JPH01217481A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain uniform images by providing a 1st engaging part to a frame holding a photosensitive body drum, a 2nd engaging part to a developing sleeve built-in container, engaging the 1st engaging part with the 2nd engaging part and maintaining parallelism between the photosensitive body drum and a developing sleeve. CONSTITUTION:A notch for engagement as the 1st engaging part 8 is provided to front and rear side plate the frame body 1 holding the photosensitive body drum 2. On the other hand, the container 4 of a developing unit B is provided with a projecting part for engagement as the 2nd engaging part 9. After the developing unit B is fitted into the main body of a device, the 1st engaging part 8 and the 2nd engaging part 9 move the developing unit B to the photosensitive body drum 2. They are engaged when the developing sleeve is abutted on the photosensitive body drum 2. The engagement itself maintains the parallelism between the photosensitive body drum 2 and the developing sleeve 3. Thus, the position of the developing sleeve is stabilized, thereby obtaining uniform images.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus, and more particularly to an electrophotographic copying apparatus equipped with a developing unit that can be inserted into and taken out from a main body, and in which the developing unit can be replaced. The present invention relates to a copying apparatus in which parallelism between a photosensitive drum and a developing sleeve is maintained during printing.

[Prior Art] In recent years, electrophotographic copying apparatuses have changed from being able to produce only black images to being able to produce color images, and this is becoming mainstream.

In order to obtain copies of images of various colors, a developer unit consisting of a container with a developing sleeve containing toner of each divine color is prepared, and the user can replace the developer unit himself and select the color he wishes to copy. It is being done. In an electrophotographic copying apparatus having such a structure, the developing unit is detachable from the photosensitive drum within the main body of the copying apparatus and can be pulled out to the outside of the main body.

After replacing the developer unit, the user manually or automatically moves the unit toward the photoreceptor drum and presses the developer sleeve against the photoreceptor drum, completing preparations for operation of the copying machine. .

Incidentally, the diameter of the photosensitive drum of the above-mentioned copying apparatus has recently become smaller and smaller. This is due to the fact that the lifespan of the photoreceptor itself has been extended, and furthermore, not only the frame (the drum cartridge that holds the photoreceptor drum) but also the size of the copying machine itself and its associated cost reduction have been achieved. Depends on.

Hereinafter, an electrophotographic copying apparatus to which the present invention is directed will be briefly described.

FIG. 3 is a schematic configuration diagram showing an electrophotographic copying apparatus to which the present invention is directed. In the figure, 10 is a document placement glass, 11 is a document, 12 is an illumination lamp as a light source, and 13 is a
, 14, 15° 16, 17, 18 are reflecting mirrors, 19 are imaging lenses, 20 are photosensitive drums 21 are primary chargers, 2
2 is a developing device, 23 is a transfer charger, 24 is a cleaner, 25
26 is a transfer paper, 26 is a cassette containing the transfer paper, 27 is a registration roller, 28 is a slip roller, 29 is a pickup roller, 30 is a transfer paper guide, 31 is a separation static eliminator, 32 is a conveyor belt, and 33 is a fixing device , 34 are discharge rollers.

In the copying apparatus having the above configuration, image formation is performed as follows. First, the original 11 placed on the original placing glass 10 is illuminated by the illumination lamp 12, and the light image is transmitted to the imaging lens 19 through the reflecting mirrors 13° and 14.15.
, and is guided onto the photoreceptor drum 20 via reflection mirrors 16, 17, and 18. At this time, lamp 12
The mirrors 13, 14, and 15 scan the original while moving at a predetermined speed in the direction of the arrow. On the other hand, the photosensitive drum 20
rotates in the direction of the arrow while uniformly charging its surface with the primary charger 21, so that electrostatic latent images corresponding to the original image are successively formed on the surface of the photosensitive drum 20. This electrostatic latent image becomes a toner image visualized by a developing device 22 containing toner. Next, this toner image is transferred onto transfer paper 25 by the action of transfer charger 23. Here, the transfer paper 25 is initially loaded in the cassette 26,
The top sheets are picked up one by one by a pickup roller 29 and moved along a transfer paper guide 30 through a slip roller 28 and a registration roller 27 to a transfer position. The transfer paper 25 on which the toner image has been transferred is separated from the drum 20 by a separation static eliminator 31, and transferred to the fixing device 3 by a conveyor belt 32.
3, and the toner image is fixed here. Thereafter, the transfer paper 25 is discharged to the outside of the apparatus via the conveyance roller 25 and the discharge roller 34.

In the electrophotographic copying apparatus described above, the developing device 22 is configured as a replaceable developing device unit consisting of a container body containing toner and a developing sleeve built into the container body. The developing sleeve is moved toward the photosensitive drum and is brought into pressure contact with the photosensitive drum via a spacer roller (not shown), leaving a slight gap between the sleeve and the drum (hereinafter referred to as the S-D gap).
is designed to be maintained.

[Problems to be Solved by the Invention] With the aforementioned reduction in the diameter of the photoreceptor drum, a problem arises when bringing the developing sleeve of the developing device unit into contact with and separating from the photoreceptor drum. The problem is how to keep them parallel and in contact with each other.

In particular, what is important in development is the size of the SD gap, and the contact position of the space roller that holds this SD gap with respect to the photosensitive drum is at both ends of the photosensitive drum. If there is a relative misalignment, the parallelism between the photoreceptor drum and the developing sleeve cannot be maintained, and the S-D gap changes along the length of the photoreceptor drum, causing the development state to fluctuate. A problem arises in that a similar image cannot be obtained.

For this reason, especially in a copying machine configured so that the developer unit can be removed from the photoreceptor drum and replaced with another developer unit, the developer unit inserted into the main body is pressed against the photoreceptor drum. At this time, the photosensitive drum and the developing sleeve must be kept parallel to each other.

In a conventional copying device with a replaceable developer unit, a guide rail is provided to serve as a holding guide when loading the developer unit into the device body, and the guide rail is moved toward and away from the photoreceptor drum. In this structure, the guide rail is held in the main body of the copying apparatus with sufficient precision and strength to maintain parallel contact accuracy between the developing sleeve of the developing unit and the photosensitive drum.

However, in a type of copying machine that has a drive gear for driving the developing sleeve of the developing device unit on the end flange of the photoreceptor drum, when the developing sleeve receives driving force from the drive gear integrated with the photoreceptor drum, , the input gear of the developing sleeve receives a force in the pressure angle direction of the meshing gear, and this force received during driving may disrupt the parallelism between the photosensitive drum and the developing sleeve. In order to cope with this, it is necessary to provide the guide rail with sufficient strength and rigidity, which also causes an increase in the cost of the device.

Furthermore, even if the guide rail has sufficient strength and precision, the following problems still occur. That is, a play is provided between the guide rail and the developing device unit in order to facilitate the insertion of the developing device unit, and due to this play, no matter how strong and precise the guide rail is required, the developing image sleeve There may be cases where parallelism cannot be guaranteed between the drum and the drum.

The present invention has been made to solve the above-mentioned problems, and includes inserting a replaceable developer unit into and out of the main body of the apparatus, moving the unit close to the photoreceptor drum,
It is an object of the present invention to provide an image forming apparatus in which perfect parallelism between the developing sleeve and the photosensitive drum is guaranteed when the developing sleeve is brought into contact with the photosensitive drum while maintaining the SD gap.

[Means for Solving the Problems] In order to achieve the above object, an image forming apparatus according to the present invention includes a main body having a frame for holding a photosensitive drum, and a container body incorporating a developing sleeve that can be inserted into and taken out from the main body. A frame for holding a photosensitive drum in an image forming apparatus comprising: a developing unit configured to move the developing unit close to the photosensitive drum to bring a developing sleeve into contact with the photosensitive drum; The body is provided with a first engaging portion, and the developing sleeve built-in container body is provided with a second engaging portion, and when the photosensitive drum and the developing sleeve come into contact when replacing the developing device unit, the first engaging portion is provided. The present invention is characterized in that parallelism between the photosensitive drum and the developing sleeve is maintained by engaging the second engaging portion with the engaging portion.

[Function] According to the present invention, the first engaging portion provided on the frame body that holds the photosensitive drum and the container body that holds the developing sleeve incorporated in the developing unit 22. The second engaging portions are the parts that engage with each other when the developing unit is moved toward the photosensitive drum and the developing sleeve is brought into contact with the photosensitive drum after the developing unit is inserted into the apparatus main body. together,
This engagement itself maintains the parallelism between the photosensitive drum and the developing sleeve.

Embodiment FIGS. 1(a) and 1(b) are side sectional views of the first embodiment of the present invention, with the main body of the apparatus omitted, and FIG. 1(a) shows the developing unit connected to the photoreceptor. FIG. 10B shows a state in which the developer unit is horizontally spaced apart from the drum, and FIG. 2B shows a state in which the developing sleeve is in contact with the photoreceptor drum after the developer unit is moved horizontally toward the photoreceptor drum.

In FIGS. 1(a) and 1(b), A is a drum cartridge consisting of a frame 1 that rotatably holds a photosensitive drum 2 and also incorporates other cleaning devices, etc., and B is a device. This is a developing unit that can be inserted into and removed from the main body. The developer unit B is composed of a container body 4 in which a developer sleeve 3 is rotatably incorporated and contains toner of each color. A guide rail 5 is provided within the main body.

The front and rear side plates of the frame 1 holding the photosensitive drum 2 include
Engagement notches 8a and 8b are provided as first engagement parts, and a line connecting the notches 8a and 8b is parallel to the generatrix of the photoreceptor drum 2, and the opening direction thereof is It faces toward the developer unit B.

On the other hand, the developer unit B is provided with engagement protrusions 9a and 9b as second engagement portions on its container body 4.
A line connecting the protrusions 9a and 9b is parallel to the generatrix of the developing sleeve 3, and when the developing unit B is moved in the direction of arrow A toward the drum cartridge A, the protrusions 9a and 9b'' are parallel to each other. The notch portion 8a.

8b.

The developing unit B is moved along with the guide rail 5 in the direction of the arrow A by a pressing means including a spring 6 and a cam 7. At this time, the developing sleeve 3 is held against the photosensitive drum by maintaining the S-D gap via a spacer roller (not shown) or the like. 2 is pressed against. In this case, the protrusions 9a and 9b of the container body 4 fit into the notches 8a and 8b of the frame body 1, respectively, and the parallel positional relationship between the photosensitive drum 2 and the developing sleeve 3 is completely maintained. It turns out.

Projection portion 9a for cutout portions 8a, 8b.

The vertical position of the developing device unit B is regulated by the engagement of 9b, so that when the developing sleeve 3 comes into pressure contact with the photosensitive drum 2, the developing sleeve 3 moves along the circumference of the photosensitive drum 2. Even if the drive gear (not shown) of the photoconductor drum 2 applies a driving force to the driven gear (not shown) of the developing sleeve 3 and receives force in the pressure angle direction of gear meshing, The developing sleeve 3 will not be tilted or displaced.

Next, FIGS. 2(a) and 2(b) are side sectional views of a second embodiment of the present invention in which the main body of the device is not shown.
Figure a) shows the developer unit moved away from the photoreceptor drum by rotating counterclockwise, and figure (b) shows the developer unit moved closer to the photoreceptor drum by rotating clockwise. It shows.

The same reference numerals as in FIGS. 1A and 1B are used for corresponding members in FIGS. 2A and 2B. In this embodiment, a developing device unit B consisting of a container body 4 incorporating a developing sleeve 3 rotates around a supporting pin shaft 10 while moving toward or away from the photosensitive drum 2. It is configured to be mobile.

The supporting pin shaft 10 passes through the container body 4 while maintaining a parallel relationship with the generatrix of the developing sleeve, and the portion of the pin shaft 10 sandwiched between the front and rear side plates of the container body 4 holds the photoreceptor drum 2. The photoreceptor drum 2 is fitted into a U-shaped hole as a first engaging portion parallel to the generatrix of the photoreceptor drum 2 in the frame body 1 . In this case, the center of the pin shaft 10 as the second engaging portion and the center of the U-shaped hole coincide, and the distance from the center of the pin shaft 10 to the center of the photoreceptor drum 2 and the distance from the center of the pin shaft 10 to the developing sleeve Since the distances to the centers of the developer sleeves 3 and 3 are kept constant, the developer unit B is rotated about the pin shaft 10 in the direction of the arrow A, and the developer sleeve 3 is pressed against the photoreceptor drum 20. When the photoreceptor drum 2 and the developing sleeve 3 are in contact with each other, their contact positions are constant, and parallelism between the photosensitive drum 2 and the developing sleeve 3 is reliably guaranteed.

Note that the U-shaped hole as the first engaging portion can be a round hole, and in this case, if the pin shaft 10 is made to be able to be pulled out from the frame 1 and the container body 4. , the developing unit B can be easily replaced.

[Effects of the Invention] As explained above, in a copying apparatus having a structure in which the apparatus body has a guide rail and the developing unit is held by the guide rail and is moved horizontally with respect to the photoreceptor drum, the position of the guide rail has conventionally been changed. Because it relied only on accuracy, the parallelism of the photoreceptor drum and developing sleeve was not always guaranteed, or if driving force was applied to the manual gear of the developing sleeve, the position of the developing unit could be displaced or the guard rail Sometimes the object itself becomes deformed. However, as in the present invention, since the container body of the developing device unit itself engages with the frame body itself that holds the photosensitive drum, the contact point between the photosensitive drum and the developing sleeve can be corrected only by the dimensional tolerance of the container body and the frame body. This enables high precision to be achieved, and even when driving force is applied, the force applied to the input gear of the developing unit is applied to the front and rear side plates of the drum cartridge, which is held with sufficient strength in the copying machine body. The position of the developing sleeve is stabilized.

These conditions make it easy to ensure parallelism even when it is difficult to maintain parallelism with the developing sleeve due to the smaller diameter of the photoreceptor drum, and the guide rail can simply move the developer unit to suppress it relative to the photoreceptor drum. Since the input gear does not need to be strong enough to sustain the force applied to it, the weight of the copying device can be reduced and its cost can be reduced accordingly.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are side sectional views of the first embodiment of the present invention. FIG. 1(a) shows the state before the developing unit is moved, and FIG. 1(b) shows the state of the developing unit. It shows the state after the edict. FIGS. 2(a) and 2(b) are side sectional views of a second embodiment of the present invention, in which FIG. 2(a) shows the state before the developing unit is rotated, and FIG. 2(b) shows the developing unit in a state before rotation. The state after rotation is shown. FIG. 3 is a schematic explanatory diagram of an electrophotographic copying apparatus to which the present invention is directed. DESCRIPTION OF SYMBOLS 1... Frame body, 2... Photosensitive drum, 3...
...Developing sleeve, 4...Container body, 5...Guide rail, 6...Spring, 7...Operation cam, 8...
-Engagement notch, 9...Engagement protrusion, 10...
Engagement pin shaft. Figure 1 (Q) Figure 2

Claims (1)

[Scope of Claims] 1. A developing unit comprising a main body having a frame for holding a photosensitive drum, and a container body incorporating a developing sleeve that can be inserted into and taken out from the main body, and the developing unit is connected to the photosensitive drum. In an image forming apparatus in which a developing sleeve is brought into contact with the photoreceptor drum by moving close to the drum, a frame holding the photoreceptor drum is provided with a first engaging portion, and a developing sleeve is installed in the frame body that holds the photoreceptor drum. A second engaging portion is provided in the container body, and the second engaging portion is engaged with the first engaging portion when the photosensitive drum and the developing sleeve come into contact when replacing the developing device unit. An image forming apparatus characterized in that parallelism between a photosensitive drum and a developing sleeve is maintained. 2. The developing device unit is of a horizontally movable type, and in this case, the first engaging portion is an engaging notch portion opened toward the developing device unit in the front and rear side plates of the frame holding the photosensitive drum. 2. The image forming apparatus according to claim 1, wherein the second engaging portion is an engaging protrusion provided on the container body of the developing device unit to engage with the engaging notch. 3. The developing device unit is of a rotary type, and in this case, the first engaging portion and the second engaging portion are both formed as engaging holes, and the engaging pin shaft is inserted into these engaging holes. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to engage the image forming apparatus by rotating the image forming apparatus.