JPS6311975A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To prevent the fogging of toner and the leakage of toner to the outside of a developing device, by causing the contact of the developing agent with the surface of an electrostatic latent image carrier to complete at the position where a developing sleeve which functions as a developing electrode approaches the surface of the carrier or at the closet position of the sleeve to the carrier surface. CONSTITUTION:A developing agent is carried on a developing agent carrying and guiding member 12 from a developing agent supplying section A to a developing area B b6 means of the rotation of a magnetic roller 11 only and comes to contact with the surface of an electrostatic latent image carrier 1 at the front end of the member 12. When the developing agent is allowed into contact with the surface of the carrier 1, the agent develops an electrostatic latent image which is previously formed on the surface of the carrier 1. Simultaneously, the developing agent is allowed into contact with the outer peripheral surface of a developing sleeve 10 and carried to the developing agent supplying section A side through the space between the sleeve 10 and developing agent carrying and guiding member 12. The contact of the developing agent with the surface of the electrostatic latent image carrier 1 is completed at a position where the sleeve 10 approaches the surface of the carrier 1 or the closest position of the sleeve 10 to the surface. As a result, the surface of the carrier 1 which is completed in contact with the developing agent is passed through the closest position which is high in electric field and the toner floating over the section is attracted by and stuck to the picture section of the electrostatic latent image or the outer peripheral surface of the developing sleeve 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic latent image developing device using a magnetic brush method used in electrophotographic copying processes and the like.

Conventionally, as a method using this type of magnetic brush type electrostatic latent image developing device, the method shown in FIGS. 8 and 9 is well known. In this method, a magnetic roller (3) is placed opposite the surface of a photoreceptor drum (1) that is rotationally driven in the direction of arrow (a).
A developing sleeve (2) with a built-in developer is provided, and the developer supplied to the developer supply section (A) by the packet roller (4) is applied onto the outer peripheral surface of the developing sleeve (2) by the magnetic force of the magnetic roller (3). While holding the magnetic roller (3) in the direction of arrow (b) and the developing sleeve (2) in the direction of arrow (C), the outer circumferential surface of the developing sleeve (2) is moved as shown in arrow (c).
The developing sleeve (2) and photoreceptor drum (1)
) in the developing area (B) adjacent to the photoreceptor drum (1).
This is a method of developing an electrostatic latent image formed on the surface of a material.

Also, in Figures 8 and 9, (5> is the height regulation plate, (6)
is a scraper, (7) is a power source for developing bias, and the developing sleeve (2) also functions as a developing electrode.

By the way, the conventional developing method (as shown in Figs. 8 and 9, not only the method in which both the developing sleeve and the magnetic roller are rotationally driven) but also the method in which the developing sleeve and the magnetic roller are Even if there is a system in which only one of them is rotationally driven), the developer passes through the closest position (x,) [distance (dl)] between the developing sleeve (2) and the photoreceptor drum (1), Thereafter, the developing sleeve (2) ends contact with the photoreceptor drum (1) at a position (x,') [distance (a+')] where it is separating from the surface of the photoreceptor drum (1). however,
This can cause toner fogging on the developed image, toner leakage to the outside of the developing device, and in the case of developers that use a carrier, toner image scratching caused by the carrier scraping off the toner image, poor fine line reproducibility, or magnetism. There is a problem in that the carrier adheres to the surface of the photoreceptor drum (1) due to the restraining force.

These problems are caused by the fact that the distance (d,') is wider than the distance (d, ), as described above, and in a developer that uses a carrier, toner fog and toner leakage occur. It has been confirmed that banding tends to occur when a low amount of toner is present in the developer. Note that in a developer using a carrier, it is inevitable that toner with a low charge amount exists in the developer at a certain ratio even if it is a small amount.

Toner with a low charge amount tends to float away from the carrier, and when the developer tries to separate from the photoreceptor drum (1), in other words, low band 1 toner floats in the space at the position (X,'). Become. As is clear from the above-mentioned condition that d1゛〉d, near the position (x,') and the position (
The electric field between the developing sleeve (2) and the photoreceptor drum (1) in the vicinity of the downstream side of the developer transport direction from X,') is weaker than that near the closest position (X,), and is not very strong. Therefore,
Floating toner cannot receive sufficient electric force from the electrostatic latent image formed on the surface of the photoreceptor drum (1), and as a result, it adheres to the background of the image and causes fog, and the developing sleeve ( 2) and the photoreceptor drum (1), and leaks downward.

Furthermore, the fact that the electric field due to the electrostatic latent image at the position (X,') is weaker than that at the closest position (X,) means that the toner attached to the surface of the photoreceptor drum (1) at the closest position (Xl) The attraction toward the photoreceptor drum (1) is at the position (X,'
) means that it is weaker than the nearest position (xl). Therefore, a phenomenon occurs in which the toner adhering to the image area at the closest position (X,) is scraped off by the ears of developer (carrier) at the position (X,'). This leads to toner image scratches and poor fine line reproducibility.

In addition, if the carrier has a small diameter and is a binder type, the magnetic binding force will be much smaller, and the band T with the polarity opposite to that of the toner will be much stronger.
, since it can hold a certain amount, it tends to adhere to the background part of the image. This phenomenon occurs because the larger the distance (dl') is, the more the magnetic roller (
This is likely to occur because the magnetic attraction force caused by 3) becomes weaker.

Means for Solving the Problems In order to solve the problems above, the electrostatic latent image developing device according to the present invention has the following features: (a) The developing electrode is a developing sleeve incorporating a magnetic roller, and the outer periphery of the developing sleeve is A developer conveyance guide member having a shape substantially along the surface is provided from the developer supply section to the vicinity of the development area, (b) the magnetic roller is rotationally driven from the development area toward the developer supply section, and the development sleeve is driven to rotate in the same direction as the magnetic roller, and the developer is conveyed from the developer supply section to the development area on the developer conveyance guide member based on the rotation of the air supply roller, and the developer after development is developed. Based on the rotation of the sleeve, the developer is conveyed between the developing sleeve and the developer conveying guide member to the developer supply section, and (c) the developer that can be conveyed by the rotation of the developing sleeve is transferred from the outer peripheral surface of the developing sleeve. The present invention is characterized in that a scraper for scraping is provided, and (d) a developer detecting means is installed facing the outer circumferential surface of the developing sleeve on the downstream side of the developing area.

In other words, in the above configuration, the developer is transported from the developer supply section to the development area on the developer transport guide member based only on the rotation of the magnetic roller, and an electrostatic latent image is formed at the tip of the developer transport guide member. It contacts the surface of the carrier and develops the electrostatic latent image previously formed on the surface. At the same time, the developer comes into contact with the outer circumferential surface of the developing sleeve, and as the developing sleeve rotates, the developer is completely conveyed between the developing sleeve and the developer conveyance guide member toward the developer supply section. In this case, the developer ends contact with the surface of the electrostatic latent image carrier at a position where the developing sleeve approaches or is closest to the surface of the electrostatic latent image carrier.

As a result, the surface of the electrostatic latent image carrier that has finished contacting with the developer passes through the closest position where the electric field is strong, and the toner floating in this area is moved by the strong electric field to the electrostatic latent image area or the developing sleeve. It will adhere to the outer peripheral surface. Further, the toner image is not scraped off by the carrier.

Furthermore, the developer before development and the developer with reduced toner concentration after development are separated by the developer transport guide member, and the developer is not replaced in both transport paths, and the developer using a carrier is The toner concentration in the developer does not decrease in the development area.

- During development, the developer does not advance to the outer peripheral surface of the developing sleeve on the downstream side of the developing area, as described above, but due to slight errors in the installation position of the developing sleeve, the developer may flow onto the outer peripheral surface of the downstream side of the developing area. If it has progressed, it can be detected by the developer detection means. Based on this detection signal, controls such as displaying "trouble" on the outside or stopping the rotation of the magnetic roller are performed to prevent the developer from spilling out of the apparatus. Note that the developed developer transported to the developer supply section side based on the rotation of the developing sleeve is scraped off by the scraper, and does not go around to the developer detection means installation position.

Embodiment Hereinafter, one embodiment of the electrostatic latent image developing device according to the present invention will be described with reference to FIGS. 1 to 7.

[Basic system of developing device, see Figure 1] This developing device is based on the well-known magnetic brush system, and contains a developer consisting of a mixture of carrier and toner that are charged with opposite polarities by frictional electrification. So-called regular development is performed in which a positive electrostatic latent image is developed into a positive image.

On the other hand, the photoreceptor drum (1) is driven to rotate in the direction of arrow (a), and its surface is charged with a polarity opposite to that of the toner before reaching the developing device, and a positive electrostatic latent image is formed on its surface. It is formed.

[Structure of the developing device, see FIG. ) has a built-in magnetic roller (11) magnetized with N and S poles on its outer periphery, and a developer transport guide member (12) located close to the upper half of the outer surface of the developing sleeve (10). The developing sleeve (10) and the magnetic roller (11) are both driven to rotate in the direction of arrow (b) at the rotation speed explained below. As shown in the figure, the developing sleeve (10) has an inner radius (r,) slightly larger than the outer radius (rl), and its center point (0,) is the developing sleeve (10).
The member (12) and the developing sleeve (1) are installed at a position slightly eccentric (d,) with respect to the center point (01) of
0) is the distance from the development area (B) to the developer supply section (A>
It is set up so that it gradually becomes wider as you move towards it.

The developing sleeve (10), the developer conveyance guide member (12)
) are both made of a conductive material, and are connected to bias power supplies (30) and (31''), respectively, as shown in FIG.

The bias TLi (30) is for making the developing sleeve (10) function as a developing electrode.
), a DC developing bias voltage having a polarity opposite to that of the toner is applied. As explained below, the bias power supply (31) is for erasing one load of developer (mainly carrier) that can be conveyed between the developing sleeve (10) and the member (12). ) is applied with an AC voltage.

The height regulating plate (21) is formed integrally with the developer casing (20), and its tip faces the developer transport guide member (12) at a constant distance (d). There is. The scraper (13) is made of an elastic thin plate, and its tip is lightly pressed against the outer peripheral surface of the developing sleeve (10).

Further, a developer stirring blade (14) is installed in the developer casing (20) so as to be rotatably driven in the direction of arrow (d), and supplies the developer to the supply section (A) while stirring the developer. A toner casing (25) is attached to the back of the developer casing (20).
), and is configured to supply toner from the supply port (27) to the developer casing (20) by rotating a toner supply blade (26) provided inside in the direction of arrow (e).

On the other hand, the areas immediately above and below the development area (B) are sealed by sealing means, respectively. The powder smoke prevention sealing member (15) for sealing the upper part is made of a flexible material, is attached to the upper end surface of the developer casing (20), and its tip is lightly touched to the surface of the photoreceptor drum (1). are in contact. At the bottom are the carrier collection member (16) and the spill prevention member (
18). Carrier collection member (16
) has its lower part attached to the lower end surface of the developer casing (20), and at least the vicinity of the attachment part is made of a flexible material, and the tip and the surface of the photoreceptor drum (1) are made of a flexible material. The distance (d4) (see Figure 6) is the member (16)
A spacer (17) made of an insulating material bonded to the developing sleeve (10) comes into contact with the outer circumferential surface of the developing sleeve (10) due to the elasticity of this member (16), thereby regulating the developing sleeve (10). This carrier recovery member (16) is for recovering the Kihelia that has been deposited on the surface of the photoreceptor drum (1), and is made of a conductive material, and is powered by a bias power source (32) so that it has a polarity opposite to that of the carrier. When the DC bias voltage is fully applied, and as shown in Figure 5,
A constant opening (16a) is formed in the width direction. A spill prevention member 18), which is another sealing means, is located outside the carrier recovery member (16), and its lower part is attached to the lower end surface of the developer casing (20).
At least the vicinity of the attachment part is made of a flexible material, and the distance (ds) between the tip and the surface of the photoreceptor drum (1) (see Figure 6) is determined by the spill prevention member (18). Due to the elasticity of this member (18), the bonded spacer (19) is attached to the carrier collecting member (16>) and the spacer (17).
This is regulated by contacting the outer circumferential surface of the developing sleeve (10) via the outer peripheral surface of the developing sleeve (10).

The photosensor (24) is a reflective type consisting of a light emitting element (24a) and a light receiving element (24b), and is installed inside the developer casing (20) facing the lower part of the developing sleeve (10). There is. This photosensor (24) is
As shown in FIG. 7, it is detected that the developer crosses the development area (B) and wraps around to the lower part of the development sleeve (10) (this state is an abnormal state as explained below). It is for. The installation position of the photosensor (24) is approximately at the center in the axial direction of the developing sleeve (10), and the spacer 17) is not provided at this position, so that if the developer exceeds the developing area (B), In this case, the developer will reach the detection part of the photosensor (24) without any problem. In addition, the output of the photosensor (24) is input to the microcomputer (CPLI), and the abnormality detection No. 2 is outputted to the abnormality display lamp (L>) and the magnetic roller drive motor (45) via the microcomputer (CPU). Ru.

[Developing device drive mechanism, see Figures 3 and 4] Figure 3 shows the drive mechanism on the back side, where the gear (40) to which the rotational driving force from the main motor is transmitted supports the stirring blade (14). The developing sleeve (10) meshes with the gear (41) fixed to the shaft end.
The gear (42) fixed to the end of the spindle and the toner supply blade (2)
The gear (43) fixed to the end of the spindle of the gear (4)
1) is engaged.

The gear (40) is driven to rotate in the direction of arrow (f) in synchronization with the on/off of the main motor, and this causes the stirring blade (14) to rotate in the direction of arrow (f).
), the developing sleeve (10), and the toner supply blade (26) can be rotated in the directions of arrows (d), (b), and (e), respectively.

Figure 4 shows the drive mechanism on the near side, showing the output pulley (46) of the magnetic roller drive motor (45) and the magnetic roller (11).
The pulley (48) fixed to the spindle end of the belt (47)
are connected. The magnetic roller drive motor (45) is normally turned on and off in synchronization with the main motor, and in conjunction with this, the magnetic roller (11) is rotationally driven in the direction of arrow (b).

[Movement of developer, see FIGS. 1 and 2] Next, the movement of developer around the developing sleeve (10) in the above-described developing device will be explained.

The developer is supplied to the supply section (A) by rotation of the stirring blade (14) in the direction of the arrow (d), and is completely attracted to the outer circumferential surface of the developing sleeve (10) by the magnetic force of the magnetic roller (11), thereby regulating the brush height. While the height of the head is regulated by the plate (21), the magnetic roller (11)
) is conveyed in the direction of arrow (c) on the developer conveyance guide member (12) based on the rotation in the direction of arrow (b). The developer conveyed in the direction of arrow (c) on the developer conveyance guide member (12) comes into contact with the surface of the photoreceptor drum (1) at the tip of the member (12), Develop the electrostatic latent image formed on the surface. At about the same time, the developer comes into contact with the outer peripheral surface of the developing sleeve (1o) and
) in the direction of arrow (b), the developing sleeve (1
arrow (b) between o) and the developer transport guide member (12).
direction, and is scraped off by a scraper (13).

In this case, the position (X,) where the developer ends contact with the surface of the photoreceptor drum (1) is the position where the developing sleeve (10) is approaching the surface of the photoreceptor drum (1), It is slightly above the closest position (xl) between the two. As a result, the developer does not exist on the outer circumferential surface of the developing sleeve (10) downstream of the closest position (X,) with respect to the moving direction of the photosensitive drum (1>, indicated by arrow a).

Here, the principle of the above-mentioned movement of the developer in a system in which the developing sleeve and the magnetic roller are driven to rotate in the same direction will be explained in principle.

In the above system, the developer is conveyed on the outer circumferential surface of the developing sleeve in a direction generally opposite to the rotational direction of the magnetic roller. To explain this in detail, the upper layer of the magnetic brush is conveyed while rotating in the direction opposite to the rotation direction of the magnetic brush due to the movement of the magnetic field based on the rotation of the magnetic roller, and the lower layer near the outer peripheral surface of the developing sleeve is transported. Based on the rotation of the sleeve, the developer is transported in the rotation direction thereof, that is, in the opposite direction to the overall developer transport direction. However, the conveyance speed is lower than the conveyance speed in the upper layer portion of the magnetic brush.

In the electrostatic latent image developing device according to the present invention, a developing electrode (e.g., a developing sleeve that also functions as a developing electrode) is brought close to an electrostatic latent image carrier (e.g., a drum having a photoreceptor layer on its surface). The contact of the developer with the photosensitive drum (this contact area is referred to as a developing area) is terminated at a certain position or the closest position. In such a system, the developer conveyance speed (V
sl) is set higher than the developer conveyance speed (Vmg) by the magnetic roller, so that the developer is not present on the outer circumferential surface of the developing sleeve on the downstream side of the developing area.

Specifically, the conveyance speed [V
mg (mm/5ec) is Vmg = hp・(Wmg/60)
--■ However, it is expressed by the following formula: h: height (mm) p: number of magnetic poles W: number of rotations of the magnetic roller (rpm).

The conveyance speed based on the rotation of the developing sleeve [Vsl (mm/
5ec)] is Vsl = D・yr・(Wsl/60)
--■ However, D = Developing sleeve diameter (mm) WSI
: Development sleeve rotation speed (rpm).

Therefore, the overall developer transport speed [Vdev (mm
/ 5ee)] is Vdev = Vmg - Vsl = (h-p-Wmg -D ・7r ・Wsl)/6
It is expressed by the formula 0-■.

By the way, at the closest position (X,) between the developing sleeve and the photosensitive drum, the height (h) is necessarily the closest position interval (dl). Therefore, in order to prevent the developer from existing on the outer circumferential surface of the developing sleeve downstream of the developing area, D ・7r ・Wsl>d, ・p−Wmg
It is sufficient if the formula −・・−■ is satisfied. That is, the diameter of the developing sleeve, the number of magnetic poles of the magnetic roller, their rotation speed, the distance between the developing sleeve and the photosensitive drum, etc. may be set so as to satisfy Equation 0.

[Specific Examples of Development Conditions] Here, the present development device and specific numerical values of the development conditions will be explained based on experiments conducted by the present inventors.

Developing sleeve: Material: stainless steel Diameter: 31 mm Number of revolutions: 60 rpm Developing bias voltage: 150 V (DC) Magnetic roller: Number of poles = 8 Magnetic force: 100OG (on the surface of the developing sleeve) Number of revolutions: 1200 rpm Stirring blade: Number of revolutions: 40 rpm Toner Supply vane: Rotation speed: 50 rpm Developer conveyance guide member: Material: stainless steel Thickness: 0.8 mm Arc radius: 17 mm Eccentricity value (ds) of (0,) with respect to (0,): 0.
Minimum distance (da) with 3mm developing sleeve: 1.2
mm Applied tolerance pressure: -150V (DC), 350Vrm
s, 1k)lz(AC) nearest position distance (dl)
: 0.4mm Hodaka standard spacing (ton): 1.8mm Voltage applied to carrier collection member: +500V Photosensitive drum: Peripheral speed: 130mm/see Maximum electrostatic latent image potential: -550V Electrostatic latent image background potential: - 100V developer: A mixture of 90% by weight of a binder-type insulating magnetic carrier with an average particle size of 38 μm and 10% by weight of an insulating non-magnetic toner with an average particle size of 11 μm. The carrier becomes negative polarity and the toner becomes positive polarity by frictional charging. is charged with electricity.

Note that under the above conditions, the developer is placed at the closest position (x
It goes without saying that the above-mentioned formula 0 must be satisfied because it is not allowed to exist on the outer circumferential surface of the developing sleeve (10) on the downstream side of the developing sleeve (10).

[Effect of satisfying the above formula 1] When copying experiments were conducted using the above development method, it was possible to obtain good copied images with no toner fog etc. even when using toner with a relatively low charge amount. . Similarly, even when 10,000 sheets were continuously copied using toner with a relatively low charge amount, almost no toner leakage was observed between the developer casing (20) and the photoreceptor drum (1). There wasn't.

This effect is due to the fact that the position (X,) where the developer ends contact with the photoreceptor drum (1) is upstream of the closest position (x,), and this interval (dt") is equal to the interval ( dl)
This is probably due to the fact that it is wider. That is, the surface of the photoreceptor drum (1) is the part where the electric field between the electrostatic latent image on the photoreceptor drum (1) and the developing sleeve (10) is strongest after the contact with the developer is completed. It will pass through the closest position (x,). The toner, which has a low charge and floats away from the carrier, is attracted to the image area when the image area passes by due to the strong electric field, and is attracted to the developing sleeve (10) when the background area passes through, and the toner is completely separated from the carrier. It adheres to the image area on the surface of the photoreceptor drum (1) or the outer peripheral surface of the developing sleeve (1o). Therefore, floating toner does not adhere to the background area and cause fog, or leak to the outside of the developing device.

In addition, in the developing area (B), the electric field between the developing sleeve (1o) and the photosensitive drum (1) is strongest at the position (X,) where the contact of the developer ends; The carrier does not scrape off the toner adhering to the image area at the (X,) portion, and the toner image does not fade or the fine line reproducibility is impaired.

Furthermore, as in this example, the carrier has a small diameter and is of a binder type, so the magnetic binding force is small. Hard to occur.

[Toner supply operation, see FIG.
) The mixing and stirring are completed by rotation in the direction of ).

Toner is stored in the toner casing (25), and the rotation of the toner supply vane (26) in the direction of arrow (e) causes stirring and supply of the toner above the toner supply port (27). . When the toner is consumed by development, the volume of the developer in the developer casing (20) decreases by an amount commensurate with the amount of toner consumed. Then, a space corresponding to the consumed amount is created in the developer casing (20), and the toner located above the toner supply port (27) automatically enters the developer casing (20). When the volume of the developer increases as a result, the toner supply port (27) is covered by the increased developer, and no new toner is supplied, and eventually the developer casing (20)
The volume of the developer within is always constant, that is, the toner concentration is always kept approximately constant.

[Function of developer transport guide member] In the present embodiment, the developer transport guide member (12) firstly controls the development area (
It functions to eliminate the decrease in toner concentration in the developer in B). That is, the developer before development is transported in the direction of arrow (c) based on the rotation of the magnetic roller (11), and the developer after development is transported in the direction of arrow (b) based on the rotation of the developing sleeve (10). This is because the developer with a reduced toner concentration is separated by the developer transport guide member (12), and the developer is not replaced in both transport paths.

By the way, the distance between this member (12>) and the developing sleeve (10) is considerably wider than the nearest position distance (dl), and according to this method, the distance between the developing sleeve (12) and the developing sleeve (10) is considerably wider, and according to this method, the outer peripheral surface of the developing sleeve (10) is moved in the direction of arrow (b). Strictly speaking, the developer that can be transported to
12), the upper layer receives a conveying force in the direction of arrow (c) expressed by the above equation 0 based on the rotation of the magnetic roller (11). but,
According to the experimental results, the developing sleeve (10) and the member (12
) was being conveyed in the direction of arrow (b) by the rotation of the developing sleeve (10). This is considered to be due to the following reasons. The conveying force accompanying the rotation of the developer due to the rotation of the magnetic roller (11) changes depending on the density of the developer. As the density of the developer increases, it becomes difficult to move, and therefore the conveying force accompanying the rotation becomes weaker. The density of the developer is relatively high between the developing sleeve (10) and the member (12), and therefore the developer as a whole is considered to move in the direction of arrow (b).

Further, as described above, the distance between the developer conveyance guide member (12) and the developing sleeve (10) is set to gradually increase from the developing area (B) toward the supply section (A). The tip interval (d,) near the region (B) is the minimum interval. Under these settings, the developing sleeve (
The torque for rotationally driving 10) did not particularly change during the above-mentioned 10,000-sheet continuous copying experiment.

However, the distance between the developer conveyance guide member (12) and the developing sleeve <10> is changed from the developer supply section (A) to the developing area (
In the case where the distance is almost constant (1,2 mm) up to the vicinity of the developing area (B), and conversely, the developer supplying part (A
), and the setting gradually becomes narrower.
When we conducted a similar comparative experiment of continuous copying, we found that in the former case, the torque that drives the rotation of the developing sleeve (10) gradually increased slightly, and in the latter case, the rotational drive torque increased significantly after making several dozen copies. It became so large that it became impossible to copy.

The reason why such a phenomenon occurs can be considered as follows. The passageway between the developer sleeve (10) and the member (12) is almost completely filled with developer material and has a relatively high density. As mentioned above, the conveying force accompanying the rotation of the developer due to the rotation of the magnetic roller (11) in the direction of arrow (b) becomes weaker, and the developer is conveyed by the rotation of the developing sleeve (10). It is. By the way, the distance between the developing sleeve (10) and the member (12) is
If it is set so that it gradually becomes narrower from the vicinity of the developing area (B) to the developer supply section <A), the developing sleeve (10)
The density of the developer conveyed by the rotation in the direction of arrow (b) becomes higher than necessary as it approaches the developer supply section (A), leading to an increase in the rotational driving torque of the developing sleeve (10). Conceivable. Further, even if the interval is set to be almost constant, it is expected that a minute partial setting failure will occur, which is thought to lead to a slight increase in the rotational drive torque.

That is, as in this embodiment, the developing sleeve (10) and the member (
12) is narrowest near the development area (B),
If the setting is made so that it gradually becomes wider as it approaches the developer supply section (A), as in the comparative experiment, the developing sleeve becomes wider.10)
The rotation of the developing sleeve (10) does not increase the density of the transported developer, and therefore the rotational driving torque of the developing sleeve (10) does not increase.

Furthermore, the developer transport guide member (12) also has the function of eliminating the burden of the carrier after development and improving the frictional charging performance with the toner. That is, this member (12)
is made of a conductive material, bias N, direct current (
-150V) superimposed AC (350Vrms, 1
kHz) can be applied. -1 for the developing sleeve (10)
Since the DC bias of 50V has been applied, as a result, there is a gap of 3.
An alternating current electric field of 50 Vrms and 1 kHz will be applied.

By the way, in the case where an insulating magnetic carrier is used as the carrier as in this embodiment, even if the toner is consumed during development, charges of opposite polarity remain on the carrier for a long time. Furthermore, carriers that already have charges of opposite polarity to the toner tend to have a lower ability to charge newly replenished toner than carriers that do not have charges.

However, in this example, the developer after development is
When the developer is conveyed through the path between the developing sleeve (10> and the member (12)), it is subjected to an alternating current electric field, and the charge is removed so that the developer as a whole has no charge.

That is, the insulating malignant carrier that has lost the toner and has an excess charge of the opposite polarity has its excess charge removed, and as a result, the newly replenished toner can be sufficiently triboelectrically charged.

Specifically, at the start of development, the amount of charge on the toner is 1.
In the case of 2 μc/g, 2,000 sheets of copied material (12)
When applying only -150V DC and no alternating current, the charge amount of the toner decreased to 9 to 10 μc/g, but if alternating current was applied in a superimposed manner as in this example, the amount of charge on the toner decreased to 12 to 1 μc/g.
It held a charge of 3 μc/g.

Note that the developer transport guide member (12) itself does not necessarily need to be entirely formed of a conductive material, and it is sufficient that at least only the inner circumferential surface facing the developing sleeve (10) has conductivity.

[Function of carrier recovery member] As described above, in this developing device, carrier adhesion to the surface of the photoreceptor drum (1) is difficult to occur. However, due to unavoidable variations in physical properties during carrier production, carrier adhesion may occur, albeit in a small amount. The carrier collecting member (16) has a function of collecting the carrier attached to the surface of the photoreceptor drum (1) to the developing sleeve (10) side. That is, the carrier attached to the surface of the photoreceptor drum (1) has a negative polarity charge that is opposite to that of the toner, but the carrier collecting member (16) has a charge of +500<'/). Since the voltage is applied, the carrier can be electrically attracted to the carrier recovery member (16). Then, as shown in FIG. 6, the carrier is transported over the carrier collection member (16) by the rotation of the magnetic roller (11) in the direction of arrow (b), and is transported over the carrier collection member (16).
6a) and returned onto the developing sleeve (10).

By the way, the tip of the carrier collecting member (16) cannot be brought into contact with the surface of the photoreceptor drum (1) in order not to disturb the toner image, but in order to perform the carrier collecting action more effectively, the distance (d4) must be adjusted. is preferably as narrow as possible in order to strengthen the recovery electric field, and the distance (d4
) is desirably uniform in the axial direction. Therefore, it was decided to use the developing sleeve (10) as a positioning reference member for installing the developing sleeves (10) at as narrow an interval (d4) as possible. The developing sleeve (10) is the photosensitive drum (1)
This is because it is precisely positioned at a distance (dl) with respect to the surface of. This allows you to install other positioning means to position the tip of the carrier recovery member (16) or to maintain the linearity of the tip of the carrier recovery member (16).
16) There is no need to form the device itself with a thick member,
The spacing (d4) can be set sufficiently narrowly and accurately using a thin member, and the carrier attached to the surface of the photoreceptor drum (1) can be almost completely recovered.

Note that the structure in which the spacer (17) comes into contact with the lower side of the developing sleeve (10) can be achieved if each condition is met so that the developer does not exist on the downstream side of the developing area (B). The setting is such that the above formula 0 is satisfied, and the developed developer that can be completely conveyed in the direction of arrow (b) on the outer circumferential surface of the developing sleeve (10) is scraped off with a scraper (13), This is because it does not go around to the installation position of the spacer (17).

[Function of Toner Spill Prevention Member] In this embodiment, as described above, it is difficult for toner to spill downward from the developing area (B).

However, due to the presence of airflow or the like along the rotation of the photoreceptor drum (1) in the direction of arrow (a), the toner tends to spill out to the outside, albeit slightly. Spill prevention member (18
) has a function of preventing such toner spillage.

The tip of this spill prevention member (18) cannot be brought into contact with the surface of the photoreceptor drum (1) similarly to the carrier recovery member (16), but the interval (d,) must be as narrow as possible and the axial direction It is desirable that it be uniform throughout. Therefore, the spill prevention member (18) is
19), carrier recovery member (16), spacer (17)
By coming into pressure contact with the developing sleeve (10) via the developing sleeve (10), a constant positional relationship is maintained at all times, and the interval (d,) is set to be sufficiently narrow and uniform in the axial direction, albeit indirectly. , toner spillage can be almost completely prevented.

In addition, when the spacer (19) is made of an insulating material and the spill prevention member (18) is made of a conductive material, a bias with a polarity opposite to the charged polarity of the toner must be applied to the spill prevention member (18). For example, the efficiency of toner collection is further improved.

[) Function of the odometer sensor In this embodiment, since there is no developer on the developing sleeve (10) downstream of the developing area (B), there is no developer on the developing sleeve (10) facing the photosensor (24). No developer is present on the outer peripheral surface. Developing sleeve (
10) is made of stainless steel, and its surface is polished, so the light emitted from the light emitting element (24) passes through the developing sleeve (10).
) and enters the light receiving element (24b), and the corresponding output can be output to the microcomputer (CPU).

By the way, in the developing device of the type as in this embodiment,
It is necessary to always maintain the distance (d, ) between the developing sleeve (10) and the surface of the photoreceptor drum (1) below a certain value.
This is because the formula is no longer satisfied, the developer proceeds downstream from the development area (B), and eventually spills out of the development device.

However, in this embodiment, the photosensor (2
Control such as stopping the rotation of the magnetic roller drive motor (45) is executed based on the developer detection signal from 4), thereby preventing the above-mentioned inconvenience.

That is, if the developing device is set incompletely for some reason and the copying machine starts operating with the gap (dl) between the developing sleeve (10) and the photoreceptor drum (1) being wide, then the first As shown in Figure 7, the developer is applied to a magnetic roller (1
1), the developer is conveyed onto the outer circumferential surface of the developing sleeve (10) on the downstream side of the developing area (B). A spacer (
17), the developer that has passed through the development area (B) is quickly conveyed onto the outer peripheral surface of the development sleeve (10) facing the photosensor (24).

As a result, the light emitted from the light emitting element (24a) is diffusely reflected or absorbed, so that it no longer enters the light receiving element (24b), and a corresponding signal is output from the light receiving element (24b) to the microcomputer (CPU). Therefore, the microcomputer (CPU) uses a magnetic roller drive motor (
45) to stop the rotation.

When the rotation of the magnetic roller (11) is stopped, the conveyance force that conveys the developer in the direction of arrow (c) disappears.

Since the in-motor is driven by M, the developer on the developing sleeve (10), including the developer that has passed through the developing area (B), rotates in the direction of the arrow (b) of the developing sleeve (10). Based on this, the developer is conveyed in the same direction on the outer peripheral surface of the developing sleeve (10) and returned into the developer casing (20). Thereafter, the microcomputer (CPU) turns on the display lamp (L) to externally display 'trouble' and stops the operation of the main motor and other parts of the copying machine.

In this embodiment, in this way, the photosensor (24) promptly detects that the developer is transported downstream from the development area (B), and the rotation of the magnetic roller (11) is stopped. , the developer that has passed through the developing area (B) is prevented from losing its destination and spilling out of the developing device;
As a result, it is possible to detect that the conditions such as the interval (d,) are not set accurately.

In addition to the reflective photosensor (24), it is also possible to use a vibrating piezoelectric sensor, a reflective ultrasonic sensor, a magnetic sensor, etc. as such a developer detecting means.

Effects of the Invention As is clear from the above explanation, the present invention provides a developer conveyance guide member having a shape that roughly follows the outer circumferential surface of the developing sleeve from the developer supply section to the vicinity of the developing area, and a magnetic roller is provided in the vicinity of the developing area. The developing sleeve is rotated in the same direction as the magnetic roller, and the developing sleeve is rotated in the same direction as the magnetic roller.
The developer is transported from the developer supply section to the development area on the developer transport guide member based on the rotation of the magnetic roller, and the developer after development is transported between the developer sleeve and the developer based on the rotation of the development sleeve. Since the developer is conveyed between the guide member and the developer supply section, the developer becomes electrostatic latent at a position where the developing sleeve functioning as a developing electrode approaches or is closest to the surface of the electrostatic latent image carrier. After the surface of the electrostatic latent image carrier finishes contact with the developer, it passes through a position where the electric field is strong between the developing sleeve and the electrostatic latent image carrier, and the electrostatic latent image carrier floats in this area. The toner adheres to the image area or the outer circumferential surface of the developing sleeve using a strong electric field, which prevents toner fogging and toner leakage to the outside of the developing device. It is possible to prevent toner image cast, poor fine line reproducibility, and adhesion of the carrier to the electrostatic latent image carrier due to the scratching of the toner image by the carrier, and it is possible to obtain copied images of good image quality. be.

Furthermore, the present invention provides a scraper for scraping off the developer conveyed by the rotation of the developing sleeve from the outer circumferential surface of the developing sleeve, and a developer detecting means is provided facing the outer circumferential surface on the downstream side of the developing area of the developing sleeve. Because it was installed at least,
It is possible to immediately detect problems where developer has progressed to the outer peripheral surface of the downstream side of the developing area due to errors in the installation of the developing sleeve, etc., and it is possible to prevent problems such as developer spilling outside the device. .

[Brief explanation of the drawing]

1 to 7 show an embodiment of the electrostatic latent image developing device according to the present invention, in which FIG. 1 is a sectional view of the entire device, FIG. 2 is a sectional view of main parts, and FIGS. Figure 4 is a rear view and front view of the drive mechanism, Figure 5 is a perspective view showing the carrier collection member and spill prevention member, Figure 6 is a sectional view of the main parts, and Figure 7 shows an abnormal state of developer transport. FIG. FIG. 8 is a partial sectional view of a conventional developing device, and FIG. 9 is a sectional view of its essential parts. (1>...Photosensitive drum, (10)...Developing sleeve, (11)...Magnetic roller, (12)...Developer conveyance guide part L (17)...Spacer, (24)... )...
Photo sensor, (45)...magnetic roller drive motor,
(Xl)... Nearest position, (X,)... Developer contact end position, (d,)... Closest position interval, <A)...
・Developer supply section, (B)...development area, (CPU)・
...Microcomputer, (L)...Error indicator lamp.

Claims (1)

[Scope of Claims] 1. A developing electrode is disposed opposite to an electrostatic latent image carrier that is rotationally driven in one direction, and a developer conveyed on the developing electrode is applied to the surface of the electrostatic latent image carrier. In an electrostatic latent image developing device configured to develop a formed electrostatic latent image, the developing electrode is a developing sleeve incorporating a magnetic roller, and a developer having a shape approximately along the outer peripheral surface of the developing sleeve. A conveyance guide member is provided extending from the developer supply section to the vicinity of the development region, and the magnetic roller is rotationally driven from the development region toward the developer supply section, and the development sleeve is rotationally driven in the same direction as the magnetic roller, and the developer is is transported from the developer supply section to the developing area on the developer transport guide member based on the rotation of the magnetic roller, and the developed developer is transported between the developer sleeve and the developer transport guide member based on the rotation of the developing sleeve. A scraper is provided for scraping off the developer transported by the rotation of the developing sleeve from the outer peripheral surface of the developing sleeve, and the developer detecting means is connected to the developing sleeve. An electrostatic latent image developing device, characterized in that it is installed facing the outer circumferential surface of a downstream side of a developing area.