JPS62226172A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To perform close toner control with small variation width of image density, to stabilize image quality, and to prevent an image from fogging and being stained owing to the excessive supply of toner by providing a toner concentration detecting means nearby a toner supply part and on the downstream side in the conveyance direction of a developer and controlling the driving of a toner supply means based on the obtained result. CONSTITUTION:A developer while mixed and agitated through the rotation of a front spiral 27 and a rear spiral 28 is conveyed in conveyance paths 25 and 26 by circulation and part of the developer is supplied to a developing sleeve 22, held on the surface of a developing sleeve 22 with the magnetic force of a magnetic roller 23, and conveyed to a development area X facing a photosensitive drum 1, so that it is used for development. If a toner concentration detection sensor S which detects toner concentration at all times detects the toner concentration falling below a specific control level during developing operation, a motor is driven with a toner supply signal from a control means 60 to supply toner to the upstream side of the conveyance path 26.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electrostatic latent image developing method used for developing an electrostatic latent image formed on the surface of an electrostatic latent image carrier in an electrophotographic process or the like. The present invention relates to an apparatus, and in particular to a means for controlling toner concentration thereof.

(Prior Art) Generally, in this type of electrostatic latent image developing device that uses a two-component developer such as a mixture of toner and carrier, new It is necessary to replenish toner.

Therefore, various automatic toner density control devices have been provided in the past. The main thing is to detect the toner concentration of the developer in the developing device, compare this detected value with a reference value corresponding to a preset standard toner concentration, and if the former is lower than the latter, the toner The toner is configured to operate the replenishing means to replenish new toner.

For example, as described in Japanese Patent Publication No. 52-123242, a detection element is brought close to at least one surface of the developer rotating in a substantially belt-like manner in the developing device, and the toner is mixed without interfering with the flow of the developer. 1. The ratio is detected as a change in magnetic permeability of the developer based on a change in the mixing ratio. Tachino is known.

(Problems to be Solved by the Invention) By the way, in a developing device in which the toner concentration detection position and the toner replenishment position are different as described in the above-mentioned publication, the toner concentration is detected at the same time as in the past. When replenishing, the following problems arise.

In other words, in reality, there is a slight time lag between the developer whose toner concentration is detected to be low and when it is transported to the replenishment section and the developer whose toner has been replenished reaches the detection position. There have been problems in that the toner concentration distribution of the developer in the conveyance path varies widely, the image quality becomes unstable, and the toner is oversupplied, resulting in powder smoke, bumps, fog, and the like.

(Means for Solving the Problems) - In order to solve the above problems, the electrostatic latent image developing device according to the present invention has the following features: (b) a developer conveying means that circulates and conveys the developer from the toner replenishing section to the developing means and from the developing means to the toner replenishing section while mixing and stirring; (c) a developer conveying means that transports new toner to the toner replenishing section; a toner replenishing means for replenishing the toner replenishing section; (d) a toner concentration detecting means provided near the toner replenishing section and on the downstream side in the developer conveying direction; and (e) a toner concentration detecting means that and control means for controlling the driving of the toner replenishing means based on the results obtained.

(Example) Hereinafter, the present invention will be described based on the accompanying drawings which are one example.

Figure 1 shows the photoreceptor section and developing section of an electrophotographic copying machine.A photoreceptor drum (1) is installed in the center so as to be rotatable in the counterclockwise direction (direction of arrow (a)), and around it , developing device (2), transfer charger (3), separation charger (4), residual toner cleaner (5), residual charge eraser lamp (6), charging charger (7), and exposure slit (8) are arranged in sequence. has been done.

That is, while the photoreceptor drum (1) rotates counterclockwise, its surface is charged with a predetermined polarity and potential by the charger (7), and the exposure slit (8) is applied from the scanning projection system. ) through which the original image is exposed. The electrostatic latent image formed here is developed by a developing device (2) and reaches the transfer area.

On the other hand, the copy paper is fed one by one from the lower left to the right, and is conveyed to the transfer area in time with the image on the photoreceptor drum (1), and the toner is toned by the discharge of the transfer charger (3). The image is transferred. After that, the copy paper is transferred to the conveyor belt (
9), the toner image is conveyed to a fixing device (not shown), the toner image is fixed thereon, and the toner image is discharged onto a tray.

The photoreceptor drum (1) continues to rotate, and the cleaner (5)
The residual toner is removed by the blade (5a), and the residual charge is erased by light irradiation from the eraser lamp (6), in preparation for the next copying.

The developing device (2) will be described below with reference to FIGS. 1 and 2.

In the developing device (2), (21) is a developing tank, and this developing tank (21) is provided with a developing sleeve (22) facing the photoreceptor drum (1), and a magnetic roller ( 23) is housed in a fixed state.

At the rear of the developing sleeve (22), transport paths (25) and (26) are formed, rising from the bottom of the developing tank (21) and partitioned by partition plates (24) cut out on both sides. A spiral (27) and a back spiral (28) are provided.

Note that a toner replenishing section (40) is formed at one end of the rear conveyance path (26) (lower side in FIG. 2).

In this toner replenishment section (40), a toner replenishment path (41) is formed by expanding a part of the developer tank (21) outward, and the toner replenishment path (41) has a coaxial shaft with the rear spiral (28). A toner supply spiral (42) is arranged at.

One end of the toner supply spiral (42) is inserted into and supported by a bearing recess (not shown) formed coaxially with one end of the support shaft (28a) of the rear spiral (28).

Further, the developing sleeve (22) is connected to the motor (31) by a gear (
32) and (33), and can be rotated in the clockwise direction (arrow (b) direction) in FIG.
A developing bias applying means (not shown) is provided.

The front spiral (27) and the rear spiral (28) are connected and driven by a motor (34) through gears (35), (36), and (37), and the front spiral (27) is driven in a clockwise direction (
The rear spiral (28) rotates in synchronization with the counterclockwise direction (direction of arrow (d)), and the front spiral (27) rotates the developer in the direction of arrow (C).
) direction, the rear spiral (28) moves the developer in the direction of arrow (D).
By conveying the carrier and toner in the respective directions, the carrier and toner are mixed and stirred while being circulated and conveyed around the partition plate (24).

A toner replenishment spiral (42) provided coaxially with the rear spiral (28) is connected to a motor (43) and can be rotated counterclockwise (in the direction of arrow (e)).

A toner hopper (51) containing new toner, which serves as toner replenishment means, is installed directly above the toner replenishment section (40), and a stirring rod (51) is installed inside the toner hopper (51).
2) and (53) are rotatably mounted to prevent cross-linking development, blocking, etc. of the replenishing toner.

Although the toner replenishing section (40) and the toner hopper (50) are shown above the developing device (2) for explanation purposes in FIG. 1, they are actually located above the developing device (2) as shown in FIG. 2), and the toner supply spiral (42) in FIG. 1 and the rear spiral (28) are coaxial as described above.

A toner concentration detection sensor (S) is installed near the toner replenishment section (40) and on the downstream side in the developer conveyance direction, that is, on the upstream side of the conveyance path (26). The detection sensor (S) constantly detects the magnetic permeability of the developer being circulated in the developer tank (21) and outputs the value as an electric signal to the control means (60).

The control means (60) uses a reference voltage and a toner detection sensor (
By comparing the comparison voltage outputted from S), it is determined whether the toner concentration (Ia) at the detection position is higher or lower than the control level (■o). And toner concentration (
If Ia) is below the control level (to), the motor (4
3) to rotate the toner replenishment spiral (42) and transfer new toner in the toner hopper (51) to the conveyance path (2).
6), and the toner concentration (I a) reaches the control level (1
When it is confirmed that the toner has recovered to 0) or more, the toner supply spiral (42) is stopped. Note that the motor (43) rotates at a constant speed, and the amount of toner replenishment per unit time is constant.

Hereinafter, the operation of the developing device (2) having the above structure will be explained with reference to FIG.

In the developing device (2), when a print switch (not shown) is turned on, the motors (31) and (34) start rotating, and the developing sleeve (22), front spiral (27),
Rear spiral (28), arrow (b),
Rotationally driven in the directions (c) and (d).

Developer is front spiral (27), rear spiral (28)
The transport path (25) is mixed and stirred based on the rotation of the
, (26), and some of the developer is supplied to the developing sleeve (22) by the front spiral (27).

The developer supplied to the developing sleeve (22) is held on the surface of the developing sleeve (22) by the magnetic force of the magnetic roller (23), and as the developing sleeve (22) rotates, the developing agent faces the photosensitive drum (1). A portion of the toner is transported to area (X) and subjected to development.

The developer whose toner concentration has decreased after passing through the development area (X) is subsequently conveyed in the direction of arrow (b) as the development sleeve (22) rotates, and is separated when it reaches the part facing the front spiral (27). do. Instead, the developing sleeve (2
2), new developer is supplied again.

By repeatedly performing the above-described developing operation, the toner content ratio of the developer gradually decreases. During the developing operation, when the toner concentration detection sensor (S) that constantly detects the toner concentration detects that the toner concentration (Ia) has become below a predetermined control level (ro), (
In state (2), the motor (43) is driven based on a toner replenishment signal from the control means (60), and toner is replenished to the upstream side of the conveyance path (26).

Here, a toner supply section (40) and a toner detection sensor (S
), and the time required for new toner to reach the toner concentration detection sensor (S) after the toner concentration (Ia) is determined to be below the control level (to) is short. From this, toner is almost replenished to the area where the toner concentration has decreased.

Toner replenishment starts and new toner is transferred to the conveyance path (26
), the toner is mixed and agitated by the rear spiral (28) along with the developer sent from the conveyance path (25) to the conveyance path (26), and moves along the arrow (D).
) direction. Then, the toner Ω degree detection sensor (
S) (state ■), the toner concentration (Ia) detected by the sensor (S) gradually increases until the toner concentration (Ia) exceeds the predetermined control level (1,,). The motor (
43) and the toner replenishment spiral (42) are stopped, and the toner replenishment operation is stopped (■-shaped 1f3).

Even if the toner replenishment operation is stopped, there is a slight distance (Q) from the toner replenishment path (41) to the toner concentration detection sensor (S), so when replenishment is stopped, new toner existing between the toner concentration detection sensor (S) and the toner concentration detection sensor (S) The toner concentration (Ia) continues to increase until it passes the concentration detection sensor (S) (state of ■).

However, the distance (I2) between the toner supply path (41) and the toner concentration detection sensor (S) is short, and the toner concentration (I a)
When it is determined that the toner has recovered to the control level (r o) (state ■), the amount of toner being replenished between the toner supply path (41) and the toner concentration detection sensor (S) is small. The amount of increase is also small.

After that, the toner concentration (Ia) gradually decreases,
When the toner concentration detection sensor (S) detects the developer that has fallen below the control level (Io) again (state 2), the toner replenishment operation starts.

However, the toner concentration detection sensor (S) and toner supply path (
Since the distance (12) from 41) is short, from ■ to ■ is 1
The cycle of toner replenishment operations is carried out in a short period of time, and the fluctuation range of the toner concentration that moves up and down during this period is small, and is not so slow as to cause overtoning or poor image quality, and fine toner control is performed.

In this way, the new toner fed into the conveyance path (26) is mixed with the magnetic carrier and stirred, frictionally charged, and fed into the conveyance path (25) for development.

In the embodiment, the toner replenishing section (40) is connected to the conveyance path (26).
), but it is not limited to this.
As shown in FIGS. 4 and 5, a toner replenishing section (40) and a toner replenishing means (50) are provided above the conveyance path (26).
Alternatively, a toner may be attached to the conveyance path (26) so that the toner is directly dropped and replenished onto the conveyance path (26). In this way, the developing device (2
) can be made smaller, and miniaturization can be achieved.

Note that even in this case, the toner concentration detection sensor (S) is
It shall be provided near the toner supply path (4I) and on the downstream side.

Further, in the above embodiment, the toner concentration is detected by measuring the magnetic permeability based on the toner content ratio of the phenomenon agent, but the present invention is not limited to this.

That is, as shown in FIG. 6, even if a vibration sensor (Sl) is attached to the conveyance path (26) and the toner concentration is detected by utilizing the characteristic that the developer volume increases when the toner concentration increases. good.

Furthermore, a reflected light amount sensor (S,
) is provided, and a bias roller (82) to which a constant voltage is applied facing the conveyance path (26) is attached to the roller accommodation chamber (81), and a roller (82) attached to the bias roller (82) is provided. Toner amount sensor (S2
) to detect the toner concentration.

Furthermore, as shown in FIG. 8, the roller storage chamber (
A current detection means (
83) to detect the toner concentration by measuring the current when the toner adheres to the conductive roller (84).

In the above embodiment, the toner is supplied by a toner replenishment spiral (42
) was supposed to be replenished by rotating at a constant speed.
The invention is not limited to this, and the number of revolutions of the motor (43) may be varied to adjust the amount of replenishment per hour.

(Effects of the Invention) As is clear from the above description, the electrostatic latent image developing device according to the present invention circulates and transports the developer to sufficiently mix the developer.
Since the toner is stirred, frictional electrification between the toner and the carrier can be performed satisfactorily.

In addition, since the toner concentration detection sensor is installed near the toner replenishment section and on the downstream side in the developer transport direction, toner can be replenished almost close to the area where the toner concentration has decreased, and the toner concentration Since only a small amount of toner is replenished between the sensor and the toner replenishment unit after the detection sensor detects a toner concentration equal to or higher than the control level until toner replenishment is stopped, excessive toner replenishment will not occur. .

Therefore, it is possible to perform fine-grained toner control with less variation in image density, and the image quality is stabilized.
Fog and spots do not occur on images due to oversupply of toner, and furthermore, there is no possibility of polluting peripheral equipment due to the generation of powder smoke.

In addition, no matter how uneven the image pattern is developed, a drop in toner density is detected near the toner replenishment unit and downstream of the toner replenishment unit, and toner is replenished. It is possible to prevent the toner concentration from decreasing.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the electrostatic latent image developing device and photoreceptor portion according to the present invention, FIG. 2 is a cross-sectional view of the developer tank, FIG. 3 is a diagram showing the state of toner concentration control, and FIG. 4 to FIG. 8 are diagrams showing other embodiments of the developing device. l... Photosensitive drum, 2... Developing device, 22
...Developing sleeve, 23...Magnetic roller, 27
... Front spiral, 28 ... Back spiral, 4
0... Toner supply unit, 50... Toner supply means,
60...Control unit, S...Toner concentration detection sensor, X...Development area.

Claims (1)

[Claims] (1) A developing means for conveying a developer made of a mixture of toner and carrier to a developing area, and a circulating conveyance of the developer from a toner replenishing section to the developing means and from the developing means to the toner replenishing section while mixing and stirring. a toner replenishing means for replenishing the toner replenishing section with new toner; a toner concentration detecting means provided near the toner replenishing section and downstream in the developer transport direction; An electrostatic latent image developing device comprising: a control means for controlling driving of the toner replenishing means based on the result obtained by the density detecting means.