JPS6318380A - Developing device - Google Patents

Abstract

PURPOSE:To remove the adhesion of a developer to a transparent window and to attain always stable and highly accurate toner concentration detection by sliding the transparent window of a toner concentration detector by the circular flow of the developer in a developing container. CONSTITUTION:The toner concentration detector 111 is arranged on the side of a down flow course in the arrow P3 direction out of the circular flow course of the developer flowing in the developer container 104 and the transparent window 111a formed on the front surface of the detector 111 is scrapped by the downflow of the developer. Infrared rays or the like are radiated from the detector 111 through the window 111a, the reflected light from the developer is converted into an electric signal and a toner concentration detecting signal is generated. A motor 108 is rotated by a control signal based upon the toner concentration and a screw feeder 107 delivers the lacking quantity of toner from a toner feeding tank 106 into the developer container 104. Consequently, the toner concentration can be highly accurately detected and the quantity of toner to be fed can be accurately controlled.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a developing device to be installed in an image forming apparatus such as an electrophotographic device, and particularly to a developing device that uses a two-component developer. The present invention relates to an improved developing device capable of controlling density.

[Background of the invention]

In a developing device that uses a two-component developer consisting of a mixture of magnetic particles and toner particles, the toner particles in the developer are consumed each time a developing operation is performed, and the magnetic particles (i.e., carrier) remain. The toner concentration in the developer decreases with each development operation. Therefore, in order to keep the toner concentration in the developer at a constant value, the toner concentration of the developer being used in the developing device must be constantly adjusted. Detect accurately.

Toner must be replenished into the developing device according to the detection result.

Therefore, in order to detect the toner concentration of the developer being used in the developing device, for example, a method for detecting the developing device or developer concentration as shown in FIG.
It is disclosed in Japanese Patent No. 853.

In FIG. 4, reference numeral 1 denotes a photosensitive drum rotating in the direction indicated by the arrow, and 2 a magnet arranged parallel to the photosensitive drum 1, facing the circumferential surface of the photosensitive drum 1.

A developing sleeve 3 is rotatably fitted onto the magnet roller 2 and rotates in the direction of arrow B in synchronization with the photosensitive drum 1 by a drive mechanism (not shown); A developer container accommodating a developer mixture made of a mixture; 5 a screw type stirrer for stirring the developer mixture in the container 4; 6 a toner replenisher accommodating toner T to be replenished into the developer container 4; 7 is a screw feeder for replenishing the toner T in the toner supply tank 6 into the developer container 4; 8 is a motor for rotating the screw feeder 7; 9a is a screw feeder located directly above the developing sleeve 3; A main body 9c of a developer concentration sensor 9 having a transparent glass window 9b extending tangentially (horizontally) to the circumferential surface of the sleeve 3;
9d is a light emitting element such as an infrared LED, 9d is an infrared transmission filter, 9 is a light receiving element, 10 is a light emitting element control circuit, 11 is a differential amplifier, and 12 is a reference value generator (reference voltage source).

In the configuration shown in FIG. 4, the developer on the developing sleeve 3 that is attracted onto the developing sleeve 3 and moved directly below the sensor 9 passes through the transparent glass window 9bi and is emitted from the light emitting element 9c. Light is irradiated, and this light is applied to the developing sleeve 3.
The light reflected by the developer adhered above is made incident on the light receiving element 9 through the infrared transmission filter 9d and converted into an electrical signal.The electrical signal is compared with a reference value in the differential amplifier 11 and the difference is calculated. It is amplified and used as a control signal for the motor 8.

Although the developer concentration detection method shown in FIG. 4 is theoretically effective, in the configuration shown in FIG. The surface of the transparent glass window 9b is rubbed with the raised portion D! of the developer, so that the surface of the transparent glass window 9b is
Since the developer is prevented from adhering to the surface of the transparent glass window 9b, it is necessary that the position of the raised portion D1 relative to the transparent glass window 9b is always stable. Since constant control is impossible, the toner concentration detection device shown in FIG. 4 uses a transparent glass window 9.
The problem is that the developer tends to adhere to the surface of b, making it impossible to always perform highly accurate detection.

[Purpose of the invention]

An object of the present invention is to provide improved practicality that allows the toner concentration of the developer being used in a developing device to be detected with high precision at all times, and to constantly accurately control the amount of toner to be replenished to the developing device. It is an object of the present invention to provide a developing device with high performance.

[Summary of the invention]

A feature of the improved developing device according to the present invention is that a toner concentration detector equipped with a transparent window is disposed on the side of the flow path of the developer circulating in the developer container. The transparent window is rubbed and cleaned by cleaning the transparent window, and a light emitting element installed in the toner concentration detector irradiates the circulating flow of the developer through the transparent window. The toner concentration in the developer container is detected by converting the reflected light from the developer into an electric signal by a light receiving element in the toner concentration detector.

In the developing device of the present invention, the transparent window of the toner concentration detector is not rubbed by the developer adsorbed on the developing sleeve, but the transparent window is rubbed by the excess developer circulating and flowing in the developer container. There is no fear that the developer will adhere to the surface of the transparent window, and therefore the toner concentration in the developer can always be accurately detected and the toner concentration in the developer can be accurately controlled.

[Embodiments of the invention]

An embodiment of the developing device of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, 101 is a photosensitive drum (that is, an electrostatic latent image carrier) rotating in the direction of arrow A, 102 is a magnet roller, and 103 is a developing sleeve (i.e., electrostatic latent image carrier) rotating in the direction of arrow B.
104 is a developer container for storing developer, 105 is a developer agitator, 106 is a toner replenishment tank, 107 is a sprifer feeder for replenishing toner T, and 108 is a screw feeder. drive motor,
109 is a blade for controlling the layer thickness of the developer adsorbed on the developing sleeve 103 (that is, a developer discharge thickness regulating member); 110 is a developing bias power source for applying a developing bias voltage to the developing sleeve 103; , 111 is a toner concentration detector equipped with a transparent window 111& on the front.
12 is a control circuit that generates a control signal for the motor 108 in accordance with the output of the toner concentration detector 111;

The toner concentration detector 111 is located in the first toner concentration detector 111 in the developer container 104.
Arrows pi and P2 and P! in FIG. 2 and FIG. The transparent window 111a provided on the front side of the downward flow path indicated by the arrow P3 is arranged to face the side of the downward flow path indicated by the arrow P3 in the circulation flow path for the developer overflowing and flowing. It is designed to be rubbed by.

As shown in FIG. 2, the toner concentration detector 111 includes a light-emitting element 111e, a light-receiving element 111d, a light-receiving element 111@ for reference signal generation, a slot,
) 1llf and 1st eye], and a front plate 111h having a transparent window 111a is provided on the front surface of the dee 111b (that is, in front of the light emitting element 111c and the light receiving element 111d). It is attached to the dee 111b.

The signal generated by the light-receiving element 111d (i.e., toner concentration detection signal) and the signal generated by the light-receiving element 111e for standard signal generation (i.e., reference signal) are applied to a control circuit 112 having a built-in differential amplifier or the like. An output signal is then generated to motor 108 that compensates for the difference between both signals.

In the apparatus shown in FIG. 1, when the developing sleeve 103 rotates in the direction of arrow B in synchronization with the rotation of the photosensitive drum 101, the electrostatic attraction force of the developing sleeve 103 causes the developer container 104 to
The developer inside the developer container 104 is sucked into the developing sleeve 103 and rises inside the developer container 104 in the direction of arrow P1 in FIG. 1 as the peripheral surface of the sleeve moves. Only an amount of developer equal to the thickness of the layer determined by the gap between the developer and the surface is carried out of the container 104 and supplied to the outer peripheral surface of the photosensitive drum 101. on the other hand,
The excess developer rises along the inner wall surface of the blade 109 as shown by arrow P2, changes direction, and further descends toward the bottom of developer container 104 as shown by arrow P1. At this time,
The downward flow of the developer passes through the transparent window 1 of the toner concentration detector 111.
11, the front surface of the transparent window 111& is cleaned as it moves while rubbing against the grass.

Further, at this time, infrared light or the like is irradiated from the light emitting element 111c through the transparent window 111at to the developer that is moving while rubbing the transparent window, and this infrared light is reflected by the developer. Thereafter, the reflected light is converted into an electrical signal by the light receiving element 111d. On the other hand, the light emitted backward from the light emitting element 111c is 111. The light passes through the reference signal generating light receiving element 111e, and is converted into an electrical signal in the light receiving element 111e.

The electric signal generated from the light-receiving element 111d and the electric signal generated from the reference signal-generating light-receiving element 111@ are input to the control circuit 112, and the control circuit 112 amplifies the difference between the two human power signals to generate a control signal for the motor 108. The control circuit 112 outputs the signal as follows. Since components such as the phase or frequency of the reflected light from the developer change in proportion to the toner concentration in the developer, the light generated by the light emitting element 111C directly enters the generated signal and the light received by the reference signal generating light receiving element 111e. By comparing the signal generated by the element 111d, the control circuit 112 generates an output signal representing the toner concentration in the developer.

Since the motor 108 is rotated according to the control signal, the screw feeder 107 is rotated so as to compensate for changes in the toner concentration in the developer, and the toner T is supplied from the toner replenishment ff106 into the developer container 104 to compensate for the insufficient amount. The amount corresponding to that amount will be sent.

In the developing device of the present invention, unlike the conventional developing device or toner concentration detection device shown in FIG.
A toner concentration detector 111 is installed inside the developer container 104, and the transparent window of the toner concentration detector is rubbed by the circulating flow of developer generated in the developer container 104. There is no risk of adhesion. Therefore, in the developing device of the above embodiment, the toner concentration can be detected with high precision and always stably, and the toner concentration of the developer in the developer container can always be maintained at a predetermined value.

FIG. 3 shows changes in the electrical signal generated from the light receiving element 111d in the above embodiment. As shown in FIG. 3, the output voltage of the light receiving element 111d is approximately proportional to the increase in toner concentration in the developer, and no abnormal fluctuations are observed. That is, it was proven that in the developing device of the present invention, the developer does not adhere to the surface of the transparent window 10'' of the toner concentration detector 111.

In the above embodiment, the toner 0 degree detector 111 was installed inside the developer container 104, but only the transparent window 111 & on the front side of the toner concentration detector 111 was fitted into the inner wall surface of the developer container 104, and the detection Dedi portion 111b of vessel 111
may be made to protrude from the outer wall of the developer container 104.

〔Effect of the invention〕

As explained above, in the developing device of the present invention,
Instead of rubbing the transparent window of the toner concentration detector with the spikes of developer formed on the developing sleeve, the transparent window of the toner concentration detector is rubbed with the circulating flow of developer in the developer container. This structure prevents the developer from adhering to the surface of the transparent window and deteriorating the detection accuracy, and allows stable and highly accurate detection to be performed at all times. Concentration can be controlled with high precision.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of essential parts showing an embodiment of a developing device according to the present invention, FIG. 2 is a cross-sectional view along the ■-■ arrow in FIG. 1, and FIG. 3 is a toner concentration in the developing device shown in FIG. 1. FIG. 4 is a diagram showing the relationship between the output of the detector and the toner concentration, and is a schematic diagram showing a known developing device or toner concentration detection method. 1.101... Photosensitive drum 2.102... Magne, troller 3.103... Developing sleeve 4.104... Developer container 5.105... Stirrer 6.106... Toner supply tank 7.107...Screw feeder 8.108...
- Motor 9...Developer concentration sensor 11...Differential amplifier 12...Reference value generator 109...Blade (developer delivery thickness regulating member) 110...Bias power supply 111...Development Agent toner concentration detector 111a... Transparent tank 111c... Light emitting element 111d... Light receiving element 111... Standard signal generation (for reference) light receiving element 112... Control circuit Figure 2 □ Toner concentration (wt%)

Claims (2)

[Claims] (1) A developer container containing a developer made of toner particles and magnetic particles, and a developer container that is placed in an opening of the developer container and rotates upward to transfer the developer in the developer container to the developer. A developer transporting body that is transported toward an electrostatic latent image carrier, etc. outside the developer container, and a developer transporting body that is disposed near the highest position of the developer transporting body and intersects with the developer carrying surface of the developer transporting body. a wall-shaped developer discharge thickness regulating member having a surface in a direction in which excess development occurs among the developer rising toward the developer discharge thickness regulating member in the developer container; In a developing device configured such that the developer rises along the surface of the developer discharge thickness regulating member and then reverses and descends into the developer container, the flow of the developer circulates within the developer container. A toner concentration detector having a transparent window on the front surface is installed adjacent to the path, and a light emitting element that irradiates light onto the developer through the transparent window and reflected light from the developer are incident on the toner concentration detector. A developing device characterized by comprising a light receiving element. (2) The developing device according to claim 1, wherein the transparent window of the toner concentration detector is provided on an inner wall surface of the developer container.