JPH0720686Y2 - Development device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a developing device used in an electrostatic recording device such as an electrophotographic copying machine.

[Effect of device]

Generally, as shown in FIG. 5, the developing device has a developing sleeve 3 having a fixed magnet built in, which is disposed in the housing 2 facing the photoconductor drum 1 in the vicinity of the photoconductor drum 1 and agitated and mixed in the housing 2. The developer is electrostatically adsorbed on the photosensitive drum 1, and the electrostatic latent image is developed as a toner image. This developing sleeve 3
The distance d between the photosensitive drum 1 and the photosensitive drum 1 was kept constant. This is because if the distance is different, the electric field changes, which affects the developability. Therefore, conventionally, in order to determine the interval d,
A roller 4 having a diameter increased by a dimension corresponding to the distance d is provided at the shaft end of the developing sleeve 3, and a means such as a spring (not shown) is used to contact the roller 4 with the surface of the photosensitive drum 1. The housing 2 was pressed toward the photosensitive drum 1 side as shown by the arrow. Therefore, in the case of the above-mentioned developing device, processing accuracy of the roller 4 is required, and since it constantly rotates in contact with the photosensitive drum 1, there is a drawback that the drum surface is damaged quickly.

Further, recently, there is also one in which the entire image forming unit including the photosensitive drum and the developing device is unitized and used by exchanging it for each color of toner so that a color copy can be easily made.
To make such a unit, the photosensitive drum and the entire developing device are installed in the same housing. In this case, it is not possible to adopt a structure in which only the developing sleeve is pressed toward the photosensitive drum side independently of the developer stirring plate and the like.

Therefore, the applicant of the present invention rotatably supports the photoconductor drum toward the developing sleeve and presses the photoconductor drum against the developer on the developing sleeve with a constant force, thereby exposing the photoconductor drum without using a roller. It has been found that the distance between the body drum and the developing sleeve can be maintained.

However, the movement of the photosensitive drum has a range or direction that is allowed by the depth of focus of the optical system, and if the regulation means is not sufficient, a clear image cannot be obtained. However, by adopting such restricting means, the mechanism should not increase in the number of parts and be complicated, and the cost should not be increased.

[Purpose of device]

In view of the above points, the present invention has an object to provide a photosensitive drum moving type developing device in which the moving range and direction of the photosensitive drum are restricted and the mechanism is not complicated.

[Constitution of device]

In order to achieve the above object, the present invention axially supports the central axis of the photosensitive drum so that it can be moved toward and away from a developing sleeve in a long hole provided in the unit side plate and having a long diameter in the horizontal direction.
The elongated hole maintains the non-contact state even when the photosensitive drum is closest to the developing sleeve due to the urging force in the direction of approaching the developing sleeve, and is most separated due to the change in the thickness of the developer on the developing sleeve. Even at this time, the movement range of the photosensitive drum can be regulated so as to maintain the range of the depth of focus of the lens used in the optical system.

〔Example〕

Next, this invention will be described based on the embodiment shown in FIGS.

In FIG. 1, reference numeral 10 is an image forming unit of a copying machine. Inside the image forming unit 10, a charging section 12, a developing section 13 and a cleaning section 14 are arranged around a photosensitive drum 11 as a center. . The transfer portion is provided so as to correspond to the lower surface of the photosensitive drum 11, and is not arranged in this unit 10.

The developing section 13 includes a developing sleeve 15, a main stirring plate 16 and an auxiliary stirring plate 17. The developing sleeve 15 is disposed in the vicinity of the photoconductor drum 11, and has a function of electrostatically adsorbing the developer on the drum surface and developing the electrostatic latent image as a toner image. The main stirring plate 16 is fixed obliquely to the rotating shaft 16a (not shown in the drawing) to stir and mix the developer (carrier and toner), and each stirring plate
The flat plate 16b provided between 16 enables the developer to be scraped in the rotating direction (arrow direction). The auxiliary stirring plate 17 mixes the toner replenished by the toner replenishing unit 18 with the developer circulating in the developing unit 13 and sends the mixed toner toward the installation site of the main stirring plate 16. Reference numeral 19 denotes a developer regulating blade having a base end side fixed to the upper plate (developing unit upper plate) 10a of the image forming unit 10. The regulating blade 19 is the second plate.
The developer D to be attached to the surface of the developing sleeve 15 as shown.
The thickness h of is regulated.

The toner replenishing section 18 is provided with a toner retention chamber 21 in which the cartridge 20 is replaceable, and a toner replenishment chamber 23 which communicates with the toner retention chamber 21 through an opening 22 in the upper portion of the toner retention chamber 21. A ladder chain 24 is installed, and the operation of the ladder chain 24 causes the toner in the retention chamber 21 to be conveyed by a plate 24 '.
The upper opening 22 allows the toner to be supplied into the toner replenishing chamber 23. Then, a replenishing roller 25 is installed in the toner replenishing chamber 23, and the rotation of the replenishing roller 25 allows the toner to be replenished into the developing portion through the space between the tongue piece 27 of the opening groove 25 provided on the lower surface of the replenishing chamber. Has become.

The photoconductor drum 11 has a shaft 50 protruding from both end surfaces which is a third shaft.
As shown in FIGS. 4 and 5, it is possible to move to the developing sleeve 16 side through a bearing member (not shown) such as a bearing in a long hole 51, 51 'having a long diameter in the horizontal direction provided in the side plates 10b, 10c of the image forming unit. Is supported by. In the illustrated example, the elongated holes 51, 51 'are shown in the shape of an ellipse having a long diameter in the horizontal direction, but may be a rectangle having an elongated length in the horizontal direction. Here, the shaft support is formed as a long hole. If the dimension L on the long diameter side is determined, the movement range of the photosensitive drum can be restricted (for example, 0.3 to 0.5 mm), and a small space can be provided even when it is closest to the developing sleeve. It becomes possible to leave it. Also, if the minor axis side is made to substantially coincide with the outer diameter of the drum shaft, the drum does not move in the vertical direction and can be accurately oriented.

Therefore, it is preferable that the cleaning blade 52 of the cleaning unit 14 applies a pressing force for pressing the photosensitive drum 11 against the developer D on the developing sleeve 15 as shown by an arrow a in FIG. That is, the cleaning blade 52 is supported on the front end side of the support member 53, and the rear end side thereof is pressed by the spring 54 and is urged to rotate counterclockwise about the hinge coupling portion 55, and the urging force of the cleaning blade 52 causes the photosensitive drum to rotate. Since it is in sliding contact with the surface, not only is the power wasted if it is used,
Even if the photosensitive drum 11 escapes to the developing sleeve 15 side, the sliding contact force of the cleaning blade 52 is not weakened.

The developer D used here is a two-component developer composed of a mixture of a carrier and a toner, and the mass of the carrier against the pressing of the photosensitive drum 11 as shown by the arrow a as shown in FIG. A repulsive force as indicated by arrow b acts. Therefore, as long as the thickness h of the developer D on the developing sleeve 15 is kept constant by the regulating blade 19, the distance d between the developing sleeve 15 and the photosensitive drum 11 should be close to the regulating thickness h (0.3 to 0.5 mm). It can be maintained.

It should be noted that the moving range of the photosensitive drum 11 is about 0.4 mm at maximum and is within the range of the depth of focus of the lens used in the optical system, so that the movement does not hinder the image formation of the document information.

Further, when the rotational drive of the photoconductor drum 11 is made from the drive gear 58 to the drum gear 57 formed on the outer periphery of the one end portion of the drum as shown in FIGS. 3 and 4, the drive gear 58 is meshed. A “flapping force” like an arrow acts on the side, and the left and right of the photoconductor drum 11 tend to tilt. Therefore,
In this embodiment, the third portion is provided on the shaft supporting portion on the side not having the drum gear 57.
As shown in the figure, a lever 59 and a tension spring 60 are provided so that the lever 59 and the tension spring 60 can be pushed out in the same direction as the acting direction of the "flapping force".
Although the invention has been described with reference to the example of the two-component developer, it goes without saying that a one-component developer can also be used.

Further, it goes without saying that the above embodiment can be variously modified based on the technical idea of the present invention.

[Effect of device]

As described above, according to the present invention, the central axis of the photosensitive drum is axially supported so that it can be moved toward and away from the developing sleeve with respect to a horizontal long hole provided in the unit side plate and having a long diameter in the horizontal direction. The non-contact state is maintained even when the drum is closest to the developing sleeve due to the urging force in the direction of being close to the developing sleeve, and the lens used for the optical system even when the drum is most separated due to the change in the thickness of the developer on the developing sleeve. Since the moving range of the photoconductor drum can be regulated so as to be maintained within the range of the focal depth of, the movement of the photoconductor drum can be easily performed within the range or direction permitted by the depth of focus of the optical system. This has an excellent effect that it can be regulated, and because of this, the number of parts is increased and the situation is complicated, and the cost is not increased at all.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is an enlarged sectional view of an image forming unit in which the developing device of the present application is assembled, and FIG. 2 is a relation between the regulation of the thickness of the developer on the developing sleeve and the photosensitive drum. FIG. 3, FIG. 3 is a plan sectional view showing the axial support state of the photosensitive drum, FIG. 4 is a side view of the same, and FIG. 5 is an explanatory view of a conventional device. 10 …… Image forming unit 11 …… Photosensitive drum 13 …… Developing section 15 …… Developing sleeve 19 …… Developer regulating blade 50 …… Photosensitive drum shaft 51,51 ′ …… Slot 52 …… Cleaning blade 53 …… Blade support member 54 …… Spring 55 …… Hinge joint

Claims (2)

[Scope of utility model registration request] 1. A central axis of a photoconductor drum is axially supported by a long hole provided in a side plate of a unit and having a long diameter in the horizontal direction so as to be able to approach and separate from a developing sleeve. The non-contact state is maintained even when closest to the developing sleeve due to the biasing force in the direction close to the developing sleeve, and the focus of the lens used for the optical system even when the developer is most separated due to the change in the thickness of the developer on the developing sleeve. A developing device capable of restricting a movement range of a photosensitive drum so as to maintain the depth range. 2. The developing device according to claim 1, wherein the minor diameter side of the long hole is an elliptical shape or a rectangular shape substantially matching the outer shape of the photosensitive drum shaft.