JP2001060037A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of reducing friction among a photoreceptor drum, a developing roller rotated while being in contact with the drum and a supply roller in press-contact with the developing roller, improving the image quality and forming an image on cardboard by nearly linearly forming the carrying path of paper. SOLUTION: Since the supply roller 55 is rotated and driven in a rotating direction reverse to that of the developing roller 56 so that the circumferential speed is as about twice of that of the developing roller 56, toner 53 is sufficiently replenished by the supply roller 55, and the toner 53 of a positive polarity is stuck with a layer thickness of two layers to the surface of the developing roller 56 in a state that about +350 V is applied as developing bias voltage, so that the toner 53 is attracted by electrostatic latent image voltage (about +100 V) lower than that thereof, and the toner 53 on the developing roller 56 is stuck to only an electrostatic latent image formed on the photoreceptive drum 20 and is developed so as to set developing efficiency as about 100%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser printer, a facsimile or a copying machine, and more particularly to a supply roller for supplying toner to a developing roller, and a toner attached to the developing roller on a photosensitive drum. The present invention relates to an apparatus for developing an electro-latent image.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer or a copying machine, a paper feed mechanism for feeding paper stored in a paper feed cassette one by one by a paper feed roller, a photosensitive drum, and the photosensitive drum A paper fed by a paper feed mechanism, including a laser scanner unit for forming an electrostatic latent image thereon, a developing unit for developing the electrostatic latent image on the photosensitive drum with toner, a transfer roller, and a fixing unit. Various kinds of images are formed on the upper side by toner.

For example, a laser printer 200 shown in FIG.
In general, at the bottom of the main body case 202,
A paper feed cassette 214 and a paper feed roller 213 that feeds the sheets P stored in the paper feed cassette 214 one by one are provided. Transfer roller 26 that comes into pressure contact with
0, a fixing unit 270 is provided near the photosensitive drum 220, and a discharge tray 277 is provided above the photosensitive drum 220. That is, the transport path PP of the paper P fed from the paper feed cassette 214
The laser printer 200 is formed in a zigzag shape which is bent plural times as shown by a dashed line, so that the laser printer 200 can be downsized.

[0004] Then, the photosensitive drum 2 is
After the charge on the photosensitive drum 220 has been wiped out, the laser beam L emitted from the laser scanner unit 230 is irradiated onto the photosensitive drum 220 in a state where the surface of the photosensitive drum 220 is uniformly charged to a predetermined polarity by the charger 240. To form an electrostatic latent image, and this electrostatic latent image is
The toner image is created by being developed into a visible image by charged toner received from the developing roller 256 which is provided integrally with the photosensitive drum 220 and is in contact with the photosensitive drum 220. Then, the toner image is transferred to the conveyed sheet P by the transfer roller 260, and the toner image on the sheet P is further fixed on the sheet P by the heating roller 271 of the fixing unit 270, and finally, an image is formed. The discharged paper P is delivered to the paper output tray 27.
It is discharged to 7.

Here, in the toner cartridge 250, the developing roller 256 and the supply roller 25 that presses and contacts the developing roller 256 to supply the toner 253 to the developing roller 256.
5 is provided rotatably, and the developing roller 25
6, a layer thickness regulating blade 257 for regulating the layer thickness of the toner 253 adhering to the predetermined thickness and charging the toner 253 by rubbing is provided above the supply roller 255. The developing roller 256 and the supply roller 255 are driven in a rotational direction as shown in the drawing so that the removed excess toner 253 falls onto the supply roller 255. That is, in order to develop the toner 253 while charging the toner 253 with static electricity of a predetermined polarity, the developing roller 256
It is driven while being pressed and contacted in a rotation direction different from the rotation direction.

Incidentally, a laser printer 20 shown in FIG.
0, since the transport path PP of the paper P is zigzag, when thick paper such as an envelope is fed as the paper P, it cannot be transported smoothly at the turnback portion included in the transport path PP. Is configured to form an image on thin flexible paper.

Therefore, recently, a laser printer has been put to practical use in which a transport path from a paper feed cassette to a paper discharge tray is formed in a substantially straight line so that an image can be formed on various types of thick paper. As shown in FIG.
In the middle of the transport path PP from the paper feed roller 313 provided to the paper discharge tray 377, the photosensitive drum 320 is below the transport path PP, and the transfer roller 360 is located on the transport path P.
P, a fixing unit 370 is provided facing the transport path PP, and a toner cartridge 35 having a developing roller 356 in contact with the photosensitive drum 320 is provided.
0 is provided on the downstream side of the photosensitive drum 320 in the sheet conveying direction, and the developing roller 356 and the supply roller 355 are so arranged that excess toner 353 removed by the layer thickness regulating blade 357 falls onto the supply roller 355. The developing roller 356 is driven to rotate in the opposite direction to the photosensitive drum 320 by rotating the photosensitive drum 320 and the photosensitive drum 320 in the rotating directions as shown in the drawing. However, in this case, the conveyance path PP and the toner cartridge 350
It is difficult to provide a laser scanner unit in addition to the static elimination lamp and the charger in a narrow place between the two.

Therefore, as shown in FIG. 10B, the transport path PP from the paper feed roller 313 to the paper discharge tray 377 is used.
10A, the photosensitive drum 320, the transfer roller 360, and the fixing unit 370 are provided, and the toner cartridge 350 is provided on the upstream side in the sheet conveyance direction with respect to the photosensitive drum 320, as in FIG. The developing roller 35 is disposed such that excess toner 353 removed by the layer thickness regulating blade 357 falls onto the supply roller 355.
6, the supply roller 355, and the photosensitive drum 320 are respectively driven to rotate in the rotation directions as illustrated. That is, the developing roller 356 is attached to the photosensitive drum 3 so that the electrostatic latent image on the photosensitive drum 320 can be developed to have a sufficient image density.
The photosensitive drum 320 is driven so as to have a predetermined peripheral speed that is at least about twice the peripheral speed of the photosensitive drum 320 in the same rotational direction as that of the photosensitive drum 320. On the other hand, in this case, the transport path PP can be formed in a substantially linear shape, and the neutralizing lamp 341 and the charger 34 can be formed.
In addition to 0, the laser scanner unit 330 can be provided upstream of the toner cartridge 350 in the rotation direction of the photosensitive drum 320.

[0009]

As described above, FIG.
0 (b), the paper feed roller 313, the photosensitive drum 320 and the transfer roller 360, and the fixing unit 370
And a paper discharge tray 377 such that the transport path PP is formed in a substantially straight line, and in a laser printer capable of printing on various types of thick paper, the photosensitive drum 320 presses against the transfer roller 360. The developing roller 356 is driven in the clockwise direction in the figure while the developing roller 356 is driven in such a manner that the excess toner 353 removed by the layer thickness regulating blade 357 falls onto the supply roller 355. The supply roller 355 is driven in the same clockwise direction as the photosensitive drum 320 and at a predetermined peripheral speed of about twice or more the peripheral speed of the photosensitive drum 320, and the supply roller 355 is used for the developing roller 356 used for development. The developing roller 356 is driven to rotate in the same rotational direction so that the upper toner can be surely replenished.

That is, the outer peripheral portion of the photosensitive drum 320 and the outer peripheral portion of the developing roller 356 relatively move in opposite directions at their contact portion.
6 and the outer peripheral portion of the supply roller 355 relatively move in opposite directions at their contact portion, so that the photosensitive drum 320, the developing roller 356, and the supply roller 355 are greatly worn. , For example, 300
Since the image quality deteriorates every time printing is performed on 0 to 4000 sheets of paper P, the toner cartridge 350 and the photosensitive drum 32
There is a problem that the running cost increases because the 0 is replaced each time.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing abrasion of a photosensitive drum, a developing roller rotating while being in contact with the photosensitive drum, and a supply roller pressing and contacting the developing roller, and improving image quality. Another object of the present invention is to provide an image forming apparatus capable of forming an image on thick paper by forming a paper transport path in a substantially linear shape.

[0012]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a feeder unit for feeding a sheet for image formation by a feed roller; a photosensitive drum; and an electrostatic latent image on the photosensitive drum. A developing unit having an exposure unit for forming, a supply roller for supplying toner, and a developing roller for developing an electrostatic latent image on the photosensitive drum with the toner supplied from the supply roller; Transfer means for transferring the photosensitive drum to the sheet, a fixing unit for heating and fixing the toner image transferred to the sheet, and a sheet discharging means for discharging the sheet on which the toner image is fixed. A driving means for rotating the developing roller in the direction opposite to the photosensitive drum while rotating and driving the developing roller in the direction opposite to the photosensitive drum, and further driving the supply roller in the direction opposite to the developing roller It is those with a door.

In operation, the photosensitive drum on which the electrostatic latent image is formed is driven in a predetermined rotation direction, and the developing roller which contacts the photosensitive drum and develops the electrostatic latent image with toner rotates in the opposite direction to the photosensitive drum. Since it is driven, the wear between the photosensitive drum and the developing roller can be reduced,
Further, since the supply roller is driven to rotate in a direction opposite to the developing roller, wear of the developing roller and the supply roller can be reduced.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect.
In the invention, the transport path for transporting the paper is arranged in a substantially linear manner across the paper feed roller, the transfer means, the fixing unit, and the paper discharge means.

The operation is the same as that of the first aspect, except that the paper fed by the paper feed roller is conveyed by a substantially linear conveyance path through these transfer means and the fixing unit. Since the paper is discharged by the paper discharging means, printing can be easily performed on thick paper.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
Alternatively, in the invention according to claim 2, the driving means drives the supply roller such that the peripheral speed of the supply roller is at least twice the peripheral speed of the developing roller.

The operation is similar to that of the first or second aspect, except that the supply roller is driven so that its peripheral speed is at least twice the peripheral speed of the developing roller. Therefore, the toner layer on the developing roller, which has become non-uniform in the developing process of the electrostatic latent image, can be made uniform to a predetermined layer thickness with a sufficient amount of toner supplied from the supply roller, and the electrostatic latent image Can always be satisfactorily developed with a sufficient developing density.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the third aspect.
A developing unit formed below the supply roller, wherein a layer thickness regulating member that regulates the amount of toner supplied from the supply roller and adhered to the development roller is provided under the development roller in a press-contact manner. The gap between the frame and the supply roller is narrowed so as to promote the transfer of the excess toner removed by the layer thickness regulating member.

The operation is the same as that of the third aspect, but the excess toner removed by the layer thickness regulating member provided in a press-contact manner below the developing roller is removed from the frame of the developing unit and the supply roller. Falls into the gap between
Since the gap is formed narrow, the transfer of the toner by the rotation of the supply roller is promoted and the toner is not deposited,
The toner supply function of the supply roller is favorably maintained.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the second aspect.
In the invention, the photosensitive drum is disposed below the transport path, and the transfer unit is disposed above the transport path.

The operation is similar to that of the second aspect. However, since the photosensitive drum is arranged below the conveyance path and the transfer means is arranged above the conveyance path, the conveyance path is maintained substantially linear. Thus, the toner image on the photosensitive drum can be reliably transferred to the paper.

An image forming apparatus according to a sixth aspect of the present invention provides the image forming apparatus according to the fifth aspect.
In the invention, the exposure means is provided below the photosensitive drum.

The operation is the same as that of the fifth aspect. However, since the exposing means is disposed below the photosensitive drum, the length in the conveying direction can be shortened, and the image forming apparatus can be made compact. The electrostatic latent image can be formed on the photosensitive drum by the exposure unit without interfering with sheet conveyance.

According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a feeder unit for feeding a sheet for image formation by a feed roller; a photosensitive drum; and an exposure unit for forming an electrostatic latent image on the photosensitive drum. A developing unit having a supply roller for supplying toner and a developing roller for developing an electrostatic latent image on the photosensitive drum with the toner supplied from the supply roller; and a transfer unit for transferring the toner image on the photosensitive drum to paper A fixing unit for heating and fixing a toner image transferred to a sheet, and a sheet discharging unit for discharging the sheet on which the toner image has been fixed; And a substantially linear transport path for transporting the paper, the photosensitive drum being rotated in a predetermined rotational direction in synchronization with the transport of the paper, and
Drive means for rotating the developing roller in a direction opposite to the photosensitive drum, and further driving the supply roller in a direction opposite to the developing roller, wherein the photosensitive drum is disposed below the transport path, and the transfer means is disposed in the transport path. It is arranged above.

In operation, the photosensitive drum on which the electrostatic latent image is formed is driven in a predetermined rotation direction, and the developing roller which contacts the photosensitive drum and develops the electrostatic latent image with toner rotates in the opposite direction to the photosensitive drum. Since it is driven, the wear between the photosensitive drum and the developing roller can be reduced,
Further, since the supply roller is driven to rotate in a direction opposite to the developing roller, wear of the developing roller and the supply roller can be reduced. In addition, the paper fed by the paper feed roller is conveyed through these transfer means and the fixing unit, is conveyed by a substantially linear conveyance path, and is discharged by the paper discharge means, so that it can be easily printed on thick paper. can do.
Further, since the photosensitive drum is disposed below the transport path and the transfer unit is disposed above the transport path, the transport path is maintained substantially linear, and the toner image on the photosensitive drum is reliably transferred to the paper. Can be.

[0026]

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

In this embodiment, the present invention is applied to a laser printer including a feeder unit, a photosensitive drum, a laser scanner unit, and the like.

As shown in FIG. 1, this laser printer 1
, A feeder unit 10 for feeding paper P for image formation, a photosensitive drum 20 for receiving a laser beam L, and a laser scanner unit for forming an electrostatic latent image on the photosensitive drum 20 (Corresponding to exposure means) 30
A developing unit 50 having a supply roller 55 and a developing roller 56; a transfer roller (corresponding to a transfer unit) 60 for transferring the toner image on the photosensitive drum 20 onto the sheet P; a fixing unit 70; A paper discharge tray (corresponding to paper discharge means) 77 for discharging the paper P, and the photosensitive drum 2
0 and a second drive mechanism 100 for driving the developing roller 56 and the like.

First, the feeder unit 10 will be described.

As shown in FIG. 1, a paper pressing plate 11 having substantially the same width as the paper P is provided in the feeder unit case 3 above the rear end of the main body case 2. The plate 11 is pivotally supported at a rear end thereof and elastically urged upward by a compression spring 12 at a front end thereof, and a sheet feeding roller 13 extending in the left-right direction is rotatably supported at the front end. The paper feed roller 13 is driven to rotate at a paper feed timing by a drive system (not shown).

In the feeder unit case 3, a paper feed cassette 14 capable of accommodating a plurality of sheets P of fixed cut paper is detachably mounted in an inclined manner, and the paper feed roller 1 is provided.
3 rotates the paper P stored in the paper feed cassette 14.
Of these, paper is fed one by one from the upper paper P. Furthermore,
In order to prevent two sheets of paper P from being inserted, a separation member 15 provided below the paper feed roller 13 is elastically urged to the paper feed roller 13 by a compression spring 16. Here, a pair of registration rollers 17 and 18 for aligning the leading ends of the fed paper P are rotatably pivoted downstream of the paper feed roller 13 in the transport direction (in FIG. 1, from the rear to the front). Supported.

As shown in FIGS. 1 to 2 and FIG. 5, the photosensitive drum 20 has a predetermined thickness (for example, a photoconductive resin dispersed in polycarbonate) on the outer peripheral portion of a cylindrical aluminum sleeve 21. , About 20 μm), and is rotatably supported by the main body case 2 with the cylindrical sleeve 21 grounded. In other words, the toner 53 charged to the positive polarity is developed by the reversal development method with respect to the electrostatic latent image having the positive polarity formed on the photosensitive drum 20.

The laser scanner unit 30 is disposed below the photosensitive drum 20 and is driven to rotate by a laser emitter 31 for generating a laser beam L for forming an electrostatic latent image on the photosensitive drum 20. Polygon mirror (pentahedral mirror)
32, a pair of lenses 33, 34, a pair of reflection mirrors 3
5, 36 and the like. Since the laser scanner unit 30 is disposed below the photosensitive drum 20 as described above, the length in the transport direction can be shortened, and the laser printer 1 can be made compact and interfere with the paper transport. No, laser scanner unit 3
An electrostatic latent image can be formed on the photosensitive drum 20 by the laser light L emitted from the zero.

On the other hand, a scorotron-type charger 40 for generating a corona discharge from a charging wire made of tungsten or the like at a position advanced in the rotation direction from the position on the photosensitive drum 20 where the laser beam L is irradiated. The discharge lamp 41 is provided at a position further advanced in the rotation direction than the charger 40, and a paper for removing paper dust on the photosensitive drum 20 is further provided at a position further advanced in the rotation direction than the charger 40. A powder removing blade 42 is provided in a pressure contact state.

Next, the developing unit 50 disposed immediately after the photosensitive drum 20 will be described.

The developing unit case 4 is provided with an agitator 52 that is driven to rotate, and an insulating toner 53 having electrical insulation.
Is mounted detachably, and is supplied to the front side of the toner box 51 by rotation of an agitator 52 via a toner supply port 51a formed in the toner box 51. Toner 53
Is formed, and a supply roller 55 is horizontally disposed in a horizontal direction in the toner storage chamber 54, and is rotatably pivoted.

Further, a developing roller 56 is horizontally arranged in the left-right direction so as to partition the front side of the toner storage chamber 54 and to be in contact with the supply roller 55 and the photosensitive drum 20, respectively. Have been. Here, the center of rotation of the developing roller 56 is provided at substantially the same height as the center of rotation of the photosensitive drum 20, but the supply roller 55 is provided so as to contact the developing roller 56 substantially obliquely from below. The gap G between the supply roller 55 and the developing unit case 4 is
It is formed narrow so as to facilitate the transfer of the toner 53. The size of the gap G is desirably 1 mm or less.

Here, the toner 53 is a polymerized toner made of styrene acrylic or the like, which is closer to a true spherical shape than the pulverized toner, and has a particle size of about 7 to 10 μm.

The supply roller 55 is a conductive elastic foam made of silicon rubber, urethane rubber, or the like.
The resistance value at the contact portion with the developing roller 56 is about 5 × 1
It is set to 04 to 1 × 10 9 Ω.

The developing roller 56 is a conductive rigid roller made of silicon rubber, urethane rubber, or the like. The resistance value from the central electrode to which the developing bias voltage is applied to the outer peripheral contact portion is approximately 5 × 10 4 -1 × 1
It is set to 07 Ω.

On the other hand, a thin plate-like elastic layer-thickness regulating blade 57 made of stainless steel or phosphor bronze is attached to the lower end of the developing unit case 4 obliquely rearward and upward, and is formed at the tip thereof. The bent portion contacts the developing roller 56 in a pressing manner from below, and the layer thickness of the toner 53 supplied from the supply roller 55 and adhered to the surface of the developing roller 56 in a layer form is determined by the layer thickness regulating blade 57. It is regulated to a predetermined thickness of about two layers (about 13 to 17 μm). That is, the radius of curvature of the bent portion is about 0.5 mm so that the amount of toner on the developing roller 56 is set to about 0.6 mg / cm @ 2. As a result, the toner 53 on the developing roller 56 after the regulation of the layer thickness is performed.
Since the toner 53 has two layers, the toner 53 that has not been subjected to the development does not accumulate on the contact portion with the photosensitive drum 20 and is securely attached to the developing roller 56 and collected.

Then, a first driving mechanism 80 and a second driving mechanism
The photosensitive drum 20 and the supply roller 5 are driven by the driving mechanism 100.
5 is rotated clockwise in side view, and the developing roller 5 is rotated.
6 is driven to rotate counterclockwise and the peripheral speed of the supply roller 55 is driven to be twice the peripheral speed of the developing roller 56, so that each toner particle 53a of the toner 53 is
As shown in FIG. 5, the supply roller 55 is charged to a positive polarity by the rubbing between the supply roller 55 and the developing roller 56, and by the pressing friction of the layer thickness regulating blade 57 against the developing roller 56.
The positively charged toner 53 adheres to the electrostatic latent image formed on the photosensitive drum 20 by the laser beam L and is developed by the reversal developing method.

Next, the transfer roller 60 is
It is provided so as to be in contact with the upper side of the
It is a foamed elastic body having conductivity made of silicon rubber, urethane rubber, or the like. The resistance value at the contact portion with the photosensitive drum 20 is set to about 1 × 10 6 to 1 × 10 10 Ω. That is, since the transfer roller 60 is in contact with the surface of the photosensitive drum 20, by increasing the resistance value,
Photosensitive drum 20 by voltage applied to transfer roller 60
The toner image on the photosensitive drum 20 is securely transferred to the sheet P so that the photoconductive layer 22 formed on the sheet P is not destroyed.

The fixing unit 70 is provided downstream of the photosensitive drum 20 in the transport direction and includes a heating roller 71 having a built-in halogen lamp and a pressing roller 72. The fixing unit 70 heats the toner image transferred to the lower surface of the paper P. And is fixed on the sheet P.

At the downstream side of the fixing unit 70 in the transport direction, a pair of transport rollers 75 for transporting the paper and a paper discharge tray 77 are provided.

That is, as shown in FIG.
The paper feed roller 13, the photosensitive drum 20, the fixing unit 70, and the paper discharge tray 77 that form a transport path PP that transports the paper P fed from the printer 4 are arranged substantially linearly. .

Next, the first drive mechanism 80 for driving the photosensitive drum 20 and the paper transport system will be described with reference to FIG.

The first drive mechanism 80 is disposed on the outer surface of the left side wall portion of the laser printer 1, and the rotational force of the gear 82 of the output shaft of the first drive motor 81 is a two-stage gear 83 ( 83a, 83b) and a two-stage gear 84 (84a, 84b).
b) to the gear 85, and the rotational force of the gear 85 is transmitted to the gear 13 a for driving the paper feed roller 13 via the gear 86. Further, the rotational force of the gear 86 is controlled by the gear 18 driving the registration roller 18 via the gear 87.
a.

The rotational force of the second gear 83 is divided into two gears 89 (89a, 89b), a gear 90 and a second gear 91 (9).
1a, 91b) and the two-stage gear 92 (92a, 92b) are transmitted to the gear 20a for driving the photosensitive drum 20.

On the other hand, the rotational force of the two-stage gear 92 is
Is transmitted to the gear 71a for driving the heating roller 71 via the gears 94 and 94. That is, when the first drive motor 81 is rotated clockwise, the paper feed roller 13, the pair of registration rollers 17, 18, the photosensitive drum 20, and the heating roller 71 rotate as indicated by the arrow. Since the paper P is driven, the paper P fed from the paper feed cassette 14 is transported along a predetermined transport path PP and is discharged to the paper discharge tray 77.

Next, the second driving mechanism 100 for driving the developing unit 50 will be described with reference to FIG. Here, the first driving mechanism 80 and the second driving mechanism 100 correspond to driving means.

The second drive mechanism 100 is disposed on the outer side of the right side wall portion toward the laser printer 1,
The rotational force of the gear 102 of the output shaft of the drive motor 101 is the gear 103 and the two-stage gear 104 (104a, 104b)
The power is transmitted to the gear 52 a that drives the agitator 52 in the toner box 51 via the step gear 105 (105 a, 105 b), the gear 106, and the gear 107. Gear 1
06 is transmitted to a gear 55a for driving the supply roller 55, and the rotational force of the gear 55a is further
6 is transmitted to the gear 56a that drives the gear 6a.

That is, when the second drive motor 101 is rotated clockwise, the agitator 52 and the supply roller 55 are rotated.
And the developing roller 56 are driven to rotate as indicated by the arrow, so that the rotation of the agitator 52 causes the toner box 51 to rotate.
Is supplied to the supply roller 55,
The rotation of the supply roller 55 supplies the toner 53 to the developing roller 56. Here, the photosensitive drum 20 and the developing roller 56
And the developing roller 5
6 is driven at a predetermined peripheral speed which is about 1.4 times the peripheral speed of the photosensitive drum 20. Further, the developing roller 56 and the supply roller 55 are driven to rotate in opposite rotation directions, and the supply roller 55 is driven to have a predetermined peripheral speed that is about twice the peripheral speed of the developing roller 56.

Next, the operation and effect of the developing process using the reversal developing method will be described with reference to FIGS.

In order to obtain "2.0" as the transmission density (image density) required for the formed image, as shown in FIG. 6, the amount of toner adhered to the paper P, that is, the amount of developed toner is about 0.78 mg / cm2 is required. By the way, as described above, the developing roller 56 is
When the upper toner amount is set to about 0.6 mg / cm @ 2, the developing efficiency is about 100%.

The amount of charge of the toner 53 ranges from about 25 μq / g in a low-temperature and low-humidity environment of about 10 ° C. and a humidity of about 20% to a high-temperature and high-humidity environment of about 32 ° C. and about 80% in humidity. Changes to about 20 μq / g,
As described above, the developing roller 56 is driven in the direction opposite to that of the photosensitive drum 20 and at a peripheral speed of 1.4 times the peripheral speed of the photosensitive drum 20, and the supply roller 55 is moved in the opposite direction to the developing roller 56. And the peripheral speed of the developing roller 56 is twice or more the peripheral speed of the developing roller 56. As shown in FIG. 7, a low-temperature low-humidity environment indicated by a one-dot chain line and a high-temperature high-humidity environment In either environment, in order to obtain a predetermined amount of developing toner (about 0.78 mg / cm @ 2), the effective developing bias voltage of the developing roller 56 is set to "about 250 V". Since the electrostatic latent image voltage, which is the voltage of the electrostatic latent image formed on the developing roller 56, is set to 350V, the developing bias voltage of the developing power source E applied to the developing roller 56 is set to 350V (see FIGS. 5 and 8). ).

When the image forming process is started, first, the charge on the photosensitive drum 20 is wiped out by the discharging lamp 41, and then the photosensitive drum 20 is turned off as shown in FIGS.
Is uniformly charged to about +800 V by the charger 40. In this state, the laser beam L emitted from the laser emitter 31 is irradiated on the photosensitive drum 20 via the lenses 33 and 34 and the reflection mirrors 35 and 36 while being scanned by the polygon mirror 32 in the main scanning direction. An electrostatic latent image is formed on the drum 20. At this time, the voltage of the portion corresponding to the electrostatic latent image on the photosensitive drum 20 drops to about + 100V.

The supply roller 55 is driven to rotate in a direction opposite to that of the developing roller 56 and at a peripheral speed of about twice the peripheral speed of the developing roller 56. The toner 53 is supplied and the surface of the developing roller 56 is applied with a developing bias voltage of about +350.
In the state where V is applied, the toner 53 having a positive polarity adheres with two layer thicknesses, so that the toner 53 is not attracted to a charging voltage (about +800 V) higher than its own voltage. , Lower electrostatic latent image voltage (about +100
V), the toner 53 on the developing roller 56 is transferred to the photosensitive drum 20 so that the developing efficiency becomes about 100%.
It is developed only by adhering to the electrostatic latent image formed thereon. As a result, defective development on the photosensitive drum 20 can be prevented.

Here, as described above, the developing roller 56
Is set to about 250 V, the developing efficiency becomes about 100%, and a sufficient image density can be obtained.
Is driven so as to have a predetermined peripheral speed of about 1.4 times the peripheral speed of the photosensitive drum 20, so that abrasion between the photosensitive drum 20 and the developing roller 56 can be reduced. As a result, the photosensitive drum 20 and the developing roller 56 can be used for a long period of time only by replenishing the toner 53 into the toner box 51, and the running cost can be reduced.

On the other hand, the gap G between the supply roller 55 and the developing unit case 4 is formed to be narrow so as to promote the transfer of the toner 53, and the size thereof is 1 mm or less. Of the large amount of toner 53, the excess toner 53 removed by the layer thickness regulating blade 57 enters the gap G between the supply roller 55 and the developing unit case 4. The toner is transferred to the outside of the gap G at an early stage through the clockwise rotation of the supply roller 55 and does not accumulate in the gap G, so that the function of supplying the toner 53 by the supply roller 55 can always be maintained satisfactorily. .

Then, the toner image of the electrostatic latent image developed with the toner 53 is reliably transferred to the sheet P by the transfer roller 60, is subjected to a fixing process by the fixing unit 70, and is discharged to the discharge tray 77. .

Here, a transport path PP for transporting the paper P fed from the paper feed cassette 14 is formed substantially linearly.
Since the image is formed while the paper P is transported along the substantially linear transport path PP, even if the paper P is a thick paper such as a postcard or an envelope, it is possible to form a clear and reliable image on the paper P. Can be.

Incidentally, the second driving mechanism 100
The rotation speeds of the supply roller 55 and the developing roller 56 can be changed according to the type of the three types and the amount of toner attached to the developing roller 56, the layer thickness regulating blade 57 can be made of elastic rubber, Various modifications can be made to the above-described embodiment based on existing technology or technologies obvious to those skilled in the art, such as using a charging roller instead of the transfer roller 60, or using a transfer brush or a corotron transfer device instead of the transfer roller 60. It could be added. Of course, the present invention can be applied to various image forming apparatuses such as a copying machine and a facsimile.

[0064]

According to the image forming apparatus of the first aspect,
The photosensitive drum on which the electrostatic latent image is formed is driven in a predetermined rotation direction, and a developing roller that contacts the photosensitive drum and develops the electrostatic latent image with toner is driven in a direction opposite to the photosensitive drum. In addition, since the supply roller is driven to rotate in the direction opposite to the developing roller, the wear of the developing roller and the supply roller can be reduced. As a result, the photosensitive drum, the developing roller, and the supply roller can be used for a long period of time, and the running cost can be reduced only by replenishing the toner.

According to the image forming apparatus of the second aspect, the same effect as that of the first aspect is obtained, but the paper fed by the paper feed roller passes through the transfer means and the fixing unit and is substantially linear. And the paper is discharged by the paper discharging means, so that printing can be easily performed on thick paper.

According to the image forming apparatus of the third aspect, the same effect as that of the first or second aspect is obtained, but the peripheral speed of the supply roller is twice or more the peripheral speed of the developing roller. The toner layer on the developing roller, which has become non-uniform in the developing process of the electrostatic latent image, is uniformly formed to a predetermined layer thickness with a sufficient amount of toner supplied from the supply roller. The electrostatic latent image can always be developed well with a sufficient developing density.

According to the image forming apparatus of the fourth aspect, the same effect as that of the third aspect is obtained, but the excess toner removed by the layer thickness regulating member provided under the developing roller in a press-contact manner is removed. The toner drops into the gap between the frame of the developing unit and the supply roller, but since the gap is formed to be narrow, the transfer of the toner by the rotation of the supply roller is promoted and the toner is not accumulated by the supply roller. The supply function is well maintained.

According to the image forming apparatus of the fifth aspect, the same effect as that of the second aspect can be obtained, but since the photosensitive drum is disposed below the transport path and the transfer means is disposed above the transport path, the transport is performed. The toner image on the photosensitive drum can be reliably transferred to the sheet by maintaining the path substantially linear.

According to the image forming apparatus of the sixth aspect, the same effect as that of the fifth aspect is obtained, but since the exposure means is disposed below the photosensitive drum, the length in the transport direction can be shortened. In addition, the image forming apparatus can be configured to be compact, and an electrostatic latent image can be formed on the photosensitive drum by the exposure unit without interfering with sheet conveyance.

According to the image forming apparatus of the present invention, the photosensitive drum on which the electrostatic latent image is formed is driven in a predetermined rotation direction, and the developing roller which contacts the photosensitive drum and develops the electrostatic latent image with toner is provided. Since the photosensitive drum and the developing roller are driven to rotate in the opposite direction, wear of the photosensitive drum and the developing roller can be reduced. Further, since the supply roller is driven to rotate in the direction opposite to the developing roller, the developing roller and the supplying roller can be rotated. Can be reduced, and the running cost can be reduced as in the first aspect.

The paper fed by the paper feed roller is transported through the transfer means and the fixing unit, is conveyed by a substantially linear conveyance path, and is discharged by the paper discharge means. It can be easily printed. Further, since the photosensitive drum is disposed below the transport path and the transfer unit is disposed above the transport path, the transport path is maintained substantially linear, and the toner image on the photosensitive drum is reliably transferred to the paper. Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of a laser printer according to an embodiment of the present invention.

FIG. 2 is a partially enlarged side view of a developing unit in FIG.

FIG. 3 is a configuration diagram of a gear system of a first drive mechanism.

FIG. 4 is a configuration diagram of a gear system of a second drive mechanism.

FIG. 5 is an enlarged side view of a main part of FIG. 2;

FIG. 6 is a diagram relating to a transmission density and a developing toner amount.

FIG. 7 is a diagram relating to a developing toner amount and an effective bias voltage.

FIG. 8 is an explanatory diagram illustrating a developing process using a reversal developing method.

FIG. 9 is a configuration diagram of a laser printer having a zigzag paper transport path according to the related art.

10A is a configuration diagram of a laser printer in which a toner cartridge is provided downstream of a photosensitive drum in a sheet conveying direction with respect to a photosensitive drum, and FIG. FIG. 2 is a configuration diagram of a laser printer provided on an upstream side in a sheet conveyance direction.

[Explanation of symbols]

 Reference Signs List 1 laser printer 4 developing unit case 10 feeder unit 13 paper feed roller 14 paper feed cassette 20 photosensitive drum 30 laser scanner unit 50 developing unit 53 toner 55 supply roller 56 developing roller 60 transfer roller 70 fixing unit 77 discharge tray 80 first drive Mechanism 81 First drive motor 100 Second drive mechanism 101 Second drive motor P Paper G Gap PP Transport path

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[Procedure amendment]

[Submission date] August 23, 2000 (2008.2
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Image forming apparatus

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser printer, a facsimile or a copying machine, and more particularly to a supply roller for supplying toner to a developing roller, and a toner attached to the developing roller on a photosensitive drum. The present invention relates to an apparatus for developing an electro-latent image.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer or a copying machine, a paper feed mechanism for feeding paper stored in a paper feed cassette one by one by a paper feed roller, a photosensitive drum, and the photosensitive drum A paper fed by a paper feed mechanism, including a laser scanner unit for forming an electrostatic latent image thereon, a developing unit for developing the electrostatic latent image on the photosensitive drum with toner, a transfer roller, and a fixing unit. Various kinds of images are formed on the upper side by toner.

For example, a laser printer 200 shown in FIG.
In general, at the bottom of the main body case 202,
A paper feed cassette 214 and a paper feed roller 213 that feeds the sheets P stored in the paper feed cassette 214 one by one are provided. Transfer roller 26 that comes into pressure contact with
0, a fixing unit 270 is provided near the photosensitive drum 220, and a discharge tray 277 is provided above the photosensitive drum 220. That is, the transport path PP of the paper P fed from the paper feed cassette 214
The laser printer 200 is formed in a zigzag shape which is bent plural times as shown by a dashed line, so that the laser printer 200 can be downsized.

[0004] Then, the photosensitive drum 2 is
After the charge on the photosensitive drum 220 has been wiped out, the laser beam L emitted from the laser scanner unit 230 is irradiated onto the photosensitive drum 220 in a state where the surface of the photosensitive drum 220 is uniformly charged to a predetermined polarity by the charger 240. To form an electrostatic latent image, and this electrostatic latent image is
The toner image is created by being developed into a visible image by charged toner received from the developing roller 256 which is provided integrally with the photosensitive drum 220 and is in contact with the photosensitive drum 220. Then, the toner image is transferred to the conveyed sheet P by the transfer roller 260, and the toner image on the sheet P is further fixed on the sheet P by the heating roller 271 of the fixing unit 270, and finally, an image is formed. The discharged paper P is delivered to the paper output tray 27.
It is discharged to 7.

Here, in the toner cartridge 250, the developing roller 256 and the supply roller 25 that presses and contacts the developing roller 256 to supply the toner 253 to the developing roller 256.
5 is provided rotatably, and the developing roller 25
6, a layer thickness regulating blade 257 for regulating the layer thickness of the toner 253 adhering to the predetermined thickness and charging the toner 253 by rubbing is provided above the supply roller 255. The developing roller 256 and the supply roller 255 are driven in a rotational direction as shown in the drawing so that the removed excess toner 253 falls onto the supply roller 255. That is, in order to develop the toner 253 while charging the toner 253 with static electricity of a predetermined polarity, the developing roller 256
It is driven while being pressed and contacted in a rotation direction different from the rotation direction.

Incidentally, a laser printer 20 shown in FIG.
0, since the transport path PP of the paper P is zigzag, when thick paper such as an envelope is fed as the paper P, it cannot be transported smoothly at the turnback portion included in the transport path PP. Is configured to form an image on thin flexible paper.

Therefore, recently, a laser printer has been put to practical use in which a transport path from a paper feed cassette to a paper discharge tray is formed in a substantially straight line so that an image can be formed on various types of thick paper. As shown in FIG.
In the middle of the transport path PP from the paper feed roller 313 provided to the paper discharge tray 377, the photosensitive drum 320 is located below the transport path PP, and the transfer roller 360 is located in the transport path P.
P, a fixing unit 370 is provided facing the transport path PP, and a toner cartridge 35 having a developing roller 356 in contact with the photosensitive drum 320 is provided.
0 is provided on the downstream side of the photosensitive drum 320 in the sheet conveying direction, and the developing roller 356 and the supply roller 355 are so arranged that excess toner 353 removed by the layer thickness regulating blade 357 falls onto the supply roller 355. The developing roller 356 is driven to rotate in a direction opposite to the photosensitive drum 320 by being driven to rotate in the rotation direction as shown in the drawing. However, in this case, the conveyance path PP and the toner cartridge 350
It is difficult to provide a laser scanner unit in addition to the static elimination lamp and the charger in a narrow place between the two.

Therefore, as shown in FIG. 10B, the transport path PP from the paper feed roller 313 to the paper discharge tray 377 is used.
10A, the photosensitive drum 320, the transfer roller 360, and the fixing unit 370 are provided, and the toner cartridge 350 is provided on the upstream side in the sheet conveyance direction with respect to the photosensitive drum 320, as in FIG. The developing roller 35 is disposed such that excess toner 353 removed by the layer thickness regulating blade 357 falls onto the supply roller 355.
6, the supply roller 355, and the photosensitive drum 320 are respectively driven to rotate in the rotation directions as illustrated. That is, the developing roller 356 is attached to the photosensitive drum 3 so that the electrostatic latent image on the photosensitive drum 320 can be developed to have a sufficient image density.
The photosensitive drum 320 is driven so as to have a predetermined peripheral speed that is at least about twice the peripheral speed of the photosensitive drum 320 in the same rotational direction as that of the photosensitive drum 320. On the other hand, in this case, the transport path PP can be formed in a substantially linear shape, and the neutralizing lamp 341 and the charger 34 can be formed.
In addition to 0, the laser scanner unit 330 can be provided upstream of the toner cartridge 350 in the rotation direction of the photosensitive drum 320.

[0009]

As described above, FIG.
0 (b), the paper feed roller 313, the photosensitive drum 320 and the transfer roller 360, and the fixing unit 370
And a paper discharge tray 377 such that the transport path PP is formed in a substantially straight line, and in a laser printer capable of printing on various types of thick paper, the photosensitive drum 320 presses against the transfer roller 360. The developing roller 356 is driven in the clockwise direction in the figure while the developing roller 356 is driven in such a manner that the excess toner 353 removed by the layer thickness regulating blade 357 falls onto the supply roller 355. The supply roller 355 is driven in the same clockwise direction as the photosensitive drum 320 and at a predetermined peripheral speed of about twice or more the peripheral speed of the photosensitive drum 320, and the supply roller 355 is used for the developing roller 356 used for development. The developing roller 356 is driven to rotate in the same rotational direction so that the upper toner can be surely replenished.

That is, the outer peripheral portion of the photosensitive drum 320 and the outer peripheral portion of the developing roller 356 relatively move in opposite directions at their contact portion.
6 and the outer peripheral portion of the supply roller 355 relatively move in opposite directions at their contact portion, so that the photosensitive drum 320, the developing roller 356, and the supply roller 355 are greatly worn. , For example, 300
Since the image quality deteriorates every time printing is performed on 0 to 4000 sheets of paper P, the toner cartridge 350 and the photosensitive drum 32
There is a problem that the running cost increases because the 0 is replaced each time.

An object of the present invention is to provide an image forming apparatus capable of reducing abrasion between a photosensitive drum, a developing roller rotating while being in contact with the photosensitive drum, and a supply roller pressing and contacting the developing roller, and improving the image quality, and a paper conveyance. It is an object of the present invention to provide an image forming apparatus capable of forming an image on cardboard by forming a path substantially in a straight line.

[0012]

An image forming apparatus according to a first aspect of the present invention comprises a sheet feeding means for feeding a sheet for image formation by a sheet feeding roller, a photosensitive drum, and an electrostatic latent image on the photosensitive drum. an exposure means for forming a developing means having a developing roller for developing an electrostatic latent image on the photosensitive drum with toner supplied from the supply roller and the supplying roller for supplying the toner,
Transfer means for transferring the toner image on the photosensitive drum to the paper, and a fixing means for heating and fixing the toner image transferred to the paper
In an image forming apparatus including a step and a sheet discharging unit that discharges a sheet on which a toner image is fixed, the photosensitive drum is driven to rotate in a predetermined rotation direction in synchronization with sheet conveyance, and the developing roller is rotated by a photosensitive drum. Drive means for driving the supply roller to rotate in the direction opposite to the developing roller, and for driving the supply roller to rotate in the direction opposite to the developing roller.
Layer thickness regulation that regulates the amount of toner adhering to the image roller
Pressure member against the lower side of the developing roller.
Position the fixed end of the material closer to the photosensitive drum than the free end
Attached upward and rotated by the drive means
The direction of rotation of the supply roller is synchronized with the frame of the developing means.
To move toner in the gap between the supply rollers away from the development roller
It is set to be transported in the direction .

In operation, the photosensitive drum on which the electrostatic latent image is formed is driven in a predetermined rotation direction, and the developing roller which contacts the photosensitive drum and develops the electrostatic latent image with toner rotates in the opposite direction to the photosensitive drum. Since it is driven, the wear between the photosensitive drum and the developing roller can be reduced,
Further, since the supply roller is driven to rotate in a direction opposite to the developing roller, wear of the developing roller and the supply roller can be reduced.

The fixed end is closer to the photosensitive drum than the free end.
And installed diagonally upward,
Excess toner removed by the layer thickness regulating member pressed down
Is in the gap between the frame of the developing means and the supply roller.
Drops, and the toner in the gap moves away from the developing roller.
The rotation direction of the supply roller is set so as to transfer in the direction
Transfer of toner due to the rotation of the supply roller
Is accelerated and does not accumulate.
The supply function of the nut is well maintained.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
In the invention, a transport path for transporting a sheet is arranged in a substantially straight line across the sheet feed roller, the transfer unit, the fixing unit, and the sheet discharge unit.

The operation is similar to that of the first aspect, except that the paper fed by the paper feed roller is conveyed by a substantially linear conveyance path through these transfer means and fixing means. Since the paper is discharged by the paper discharging means, printing can be easily performed on thick paper.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
Alternatively, in the invention according to claim 2, the driving means drives the supply roller such that the peripheral speed of the supply roller is at least twice the peripheral speed of the developing roller.

The operation is similar to that of the first or second aspect, except that the supply roller is driven so that its peripheral speed is at least twice the peripheral speed of the developing roller. Therefore, the toner layer on the developing roller, which has become non-uniform in the developing process of the electrostatic latent image, can be made uniform to a predetermined layer thickness with a sufficient amount of toner supplied from the supply roller, and the electrostatic latent image Can always be satisfactorily developed with a sufficient developing density.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
In the invention of any one to 3 of the gaps, excessive transfer of toner removed by said layer thickness regulating member between the frame and the supply roller of a developing means formed on the lower side of the feed roller It is formed narrow so as to promote it.

The operation will be described .
Exhibits the same effect as the invention described in any of the above aspects, but the excess toner removed by the layer thickness regulating member pressed against the lower side of the developing roller falls into the gap between the frame of the developing means and the supply roller. However, since the gap is formed to be narrow, the transfer of the toner by the rotation of the supply roller is promoted and the toner is not accumulated, and the function of supplying the toner by the supply roller is favorably maintained.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the second aspect.
In the invention, the photosensitive drum is disposed below the transport path, and the transfer unit is disposed above the transport path.

The operation is similar to that of the second aspect. However, since the photosensitive drum is arranged below the conveyance path and the transfer means is arranged above the conveyance path, the conveyance path is maintained substantially linear. Thus, the toner image on the photosensitive drum can be reliably transferred to the paper.

According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the fifth aspect.
In the invention, the exposure means is provided below the photosensitive drum.

The operation is the same as that of the fifth aspect. However, since the exposing means is disposed below the photosensitive drum, the length in the conveying direction can be shortened, and the image forming apparatus can be made compact. The electrostatic latent image can be formed on the photosensitive drum by the exposure unit without interfering with the sheet conveyance.

[0025]

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

In the present embodiment, the present invention is applied to a laser printer having a feeder unit, a photosensitive drum, a laser scanner unit, and the like.

As shown in FIG. 1, this laser printer 1
In the main body case 2, a feeder unit 10 (corresponding to a paper feeding unit ) for feeding paper P for image formation, a photosensitive drum 20 receiving the laser beam L, and the photosensitive drum 2
A laser scanner unit (corresponding to an exposing unit) 30 for forming an electrostatic latent image on the developing unit 50 and a developing unit 50 (corresponding to a developing unit) having a supply roller 55 and a developing roller 56
) , A transfer roller (corresponding to a transfer unit) 60 for transferring the toner image on the photosensitive drum 20 to the sheet P, a fixing unit 70, and a sheet discharge tray (sheet discharge unit) for discharging the sheet P on which the image is formed. 77), a first drive mechanism 80 for driving the photosensitive drum 20, and a second drive mechanism 100 for driving the developing roller 56 and the like.

First, the feeder unit 10 will be described.

As shown in FIG. 1, a paper pressing plate 11 having substantially the same width as the paper P is provided in the feeder case 3 above the rear end of the main body case 2. The plate 11 is pivotally supported at a rear end thereof and elastically urged upward by a compression spring 12 at a front end thereof, and a sheet feeding roller 13 extending in the left-right direction is rotatably supported at the front end. The paper feed roller 13 is driven to rotate at a paper feed timing by a drive system (not shown).

In the feeder unit case 3, a sheet cassette 14 capable of accommodating a plurality of sheets P of fixed cut paper is removably mounted in an inclined manner, and a sheet feeding roller 1 is provided.
3 rotates the paper P stored in the paper feed cassette 14.
Of these, paper is fed one by one from the upper paper P. Furthermore,
In order to prevent two sheets of paper P from being inserted, a separation member 15 provided below the paper feed roller 13 is elastically urged to the paper feed roller 13 by a compression spring 16. Here, a pair of registration rollers 17 and 18 for aligning the leading ends of the fed paper P are rotatably pivoted downstream of the paper feed roller 13 in the transport direction (in FIG. 1, from the rear to the front). Supported.

As shown in FIGS. 1 to 2 and 5, the photosensitive drum 20 has a predetermined thickness (for example, a photoconductive resin dispersed in polycarbonate) on the outer periphery of a cylindrical aluminum sleeve 21. , About 20 μm), and is rotatably supported by the main body case 2 with the cylindrical sleeve 21 grounded. In other words, the toner 53 charged to the positive polarity is developed by the reversal development method with respect to the electrostatic latent image having the positive polarity formed on the photosensitive drum 20.

The laser scanner unit 30 is disposed below the photosensitive drum 20 and is driven to rotate by a laser emitter 31 for generating a laser beam L for forming an electrostatic latent image on the photosensitive drum 20. Polygon mirror (pentahedral mirror)
32, a pair of lenses 33, 34, a pair of reflection mirrors 3
5, 36 and the like. Since the laser scanner unit 30 is disposed below the photosensitive drum 20 as described above, the length in the transport direction can be shortened, and the laser printer 1 can be made compact and interfere with the paper transport. No, laser scanner unit 3
An electrostatic latent image can be formed on the photosensitive drum 20 by the laser light L emitted from the zero.

On the other hand, a scorotron-type charger 40 for generating a corona discharge from a charging wire made of tungsten or the like at a position advanced in the rotation direction from the position on the photosensitive drum 20 where the laser beam L is irradiated. The discharge lamp 41 is provided at a position further advanced in the rotation direction than the charger 40, and a paper for removing paper dust on the photosensitive drum 20 is further provided at a position further advanced in the rotation direction than the charger 40. A powder removing blade 42 is provided in a pressure contact state.

Next, the developing unit 50 disposed immediately after the photosensitive drum 20 will be described.

The developing unit case 4 has an agitator 52 that is driven to rotate, and an insulating toner 53 having electrical insulation.
Is mounted detachably, and is supplied to the front side of the toner box 51 by rotation of an agitator 52 via a toner supply port 51a formed in the toner box 51. Toner 53
Is formed, and a supply roller 55 is horizontally disposed in a horizontal direction in the toner storage chamber 54, and is rotatably pivoted.

Further, a developing roller 56 is horizontally disposed in the left-right direction so as to partition the front side of the toner storage chamber 54 and to be in contact with the supply roller 55 and the photosensitive drum 20, respectively. Have been. Here, the center of rotation of the developing roller 56 is provided at substantially the same height as the center of rotation of the photosensitive drum 20, but the supply roller 55 is provided so as to contact the developing roller 56 substantially obliquely from below. The gap G between the supply roller 55 and the developing unit case 4 is
It is formed narrow so as to facilitate the transfer of the toner 53. The size of the gap G is desirably 1 mm or less.

Here, the toner 53 is a polymerized toner made of styrene acrylic or the like, which has a more spherical shape than the pulverized toner, and has a particle size of about 7 to 10 μm.

The supply roller 55 is a conductive elastic foam made of silicon rubber, urethane rubber, or the like.
The resistance value at the contact portion with the developing roller 56 is about 5 × 1
It is set to 0 ⁴ to 1 × 10 ⁹ Ω.

The developing roller 56 is a conductive rigid roller made of silicon rubber, urethane rubber, or the like. The resistance from the central electrode to which the developing bias voltage is applied to the contact portion on the outer periphery is approximately equal. 5 × 10 ⁴ -1 × 1
It is set to 0 ⁷ Ω.

On the other hand, the lower end portion of the developing unit casing 4, the layer thickness regulating blade 57 having a thin plate-like elastic of stainless steel or phosphor bronze is attached to the rear obliquely upward, the layer thickness regulating blade 57 The fixed end of the free end
(End), is disposed closer to the photosensitive drum 20 than the
The bent portion formed at the tip of the blade 57 is
The layer thickness of the toner 53 supplied from the supply roller 55 and adhered in a layer on the surface of the developing roller 56 is reduced by the layer thickness regulating blade 57 to a predetermined thickness of about two layers. (About 13 to 17 μm). That is, the radius of curvature of the bent portion is about 0.5 mm so that the amount of toner on the developing roller 56 is set to about 0.6 mg / cm ² .
Thus, the toner 5 on the developing roller 56 after the regulation of the layer thickness is formed.
Since 3 has two layers, the toner 53 that has not been subjected to development does not accumulate on the contact portion with the photosensitive drum 20 and is securely attached to the developing roller 56 and collected.

Then, a first drive mechanism 80 and a second drive mechanism
The photosensitive drum 20 and the supply roller 5 are driven by the driving mechanism 100.
5 is rotated clockwise in side view, and the developing roller 5 is rotated.
6 is driven to rotate counterclockwise and the peripheral speed of the supply roller 55 is driven to be twice the peripheral speed of the developing roller 56, so that each toner particle 53a of the toner 53 is
As shown in FIG. 5, the supply roller 55 is charged to a positive polarity by the rubbing between the supply roller 55 and the developing roller 56, and by the pressing friction of the layer thickness regulating blade 57 against the developing roller 56.
The positively charged toner 53 adheres to the electrostatic latent image formed on the photosensitive drum 20 by the laser beam L and is developed by the reversal developing method.

Next, the transfer roller 60 is
It is provided so as to be in contact with the upper side of the
It is a conductive foamed elastic body made of silicon rubber, urethane rubber, or the like, and has a resistance value of about 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω at a contact portion with the photosensitive drum 20. That is, since the transfer roller 60 is in contact with the surface of the photosensitive drum 20, by increasing the resistance value,
Photosensitive drum 20 by voltage applied to transfer roller 60
The toner image on the photosensitive drum 20 is securely transferred to the sheet P so that the photoconductive layer 22 formed on the sheet P is not destroyed.

Fixing unit 70 (corresponding to fixing means)
Is provided downstream of the photosensitive drum 20 in the transport direction,
The toner image transferred to the lower surface of the sheet P is pressed while being heated and is fixed on the sheet P. The heating roller 71 includes a heating roller 71 having a halogen lamp and a pressing roller 72.

At the downstream side of the fixing unit 70 in the transport direction, a pair of transport rollers 75 for transporting the paper and a paper discharge tray 77 are provided, respectively.

That is, as shown in FIG.
The paper feed roller 13, the photosensitive drum 20, the fixing unit 70, and the paper discharge tray 77 that form a transport path PP that transports the paper P fed from the printer 4 are arranged substantially linearly. .

Next, the first drive mechanism 80 for driving the photosensitive drum 20 and the paper transport system will be described with reference to FIG.

The first drive mechanism 80 is disposed on the outer surface of the left side wall portion of the laser printer 1, and the rotational force of the gear 82 of the output shaft of the first drive motor 81 is a two-stage gear 83 ( 83a, 83b) and a two-stage gear 84 (84a, 84b).
b) to the gear 85, and the rotational force of the gear 85 is transmitted to the gear 13 a for driving the paper feed roller 13 via the gear 86. Further, the rotational force of the gear 86 is controlled by the gear 18 driving the registration roller 18 via the gear 87.
a.

The rotational force of the second gear 83 is divided into two gears 89 (89a, 89b), a gear 90 and a second gear 91 (9).
1a, 91b) and the two-stage gear 92 (92a, 92b) are transmitted to the gear 20a for driving the photosensitive drum 20.

On the other hand, the rotational force of the two-stage gear 92 is
Is transmitted to the gear 71a for driving the heating roller 71 via the gears 94 and 94. That is, when the first drive motor 81 is rotated clockwise, the paper feed roller 13, the pair of registration rollers 17, 18, the photosensitive drum 20, and the heating roller 71 rotate as indicated by the arrow. Since the paper P is driven, the paper P fed from the paper feed cassette 14 is transported along a predetermined transport path PP and is discharged to the paper discharge tray 77.

Next, the second driving mechanism 100 for driving the developing unit 50 will be described with reference to FIG. Here, the first driving mechanism 80 and the second driving mechanism 100 correspond to driving means.

The second drive mechanism 100 is disposed on the outer side of the side wall on the right side toward the laser printer 1.
The rotational force of the gear 102 of the output shaft of the drive motor 101 is the gear 103 and the two-stage gear 104 (104a, 104b)
The power is transmitted to the gear 52 a that drives the agitator 52 in the toner box 51 via the step gear 105 (105 a, 105 b), the gear 106, and the gear 107. Gear 1
06 is transmitted to a gear 55a for driving the supply roller 55, and the rotational force of the gear 55a is further
6 is transmitted to the gear 56a that drives the gear 6a.

That is, when the second drive motor 101 is rotated clockwise, the agitator 52 and the supply roller 55
And the developing roller 56 are driven to rotate as indicated by the arrow, so that the rotation of the agitator 52 causes the toner box 51 to rotate.
Is supplied to the supply roller 55,
The rotation of the supply roller 55 supplies the toner 53 to the developing roller 56. Here, the photosensitive drum 20 and the developing roller 56
And the developing roller 5
6 is driven at a predetermined peripheral speed which is about 1.4 times the peripheral speed of the photosensitive drum 20. Further, the developing roller 56 and the supply roller 55 are driven to rotate in opposite rotation directions, and the supply roller 55 is driven to have a predetermined peripheral speed that is about twice the peripheral speed of the developing roller 56.

Next, the operation and effect of the developing process using the reversal developing method will be described with reference to FIGS.

In order to obtain "2.0" as the transmission density (image density) required for the formed image, as shown in FIG. 6, the toner adhering amount to the sheet P, that is, the developing toner amount is about 0.78 mg / cm ² is required. By the way, as described above, the developing roller 56 is
When the upper toner amount is set to about 0.6 mg / cm ² , the developing efficiency is about 100%.

The amount of charge of the toner 53 ranges from about 25 μq / g in a low-temperature and low-humidity environment of about 10 ° C. and about 20% humidity to about 32 ° C. in a high-temperature and high-humidity environment of about 80% humidity. Changes to about 20 μq / g,
As described above, the developing roller 56 is driven in the direction opposite to that of the photosensitive drum 20 and at a peripheral speed of 1.4 times the peripheral speed of the photosensitive drum 20, and the supply roller 55 is moved in the opposite direction to the developing roller 56. And the peripheral speed of the developing roller 56 is twice or more the peripheral speed of the developing roller 56. As shown in FIG. 7, a low-temperature low-humidity environment indicated by a one-dot chain line and a high-temperature high-humidity environment In either environment, in order to obtain a predetermined amount of developing toner (about 0.78 mg / cm ² ), the effective developing bias voltage of the developing roller 56 is set to “about 250 V”, Since the electrostatic latent image voltage which is the voltage of the electrostatic latent image formed on the developing roller 20 is “100 V”, the developing bias voltage of the developing power source E applied to the developing roller 56 is set to 350 V (FIGS. 5 and 8). reference).

When the image forming process is started, first, the charge on the photosensitive drum 20 is wiped out by the discharging lamp 41, and then the photosensitive drum 20 is turned off as shown in FIGS.
Is uniformly charged to about +800 V by the charger 40. In this state, the laser beam L emitted from the laser emitter 31 is irradiated on the photosensitive drum 20 via the lenses 33 and 34 and the reflection mirrors 35 and 36 while being scanned by the polygon mirror 32 in the main scanning direction. An electrostatic latent image is formed on the drum 20. At this time, the voltage of the portion corresponding to the electrostatic latent image on the photosensitive drum 20 drops to about + 100V.

The supply roller 55 is driven to rotate in a direction opposite to that of the developing roller 56 and at a peripheral speed that is about twice the peripheral speed of the developing roller 56. The toner 53 is supplied and the surface of the developing roller 56 is applied with a developing bias voltage of about +350.
In the state where V is applied, the toner 53 having a positive polarity adheres with two layer thicknesses, so that the toner 53 is not attracted to a charging voltage (about +800 V) higher than its own voltage. , Lower electrostatic latent image voltage (about +100
V), the toner 53 on the developing roller 56 is transferred to the photosensitive drum 20 so that the developing efficiency becomes about 100%.
It is developed only by adhering to the electrostatic latent image formed thereon. As a result, defective development on the photosensitive drum 20 can be prevented.

Here, as described above, the developing roller 56
Is set to about 250 V, the developing efficiency becomes about 100%, and a sufficient image density can be obtained.
Is driven so as to have a predetermined peripheral speed of about 1.4 times the peripheral speed of the photosensitive drum 20, so that abrasion between the photosensitive drum 20 and the developing roller 56 can be reduced. As a result, the photosensitive drum 20 and the developing roller 56 can be used for a long period of time only by replenishing the toner 53 into the toner box 51, and the running cost can be reduced.

Meanwhile, the gap G between the supply roller 55 and the developing unit case 4, the transfer being narrowly formed to facilitate the toner 53, so the size thereof is 1mm or less, or
In addition, the tip of the layer thickness regulating blade 57 is
Since the toner is located near the contact point with the image roller 56, of the large amount of toner 53 supplied by the supply roller 55, the excess toner 53 removed by the layer thickness regulating blade 57 is supplied to the supply roller 55 and the developing unit case 4. The excess toner 53 that has entered the gap G is supplied to the supply roller 5.
5 away from the developing roller 56 via the clockwise rotation
The toner is transported in such a direction, is quickly transported outside the gap G, does not accumulate in the gap G, and the function of supplying the toner 53 by the supply roller 55 can always be maintained in a good condition.

Then, the toner image of the electrostatic latent image developed with the toner 53 is reliably transferred to the sheet P by the transfer roller 60, is fixed by the fixing unit 70, and is discharged to the discharge tray 77. .

Here, a transport path PP for transporting the paper P fed from the paper feed cassette 14 is formed substantially linearly.
Since the image is formed while the paper P is transported along the substantially linear transport path PP, even if the paper P is a thick paper such as a postcard or an envelope, it is possible to form a clear and reliable image on the paper P. Can be.

Incidentally, the second driving mechanism 100
The rotation speeds of the supply roller 55 and the developing roller 56 can be changed according to the type of the three types and the amount of toner attached to the developing roller 56, the layer thickness regulating blade 57 can be made of elastic rubber, Various modifications can be made to the above-described embodiment based on existing technology or technologies obvious to those skilled in the art, such as using a charging roller instead of the transfer roller 60, or using a transfer brush or a corotron transfer device instead of the transfer roller 60. It could be added. Of course, the present invention can be applied to various image forming apparatuses such as a copying machine and a facsimile.

[0063]

According to the image forming apparatus of the first aspect,
The photosensitive drum on which the electrostatic latent image is formed is driven in a predetermined rotation direction, and a developing roller that contacts the photosensitive drum and develops the electrostatic latent image with toner is driven in a direction opposite to the photosensitive drum. In addition, since the supply roller is driven to rotate in the direction opposite to the developing roller, the wear of the developing roller and the supply roller can be reduced. As a result, the photosensitive drum, the developing roller, and the supply roller can be used for a long period of time, and the running cost can be reduced only by replenishing the toner. And the fixed end
Place it on the photosensitive drum side from the free end and
Layer thickness regulating part attached and pressed under the developing roller
The excess toner removed by the material
It falls into the gap between the supply roller and
The developer in the direction away from the developing roller.
Since the rotation direction of the feed roller is set, the feed roller
The transfer of toner due to the rotation of
And maintain good toner supply function by the supply roller
Is done.

According to the image forming apparatus of the second aspect, the same effect as that of the first aspect is obtained, but the sheet fed by the sheet feeding roller is substantially linearly fed through these transfer means and fixing means. And the paper is discharged by the paper discharging means, so that printing can be easily performed on thick paper.

According to the image forming apparatus of the third aspect, the same effect as that of the first or second aspect is obtained, but the peripheral speed of the supply roller is twice or more the peripheral speed of the developing roller. The toner layer on the developing roller, which has become non-uniform in the developing process of the electrostatic latent image, is uniformly formed to a predetermined layer thickness with a sufficient amount of toner supplied from the supply roller. The electrostatic latent image can always be developed well with a sufficient developing density.

According to the image forming apparatus of the fourth aspect, the same operation as the invention of any one of the first to third aspects is achieved, but it is removed by the layer thickness regulating member pressed against the lower side of the developing roller. The excess toner dropped into the gap between the frame of the developing means and the supply roller, but since the gap is formed to be narrow, the transfer of the toner due to the rotation of the supply roller is promoted and the toner may accumulate. Therefore, the toner supply function of the supply roller is favorably maintained.

According to the image forming apparatus of the fifth aspect, the same effects as those of the second aspect can be obtained, but since the photosensitive drum is disposed below the transport path and the transfer means is disposed above the transport path, the transport is performed. The toner image on the photosensitive drum can be reliably transferred to the sheet by maintaining the path substantially linear.

According to the image forming apparatus of the sixth aspect, the same effect as that of the fifth aspect is obtained, but since the exposure means is disposed below the photosensitive drum, the length in the transport direction can be shortened. In addition, the image forming apparatus can be configured to be compact, and an electrostatic latent image can be formed on the photosensitive drum by the exposure unit without interfering with sheet conveyance.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of a laser printer according to an embodiment of the present invention.

FIG. 2 is a partially enlarged side view of a developing unit in FIG.

FIG. 3 is a configuration diagram of a gear system of a first drive mechanism.

FIG. 4 is a configuration diagram of a gear system of a second drive mechanism.

FIG. 5 is an enlarged side view of a main part of FIG. 2;

FIG. 6 is a diagram relating to a transmission density and a developing toner amount.

FIG. 7 is a diagram relating to a developing toner amount and an effective bias voltage.

FIG. 8 is an explanatory diagram illustrating a developing process using a reversal developing method.

FIG. 9 is a configuration diagram of a laser printer having a zigzag paper transport path according to the related art.

10A is a configuration diagram of a laser printer in which a toner cartridge is provided downstream of a photosensitive drum in a sheet conveying direction with respect to a photosensitive drum, and FIG. FIG. 2 is a configuration diagram of a laser printer provided on an upstream side in a sheet conveyance direction.

DESCRIPTION OF REFERENCE NUMERALS 1 laser printer 4 developing unit case 10 feeder unit 13 paper feed roller 14 paper feed cassette 20 photosensitive drum 30 laser scanner unit 50 developing unit 53 toner 55 supply roller 56 developing roller 60 transfer roller 70 fixing unit 77 paper discharge Tray 80 First drive mechanism 81 First drive motor 100 Second drive mechanism 101 Second drive motor P Paper G Gap PP Transport path

Claims (7)

[Claims] A feeder unit for feeding paper for image formation by a feed roller; a photosensitive drum; an exposing unit for forming an electrostatic latent image on the photosensitive drum; a supply roller for supplying toner; A developing unit having a developing roller for developing an electrostatic latent image on a photosensitive drum with toner supplied from a supply roller, a transfer unit for transferring a toner image on the photosensitive drum to paper, and a toner image transferred to paper An image forming apparatus provided with a fixing unit that heats and fixes the toner image, and a sheet discharging unit that discharges the sheet on which the toner image has been fixed, wherein the photosensitive drum is rotationally driven in a predetermined rotation direction in synchronization with sheet conveyance, and Driving means for driving the developing roller to rotate in the direction opposite to the photosensitive drum and for driving the supply roller to rotate in the direction opposite to the developing roller. Apparatus. 2. The image forming apparatus according to claim 1, wherein a transport path for transporting the paper is disposed in a substantially linear manner across the paper feed roller, the transfer unit, the fixing unit, and the paper discharge unit. 3. The driving device according to claim 1, wherein the peripheral speed of the supply roller is:
3. The supply roller is driven so that the peripheral speed is at least twice the peripheral speed of the developing roller.
An image forming apparatus according to claim 1. 4. A layer thickness regulating member for regulating the amount of toner supplied from the supply roller and adhering to the developing roller is provided under the developing roller in a pressure-contact manner, and a developing member formed below the supply roller is provided. 4. The image forming apparatus according to claim 3, wherein a gap between the unit frame and the supply roller is formed to be narrow so as to facilitate transfer of excess toner removed by the layer thickness regulating member. 5. The image forming apparatus according to claim 2, wherein the photosensitive drum is disposed below the transport path, and the transfer unit is disposed above the transport path. 6. The image forming apparatus according to claim 5, wherein the exposure unit is provided below the photosensitive drum. 7. A feeder unit for feeding a sheet for image formation by a feed roller, a photosensitive drum, an exposure unit for forming an electrostatic latent image on the photosensitive drum, a supply roller for supplying toner, and A developing unit having a developing roller for developing an electrostatic latent image on a photosensitive drum with toner supplied from a supply roller, a transfer unit for transferring a toner image on the photosensitive drum to paper, and a toner image transferred to paper An image forming apparatus provided with a fixing unit that heats and fixes the toner image, and a paper discharging unit that discharges the paper on which the toner image is fixed, wherein the paper feeding roller, the transfer unit, the fixing unit, and the paper discharging unit are provided, A photosensitive drum is rotated in a predetermined rotation direction in synchronization with paper transport, and the developing roller is rotated in a direction opposite to the photosensitive drum. Driving means for driving the supply roller to rotate in a direction opposite to the developing roller, wherein the photosensitive drum is disposed below the transport path, and the transfer means is disposed above the transport path. An image forming apparatus comprising: