JP3038024B2 - Image forming device - Google Patents

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,
Particularly, the position accuracy of the toner density sensor with respect to the photosensitive drum is improved.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus has a structure in which a support frame for a photosensitive drum is provided so that the photosensitive drum can be easily attached and detached, and the support frame can be detachably attached to the apparatus main body. Has been adopted.

For example, as disclosed in Japanese Utility Model Unexamined Publication No. 62-146139, a projection with a hook is provided on an apparatus main body side for mounting a photosensitive drum unit in a drum axial direction, and a hook is provided when the photosensitive drum unit is mounted. There is a configuration in which it is stopped.

A toner density sensor for detecting the density of the toner is provided in proximity to the photosensitive drum, and its arrangement is, as shown in FIG. The photosensitive drum 2 is connected to the front and rear side plates 1a, 1
A support frame guide 5 for guiding the photoreceptor support frame 1 supported by b or the like is fixed, and two sensor brackets 6 for supporting the toner density sensor 3 are provided on the rear side plate 10 and the front side plate 9 of the apparatus main body, respectively. Screwed in. The toner density sensor 3 is inserted into the guide portion 6a of the sensor bracket 6, and is positioned by being pressed against the guide portion 6a by the leaf spring 4. Further, the photosensitive member support frame 1 is detachable along the support frame guide 5, so that the photosensitive drum 2 can be easily replaced.

[0005]

However, the conventional sensor bracket 6 is provided with front and rear side plates 9 and 1 of the apparatus main body.
In particular, since it is fixed to 0, the dimensional tolerance is accumulated between the front side plate 1a of the photosensitive member support frame 1 and the front side plate 9 of the apparatus main body on the front side (small dimensional errors overlap), and the toner density is increased. There is a problem that the position accuracy of the sensor 3 is difficult to obtain. In the future, with the spread of color toner, it is inevitable that the positioning accuracy of the toner density sensor 3 will be strictly required, and a high-precision positioning method instead of the conventional method is desired.

Further, the photosensitive member support frame 1 and the support frame guide 5
In the method of attaching and detaching the photosensitive drum 2, when the photosensitive drum 2 is inserted into or removed from the apparatus main body, the parts approaching the photosensitive drum 2 due to the wobble of the photosensitive drum 2 due to asobi of the support frame guide 5. In particular, the sensor bracket 6 to which the toner density sensor 3 is mounted is required to be provided close to the function, so that the contact is easy. As a result, each contacting part is damaged,
There has been a problem that the position accuracy is deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, to improve the accuracy of the position of the toner density sensor, and to improve the toner density sensor when the photosensitive drum is mounted on the apparatus main body. An object of the present invention is to provide an image forming apparatus capable of preventing contact with the image forming apparatus as much as possible.

The gist of the present invention is to provide a photosensitive drum unit which is detachable in the axial direction of the drum and comprises a photosensitive drum and a photosensitive support frame for supporting the photosensitive drum with front and rear side plates; And a sensor bracket mounted with a toner density sensor disposed in close proximity to the photosensitive drum, wherein the sensor bracket has a predetermined portion such that the toner density sensor is rotatable with respect to the photosensitive drum. Is rotatably mounted on the apparatus main body side about a central axis parallel to the drum axis, and a positioning member is provided at a predetermined position in contact with the front and rear side plates of the photoconductor support frame. Positioning for positioning the sensor bracket with respect to the photosensitive drum by fitting the positioning member to the front and rear side plates In that the member is provided.

[0009]

Therefore, when the photosensitive drum is mounted on the apparatus main body, the portion of the sensor bracket where the toner density sensor is mounted is lowered by its own weight, so that the photosensitive drum is brought into contact with the toner density sensor. In addition, after the mounting is completed, the sensor bracket is positioned by fitting the positioning member of the sensor bracket and the member to be positioned of the photoconductor support frame, thereby improving the positioning accuracy.

[0010]

1 is a front view of a photosensitive drum 2 shown in FIG.
The photoreceptor support frame 1 is rotatably supported about a shaft 11 and is fitted to a support frame guide member 5 fixed to a rear plate 10 of the apparatus main body. Supported by. On the other hand, the toner density sensor 3 for detecting the toner density is fitted on the guide portion 6a of the sensor bracket 6, and is mounted with the leaf spring 4 pressing the guide portion 6a. The sensor bracket 6 is rotatably attached to the rear plate 10 and the front plate 9 of the apparatus body by screws 12 through circular holes 10a, 9a with the right end side in the drawing as an axis.

In the above configuration, when the photosensitive member support frame 1 is mounted on the support frame guide member 5, the sensor bracket 6
The side on which the toner density sensor 3 is mounted is lowered (separated from the photosensitive drum 2) by its own weight with the right side as an axis. Therefore, there is no fear that the photosensitive drum 2 comes into contact with the sensor bracket 6. Then, after the photosensitive drum supporting frame 1 is pushed all the way in and the mounting of the photosensitive drum 2 is completed,
When positioning the toner density sensor 3, the sensor bracket 6 is positioned by fitting a projection 7, which is a positioning member of the sensor bracket 6, into a hole 8, which is a member to be positioned, of the photosensitive member support frame 1. As a result, the accumulation of the tolerance is small, and the positional accuracy of the toner density sensor 3 with respect to the photosensitive drum 2 is easily obtained.

[0012]

As described above, according to the present invention, the portion of the sensor bracket on which the toner density sensor is mounted is rotatable with respect to the photosensitive drum, and the photosensitive drum is mounted on the apparatus main body. When the mounting is completed, the positioning member of the sensor bracket and the positioning target member of the photoconductor support frame are fitted to fix the sensor bracket to the apparatus main body. In addition, the toner density sensor can be freely retracted from the photosensitive drum, and it is possible to prevent the toner density sensor from being damaged by contact with the photosensitive drum as in the related art. Further, when the mounting of the photosensitive drum is completed, the positioning of the sensor bracket is performed, so that the positional accuracy of the toner density sensor with respect to the photosensitive drum can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a photosensitive drum unit and a sensor bracket showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional photosensitive drum unit and a sensor bracket.

[Description of Signs] 1 Photoconductor support frames 1a, 1b Front and rear side plates 2 Photoconductor drum 3 Toner density sensor 6 Sensor bracket 7 Positioning member 8 Positioning member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/00 550 G03G 21/16-21/18 G03G 21/00 370-540

Claims (1)

(57) [Claims] A photosensitive drum unit which is detachable in an axial direction of the drum and comprises a photosensitive drum and a photosensitive member supporting frame for supporting the photosensitive drum with front and rear side plates; and a photosensitive drum unit disposed close to the photosensitive drum. An image forming apparatus including a sensor bracket on which a toner density sensor is mounted, wherein the sensor bracket has a predetermined portion on the drum body side such that the toner density sensor is rotatable with respect to the photosensitive drum. A positioning member is provided at a predetermined position that is rotatably mounted on a central axis parallel to the axis and abuts on the front and rear side plates of the photoconductor support frame, and on the front and rear side plates of the photoconductor support frame, A positioning member for positioning the sensor bracket with respect to the photosensitive drum by fitting a positioning member is provided. An image forming apparatus.