JPS6056266A - Surface-electrometer - Google Patents

Abstract

PURPOSE:To make it possible to certainly detect the abnormalilty of a surface- electrometer, by detecting the operation state of the surface-electrometer from the signal voltage of the surface-electrometer and the output voltage from an amplifier for applying voltage to a housing. CONSTITUTION:The electric field between a photosensitive drum 47 and a measuring electrode 85 is intermittently blocked by a chopper electrode and the AC signal induced in the measuring electrode 85 is inputted to a clamp circuit 113 through a band pass filter 102 and a photocoupler 104. The driving signal of a vibrator 82 is inputted to a vibrator driving circuit 105 through a photocoupler 107 and the feedback signal S3 from the vibrator 82 is inputted to the clamp circuit 113 through a synchronous circuit 108 and a differentiation circuit 111. Clamp output is fed back to the vibrator 82 and a housing 81 as shield potential through an integration circuit 114 and an inverter 116 while measured potential is read by MPU122. On the other hand, MPU122 measures the output voltage of the integration circuit 114 and surface potential being the output of a voltage dividing circuit 117 to detect the operation state of a surface-electrometer.

Description

TECHNICAL FIELD The present invention relates to a surface electrometer, and more particularly to a surface electrometer for measuring the surface potential of an object to be measured, such as a photosensitive drum of a copying machine.

Prior Art Conventionally, a chopper is placed between a measurement electrode and an object to be measured, such as a photosensitive drum of a copying machine, and the chopper is vibrated to cut off the electric field and detect the surface potential of the object to be measured as an alternating current signal. Surface electrometers are known.

A conventional surface electrometer of this type detects an alternating current signal obtained from the above-mentioned chopper drive circuit, and displays the detected alternating current signal using a display element to display the operating state of the drive circuit.

However, the above-mentioned conventional surface electrometer cannot distinguish between oscillations in other modes of the chopper, that is, spurious oscillations, so there is a possibility that an abnormal state may be regarded as a normal state.

Purpose The present invention has been made in order to eliminate the drawbacks of the conventional surface potential meter as described above. The purpose is to provide a measurement.

EXAMPLES Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

FIG. 1 and the following illustrate one embodiment of the present invention. In the figure, the one indicated by the reference numeral 81 covers the entire surface electrometer;
The housing 81 is made of metal to eliminate the influence of external electric fields, and this housing 81 is fixed to a base 95 that is also made of metal.

An opening 88 serving as a measurement window is formed in a part of the housing 81, and this opening 88 is arranged to face the portion to be measured of the drum 47.

A tuning fork-shaped vibrator 82 is mounted on the base 95 in an electrically conductive state.

A driving piezoelectric element 84 is provided on each of the two arms of this tuning fork-shaped vibrator 82.

When a DC voltage is applied to these piezoelectric elements 84 in the thickness direction from a drive circuit to be described later, the vibrator 82 moves in the plane direction.

On the other hand, a chopper electrode 83 is provided at the tip of one arm of the vibrator 82 in a state perpendicular to the arm, and when the vibrator 82 vibrates, a measurement opening 88 is opened and closed at a constant cycle.

A printed circuit board 86 fixed to a base 95 is fixed to the rear [phase] side of the rathopper electrode 83, and a measurement electrode 85 having the same shape as the opening is disposed on the printed circuit board 86 at a position facing the opening 88. is formed.

With this structure, lines of electric force based on the surface charge of the photosensitive drum 47 pass through the opening 88 and reach the measurement electrode 85, but when the chopper electrode 83 is vibrated, these lines of electric force are intermittently cut. Therefore, the photosensitive drum 4 is attached to the measurement electrode 85.
An alternating voltage with an amplitude proportional to the voltage difference between the surface potential on the chopper electrode and the chopper electrode is induced.

This alternating current voltage signal is converted into a low impedance signal by a preamplifier circuit (indicated by reference numeral 101 in FIG. 5) consisting of a source follower built into the printed circuit board 86, and then taken out to the outside as the output of the electrometer. be done.

In addition, in FIG. 4 (the symbol 89 in Bl is a piezoelectric element 84
This is an internal shield member for preventing the drive signal from being guided to the measurement electrode 85.

By the way, as shown in FIG. 4 (C1), the piezoelectric element 84 is sandwiched between electrodes 99 on both sides, and is fixed with a conductive adhesive 98 to a vibrator 82 made of an elastic metal such as phosphorus-rusted copper. Together with the child, it forms a unimorph oscillator.

The base 95 is fixed to a printed circuit board 97 (fixed), and one end of this printed circuit board 97 is connected to a connector 94 and a board guide 87.
is supported on the main body side.

Surface electrometers with this structure can be driven without the need for a motor to drive the vibrator, making it possible to achieve low cost and miniaturization.Moreover, since the resonant frequency of the piezoelectric element is constant, it can be driven with high accuracy. Detection and device control become possible.

Next, the fifth control circuit applied to the surface electrometer described above is
This will be explained with figures.

When the electric field between the photosensitive drum 47 and the measurement electrode 85 is intermittently interrupted by the chopper electrode 83, a high-impedance AC signal is induced in the measurement electrode 85, which is transmitted to the preamplifier 1.
01, the signal is converted into a low impedance signal S1 and input to the bandpass filter 102.

Incidentally, in FIG. 5, the entire surface electrometer is designated by the reference numeral 67.

Noise is removed from the signal S1 by a bandpass filter 102, and the signal S1 is passed through an amplifier 103,] and a first coupler 104 f! r
: is input to the clamp circuit 113 via.

The input signal S to this clamp circuit 113 is the signal S
The phase has changed somewhat compared to I.

On the other hand, a vibrator 8 is connected to a terminal indicated by reference numeral 120 in FIG.
When the drive signal No. 2 is input, the photocoupler 10 ends, and the transducer drive circuit +05 passes through the transducer drive switch 106.
operates to cause the vibrator 82 to vibrate.

A feedback signal S3 from the vibrator is input to a synchronization circuit 108 composed of a phase shift circuit 108a and a comparator 108b.

The symbol S is an output signal from the phase shift circuit 108a.

Although the feedback signal S3 is different in phase from the signal S1, since they are synchronized, the phase is advanced by the phase shift circuit 108a and compared by the comparator 1081 to obtain the signal S through the photocoupler 110. The synchronizing signal ε6 is obtained by differentiating it with the differentiating circuit 111.

This synchronization signal S. is input to the clamp circuit 113 via the display circuit 112.

The clamp circuit 113 clamps the signal S2 using the synchronizing signal S to determine whether the surface potential of the photosensitive drum 47 is positive or negative, and obtains an output signal S7.

The signal S7 is integrated by the integrating circuit 114 and converted into a signal by a factor of Iαα.
It is converted into a high voltage by an inverter 116.

The output voltage of the DC-DC inverter 116 is fed back to the vibrator 82t and the potential type housing 81 as a shield potential.

In addition, from the preamplifier 101 to the DC-DC Innoku Ichiyo 11
When considered as an amplifier with up to 6 circuits, this works as an inverting amplifier.

That is, this inverting amplifier works to raise the shield potential when the surface potential of the drum is smaller than the shield potential, and to lower the shield potential when it is larger than the shield potential. operates so that the surface potentials of both are the same.

Therefore, the potential at the terminal 11 obtained by dividing this shield potential by the voltage dividing circuit 117 becomes the surface potential of the photosensitive drum 47.

All the circuits surrounded by the broken line 100 in FIG. Preventing occurrence.

That is, the output obtained by dividing the potential of the surface electrometer by the voltage dividing circuit 117 measures the surface potential of the drum.

Further, the output voltage of the voltage dividing circuit 117 is converted into a digital value by a width exchanger 121, and the measured potential is read by the MPU+22.

In addition, the output of the integrating circuit 114 is input to a converter 121.

On the other hand, the signals 81 to 0 shown in FIG.
The signal waveform of S7 is shown.

Next, the seventh section describes a method for determining the operating state of the surface electrometer configured as described above using a microcomputer.
This will be explained with reference to the flowchart shown in the figure.

First, when the control operation starts, in step S21, the surface potential ■m, which is the output of the voltage dividing circuit 117, and the integrating circuit 1
Measure the output voltage Vs of 14.

The gains of the inverter drive circuit 115 and the DC-DC inverter 116 are large, and the signal voltage is 1.2V during normal operation.

Next, the process proceeds to step S22, where it is determined whether or not Vs is greater than 12V. If Vs>12V, the process proceeds to step 823; if VS<12V, the process proceeds to step S26.

In step 823, it is determined whether the surface layer ■m is at its maximum or not, and if it is at its maximum, the process proceeds to step S24.

In step S24, it is found that the measured potential exceeds the upper limit of the measurement range.

If the reduced Vm is not the maximum, the process proceeds to step S25, where it is found that the surface potential word 1 is in an abnormal state.

On the other hand, it is determined in steps S, .

In step S2□, it is determined whether 7 m is the minimum or not, and if it is the minimum, the process advances to step 828 and it is found that the measured potential exceeds the lower limit of the measurement range.

Further, if Vm is not the minimum, the process advances to step 829 and it is found that the surface electrometer is abnormal.

On the other hand, if it is determined in step 826 that VS<12V is not found, the process proceeds to step 830, where it is determined whether 7m is the maximum value or the minimum value, and if it is the maximum value or the minimum value, the process proceeds to step S31. It turns out that the surface electrometer is abnormal.

Step S. When it is determined that Vm is neither the maximum value nor the minimum value, step 834
Since the water diversion embodiment is constructed as described above, the operating state of the surface electrometer can be automatically determined, and an abnormal state can be reliably detected.

Further, since the operating state test signal is obtained from the signal voltage and drive voltage, abnormalities in the surface electrometer can be detected without using a special measuring device, and maintenance and inspection can be easily performed.

Effects As is clear from the above explanation, according to the present invention, the operating state of the surface electrometer can be detected from the signal voltage of the surface electrometer and the output voltage from the amplifier that applies voltage to the casing. Therefore, abnormalities in the surface electrometer can be detected without the need for special measuring means.

[Brief explanation of drawings]

The figures are for explaining one embodiment of the present invention, and Fig. 1 is a perspective view of a surface electrometer, Fig. 4 is a perspective view of the housing, Fig. 4 is a partially enlarged sectional view of the vibrator, and Fig. FIG. 5 is a block diagram of the control circuit, FIGS. ...Surface electrometer 81...
・Housing 82... Vibrator 83... Chomper' electrode 84... Pressure' turtle element 85...
...Measurement type Jf86.97...Printed circuit board 101.
...Preamplifier 104, +07...Photocoupler 108・Phase shift circuit 111...Differentiating circuit 113・
Clamp circuit 114... Integrating circuit 116... DC-
1) C inverter 117... voltage divider circuit 121... A/D converter 12
2...MPU

Claims (3)

[Claims] (1) Equipped with a measurement electrode that detects the surface potential of the measurement object, and an amplifier that amplifies the signal voltage from the measurement electrode and applies the output voltage to a casing that covers the measurement electrode, the signal from the measurement electrode is 1. A surface electrometer characterized by being configured to detect an operating state of the surface electrometer based on a voltage and an output voltage from an amplifier. (2) A patent claim characterized in that the signal voltage from the measurement electrode and the output voltage from the amplification 2:÷ are A7D converted, and the operational state of the surface electrometer 1 μ is detected from the arithmetic and control means stand. The surface electrometer according to item 1. (3) According to any one of claims 1 and 2, the display means is configured to display this when the operating state of the surface electrometer is abnormal. The surface potential of