JPS59164576A - Developing device - Google Patents

Abstract

PURPOSE:To hold a fixed toner concentration and to obtain picture quality with uniform concentration by arranging a toner concentration detecting means close to the flow of a two-component developer related to development and detecting always stable and precise toner concentration. CONSTITUTION:A flowing plate 7 is arranged so that the developer 3 regulated by a blade 6 is carried to the back of a mixing spiral 9 and a detecting head 12 of a toner detector is arranged on the lower part of the flowing plate 7 between a sleeve 5 and the mixing spiral 9. Since the developer 3 carried from the mixing spiral 9 to the sleeve 5 is made flow while contacting with the detecting surface 12a of the detecting head 12, the toner concentration change of the developer 3 is detected as the change of the magnetic permeability by the detecting head 12. Consequently, always stable and precise toner concentration can be detected and picture quality with uniform concentration can be obtained.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a developing device for, for example, a copying machine.

[Technical background of the invention]

For example, in a copying machine, an electrostatic latent image on a photoreceptor is developed using a magnetic brush method using a two-component developer consisting of a carrier made of magnetic powder and a toner made of non-magnetic powder. In the developing device, it is necessary to detect the toner concentration of the developer and control the toner supply.

Therefore, conventionally, for example, a magnetic toner concentration detection means is used. That is, by placing a cylinder around which the detection coil is wound in the flow of developer that is returned to the main body of the apparatus after development, and allowing the developer to pass through the cylinder,
The toner concentration is detected by changes in the inductance of the detection coil, and the toner supply is controlled.

[Problems with background technology]

However, in the conventional developing device described above, the toner concentration of the developer returned to the main body of the device after development is detected, so the toner concentration of the detected developer is the toner concentration of the developer that actually performs development. ', - are not the same as degrees. Therefore, it is impossible to always detect stable and accurate toner humidity, and as a result, the toner concentration of the developer cannot always be kept constant, resulting in the problem that it is not always possible to obtain uniform copy quality. .

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to constantly detect stable and accurate toner concentration, to maintain a constant toner concentration of a two-component developer, and to maintain uniform density image quality at all times. An object of the present invention is to provide a developing device.

[Summary of the invention]

The developing device of the present invention has a toner concentration detection means installed close to the flow of the two-component developer involved in actual development, so that stable, constant and accurate toner concentration detection can be performed at all times. It is.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a magnetic brush developing device according to the present invention. That is, numeral 1 denotes a photosensitive drum of a copying machine, which rotates in the direction of arrow a in the figure, and an electrostatic latent image corresponding to an image of a document is formed on its surface. A developing roller 2 is provided opposite to the surface of the photoreceptor drum 1, and rotates in the direction indicated by the arrow in the figure to convey the two-component developer 3 to the surface (development area) of the photoreceptor drum 1. . The developing roller 2 includes a fixed magnet roller 4 containing a permanent magnet inside;
It is composed of a rotating IJ-blade 5 made of a non-magnetic material that rotates on the outer circumferential surface of the row 24 in the direction indicated by the arrow. Note that the broken line inside the magnet row 24 indicates the magnetic pole position of the permanent magnet. Here, the developer 3 is composed of a carrier made of magnetic powder (for example, ferrite powder) and a toner made of non-magnetic powder (for example, styrene-acrylic resin), and the toner is charged by abrasion and electrification. attached to the carrier.

Reference numeral 6 denotes a blade that regulates excess developer 3 to keep the amount of developer 3 supplied to the surface of the photosensitive drum 1 constant. A sink plate 7 conveys the developer 3 regulated by the blade 6 to the rear side of a stirring spiral 9, which will be described later. A scraper 8 scrapes off the developer 3 from which toner has been removed by contact with the photoconductor tram 1 from the surface of the sleeve 5.
1. Reference numeral 9 denotes an agitation spiral, which collects the developing material 3 carried by the sink plate 7 and the developer 3 scraped off by the scraper 8.
is sent to sleeve 5 while stirring. Reference numeral 10 denotes a main body of the apparatus 6 which houses the above-mentioned components and the developer 3. 11
1 is a toner hopper that stores toner for replenishment, and when a toner supply device (not shown) operates in response to a toner replenishment signal, the toner in the toner hopper 11 is supplied to the main body 1.
It is designed to be supplied within 0.

A detection head (coil block) 12 of a toner concentration detection device, which will be described later, is installed below the sink plate 7 between the sleeve 5 and the stirring spiral 9. In this case, the detection surface 12a of the detection head 12 faces downward and comes into contact with the flow of the developer 3 sent from the stirring shaft A' spiral 9 to the sleeve 5, so as to detect the toner concentration of the flowing developer 3. It has become.

The operation of FIG. 1 in such a configuration will be explained. The rotation directions of the photosensitive drum 1 and the sleeve 5 are opposite to each other as indicated by arrows a and b, but in the developing area, they are in the same direction (downward direction), which is the with mode.

Further, the stirring spiral 9 rotates in the direction of arrow C in the figure.

The developer 3 stirred by the rotation of the stirring spiral 9
is stirred up and sent to the top of the stirring spiral 9,
Scree ′? 8 in the direction of the sleeve 5 as shown by the arrow, and is attracted by the magnetic force of the permanent magnet in the magnet roller 4 and attached to the surface of the sleeve 5. At this time,
Since the developer 3 sent from the stirring spiral 9 to the sleeve 5 flows while contacting the detection surface 12h of the detection head 12, a change in the toner concentration of the developer 3 is detected by the detection head 12 as a change in magnetic permeability. -However,
Developer 3 conveyed to blade 6 by sleeve 5
The excess amount is removed by the blade 6. Most of the removed excess developer 3 passes over the sink plate 7 and is carried to the rear of the stirring spiral 9 (on the side of the main body 10), where it is stirred by the stirring spiral 9.

On the other hand, the developer 3 on the sleeve 5 whose thickness is regulated by the blade 6 is conveyed by the sleeve 5, and the photosensitive drum 1 (l!
: A of the permanent magnet in the magnet roller 4 at a close position
The force forms soft brush-like spikes, and the toner in the developer 3 is transferred to the electrostatic latent image on the surface of the photoreceptor drum 1. The developer 3 deprived of toner is transported by the sleeve 5, and then falls to the bottom of the main body 10 due to gravity and centrifugal force, and is moved to the stirring station by the inclined surface formed at the bottom of the main body 10, as shown by the arrow in the figure.・The developer 3 that has been transported to the vicinity of the 9th floor and remains on the other sleeves 5 is removed by the scraper 8.
Scraped off by the stirring spiral 9? The mixture is scattered and stirred.

The amount of the developer 3 regulated by the blade 6 and flowing over the sink plate 7 can be adjusted by adjusting the gap between the sleeve 5 and the blade 6, and the flow rate of the developer 3 on the sink plate 7 can be adjusted by adjusting the gap between the sleeve 5 and the blade 6. can be adjusted by adjusting the angle of the blade θ, the inclination and shape of the sink plate 7. The developer 3 is sent from the stirring spiral 9 to the sleeve 5.
Since the toner concentration is the same in the developer 3 that passes through the blade 6 and the developer 3 for development, the detection head 1
The toner concentration of the developer 3 detected in step 2 is the same as the toner concentration of the developer 3 that actually performs development. Furthermore, it is easy to understand that the amount of developer 3 sent from stirring spiral 9 to sleeve 5 and its flow rate are always constant while sleeve 5 and stirring spiral 9 are rotating. 'Therefore, stable detection of toner acidity is possible at all times.

In this way, between the sleeve 5 and the 4m stirring spiral 9, the developer 3 is attracted to the permanent magnet in the magnet roller 4 and transferred from the stirring spiral 9 to the sleeve 51. The toner concentration is considered to be the same as the toner concentration of the developer 3 involved in actual development, and the flow of the developer 3 is always uniform and does not stagnate. By providing this, it is possible to detect the toner concentration of the developing agent 3U) that is actually available in the real world, and its effectiveness is extremely large in obtaining copying image quality with uniform density.Then, the detected toner concentration When the value is outside the preset range, the toner concentration of the developer 3 can be kept constant by operating a toner supply unit (not shown) and supplying toner from the toner hole 711. Moreover, stable detection is possible even when the flow plate 7 is not provided, depending on the structure of the developing device.

FIG. 2 shows the structure of the detection head 12 shown in FIG. That is, 21 is a sealed cylindrical main body, the lower surface of which is a detection surface 12a, and this detection surface 1.2
a comes into contact with the developer 3. A detection coil 22, a coil holding member 23, and an adjustment core 24 serving as a reference magnetic body are housed in the main body 21, respectively.

The detection coil 22 is fixed to the main body 211 by a coil holding member 23, so that no looseness occurs between the detection coil 22 and the main body 21.

The adjustment core 24 is screwed into the approximate center of the upper surface 21a of the main body 21, and by rotating the adjustment core 24 with a screwdriver or the like, the distance from the center of the detection coil 22 can be changed. It's happening. The detection coil 22 includes a core 251, 252, oscillation windings 261+262, and detection windings 271+2724. An oscillation winding 261 and a detection winding 271 are wound around the core 251, and an oscillation winding 261 and a detection winding 272 are wound around the core 252, respectively. The detection winding 27. is located on the adjusting core 24 side (the detection winding 27□ is located on the detection surface 12a11 side). 3, and therefore is not contaminated by the developer 3.

FIG. 3 schematically shows the configuration of the toner concentration detection device according to the present invention, which includes a stabilized power source section 31, an oscillating section 32. Detection unit 33. Comparison section 34. and an output section 35. That is, the stabilized power supply unit 3) is supplied with a predetermined DC voltage (for example, 24 volts) from an external power source (not shown), so that the stabilized power supply unit 3) generates a predetermined stabilized DC voltage (for example, 1 volt).
6 volts) and supplies it to each part.

The oscillation section 32 is constructed using the oscillation winding 261°26 shown in FIG.
2, and generates a predetermined high frequency oscillation output. This oscillation output is applied to the detection section 33. The detection unit 33 is
It includes detection windings 271 and 272 shown in FIG. 2, and as the inductance of the detection winding 272 changes in accordance with changes in the magnetic permeability of the developer 3, the phase of its output changes. Two signals are outputted from the detection section 33 in response to this phase change and inputted to the comparison section 34. The comparison section 34 discriminates the magnitude of the two input signals, generates an output, and inputs this to the output section 35. Then, the output section 35 outputs it as a toner concentration detection signal.

FIG. 4 is a circuit example specifically showing each part of FIG. 3. First, in the stabilized power supply section 30, the collector of the NPN transistor 41 is connected to one input terminal 428, and the emitter is connected to one output terminal 44. The other input terminal 43 is connected to the other output terminal 45. The base of the transistor 41 is connected to the input terminal 43LL via a Zener diode 46. The transistor 41
A resistor 47 is connected between the collector and base of.

A capacitor 48 is connected between the output terminals (4 and 45).Next, in the oscillation section 32, an NPN transistor 51
The base of is connected to the output terminal 45 through a resistor 52 and a capacitor 53 in parallel, and a resistor 54.
The output terminal 44j is connected to the output terminal 44j. The emitter of the transistor 51 is connected to the output terminal 4.5I via a resistor 55, and is also connected to the output terminal 45 via a resistor 56 and a capacitor 57 in series. A capacitor 58 is connected between the connection point with the capacitor 57 and the collector of the transistor 51.The collector of the transistor 51 is connected to one end of the oscillation winding 261. The other end of the wire 261 is connected to one end of the oscillation winding 262 (
The other end of this oscillation winding 262 is connected to the output terminal 44.

Next (・In the detection section 33, the detection winding 271
One end is a PLL-rc (phase-locked loop integrated circuit, hereinafter referred to as a single O-PLL) as a phase difference detection circuit.
The other end is connected to one end of the detection winding 272 and the input terminal (2) of the PLL circuit 61 (hereinafter referred to as a circuit), and the other end is connected to one end of the detection winding 272 and the input terminal (2) of the PLL circuit 61. and is connected to the output terminal 45.

Further, one end of the detection winding 272 is connected to the output terminal 44 via the resistor 64, and the other end is connected to the input terminal (2) of the PLL circuit 61. Further, the detection winding 272
A capacitor 65 is connected in parallel. And P.L.
One power supply terminal ■ of the L circuit 61 is connected to the output terminal 45 (this), and the other power supply terminal [share] is connected to the output terminal 44. The output terminal of the PLL circuit 61 and the power supply terminal [phase] The period Q is a low-pass filter 73, which will be described later.
A capacitor 66 constituting the circuit is connected.

Reference voltage output terminal ■ and output terminal ■ of the above PLL circuit 61
A capacitor 67 is connected between the two.

The PLL circuit 61 uses, for example, NE565 manufactured by Shida Futenox Co., Ltd., and is composed of a phase detector 71, an amplifier 72, a loaf 4 filter 3, and a voltage controlled oscillator 74 as shown in FIG. That is,
The phase detector 71 detects the phase difference between the phase of the input voltage at the input terminal (2) and the phase of the input voltage at the input terminals (2) and (2), and generates a voltage according to the phase difference. This generated voltage is amplified by an amplifier 72 and sent to a low-pass filter 73.

This low-pass filter 3 is constituted by a resistor 75 and the capacitor 66, and extracts only the voltage of the low frequency component from the output of the amplifier 72, and sends it to the output terminal of the voltage controlled oscillator 74 (which is connected to the voltage controlled oscillator 74). The voltage controlled oscillator 74 changes the oscillation frequency according to the input voltage and sends the oscillation output to the output terminal ■.In addition, in the original PLL circuit ζ, the output terminal ■ and the input terminal ■
The PLL circuit is controlled so that the phase difference with the input voltage becomes zero by connecting it to ing. That is, only the phase detector 21, the amplifier 72, and the low frequency filter 3 are used, and the voltage controlled oscillator 74 is not used. Also, amplifier 7
2 always generates a constant reference voltage regardless of the phase of the input voltage of this PLL circuit 6), and sends it to the output terminal The terminal is connected to the output terminal ■ of the PLL circuit 61,
The inverting input terminal is connected to the output terminal of the PLL circuit 61 via a resistor 82, and a resistor 83 is connected between the output terminal of the operational amplifier 81 and the inverting input terminal. At 35, the NPN transistor 9
1 is connected to the output terminal of the fourth amplifier 81 via a resistor 92. And the transistor 91
The collector is connected to the output terminal 93f, and the emitter is connected to the output terminal 45.

The operations shown in FIGS. 2 to 5 in the above configuration will be explained. The oscillator 32 operates in oscillation by a Colpitts oscillation circuit in which the collector output of the transistor 51 is fed back to the base of the transistor 51 via the oscillation windings 261 and 262 of the detection coil 22 and the resistor 54. Its oscillation frequency is set to 200 kHz, for example. The oscillation frequency can be changed by changing the capacitance of the capacitors 53, 57 and 58 and the inductance of the detection coil 22.

Thus, the detection winding 27X of the detection coil 22.

272 is wrapped in ζ as shown in Figure 2, so
An output voltage is generated between each end due to electromagnetic induction. In this case, output voltages are obtained from the detection winding 272 on the developer 3 side and from the detection winding 27□ on the adjustment core 24 side. Here, the flow of magnetic lines of force in the protruding coil 22 is the 217th (as shown in the adjustment core 2
4. Loop 28.28 for old 1j, loop 2 for developer 3 side
The angle is 9°29, and the loop 28.28 is the adjustment core 2.
A shadow 9 is applied depending on the position of the developer 3, and the root f29°29 is affected by a change in magnetic permeability due to a change in the toner concentration of the developer 3. In addition, a voltage obtained by dividing the power supply voltage by resistors 62 and 6'4 is applied to the connection point of the detection windings 271 and 272.
It is applied as asumi pressure. Therefore, a voltage corresponding to the position of the adjustment core 24 serving as a reference is generated between both ends of the detection winding 271, and a voltage corresponding to the toner concentration of the developer 3 is generated between both ends of the detection winding 272. Occur.

In this case, the detection winding 271 is adjusted according to the change in magnetic permeability due to the position of the adjustment core 24 and the change in toner concentration of the developer 3.
The phase of the pressure output 1272 is changed.

That is, the phase difference between the voltage applied to the input terminal (2) and the voltage applied to the input terminal (2) of the 'PLL circuit 6] varies depending on the toner concentration of the developer 3 and the position of the adjustment core 24.
For example, the phase difference is made to vary from 0° to 180°. Then, by pressing the production surface 12a of the detection head 12 against the developer having a certain specified toner concentration and turning the adjustment core 24, the phase difference between the detection voltages input to the input terminals (2) and (2) of the PLL circuit 61 becomes 90°. If adjusted as follows, the phase difference of the detection voltage will be 00 to 18 depending on the toner concentration of the developer 3.
An example of the waveform of one pressure detected by the detection coil 22 is shown in which the toner concentration of the developer 3 is determined by detecting this phase difference. First, set the toner RP degree to 4 (weight ratio)
At this time, adjust the adjustment core 24 so that the phase difference of the detected voltage is 90', and then adjust the toner concentration by
FIG. 6 shows an example of the waveform of the detected air pressure when .

In the figure, curve A is the detected voltage waveform from the detection winding 271, and curve B is the detected voltage waveform from the detection winding 272. As is clear from the figure, curves A and B are in the same phase and have a phase difference of 90°.

It can be seen that the value changed from to Oo. FIG. 7 shows an example of the waveform of the detected voltage when the toner density is set to 3. As is clear from the figure, curves A and B have opposite phases, and the phase difference is 90
You can see that it changed from ° to 180 °. In the above example, the phase difference is 0° even if the toner density is lower than 5.
The state of the phase difference 1800 does not change even if the toner concentration is made smaller than 3 cm, and the state of the phase difference 1800 remains stable. and,
When the toner concentration changes from the third to fifth ratio, the phase difference also changes from 180° to 00 accordingly. .

In this way, the detection winding 271 of the detection coil 22,
When the detection voltage obtained from 272 is input to the PLLM circuit 61f, the PLI circuit 61 temporarily calculates the phase difference of the input voltage by an operation similar to i'nJ:,%, and generates a DC voltage corresponding to the phase difference. Output to output AM child■. Also,
At this time, the voltage output from the output terminal 0 is constant regardless of the phase of the input voltage. Therefore, the output terminal ■,
By measuring the potential difference between (2), the phase difference of the input voltage can be determined.

Figure 8 shows the PLL circuit 61 when changing the toner density.
The figure shows the change in voltage between the output terminals ■ and ■ of the
In the case where the adjustment core 24 is adjusted so that the voltage is (10 volts), the toner concentration is lowered to 3%, the phase difference becomes 180', and the voltage is approximately +1
Becomes a bolt. Then, even if the toner concentration is further lowered by t, the voltage does not change. Conversely, when the toner concentration is increased to 5%, the phase difference becomes oo and the voltage becomes approximately -1 delt. In this case, even if the toner fatigue level is increased further, the voltage does not change.In addition, in this example, when the toner concentration is 4, the voltage is 0.
(I've had sex for the last 5 weeks, but of course this can be adjusted at any time.)

As described above, a phase change in the detection voltage of the detection coil 22 due to a change in toner concentration can be obtained as a change in DC voltage. As shown in FIG. 8, since changes in the direct pressure can be detected in a switching manner, accurate detection can be achieved.

Thus, the output voltages from the output terminals ① and ② of the PLL circuit 61 are respectively input to the operational amplifier f81. The operational amplifier 81 operates as a differential amplifier, and amplifies the difference between the output voltage of the output terminal (2) and the output voltage of the output terminal (2). Even if you want to do so, even if the output of the output terminal
If the voltage is higher than the output quasi-voltage of 1111 and 1111, the output of Obean No. 8 becomes high level, which turns on transistor 9 and turns on the toner concentration 1 (
No. 16 indicating the status of ``1-small'' is output. Conversely, if the output voltage of the output terminal ■ is smaller than the output voltage of the output terminal
Outputs a signal indicating the status of the dog. This output signal may be used in any way. For example, by directly driving the solenoid of the toner supply spring clutch of the toner supply device with the transistor 91, the toner supply with a "low" toner concentration may be performed. In addition, the transistor 91
The on/off signals may be read into the microprocessor that tilts the entire copying machine sideways, and the toner supply when the toner density is "low" may be performed at a timing that has little effect on the copied image, for example, at the end of document scanning. .

In the above embodiment, PLL1 is used as the phase difference detection circuit.
Although a circuit is used, it is not limited to this, and any circuit may be used as long as it can detect a phase difference.

Further, in the above embodiments, the case where the present invention is applied to a developing device of a copying machine has been described, but the present invention is not limited to this and can be applied to any developing device such as a Kameko Grinter or a facsimile machine.

['I color effect]

As detailed above, according to the present invention, it is possible to provide a developing device that can always detect a stable and accurate toner concentration, keep the toner concentration of a two-component developer constant, and always obtain uniform density image quality. .

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention. Fig. 1 is a 1111I sectional view showing the structure of the developing device, Fig. 2 is a side sectional view showing the structure of the detection head, and Fig. 3 is the toner concentration. The configuration of the detection device is schematically shown in the furnace block diagram.
A circuit diagram specifically showing each part in the figure. - Figure 5 is a configuration diagram of the PLL circuit. - Figures 6 and 7 are waveform diagrams showing an example of the detection voltage from the detection coil. Figure 8 is a diagram showing the toner concentration. FIG. 3 is a characteristic diagram showing the output voltage of the PLL circuit with respect to FIG. DESCRIPTION OF SYMBOLS 1... Photoreceptor drum (photoreceptor), 2... Developing roller (first conveyance means), 3... Two-component developer, 6... Blade (regulating means), 7... Sink plate (Third conveyance means)
, 9... Stirring spiral (second conveying means), 10...
・Device body, 11... Toner hopper, 12... Detection head of toner concentration detection device (toner donation detection means). Applicant's Representative Patent Attorney Takehiko E No. 1 Figure 2 Figure 5 Figure $8

Claims (3)

[Claims] (1) In a system in which an electrostatic latent image formed on an image support is developed using a two-component developer composed of a magnetic carrier and a non-magnetic toner, the two-component developer is transported to a developing area. a first conveyance means; a second conveyance means for stirring the two-component developer and conveying it to the first conveyance means; and a flow of the two-component developer between the second conveyance means and the first conveyance means. What is claimed is: 1. A developing device comprising: a toner concentration detecting means installed close to the toner concentration detecting means for detecting the toner concentration of the two-component developer. (2) The developing device according to claim 1, wherein the conveying direction of the fourteenth general conveying means is the same direction as the moving direction of the image support that moves in the developing section. (3) The developing device according to claim 1, wherein the toner concentration detecting means detects the toner concentration based on a change in magnetic permeability of the two-component developer.