JPH01251072A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the bedewing of steam rising from a sheet and to prevent the sheet being spotted with water droplets by providing a heat insulating material on the down surface of a metallic member arranged above and facing a fixing unit. CONSTITUTION:The heat insulating material 56 is provided on the down surface of the metallic member 55 arranged above and facing the fixing unit 33. When the sheet is fed to the fixing unit 33, the sheet is heated and steam rises from the sheet with the heating. The heat insulating material 56 is provided on the down surface of the metallic member 55 arranged above the fixing unit 33, whereby the steam is cut off by the heat insulating material 56 and is not directly brought into contact with the metallic member 55. Thus, the bedewing of the steam rising from the sheet can be prevented so as not to spot the sheet.

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 particularly to an image forming apparatus that forms images using an electrophotographic process.

(Prior Art) Generally, in this type of image forming apparatus, an image transfer section and a fixing unit are provided in the main body of the apparatus, the image transfer section transfers an image onto paper, the paper is sent to a fixing unit, and the fixing unit The paper is then heated to about 160° C. to fix the image.

The top surface of the main body of the device is open, and a plastic cover that can be opened and closed is provided on this open portion, and a metal plate is attached to the inner surface of this cover for reinforcement purposes.

(Problems to be Solved by the Invention) Paper used in such image forming apparatuses contains moisture of 4 to B% in normal times and 10 to 12% in humid conditions. When the paper is fed into the fixing unit and heated, water vapor rises from the paper and comes into contact with a metal plate provided on the inner surface of the cover. This metal plate is normally at a relatively low temperature of about 20°C, so when water vapor comes into contact with this metal plate, the heat of this water vapor is absorbed by the metal plate, and as a result, the water vapor condenses and forms dew. Such condensed water gradually condenses and grows into relatively large droplets that drip onto the paper below, which can cause stains on the paper.

The present invention has been made in view of these points, and an object of the present invention is to provide an image forming apparatus that prevents condensation of water vapor and prevents smearing on paper.

[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, sends this sheet of paper to a fixing unit,
In the image forming apparatus in which the fixing unit heats the paper and fixes the image, a heat insulating material is provided on the lower surface of a metal member disposed above and facing the fixing unit.

(Function) When paper is fed into the fusing unit, the paper is heated, and water vapor rises from the paper as a result of this heating. Because of this, the water vapor is blocked by the heat insulating material and does not come into direct contact with the metal components, thus preventing the water vapor from condensing.

(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 in the center of the front end of the paper ejection tray 9, and a rotatable U-shaped auxiliary ejection that can be accommodated in the notch 9a or unfolded as shown in FIG. A tray 10 is provided. Then, the paper P to be ejected
The size of the paper discharge section 6 can be adjusted according to the size of the paper.

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 discharge portion 6, a display LED II is provided.

7 segments for 2-digit status display12. A control panel 14 with switches 13 and a switch 13 is arranged, and a manual feed tray 1
5 is attached.

Next, charging, exposure, development, transfer, peeling, 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 .

When a print start signal is received from the host system, the drum-shaped photoreceptor 20 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 20 using the laser exposure unit 22, and an electrostatic charge corresponding to the image signal is created on the photoreceptor 20. Form a latent image. This electrostatic latent image on the photoreceptor 20 is developed and visualized by the toner t in the developer magnetic brush D' of the developing 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 placed on the photoreceptor 20 in advance. The formed toner image is transferred onto 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.

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 made of plastic 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, the conveyance guide 37. and the discharge roller unit 3 including the static elimination brush 52.
4 upper rollers 51 are attached. 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 paper conveyance path 29 are exposed, which makes it difficult to remove jammed paper P and perform maintenance on the equipment. Inspection and replacement work can be performed easily and efficiently.

Further, the rear cover 64 of the apparatus main body 1 shown in FIG. The curved conveyance section can be opened, and sheets 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.

A metal plate 55 such as an iron plate is attached to the inner surface of the top cover 60 for the purpose of reinforcement, etc., and this metal plate 55 is disposed facing above the fixing unit 33.
A heat insulating material 56 made of polyethylene terephthalate or the like is attached to the lower surface of the housing.

When the paper P is fed into the fixing unit 33, the paper P is heated, and water vapor rises from the paper P as a result of this heating. However, as described above, the heat insulating material 56 is attached to the lower surface of the metal plate 55 disposed above the fixing unit 33, so that water vapor is blocked by the heat insulating material 56 and does not come into direct contact with the metal plate 55. This prevents water vapor from condensing. Since condensation of water vapor is thus prevented, water droplets do not drip onto the paper P and cause stains. Note that the fixing unit 33
The water vapor rising upward is diffused by air blown by the operation of the cooling fan unit 35 and is discharged to the outside of the apparatus main body 1.

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 60x 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 bottle 73 as a charging means power supply section is screwed. The power supply pin 73 and the metal fitting 74 are fixed within 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.

Moreover, the shield case 7o is 0. 3IIJl thickness (7
) It is made of stainless steel and has a mesh on the side facing the photoreceptor 2o, as shown in FIG. 5, and serves as a grid 70a of the scorotron charger. Also,
The grid 70a can maintain sufficient accuracy such as its 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 occurs, the 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 (-5kV) is applied to the corona wire 71 via the power supply bottle 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, which is 2rttmM 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 (colored powder) t and carrier (@color 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.
8.129, and a non-magnetic sleeve 131 that is fitted onto the magnetic roll 130 and rotates clockwise in the figure. magnetic roll 130
Of the three magnetic pole parts 127, 128, and 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
27 and the magnetic pole part 128 (see Figure 2) is 150'', and the angle θ between the magnetic pole part 128 and the magnetic pole part 129 is
2 (see Figure 2) is set at 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'. At the same time as the latent image is developed, residual toner t is collected mechanically and electrically.

Further, the developing means 23 includes a photoreceptor 20. Charging means 21
．． Memory removing means 25 and the like are integrated into a process cartridge 85, and one end of this 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, and 142 are inserted into a power supply connector provided in the device main body 1.

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 a presence 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 the 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 developing sleeve 131 via a conductive plate spring 162. Auto toner sensor ring 60. Doctor 124. and current 1st 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).

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

Further, the brush 200 has one side, as shown in FIG.
Holding metal fitting 202 is held with backing member 201 made of polyester film having thickness to (about 0.11IIjI) protruding from the tip of brush 200 by dM (about 0.1g).
It is designed to be attached to

The brush 200 is mounted upstream of the charging means 21 so that the brush surface is in contact with the photoreceptor 20 at a position of 3 mJ!I from the tip of the brush 200 at the corner.

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, the image transfer section transfers an image onto paper, the paper is sent to the fixing unit,
In an image forming apparatus that heats the paper in this fixing unit to fix the image, a heat insulating material is provided on the lower surface of a metal member disposed above and facing the fixing unit, so that water vapor rises from the paper. It is possible to prevent dew condensation, and therefore, there is an effect that there will be no smearing of water droplets on the paper.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a block diagram showing the internal structure of an image forming apparatus, FIG. 2 is a block diagram showing an enlarged view of its main parts, and FIG. 3 is a block diagram showing the image forming apparatus. FIG. 4 is a perspective view of the exterior 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. , 14th
15 is a cross-sectional view of the vicinity of the driving force transmission side of the photoconductor, FIG. 16 is a diagram schematically showing the power supply state to the auto toner ring, and FIG. 18 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 arrow A in FIG. 17, and FIG. A sectional view taken along the line B-B in the figure, FIG. 20 is a sectional view taken along the line C-C in FIG. 17,
FIG. 21 is a plan view of the memory removing means, FIG. 22 is a front view, FIG. 23 is a bottom view, and FIG. 24 is a sectional view taken along line A--A in FIG. 21. 28... Image transfer section, 33... Fixing unit, 55
...Metal plate (metal member), 56...Insulating material. Applicant's agent Patent attorney Takehiko Suzue Figure 3! Figure 4 Figure 9 Figure 10 Figure 14

Claims (1)

[Claims] In an image forming apparatus in which an image is transferred to a paper in an image transfer section, the paper is sent to a fixing unit, and the fixing unit heats the paper to fix the image, the fixing unit is disposed facing above the fixing unit. An image forming apparatus characterized in that a heat insulating material is provided on the lower surface of a metal member.