JPH03131876A - Image forming device - Google Patents

Abstract

PURPOSE:To set a proper development bias value which meets a plural development mode by providing a development bias generating means, which outputs a development bias in accordance with a respective development mode, in a developing unit or a unit having a developing unit. CONSTITUTION:The development bias generating means 1 and 2 are disposed in the negative developing unit 3 and the positive developing unit 4, respectively. Even when both the negative and positive developing units 3 and 4 are used, the negative one is usually set; the development bias generating means 1 operates based on a signal form a sequence control circuit 5, and a development bias value which corresponds to negative development is set. When positive development is selected, the signal from a N/P change-over switch 6 is inputted to the sequence control circuit 5, the negative developing unit 3 is released, and the positive developing unit 4 is set; also the development bias generating means 2 operates based on a signal from the sequence control circuit 5, and a development bias value which corresponds to positive development is set. Thus, a proper development bias value is set.

Description

DETAILED DESCRIPTION OF THE INVENTION Industry 1 The present invention relates to an electrophotographic or electrostatic recording image forming apparatus, and can be suitably embodied in an electrophotographic copying machine, a microfilm reader printer, and the like.

[Toritsu and I] Conventionally, for example, electrophotographic microfilm reader printers have been configured so that high voltage output, toner polarity, etc. can be switched in order to obtain positive copies of both negative and positive films.

In such an apparatus, since the toner components or development methods are different between negative development (obtaining a positive copy from negative film) and positive development (obtaining a positive copy from positive film), when the same development bias is applied, The density of the developed toner image is different, and the resolution and sharpness are different. For this reason, normally, when the developing device is replaced or switched, the developing bias generating means changes the magnitude of the DC component or the frequency and peak value of the AC component of the developing bias depending on each case. set to be appropriate.

When the difference between negative development and positive development is slight, the development conditions for negative development and positive development are set to be as common as possible.

FIG. 7 shows a schematic block diagram of a conventional microfilm reader printer.
3. The positive developing device 54 is switchable. Normally,
The sequence control circuit 5 sets the negative developer 53 and controls the developing bias generating means 51 so as to generate a negative developing bias. The positive developing device 54 is set, and a signal is sent to the developing bias generating means 51 to generate a positive developing bias.

The developing bias generating means 51 is designed to be capable of both negative and positive development. For example, developing bias DC
The components are -250 to -IoooV for negatives and -5 for positives.
Since 0 to -500■ is required, -50 to -100
It can be varied up to 0V, and the developing bias A
The C component for negative has a peak value of +200Vp-p and a frequency of 15.
For 00Hz, the positive wave height value is 1000Vp-p,
It is configured so that the alternator, peak value, and frequency can be switched at a frequency of 1000 Hz.

In addition, multicolor electrophotographic copying machines that can perform color development in addition to normal black development have been developed and are actually commercially available, but in such devices, the toner components are different for black development and color development. , or because the developing method is different, the developing bias DC variable range, developing bias AC frequency, and peak value are set to be appropriate as the developing device is replaced or switched.

However, as mentioned above, reader printers that can handle both negative and positive films use a single high-pressure control circuit to control the development bias DC variable range to support two development modes (negative development and positive development). Take a wide range of
Since the AC frequency and peak value of the developing bias can be changed, the control circuit becomes complicated, and the cost becomes high for users who only use either negative film or positive film. or,
If the two development modes are made as common as possible and switching is eliminated, the control circuit becomes simpler, but this has the disadvantage that image quality deteriorates because resolution, sharpness, density, etc. differ between the two development modes. .

In fact, in microfilm reader printers, there are very few users who use both negative film and positive film, and even fewer who use only positive film. That is, most users use only negative film. For this reason, there are reader printers exclusively for negative film and reader printers exclusively for positive film, but these printers can only use one type of film, and users who only use the other type of film or those who use negative/positive film It is useless for users who use both.

Therefore, at least a user who uses both negative and positive films has the disadvantage of having to have both a reader printer exclusively for negative films and a reader printer exclusively for positive films, and use the two printers depending on whether the film is negative or positive.

In addition, even in multicolor electrophotographic copying machines capable of color development, it is possible to widen the DC bias variable range and switch the development bias AC frequency and peak value to support two development modes (black development, color development). As a result, the control circuit becomes complicated, which increases costs for users who only perform black development.

Therefore, an object of the present invention is to provide a developing bias generating means for outputting a developing bias according to each developing mode (negative/positive development, black/color development, etc.) in a developing device or a unit having a developing device. By providing this, it is possible to set an appropriate development bias value suitable for each development mode, and the image forming apparatus has high cost performance and good image quality even for users who only use one of each development mode. The goal is to provide the following.

in order to The above object is achieved by an image forming apparatus according to the present invention.

In summary, the present invention includes an image carrier on which a latent image is formed, one or more developing devices for developing the latent image on the image carrier, and a developing bias applied to the developing device. The image forming apparatus is characterized in that the developing bias generating means is provided integrally with the developing device or a unit including the developing device.

Further, if necessary, the developing device or a unit including the developing device, which is provided with the developing bias generating means, is configured to be detachable from the main body of the apparatus.

Next, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is embodied in an electrophotographic microfilm reader printer. In this embodiment, a microfilm original (not shown) is placed in a carrier glass 13, and an illumination lamp 11,
It is illuminated by an illumination device consisting of a mirror 12, etc., and the image light of the microfilm is transmitted through a lens 14 and mirrors 15 to 18.
The image is projected onto an electrophotographic photosensitive drum 19, which is an image carrier. The photosensitive drum 19 is supported rotatably in the direction of the arrow, and image forming means is arranged around the photosensitive drum 19.

That is, the pre-exposure lamp 21 is arranged to erase the residual charge on the surface of the photosensitive drum 19, and the photosensitive drum 19 from which the residual charge has been removed is uniformly negatively charged by the primary charger 22. . A latent image is formed on the photosensitive drum 19 by the previous image projection light, and when either the negative developing device 3 or the positive developing device 4 is close to the photosensitive drum I9, the negative developing device 3) in FIG. Visualize. Photosensitive drum 1
After the toner image on 9 is properly charged with a pre-transfer charger 24, the toner image is transferred onto a transfer material (print paper) P with a transfer charger 25.

The printing paper P is transferred to the photosensitive drum 1 by the separation charger 26.
Except for the electrostatic adsorption force between 9 and the printing paper, the photosensitive drum 1
The image is separated from the image forming apparatus 9, conveyed to the fixing device 28, and discharged from the apparatus after being fixed.

According to the present invention, the developing bias generating means 1 is disposed in the negative developing device 3, and the developing bias generating means 2 is disposed in the positive developing device 4.

In such a configuration, even if both the negative developing device 3 and the positive developing device 4 are used, the negative developing device is normally set as shown in FIG. 1, and in FIG. The developing bias generating means 1 is activated and set to a developing bias value corresponding to negative development.

When positive development is selected, the signal from the N/P changeover switch 6 is input to the sequence control circuit 5, and the negative development unit 3
is released, the positive developing device 4 is set, and the developing bias generating means 2 is activated based on a signal from the sequence control circuit 5, and is set to a developing bias value corresponding to positive development.

When only the negative developing device 3 is used, only the negative developing device is set as shown in FIG. 1, and the developing bias generating means 1 is activated based on the signal from the sequence control circuit 5 as shown in FIG. A developing bias value corresponding to negative development is set. Similarly, when using only the positive developer 4,
In FIG. 1, only the positive developer 4 is set, and as shown in FIG. 4, based on the signal from the sequence control circuit 5,
The developing bias generating means 2 is activated and set to a developing bias value corresponding to positive development.

FIG. 5 shows a simple block diagram when the present invention is applied to a multicolor electrophotographic copying machine capable of color development.

Since the structure of the multicolor electrophotographic copying machine itself is well known to those skilled in the art, a detailed explanation of its structure and operation will be omitted, but except for the optical system, the structure is essentially as shown in FIG.
It has a similar effect.

In FIG. 5, a signal from a black development/color development changeover switch 36 provided in an operation section (not shown) of the copying machine is input to a sequence control circuit 35, and normally a black development device 33 is inputted to a sequence control circuit 35.
is set, and the developing bias generating means 31 is activated based on the signal from the sequence control circuit 35, and the developing bias value corresponding to black development is set, but the changeover switch 36 is set to the color development side. Then, the sequence control circuit 35 enters the color development mode, and the black developer 3
3 and set the color developing device 34. and,
The developing bias generating means 32 operates based on the signal from the sequence control circuit 35, and is set to a developing bias value corresponding to color development.

When only the black developing mode is used, the color developing device 34 is omitted.

FIG. 6 shows an embodiment in which the present invention is embodied in a microfilm reader printer that is the same as the microfilm reader printer shown in FIG. 1 but has only one developing device. 41 is, for example, a negative developing device, and a developing device 42, which is selected as an alternative to the negative developing device 41 and set in the main body of the apparatus, is, for example, a positive developing device. Each developing device 41, 42 is provided with developing bias generating means 1 and 2, respectively.

In the configuration of this embodiment, although it is not possible to change the development mode with a single touch using a switch, it is possible to change the development mode for a number of times. In the case of microfilm, most users use only negative film and only positive film, so this method is effective because the device can be smaller.

In the case of a copying machine having this configuration, the developing device 41 can be a black developing device, and the developing device 42 can be a color developing device. Copying machines also mainly develop black images, so by adopting this system in which one developing unit is set in the main body of the apparatus, the size of the apparatus can be reduced.

Further, even in a cartridge-type image forming apparatus in which a photosensitive drum, a primary charger, a cleaner unit, etc. are integrated in addition to a developing device, a developing bias generating means is individually arranged in the unit including the developing device, that is, the cartridge. The present invention can be applied to a system in which the development mode is switched by replacing the cartridge.

In other words, the present invention can be very suitably employed in any image forming apparatus that includes a developing device alone or as a unit together with other devices.

As explained above, the image forming apparatus according to the present invention includes a developing device equipped with a developing bias generating means according to each developing mode (negative/positive development, black/color development, etc.), or Since it is arranged in a unit that includes at least the developing device, it has high cost performance even for users who only use one of the developing modes, and it is also possible to use multiple developing modes. teeth,
It has the advantage of always being able to obtain high-quality images. Further, according to the present invention, since the developing bias generating means is provided in the developing device or close to the developing device inside the unit including the developing device, the wiring can be simplified and the cost can be reduced. There is also an advantage.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a microfilm reader printer that is an embodiment of the present invention. FIGS. 2 to 5 are block diagrams showing how the developing device is controlled. FIG. 6 is a schematic diagram of a microfilm reader printer according to another embodiment of the present invention. FIG. 7 is a block diagram showing a conventional developing device control mode. 1, 2: Developing bias generating means 3: Negative developer 4: Positive developer 5 Shift control circuit 6: N/P selector switch Figure 2 Figure 3 Figure 5 Figure 7

Claims (1)

[Claims] 1) An image carrier on which a latent image is formed, at least one developer for developing the latent image on the image carrier, and a developing bias applied to the developer. An image forming apparatus comprising: a developing bias generating means for generating an image, the developing bias generating means being integrally provided with the developing device or a unit including the developing device. 2) The image forming apparatus according to claim 1, wherein the developing device or a unit including the developing device, which includes the developing bias generating means, is configured to be detachably attached to the main body of the apparatus.