JPS61270741A - Image forming device - Google Patents

Abstract

PURPOSE:To adjust picture density easily by arranging a liquid crystal filter in an optical path from an exposing lamp to a photosensitive body and controlling voltage to be applied to the liquid crystal filter to control the quantity of exposing light to the photosensitive body. CONSTITUTION:The photosensitive drum 2 to be rotated in the arrow (b) direction is arranged on the approximately center part of a copying machine case 1 and an original platen 3 is set up on the upper part so as to be reciprocated in the arrow (a) direction. The rays of light irradiated from the exposing lamp 5 are reflected by an original set up on the original platen 3 and the reflected light forms an image on the drum 2 through a converging light transmitting body 6. The liquid crystal filter 23 formed by a liquid crystal plate is arranged between the front of the lamp 5 and the original platen 3 and the filter 23 is fixed on the periphery of the lamp 5 or on a reflector 24. The rays of light to be transmitted through the filter 23 are changed by variably controlling the voltage to be applied to the filter 23. Thus, the picture density can be easily adjusted.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an image forming apparatus such as a copying machine,
In particular, it relates to improvements in the exposure means.

[Technical background of the invention and its problems] Conventionally, for example, in a copying machine, as a means for adjusting image density, a method of controlling the amount of exposure light to a photoreceptor by varying the voltage applied to an exposure lamp, or a method of controlling the amount of exposure light to a photoreceptor, or There is a method of varying the developing bias voltage applied to the device. However, in all of these methods, the control voltage is high and the control requires high power, so the configuration of the control circuit becomes complicated and the cost becomes high.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its object is to provide an image forming apparatus that allows image density to be easily adjusted by simple and inexpensive means. .

[Summary of the Invention] In order to achieve the above object, the present invention provides a liquid crystal filter in the optical path from the exposure lamp to the photoreceptor, and variably controls the voltage applied to the liquid crystal filter, thereby reducing the amount of exposure light to the photoreceptor. It is configured to control the

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a copying machine as an example of an image forming apparatus according to the present invention. That is, 1 is a housing, and a photosensitive drum 2 that rotates in the direction indicated by the arrow in the figure is provided approximately at the center of the housing. Further, at the upper part of the housing 1, a document table 3 for supporting a document is provided so as to be movable back and forth in the direction of arrow a in the figure, and a document cover 4 is provided on the document table 3 so as to be openable and closable. . By moving the document table 3 in synchronization with the rotation of the photoreceptor drum 2, the light emitted from the exposure lamp 5 is reflected by the document on the document table 3, and the reflected light is transmitted through convergent light transmission. An image is formed on the photoreceptor drum 2 by the body (Selfoc lens) 6, and is reflected on the photoreceptor drum 2 as an inverted image of the original. At this time, by charging the surface of the photoreceptor drum 2 with the charging charge l17, an inverted image of the original is formed on the photoreceptor drum 2 as an electrostatic latent image, and this electrostatic latent image is transferred to the developing device. 8, the image is visualized by adhering toner thereto.

On the other hand, below the developing device 8, a paper feeding device 9 is provided that supplies the paper P to the lower part of the photosensitive drum 2 (Il! transfer section 14). The paper feeding device 9 is removably attached to the side of the housing 1 and can feed a plurality of sheets of paper P.

..., a manual paper feed tray 11 formed on the upper part of the paper feed cassette 10 for manually feeding paper P, and a paper feed tray 11 for feeding paper P one by one from the paper feed cassette 10. It has a paper feed roller 12 for feeding out, and also temporarily stops the paper P fed by the paper feed roller 12 or the paper P fed manually,
A registration roller 13 corrects the inclination of the leading edge of the paper P and sends it to the image transfer unit 14 at a timing such that the leading edge of the paper P and the leading edge of the toner image on the photoreceptor drum 2 match.
It has a configuration with.

The paper P conveyed by the registration rollers 13 is sent to the image transfer section 14 . The paper P sent to the image transfer section 14 is
By bringing the transfer charger 15 into close contact with the surface of the photoreceptor drum 2, the charger 15 causes the paper P to
The toner image on the photosensitive drum 2 is transferred by the charging. After the transfer, the photosensitive drum 2 is cleaned by a cleaner 16.
The residual toner on the surface is removed by the snow removal lamp 17, and the afterimage is erased by the snow removal lamp 17, so that the initial state is returned. On the other hand, the paper P after the transfer is electrostatically peeled off from the photosensitive drum 2 by the action of the peeling charger 18, and then guided along the conveyance path 19 and passes through a heat roller 20 as a fixing device. In particular, the transferred image is heat-fixed. The sheet P after fixing is configured to be ejected to the tray 22 outside the housing 1 by the ejection row 521. .

By the way, a liquid crystal filter 23 formed of a liquid crystal plate is provided in front of the exposure lamp 5 and between the document table 3 and the liquid crystal filter 23 is provided around the exposure lamp 5 or fixed to the flapper 24. has been done. The liquid crystal filter 23 changes the amount of transmitted light by variably controlling the applied voltage, and has characteristics as shown in FIG. 2, for example. As a result, a constant amount of light emitted from the exposure lamp 5 is transmitted through the liquid crystal filter 23, and the amount of light is controlled and irradiated onto the original.
Therefore, the amount of exposure light to the photoreceptor drum 2 is also controlled.

FIG. 3 shows an example of a control means for variably controlling the voltage applied to the liquid crystal filter 23. In FIG.

That is, numeral 31 is a microcomputer (hereinafter simply referred to as microcomputer) that controls the tiIJva of the entire copying machine, and the liquid crystal filter 23 is connected to this microcomputer 31 via a power supply circuit 32. Further, an image density setting device (exposure light amount setting device) 33 provided on an operation panel (not shown) is connected to the microcomputer 31. When the user sets a desired value using the image density setting device 33, the microcomputer 31 reads the set value and controls the power supply circuit 32 according to the set value to control the voltage applied to the liquid crystal filter 23. The voltage is varied and set to a predetermined voltage corresponding to the above set value. As a result, the amount of light transmitted through the liquid crystal filter 23 becomes an optimum value corresponding to the set value, and the amount of light exposed to the photosensitive drum 2 also becomes an optimum value, so that copying is performed at the set image density.

In this way, the liquid crystal filter 23 is provided in the optical path between the exposure lamp 5 and the document, and the voltage applied to the liquid crystal filter 23 is variably controlled according to the settings of the image density setting device 33. The amount of exposure light to the drum 2 is controlled. This makes it possible to easily adjust the image density using simple and inexpensive means. That is, in general, the voltage applied to the liquid crystal is 3 to 10 volts and the current is several microns or less, whereas the voltage and current of the exposure lamp are both higher than that, and the developing bias voltage is also very high. In controlling these, the lower the power consumption, the lower the power consumption, and the simpler and cheaper the control circuit. Therefore, by using the liquid crystal filter 23 as in the present invention, it is possible to perform control with low voltage and low power, and as a result, the control circuit and the like need only have a simple configuration, thereby reducing costs.

In the above embodiment, a liquid crystal filter is provided in the optical path between the exposure lamp and the original, but the filter is not limited to this, and for example, the liquid crystal filter is provided between the original and the convergent light transmitter or between the convergent light transmitter and the photoreceptor. It may also be provided in the optical path between the drum and the drum. In addition, when using a normal optical lens without using a focusing light transmitter,
Liquid crystal filters may be provided before and after the lens, or may be incorporated within the lens system.

Further, in the above embodiment, the case where the application is applied to a copying machine has been described, but the present invention is not limited to this.
It can also be applied to other image forming apparatuses.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to easily and safely
f-194: J:'i'ipi image 1 degree + 7) III! 1
It is possible to provide an image forming apparatus that is “easily 1 possible 1”.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention. Fig. 1 is a side view showing the configuration of a copying machine, Fig. 2 is a characteristic diagram of the amount of transmitted light with respect to the applied voltage of the liquid crystal filter, and Fig. 3 is a characteristic diagram of the amount of transmitted light with respect to the applied voltage of the liquid crystal filter. FIG. 3 is a block diagram showing an example of a control means that variably controls the voltage applied to the filter. 2... Photosensitive drum, 3... Document table, 5... Exposure lamp, 8... Developing device, 9... Paper feeding device, 20...
・Heat roller, 23...Liquid crystal filter, 31...
Microcomputer, 32...power supply circuit, 33...image density setting device. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (3)

[Claims] (1) In an image forming apparatus that forms an image corresponding to the image of the original on a photoreceptor by irradiating the original with an exposure lamp and exposing light from the original to a photoreceptor, the exposure lamp An image forming apparatus characterized in that a liquid crystal filter is provided in an optical path from the to the photoreceptor, and the amount of exposure light to the photoreceptor is controlled by variably controlling the voltage applied to the liquid crystal filter. (2) The image forming apparatus according to claim 1, wherein the liquid crystal filter is provided in an optical path between an exposure lamp and an original. (3) Claim 1, wherein the liquid crystal filter is provided in an optical path between the original and the photoreceptor.
The image forming apparatus described in .