JPS6146832B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electrophotographic image recording device.

Conventionally, in electrophotography, corona discharge is generally used to uniformly charge or remove static electricity from a photosensitive member, and corona discharge electrodes include:
A thin conductive wire such as a tungsten wire with a diameter of 0.05 to 0.20 mm is used.

Further, the structure of the charger includes at least one wire electrode for corona discharge, a shield member surrounding the wire electrode, and, if necessary, at least one wire electrode provided between the wire electrode and the photosensitive member. It is based on a grid consisting of one or more conductive wires. Furthermore, the shield member has an opening for applying a corona discharge to the photosensitive member, and in the case of a special charging device, an opening for guiding a light image onto the photosensitive member.

In general, local non-uniformity of corona discharge and decrease in corona discharge current are caused by the following reasons, and result in failure to obtain good image output in an electrophotographic apparatus.

1 In the case of dry type developer, due to dust such as toner,
In addition, in the case of a wet developer, the wire electrode becomes dirty due to carrier liquid vapor, etc.

2 Ambient temperature is low.

3 Ambient relative humidity is high.

Furthermore, if the imaging optical element, reflective optical element, light source, etc. in the optical device for exposing the photosensitive member with a light image becomes contaminated with dust such as the toner, carrier liquid vapor, etc., the photosensitive member will be exposed to light. This results in an insufficient amount of light and local non-uniformity, making it impossible to obtain a good image output as in the case of a charging device.

In conventional devices, the wire electrodes and optical elements must be frequently cleaned in order to always obtain good images. In other words, it was necessary for the users and maintenance personnel of the device to periodically perform these tasks. Various devices have also been proposed for mechanically cleaning contaminants such as toner adhering to the wire electrodes or grids. In such conventional methods, cleaning intervals are very short, especially in equipment that operates at high speeds and over long periods of time, such as computer output printers and duplicators, and the wire electrodes are subject to wear due to repeated cleaning or carelessness. In practical use, there were serious problems such as damage, damage, and scratches on optical elements.

The purpose of the present invention is to eliminate these causes of contamination,
This significantly lengthens the interval between wire cleaning and optical system maintenance work in order to use the device in good condition, and reduces troubles associated with cleaning work.

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

FIG. 1 schematically shows the basic configuration of a computer output printer including an embodiment of the present invention. A laser beam emitted from a laser oscillator 1-1 enters an optical modulation system composed of a lens 1-2, an A/O modulation element 1-3 using a known acousto-optic effect, and a lens 1-4. Here, the lens 1-2 serves to condense and project the laser beam using the black reflection surface generated in the A/O modulation element, and the lens 1-4 serves to project the laser beam while converging it from the black reflection surface. It functions to convert the light into parallel light flux.

Lenses 1-2 and 1-4 are unnecessary when using an E/O modulation element that utilizes a known electro-optic effect, and when the laser oscillator is a gas laser or the like capable of current modulation, the optical modulation system described above is not required. Needless to say, it is possible to omit it.

The laser beam emitted from the lens 1-4 becomes a parallel beam and enters the beam expander 1-7, where the beam diameter is expanded while remaining a parallel beam.

Furthermore, the laser beam whose beam diameter has been expanded is incident on a rotating mirror 1-8 having one or more mirror surfaces. The rotating mirrors 1-8 are mounted on shafts supported by high-precision bearings (e.g. air bearings),
It is driven by a constant speed rotation drive source (eg, hysteresis synchronous motor, DC servo motor) 1-9. A laser beam swept horizontally by a rotating mirror 1-8 is passed through an imaging lens 1- having an f-θ characteristic and having the function of moving the beam at a constant speed on a photoreceptor.
13, an image is formed as a spot on the electrophotographic photosensitive drum 1-14.

As described above, the deflected and modulated laser beam (2-2 in the second diagram) is irradiated onto the photosensitive drum 1-14, visualized by an electrophotographic processing process, transferred to plain paper, fixed, and hardened. Output as a copy. As an example of the electrophotographic process applied to this embodiment, as described in Japanese Patent Publication No. 42-23910, a photosensitive drum 1-14 whose basic components are a conductive support, a photoconductive layer and an insulating layer is used. The surface of the insulating layer is uniformly charged positively or negatively in advance by the first corona charger 1-16, and a layer with a polarity opposite to the charged polarity is applied to the interface between the photoconductive layer and the insulating layer or inside the photoconductive layer. Charges are captured, and then the surface of the insulating layer is irradiated with the laser beam, and at the same time, an alternating current corona discharge is applied by an alternating current corona discharger 1-17. A pattern is formed on the surface of the insulating layer, and the entire surface of the insulating layer is uniformly exposed with a full-surface exposure lamp 1-18 to form a high-contrast electrostatic latent image on the surface of the insulating layer, and the electrostatic latent image is formed on the surface of the insulating layer. After the latent image is developed and visualized by a developing device 1-19 using a developer mainly composed of charged colored particles, the visible image is transferred to a fan-hold paper (hereinafter referred to as paper) 1-30 by a charging device 1. -22, the transferred image is then fixed by a fixing means to obtain an electrophotographic print image, and after the transfer is performed, the surface of the insulating layer is cleaned by a cleaning device 1-23 to remove any remaining insulating layer. The photosensitive drum 1-14 is used repeatedly after removing the charged particles. As yet another embodiment, an electrophotographic electrostatic line forming process as described in Japanese Patent Publication No. 19748/1974 is applied.

Note that 1-15 is a charger for pre-static elimination, and 1-16' is a pre-exposure lamp. ' is to make the characteristics of the photosensitive layer constant and uniform, and these work together to erase various previous history, such as residual potential, remaining on the photosensitive drum 1-14 after passing through the cleaning device 1-23. None is always helpful in obtaining stable images.

The present applicant has proposed an electrostatic latent image stabilization method (Japanese Patent Application No. 111562/1986) as a means to always obtain stable and good images in the electrophotographic process applied to this embodiment. Reference numeral 1-21 is an electrostatic electrometer for realizing such a means, which measures the electrostatic potential of each photosensitive drum 1-14 by providing a bright area, that is, an exposed area by scanning with a laser beam, and a dark area. .
1-20 is a carrier removal device in which the carrier mixed in the developer in the developing device 1-19 is removed from the photosensitive drum 1-1.
4 to prevent it from adhering to the paper or getting mixed into the cleaning device 1-23.

FIG. 2 shows the arrangement of the optical system in FIG. 1 three-dimensionally, and in the explanation of FIG. 1, parts having the same functions are given the same numbers. (The same applies hereinafter) In Fig. 2, 2-1 is a small entrance slit and a photoelectric conversion element with a fast response time (for example,
A beam detector consisting of a laser beam (PIN diode) detects the scanning start position of the swept laser beam 2-2, and with this detection signal, the photosensitive drum 1-14 is detected.
Determine the start timing of the modulation control signal to give the desired optical information to the top. Note that the scanning direction of the laser beam 2-2 in FIG. 2 is indicated by an arrow 2-3.

Next, if we are to describe paper conveyance, 1--
Reference numeral 30 denotes an unprinted sheet of paper, such as the one normally used for output from a computer, etc., and has feed holes at both ends in the width direction. 1-32 is a holding rod provided to help convey the paper smoothly;
1-33 is a light source such as a light emitting diode, 1-34
is a photoreceptor like a photodiode, and 1-3
3, 1-34 cooperate to constitute a paper end detector. Reference numeral 1-35 denotes a known tractor in which pins are arranged to engage with the feed holes, and the pins rotate according to the rotation of a tractor shaft (not shown) to convey paper. 1-37 is a tractor for conveying paper. This is a guide roller for. 1-38, as described later, the paper is brought into pressure contact with the photosensitive drum 1-14 by the operation of the transfer rollers 1-39 and 1-40, and further by the operation of the transfer charger 1-22, the paper is brought into contact with the photosensitive drum 1-14. Although the transfer is completed and the transfer charger 1-22 stops operating and the transfer rollers 1-39 and 1-40 are separated from the photosensitive drum 1-14, the paper is kept in close contact with the photosensitive drum 1-14. This is a separation claw for separating the photosensitive drum 1-14 from the photosensitive drum 1-14.

Transfer rollers 1-39 and 1-40 operate simultaneously in the same direction to press the paper against the photosensitive drum 1-14.

1-41 is a guide roller that also serves to absorb the tension applied to the paper when it changes more than a specified value when the paper is conveyed, and 1-42 is a hollow cylindrical shape with a heater etc. in the center of the cylinder. It is a preheating roller having a heat source, a fixing roller 1-43 for fixing the toner transferred to paper, and a back-up roller 1-43.
Together with 44, it constitutes a fixing device.

A fixing roller 1-43 has a hollow cylindrical shape and has a heat source such as a heater in the center of the cylinder. A fixing roller 1-44 presses the paper onto which the toner has been transferred between it and the fixing roller 1-43. This is a back-up roller that makes it easier for the heat from -43 to be transferred to the toner and paper, and also applies high pressure to the toner to fix it. 1-45 and 1-46 are discharge rollers for discharging the paper on which fixing has been completed, and 1-47 is a paper on which printing has been completed.

Furthermore, with reference to FIG. 3, an embodiment of the present invention applied to the above-mentioned image recording apparatus will be described in further detail.

FIG. 3 shows in detail the parts of the basic configuration of the image recording apparatus shown in FIG. 1 that are particularly relevant to the present invention, and other parts are omitted as appropriate.

In FIG. 3, the portion indicated by line 9-1 indicates the housing of the image recording apparatus. A fan 9-3 is introduced into the housing 9-1 through a coarse particle filter 9-2.
External air is sucked in. A part of the sucked outside air from which coarse particles have been removed is passed through a fine particle filter 9-6 by a fan 9-5 to the optical devices (laser generator 1-1, modulation optical system 1-2,
1-3, 1-4, beam expander 1-7,
Rotating polygon mirror 1-8, motor 1-9, imaging lens 1
-13, beam detector 2-1, etc.) and the charging device (including pre-static charger 1-15, pre-exposure lamp 1-16', corona charger 1-16, corona discharger 1-17, etc.) ) is blown into the housing 9-4 that separates it from other parts of the housing 9-1. This housing 9-4 has a sealed structure,
The openings are the opening 9-5' of the fan 9-5 that takes in air, and the charger 1-1 that exhausts air.
5, 1-16, 1-17 and the photosensitive drum 1-14. The clean air that has passed through the coarse particle filter 9-2 and the fine particle filter 9-6 first passes through the optical device, then the charging device, and then the photosensitive drum 1-14 side of the charging device. is discharged from the housing 9-4 through the opening. Further, a part of the outside air sucked into the housing 9-1 is blown onto the cleaning device 1-23 by the cooling fan 9-10 to cool the cleaning device 1-23, and is then discharged from the housing 9-4. The air is discharged from the housing 9-1 by a fan 9-9 through a coarse particle filter 9-8 and an ozone filter 9-7.

On the other hand, the toner scattered from the developing device 1-19 is guided to the suction duct 1-48, passes through a conduit (not shown), is sucked in by the fan 9-9, is passed through the filter 9-8, and is passed through the activated carbon 9-7. Release clean air to the outside of the enclosure.

Here, the relationship between the amount of outside air V ₁ sucked into the housing by the fan 9-3 and the amount of released air V ₂ released to the outside of the housing by the fan 9-9 is V ₁ <V ₂ . .

In other words, the air pressure inside the casing is set lower than the air pressure outside the casing to prevent contaminated air inside the casing from leaking to the outside of the casing. On the other hand, if configured in this way, the housing 9-4
The air pressure inside the housing 9-4 can be maintained higher than the air pressure outside the housing 9-4 by the action of the fan 9-5. Therefore, the inside of the housing 9-4 is filled with high-pressure clean air, and contamination particles are prevented from entering the housing 9-4 from sources of contamination dust such as the developing device 1-19 and the cleaning device 1-23. .

The optical device includes a laser oscillator 1-
1. There are elements that generate heat, such as the A/O modulation element 1-3 and the motor 1-9 that drives the rotating polygon mirror. Therefore, the airflow flowing within the housing 9-4 cools these heat generating elements and the airflow is consequently warmed, necessarily reducing the relative humidity of the air. This eliminates two of the causes of decreasing the corona discharge flow: 2. Low ambient humidity and 3. High ambient relative humidity.

In this embodiment, coarse particle filter 9-2
In addition, a polypropylene dry filter (Filedon Filter made by Nippon Vilene) that allows 99% or more of particles with a diameter of 5 μ or more to pass, a propeller fan rated for suction fan 9-3, an air flow rate of 2000 I/min, and a wind pressure of 10 mm H ₂ O, fan 9-5. Rated air volume 2500I/min wind pressure 20
Sirotskov fan of mmH ₂ O, particulate filter 9-
6, as a result of using a glass asbestos-based glass filter (manufactured by HEPA Filter Flanders) that filters 99.97% of particles with a diameter of 0.3μ or more, the air flow rate in the housing 9-4 is approximately 1000I/
min, the ambient pressure difference inside the housing 9-4 was about 7 to 10 mmHg near the charger 1-17. Operating the image recording device under this condition,
FIG. 4 shows the results of measuring changes in surface potential on the photosensitive drum 1-14 with respect to operating time.

In Fig. 4, 10-1, 10-2 are changes in dark area potential on the photosensitive drum, 10-3, 10-4,
10-1 and 10-3 are those in which the present invention was implemented, and 10-2 and 10-4 are conventional ones. Here, the dark potential is the surface potential of the photosensitive drum 1-14 measured at the position of the developing device 1-19 in FIG.
2 refers to the part that is not exposed to light. Similarly, the bright area potential corresponds to the area exposed to the laser beam 2-2.

As shown in FIG. 4, by carrying out the present invention, there is almost no change in the bright and dark potentials even after 30 hours of operation. On the other hand, in the conventional method, the change in the dark potential is particularly significant as shown in 10-2. Furthermore, in a state where the potential is lowered, charging unevenness also occurs in the length direction of the wire electrode of the charger, and the output image in this state becomes unsuitable for practical use.

In FIG. 4, 〓1 represents the potential after 30 hours of operation, after the charging wire electrode was wiped with a paper towel or the like and further cleaned with a solvent containing isopropyl alcohol as a main component. Further, 〓2 shows the potential after cleaning the dirt from each part of the optical system, clearly showing the effect of the present invention.

As explained above, according to the present invention, it is possible to prevent contamination of the charging device and the optical device, which have conventionally determined the shortest maintenance intervals to maintain good image output in image recording devices. This method has a remarkable effect on extending maintenance intervals and improving reliability in recording devices that are continuously operated for long periods of time (eg, computer output printers, high-speed duplicators).

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the basic configuration of an image recording apparatus to which the present invention is applied, FIG. 2 is a perspective view of essential parts showing the arrangement of the optical system shown in FIG. 1, and FIG. FIG. 4 is a side sectional view of an image recording apparatus to which such a contamination prevention device is applied, and is a surface potential characteristic diagram showing the effects of the present invention by changes in surface potential in bright areas and dark areas. Here, 1-1 is a laser oscillator, 1-2, 1-
4 is a lens, 1-3 is a modulation element, 1-7 is a beam expander, 1-8 is a rotating polygon mirror, 1-9 is a motor, 1-13 is an imaging lens, 1-14 is a photosensitive drum, 1- 15 is a pre-static charger, 1-16 is a corona charger, 1-16' is an exposure lamp, 17 is a corona discharger, 9-1 is a housing, 9-2 and 9-8 are coarse particle filters, 9 -3, 9-5, 9-9, 9-1
0 is a fan, and 9-4 is a housing.

Claims (1)

[Scope of Claims] 1. An optical system comprising: an electrophotographic photosensitive member that rotates; a charging device that applies a corona discharge to the photosensitive member; and an optical device that exposes the photosensitive member, the components of which generate heat. a developing device that develops the electrostatic latent image formed on the photosensitive member by the exposure, a transfer device that transfers the developed image to a transfer material, and a cleaning device that cleans the photosensitive member after the transfer. An image forming apparatus comprising: a housing in which the charging device and the optical device are disposed, the housing separating both devices from the other devices and the photosensitive member, the housing facing the photoreceptor, the charging device a housing having an air exhaust opening disposed therein; and means for admitting air into the housing from outside the housing through a filter;
An image recording apparatus characterized in that the air is heated through an optical system including the heat generating component, and then discharged through the charging device through the air discharge opening.