JPH05142886A - Image forming device - Google Patents

Abstract

PURPOSE:To form a positive image both from negative and positive originals without lowering image quality with the simple structure. CONSTITUTION:A positive process cartridge 13 in which a positive photosensitive member 15 is incorporated and a negative process cartridge in which a negative photosensitive member is incorporated are selectively and removably attached to a device body. The selection is made based on whether an original is a positive image or a negative image. For the two types of photosensitive members, one type of a toner is used for developing an electrostatic latent image formed on the photosensitive member. By this, change of image forming conditions required when two types of toners are used is made unnecessary and equipment or mechanisms for change can be omitted. The process cartridge is distinguished by a cartridge distinguishing means and a cartridge detecting means 40, and a control device 90 control each image forming process based on the detection results.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a drum unit or a process cartridge is detachably attached to an apparatus main body, and more specifically, an original image is a general positive image or a negative image such as microfilm. The present invention relates to an image forming apparatus that selectively uses two types of drum units or process cartridges each having two types of photoconductors having different photosensitivity depending on a difference in image.

[0002]

2. Description of the Related Art Conventionally, there is known an image forming apparatus such as a copying machine which reverses black and white of an original image and makes a copy.

Like a general copying machine, this one can copy a positive image such as an ordinary character original as an original, and in addition, a negative image such as microfilm can be used as an original, which will be used in the future. It is configured so that a black-and-white inverted copy of the original can be obtained.

The following two are known as the general image forming method.

One of them is to selectively use two types of toner (developer) having different polar characteristics. In an image forming process in which a charger, an exposure device, a cleaning device, and the like are arranged around the photoconductor as a center, a photoconductor having sensitivity to only one of positive polarity and negative polarity is provided, and Two different types of developers (toners) are selectively used depending on whether the original image is a positive image or a negative image, whereby a copy corresponding to the negative image or the positive image is obtained.

The other is to provide a photosensitive member having sensitivity to both positive and negative polarities. This photoconductor is selectively charged positively or negatively, and then one kind of toner which is positively or negatively charged is used to form a positive copy.

[0007]

However, the above-mentioned conventional example has the following drawbacks.

First, in the case of forming an image using the latter bipolar photoreceptor, the sensitivity of the photoreceptor is significantly different between positive polarity and negative polarity.
In the low-sensitivity polarity, a larger exposure amount than that of a general photoconductor was required. There is a theoretical structural problem with the bipolar photoreceptor in that the potential shift is large in terms of durability, the potential shift due to the environment is larger than that of a general photoreceptor, and the potential tends to be unstable. High cost. There are various drawbacks with respect to the photoconductors such as the above, and the practical problems are large.

On the other hand, in the case of selectively using the former two types of toner, positive and negative, the output and charge polarity are switched depending on each charger such as pre-transfer (post) charging, transfer charging and separation charging. Is required, and a large number of high voltage transformers and high voltage relays are required. In fixing, since the fixing temperature, the offset temperature, etc. are originally different depending on the toner, the set temperature must be changed according to the toner used. If this is set to the same setting, unfixed toner or offset is likely to occur. Also in the cleaner, due to the characteristics of each toner,
Since the abrasion of the photoconductor (thickness reduction due to rubbing against the photoconductor) is different, it is necessary to change the contact pressure and contact angle of the cleaning blade with respect to the photoconductor, which is complicated to make the cleaner common. Is also happening. In the development, similarly, the fluidity of the toner, the developing conditions, etc. are different, and the stirring, the developing bias voltage, etc. need to be changed, and it is difficult to share the developing device. Problems such as are raised.

Therefore, the present invention uses two types of drum units or process cartridges of positive and negative polarities,
By developing with one kind of developer, the above-mentioned drawbacks and problems of the prior art are solved, that is, suitable image formation is performed without degrading image quality with a simple and inexpensive structure. It is an object of the present invention to provide an image forming apparatus.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a drum unit having at least a photoconductor incorporated therein is detachably attached to the apparatus main body, In an image forming apparatus that charges and exposes an electrostatic latent image to form an electrostatic latent image and develops the electrostatic latent image with a developer, a positive drum unit to which a positive polarity photoconductor is attached and a negative polarity photoconductor are attached. And a developing device for developing the electrostatic latent image by supplying the same developer to the positive-polarity photoconductor and the negative-polarity photoconductor.

Further, a process cartridge in which at least a photoconductor, a charger and a cleaner are integrally incorporated in a cartridge case is detachably attached to the apparatus main body, and the photoconductor is charged, exposed and electrostatically charged. In an image forming apparatus for forming a latent image and developing the electrostatic latent image with a developer, a positive process cartridge containing a positive photoconductor, a negative process cartridge containing a negative photoconductor, It is also possible to provide a developing device for developing the electrostatic latent image by supplying the same developer to the positive and negative photosensitive members.

At this time, the developing device may be incorporated in the positive process cartridge and the negative process cartridge, and may have a replenishing container for replenishing the developer.

Further, the developing device may be arranged on the side of the main body of the device.

Further, the positive process cartridge and the negative process cartridge have cartridge identifying means for identifying each other, and the apparatus main body detects the cartridge identifying means, and a detection signal of the cartridge detecting means. A control device for switching image forming conditions may be provided.

Similarly, for the positive drum unit and the negative drum unit, the image forming conditions can be switched by the drum unit detecting means.

[0017]

Based on the above construction, the drum unit or the process cartridge is of two types, a positive process cartridge containing a positive photosensitive member and a negative process cartridge containing a negative process cartridge, for example. Since each of them can be detachably attached to the main body of the apparatus, they can be easily used according to whether the original image is positive or negative. Then, the electrostatic latent image formed by both the positive and negative photoconductors is
Develop with different types of developers. That is, for example, by electrostatically developing the electrostatic latent image by the positive-polarity photoconductor with the negative-polarity developer, and reversal developing the electrostatic latent image by the negative-polarity photoconductor with the same negative-polarity developer, Positive copies can be obtained from positive and negative originals, respectively.

Further, since positive and negative photoconductors are used separately, a sufficiently large sensitivity can be obtained in each mode, and the potential shift is small, and a stable image with high contrast can be obtained.

Since there is only one type of developer, it is not necessary to change the image forming conditions, which was necessary when there were two types of developers, and special equipment or mechanism for the change is positively excluded. be able to.

In this case, the developing device may be installed in each of the positive and negative process cartridges, or may be installed in the main body of the device. At this time, it is not necessary to install the developing device in each of the positive and negative process cartridges. A common developing device can develop the respective photoconductors of the positive and negative process cartridges.

Further, even when the developing device is built in each process cartridge side, if a replenishing container for accommodating the developer is provided, the attaching / detaching operation of each process cartridge to / from the apparatus main body, Supply will be enough.

In addition, when a cartridge identifying means is attached to each of the positive and negative process cartridges, a cartridge detecting means for detecting this is provided on the apparatus main body side, and a control device for switching image forming conditions by the output of the cartridge detecting means is provided. The operator can set the image forming conditions suitable for the process cartridge as long as the operator mounts the corresponding process cartridge on the main body of the apparatus depending on whether the original image is positive or negative. To do.

[0023]

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

FIG. 1 shows a schematic configuration of a reader printer as an example of an image forming apparatus according to the present invention.
In the figure, a film illumination light source 1, a condenser lens 2, a field lens 3, a film F, and a projection lens 5 are provided.
Depending on the, the projection unit is configured. Mirrors 7, 7 ',
The screen 8 is a reader unit for observing the original image of the film F. Reference numeral 7'denotes a number-matching mirror for adjusting the front and back of the image. The image light from the projection unit is guided by the scanning mirrors 10 and 11 and is also projected on the copying unit. The copying unit is provided with process equipment (details described later) for forming an image by electrophotography. Reference numeral 13 denotes a positive process cartridge, in which a part of the process equipment including the photoconductor 15 having a positive polarity is incorporated. Reference numeral 19 is a pre-exposure lamp, 21 is a transfer material cassette, 22 is a paper feed roller, 2
3 is a pair of register rollers, and 25 is a fixing device.

When projecting on the screen 8 in such a reader printer, the scanning mirrors 10 and 11 are at the home position H apart from the optical path from the projection lens 5 to the screen 8. At the time of copying, it is driven by a driving source (not shown), advances into the optical path, and projects the original image on the film F onto the rotating photoconductor 15 while operating it. The scanning speed at this time is 1/2 of the rotation speed of the photoconductor 15.
Is. Further, the scanning mirrors 10 and 11 are orthogonal to each other,
At the intersection, O starts moving from the home position H and operates the original image at a constant speed from O ₁ to O ₂ . The light from the operation mirror 11 is shielded by the light shielding plates 44 and 4 shown in the upper part of FIG.
The photoconductor 15 is irradiated with the light through the opening 50 of No. 5.

2 and 3 are schematic diagrams for explaining the blank exposure switching mechanism of the reader printer.

FIG. 2 shows a positive / positive mode (a mode in which a positive image copy is obtained from a positive image original, the same applies hereinafter).
The state when processing is shown in. In the figure, the normal process cartridge 13 is a cartridge case 13a.
The process equipment is housed inside and can be inserted / removed in the frontward direction in the figure along a pair of rails 28 attached to the chassis of the main body of the printer. Reference numeral 30 denotes a blank exposure plate (light shielding plate) when the scanning mirrors 10 and 11 are pivotally supported on the main body chassis by a rotating shaft 31 and are moved in a direction opposite to the scanning direction, or when the scanning mirror is outside the image exposure scanning area such as a reader state. Is held by the tension spring 39 in the position indicated by the solid line so as to close the image optical path. The light shielding plate 30 has a lower surface serving as a reflecting surface. During the image exposure scanning, the light shielding plate 30 is rotated by the energization of the solenoid 32.
It rotates about 1, and abuts on the stopper 35 at the position of the chain double-dashed line to stop. This opens the image light path and closes the blank exposure path. This energization is performed according to the length of the transfer material. Reference numeral 37 denotes a shutter, which is pivotally supported by the main body chassis by a rotating shaft 38, is opened so as to open the blank exposure optical path in the positive / positive mode state, and is supported by the stopper 35. Reference numeral 40 denotes a switch (cartridge detection means) for switching the process condition of the image forming apparatus outside the cartridge, which is installed on the rotation locus of the shutter 37 and has either positive or negative mode process cartridges 13 and 13 '.
When the cartridge is mounted, it is switched by the cartridge identifying means described later. The signal from the cartridge identification means is input to the control device 90, and the control device 90
Based on this, a predetermined image forming condition (described later) is changed.

FIG. 3 shows a state in which processing is performed in the negative / positive mode (a mode in which a copy of a positive image is obtained from a document of a negative image; the same applies hereinafter). In the figure,
The negative process cartridge 13 'is a negative photosensitive member 15'.
When it is inserted along the rail 28, the cam 52 (cartridge identifying means) pushes the shutter 37 up to a position where it partially overlaps the light shield plate 36, and the shutter 37 reflects the light shield plate 30 from the lamp 19. Close the optical path towards the surface. In FIG. 3, the solid line arrow indicates the direction in which the negative process cartridge 13 'is inserted and the shutter 37 rotates, and the dotted line arrow indicates the negative process cartridge 13'.
Are pulled out and the shutter 37 is rotated to open the optical path. Further, the shutter 37 pushes the upper switch 40 to switch to the negative / positive mode. Next, the copying section will be described.

FIG. 4 shows a state in which the positive process cartridge 13 in the positive / positive mode is inserted into the reader printer body. The positive process cartridge 13 includes a photoconductor 15 that is positively charged, a primary charger 16 that uniformly charges the photoconductor 15, a developing device (charging device) 17 that contains a one-component magnetic toner that is triboelectrically negatively charged, and a cleaner. 18 is integrally attached. In addition, the positive process cartridge 1
In the opening of the cartridge case 13a of No. 3, the coloring filter 4 whose spectral transmittance matches the sensitivity wavelength characteristic of the photoconductor 15 is provided.
2 is fitted.

Therefore, when the positive process cartridge 13 in the positive / positive mode is inserted into the main body of the reader printer, the positive process cartridge 13 is first identified. In this case, since the switch 40 does not change as described above, C
The PU (not shown) determines that the positive / positive positive process cartridge 13 is selected, the positive / positive mode is selected, and the primary charger 16 is switched to the high voltage transformer 70 that outputs a positive high voltage by the high voltage relay RL or the like. .. When the copying operation is started, the photoconductor 15 is positively and uniformly charged by the primary charger 16. Next, in the exposure section, blank exposure is performed outside the image area to remove the electric charge on the photoconductor 15, and in the image area, the light shielding plate 30 is opened and image exposure is performed to form an electrostatic latent image. Next, in the developing portion, a bias voltage in which alternating current is superimposed on direct current is applied to the latent image so that the toner (developer) having a negative polarity is normally developed on the photoconductor 15. Further, it has the same polarity as the toner (negative polarity) by the pre-transfer (post) charger 72.
After being charged, the transfer charger 73 charges the toner having a polarity (positive polarity) opposite to that of the toner through the transfer material P in the transfer portion, and the toner image on the photoconductor 15 is transferred onto the transfer material P. .. The transfer material P is separated from the photoconductor 15 by the separation charger 74, which is charged by superimposing a transfer charge and a direct current having a polarity opposite to that of the transfer charge. The separated transfer material P is then transferred to the fixing device 25.
It is fixed by and discharged to the outside of the main body of the device. Further, the toner remaining on the photoconductor 15 at the time of transfer is cleaned by the cleaner 18, pre-exposed through the coloring filter 42, and the photoconductor 15 is discharged.

FIG. 5 is a schematic view when a negative / positive negative process cartridge 13 'is inserted. In the figure, a negative process cartridge 13 'is provided with a negatively chargeable photoconductor 15'. Note that the other components are the same as those for the positive / positive mode, and the description thereof will be omitted.

When the negative process cartridge 13 'in the negative / positive mode is inserted into the main body of the reader printer, the negative process cartridge is first identified. In this case, as described above, the shutter 37 is switched by pressing the switch 40. Therefore, the CPU (not shown) determines that the negative / positive negative process cartridge 13 'is selected, the negative / positive mode is selected, and the primary charging is performed. Vessel 16 is a high voltage relay R
The voltage is switched to the high voltage transformer 71 that outputs negative high voltage by L or the like. When the copying operation is started, the photosensitive member 15 ′ is negatively and uniformly charged by the primary charger 16. next,
In the exposure section, blank exposure is not performed outside the image area as described above, and in the image area, the light shielding plate 30 is opened and image exposure is performed to form an electrostatic latent image. Next, in the developing section, the latent image is applied with a bias voltage in which a direct current is superimposed on a direct current to reversely develop the negative toner on the photoconductor 15 '. After that, as in the positive / positive mode, after being charged with the same polarity (negative polarity) as the toner by the pre-transfer (post) charger 72, the transfer charger 73 charges the opposite polarity (positive) with the toner at the transfer portion. Is transferred via the transfer material P, and the toner image on the photoconductor 15 ′ is transferred onto the transfer material P. The transfer material P is separated by the separation charger 74 from the photoconductor 15 ′ by being charged by superimposing alternating current with direct current having a polarity opposite to that of the transfer charging. The separated transfer material P is then fixed by the fixing device 25 and discharged to the outside of the apparatus main body. Further, the toner remaining on the photoconductor 15 ′ at the time of transfer is cleaned by the cleaner 18 and is exposed to the pre-exposure via the color filter 42, so that the photoconductor 15 ′ is exposed.
Is discharged.

In this way, the positive process cartridge 13
When either the negative process cartridge 13 'or the negative process cartridge 13' is used by being attached to the apparatus main body, each type of toner can be used to form an image.

In the embodiment shown in FIG. 2, the developing device 17 is provided with a replenishing container 17 ', for example, a replenishing container 17'.
When the cartridge case 13a is formed so as to be openable and closable, it is convenient because the toner can be replenished independently of the attaching / detaching operation of the primary process cartridge 13.

Further, the developing device 17 is not installed in the positive and negative process cartridges 13 and 13 ', but instead of the positive and negative process cartridges 13 and 1 as shown in FIG.
It can also be arranged outside 3 ', that is, on the apparatus main body side. In this case, no developing device is required for each of the process cartridges 13 and 13 ', and the electrostatic latent images formed on the photoconductors 15 and 15' in both the positive and negative process cartridges 13 and 13 'are processed by one developing device 17. It will be developed.

The above is the positive and negative process cartridge 1
Although an example using 3, 13 'has been described, as another embodiment, a charging device, a developing device, a cleaner and the like are incorporated in the apparatus main body, and a positive or negative photosensitive member is provided as shown in FIG. By mounting the drum unit 20 and replacing the drum unit 20, it is possible to select a negative-positive or positive-positive image forming process.

That is, the drum unit 20 is equipped with the positive or negative photoconductors 15 and 15 ', and the photoconductors 15 and 1 are framed by the side plate 56, the stay 33, the exchange grip 57, and the like.
5'is held and attached, and if necessary, the photoconductor 15,
Modifications such as providing a cover (not shown) for protecting 15 'from sunlight and external damage can be considered.

The drum unit 20 includes photoconductors 15, 1
A driving force transmission means 34 for rotationally driving 5'is provided, and the photoconductors 15 and 15 'are rotated by a driving device from the main body of the apparatus during image formation. Further, the drum unit 20 has a drum unit identifying means 54 and functions in the same manner as the cam 52 of the negative cartridge described above. For example, the process on the apparatus main body side is switched to the state when processing in the negative / positive mode. Similarly, in the case of the drum unit 20 without the drum unit identification means 54, the process of the apparatus main body is switched to the positive / positive mode.

As another configuration example of the drum unit, the photoconductors 15 and 15 'are constructed on the cylindrical frame 55 without taking the construction of the frame of the stay 33, the side plate 56, the exchange grip 57 and the like. , Drum unit identification means 53
May be provided, and each image forming unit may be selected with or without. It should be noted that the drum unit detection means on the apparatus main body side, which is activated by engaging with the drum unit identification means 53, 54, is not shown.

In the embodiment of the drum unit 20 of the present invention, when the switching is frequently performed for each image formation, in the conventional process cartridge, the toner is supplied to the outside from the unit in which the toner is contained in the cleaner or the developing device. Leakage and a complicated structure for preventing this have been required, but since the drum unit 20 does not have a unit containing toner, toner does not leak to the outside even when the image formation is changed frequently.

Further, since the cleaner, the developing device, the charging device, etc. are not included in the drum unit 20, the size and weight can be reduced and the user can use one hand even when the image formation is frequently changed. It became easy to operate lightly.

[0042]

As described above, according to the present invention,
A positive drum unit or a positive process cartridge having a positive photoconductor and a negative drum unit or a negative process cartridge having a negative photoconductor are selectively mounted depending on whether the image of the original is positive or negative, for example. The image forming conditions are changed by the developer by developing the photoconductors having different photosensitivity, which are mounted on the sheet, with one type of developer, as compared with the conventional example in which two types of developers are used. Therefore, no special device or mechanism for this change is required, and the entire structure can be simplified, and the image quality is not deteriorated.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an image forming apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing the positive process cartridge mounted on the apparatus main body.

FIG. 3 is a diagram showing an engagement relationship between a cartridge identification unit and a cartridge detection unit.

FIG. 4 is an explanatory view of using the positive process cartridge.

FIG. 5 is an explanatory view of using the negative process cartridge.

FIG. 6 is a vertical sectional view showing another embodiment of the process cartridge.

FIG. 7 is an explanatory perspective view showing a drum unit.

[Explanation of symbols]

 13 Positive Process Cartridge 13 'Negative Process Cartridge 13a Cartridge Case 15, 15' Photoconductor 16 Charger 17 Developing Device 17 'Replenishing Container 18 Cleaner 20 Drum Unit 40 Cartridge Detecting Means (Switch) 52 Cartridge Identifying Means (Cam) 53, 54 Drum Units Identification means 90 Control device

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Claims (7)

[Claims] 1. A drum unit having at least a photoconductor incorporated in the unit is detachably attached to the apparatus main body, the photoconductor is charged and exposed to form an electrostatic latent image, and the electrostatic latent image is formed. In an image forming apparatus that develops with a developer, a positive drum unit that mounts a positive-polarity photoconductor, a negative drum unit that mounts a negative-polarity photoconductor, and the same positive-polarity photoconductor and negative-polarity photoconductor And a developing device for developing the electrostatic latent image by supplying the developing agent of the above. 2. The positive drum unit and the negative drum unit have a drum unit identifying means for identifying each other, and the apparatus body detects a drum unit detecting means for detecting the drum unit identifying means, and an image by a detection signal of the drum unit detecting means. The image forming apparatus according to claim 1, further comprising a control device that switches a forming condition. 3. A process cartridge in which at least a photoconductor, a charger, and a cleaner are integrally incorporated in a cartridge case is detachably attached to an apparatus main body, and the photoconductor is charged, exposed, and electrostatically charged. In an image forming apparatus for forming a latent image and developing the electrostatic latent image with a developer, a positive process cartridge containing a positive photoconductor, a negative process cartridge containing a negative photoconductor, An image forming apparatus comprising: a developing device that supplies the same developer to a positive-polarity photoconductor and a negative-polarity photoconductor to develop an electrostatic latent image. 4. The image forming apparatus according to claim 3, wherein the developing device is provided inside the positive process cartridge and the negative process cartridge. 5. The image forming apparatus according to claim 4, wherein the developing device has a replenishing container for replenishing the developer. 6. The image forming apparatus according to claim 3, wherein the developing device is disposed on the main body side of the device. 7. The positive process cartridge and the negative process cartridge have cartridge identifying means for identifying each other, and the apparatus main body detects cartridge detecting means, and a detection signal of the cartridge detecting means. The image forming apparatus according to any one of claims 3 to 6, further comprising: a controller that switches the image forming condition according to the above.