JP5083485B2 - Surface potential detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface potential detection device that detects a surface potential in a non-contact manner.
[0002]
[Prior art]
This type of surface potential detection device is used as means for detecting the surface potential of a photosensitive drum, which is a measurement object, in a copying machine, a laser beam printer, or the like. As disclosed in Japanese Patent Publication No. 3-6467 and the like, this type of surface potential detection apparatus mechanically interrupts the electric field between the detection electrode and the photosensitive drum by means of a tuning fork. An AC signal corresponding to the surface potential is obtained. The AC signal is amplified by a preamplifier, guided to a detection circuit via an isolator, and detected by a signal synchronized with mechanical interruption. The synchronous detection output signal output from the detection circuit is converted into a direct current by the integration circuit. The DC signal obtained by the integration circuit is input to the high voltage generator.
[0003]
The high voltage generator includes a high voltage transformer for generating a high voltage insulated from the primary side circuit and other various high voltage components, and based on the input DC signal, it has the same potential as the surface of the photosensitive drum. A common ground potential is generated, and this common ground potential is fed back to the integrating circuit. This common ground potential is in a floating relationship with the primary circuit, ground potential, or frame ground potential. The common ground potential is processed using an attenuator, a buffer, or the like, and is output as a surface potential detection signal.
[0004]
The greatest advantage of this method is that even if the distance between the detection electrode and the surface of the photosensitive drum changes, a highly accurate surface potential detection signal with very little distance dependency can be obtained.
[0005]
Recently, image forming apparatuses such as high-speed tandem type copying machines and laser beam printers using four (cyan, magenta, yellow, black) photosensitive drums have been proposed and put into practical use. These image forming apparatuses control the surface potential of the photosensitive drum to be constant by giving a predetermined control signal to the charger based on the surface potential of the photosensitive drum detected by the surface potential detector. . Therefore, in order to accurately control the surface potentials of these four photosensitive drums, the surface potentials of the four photosensitive drums are detected simultaneously and continuously, and based on the detected surface potentials. A control signal needs to be generated. Therefore, conventionally, a configuration in which one surface potential detection device is provided for each of the four photosensitive drums has been adopted. Therefore, in the image forming apparatus including four photosensitive drums, four surface potential detection devices are necessary.
[0006]
However, the high voltage generation unit of the surface potential detection device includes a high voltage transformer that is a component having a large shape, mass, and power consumption, and a high voltage component that is generally an expensive component. For this reason, when four surface potential detectors are used for one image forming apparatus, four high voltage generators are required, resulting in an increase in size, weight, and consumption of the four surface potential detectors as a whole. There has been a problem that the increase in power and cost increase become significant.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a surface potential detection device capable of suppressing an increase in shape, an increase in weight, an increase in power consumption, and an increase in cost.
[0008]
Another object of the present invention is to provide a surface potential detection device capable of simultaneously and continuously detecting potentials of a plurality of objects to be measured.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problem, a surface potential detection device according to the present invention includes one high-voltage transformer and a plurality of potential sensors. The high voltage transformer generates a high voltage insulated from the primary coil in one secondary coil. Each of the plurality of potential sensors is independent from each other, and includes a sensor unit, a potential detection circuit, and a voltage conversion circuit.
[0010]
The sensor unit generates a detection signal corresponding to the potential of the measured object. The potential detection circuit generates a voltage signal using a common ground potential corresponding to the potential of the measured object and a detection signal supplied from the sensor unit. The voltage conversion circuit generates a common ground potential by controlling a high voltage commonly supplied from the high-voltage transformer with a voltage signal.
[0011]
The common ground potential is fed back to the potential detection circuit and output as a surface potential detection signal.
[0012]
As described above, in the surface potential detection device according to the present invention, the high voltage transformer can generate a high voltage insulated from the primary coil in one secondary coil. That is, a high voltage insulated from the ground potential or the frame ground potential can be generated in the secondary coil.
[0013]
The surface potential detection apparatus according to the present invention includes a plurality of potential sensors, each of which is independent of each other. For this reason, the electric potential of a several to-be-measured body can be detected simultaneously and continuously. For example, in an image forming apparatus such as a high-speed tandem type copying machine or a laser beam printer, four potential sensors are made to correspond to four (cyan, magenta, yellow, black) photosensitive drums, and the surface potential is individually set. Can be detected. Further, even when a large number of potential sensors are provided in a distributed manner as in the case of detecting the charge of the film being conveyed, the surface potential can be individually detected at different locations on the film.
[0014]
In the surface potential detection apparatus according to the present invention, the sensor unit can generate a detection signal corresponding to the potential of the measured object.
[0015]
Further, the potential detection circuit can generate a voltage signal using the common ground potential corresponding to the potential of the measured object and the detection signal supplied from the sensor unit. The voltage conversion circuit can generate a common ground potential by controlling the high voltage supplied from the high-voltage transformer using a voltage signal. The common ground potential can be output as a surface potential detection signal.
[0016]
Therefore, for example, by using a potential substantially equal to the potential of the device under test as the common ground potential, a potential almost independent of the distance between the sensor unit and the device under test can be generated. By outputting the potential detection signal, the surface potential can be detected with high accuracy. Further, the surface potential detection signal can be output after being decompressed via an output circuit, for example.
[0017]
Further, in the surface potential detection device according to the present invention, the common ground potential is fed back to the potential detection circuit, so that the potential detection circuit can perform processing using the common ground potential.
[0018]
Moreover, in the surface potential detection device according to the present invention, as described above, the high voltage transformer generates a high voltage that is insulated. Therefore, the voltage conversion circuit does not need to have an insulation function, and the supplied high voltage is obtained. It is only necessary to convert it to a desired voltage value and output it. Therefore, since the voltage conversion circuit can be configured by a circuit having a simple configuration that does not include a transformer, for example, a chopper circuit, cost reduction can be achieved.
[0019]
Further, in the surface potential detection device according to the present invention, as described above, the high voltage transformer generates a high voltage, so that the voltage conversion circuit does not need to boost the voltage and supplies the supplied high voltage to a desired voltage value. It is only necessary to convert the data to output. Therefore, since the voltage conversion circuit can be a step-down circuit having a simple configuration, for example, a dropper circuit, the cost can be reduced.
[0020]
In the surface potential detection device according to the present invention, each of the voltage conversion circuits is commonly supplied with a high voltage from one secondary coil provided in the high-voltage transformer. However, one high voltage transformer is sufficient. For this reason, shape enlargement, weight increase, increase in power consumption, and cost increase can be suppressed.
[0021]
For example, the shape, weight, power consumption, and cost are remarkably reduced as compared with the prior art in which it is necessary to provide four high-voltage transformers for four photosensitive drums to be measured.
[0022]
In addition, by using a high-voltage transformer in common, it is possible to simplify a circuit for generating an insulated high voltage. For this reason, the high voltage | pressure-resistant components used for these circuits, for example, the transistor for switching, can be reduced and cost is reduced significantly. The above advantages become more prominent as the number of detection points increases.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram schematically showing a configuration in the case of detecting the surface potentials of four photosensitive drums arranged in tandem using the surface potential detection device according to the present invention. In the figure, four photosensitive drums C, M, Y, and K, which are measured bodies, are arranged in tandem. The photosensitive drum C is for cyan and has a surface potential Vc = −200V. The photosensitive drum M is for magenta and has a surface potential Vm = −400V. The photosensitive drum Y is for yellow and has a surface potential Vy = −600V. The photosensitive drum K is for black and has a surface potential Vk = −800V.
[0024]
The illustrated surface potential detection device 1 includes a high voltage generation circuit 53 and a plurality of potential sensors 10, 20, 30, and 40. The illustrated embodiment shows a case where the surface potentials of the four photosensitive drums C to K arranged in tandem are detected. Therefore, the number of the potential sensors 10 to 40 is four, but the number is the number of measured objects. Increase or decrease depending on Each of the potential sensors 10 to 40 is individually provided for each of the photosensitive drums C to K, and is fixedly disposed at a distance of, for example, 2.5 mm from the surface of the photosensitive drums C to K. .
[0025]
The high voltage generation circuit 53 includes one high voltage transformer 50. The primary coil 51 of the high-voltage transformer 50 is connected to a ground terminal or a frame potential, and a voltage of about 24 V is supplied from the power supply terminal Vin. There is one secondary coil 52 and generates a high voltage Vh insulated from the primary coil 51. The high voltage Vh generated in the secondary coil 52 is, for example, −1000V. One high-voltage transformer 50 is connected to and shared by the four potential sensors 10-40.
[0026]
Each of the plurality of potential sensors 10 to 40 is independent of each other. The potential sensors 10-40 include sensor units 110, 210, 310, 410, potential detection circuits 120, 220, 320, 420, voltage conversion circuits 130, 230, 330, 430, and output circuits 140, 240, 340, 440.
[0027]
The sensor units 110 to 410 are arranged to face the four photosensitive drums C to K, and generate detection signals S11, S21, S31, and S41 corresponding to the potentials Vc to Vk of the photosensitive drums C to K. The detection signals S11 to S41 are sent to the potential detection circuits 120 to 420 via a coaxial cable or the like.
[0028]
The potential detection circuits 120 to 420 use common ground potentials Vcom1, Vcom2, Vcom3, and Vcom4 corresponding to the potentials Vc to Vk of the photosensitive drums C to K, and detection signals S11 to S41 supplied from the sensor units 110 to 410. The voltage signals S12, S22, S32, and S42 are generated.
[0029]
The voltage conversion circuits 130 to 430 generate the common ground potentials Vcom1 to Vcom4 by controlling the high voltage Vh supplied in common from the high voltage transformer 50 by the voltage signals S12 to S42.
[0030]
The common ground potentials Vcom1 to Vcom4 are fed back to the potential detection circuits 120 to 420 and output as surface potential detection signals Vout1, Vout2, Vout3, and Vout4 via the output circuits 140 to 440. The output circuits 140 to 440 are circuits for outputting the common ground potentials Vcom1 to Vcom4 with a reduced pressure, and can be omitted.
[0031]
As described above, in the surface potential detection device according to the present embodiment, the high voltage transformer 50 can generate the high voltage Vh insulated from the primary coil 51 in the secondary coil 52. That is, the secondary coil 52 can generate a high voltage Vh that is insulated from the ground potential or the frame ground potential.
[0032]
The surface potential detection apparatus according to the present embodiment includes a plurality of potential sensors 10 to 40, each of which is independent of each other. For this reason, a plurality of objects to be measured can be detected simultaneously and continuously. For example, as shown in the illustrated embodiment, in a high-speed image forming apparatus such as a tandem type copying machine or a laser beam printer, four photosensitive drums C (four cyan sensors, magenta, yellow, and black) are used. The surface potential can be detected individually corresponding to .about.K. Further, even when a large number of potential sensors are provided in a distributed manner as in the case of detecting the charge of the film being conveyed, the surface potential can be individually detected at different locations on the film.
[0033]
In the surface potential detection apparatus according to the present embodiment, the sensor units 110 to 410 can generate detection signals S11 to S41 corresponding to the potentials Vc to Vk of the measured object.
[0034]
In addition, the potential detection circuits 120 to 420 use the common ground potentials Vcom1 to Vcom4 corresponding to the potentials Vc to Vk of the measured object, and the detection signals S11 to S41 supplied from the sensor units 110 to 410, and the voltage signal S12. ~ S42 can be generated. The voltage conversion circuits 130 to 430 can generate the common ground potentials Vcom1 to Vcom4 by controlling the high voltage Vh supplied from the high voltage transformer 50 using the voltage signals S12 to S42.
[0035]
Therefore, for example, by using a potential that is substantially equal to the potential of the measured object as the common ground potentials Vcom1 to Vcom4, a potential that hardly depends on the distance between the sensor units 110 to 410 and the measured object can be generated. By outputting this potential as the surface potential detection signals Vout1 to Vout4, it is possible to detect the surface potential with high accuracy. Further, the surface potential detection signals Vout1 to Vout4 can be decompressed and output through an output circuit, for example.
[0036]
Further, in the surface potential detection device according to the present invention, since the common ground potentials Vcom1 to Vcom4 are fed back to the potential detection circuits 130 to 430, the potential detection circuits 130 to 430 perform processing using the common ground potentials Vcom1 to Vcom4. It can be performed.
[0037]
Further, in the surface potential detection device according to the present embodiment, as described above, the high voltage transformer 50 generates the insulated high voltage Vh. Therefore, the voltage conversion circuits 130 to 430 need not have an insulation function. It is only necessary to convert the supplied high voltage Vh into a desired voltage value and output it. Therefore, the voltage conversion circuits 130 to 430 can be configured by a circuit having a simple configuration that does not include a transformer, for example, a chopper circuit, so that the cost can be reduced.
[0038]
In the surface potential detection device according to the present embodiment, as described above, the high-voltage transformer 50 generates the high voltage Vh, so that the voltage conversion circuits 130 to 430 need not perform the boosting and the supplied high voltage It is only necessary to convert the voltage Vh into a desired voltage value and output it. Therefore, the voltage conversion circuits 130 to 430 can be a step-down circuit having a simple configuration, for example, a dropper circuit, so that the cost can be reduced.
[0039]
In the surface potential detection apparatus according to the present embodiment, the voltage conversion circuits 130 to 430 are commonly supplied with the high voltage Vh from the high-voltage transformer 50, so that it is not necessary to provide a plurality of high-voltage transformers 50. Moreover, since only one high-voltage transformer 50 needs to be provided, the number of high-voltage transformers 50 does not increase even when measuring a plurality of objects to be measured. For this reason, shape enlargement, weight increase, increase in power consumption, and cost increase can be suppressed.
[0040]
For example, as compared with the conventional technique in which four high-voltage generators including the high-voltage transformer 50 are required for the four photosensitive drums C to K which are measurement objects, the shape, weight, power consumption, and Cost is significantly reduced.
[0041]
Further, by using the high-voltage transformer 50 in common, it is possible to simplify a circuit for generating an insulated high voltage. For this reason, the high voltage | pressure-resistant components used for these circuits, for example, the transistor for switching, can be reduced and cost is reduced significantly. And if the detection location increases, the said advantage will become more remarkable.
[0042]
Next, the configuration of the surface potential detection device shown in FIG. 1 will be described more specifically with reference to FIGS. FIG. 2 is a block diagram more specifically showing the sensor unit and the potential detection circuit of the surface potential detection apparatus shown in FIG. In the figure, each of the sensor units 110 to 410 includes a detection electrode 111, a chopper 112, and a preamplifier 113. Each of the potential detection circuits 120 to 420 includes an amplification circuit 121, a detection circuit 122, an integration circuit 123, an adjustment circuit 124, a drive circuit 125, and a DC / DC converter 34.
[0043]
The detection electrodes 111, the chopper 112, the preamplifier 113, and the adjustment circuit 124 of the sensor units 110 to 410 are provided in the probes 61, 62, 63, and 64, respectively. The amplifier circuit 121, the detection circuit 122, the integration circuit 123, the drive circuit 125, and the DC / DC converter 34 of the sensor units 110 to 410 are provided on the circuit board 70 together with the voltage conversion circuits 130 to 430 and the high voltage generation circuit 53. Yes.
[0044]
FIG. 3 is a circuit diagram more specifically showing a portion including the high voltage generation circuit of the surface potential detection device shown in FIG. In the figure, a high voltage generation circuit 53 includes a high voltage transformer 50, transistors Q2 and Q3, capacitors C3 and C7, an inductor L1, and a diode D4.
[0045]
The high voltage generation circuit 53 excites the primary coil 51 by the switching operation of the transistors Q2 and Q3 and supplies a feedback signal to the bases of the transistors Q2 and Q3 via the auxiliary winding Nb2 inductively coupled to the primary coil 51. To do. The transistors Q2 and Q3 continue the self-oscillation operation by the above-described feedback signal and the resonance phenomenon of the LC resonance circuit including the capacitor C3 and the inductor L1.
[0046]
The secondary coil 52 rectifies the AC voltage generated by the oscillation operation via the capacitor C7 and the diode D4, and generates a high voltage Vh. The high voltage Vh is supplied to the voltage conversion circuits 130 to 430.
[0047]
FIG. 4 is a circuit diagram more specifically showing a portion including the sensor section and the potential detection circuit of the surface potential detection apparatus shown in FIG. Since each of the four potential sensors 10 to 40 shown in FIG. 1 has the same configuration, the potential sensor 10 will be representatively described here.
[0048]
The sensor unit 110 of the potential sensor 10 includes a detection electrode 111, a chopper 112, and a preamplifier 113.
[0049]
The chopper 112 periodically chops the electric field between the photosensitive drum C and the detection electrode 111. Its specific structure is already known. For example, the chopper 112 is configured by attaching piezoelectric vibrators 162 and 163 and a metal piece 114 to the free end side of the tuning fork 161. The chopper 112 is provided so that the metal piece 114 is disposed between the surface of the photosensitive drum C (see FIG. 2) and the detection electrode 111.
[0050]
The piezoelectric vibrator 162 is supplied with a drive signal having a predetermined frequency, and excites the tuning fork 161 at a predetermined frequency. When the metal piece 114 vibrates due to the excitation of the tuning fork 161, the capacitance between the photosensitive drum C and the detection electrode 111 increases or decreases in a substantially sinusoidal shape centering on the capacitance Co at the time of non-excitation. Then, an AC signal is output. The excitation of the tuning fork 161 is detected by the piezoelectric vibrator 163.
[0051]
The preamplifier 113 is a circuit that converts the impedance of the AC signal output from the detection electrode 111 into a low impedance. More specifically, the preamplifier 113 includes an amplifying element Q0 composed of an FET (field effect transistor), a gate resistance R1, and a source resistance R2, and the source of the FET constituting the amplifying element Q0 is connected to the common through the resistor R2. It is connected to the ground potential Vcom1. The common ground potential Vcom1 is floating (floating) from the frame ground GND.
[0052]
The AC signal appearing on the detection electrode 111 is applied to the gate of the amplifying element Q0, and when the amplifying element Q0 operates, the high impedance signal seen on the input side of the amplifying element Q0 is impedance-converted into a low impedance signal, and the amplifying element A detection signal S11 appears at the drain D of Q0. The detection signal S11 output from the preamplifier 113 is supplied to the amplifier circuit 121.
[0053]
The drive circuit 125 includes an operational amplifier IC5, resistors R18, R17, R16, and a capacitor C12. The drive circuit 125 supplies a drive signal to the piezoelectric vibrator 162 and detects a signal output from the piezoelectric vibrator 163. The operational amplifier IC5 is positively fed back by the signal output from the piezoelectric vibrator 163 and applies the next drive signal to the piezoelectric vibrator 162. By repeating this operation, the tuning fork 161 continues to vibrate at a specific frequency (for example, 680 Hz).
[0054]
The amplifier circuit 121 includes an operational amplifier IC6, resistors R87 and R89, and a capacitor C10, and amplifies the detection signal S11. The signal amplified by the amplifier circuit 121 is supplied to the detection circuit 122.
[0055]
The detection circuit 122 includes an operational amplifier IC3, resistors R9, R10, R11, R12, and R86, and an FET (field effect transistor) Q5 that constitutes a switch element. The detection circuit 122 synchronously detects the signal supplied from the amplifier circuit 121 based on the drive signal supplied from the drive circuit 125 to the gate of the FET Q5 via the resistor R86. The synchronously detected signal is supplied to the integration circuit 123.
[0056]
The integration circuit 123 includes an operational amplifier IC2, a capacitor C6, and a diode D3, and generates a DC voltage signal S12 using the signal supplied from the adjustment circuit 124 and the signal supplied from the detection circuit 122.
[0057]
The voltage conversion circuit 130 controls the high voltage Vh (see FIG. 3) commonly supplied from the high voltage transformer 50 by the voltage signal S12 to generate the common ground potential Vcom1. The common ground potential Vcom1 is fed back to the integration circuit 123 via the DC / DC converter 34 (see FIG. 5) and the adjustment circuit 124. As a result, feedback control is performed so that the common ground potential Vcom1 becomes substantially equal to the potential Vc of the photosensitive drum C.
[0058]
The output circuit 140 includes an operational amplifier IC7 and resistors R41 and R42, and depressurizes the input common ground potential Vcom1 and outputs it as a surface potential detection signal Vout1. For example, the output circuit 140 preferably outputs the common ground potential Vcom1 after reducing the common ground potential Vcom1 to about 1/200.
[0059]
FIG. 5 is a circuit diagram more specifically showing a portion including the adjustment circuit and the DC / DC converter of the surface potential detection device shown in FIG. FIG. 6 is a sectional view showing an embodiment of the transformer shown in FIG. In the figure, the DC / DC converter 34 includes one conversion transformer T1.
[0060]
The conversion transformer T1 includes one input coil Np1, a plurality of output coils Ns1, Ns2, Ns3, Ns4, and an auxiliary winding Nb1. As shown in FIG. 6, in this conversion transformer T1, an input coil Np1, output coils Ns1 to Ns4, and an auxiliary winding Nb1 are integrated. Each of the output coils Ns1 to Ns4 includes a center tap and is insulated from the input coil Np1. The center taps of the output coils Ns1 to Ns4 are connected to the common ground potentials Vcom1 to Vcom4, respectively.
[0061]
Adjustment circuit 124 includes resistors R90, R91, and R92. One end of the resistor R90 is connected to one end of the output coils Ns1 to Ns4. The other end of the resistor R90 is connected to one end of the resistor R91 and to the integrating circuit 123. The other end of the resistor R91 is connected to one end of the resistor R92, and the other end of the resistor R92 is connected to the other ends of the output coils Ns1 to Ns4.
[0062]
Since the adjustment circuit 124 and the output coils Ns1 to Ns4 of the potential sensors 10 to 40 have the same configuration, here, the DC / DC converter 34 that is representatively described with respect to the potential sensor 10 is input to the conversion transformer T1. The input voltage Vin supplied through the coil Np1 is switched by the switching element Q1. The auxiliary winding Nb1 supplies a feedback signal to the transistor Q1. The output coil Ns1 of the conversion transformer T1 rectifies the voltage generated by the switching operation by the diodes D1 and D2, and smoothes the voltage by the capacitors C4 and C5. A DC voltage + Vcc having a positive potential is generated at one end of the output coil Ns1 with reference to the common ground potential Vcom1, and a negative potential with respect to the common ground potential Vcom1 is generated at the other end of the output coil Ns1. A DC voltage -Vcc having The DC voltages + Vcc and −Vcc are supplied to the adjustment circuit 124, an operational amplifier included in the potential sensor 10, and the like.
[0063]
In the adjustment circuit 124, the voltage between the terminals of the output coil Ns1 is input between one end of the resistor R90 and the other end of the resistor R92, and the divided voltage is output from the other end of the resistor R90. Therefore, by setting the resistors R90, R91, and R92 to predetermined resistance values, the common ground potential Vcom1 input to the center tap of the output coil Ns1 can be adjusted and output. Therefore, even when the periphery of the sensor unit 110 is positively or negatively charged, there is no problem that an offset voltage is generated in the voltage signal S12 output from the integrating circuit 123.
[0064]
The adjustment circuit 124 is provided in the probe 61 (see FIG. 4) and is independent of the circuit board 70. For this reason, it is possible to adjust the offset voltage by adjusting only the probe 61, and the adjustment work is facilitated.
[0065]
Further, in the surface potential detection apparatus according to the present embodiment, the DC / DC converter 34 is composed of only one conversion transformer T1, so that only one set of the switching transistor Q1 and other components used in the primary side circuit is sufficient. For this reason, the number of parts can be suppressed, and an increase in cost can be suppressed.
[0066]
Further, in the surface potential detection apparatus according to the present embodiment, the DC / DC converter 34 includes only one conversion transformer T1, and therefore, even when measuring the surface potential of a plurality of measured objects, the number of transformers Will not increase. For this reason, since an increase in the transformer can be suppressed, an increase in shape, weight, and cost can be suppressed.
[0067]
【Effect of the invention】
As described above, according to the present invention, the following effects can be obtained.
(A) It is possible to provide a surface potential detection device capable of suppressing an increase in shape, an increase in weight, an increase in power consumption, and an increase in cost.
(B) It is possible to provide a surface potential detection apparatus capable of detecting the potentials of a plurality of measured objects simultaneously and continuously.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a surface potential detection device according to the present invention.
2 is a block diagram specifically showing a sensor unit and a potential detection circuit of the surface potential detection device shown in FIG. 1; FIG.
FIG. 3 is a circuit diagram more specifically showing a portion including a high voltage generation circuit of the surface potential detection device shown in FIG. 1;
4 is a circuit diagram more specifically showing a portion including a sensor unit and a potential detection circuit of the surface potential detection device shown in FIG. 1; FIG.
5 is a circuit diagram more specifically showing a part including an adjustment circuit of the surface potential detection device shown in FIG. 2; FIG.
6 is a cross-sectional view showing an embodiment of the transformer shown in FIG.
[Explanation of symbols]
1 Surface potential detector
50 High voltage transformer
51 Primary coil
52 Secondary coil
10, 20, 30, 40 Potential sensor
110, 210, 310, 410 Sensor unit
120, 220, 320, 420 Potential detection circuit
130, 230, 330, 430 Voltage conversion circuit
C, M, Y, K Photosensitive drums C to K
Vh high voltage

Claims (3)

A surface potential detection device including a high voltage generation circuit, a conversion transformer, and a plurality of potential sensors,
The high voltage generation circuit supplies a high voltage obtained by rectifying an alternating voltage to the plurality of potential sensors in common,
The conversion transformer includes an input coil shared by the plurality of potential sensors, and the same number of output coils as the plurality of potential sensors,
Each of the plurality of potential sensors is independent from each other, and includes a sensor unit, a potential detection circuit, and a voltage conversion circuit,
The sensor unit generates a detection signal corresponding to the potential of the measured object,
The potential detection circuit includes a DC / DC converter configured to include the input coil and one of the output coils.
The output coil has a center tap to which a common ground potential corresponding to the potential of the object to be measured is applied,
The DC / DC converter rectifies and smoothes a voltage obtained by switching an input voltage supplied via the input coil to generate a DC voltage with the common ground potential as a reference,
The voltage conversion circuit generates the common ground potential from the high voltage based on a voltage signal generated using the DC voltage and the detection signal supplied from the sensor unit ,
The common ground potential is fed back to the potential detection circuit and is output as a surface potential detection signal. The surface potential detection device according to claim 1,
The potential detection circuit includes a detection circuit, an integration circuit, and an adjustment circuit,
The detection circuit detects and outputs the detection signal supplied from the sensor unit,
The adjustment circuit adjusts and outputs the common ground potential by dividing a voltage between terminals of the output coil of the DC / DC converter,
The integration circuit is a surface potential detection device that generates the voltage signal using a signal output from the adjustment circuit and a signal supplied from the detection circuit. The surface potential detection device according to claim 2,
The detection circuit, the integration circuit, the DC / DC converter, the voltage conversion circuit, and the high-voltage generation circuit are provided on a circuit board,
The adjustment circuit is provided in a probe and is independent from the circuit board,
Surface potential detector.

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