming unit 5, the conveyance rollers 15 and 17 are appropriately stopped so that the leading edge of the recording paper is locked and the skew of the recording paper is corrected. Rollers 19 are sequentially arranged.

The conveying rollers 15 and 17 are constituted by a driving roller that rotates by receiving a drive from a motor, and a driven roller that rotates along with the movement of the recording paper.
The open / close cover 7 includes a multi-purpose tray 23, and feeds the recording paper stacked on the multi-purpose tray 23 to the recording paper transport path from the multi-purpose tray 23 to the image forming unit 5. The multi-purpose-side sheet feeding roller 24 and the multi-purpose-side sheet feeding pad 24a are arranged in opposition to each other, and a multi-purpose-side sheet feeding pad is provided by a spring (not shown) disposed on the back side of the multi-purpose-side sheet feeding pad 24a. 24 a is pressed toward the multi-purpose side paper feed roller 24. The recording papers stacked on the multi-purpose tray 23 are fed between the multi-purpose side paper feed roller 24 and the multi-purpose side paper feed pad 24a by the rotation of the multi-purpose side paper feed roller 24 and then fed one by one. Paper.

The image forming unit 5 includes a photosensitive drum 27 and a developing roller 28 provided in the process cartridge 25, and a transfer roller 29 disposed to face the photosensitive drum 27.
A fixing device 33 mainly including a heating roller 35 and a pressure roller 37 is provided on the downstream side (right side in the drawing) of the image forming unit 5 with a conveyance belt 31 interposed therebetween.

  Further, on the downstream side of the fixing device 33, three pairs of paper discharge rollers 39a to 39c are arranged along the conveyance path, and on the upper surface of the main body case 2, the recording paper discharged from the last paper discharge roller 39c. A paper discharge tray 6 is provided.

A scanner unit 41 that scans and exposes the photosensitive drum 27 with the laser beam L is disposed between the paper discharge tray 6 and the process cartridge 25.
The scanner unit 41 includes a polygon mirror 43 that is rotated by a motor (not shown) for the purpose of scanning laser light emitted from a laser diode (not shown) for image formation. Various optical elements and the like are arranged.

Next, the process cartridge 25 will be described with reference to FIG.
First, as shown in FIG. 2, the process cartridge 25 is detachably mounted (moving forward and backward in the directions of arrows A and B) in a mounting portion 21 that is a recess opening above the main body case 2. . Note that the upper opening of the mounting portion 21 is always covered with the opening / closing cover 7, and the process cartridge 25 can be attached and detached by rotating the opening / closing cover 7 downward.

  The process cartridge 25 is rotatably provided with a photosensitive drum 27 having a photosensitive layer on its surface, and further includes a charging roller (not shown) for uniformly charging the surface of the photosensitive drum 27, and the charged photosensitive drum 27. A developing roller 28 for supplying toner to the surface is provided.

  An electrostatic latent image is formed on the surface of the photosensitive drum 27 charged by the charging roller by the laser light L incident from the scanner unit 41. Subsequently, the developing roller 28 is applied to the surface of the photosensitive drum 27 as a developer. By supplying the toner, the electrostatic latent image is developed on the photosensitive drum 27 to form a toner image (visible image).

Next, an image forming procedure in the present embodiment will be described.
The recording paper taken out from the paper feed cassette 4 by the supply roller 13 is sent to the registration rollers 19 by the transport rollers 15 and 17, where the skew of the recording paper is corrected.

  Thereafter, when the recording paper is sent to the image forming unit 5, the toner attached to the photosensitive drum 27 passes between the transfer roller 29 and the recording paper when passing between the photosensitive drum 27 and the transfer roller 29. As a result, an image (toner image) is formed on the recording paper.

  The recording paper on which the toner image is formed is transported to the fixing device 33 by the transport belt 31. In the fixing device 33, the toner image is sandwiched between the heating roller 35 and the pressure roller 37 and heated by the heating roller 35 to fix the toner image onto the recording paper, thereby completing the image formation.

Thereafter, the recording paper on which the image is fixed is discharged to a paper discharge tray 6 provided on the upper surface of the main body case 2 via three pairs of paper discharge rollers 39a to 39c.
Next, the structure of the link mechanism 110 and the fixing device 33 will be described with reference to FIGS. 3 to 5 are side views showing the structures of the link mechanism 110 and the fixing device 33. In particular, FIG. 3 shows a state when the opening / closing cover 7 is fully closed, FIG. 4 shows an initial opening state, and FIG. ing.

As shown in FIG. 3, the fixing device 33 includes a heating roller 35, a pressure roller 37, a release lever 130, and an urging support portion 140.
The urging support portion 140 includes a support portion main body 141, a rotating shaft 142, a spring 143, and a support portion 144. The support portion main body 141 includes a recess for placing the shaft of the pressure roller 37 and is rotatably supported by a rotation shaft 142 fixed to the fixing frame 33a. The spring 143 has one end fixed to a support portion 144 fixed to a fixing frame 33a (see FIG. 2) that supports the components of the fixing device 33 such as the heating roller 35, and urges the support portion main body 141 from below. is doing. By this urging force, the support portion main body 141 is urged counterclockwise (counterclockwise in FIG. 3) about the rotation shaft 142 and presses the pressure roller 37 against the heating roller 35.

  One end of the release lever 130 is rotatably supported by a rotation shaft 132 fixed to the fixing frame 33a above a contact portion 141a described later. A cam 131 is provided at a support end supported by the rotation shaft 132. The release lever 130 is rotated about the rotation shaft 132 in conjunction with the opening and closing of the opening / closing cover 7 by a link mechanism 110 described later, and is attached when the opening / closing cover 7 is fully closed. The contact portion 141a provided at one end of the force support portion 140 opposite to the one supported by the rotating shaft 142 and the cam 131 are disposed so as not to contact each other. When the opening / closing cover 7 is opened, the release lever 130 rotates clockwise (clockwise in FIG. 3), and the cam 131 pushes the contact portion 141a from above.

  That is, when the free end of the release lever 130 (opposite to the support end of the rotating shaft 132) is operated and displaced upward in the figure, the pressure roller 37 is released, and the operation is released. The release lever 130 is returned to the original position by the urging force of the spring 143 so that the pressure roller 37 returns to the state in which the heating roller 35 is pressed.

The link mechanism 110 includes connecting arms 111 and 112, a connecting fan 113, and rotating shafts 114 and 115.
A connecting arm 112 is connected to one end of the connecting arm 111, and a connecting sector 113 is connected to the other end via a hinge. In FIG. 3, the intermediate portion of the connecting arm 111 is omitted, but has a length from the vicinity of the opening / closing cover 7 to the vicinity of the fixing device 33.

  The connection arm 112 is rotatably supported by a rotation shaft 114 fixed to the main body frame at the center thereof, and the rotation shaft at the lower end of the opening / closing cover 7 is connected to one end where the connection arm 111 is not connected. A part of the opening / closing cover protruding from the upper part is connected via a hinge.

That is, when the opening / closing cover 7 is opened, the connecting arm 112 rotates counterclockwise about the rotating shaft 114, and in conjunction with this, the connecting arm 111 moves to the right in FIG. When the connecting arm 111 moves to the right, the connecting sector 113 rotates about the rotating shaft 115, and the projection 116 provided on the connecting sector 113 pushes the free end of the release lever 130 upward. It comes to move.

  Further, one end of a spring 120 is fixed to an intermediate portion between one end of the connecting arm 112 to which the connecting arm 111 is connected and the rotating shaft 114, and the connecting arm 112 is biased in a clockwise rotating direction. is doing. That is, the open / close cover 7 is biased in the opening direction in the fully closed state. One end of the spring 120 that is not fixed to the connecting arm 112 is fixed to the main body frame. Further, the biasing force of the spring 143 is set larger than the biasing force of the spring 120.

  When the cover release button 8 is pressed while the open / close cover 7 is fully closed, the engagement between the main body case 2 and the open / close cover 7 is released, and the open / close cover 7 is displaced in the opening direction by the biasing force of the spring 120. .

  Then, the displacement is transmitted through the link mechanism 110, and when the protrusion 116 pushes the free end of the release lever 130 upward, the release lever 130 rotates clockwise, as shown in FIG. 131 abuts against the abutting portion 141a. At this time, since the urging force of the spring 143 is larger than the urging force of the spring 120, the displacement of the opening / closing cover 7 in the opening direction by the urging force of the spring 120 stops when the cam portion 131 abuts against the abutting portion 141a. . A gap with a distance A is formed between the main body case 2 and the opening / closing cover 7.

  Then, when the opening / closing cover 7 is further displaced in the opening direction from the state in which the gap of the distance A is opened between the main body case 2 and the opening / closing cover 7, the displacement is transmitted via the link mechanism 110, and the cam portion 131. Pushes the contact portion 141a downward. As a result, the support portion main body 141 rotates downward, the pressure roller 37 supported by the support portion main body 141 is displaced downward, and the pressure contact with the heating roller 35 is released.

  When the open / close cover 7 is displaced to the fully open state, the state shown in FIG. 5 is obtained. Here, an angle formed by a line BB connecting the center of the rotation shaft 115 and the center of the protrusion 116 and a plane CC perpendicular to the direction of the force applied to the protrusion 116 from the free end of the release lever 130. D (see FIG. 5) is set to be smaller than 90 °, that is, an acute angle.

  In this way, in the fully open state, when the protrusion 116 moves to a position where the angle D is an acute angle (hereinafter referred to as a fully open holding position), the bias of the spring 142 prevents the opening / closing cover 7 from being displaced in the closing direction, The fully open state can be maintained.

  In other words, when the angle D is an obtuse angle, the urging force on the protrusion 116 via the release lever 130 in the downward (lower side in FIG. 5) direction, that is, the force that displaces the protrusion 116 downward. It takes. On the other hand, when the angle D is an acute angle, an urging force in the upper direction (upper side in FIG. 5) with respect to the line BB, that is, a force that displaces the protrusion 116 upward is applied. Therefore, the protrusion 116 is moved to the fully open holding position in the fully open state, and the position of the protrusion 116 is held in the fully open state by adjusting the weight of the connecting sector 113 so as to balance this upward force. be able to. In order to prevent the angle D from becoming obtuse due to vibration or the like when the opening / closing cover 7 is held in the fully open state, and the release of the fully open state being released, the size of the angle D is obtuse due to vibration or the like. It is desirable to set it as small as possible.

  Next, in conjunction with opening / closing of the opening / closing cover 7, a developing roller driving shaft for receiving a driving force for driving the developing roller 28 from a main motor (not shown), and a driving force from the main motor for driving the developing roller. A configuration of the switching mechanism 200 that switches between connection and release of the developing roller driving gear transmitted to the shaft will be described with reference to FIG.

  As shown in FIG. 6A, the switching mechanism 200 includes an interlocking member 210 that moves in conjunction with opening / closing of the opening / closing cover 7, and a support plate 220 that is fixed to the main body frame and guides the movement of the interlocking member 210. I have. FIG. 6A is a side view showing the configuration of the switching mechanism 200, and shows a state when the open / close cover 7 is fully closed.

  The interlocking member 210 includes a moving hole 213 in which a developing roller driving gear 250, which will be described later, is disposed. The position of the developing roller driving gear 250 in the moving hole 213 when the opening / closing cover 7 is fully opened and fully closed. Is configured to change. Further, the interlocking member 210 includes a detection protrusion 211 used for detecting opening / closing of the opening / closing cover 7 and a guide protrusion 212 used for guiding during movement.

  The support plate 220 includes a guide hole 223 in which the guide protrusion 212 provided in the interlocking member 210 is disposed, and a movement hole 221 in which the detection protrusion 211 is disposed. That is, the movement of the interlocking member 210 is restricted by the guide protrusion 212 and the guide hole 223. Further, when the interlocking member 210 moves, the position of the detection projection 211 in the movement hole 221 changes.

  Further, the interlocking member 210 is opened in the opening direction of the open / close cover 7 (rightward in FIG. 6A) by a spring 240 fixed to the interlocking member 210 and the support plate 220 through a long hole 222 provided in the support plate 220. ).

  An opening / closing sensor 230 made of a known micro switch is attached to the support plate 220. The open / close sensor 230 includes a detection lever 231, and is disposed at a position where the detection lever 231 contacts the detection protrusion 211 when the open / close cover 7 is fully closed.

  The developing roller driving gear 250 is disposed on the main body frame so as to face the developing roller driving shaft described above, and is a main motor (not shown) as a driving source attached in the laser printer 1 via a gear train (not shown). ) Is transmitted. The developing roller drive gear 250 is urged by a spring (not shown) in the direction from the surface on the side surface of the main body frame where the switching mechanism 200 is attached to the opposite side, and in the axial direction of the developing roller drive shaft. It is movable, and is configured to mesh with the developing roller drive shaft when moved to a position where it abuts on the developing roller drive shaft.

  As shown in FIG. 6A, the opening / closing cover 7 includes a pushing projection 7a that abuts the interlocking member 210 when the opening / closing cover 7 is closed and pushes the interlocking member 210 leftward in FIG. 6A. Thus, the interlocking member 210 moves to a position where the upper part of the moving hole 213 comes into contact with the developing roller drive gear 250 and the detection projection 211 comes into contact with the detection lever 231. When the detection protrusion 211 comes into contact with the detection lever 231, the open / close sensor 230 is turned on, and the fully closed state of the open / close cover 7 is detected. In the fully closed state, the opening / closing cover 7 is urged in the opening direction of the opening / closing cover 7 by the spring 240 via the pushing projection 7a.

  When the opening / closing cover 7 is opened, the interlocking member 210 is brought into contact with the developing roller driving gear 250 by the biasing force of the spring 240 and the lower portion of the moving hole 213 comes into contact with the developing roller driving gear 250 as shown in FIG. It moves to a position where the contact with the detection lever 231 is released. When the contact between the detection protrusion 211 and the detection lever 231 is released, the open / close sensor 230 is turned OFF, and the opening of the open / close cover 7 is detected.

  Further, as shown in FIG. 6C, a protruding portion 210 a is provided around the moving hole 213 of the interlocking member 210 so that the protruding amount gradually increases from the upper portion to the lower portion of the moving hole 213. When the open / close cover 7 is fully closed, the developing roller driving gear 250 is closest to the side surface of the main body frame because the developing roller driving gear 250 is not in contact with the protruding portion 210a as shown in the left diagram of FIG. By contacting the shaft, it engages with the developing roller drive shaft. On the other hand, in the opened state of the opening / closing cover 7, as shown in the right view of FIG. 6C, the developing roller driving gear 250 is in contact with the portion with the largest protruding amount of the protruding portion 210a. The engagement with the developing roller drive shaft is released by being farthest away from the developing roller drive shaft.

  In the embodiment described above, the pressure roller 37 is the pressure contact member in the present invention, the springs 120 and 240 are the initial opening force generating means in the present invention, the cover opening button 8 is the locking mechanism in the present invention, and the multipurpose tray 23 is in the present invention. This corresponds to the paper tray.

  Further, the link mechanism 110, the release lever 130, and the urging support portion 140, which are configured so that the angle D becomes an acute angle when the opening / closing cover 7 is fully opened, correspond to the holding means in the present invention.

The switching mechanism 200 corresponds to switching means in the present invention, the detection projection 211 corresponds to a movable member in the present invention, and the open / close sensor 230 corresponds to detection means in the present invention.
The developing roller driving shaft corresponds to the main body side driving shaft in the present invention, and the developing roller driving gear 250 corresponds to the process side driving shaft in the present invention.

  In the laser printer 1 of this embodiment configured as described above, when the opening / closing cover 7 is in the fully closed state, the lock is released when the cover release button 8 is pushed down by the operator. When the lock is released, the opening / closing cover 7 is opened by the urging force of the springs 120 and 240. When the gap of the distance A is opened between the main body case 2 and the opening / closing cover 7, the opening / closing cover 7 is stopped by the urging force of the spring 143. After that, when the operator displaces the opening / closing cover 7 in the direction of further opening against the urging force of the spring 143 to make it fully open, the protrusion 116 moves to the fully open holding position and resists the urging force of the spring 143. Thus, the positions of the link mechanism 110, the release lever 130, and the urging support portion 140 are maintained, whereby the fully open state of the open / close cover 7 is maintained.

  That is, when the operator depresses the cover release button 8, the operator puts his hand into the gap formed between the open / close cover and the image forming apparatus main body and grasps the end of the open / close cover 7 to perform the operation of fully opening the open / close cover 7. Therefore, the opening operation of the opening / closing cover 7 is facilitated. Further, since the fully opened state is maintained even if the operator does not hold down the opening / closing cover 7, the replacement of the process cartridge and the paper jam processing are facilitated. Further, the distance A of the gap does not change due to the fluctuation of the urging force of the springs 120 and 240.

  Further, since the opening / closing cover 7 includes the multi-purpose tray 23, the weight of the opening / closing cover 7 is increased by the weight of the multi-purpose tray 23, and the opening / closing cover 7 is displaced in the opening direction against the urging force of the spring 143. In doing so, the operator can reduce the force for opening the opening / closing cover 7 by the weight of the multi-purpose tray 23, and can facilitate the operation of the opening / closing cover 7.

  Further, since the link mechanism 110 and the fixing device 33 are detachably contacted with each other via the protrusion 116 and the release lever 130, when replacing the pressure roller 37, the link mechanism 110 is not removed. The replacement work of the pressure roller 37 is facilitated.

  Since the spring 120 is attached to one side of the main body frame that supports the open / close cover 7 and the spring 240 is attached to the other side of the main body frame that supports the open / close cover 7, the fully closed lock is released and the open / close cover 7 is released. When opening, the opening / closing cover 7 can be opened in a balanced manner on both side surfaces.

  Further, since the spring 240 used in the switching mechanism 200 and the opening / closing sensor 230 is also used for urging the opening / closing cover 7 in the opening direction, the parts constituting the laser printer 1 can be saved.

As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken.
For example, in the above embodiment, the laser printer 1 applied with the configuration as the image forming apparatus of the present invention is exemplified. However, the apparatus to which the configuration of the image forming apparatus according to the present invention is applied can be similarly applied to a copying machine, a facsimile, or the like as long as it has an image forming function.

  Further, in the above embodiment, when the cover release button 8 is pressed down, the opening / closing cover 7 is opened by the biasing force of the springs 120 and 240, and when the gap A is opened between the main body case 2 and the opening / closing cover 7. The spring 143 urges the opening / closing cover 7 in the closing direction so that the opening of the opening / closing cover 7 is stopped. Thus, the spring 143 urges the opening / closing cover 7 in the closing direction. Thus, the distance of the gap between the main body case 2 and the opening / closing cover 7 is not set, but the distance of the gap may be set according to the magnitude of the urging force of the springs 120 and 240.

  In the above-described embodiment, the engagement between the driving shaft of the developing roller 28 and the developing roller driving gear 250 is linked to the opening / closing of the opening / closing cover 7 using the switching mechanism 200. The engagement of the driving shafts such as a cleaning roller for removing toner and a charging roller for charging the photosensitive drum 27 and a driving gear for transmitting a driving force to these driving shafts may be interlocked with opening / closing of the opening / closing cover 7.

The perspective view of the laser printer in an embodiment. 1 is a schematic sectional side view of a laser printer in an embodiment. The side view which shows the state of the link mechanism at the time of opening-and-closing cover full closure in embodiment. The side view which shows the state of the link mechanism at the time of the opening / closing cover initial opening in embodiment. The side view which shows the state of the link mechanism at the time of full opening of the opening / closing cover in embodiment. The figure explaining the switching mechanism in embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer, 2 ... Main body case, 3 ... Display panel, 4 ... Paper feed cassette, 5 ... Image forming part, 6 ... Paper discharge tray, 7 ... Open / close cover, 8 ... Cover open button, 11 ... Support plate, 13 DESCRIPTION OF SYMBOLS Supply roller, 15 ... Conveying roller, 17 ... Conveying roller, 19 ... Registration roller, 21 ... Mounting part, 23 ... Multipurpose tray, 25 ... Process cartridge, 27 ... Photosensitive drum, 28 ... Developing roller, 29 ... Transfer roller, DESCRIPTION OF SYMBOLS 31 ... Conveyance belt, 33 ... Fixing device, 35 ... Heating roller, 37 ... Pressure roller, 39a-c ... Paper discharge roller, 41 ... Scanner unit, 43 ... Polygon mirror, 110 ... Link mechanism, 111, 112 ... Connection arm , 113 ... connecting fan-shaped part, 114, 115, 132, 142 ... rotating shaft, 116 ... projection, 120, 143, 240 ... spring, 130 ... release lever, DESCRIPTION OF SYMBOLS 31 ... Cam part, 140 ... Energizing support part, 141 ... Support part main body, 144 ... Support part, 200 ... Switching mechanism, 210 ... Interlocking member, 211 ... Detection protrusion, 212 ... Guide protrusion, 213, 221 ... Moving hole, 220 ... support plate, 222 ... long hole, 223 ... guide hole, 230 ... open / close sensor, 231 ... detection lever, 250 ... developing roller drive gear.

Claims (4)

A pressure contact member that is provided in a fixing mechanism for fixing the toner image on the paper by pressing the paper on which the toner image is formed, and that generates a pressure contact force in the fixing mechanism by being urged by the urging means; ,
A cover that is disposed on the front side of the image forming apparatus main body and that can be opened to the front side with the lower side as a fulcrum. A process unit for forming a toner image on a sheet is formed on a sheet inside the image forming apparatus. An open / close cover that is opened and closed to be attached to and detached from the process unit mounting portion facing the conveyance path, and covers the process unit mounting portion in a closed state;
A link mechanism for displacing the pressing member in a direction opposite to the pressing force against the biasing force of the biasing means in linkage with the opening operation of the opening and closing cover;
Holding means for holding the open state of the open / close cover against the biasing force of the biasing means;
An initial opening force generating means for generating an opening force acting in a direction in which the opening / closing cover opens with respect to the opening / closing cover in the fully closed state;
A locking mechanism that can resist the opening force of the initial opening force generating means and can lock the open / close cover in the fully closed state, and can be unlocked by a predetermined operation;
Equipped with a,
The biasing means biases the opening / closing cover when the opening / closing cover is displaced from the fully closed state beyond a preset intermediate position,
The pressure contact force is greater than the opening force;
An image forming apparatus comprising and this. The image forming apparatus according to claim 1, wherein the opening / closing cover includes a sheet tray attached to insert a sheet into the image forming apparatus. The image forming apparatus according to claim 1, wherein the link mechanism and the press contact member are configured to be separable . In conjunction with opening and closing of the opening / closing cover, a process side drive shaft for receiving a driving force for operating each part of the process unit detachable from the image forming apparatus main body from the apparatus main body side, and driving on the apparatus main body side Switching means for switching between connection and release with the main body side drive shaft for transmitting the rotational force applied from the source to the drive shaft;
In conjunction with the operation of the switching means, a movable member that reciprocates along the opening / closing direction of the opening / closing cover,
Detecting means for detecting the open / closed state of the open / close cover in conjunction with the reciprocating movement of the movable member;
Further comprising
The initial opening force generating means comprises a spring attached to the switching means or a movable member.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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