JPH02187781A - Developing device - Google Patents

Abstract

PURPOSE:To improve a copied image quality by providing a toner control means, replenishing toner based on a toner insufficiency signal only when stirring can be possible in a developing tank and securing the uniform concentration of the developer. CONSTITUTION:The toner concentration is detected by a toner concentration detecting means 28 on the way that the developing roller 22 is supplied with the developer. In response to the detection output, the control for replenishing from a toner replenishing tank to the developing tank is performed in a toner replenishing means 55. And the result detected by the detecting means 28 is stored in a storage means 59, when the toner is insufficient at the acting time of copying, the toner insufficiency signal is transmitted to the replenishing means 55 by the storage means 59. Then, the replenishing means 55 is controlled by a toner control means 61 so as to replenish the toner only when stirring can be possible in the developing tank. Thus, the uniform concentration of the developer can be maintained and the copied image quality can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a developing device for a copying machine for developing, for example, an electrostatic latent image formed on a recording medium, and can also be applied to a laser printer.

<Prior Art> Copying machines and the like are equipped with a developing device that attaches toner made of colored pigments to the electrostatic latent image in order to visualize the electrostatic latent image formed on a recording medium such as a photoreceptor. ing. Furthermore, copying machines and the like are equipped with a plurality of developing devices each containing toner of each color in order to make the electrostatic latent image not only black but also colored, and these developing devices are selectively used. For example, when forming a full color image, a developing device containing cyan, magenta, yellow, and, if necessary, black toner is provided, and the electrostatic potential on the recording medium is separated through a filter for each color. The image is developed with toner of each color, and the toners of each color are superimposed on transfer paper to obtain a full-color copy image.

<Problems to be Solved by the Invention> In the case of the above-mentioned full-color copying machine, ■The time required for the developing device to be driven per copy is extremely short, approximately 3 seconds, and the toner density is detected and toner replenishment is performed within that time. It was difficult to do so.

Therefore, it may be possible to configure a system that allows toner to be replenished into the stopped developing tank even after the developing device stops, but in this case, the supplied toner is not stirred and the developer concentration in the developing tank becomes uneven, resulting in copying. This will significantly reduce image quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that can solve the above problems, ensure uniform developer concentration, and improve copy image quality.

<Means for Solving the Problem> The problem solving means according to the present invention includes a toner concentration detection means 28 for detecting the concentration of toner in the developer tank 7, and a toner supply tank 20 based on a detection signal of the toner concentration detection means 28. The developing device includes a toner replenishing means 55 for replenishing toner from the toner to the developing tank 7, a storage means 59 for storing the detection result of the toner concentration detection means 28, and a toner shortage signal of the storage means 59 at the time of the next copying operation. The toner control means 61 outputs a toner replenishment signal to the toner replenishment means 55 based on the toner replenishment means 55.

Effects> In the above-mentioned means for solving the problem, the toner concentration detection means is controlled to turn on while the developer is being supplied to the developing roller 22.

<Embodiment> An embodiment in which a developing device according to the present invention is used in a full-color copying machine will be described below with reference to FIGS. 1 to 7.

Fig. 1 is a functional block diagram of a developing device of a copying machine showing an embodiment of the present invention, Fig. 2 is a chart showing the drive timing of each member, Fig. 3 is a configuration diagram showing the electrophotographic process, and Fig. 4 5 is a sectional view of the developer tank, FIG. 5 is a perspective view of the stirring roller, FIG. 6 is a sectional view of the clutch, and FIG. 7 is a front view of the shutter switching means.

First, an overview of a full-color copying machine will be explained. As shown in FIG. A plurality of developer tanks 4, 5, 6.7 are arranged close to 3 and can be switched between a developing position and a non-developing position; 3
The toner density is detected by the endless belt-shaped intermediate transfer body 11 that is in contact with the intermediate transfer body 11 and the other drive port 28 . In response to this detection output, toner is controlled to be replenished from the supply tank 20 into the developer tank 7 .

Conventionally, the operation timing is such that the toner concentration is detected by D in FIG. 2, and if the signal is, for example, I-right, toner is immediately replenished by the replenishing means 55 as shown in E in FIG.

However, even after the developing device stops (after the first and second stirring rollers 24 and 25 stop), the toner motor continues to rotate the replenishment roller 55, so the toner that is replenished during t2 in FIG. is not stirred.

Therefore, it is conceivable to extend the driving time of the first agitating roller shown in B in FIG. 2, but in this case, extra stress will be applied to the developer and the life of the developer will be shortened.

Therefore, in the present invention, if the signal from the toner concentration detection means 28 is High as shown in D in FIG. 2, the developer will form spikes during the next development cycle as shown in F in FIG. The main charger I2 located on the side of the main charger I2
and a first transfer charger 13 disposed on the intermediate transfer body 11;
A second transfer charger 15 is provided below the transfer paper conveyed to the intermediate transfer member 11, and a cleaning blade 16 is provided below the photoreceptor 3. In addition, in Figure 3,
17 is a paper feeding device, 18 is a fixing device, and 19 is an exposure device. Further, a supply tank 20 is arranged above each of the developer tanks 4 to 7.

Since each of the developer tanks 4 to 7 has the same structure, the developer tank 7
We will explain its structure. As shown in FIG. 4, the developing tank 7 includes a developing roller 22 rotatably disposed in an opening for transferring toner to the photoreceptor 3, and a developer conveying roller rotatably disposed above the developing roller 22. a roller 23 , a first stirring roller 24 for stirring the developer scraped off from the conveyance roller 23 , and a second stirring roller 24 for stirring the developer from the first stirring roller 24 and supplying it to the developing roller 22 roller 2
5 is installed inside. Further, in the developing tank 7, a doctor 2 is disposed at a constant distance from the developing roller 22.
7, a toner concentration sensor 28 as a toner concentration detection means for detecting the concentration of developer, and the developing roller 22,
A developer circulation partition member 29 disposed between the conveyance roller 23, the first stirring roller 24, and the second stirring roller 25 is installed inside.

The developing roller 22 includes a magnet body 22a that is fixed to the developer tank 7 and has a magnet whose outer circumference is magnetized to each pole, and a cylinder that is loosely fitted into the magnet body 22a and rotatably supported by the developer tank 7. It consists of an aluminum non-magnetic sleeve 22b having a shape. The conveying roller 23 is also constructed in the same manner as the developing roller 22.

The first stirring roller 24 and the second stirring roller 25 are
A central shaft 30 is rotatably supported in each developer tank 7, and as shown in FIG. 5, a plurality of stirring fins 31 are spirally arranged around the central shaft 30.

The toner is stored in a replenishment tank 20 above the developer tank 7, and is supplied to the vicinity of the first stirring roller 24 in accordance with a command from the developer toner concentration sensor 28. Solenoid 44 for opening and closing the shutter and the arm 43
and a spring 45 that urges the nail in the direction of engagement.

The spring clutch 39 is connected to the center shaft 30 as shown in FIG.
The boss portion 46 and the shaft portion 37 of the flange 37 are fixed to the
A coil spring 47 is wound between the spring 47 and the clutch cover 40. One end of the spring 47 is fixed to the notch 40a of the clutch cover 40 arranged around the outer periphery of the spring 47, and the other end of the spring 47 is fixed to the notch 40a of the clutch cover 40 arranged around the outer periphery of the spring 47. It is fixed to the shaft portion 37a. The spring 47 is wound in a direction that tightens the boss portion 46, but when the clutch cover 40 is braked (rotation restricted state), it is moved away from the boss portion 46, that is, in a loosened state, and the center shaft 3
It has a structure that does not transmit zero rotational force.

The arm 43 has a central portion attached to a shaft 48 on the outer wall surface of the developer tank 7.
A stopper 49 is formed at the tip to engage with the pawls 41 and 42 of the clutch cover 40, and the developer mixed and stirred with the solenoid 4 is transferred to the second stopper 49. The stirring roller 25 is reached.

The second stirring roller 25 has an opening/closing device 3 that controls supply of the developer on the first stirring roller 24 side to the developing roller 22.
5, and a switching means 36 for switching the opening/closing device 35 between an open state and a closed state.

As shown in FIGS. 5 and 6, the opening/closing device 35 is connected to the second stirring roller 2.
5, a pair of arc-shaped shutters 38 fixed to the outer periphery of the flange 37 at points symmetrical positions with respect to the central axis 30; A pair of arcuate openings 38a are formed between the shutters 38.

As shown in FIG. 6.7, the switching means 36 includes a spring clutch 39 provided at the end of the central shaft 30, and a spring clutch 39 provided at the end of the central shaft 30.
9 at equal intervals on the outer peripheral surface of the cylindrical clutch cover 40 (9
A swinging arm 43 that removably engages with four claws 41 and 42 arranged at intervals of 0° and a plunger 50 that does not forcibly rotate the arm 43 in the claw release direction are connected. ing.

The clutch cover 40 also includes a protruding piece 52 that protrudes in the radial direction of the central shaft 30 in accordance with the position of the shutter 38.
A shutter position detection switch 53 is provided in the developer tank 7 and is turned on by the protrusion 52 . Further, a drive gear 54 to which rotational force is transmitted is fixed to the end of the central shaft 30 opposite to the spring clutch 39, and rotates the stirring roller 25 in a fixed direction.

In the replenishing tank 20, as shown in FIG. 4, a replenishing roller 55 serving as a toner replenishing means for replenishing toner into the developer tank 7 is disposed at a replenishing port 56. Power is transmitted to the supply roller 55 from the copying machine main body side through a gear (not shown) fixed to the end of the roller shaft.

Further, the developing roller 22, the conveyance roller 23, the first and second stirring rollers 24. , 25, power is also transmitted from the copying machine main body side through gears at the ends of each of them.

In this example, these are collectively referred to as a developing section driving means 57 as shown in FIG.

The developing unit driving means 57 and the toner replenishing means 55
The control unit 58 includes a storage unit 59 that stores the detection result of the toner concentration detection unit 28, and a toner shortage signal of the storage unit 59 based on an output signal from the copy start unit IO during the next copying operation. A toner control means 61 for outputting a toner replenishment signal to the toner replenishment means 55 is provided.

The control unit 58 is a general one-deep microcomputer, and has a data RAM inside.

It has a program ROM, CPU, etc. Then, the toner control means 61 rotates the replenishment roller 55 for a predetermined time t3 at the timing shown in FIG. 2 to replenish toner.

The copying operation in the above configuration will be explained.

When the copy switch is turned on, the photoreceptor 3 rotates at a constant circumferential speed as indicated by the arrow in FIG. After being charged and exposed by the main charger 12, the spike of developer in the developer tank 7, which is set in a developing position according to the purpose, is brought into contact with the photoreceptor 3 to perform development. Note that the spring 47 moves toward the central axis 30 depending on whether the photoreceptor 3 is present or not.
The shutter 38 rotates and opens so that the developer is supplied to the developing roller 22.

The solenoid 44 is de-energized before the arm 43 passes over the pawl 41 and engages the next pawl 42 .

As a result, the tip of the arm 43 engages with the next claw 42, the spring 47 is loosened, and the shutter 38 stops rotating, maintaining the open position.

Then, the developer is supplied to the developing roller 22, and after the development is completed, it is sent to the conveying roller 23 according to the rotation of the developing roller 22, and is further conveyed upward by the conveying roller 23, and is again passed along the scraping plate 26. It is circulated and supplied to the second stirring roller 25.

Thereafter, when the development of the photoreceptor 3 is completed and the development by the developing device is no longer necessary, the solenoid 44 is energized to stop the supply of developer as shown in FIG.
3 is disengaged from the claws 41 and 42, the shutter 38 is rotated via the spring clutch 39 to the closed position, and the ears of the developer tanks 4 to 7 are closed to the opening/closing device 3 during developer development.
5, it is not formed on the developing roller 22.

The developed toner image moves in the direction of the arrow and is transferred onto the transfer intermediate 11 by the first transfer charger 13. after that,
After being transferred onto the transfer paper in the direction of the arrow by the second transfer charger 15, it is fixed.

When the developer tank 7 is used for development, it is necessary to open the path for supplying the developer to the developing roller 22.

Therefore, in accordance with the rotation of the developing roller 22 (rotation of the sleeve), the various rollers also rotate at the timing shown in FIG. 2. The developer is supplied to the developing roller 22 by the shutter 38.
This is done by opening the .

That is, as shown in FIG. 2, when the second stirring roller 25 is rotated, the rotational force of the central shaft 30 is transmitted to the shutter 38 via the spring clutch 39 in response. At this time, if the solenoid 44 that opens and closes the shutter 38 is energized at the timing shown in FIG. 2, the arm 4 will open and close as shown in FIG.
3 clockwise (direction P), the engagement between the end stopper 49 of the arm 43 and the claw 41 is released, and the rotation of the central shaft 30 stops the supply to the roller 22.

By the way, while the developer is being supplied to the developing roller 22, the toner concentration is detected by the toner concentration sensor 28. In response to this detection output, toner is controlled to be replenished from the supply tank 20 into the developer tank 7 .

Conventionally, the operation timing is such that the toner concentration is detected by D in FIG. 2, and if the signal is, for example, High,
Immediately rotate the replenishment roller 55 as shown in E in FIG.
Toner was being replenished for a specified period of time.

However, even after the developing device stops (after the first and second stirring rollers 24 and 25 stop), the toner motor continues to rotate the replenishment roller 55, so the replenishment occurs between t2 in FIG. Toner is not agitated.

In order to solve this problem, it may be possible to extend the driving time of the stirring port B in Fig. 2, but in this case,
This puts extra stress on the developer and shortens its lifespan.

Therefore, in the present invention, if the signal from the toner density sensor 28 is High as shown in D in FIG. 2, the developer will form spikes as shown in F in FIG. 2 during the next development cycle. , and the toner is controlled to be replenished at the same time within the time period tl in which stirring is possible. By doing so, the above-mentioned problems can be solved.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, the photoreceptor 3 is not limited to the belt-shaped one as in the above embodiment, but may be drum-shaped.

Further, the number of developer tanks is not limited to a plurality of developer tanks, and the present invention may be applied to one developer tank.

<Effects of the Invention> As is clear from the above description, according to the present invention, a toner control means is provided which outputs a toner replenishment signal to the toner replenishment means based on the toner shortage signal of the storage means during the next copying operation. By replenishing toner only when the developer tank is in an agitable state, it is possible to maintain a more uniform developer concentration, which has the excellent effect of improving copy image quality.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of a developing device of a copying machine showing an embodiment of the present invention, FIG. 2 is a chart showing the drive timing of each member, and FIG. 3 is a configuration showing the electrophotographic process of the developing device of a copying machine. 4 is a sectional view of the developer tank, FIG. 5 is a perspective view of the stirring roller, FIG. 6 is a sectional view of the clutch, and FIG. 7 is a front view of the shutter switching means. 7; developer tank, 20: toner supply tank, 28; toner concentration detection means, 55: toner supply means, 59; storage means, 60
: copy start means, 61: toner control means. Applicant Sharp Corporation

Claims (1)

[Claims] A developing device comprising: a toner concentration detection means for detecting the concentration of toner in a developer tank; and a toner replenishment means for replenishing toner from a toner supply tank to the developer tank based on a detection signal from the toner concentration detection means; The invention is characterized by being provided with a storage means for storing the detection result of the density detection means, and a toner control means for outputting a toner replenishment signal to the toner replenishment means based on a toner shortage signal from the storage means during the next copying operation. developing device.