JPH01225974A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain adaptability for the change of the quantity and the density of a developer carried to a developing area by providing a gap adjusting means which adjusts a developing gap corresponding to the quantity and the density of the developer carried to the developing area on a gap holding means. CONSTITUTION:Elastic members 16 and 16 are provided on the outer periphery of gap adjusting rollers 11 and 11 functioning as the gap holding means. And repulsion on the developing area is increased when the quantity and the density of the developer going through a napping controlling gap Db are increased. As a result, repulsion acting to the elastic member 16 is decreased so that repulsion is balanced with the energizing power F0 of a developing roller 4. Therefore, the compressed deforming quantity of the elastic member 16 is minimized, and a developing gap Ds is widened and the developer can pass through the developing area without trouble. Thus, the developing gap Ds is automatically changed with the change of the developer quantity and the developer density so that a proper image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus that visualizes an electrostatic latent image using a developing roller that holds developer on its outer periphery.

(Prior Art and its Problems) Conventionally, as the image forming apparatus, one equipped with a developing device (2) shown in FIG. 5.6 has been provided.

This developing device (2) generally has a conveyance path (5) before and after a developing roller (4) provided at the front of a housing (3).

(6), each of which is provided with a packet roller (7) and a conveying blade (8), and a height regulating blade (9) is disposed opposite to the outer peripheral portion of the developing roller (4).

Further, in the developing device (2), the developer consisting of toner and carrier contained in the conveyance paths (5) and (6) is distributed as shown in the figure based on the rotation of the packet roller (7) and the conveyance blade (8). The developer is circulated through the conveyance paths (5) and (6) through a communication path that does not pass through, and some of the developer is transferred to the developing roller (
4) is supplied to the outer periphery. The developer supplied to the surface of the developing roller (4) is conveyed in the direction of arrow (a), and the amount of conveyance is regulated by the height regulating blade (9). [Development area] (
X), the electrostatic latent image formed on the surface of the photoreceptor drum (1) is visualized, and then sent back to the transport path (5).

In such a developing device (2), the height regulating blade (9
) and the developing roller (4), and the developing gap (Ds), which is the distance between the photosensitive drum (1) and the developing roller (4), are determined by the resolution of the reproduced image, It is a factor that has an important effect on fine line reproducibility and developer clogging, so it must be strictly controlled.

Therefore, conventionally, the tips of the frames (12) (12X one not shown) provided on both sides of the housing (3) were connected to the shaft (1
3) and the shaft (l) of the developing roller (4) protruding from the side wall of the housing (3), as shown in FIG.
Gap adjustment rollers (11) made of hard resin such as Delrin are rotatably or fixedly attached to both ends of the shaft (13), and the bearing of the image forming apparatus main body is attached to the shaft (13) in the part (14). The developing device (2) is urged in the direction of the arrow (b) by its own weight and the spring (15) provided at the rear, and the rollers (11) are attached to the photoreceptor drum (1).
The developing gap (Ds) is kept constant by pressing against both ends of the developer.

Therefore, in the developing device (2), the developing gap (Ds) is fixed. Therefore, if a large amount of developer is sometimes transported to the development area (X) through the head height regulation gap (Db), the upstream side of the development area (X) may be clogged with developer, making development impossible. , vibrations may occur, and when the amount of developer decreases, the image becomes thinner.

That is, in an image forming apparatus equipped with the developing device (2),
This method has a drawback of lacking adaptability to changes in the amount of developer transported to the development area (X) and the developer density.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and as shown in FIG. Photoreceptor drum〕(1) is energized,
The development gap (Ds) between the development roller (4) and the electrostatic latent image carrier (1) is controlled by a gap holding means [in this embodiment,
Gap adjustment rollers (1) provided at both ends of the developing roller (4)
1) and (11)], as shown in FIG.
The gap holding means [gap adjustment roller (11), (
11)) the amount of developer carried to the development area (X);
Gap adjustment means for adjusting the development gap (Ds) according to developer density [in this embodiment, rollers (11),
Elastic members (16) provided on the outer periphery of (11), (16)
).

(Function) In the image forming apparatus having the above configuration, as shown in FIG. 1.2, the development gap (Ds) is variable by the gap adjusting means (16), (16).

Then, in any state, as shown in FIG. 2, the biasing force (
Fo) is caused by the reaction force (F,) exerted by the electrostatic latent image carrier (1) on the developing roller (4) via the elastic member (16) and the developer conveyed through the developing area (X). (4)
is the sum (F l+
In balance with F t), the development gap (D s) becomes (D
S, ).

From this state, when the amount and density of the developer passing through the height regulating gap (Db) increases, the repulsive force in the development area (X) increases to (pto) (〉F2), as shown in Figure 3. increase

As a result, the reaction force acting on the elastic member (16) is (F,
'X<F,).

Therefore, the amount of compressive deformation of the elastic member (16) is reduced,
The development gap (Ds) widens by (Ds), and the developer passes through the development area (X) without difficulty.

Conversely, when the amount and density of the developer passing through the head height regulation gap (Db) decreases, the repulsive force (F,) decreases to (p 2''). The force (F,) increases to (p+''), the amount of compressive deformation of the elastic member (16) increases, and the development gap (DS) becomes (D
sp') narrows.

Therefore, the developer passes through the development area (X) while fully contacting the electrostatic latent image carrier (1).

That is, the development gap (Ds) is automatically changed according to changes in the amount of developer and the development density, and a proper image can be obtained.

(Example) The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a part of the image forming apparatus according to the present invention, and the gap adjustment roller (2) of the conventional developing device (2) shown in FIG.
11), the outer peripheries of (11) are covered with elastic members (16), (16) made of silicone rubber, for example. Note that since the other configurations are the same, the same parts are given the same reference numerals and the explanation will be omitted.

In the image forming apparatus having the above configuration, in the state shown in FIG.
2) and the spring (15), the photoreceptor drum (
1) is biased by a biasing force (FO), and this biasing force (
po) is caused by the reaction force (Fl) received from the photoreceptor drum (1) via the elastic member (16) and by the developer being conveyed in the development area (X) being pushed back to the rear of the development roller (4). The sum (F,) of the repulsive force (F, ) that attempts to do so.

10F2). Note that in this state, the development gap (Ds) is assumed to be (D s l).

From this, when the amount of developer passing through the height regulating gap (Db) or the developer density increases, the repulsive force of the developer in the development area (X) increases from (F2) to (F2°) (>pt). Then, in order to balance the biasing force (Fo), the increase in the repulsive force (F2°-F,) is increased by the photoreceptor drum (
+), the reaction force exerted on the elastic member (16) decreases from (Fl) to (F+°X<F I).

As a result, the amount of compressive deformation of the elastic member (16) decreases, and the development gap (Ds) changes from (Dsυ to (Dst'X>Ds
,).

Therefore, the developer conveyed to the development area (X) passes smoothly and without clogging, and develops the electrostatic latent image on the photoreceptor drum (1).

On the contrary, the amount of developer passing through the height regulation gap (Db),
Alternatively, when the development density decreases, the repulsive force of the developer in the developing area (X) decreases from (F2) to (F2''X<F2).Then, in order to balance the biasing force (FO), the repulsive force of the developer decreases. As for the decrease (Fz Fzl), the reaction force exerted on the elastic member (16) from the photoreceptor drum (1) is (F,
) to (F,"X>F,).

As a result, the amount of compressive deformation of the elastic member (16) increases, and the development gap (Ds) decreases to (Ds, ) to (Dst'').
(<DSL).

Therefore, the developer conveyed to the development area (X) comes into contact with the surface of the photoreceptor drum (1) with a sufficient nip width, and supplies sufficient toner to the electrostatic latent image.

In this way, the development gap (Ds) is automatically adjusted to an appropriate value according to the amount of developer passing through the height regulation gap (Db) and the developer density.

In other words, even if there is a slight error in the setting of the height regulation gap (Db>), the development gap (Ds) is automatically adjusted to a value that provides an appropriate image.

The thickness and hardness of the elastic member (16) are the same as those of the developing roller (4).
) to the photoreceptor drum (1), the mounting accuracy of the brush height regulation blade (9), the standard setting value (target value) of the brush height regulation gap (Db), etc., and the developing gap (D s
) changes, the amount of change must be able to be absorbed as the amount of deformation of the elastic member (16).

Hereinafter, an experiment was conducted using silicone rubber as an elastic member under the conditions described below, and the results of observing the development state were as shown in the table below.

In addition, the elastic member (16) and the gap adjustment roller (ll)
The width of the developing roller (4) is 10 mm, and the pressing force of the developing roller (4) against the photosensitive drum (1) is approximately 1 due to the weight of the developing device (2).
．． It was 5-2.0 kg.

In addition, "Good" in the table means that there was no clogging of the developer and the fine line reproducibility and resolution were good.

[Margin below]

From this table, when silicone rubber is used as the elastic member (16), the height regulation gap ( It has been found that high quality images can be obtained even when Db) is varied within a range of ±0.05 mm.

Although not shown, similar results were obtained in experiments using urethane rubber or chloroprene rubber instead of silicone rubber as the elastic member (16).

In the above explanation, it is assumed that hard gap adjustment rollers (l I), (11) are provided at both ends of the developing roller shaft (lO), and that the outer periphery thereof is covered with an elastic member (16) of a predetermined thickness. However, hard rollers may be provided at both ends of the shaft of the photoreceptor drum (1), and the outer periphery thereof may be covered with an elastic member, or the outer periphery of both ends of the developing roller (4) or the photoreceptor drum (1) may be covered with an elastic member. An elastic member may be disposed in a ring shape so as to protrude from the outer surface of the parts at a predetermined height to adjust the development gap, or as shown in FIG. Between the rollers or photoreceptor drum? 4. A roller covered with an elastic member may be interposed.

In the one shown in FIG. 4, support frames (21) are provided on both sides of the developing device main body (20), with the shaft (22) as the center, respectively.
(21X, one not shown) is rotatably supported.

A developing roller (27) is rotatably supported on the frames (21), (21) via a shaft (26), and one end is engaged with a pin (24) of the developing device main body (20). The other end of the stopped spring (25) is Flare A (21)
The developing roller (27) is urged against the photoreceptor drum (1).

In addition, the developing device main body (20) includes shafts (28), (28).
A frame (27) and (one of both 27X and 27X is not shown) are rotatably supported on the shaft (29) connecting their tips, and an elastic member (3I) of a predetermined thickness is attached to the outer periphery of the shaft (29). A roller (30) coated with is rotatably mounted.

Further, the frames (21) and (27) are drawn to each other by locking both ends of the spring (34) to the pins (33) and (32) provided respectively, and the roller (30) is connected to the elastic member (31). ) is sandwiched between the developing roller (27) and the photosensitive drum (1).

Therefore, similarly to the embodiment described above, depending on the amount and density of the developer conveyed to the developing area (X'), the developing roller (27) may move slightly closer to or away from the elastic member (31). , adjust the development gap (Ds).

(Effects of the Invention) As is clear from the above description, in the image forming apparatus according to the present invention, the gap holding means that maintains the development gap between the development roller and the electrostatic latent image carrier at a predetermined value has a development area (
A gap adjustment means is provided for automatically adjusting the development gap according to the amount of developer carried and the density of the developer.

Therefore, even if a large amount of developer is sometimes conveyed to the developing area, the developing area will not be clogged with developer, making development impossible, or causing vibration.

Furthermore, even if the amount of developer transported to the development area temporarily decreases, the electrostatic latent image carrier comes into contact with the developer with a sufficient nip width in the development area, so image reproducibility is maintained at an appropriate level. .

In addition, even if an error occurs in the adjustment of the head height regulation gap and the amount of developer transported between the gaps increases, the development gap will widen or narrow according to the increased amount, so the developer will The image is transported smoothly and effortlessly across the area, and image reproducibility is maintained at an appropriate level.

Therefore, according to the image forming apparatus according to the present invention, the permissible range of error in setting the height regulating gap is widened, and assembly and design are simplified.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of the image forming apparatus, FIG. 2 is a partial sectional view of the gap adjustment roller, and FIG. 3 is a sectional view of the developing roller.
FIG. 4 is a sectional view of another embodiment, FIG. 5 is a sectional view of the developing device, and FIG. 6 is a partial sectional view of the image forming apparatus. l...Photosensitive drum, 2...Developing device, 3...
Housing, 4...Developing roller, 9...Blade height regulation gap, 11...Gap adjustment roller, 16...Elastic member, Db...Blade height regulation gear knob, Ds...
-Development gap, X...Development area. Patent applicant Minolta Camera Co., Ltd. Representative Patent attorney Aoyama Aoyama and one other person Figure 4 Figure 6

Claims (1)

[Claims] (1) An image forming apparatus in which a developing roller is urged against an electrostatic latent image carrier, and a development gap between the developing roller and the electrostatic latent image carrier is maintained at a predetermined value by a gap holding means, An image forming apparatus characterized in that the gap holding means is provided with a gap adjustment means for adjusting the development gap according to the amount of developer conveyed to the development area and the density of the developer.