JPH071409B2 - Development device - Google Patents

Description

The present invention relates to a developing device for developing a latent image on the surface of a latent image bearing member with a dry developer.

More specifically, the present invention relates to a structure for stirring, transporting, regulating, and circulating a developer in a developing device.

[Conventional technology]

Conventionally, various types of dry developing methods / apparatuses for electric latent images such as electrostatic latent images / potential latent images have been proposed and put into practical use, but each has advantages and disadvantages.

For example, in the developing method using a two-component developer, when the image portion of the latent image is developed by the developer applied on the developing roller, the toner in the developer is the same as the toner applied on the developing roller. We use less than a few percent of them. This is extremely inefficient considering the developing device configuration. This is because it is necessary to apply a large amount of developer on the developing roller with a constant amount and uniform toner concentration every rotation of the developing roller in order to obtain a predetermined sufficient developing density. For this reason, the structure of the developing device has become large and complicated.

Of course, attempts have been made to improve the developing efficiency even in this type of developing method. For example, the applicant of the present invention is JP-A-55-32060,
The improvement method was proposed in Sho 55-133058, Sho 56-70560, etc., and is also put to practical use (Canon model NP8500).
According to this, the developing density can be increased and the developing efficiency can be increased. However, even then, the development efficiency in the image area has not reached nearly 100%.

The one-component developing method is superior to the two-component developing method in terms of improving the developing efficiency. Among them, the developing method or developing device of Japanese Patent Application Laid-Open No. 54-43037, which the applicant of the present invention previously applied, forms a toner thin layer of 100 μ or less on the developing roller (sleeve), and applies the toner applied on the sleeve. In the image area, development can be performed at a high development rate close to 100%. Therefore, it was possible to put the developing device into a compact and simple structure for practical use.

This was achieved because the toner thin layer of 100 μm or less could be formed on the developing roller. However, this developing method uses a magnetic toner as the toner, and in order to give the magnetic toner magnetism, it is necessary to internally add a magnetic material to the toner, which thermally fixes the developed image transferred to the transfer paper. In this case, there are problems such as poor fixability and a magnetic substance internally added to the developer itself (usually the magnetic substance is black).

Therefore, as a method for forming a thin layer of non-magnetic toner, a brush having a cylindrical shape that is soft like beaver hair is used, and toner is adhered and applied to the brush, or a developing roller whose surface is made of fiber such as velvet is used as a doctor blade. A method of coating by using the above method has been proposed.

However, when an elastic blade is used as a doctor blade for the fiber brush, the amount of toner can be regulated, but uniform coating is not performed, and rubbing the fiber brush on the developing roller does not cause the fibers of the brush to rub. Since triboelectrification charges are not imparted to the toner existing between them, there is a problem that fog or the like is likely to occur.

Thus, the applicant of the present invention uses a non-magnetic toner and magnetic particles as a developing device which is completely different from the above-mentioned conventional methods, and provides a magnetic particle restraining member facing the toner carrier to determine the moving direction of the toner carrier surface. With respect to the magnetic particle restraint member, a magnetic brush of magnetic particles is formed by the magnetic force of the magnetic field generation means upstream of the magnetic particle restraint member, and the magnetic brush is restrained by the magnetic particle restraint member,
A method has already been proposed for forming a thin brush-like magnetic adsorption layer of a small amount of magnetic particles containing non-magnetic toner on the surface of a toner carrier (JP-A-58-143360). Then, the toner bearing member and the latent image bearing member are opposed to each other, and the gap between the latent image bearing member and the toner bearing member is set to the toner layer thickness (toner bearing member) in the developing section (the facing portion of the latent image bearing member and the toner bearing member). It is set wider than a thin brush-like magnetic adsorption layer of a small amount of magnetic particles containing non-magnetic toner formed on the surface of the body, and an alternating electric field is applied to the surface of the latent image carrier to form a positive or a positive image corresponding to the latent image pattern. A method for obtaining a negative non-magnetic toner developed image has been put into practical use.

This is because in the developing area, a thin brush-like magnetic adsorption layer of magnetic particles containing non-magnetic toner on the toner carrier side is formed longer than the gap length between the latent image carrier and the toner carrier, or acts on the developing unit. The surface of the latent image carrier is extended by the applied electric field and rubs against the surface of the latent image carrier, and the non-magnetic toner contained in the brush-like magnetic adsorption layer of the magnetic particles causes reciprocating motion between the toner carrier and the latent image carrier. The latent image on the latent image carrier side is positively or negatively developed with a non-magnetic toner corresponding to the latent image pattern.

As a result, it is possible to construct a small and simple developing device having extremely high developing efficiency, and it is possible to obtain a color developed image with good colorability by using the non-magnetic toner. In particular, a solid image can be obtained during the two-component magnetic brush rubbing development.

[Problems to be solved by the invention]

Of the various development type devices described above, the last development type device is particularly recommended because it has excellent development characteristics, but it also maintains stable development image quality such as high quality, high density, and good gradation. However, it has been desired to develop a highly durable and reliable device that can be applied to high-speed image forming apparatuses.

The present invention responds to this. That is, with respect to the system of developing the latent image carrier surface by carrying the developer composed of the toner and the magnetic particles on the developer carrying member, always stable,
It is an object of the present invention to provide a high-quality (high-quality) developed image free from image unevenness and fog.

B, Configuration of the Invention [Means for Solving the Problems] The present invention for solving the above problems is directed to a developer carrying member carrying a developer having toner particles and magnetic particles, and the developer carrying member. A developer amount regulating member that regulates the upper developer amount, a first magnetic pole provided in the developer carrier near the developer amount regulating member, and an upstream side in the moving direction of the developer carrier of the first magnetic pole. In a developing device having a second magnetic pole adjacent to the first magnetic pole and having a polarity opposite to that of the first magnetic pole, the developer between the developer amount regulating portion by the developer amount regulating member and the upstream side in the moving direction of the developer carrying member. It has a circulation restricting member for restricting circulation, and the tip of the circulation restricting member on the upstream side in the moving direction of the developer carrying member has the minimum magnetic field strength in the direction normal to the surface of the developer carrying member between the first and second magnetic poles. Within the angular range between the position at which the magnetic field strength is maximized by the second magnetic pole It is characterized in that there.

[Work]

With the above-described structure, the stirring / circulating state of the developer in the developing container portion and the subsequent regulation effect are improved, which makes it possible to stably obtain a high-quality developed image without image unevenness or fog.

〔Example〕

 The drawing shows an embodiment of the developing device of the present invention.

In FIG. 1, A is a drum-shaped or belt-shaped electrophotographic photosensitive member or electrostatic recording dielectric as a latent image carrier,
The surface is driven in the direction of the arrow at a predetermined speed, a latent image is formed by an image forming process device (not shown), and the latent image is developed as a visible image by the developing device B.

In the developing device B, reference numeral 1 denotes a developing container, which has a partition wall 2 inside thereof, a toner storage portion 3, and a developer storage portion (developer container portion) 4 for storing a developer including toner and magnetic particles.
It is divided into and. Toner stored in the toner storage portion 3,
The developer in the developer storage unit 4 is omitted in the drawing. The toner stored in the toner storage portion 3 is sequentially transported in the direction of the partition wall 2 by rotating the toner transport members 6 ₁ and 6 ₂ , and is replenished into the developer storage portion 4 from the toner replenishing port 16.

7 is a developer carrying member which is disposed in a developer accommodating portion 4, and a developing sleeve ₇₁ made of a nonmagnetic material having a built-in magnet roller 7 _2. The developing sleeve 7 ₁ has a right oblique lower surface exposed to the outside through an opening provided in the developer accommodating portion 4. In the developing device B, the external exposing surface of the developing sleeve 7 ₁ is exposed to the latent image carrier A surface. On the other hand, the support member is positioned and held so as to be opposed to each other with a predetermined small gap. Facing portion a between the latent image bearing member A and the developing sleeve ₇₁ is a developing unit.

_{S 1 ~S 3, N 1 ~N} 3 shows the magnetization positions of the magnet roll 7 _2. The magnet roll 7 ₂ is fixedly supported at both ends and does not rotate, and the developing sleeve 7 _{1 on the} outer side thereof is rotationally driven around the magnet roll 7 _{2 at} a predetermined peripheral speed in the arrow direction.

In 8.9 the developer accommodating portion 4, a screw shaft as a developer stirring and conveying means arranged vertically in substantially parallel with the developing sleeve ₇₁ is rotated in the respective arrow directions. Reference numeral 17 denotes a developer circulation restricting member provided between the upper and lower screw shafts 8 and 9.

10 - 14 circulation regulating member of the developer on the developing sleeve ₇₁ peripheral surface which is disposed on the upper and lower portions of the developer accommodating portion 4, 11, 13 and the bottom surface of the developer accommodating portion 4 and the developing sleeve ₇₁ lower surface magnetic member and a magnet housing developer from the gap portion is disposed on the bottom side of the developer accommodating portion 4 in order to prevent the flow leaking into the image bearing member a direction, 12 in the peripheral surface of the developing sleeve 7 ₁ in order to regulate the layer thickness of the developer forming, so as to face is a non-magnetic blade disposed with presence of gaps of a predetermined僅小the developing sleeve top surface lower the upper surface of the developing sleeve 7 ₁ .

Reference numeral 15 denotes a sensor for detecting the concentration of the developer (mixing ratio of toner with magnetic particles) in the developer accommodating portion 4. The output of this sensor is input to a control circuit (not shown), and the toner is correspondingly discharged. The rotation driving of the toner conveying members 6 ₁ and 6 ₂ in the storage unit 3 is controlled.

Among the respective magnetic poles of the magnet roll _{7 2 S 1 ~S 3, N} 1 ~N 3, first, second and the magnetic pole N ₂ · N ₁ · S ₃ is respectively present invention device
It corresponds to each of the third magnetic field generating means (hereinafter, the first magnetic pole N ₂
- referred to as the second magnetic pole N _1-third pole S _3). Other magnetic poles S ₁ , S ₂ ,
N ₃ is a magnetic field generating means for carrying the developer and the like. Further, the non-magnetic blade 12 and the developer circulation restricting member 10 provided on the upper side inside the developer accommodating portion 4 correspond to the first and second developer restricting members in the apparatus of the present invention, respectively.

The second developer regulating member serving developer circulating regulating member 10 is opposite to the developer carrying member serving developing sleeve 7 _1, first and second second and third serving magnetic field generating means of the magnetic pole N ₁ · S ₃ on the side, spaced with a predetermined gap therebetween from the developing sleeve ₇₁ surface, the first development sleeve to the developing sleeve rotation direction upstream side along the developing sleeve surface from the position of the developer regulating member serving non magnetic blade 12 provided opposite to 7 ₁ and the non-magnetic blade 12 side opposite the tip portion 10a, between the second magnetic poles N ₁ and the third magnetic pole S _3, the developing sleeve ₇₁ on the normal direction, The magnetic field strength I (FIG. 2) of the second magnetic pole N _{1 and} the magnetic field strength II of the third magnetic pole S ₃ are the minimum and are substantially zero in the present embodiment (second
From the drawing) to the position where the magnetic field strength in the upper normal direction of the developing sleeve 7 ₁ of the third magnetic pole S ₃ becomes the maximum, it exists in the angle θ range position.

When the developing device is in operation, the developing sleeve 7 ₁ and the screw shafts 8 and 9 are rotationally driven at predetermined speeds, and an alternating voltage is applied between the developing sleeve 7 ₁ and the latent image carrier A by the bias power source S.

Developer in the developer accommodating portion 4 by the rotation of the screw shaft 8, 9 are sufficiently stirred in the longitudinal direction of the developing sleeve _71, a mixing ratio of substantially uniform toner and magnetic particles in the developing sleeve 7 near ₁ is obtained, substantially unevenness in the longitudinal direction each portion of the developing sleeve ₇₁ is removed.

The screw shafts 8 and 9 rotate in the directions of the arrows, respectively, so that the developer in the developer accommodating portion 4 is moved upwards.
The directions of the screw blades of the upper and lower screw shafts 8 and 9 are reversed so that the nearby developer and the developer near the lower screw shaft 9 are conveyed in opposite directions with respect to the longitudinal direction of the respective screw shafts. The orientation is set.

Movement on the developer accommodating portion cross section of the developer in the developer accommodating portion 4, rotation of the developing sleeve _71, screw shaft 8,
9 rotation of the magnetic field of the magnet roll 7 _2, the frictional force of the presence of the developer circulation limiting member 10, 14, 17, the developing sleeve ₇₁ and the developer, the white of FIG. 1 by gravity or the like of the developer arrow It becomes a cyclical flow motion such as.

Thus to magnetic developer i.e. magnetic particles comprising a toner in the vicinity thereof on the surface region of the developing sleeve ₇₁ that faces the developer reservoir of the developer accommodating portion 4 by the magnetic force of the magnet roller 7 _second sleeve 7 ₁ conveyed are deposited maintained as the brush adsorption layer to wake no non magnetic blade 12 located on the rotation of the developing sleeve _71, a layer thickness in the process of passing through the non-magnetic blade 12 position is restricted, a small amount of magnetic particles comprising a toner facing portion of the developing sleeve ₇₁ and the developing unit a (latent image carrier a becomes thin layer, the magnetic poles N ₂
Near).

Due to the electric field acting on the developing portion a in the course of passing through the developing portion a and the magnetic field action of the first magnetic pole N ₂ , the developing sleeve 7 ₁
The toner of the developer layer on the side is transferred to and adheres to the surface A of the latent image carrier corresponding to the latent image pattern, and the toner development of the latent image on the surface A of the latent image carrier is sequentially performed.

Is used for development, it sleeve by the magnetic field of the developer accommodating portion 4, the pole S ₂ · N ₃ by the developing sleeve ₇₁ side of the developer layer is subsequent rotation of the developing sleeve ₇₁ which has passed through the developing portion a
7 Held on the _1st side, returned and conveyed, and mixed with the developer in the developer storage unit 4.

The toner content in the developer in the developer accommodating portion 4 is consumed for developing the latent image, so that the mixing ratio with the magnetic particles decreases with time. The degree of decrease is detected by the sensor 15, the detection information is input to a control circuit (not shown), and when the degree of decrease reaches a predetermined lower limit, the signal indicates that the toner supply members 6 ₁ , 6 ₂ in the toner storage unit 3 As a result of rotation, the toner in the toner storage unit 3 is successively introduced and replenished from the toner supply port 16 into the developer storage unit 4.

The replenished toner is taken into the developer in the developer accommodating portion 4 and uniformly and rapidly mixed into the entire developer. This toner replenishment increases the toner component mixing ratio of the developer in the developer accommodating portion 4 and a predetermined allowable increase is detected.
When detected by 15, the rotational driving of the toner supply members 6 ₁ and 6 ₂ is stopped. As a result, the mixing ratio of the toner particles to the magnetic particles of the developer in the developer accommodating portion 4 is always kept substantially constant, and stable high-quality images can be obtained.

The developer circulation limiting member 17, with the sleeve ₇₁ side to regulate the circulation and transport in the vicinity of the magnetic pole S ₃ of the developer, the screw shaft 8
Alternatively, it plays a role of a guide plate with respect to No. 9 and also contributes to stabilization of stirring and carrying of the developer. Also in the sleeve ₇₁ and the opposite side has a gap between the developing container 1, and also act to guide a part of the circulating-transported developer in the direction of the screw shaft 9 by the screw shaft 8.

As the sensor 15, for example, a developer volume detection method, a piezoelectric element, an inductance change detection element, an antenna method using an alternating bias, or the like can be used.

Thus, the tip portion 10 of the second developer regulating member 10 is
When a is configured in the form in which it is present in the angle θ range position including the above-described position and position according to the present invention as in the apparatus of FIGS. 1 and 2, the developing sleeve is more than the position as in the example of FIG. In the case where it is configured to be located downstream in the rotation direction, and when it is configured to be located upstream in the development sleeve rotation direction relative to the position, as in the example of FIG. 4, the above In each case, the density, fogging, and axial unevenness of the copy image were examined. The results are shown in the table below.

That is, when the developer in the developer accommodating portion 4 is sufficiently agitated by the third magnetic pole S ₃ vicinity copy for the developer to the screw shaft 8 side is circulated further position of the distal end portion 10a of the member 10 although the image density is high, weak regulation of the developer circulation, fog and uneven copy image for rubbing is weak and toner particles was the developing sleeve ₇₁ and the magnetic particles content of the developer is liable to occur. The developer on the developing sleeve ₇₁ is weak effect stripped by member 10, not be reversed completely developer after development in recent developing sleeve neighbor, the ghost image of the previous developed image appear on the copy image easy.

In this case, although the circulation of the developer was sufficiently regulated, the density of the copied image was difficult to obtain in practice, and the circulation of the developer was insufficient, resulting in unevenness.

In the case of No. 2, the copy density was good, and no fog or unevenness was observed, and good high-quality images could be stably obtained.

In this case, the tip 10a of the member 10 is within the angle θ range,
Preferably position range field strength of the third developing sleeve 7 ₁ above normal direction of the magnetic pole S ₃ becomes 1 / 5-4 / 5 of the maximum intensity theta _{1 (second}
(Fig.), So that the developer circulation
Stirring and regulation are particularly good, and high-quality images can be stably obtained.

Note screw shaft 8, 9 as a developer agitating and conveying unit in the above embodiment, the rotation direction of the developing sleeve ₇₁ is not intended to be limited to the examples.

Further, the stirring / conveying means 8 and 9 are not limited to screw shafts and may be rotary blades. The number of magnetic poles of the magnet roll 7 _2, do not even pole species are limited to the Examples.

C. Effect of the Invention As described above, according to the present invention, a high-quality developed image (or copy image) can be stably output, and the intended purpose is well achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional side view of an embodiment of the developing device of the present invention.
Figures 4 to 4 show the magnetic field strengths of the second and third magnetic poles, respectively.
FIG. 9 is an explanatory diagram of the relationship with the position of the tip of the second developer regulating member. A is a latent image carrier, B is a developing apparatus, 7 ₁ screw shaft as a developing sleeve, a developer stirring and conveying means 8.9 as a developer bearing member, N ₂ · N ₁ · S ₃ is first・ Second and third magnetic poles, and 12 and 10 are first and second developer regulating members.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Tada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-56-150773 (JP, A) JP-A-51 -15443 (JP, A)

Claims (1)

[Claims] 1. A developer carrying member carrying a developer having toner particles and magnetic particles, a developer amount regulating member for regulating the developer amount on the developer carrying member, and the developer amount regulating member. A developing device having a first magnetic pole provided in the developer carrier near the member, and a second magnetic pole adjacent to the upstream side of the first magnetic pole in the moving direction of the developer carrier and having a polarity opposite to the first magnetic pole. In the above-mentioned developer amount regulating member, there is provided a circulation regulating member for regulating the circulation of the developer between the developer amount regulating portion and the upstream side in the moving direction of the developer bearing member. The tip on the upstream side in the moving direction exists within the angular range between the position where the magnetic field strength in the direction normal to the surface of the developer carrier between the first and second magnetic poles is minimum and the position where the magnetic field strength by the second magnetic pole is maximum. A developing device.