JP2646147B2 - Method for setting stable toner concentration structure of developing device using two-component developing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for electrophotography, which uses a two-component developing method in which a toner and a carrier are mixed at a predetermined ratio. Related to the structure setting method.

[Prior art] Conventionally, an electrophotographic method used in an image forming apparatus such as an electronic copying machine or a laser beam printer forms a latent image by exposing a photoconductor on the surface of a photosensitive drum to form a latent image. The developing device attaches toner as a developer to form a toner image, and the toner image is transferred to recording paper and fixed by a fixing device to form a hard copy.

The developer used in such an electrophotographic method includes a one-component developer containing only a toner and a two-component developer containing a toner and a carrier mixed at a predetermined ratio.
Two-component developers having advantages such as high resolution are widely used.

The carrier of the two-component developer is formed of a magnetic material, and serves to frictionally charge the toner and transport the toner to the developing space.

In such a two-component developer containing a carrier, the toner is consumed during the development but the carrier is not consumed, so that the amount of the toner in the developer decreases with the developing action and the ratio of the toner to the carrier (that is, the ratio of the toner to the carrier) (Toner density) changes. In order to perform good development, it is necessary to always maintain the ratio of the toner and the carrier with high accuracy and to be constant. Therefore, in a developing device using a two-component type developer, a toner sensor is used. The toner sensor detects the toner concentration and changes (decreases) the toner concentration.
In this case, the toner is replenished to maintain a constant toner density.

The toner sensor is configured by a sensor coil for magnetic detection, an oscillator, and a detector for detecting a detection signal,
It detects the apparent magnetic permeability of the developer close to the surface of the sensor coil and outputs a corresponding DC voltage.

[Problems of the Related Art] However, in the method of detecting magnetic permeability, it is not possible to distinguish between a toner that is a non-magnetic material and a space portion where no toner exists, and therefore, a toner sensor that depends on such magnetic permeability In this case, the density (positional relationship) of the magnetic carrier is detected. Therefore, such a toner sensor detects a decrease in the toner density when the carrier density increases as the toner is consumed and the amount of the toner in the developer decreases. There is a problem that even if the toner amount decreases, the toner density is detected (understood) as the same toner density, that is, an actual change in toner density cannot be detected.

As a result, a developing device that controls the supply of toner based on the uncertain toner concentration detected by such a toner sensor cannot maintain the toner concentration at a high accuracy and a constant level. It could not be done.

By the way, the density of the whole developer is determined depending on the mechanical factors of the developing device (particularly, the pressure under the cutting board).
If the configuration of the developing device can be set so that the developer is stabilized at an appropriate density, it is possible to control the toner concentration stably by increasing the accuracy of toner concentration detection by the toner sensor as described above.

Here, in a developing device in which the density of the entire developer is low (the pressure under the plate of the ear cutting is low), since the density of the entire developer is low, the toner in the developer may be present. The space area (inter-carrier space) is wide, and the toner enters the inter-carrier space during repeated consumption and replenishment of the toner. As a result, the actual toner density increases even if the magnetic permeability (carrier density) is the same.

When the toner density increases, the amount of toner supplied to the photosensitive drum increases, so that extra toner adheres to the recording paper and stains occur.

On the other hand, in a developing device in which the density of the entire developer is high (the pressure under the ear-cutting plate is high), since the density of the entire developer is high, the distance between the carriers in which the toner can exist in the developer is reduced. Although the space is small and the toner density is high,
When replenishment is repeated, the toners repel each other to obtain an appropriate toner density in the inter-carrier space (the toner density decreases). As a result, even if the magnetic permeability (carrier density) is the same, the actual The toner density becomes lower.

When the toner density is low, the amount of toner supplied to the photosensitive drum is reduced, so that print fading occurs.

[Object of the Invention] In the present invention, in view of the circumstances described above, the mechanical factors of the developing device can be set so that the developer can be stably maintained at an ideal density at which the developing operation can be performed well. , 2
It is an object of the present invention to provide a method for setting a stable toner concentration structure of a developing device using a component developing method.

Means for Solving the Problems To achieve the above object, a method for setting a stable toner concentration structure of a developing device using a two-component developing method according to the present invention includes a toner sensor for detecting a toner concentration, A developing roller for replenishing a fixed amount of toner when a toner concentration detection value detected by a sensor becomes equal to or less than a certain set value; In the developing device having a cutting board for controlling the amount of the developer adsorbed to the developing device, the developing device is charged with the developer prepared by mixing the toner and the carrier with a predetermined toner concentration, and the developing device is operated for a predetermined time. After that, idling is performed until the toner concentration detection value is stabilized, and then the developer is sampled. The actual measured value of the toner concentration in the sampled developer and the predetermined toner concentration are compared. By changing the pressure under the cutting board against the developing roll according to the difference, and repeating this series of operations until the measured value and the predetermined toner concentration become substantially the same, Determining the pressure under the ear-cutting plate.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram of a structure of a configuration in which a developing device is set using a toner concentration stable structure setting method of a developing device using a two-component developing method according to the present invention.

In the drawing, reference numeral 10 denotes a developing device, in which two August screws 13 and 14 for stirring and circulating the toner in the toner containing portion 12 are arranged in parallel in a toner containing portion 12 below the developing roll 11. A toner sensor 15 for detecting the magnetic permeability of the toner agitated and circulated by the August screws 13, 14 is arranged adjacent to one August screw 13.

The developing roll 11 is driven to rotate counterclockwise as shown by an arrow in the drawing, and the edge of the toner container 12 (the side plate 10
A), an ear-cutting plate 17 is mounted via a pedestal 16.

The pedestal 16 is mounted so that its position can be moved up and down along a vertical housing side plate 10A.

The surface of the pedestal 16 facing the developing roll 11 (the lower surface of the
16A), the developing roll 11 slightly has
Is formed in an arc shape substantially along the outer periphery of the developing roll 11 approaching the surface of the developing roll 11, and by moving the pedestal 16 along the side plate 10A, an interval (dactor gap) between the tip of the ear cutting plate 17 and the surface of the developing roll 11 Changes, and the bottom of the cutting board
16A separates from and contacts the developing roll 11 so that the distance between the developing roll 16 and the outer periphery changes, and the pressure on the developer also changes.

An output from the toner sensor 15 is input to a recording unit 22 such as a pen recorder via an integration circuit 21 and recorded. On the other hand, the input is also input to the control unit 30 of the developing device 10, and the control unit 30 determines the input value (output of the toner sensor 15: V _A ) by a comparator as shown in the flowchart of FIG. Value: When the input value exceeds the reference value as compared with V (when it is determined that the toner density has decreased), the toner hopper 18 disposed above the toner containing The toner is replenished into the toner storage section 12 so that the toner concentration is always maintained at a constant level.

Adjacent to the developing roll 11 of the developing device 10, a toner suction roll 40 formed of a conductive member in a cylindrical shape is disposed downstream of the ear cutting plate 17 in the rotation direction.

The toner suction roll 40 is driven to rotate clockwise as indicated by an arrow in the drawing, and a cleaning blade 41 is disposed in contact with the cleaning blade 41 at a position downstream of the position facing the developing roll 11 in the rotation direction. The cleaning blade 41 scrapes off the toner adsorbed on the toner suction roll 40.

A predetermined bias voltage is applied to each of the toner suction roll 40 and the developing roll 11 of the developing device 10, and each bias voltage is -500 V in the configuration of the present embodiment. , And the developing roller 11 is at -800V.

Thus, according to the above configuration, when the developing device 10 is operated, the developer is adsorbed on the surface of the developing roll 11 at a position opposed to the toner accommodating section 12, and the adsorbed developer is applied to the developing roll 11. With the rotation of the eleventh, the height can be made uniform by the ear-cutting plate 17. Then, when the rotation of the developing roll 11 reaches a position facing the toner suction roll 40, the toner in the developer is suctioned to the toner suction roll 40 due to a difference in bias voltage. That is, the toner suction roll 40 functions in the same manner as the photosensitive drum at the time of the actual developing operation, and the toner is consumed. The toner adsorbed on the toner adsorbing roll 40 is scraped off by the cleaning blade.

With the above configuration, the stable toner density structure can be set by the stable toner density search step shown in the flowchart of FIG.

First, the developer having a predetermined toner concentration is filled into the developing device 10 (S1), and the developing device is operated without consuming toner. Then, the output of the toner sensor 15 detecting the developer is output. Confirm and record (S2). After that, the developing device
10 to operate the toner suction roll 40 as described above.
To be consumed by the toner and toner replenishment accompanying the toner consumption (normal control by the control unit 30 of the developing device 10)
Is a cycle, and this process is repeated for a predetermined cycle (S
3, S4).

After repeating the predetermined cycle, the toner consumption is stopped and the idle operation is performed until the output from the toner sensor 15 is stabilized (that is, until the developer is in a uniform state) (S5).
Is stable (S6), and when the output value is substantially equal to the value at which the developer having the predetermined toner density is detected (S6).
7) The developer in the developing device 10 is sampled and its actual toner density is inspected (S9), and it is confirmed whether or not this toner density is a predetermined toner density (S10, S11). still,
When the output from the toner sensor 15 is stabilized at a value different from the value at which the developer having the predetermined toner concentration is detected, the toner is increased or decreased (S8). Stabilize to a value approximately equal to

When the actual toner concentration of the developer when the output from the toner sensor 15 is stabilized at a value substantially equal to the value at which the developer having the predetermined toner concentration is detected is the predetermined toner concentration, the developing device 10 Can be said to be a configuration with little change in density.

Here, when the actual toner concentration is higher than the predetermined toner concentration, it means that the density of the developer is low. Therefore, the pedestal 16 of the cutting board 17 is moved and adjusted in a direction to approach the developing roll 11, and Set so that the pressure below the cutting plate 17 is increased (the distance between the bottom surface 16A of the cutting board and the developing roll 11 is narrowed)
(S13), and repeat the above steps again.

When the toner concentration is lower than the predetermined toner concentration, the density of the developer is high. Therefore, the pedestal 16 of the scissoring plate 17 is adjusted by moving the pedestal 16 in a direction away from the developing roll 11. 17 is set so that the pressure below (lower the gap between the lower surface 16A of the cutting board and the developing roll 11 is reduced) (S1
2), repeat the above steps again.

That is, the density of the developer in the developing device 10
Is determined by the pressure under the cutting board 17 (that is, the distance between the bottom face 16A of the cutting board and the developing roll 11), and the pressure under the cutting board 17 becomes an optimum value. By setting the shape and position of the plate lower surface 16A, it is possible to configure a developing device with a small change in developer density.

FIG. 4 is a graph showing a change in toner density with respect to the distance between the lower surface 16A of the cutting board and the developing roll 11 when a developing operation is performed using a developer having an initial toner density of 4%. Thus, it can be understood that the toner density changes by moving the position of the pedestal 16 (changing the interval between the lower surface 16A of the cutting board and the developing roll 11). Of course, the position where the toner density does not change at 4% in the figure is the most desirable position.

The above-described stable toner concentration detection process is repeated while adjusting the position of the pedestal 16 of the ear-cutting plate 17 as described above, and when the output from the toner sensor 15 is stabilized at a value substantially equal to the value at which the developer having the predetermined toner concentration is detected. If a position where the toner concentration of the developer becomes a predetermined toner concentration is found, and the developing device 10 is configured to follow the shape of the lower surface of the cutting board 17 of the pedestal 16 at the position, the developing device 10 The change in the density of the developer is small, so that the toner concentration can be grasped with high accuracy based on the magnetic permeability, and the toner concentration can be maintained with high accuracy by the toner replenishment control that is effective for the detection output of the toner sensor 15. The developing device 10 can be configured.

Incidentally, the developing device 10 used in the stable toner concentration detecting step is used.
Is a prototype jig which is configured so that the pressure applied to the toner can be variably adjusted by moving and adjusting the pedestal 16 of the scissor plate 17 to change the distance between the lower surface of the scissor plate 17 and the developing roll. After the configuration is set by the tool, the developing device 10 may be configured according to the configuration.

[Effects of the Invention] As described above, according to the toner concentration stable structure setting method of the developing device using the two-component developing method according to the present invention, it is possible to rationally search for a developing device configuration in which the density of the developer is small. With this configuration, the toner density can be maintained with high accuracy even by toner replenishment control based on the detection output of the toner sensor depending on the magnetic permeability, and the developing operation can be performed well. It can be realized as a developing device capable of performing the following.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a configuration in which the configuration of a developing device is set using a toner density stable structure setting method of a developing device using a two-component developing method according to the present invention, and FIG. FIG. 3 is a flowchart showing the control of the developing device, and FIG. 4 is a graph showing the relationship between the pressure under the ear cutting plate and the toner concentration. 10 Developing device 15 Toner sensor 16 Pedestal 16A Bottom surface of cutting board 17… Cutting board

Claims (1)

(57) [Claims] 1. A developing device using a two-component developer composed of a toner and a carrier, comprising a toner sensor for detecting a toner density, and having a toner density detection value detected by the toner sensor. A developing roll for adsorbing the developer and transporting the developer to a development area, and a spike for controlling the amount of the developer adsorbed to the developing roll, including a replenishing means for replenishing a fixed amount of toner when the amount becomes equal to or less than a set value. In a developing device having a cutting plate, a toner and a carrier are charged with a developer prepared to have a predetermined toner concentration, and the developing device is operated for a predetermined time. After idling until stable, the developer is sampled, and the measured toner concentration of the sampled developer is compared with the predetermined toner concentration. Accordingly, the pressure under the scribing plate with respect to the developing roll is changed, and the series of operations are repeated until the measured value and the predetermined toner concentration become substantially the same, whereby the scribing with respect to the developing roll is performed. A method for setting a stable toner concentration structure of a developing device using a two-component developing method, wherein a pressure under the plate is determined.