JP3223688B2 - blade - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device incorporated in an electrophotographic image forming apparatus, a blade for contacting a toner carrying surface such as a developing roller and holding the toner in a thin layer on the toner carrying surface. It is about.

[0002]

2. Description of the Related Art Conventionally, as a developing device of an image forming apparatus using a powder developer, a developing roller for supplying a toner to a photoreceptor, or a plate-shaped toner supply surface for supplying a toner to the developing roller is provided. Is known in which a thin layer of toner is formed on the toner carrying surface that has passed through the blade contact portion.

[0003]

However, in the conventional developing device, the amount of toner held on the roller fluctuates greatly due to a slight setting error of the blade.
If a predetermined amount of toner is to be held on the roller, much time and effort is required for mounting and setting the blade. Also,
There is a problem that the amount of toner held at both ends on the roller is larger than that at the center of the roller, and the toner layer becomes non-uniform in the axial direction of the roller, resulting in image density unevenness.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention comprises a base end, a free end, and a side surface extending from the base end to the free end, wherein the base end is fixed and a side surface near the free end is provided. A blade that contacts the carrier holding the toner and forms a thin toner layer on the surface of the carrier that passes through the contact portion based on the movement of the carrier. It bends at a predetermined inclination angle toward the outside of the carrier at or near the contact portion, and a portion is provided that extends linearly from the bent portion toward the free end, and the predetermined inclination angle is 4 ° to 15 °. ° range,
Further, the length of the linearly extending portion is shorter at both ends of the blade than at the center thereof.

[0005]

According to the blade having the above construction, the amount of toner conveyed based on the movement of the carrier is restricted to a substantially constant amount in a wedge-shaped region formed by a linearly extending portion of the carrier and the blade. Thereafter, the light passes through the contact portion between the subsequent blade and the carrier while being regulated and in contact with the blade. Thereby, the toner that has passed through the contact portion between the blade and the carrier is charged to a predetermined polarity by contact with the blade, and forms a charged toner layer having a substantially constant thickness on the surface of the carrier. Therefore, even if there is some error in the length from the fixed position to the free end in the state where the blade is set, the carrier holds an approximately appropriate amount of toner.

At both ends of the blade, more toner tends to pass through the contact portion between the blade and the carrier than in the central region due to insufficient contact pressure of the blade with the carrier. However, in the above blade, the length from the bent portion to the free end is reduced, and the wedge-shaped region formed by the linearly extending portion of the blade and the carrier is smaller than the central region. Therefore, at both ends, the amount of toner blocked by the blade is smaller than that at the central region, thereby preventing excess toner from passing due to insufficient contact pressure, and maintaining a substantially constant amount over the entire length of the blade. It ensures that the toner is held on the carrier.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, a photoreceptor generally denoted by reference numeral 50 is incorporated in a copying machine, a printer, or the like based on an electrophotographic method. This photoreceptor is composed of a cylindrical body or an endless belt having a photosensitive layer on the surface, and is driven to rotate at a constant speed by a drive motor. In addition, around the photoreceptor, there is a charged area for applying a charge to the photosensitive layer, an exposed area for projecting an image on the surface of the photosensitive layer to form an electrostatic latent image, and a toner to visualize the electrostatic latent image. Developing area, a transfer area for transferring a toner image to a recording medium such as paper, a cleaning area for removing untransferred toner remaining on the photoreceptor surface, and a charge elimination for removing residual charges in preparation for the next copy cycle. An area is provided.

Next, a developing device generally designated by reference numeral 1 is arranged in the developing area. In the developing device 1, an opening 3 is formed in a portion of the housing 2 facing the photoconductor, and a developing roller 4 is accommodated in the opening 3. The developing roller 4 is composed of a driving roller 6 that is driven to rotate around the support shaft 5 in the direction of arrow a, and a flexible thin film sleeve 7 having a thickness of 0.16 mm, which is provided on the driving roller 6. I have. The sleeve 7 has an outer diameter (2
Inner diameter (24.53 m) slightly larger than 4.0 mm)
m), and is pressed against the drive roller 6 at the rear (right side in the figure) by pressing guides 8, 8 (both of which are not shown) provided on the housing side walls 21, 21. The formed slack portion 7a is in light contact with the outer peripheral surface of the photoconductor 50. A seal member 9 is disposed between the housing bottom 22 and the developing roller 4 to prevent leakage of toner contained in the housing. One end of a plate-shaped blade 10 according to the present invention disposed parallel to the drive roller 6 is fixed inside the housing upper portion 23, and the side surface on the free end side is the outer peripheral surface of the sleeve 7 between the pressing guides 8. Is pressed against. The blade 1
Numeral 0 is a metal plate such as stainless steel, a plate of synthetic resin, rubber, or a member in which the surface thereof is appropriately coated. The thickness t of the blade 10 is suitably about 0.1 mm. A buffer chamber 12 facing the developing roller 4 and a toner supply chamber 13 located at the rear of the developing roller 4 are formed by a partition wall 11 rising from a housing bottom 22 at the rear of the developing roller 4. Rotating blades 14 and 15 are arranged in the chamber 13 so as to be rotatable.

In the developing device 1 having the above configuration, the toner T stored in the toner supply chamber 13 is supplied to the buffer chamber 12 by the rotating blade 15 rotating in the direction of arrow c. The toner T in the buffer chamber 12 is supplied to the outer peripheral surface of the sleeve 7 by rotating blades 14 rotating in the direction of arrow b. The sleeve 7 is driven to rotate in the direction of arrow a by the frictional force received from the drive roller 6 based on the rotation of the drive roller 6. Then, the toner T supplied to the sleeve 7 is
It passes through the contact portion Y of the blade 10 and is held in a thin layer on the outer periphery of the sleeve 7. Further, when the toner T passes through the contact portion Y, the toner T comes into contact with the blade 10 and is frictionally charged. The toner T held on the sleeve 7 is conveyed in the direction of the arrow a, and is supplied to the electrostatic latent image on the photoconductor 50 in a development area X where the sleeve 7 is in contact with the photoconductor 50. The toner that has passed through the development area X without being used for development moves with the rotation of the sleeve 7, passes through the contact portion of the seal member 9, and is sent back to the buffer chamber 12.

Next, the first feature of the blade 10 will be described. As shown in detail in FIG. 2, the front-end-side sleeve-facing surface of the blade 10 is formed such that the thickness gradually decreases from the start end 102 located at a predetermined distance S from the front end 101 toward the front end 101. It is cut linearly, and a linear inclined surface 10 formed by cutting in this manner.
3 and the fixed-side surface 104 form an outer angle (18) on the sleeve side of the start end portion 102 (hereinafter referred to as the “bent portion 102”).
An obtuse angle of 0 ° -θ) is formed. In addition, blade 1
0 is cut to form the inclined surface 103, the inclined surface 10
It is desirable to process the surface 3 so as not to have minute irregularities. The blade 10 is pressed against the outer periphery of the sleeve 7 in a surface contact state in a region (contact portion) Y slightly moved from the bent portion 102 to the fixed side. The pressing force of the blade 10 against the sleeve 7 at the contact portion Y is about 9.0 g / m.
m is preferable. Therefore, when the developing roller 4 and the sleeve 7 are not mounted and are not in pressure contact with the sleeve 7, the developing roller 4 and the sleeve 7 are in a dotted line position shown in FIG.

By forming the blade 10 as described above, as shown in FIG. 3, the toner conveyed with the movement of the sleeve 7 is formed on the inclined surface 103 of the blade 10 and the outer peripheral surface of the sleeve 7. The toner is sent to a wedge-shaped area where the amount of toner is regulated.
The toner is fed to the contact portion Y of the sleeve 7 and the outer peripheral surface of the sleeve 7 passing through the contact portion Y holds a substantially constant amount of toner.

The angle θ between the inclined surface 103 and the surface extending from the fixed surface 104 is 3 °, 5 °, 7 °, 14 °,
Set to 20 °, blade 10 for each angle.
Free length (distance from fixed part 105 to tip part 101:
While changing L, the amount of toner retained on the sleeve 7 after passing through the blade contact portion was measured. The distance S from the tip portion 101 of the blade 10 to the bent portion 102 is 0.3 mm, the radius r of the drive roller 6 is 12 mm, the vertical distance H from the center of the drive roller 6 to the blade fixing portion 105, and the horizontal distance B are respectively They were 18.7 mm and 7.3 mm. FIG. 4 shows the results of the experiment. Further, from this figure, the free length of the blade that allows the sleeve 7 to hold the toner supply amount (0.6 to 0.7 mg / cm ² ) necessary to develop the electrostatic latent image on the photoconductor 50 at an appropriate density (0.6 to 0.7 mg / cm ² ). The minimum: L _MIN / max: L _MAX ) and the allowable setting width (L _DF ) were as shown in Table 1.

[0013]

TABLE 1 θ (°) L _MIN (mm) L _MIN (mm) L _DF (mm) Experimental Example 13 15.1 15.5 0.4 〃 25 14.7 15.7 1.0 ３ 3 7 14.3 15.8 1.5 〃 4 14 13.7 16.2 2.5

As a comparative example, as shown in FIG. 5, a blade 200 having a straight tip portion and a blade 30 having a tip portion bent by approximately 90 ° through a curved portion as shown in FIG.
For 0, the amount of toner held on the sleeve 7 was measured while changing the free length L. Other conditions are Blade 1
The experiment was the same as the experiment for 0. The results are also shown in FIG. 4 showing the experimental results of the present invention. Table 2 shows the blade free length (minimum: L _MIN / maximum: L _MAX ) and the allowable setting width (L _DF ) for obtaining the toner supply amount (0.6 to 0.7 mg / cm ² ).

[0015]

Table 2 L _MIN (mm) L _MAX (mm) L _DF (mm) Comparative Example (Blade 200) 15.0 15.3 0.3 〃 (Blade 300) 15.8 16.1 0.3

As can be seen from FIG. 4 and Tables 1 and 2, the blades 200 and 300 of the comparative example have a proper toner supply amount (0.6 to 0.7 mg / cm ² ) on the sleeve. The blade setting allowable width _LDF was narrow (0.3 m
m). However, in the present invention, it can be understood that the allowable setting width _LDF is much longer than that of the comparative example, and the mounting and adjustment of the blade are extremely easy. The blade inclination angle θ is 4
It is preferable to set the angle to １５15 °.

In each of the experimental examples shown in Table 1, the distance S from the tip portion 101 of the blade 10 to the bent portion 102 was 0.3 mm, but this distance S was 0.4 mm, and the inclination of the inclined surface 103 was 0.4 mm. When the amount of toner on the sleeve 7 was measured using the blade 10 having an angle θ of 7 ° and the other conditions were set to be the same as those in the above-described experimental example, 0.7 to 0.8 mg / cm ^2.
Was stable.

Next, a second feature of the blade 10 will be described. In general, when a plate-shaped blade is pressed against a sleeve, the pressing force on the sleeve, that is, the toner regulating force, is lower at both ends of the blade than in the central region. Therefore, more toner is held at both ends of the sleeve that has passed through the blade contact portion than at the central region,
As a result, the image density at both ends of the image tends to be higher than that in the central region. Therefore, in the blade 10, FIG.
As shown in FIG. 7, corners (regions indicated by dotted lines) included in the regions B1 and B1 from the end portions 110 and 110 to the positions 111 and 111 moved by the distance D are cut off, and the inclined portions, that is, the toner amount adjusting portions 112 and 112 are removed. Is formed. as a result,
In the regions B1 and B1, the wedge-shaped region formed by the inclined surface 103 of the blade 10 and the sleeve 7 becomes smaller toward the end, and the toner regulating force is weakened. Excessive transportability is canceled, and the same amount of toner as that of the central area B2 except for the areas B1 and B1 at both ends is retained in the sleeve 7 even in the both end areas B1 and B1.

To prove the effect based on the second characteristic, the following experiment was conducted. First, the length of the inclined surface 103 is set to 0.2 mm using a blade having no toner adjusting portion at both ends on the leading end side, and the amount of toner retained on the sleeve 7 after passing through the blade contact portion Y is measured. did. The blade was made of a stainless steel plate having a thickness of 0.1 mm and a width of 215 mm, and the inclination angle θ of the inclined surface 103 was set to 11 °. FIG. 8 shows the results of the experiment. As is apparent from this figure, both ends of the region of the sleeve 7 corresponding to the blade (hereinafter, simply referred to as "sleeve both ends") 70, 70.
B1 ', B1' at a predetermined distance D '(20 mm) from
The toner amount held in the central region B2 'of the sleeve 7 excluding the above is stable at 0.6 mm / cm ² , but the pressing force of the blade 10 against the sleeve 7 is weak in the regions B1' and B1 'at both ends. The toner amount gradually increases in a quadratic curve as approaching both ends 70, 70 of the sleeve, and approximately 0.75 mg / cm near both ends 70, 70 of the sleeve.
It became ² .

Next, when the length S of the inclined surface 103 of the blade 10 was changed from 0.16 mm to 0.6 mm, the amount of toner held on the sleeve 7 was measured.
As shown in FIG. 5, it has been found that there is a relationship that the toner amount on the sleeve 7 increases in a curve as the length S of the inclined surface 103 increases. Therefore, the length S of the inclined surface 103 of the blade 10 is set to
If the distance is gradually shortened from the position 111, 111, which is a distance D (20 mm) from 0 toward the center, toward the end, the corresponding regions B1 ′, B at both ends of the sleeve are reduced.
In 1 ′, the cross-sectional area of the wedge-shaped region formed by the sleeve 7 and the blade inclined surface 103 is smaller than that of the sleeve central region B2 ′, that is, the amount of toner introduced into the blade contact portion Y is reduced. It can be understood that the excessive toner transportability is offset by the insufficient pressing force, and a uniform amount of toner can be held on the sleeve 7 over the entire length of the blade 10.

Based on the above experimental results and considerations, the length S of the inclined surface 103 in the central region B2 of the blade 10 is set to 0.2.
mm, regions B1 and B1 from positions 111 and 111 to both ends 110 and 110 which are moved by 20 mm from both ends 110 and 110 on the tip side, that is, regions B at both ends of the sleeve.
In the region corresponding to 1 ′, B1 ′, both ends 110, 11
The amount of toner held on the sleeve 7 was measured using a blade on which the toner amount adjusting portions 112, 112 were formed such that the length S of the inclined surface 103 was 0.13 mm at 0.
The blade thickness t and the inclination angle θ of the inclined surface 103 are as follows:
They were set to 0.1 mm and 11 °, respectively, as in the above experiment. The result is shown in FIG. As is apparent from this figure, compared to the experimental result when the length S of the inclined surface 103 is uniformly set to 0.2 mm (see FIG. 8), the inclined surface 103 is held near both ends 70, 70 on the sleeve 7. 0.6m
g / cm ² , indicating that the toner amount on the sleeve is uniform.

In each of the above embodiments, a plate material is used as a blade. However, as shown in FIG. 11, a part of a member 120 having a circular cross section is cut to form an inclined surface 121, and an end portion thereof is formed. 122 or its vicinity may be brought into contact with the sleeve 7. Further, the inclined surface is formed by cutting the sleeve-facing surface on the blade tip side, but the working method is not limited to this. Further, as shown in FIG. 12, the blade 130 may be bent, and a slightly fixed end side of the bent portion 131 may be pressed against the sleeve 7. Further, when the blade 10 is formed of a conductive material, a conductive bias voltage may be applied to the blade 10 and the sleeve 7, or a bias voltage may be applied only to the sleeve 7.

In the above embodiment, the case where the blade according to the present invention is brought into contact with the sleeve for supplying toner to the photosensitive member has been described. However, the blade according to the present invention may be a roller-shaped or belt-shaped toner carrier. The present invention is applicable as long as it forms a toner layer on the substrate.

[0024]

As is apparent from the above description, according to the blade of the present invention, an appropriate amount of toner can be held on the carrier irrespective of its length being slightly longer or shorter.
The blade can be easily set, so that the assembly and adjustment operations can be simplified, and a uniform thin toner layer can be formed on the surface of the carrier in the axial direction. And background fog can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a developing device.

FIG. 2 is an enlarged sectional view of a blade tip.

FIG. 3 is an enlarged sectional view illustrating a toner regulating state of a blade.

FIG. 4 is a diagram illustrating a relationship between a blade free length and a toner supply amount.

FIG. 5 is an enlarged sectional view showing a blade of a comparative example.

FIG. 6 is an enlarged sectional view showing a blade of another comparative example.

FIG. 7 is an enlarged sectional view showing an embodiment of the blade.

FIG. 8 is a diagram illustrating a relationship between an axial position on a sleeve and a toner supply amount.

FIG. 9 is a diagram showing the relationship between the length of the inclined surface of the blade and the toner supply amount.

FIG. 10 is a diagram illustrating a relationship between an axial position on a sleeve and a toner supply amount.

FIG. 11 is an enlarged sectional view showing another embodiment of the blade.

FIG. 12 is an enlarged sectional view showing another embodiment of the blade.

[Explanation of symbols]

4 ... Developing roller, 7 ... Sleeve (developer carrier), 10
... blade, 102 ... bent part, 103 ... inclined surface, Y ... contact part.

Continuation of the front page (72) Inventor Hiroshi Toda 2-3-113 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. In-house (72) Inventor Akihiro Kawasaki 2-chome Azuchicho, Chuo-ku, Osaka-shi, Osaka No. 3-13 Osaka International Building Minolta Camera Co., Ltd. In-house (56) References JP-A-63-85654 (JP, A) JP-A-4-235578 (JP, A) JP-A-5-307321 (JP, A) (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08 504

Claims (1)

(57) [Claims] A base end, a free end, and a side surface extending from the base end to the free end, wherein the base end is fixed, and a side surface near the free end contacts the carrier holding the toner; Based on the movement of the carrier, a blade that forms a thin toner layer on the surface of the carrier that passes through the contact portion is provided on the side surface of the blade that contacts the carrier, and the outside of the carrier at or near the contact portion. And a portion extending straight from the bent portion toward the free end is provided, and the predetermined inclination angle is set to 4 ° to 15 °.
°, and the length of the linearly extending portion is shorter at both ends of the blade than at the center thereof.