JPH08191U - Development device - Google Patents

Abstract

(57) [Summary] [Object] To provide a developing device that can operate based on accurate toner concentration information. [Structure] A developer carrier 15 which carries a developer by the magnetic force of magnetic bodies 152 to 156 contained therein and develops the electrostatic latent image on the electrostatic latent image carrier 1, and a developer carrier 15 which is close to the developer carrier. An agitating / conveying member for conveying the developer to the magnetic field of the magnetic body, and a guide means 114 having an inclined surface 115 for allowing the developed developer to flow down to the drawing position P2 of the agitating / conveying member 14 by its own weight. The inclined surface 115 and between the developer carrying member 15 and the agitating / conveying member 14,
With respect to the flow direction of the developer, the inclined surface 1 is provided at a position upstream of and close to the drawing position P2 of the developer by the stirring and conveying member 14.
The toner concentration detecting means 19 for detecting the concentration of the developer flowing down the toner 15 is provided, and the guide means 114 and the agitating / conveying member 14 are arranged close to each other.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a developing device used in a recording device, and more particularly to a developing device that is frequently used in an electrophotographic copying device or an electrostatic recording device and uses a powdery developer.

[0002]

[Prior art]

 In an electrophotographic copying apparatus or an electrostatic recording apparatus, a latent image carrier such as a photoconductor or a dielectric is used, and an electrostatic latent image is formed on the surface of the latent image carrier according to a predetermined method. Then, the electrostatic latent image on the latent image carrier is developed by supplying toner, which is colored fine powder charged in the opposite polarity to the electrostatic latent image, as a developer. By the way, the developer used for developing the electrostatic latent image is sequentially circulated and supplied to a predetermined developing position while the supply amount of the developer is kept substantially constant by the developing device.

However, in the case of a two-component developer composed of a mixture of magnetic fine powder or resin called toner and carrier, only the toner is consumed during development, so that the toner and carrier are separated at each development. The composition ratio changes. If this state is left as it is, density unevenness will occur in the obtained image, so a normal developing device is provided with a means for obtaining toner density information. Based on the information obtained by this, the toner supply amount is controlled by supplying an appropriate amount of toner into the developer or, on the contrary, temporarily refraining from supplying toner.

For example, by utilizing the properties of a toner concentration sensor of a development amount detection type that obtains toner concentration information based on the amount of light reflected from the toner adhering to the photoconductor, and the toner with low fluidity contained in the developer, A toner concentration sensor of fluidity change detection type is used in which the developer is caused to flow into the funnel-shaped member and the toner concentration information is obtained based on the magnitude change of the fluidity.

[0005]

By the way, in the case of the development amount detection type, it is necessary that the spectral reflectances of the toner and the photoconductor surface have a sufficient difference in the wavelength region in which the sensor is sensitive. It is very difficult to choose such a combination for. On the other hand, in the case of the fluidity change detection type, the funnel-shaped member occupies space, which is disadvantageous for downsizing, and also requires a tapping member or the like to prevent the developer from being clogged, and the structure tends to be complicated. Moreover, the developer may stay in the developer circulation system due to the relative relationship between its fluidity and the shape of the flow path.

When the retention of the developer occurs at the toner concentration detection position, even if the toner concentration detection is normally performed, the obtained toner concentration information is only the concentration information of the lumped developer that is retained. There is a problem that it is not possible to obtain the toner concentration information of the developer that is actually circulating. An object of the present invention is to provide a developing device that can operate based on accurate toner density information.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a developer carrier for supporting a developer by the magnetic force of a magnetic material contained therein and developing an electrostatic latent image on the electrostatic latent image carrier, and the developer carrier. An agitating / conveying member which is provided in the vicinity of the magnetic material and conveys the developer to the magnetic field of the magnetic material; and a guide means having an inclined surface for allowing the developer after development to flow down to the drawing position of the agitating and conveying member by its own weight. At a position on the inclined surface of the guide means and between the developer carrier and the agitating / conveying member, upstream and close to the developer drawing position by the agitating / conveying member in the flow direction of the developer. The toner concentration detecting means for detecting the concentration of the developer flowing down the inclined surface is provided, and the guide means and the agitating / conveying member are arranged close to each other.

[0008]

With the inclined surface of the guide means and between the developer carrier and the agitating / conveying member, with respect to the flow direction of the developer, it is located at a position upstream and close to the position where the agitating / conveying member draws the developer. Since the toner concentration detecting means for detecting the concentration of the developer flowing down the inclined surface is provided and the guide means and the agitating / conveying member are arranged in close proximity to each other, the agitating / conveying member can constantly draw the developer at the drawing position. As a result, it is possible to reliably prevent the developer from staying on the inclined surface at a position adjacent to the upstream side, and the toner concentration detecting means detects the concentration of the developer flowing down the same position.

[0009]

【Example】

 FIG. 1 shows a printing apparatus having a developing device as an embodiment of the present invention. In this printing apparatus, a photosensitive drum 1 as an electrostatic latent image bearing member is arranged in the center, and an exposing device 2, a developing device 3 provided with a toner tank 4 and a whole surface exposing device 5 are arranged in a clockwise direction from the upper part of the outer periphery thereof. A corona transfer separator 6, a separation assisting member 7, a residual toner collector 8, and a corona charger 26 are sequentially arranged. The exposure device 2 of this printing device is connected to an optical writing device (not shown), and guides the predetermined image information to the photoconductor surface 9 as a laser beam converted into an optical signal to perform an exposure process. Then, as the photoconductor drum 1 rotates, each well-known component in the printing apparatus operates and a well-known image forming process is performed, so that a visible image corresponding to the input image information is formed on the transfer paper 10. Obtainable.

By the way, the developing device performs a developing process using toner of an electrostatic latent image which is a part of an image forming process, and as shown in FIG. 2, the housing 11 includes a stirring unit and a conveying unit. . The housing 11 has a toner supply port 111 formed on the right side and a facing port 112 facing the photoconductor drum 1 on the left side, and is entirely box-shaped having a predetermined width in the direction perpendicular to the plane of the drawing. A dish-shaped agent reservoir 113 is formed on the bottom of the housing, and an inclined plate portion 114 as guide means is formed toward the facing port 112 side above the agent reservoir. The inclined plate portion 114 is arranged between a dropping position P1 immediately below a sleeve 151, which will be described later, and a developer collecting position (hereinafter, simply referred to as a drawing position) P2 on the side of the agent reservoir 113, which is a position below the falling position P1. The inclination angle θ of the inclined surface 115 with respect to the horizontal plane is set to about 35 ° here.

Further, a toner concentration detection position C is set on the inclined plate portion 114. The tilting plate portion 114 has an inductance sensor 19 as a fluidity change detection type toner concentration sensor attached at a toner concentration detection position C near the drop position P1. Since the inductance sensor 19 forms a part of the inclined surface 115 by the protrusion thereof, the inclined surface 115 is formed as a uniform flat surface. It should be noted that the toner concentration detection position C here is set as a position upstream and close to the developer drawing position P2 by the paddle wheel 14 which is an agitating / conveying member in the flow direction of the developer.

By the way, the tilt angle θ is set as follows. That is, the internal friction angle α, which is the limit angle at which the developer used in this developing device can flow down based on its own weight, is first obtained. For example, as shown in FIG. 3, when a well-known developer is put in a roll mill R and the roll mill is rotated, the developer balances its own internal frictional force and the fluid force due to its own weight in the surface layer portion. It will be broken and the internal friction angle α, which is the inclination angle appearing in the surface layer portion, will not be increased any further.

Based on this internal friction angle α, the inclination angle θ is determined here, and it has been measured that the conventional two-component developer has a maximum of 30 °. Further, as shown in FIG. 4, the developer is supplied from the hopper 22 to the plate 20 which is inclined at an angle (α ± Δα) before and after the internal friction angle α, and the lump of the developer on the inclined surface 21 is visually observed. Occurrence of parts was measured. A carrier 24 is attached to the lower end of the plate 20 with a double-sided tape 23 to form a flow state that is similar to the flow-down of the developer in the surface layer portion. In this case, even if the inclination angle is the same, the measurement result that the generation of the lumpy portion is different depending on the height h of the hopper 22 was obtained. That is, when α = 30 ° and h> 10 cm, no lump portion of the developer was generated. Similarly, when α> 35 ° and h = 0, no lump portion of the developer was generated.

Based on these results, and also considering the actual flow state of the developer in the agent reservoir 113, the inclination angle θ of the inclined surface 115 of the inclined plate portion 114 in this embodiment is about 35 °. In addition, the substantial inclination angle θ1 (in consideration of the agent immovable portion D) is set to about 30 ° (see FIG. 2). The stirring means is a guide plate 25 that is an inclined plate, a fin 12 that deflects the flow direction of the developer flowing down on the guide plate in a predetermined direction, and the developer flowed down in a predetermined direction by the fin in the opposite direction. It is formed by a screw 13 that is deflected and moved.

As shown in FIG. 2, the conveying means is formed of a paddle wheel 14 as an agitating and conveying member for scraping off the developer flowing down to the drawing position P2 and a mag roller 15 as a developer carrying member. The magnet roller 15 includes a non-magnetic sleeve 151 that rotates counterclockwise, magnets 152, 153, 154, 155, 156 and a magnetic short-circuit plate 157 that are mounted inside and fixedly supported on the housing side. Is formed by.

During operation, the developer flowing in the developer circulating system B in the developing device is first pumped up from the pumping position P 2 of the developer reservoir 113 by the paddle wheel 14 rotating in the counterclockwise direction, and the mag roller 15 is moved. The magnetic fields of the magnets 152, 153 and 154 inside are sequentially attracted and held on the sleeve 151 side. By rotation of the sleeve 151 in the counterclockwise direction, the developer first faces the straightening plate 16 connected to the guide plate 25 side, is appropriately pressed and is fixed to the upper side of the sleeve 151. The thickness of the developer on the sleeve 151 is adjusted to be constant so as to face the doctor 17 as a member. The removed excess agent is guided onto the guide plate 25.

After reaching the guide plate 25, the developer flows down by its own weight, but is agitated by the fins 12 and the screws 13. In addition, when the developer is supplied with toner from the toner tank 4 in the gutter 18, the developer is mixed and agitated with the toner, and flows down to the developer reservoir 113 side through the hole 181 on the gutter 18. On the other hand, the developer on the sleeve passes through the doctor 17 and is then sent to the magnetic field of the magnet 155, thereby forming a spike that is suitable for development. The electrostatic latent image is developed by the toner. The developed developer is released from contact with the photoconductor surface 9 by the action of the magnetic field created by the magnets 155 and 156, and is drawn into the housing 11 side.

Further, the magnetic force of the magnet 156 is adjusted so that the developer facing the magnetic short-circuit plate 157 receives a centrifugal force larger than the attraction force to the sleeve 151 side due to the magnetic field at that position. A predetermined height (h '> 10 cm) is maintained between the sleeve 151 and the dropping position P1, and the developing spray that falls there and flows down the inclined surface 115 smoothly returns to the agent reservoir 113. In particular, the paddle wheel 14 provided in the vicinity of the inclined plate portion 114 scrapes off the developer at the drawing position P2, so that the developer is surely retained on the inclined surface 115 due to the developer clogged there. Can be prevented. For this reason, the fluidity of the developer at the toner concentration detection position C is stabilized, and the inductance sensor 19 is sensitive to the amount of magnetic material (carrier) in the developer and is constantly flowing in the developer circulation system B. The toner concentration information is accurately detected from the agent. Then, based on the signal corresponding to the toner concentration, the toner tank 4 performs a predetermined toner replenishing operation, and the toner can be replenished into the developer circulating system B.

Although the inductance sensor is used as the toner concentration sensor in the above-described process, a well-known optical sensor that is sensitive to the difference in color tone between the toner and the carrier in the developer may be used instead of the inductance sensor. Further, a transparent glass (not shown) is provided at the toner concentration detection position C to form a part of the inclined surface 115, and the toner concentration information is obtained by an optical sensor attached to the outside of the inclined plate portion 114 via this transparent glass. In some cases, toner concentration information may be visually obtained through transparent glass to replenish the toner.

[0020]

[Effect of device]

 As described above, in the developing device according to the present invention, between the developer carrier and the agitating / conveying member on the inclined surface of the guide means, in the flow direction of the developer, the agitating / conveying member can be used to draw the developer at the drawing position. Since the toner concentration detecting means for detecting the concentration of the developer flowing down the inclined surface is provided at a position upstream and close to the guide means and the agitating / conveying member are disposed in close proximity to each other, the agitating / conveying member develops at the drawing position. By constantly drawing the developer, it is possible to reliably prevent the developer from staying on the inclined surface at the upstream position and the adjacent position, and the toner concentration detecting means detects the concentration of the developer flowing down the same position. . For this reason, the toner concentration detecting means at a position upstream of and close to the drawing position can surely detect the toner concentration of the developer after development without making an erroneous detection due to retention of the developer, etc. It can operate based on accurate toner concentration information.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a printing apparatus including a developing device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a developing device as an embodiment of the present invention.

FIG. 3 is a schematic explanatory view of an experimental device used for setting a tilt angle θ.

FIG. 4 is a schematic explanatory view of an experimental device used for setting a tilt angle θ.

[Explanation of symbols]

 1 Photoreceptor Drum 12 Fin 13 Screw 14 Paddle Wheel 15 Mag Roller 19 Inductance Sensor 17 Doctor 25 Guide Plate 114 Inclined Plate 115 Inclined Surface 152 Magnet 153 Magnet 154 Magnet 155 Magnet 156 Magnet C Toner Concentration Detection Position P2 Pumping Position

Claims (1)

[Scope of utility model registration request] 1. A developer carrier for supporting a developer by a magnetic force of a magnetic material contained therein and developing an electrostatic latent image on the electrostatic latent image carrier, and a developer carrier provided close to the developer carrier. And a guide means having an inclined surface for flowing the developer to the magnetic field of the magnetic body, and a guide means for allowing the developer after development to flow down to the drawing position of the stirring and transport member by its own weight. The inclined surface of the means is between the developer carrier and the stirring / transporting member, and flows down to a position upstream of and close to the position where the developer is drawn by the stirring / transporting member in the flow direction of the developer. A developing device, which is provided with a toner concentration detecting means for detecting the concentration of a developer, and is arranged such that the guide means and the agitating / conveying member are arranged in proximity to each other.