JP2539434B2 - Image forming device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image forming apparatus that performs writing by laser light.

2. Description of the Related Art In a conventional image forming apparatus of the type described above, an optical writing system is arranged on the upper side of a photoconductor, and a writing beam for forming an electrostatic latent image is very often projected onto the photoconductor from the upper side. Many. In this case, the lens of the optical writing system was rarely contaminated by the toner scattering of the developing device. However, since the transfer paper is guided below the photoconductor, if a paper jam occurs, the paper removal operation is complicated because the photoconductor, the optical writing system and other devices are placed on the paper guide path. There was a problem that it took time.

It is preferable to arrange the guide path of the transfer paper, which is intended to simplify the paper jam processing, above the take-up device. For this reason,
The applicant has proposed that the optical writing system is arranged below the photoconductor. With this arrangement,
Particularly in a printer, face-down paper ejection becomes easy and the user's request can be met.

However, since the optical writing system is located below the photoconductor, the scattered toner easily reaches the lens through the optical path for optical writing. As a result, there is a problem in that toner stains occur on the lens, and the stains directly cause image stains.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide an image forming apparatus in which a lens is less likely to be contaminated with toner even in a downward writing mode.

In order to achieve the above object, the present invention provides a photoconductor, a laser generating means for generating a laser beam for forming an electrostatic latent image on the photoconductor, and a lens on the lower side of the photoconductor. And an optical system that irradiates the laser beam toward the photoconductor from obliquely below the photoconductor, and is provided between the optical system and the photoconductor so as to sandwich the optical path of the laser beam. An optical path plate having an upper plate and a lower plate formed thereon, a developing unit that visualizes the electrostatic latent image formed on the photoconductor with toner, and a transfer unit that transfers the developed visible image onto a transfer material. And, in the opening from which the laser light on the side of the photoconductor of the optical path plate is emitted, the hanging line from the upper side plate is projected to the downstream side in the laser beam irradiation direction with respect to the hanging line from the lower side plate It is characterized in that a step is formed on.

Example The details of the configuration and operation of the present invention will be described based on an example shown in the drawings.

FIG. 1 shows a laser printer as an example of the image forming apparatus according to the present invention.

In FIG. 1, the laser printer is an OPC as a photoconductor.
An optical writing system 2 is arranged below the drum 1.

The optical writing system 2 includes a laser generating means 4 for generating a laser light 3 in accordance with an image information signal and a first mirror 5 for reflecting the laser light from the laser generating means 4 in FIGS.
And the deflecting mirror 6 which receives the reflected light from the first mirror 5.
And a scanner motor 7 having the deflection mirror 6 attached to the output shaft.

The laser generation means 4 is composed of a laser diode, a laser diode drive board, a collimator lens, and an aperture. The emission wavelength of the laser diode is, for example, about 780 ± 10 nm, and the output is about 3 nm. The laser diode emits light upon receiving a control signal from the engine drive board. Further, the emission power of the laser diode is fed back to the engine drive board to keep the reference value of the emission power constant. The collimating lens is a lens that converts divergent light emitted from a laser diode, which is a point light source, into parallel light. The beam size is shaped by the aperture. The deflection mirror 6 is driven and rotated at high speed by the scanner motor 7, and scans the laser light emitted from the laser unit 360 °. The scanned laser light is
It is detected by the synchronization detection sensor and controls the emission start timing of the image forming laser light. The scanning angle of the image forming laser beam is about 104 °, and the light emission is controlled for each dot during this period. The laser beam operated by the deflection mirror 6 is f
The θ lens 8 corrects the image curvature of the laser beam in the main scanning direction and the sub scanning direction on the surface of the OPC drum 1 and the constant velocity property during one scanning. The laser light corrected by the fθ lens 8 is reflected by the second mirror 9 which is an optical system, and scans the surface of the OPC drum 1 through the cylindrical lens 10.

The cylindrical lens 10 has a mounting error of the motor 7,
The angle deviation of the laser light is corrected by the mounting error of each mirror. When the laser light is applied to the OPC drum 1, (-)
The surface potential charged in the area is attenuated to form an electrostatic latent image according to the image signal. A charger 11, a developing device 12, a transfer charger 13, and a cleaning device 14 are arranged around the OPC drum 1 in a known manner.

Due to the discharge of the charger, (-) appears on the surface of the OPC drum 1.
Is charged (less than about 800V). Cylindrical lens 10
Corrects the angular deviation of the laser beam due to the mounting error of the motor 7 and the mounting error of each mirror. When the laser light is applied to the OPC drum 1, the surface potential of the (-) charged OPC drum is attenuated to form an electrostatic latent image according to the image signal.
The toner inside the developing device 12 is transferred to the developing roller by the agitator 15.
It is sent to the vicinity of 16. Developing roller 16 with magnetism or static electricity
The toner adhering to the surface of (1) is thinned to a suitable thickness by the doctor blade 17 and sent to the position of contact with the OPC drum 1. The toner on the surface of the developing roller 16 adheres to the electrostatic latent image on the OPC drum 1 to make the latent image visible. When the developing method is the positive / positive method, the toner adheres to portions other than the exposed portion (low potential portion) of the OPC drum 1, and when the developing method is the negative or positive method, the toner adheres to the exposed portion. Corona discharge is applied by the transfer charger 13 to the surface of the OPC drum 1 on which a visible image is formed by the toner to give a charge having a polarity opposite to the charge of the toner, and the toner is moved onto the transfer paper by electrostatic force. Since the toner image on the transfer paper is in an unstable state on the transfer paper, the toner on the paper is heated by passing between the heating roller 18 and the pressure roller 19 pressed against the heating roller 20 by the spring 27. Apply pressure to fix. The surface temperature of the heating roller 20 is maintained at about 160 to 175 ° C. by the thermistor 21, and a temperature fuse 22 is provided for safety. The OPC drum 1 after the transfer is not transferred by the blade 23 of the cleaning device 14 and is not transferred to the OPC drum 1.
Residual toner adhering to the drum surface is scraped off and cleaned. The scraped toner is collected in the waste toner tank 24. Transfer paper from the paper feed cassette 25 to the feed roller.
Sent by 26. The feed roller is turned on and off by a clutch (not shown) and is pressed against the transfer paper. A friction pad 27 is pressed against the feed roller 26 to prevent double feeding of transfer sheets, and the second transfer sheet is prevented from being fed by the frictional force of the friction pad, and only the uppermost transfer sheet is fed. . The transfer sheet fed by the feed roller 26 is detected by the registration sensor, is sent to the registration roller 28, and stops. The feed clutch is turned off by the detection signal of the registration sensor and the feed roller 2
6 stops. When the registration clutch operates under the control of the control board, the transfer paper will be transferred to the registration roller 28
Then, it is conveyed by the guide roller 29, and transferred and fixed as described above. The sheets after fixing are stacked. The transfer paper may be manually fed as indicated by arrow A.

In the laser printer using the lower writing system,
As described above, the fall of the scattered toner may cause toner stains on the cylindrical lens 10 or the toroidal lens, which may disturb the image.

 Therefore, the present invention takes the following measures.

In FIG. 3, the cylindrical lens 10 is arranged obliquely downward with respect to the OPC drum 1, so that the laser light 3 from the cylindrical lens 1 is irradiated toward the drum from obliquely below the OPC drum 1. The optical path of the laser light 3 emitted from the cylindrical lens 10 toward the surface of the OPC drum 1 is surrounded by an optical path plate having an upper plate 32 and a lower plate 31 provided so as to sandwich it. And, the upper plate 32 and the lower plate 31 have their tips at the OPC drum 1.
Has reached close to. The upper end 32a of the upper plate 32 is formed in an inverted V shape, and the opening 3 through which the laser beam 3 is emitted is formed between the bent front end 32b and the upper end 31a of the lower plate 31.
3 is formed. In the opening 33, the hanging line 32c from the tip 32b of the upper plate 32 is projected by 1 part downstream of the hanging line 31c from the upper end 31a of the lower plate 31 in the laser beam irradiation direction. That is, the upper plate 32 and the lower plate 31 are provided in the opening 33.
Further, a step is formed so that the upper plate 32 protrudes leftward from the lower plate 31 in the figure.

In the laser printer configured as described above, the tip 32b of the upper plate 32 is projected to the downstream side of the upper end 31a of the lower plate 31 in the laser light irradiation direction by an amount of l, so that the toner is opened 33.
As a result, it is more difficult for the laser light 3 to enter the optical path, and it is possible to prevent the cylindrical lens 10 from being contaminated by scattered toner.

Effect According to the above configuration, since the toner scattered and falling from above does not easily enter the opening through which the laser light is emitted, the lens can be prevented from being contaminated with toner.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an image forming apparatus according to the present invention, and FIG.
FIG. 1 is a partially enlarged view of the exposure unit shown in FIG. 1, and FIG. 3 is a sectional view showing an embodiment of the present invention. 1 …… OPC drum 4 …… Laser generator 10 …… Cylindrical lens 12 …… Developer 13 …… Transfer charger 31 …… Lower plate 31c …… Pendant line from lower plate 32 …… Upper plate 32c …… Upper plate Line 33 from ... Opening

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Shimazaki 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (56) Reference JP-A-63-123064 (JP, A) JP-A-SHO 63-123066 (JP, A) Actually opened 62-14444 (JP, U) Actually opened 61-179567 (JP, U) Actually opened 59-166250 (JP, U) Actually opened 63-41117 (JP, U)

Claims (1)

(57) [Claims] 1. A photoconductor, a laser generator for generating a laser beam for forming an electrostatic latent image on the photoconductor, a lens below the photoconductor, and a laser beam. An optical system that irradiates the photoconductor from diagonally below the photoconductor, and an upper plate and a lower plate provided between the optical system and the photoconductor so as to sandwich the optical path of the laser beam. An optical path plate having: a developing unit that visualizes the electrostatic latent image formed on the photoreceptor with toner; and a transfer unit that transfers the developed visible image onto a transfer material. At the opening of the optical path plate where the laser light is emitted on the side of the photoconductor, the hanging line from the upper plate projects further downstream than the hanging line from the lower plate in the laser light irradiation direction, and a step is formed in the opening. An image forming apparatus characterized by the above.