JP3266474B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an electrophotographic or electrostatic recording type image forming apparatus, and more particularly to a method for forming a visible image on an image carrier and rotating the visible image. The present invention relates to an image forming apparatus which transfers an image onto a transfer material carried on a material carrier to obtain an image, and can be suitably embodied in, for example, a multi-color or single-color electrophotographic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art An example of a multicolor laser beam printer is shown in FIG. The multicolor laser beam printer has a drum-shaped electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 4a, which is rotatably supported at a substantially central portion thereof and rotates in an arrow direction. A primary charger 4b for uniformly charging the photosensitive drum 4a is provided around the photosensitive drum 4a, and a laser beam exposure unit 1 for irradiating image information to form a latent image.
0, a plurality of developing devices 5 (5M, 5C, 5Y, 5K) for developing a latent image into a visible image (toner image), and a transfer for carrying and transporting the transfer material 2 fed from the paper feeding device 1 A transfer material carrier 3a serving as a drum is arranged. The toner image formed on the photosensitive drum 4a is transferred to the transfer material 2 on the transfer drum 3a. The residual toner on the photosensitive drum 4a is
The photosensitive drum 4a is removed in step c, and is subjected to the next image forming step.

[0005] By repeating such an image forming process, a multicolor toner image is superimposedly transferred onto the transfer material 2 on the transfer drum 3a.

Thereafter, the transfer material 2 is separated from the transfer drum 3a, the toner image is fixed on the transfer material 2 by the fixing device 6, and is sent out of the apparatus.

When the photosensitive drum cartridge 4 having the photosensitive drum 4a and the like is attached and detached, and the transfer of the transfer material 2 is not performed normally, the transfer material remaining on the transfer drum 3a is stopped and removed to stop the apparatus. In some cases, the transfer drum 3a needs to be separated from the photosensitive drum 4a in order to prevent the photosensitive drum 4a and the transfer drum 3a from being damaged.

In order to reduce the size of the apparatus, a separation point where the transfer material 2 is separated from the transfer drum 3a and the fixing device 6
When a transfer material (for example, an OHP sheet) having a different transfer speed and a different fixing speed is used in an apparatus in which the distance between the transfer material 2 and the transfer material 2 is shorter than the length of the transfer material 2, It is necessary to separate the drum 4a from the transfer drum 3a, adjust the peripheral speed of the transfer drum 3a to the fixing speed, rotate the transfer drum 3a one more revolution, separate the transfer material, and send it to the fixing device 6.

FIGS. 7 and 8 show an example of a mechanism for separating the transfer drum 3a and the photosensitive drum 4a. FIG. 7 is a diagram showing the vicinity of the transfer drum unit 3 including the transfer drum 3a and the like as viewed from obliquely upper rear inside the apparatus main body, and FIG. 8 is a diagram schematically showing the separating operation of the transfer drum unit 3.

In FIG. 7, the transfer drum unit 3
It is located between the front and rear side plates of the device body. Separation guides 20 are provided on the side plates on the front and rear sides of the apparatus main body, respectively. The transfer drum shaft 3 rotatably supports the transfer drum 3a.
The shaft end of s is supported. A compression coil spring 21 is mounted inside the separation guide 20, and presses the transfer drum 3a against the photosensitive drum 4a. Further, a separation lever 30 for separating the transfer drum 3a from the photosensitive drum 4a is provided so as to be swingable about a shaft 31 fixed to the side plate, and a protrusion 30d formed at an appropriate portion thereof is provided with a transfer drum shaft 3s.
Of the shaft.

As shown in FIG. 8, usually, the transfer drum 3a
Is pressed in the direction of the photosensitive drum 4a by the action of the compression coil spring 21, the position of the separation lever 30 is determined by the position of the shaft end of the transfer drum shaft 3s.

As a means for manually separating the transfer drum 3a when the photosensitive drum cartridge 4 is attached or detached or when the transfer material on the transfer drum 3a is removed, manual separation cams 40 are provided near both ends of the transfer drum 3a, respectively. The two separating cams 40 are connected to each other by a manual separating shaft 41.

An operation lever 42 indicated by a broken line is provided at one end of the manual separation shaft 41. Further, the manual separation shaft 41 is rotatably supported by the front and rear side plates, and when the operation lever 42 is swung, the manual separation cam 40 is also integrally rotated via the manual separation shaft 41. Accordingly, when the manual separation cam 40 rotates, the separation lever 30 comes into contact with the separation lever 30. When the manual separation cam 40 further rotates, the separation lever 3
0 is rotated about its axis 31, and the transfer drum shaft 3 s is pressed and oscillated against the urging force of the compression coil spring 21 inside the separation guide 20 via the protrusion 30 d, and as a result, the transfer is performed. The drum 3a is separated from the photosensitive drum 4a.

When the transfer speed and the fixing speed are different from each other, the sequence separation cam 50 for separating the transfer drum 3a in the image forming sequence is replaced with the manual separation cam 40.
, Is fixed to a sequence cam shaft 51 extending parallel to the manual separation shaft 41. The sequence cam shaft 51 is rotatably supported by the front and rear device side plates, and is driven by driving means (not shown) by half-rotation control or the like.

When the sequence separating cam 50 rotates, it comes into contact with the roller 60. The roller 60 is guided by a guide member (not shown), linearly moves and abuts on the separation lever 30, and resists the urging force of the compression coil spring 21 inside the separation guide 20, and moves the separation lever 30 to the shaft 31. The transfer drum 3a is rotated around to separate the transfer drum 3a from the photosensitive drum 4a in the same manner as described above.

By the way, around the transfer drum 3a, as shown in FIG. 6, a suction roller 3g for sucking the transfer material 2 on the surface of the transfer drum 3a, a guide plate 3m for guiding the transfer material 2 to the transfer drum 3a, A separation guide 3u for separating the material 2 from the transfer drum 3a, a charge removing roller 3n for adjusting the surface potential of the transfer drum 3a after the completion of the image forming process, and the like are arranged. In an image forming apparatus in which the transfer drum 3a is separated from the photosensitive drum 4a, the various members disposed around the transfer drum 3a are integrally supported in order to accurately maintain a positional relationship with the transfer drum 3a. It is desirable.

In FIG. 7, side plates 100 and 110 are side plates for integrally supporting the transfer drum 3a and its peripheral members. The side plates 100 and 110 are fixed to a transfer drum shaft 3s which supports the transfer drum 3a for free rotation. I have. In FIG. 7, peripheral members of the transfer drum are not shown for simplification of the drawing. The pins 101 on the side plate 100 prevent the transfer drum 3a and the side plates 100 and 10 from rotating integrally, and are parallel to the direction of separation of the transfer drum 3a on the apparatus main body side plate as shown in FIG. Slot or groove 300 formed in
And so on.

A sensor 200 for detecting the rotational position of the transfer drum 3a is fixed to the side plate 100. A flag 3z formed on the transfer drum 3a is
The top position of the transfer drum 3a is detected by passing through the sensor 200 by the rotation of. The top signal serves as a reference for determining the timing of each unit of the apparatus, such as feeding and drawing of the transfer material 2.

[0017]

However, the configuration of the above-mentioned conventional example has the following disadvantages.

Since the flag 3z and the sensor 200 for detecting the top signal of the transfer drum 3a are provided at the transfer material winding position of the transfer drum 3a, that is, radially inward from the outer peripheral surface of the transfer drum 3a, the detection of the top signal is performed. , An error in the drawing position increases in proportion to the difference between the position of the flag 3z and the sensor 200 and the transfer material winding position.

The side plate 1 to which the sensor 200 is fixed
When the transfer drum 3a separates from the photosensitive drum 4a, it smoothly moves between the pin 101 on the side plate for preventing rotation between the transfer drum 3a and the transfer drum 3a and the elongated hole or groove 300 on the main body side plate. A gap is required for sliding. Therefore, when a load change occurs on the transfer drum 3a, and when a load is applied or vibration is transmitted to the side plates 100, 110 that support the suction roller 3g disposed around the transfer drum, the side plates 100, 110 Pin 101 and slot or groove 3
There is a possibility of movement by the gap of 00. Side plate 10
If 0 and 110 move by the gap, the detection of the transfer drum top signal will fluctuate, and as a result, the drawing position will be shifted.

In particular, in the case of a multi-color image forming apparatus, if the detection of the top signal fluctuates, the drawing position differs for each color, and a so-called color shift occurs.

It is an object of the present invention to provide an image forming apparatus capable of stably detecting a transfer drum top signal and obtaining a high-quality image with very little deviation in drawing position and color deviation.

[0022]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image forming apparatus for forming a visible image on an image carrier, and transferring the visible image onto a transfer material carried and conveyed by a rotating transfer material carrier to obtain an image. A photo-interrupter for detecting a rotational position of the body, a detected portion provided on the transfer material carrier, and a mechanism for separating the transfer material carrier from the image carrier, The photo interrupter is attached to the device body frame or a member firmly coupled to the device body frame, and
The image forming apparatus is characterized in that the photointerrupter is arranged so that the direction of separation of the transfer material carrier is perpendicular to the optical axis of light emission and light reception of the photointerrupter.

According to one embodiment of the present invention, the detected portion is provided at a position equal to a transfer material carrying position of the transfer material carrier.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Reference Example One example of an image forming apparatus to which the present invention can be applied will be described with reference to FIGS. FIG. 2 is an overall configuration diagram showing an image forming apparatus which is a color laser beam printer, for example.

First, the color image forming apparatus of the reference example shown in FIG. 2 has an electrophotographic photosensitive drum 4a as an image carrier, and rotationally develops the electrostatic latent images of each color formed on the photosensitive drum 4a by exposure. The toner image of each color is formed by developing with the device 5A, and the toner image of each color is fed from the feeding unit 1 and multiplex-transferred onto the transfer material 2 wound around the transfer drum 3a as a transfer material carrier. To form a color image. The transfer material 2 onto which the toner images of the respective colors have been transferred is separated from the transfer drum 3a and sent to the fixing unit 6, where the toner image is mixed and fixed to the transfer material 2 by fixing to form a full-color permanent image. After that, the discharge roller 8 at the upper part of the apparatus is driven by the discharge roller 7.
Is discharged to

Exposure to the photosensitive drum 4a is performed by the scanner unit 1.
Performed by 0. The scanner unit 10 has a laser diode (not shown). When the laser diode receives an image signal, the laser diode generates image light λ corresponding to the image signal and irradiates it to the polygon mirror 10a. The polygon mirror 10a is rotated at a high speed by a scanner motor and reflects the image light λ.
The photosensitive drum 4a is selectively exposed from the exposure unit of the image carrier unit via the reflection mirror 10b and the reflection mirror 10c.

Next, the configuration of each part of the image forming apparatus will be described in detail.

The feeding section 1 is for feeding the transfer material 2 to the transfer drum 3a, and has a paper feed cassette 1a for storing the transfer material 2 loaded at the bottom in the apparatus main body 9.
At the time of image formation, the feed roller 1b rotates in accordance with the image forming operation, and separates the transfer materials 2 from the cassette 1a one by one and feeds them to the transfer drum 3a. Transfer material 2 is guide plate 1
While being guided by c, the paper is fed to the transfer drum 3a through the registration roller 1e.

The transfer drum 3a winds the fed transfer material 2, and transfers the toner images of each color on the photosensitive drum 4a to the transfer material 2.
In order to transfer the image onto the photosensitive drum 4a, the photosensitive drum 4a rotates at the same speed as the peripheral speed of the photosensitive drum 4a in the direction of the arrow in FIG. The transfer drum 3a is rotatably supported by a fixed shaft 3s, and rotates in the above-described arrow direction according to an image forming operation by transmitting a driving force from a drive motor to a gear (not shown) fixed to the transfer drum 3a.

At a predetermined position on the outer periphery of the transfer drum 3a, a gripper 3f for gripping the leading end of the fed transfer material 2 is provided. When the gripper 3f grips the leading end of the transfer material 2, the transfer material guide member 3m guides the transfer material 2. Further, an electrostatic attraction roller 3g is detachably attached to the outer periphery of the transfer drum 3a.
Is provided, and the suction roller 3g transfers the transfer material 2 to the transfer drum 3
a, and is pressed against the outer periphery of the transfer drum 3a so as to be sandwiched between the transfer drum 3a. By applying a voltage between the suction roller 3g and the transfer drum 3a, the transfer material 2 which is a dielectric material is applied.
And an electric charge is induced in a dielectric layer (not shown) of the transfer drum 3a,
The transfer material 2 is electrostatically attracted to the outer periphery of the transfer drum 3a.

The photosensitive drum 4a, which is an image carrier, is rotatably supported on its rotating shaft by an image carrier cover 4e. The photosensitive drum 4a rotates in a direction indicated by an arrow in FIG. 2 according to an image forming operation by transmitting a driving force from a driving motor to one end of a rotating shaft thereof via a gear (not shown). A primary charger 4b and a cleaner 4c are arranged on the outer periphery of the photosensitive drum 4a.

The primary charger 4b is disclosed in
No. 49669, which uses a so-called contact charging method, and includes a conductive roller. The conductive roller is brought into contact with the photosensitive drum 4a, and a voltage is applied to the conductive roller. Is uniformly charged.

The cleaner 4c is for cleaning the toner remaining on the photosensitive drum 4a after transferring the toner image formed on the photosensitive drum 4a to the transfer material 2 by the rotary developing device 5A. In the reference example, the waste toner cleaned by the cleaner 4c is transported to a waste toner container (not shown) attached to a side surface of the apparatus main body by a transport screw 4d inserted into the container. When the waste toner container is full of waste toner, it is removed and replaced with a new waste toner container.

The rotary developing device 5A has developing devices 5 for each color, that is, developing devices 5M, 5C, 5Y and 5K provided with magenta, cyan, yellow and black toners. These four-color developing units 5 are rotatably arranged around a rotation shaft 5e, and the centers of the respective developing units 5 rotate in conjunction with self-rotating gears arranged on the outer periphery of the revolving gear, and their postures are changed. Is always kept constant.

When forming an image, the developing device 5 is rotated about the shaft 5e, and the developing device 5 of the color corresponding to the latent image is stopped at the developing section facing the photosensitive drum 4a. After the developing sleeve 5b is positioned so as to be opposed to the photosensitive drum 4a with a small gap (about 300 μm), the latent image on the photosensitive drum 4a is developed with the toner contained in the developing container.

In the developing device 5 for developing, the toner contained in the container is fed to the application roller 5a by a feed mechanism, and is rotated by the supply by the rotation of the application roller 5a and the regulation of the toner layer thickness by the blade 5c. A predetermined thin toner layer is applied on the developing sleeve 5b, and a triboelectric charge is applied to the toner.

At the time of development, a developing bias is applied between the developing sleeve 5b and the photosensitive drum 4a, whereby the toner on the developing sleeve 5b transfers corresponding to the latent image on the photosensitive drum 4a, and the latent image is developed. This is visualized as a toner image. The developing sleeve 5b of each developing device 5 is
Is rotated to the developing position, it is connected to a high-voltage power source for each color provided in the apparatus main body 9, and a developing bias of a voltage selected for each color is applied.

As shown in FIG. 2, the fixing section 6 includes a pressure roller 6a which is driven to rotate, and a fixing roller 6b which presses the roller 6a to apply heat and pressure to the transfer material 2. The transfer material 2 peeled from the transfer drum 3 and sent to the fixing unit 6 is
The toner image of each color is fixed on the transfer material 2 by the heat and the pressure of the fixing roller 6b when the toner image passes through the fixing unit 6 by the conveyance by the pressure roller 6a.

A cleaning member 6c is in contact with the fixing roller 6b, and the toner adhered to the roller 6b is removed by the cleaning member 6c.

Next, an image forming operation of the image forming apparatus provided with each unit having the above-described configuration will be described.

By rotating the feed roller 1b shown in FIG. 2, the transfer material 2 in the paper feed cassette 1a is separated and fed to the transfer drum 3a. The transfer drum 3a rotates in the direction of the arrow in FIG. 2, and the leading end of the transfer material 2 fed thereto is gripper 3
f, and is electrostatically attracted to the peripheral surface.

The photosensitive drum 4a is rotated in the direction of the arrow in FIG. 2 in synchronization with the rotation of the transfer drum 3a, and the surface of the photosensitive drum 4a is uniformly charged by the primary charger 4b. Irradiates magenta image light λ to form a magenta image latent image on the photosensitive drum 4a. Simultaneously with the formation of the latent image, the magenta developing device 5M is driven, and the developing bias voltage having the same polarity as the charging polarity of the image carrier 4a and substantially the same potential so that the magenta toner adheres to the latent image formed on the photosensitive drum 4a. Is applied to develop a magenta toner image on the photosensitive drum 4a. Then, a transfer voltage having a polarity opposite to that of the magenta toner is applied to the transfer drum 3 through the shaft 3e, and the photosensitive drum 4a
The upper magenta toner image is transferred onto the transfer material 2 on the transfer drum 3a.

When the transfer of the magenta toner image is completed as described above, the next developing unit is rotated and positioned at the developing position facing the photosensitive drum 4a, and similarly, the formation of the cyan, yellow and black latent images is performed. , Development, and transfer of the obtained toner image are sequentially performed, and a color image is formed on the transfer material 2.

The transfer material 2 onto which the toner image has been transferred is separated from the transfer drum 3a by a transfer material separating member 3u, conveyed to a fixing section 6, where the toner image is fixed by the fixing section 6, and then discharged. It is discharged to the discharge tray 8 by the pair 7,
Image formation ends. When the transfer material 2 is separated from the transfer drum 3a, the surface potential of the transfer drum 3a is adjusted by the transfer drum surface charge eliminating roller 3n to prepare for the next transfer material adsorption.

Next, the configuration of a sensor and a flag for detecting the top signal of the transfer drum will be described.

FIG. 1 is a view of the vicinity of the transfer drum unit inside the image forming apparatus as viewed obliquely from the upper rear similarly to FIG. 7 described above. Omitted.

Also in this embodiment, a sensor 200 such as a photo interrupter for detecting the top position of the transfer drum 3a is fixed to the side plate 100.
The top detection flag 3z is formed at the end of the transfer drum 3a.
7 is significantly different from the configuration shown in FIG. That is, in this reference example, the flag 3z
Is substantially equal to the transfer material winding diameter, and the fixed position of the sensor 200 corresponds to this flag position.

With this configuration, the transfer drum top signal detection position and the transfer material position become equal, so that
Even if a shift occurs in the detection of the top signal, the drawing position on the transfer material is not further amplified and does not shift.

Embodiment 1 Next, a first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a view of the vicinity of the transfer drum unit inside the image forming apparatus according to the first embodiment of the present invention viewed obliquely from the upper rear similarly to FIGS. 1 and 7 described above. Reference numerals are given and detailed description is omitted.

In this embodiment, although not shown, the sensor 200 for detecting the top position of the transfer drum is fixed on the apparatus body frame, that is, on a side plate or a member firmly attached to this side plate. This is different from the above reference example. Also in this embodiment, the sensor 200 is a photo interrupter as in the reference example.

In the present embodiment, the sensor 200 is fixed in such a position that the optical axis of light emission and light reception is perpendicular to the direction in which the transfer drum 3a is separated from the photosensitive drum 4a. This positional relationship is shown in FIG.

With such a configuration, a load fluctuation occurs on the transfer drum 3a, and the side plates 100, 1 supporting the suction roller 3g disposed around the transfer drum 3a.
Even if a load is applied or vibration is transmitted to the side plate 10 and the side plate moves by the gap between the pin 101 and the elongated hole or the groove 300 on the main body side plate, the sensor 200 is fixed on the main body side plate. The top signal can be detected.

The case where the transfer drum 3a is separated from the photosensitive drum 4a will be described with reference to FIG. 4. In this embodiment, the separation direction of the transfer drum 3a and the opening through which the flag 3z of the sensor 200 passes are parallel. With this configuration, the sensor 200 does not interfere with the flag 3z of the transfer drum 3a. On the other hand, in the case of the sensor 201 shown by a broken line in FIG. 3, it is clear that the flag 3z and the sensor 20 interfere with each other when the transfer drum 3a is separated, and the effectiveness of the configuration of the present embodiment is understood. Will be done.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a view of the vicinity of the transfer drum unit inside the image forming apparatus according to the second embodiment of the present invention, as viewed from obliquely upper rear, similar to FIGS. Are denoted by the same reference numerals, and detailed description is omitted.

The configuration of this embodiment is different from that of the first embodiment shown in FIGS. 1 and 3 in that the formation position of the flag 3z of the transfer drum 3a is the outer diameter of the transfer drum and the sensor 2
00 is a positional relationship in which the optical axis of light emission and light reception is perpendicular to the direction in which the transfer drum 3a is separated from the photosensitive drum 4a. In that it is fixed on a member attached to the.

Thus, even if the detection of the top signal is deviated, the drawing position on the transfer material is not further amplified and does not blur, so that the load on the transfer drum 3a fluctuates or the transfer drum 3a is arranged around the transfer drum 3a. Side plate 10 for supporting members
Even if a load is applied to 0 or 110 or vibration is transmitted, the top signal can be detected stably without being affected by these.

[0058]

As described above, according to the present invention, the top signal can be detected stably without being affected by the operation of each unit of the apparatus, and the deviation of the drawing position and the color deviation in the case of the multi-color system can be detected. Is extremely reduced, and a high-quality image can be obtained. Further, even when the transfer material carrier is separated from the image carrier, the transfer material carrier and the photointerrupter do not interfere with each other. obtain.

[0059]

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration near a transfer drum according to a reference example of the present invention.

FIG. 2 is an overall configuration diagram of a reference example of an image forming apparatus to which the present invention can be applied.

FIG. 3 is a perspective view showing a configuration near a transfer drum of the first embodiment of the image forming apparatus according to the present invention.

FIG. 4 is a side view for explaining the separation operation of the transfer drum of the first embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a perspective view showing a configuration near a transfer drum of a second embodiment of the image forming apparatus according to the present invention.

FIG. 6 is an overall configuration diagram of a conventional image forming apparatus.

FIG. 7 is a perspective view illustrating a configuration near a transfer drum of the image forming apparatus of FIG. 6;

FIG. 8 is a side view for explaining a separating operation of the transfer drum of FIG. 7;

[Explanation of symbols]

 3a Transfer material carrier (transfer drum) 3z Detected part (flag) 4a Image carrier (photosensitive drum) 20 Separation guide 30 Separation lever 100, 110 Side plate 200 Detecting means (photo interrupter)

Continuation of the front page (56) References JP-A-5-61368 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 114

Claims (2)

(57) [Claims] 1. An image forming apparatus for forming a visible image on an image carrier and transferring the visible image onto a transfer material carried and conveyed by a rotating transfer material carrier to obtain an image. A photo-interrupter for detecting a rotational position of the transfer material carrier, a detected portion provided on the transfer material carrier, and a mechanism for separating the transfer material carrier from the image carrier. The photo-interrupter is attached to an apparatus main body frame or a member firmly connected to the apparatus main body frame, and the photo-interrupter is configured to emit light and receive light from the photo-interrupter in a direction in which the transfer material carrier is separated. An image forming apparatus, wherein the optical axes are arranged at right angles. 2. The image forming apparatus according to claim 1, wherein the detected portion is provided at a position equal to a transfer material carrying position of the transfer material carrier.