JPH11327299A - Pressing structure for developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent toner from being scattered by setting pressing force so that the driving force of a driving means becomes stronger than the force received by a driven gear from a driving gear and advanced toward in the direction of a photoreceptor drum and weaker than the pressing force of a pressing means when the driving force of the driving means is transmitted to the driven gear from the driving gear. SOLUTION: The pressing force of a compression coil spring 36d attached to the first guide groove 36b of a guide member 36 is set so as to be stronger than the force by which a third gear 312 is pressed forward by the driving gear 83 by the driving of a driving motor 81 and weaker than the pressing force of the pressing means. Thus, even when a developing unit driving mechanism 8 is driven, a developing unit 3 is suppressed from projecting forward. Besides, the toner existing in the unit 3 is surely prevented from being scattered. To put it concretely, the pressing force of the spring 36d is set so that a distance between a positioning roller 307 and the circumferential surface of the photoreceptor drum 2 becomes 0.5 mm to 1 mm when the motor 81 is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressing structure of a developing device for sequentially pressing a plurality of developing devices applied to an image forming apparatus such as a copying machine, a printer, a facsimile machine, etc. toward a photosensitive drum. It is.

[0002]

2. Description of the Related Art Conventionally, an object to be transferred is scanned with light, and the reflected light is applied to the peripheral surface of a rotating photosensitive drum to form an electrostatic latent image on the peripheral surface. 2. Description of the Related Art There is known an image forming apparatus configured to form a toner image by supplying toner to a latent image and transfer the toner image to a transfer sheet. Such an image forming apparatus employs a developing device that supplies a toner loaded therein to a peripheral surface of a photosensitive drum to form a toner image along an electrostatic latent image. When the image forming apparatus is for transferring a color image, the developing device has a total of four units including three units for three color components (yellow, cyan, and magenta) and one unit for black.
A table is employed, and these four developing devices are arranged side by side along the peripheral surface of the photosensitive drum.

[0003] Of these four developing devices, one for each rotation of the photosensitive drum approaches one to the peripheral surface of the photosensitive drum so that the toner is applied to the photosensitive drum and the other three developing devices are used. The developing device is separated from the photosensitive drum so that the toner is not supplied to the photosensitive drum. After this toner image is once transferred to a transfer belt,
In the next rotation, the toner of the next color is supplied to the photosensitive drum and is transferred to the transfer belt. Therefore, the color image is transferred to the transfer paper after the photoreceptor drum rotates four times to form a color image in which the toner of the four colors is overcoated on the transfer belt.

Each of the developing devices is separated from the peripheral surface of the photosensitive drum by a predetermined distance by the urging force of the urging means, and only the toner supply target is biased by the cam mechanism. And is pushed out toward the photosensitive drum against the urging force. With respect to the pressing structure of such a developing device, see, for example,
No. 367.

In this publication, a tension coil spring as a biasing means is bridged between a rear end portion of the developing device and a predetermined frame of the image forming apparatus. It is separated from the drum and is configured to be pushed in the direction of the photosensitive drum by driving a rod-shaped cam whenever necessary.

[0006] Inside the developing device, there is provided a stirring mechanism for stirring the toner and sending it to the opening. The stirring mechanism includes, for example, a predetermined number of screw shafts provided so as to be able to co-rotate around the axis in a casing of the developing device, and a developing roller provided so as to co-rotate around the axis at an opening portion in the developing device. , Provided on one side of the casing so as to be concentric and corotatable with each screw shaft and the developing roller,
Further, it is configured to include a plurality of driven gears that are sequentially meshed, and a drive gear that is meshed with any one of the driven gears to rotate the screw shaft and the developing roller.

When the drive gear is driven by the drive motor, this drive rotation is transmitted to each screw shaft via each driven gear, and the rotation of the screw shaft causes the toner in the developing device to be stirred while opening. It is sent to the developing roller, and is supplied from the rotating developing roller to the peripheral surface of the photosensitive drum.

[0008]

By the way, in the above-described conventional pressing structure of the developing device, when the driving motor is driven, the driving gear first rotates, and this driving rotation is transmitted to the driven gear. However, the driven gear is hardly rotated around the axis because a large load is applied by the internal toner via the screw shaft, and therefore, the driving of the driving gear until the screw shaft rotates steadily. The force is consumed as a force for pressing the developing device toward the photosensitive drum against the urging force of the urging means.

If the force generated in the initial stage of the driving rotation is larger than the urging force of the urging means, the developing device is not yet pressed by the cam at the beginning of the driving rotation of the driving gear. And the positioning roller attached to the developing roller collides with the peripheral surface of the photosensitive drum, causing the toner in the developing device to scatter from the opening due to the impact and contaminate the peripheral surface of the photosensitive drum. Problem arises.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a pressing structure of a developing device which can surely prevent toner scattering which tends to occur at the beginning of driving of the developing device. It is intended to be.

[0011]

According to a first aspect of the present invention, there is provided a pressing structure for a developing device, comprising: an electrostatic latent formed on a photosensitive drum rotatably supported on a frame of an image forming apparatus around an axis; A pressing structure of a developing device that presses a developing device that forms a toner image by supplying toner to an image from a separated position separated from the photosensitive drum by a pressing unit to a close position close to the photosensitive drum. Wherein the developing device stores the toner therein, and supplies the toner to the photosensitive drum through an opening provided opposite to the peripheral surface of the photosensitive drum, and stirs the toner. A stirring shaft to be sent out toward the opening, and a driven gear provided to be exposed to the outside so as to be rotatable around the axis of the stirring shaft and provided to the frame. Mesh with the driven gear A driving gear for rotating the driving gear; a driving unit for rotating the driving gear; and an urging unit for urging the developing device in a direction away from the photosensitive drum. The urging unit is configured to drive the driving unit. When the force is transmitted from the drive gear to the driven gear, the biasing force is set so that the driven gear receives a greater force from the drive gear toward the photosensitive drum and less than the pressing force of the pressing means. It is characterized by the following.

According to this pressing structure of the developing device, when the rotation of the driving gear by the driving of the driving means is transmitted to the driven gear, the developing device contains a developer (toner mixed with carrier or the like, hereinafter the same). Due to the increased load on the stirring shaft due to the loading of the driven gear, a force component of the force applied to the driven gear toward the photosensitive drum acts to cause the developing device to move in the direction of the photosensitive drum. Since the urging force of the urging means is set to be larger than the above-described force component, the urging force prevents the developing device from moving in the direction of the photosensitive drum. Therefore, when the driving unit is driven, the developing device rapidly moves toward the photoconductor drum, collides with the photoconductor drum, and the impact scatters the toner from the opening to the outside.
The inconvenience of contaminating the peripheral surface of the photosensitive drum is reliably prevented.

According to a second aspect of the present invention, there is provided the pressing structure of the developing device according to the first aspect, wherein the developing device is provided with a peripheral portion of the photosensitive drum which is set at a close position. A positioning roller contacting the surface is provided, and the urging force of the urging means is set such that a distance between the positioning roller and the peripheral surface of the photosensitive drum becomes 0.5 mm to 1 mm by driving the driving means. Is set to.

According to the pressing structure of the developing device, since the positioning roller of the developing device is stopped at 0.5 mm to 1 mm before the photosensitive drum by the rotation of the driving gear driven by the driving means, When the developing device is pressed by driving the pressing means in this state, the pressing distance is only 0.5 mm to 1 mm. Therefore, even if the positioning roller contacts the peripheral surface of the photosensitive drum, the impact is extremely small. Therefore, it is possible to effectively suppress the scattering of the toner in the developing device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an image forming apparatus to which the present invention is applied will be described with reference to FIG. FIG. 1 is an explanatory side sectional view showing an embodiment of an image forming apparatus to which a pressing structure of a developing device of the present invention is applied. As shown in FIG. 1, the image forming apparatus 1 includes a paper supply unit 12, which is provided inside a box-shaped casing 11 and holds and discharges a predetermined number of sheets one by one, and a rotating photosensitive drum. A main charging unit 13 for uniformly applying a charge to the surface of the photoreceptor 2 and an optical unit for projecting light onto the transfer object and projecting the reflected light on the peripheral surface of the photosensitive drum 2 after the charge is applied A developing unit 15 for developing an electrostatic latent image on the peripheral surface of the photosensitive drum 2 by projecting light; and a transfer belt 4 for transferring the electrostatic latent image formed on the peripheral surface of the photosensitive drum 2 A transfer / separation unit 16 that separates the remaining toner on the transfer belt 4 after the transfer, a cleaning unit 17 that removes the toner remaining on the peripheral surface of the photosensitive drum 2 to clean the photosensitive drum 2, and A charge removing section 18 for releasing the charged state of the peripheral surface of the body drum 2; It has a basic structure in which a fixing-discharging portion 19 for discharging to fix the transferred image on the sheet that has been transferred by the release unit 16.

The paper for image transfer is conveyed from the paper supply unit 12 to the transfer / separation unit 16 along the paper conveyance path 1a indicated by the thick arrow, while the light source reflected on the surface of the transfer object Is projected along the optical path 1b and onto the peripheral surface of the photosensitive drum 2 rotating in synchronism with the conveyance of the sheet, and an electrostatic latent image is formed on the surface of the photosensitive drum 2 by the projection. In addition, the developing unit 15 develops the electrostatic latent image and the transfer / separation unit 16
The image formed by the above development is primarily transferred.

The transfer belt 4 to which the image on the photosensitive drum 2 has been transferred by the transfer / separation unit 16 further rotates in synchronization with the sheet supplied from the sheet supply unit 12, and a predetermined amount on the sheet transport path 1 a. The transfer image on the surface of the transfer belt 4 is secondarily transferred to the sheet passing through the position, whereby an image is formed on the surface of the sheet. After the transfer of the image is completed, the sheet is supplied to the fixing / discharging section 19 through the sheet conveying path 1a on the downstream side, where the sheet is subjected to a predetermined fixing process, and then discharged to the discharge tray attached to the casing 11. 11a.

The paper feeding section 12 includes a cassette section 12a in which a plurality of extractable cassettes 12b are mounted in a stackable state so that they can be pulled out, and a cassette section 12a on the opposite side to the surface of the casing 11 provided with the discharge tray 11a. And a manual feed tray 12c protruding outward from the surface. At the time of the transfer operation, one of the cassette 12b and the manual feed tray 12c is selected, and the paper loaded in the selected cassette 12b or the manual feed tray 12c is transferred to a predetermined one of the transport rollers 11c provided at various places. The sheet is drawn out by driving, and supplied to the transfer / separation unit 16 through the sheet conveyance path 1a.

The main charging section 13 applies a charge to the outer peripheral surface of the photosensitive drum 2 rotating counterclockwise around the central axis 21 in FIG. 1 by corona discharge. And a charger 22 extending in the width direction (perpendicular to the plane of FIG. 1) provided so as to oppose the peripheral surface at the top. The charger 22 is provided with a charging wire 23 extending so as to extend in the width direction. The corona discharge caused by the high voltage applied to the charging wire 23 causes the peripheral surface of the photosensitive drum 2 to be uniformly formed at a predetermined position. It is charged by voltage.

The optical section 14 is provided with a transparent plate glass 14a on which an object to be transferred is placed with the surface to be transferred facing downward, and reciprocally movable in the left-right direction in the casing 11 below the transparent plate glass 14a. A light source 14b whose projection direction is directed to the object to be transferred, and a condensing lens 14 which receives reflected light from the object to be transferred via a predetermined number of reflecting mirrors 14d.
and a CCD (charge-coupled-device: CCD) that receives light passing through the condenser lens 14c and converts the light into a digital signal.
A charge-coupled device) 14e, and a laser emitter 14g for emitting a laser beam corresponding to the digital signal from the CCD 14e onto the peripheral surface of the photosensitive drum 2 downstream of the charger 22 via a reflecting mirror 14f. .

The light emitted from the light source 14b is
The light is reflected on the transfer surface of the transfer object on the transparent glass plate 14a, reflected by the plurality of reflecting mirrors 14d, and formed on the CCD 14e through the optical path 1b passing through the condenser lens 14c, where it is once converted into a digital signal. Is done. The digital signal is subjected to predetermined signal processing by a control unit (not shown), and a signal corresponding to each color component (yellow, cyan, magenta, black) is given to a laser projector 14g, and is converted into a laser beam. Is applied to the uniformly charged peripheral surface of the photosensitive drum 2 downstream of the charger 22 via the reflecting mirror 14f. As a result, the potential of the portion of the peripheral surface of the photosensitive drum 2 irradiated by the laser beam decreases, and a so-called electrostatic latent image, which is an image due to the decrease in the potential, is formed on the peripheral surface of the photosensitive drum 2 for each color component. It has become so.
Therefore, for one forward movement of the light source 14b, the laser beam radiator 14g emits light to the photosensitive drum 2 four times, and for each light, the photosensitive drum 2 moves one around the central axis 21.
Due to the rotation, the photosensitive drum 2 rotates four times for one forward movement of the light source 14b.

The developing unit 15 is provided on the downstream side of the position where the electrostatic latent image is formed, and is provided with four developing units 3 radially arranged on the peripheral surface of the photosensitive drum 2 with a slight space therebetween. Is formed by The four developing devices 3 include a yellow developing device 3 a loaded with yellow toner, a cyan developing device 3 b loaded with cyan toner, a magenta toner And a black developing device 3d loaded with black toner, which is a black toner. Note that these developing devices 3 can be integrally pulled out of the casing 11 as the image forming unit 30 together with the photosensitive drum 2, the main charging unit 13, and the like. This will be described later.

During the first rotation of the photosensitive drum 2 around the central axis 21 by one forward movement of the light source 14b, yellow toner is supplied from the yellow developing unit 3a to the peripheral surface to form a yellow image. First, this yellow image
The image is transferred to the transfer belt 4 by the transfer / separation unit 16. Next, when the photosensitive drum 2 rotates for the second time, cyan toner from the cyan developing unit 3b is supplied to the peripheral surface of the photosensitive drum 2 to form a cyan image, and the cyan image is transferred onto the yellow image on the transfer belt 4 in a superimposed manner. Is done. Further, during the third rotation of the photosensitive drum 2, the magenta toner from the magenta developing unit 3c is supplied to the peripheral surface of the photosensitive drum 2 to form a magenta image, and this magenta image is superimposed on yellow and cyan of the transfer belt 4. Transcribed. Then, at the time of the fourth rotation of the photosensitive drum 2, the black toner from the black developing device 3 d is supplied to the peripheral surface of the photosensitive drum 2 to form a black image, and the black image is transferred to the transfer belt 4. As a result, a color image in which yellow, cyan, magenta, and black toners are overcoated is formed on the surface of the transfer belt 4. This color image is secondarily transferred to a sheet sent from the sheet feeding unit 12.

The transfer / separation unit 16 is provided in close proximity to the transfer belt 4 and a roller group 41 including one drive roller 41a and a plurality of driven rollers 41b around which the transfer belt 4 is wound. And a belt cleaner 42. The drive roller 41a is a photosensitive drum 2
1, four driven rollers 41b are arranged side by side so that the four driven rollers 41b are arranged in a substantially vertical direction at a diagonally lower right position of the photosensitive drum 2, and one driven roller 41b is driven. It is provided slightly below the roller 41a.

The driven roller 41b (primary transfer roller 41c) provided opposite to the peripheral surface of the photosensitive drum 2 presses the transfer belt 4 toward the peripheral surface of the photosensitive drum 2. The toner image on the peripheral surface of the photosensitive drum 2 is transferred to the transfer belt 4 by the clockwise rotation of the transfer belt 4 while the primary transfer roller 41c abuts on the photosensitive drum 2. The driven roller 4
1b (backup roller 41d) is provided at the lowermost position with a secondary transfer roller 41e opposed to it at a small interval via the transfer belt 4 below the transfer belt 4 to form an opposing electrode. When the paper passes between these opposing electrodes via the intermediary, a color image formed on the peripheral surface of the transfer belt 4 is transferred to the paper.

Further, of the driven rollers 41b, one provided immediately below the driving roller 41a (the tension roller 41b).
f) The transfer belt 4 is driven by an urging force of an unillustrated urging means.
Of the transfer belt 4 is prevented from being loosened by the action of the tension roller 41f.

The belt cleaner 42 cleans the transfer belt 4 by removing the toner remaining on the transfer belt 4 after the color transfer image formed on the transfer belt 4 is transferred to a sheet. It is provided downstream of the roller 41d.

The cleaning section 17 includes the transfer belt 4
After the transfer, the toner remaining on the peripheral surface of the photosensitive drum 2 is removed for cleaning. This cleaning unit 17
Is disposed outside the peripheral surface of the photosensitive drum 2 and between the developing device 3 and the transfer belt 4.

The fixing / discharging section 19 includes a sheet conveying path 1a.
And a pair of upper and lower fixing rollers 5 sandwiching the fixing roller 5. At least one of the fixing rollers 5 has a heating unit such as an electric heater therein, and the heating unit is heated to a predetermined temperature (a temperature at which the toner melts). Then, the paper after the color transfer passes between the fixing rollers 5 while being pressed, so that the toner of the color image transferred by the transfer / separation unit 16 is fused and fixed to the paper. The sheet after the toner is fixed is discharged toward the discharge tray 11a.

FIGS. 2 and 3 are perspective views showing an embodiment of the image forming unit 30 to which the developing device according to the present invention is mounted. FIG.
3 shows a state in which the image forming unit 30 is pulled out of the casing 11. 2 and 3, the XX direction is referred to as the width direction, the YY direction is referred to as the front-rear direction, and especially the -X direction is leftward, the + X direction is rightward, the -Y direction is forward, and the + Y direction is It is called backward.

As shown in FIGS. 2 and 3, the image forming unit 30 includes a photosensitive drum 2, a main charging unit 13, a cleaning unit 17, and a developing unit 3 supported by a frame 31. The frame body 31 includes a left-side plate 32, a right-side plate 33, and a right-side plate 33 having a tapered pentagonal shape in a side view.
It comprises a plurality of connecting rods 34 bridged between the corners of 2, 33. The photoreceptor drum 2 includes these two side plates 3.
A central portion between the shafts 2 and 33 is rotatably supported around the central axis 21 and is rotated counterclockwise by a drive motor (not shown) provided on the left side of the left side plate 32. The main charging section 13 is provided at an obliquely upper front portion between the side plates 32 and 33, and the cleaning section 17 is provided adjacent to the main charging section 13 at an obliquely forward position.

Four developing units 3 (a yellow developing unit 3a, a cyan developing unit 3b, a magenta developing unit 3c, and a black developing unit 3a) are provided along the photosensitive drum 2 behind the side plates 32 and 33. A developing device 3d) is provided. Three of the four units (the yellow developing unit 3a, the cyan developing unit 3b, and the magenta developing unit 3c)
Are arranged in the vertical direction along the rear surface of the photoconductor drum 2, but only one (the black developing device 3d) is provided immediately below the photosensitive drum 2, and therefore FIG. 2 and FIG. The main body of the black developing device 3d is hidden behind and is not shown.

In the rear part of the right side plate 33, four mounting windows 35 arranged side by side along the circular shape of the photosensitive drum 2 are opened, while the left side plate 32 and the right side plate 3 are opened.
3 is provided with a pair of guide members 36 at positions slightly above the mounting windows 35 and opposed to each other in the width direction (the right guide member 3 in FIGS. 2 and 3).
6 is shaded by the right side plate 33 and is not shown in the figure), and the right end of the developing unit 3 is attached from the inside of the right side plate 33 to the mounting window 3.
5 is fitted to the frame 31 by fitting both sides in the width direction into the guide member 36 in a state where the guide member 36 is inserted. Each of the mounting windows 35 is provided with a tray 35a protruding outward from the right side plate 33, and the right end of the developing device 3 protruding outside from the mounting window 35 is mounted on the tray 35a.

The image forming unit 30 is moved in the width direction by a pair of rail members 37 in the front-rear direction (the front rail member 37 is not shown in the drawings behind the image forming unit 30 in FIGS. 2 and 3). The storage posture accommodated in the casing 11 so as to be movable forward and backward (FIG. 2)
And a withdrawal posture (FIG. 3) withdrawn from the casing 11. The rail member 37 includes a fixed rail 37a extending in the width direction fixed to a predetermined frame in the casing 11, and
An outer rail 37b supported by the fixed rail 37a and protruding and retracting in the width direction;
Inner rail 37c supported by b and emerging in the width direction
It is composed of

The lower end corners of both side plates 32 and 33 are fixed to the inner rail 37c, so that the image forming unit 30 can protrude and retract into the image forming apparatus 1 while being guided by the rail member 37. Has become.

FIGS. 4 and 5 are perspective views showing an embodiment of the guide member 36. FIG. 4 shows a state in which the developing device 3 is removed, and FIG. 5 shows a state in which the developing device 3 is mounted. Each is shown. 4 and 5, the XX direction is referred to as the width direction, the YY direction is referred to as the front-back direction, and in particular, the -X direction is referred to as left, the + X direction is referred to as right, the -Y direction is referred to as front, and the + Y direction is referred to as rear. . For convenience of illustration, FIG. 4 illustrates a state in which the guide member 36 and the developing device 3 are arranged in parallel with each other, but actually, both are relatively positioned as shown in FIG. Never.

As shown in FIGS. 4 and 5, the guide member 36 is composed of a tapered substrate 361 that is long in the front-rear direction and fixed to the side plates 32 and 33 of the frame 31, and this substrate 361.
A bottom plate 362 protruding toward the inside of the frame 31 so as to extend in the front-rear direction at the lower end edge of the base plate 361, and a front-rear extension projecting in the same direction as the bottom plate 362 at the upper edge of the substrate 361 and extending in the front-rear direction The top plate 363, the front edge of the top plate 363, and the bottom plate 3
A front plate 364 bridged between the front plate 362 and the front edge of the top plate 363, an intermediate plate 365 extending rearward from a rear end edge of the top plate 363, and an upper edge of the substrate 361 above the intermediate plate 365. Second top plate 366 provided in the portion to extend in the front-rear direction
And a second front plate 367 bridged between the front edge of the second top plate 366 and the front edge of the intermediate plate 365. 4 and 5 show the guide member 36 attached to the left side plate 32.

A bracket 368 projecting downward is provided on the front lower edge of the substrate 361, and a hook projection projecting leftward is provided on the second top plate 366. 369 are provided. Then, the bracket 368 is screwed to the left side plate 32 in a state where the hook projection 369 is fitted and locked in a locking hole 32a formed in the left side plate 32, so that the guide member 36 Is to be fixed.

In the guide member 36, the bottom plate 36
2 and a first guide groove 36a extending in the front-rear direction is formed between the top plate 363 and the intermediate plate 365;
The second guide groove 3 is provided between the intermediate plate 365 and the second top plate 366.
6b are formed. The developing device 3 mounted between the guide members 36 is guided by these guide grooves 36a and 36b to move back and forth. Each guide groove 3
The rear ends of 6a and 36b are opened, so that a later-described guide wheel 304 and guide rod 305 of the developing device 3 are opened.
To the first guide groove 36a and the second guide groove 36, respectively.
b can be attached and detached through the open portion.

The intermediate plate 365 includes a front intermediate plate 365a provided at a front position and a front intermediate plate 365.
a, and the second top plate 366 is opposed to the front second top plate 366a facing the front middle plate 365a, and is opposed to the rear middle plate 365b. Rear second top plate 366b
It consists of The width of the groove between the front intermediate plate 365a and the front second top plate 366a is determined by the compression coil spring 3
6d, the groove width between the rear intermediate plate 365b and the rear second top plate 366b is larger than the outer diameter of a later-described guide rod of the developing device 3. The dimensions are slightly larger.

The rear edge of the rear intermediate plate 365b is provided with a locking projection 365c projecting upward, and a rear portion of the rear second top plate 366b is provided with a locking projection 365c.
An elastic deformation portion 366c whose rear end portion is turned up is provided, and the guide rod can be easily moved with respect to the second guide groove 36b by expanding the width of the second guide groove 36b by the elastic deformation of the elastic deformation portion 366c. It can be attached to and detached from.

The developing device 3 includes a developing device main body 301 having a storage space for storing toner therein and a screw shaft (stirring shaft) 318 (FIG. 6) for feeding the stored toner to the front end side while stirring. A developing roller 303 rotatably supported around a first horizontal axis 302 at a front end side of the developing device main body 301; and a pair of widthwise guide wheels rotatably supported around the first horizontal axis 302. (First guided member) 304 and a pair of widthwise guide rods 3 protruding in the width direction from the rear upper side wall of the developing device main body 301.
05 is provided.

The guide wheel 304 is fitted in the first guide groove 36a of the guide member 36, and the guide rod 305 is fitted in the second guide groove 36b. Then, the guide wheel 304 and the guide rod 3
The developing device 3 is inserted into the first guide groove 36a and the second guide groove 36b so that the developing device 3 is mounted on the guide member 36 so as to be able to move back and forth. In the present embodiment, the guide rod 305 is formed in a semicircular shape having a flat front side in a side view, and the flat portions abut against rear edges of the front intermediate plate 365a and the front second top plate 366a. Excessive forward movement of the guide rod 305 is prevented.

The developing roller 303 is connected to the developing device main body 30.
1 is disposed so as to close the opening at the front end. A long toner supply opening 306 extending in the width direction for discharging the toner inside is formed between the outer peripheral surface of the developing roller 303 and the front edge of the top plate of the developing device main body 301. FIG. 4 around the first horizontal axis 302 of FIG.
The toner in the developing device main body 301 is supplied to the outer peripheral surface of the developing roller 303 by the counterclockwise rotation of the roller. The toner supplied to the outer peripheral surface of the developing roller 303 in a state where the developing device 3 is mounted on the guide member 36 is supplied to the outer peripheral surface of the photosensitive drum 2 rotating around the central axis 21, and is supplied to the outer peripheral surface. A toner image will be formed.

The first horizontal shaft 302 has a pair of positioning rollers 307 on the inner side of each guide wheel 304 in the width direction.
Are concentrically rotatably supported around the axis. These positioning rollers 307 come into contact with the peripheral surfaces on both sides of the photosensitive drum 2 in a state where the developing device 3 is mounted on the guide member 36 and pressed toward the photosensitive drum 2, whereby the developing roller 303 It serves as a spacer for forming a predetermined gap between the outer peripheral surface and the outer peripheral surface of the photosensitive drum 2.

Between the left guide wheel 304 and the positioning roller 307, there is provided a first gear 308 concentric with the first horizontal shaft 302 and co-rotating therewith, and behind the first gear 308. Is provided with a second gear 310 rotatably supported about a second horizontal shaft 309 and meshing with the first gear 308.
A third gear 312 that meshes with the second gear 310 and rotates around the third horizontal shaft 311 is provided further behind the zero gear 0.

The second and third horizontal axes 309 and 311 are
It rotates coaxially with the screw shaft in the developing device main body 301, thereby sending out the toner in the developing device main body 301 toward the toner supply opening 306. The first gear 308 is meshed with a drive gear of a drive shaft of a drive motor (not shown) disposed at an appropriate position in the casing 11 (FIG. 1) in a state where the developing device 3 is mounted on the guide member 36. When the drive rotation of the drive motor is transmitted to the first gear 308 via the drive gear, the first gear 308 rotates, and the rotation causes the second gear 310 and the third gear 312 which are respectively sequentially meshed with each other. It is designed to rotate synchronously.

On the right side of the developing device main body 301, there is provided a main body extending portion 313 having a hollow interior and extending toward the right with a shared bottom plate. This main body extension 313
Is set to be slightly thinner than the vertical dimension of the mounting window 35 (FIGS. 2 and 3) of the right side plate 33, and the main body extending portion 313 is inserted into the mounting window 35 from the inside to develop. The container 3 is mounted on the frame 31 of the image forming unit 30.

A toner supply hole 314 for supplying toner into the developing device main body 301 is formed on the upper surface of the main body extending portion 313.
An annular packing material 315 made of a flexible material such as a foamable synthetic resin is adhered to a peripheral portion of 14. A toner supply pipe (not shown) is connected to the toner supply hole 314 via the packing material 315, so that toner from the toner supply pipe is supplied into the developing device main body 301 whenever necessary.

The diameter of the guide wheel 304 is set slightly smaller than the groove width of the innermost portion (front end) of the first guide groove 36a, and the guide rod 305 has a vertical width. Is the second guide groove 3 at the entrance
The dimension is set to be the same as the groove width dimension of 6b. Further, on the lower rear of the guide rod 305, the locking protrusion 365c is provided.
Is formed, and the guide rod 305 is fitted into the second guide groove 36b, and the guide rod 305 is compressed by fitting the lock recess 305a to the locking protrusion 365c. This prevents the coil spring 36d from dropping from the second guide groove 36b against the urging force of the coil spring 36d.

The guide wheel 304 is connected to the first guide groove 36.
a, and the guide rod 305 is fitted in the second guide groove 36b, so that the developing device 3 can move back and forth within a predetermined range while being guided by the guide member 36.

Further, the developing device main body 301 is connected to the rear wall 30.
The lower portion of 1a has a recessed portion 301b formed by being recessed forward substantially over the entire length in the width direction. And
On the rear wall 301a, a pair of widthwise pressing plates (elastically pressed portions) 316 made of a leaf spring material, the lower half of which extends to the depressed portion 301b, are fixed by screws. When the developing device 3 is pressed by the pressing cam mechanism 38 shown in FIG.
d moves forward against the urging force of d, and is set in the position of being positioned with respect to the photosensitive drum 2, and when the above-mentioned pressing is released, it is retracted by the urging force of the compression coil spring 36d to the retracted position. The position is set.

As shown in FIG. 2, the pressing cam mechanism 38 has an eccentric cam driving mechanism 381 formed at the rear left portion of the image forming unit 30 and a projecting rightward from the eccentric cam driving mechanism 381. And a plurality of camshafts 382 which are fixed to these camshafts 382 so as to be co-rotatable around the axis.
Each camshaft 382 is provided with a pair of eccentric cams 383. In FIG. 2, the cam shaft 382 and the eccentric cam 383 for the black developing device 3d are not shown in the drawing because they are hidden by the frame 31 for convenience of illustration.

The eccentric cam drive mechanism 381 is formed by combining various gears (not shown) which rotate in association with each other when driven by a drive motor (not shown). The camshafts 382 rotate synchronously with each other via a gear mechanism when driven by a drive motor.

Each of the cam shafts 382 is provided at a position behind the developing device 3 mounted on the frame 31 with a predetermined distance from the developing device 3. The eccentric cams 383 are fixed to the positions facing each other. The eccentric cam 383 is in contact with the pressing plate 316 by the rotation of the cam shaft 382 around the axis driven by the eccentric cam driving mechanism 381, and is separated from the pressing plate 316 to release the pressing. The dimensions and the shape are set so that the posture can be changed between the separated postures.

In the present embodiment, only the eccentric cam 383 for the yellow developing device 3a is set in the contact position at the first rotation of the photosensitive drum 2, and the photosensitive drum 2
Eccentric cam 3 for cyan developing unit 3b at the time of second rotation of
83 is set in the abutting posture, and the eccentric cam 383 for the magenta developing device 3c at the time of the third rotation of the photosensitive drum 2
Only the eccentric cam 383 for the black developing device 3d is set in the abutting posture at the time of the fourth rotation of the photosensitive drum 2 so that the cam shafts 382 rotate synchronously. Has become.

By changing the position of the eccentric cam 383, each developing unit 3 urged rearward by the compression coil spring 36d advances and retreats with respect to the photosensitive drum 2 while being guided by the guide member 36. The toner in the developing device main body 301 is supplied to the photosensitive drum 2 by the rotation of the developing roller 303 when the developing device main body 301 moves forward, and the photosensitive drum 2 is
Is stopped.

When the pressing cam mechanism 38 is stopped, all the eccentric cams 383 are set to the separated positions, whereby the pressing force of the developing device 3 which has retreated to the rear end position by the urging force of the compression coil spring 36d. A gap of a predetermined interval is formed between the plate 316 and the eccentric cam 383, and the interference between them is released, so that the image forming unit 30 can be pulled out of the casing 11.

Then, the rear wall 301a of the developing device main body 301
A pair of protection protrusions (protection members) 317 are provided so as to protrude from the depressed portion 301b so as to sandwich each pressing plate 316 from the left and right. The rear end of the protection projection 317 is formed in an arc shape including a circular arc. As a result, when the image forming unit 30 is moved in and out of the casing 11, the eccentric cam 383 interferes with the arc-shaped protection projection 317 and is guided gently to the developing unit 3 in a state of being guided to the arc-shaped edge. And press it. Therefore, when the image forming unit 30 is taken in and out of the casing 11, the pressing plate 316 is prevented from directly colliding with the eccentric cam 383, and the toner in the developing device main body 301 is opened by the impact of the collision. The inconvenience of spouting out of the photoconductor drum 2 from the surface 306 and contaminating the surface of the photosensitive drum 2 does not occur.

FIG. 6 is a perspective view showing an embodiment of a developing device driving mechanism for driving a screw shaft and a developing roller in the developing device. As shown in FIG.
A drive motor 81 provided on the left wall surface of the left side plate 32 of the frame body 31 and a drive gear 83 provided concentrically and corotatably around the axis at the tip end of a drive shaft 82 of the drive motor 81.
And a third gear 312, a second gear 310, and a first gear 308 provided in the developing device 3 as a driven gear so as to sequentially mesh with the drive gear 83.
An insertion window 32b is formed in the left side plate 32 at a position slightly lower than a rear portion of the guide member 36, and the drive shaft 82 is inserted from the left side to the right side of the left side plate 32 through the insertion window 32b to thereby develop the developing device. The installation position of the drive motor 81, the length of the drive shaft 82, and the diameter of the drive gear 83 are set so that the drive gear 83 meshes with the third gear 312 when the drive gear 3 is mounted on the guide member 36. .

Then, the third gear 312 and the second gear 3
Each of the horizontal shafts 311 and 309, which are concentric with and integral with 10, are concentrically and integrally connected to a pair of screw shafts 318 in the front-rear direction in the developing device 3, so that the drive motor 81 is driven to drive the drive gear 83 clockwise. The driving rotation is sequentially transmitted to the third gear 312, the second gear 310, and the first gear 308, and the screw shaft 318 at this time is rotated.
Of the developing device 3 by the rotation of the developing roller 303
To be sent out. Therefore, by driving the eccentric cam 383 immediately after driving the drive motor 81, the toner in the developing device 3
The developing roller 303 comes close to the peripheral surface of the photosensitive drum 2 while being sent out toward 3, and the rotation of the developing roller 303 supplies the toner to the peripheral surface of the photosensitive drum 2.

When the drive motor 81 is driven,
The driving force is transmitted to the third gear 312 via the driving gear 83. In this transmission, the third gear 312 receives a forward force from the driving gear 83 and rotates around the third horizontal shaft 311. The second gear 310 meshing with the gear 312 also rotates around the second horizontal axis 309, but the developing device 3
The third gear 312 and the second gear 310 receive the load of the developer via the screw shaft 318, so that the third gear 312 and the second gear 310 are hard to rotate. It is movable forward while being guided by the member 36.

Accordingly, when the drive motor 81 is driven in the clockwise direction, the third gear 312 is not rotated by the large load even if the drive gear 83 is rotated in the clockwise direction.
The gear 312 will be pressed forward. When the pressing force is large, the developing device 3 moves abruptly forward against the urging force of the compression coil spring 36d without rotating the third gear 312, whereby the positioning roller 307 is moved to the photosensitive drum. 2, the toner scatters from the toner supply opening 306 due to the impact, and the peripheral surface of the photosensitive drum 2 is contaminated.

In the present invention, the guide member 3
6, the compression coil spring 3 mounted in the second guide groove 36b
The urging force of 6d is set to be greater than the force of the drive gear 83 pressing the third gear 312 forward by the drive of the drive motor 81, and smaller than the pressing force of the pressing means. By doing so, even if the developing device driving mechanism 8 is driven, it is possible to suppress the developing device 3 from protruding forward, and it is possible to reliably prevent the toner in the developing device 3 from scattering.

In the present embodiment, the urging force of the compression coil spring 36 d is applied to the drive motor 81 so that the distance between the positioning roller 307 and the peripheral surface of the photosensitive drum 2 is 0.5 mm to It is set to be 1 mm. In this way, when the drive motor 81 is driven, the rotation of the drive gear 83 causes the developing device 3 to move forward once against the urging force of the compression coil spring 36d, and to move to a position 0.5 mm to 1 mm before the photosensitive drum 2. By driving the eccentric cam 383 in accordance with this timing, the remaining 0.5 mm to 1 mm is pressed by the eccentric cam 383 and the positioning roller 307 abuts on the peripheral surface of the photosensitive drum 2. Since the developing device 3 is positioned and the pressing distance by the eccentric cam 383 is short, the impact when the positioning roller 307 comes into contact with the photosensitive drum 2 can be suppressed small, and the scattering of toner can be more reliably prevented. can do.

An embodiment of a method for setting the biasing force of the compression coil spring 36d will be described below. First, the third gear 312
As the first sample, a developer filled in the developing device 3 until the developer is full so that the rotational torque of the developing device 3 is maximized is adopted. The developing device 3 of the first sample is mounted on the guide member 36 with the compression coil spring 36d removed, and the drive motor 81 is driven, whereby the positioning roller 307 of the developing device 3 is placed on the peripheral surface of the photosensitive drum 2. Abut. In this state, the developing device 3 is pulled rearward through a predetermined spring balance, and the distance between the positioning roller 307 and the peripheral surface of the photosensitive drum 2 is set to a predetermined value within a range of 0.5 mm to 1 mm. Read the scale of the spring scale when it becomes, and check the tensile strength of the spring at that time.

By employing the compression coil spring 36d having the elastic force obtained in the above confirmation, the third gear 31
Even when the torque of No. 2 is the maximum, the positioning roller 307 stays within the range of 0.5 mm to 1 mm before the peripheral surface of the photosensitive drum 2 even when the developing device 3 advances at the initial stage of driving of the driving motor 81. Therefore, the disadvantage that the positioning roller 307 collides with the photosensitive drum 2 and the toner scatters due to the impact is reliably prevented.

According to the present invention, as described in detail above, the developing device 3
A screw shaft 318 that feeds the toner toward an opening facing the peripheral surface of the photosensitive drum 2 while stirring the toner, and a third screw shaft 318 that is provided to be exposed to the outside so as to be rotatable around the axis. While the gear 312 is provided, the frame 31 includes a drive gear 83 that meshes with the third gear 312 to rotate the third gear 312, a drive motor 81 that drives the drive gear 83 to rotate, and the developing device 3. A compression coil spring 36d that presses the third gear 312 when the driving force of the drive motor 81 is transmitted from the drive gear 83 to the third gear 312; Is set to be larger than the force in the direction of the photosensitive drum 2 received from the driving gear 83 and smaller than the pressing force of the pressing means.
The rotation of the drive gear 83 driven by the drive motor 81 is the third
When the load is transmitted to the gear 312, the load applied to the screw shaft 318 due to the fact that the developer is loaded in the developing device 3 increases the force component of the force applied to the third gear 312 toward the photosensitive drum 2. Acts to move the developing device 3 toward the photosensitive drum 2, the compression coil spring 36d
Is set to be larger than the above-mentioned force component, it is possible to suppress the developing device 3 from moving in the direction of the photosensitive drum 2 due to this urging force.

Accordingly, when the drive motor 81 is driven, the developing device 3 moves rapidly toward the photosensitive drum 2, collides with the photosensitive drum 2, and the toner scatters from the opening to the outside due to the impact. The inconvenience of contaminating the peripheral surface of No. 2 can be reliably prevented.

The biasing force of the compression coil spring 36d is applied to the drive motor 81 so that the distance between the positioning roller and the peripheral surface of the photosensitive drum 2 is 0.5 mm to 1 mm.
mm so that the drive motor 8
The rotation of the driving gear 83 by the driving of the developing device 3 causes the developing device 3
Means that the positioning roller is 0.5 mm
In this state, the developing device 3 is pressed by driving the pressing means, and the pressing distance is only 0.5 mm to 1 mm. Even if it comes into contact with the peripheral surface, the impact is extremely small, so that scattering of the toner in the developing device 3 can be effectively suppressed.

[0071]

According to the pressing structure of the developing device according to the first aspect of the present invention, the stirring shaft that feeds the toner toward the opening while stirring the toner into the developing device; A driven gear provided to be exposed to the outside so as to be rotatable with the outside is provided, and the frame body includes a driving gear that meshes with the driven gear to rotate the driven gear, a driving unit that rotationally drives the driven gear, and a developing device. An urging means for urging the apparatus in a direction away from the photosensitive drum, wherein the urging means receives the light received by the driven gear from the driving gear when the driving force of the driving means is transmitted from the driving gear to the driven gear. Since the urging force is set so as to be larger than the force toward the body drum and smaller than the pressing force of the pressing means, when the rotation of the driving gear by the driving of the driving means is transmitted to the driven gear, the developing device includes a developing device. The agent is loaded Due to the increase in the load on the agitating shaft due to this, even if the force component toward the photoconductor drum out of the force applied to the driven gear acts to cause the developing device to move in the direction of the photoconductor drum, the urging means is not required. Since the force is set to be larger than the force component, it is possible to prevent the developing device from moving in the direction of the photosensitive drum due to the force.

Therefore, when the driving means is driven, the developing device rapidly moves toward the photosensitive drum, collides with the photosensitive drum, and the impact scatters the toner from the opening to the outside, so that the peripheral surface of the photosensitive drum is damaged. The inconvenience of contamination can be reliably prevented.

According to the pressing structure of the developing device according to the second aspect of the present invention, the developing device is provided with a positioning roller that comes into contact with the peripheral surface of the photosensitive drum in a state where the developing device is positioned at a close position. The urging force of the urging means is set so that the distance between the positioning roller and the peripheral surface of the photosensitive drum becomes 0.5 mm to 1 mm by driving the driving means. The positioning roller of the developing device is 0.5 mm of the photosensitive drum.
When the developing device is pressed by driving the pressing means in this state, the pressing distance is only 0.5 mm to 1 mm. , The impact is extremely small, so that the scattering of the toner in the developing device can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory side sectional view showing an embodiment of an image forming apparatus to which a pressing structure of a developing device of the present invention is applied.

FIG. 2 is a perspective view showing an embodiment of an image forming unit to which a developing device according to the present invention is mounted, and shows a state where the image forming unit is mounted in a casing.

FIG. 3 is a perspective view illustrating an embodiment of an image forming unit to which a developing device according to the present invention is attached, and illustrates a state where the image forming unit is pulled out of a casing.

FIG. 4 is a perspective view showing one embodiment of a guide member;
This shows a state in which the developing device has been removed.

FIG. 5 is a perspective view showing one embodiment of a guide member;
This shows a state where the developing device is mounted.

FIG. 6 is a perspective view showing an embodiment of a driving mechanism for driving a screw shaft and a developing roller in the developing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Casing 11a Discharge tray 11c Conveying roller 12 Paper feed unit 12a Cassette unit 12b Cassette 12c Manual feed tray 13 Main charging unit 14 Optical unit 14a Transparent plate glass 14b Light source 14c Condensing lens 14d Reflecting mirror 14e CCD 14f Reflecting mirror 14g Laser Emitter 15 Developing unit 16 Transfer / separation unit 17 Cleaning unit 18 Static elimination unit 19 Fixing / discharging unit 2 Photoconductor drum 21 Central axis 3 Developing unit 3a Yellow developing unit 3b Cyan developing unit 3c Magenta developing unit 3d Black developing unit 301 Developing unit Main body 301a Rear wall 301b Depressed portion 302 First horizontal axis 303 Developing roller 304 Guide wheel (second guided member) 305 Guide rod (first guided member) 305a Locking recess 306 Toner supply opening 307 Positioning roller 3 8 1st gear 309 2nd horizontal axis 310 2nd gear 311 3rd horizontal axis 312 3rd gear 313 Body extension 314 Toner supply hole 315 Packing material 316 Press plate 317 Protective projection 31 Frame 32 Left side plate 32a Lock hole 33 Right plate 34 Connecting rod 35 Mounting window 35a Receiving tray 36 Guide member 36a Lower guide groove (second guide groove) 36b Upper guide groove (first guide groove) 361 Substrate 362 Bottom plate 363 Top plate 364 Front plate 365 Intermediate plate 365a Front intermediate Plate 365b Rear intermediate plate 366 Second top plate 366a Front second top plate 366b Rear second top plate 367 Second front plate 368 Bracket Pressing cam mechanism 38 381 Driving mechanism 382 Cam shaft 383 Eccentric cam 390 Drive motor 4 Transfer belt 41 Roller Group 41a drive roller 41b driven roller 41c Next transfer roller 41e tension roller 41d backup roller 42 the belt cleaner 5 fixing roller 8 developing device drive mechanism 81 drives the motor 82 drive shaft 83 drive gear

Claims (2)

[Claims] A developing device that supplies toner to an electrostatic latent image formed on a photosensitive drum rotatably supported on a frame of the image forming apparatus so as to be rotatable around an axis; In a pressing structure of a developing device for pressing from a separated position separated from the photosensitive drum by pressing toward a close position close to the photosensitive drum, the developing device stores toner inside the developing device, and stores the toner therein. A stirring shaft that supplies toner to the photosensitive drum through an opening provided opposite to the peripheral surface of the photosensitive drum, and feeds the toner toward the opening while stirring the toner.
A drive gear for rotating the driven gear by meshing with the driven gear, the driven gear comprising: There is provided a driving unit for rotating and driving the driving gear, and an urging unit for urging the developing device in a direction away from the photosensitive drum, wherein the urging unit is configured such that the driving force of the driving unit is a driven gear from the driving gear. Wherein the biasing force is set so as to be greater than the force of the driven gear from the drive gear toward the photosensitive drum and less than the pressing force of the pressing means. Pressing structure. 2. The developing device according to claim 1, wherein the developing device is provided with a positioning roller that contacts the peripheral surface of the photosensitive drum in a state where the developing device is positioned at a close position, and the urging force of the urging unit is driven by the driving unit. 2. The pressing structure according to claim 1, wherein the distance between the positioning roller and the peripheral surface of the photosensitive drum is set to 0.5 mm to 1 mm.