JPS59164575A - Toner density detector - Google Patents

Abstract

PURPOSE:To simplify structure and to detect always stable toner concentration by detecting the variation of magnetic permeability of a two-component developer due to the variation of toner density as a phase difference of each detected voltage of a magnetic detection means. CONSTITUTION:A detecting head 12 of a toner concentration detector is arranged so that its detecting surface 12a is opposed to a flowing plate 7 and the developer 3 regulated by a brade 6 is made flow between the detecting surface 12a and the flowing plate 7 to detect the toner density of the flowing developer. A detecting part 33 includes detecting windings 271, 272 and its output phase is changed by the change of the inductance of the detecting windings 271, 272 in accordance with the change of the magnetic permeability of the developer 3. Two signals are outputted from the detecting part 33 in accordance with the change of the phase and compared by a comparator part 34 and the compared result is inputted to an output part 35 and outputted as a toner density detecting signal from the output part 35.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a toner concentration detection device for detecting the toner concentration of image material in, for example, a dust image device of a copying machine.

[Technical background of the invention and its problems]

For example, in a copying machine, an electrostatic M image is formed on a sensitive material using a magnetic plan method using a two-component image agent composed of a carrier made of magnetic powder and a toner made of non-magnetic powder. In a clear image device for recording, it is necessary to detect the toner concentration of the developer and control the toner supply. Many conventional methods are known as means for detecting such toner concentration. The main methods include optical detection methods and magnetic detection methods. However, the optical detection method has the disadvantage that detection is unstable due to stains of the detection section with the yl image agent. First, the magnetic detection method has a structure in which dust particles pass through a cylinder wrapped around a coil, which has the disadvantage that the detection part is large and expensive. .

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a toner concentration detection device that is capable of constantly and stably detecting the level of toner, and has a simple structure, is small, and is inexpensive. There is a particular thing.

[Summary of the invention]

The toner concentration detection device of the present invention uses a magnetic detection means constituted by a first magnetic circuit including a reference magnetic body and a second magnetic circuit including a two-component developer to detect changes in toner concentration of a two-component developer. By detecting the change in magnetic permeability caused by this as a phase difference between the detection voltages of the magnetic detection means, a signal corresponding to the toner concentration is obtained.

[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-like image 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, rotates in the direction shown by the arrow in the figure, and applies the two-component developer 3 to the surface of the photoreceptor drum L (up to the paddy image area). The developing roller 2 is composed of a fixed magnet roller 4 containing a permanent magnet therein, and a rotating sleeve 5 made of a non-magnetic material that rotates around the outer periphery of the roller 4 in the direction indicated by the arrow. Note that the broken line inside the magnet roller 4 indicates the magnetic pole position of the permanent magnet. The toner is composed of a toner made of resin), and the toner is attached to the carrier by electrostatic charge.

A blade 6 controls excess diluent 3 in order to keep the amount of developer 3 supplied to the surface of photoreceptor drum 1 constant. Reference numeral 2 denotes a sink plate that conveys developer 3 regulated by grade 6 to the rear side of a stirring spiral 9, which will be described later. Reference numeral 8 denotes a scraper 1 that scrapes off the developer 3, which has lost its toner due to contact with the photosensitive drum 1, from the surface of the sleeve 5.
, 9 is an agitating spiral which sends the dripping developer 3 and the developer 3 scraped off by the scraper 8 to the sleeve 5 while stirring it. Reference numeral 10 denotes an apparatus main body that houses the above-mentioned components and the developer 3. 11/'i,
The toner hopper stores toner for replenishment, and a toner supply device (not shown) operates in response to a toner replenishment signal, so that the toner in the toner hopper 11 is supplied into the main body 10. .

In the vicinity of the blade 6 and above the sink plate 7, a detection head (coil block) 12 of the TOCHI concentration detection device according to the present invention is installed. In this case, the detection part 12a of the detection head 12 faces the sink plate 7,
The developer 3 regulated by the blade 6 flows between the detection surface 12a and the sink plate 7, and the toner concentration of the flowing developer 3 is detected.

The operation of FIG. 1 in such a configuration will be explained. The rotation directions of the photosensitive drum 1 and the sleeve 50 are opposite directions as shown by arrows a and 1), but in the developing area they are in the same direction (downward direction), which is the with mode. Further, the stirring spiral y rotates in the direction of arrow C in the figure. The developer 3 stirred by the 90 rotations of the stirring spiral is scraped up and sent to the upper part of the stirring spiral 9, and sent by the scraper 8 in the direction of the sleeve 5 as shown by the arrow in the figure, where it is permanently stored in the magnetic roller 4. It is attracted by the magnetic force of the magnet and adheres to the surface of the sleeve 5. The excess amount of the developer 3 conveyed to the blade 6 by the sleeve 5 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 (main body 1011111), where it is stirred by the stirring spiral 9. The developer 3 on the sleeve 5 whose thickness is regulated is conveyed by the sleeve 5, and is formed into soft brush-like spikes by the magnetic force of the permanent magnet in the magnet roller 4 at a position close to the photoreceptor drum 1. 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 the toner is conveyed by the sleeve 5, and then falls to the bottom of the main body 10 due to the centrifugal force and falls on the inclined surface formed at the bottom of the main body 1θ as shown by the arrow in the figure. The developer 3 carried to the vicinity of the stirring spiral 9 and remaining on the other threes 25 is scraped off by the scraper/f8, scattered around the stirring spiral 9, and stirred, respectively. Further, the excess developer 3 regulated by the blade 6 flows on the sink plate z as described above and flows between the detection surface 12h of the detection head 12, but at this time, the toner rust of the developer 3 is detected by the detection head 12 as a change in magnetic permeability.

The flow rate 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 6 and the inclination and shape of the sink plate 7. In addition, since the toner density of the excess developer 3 regulated by the blade 6 and the developer 3 that passes through the blade 6 and is developed is the same, the yl developer 3 detected by the detection head 12 The toner concentration of is the same as the toner concentration of the developer 3 that actually performs stationary imaging. Further, it is easy to understand that the lid of the excess developer 3 regulated by the blade 6 and its flow rate are always constant during the rotation of the sleeve 5 and the stirring spiral 90. Therefore, stable toner concentration detection is possible at all times.

FIGS. 2 and 3 show other installation states of the detection head 12. FIG. That is, FIG. 2 shows the detection head 12
is installed below the tip of the blade 6, and the detection surface 12a is brought into contact with the developer 3 regulated by the blade 6. FIG. 3 also shows that the detection head 12 is connected to the sleeve 5 at the lower part of the sink plate 7 at t'I'.
The detection surface 1 is installed between the agitator 4 and the rotor 9, and the detection surface 1 is connected to the flow of the developer 3 sent from the agitator rotor 9 to the sleeve 5.
2a are brought into contact with each other. In these cases, stable detection is possible even when the sink plate 7 is not provided, depending on the structure of the developing device.

FIG. 4 shows the structure of the detection head 12.

That is, 2 is a sealed cylindrical main body, the lower surface of which is a detection surface 12a, and this detection surface 12a is a main body in the form of a closed cylinder.
come into contact with. Inside this main body 21 is a detection coil 2.
2, a coil holding member 23, and an adjustment core 24 serving as a reference magnetic body are housed in the housing. The detection coil 22 is fixed to the main body 2 by a coil holding member 23 to prevent rattling between the detection coil 22 and the main body 21. The adjustment core 24 is located on the upper surface 21a of the main body 21.
By rotating this adjustment core 24 with a screwdriver or the like, the distance from the center of the detection coil 22 can be changed. 'The detection coil 22 includes cores 25□, 252, oscillation windings 26126□, detection windings 27□, 27
It is composed of 2. An oscillation winding 26□ and a detection winding 27□ are wound around the core 251, and an oscillation winding 26□ and a detection winding 272 are wound around the core 252, respectively. The detection winding 271 is located on the adjustment core 24 side, and the detection winding 27□ is located on the detection surface 12a side. 3, and therefore is not contaminated by the developer 3.

FIG. 5 schematically shows the configuration of the toner concentration detection device according to the present invention, which is composed of a stabilized power supply section 31, an excavation section 32, a detection section 33, a comparison section 34, and an output section 35. That is, the stabilized power supply section 31 generates a predetermined stabilized DC voltage (for example, 16 volts) by being supplied with a predetermined DC voltage (for example, -24 volts) from an external power source (not shown), and supplies it to each part. .

The oscillation section 32 includes oscillation windings 26, . 26
□ and generates a predetermined high frequency oscillation output. This oscillation output is applied to the detection section 33. The detection unit 33 is
The detection winding 27□ and 272 shown in FIG.
By changing the inductance of the inductance, 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. and,
The output unit 35 outputs the toner concentration detection signal.

FIG. 6 is a circuit example specifically showing each part of FIG. 5. First, in the stabilized power supply section 31, the collector of the NPN transistor 41 is connected to one input terminal 42, and the emitter is connected to one output terminal 44. The other input terminal 43 is connected to the other output terminal 45. The pace of the transistor 41 is connected to an input terminal 43 via a Zener diode 46. A resistor 47 is connected between the collector of the transistor 41 and the pace. stop,
A capacitor 48 is connected between the output terminals 44 and 45.

Next, in the oscillation section 32, the NPN transistor 51
The 0 base can be connected to the output terminal 45 via a resistor 52 and a capacitor 53 in parallel, and is also connected to the output terminal 44 via a resistor 54. The emitter of the transistor 5 is connected to the output terminal 4 via a resistor 55.
5, and can also be 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 between the resistor 56 and the capacitor 57 and the collector of the transistor 5.

The collector of the transistor 5 is connected to one end of the oscillation winding 26□. This oscillation winding 26
The other end of the oscillation winding 26□ is connected to one end of the oscillation winding 26□, and the other end of the oscillation winding 26□ is connected to the output terminal 44.

Next, in the detection section 33, one end of the detection winding 271 is connected to the input terminal (2) of a PLL-IC (phase-locked loop integrated circuit, hereinafter simply referred to as PLL circuit) 61 as a phase difference detection circuit. The other end is connected to one end of the detection winding 27□ and the input terminal of the PLL circuit 6
It is also connected to the output terminal 45 via a resistor 62 and a capacitor 63 in parallel.

Further, one end of the detection winding 27□ is connected to the output terminal 44 via a resistor 64, and the other end is connected to the input terminal □ of the PLL circuit 61. In addition, C1] detection winding 2
A capacitor 65 is connected in parallel to 7□. and,
One power supply terminal ■ of the PLL circuit 61 is connected to the output terminal 45.
Then, the other power supply terminal [phase] is connected to the output terminal 44, respectively. Output terminals ■ and ' of the above PLL circuit 61
A capacitor 66 constituting a low-pass filter 73, which will be described later, is connected between the terminal and the terminal [phase]. Above PL
A capacitor 67 is connected between the reference voltage output terminal (■) and the output terminal (■) of the L circuit 61. The above-mentioned PLL circuit 61 uses, for example, NE565 manufactured by Shidanetex Corporation, and as shown in FIG.
, a loaf filter 73, and a voltage controlled oscillator 74.
Consisted of. 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 based on the phase difference. This generated voltage is amplified by an amplifier 72 and sent to a low-pass filter 73. This low-pass filter 73 is configured with a resistor 75 and a capacitor 66, extracts only the voltage of the low frequency component from the output of the amplifier 72, sends it to the output terminal 7, and controls the voltage 9j. input to the device 74. Voltage? 1jIJ
The fai1 oscillator 74 changes the oscillation jΔJ wave number according to the input voltage, and sends the oscillation output to the output terminal ■. In addition, in the original PLL circuit VC, the output terminal ■
By connecting PL and input terminal ■, control is performed so that the phase difference with the input voltage becomes zero.
Since the L circuit is only used as a phase difference detection circuit,
The method of use is quite different from normal usage. That is, only the phase detector 7, amplifier 72, and low-pass filter 73 are used for convenience, and the electric EE ffrlJ control oscillator 24 is not used. Further, the amplifier 72 always generates a constant reference voltage regardless of the phase of the input voltage of the PLL circuit 61 and sends it to the output terminal (2).

Next, in the comparison section 34, the non-inverting input terminal of the operational amplifier 8 is connected to the output terminal 2 of the PLL circuit 61,
The inverting input terminal is connected to the output terminal (2) of the PLL circuit 61 via a resistor 82. A resistor 83 is connected between the output terminal and the inverting input terminal of the operational amplifier f81.

Next, in the output section 35, the base of the NPN transistor 9 is connected forward through a resistor 92 to the output terminal of the operational amplifier 8. And the transistor 91
The collector of is connected to the output terminal 7-93, and the emitter is connected to the output terminal 45.

The operations shown in FIGS. 4 to 7 in the above configuration will be explained. Oscillation unit 3: HfJ, collector output of transistor 5I is the oscillation winding 261 p2 of the detection coil 22
6x and the resistor 54 to the base of the transistor 51, the Corbyn oscillator circuit operates as an original oscillator. The oscillation frequency is set to 200 kHz, for example.

The number of oscillation cycles above is 53°57.
58 W% can be varied by changing the inductance of the transmission and detection coil 22. However, the detection winding of the detection coil 22! 271.27°t, as shown in FIG. 4, an output cuff a pressure is generated at each end 1i-iJ due to the LIL magnetic rust conduction action. In this case, the detection winding 27□
Therefore, the adjusting cores 24 and 24j are obtained from the ignition windings 271 at the respective outputs. Here, the flow of magnetic lines of force in the detection coil 22 is as shown in FIG.
4 side is loop 28.28, developer 3 side is loop 29.2
9, the loops 28.degree. 28 are affected by the position of the adjusting core 24, and the loops 29.29 are affected by changes in magnetic permeability due to changes in the toner concentration of the developer 3. Further, a voltage obtained by dividing the power supply voltage by a resistor 62.64 is applied as a bias voltage to the connection point between the detection windings 27□ and 272 until t. Therefore, the detection winding 2
A voltage corresponding to the position of the adjustment core 24 serving as a reference is generated between both ends of the detection winding 272, and a voltage corresponding to the toner concentration of the developer 3 is generated between both ends of the detection winding 272. This - combination,
The phase of the output voltage of the detection windings 271 and 272 changes depending on the position of the adjustment core 24 and the change in magnetic permeability due to the change in toner concentration of the developer 3. 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, from 0° to 180°. Allow it to vary up to °. and,
Press the detection surface 12a of the detection head 12 against the developer having a certain specified toner concentration, and turn the adjustment core 24 so that the phase difference between the detection voltages input to the input terminals (2) and (2) of the PLL circuit 6 becomes 90°. When adjusted, the phase difference of the detection voltage changes from θ° to 180° depending on the toner concentration of the developer 3, and by detecting this phase difference r, the toner concentration level j of the station image uniformity 3 can be known. be able to.

FIGS. 8 and 9 show examples of waveforms of the detection voltage of the detection coil 22 when the above-mentioned adjustment is performed. First, the toner concentration is set to 4% (weight ratio), the adjustment core 24 is adjusted so that the phase difference of the detected voltage is 90 degrees, and then the waveform of the detected voltage when the toner concentration is set to 5%. Example number 8
It is a diagram. 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, curve A,
It can be seen that B was in the same phase and the phase difference changed from 90° to 00°. FIG. 9 shows an example of the waveform of the detection voltage when the toner concentration is 3%. As is clear from the figure, curve A
, Bid are in opposite phase, and the phase difference is from 90° to 180°
You can see that it has changed to. In the above example, even if the toner concentration is made larger than the 5th factor, the state of the phase difference O0 does not change, and even if the toner density is made smaller than 3%, the state of the phase difference of 180° does not change and remains stable. ing.

Then, when the toner density changes from 3 tib to 5 yu,
Accordingly, the phase difference also changes from 180° to 0°.

In this way, the detection winding 27□ of the detection coil 22
, 272 is input to the PLL circuit 61, the PLL circuit 61Fi detects the phase difference of the reverse input voltage by the operation described above, and outputs a DC voltage corresponding to the phase difference to the output terminal Output. Further, at this time, the voltage outputted to the output terminal (2) is constant regardless of the phase of the input voltage. Therefore, by measuring the potential difference between the output terminals (1) and (2), the phase difference of the input voltage can be determined.

Figure 10 shows the PLL circuit 6 when changing the toner density.
This figure shows the change in voltage between the output terminals ① and ② of . The figure shows a phase difference of 90° when the toner density is 4.
In this case, the adjustment core 24 is adjusted so that the voltage becomes 0 voltage. Next, when the toner concentration is lowered to 3 pixels, the μ phase difference becomes 180° and the voltage becomes about +1 volt. Even if the toner concentration is further reduced, the voltage does not change. On the other hand, if the toner concentration is increased to 5 volts, the phase difference will be θ° and the voltage will be about −1 volt. In this case, the voltage does not change even if the toner concentration is further increased. In this example, the voltage was adjusted to be 0 volts when the toner concentration was 4%, but it goes without saying that this can be adjusted any number of times.

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. 10, voltage changes can be obtained by switching, resulting in highly accurate detection.

Therefore, the output voltages from the output terminals (2) and (2) of the PLL circuit 6 are input to the operational amplifier 8, respectively. The operational amplifier 8 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). Therefore, for example, if the output voltage of the output terminal (■) is lower than the output voltage of the output terminal (■), the output of the operational amplifier 81 will be at a high level), and the transistor 91 will be turned on and the toner concentration will be "low". Outputs a signal indicating the status. Conversely, if the output voltage of the output terminal ■ is smaller than the output voltage of the output terminal ■, the output of the operational amplifier 81 becomes a low level, which turns off the transistor 9, and the toner density is in a state of "high". Outputs a signal indicating. This output signal may be used in any way. For example, toner may be supplied when the toner discretion is "small" by directly driving the solenoid of the toner supply spring clutch of the toner supply device by the transistor 9.

In addition, the on/off signal of the transistor 91 is once read into the microprocessor that controls the entire copying machine, and the toner supply when the toner density is "low" is performed at a timing that has little effect on the copied image, for example, at the end of scanning the original. 1. In the above-described toner concentration detection device, the change in magnetic permeability caused by the change in toner concentration of the atomizer 3 is detected in the detection coil 22 not as a voltage but as a phase difference between the detection voltages. Therefore, it is stable against environmental changes such as temperature or humidity and changes in power supply voltage, and can detect toner concentration much better than conventional methods. In addition, the construction is very simple, the number of components is small, it can be manufactured compactly and at low cost, and the detected toner longitude can be easily changed according to the optimum toner concentration of the glaze.

The installation angle of the detection head 12 in FIG.
The flow of the developer 3 may be more stable if the installation angle of the developer 3 is made larger.

Further, in the above embodiment, a PLL circuit is used as the phase difference detection circuit, but the present invention is not limited to this, and any suitable circuit that can detect a phase difference may be used.

Further, in the above embodiment, the toner concentration of the developer is detected in the cultivation device of a copying machine, but the toner concentration of the developer is not limited to this. It can also be applied to detecting

[Effects of the Invention] As detailed above, according to the VC of the present invention, it is possible to always detect a stable toner concentration regardless of whether it is dirty with a spy agent, and the toner concentration is simple, compact, and inexpensive. A detection device can be provided.

[Brief explanation of drawings]

The figures are for explaining one embodiment of the present invention, and FIG. 1 is a side sectional view showing the configuration of the dust imaging device, and FIGS. 2 and 3 are side sectional views showing other installation states of the detection head. 4 is a side sectional view showing the structure of the detection head, FIG. 5 is a block diagram schematically showing the structure of the toner concentration detection device, and FIG. 6 is a circuit diagram specifically showing each part of FIG. 5. , FIG. 7 is a configuration diagram of the PLL circuit, FIGS. 8 and 9 are waveform diagrams showing an example of the detection voltage from the detection coil, and FIG. 10 is a characteristic diagram showing the output voltage of the PLL circuit with respect to toner concentration. . 3 3... Two-component Sl image agent, 12... Detection head, 12
a...Detection section, 22...Detection coil, 24...
Adjustment core (reference magnetic material), 251 1252... Core, 26, . 26□...Oscillation winding, 27□, 27
□... Detection winding, 32... Oscillation section, 33... Detection section, 34... Comparison section, 6... PLL circuit (phase difference detection circuit). Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 7 Figure 8 Figure 9 m 1 hour (psec) - 1 hour 0
-JSeC) Figure 10

Claims (5)

[Claims] (1) 'IWI' by magnetic carrier and non-magnetic toner
In the device for detecting the toner concentration of the two-component developer produced, a magnetic detection means is formed of a first magnetic circuit including a reference magnetic material and a second magnetic circuit including the two-component dust imager. and a phase difference detection means for detecting a phase difference between each detection voltage between the first magnetic circuit and the second magnetic circuit of the magnetic detection means, and a signal corresponding to the toner concentration is obtained from the output of the phase difference detection means. A toner concentration detection device characterized in that: (2) The magnetic detection means is a coil having a first detection winding provided near the reference magnetic body and a second detection winding provided near the two-component developer, and the phase difference detection means 2. The toner concentration detecting device according to claim 1, wherein the means detects a phase difference between the detection voltages of the first and second detection windings. (3) Above 1. 3. The toner concentration detection device according to claim 2, wherein the second magnetic circuit is a coil that also has an oscillation winding that can be connected to the oscillation circuit. (4) In the first magnetic circuit, by changing the magnetic resistance of the reference magnetic body, a detection voltage corresponding to an arbitrary toner concentration of the two-component developer is obtained. 2. The toner concentration detection device according to item 1. (5) The toner concentration detection device according to claim 4, wherein the magnetic resistance of the reference magnetic body is changed by changing the strength or position of the magnetic flux of the reference magnetic body.