JPH0631486Y2 - Toner concentration monitoring circuit - Google Patents

Description

The present invention relates to a toner concentration monitoring circuit that monitors a toner concentration detection signal in an electrophotographic developer and indicates that the toner concentration is at a predetermined value. A transistor to which a signal is input; a first light emitting diode connected in series to this transistor; and a second light emitting diode and a diode connected in parallel to a series circuit of the first light emitting diode and the transistor. By providing a circuit configuration including a series circuit, it is possible to obtain a highly reliable toner concentration monitoring circuit that has a simple circuit configuration, is small in size, is inexpensive, and is easy to adjust and set.

2. Description of the Related Art A toner concentration monitoring circuit is provided as a means for easily visually confirming whether the toner concentration in an electrophotographic developer is maintained at a prescribed concentration or not, during equipment adjustment or operation. A means for providing and lighting a display element such as a light emitting diode may be considered. Fig. 3 shows the conventional example,
1 is an electrophotographic developer containing a magnetic carrier and insulating toner, 2 is a developer container, 3 is a stirrer, 4 is a magnet roller, 5 is a photosensitive drum, 6 is a toner supply valve, 7 is a toner sensor, and 8 is signal processing. A circuit 9 is a toner concentration monitoring circuit.

The signal processing circuit 8 is configured to include a detection circuit 81, a comparator 82, a control circuit 83 for driving and controlling the toner supply valve 6, and the like. Based on a detection signal input from the toner sensor 7, the toner concentration becomes a predetermined prescribed concentration. Determine if there is. Between the toner concentration and the output voltage Vo of the detection circuit 81, as shown in FIG. 4, when the toner concentration increases, the output voltage Vo of the detection circuit 81 decreases, and conversely, when the toner concentration increases, the output voltage Vo increases. There is a relation that the voltage Vo becomes low.
Therefore, when setting the toner density to the specified density Tc ₁ ,
The threshold of the comparator 82 is set to the specified concentration Tc.
It is set in the vicinity of the output voltage Vo ₁ corresponding to _1. The toner density becomes lower than the specified density Tc ₁ , and the detection circuit 8
When the output voltage Vo of ₁ becomes higher than the threshold Vo _{1 of} the comparator 82, a signal of logical value 1 is given from the comparator 82 to the control circuit 83, and the toner supply valve 6 is opened by the output of the control circuit 83, and the toner supply valve 6 is opened. Is supplied. On the contrary, when the toner concentration is higher than the prescribed concentration Tc ₁ , the comparator 82 gives a signal of logical value 0 to the control circuit 83 to control the toner supply valve 6 to be closed. 84 and 85 are dividing resistors, 86 is a variable resistor,
The threshold of the comparator 82 is the resistance 8 of these resistors.
4, 85 and variable resistor 86.

Next, the toner concentration monitoring circuit 9 uses the comparators 91 and 92.
Equipped with. The output voltage Vo of the detection circuit 81 is commonly supplied to the input terminals (-) of these comparators 91 and 92, while the input terminals (+) are divided by the resistors 95 to 97 to have different voltages V ₉₁ and V _92. , Which gives different thresholds V ₉₁ , V ₉₂ . In this example, the voltage V ₉₁ applied to the input terminal (+) of the comparator 91 is higher than the voltage V ₉₂ applied to the input terminal (+) of the comparator 92, and the threshold V ₉₁ of the comparator ₉₁ is It is set higher than the threshold V ₉₂ of comparator 92. Threshold V ₉₁ of comparator ₉₁ and comparator 92
And the threshold V _92, the relationship between the output voltage Vo ₁ for normal concentration Tc _1, previously selected as _{V 91> Vo 1> V 92} . Also, the threshold V ₉₁ ,
_V92 is set so that the difference is a voltage difference within the allowable value of the toner density.

A series circuit of a resistor 98 and a light emitting diode 93 and a series circuit of a resistor 99 and a light emitting diode 94 are connected to the output sides of the comparators 91 and 92, respectively.

Light emitting diode 9 in the toner concentration monitoring circuit 9
The light emitting modes of 3, 94 are as follows.

(A) When V ₉₁ > Vo, the light emitting diodes 93 and 94 both emit no light.

(B) When V ₉₁ >Vo> V ₉₂ , the light emitting diode 94 emits light and the light emitting diode 93 does not emit light.

(C) When Vo> V ₉₁ , both the light emitting diode 93 and the light emitting diode 94 emit light.

V ₉₁ >Vo> V ₉₂ means that the output voltage Vo corresponds to a value within the toner density allowable value. Therefore, since the light emitting diode 94 emits light and the light emitting diode 93 does not emit light, it can be known that the toner concentration is within the allowable value.

Problems to be Solved by the Invention However, the above-described conventional toner concentration monitoring device has the following problems.

(A) Since the two comparators 91 and 92 are required, the circuit configuration becomes complicated, and it is unsuitable for toner concentration detection, which is strongly demanded for simplification, miniaturization, and high-density mounting of the circuit configuration.

(B) In the output adjustment work, the light emitting diode 91 emits light and the light emitting diode 92 does not emit light by adjusting the adjuster 811 while keeping the toner concentration of the electrophotographic developer 1 at a predetermined set value. After adjusting to the state, it is necessary to further adjust the variable resistor 86 and adjust the threshold of the comparator 82.
Therefore, the adjustment work is troublesome.

Means for Solving the Problems In order to solve the above problems, the present invention is a toner concentration monitoring circuit that monitors the toner concentration detection signal and indicates that the toner concentration is at a predetermined concentration. A transistor to be input, a first light emitting diode connected in series to this transistor, and a second light emitting diode and diode connected in parallel to a series circuit of the first light emitting diode and the transistor. And a circuit.

When the level of the toner concentration detection signal input to the base of the transistor is low and the transistor is off, the first light emitting diode connected in series to the transistor does not emit light, but the transistor and the first light emitting diode do not emit light. A second light emitting diode connected in parallel to the series circuit of the light emitting diodes and an operation power supply are applied to the series circuit of the diodes, and the second light emitting diodes emit light.

Next, when the level of the toner concentration detection signal rises and the transistor is turned on, the first light emitting diode emits light. When the transistor is turned on, the collector-emitter ON voltage V _CE (about 0.2 V) is lower than the forward voltage drop V _DF (about 0.7 V) of the diode connected in series with the second light emitting diode. since the forward voltage drop VF ₂ of the forward voltage drop VF ₁ and the second light-emitting diodes of the first light-emitting diode is substantially equal at all _{times, V CE + VF 1 <V} DF + VF 2 is established. Therefore, the second light emitting diode does not emit light.

When the level of the toner concentration detection signal is near the threshold of the transistor, both of the above conditions are satisfied at the same time, and the first light emitting diode and the second light emitting diode emit light at the same time. Therefore, since the first light emitting diode and the second light emitting diode emit light at the same time, it can be known that the toner concentration detection signal is at the threshold value that gives the toner concentration specified value.

Embodiment 1 FIG. 1 is an electric circuit diagram of a toner concentration detecting device having a toner concentration monitoring circuit according to the present invention. In the figure, the third
Reference numerals that are the same as those in the drawings indicate components that are the same. Reference numeral 10 is a toner concentration monitoring circuit. The toner concentration monitoring circuit 10 includes a transistor 101 whose base B receives a toner concentration detection signal, a first light emitting diode 102 connected in series to a collector C of the transistor 101, a transistor 101 and a first light emitting diode. A series circuit of a second light emitting diode 103 and a diode 104 connected in parallel to the series circuit of 102 is provided.

105 and 106 are resistors, and VB is an operating power supply. 87 is resistance,
Reference numeral 88 is a capacitor, which is provided to average the output of the detection circuit 81.

The toner concentration detection signal Vo output from the detection circuit 81 is input to the base B of the transistor 101 via the exclusive OR gate 11. Also, the transistor 10
The collector C of 1 is connected to the control circuit 83, and the transistor 1
The output of 01 is used as a control signal for controlling the toner supply valve 6. However, as shown by the dotted line in FIG. 1, another transistor 13 may be provided and the collector of this transistor 13 may be connected to the control circuit 83 to control the toner supply valve 6.

Reference numeral 12 is a variable resistor for adjusting the voltage input to one input terminal of the exclusive OR gate 11. Exclusive OR gate 1 for the input toner concentration detection signal Vo
The threshold at which the output of 1 becomes the logical value 1 or 0 is adjusted by the variable resistor 12.

When adjusting the light emission thresholds of the light emitting diodes 102 and 103, the toner sensor 7 is kept while the toner concentration of the electrophotographic developer 1 in the developer container 2 is maintained at the specified concentration Tc _1.
And the detection signal is input to the exclusive OR gate 11 via the detection circuit 81. The threshold at which the output of the exclusive OR gate 11 becomes the logical value 1 or the logical value 0 with respect to the inputted toner concentration detection signal Vo is adjusted by the variable resistor 12 so that the toner concentration becomes the prescribed concentration Tc _1. 1), the first light emitting diode 102 and the second light emitting diode 103 are set to emit light at the same time. By this adjustment, the output adjustment to be given to the control circuit 83 is also performed, so that the adjustment work is very easy.

After the adjustment as described above, when the toner concentration in the electrophotographic developer 1 becomes lower than the specified concentration Tc ₁ , the toner concentration detection signal Vo input to the exclusive OR gate 11 becomes high level, and the exclusive The output of the logical OR gate 11 becomes a logical value 0, and the transistor 101 is turned off. When the transistor 101 is turned off, the first light emitting diode 102 connected in series to the transistor 101 does not emit light, but the operating power supply VB is added to the series circuit of the second light emitting diode 103 and the diode 104, and Light emitting diode 10
3 lights up. Therefore, since the first light emitting diode 102 does not emit light and the second light emitting diode 103 emits light, it can be visually confirmed that the toner concentration is lower than the specified concentration Tc ₁ . At the same time, a high level output is given from the collector C side of the transistor 101 to the control circuit 83, and the toner supply valve 6 is opened by the control circuit 83 to supply the toner.

On the other hand, when the toner density becomes higher than the specified density Tc ₁ ,
Since the level of the toner concentration detection signal Vo input to the exclusive OR gate 11 becomes low, the exclusive OR gate 1
The output of 1 becomes a logical value 1 and the transistor 101 is turned on. When the transistor 101 is turned on, the first light emitting diode 102 emits light. Here, the collector-emitter on-voltage V _CE of the transistor 101 is about 0.2 V, and the diode 104 connected in series to the second light emitting diode 103.
Forward voltage drop V _DF is about 0.7V, V _CE <V
Become _DF . If the first light emitting diode 102 and the second light emitting diode 103 having the same characteristics are used, the forward voltage drop VF ₁ of the _first light emitting diode 102 and the forward voltage drop of the second light emitting diode 102 The voltage drop VF ₂ becomes substantially equal. Therefore, when the transistor 101 is turned on, V _CE + VF ₁ <V _DF + VF ₂ holds. Therefore, when the transistor 101 is on, the second light emitting diode 103 does not emit light. Therefore, since the first light emitting diode 102 emits light and the second light emitting diode 103 does not emit light, it is visually confirmed that the toner concentration in the electrophotographic developer ₁ is higher than the specified concentration Tc _1. it can.

Next, when the level of the toner concentration detection signal Vo is near the threshold of the exclusive OR gate 11, the first light emitting diode 102 and the second light emitting diode 103 emit light at the same time. Therefore, since the first light emitting diode 102 and the second light emitting diode 103 are emitting light at the same time, it can be visually confirmed that the toner concentration is at the specified concentration Tc ₁ .

As described above, since the toner concentration monitoring circuit according to the present invention has a simple circuit configuration including the transistor 101, the first light emitting diode 102 and the second light emitting diode 103, it is small and inexpensive, and A toner concentration monitoring circuit that is easy to adjust and set and has high reliability can be obtained.

FIG. 2 is a more specific circuit diagram of the toner concentration detecting device incorporating the toner concentration monitoring circuit according to the present invention. In the figure, 7 is a toner sensor formed of a differential transformer, 812 is an inverter, 813 is an amplifier, 814 is a phase comparator, 815 and 816 are capacitors, and 817 is a resistor. The capacitors 815 and 816 and the resistor 817 form an oscillation circuit together with the inverter 812.

The toner sensor 7 formed of a differential transformer has, as a general structure, an exciting coil N ₁ and a first output coil N ₂₁ which is coupled to the exciting coil N ₁ and whose output voltage E ₁ changes according to the toner concentration. , And a second output coil N ₂₂ whose output does not change depending on the toner concentration. Then, the first output coil N ₂₁ and the second output coil N ₂₂ are differentially connected,
The output voltage E ₁ of the output coil N ₂₁ and the differential output Eo of the output voltage E ₂ of the second output coil N ₂₂ are input to the phase comparator 814 through the amplifier 813 and the exciting current of the exciting coil N ₁ A phase detection output is generated by comparing the phase with the synchronized reference voltage. Differential output Eo
Since the phase of the toner changes depending on the toner density, the toner density can be detected by discriminating this phase change by the phase comparator 814.

818 and 819 are capacitors. The condenser 818 is the second
With the output inductance L ₂₂ and the inductance L ₂₁ of the first output coil N ₂₁ of the coil N _22, constitute a tuning circuit. The tuning circuit is provided to take out a large output by utilizing the resonance characteristic.

In the case of the embodiment shown in FIG. 2, it is needless to say that the same operation and effect as the embodiment shown in FIG. 1 can be obtained, but the exclusive OR gate 11, the inverter 812, the amplifier 813 and the phase shift comparator are obtained.
As 814, a general IC which is commercially available as a set of two or a set of four can be used, so that a small and inexpensive toner concentration monitoring circuit can be realized without waste. In the case of the conventional circuit shown in FIG. 3, this is a set of two or four ones.
If a pair of IC comparators are used, one comparator will be left over, resulting in waste, which is disadvantageous in terms of downsizing and high in cost.

Effect of the Invention As described above, according to the present invention, in the toner concentration monitoring circuit that monitors the toner concentration detection symbol and indicates that the toner concentration is at the specified concentration, a transistor to which a toner concentration detection signal is input is added to the base. A first light emitting diode connected in series to the transistor, and a second light emitting diode and diode series circuit connected in parallel to the first light emitting diode and the transistor series circuit. Therefore, it is possible to provide a toner concentration monitoring circuit having a simple circuit configuration, a small size, a low cost, easy adjustment and setting, and high reliability.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a toner concentration detecting device having a toner concentration monitoring circuit according to the present invention, and FIG. 2 is a more specific circuit of the toner concentration detecting device incorporating the toner concentration monitoring circuit according to the present invention. FIG. 3 and FIG. 3 are electric circuit diagrams of a toner concentration detecting device having a conventional toner concentration monitoring circuit, and FIG. 4 is a toner concentration-output voltage characteristic diagram. 10 ... Toner concentration monitoring circuit 101 ... Transistor 102 ... First light emitting diode 103 ... Second light emitting diode 104 ... Diode

Claims (1)

[Scope of utility model registration request] 1. A toner concentration monitoring circuit for monitoring a toner concentration detection signal and displaying that the toner concentration is at a predetermined value. A transistor to which a toner concentration detection signal is input to a base and a transistor connected in series to this transistor. A toner concentration monitoring circuit comprising: a first light emitting diode; and a second light emitting diode and a series circuit of the diode connected in parallel to the series circuit of the first light emitting diode and the transistor.