JPH01252456A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the breakage of an image by forming a transport guide form the electric conductive material and electrically grounding said transport guide and sending a paper which is supplied from an image copying part to a fixation unit, floating up the paper by the electrostatic attractive action between the transport guide arranged above. CONSTITUTION:An image is copied onto the undersurface of a paper by an image copying part 28, and the paper is sent into a fixation unit 33 along a transport guide 37 arranged over the image copying part 28, in other word along a paper transporting passage 29, and then the image is fixation-processed, and the paper is discharged from a paper feed roller unit 34. In this case, the transport guide 37 is constituted of the electric conductive material and grounded electrically. Therefore, the paper which is sent out from the image copying part 28 and electrified with a plus charge in copying is floated up by the electrostatic attractive action with the transport guide 37, and then sent into the fixation unit 33, prevented from dangling. Thus, even in case of the type in which an image is copied onto the undersurface of the paper, the breakage of the image can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus such as a laser printer, and more particularly to an image forming apparatus that forms images using an electrophotographic process.

(Prior Art) In this type of image forming apparatus, an image transfer section transfers an image onto a sheet of paper, and the sheet is conveyed along a conveyance guide placed above the sheet and sent to a fixing unit. The image is fixed onto the paper.

(Problem to be Solved by the Invention) When an image is transferred to paper in an image transfer section, since the polarity of the image transfer section is generally positive, the paper is charged with a positive charge, and in this state, the paper is The paper is sent out from the image transfer unit, but at this time, since various grounded metal members are placed below the paper, the paper curves downward due to the electrostatic attraction between it and the metal members. If the paper is of a type where the image is transferred to the bottom side of the paper and then transported, the unfixed image may be damaged by this contact. Sometimes. Such a phenomenon is particularly likely to occur under conditions of low temperature and low humidity.

The present invention has been made with this point in mind, and an object of the present invention is to provide an image forming apparatus that prevents sheets from sagging and does not damage images.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention transfers an image onto a sheet of paper in an image transfer section, and transports this sheet along a transport guide disposed above it. In an image forming apparatus in which the image is fixed on the paper by the fixing unit, the conveyance guide is made of a conductive material and electrically grounded, and the paper sent out from the image transfer section is fixed. The electrostatic attraction between the paper and the conveyance guide causes the paper to float while being fed into the fixing unit.

(Function) The suction between the paper and the conveyance guide prevents the paper from hanging down, so even if the image is transferred to the bottom side of the paper, the image will not be damaged. do not have.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

3 and 4 show the appearance of an electrophotographic image forming apparatus using a semiconductor laser, and FIGS.
The figure shows its internal configuration. This image forming apparatus (laser printer) is connected to a host system (not shown), which is an external output device such as an electronic computer or a word processor, via a transmission controller such as an interface circuit. When a print start signal is received from the host system, the image recording operation is started, and the image is recorded on paper as a transfer material and output.

Describing the structure of this image forming apparatus, reference numeral 1 in the figure is the main body of the apparatus. A control board 2 is arranged. An electrophotographic process unit 3 for forming images is arranged behind the main control board 2 (toward the right side in the state shown in Fig. 1), and a plurality of function-adding controls are arranged at the front lower part. A control board accommodating section 5 for accommodating a plurality of boards 4 is provided, and a paper discharging section 6 is further formed in the upper front part.

The function addition control board 4 is used to add functions (for example, typeface,
Up to three boards can be installed depending on the degree of addition (such as adding more types of kanji, etc.), and an additional three boards are installed on the front edge of the control board 4 for adding functions located at the bottom.
Further functions can be added by inserting a function-adding IC card 17 into the IC card connector 16. In addition, two interfaces (not shown) are arranged on the left end surface of the control board 4 for adding functions located at the bottom, and these interfaces are formed on the left side surface of the device main body 1. It faces the opening 18 (see FIG. 3).

Further, a lower portion inside the apparatus main body 1 is a cassette accommodating section 8 that accommodates a paper feed cassette 7.

As shown in FIGS. 3 and 4, the paper discharge section 6 consists of a recess formed on the front upper surface of the apparatus main body 1, and the front edge of the paper discharge section 6 has a recess that is folded into the paper discharge section 6. A rotatable paper discharge tray 9 that can be unfolded as shown in the figure is provided. moreover,
A notch 9a is formed at the center of the front end of the paper ejection tray 9, and a sheet can be accommodated in the notch 9a as shown in FIG.

Rotatable U-shaped auxiliary paper output tray 10 that can be unfolded
is provided. The size of the paper discharge section 6 can be adjusted according to the size of the paper P to be discharged.

Further, on the upper surface of the left frame portion 1a of the apparatus main body 1 located on the left side of the paper ejecting portion 6, there is a 7-segment LED 12 for displaying a 1° 2-digit status display. A control panel 14 on which switches 13 and switches 13 are arranged is disposed, and a manual feed tray 15 is attached to the rear side of the main body 1 of the apparatus.

Next, charging, exposure, development, transfer, stripping, and cleaning.

The electrophotographic process unit 3 that performs electrophotographic processes such as fixing and fixing will be described with reference to FIGS. 1 and 2.

A drum-shaped photoreceptor 20 serving as an image carrier is disposed approximately in the center of the unit accommodating portion, and this photoreceptor 2
Charging means 21.0 consisting of a scorotron is arranged around the rotating direction of the charging means. An exposure section 22a of a laser exposure unit 22 as an electrostatic latent image forming means, a magnetic brush type development unit 23 that performs a development process and a cleaning process at the same time, and a transfer unit 24 consisting of a scorotron. Memory removing means 25 consisting of a brush member. and pre-exposure means 26 are arranged in this order.

Also, inside the apparatus main body 1, paper P fed from the paper feed cassette 7 via the paper feed means 27 and the manual feed tray 15 are stored.
A paper conveyance path 29 is formed which guides the paper P manually fed from the photoreceptor 20 and the transfer means 24 to the paper discharge section 6 provided on the upper surface side of the apparatus main body 1 via the image transfer section 28. ing.

A pair of transport rollers 30. A pair of aligning rollers 31 and a pair of transport rollers 32 are arranged, and a fixing unit 33 and a paper ejection roller unit 34 are arranged on the downstream side. A cooling fan unit 35 is disposed above the position where the pair of transport rollers 32 are disposed, and the pair of aligning rollers 3
An aligning switch 36 is provided near the image transfer section 1 , and a conveyance guide 37 is provided above the image transfer section 28 . The conveyance guide 37 is made of a conductive material such as an iron plate, and is electrically grounded.

When a print start signal is received from the host system, the drum-shaped photoreceptor 2o rotates, and the photoreceptor 20 is charged by the charging means 21. In this state, the laser beam a modulated in response to the dot image data from the host system is scanned and exposed onto the photoreceptor 2o using the laser exposure unit 22, and the photoreceptor 20 is exposed to the image signal corresponding to the image signal. Forms an electrostatic latent image. This electrostatic latent image on the photoreceptor 2o is developed and visualized by the toner t in the developer magnetic brush D' of the development unit 23.

On the other hand, in synchronization with this toner image forming operation, the paper P taken out from the paper feed cassette 7 or manually fed from the manual tray 15 is fed through a pair of aligning rollers 31 and is previously placed above the photoreceptor 2°. The toner image formed on the paper P is transferred to the paper P by the action of the transfer means 24. Then, the paper P is guided by the transport guide 37 to the paper transport path 2.
9 and is sent to the fixing unit 33, where the toner image is melted and fixed onto the paper P. Thereafter, the paper is discharged to the paper discharge section 6 via the paper discharge roller unit 34.

When the toner image (image) is transferred to the paper P, the paper P is charged with a positive charge, and the paper P is sent out from the image forming section 28 in this state. Here, the conveyance guide 37
Since it is made of a grounded conductive material, a negative charge is generated on the conveyance guide 37 as the paper P is fed out.
Due to the electrostatic attraction effect based on the potential difference, a force is applied to the paper P that tends to float upward, which cancels out the force that tends to cause the paper P to droop downward, thus preventing the paper P from sagging. This is prevented, and the paper P is always fed into the fixing unit 33 while maintaining a proper state.

Note that after the toner image is transferred onto the paper P, the residual toner remaining on the photoreceptor 20 is removed by a memory removing means 25 consisting of a conductive brush, thereby performing memory removal.

Further, as shown in FIG. 2, the fixing unit 33 includes a heat roller 41 having a built-in heater lamp 40 and a pressure roller 42 that is in pressure contact with the heat roller 41. The toner image is fused and fixed onto the paper P by passing through the paper P.

Further, the heat roller 41 and the pressure roller 42 are surrounded by a lower casing 43 and an upper casing 44, and are structured to prevent heat from escaping to the outside as much as possible to ensure a favorable temperature atmosphere necessary for fixing. ing.

A cleaner 45 is in contact with the heat roller 41, and the temperature is controlled by a thermistor 46 to maintain the temperature necessary for fixing. The structure is such that

Further, a paper guide 48 is disposed within the upper casing 44 and near the upstream side of the contact portion 47 between the heat roller 41 and the pressure roller 42 to ensure that the leading edge of the paper P guided to the fixing unit 33 is heated. Roller 41 and pressure roller 42
It is designed to guide you between. A paper guide 49 is provided integrally with the lower casing 43 on the paper exit side of the fixing unit 33 to guide the fixed paper P to the paper discharge roller unit 34.

Further, the paper ejection roller unit 34 includes a lower roller 50
and an upper roller 51, and the paper P is
A static eliminating brush 52 is provided in contact with the non-image forming surface of the image forming apparatus.

A top cover 60 is provided in the open portion 1a on the upper surface of the apparatus main body 1 so as to be openable and closable, and the transfer means 24. Conveyance guide 37° and static elimination brush 5
2 and the upper roller 5 of the paper ejection roller unit 34.
1 is installed.

The top cover 60 can be rotated upward by a maximum of about 120°, as shown in FIG. There is.

When the top cover 60 is rotated upward, the transfer means 24. Conveyance guide 37. The upper roller 51 including the static elimination brush 52 is located at the open part 1a of the apparatus main body 1
Therefore, most of the paper conveyance path 29 and most of the equipment in the electrophotographic process unit facing the two paper conveyance paths are exposed, and therefore, when the paper P becomes jammed, removal work and the above-mentioned equipment cannot be performed. Maintenance inspection, replacement work, etc. can be performed easily and efficiently.

Further, the rear cover 64 of the apparatus main body 1 shown in FIG. The curved conveying section can be opened, and the paper P stuck in this section can be easily removed. Note that 62 shown in FIG. 4 is an ozone filter, and 63 is a toner cartridge.

Next, the main electrophotographic process components mentioned above will be explained in detail.

First, as shown in FIGS. 5 to 8, the charging means 21
consists of a scorotron. That is, a corona wire 71 with a diameter of 60p is stretched inside a shield case 70, and the surface of the corona wire 71 is made of white tungsten to prevent negative corona from being generated unevenly.

One end of the corona wire 71 is fixed to a metal fitting 74 to which a power supply pin 73 serving as a charging means power supply section is screwed. The power supply bottle 73 and the metal fitting 74 are fixed inside the power supply terminal 75. On the other hand, the other end of the corona wire 71 is secured to a terminal 77 by a plastic hook 76 via a tension spring 72. The terminals 75 and 77 are each covered with terminal covers 78 and 79 so that the parts to which high voltage is applied are not exposed.

The shield case 70 is made of stainless steel with a thickness of 0.3 mm, and has a mesh on the side facing the photoreceptor 20, as shown in FIG. 5, and serves as a grid 70a of the scorotron charger. Also, grid 7
0a can maintain sufficient accuracy such as flatness without using special parts for integration with the side cases 70b and 70c.

Furthermore, since the same bias voltage is applied to both side cases 70b and 70c when corona discharge is performed, the corona current flowing through both side cases 70b and 70c is reduced, resulting in a charger with good current efficiency.

Further, the shield case 70 is connected to the anode of a 560V Zener diode 82 (see FIG. 12), and is connected to a charger guide 83 (see FIG. 12) through the cathode of the Zener diode 82. On the other hand, the charger guide 83 is coupled to the ground terminal of the main body. Therefore, when a high voltage (-5 kV) is applied to the corona wire 71 via the power supply pin 73 by a high voltage transformer (not shown) in the main body of the device, corona discharge occurs in the shield case 70 and current flows in the shield case 70. However, due to the rectifying characteristics of the Zener diode 82, the potential of the shield case 70 rises to -560V and is kept constant.

Therefore, since the grid 70a naturally becomes -560V, the surface potential of the photoreceptor 20 located 21!1 meters away from the grid 70a is kept constant at -500V, which is slightly lower than the potential of the grid 70a. In addition, 80.81 in the figure is the charging means 21.
When integrally assembled into a process cartridge 85 (see FIGS. 11 and 12), which will be described later, there is an engagement that engages with an engaged portion 84 (see FIGS. 13 and 14) formed on the process cartridge 85. It is a joint.

As shown in FIGS. 2 and 9, the laser exposure unit 22 includes a semiconductor laser oscillator 90 (not shown in detail), a polygon scanner 93 consisting of a polygon mirror 91 and a mirror motor 92, and a second lens for FE. 95,
It is composed of a second lens 95 for FE, reflective mirrors 96 and 97 for scanning the scanned laser beam a to a predetermined position, and the like. An opening 99 formed in the base 98 located below the installation position of the laser exposure unit 22, that is, on the upper surface side of the cassette accommodating section 8, and an opening 100 formed on the lower surface side of the apparatus main body 1, By pulling out the paper feed cassette 7 forward (in the direction of the arrow in FIG. 1), it can be attached or removed from below (see FIG. 9).

Moreover, the control board 101 of this laser exposure unit 22
is connected to the main control board 2 via a connector 102.

Furthermore, the laser exposure unit 22 is housed in a synthetic resin casing 103 whose bottom side is open, and the bottom opening of this casing 103 is connected to a metal shield plate 10.
4, and a metal shield cover 105 which also serves as a reinforcing plate is superimposed on the upper surface side of the casing 103. A conductive contact piece 106 is connected to the shield cover 105, and this contact piece 106 slidably guides the developing unit 23 when the laser exposure unit 22 is attached to a predetermined position via an attachment means (not shown). This is in contact with a metal guide rail 107, which prevents malfunctions due to electrostatic adverse effects from the charging means 21 and the like reaching the inside.

Note that the photoreceptor 20 uses an organic photoconductor,
It has a structure in which a charge generation layer and a charge transport layer covering this charge generation layer are formed on the surface of an aluminum tube.

Further, in order to simplify the electrophotographic process, the developing unit 23 employs a reversal developing method, and also employs a method in which the residual toner t after transfer is removed at the same time as the developing. This developing unit 23 is shown in FIG.
As shown in FIG. 0, a photoreceptor 20 and a developing roller 122 are provided in a casing 121 having a developer storage portion 120.
20 contains toner (young color powder) t and carrier (magnetic powder) C.
A two-component developer consisting of the following is housed. Further, the sliding contact portion of the developer magnetic brush D' formed on the surface of the developing roller 122 with the photoreceptor 20, that is, the developing position 12
A doctor 124 for regulating the thickness of the developer magnetic brush D' is provided upstream of the photoconductor 3 in the rotational direction of the photoreceptor 20. Furthermore, in the developer storage section 120,
1st. Second developer stirring bodies 125 and 126 are housed.

Note that the developing unit 23 is equipped with a toner cartridge 63 (see FIG. 1) as a toner replenishing device, so that the toner t is appropriately replenished into the developer storage section 120.

Further, the developing roller 122 has three magnetic pole parts 127.12.
The magnetic roll 130 has magnetic rolls 8 and 129, and a non-magnetic sleeve 131 that is fitted around the magnetic roll 130 and rotates clockwise in the figure. magnetic roll 130
Of the three magnetic pole parts 127, 128, 129, the magnetic pole part 128 facing the development position 123 is the north pole, and the other magnetic pole parts 127, 128 are the south pole. In addition, the magnetic pole part 1
The angle e+ (see FIG. 2) between the magnetic pole portion 27 and the magnetic pole portion 128 is set to 150°, and the angle e2 (see FIG. 2) between the magnetic pole portion 128 and the magnetic pole portion 129 is set to 120°.

The electrostatic charge on the photoreceptor 20 is caused by the potential difference between the mechanical scraping force caused by the magnetic brush development using the two-component developer, the charging potential caused by the reversal development, and the development bias applied to the magnetic brush D'. The residual toner 1 is collected mechanically and electrically at the same time as the latent image is developed.

　　.

Further, the developing means 23 includes a photoreceptor 20. Charging means 21
．． The memory removal means 25 and the like are integrated into the process cartridge 85, and one end of the process cartridge 85 has a handle 1 for inserting and removing the cartridge.
32 (see FIGS. 12 and 13), it can be taken in and out of the device body 1. Further, at the other end side, a developing bias power supply section 140. A memory removal means power supply section 141 and a charging means power supply section 142 consisting of a power supply pin 73 are provided in a protruding manner.
0,141.142 is inserted into a power supply connector provided inside the main body 1 of the device.

Further, a foldable handle 143 for carrying is provided on the top side of the process cartridge 85, and a cleaning brush 144 for cleaning the lower roller 31a of the aligning roller pair 31 is attached.

Furthermore, as shown in FIGS. 11 and 14, on the other end side of the developing means 23, the developing sleeve 131, the first. A gear group 147 that is connected to the second developer stirring bodies 125, 126, a winding shaft 146 (see FIG. 10) for winding up the photoreceptor protection sheet 145, etc., and that interlocks with each other is provided. It becomes. The gear 147a meshes with a drive gear (not shown) provided on the device main body 1 side, and by driving the gear 147a, each of the rotating members described above is rotated in a predetermined direction at a predetermined speed. It has become. Note that the photoreceptor protection sheet 145 wound around the winding shaft 146 is housed in a guide tube 148 surrounding the winding shaft 146, so that the end portion does not protrude to the outside.

Note that 150 shown in FIG. 14 is the process cartridge 8.
5 is a rod for pressing the presence/absence detection switch (not shown), 151 is a shutter for a toner replenishing port that opens when the toner cartridge 63 is attached, and 152 is a spring for a shutter. Further, 153 is a pin for fixing the photoreceptor.

Further, as shown in FIG. 12, an auto-toner sensor ring 160 is provided at one end of the photoreceptor 20.
The configuration is such that the developer concentration can be detected at this portion.

As shown in FIG. 16, this auto-toner sensor ring 160 is connected to the doctor 124 via a conductive plate spring 161 made of phosphor bronze or the like, and further to the current sleeve 131 via a conductive plate spring 162. , the auto toner sensor ring 60. Doctor 124. and developing sleeve 1
31 are at the same potential. In other words, power can be supplied to the auto toner sensor ring 160 without using a dedicated power supply means.

Further, as shown in FIG. 16, at one end of the photoreceptor 20,
A plated metal cap 170, a portion of which becomes the auto toner sensor ring 160;
Bearing member 171 fitted into the bearing member 171. A flange 174 equipped with an engaging member 173 made of a leaf spring member attached to the end face of this bearing member 171 via a fixing member 172...
is attached to the shaft insertion hole 1 of the flange 174 when the process cartridge 85 is assembled into the apparatus main body 1.
A photoreceptor drive shaft 175 provided on the apparatus main body 1 side is inserted into 74a. At this time, the locking tongue portions 173a, which are cut and formed on the engagement member 173 and supported by support protrusions (not shown) whose back side protrudes from the bearing member 171, are attached to the photoreceptor drive shaft. Engaged groove 176 made of knurling formed along the axial direction of 175
. . , so that the driving force of the photoreceptor drive shaft 175 is transmitted to the photoreceptor 20.

A flange (not shown) comprising a cap and a bearing member is also attached to the other end of the photoreceptor 20, and is pivotally supported by the photoreceptor drum fixing pin 153.

Further, as shown in FIGS. 17 to 20, the transfer means 24 is composed of a scorotron.

That is, the corona wire 19 is placed inside the shield case 190.
One end of this corona wire 191 is connected to a metal fitting 193 screwed to a power supply terminal 192 as shown in FIGS. 17 and 18, and the other end is connected to a metal fitting 193 as shown in FIG. Axis 1 of terminal 194
95 via a tension spring 196.

Further, the portion of the shield case 190 facing the photoreceptor 20 is a mesh as shown in FIG. 17, and constitutes a grid 190a.

17 and 2 on the power supply terminal 192 side.
As shown in FIG. 0, a grid voltage power supply section 197 and a wire high voltage power supply section 198 are provided.

Further, as shown in FIGS. 21 to 24, the memory removing means 25 includes a conductive brush 200. Backing member 201
．． and a holding fitting 202 that holds them. There are mounting holes 203 on both ends of the holding fitting 202.
, 203 are provided, and are fixed to the process cartridge 85 via set screws 204, 204 (see FIG. 12, 2).

The brush 200 is made of, for example, rayon impregnated with carbon to have a specific resistance of 106 Ω·mm and made into fibers with a thickness of 6D (denier), each made into a bundle of 100 fibers, and 82 bundles/bundle.
It is constructed by making a satin weave with a density of 1 nch, stacking two layers and removing the weft.

Further, the brush 200 has one side, as shown in FIG.
Thickness tIII! Holding metal fitting 201 with the backing member 201 made of polyester film (about 0.1 mm) protruding from the tip of the brush 200 by dM (about 0.1 B)
It is supposed to be attached to 02.

Approximately 156 points are attached to the photoreceptor 20 upstream of the charging means 21 so that the brush surface contacts the brush 200 at a corner at a position 3M from the tip.

Note that the present invention is not limited to the above-mentioned embodiment, but can be implemented with various modifications without changing the gist.

[Effects of the Invention] As explained above, according to the present invention, an image is transferred to paper in the image transfer section, and the paper is conveyed along the conveyance guide disposed above the paper and sent to the fixing unit. In an image forming apparatus that fixes the image on the paper in a unit, the transport guide is made of a conductive material and is electrically grounded, and the paper sent out from the image transfer section is connected to the transport guide due to static electricity. Since the paper is fed into the fixing unit while being floated by a suction action, the paper does not come into contact with the member placed below it, and therefore the image is transferred to the bottom side of the paper. This also has the effect that there is no risk of damaging the image.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show one embodiment of the present invention, in which FIG. 1 is a configuration diagram showing the internal structure of an image forming apparatus, FIG. 2 is a configuration diagram showing an enlarged view of its main parts, FIG. 3 is an external perspective view of the image forming apparatus, FIG. 4 is an external perspective view with the top cover open, FIG. 5 is a view of the charging means as seen from the grid side, and FIG.
The figure is a front view, FIG. 7 is a sectional view taken along the line A-A in FIG. 5, FIG. 8 is a side view seen from the direction of arrow B in FIG. 6, and FIG. FIG. 10 is a schematic sectional view of the process cartridge, FIG. 11 is a schematic perspective view, FIG. 12 is a schematic plan view, and FIG. 13 is a side view of one end. FIG. 14 is a side view of the other end side of only the developing means, FIG. 15 is a sectional view of the vicinity of the driving force transmission side of the photoreceptor, and FIG. 16 is a diagram schematically showing the state of power supply to the auto toner ring. FIG. 17 is a partially cutaway view of the transfer means as seen from the grid side, FIG. 18 is a partially cutaway view of the transfer means as seen from the arrow IA in FIG. 20 is a sectional view taken along line C-C in FIG. 17, FIG. 21 is a plan view of the memory removal means, FIG. 22 is a front view, and FIG. 23 is a sectional view taken along line B-B in FIG. The figure is also a bottom view, and FIG. 24 is a sectional view taken along the line A--A in FIG. 21. 28... Image transfer section, 33... Fixing unit, 37
...Transportation guide. Applicant's Representative Patent Attorney Takehiko Suzue Figure 3, Section 4, Section 9, Figure 1o, Figure 14, Figure 7 [Figure 22, Figure 23]

Claims (1)

[Claims] An image forming apparatus in which an image is transferred to a sheet of paper by an image transfer section, the sheet of paper is conveyed along a conveyance guide disposed above the sheet of paper, and sent to a fixing unit, and the image is fixed to the sheet of paper by this fixing unit. The conveyance guide is made of a conductive material and is electrically grounded, and the paper sent from the image transfer section is sent to the fixing unit while floating due to the electrostatic attraction between the conveyance guide and the conveyance guide. image forming device.