JP2586549B2 - Surface potential measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface potential measuring device, and more particularly, to a surface potential measuring device for measuring a surface potential of an object to be measured such as an electrostatic drum of a copying machine.

[Conventional technology]

Conventionally, a potential sensor used in this type of surface potential measuring device has a detection hole 15 for introducing a line of electric force 7 radiated from an object to be measured, as shown in FIGS. 4 (a) and 4 (b). a case 8 _a having a substrate 1 _a, is fixed at one end to the substrate 1 _a by the ground terminal 9, the piezoelectric ceramic 6 tuning fork vibrator 12 driven by the tuning fork vibrator 12 plate attached to the tip of the Chopper section consisting of piece 13 and detection electrode section below it
The drive current from the drive terminal 4 drives the piezoelectric ceramic 6, the tuning fork vibrator 12 vibrates at a natural frequency, and the electric flux 7 introduced from the detection hole 15 is a plate-like piece 13.
And is detected by the detection electrode unit 14.

In the conventional surface potential measuring device, the output voltage detected by the detection electrode unit 14 was amplified to measure the surface potential.

[Problems to be solved by the invention]

In the conventional surface potential measuring device described above, the output voltage is substantially proportional to the amount of electric lines of force cut off by the tip of the tuning fork and the charged potential of the device under test due to the structure of the potential sensor used. Therefore, in order to increase the output voltage and increase the measurement sensitivity, it is necessary to increase the amount of electric lines of force cut off by the tip of the tuning fork. For this purpose, it is necessary to increase the vibration amplitude of the tuning fork or the length of the tip of the tuning fork, and the length of the plate-like piece, the detection electrode portion, and the detection hole. In order to increase the vibration amplitude of the tuning fork, it is necessary to lower the resonance frequency of the tuning fork or increase the driving power of the tuning fork. However, if the tuning fork is made thinner in order to lower the resonance frequency of the tuning fork, the mechanical strength is reduced, and if the tuning fork is made longer, the shape of the potential sensor becomes larger. Further, there is a disadvantage that the drive circuit capacity must be increased in order to increase the drive power.

[Means for solving the problem]

The surface potential measuring device of the present invention comprises a substrate, a rod-shaped bending oscillator fixed to the substrate and driven by piezoelectric ceramic, and lines of electric force externally fixed to both ends and a center portion of the rod-shaped bending oscillator. Are cut in a predetermined cycle, and two first plate-shaped pieces, one second plate-shaped piece, and the first plate-shaped piece and the second plate-shaped piece are provided so as to face each other and cut. The two first detection electrode portions and the one second detection electrode portion that generate an AC signal by receiving the lines of electric force, and the three first electrodes that are fixed to the outer periphery of the substrate and introduce the lines of electric force. A potential sensor including a case having a window; two first amplifiers for amplifying an output from the first detection electrode unit; and a first for amplifying an output from the second detection electrode unit. An amplifier and one second amplifier whose output characteristics are inverted, the first amplifier and the second amplifier Configured to include an adder circuit for adding the output.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

 FIG. 1 is a block diagram of one embodiment of the present invention.

As shown in FIG. 1, a plate-like piece fixed to both ends of a rod-shaped bending vibrator 2 driven by a piezoelectric ceramic 6
2 _a, 2 _b and, plate-like pieces 2 _c which is secured to the central portion of the bending vibrator 2
If, plate-like pieces 2 _a, 2 _b detection electrode 3 is disposed opposite to _a, 3 _b
When, the potential sensor 20 and a detection electrode 3 _c arranged to face the plate-like pieces 2 _c, the detection electrode 3 _a, 3 _b, 3 prior to amplifying the output from the _c-amplifier 21 _a, and 21 _b, 21 _c, preamplifiers 21 _a, 21 _b
The amplification and the non-inverting amplifier 22 _a, 22 _b of the first amplifier for amplifying the output from the output from the preamplifier 21 _c 1
Comprising the inverting amplifier 22 _c as a second amplifier that amplifier and the output of the phase is inverted and a non-inverting amplifier 22 _a, 22 _b adder circuit 23 for adding the output of the output and the inverting amplifier 22 _c of.

FIGS. 2 (a) and 2 (b) are a plan view and a sectional view taken along line AA 'of the potential sensor of FIG. 1, respectively.

As shown in FIG. 2 (a) and (b), case 8 having potential sensor 20 of FIG. 1 is a substrate 1, a window 10 _a, 10 _b, 10 _c of the three being secured to an outer periphery of the substrate 1 And a piezoelectric ceramic 6 adhered to the center portion, and a rod-shaped bending oscillator 2 supported on the substrate 1 at two places of the ground terminal 9 and the fixed terminal 11, and attached to both ends and a center portion of the bending oscillator 2. _2a , 2 _b ,
2 _c and output terminals 5 _a , 5 _b , 5 _c each fixed to the substrate 1
, And detecting electrode portions 3 _a , 3 _b , 3 _c for potential detection connected to the piezoelectric ceramic 6 and driving terminals 4 _a , 4 _b connected to the piezoelectric ceramic 6.
The plate-like pieces 2 _a , 2 _b , 2 _{c chop the} corresponding electric lines of force 7 _a , 7 _b , 7 _c by the vibration of the bending oscillator 2.

3 (a) and 3 (b) are side views of the bending oscillator for explaining the operation of the potential sensor of FIG.

As shown in FIG. 2 (a), when the central portion of the bending vibrator 2 is moved upward, the detection electrode 3 _a, 3 _b of both ends receives a lot of electric power lines, the detection of the central part in opposite electrode portion 3 _c is not a little only receives the electric power line.

As shown in FIG. 3 (b), when both ends of the bending oscillator 2 move upward and the center portion moves downward, the detection electrode
3 _a, 3 _b is not a little only receive electric lines of force, the detection electrode 3 _c receives many electric lines of force.

Accordingly, by vibrating the bending vibrator 2, AC signal detection electrode 3 _a, 3 _b and voltage shift of 180 ° out of phase with each other in the detection electrode 3 _c is obtained.

Accordingly, as shown in FIG. 1, and amplifies the output from the detection electrode unit 3 _a, 3 _b at the non-inverting amplifier 22 _a, 22 _b, the detection electrode 3 _c
Are inverted and amplified by the inverting amplifier _22c , so that the three AC signals at the input of the adder circuit 23 all have the same phase. Can be obtained.

〔The invention's effect〕

As described above, according to the present invention, a rod-shaped bending vibrator is used instead of a tuning fork vibrator, and outputs from three plate-like pieces for electric field line chopping and three detection electrode portions are added in the same phase. By doing so, it is possible to increase the detection output to about three times the conventional value without changing the size of the potential sensor and without increasing the driving power, and therefore, it is possible to improve the detection accuracy and stabilize the detection.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
3 (a) and 3 (b) are a plan view and a sectional view taken along line AA 'of the potential sensor shown in FIG. 1, respectively, and FIGS. 3 (a) and 3 (b) respectively explain the operation of the potential sensor shown in FIG. 4 (a) and 4 (b) are a plan view in which a case of a potential sensor used in an example of a conventional surface potential measuring device is cut away and a sectional view taken along line BB ', respectively. is there. 1, 1 _a ... board, 2 ... bending oscillator, 2 _a , 2 _b , 2 _c ... plate-like piece, 3 _a , 3 _b , 3 _c ... detection electrode part, 4, 4 _a , 4 _b … Driving terminals, 5,5 _a , 5 _b , 5 _c … Output terminals, 6… Piezoelectric ceramic,
7,7 _a , 7 _b , 7 _c … electric line of force, 8,8 _a … board, 9… ground terminal, 10 _a , 10 _b , 10 _c … window, 11… fixed terminal, 12… ... tuning fork vibrator, 13 ...... plate-shaped piece, 14 ...... detection electrode, 15 ...... detection hole, 20 ...... potential _{sensor, 21 a, 21 b, 21} c ...... preamplifier 2
2 _a , 22 _b …… Non-inverting amplifier, 22 _c …… Inverting amplifier, 23 ……
Addition circuit.

Claims (1)

(57) [Claims] A predetermined period of time between a substrate, a rod-shaped bending vibrator fixed to the substrate and driven by piezoelectric ceramic, and external lines of electric force fixed to both ends and a center of the rod-shaped bending vibrator, respectively. The first force, the second force, and the electric force provided to face the first force and the second force, respectively. A case having two first detecting electrode portions for receiving an electric line and generating an AC signal, one second detecting electrode portion, and three windows fixed to the outer periphery of the substrate and for introducing the lines of electric force. , Two first amplifiers that amplify the output from the first detection electrode unit, the first amplifier that amplifies the output from the second detection electrode unit, and output characteristics 1 is reversed
A surface potential measuring device comprising: a plurality of second amplifiers; and an adding circuit for adding outputs of the first amplifier and the second amplifier.