JPS59113463A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To automate the supplementation of toner to a developer by providing a variable bias electric power source which generates a potential difference between a nonmagnetic sleeve and a toner supply roller which is controlled on the basis of a detection signal from a detecting means. CONSTITUTION:A developing device inputs the detection signal from the detecting element 27 to a control circuit 28 and controls the variable bias power source 29 which applies a bias voltage between the nonmagnetic sleeve 22 and toner supply roller 23 on the bais of the output signal of the control circuit. Then, one power source 31 of the variable bias power source 29 is a bias power source which applies the toner supply roller with a positive low potential (or negative potential) viewed from the nonmagnetic sleeve and the other power source 32 is a bias power source which applies a positive high potential. Consequently, the supplementation of the toner to the developer is performed automatically by adjusting the variable bias power source.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a developing device for forming a toner image by applying a magnetic two-component developer consisting of a magnetic carrier and a toner to an electrostatic latent image formed on a charge holding member. Regarding.

FIG. 1 is a schematic diagram showing an example of the configuration of an electrostatic latent image developing device that forms a toner image using a conventional magnetic two-component developer.

In the figure, reference numeral 1 denotes a charge retaining member such as an electrophotographic photoreceptor or an electrostatic recording medium, on the surface of which an electrostatic latent image is formed. 2
3 is a fixed magnetic roller, and 3 is a non-magnetic sleeve, which is disposed so as to surround the magnetic roller 2 and is supported to rotate in the direction of the arrow.

Reference numeral 4 denotes a scraper that removes developer (not shown) held on the non-magnetic sleeve 3 from the sleeve 3 and also serves as a guide plate at that time.

5 is a stirring blade, 6 is a doctor blade, 7 is a toner replenishment roller, 8 is a developer nozzle, 9 is a toner pumper, 1o is a toner mixture ratio detection element, and 1] is a toner replenishment control circuit.

In a developing device that uses a magnetic two-component developer with such a configuration, only toner is consumed during development, so in order to compensate for this, the toner mixing ratio in the developer is detected and the detection signal is Generally, the amount of toner replenishment is controlled by controlling the rotation of the toner replenishing roller, that is, by mechanical control. Detection element 0 in the one shown in Fig. 1 is composed of a piezo vibrator with a diaphragm attached, and a plate integrally attached to this diaphragm to partially block the flow of developer. The change in the amount of developer staying in the dam plate portion due to the change in the fluidity of the developer due to the change in is electrically detected as a change in the amplitude of the diaphragm. The detection signal from the detection element 1o is used as a signal for controlling mechanical means such as a motor and a clutch (not shown) for rotating the toner supply roller 7 via the control circuit 11.

In this way, in conventional developing devices, in order to control toner replenishment, there is a means for detecting the toner mixture ratio in the developer or a means for detecting the density of the developed image, and a mechanical device for controlling toner replenishment. This requires additional means, complicates the developing device, and becomes an obstacle to realizing a simple developing device.

The present invention has been made to solve the problems of the prior art, and controls toner replenishment to the developer by controlling a variable bias power supply without using a mechanical toner replenishment control means. It is an object of the present invention to provide a developing device equipped with a simple high-performance toner replenishing means configured to maintain developer performance at a predetermined level.

The present invention will be described in detail below based on Examples.

FIG. 2 is a schematic diagram of an embodiment of the developing device according to the present invention. In the figure, 1 is a drum-shaped charge holding member on which an electrostatic latent image is formed, and 1' is grounded through its conductive support. 21 is a magnet roller, 22 is a non-magnetic sleeve disposed to surround the magnet roller 21, and either or both of them are configured to be rotatable. 23 is a lower opening 25 of the toner hopper 25
' is a toner supply roller disposed at 24, and 24 is a grade that extends from the lower end of the side wall of the toner hopper 25 on the downstream side in the rotational direction of the toner supply roller 23 toward the toner supply roller 23 so as to contact the roller 23. It is located in 26 is a seal plate, and the toner supply roller 2
The toner supply roller 23 is disposed from the lower end of the side wall of the toner hopper 25 on the upstream side in the rotational direction of No. 3 toward the toner supply roller 23 so as to be in contact therewith. And these blades 24
and the seal plate 26 are configured to seal the gap between the toner hopper 25 and the toner supply roller 23. 27 is a detection element that detects the toner mixing ratio of the developer 33 held on the non-magnetic sleeve 22; 28 receives the detection signal from the detection element 27 and outputs a signal for controlling the variable bias power supply 29; A control circuit, 30 is a bias changeover switch for the variable bias power supply 29, 31 and 32 are bias power supplies constituting the variable bias power supply, 34 is a toner, and 40 is a developing bias power supply.

The developing device configured in this manner holds the developer 33 on the non-magnetic sleeve 22 to a thickness dl by the magnetic force of the magnetic roller 21, and holds the developer 33 on the non-magnetic sleeve 22 to a thickness dl, and either the magnetic roller 21 or the sleeve 22, or The developer 33 is conveyed in a circulating manner on the sleeve 22 by rotating both of them, and the spikes of the developer 33 are brought into contact with the charge holding member 1 and the toner supply roller 23 to develop the electrostatic latent image and toner. Replenish supplies. Toner 34 for replenishment is stored in the hopper 25, and the hopper lower opening 25'
The toner is supplied by a toner supply roller 23 arranged so as to cover the toner. The toner supply roller 23 is made of rubber,
It is preferably made of plastic, metal, or the like, and its surface is finished to have a surface roughness equal to or slightly larger than the toner particle size, that is, minute irregularities 23' of 10 microns or more. Note that since a bias voltage is applied to the toner supply roller 23, it needs to be conductive or semiconductive. The blade 24 is the toner supply roller 2
It has the function of forming a uniform thin layer of toner on the surface of the toner 3 and charging the toner to a predetermined polarity. A means for forming the toner into a thin layer and charging it in this manner is disclosed in Japanese Patent Publication No. 51-36070 (U.S. Pat. No. 3,731).
No. 146), etc., but that means can be applied as a means for forming one layer of toner on the toner supply roller of the present invention.

The state in which a single layer of toner is formed and charged on the surface of the toner supply roller 23 having minute irregularities 23' is shown in the enlarged schematic diagram of FIG. That is, as shown in FIG. 3, when the roller 23 is rotated in the direction of the arrow with the tip of the blade 24 in pressure contact with the toner supply roller 23, most of the toner 34 is intercepted by the blade 24. However, one or two layers of toner in contact with the toner supply roller 23 passes through the tip of the blade 24 due to the strong frictional force with the roller 23, leaving a thin layer of toner on the surface of the toner supply roller 23. is formed. At this time, the toner rubs against the blade 24 or the toner supply roller 23, and the toner is charged to a predetermined polarity required for development. The means for forming a thin layer of toner on the toner supply roller 23 and charging it to a predetermined polarity is not limited to the above means, and for example, a magnetic blade as disclosed in Japanese Patent Laid-Open No. 54-43037 can also be used. can do. However, in this case, it is necessary to use magnetic toner as the toner.

The thin layer of toner formed on the toner supply roller 23 comes into contact with the spikes of the developer 33 held in the sleeve 22 and is drawn into the developer 33. The toner that has not been taken into the hopper 33 passes through the seal plate 26 and is conveyed into the hopper 25 again. The seal plate 26 is attached to the hopper 2 when moving the developing device or when replenishing the toner 34 into the hopper 25.
The roller 5 serves to prevent the toner 34 from leaking from the roller 5, and is configured so as not to prevent the toner on the toner supply roller 23 from passing. The seal plate 26 is made of an elastic plate such as a plastic plate or a thin metal plate, and has the above-mentioned function.

The toner on the toner supply roller 23 is charged and the mechanism by which the toner is taken into the developer 33 is based on electrostatic attraction. That is, toner supply roller 2
The movement of the toner is determined by the electric field formed between the magnetic sleeve 3 and the nonmagnetic sleeve 220.

When the toner is negatively charged, if the toner supply roller 23 is maintained at a negative potential or a low positive potential when viewed from the non-magnetic sleeve 22, the toner will be transferred to the non-magnetic sleeve 22.
It is taken into the developer 33 above. Conversely, when the toner supply roller 23 is maintained at a high positive potential, the toner does not separate from the toner supply roller 23 and the toner is not replenished into the developer 33. In this way, a conventional developing device using a magnetic two-component developer has the advantage that toner replenishment and non-replenishment can be achieved only by switching the bias power supply that determines the potential of the toner supply roller, rather than by mechanical means. This is one of the features of the present invention that is not found in toner replenishment devices.

In the present invention, toner replenishment and non-replenishment are performed by detecting the developing ability of the developer. The scale indicating the developing ability of the developer is the toner mixture ratio contained in the developer, and the detection means 27 in the embodiment shown in FIG. 2 is a detection means for detecting this toner mixture ratio. be. An example of means for detecting the toner mixing ratio of the developer 33 held on the non-magnetic sleeve 22 is an optical detection element as shown in FIG. This sensing element 27 was previously proposed by the inventor of the present application (Japanese Patent Application No. 56-5763).
No. 3), the detection principle of this element is that a light source and a light receiver 36 are sealed with a translucent sealing plate 35 in contact with the spikes 33' of the developer 33 formed on the non-magnetic sleeve 22.
．． A detection element 27 consisting of 37 is arranged to detect changes in optical reflectance due to changes in the toner mixing ratio of the developer 33.

Similarly, as a means for detecting the toner mixing ratio of the developer on the non-magnetic sleeve, it is also possible to use a detection element using a piezo vibrator, which is used in the conventional example shown in FIG. 1.

The detection signal from the detection element 27 is input to a control circuit 28, and the output signal thereof controls a variable bias power supply 29 that applies a bias voltage between the non-magnetic sleeve 22 and the toner supply roller 23. One power supply 31 of the variable bias power supply 29 is a bias power supply for applying a positive low potential (or negative potential) to the toner supply roller when viewed from the non-magnetic sleeve, and the other power supply 32 provides a positive high potential. It is a bias power supply. A changeover switch 30 for selectively connecting the bias power supplies 31 and 32 to the non-magnetic sleeve 22 includes:
A non-magnetic sleeve 22 is attached to the common terminal C, and a switching terminal S
, NS are connected to bias power supplies 31 and 32, respectively.

This changeover switch 30 is controlled by a control signal from the control circuit 28, but when the detection element 27 detects that the toner mixing ratio in the developer is higher than a predetermined level,
The control circuit 28 controls the C terminal of the control circuit 3o to be connected to the NS terminal. As a result, toner supply roller 2
3 is biased to a high positive potential with respect to the non-magnetic sleeve 22, toner is not easily separated from the toner supply roller 23, and toner replenishment is no longer performed. On the contrary,
If it is detected that the toner mixing ratio has fallen below a predetermined level, the switch 30 is switched to the S terminal and the toner supply roller 23 is biased to a positive low potential with respect to the non-magnetic sleeve 22, thus stopping the toner supply. The toner on the roller 23 is replenished into the developer.

FIG. 5 shows the non-magnetic sleeve 22 and the toner supply roller 2.
FIG. 3 is a diagram illustrating how the amount of toner on a toner supply roller changes in response to the toner mixing ratio in the developer when the bias voltage applied during the third period is changed. In the figure, a, b, c, d, and e indicate that the amount of toner on the toner supply roller is 07.0.8.0.9, respectively, in optical density.
This is a characteristic curve obtained by plotting the positions where 1.0.1.1. Increasing the developer action time increases bSc,
The curves d and e change as shown by dotted lines b', e', d', and e'. Such a characteristic curve changes depending on the composition of the developer and the contact situation of the developer spikes with the toner supply roller, but in the case of negatively charged toner, it generally depends on the potential of the toner supply roller 23. is +1
It can be seen that when the voltage is below 00V, toner is supplied from the toner supply roller to the developer, and when it is above +300V, the toner is reliably transferred from the developer to the toner supply roller. Therefore, when stopping the toner supply, it is not impossible to apply a high positive bias voltage to the toner supply roller 23, but the positive bias voltage applied to the toner supply roller 23 is difficult to apply. It is preferable not to set it to a high value, but to configure it so as to prevent the toner from moving backward from the developer to the toner supply roller 23 when toner supply is stopped. Regarding the relationship between the charge polarity of the toner and the polarity of the bias voltage, when the charge polarity of the toner becomes opposite, the polarity of the bias voltage may also be reversed.

In the embodiment shown in FIG. 2, a detection means for detecting the toner mixing ratio of the magnetic two-component developer is provided, and a variable bias power supply is controlled based on a detection signal from the detection means, so that the toner is supplied from the toner supply roller to the developer. Although a configuration has been shown in which the toner replenishment of the toner is controlled, it is also possible to measure the developing performance of the developer based on another principle and to control the donor replenishment. For example, in the embodiment shown in FIG. 6, an electrostatic charge pattern of a specific potential for measuring developer performance is formed on the charge holding member 1, and the pattern is developed by the developing device. The toner image density is measured by a photoelectric measuring element 38, a control circuit 39 is operated by the measurement signal, and a variable bias power supply 29 is controlled by an output signal from the control circuit 39. In this embodiment, when the developed toner concentration of the electrostatic charge pattern for measurement is high, the voltage applied to the toner supply roller 23 (
The configuration is such that the ear-swiping pressure is increased to stop toner supply from the toner supply roller to the developer, and in the opposite case, the bias voltage is lowered to allow toner to be supplied to the developer.

In each of the above embodiments, the developer is configured to circulate on the non-magnetic sleeve without separating from the sleeve. Similarly, it is also possible to adopt a configuration in which the developer is once separated from the non-magnetic sleeve and then sucked onto the sleeve again. Further, it is also possible to use a magnetic toner containing magnetic powder as the toner constituting the developer so as to more effectively prevent the occurrence of background capri and toner scattering. Further, in each embodiment of the present application, the variable bias power supply has a basic configuration, but the present invention is not limited to this, and variable power supplies with various configurations can be applied.

As described above in detail based on the embodiments, the present invention connects a variable bias power supply that creates a potential difference between the toner supply roller on which a thin layer of charged toner is formed and the nonmagnetic sleeve that holds developer, The variable bias power supply,
Since the configuration is configured to control the replenishment of toner from the toner supply roller to the developer on the non-magnetic sleeve by controlling the detection signal from the means for detecting the development performance of the developer, the replenishment of toner to the developer is controlled. This can be done automatically by adjusting the variable bias power supply using a control signal without using a mechanical replenishment control means, and a developing device with high operational stability and simple configuration can be obtained.

Furthermore, in the present invention, the thin layer of toner on the toner supply roller is charged in advance, and the toner is replenished uniformly in small amounts due to the electrostatic attraction of the developer. Compared to a method that replenishes unevenly, the toner mixture ratio in the developer is uniform and does not contain poorly charged toner, and even if any unexpected situation occurs, the developer has more than the ability to hold carrier. Since the toner is not mixed with the toner, effects such as the ability to effectively prevent the occurrence of non-image capri and toner scattering can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of the configuration of a conventional electrostatic latent image developing device, FIG. 2 is a schematic diagram of an embodiment of an electrostatic latent image developing device according to the present invention, and FIG. 4 is a diagram showing an example of the configuration of the detection element of the device shown in FIG. 2, and FIG. 5 is an enlarged explanatory view of the blade portion of the device shown in FIG. A characteristic curve diagram for explaining the transition of
FIG. 6 is a schematic diagram of another embodiment. In the figure, 1 is a charge retention member, 21 is a magnetic roller, 22 is a non-magnetic sleeve, 23 is a toner supply roller, 24 is a blade, 25 is a toner hopper, 26 is a seal plate, 27 is a detection element, 28 is a control circuit, 29 is a variable bias power supply, 33 is a developer, 34 is a toner, 36 is a light source, 37 is a light receiver, 38 is a detection element, and 39 is a control circuit. Patent Applicant Olympus Optical Industry Co., Ltd. Representative Patent Attorney Kenji Mogami =-, Figure 2 1 *4 Figure 5 Toner Regulations

Claims (1)

[Claims] A magnetic two-component developer consisting of toner and a magnetic carrier is applied to the electrostatic latent image formed on the charge retaining member while being conveyed by a magnetic conveying means consisting of a magnetic roller and a non-magnetic sleeve to form a toner image. In the developing device, there is provided a rotatable toner supply roller that supplies toner in contact with the spikes of developer formed on the non-magnetic sleeve, and a uniform thin layer of toner is applied to the surface of the toner supply roller while being electrically charged. A means for forming a layer, a means for detecting the developing performance of the developer, and a variable bias power supply for forming a potential difference between the toner supply roller and the non-magnetic sleeve, which is controlled based on a detection signal from the detecting means. An electrostatic latent image developing device, characterized in that it is configured to control toner replenishment to the developer by controlling a υ variable bias power supply based on the detection signal from the detection means.