JPS6310176A - Toner density control mechanism - Google Patents

Abstract

PURPOSE:To susceptibly respond against a drop of a toner density by providing a density detecting sensor on both sides in the axial direction of a photosensitive drum, supplying a toner to a developing tank, based on a result of detection, and also, carrying a supplied developer at a high speed until the toner density is restored. CONSTITUTION:Toner density detecting sensors 51, 52 are attached adjacently to both end parts of the lower end part of a photosensitive drum side of a case 50 of a cleaning device 5, and detect density of a toner which adheres to a reference latent image of a prescribed potential formed on the photosensitive drum every time prior to a copying operation. Subsequently, a signal corresponding to each toner density which has been detected is inputted as a voltage value to a comparing input terminal of comparators 61a, 61b, and compared with a reference voltage. In case when the toner density is below a reference density, a motor 63 is driven and a toner is replenished, and also, a motor 32 rotates at a high speed and drives a first and a second screws 27, 28 at a high speed. In this way, a fall of the toner density is obviated quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a toner concentration control mechanism for copying machines and the like.

(Prior Art) Conventionally, as one aspect of an electrophotographic copying machine, two adjacent developer conveyance paths are formed in a developer tank, and developer conveyance means such as a screw is provided in each of these conveyance paths. It has been proposed that a developer consisting of carrier and toner is mixed and stirred by a means and circulated through a conveyance path, thereby providing toner with excellent chargeability for development.

In order to control the concentration of toner replenished into the developer tank, a toner concentration detection sensor is mounted on a cleaning device or the like provided on the side of the photoreceptor drum, and is mounted close to and facing the center of the photoreceptor drum. A reference latent image of a constant potential is formed on the surface of the photoreceptor drum each time before image formation, and after this is developed, the toner density adhering to the reference latent image is detected by the toner density detection sensor. Based on the results, drive the toner replenishment roller to keep the toner concentration in the developer in the developer tank constant M11#? I try to do that.

(Problems to be Solved by the Invention) However, in the above-mentioned apparatus, since the developer is configured to be conveyed in circulation as described above, the conveyance path is long, and the toner concentration is detected at the center of the photoreceptor drum. Because the path from the toner replenishment unit to the toner concentration detection sensor is long, if the toner concentration detection sensor determines that the toner concentration does not meet the standard value, the toner replenishment operation is started and then the toner is refilled. It takes a considerable amount of time for the toner to reach the toner concentration detection sensor.

As a result, by the time the toner concentration detection sensor has confirmed that the toner concentration has reached the reference level and the toner replenishment operation is stopped, a considerable amount of toner has already been oversupplied into the developer tank, causing fog on the image. There have been problems in that it causes dust spots and powder smoke that contaminates peripheral equipment.

In addition, if a document with uneven images or a large number of reduced copies are copied in succession, and these images are located downstream of the toner concentration detection sensor in the developer transport direction, the toner in this area may There have been problems in that the decrease in density cannot be detected immediately, the timing of starting the toner replenishment operation is delayed, and the copied image becomes unclear.

(Means for solving the problems) The present invention has been made to solve the problems mentioned above.
Toner concentration detection means are located at least on both ends of the electrostatic latent image carrier in the axial direction, and the toner concentration obtained by the toner concentration detection means is determined to be high or low relative to a predetermined reference value, and the result is also determined. and a control mechanism that supplies toner to the conveyance path and rotates the conveyance means at high speed while toner is being supplied.

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

Fig. 1 shows the photosensitive drum (1) and the developing unit of a copying machine. , transfer charger (3), one separation charger (4), cleaning device (5), and eraser lamp (6).

A charger (7) and an exposure slit (8) are sequentially arranged.

That is, while the photosensitive drum (1) rotates counterclockwise, its surface is charged with a predetermined polarity and potential by the charger (7), and an exposure slit ( 8) the 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 (P) is fed to the right one by one from the paper feed section at the lower left, and is conveyed to the transfer area in time with the image on the photoreceptor drum (1), and then transferred to the transfer charger (3). )
The toner image is transferred by the discharge. Thereafter, the copy paper (P) separated from the photoreceptor drum (1) by the separation charger (4) is conveyed to a fixing step (not shown) through a conveyor belt (9), where the toner image is fixed, and is placed on a tray. be discharged.

The photosensitive drum (1) continues to rotate, residual toner is removed by a cleaning device (5), and residual charges are erased by light irradiation from an eraser lamp (6), in preparation for the next copy.

Next, the configuration of the developing device (2) and its toner density control mechanism will be described in detail.

Developing department! ! In (2), (21) is a developer tank, and at the rear of the inner surface of this developer tank (21) is a transport path (25) partitioned by a partition plate (24) rising from the bottom of the developer tank (21). , (26) are formed, and a conveyance path (25
) is parallel to the photoreceptor drum (1), and the transport path (2
6) are slightly inclined so that they are higher at the bottom and lower at the top in Fig. 2, and these transport paths (25), (26)
) are openings (24a) provided at both ends of the partition plate (24).
, (24b).

A developing sleeve (22) is provided on the side of the photoreceptor drum (1) in the developer tank (21) in close proximity to the photoreceptor drum (1), and a motor (22) provided on the side of the developer tank (21) 31), and is rotatably driven in the direction of arrow (b), and is provided with a fixed magnetic roller (23) inside which is sequentially magnetized with an S pole and an N pole in the circumferential direction for rolling in the axial direction.

Conveyance path (25) located behind the developing sleeve (22)
, (2B) are provided with a first screw (27) and a second screw (28), respectively.

These first screw (27) and second screw (28) are operated by a motor (
32X (see Figure 2), the first screw (27)
is in the direction of arrow (c), and the second screw (28) is in the direction of arrow (c).
d) The rotational speed is high (
There are two speeds: vh) and low speed (vQ), and the switching is controlled by a control device (60) described below.

A toner hopper (40) is installed directly above the developing device (2), and a groove (41) with a U-shaped cross section that projects downward is formed at the bottom of the toner hopper (40).
41), a toner supply screw (42) is attached so that it can be rotated in the direction of arrow (e) by a motor (63) shown in FIG. Note that the motor (63) is driven and controlled by a control device (60) described below. Further, the groove portion (41) is connected to the conveyance path (26) by a drop guide (not shown).
).

Further, inside the toner hopper (40) is a stirring frame (43a).
) and (43b) are rotatably mounted to prevent cross-linking development, blocking, etc. of the replenishing toner.

Toner concentration detection sensor (51), (52 is the case (50) of the cleaning device (5) as shown in FIG.
The upper end of the photoreceptor drum (1) side of the photoreceptor drum (1)
They are mounted close to both ends of the photoreceptor drum (1) to detect the toner density adhering to a constant potential reference latent image formed on the photoreceptor drum (1) each time prior to each copying operation.

The general operation of the developing device (2) will be described below.

First, the motor (6) is driven by a signal from the control device (60).
3) is driven, the toner supply screw (42) rotates in the direction of arrow (e) and supplies the toner in the toner hopper to the conveyance path (26) via the falling guide.

The toner fed into the conveyance path (26) is mixed with the developer conveyed from the conveyance path (25) through the opening (24b) based on the rotation of the second screw (28) in the direction of arrow (d). It is conveyed in the direction of arrow (D) while being mixed and stirred,
The developer that has reached the end is sent into the transport path (25) through the opening (24a). In the conveyance path (25), the developer is conveyed in the direction of arrow (C) by the first screw (27), and a portion of the developer is supplied to the surface of the developing sleeve (22).

In addition, when the developer that has not been supplied to the developing sleeve (22) reaches the end of the conveyance path (25), it passes through the opening (24b).
It is sent into the conveyance path (26) via the conveyance path (26).

Thereafter, the same operation is repeated, and the developer is transferred to the conveyance path (25).
, (26).

Note that the developer supplied to the surface of the developing sleeve (22) is transferred to the magnetic roller (2) provided inside the developing sleeve (22).
While being held on the surface of the developing sleeve (22) by the magnetic force of (3), the photosensitive drum (22) rotates in the direction of arrow (b) in the developing area facing the photosensitive drum (1). 1) Develop the electrostatic latent image formed on the surface.

Next, the toner density control mechanism and toner density control operation will be explained.

FIG. 4 is a circuit diagram of the control device (60), in which the signals corresponding to the toner concentrations (Ti) and (TD) detected by the toner degree detection sensors (51) and (52) are expressed as voltage values. By manually inputting the comparison input terminals of the comparators (61a) and (6lb) and comparing them with the base voltage inputted from another reference input terminal, the respective toner densities (Ti) and r (1), the central control unit (62
) is done manually.

The central control device (62) is a comparator ('61a).

Based on the signal input from (6tb), the motor (63) is driven according to the control mode shown in the table below.
26) as well as supplying toner to the motor.

The first screw (27) and the second screw (28) are rotated by driving the screw (32) to mix and stir the developer while conveying it.

In addition, in the table below, rHJ is toner concentration (Ti)
or (T D is higher than the reference level (To) < (T
i.

Tj>To), rLJ is conversely low (Ti, T
j<To).

In other words, before copying a document, light from an exposure lamp is irradiated onto a standard pattern provided on the main body of the copying machine.
) on which a reference latent image is formed.

After the reference latent image is developed by the developing device (2), the toner density (Ti) and (TD) are detected by the toner density detection sensors (51) and (52), and this detection signal is converted into a voltage value. is inputted to the comparators (61a) and (6th), where it is compared with the reference voltage, and a signal indicating whether or not the toner density is insufficient with respect to the reference density (To) value is sent manually to the central controller (62). be done.

(i) Control mode■ Then, if the toner concentration (T i) and (T D detected by the toner concentration detection sensors (51) and (52) are both higher than the reference concentration (T o), (Ti, '
rj>To), toner is not replenished and a normal developing operation is performed. During this time, the first screw (27) and the second screw (28) rotate at low speed (V12).

(ii) If either control mode ■ or ■ does not reach the standard concentration (To) (T
+ < T o or T j < T o ), the motor (65) is driven and the toner replenishment operation is started, and the first screw (27) and the second screw (28) are driven at high speed by the motor (32). Rotate with (Vh),
To quickly replenish toner to a location where the toner density has decreased to restore the toner concentration to a normal state and prevent a decrease in image density.

After that, toner concentration detection sensors (51) and (52)
), when it is detected that the toner concentration (T i) and (TD) have recovered to the reference concentration (TO) or higher, the motor (
32) returns to the normal low speed (vi2), and the normal developer conveying operation is performed.

Note that when the screws (27) and (2B) are rotated at high speed, stress is applied to the developer, but since the time for rotating at high speed is limited, this does not pose a particular problem.

(iii) Control mode■ Both toner density (Ti) and (TD) are set to the reference density (T
. ) In the following cases, the motor (63) is driven to replenish toner, and the motor (32) rotates at high speed to supply the first screw (
27), the second screw (28) is driven at high speed (Vh), and the decrease in toner concentration is quickly resolved.

After that, both the toner concentration (Ti) and (TD) detected by the sensors (51) and (52) are set to the reference concentration ('r o
) If it is determined that the control mode is above (2), the control mode (3) is entered, the toner replenishment operation is stopped, and the first screw (27) and second screw (28) rotate at a low speed (VI2).

By the way, the image to be copied is detected by the toner density detection sensor (51
), (52), and even when a large number of copies are made in succession, the sensor (52) located on the downstream side in the developer conveyance direction in the conveyance path (25) detects the decrease in toner. Detects immediately and replenishes toner. Moreover, since the developer and the replenished toner are transported at high speed until the toner concentration (Ti) and (TD are restored to the reference concentration ('r o)), the recovery speed of the developer concentration becomes faster and the excess toner is removed. It does not cause any condition.

In addition, in the embodiment, the toner concentration detection sensor (51)
, (52) are attached to the cleaning device (5), but the present invention is not limited to this, and they may be attached anywhere between the developing device (2) and the cleaning device (5).

In addition, the photoreceptor drum (1) is used as a toner concentration detection sensor.
Although the density of the reference latent image formed thereon is detected, a sensor that directly detects the toner density may be attached behind the developing sleeve (22) in the developing tank (2I).

Further, although two toner concentration detection sensors (51) and (52) are provided at both ends of the photoreceptor drum (1), the present invention is not limited to this. They may be provided, or the number may be further increased if necessary.

(Effects of the Invention) As is clear from the above description, the toner concentration control mechanism according to the present invention has at least two toner concentration detection sensors positioned at least on both sides of the photoreceptor drum in the axial direction. Based on the result detected by the sensor, toner is supplied to the developer tank, and the supplied developer is transported at high speed until the toner concentration is restored.

Therefore, it is possible to respond sensitively to a decrease in toner concentration, and since an appropriate amount of toner is supplied to the developer tank in response to a decrease in toner concentration, fogging and spots do not occur on images due to oversupply of toner. There is no possibility that peripheral equipment will be contaminated by the generation of powder smoke.

In addition, no matter how uneven the image pattern is copied, a drop in toner density is detected early and toner is replenished, thereby preventing an extreme drop in toner density due to response delay. Can be done.

In other words, it is possible to make fine adjustments to the toner density by reducing the fluctuation range of the toner density, and to obtain an image with a stable density.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a photoreceptor section and a developing section of a copying machine, etc.;
FIG. 2 is a cross-sectional view of the developing device, FIG. 3 is a perspective view showing the arrangement of toner concentration detection sensors, and FIG. 4 is a perspective view showing a circuit diagram showing the internal circuit of the control device. ! ... Photosensitive drum, 2... Developing device, 25.26... Conveyance path, 27...
・First screen, 28...Second screen, 51.
52.53... Toner concentration detection sensor, 60... Control device. Patent applicant Minolta Camera Co., Ltd. Agent
Person Patent attorney Aoyama Ao and 2 others 11L2WJ Figure 4, 3m! 1

Claims (1)

[Claims] (1) Two adjacent transport paths are each provided with a rotationally driven transport means, and the developer is circulated and transported in the transport path, and a part of the developer is supplied to a developing sleeve to face the electrostatic latent image carrier. In a copying machine equipped with a developing device configured to transport the electrostatic latent image carrier, toner concentration detection means are located at least on both ends of the electrostatic latent image carrier in the axial direction; a control mechanism that determines whether the toner concentration is high or low relative to a predetermined reference value, replenishes the conveying path with toner based on the result, and drives the conveying means at high speed while the toner is being supplied; A toner density control mechanism characterized by having: